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Sample records for high-strength low-alloy steels

  1. High-strength, low-alloy steels.

    Science.gov (United States)

    Rashid, M S

    1980-05-23

    High-strength, low-alloy (HSLA) steels have nearly the same composition as plain carbon steels. However, they are up to twice as strong and their greater load-bearing capacity allows engineering use in lighter sections. Their high strength is derived from a combination of grain refinement; precipitation strengthening due to minor additions of vanadium, niobium, or titanium; and modifications of manufacturing processes, such as controlled rolling and controlled cooling of otherwise essentially plain carbon steel. HSLA steels are less formable than lower strength steels, but dualphase steels, which evolved from HSLA steels, have ferrite-martensite microstructures and better formability than HSLA steels of similar strength. This improved formability has substantially increased the utilization potential of high-strength steels in the manufacture of complex components. This article reviews the development of HSLA and dual-phase steels and discusses the effects of variations in microstructure and chemistry on their mechanical properties.

  2. Analysis of phase transformation in high strength low alloyed steels

    OpenAIRE

    A. Di Schino

    2017-01-01

    The effect of low-alloy additions on phase transformation of high strength low alloyed steels is reported. Various as-quenched materials with microstructures consisting of low carbon (granular) bainitic, mixed bainitic/martensitic and fully martensitic microstructures were reproduced in laboratory. Results show that for a given cooling rate, an increase of austenite grain size (AGS) and of Mo and Cr contents decreases the transformation temperatures and promotes martensite formation.

  3. Cold weld cracking susceptibility of high strength low alloyed (HSLA steel NIONIKRAL 70

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    A. S. Tawengi

    2014-10-01

    Full Text Available In view of the importance of high strength low alloy (HSLA steels, particularly for critical applications such as offshore plat forms, pipeline and pressure vessels, this paper reports on an investigation of how to weld this type of steel without cold cracking. Using manual metal arc welding process and Tekken test (Y - Grove test has been carried out both to observe the cold cracking phenome non, and to investigate the influencing factors, such as preheating temperature and energy input, as well as electrode strength and diameter. How ever the results of the experiments show that there is a risk of cold cracking.

  4. Dissimilar ultrasonic spot welding of Mg-Al and Mg-high strength low alloy steel

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    V.K. Patel

    2014-01-01

    Full Text Available Sound dissimilar lap joints were achieved via ultrasonic spot welding (USW, which is a solid-state joining technique. The addition of Sn interlayer during USW effectively blocked the formation of brittle al12Mg17 intermetallic compound in the Mg-Al dissimilar joints without interlayer, and led to the presence of a distinctive composite-like Sn and Mg2Sn eutectic structure in both Mg-Al and Mg-high strength low alloy (HSLA steel joints. The lap shear strength of both types of dissimilar joints with a Sn interlayer was significantly higher than that of the corresponding dissimilar joints without interlayer. Failure during the tensile lap shear tests occurred mainly in the mode of cohesive failure in the Mg-Al dissimilar joints and in the mode of partial cohesive failure and partial nugget pull-out in the Mg-HSLA steel dissimilar joints.

  5. Development of High Strength Low Alloy Steel for Nuclear Reactor Vessel

    Energy Technology Data Exchange (ETDEWEB)

    Lee, B. S.; Kim, M. C.; Yoon, J. H; Choi, K. J.; Kim, J. M.; Hong, J. H.

    2013-11-15

    SA508 Gr. 4N Ni-Cr-Mo low alloy steel has an improved strength and fracture toughness, compared to commercial low alloy steels such as SA508 Gr. 3 Mn-Mo-Ni low alloy steel. In this study, the microstructural observation and baseline test were carried out using SA508 Gr. 4N model alloy of 1 ton scale. Thermal embrittlement and neutron irradiation embrittlement behaviors of SA508 Gr. 4N model alloy were also evaluated. The yield strength of 540MPa, Charpy transition temperature, T{sub 41J} of -132 .deg. C, Reference temperature, T{sub 0} of -146 .deg. C, and RT{sub NDT} of -105 .deg. C were obtained from large scale SA508 Gr. 3 low alloy steel. Effect of alloy elements on thermal embrittlement was carefully evaluated and embrittlement mechanism was characterized using small scale model alloys with various alloy composition. Neutron irradiation behavior at high fluence level up to 1.5x10{sup 20} n/cm{sup 2} corresponding over 80 years operation of RPV were investigated using irradiated samples from research reactor 'HANARO'. The irradiation embrittlement behavior of SA508 Gr. 4N model alloy was similar to that of commercial RPV steel. However, after neutron irradiation up to 1.3x10{sup 20} n/cm{sup 2}, SA508 Gr. 4N model alloy shows lower transition temperature(T{sub 41J} = -63 .deg. C) than unirradiated commercial RPV steel because it has a superior initial toughness.

  6. Cleavage Fracture Toughness of SA508 Gr.4N High Strength Low Alloy Steel with Different Phase Fraction

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    Lee, Ki Hyoung; Kim, Min Chul; Choi, Kwon Jae; Lee, Bong Sang [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2012-05-15

    Materials for reactor pressure vessel (RPV) are required to have good mechanical properties to endure the severe operating conditions inside the reactor. Various researches have focused on improving mechanical properties by the controlling the heat treatment process of commercial SA508 Gr.3 RPV steel. Some studies for identifying new material with high strength and toughness for larger capacity and longer lifetime of reactor are being performed. SA508 Gr.4N low alloy steel may be a promising RPV material due to its excellent mechanical properties from its tempered martensitic microstructure. Recently, some research showed that F/M steel composed of the tempered martensite has a steeper temperature dependency of the fracture toughness than the master curve expression. We have also focused on the steep transition properties of tempered martensitic SA508 Gr.4N steel in previous research. However, it has not yet confirmed that the transition behavior including temperature dependency with tempered martensite fraction. This investigation aims to evaluate the relationship between cleavage fracture toughness and tempered martensite fraction for SA508 Gr.4N low alloy steel. For this purpose, the model alloys were prepared by controlling the cooling rate from the austenitization temperature. The cleavage fracture toughness was characterized in transition temperature region by 3-point bending tests. Based on the test results and a stress distribution near crack tip calculated in FE analysis, the relationship between the carbide size distributions and the transition properties are analyzed

  7. Effect of welding processes on mechanical and microstructural characteristics of high strength low alloy naval grade steel joints

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    S. Ragu Nathan

    2015-09-01

    Full Text Available Naval grade high strength low alloy (HSLA steels can be easily welded by all types of fusion welding processes. However, fusion welding of these steels leads to the problems such as cold cracking, residual stress, distortion and fatigue damage. These problems can be eliminated by solid state welding process such as friction stir welding (FSW. In this investigation, a comparative evaluation of mechanical (tensile, impact, hardness properties and microstructural features of shielded metal arc (SMA, gas metal arc (GMA and friction stir welded (FSW naval grade HSLA steel joints was carried out. It was found that the use of FSW process eliminated the problems related to fusion welding processes and also resulted in the superior mechanical properties compared to GMA and SMA welded joints.

  8. Evaluation of the stress corrosion cracking resistance of several high strength low alloy steels

    Science.gov (United States)

    Humphries, T. S.; Nelson, E. E.

    1980-01-01

    The stress corrosion cracking resistance was studied for high strength alloy steels 4130, 4340, for H-11 at selected strength levels, and for D6AC and HY140 at a single strength. Round tensile and C-ring type specimens were stressed up to 100 percent of their yield strengths and exposed to alternate immersion in salt water, salt spray, the atmosphere at Marshall Space Flight Center, and the seacoast at Kennedy Space Center. Under the test conditions, 4130 and 4340 steels heat treated to a tensile strength of 1240 MPa (180 ksi), H-11 and D6AC heat treated to a tensile strength of 1450 MPa (210 ksi), and HY140 (1020 MPa, 148 ksi) are resistant to stress corrosion cracking because failures were not encountered at stress levels up to 75 percent of their yield strengths. A maximum exposure period of one month for alternate immersion in salt water or salt spray and three months for seacoast is indicated for alloy steel to avoid false indications of stress corrosion cracking because of failure resulting from severe pitting.

  9. Guide for Recommended Practices to Perform Crack Tip Opening Displacement Tests in High Strength Low Alloy Steels

    Directory of Open Access Journals (Sweden)

    Julián A. Ávila

    Full Text Available Abstract: Fracture mechanics approach is important for all mechanical and civil projects that might involve cracks in metallic materials, and especially for those using welding as a structural joining process. This methodology can enhance not only the design but also the service life of the structures being constructed. This paper includes detailed consideration of several practical issues related to the experimental procedures to assess the fracture toughness in high strength low alloy steels (HSLA using the crack tip opening displacement (CTOD parameter, specifically pipeline steels for oil and gas transportation. These considerations are important for engineers who are new in the field, or for those looking for guidelines performing different procedures during the experimentation, which usually are difficult to understand from the conventional standards. We discuss on topics including geometry selection, number of replicate tests, fatigue precracking, test procedure selection and realization, reports of results and other aspects.

  10. A Method to Determine Lankford Coefficients (R-Values) for Ultra High Strength Low Alloy (Uhsla) Steels

    Science.gov (United States)

    Gösling, M.

    2017-09-01

    For Ultra High Strength Low Alloy Steels (UHSLAS) it is difficult to determine Lankford parameters, since the measurement of a stable strain ratio is often not possible. This report presents a method for determining Lankford coefficients for UHSLA Steels. The method is based on a combination of a theoretical material model and on experiences from a material data base. The Hill’48 yield condition is used to calculate the Lankford coefficients as a function of the yield stress. An empirical model based on the BILSTEIN material data base is used to predict the anisotropy. The result from earing test is used as an input parameter for the empirical model. The method is first checked using data from tensile tests. The predicted Lankford coefficients are compared with measured Lankford coefficients. In a further step, this method is applied to low alloyed steels with a yield stress of more than 900 MPa. For these materials the Lankford coefficients could not be measured by tensile tests. Predicted Lankford coefficients are used in the numerical simulation of earing test and compared with experimental results. In summary, it can be stated that the method presented here is suitable for predicting Lankford coefficients in case of an impossible direct measurement.

  11. Effect of Cooling Rate on Microstructures and Mechanical Properties in SA508 Gr4N High Strength Low Alloy Steel

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    Kim, Minchul; Park, Sanggyu; Choi, Kwonjae; Lee, Bongsang [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2013-05-15

    The microstructure of Ni-Cr-Mo low alloy steel is a mixture of tempered martensite and tempered lower bainite and that of Mn-Mo-Ni low alloy steel is predominantly tempered upper bainite. Higher strength and toughness steels are very attractive as an eligible RPV steel, so several researchers have studied to use the Ni-Cr-Mo low alloy steel for the NPP application. Because of the thickness of reactor vessel, there are large differences in austenitizing cooling rates between the surface and the center locations of thickness in RPV. Because the cooling rates after austenitization determine the microstructure, it would affect the mechanical properties in Ni-Cr-Mo low alloy steel, and it may lead to inhomogeneous characteristics when the commercial scale of RPV is fabricated. In order to apply the Ni-Cr-Mo low alloy steel to RPV, it is necessary to evaluate the changes of microstructure and mechanical properties with varying phase fractions in Ni-Cr-Mo low alloy steel. In this study, the effects of martensite and bainite fractions on mechanical properties in Ni-Cr-Mo low alloy steel were examined by controlling the cooling rate after austenitization. First of all, continuous cooling transformation(CCT) diagram was established from the dilatometric analyses. Then, the phase fractions at each cooling rate were quantitatively evaluated. Finally, the mechanical properties were correlated with the phase fraction, especially fraction of martensite in Ni-Cr-Mo low alloy steel.

  12. Effects of the Microstructure on Segregation behavior of Ni-Cr-Mo High Strength Low Alloy RPV Steel

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    Park, Sang Gyu; Wee, Dang Moon [Korea Advanced Institute of Science and Technology, Daejeon (Korea, Republic of); Kim, Min Chul; Lee, Bong Sang [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2010-10-15

    SA508 Gr.4N Ni-Cr-Mo low alloy steel has an improved fracture toughness and strength, compared to commercial Mn-Mo-Ni low alloy RPV steel SA508 Gr.3. Higher strength and fracture toughness of low alloy steels could be achieved by adding Ni and Cr. So there are several researches on SA508 Gr.4N low alloy steel for a RPV application. The operation temperature and time of a reactor pressure vessel is more than 300 .deg. C and over 40 years. Therefore, in order to apply the SA508 Gr.4N low alloy steel for a reactor pressure vessel, it requires a resistance of thermal embrittlement in the high temperature range including temper embrittlement resistance. S. Raoul reported that the susceptibility to temper embrittlement was increasing a function of the cooling rate in SA533 steel, which suggests the martensitic microstructures resulting from increased cooling rates are more susceptible to temper embrittlement. However, this result has not been proved yet. So the comparison of temper embrittlement behavior was made between martensitic microstructure and bainitic microstructure with a viewpoint of boundary features in SA508 Gr.4N, which have mixture of tempered bainite/martensite. In this study, we have compared temper embrittlement behaviors of SA508 Gr.4N low alloy steel with changing volume fraction of martensite. The mechanical properties of these low alloy steels) were evaluated after a long-term heat treatment(450 .deg. C, 2000hr. Then, the images of the segregated boundaries were observed and segregation behavior was analyzed by AES. In order to compare the misorientation distributions of model alloys, grain boundary structures were measured with EBSD

  13. Stress Corrosion Cracking and Hydrogen Embrittlement of Thick Section High Strength Low Alloy Steel

    Science.gov (United States)

    1986-06-01

    corrosion cracking of alpha brass in ammoniacal copper sulfate and concluded that the experimental results were best supported by the film r.Apture...steel heat treatment was that a stronger product could be produced without resort to quenching with its attendant danger of warping and cracking; the

  14. Microstructural Characterization of Clad Interface in Welds of Ni-Cr-Mo High Strength Low Alloy Steel

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Hong-Eun; Kim, Min-Chul; Lee, Ho-Jin; Kim, Keong-Ho [KAERI, Daejeon (Korea, Republic of); Lee, Ki-Hyoung [KAIST, Daejeon (Korea, Republic of); Lee, Chang-Hee [Hanyang Univ., Seoul (Korea, Republic of)

    2011-08-15

    SA508 Gr.4N Ni-Cr-Mo low alloy steel, in which Ni and Cr contents are higher than in commercial SA508 Gr.3 Mn-Mo-Ni low alloy steels, may be a candidate reactor pressure vessel (RPV) material with higher strength and toughness from its tempered martensitic microstructure. The inner surface of the RPV is weld-cladded with stainless steels to prevent corrosion. The goal of this study is to evaluate the microstructural properties of the clad interface between Ni-Cr-Mo low alloy steel and stainless weldment, and the effects of post weld heat treatment (PWHT) on the properties. The properties of the clad interface were compared with those of commercial Mn-Mo-Ni low alloy steel. Multi-layer welding of model alloys with ER308L and ER309L stainless steel by the SAW method was performed, and then PWHT was conducted at 610°C for 30 h. The microstructural changes of the clad interface were analyzed using OM, SEM and TEM, and micro-Vickers hardness tests were performed. Before PWHT, the heat affected zone (HAZ) showed higher hardness than base and weld metals due to formation of martensite after welding in both steels. In addition, the hardness of the HAZ in Ni-Cr-Mo low alloy steel was higher than that in Mn-Mo-Ni low alloy steel due to a comparatively high martensite fraction. The hardness of the HAZ decreased after PWHT in both steels, but the dark region was formed near the fusion line in which the hardness was locally high. In the case of Mn-Mo-Ni low alloy steel, formation of fine Cr-carbides in the weld region near the fusion line by diffusion of C from the base metal resulted in locally high hardness in the dark region. However, the precipitates of the region in the Ni-Cr-Mo low alloy steel were similar to that in the base metal, and the hardness in the region was not greatly different from that in the base metal.

  15. The influence of high heat input and inclusions control for rare earth on welding in low alloy high strength steel

    Science.gov (United States)

    Chu, Rensheng; Mu, Shukun; Liu, Jingang; Li, Zhanjun

    2017-09-01

    In the current paper, it is analyzed for the influence of high heat input and inclusions control for rare earth on welding in low alloy high strength steel. It is observed for the structure for different heat input of the coarse-grained area. It is finest for the coarse grain with the high heat input of 200 kJ / cm and the coarse grain area with 400 kJ / cm is the largest. The performance with the heat input of 200 kJ / cm for -20 °C V-shaped notch oscillatory power is better than the heat input of 400 kJ / cm. The grain structure is the ferrite and bainite for different holding time. The grain structure for 5s holding time has a grain size of 82.9 μm with heat input of 200 kJ/cm and grain size of 97.9 μm for 10s holding time. For the inclusions for HSLA steel with adding rare earth, they are Al2O3-CaS inclusions in the Al2O3-CaS-CaO ternary phase diagram. At the same time, it can not be found for low melting calcium aluminate inclusions compared to the inclusions for the HSLA steel without rare earth. Most of the size for the inclusions is between 1 ~ 10μm. The overall grain structure is smaller and the welding performance is more excellent for adding rare earth.

  16. The influence of the corrosion product layer generated on the high strength low-alloy steels welded by underwater wet welding with stainless steel electrodes in seawater

    Science.gov (United States)

    Bai, Qiang; Zou, Yan; Kong, Xiangfeng; Gao, Yang; Dong, Sheng; Zhang, Wei

    2017-02-01

    The high strength low-alloy steels are welded by underwater wet welding with stainless steel electrodes. The micro-structural and electrochemical corrosion study of base metal (BM), weld zone (WZ) and heat affected zone (HAZ) are carried out to understand the influence of the corrosion product layer generated on the high strength low-alloy steels welded by underwater wet welding with stainless steel electrodes, methods used including, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and scanning electron microscope (SEM). The results indicate that the WZ acts as a cathode and there is no corrosion product on it throughout the immersion period in seawater. The HAZ and BM acts as anodes. The corrosion rates of the HAZ and BM change with the immersion time increasing. In the initial immersion period, the HAZ has the highest corrosion rate because it has a coarse tempered martensite structure and the BM exhibites a microstructure with very fine grains of ferrite and pearlite. After a period of immersion, the BM has the highest corrosion rate. The reason is that the corrosion product layer on the HAZ is dense and has a better protective property while that on the BM is loose and can not inhibit the diffusion of oxygen.

  17. Neutron irradiation effects on mechanical properties in SA508 Gr4N high strength low alloy steel

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    Kim, Minchul; Lee, Kihyoung; Park, Sanggyu; Choi, Kwonjae; Lee, Bongsang [Korea Atomic Energy Research Institute, Nuclear Material Research Div., Daejeon (Korea, Republic of)

    2012-10-15

    The Reactor Pressure Vessel (RPV) is the key component in determining the lifetime of nuclear power plants because it is subject to the significant aging degradation by irradiation and thermal aging, and there is no practical method for replacing that component. Advanced reactors with much larger capacity than current reactor require the usage of higher strength materials inevitably. The SA508 Gr.4N Ni Cr Mo low alloy steel, in which Ni and Cr contents are larger than in conventional RPV steels, could be a promising RPV material offering improved strength and toughness from its tempered martensitic microstructure. For a structural integrity of RPV, the effect of neutron irradiation on the material property is one of the key issues. The RPV materials suffer from the significant degradation of transition properties by the irradiation embrittlement when its strength is increased by a hardening mechanism. Therefore, the potential for application of SA508 Gr.4N steel as the structural components for nuclear power reactors depends on its ability to maintain adequate transition properties against the operating neutron does. However, it is not easy to fine the data on the irradiation effect on the mechanical properties of SA508 Gr.4N steel. In this study, the irradiation embrittlement of SA508 Gr.4N Ni Cr Mo low alloy steel was evaluated by using specimens irradiated in research reactor. For comparison, the variations of mechanical properties by neutron irradiation for commercial SA508 Gr.3 Mn Mo Ni low alloy steel were also evaluated.

  18. Effect of different stages of tensile deformation on micromagnetic parameters in high-strength, low-alloy steel

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    Vaidyanathan, S.; Moorthy, V.; Kalyanasundaram, P.; Jayakumar, T.; Raj, B. [Indira Gandhi Centre for Atomic Research, Kalpakkam (India). Metallurgy and Materials Group

    1999-08-01

    The influence of tensile deformation on the magnetic Barkhausen emissions (MBE) and hysteresis loop has been studied in a high-strength, low-alloy steel (HSLA) and its weldment. The magnetic measurements were made both in loaded and unloaded conditions for different stress levels. The root-mean-square (RMS) voltage of the MBE has been used for analysis. This study shows that the preyield and postyield deformation can be identified from the change in the MBE profile. The initial elastic deformation showed a linear increase in the MBE level in the loaded condition, and the MBE level remained constant in the unloaded condition. The microplastic yielding, well below the macroyield stress, significantly reduces the MBE, indicating the operation of grain-boundary dislocation sources below the macroyield stress. This is indicated by the slow increase in the MBE level in the loaded condition and the decrease in the MBE level in the unloaded condition. The macroyielding resulted in a significant increase in the MBE level in the loaded condition and, more clearly, in the unloaded condition. The increase in the MBE level during macroyielding has been attributed to the grain rotation phenomenon, in order to maintain the boundary integrity between adjacent grains, which would preferentially align the magnetic domains along the stress direction. This study shows that MBE during tensile deformation can be classified into four stages: (1) perfectly elastic, (2) microplastic yielding, (3) macroyielding, and (4) progressive plastic deformation. A multimagnetic parameter approach, combining the hysteresis loop and MBE, has been suggested to evaluate the residual stresses.

  19. Characterization of high strength and high toughness Ni-Mo-Cr low alloy steels for nuclear application

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    Lee, B.S., E-mail: BONGSL@kaeri.re.k [KAERI, Dukjin-dong 150, Yuseong, Daejeon (Korea, Republic of); Kim, M.C.; Yoon, J.H.; Hong, J.H. [KAERI, Dukjin-dong 150, Yuseong, Daejeon (Korea, Republic of)

    2010-01-15

    The reactor pressure vessels of PWRs have mostly been made of SA508 Grade 3 (Class 1) low alloy steels which have revealed moderate mechanical properties and a moderate radiation resistance for a 40 or 60 year operation. The specified minimum yield strength of the material is 345 MPa with a ductile-brittle transition temperature of about 0 deg. C. While other materials, most of which are non-ferrous alloys or high alloyed steels for a higher temperature application, are being developed for the Generation-4 reactors, low alloy steels with a higher strength and toughness can help to increase the safety and economy of the advanced PWR systems which will be launched in the near future. The ASME specification for SA508 Grade 4N provides a way to increase both the strength and toughness by a chemistry modification, especially by increasing the Ni and Cr contents. However, a higher strength steel has a deficiency due to a lack of operating data for nuclear power plants. In this study, experimental heats of SA508 Grade 4N steels with different chemical compositions were characterized mechanically. The preliminary results for an irradiation embrittlement and the HAZ properties are discussed in addition to their superior baseline properties.

  20. Impact of choice of stabilized hysteresis loop on the end result of investigation of high-strength low-alloy (HSLA steel on low cycle fatigue

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    S. Bulatović

    2014-10-01

    Full Text Available High strength low-alloy steel under low cycle fatigue at a certain level of strain controlled achieve stabilized condition. During the fatigue loading stabilized hysteresis loop is determined, which typical cycle of stabilization is calculated as half number of cycles to failure. Stabilized hysteresis loop is a representative of all hysteresis and it’s used to determine all of the parameters for the assessment of low cycle fatigue. This paper shows comparison of complete strain-life curves of low cycle fatigue for two chosen stabilized hysteresis loop cycles of base metal HSLA steel marked as Nionikral 70.

  1. Influence of Hot Plastic Deformation in γ and (γ + α) Area on the Structure and Mechanical Properties of High-Strength Low-Alloy (HSLA) Steel.

    Science.gov (United States)

    Sas, Jan; Kvačkaj, Tibor; Milkovič, Ondrej; Zemko, Michal

    2016-11-30

    The main goal of this study was to develop a new processing technology for a high-strength low-alloy (HSLA) steel in order to maximize the mechanical properties attainable at its low alloy levels. Samples of the steel were processed using thermal deformation schedules carried out in single-phase (γ) and dual-phase (γ + α) regions. The samples were rolled at unconventional finishing temperatures, their final mechanical properties were measured, and their strength and plasticity behavior was analyzed. The resulting microstructures were observed using optical and transmission electron microscopy (TEM). They consisted of martensite, ferrite and (NbV)CN precipitates. The study also explored the process of ferrite formation and its influence on the mechanical properties of the material.

  2. Influence of Hot Plastic Deformation in γ and (γ + α Area on the Structure and Mechanical Properties of High-Strength Low-Alloy (HSLA Steel

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    Jan Sas

    2016-11-01

    Full Text Available The main goal of this study was to develop a new processing technology for a high-strength low-alloy (HSLA steel in order to maximize the mechanical properties attainable at its low alloy levels. Samples of the steel were processed using thermal deformation schedules carried out in single-phase (γ and dual-phase (γ + α regions. The samples were rolled at unconventional finishing temperatures, their final mechanical properties were measured, and their strength and plasticity behavior was analyzed. The resulting microstructures were observed using optical and transmission electron microscopy (TEM. They consisted of martensite, ferrite and (NbVCN precipitates. The study also explored the process of ferrite formation and its influence on the mechanical properties of the material.

  3. Effect of notch location on fatigue crack growth behavior of strength-mismatched high-strength low-alloy steel weldments

    Science.gov (United States)

    Ravi, S.; Balasubramanian, V.; Nasser, S. Nemat

    2004-12-01

    Welding of high-strength low-alloy (HSLA) steels involves the use of low-strength, equal-strength, and high-strength filler materials (electrodes) compared with the parent material, depending on the application of the welded structures and the availability of filler material. In the present investigation, the fatigue crack growth behavior of weld metal (WM) and the heat-affected zone (HAZ) of undermatched (UM), equally matched (EM), and overmatched (OM) joints has been studied. The base material used in this investigation is HSLA-80 steel of weldable grade. Shielded metal arc welding (SMAW) has been used to fabricate the butt joints. A center-cracked tension (CCT) specimen has been used to evaluate the fatigue crack growth behavior of welded joints, utilizing a servo-hydraulic-controlled fatigue-testing machine at constant amplitude loading (R=0). The effect of notch location on the fatigue crack growth behavior of strength mismatched HSLA steel weldments also has been analyzed.

  4. Effect of prestrain on stretch-zone formation during ductile fracture of Cu-strengthened high-strength low-alloy steels

    Science.gov (United States)

    Sivaprasad, S.; Tarafder, S.; Ranganath, V. R.; Das, S. K.; Ray, K. K.

    2002-12-01

    The effects of prestrain on the ductile fracture behavior of two varieties of Cu-strengthened high-strength low-alloy (HSLA) steels have been investigated through stretch-zone geometry measurements. It is noted that the ductile fracture-initiation toughness of both the steels remained unaltered up to prestrains of ˜2 pct, beyond which the toughness decreased sharply. A methodology for estimating the stretch-zone dimensions is proposed. Fracture-toughness estimations through stretch-zone width (SZW) and stretch-zone depth (SZD) measurements revealed that the nature of the variation of ductile fracture toughness with prestrain can be better predicted through SZD rather than the SZW measurements. However, for the specimen geometries and prestrain levels that were investigated, none of these methods were found suitable for quantifying the initiation fracture toughness.

  5. Pitting corrosion resistance and bond strength of stainless steel overlay by friction surfacing on high strength low alloy steel

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    Amit Kumar Singh

    2015-09-01

    Full Text Available Surface modification is essential for improving the service properties of components. Cladding is one of the most widely employed methods of surface modification. Friction surfacing is a candidate process for depositing the corrosion resistant coatings. Being a solid state process, it offers several advantages over conventional fusion based surfacing process. The aim of this work is to identify the relationship between the input variables and the process response and develop the predictive models that can be used in the design of new friction surfacing applications. In the current work, austenitic stainless steel AISI 304 was friction surfaced on high strength low alloy steel substrate. Friction surfacing parameters, such as mechtrode rotational speed, feed rate of substrate and axial force on mechtrode, play a major role in determining the pitting corrosion resistance and bond strength of friction surfaced coatings. Friction surfaced coating and base metal were tested for pitting corrosion by potentio-dynamic polarization technique. Coating microstructure was characterized using optical microscopy, scanning electron microscopy and X-ray diffraction. Coatings in the as deposited condition exhibited strain-induced martensite in austenitic matrix. Pitting resistance of surfaced coatings was found to be much lower than that of mechtrode material and superior to that of substrate. A central composite design with three factors (mechtrode rotational speed, substrate traverse speed, axial load on mechtrode and five levels was chosen to minimize the number of experimental conditions. Response surface methodology was used to develop the model. In the present work, an attempt has been made to develop a mathematical model to predict the pitting corrosion resistance and bond strength by incorporating the friction surfacing process parameters.

  6. Comparison of the Microstructure and Segregation behavior between SA508 Gr.3 and SA508 Gr.4N High Strength Low Alloy RPV Steel

    Energy Technology Data Exchange (ETDEWEB)

    Park, Sang Gyu; Wee, Dang Moon [KAIST, Daejeon (Korea, Republic of); Kim, Min Chul; Lee, Bong Sang [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2010-05-15

    It is generally known that SA508 Gr.4N low alloy steel has an improved fracture toughness and strength, compared to commercial low alloy steels such as SA508 Gr.3 which have lower than 1% Ni. Higher strength and fracture toughness of low alloy steels could be achieved by adding Ni and Cr. So there are several researches on SA508 Gr.4N low alloy steel for a RPV application. The operation temperature and time of a reactor pressure vessel is more than 300 .deg. C and over 40 years. Therefore, in order to apply the SA508 Gr.4N low alloy steel for a reactor pressure vessel, it requires a phase stability in the high temperature range including temper embrittlement resistance. S. Raoul reported that the susceptibility to temper embrittlement was increasing an function of the cooling rate in SA533 steel, which suggests the martensitic microstructures resulting from increased cooling rates are more susceptible to temper embrittlement. However, this result has not been proved yet. So comparison was made between the temper embrittlement behaviors of SA508 Gr.3 and Gr.4N low alloy steel with a viewpoint of boundary features, which have different microstructures of tempered bainite(SA508 Gr.3) and tempered martensite(SA508 Gr.4N). In this study, we have compared temper embrittlement behaviors of SA508 Gr.3 and SA508 Gr.4N low alloy steel. The mechanical properties of these low alloy steels after a long-term heat treatment(450 .deg. C, 2000hr) were evaluated. Then, the images of the fracture surfaces were observed and grain boundary segregation was analyzed by AES. In order to compare the misorientation distributions of two model alloys, the grain boundary structures of the low alloy steels with EBSD were measured

  7. Effects of the phase fractions on the carbide morphologies, Charpy and tensile properties in SA508 Gr.4N High Strength Low Alloy RPV Steel

    Energy Technology Data Exchange (ETDEWEB)

    Park, Sang Gyu; Wee, Dang Moon [KAIST, Daejeon (Korea, Republic of); Kim, Min Chul; Lee, Bong Sang [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2011-05-15

    To improve the strength and toughness of RPV (reactor pressure vessel) steels for nuclear power plants, an effective way is the change of material specification from tempered bainitic SA508 Gr.3 Mn-Mo-Ni low alloy steel into tempered martensitic/bainitic SA508 Gr.4N Ni-Cr-Mo low alloy steel. It is known that the phase fractions of martensitic/bainitic steels are very sensitive to the austenitizing cooling rates. Kim reported that there are large differences of austenitizing cooling rates between the surface and the center locations in RPV due to its thickness of 250mm. Hence, the martensite/bainite fractions would be changed in different locations, and it would affect the microstructure and mechanical properties in Ni-Cr-Mo low alloy steel. These results may lead to inhomogeneous characteristics after austenitizing. Therefore, it is necessary to evaluate the changes of microstructure and mechanical properties with varying phase fractions in Ni-Cr-Mo low alloy steel. In this study, the effects of martensite/bainite fractions on microstructure and mechanical properties in Ni-Cr-Mo low alloy steel were examined. The changes in phase fractions of Ni-Cr-Mo low alloy steel with different cooling rates were analyzed, and then the phase fractions were correlated with its microstructural observation and mechanical properties

  8. Relationship Between Solidification Microstructure and Hot Cracking Susceptibility for Continuous Casting of Low-Carbon and High-Strength Low-Alloyed Steels: A Phase-Field Study

    Science.gov (United States)

    Böttger, B.; Apel, M.; Santillana, B.; Eskin, D. G.

    2013-08-01

    Hot cracking is one of the major defects in continuous casting of steels, frequently limiting the productivity. To understand the factors leading to this defect, microstructure formation is simulated for a low-carbon and two high-strength low-alloyed steels. 2D simulation of the initial stage of solidification is performed in a moving slice of the slab using proprietary multiphase-field software and taking into account all elements which are expected to have a relevant effect on the mechanical properties and structure formation during solidification. To account for the correct thermodynamic and kinetic properties of the multicomponent alloy grades, the simulation software is online coupled to commercial thermodynamic and mobility databases. A moving-frame boundary condition allows traveling through the entire solidification history starting from the slab surface, and tracking the morphology changes during growth of the shell. From the simulation results, significant microstructure differences between the steel grades are quantitatively evaluated and correlated with their hot cracking behavior according to the Rappaz-Drezet-Gremaud (RDG) hot cracking criterion. The possible role of the microalloying elements in hot cracking, in particular of traces of Ti, is analyzed. With the assumption that TiN precipitates trigger coalescence of the primary dendrites, quantitative evaluation of the critical strain rates leads to a full agreement with the observed hot cracking behavior.

  9. Comparison of the segregation behavior between tempered martensite and tempered bainite in Ni-Cr-Mo high strength low alloy RPV steel

    Energy Technology Data Exchange (ETDEWEB)

    Park, Sang Gyu; Kim, Min Chul; Kim, Hyung Jun; Lee, Bong Sang [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2012-05-15

    SA508 Gr.4N Ni-Cr-Mo low alloy steel has an superior fracture toughness and strength, compared to commercial Mn-Mo-Ni low alloy RPV steel SA508 Gr.3. Higher strength and fracture toughness of low alloy steels could be obtained by adding Ni and Cr. So several were performed on researches on SA508 Gr.4N low alloy steel for a RPV application. The operation temperature and term of a reactor pressure vessel is more than 300 .deg. C and over 40 years. Therefore, in order to apply the SA508 Gr.4N low alloy steel for a reactor pressure vessel, the resistance of thermal embrittlement in the high temperature range including temper embrittlement is required. S. Raoul reported that the susceptibility to temper embrittlement was increasing a function of the cooling rate in SA533 steel, which suggests the martensitic microstructures resulting from increased cooling rates are more susceptible to temper embrittlement. However, this result has not been proved yet. So the comparison of temper embrittlement behavior was made between martensitic microstructure and bainitic microstructure with a viewpoint of boundary features in SA508 Gr.4N, which have mixture of tempered bainite/martensite. We have compared temper embrittlement behaviors of SA508 Gr.4N low alloy steel with changing volume fraction of martensite. The mechanical properties of these low alloy steels were evaluated after a long-term heat treatment. Then, the the segregated boundaries were observed and segregation behavior was analyzed by AES. In order to compare the misorientation distributions of model alloys, grain boundary structures were measured with EBSD

  10. Study of the Impact of Heat Treatment Modes on Formation of Microstructure and a Given Set of Mechanical Properties of High-Strength Flat Products with Guaranteed Hardness (400 to 450 HB) from Low-Alloyed Steel

    Science.gov (United States)

    Matrosov, M. Yu; Martynov, P. G.; Goroshko, T. V.; Zvereva, M. I.; Mitrofanov, A. V.; Barabash, K. Yu

    2017-12-01

    The results of the study of influence of heat treatment modes on microstructure, size and shape of grains, mechanical properties of high-strength flat products from low-alloyed C-Mn-Cr-Si-Mo steel microalloyed by boron are presented. Heat treatment modes, which provide a combination of high impact viscosity at negative temperatures and guaranteed hardness, are determined.

  11. Application of ANFIS for modeling of microhardness of high strength low alloy (HSLA steels in continuous cooling

    Directory of Open Access Journals (Sweden)

    Gholamreza Khalaj

    2013-01-01

    Full Text Available The paper presents some results of the research connected with the development of new approach based on the Adaptive Network-based Fuzzy Inference Systems (ANFIS of predicting the Vickers microhardness of the phase constituents occurring in five steel samples after continuous cooling. The independent variables in the model are chemical compositions, initial austenite grain size and cooling rate over the temperature range of the occurrence of phase transformations. To construct these models, 114 different experimental data were gathered from the literature. The data used in the ANFIS model is arranged in a format of twelve input parameters that cover the chemical compositions, initial austenite grain size and cooling rate, and output parameter which is Vickers microhardness. In this model, the training and testing results in the ANFIS systems have shown strong potential for prediction of effects of chemical compositions and heat treatments on hardness of microalloyed steels.

  12. High-Cycle Fatigue of High-Strength Low Alloy Steel Q345 Subjected to Immersion Corrosion for Mining Wheel Applications

    Science.gov (United States)

    Dicecco, Sante; Altenhof, William; Hu, Henry; Banting, Richard

    2017-04-01

    In an effort to better understand the impact of material degradation on the fatigue life of mining wheels made of a high-strength low alloy carbon steel (Q345), this study seeks to evaluate the effect of surface corrosion on the high-cycle fatigue behavior of the Q345 alloy. The fatigue behavior of the polished and corroded alloy was investigated. Following exposure to a 3.5 wt.% NaCl saltwater solution, polished and corroded fatigue specimens were tested using an R.R. Moore rotating-bending fatigue apparatus. Microstructural analyses via both optical microscopy and scanning electron microscopy (SEM) revealed that one major phase, α-iron phase, ferrite, and one minor phase, colony pearlite, existed in the extracted Q345 alloy. The results of the fatigue testing showed that the polished and corroded specimens had an endurance strength of approximately 295 and 222 MPa, respectively, at 5,000,000 cycles. The corroded surface condition resulted in a decrease in the fatigue strength of the Q345 alloy by 24.6%. Scanning electron microscope fractography indicated that failure modes for polished and corroded fatigue specimens were consistent in the high-cycle low loading fatigue regime. Conversely, SEM fractography of low-cycle high-loading fatigue specimens found considerable differences in fracture surfaces between the corroded and polished fatigue specimens.

  13. Thermodynamic calculation and observation of microstructural change in Ni-Mo-Cr high strength low alloy RPV steels with alloying elements

    Energy Technology Data Exchange (ETDEWEB)

    Park, Sang Gyu; Wee, Dang Moon [Korea Advanced Institute of Science and Technology, Daejeon (Korea, Republic of); Kim, Min Chul; Lee, Bong Sang [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2008-12-15

    An effective way of increasing the strength and fracture toughness of reactor pressure vessel steels is to change the material specification from that of Mn-Mo-Ni low alloy steel (SA508 Gr.3) to Ni-Mo-Cr low alloy steel(SA508 Cr.4N). In this study, we evaluate the effects of alloying elements on the microstructural characteristics of Ni-Mo-Cr low alloy steel. The changes in the stable phase of the SA508 Gr.4N low alloy steel with alloying elements were evaluated by means of a thermodynamic calculation conducted with the software ThermoCalc. The changes were then compared with the observed microstructural results. The calculation of Ni-Mo-Cr low alloy steels confirms that the ferrite formation temperature decreases as the Ni content increases because of the austenite stabilization effect. Consequently, in the microscopic observation, the lath martensitic structure becomes finer as the Ni content increases. However, Ni does not affect the carbide phases such as M{sub 23}C{sub 6} and M{sub 7}C{sub 3}. When the Cr content decreases, the carbide phases become unstable and carbide coarsening can be observed. With an increase in the Mo content, the M{sub 2}C phase becomes stable instead of the M{sub 7}C{sub 3} phase. This behavior is also observed in TEM. From the calculation results and the observation results of the microstructure, the thermodynamic calculation can be used to predict the precipitation behavior.

  14. Damage and fracture loci for a dual-phase steel and a high-strength low-alloyed steel: Revealing the different plastic localization-damage-ductile fracture pattern

    Science.gov (United States)

    Lian, Junhe; Münstermann, Sebastian; Bleck, Wolfgang

    2016-10-01

    The ductile fracture locus has been developed in the recent years as a relevant tool to predict the ductile fracture and assess the structure safety. In the various developed models, the occurrence of the final fracture or the initiation of the fracture is considered as the critical phase of deformation for materials or structures. However, in the application of high-strength steels, the damage onset and evolution are of significant importance in the forming processes, as they are naturally interacting with the plastic localization and ductile fracture and eventually creating various possible failure patterns. The present study contributes to a demonstration of the differences of these features in different steels by quantitatively comparing the material parameters of a hybrid damage mechanics model. A dual-phase steel sheet (DP600) and a high-strength low-alloy steel plate (S355J2+N), which show very different relation patterns between damage and fracture, are investigated. The aim of this study is to compare the plastic localization, damage and fracture loci of them and reveal the differences in their localization-damage initiation-ductile fracture patterns. The reasons for the observed different patterns are discussed and it is concluded that the microstructural features are ultimately contributing to the different patterns and the criteria for evaluating the cold formability of these steels shall be varied depending on their failure patterns.

  15. Experimental determination of TRIP-parameter K for mild- and high-strength low-alloy steels and a super martensitic filler material.

    Science.gov (United States)

    Neubert, Sebastian; Pittner, Andreas; Rethmeier, Michael

    2016-01-01

    A combined experimental numerical approach is applied to determine the transformation induced plasticity (TRIP)-parameter K for different strength low-alloy steels of grade S355J2+N and S960QL as well as the super martensitic filler CN13-4-IG containing 13 wt% chromium and 4 wt% nickel. The thermo-physical analyses were conducted using a Gleeble (®) 3500 facility. The thermal histories of the specimens to be tested were extracted from corresponding simulations of a real gas metal arc weldment. In contrast to common TRIP-experiments which are based on complex specimens a simple flat specimen was utilized together with an engineering evaluation method. The evaluation method was validated with literature values for the TRIP-parameter. It could be shown that the proposed approach enables a correct description of the TRIP behavior.

  16. SCC investigation of low alloy ultra-high strength steel 30CrMnSiNi2A in 3.5wt% NaCl solution by slow strain rate technique

    Directory of Open Access Journals (Sweden)

    Liu Jianhua

    2014-10-01

    Full Text Available To evaluate stress corrosion cracking (SCC mechanism of low alloy ultra-high strength steel 30CrMnSiNi2A in environment containing NaCl, SCC behavior of the steel in 3.5wt% NaCl solution is investigated by slow strain rate technique (SSRT with various strain rates and applied potentials, surface analysis technique, and electrochemical measurements. SCC susceptibility of the steel increases rapidly with strain rate decreasing from 1 × 10−5 s−1 to 5 × 10−7 s−1, and becomes stable when strain rate is lower than 5 × 10−7 s−1. SCC propagation of the steel in the solution at open circuit potential (OCP needs sufficient hydrogen which is supplied at a certain strain rate. Fracture surface at OCP has similar characteristics with that at cathodic polarization −1000 mVSCE, which presents characteristic fractography of hydrogen induced cracking (HIC. All of these indicate that SCC behavior of the steel in the solution at OCP is mainly controlled by HIC rather than anodic dissolution (AD.

  17. Corrosion and Corrosion Inhibition of High Strength Low Alloy Steel in 2.0 M Sulfuric Acid Solutions by 3-Amino-1,2,3-triazole as a Corrosion Inhibitor

    Directory of Open Access Journals (Sweden)

    El-Sayed M. Sherif

    2014-01-01

    Full Text Available The corrosion and corrosion inhibition of high strength low alloy (HSLA steel after 10 min and 60 min immersion in 2.0 M H2SO4 solution by 3-amino-1,2,4-triazole (ATA were reported. Several electrochemical techniques along with scanning electron microscopy (SEM and energy dispersive X-ray (EDS were employed. Electrochemical impedance spectroscopy indicated that the increase of immersion time from 10 min to 60 min significantly decreased both the solution and polarization resistance for the steel in the sulfuric acid solution. The increase of immersion time increased the anodic, cathodic, and corrosion currents, while it decreased the polarization resistance as indicated by the potentiodynamic polarization measurements. The addition of 1.0 mM ATA remarkably decreased the corrosion of the steel and this effect was found to increase with increasing its concentration to 5.0 mM. SEM and EDS investigations confirmed that the inhibition of the HSLA steel in the 2.0 M H2SO4 solutions is achieved via the adsorption of the ATA molecules onto the steel protecting its surface from being dissolved easily.

  18. Application of the Materials-by-Design Methodology to Redesign a New Grade of the High-Strength Low-Alloy Class of Steels with Improved Mechanical Properties and Processability

    Science.gov (United States)

    Grujicic, M.; Snipes, J. S.; Ramaswami, S.

    2016-01-01

    An alternative to the traditional trial-and-error empirical approach for the development of new materials is the so-called materials-by-design approach. Within the latter approach, a material is treated as a complex system and its design and optimization is carried out by employing computer-aided engineering analyses, predictive tools, and available material databases. In the present work, the materials-by-design approach is utilized to redesign a grade of high-strength low-alloy (HSLA) class of steels with improved mechanical properties (primarily strength and fracture toughness), processability (e.g., castability, hot formability, and weldability), and corrosion resistance. Toward that end, a number of material thermodynamics, kinetics of phase transformations, and physics of deformation and fracture computational models and databases have been developed/assembled and utilized within a multi-disciplinary, two-level material-by-design optimization scheme. To validate the models, their prediction is compared against the experimental results for the related steel HSLA100. Then the optimization procedure is employed to determine the optimal chemical composition and the tempering schedule for a newly designed grade of the HSLA class of steels with enhanced mechanical properties, processability, and corrosion resistance.

  19. Microalloyed HSLA (High Strength Low Alloy) Steels: Proceedings of Microalloying 󈨜 Held in Conjunction with the 1988 World Materials Congress, Chicago, Illinois, USA, 24-30 September 1988

    Science.gov (United States)

    1988-01-01

    Qualidade Trade. Metal Bulletin Monthly, May 1987, pp. do Material Produzido no Lingotamento Continuo 49-52. da USIMINAS. Metalurgia, ABM, 33(238...tearing was a major problem for structural steel Tensile stresses fabricators, occurring in those joints experi- Temperatures near to normal ambient ...Breaking welding and high heat input welding can be used Ships Designed to Operate in Low Ambient for these newly developed steel plates. Temperature

  20. Application of Niobium Low Carbon Low Alloy Structural Steel Approach

    Science.gov (United States)

    Jansto, Steven G.; Silvestre, Leonardo; Wang, Houxin

    Niobium Bearing Low Carbon Low Alloy (LCLA) value-added S355 structural steels reduces the overall material and construction costs for many high strength construction steel and heavy equipment applications. The recent development of the Nb-LCLA Approach is a value-added low cost approach for many structural steel applications including windtower supports, beams and other structural plate applications. Case examples are presented from Brazil, China and the USA. These Nb-bearing steels at lower carbon content compared to the traditional higher carbon normalize heat treated grades are more cost effective and reduce structural fabrication time through improved weldability as well.

  1. Advanced characterization techniques in understanding the roles of nickel in enhancing strength and toughness of submerged arc welding high strength low alloy steel multiple pass welds in the as-welded condition

    Science.gov (United States)

    Sham, Kin-Ling

    Striving for higher strength along with higher toughness is a constant goal in material properties. Even though nickel is known as an effective alloying element in improving the resistance of a steel to impact fracture, it is not fully understood how nickel enhances toughness. It was the goal of this work to assist and further the understanding of how nickel enhanced toughness and maintained strength in particular for high strength low alloy (HSLA) steel submerged arc welding multiple pass welds in the as-welded condition. Using advanced analytical techniques such as electron backscatter diffraction, x-ray diffraction, electron microprobe, differential scanning calorimetry, and thermodynamic modeling software, the effect of nickel was studied with nickel varying from one to five wt. pct. in increments of one wt. pct. in a specific HSLA steel submerged arc welding multiple pass weldment. The test matrix of five different nickel compositions in the as-welded and stress-relieved condition was to meet the targeted mechanical properties with a yield strength greater than or equal to 85 ksi, a ultimate tensile strength greater than or equal to 105 ksi, and a nil ductility temperature less than or equal to -140 degrees F. Mechanical testing demonstrated that nickel content of three wt. pct and greater in the as-welded condition fulfilled the targeted mechanical properties. Therefore, one, three, and five wt. pct. nickel in the as-welded condition was further studied to determine the effect of nickel on primary solidification mode, nickel solute segregation, dendrite thickness, phase transformation temperatures, effective ferrite grain size, dislocation density and strain, grain misorientation distribution, and precipitates. From one to five wt. pct nickel content in the as-welded condition, the primary solidification was shown to change from primary delta-ferrite to primary austenite. The nickel partitioning coefficient increased and dendrite/cellular thickness was

  2. Impact toughness of high strength low alloy TMT reinforcement ...

    Indian Academy of Sciences (India)

    Unknown

    method requiring small investment, test specimens are of small size and simpler to machine (Wullaert 1970, 1974). The Charpy test data can be used to predict the perfor- mance of material in service condition. It reproduces the ductile to brittle transition of steel in about the same temperature range as it is actually observed ...

  3. Impact toughness of high strength low alloy TMT reinforcement ...

    Indian Academy of Sciences (India)

    ... of copper–molybdenum and copper–chromium rebars was 52 J. The lower toughness of phosphorus steel is attributed to solid solution strengthening and segregation of phosphorus to grain boundaries. Due to superior corrosion resistance, copper–phosphorus TMT rebar is a candidate material in the construction sector.

  4. Current Status of Development of High Nickel Low Alloy Steels for Commercial Reactor Pressure Vessel

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Min Chul; Lee, B. S.; Park, S. G.; Lee, K. H. [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2008-12-15

    SA508 Gr.3 Mn-Mo-Ni low alloy steels have been used for nuclear reactor pressure vessel steels up to now. Currently, the design goal of nuclear power plant is focusing at larger capacity and longer lifetime. Requirements of much bigger pressure vessels may cause critical problems in the manufacturing stage as well as for the welding stage. Application of higher strength steel may be required to overcome the technical problems. It is known that a higher strength and fracture toughness of low alloy steels such as SA508 Gr.4N low alloy steel could be achieved by increasing the Ni and Cr contents. Therefore, SA508 Gr.4N low alloy steel is very attractive as eligible RPV steel for the next generation PWR systems. In this report, we propose the possibility of SA508 Gr.4N low alloy steel for an application of next generation commercial RPV, based on the literature research result about development history of the RPV steels and SA508 specification. In addition, we have surveyed the research result of HSLA(High Strength Low Alloy steel), which has similar chemical compositions with SA508 Gr.4N, to understand the problems and the way of improvement of SA508 Gr.4N low alloy steel. And also, we have investigated eastern RPV steel(WWER-1000), which has higher Ni contents compared to western RPV steel.

  5. Crack stability analysis of low alloy steel primary coolant pipe

    Energy Technology Data Exchange (ETDEWEB)

    Tanaka, T.; Kameyama, M. [Kansai Electric Power Company, Osaka (Japan); Urabe, Y. [Mitsubishi Heavy Industries, Ltd., Takasago (Japan)] [and others

    1997-04-01

    At present, cast duplex stainless steel has been used for the primary coolant piping of PWRs in Japan and joints of dissimilar material have been applied for welding to reactor vessels and steam generators. For the primary coolant piping of the next APWR plants, application of low alloy steel that results in designing main loops with the same material is being studied. It means that there is no need to weld low alloy steel with stainless steel and that makes it possible to reduce the welding length. Attenuation of Ultra Sonic Wave Intensity is lower for low alloy steel than for stainless steel and they have advantageous inspection characteristics. In addition to that, the thermal expansion rate is smaller for low alloy steel than for stainless steel. In consideration of the above features of low alloy steel, the overall reliability of primary coolant piping is expected to be improved. Therefore, for the evaluation of crack stability of low alloy steel piping to be applied for primary loops, elastic-plastic future mechanics analysis was performed by means of a three-dimensioned FEM. The evaluation results for the low alloy steel pipings show that cracks will not grow into unstable fractures under maximum design load conditions, even when such a circumferential crack is assumed to be 6 times the size of the wall thickness.

  6. Low alloy steel versus ADI – differences and similarities

    Directory of Open Access Journals (Sweden)

    A. Krzyńska

    2009-01-01

    Full Text Available The results of comparison between the microstructure of selected bainitic low alloy steel and austempered ductile iron ADI are presented. The aim of the comparison was to find out differences and similarities existing in these iron carbon commercial alloys. In this paper our own results on ADI structure and literature data were used. It follows from discussion presented here that both microstructure and properties of ADI are very close that which are observed in low alloy carbon steel. Moreover, we suggest that there is no so doubt to treat ADI mechanical properties as steel containing nodular inclusions of graphite.

  7. Advanced high strength steels for automotive industry

    Directory of Open Access Journals (Sweden)

    Galán, J.

    2012-04-01

    Full Text Available The car industry is facing pressure because of the growing demand for more fuel-efficient passenger cars. In order to limit energy consumption and air pollution the weight of the carbody has to be reduced. At the same time, high levels of safety have to be guaranteed. In this situation, the choice of material becomes a key decision in car design. As a response to the requirements of the automotive sector, high strength steels and advanced high strength steels have been developed by the steel industry. These modern steel grades offer an excellent balance of low cost, light weight and mechanical properties.

    La industria del automóvil se enfrenta a una creciente demanda de vehículos de pasajeros más eficientes. Con el fin de disminuir el consumo de energía y la contaminación ambiental, el peso del vehículo tiene que ser reducido, al mismo tiempo que se garantizan altos niveles de seguridad. Ante esta situación, la elección de material se convierte en una decisión crucial en el diseño del vehículo. Como respuesta a las necesidades del sector automovilístico, nuevos aceros avanzados y de alta resistencia, han sido desarrollados por la industria siderúrgica. Dichos tipos de acero ofrecen un excelente equilibrio de precio, peso y propiedades mecánicas.

  8. OF PLAIN CARBON AND LOW ALLOY STEELS

    African Journals Online (AJOL)

    Two steels En 3 and En 39 were given a TiC-TiN. CVD coating in the carburized and uncarburized conditions. The continuity of the coatings and their adherance to the substrate were examined. The thickness of the deposited coatings were also measured, their adherence to the substrate and their thickness was off ected by ...

  9. Factors affecting the strength of multipass low-alloy steel weld metal

    Science.gov (United States)

    Krantz, B. M.

    1972-01-01

    The mechanical properties of multipass high-strength steel weld metals depend upon several factors, among the most important being: (1) The interaction between the alloy composition and weld metal cooling rate which determines the as-deposited microstructure; and (2) the thermal effects of subsequent passes on each underlying pass which alter the original microstructure. The bulk properties of a multipass weld are therefore governed by both the initial microstructure of each weld pass and its subsequent thermal history. Data obtained for a high strength low alloy steel weld metal confirmed that a simple correlation exists between mechanical properties and welding conditions if the latter are in turn correlated as weld cooling rate.

  10. Compensative alloying of Cr-Si low-alloyed steels

    Energy Technology Data Exchange (ETDEWEB)

    Lunika, M., E-mail: mlunika@ipflab.sumy.ua [Institute of Applied Physics, National Academy of Science of Ukraine, 58, Petropavlovskaja Str., 40030 Sumy (Ukraine)

    2010-03-25

    The principle of choosing alloy elements in order to suppress the embrittlement of solid solution strengthening is proposed. In the case of Cr-Si low-alloyed steels, the effects of compensative alloying are studied. The ultimate tensile strength and impact toughness of Cr-Si steels microalloyed with Mo, V, and Ti are determined to prove the aspects. The structure of these steels is studied using optical and transmission electron microscopy techniques after applying the optimum heat treatment. The kinetics of phase transformation after quenching and tempering have been examined by means of measurements of specific electrical resistance and magnetic parameters. It is shown that at the Si-content of about 1 wt% high values of tensile strength and impact toughness are simultaneously obtained. It is established by calculations that, for the indicated steel, long-range distortions of the crystal lattice become close to zero at the Si-content of about 1 wt%.

  11. Recent Progress in High Strength Low Carbon Steels

    Directory of Open Access Journals (Sweden)

    Zrník J.

    2006-01-01

    Full Text Available Advanced High Strength (AHS steels, among them especially Dual Phase (DP steels, Transformation Induced Plasticity (TRIP steels, Complex Phase (CP steels, Partially Martensite (PM steels, feature promising results in the field. Their extraordinary mechanical properties can be tailored and adjusted by alloying and processing. The introduction of steels with a microstructure consisting at least of two different components has led to the enlargement of the strength level without a deterioration of ductility. Furthermore, the development of ultra fine-grained AHS steels and their service performance are reviewed and new techniques are introduced. Various projects have been devoted to develop new materials for flat and long steel products for structural applications. The main stream line is High Strength, in order to match the weight lightening requirements that concern the whole class of load bearing structures and/or steel components and one of the most investigated topics is grain refinement.

  12. Formability Characterization of a New Generation High Strength Steels

    Energy Technology Data Exchange (ETDEWEB)

    Sriram Sadagopan; Dennis Urban; Chris Wong; Mai Huang; Benda Yan

    2003-05-16

    Advanced high strength steels (AHSS) are being progressively explored by the automotive industry all around the world for cost-effective solutions to accomplish vehicle lightweighting, improve fuel economy, and consequently reduce greenhouse emissions. Because of their inherent high strength, attractive crash energy management properties, and good formability, the effective use of AHSS such as Duel Phase and TRIP (Transformation Induced Plasticity) steels, will significantly contribute to vehicle lightweighting and fuel economy. To further the application of these steels in automotive body and structural parts, a good knowledge and experience base must be developed regarding the press formability of these materials. This project provides data on relevant intrinsic mechanical behavior, splitting limits, and springback behavior of several lots of mild steel, conventional high strength steel (HSS), advanced high strength steel (AHSS) and ultra-high strength steel (UHSS), supplied by the member companies of the Automotive Applications Committee (AAC) of the American Iron and Steel Institute (AISI). Two lots of TRIP600, which were supplied by ThyssenKrupp Stahl, were also included in the study. Since sheet metal forming encompasses a very diverse range of forming processes and deformation modes, a number of simulative tests were used to characterize the forming behavior of these steel grades. In general, it was found that formability, as determined by the different tests, decreased with increased tensile strength. Consistant with previous findings, the formability of TRIP600 was found to be exceptionally good for its tensile strength.

  13. Behaviour of high strength steel moment joints

    NARCIS (Netherlands)

    Girão Coelho, A.M.; Bijlaard, F.S.K.

    2010-01-01

    The design of joints to European standard EN 1993 within the semi-continuous/partially restrained philosophy is restricted to steel grades up to S460. With the recent development of high performance steels, the need for these restrictions should be revisited. The semicontinuous joint modelling can

  14. Fatigue Life of High-Strength Steel Offshore Tubular Joints

    DEFF Research Database (Denmark)

    Petersen, Rasmus Ingomar; Agerskov, Henning; Lopez Martinez, Luis

    1996-01-01

    In the present investigation, the fatigue life of tubular joints in offshore steel structures is studied. Two test series on full-scale tubular joints have been carried through. One series was on joints in conventional offshore structural steel, and the other series was on joints in high......-strength steel with a yield stress of 820-830 MPa and with high weldability and toughness properties. The test specimens of both series had the same geometry. The present report concentrates on the results obtained in the investigation on the high-strength steel tubular joints.The test specimens were fabricated...... amplitude fatigue test results showed shorter fatigue lives in variable amplitude loading than should be expected from the linear fatigue damage accumulation formula. Furthermore, the fatigue tests on high-strength steel tubular joints showed slightly longer fatigue lives than those obtained...

  15. Comparison of SA508 Gr.3 and SA508 Gr.4N Low Alloy Steels for Reactor Pressure Vessel Steel

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Min Chul; Lee, B. S

    2009-12-15

    The microstructural characteristics and mechanical properties of SA508 Gr.3 Mn-Mo-Ni low alloy steel and SA508 Gr.4N Ni-Mo-Cr low alloy steel were investigated. The differences in the stable phases between these two low alloy steels were evaluated by means of a thermodynamic calculation using ThermoCalc. They were then compared to microstructural features and correlated with mechanical properties. Mn-Mo-Ni low alloy steel shows the upper bainite structure which has the coarse cementite in the lath boundaries. However, Ni-Mo-Cr low alloy steel shows the mixture of lower bainite and tempered martensite structure that homogeneously precipitates the small carbides such as M{sub 23}C{sub 6} and M{sub 7}C{sub 3} due to an increase of hardenability and Cr addition. In the mechanical properties, Ni-Mo-Cr low alloy steel has higher strength and toughness than Mn-Mo-Ni low alloy steel. Ni and Cr additions increase the strength by solid solution hardening. Besides, microstructural changes from upper bainite to tempered martensite improve the strength of the low alloy steel by grain refining effect. And the changes in the precipitation behavior by Cr addition improve the ductile-brittle transition behavior along with a toughening effect of Ni addition.

  16. Optimal welding technology of high strength steel S690QL

    Directory of Open Access Journals (Sweden)

    Dusan Arsic

    2015-02-01

    Full Text Available In this paper is presented the detailed procedure for defining the optimal technology for welding the structures made of the high strength steel S690QL. That steel belongs into a group of steels with exceptional mechanical properties. The most prominent properties are the high tensile strength and impact toughness, at room and at elevated temperatures, as well. However, this steel has a negative characteristic - proneness to appearance of cold cracks.  That impedes welding and makes as an imperative to study different aspects of this steel's properties as well as those of eventual filler metal. Selection and defining of the optimal welding technology of this high strength steel is done for the purpose of preserving the favorable mechanical properties once the welded joint is realized; properties of the welded metal and the melting zone, as well as in the heat affected zone, which is the most critical zone of the welded joint.

  17. Press hardening of alternative high strength aluminium and ultra-high strength steels

    Science.gov (United States)

    Mendiguren, Joseba; Ortubay, Rafael; Agirretxe, Xabier; Galdos, Lander; de Argandoña, Eneko Sáenz

    2016-10-01

    The boron steel press hardening process takes more and more importance on the body in white structure in the last decade. In this work, the advantages of using alternative alloys on the press hardening process is analysed. In particular, the press hardening of AA7075 high strength aluminium and CP800 complex phase ultra-high strength steel is analysed. The objective is to analyse the potential decrease on springback while taking into account the strength change associated with the microstructural modification carried out during the press hardening process. The results show a clear improvement of the final springback in both cases. Regarding the final mechanical properties, an important decrease has been measured in the AA7075 due to the process while an important increase has been found in the CP800 material.

  18. Fatigue experiments on connections made of very high strength steels

    NARCIS (Netherlands)

    Pijpers, R.; Kolstein, H.; Bijlaard, F.

    2013-01-01

    An effective application of Very High Strength Steels (VHSS) can be expected in truss-like structures, typically made of hollow sections. Improved design of VHSS truss structures could incorporate the application of cast joints, since an appropriate design of cast joints limits the stress

  19. Fatigue Strength and Crack Initiation Mechanism of Very-High-Cycle Fatigue for Low Alloy Steels

    Science.gov (United States)

    Hong, Youshi; Zhao, Aiguo; Qian, Guian; Zhou, Chengen

    2012-08-01

    The fatigue strength and crack initiation mechanisms of very-high-cycle fatigue (VHCF) for two low alloy steels were investigated. Rotary bending tests at 52.5 Hz with hour-glass type specimens were carried out to obtain the fatigue propensity of the test steels, for which the failure occurred up to the VHCF regime of 108 cycles with the S-N curves of stepwise tendency. Fractography observations show that the crack initiation of VHCF is at subsurface inclusion with "fish-eye" pattern. The fish-eye is of equiaxed shape and tends to tangent the specimen surface. The size of the fish-eye becomes large with the increasing depth of related inclusion from the surface. The fish-eye crack grows faster outward to the specimen surface than inward. The values of the stress intensity factor ( K I ) at different regions of fracture surface were calculated, indicating that the K I value of fish-eye crack is close to the value of relevant fatigue threshold (Δ K th ). A new parameter was proposed to interpret the competition mechanism of fatigue crack initiation at the specimen surface or at the subsurface. The simulation results indicate that large inclusion size, small grain size, and high strength of material will promote fatigue crack initiation at the specimen subsurface, which are in agreement with experimental observations.

  20. Galvanic Interaction between Chalcopyrite and Pyrite with Low Alloy and High Carbon Chromium Steel Ball

    Directory of Open Access Journals (Sweden)

    Asghar Azizi

    2013-01-01

    Full Text Available This study was aimed to investigate the galvanic interaction between pyrite and chalcopyrite with two types of grinding media (low alloy and high carbon chromium steel ball in grinding of a porphyry copper sulphide ore. Results indicated that injection of different gases into mill altered the oxidation-reduction environment during grinding. High carbon chromium steel ball under nitrogen gas has the lowest galvanic current, and low alloy steel ball under oxygen gas had the highest galvanic current. Also, results showed that the media is anodic relative to pyrite and chalcopyrite, and therefore pyrite or chalcopyrite with a higher rest potential acted as the cathode, whilst the grinding media with a lower rest potential acted as the anode, when they are electrochemically contacted. It was also found that low alloy steel under oxygen produced the highest amount of EDTA extractable iron in the slurry, whilst high carbon chromium steel under nitrogen atmosphere led to the lowest amount.

  1. Investigation of Wear Resistant of Low-Alloyed and Chromium Cast Steel

    Directory of Open Access Journals (Sweden)

    A. Studnicki

    2012-04-01

    Full Text Available Results of investigations of wear resistant of two species of cast steel were introduced in the article (low-alloyed and chromium cast steel on the background of the standard material which was low alloy wear resistant steel about the trade name CREUSABRO ®8000. The investigations were executed with two methods: abrasive wears in the stream of loose particles (the stream of quartz sand and abrasive wears particles fixed (abrasive paper with the silicon carbide. Comparing the results of investigations in the experiments was based about the counted wear index which characterizes the wears of the studied material in the relation to the standard material.

  2. New heat treatment process for advanced high-strength steels

    Science.gov (United States)

    Bublíková, D.; Jeníček, Š.; Vorel, I.; Mašek, B.

    2017-02-01

    Today’s advanced steels are required to possess high strength and ductility. It can be achieved by choosing an appropriate steel chemistry which has a substantial effect on the properties obtained by heat treatment. Mechanical properties influenced the presence of retained austenite in the final structure. Steels of this group typically require complicated heat treatment which places great demands on the equipment used. The present paper introduces new procedures aimed at simplifying the heat treatment of high-strength steels with the use of material-technological modelling. Four experimental steels were made and cast, whose main alloying additions were manganese, silicon, chromium, molybdenum and nickel. The steels were treated using the Q-P process with subsequent interrupted quenching. The resulting structure was a mixture of martensite and retained austenite. Strength levels of more than 2000 MPa combined with 10-15 % elongation were obtained. These properties thus offer potential for the manufacture of intricate closed-die forgings with a reduced weight. Intercritical annealing was obtained structure not only on the basis of martensite, but also with certain proportion of bainitic ferrite and retained austenite.

  3. Effect of Stress Relief Annealing on Microstructure & Mechanical Properties of Welded Joints Between Low Alloy Carbon Steel and Stainless Steel

    Science.gov (United States)

    Nivas, R.; Das, G.; Das, S. K.; Mahato, B.; Kumar, S.; Sivaprasad, K.; Singh, P. K.; Ghosh, M.

    2017-01-01

    Two types of welded joints were prepared using low alloy carbon steel and austenitic stainless steel as base materials. In one variety, buttering material and weld metal were Inconel 82. In another type, buttering material and weld metal were Inconel 182. In case of Inconel 82, method of welding was GTAW. For Inconel 182, welding was done by SMAW technique. For one set of each joints after buttering, stress relief annealing was done at 923 K (650 °C) for 90 minutes before further joining with weld metal. Microstructural investigation and sub-size in situ tensile testing in scanning electron microscope were carried out for buttered-welded and buttered-stress relieved-welded specimens. Adjacent to fusion boundary, heat-affected zone of low alloy steel consisted of ferrite-pearlite phase combination. Immediately after fusion boundary in low alloy steel side, there was increase in matrix grain size. Same trend was observed in the region of austenitic stainless steel that was close to fusion boundary between weld metal-stainless steel. Close to interface between low alloy steel-buttering material, the region contained martensite, Type-I boundary and Type-II boundary. Peak hardness was obtained close to fusion boundary between low alloy steel and buttering material. In this respect, a minimum hardness was observed within buttering material. The peak hardness was shifted toward buttering material after stress relief annealing. During tensile testing no deformation occurred within low alloy steel and failure was completely through buttering material. Crack initiated near fusion boundary between low alloy steel-buttering material for welded specimens and the same shifted away from fusion boundary for stress relieved annealed specimens. This observation was at par with the characteristics of microhardness profile. In as welded condition, joints fabricated with Inconel 82 exhibited superior bond strength than the weld produced with Inconel 182. Stress relief annealing

  4. FE Simulation Models for Hot Stamping an Automobile Component with Tailor-Welded High-Strength Steels

    Science.gov (United States)

    Tang, Bingtao; Wang, Qiaoling; Wei, Zhaohui; Meng, Xianju; Yuan, Zhengjun

    2016-05-01

    Ultra-high-strength in sheet metal parts can be achieved with hot stamping process. To improve the crash performance and save vehicle weight, it is necessary to produce components with tailored properties. The use of tailor-welded high-strength steel is a relatively new hot stamping process for saving weight and obtaining desired local stiffness and crash performance. The simulation of hot stamping boron steel, especially tailor-welded blanks (TWBs) stamping, is more complex and challenging. Information about thermal/mechanical properties of tools and sheet materials, heat transfer, and friction between the deforming material and the tools is required in detail. In this study, the boron-manganese steel B1500HS and high-strength low-alloy steel B340LA are tailor welded and hot stamped. In order to precisely simulate the hot stamping process, modeling and simulation of hot stamping tailor-welded high-strength steels, including phase transformation modeling, thermal modeling, and thermal-mechanical modeling, is investigated. Meanwhile, the welding zone of tailor-welded blanks should be sufficiently accurate to describe thermal, mechanical, and metallurgical parameters. FE simulation model using TWBs with the thickness combination of 1.6 mm boron steel and 1.2 mm low-alloy steel is established. In order to evaluate the mechanical properties of the hot stamped automotive component (mini b-pillar), hardness and microstructure at each region are investigated. The comparisons between simulated results and experimental observations show the reliability of thermo-mechanical and metallurgical modeling strategies of TWBs hot stamping process.

  5. Behaviour of High Strength Steel Endplate Connections in Fire and after Fire

    NARCIS (Netherlands)

    Qiang, X.

    2013-01-01

    The aim of this research is to reveal more information and understanding on behaviour and failure mechanisms of high strength steel endplate connections (combining high strength steel endplates with either mild steel or high strength steel beams and columns in endplate connections) in fire and after

  6. Ultrahigh Charpy impact toughness (~450J) achieved in high strength ferrite/martensite laminated steels.

    Science.gov (United States)

    Cao, Wenquan; Zhang, Mingda; Huang, Chongxiang; Xiao, Shuyang; Dong, Han; Weng, Yuqing

    2017-02-02

    Strength and toughness are a couple of paradox as similar as strength-ductility trade-off in homogenous materials, body-centered-cubic steels in particular. Here we report a simple way to get ultrahigh toughness without sacrificing strength. By simple alloying design and hot rolling the 5Mn3Al steels in ferrite/austenite dual phase temperature region, we obtain a series of ferrite/martensite laminated steels that show up-to 400-450J Charpy V-notch impact energy combined with a tensile strength as high as 1.0-1.2 GPa at room temperature, which is nearly 3-5 times higher than that of conventional low alloy steels at similar strength level. This remarkably enhanced toughness is mainly attributed to the delamination between ferrite and martensite lamellae. The current finding gives us a promising way to produce high strength steel with ultrahigh impact toughness by simple alloying design and hot rolling in industry.

  7. Ultrahigh Charpy impact toughness (~450J) achieved in high strength ferrite/martensite laminated steels

    Science.gov (United States)

    Cao, Wenquan; Zhang, Mingda; Huang, Chongxiang; Xiao, Shuyang; Dong, Han; Weng, Yuqing

    2017-02-01

    Strength and toughness are a couple of paradox as similar as strength-ductility trade-off in homogenous materials, body-centered-cubic steels in particular. Here we report a simple way to get ultrahigh toughness without sacrificing strength. By simple alloying design and hot rolling the 5Mn3Al steels in ferrite/austenite dual phase temperature region, we obtain a series of ferrite/martensite laminated steels that show up-to 400-450J Charpy V-notch impact energy combined with a tensile strength as high as 1.0-1.2 GPa at room temperature, which is nearly 3-5 times higher than that of conventional low alloy steels at similar strength level. This remarkably enhanced toughness is mainly attributed to the delamination between ferrite and martensite lamellae. The current finding gives us a promising way to produce high strength steel with ultrahigh impact toughness by simple alloying design and hot rolling in industry.

  8. Effect of tempering temperature on the properties of low-alloy cast steel

    Directory of Open Access Journals (Sweden)

    D. Bartocha

    2011-07-01

    Full Text Available The mechanical properties of cast steel are primarily a function of chemical composition and solidification conditions i.e. primary structure, however, them can be change in a limited extent, by heat treatment. In the article the influence parameters of quenching on mechanical properties of low-alloy structural cast steel, modeled in terms of chemical composition, on the cast steel L20HGSNM, are presented. An attempt to quantify this relationship was made.

  9. Corrosion Behaviour of Low-Alloyed Cast Steel in Diverse State

    Directory of Open Access Journals (Sweden)

    Kondracki M.

    2015-03-01

    Full Text Available In the paper the results and analysis of corrosion tests were presented for low-alloyed cast steel in as-cast state and after heat treatment operations. Such alloys are applied for heavy loaded parts manufacturing, especially for mining industry. The corrosion test were performed in conditions of high salinity, similar to those occurring during the coal mining. The results have shown, that small changes in chemical composition and the heat treatment influence significantly the corrosion behaviour of studied low-alloyed cast steels.

  10. Microstructures and properties of low-alloy fire resistant steel

    Indian Academy of Sciences (India)

    Unknown

    Fire resistant steel; thermomechanical processing; microstructure; strength; thermal conductivity. 1. Introduction. Steel structures using mild steel in fire sensitive areas are protected from fire by providing fire resistant coating or insulation. This adds to the constructional cost. The problem with unprotected carbon–manganese ...

  11. Additively manufactured hierarchical stainless steels with high strength and ductility

    Science.gov (United States)

    Wang, Y. Morris; Voisin, Thomas; McKeown, Joseph T.; Ye, Jianchao; Calta, Nicholas P.; Li, Zan; Zeng, Zhi; Zhang, Yin; Chen, Wen; Roehling, Tien Tran; Ott, Ryan T.; Santala, Melissa K.; Depond, Philip J.; Matthews, Manyalibo J.; Hamza, Alex V.; Zhu, Ting

    2018-01-01

    Many traditional approaches for strengthening steels typically come at the expense of useful ductility, a dilemma known as strength-ductility trade-off. New metallurgical processing might offer the possibility of overcoming this. Here we report that austenitic 316L stainless steels additively manufactured via a laser powder-bed-fusion technique exhibit a combination of yield strength and tensile ductility that surpasses that of conventional 316L steels. High strength is attributed to solidification-enabled cellular structures, low-angle grain boundaries, and dislocations formed during manufacturing, while high uniform elongation correlates to a steady and progressive work-hardening mechanism regulated by a hierarchically heterogeneous microstructure, with length scales spanning nearly six orders of magnitude. In addition, solute segregation along cellular walls and low-angle grain boundaries can enhance dislocation pinning and promote twinning. This work demonstrates the potential of additive manufacturing to create alloys with unique microstructures and high performance for structural applications.

  12. Deformation behavior of a high strength multiphase steel at macro- and micro-scales

    Energy Technology Data Exchange (ETDEWEB)

    Diego-Calderón, I. de, E-mail: irenedediego.calderon@imdea.org [IMDEA Materials Institute, Calle Eric Kandel 2, Getafe 28906, Madrid (Spain); Santofimia, M.J. [Department of Materials Science and Engineering, Delft University of Technology, 2628 CD Delft (Netherlands); Molina-Aldareguia, J.M.; Monclús, M.A.; Sabirov, I. [IMDEA Materials Institute, Calle Eric Kandel 2, Getafe 28906, Madrid (Spain)

    2014-08-12

    Advanced high strength steels via quenching and partitioning (Q and P) process are a mainstream trend in modern steel research. This work contributes to a better understanding of their local mechanical properties and local deformation behavior at the micro-scale in relation to their local microstructure. A low alloyed steel was subjected to Q and P heat treatments leading to the formation of complex multiphase microstructures. Nanoindentation tests were performed to measure nanohardness of individual phases and to generate 2D maps showing nanohardness distribution on the surface of the material. To study local in-plane plastic strain distribution during deformation, in situ tensile tests were carried out using the digital image correlation technique. Significant partitioning of plastic strain between phase microconstituents during tensile deformation is shown. The effect of the microstructure on the mechanical behavior of the Q and P processed steel is analyzed. The local plastic deformation behavior of individual phases is discussed with respect to their strength and their spatial orientation.

  13. Crack propagation modelling for high strength steel welded structural details

    Science.gov (United States)

    Mecséri, B. J.; Kövesdi, B.

    2017-05-01

    Nowadays the barrier of applying HSS (High Strength Steel) material in bridge structures is their low fatigue strength related to yield strength. This paper focuses on the fatigue behaviour of a structural details (a gusset plate connection) made from NSS and HSS material, which is frequently used in bridges in Hungary. An experimental research program is carried out at the Budapest University of Technology and Economics to investigate the fatigue lifetime of this structural detail type through the same test specimens made from S235 and S420 steel grades. The main aim of the experimental research program is to study the differences in the crack propagation and the fatigue lifetime between normal and high strength steel structures. Based on the observed fatigue crack pattern the main direction and velocity of the crack propagation is determined. In parallel to the tests finite element model (FEM) are also developed, which model can handle the crack propagation. Using the measured strain data in the tests and the calculated values from the FE model, the approximation of the material parameters of the Paris law are calculated step-by-step, and their calculated values are evaluated. The same material properties are determined for NSS and also for HSS specimens as well, and the differences are discussed. In the current paper, the results of the experiments, the calculation method of the material parameters and the calculated values are introduced.

  14. Analysis Of The Austenite Grain Growth In Low-Alloy Boron Steel With High Resistance To Abrasive Wear

    Directory of Open Access Journals (Sweden)

    Białobrzeska B.

    2015-09-01

    Full Text Available Today low-alloy steels with boron achieve high resistance to abrasive wear and high strength. These features are obtained by using advanced technology of manufacturing. This makes boron steels increasingly popular and their application more diverse. Application of these steels can extend the lifetime of very expensive machine construction in many industries such as mining, the automotive, and agriculture industries. An interesting subgroup of these materials is steel with boron intended for heat treatment. These steels are supplied by the manufacturer after cold or hot rolling so that it is possible for them to be heat treated in a suitable manner by the purchaser for its specific application. Very important factor that determines the mechanical properties of final product is austenite grain growth occurring during hot working process such us quenching or hot rolling. Investigation of the effect of heating temperature and holding time on the austenite grain size is necessary to understand the growth behavior under different conditions. This article presents the result of investigation of austenite grain growth in selected low-allow boron steel with high resistance to abrasive wear and attempts to describe the influence of chemical composition on this process.

  15. Damage characterization of high-strength multiphase steels

    Science.gov (United States)

    Heibel, S.; Nester, W.; Clausmeyer, T.; Tekkaya, A. E.

    2016-11-01

    High-strength steels show an entirely different material behavior than conventional deep-drawing steels. This fact is caused among others by the multiphase nature of their structure. The Forming Limit Diagram as the classic failure criterion in forming simulation is only partially suitable for this class of steels. An improvement of the failure prediction can be obtained by using damage mechanics. Therefore, an exact knowledge of the material-specific damage is essential for the application of various damage models. In this paper the results of microstructure analysis of a dual-phase steel and a complex-phase steel with a tensile strength of 1000 MPa are shown comparatively at various stress conditions. The objective is to characterize the basic damage mechanisms and based on this to assess the crack sensitivity of both steels. First a structural analysis with regard to non-metallic inclusions, the microstructural morphology, phase identification and the difference in microhardness between the structural phases is carried out. Subsequently, the development of the microstructure at different stress states between uniaxial and biaxial tension is examined. The damage behavior is characterized and quantified by the increase in void density, void size and the quantity of voids. The dominant damage mechanism of the dual-phase steel is the void initiation at phase boundaries, within harder structural phases and at inclusions. In contrast the complex-phase steel shows a significant growth of a smaller amount of voids which initiate only at inclusions. To quantify the damage tolerance and the susceptibility of cracking the criterion of the fracture forming limit line (FFL) is used. The respective statements are supported by results of investigations regarding the edge-crack sensitivity.

  16. The Effect of Microstructure on the Abrasion Resistance of Low Alloyed Steels

    NARCIS (Netherlands)

    Xu, X.

    2016-01-01

    The thesis attempts to develop advanced high abrasion resistant steels with low hardness in combination with good toughness, processability and low alloying additions. For this purpose, a novel multi-pass dual-indenter (MPDI) scratch test approach has been developed to approach the real continuous

  17. Crystallization of Low-alloyed Construction Cast Steel Modified with V and Ti

    OpenAIRE

    Studnicki A.; Kondracki M.; Szajnar J.; Wróbel T.

    2013-01-01

    In this paper crystallization studies of low-alloyed construction cast steel were presented for different additions of chromium, nickel and molybdenum modified with vanadium and titanium. Studies were conducted using developed TDA stand, which additionally enabled evaluation of cooling rate influence on crystallization process of investigated alloys.

  18. Crystallization of Low-alloyed Construction Cast Steel Modified with V and Ti

    Directory of Open Access Journals (Sweden)

    Studnicki A.

    2013-09-01

    Full Text Available In this paper crystallization studies of low-alloyed construction cast steel were presented for different additions of chromium, nickel and molybdenum modified with vanadium and titanium. Studies were conducted using developed TDA stand, which additionally enabled evaluation of cooling rate influence on crystallization process of investigated alloys.

  19. Secondary hardening of low-alloyed creep-resistant steel welds

    Directory of Open Access Journals (Sweden)

    P. Mohyla

    2014-01-01

    Full Text Available The T24 steel represents the new generation of low-alloyed creep resistant steels with higher creep resistance and lower carbon content. It was designed as prospective material for membrane waterwalls of ultra super critical (USC power plants, enabling to avoid preheating and post weld heat treatment (PWHT during welding. However, our investigations concerning secondary hardening of vanadium containing low-alloyed steels show that non-tempered welded joints undergo a significant increase in hardness during exposure to operating temperature. The results then imply that PWHT of T24 steel welds is necessary and this idea is at present supported by the occurrence of several troubles with new installations of USC blocks in Europe.

  20. Microstructure-property relationship in microalloyed high-strength steel welds

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Lei

    2017-04-01

    High-strength steels are favoured materials in the industry for production of safe and sustainable structures. The main technology used for joining the components of such steel is fusion welding. Steel alloy design concepts combined with advanced processing technologies have been extensively investigated during the development of High-Strength Low-Alloy (HSLA) steels. However, very few studies have addressed the issue of how various alloy designs, even with limited microalloy addition, can influence the properties of high-strength steel welds. In high-strength steel welding practices, the challenges regarding microstructure evolution and the resulting mechanical properties variation, are of great interest. The main focus is the debate regarding the role of microalloy elements on phase transformation and weld performance. Limited Heat Affected Zone (HAZ) softening and limited austenite grain coarsening are significant design essentials, but the primary goal is to ensure excellent toughness and tensile properties in the steel weld. To achieve this purpose, microalloy elements such as Ti, Nb, or V were intentionally added to modern high-strength steels. The focus of this work was to understand the mechanical properties of HSLA steels resulting from differences in alloy design after joining by modern welding processes. To begin, three microalloyed S690QL steels (Nb, Ti, and Ti+V addition) were investigated. Optical microscopy confirmed that similar mixtures of tempered bainite and martensite predominated the parent microstructure in the three steels, different types of coarse microalloy precipitates were also visible. These precipitates were analysed by using a thermodynamic-based software and then identified by Transmission Electron Microscopy (TEM). Results of mechanical testing revealed that all three steels performed above the standard toughness and tensile strength values, but with varied yielding phenomena. During the welding operation, each of the three steels

  1. Microstructural and hardness characterisation of sintered low alloyed steel

    OpenAIRE

    Yilmaz, R.; M.R. Ekici

    2008-01-01

    Purpose: The purpose of the present study is to produce low ally PM steel without any addition and with addition of ferro-boron addition by conventional PM manufacturing route at the different sintering temperature.Design/methodology/approach: Fe-Ni-Cu-Mo-C sintered steel containing 0.5 percent ferro-boron addition was used in this study. The compacts were prepared by powder metallurgy method involving powder mixing, cold pressing at 700 MPa pressure and sintering at temperatur...

  2. Evaluation of the Temper embrittlement in SA508 Gr. 4N Low Alloy Steel with Ni, Cr Contents Variation

    Energy Technology Data Exchange (ETDEWEB)

    Park, Sang Gyu; Wee, Dang Moon [KAIST, Daejeon (Korea, Republic of); Kim, Min Chul; Lee, Bong Sang [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2009-10-15

    It is well known that SA508 Gr.4N low alloy steel has an improved fracture toughness and strength, compared to commercial low alloy steels such as SA508 Gr.3 and SA533B which have less than 1% Ni. Higher strength and fracture toughness of low alloy steels could be achieved by Ni and Cr addition. So there are several researches on SA508 Gr.4N low alloy steel for a RPV application. The operation temperature of a reactor pressure vessel is more than 300 .deg. C and it operates for over 40 years. Therefore, in order to apply the SA508 Gr.4N low alloy steel for a reactor pressure vessel, it requires phase stability in the high temperature range including temper embrittlement resistance. Although temper brittlement has not been reported in SA508 Gr.4N low alloy steel, the evaluation of the temper embrittlement phenomena on SA508 Gr.4N is required for an RPV application. In a previous study, we have concluded that additional Ni and Cr could change the microstructures of SA508 Gr.4N low alloy steel, and changed microstructure may affect the susceptibility of temper embrittlement in SA508 Gr.4N. In this study, we have performed a Charpy impact test of SA508 Gr.4N low alloy steel with changing alloying element contents such as Ni and Cr. The mechanical properties of these low alloy steels after a long-term heat treatment(450 .deg. C, 2000hr) are also evaluated. Then, the fracture modes of each impact specimens are examined and grain boundary segregation is analyzed by AES. The precipitation behaviors of the low alloy steels are observed by SEM.

  3. Study on the Segregation Behavior in SA508 Gr. 4N Low Alloy Steel with Mn Contents Variation

    Energy Technology Data Exchange (ETDEWEB)

    Park, Sang Gyu; Wee, Dang Moon [KAIST, Daejeon (Korea, Republic of); Kim, Min Chul; Lee, Bong Sang [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2009-05-15

    It is generally known that SA508 Gr.4N low alloy steel has an improved fracture toughness and strength, compared to commercial low alloy steels such as SA508 Gr.3 and SA533B which have lower than 1% Ni. Higher strength and fracture toughness of low alloy steels could be achieved by adding the Ni and Cr. So there are several researches on SA508 Gr.4N low alloy steel for a RPV application. The operation temperature of a reactor pressure vessel is more than 300 .deg. C and it operates for over 40 years. Therefore, in order to apply the SA508 Gr.4N low alloy steel for a reactor pressure vessel, it requires a phase stability in the high temperature range including temper embrittlement resistance. Although no temper embrittlement has been reported in SA508 Gr.4N low alloy steel, we need to evaluate the temper embrittlement phenomena on SA508 Gr.4N for an RPV application. In a previous study, we have concluded that additional Mn may accelerate the temper embrittlement effect in SA508 Gr.4N low alloy steel. So we need to examine the reason why Mn changes the susceptibility to temper embrittlement in SA508 Gr.4N. In this study, we have performed a Charpy impact test of SA508 Gr.4N low alloy steel at varing Mn contents. The mechanical properties of these low alloy steels after a long-term heat treatment(450 .deg. C, 2000hr) are evaluated. Then, the images of the fracture surfaces are observed and a grain boundary segregation is analyzed by AES and SIMS. We also analyze the grain boundary structures of the low alloy steels with EBSD.

  4. Technological Aspects of Low-Alloyed Cast Steel Massive Casting Manufacturing

    Directory of Open Access Journals (Sweden)

    Szajnara J.

    2013-12-01

    Full Text Available In the paper authors have undertaken the attempt of explaining the causes of cracks net occurrence on a massive 3-ton cast steel casting with complex geometry. Material used for casting manufacturing was the low-alloyed cast steel with increased wear resistance modified with vanadium and titanium. The studies included the primary and secondary crystallization analysis with use of TDA and the qualitative and quantitative analysis of non-metallic inclusions.

  5. The influence of grinding parameters of the surface layer of low-alloyed high-speed steel

    Directory of Open Access Journals (Sweden)

    J. Jaworski

    2009-01-01

    Full Text Available The measurements of machining forces, temperature and quality parameters of surface layer and ratio of grinding property of selected grades of low-alloyed high speed steels were carried out. It was shown that improvement of grinding properties of low-alloyed high-speed steels is possible on the way of efficient selection of their chemical constitution, which is confirmed by results of researches of grinding properties of SW2M5 steel

  6. Comparison and Analysis of Steel Frame Based on High Strength Column and Normal Strength Column

    Science.gov (United States)

    Liu, Taiyu; An, Yuwei

    2018-01-01

    The anti-seismic performance of high strength steel has restricted its industrialization in civil buildings. In order to study the influence of high strength steel column on frame structure, three models are designed through MIDAS/GEN finite element software. By comparing the seismic performance and economic performance of the three models, the three different structures are comprehensively evaluated to provide some references for the development of high strength steel in steel structure.

  7. Localized bending fatigue behavior of high-strength steel monostrands

    DEFF Research Database (Denmark)

    Winkler, Jan; Fischer, Gregor; Georgakis, Christos T.

    2012-01-01

    of the strain distribution in the strand and helps in identifying potential failure mechanisms along the strand and at the wedge location. Initial analysis of the deformations shows that the bending fatigue behavior of the monostrand may be controlled either by local bending deformations or by relative......In this paper, the localized bending fatigue behavior of pretensioned high strength steel monostrands is investigated. Furthermore, a new methodology using an optical photogrammetry system, which can quantify surface deformations on the strand is presented. The system allows measurement...... displacement (opening/closing and sliding) of the helically wound wires. Moreover, the results are a step towards understanding the bending fatigue damage mechanisms of monostrand cables....

  8. Effect of the Strain Kind on the Texture and Microstructure of Low-Alloyed Steel

    Directory of Open Access Journals (Sweden)

    N. M. Shkatulyak

    2016-01-01

    Full Text Available Crystallographic texture and microstructure of low-alloyed steel after twist extrusion (TE and subsequent cold rolling along and across the TE axis were studied. The double axial cylindrical texture with axes 110 and 100 parallel to the TE axis and the vortex-like microstructure are formed in the steel during the TE. The subsequent rolling of extruded steel along the TE axis promotes the forming of typical steel rolling texture as well as the microstructure with elongated grains in rolling direction. Typical steel rolling texture as well as the equiaxed microstructure is formed in extruded steel after rolling in the direction transverse to the TE axis. The mechanisms of formation of the texture are discussed.

  9. Literature Survey on the Stress Corrosion Cracking of Low-Alloy Steels in High Temperature Water

    Energy Technology Data Exchange (ETDEWEB)

    Seifert, H.P

    2002-02-01

    The present report is a summary of a literature survey on the stress corrosion cracking (SCC) behaviour/ mechanisms in low-alloy steels (LAS) in high-temperature water with special emphasis to primary-pressure-boundary components of boiling water reactors (BWR). A brief overview on the current state of knowledge concerning SCC of low-alloy reactor pressure vessel and piping steels under BWR conditions is given. After a short introduction on general aspects of SCC, the main influence parameter and available quantitative literature data concerning SCC of LAS in high-temperature water are discussed on a phenomenological basis followed by a summary of the most popular SCC models for this corrosion system. The BWR operating experience and service cracking incidents are discussed with respect to the existing laboratory data and background knowledge. Finally, the most important open questions and topics for further experimental investigations are outlined. (author)

  10. Advanced High Strength Steel in Auto Industry: an Overview

    Directory of Open Access Journals (Sweden)

    N. Baluch

    2014-08-01

    Full Text Available The world’s most common alloy, steel, is the material of choice when it comes to making products as diverse as oil rigs to cars and planes to skyscrapers, simply because of its functionality, adaptability, machine-ability and strength. Newly developed grades of Advanced High Strength Steel (AHSS significantly outperform competing materials for current and future automotive applications. This is a direct result of steel’s performance flexibility, as well as of its many benefits including low cost, weight reduction capability, safety attributes, reduced greenhouse gas emissions and superior recyclability. To improve crash worthiness and fuel economy, the automotive industry is, increasingly, using AHSS. Today, and in the future, automotive manufacturers must reduce the overall weight of their cars. The most cost-efficient way to do this is with AHSS. However, there are several parameters that decide which of the AHSS types to be used; the most important parameters are derived from the geometrical form of the component and the selection of forming and blanking methods. This paper describes the different types of AHSS, highlights their advantages for use in auto metal stampings, and discusses about the new challenges faced by stampers, particularly those serving the automotive industry.

  11. Surface Layer Properties of Low-Alloy High-Speed Steel after Grinding

    Directory of Open Access Journals (Sweden)

    Jaworski Jan

    2016-12-01

    Full Text Available Investigations of the surface layer characteristics of selected kinds of low-alloy high-speed steel after grinding were carried out. They were carried out on the flat-surface grinder with a 95A24K grinding wheel without cooling. The influence of grinding parameters was defined especially for: the quantity of secondary austenite, surface roughness, microhardness and grinding efficiency with a large range of grinding parameters: grinding depth 0.005–0.035 mm, lengthwise feed 2–6 m/min, without a cross-feed on the whole width of the sample. It was found that improvement of grinding properties of low-alloy high-speed steels is possible by efficient selection of their chemical composition. The value of the grinding efficiency is conditioned by grinding forces, whose value has an impact on the grinding temperature. To ensure high quality of the tool surface layer (i.e. a smaller amount of secondary austenite, lack of wheel burn and micro-cracks in the case of sharpening of tools made of low-alloy high-speed steel, the grinding temperature should be as low as possible.

  12. Internal and External Oxidation of Manganese in Advanced High Strength Steels

    NARCIS (Netherlands)

    Aghaei Lashgari, V.

    2014-01-01

    Advanced high strength steels (AHSS) have been used extensively in the automotive industries. The main characteristic of these steels is combination of high strength and enhanced formability that makes them very attractive for automotive application. However, the major drawback of these steels is

  13. Effect of chromium on the corrosion behavior of low alloy steel in sulfuric acid

    Science.gov (United States)

    Park, Sun-Ah; Lee, Seung-Hwan; Kim, Jung-Gu

    2012-12-01

    The effects of a chromium (Cr) addition on the corrosion resistance of low alloy steel used in flue gas desulfurization systems were examined by electrochemical (potentiodynamic polarization tests, linear polarization measurements and electrochemical impedance spectroscopy) and weight loss measurements in a 10 wt% H2SO4 solution at room temperature. All measurements revealed a decrease in corrosion rate with increasing Cr content. SEM, EPMA and XPS examinations of the corroded surfaces after the immersion test indicated that 0.6% Cr addition decreased corrosion damage to the steels because protective Cr oxides formed in all the rust layers and Fe oxides dominated over Fe sulphate compounds in the inner rust layers.

  14. Estimation of cyclic stress-strain curves for low-alloy steel from hardness

    Directory of Open Access Journals (Sweden)

    R. Basan

    2010-04-01

    Full Text Available This article describes investigations into the existence of correlation between experimentally determined cyclic parameters and hardness of quenched and tempered representative low-alloy steel 42CrMo4. A good correlation was found to exist between cyclic strength coefficient K’ and Brinell hardness HB, but not between cyclic strain hardening exponent n‘ and hardness HB. Nevertheless, good agreement between calculated and experimental cyclic stress-strain curves shows that cyclic parameters i.e. cyclic stress-strain curves of the investigated steel can be successfully estimated from its hardness.

  15. Study of austenitic stainless steel welded with low alloy steel filler metal. [tensile and impact strength tests

    Science.gov (United States)

    Burns, F. A.; Dyke, R. A., Jr.

    1979-01-01

    The tensile and impact strength properties of 316L stainless steel plate welded with low alloy steel filler metal were determined. Tests were conducted at room temperature and -100 F on standard test specimens machined from as-welded panels of various chemical compositions. No significant differences were found as the result of variations in percentage chemical composition on the impact and tensile test results. The weldments containing lower chromium and nickel as the result of dilution of parent metal from the use of the low alloy steel filler metal corroded more severely in a marine environment. The use of a protective finish, i.e., a nitrile-based paint containing aluminum powder, prevented the corrosive attack.

  16. High Strength Concrete Columns under Axial Compression Load: Hybrid Confinement Efficiency of High Strength Transverse Reinforcement and Steel Fibers.

    Science.gov (United States)

    Perceka, Wisena; Liao, Wen-Cheng; Wang, Yo-de

    2016-04-01

    Addition of steel fibers to high strength concrete (HSC) improves its post-peak behavior and energy absorbing capability, which can be described well in term of toughness. This paper attempts to obtain both analytically and experimentally the efficiency of steel fibers in HSC columns with hybrid confinement of transverse reinforcement and steel fibers. Toughness ratio (TR) to quantify the confinement efficiency of HSC columns with hybrid confinement is proposed through a regression analysis by involving sixty-nine TRs of HSC without steel fibers and twenty-seven TRs of HSC with hybrid of transverse reinforcement and steel fibers. The proposed TR equation was further verified by compression tests of seventeen HSC columns conducted in this study, where twelve specimens were reinforced by high strength rebars in longitudinal and transverse directions. The results show that the efficiency of steel fibers in concrete depends on transverse reinforcement spacing, where the steel fibers are more effective if the spacing transverse reinforcement becomes larger in the range of 0.25-1 effective depth of the section column. Furthermore, the axial load-strain curves were developed by employing finite element software (OpenSees) for simulating the response of the structural system. Comparisons between numerical and experimental axial load-strain curves were carried out.

  17. High Strength Concrete Columns under Axial Compression Load: Hybrid Confinement Efficiency of High Strength Transverse Reinforcement and Steel Fibers

    Science.gov (United States)

    Perceka, Wisena; Liao, Wen-Cheng; Wang, Yo-de

    2016-01-01

    Addition of steel fibers to high strength concrete (HSC) improves its post-peak behavior and energy absorbing capability, which can be described well in term of toughness. This paper attempts to obtain both analytically and experimentally the efficiency of steel fibers in HSC columns with hybrid confinement of transverse reinforcement and steel fibers. Toughness ratio (TR) to quantify the confinement efficiency of HSC columns with hybrid confinement is proposed through a regression analysis by involving sixty-nine TRs of HSC without steel fibers and twenty-seven TRs of HSC with hybrid of transverse reinforcement and steel fibers. The proposed TR equation was further verified by compression tests of seventeen HSC columns conducted in this study, where twelve specimens were reinforced by high strength rebars in longitudinal and transverse directions. The results show that the efficiency of steel fibers in concrete depends on transverse reinforcement spacing, where the steel fibers are more effective if the spacing transverse reinforcement becomes larger in the range of 0.25–1 effective depth of the section column. Furthermore, the axial load–strain curves were developed by employing finite element software (OpenSees) for simulating the response of the structural system. Comparisons between numerical and experimental axial load–strain curves were carried out. PMID:28773391

  18. High Strength Concrete Columns under Axial Compression Load: Hybrid Confinement Efficiency of High Strength Transverse Reinforcement and Steel Fibers

    Directory of Open Access Journals (Sweden)

    Wisena Perceka

    2016-04-01

    Full Text Available Addition of steel fibers to high strength concrete (HSC improves its post-peak behavior and energy absorbing capability, which can be described well in term of toughness. This paper attempts to obtain both analytically and experimentally the efficiency of steel fibers in HSC columns with hybrid confinement of transverse reinforcement and steel fibers. Toughness ratio (TR to quantify the confinement efficiency of HSC columns with hybrid confinement is proposed through a regression analysis by involving sixty-nine TRs of HSC without steel fibers and twenty-seven TRs of HSC with hybrid of transverse reinforcement and steel fibers. The proposed TR equation was further verified by compression tests of seventeen HSC columns conducted in this study, where twelve specimens were reinforced by high strength rebars in longitudinal and transverse directions. The results show that the efficiency of steel fibers in concrete depends on transverse reinforcement spacing, where the steel fibers are more effective if the spacing transverse reinforcement becomes larger in the range of 0.25–1 effective depth of the section column. Furthermore, the axial load–strain curves were developed by employing finite element software (OpenSees for simulating the response of the structural system. Comparisons between numerical and experimental axial load–strain curves were carried out.

  19. AN INVESTIGATION OF METALLURGICAL FACTORS WHICH AFFECT THE FRACTURE TOUGHNESS OF ULTRA HIGH STRENGTH STEELS

    Energy Technology Data Exchange (ETDEWEB)

    Wood, William E.; Parker, Earl R.; Zackay, Victor F.

    1973-05-01

    The relationship between microstructure, heat treatment and room temperature fracture toughness has been determined for the low alloy ultra-high strength steels 4130, 4330, 4340, 4140 and 300-M. Optical metallography, microprobe analysis, and scanning electron microscopy were used to characterize the structure and morphology, while both Charpy V-notch impact tests and plane strain fracture toughness tests were used to determine the fracture properties. The normal commercial heat treatment resulted in the formation of some bainite in all the alloys. MnS inclusions on prior austenite grain boundaries were found to initiate cracks during loading. By increasing the austenitizing temperature to l200 C, the fracture toughness could be increased by at least 60%. For some alloys increasing the severity of the quench in conjunction with the higher austenitizing temperatures resulted in further increases in the fracture toughness, and the elimination of any observable upper bainite. There was no correlation between the Charpy impact test results and the fracture toughness results. The alloys 4130, 4140, 4340 all showed a severe intergranular embrittlement when austenitized at high temperatures and tempered above 200 C, while the alloys 4330 and 300-M exhibited no drop in toughness for the same heat treatment conditions. The as-quenched tensile specimens had a very low 'micro' yield strength which rapidly increased to the level of the 'macro' yield strength when tempered.

  20. Heterogeneities in local plastic flow behavior in a dissimilar weld between low-alloy steel and stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Mas, Fanny [Université Grenoble Alpes, SIMAP, 38000 Grenoble (France); CNRS, SIMAP, 38000 Grenoble (France); Martin, Guilhem, E-mail: guilhem.martin@simap.grenoble-inp.fr [Université Grenoble Alpes, SIMAP, 38000 Grenoble (France); CNRS, SIMAP, 38000 Grenoble (France); Lhuissier, Pierre; Bréchet, Yves; Tassin, Catherine [Université Grenoble Alpes, SIMAP, 38000 Grenoble (France); CNRS, SIMAP, 38000 Grenoble (France); Roch, François [Areva NP, Tour Areva, 92084 Paris La Défense (France); Todeschini, Patrick [EDF R& D, Avenue des Renardières, 77250 Moret-sur-Loing (France); Simar, Aude [Institute of Mechanics, Materials and Civil Engineering (iMMC), Université catholique de Louvain, 1348 Louvain-la-Neuve (Belgium)

    2016-06-14

    In dissimilar welds between low-alloy steel and stainless steel, the post-weld heat-treatment results in a high variety of microstructures coexisting around the fusion line, due to carbon diffusion and carbides dissolution/precipitation. The local constitutive laws in the vicinity of the fusion zone were identified by micro tensile specimens for the sub-millimeter sized zones, equivalent bulk materials representing the decarburized layer using both wet H{sub 2} atmosphere and diffusion couple, and nano-indentation for the carburized regions (i.e. the martensitic band and the austenitic region). The decarburized zone presents only 50% of the yield strength of the low-alloy steel heat affected zone and a ductility doubled. The carburized zones have a yield strength 3–5 times higher than that of the low-alloy steel heat affected zone and have almost no strain hardening capacity. These properties result in heterogeneous plastic deformation happening over only millimeters when the weld is loaded perpendicularly to the weld line, affecting its overall behavior. The constitutive laws experimentally identified were introduced as inputs into a finite elements model of the transverse tensile test performed on the whole dissimilar weld. A good agreement between experiments and simulations was achieved on the global stress-strain curve. The model also well predicts the local strain field measured by microscale DIC. A large out-of-plane deformation due to the hard carburized regions has also been identified.

  1. Page 1 Ductile fracture initiation in a high-strength low alloy steel ...

    Indian Academy of Sciences (India)

    The void volume fraction f is allowed to evolve both due to growth of existing voids and nucleation of new voids, so that. f e fore -- Julair (1 1). The growth law, which is described by down -(1-f)D. (12) is an outcome of the plastic incompressibility of the matrix material. It should, however, be noted that the macroscopic material ...

  2. A constitutive model for the anelastic behavior of Advanced High Strength Steels

    NARCIS (Netherlands)

    Torkabadi, Ali; van Liempt, P.; Meinders, Vincent T.; van den Boogaard, Antonius H.

    2015-01-01

    In this work a physically based model describing the anelastic behaviour and nonlinear unloading in Advanced High Strength Steels (AHSS) is proposed. The model is fitted to the experimental data obtained from uni-axial tests on a dual-phase high strength steel grade (HCT780). The results show a good

  3. The measurement of phosphorus in low alloy steels by electrochemical methods

    Energy Technology Data Exchange (ETDEWEB)

    Rahier, A.; Campsteyn, A.; Verheyen, E.; Verpoucke, G.

    2008-08-15

    The oscillo-polarographic method reported by Chen for the determination of phosphorus in silicates, iron ores, carbonates and tea leaves has been thoroughly studied and enhanced in view of the determination of P in various steels. Together with a carefully selected sample dissolution method, the chromatographic separation reported by Hanada et al. for eliminating the matrix has also been examined. The results of these investigations allowed finding out a path towards the successful electrochemical measurement of P in low alloy ferritic steels without eliminating the matrix. The limit of detection is 5.2 micro gram{sup -1} in the metal. The precision ranges between 5 and 15 % relative to the mean measured values. The finely tuned method has been successfully validated using five NIST standard steels. The chromatographic method remains an option for addressing other metals in the future, should they contain unacceptable levels of possibly interfering elements.. Detailed experimental procedures are given.

  4. Effect of Cu and Ni on Corrosion Resistance of Low Alloyed Steels for Cargo Oil Tank

    Science.gov (United States)

    Xiaobing, Luo; Feng, Chai; Hang, Su; Caifu, Yang; Hao, Li; Yaqing, Hou; Zhengyan, Zhang

    The corrosion behavior of four kinds of low alloyed steels in acid chloride solution (10%NaCl, pH=0.85) was studied on the basis of International Maritime Organization(IMO) standard. Results indicated that, with the increase of Cu and Ni content in steels, the corrosion rate exhibited a law of linear decline, polarization curve moved to positive direction, corrosion potential raised, current density significantly decreased and the interface electric resistance obviously increased. The mechanism of improvement the corrosion resistance of Cu bearing steel can be mainly attributed to the Cu enrichment on the surface of rust layer by means of re-deposition particles(100 500 nm) and keeping high stability. However, Ni was not found in the rust layer but improved the corrosion potential of matrix.

  5. Effects of heat treatment on properties of multi-element low alloy wear-resistant steel

    Directory of Open Access Journals (Sweden)

    SONG Xu-ding

    2007-02-01

    Full Text Available The paper has studied the mechanical properties and heat treatment effects on multi-element low alloy wear-resistant steel (MLAWS used as a material for the liner of rolling mill torii. The results show that when quenched at 900-920℃ and tempered at 350-370℃, the MLAWS has achieved hardness above 60 HRC, tensile strength greater than 1 600 MPa, impact toughness higher than 18J/cm2 and fracture toughness greater than 37 MPa

  6. Low Alloy Steel Structures After Welding with Micro-Jet Cooling

    OpenAIRE

    Węgrzyn T.; Piwnik J.; Hadryś D.; Wszołek Ł.

    2017-01-01

    The paper focuses on low alloy steel after innovate welding method with micro-jet cooling. Weld metal deposit (WMD) was carried out for welding and for MIG and MAG welding with micro-jet cooling. This method is very promising mainly due to the high amount of AF (acicular ferrite) and low amount of MAC (self-tempered martensite, retained austenite, carbide) phases in WMD. That structure corresponds with very good mechanical properties, ie. high impact toughness of welds at low temperature. Mic...

  7. Microstructural Developments Leading to New Advanced High Strength Sheet Steels: A Historical Assessment of Critical Metallographic Observations

    Energy Technology Data Exchange (ETDEWEB)

    Matlock, David K [CSM/ASPPRC; Thomas, Larrin S [CSM/ASPPRC; Taylor, Mark D [CSM/ASPPRC; De Moor, Emmanuel [CSM/ASPPRC; Speer, John G [CSM/ASPPRC

    2015-08-03

    In the past 30+ years significant advancements have been made in the development of higher strength sheet steels with improved combinations of strength and ductility that have enabled important product improvements leading to safer, lighter weight, and more fuel efficient automobiles and in other applications. Properties of the primarily low carbon, low alloy steels are derived through careful control of time-temperature processing histories designed to produce multiphase ferritic based microstructures that include martensite and other constituents including retained austenite. The basis for these developments stems from the early work on dual-phase steels which was the subject of much interest. In response to industry needs, dual-phase steels have evolved as a unique class of advanced high strength sheet steels (AHSS) in which the thermal and mechanical processing histories have been specifically designed to produce constituent combinations for the purpose of simultaneously controlling strength and deformation behavior, i.e. stress-strain curve shapes. Improvements continue as enhanced dual-phase steels have recently been produced with finer microstructures, higher strengths, and better overall formability. Today, dual phase steels are the primary AHSS products used in vehicle manufacture, and several companies have indicated that the steels will remain as important design materials well into the future. In this presentation, fundamental results from the early work on dual-phase steels will be reviewed and assessed in light of recent steel developments. Specific contributions from industry/university cooperative research leading to product improvements will be highlighted. The historical perspective provided in the evolution of dual-phase steels represents a case-study that provides important framework and lessons to be incorporated in next generation AHSS products.

  8. Comparison of Corrosion Behavior of Low-Alloy Steel Containing Copper and Antimony with 409L Stainless Steel for a Flue Gas Desulfurization System

    Energy Technology Data Exchange (ETDEWEB)

    Park, Sun-Ah; Shin, Su-Bin; Kim, Jung-Gu [Sungkyunkwan University, Suwon (Korea, Republic of)

    2016-07-15

    The corrosion behavior of low alloy steel containing Cu, Sb and 409L stainless steel was investigated for application in the low-temperature section of a flue gas desulfurization (FGD) system. The electrochemical properties were evaluated by potentiodynamic polarization testing and electrochemical impedance spectroscopy (EIS) in 16.9 vol% H{sub 2}SO{sub 4} + 0.35 vol% HCl at 60 ℃. The inclusions in these steels ere identified by electron probe microanalyzer (EPMA). The corrosion products of the steels were analyzed using scanning electron microscope (SEM) with energy dispersive spectroscopy (EDS) and transmission electron microscopy (TEM). The corrosion rate of the low alloy steel containing Cu, Sb was about 100 times lower than that of 409L stainless steel. For stainless steel without passivation, active corrosion behavior was shown. In contrast, in the low alloy steel, the Cu, Sb compounds accumulated on the surface improved the corrosion resistance by suppressing the anodic dissolution reaction.

  9. Three-Sheet Spot Welding of Advanced High-Strength Steels

    DEFF Research Database (Denmark)

    Nielsen, Chris Valentin; Friis, Kasper Storgaard; Zhang, W.

    2011-01-01

    The automotive industry has introduced the three-layer weld configuration, which represents new challenges compared to normal two-sheet lap welds. The process is further complicated by introducing high-strength steels in the joint. The present article investigates the weldability of thin, low....... The weld mechanisms are analyzed numerically and compared with metallographic analyses showing how the primary bonding mechanism between the thin, low-carbon steel sheet and the thicker sheet of high-strength steel is solid-state bonding, whereas the two high-strength steels are joined by melting, forming...... a weld nugget at their mutual interface. Despite the absence of the typical fusion nugget through the interface between the low-carbon steel and high-strength steel, the weld strengths obtained are acceptable. The failure mechanism in destructive testing is ductile fracture with plug failure....

  10. Environmental influence on the near-threshold fatigue crack propagation behaviour of a high-strength steel

    Science.gov (United States)

    Henaff, G.; Petit, J.; Bouchet, B.

    1992-07-01

    The near-threshold fatigue crack propagation behavior of a high-strength low-alloy steel has been investigated in ambient air and in vacuum so as to determine the role of the environment precisely. The analysis of the results is conducted by taking crack closure effects into account. It is concluded that fatigue crack growth rates measured in ambient air depend upon three processes: intrinsic fatigue crack propagation as observed in vacuum, adsorption of water vapor molecules on freshly created rupture surfaces, which enhances crack propagation, and a subsequent step of hydrogen-assisted cracking. The appearance of intergranular ruptures and oxide layers on rupture surfaces in ambient air is also discussed.

  11. Welding simulation and fatigue assessment of tubular K-joints in high-strength steel

    Energy Technology Data Exchange (ETDEWEB)

    Zamiri Akhlaghi, F.

    2014-07-01

    were conducted to evaluate the residual stress field in the gap region of K-joint, which was critical location for fatigue cracking. Transversal residual stresses of up to 0.60f{sub y} nominal were registered at some depth from the surface of the chord. The σ{sub res} l{sub y} ratio for the high strength steel S690QH was lower than similar measurements previously done by Acevedo (2011) on steel grade S355J2H. This is believed to be mainly due to welding with low heat input and solid-state phase transformations in high strength steel material. Microstructural changes in the heat affected zone (HAZ) for low alloy carbon steels favorably act in reducing tensile residual stresses by adding compressive residual stresses during part of cooling. These effects were modelled numerically using a coupled thermal mechanical- metallurgical analysis of welding process. Welding sequence was registered and temperature data acquired during fabrication stage of the test trusses; they were employed for creation of calculation model. There has been considerable progress in the methods and tools for computational weld modelling since early 90’s, from 2D to 3D possibilities. Since welded details involved in structural engineering design have generally complex shapes, one major objective of this study was to apply the state of the art in weld modelling into a purposely-selected complex detail with several weld passes. This led to recommendations regarding modelling procedures and simplifying assumptions, as well as FEM practical issues that arise for the case of such intricate geometries. Investigated parameters include weld pass reduction by lumping, welding start/stop positions, and microstructural transformation assumptions. Finally, an extended finite element model (XFEM) was used for fatigue crack propagation analysis in 3D in a K-joint under combined effect of external compressive loading and tensile residual stresses at crack site. Limitations of the utilized finite element code

  12. Standard guide for estimating the atmospheric corrosion resistance of low-alloy steels

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2004-01-01

    1.1 This guide presents two methods for estimating the atmospheric corrosion resistance of low-alloy weathering steels, such as those described in Specifications A242/A242M, A588/A588M, A606 Type 4, A709/A709M grades 50W, HPS 70W, and 100W, A852/A852M, and A871/A871M. One method gives an estimate of the long-term thickness loss of a steel at a specific site based on results of short-term tests. The other gives an estimate of relative corrosion resistance based on chemical composition. 1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.

  13. A comparison between ultra-high-strength and conventional high-strength fastener steels : Mechanical properties at elevated temperature and microstructural mechanisms

    NARCIS (Netherlands)

    Ohlund, C.E.I.C.; Lukovic, M.; Weidow, J; Thuvander, M; Offerman, S.E.

    2016-01-01

    A comparison is made between the mechanical properties of the ultra-high-strength steel KNDS4 of fastener grade 14.9 and of conventional, high-strength steels 34Cr4 of fastener grade 12.9 and 33B2 of grade 10.9. The results show that the ratio of the yield strength at elevated temperatures to the

  14. Gigacycle Fatigue Properties of Hydrogen-Charged JIS-SCM440 Low-Alloy Steel Under Ultrasonic Fatigue Testing

    Science.gov (United States)

    Furuya, Yoshiyuki; Hirukawa, Hisashi; Hayakawa, Masao

    2010-09-01

    Gigacycle fatigue tests were conducted on hydrogen-charged low-alloy steel. In this study, high- and low-strength specimens were prepared to investigate the effects of hydrogen on internal and surface fractures, respectively. The fatigue tests were conducted mainly by ultrasonic fatigue testing at 20 kHz and additionally by conventional servohydraulic fatigue testing at 50 Hz. All high-strength specimens revealed internal fractures. The fatigue strength of the hydrogen-charged specimens was much lower than that of the uncharged specimens. In the low-strength specimens, the uncharged specimens revealed surface fractures in the short-life regions in addition to internal fractures in the long-life regions. However, the hydrogen-charged specimens revealed internal fractures only that were combined with a much lower fatigue strength. The difference in fracture surfaces was small between the hydrogen-charged and the uncharged specimens, whereas the optically dark areas of the hydrogen-charged specimens seemed smaller than those of the uncharged specimens.

  15. Effect of applied tensile stress on the transformation behavior of medium carbon low alloy steels. Chutanso tei gokinko no hentai kyodo ni oyobosu hippari oryoku fuka no koka

    Energy Technology Data Exchange (ETDEWEB)

    Kanetsuki, Y.; Katsumata, M.; Kaida, O.; Kaiso, M. (Kobe Steel, Ltd., Tokyo (Japan))

    1991-06-01

    Techniques of controlled rolling and cooling are actively being used as the manufacturing process of high strength and high tenacity steel plates. The reason behind this is that the ferrite-pearlite texture can be made very finely. However, with regard to low alloy carbon steel bars with enhanced hardenability, its texture becomes hard bainite texture in the cooling process after rolling, hence its workability is not good. In this research, in lieu of controlled rolling, the possibility of the process that the tensile stress, whose effect of facilitating transformation is known, is applied before the transformation and its texture is controlled to the ferrite-pearlite texture at the cooling rate of air cooling. In other words, with regard to medium carbon low alloy steels, its transformation behavior was studied by a tensile test in which additional stress was controlled during its continuous cooling. The results are as follows: It was found that by adding stress, the ferrite transformation was expedited. This was because the nuclei formation of ferrite, which was enhanced by inner stress, was facilitated. Furthermore, when the above transformation took place at the same time of deformation, an uniform elongation about 60% was obtained. 13 refs., 13 figs., 1 tab.

  16. The Effect of Phosphate Coatings on Fatigue Crack Initiation in Quenched and Tempered Low Alloy Steel

    Science.gov (United States)

    1990-12-01

    zinc and manganese phosphate on fatigue life to crack initiation was determined at two levels of applied stress, selected to... manganese phosphate or zinc phosphate which is then given a supplementary coating such as oil or solid film lubricant. The manganese phosphate is typically...surface with phosphate ( zinc or manganese ) has on the initiation of fatigue cracks in a representative high strength cannon steel. This report descries

  17. An Investigation on Fatigue in High-Strength Steel Offshore Structures

    DEFF Research Database (Denmark)

    Agerskov, Henning; Petersen, R.I.; Lopez Martinez, L.

    1997-01-01

    In the present investigation, the fatigue life of offshore steel structures in high-strength steel is studied. The material used has a yield stress of 800-1000 MPa, and high weldability and toughness properties. Of special interest is the fatigue life under a realistic stochastic loading....... In the experimental part of the investigation, fatigue test series have been carried through on both full-scale tubular joints and smaller welded plate test specimens, in high-strength steel as well as in conventional offshore structural steel. The present document gives a summary of the main results presented in two......, in general longer fatigue lives were obtained for the test specimens in high-strength steel than those obtained in corresponding tests on joints in conventional offshore structural steel....

  18. An investigation on fatigue in high-strength steel offshore structures

    DEFF Research Database (Denmark)

    Agerskov, Henning; Petersen, R.I.; Martinez, L. Lopez

    1998-01-01

    The fatigue life of offshore steel structures in high-strength steel is studied. The material used has a yield stress of 800-1000 MPa and high weldability and toughness properties. Of special interest is the fatigue life under a realistic stochastic loading. In the experimental part...... of the investigation, fatigue test series were carried out on both full scale tubular joints and smaller welded plate test specimens in high-strength steel as well as in conventional offshore structural steel. This paper gives a summary of the main results presented in two recent research reports [15, 16], from...... specimens in high-strength steel than those obtained in corresponding tests on joints in conventional offshore structural steel....

  19. Chrome-Free Paint Primer for Zn/Ni Plated High-Strength Steel (Briefing Charts)

    Science.gov (United States)

    2014-11-19

    Chrome -Free Paint Primer for Zn/Ni Plated High- Strength Steel 11-19-14 Presentation at ASETSDefense 2014 George Zafiris Team: Mark Jaworowski, Mike...AND SUBTITLE Chrome -Free Paint Primer for Zn/Ni Plated High-Strength Steel 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6... Chrome -free Primer TCP LHE= Low Hydrogen Embrittlement CCC= Chromate (Cr6+) Conversion Coating TCP= Trivalent (Cr3+) Chromium Process  Regulatory EHS

  20. Experimental and numerical analysis of hydrogen interaction with plastic strain in a high strength steel

    OpenAIRE

    Vucko, Flavien; Bosch, Cédric; Delafosse, David

    2012-01-01

    8 pages; International audience; Cyclic loading tests were performed on micro-notched samples of high-strength steel S690QT in air and under cathodic polarisation in a saline solution. These specimens were modelled and their behaviour simulated by finite elements calculations with a combined nonlinear isotropic-kinematic hardening constitutive law. This model can simulate cyclic softening and ratcheting effect of the high-strength steel. Stress and strain fields in the vicinity of the notch-t...

  1. Properties of stainless high-strength chrome steels for bearings

    Science.gov (United States)

    Talyzin, V. M.; Burkin, V. S.; Doronin, V. M.

    1981-10-01

    Steel 40Kh11M3F-Sh has fairly high resistance to contact fatigue stresses at elevated temperatures and can be recommended for bearings operating in aggressive media at such temperatures, including large bearings.

  2. Design of Reforma 509 with High Strength Steel

    Science.gov (United States)

    Smith, Stuart; Whitby, William; Easton, Marc

    Reforma 509 is a high-rise building located in the heart of the Central Business District of Mexico City. The building is comprised of office, hotel, residential and parking and forms part of a cluster of tall buildings in the area. If completed today, Reforma 509 would be the tallest building in Mexico, at 238m. All of the building's gravity and lateral (wind and seismic) loads are carried by an architecturally expressed perimeter frame that is formed from highly efficient Steel Reinforced Concrete (SRC) columns coupled together by steel tube perimeter bracing. This paper investigates the implications of substituting a grade 50 (fy=345 MPa) carbon steel with a higher strength micro-alloyed grade 70 (fy=480 MPa) steel in the design of Reforma 509.

  3. Predicting the creep life and failure mode of low-alloy steel weldments

    Energy Technology Data Exchange (ETDEWEB)

    Brear, J.M.; Middleton, C.J.; Aplin, P.F. [ERA Technology Ltd., Leatherhead (United Kingdom)

    1998-12-31

    This presentation reviews and consolidates experience gained through a number of research projects and practical plant assessments in predicting both the life and the likely failure mode and location in low alloy steel weldments. The approach adopted begins with the recognition that the relative strength difference between the microstructural regions is a key factor controlling both life and failure location. Practical methods based on hardness measurement and adaptable to differing weld geometries are presented and evidence for correlations between hardness ratio, damage accumulation and strain development is discussed. Predictor diagrams relating weld life and failure location to the service conditions and the hardness of the individual microstructural constituents are suggested and comments are given on the implications for identifying the circumstances in which Type IV cracking is to be expected. (orig.) 6 refs.

  4. Low Alloy Steel Structures After Welding with Micro-Jet Cooling

    Directory of Open Access Journals (Sweden)

    Węgrzyn T.

    2017-03-01

    Full Text Available The paper focuses on low alloy steel after innovate welding method with micro-jet cooling. Weld metal deposit (WMD was carried out for welding and for MIG and MAG welding with micro-jet cooling. This method is very promising mainly due to the high amount of AF (acicular ferrite and low amount of MAC (self-tempered martensite, retained austenite, carbide phases in WMD. That structure corresponds with very good mechanical properties, ie. high impact toughness of welds at low temperature. Micro-jet cooling after welding can find serious application in automotive industry very soon. Until that moment only argon, helium and nitrogen were tested as micro-jet gases. In that paper first time various gas mixtures (gas mixtures Ar-CO2 were tested for micro-jet cooling after welding.

  5. Effects of LWR coolant environments on fatigue design curves of carbon and low-alloy steels

    Energy Technology Data Exchange (ETDEWEB)

    Chopra, O.K.; Shack, W.J. [Argonne National Lab., IL (United States)

    1998-03-01

    The ASME Boiler and Pressure Vessel Code provides rules for the construction of nuclear power plant components. Figures I-9.1 through I-9.6 of Appendix I to Section III of the code specify fatigue design curves for structural materials. While effects of reactor coolant environments are not explicitly addressed by the design curves, test data indicate that the Code fatigue curves may not always be adequate in coolant environments. This report summarizes work performed by Argonne National Laboratory on fatigue of carbon and low-alloy steels in light water reactor (LWR) environments. The existing fatigue S-N data have been evaluated to establish the effects of various material and loading variables such as steel type, dissolved oxygen level, strain range, strain rate, temperature, orientation, and sulfur content on the fatigue life of these steels. Statistical models have been developed for estimating the fatigue S-N curves as a function of material, loading, and environmental variables. The results have been used to estimate the probability of fatigue cracking of reactor components. The different methods for incorporating the effects of LWR coolant environments on the ASME Code fatigue design curves are presented.

  6. The research on delayed fracture behavior of high-strength bolts in steel structure

    Science.gov (United States)

    Li, Guo dong; Li, Nan

    2017-07-01

    High-strength bolts have been widely used in power plants. However, the high-strength bolts which being employed in pumping station, steel structure and pipeline anti-whip structure have been found delayed fracture for many times in a power plant, this will affect the reliability of steel fracture and bring blow risk caused by falling objects. The high-strength bolt with delayed fracture was carried out fracture analysis, metallurgical analysis, chemical analysis, mechanical analysis, as well as bolts installation analysis, it can be comprehensively confirmed that the direct cause of high-strength bolts delayed fracture is the stress corrosion, and the root cause of high-strength bolts delayed fracture should be the improper installation at the initial and the imperfect routine anti-corrosion maintenance.

  7. Fatigue crack Behaviour in a High Strength Tool Steel

    DEFF Research Database (Denmark)

    Højerslev, Christian; Carstensen, Jesper V.; Brøndsted, Povl

    2002-01-01

    The influence of microstructure on fatigue crack initiation and crack growth of a hardened and tempered high speed steel was investigated. The evolution of fatigue cracks was followed in four point bending at room temperature. It was found that a carbide damage zone exists above a threshold load...... value of maximally 80% of the yield strength of the steel. The size of this carbide damage zone increases with increasing load amplitude, and the zone is apparently associated with crack nucleation. On fatigue crack propagation plastic deformation of the matrix occurs in a radius of approximately 4...

  8. Probabilistic finite element analysis of high strength steel structures

    NARCIS (Netherlands)

    Waarts, P.H.; Vrouwenvelder, A.C.W.M.

    1996-01-01

    In structural steel design the ultimate design limit is governed by full cross-sectional plasticity, where an elastic-perfectly plastic material behaviour is used. Hardening of the material is not used. Some loads are not considered such as settlements of supports and temperature loads in static

  9. Optimization of microstructure and properties of high strength spring steel

    NARCIS (Netherlands)

    Choi, S.

    2011-01-01

    This thesis describes a research project on the development of a new grade of low cost spring steel with exceptional mechanical properties on the basis of a complete understanding and quantification of the metallurgical processes taking place during the various stages of the heat treatment. The new

  10. Weldability prediction of high strength steel S960QL after weld thermal cycle simulation

    Directory of Open Access Journals (Sweden)

    M. Dunđer

    2014-10-01

    Full Text Available This paper presents weld thermal cycle simulation of high strength steel S960QL, and describes influence of cooling time t8/5 on hardness and impact toughness of weld thermal cycle simulated specimens. Furthermore, it presents analysis of characteristic fractions done by electron scanning microscope which can contribute to determination of welding parameters for S960QL steel.

  11. Fatigue experiments on very high strength steel base material and transverse butt welds

    NARCIS (Netherlands)

    Pijpers, R.J.M.; Kolstein, M.H.; Romeijn, A.; Bijlaard, F.S.K.

    2009-01-01

    Very High Strength Steels (VHSS) with nominal strengths up to 1100 MPa have been available on the market for many years. However, the use of these steels in the civil engineering industry is still uncommon, due to lack of design and fabrication knowledge and therefore limited inclusion in codes.

  12. High strength reinforcing steel bars : low-cycle fatigue behavior : final report - part B.

    Science.gov (United States)

    2017-03-01

    High-strength steel (HSS) reinforcing steel, specifically ASTM A706 Grade 80 (550), is now permitted by the AASHTO LRFD Bridge Design Specifications for use in reinforced concrete bridge components in non-seismic regions. Using Grade 80 (550) reinfor...

  13. High strength reinforcing steel bars : low cycle fatigue behavior : final report - part B.

    Science.gov (United States)

    2017-03-01

    High-strength steel (HSS) reinforcing steel, specifically ASTM A706 Grade 80 (550), is now permitted by the AASHTO LRFD Bridge Design Specifications for use in reinforced concrete bridge components in non-seismic regions. Using Grade 80 (550) reinfor...

  14. High strength reinforcing steel bars : concrete shear friction interface : final report : Part A.

    Science.gov (United States)

    2017-03-01

    High-strength steel (HSS) reinforcement, specifically ASTM A706 Grade 80 (550), is now permitted by the AASHTO LRFD Bridge Design Specifications for use in reinforced concrete bridge components in non-seismic regions. Using Grade 80 (550) steel reinf...

  15. Fatigue in Welded High-Strength Steel Plate Elements under Stochastic Loading

    DEFF Research Database (Denmark)

    Agerskov, Henning; Petersen, R.I.; Martinez, L. Lopez

    1999-01-01

    The present project is a part of an investigation on fatigue in offshore structures in high-strength steel. The fatigue life of plate elements with welded attachments is studied. The material used has a yield stress of ~ 810-840 MPa, and high weldability and toughness properties. Fatigue test...... series with constant amplitude loading and with various types of stochastic loading have been carried through on test specimens in high-strength steel, and - for a comparison - on test specimens in conventional offshore structural steel with a yield stress of ~ 400-410 MPa.A comparison between constant...... amplitude and variable amplitude fatigue test results shows shorter fatigue lives in variable amplitude loading than should be expected from the linear fatigue damage accumulation formula. Furthermore, in general longer fatigue lives were obtained for the test specimens in high-strength steel than those...

  16. Modification of Low-Alloy Steel Surface by High-Temperature Gas Nitriding Plus Tempering

    Science.gov (United States)

    Jiao, Dongling; Li, Minsong; Ding, Hongzhen; Qiu, Wanqi; Luo, Chengping

    2018-01-01

    The low-alloy steel was nitrided in a pure NH3 gas atmosphere at 640 660 °C for 2 h, i.e., high-temperature gas nitriding (HTGN), followed by tempering at 225 °C, which can produce a high property surface coating without brittle compound (white) layer. The steel was also plasma nitriding for comparison. The composition, microstructure and microhardness of the nitrided and tempered specimens were examined, and their tribological behavior investigated. The results showed that the as-gas-nitrided layer consisted of a white layer composed of FeN0.095 phase (nitrided austenite) and a diffusional zone underneath the white layer. After tempering, the white layer was decomposed to a nano-sized (α-Fe + γ'-Fe4N + retained austenite) bainitic microstructure with a high hardness of 1150HV/25 g. Wear test results showed that the wear resistance and wear coefficient yielded by the complex HTGN plus tempering were considerably higher and lower, respectively, than those produced by the conventional plasma nitriding.

  17. Transformation of carbide phases during tempering a low-alloyed Cr-Mo-V-steel

    Energy Technology Data Exchange (ETDEWEB)

    Janovec, J.; Vyrostkova, A.; Stefan, B.; Gueth, A.

    1989-03-01

    The influence of a tempering treatment (550 to 750/sup 0/C/1 to 100 h) on the precipitation of carbides was studied in a low-alloyed Cr-Mo-V-steel using analytical electron microscopy (STEM/EDXS) and electron diffraction techniques (ED). The morphology, crystallography and chemistry of each of the various types of carbides examined, has been established. Four types of carbide phases were detected in the microstructure: M/sub 3/C, M/sub 7/C/sub 3/, M/sub 23/C/sub 6/ and MC. With increasing Larsen-Miller-parameter chromium is enriched in M/sub 3/C particles. This process is limited by the chemical composition of the M/sub 7/C/sub 3/ carbide formed by 'in-situ' transformation M/sub 3/C->M/sub 7/C/sub 3/. The composition of the M/sub 7/C/sub 3/ carbide is almost constant for different tempering conditions. The V/Mo ratio in the MC particles depends on the Larsen-Miller-parameter. From the observations a diagram of the existence of carbide phases was derived for the experimental steel. (orig.).

  18. Influence of the welding process on martensitic high strength steel

    Directory of Open Access Journals (Sweden)

    Petr Hanus

    2014-07-01

    Full Text Available The subject of the study is martensitic 22MnB5 steels, which are used in the automotive industry. The main purpose of the performed analyses is a study of strength differences in heat affected zones of the spot welding. For the needs of the strength decrease assessment, the critical layer of the heat affected area was experimentally simulated. The aim of the work is to determine the most suitable methodology for evaluating the local changes of the elastic-plastic material response. The aim of this work is to determine the optimal methods for the determination of the yield strength and to find a firming trend in these zones.

  19. Dynamic hardness of high-strength steel and titanium alloy

    Energy Technology Data Exchange (ETDEWEB)

    Stepanov, G.; Zubov, V. [Natsional' na Akademyiya Ukrayini, Kiev (Ukraine). Inst. of Strength Problems

    2000-09-01

    Essential results of experimental studies on dynamic hardness (an average pressure on the cone face of a rigid rod at its impact indentation into the surface layer of a thick plate) of a homogeneous rolled steel (HRA) and a titanium alloy are presented in this paper. Significant influence of the impact velocity on dynamic hardness of materials tested follows from the analysis of the experimental data. Specific energy of the formation of a conical cavity (per unit volume of displaced material) decreases with an increase in the indentation velocity and the conical cavity depth. At further process of indentation, corresponding to the initial stage of penetration (the cavity depth exceeds the length of the rod conical head) the average pressure increases with the impact velocity. Combined influence of viscosity effect and rise in temperature at plastic flow should be taken into account in order to explain the above relations. (orig.)

  20. Application technologies for effective utilization of advanced high strength steel sheets

    Energy Technology Data Exchange (ETDEWEB)

    Suehiro, Masayoshi, E-mail: suehiro.kp5.masayoshi@jp.nssmc.com [Steel Research Laboratories, Nippon Steel and Sumitomo Metal Corporation, 20-1 Shintomi, Futtsu, Chiba 293-8511 (Japan)

    2013-12-16

    Recently, application of high strength steel sheets for automobiles has increased in order to meet a demand of light weighting of automobiles to reduce a carbon footprint while satisfying collision safety. The formability of steel sheets generally decreases with the increase in strength. Fracture and wrinkles tend to occur easily during forming. The springback phenomenon is also one of the issues which we should cope with, because it makes it difficult to obtain the desired shape after forming. Advanced high strength steel sheets with high formability have been developed in order to overcome these issues, and at the same time application technologies have been developed for their effective utilization. These sheets are normally used for cold forming. As a different type of forming, hot forming technique has been developed in order to produce parts with ultra high strength. In this report, technologies developed at NSSMC in this field will be introduced.

  1. Rust Formation Mechanism on Low Alloy Steels after Exposure Test in High Cl− and High SOx Environmen

    Directory of Open Access Journals (Sweden)

    Toshiyasu Nishimura

    2017-02-01

    Full Text Available Exposure tests were performed on low alloy steels in high Cl− and high SOx environment, and the structure of the rust were analyzed by TEM (Transmission Electron Microscopy and Raman Spectroscopy. In the exposure test site, the concentrations of Cl− and SOx were found to be high, which caused the corrosion of the steels. The conventional weathering steel (SMA: 0.6% Cr-0.4% Cu-Fe showed higher corrosion resistance as compared to the carbon steel (SM, and Ni bearing steel exhibited the highest one. Raman spectroscopy showed that the inner rust of Ni bearing steel was mainly composed of α-FeOOH and spinel oxides. On the other hand, SMA contained β- and γ-FeOOH in inner rust, which increased the corrosion. TEM showed that nano-scale complex iron oxides containing Ni or Cr were formed in the rust on the low alloy steels, which suppressed the corrosion of steels in high Cl− and high SOx environment.

  2. Rust Formation Mechanism on Low Alloy Steels after Exposure Test in High Cl− and High SOx Environment

    Science.gov (United States)

    Nishimura, Toshiyasu

    2017-01-01

    Exposure tests were performed on low alloy steels in high Cl− and high SOx environment, and the structure of the rust were analyzed by TEM (Transmission Electron Microscopy) and Raman Spectroscopy. In the exposure test site, the concentrations of Cl− and SOx were found to be high, which caused the corrosion of the steels. The conventional weathering steel (SMA: 0.6% Cr-0.4% Cu-Fe) showed higher corrosion resistance as compared to the carbon steel (SM), and Ni bearing steel exhibited the highest one. Raman spectroscopy showed that the inner rust of Ni bearing steel was mainly composed of α-FeOOH and spinel oxides. On the other hand, SMA contained β- and γ-FeOOH in inner rust, which increased the corrosion. TEM showed that nano-scale complex iron oxides containing Ni or Cr were formed in the rust on the low alloy steels, which suppressed the corrosion of steels in high Cl− and high SOx environment. PMID:28772560

  3. Rust Formation Mechanism on Low Alloy Steels after Exposure Test in High Cl- and High SOx Environmen.

    Science.gov (United States)

    Nishimura, Toshiyasu

    2017-02-17

    Exposure tests were performed on low alloy steels in high Cl- and high SOx environment, and the structure of the rust were analyzed by TEM (Transmission Electron Microscopy) and Raman Spectroscopy. In the exposure test site, the concentrations of Cl- and SOx were found to be high, which caused the corrosion of the steels. The conventional weathering steel (SMA: 0.6% Cr-0.4% Cu-Fe) showed higher corrosion resistance as compared to the carbon steel (SM), and Ni bearing steel exhibited the highest one. Raman spectroscopy showed that the inner rust of Ni bearing steel was mainly composed of α-FeOOH and spinel oxides. On the other hand, SMA contained β- and γ-FeOOH in inner rust, which increased the corrosion. TEM showed that nano-scale complex iron oxides containing Ni or Cr were formed in the rust on the low alloy steels, which suppressed the corrosion of steels in high Cl- and high SOx environment.

  4. Environmentally-Assisted Cracking of Low-Alloy Reactor Pressure Vessel Steels under Boiling Water Reactor Conditions

    Energy Technology Data Exchange (ETDEWEB)

    Seifert, H.P.; Ritter, S

    2002-02-01

    The present report summarizes the experimental work performed by PSI on the environmentally-assisted cracking (EAC) of low-alloy steels (LAS) in the frame of the RIKORR-project during the period from January 2000 to August 2001. Within this project, the EAC crack growth behaviour of different low-alloy reactor pressure vessel (RPV) steels, weld filler and weld heat-affected zone materials is investigated under simulated transient and steady-state BWR/NWC power operation conditions. The EAC crack growth behaviour of different low-alloy RPV steels was characterized by slow rising load (SRL) / low-frequency corrosion fatigue (LFCF) and constant load tests with pre-cracked fracture mechanics specimens in oxygenated high-temperature water at temperatures of either 288, 250, 200 or 150 C. These tests revealed the following important interim results: Under low-flow and highly oxidizing (ECP >= 100 mV SHE) conditions, the ASME XI 'wet' reference fatigue crack growth curve could be significantly exceeded by cyclic fatigue loading at low frequencies (<0.001 Hz), at high and low load-ratios R, and by ripple loading near to DKth fatigue thresholds. The BWR VIP 60 SCC disposition lines may be significantly or slightly exceeded (even in steels with a low sulphur content) in the case of small load fluctuations at high load ratios (ripple loading) or at intermediate temperatures (200 -250 C) in RPV materials, which show a distinct susceptibility to dynamic strain ageing (DSA). (author)

  5. Quantitative observations of hydrogen-induced, slow crack growth in a low alloy steel

    Science.gov (United States)

    Nelson, H. G.; Williams, D. P.

    1973-01-01

    Hydrogen-induced slow crack growth, da/dt, was studied in AISI-SAE 4130 low alloy steel in gaseous hydrogen and distilled water environments as a function of applied stress intensity, K, at various temperatures, hydrogen pressures, and alloy strength levels. At low values of K, da/dt was found to exhibit a strong exponential K dependence (Stage 1 growth) in both hydrogen and water. At intermediate values of K, da/dt exhibited a small but finite K dependence (Stage 2), with the Stage 2 slope being greater in hydrogen than in water. In hydrogen, at a constant K, (da/dt) sub 2 varied inversely with alloy strength level and varied essentially in the same complex manner with temperature and hydrogen pressure as noted previously. The results of this study provide support for most of the qualitative predictions of the lattice decohesion theory as recently modified by Oriani. The lack of quantitative agreement between data and theory and the inability of theory to explain the observed pressure dependence of slow crack growth are mentioned and possible rationalizations to account for these differences are presented.

  6. Microstructural Evolution of Inverse Bainite in a Hypereutectoid Low-Alloy Steel

    Science.gov (United States)

    Kannan, Rangasayee; Wang, Yiyu; Li, Leijun

    2017-12-01

    Microstructural evolution of inverse bainite during isothermal bainite transformation of a hypereutectoid low-alloy steel at 773 K (500 °C) was investigated through a series of interrupted isothermal experiments using a quench dilatometer. Microstructural characterization revealed that the inverse bainitic transformation starts by the nucleation of cementite (Fe3C) from parent austenite as a midrib in the bainitic microstructure. The inverse bainite becomes "degenerated" to typical upper bainite at prolonged transformation times. Crystallographic orientation relationships between the individual phases of inverse bainite microstructure were found to obey { _{γ } || _{θ } } { _{α } || _{θ } } { _{γ } || _{α } } 111_{γ } || { \\overline{2} 21} _{θ } } { 110} _{α } || { \\overline{2} 21} _{θ } } { 111} _{γ } || { 110 } _{α } {111} _{γ } || {211} _{θ } {110} _{α } || {211} _{θ } Furthermore, the crystallographic orientation deviations between the individual phases of inverse bainite microstructure suggest that the secondary carbide nucleation occurs from the inverse bainitic ferrite. Thermodynamic driving force calculations provide an explanation for the observed nucleation sequence in inverse bainite. The degeneracy of inverse bainite microstructure to upper bainite at prolonged transformation times is likely due to the effects of cementite midrib dissolution at the early stage and secondary carbide coarsening at the later stage.

  7. Microstructural Evolution of Inverse Bainite in a Hypereutectoid Low-Alloy Steel

    Science.gov (United States)

    Kannan, Rangasayee; Wang, Yiyu; Li, Leijun

    2017-10-01

    Microstructural evolution of inverse bainite during isothermal bainite transformation of a hypereutectoid low-alloy steel at 773 K (500 °C) was investigated through a series of interrupted isothermal experiments using a quench dilatometer. Microstructural characterization revealed that the inverse bainitic transformation starts by the nucleation of cementite (Fe3C) from parent austenite as a midrib in the bainitic microstructure. The inverse bainite becomes "degenerated" to typical upper bainite at prolonged transformation times. Crystallographic orientation relationships between the individual phases of inverse bainite microstructure were found to obey { _{γ} || _{θ } } { _{α} || _{θ } } { _{γ } || _{α } } {111}_{γ } || { \\overline{2} 21} _{θ } } {{110} _{α } || { \\overline{2} 21} _{θ } } { {111} _{γ } || {110} _{α } } {111} _{γ } || {211} _{θ } } { {110} _{α } || {211} _{θ } } Furthermore, the crystallographic orientation deviations between the individual phases of inverse bainite microstructure suggest that the secondary carbide nucleation occurs from the inverse bainitic ferrite. Thermodynamic driving force calculations provide an explanation for the observed nucleation sequence in inverse bainite. The degeneracy of inverse bainite microstructure to upper bainite at prolonged transformation times is likely due to the effects of cementite midrib dissolution at the early stage and secondary carbide coarsening at the later stage.

  8. Investigation on dissimilar laser welding of advanced high strength steel sheets for the automotive industry

    Energy Technology Data Exchange (ETDEWEB)

    Rossini, M., E-mail: matteo.rossini@unibz.it [Faculty of Science and Technology, Free University of Bozen-Bolzano, Piazza Università 5, 39100 Bolzano (Italy); Spena, P. Russo, E-mail: pasquale.russospena@unibz.it [Faculty of Science and Technology, Free University of Bozen-Bolzano, Piazza Università 5, 39100 Bolzano (Italy); Cortese, L., E-mail: luca.cortese@unibz.it [Faculty of Science and Technology, Free University of Bozen-Bolzano, Piazza Università 5, 39100 Bolzano (Italy); Matteis, P., E-mail: paolo.matteis@polito.it [Department of Applied Science and Technology, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Torino (Italy); Firrao, D., E-mail: donato.firrao@polito.it [Department of Applied Science and Technology, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Torino (Italy)

    2015-03-25

    To support the use of advanced high strength steels in car body design and fabrication, an investigation was carried out on dissimilar butt laser welding between TWinning Induced Plasticity (TWIP) steels, Dual Phase (DP) steels, hot stamping boron (22MnB5) steels, and TRansformation Induced Plasticity (TRIP) steels. The base materials and the weldments were fully characterized by means of metallography, microhardness, and tensile tests. Digital image analysis was also used to provide additional information on the local strain field in the joint during the tensile tests. Fractographic examination was finally performed on the fracture surfaces of the tensile samples. The dissimilar joints between the DP, 22MnB5, and TRIP steels exhibit good resistance properties. On the contrary, the dissimilar joints encompassing the TWIP steel exhibit poor mechanical strength and fail along the weld seam by intergranular fracture, probably due to presence of Mn segregations. Therefore, the laser welding of TWIP steel with other advanced high strength steels is not recommended without the use of proper metal fillers. Dissimilar laser welding of DP, TRIP and 22MnB5 combinations, on the contrary, can be a solution to assemble car body parts made of these steel grades.

  9. Properties of Galvanized and Galvannealed Advanced High Strength Hot Rolled Steels

    Energy Technology Data Exchange (ETDEWEB)

    V.Y. Guertsman; E. Essadiqi; S. Dionne; O. Dremmailova; R. Bouchard; B. Voyzelle; J. McDermid; R. Fourmentin

    2008-04-01

    The objectives of the project were (i) to develop the coating process information to achieve good quality coatings on 3 advanced high strength hot rolled steels while retaining target mechanical properties, (ii) to obtain precise knowledge of the behavior of these steels in the various forming operations and (iii) to establish accurate user property data in the coated conditions. Three steel substrates (HSLA, DP, TRIP) with compositions providing yield strengths in the range of 400-620 MPa were selected. Only HSLA steel was found to be suitable for galnaizing and galvannealing in the hot rolled condition.

  10. Forming of High-strength Steels Using a Hot-melt Dry Lubricant

    DEFF Research Database (Denmark)

    Hörnström, Sven-Erik; Karlsson, Erik; Olsson, Mikael

    2008-01-01

    with a conventional rust protection oil using four different tests methods, i.e. a strip reduction test, a bending under tension test, a stretch-forming test and a pin-on disc test. In the tests, two different cold work tool steels, a conventional steel grade and a nitrogen alloyed PM steel grade were evaluated...... show that the dry lubricant provides better lubrication and generates less galling than the rust protection oil. Also, the nitrogen alloyed PM steel grade shows a significantly higher galling resistance as compared with the conventional steel grade and can, in combination with a dry lubricant......The increasing use of high strength steels in a variety of mechanical engineering applications has illuminated problems associated with galling in sheet metal forming operations. Galling is a tribological phenomenon associated with transfer of material from the steel sheet to the tool surface...

  11. Evaluation of the cleavage fracture toughness of SA508 Gr. 4N low alloy steels in the transition region

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Min-Chul; Lee, Bong-Sang (Nuclear Material Research Div., Korea Atomic Energy Research Inst., Daejeon (Korea)), e-mail: mckim@kaeri.re.kr; Lee, Ki-Hyoung (Dept. of Materials Science and Engineering, Daejeon (Korea))

    2009-07-01

    In this study, fracture toughness properties of several SA508 Gr.4N model alloys with different alloying elements contents were evaluated in the transition region. Moreover, effects of alloying elements and impurities on the transition properties of SA508 Gr.4N low alloy steels were investigated based on fractographs and micrographs. Fracture toughness tests were conducted following the ASTM standard E1921-05. All toughness data were size-corrected corresponding to those of 1T specimens

  12. Spinnability Investigation of High Strength Steel in Draw-spinning and Flow-spinning

    Science.gov (United States)

    Shi, L.; Xiao, H.; Xu, D. K.

    2017-09-01

    High strength steels are difficult to process in spinning due to their high yield and tensile strength, poor ductility and large springback. In this paper, formability of dual phase steel has been investigated on the basis of spinnability evaluation in draw-spinning and flow-spinning processes. The influences of key process parameters such as feed ratio and wheel fillet radius on forming limit coefficient in draw-spinning and maximum thinning ratio in flow-spinning are studied in detail.

  13. Microstructural Differences in the SCCG, ICCG HAZs of SA 508 Gr. 3 and 4N Low Alloy Steels

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Ki Hyoung; Wee, Dang Moon [KAIST, Advanced High Temperature Materials LAb., Daejeon (Korea, Republic of); Lee, Yoon Sun; Kim, Min Chul; Lee, Bong Sang [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2008-05-15

    Microstructural changes, such as a grain coarsening, carbide precipitation and martensite formation, in the heat-affected zones (HAZ) of low alloy steels as in a nuclear pressure vessel generally occur and induce a deterioration of the toughness and an increase of the sensitivity to brittle fracture. Metallographic analyses of low alloy steel welds reveal considerably different regions in HAZ microstructures. In 2-pass welds, they could be categorized as seven characteristic regions that are determined by the peak temperature in the HAZ during weld thermal cycle: a coarse-grained region, a fine-grained region, an intercritical region, and subcritical region. The coarse-grained region can be categorized into four regions that are determined by the reheating temperature as follows : an unaltered coarse-grained zone (UCGHAZ), a supercritically reheated coarse-grained zone (SCRCGHAZ), an intercritically reheated coarse-grained zone (ICCGHAZ), and an subcritically reheated coarse-grained zone (SCCGHAZ). The purpose of this study is to investigate the differences of the microstructure and mechanical properties in the sub-HAZ of SA508 Gr.3 and 4N low alloy steels. From these results, the cause of a toughness degradation in the ICCG, SCCG HAZs of SA508 Gr. 3 and 4N is discussed.

  14. Fretting fatigue behavior of high-strength steel monostrands under bending load

    DEFF Research Database (Denmark)

    Winkler, Jan; Georgakis, Christos T.; Fischer, Gregor

    2015-01-01

    In this paper, the fretting fatigue behavior of pretensioned high-strength steel monostrands is investigated. To measure the local deformations on the strands, a novel method based on the digital image correlation (DIC) technique was used to quantify the relative movement between individual wires...

  15. Fatigue strength of truss girders made of very high strength steel

    NARCIS (Netherlands)

    Pijpers, R.J.M.; Kolstein, M.H.

    2010-01-01

    An effective application of Very High Strength Steel (VHSS) in civil engineering structures is expected in stiff, truss like structures, typically made of Circular Hollow Sections (CHS). Use of castings in combination with CHS could be promising for the design of highly fatigue resistant joints.

  16. The Effect of Cathodic Protection on Stress Corrosion Cracking of High-Strength Pipeline Steels, #350

    Science.gov (United States)

    2009-12-02

    The objective of this study was to establish the effect of cathodic protection (CP) to produce hydrogen that can cause cracking and in-service failures of high-strength pipeline steels, from X-70 to X-120, and to establish the effectiveness of cathod...

  17. Fatigue strength of repaired cracks in welded connections made of very high strength steels

    NARCIS (Netherlands)

    Akyel, A.

    2017-01-01

    For cyclically loaded structures, fatigue design becomes one of the important design criteria. The state of art shows that with modification of the conventional structural design methodology, the use of very high strength steels may have a positive effect on fatigue strength of welded connections.

  18. Experimental Analysis of the Feasibility of Shaving Process Applied for High-Strength Steel Sheets

    Directory of Open Access Journals (Sweden)

    Wiriyakorn Phanitwong

    2016-01-01

    Full Text Available In recent years, the engineered materials were developed to improve their mechanical properties. A high-strength steel sheet is one of them, developed to serve the requirement of reducing weight of vehicles. Therefore, as a new material, many researches have been carried out to examine the use of sheet metal forming process applied for high-strength steel sheet. However, the feasibility of shaving process applied for it has not been investigated yet. In the present study, this feasibility was revealed by using experiments on two types of high-strength steel sheets: SAPH 440 and SPFH 590Y (JIS. The relationship between shaved surface feature and shearing clearance of high-strength steel sheets corresponded well with those of their conventional metal sheets. However, due to the high ultimate strength of these materials, it was revealed in this present study that there were not any suitable conditions of shaving process that could be applied to achieve the requirements of smooth cut surface overall material thickness.

  19. STRESS CORROSION CRACKING OF ALLOY 152 WELD BUTTER NEAR THE LOW ALLOY STEEL INTERFACE

    Energy Technology Data Exchange (ETDEWEB)

    Alexandreanu, Bogdan; Chen, Yiren; Natesan, Ken; Shack, William J.

    2015-01-01

    The objective of this work was to obtain SCC growth data in Alloy 152 weld butter near the interface with Low Alloy Steel (LAS), which is a region where some dilution of Cr was expected to have occurred, thus presumably exhibiting an increased SCC-susceptibility vs. the bulk of the weld. The LAS piece used in this application was Alloy 533-Gr B from the Midland reactor lower head, and the Alloy 152 weld butter received a prototypical Post Weld Heat Treatment (PWHT) prior to joining by Alloy 152 to an Alloy 690 piece according to a procedure qualified to ASME IX. The compact tension specimens for SCC testing were aligned in the first layer of the Alloy 152 butter. The experimental approach based on tracking environmental enhancement vs. location was successful in identifying SCC-susceptible locations, and SCC rates ranging from 10-12 m/s to as high as 10-10 m/s were measured. The post-test examination of the specimens found that the fracture had the intergranular/interdendritic appearance typical of welds, and that the propagation was arrested wherever an intersection with the LAS occurred. The large range of SCC rates measured does not appear to correlate well with the local concentration of Cr (approx. 25% at the SCC locations), and, in fact, low Cr (20%) – high Fe “streaks” seemed to slow/arrest crack propagation. In short, simple “Cr dilution” does not seem to fully account for the “SCC-susceptible” microstructure that yielded the 10-10 m/s growth rate in this weld.

  20. High strength, low carbon, dual phase steel rods and wires and process for making same

    Science.gov (United States)

    Thomas, Gareth; Nakagawa, Alvin H.

    1986-01-01

    A high strength, high ductility, low carbon, dual phase steel wire, bar or rod and process for making the same is provided. The steel wire, bar or rod is produced by cold drawing to the desired diameter in a single multipass operation a low carbon steel composition characterized by a duplex microstructure consisting essentially of a strong second phase dispersed in a soft ferrite matrix with a microstructure and morphology having sufficient cold formability to allow reductions in cross-sectional area of up to about 99.9%. Tensile strengths of at least 120 ksi to over 400 ksi may be obtained.

  1. Aspects of flexural behavior of high strength concrete elements with or without steel fibers

    Directory of Open Access Journals (Sweden)

    Gheorghe-Alexandru Bărbos

    2013-06-01

    Full Text Available Steel fiber reinforced high strength concrete (SFRHSC is concrete made of hydraulic cements containing fine or fine and coarse aggregate and discontinuous discrete steel fibers. In tension, SFRHSC fails only after the steel fiber breaks or is pulled out of the cement matrix. A more general and current approach to the mechanics of fiber reinforcing assumes a crack arrest mechanism based on fracture mechanics. In this model, the energy to extend a crack and debond the fibers in the matrix relates to the properties of the composite. The designers may best view SFRHSC as a concrete with increased strain capacity, impact resistance, energy absorption, fatigue endurance and tensile strength.

  2. Investigation on Friction and Wear of Cold Rolled High Strength Steel against an AISI52100 Counterpart

    Directory of Open Access Journals (Sweden)

    Jiwon Hur

    2017-03-01

    Full Text Available This article investigates the friction and wear of cold rolled high strength steel at various displacement amplitudes. Reciprocal sliding tests are carried out using a ball-on-flat testing apparatus. The tangential force occurring at the contact surface between a high strength steel specimen and an AISI52100 ball is measured during the tests. After each test, the worn surface profile on the steel specimen is determined. Experimental results show that the ratio of the maximum tangential to the normal force remains at 0.7 after an initial rapid increase, and the ratio does not greatly change according to the imposed displacement amplitudes (in the range of 0.05 mm and 0.3 mm. The wear volume loss on the steel specimen increases according to the number of cycles. It is determined that the wear rate of the specimen changes with respect to the imposed displacement amplitude. That is, the wear rate rapidly increases within the displacement amplitude range of 0.05 mm to 0.09 mm, while the wear rate gradually increases when the displacement amplitude is greater than 0.2 mm. The obtained results provide the friction and wear behaviors of cold rolled high strength steel in fretting and reciprocal sliding regimes.

  3. Influence of laser cutting on the fatigue limit of two high strength steels

    Energy Technology Data Exchange (ETDEWEB)

    Mateo, Antonio; Fargas, Gemma; Calvo, Jessica; Roa, Joan Josep [Univ. Politecnica de Catalunya, Barcelona (Spain). Dept. of Materials Science and Metallurgical Engineering

    2015-02-01

    Laser cutting is widely used in the metal industry, particularly when components of high strength steel sheets are produced. However, the roughness of cut edges produced by laser differs from that obtained by other methods, such as mechanical blanking, and this fact influences the fatigue performance. In the present investigation, specimens of two grades of high strength austenitic steels, i.e. AISI 301LN and TWIP17Mn, were cut by laser and tested in the high cycle fatigue regime to determine their corresponding fatigue limits. A series of fatigue specimens were tested without polishing and other series after a careful polishing of the cut edges, in order to assess the influence of the cut edges condition. Results indicate a significant influence of the edge roughness, more distinctive for AISI 301LN than for TWIP steel.

  4. Comparison of Post Weld Treatment of High Strength Steel Welded Joints in Medium Cycle Fatigue

    DEFF Research Database (Denmark)

    Pedersen, Mikkel Melters; Mouritsen, Ole Ø.; Hansen, Michael Rygaard

    2010-01-01

    the stress range can exceed the yield-strength of ordinary structural steel, especially when considering positive stress ratios (R > 0). Fatigue experiments and qualitative evaluation of the different post-weld treatments leads to the selection of TIG dressing. The process of implementing TIG dressing......This paper presents a comparison of three post-weld treatments for fatigue life improvement of welded joints. The objective is to determine the most suitable post-weld treatment for implementation in mass production of certain crane components manufactured from very high-strength steel....... The processes investigated are: burr grinding, TIG dressing and ultrasonic impact treatment. The focus of this investigation is on the so-called medium cycle area, i.e. 10 000-500 000 cycles and very high stress ranges. In this area of fatigue design, the use of very high strength steel becomes necessary, since...

  5. Master curve characterization of the fracture toughness behavior in SA508 Gr.4N low alloy steels

    Science.gov (United States)

    Lee, Ki-Hyoung; Kim, Min-Chul; Lee, Bong-Sang; Wee, Dang-Moon

    2010-08-01

    The fracture toughness properties of the tempered martensitic SA508 Gr.4N Ni-Mo-Cr low alloy steel for reactor pressure vessels were investigated by using the master curve concept. These results were compared to those of the bainitic SA508 Gr.3 Mn-Mo-Ni low alloy steel, which is a commercial RPV material. The fracture toughness tests were conducted by 3-point bending with pre-cracked charpy (PCVN) specimens according to the ASTM E1921-09c standard method. The temperature dependency of the fracture toughness was steeper than those predicted by the standard master curve, while the bainitic SA508 Gr.3 steel fitted well with the standard prediction. In order to properly evaluate the fracture toughness of the Gr.4N steels, the exponential coefficient of the master curve equation was changed and the modified curve was applied to the fracture toughness test results of model alloys that have various chemical compositions. It was found that the modified curve provided a better description for the overall fracture toughness behavior and adequate T0 determination for the tempered martensitic SA508 Gr.4N steels.

  6. Master curve characterization of the fracture toughness behavior in SA508 Gr.4N low alloy steels

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Ki-Hyoung, E-mail: shirimp@kaist.ac.k [Department of Materials Science and Engineering, KAIST, Daejeon 305-701 (Korea, Republic of); Kim, Min-Chul; Lee, Bong-Sang [Nuclear Materials Research Division, KAERI, Daejeon 305-353 (Korea, Republic of); Wee, Dang-Moon [Department of Materials Science and Engineering, KAIST, Daejeon 305-701 (Korea, Republic of)

    2010-08-15

    The fracture toughness properties of the tempered martensitic SA508 Gr.4N Ni-Mo-Cr low alloy steel for reactor pressure vessels were investigated by using the master curve concept. These results were compared to those of the bainitic SA508 Gr.3 Mn-Mo-Ni low alloy steel, which is a commercial RPV material. The fracture toughness tests were conducted by 3-point bending with pre-cracked charpy (PCVN) specimens according to the ASTM E1921-09c standard method. The temperature dependency of the fracture toughness was steeper than those predicted by the standard master curve, while the bainitic SA508 Gr.3 steel fitted well with the standard prediction. In order to properly evaluate the fracture toughness of the Gr.4N steels, the exponential coefficient of the master curve equation was changed and the modified curve was applied to the fracture toughness test results of model alloys that have various chemical compositions. It was found that the modified curve provided a better description for the overall fracture toughness behavior and adequate T{sub 0} determination for the tempered martensitic SA508 Gr.4N steels.

  7. Fatigue crack initiation in carbon and low-alloy steels in light water reactor environments : mechanism and prediction.

    Energy Technology Data Exchange (ETDEWEB)

    Chopra, O. K.; Shack, W. J.

    1998-01-27

    Section 111 of the ASME Boiler and Pressure Vessel Code specifies fatigue design curves for structural materials. The effects of reactor coolant environments are not explicitly addressed by the Code design curves. Recent test data illustrate potentially significant effects of light water reactor (LWR) coolant environments on the fatigue resistance of carbon and low-alloy steels. Under certain loading and environmental conditions, fatigue lives of test specimens may be shorter than those in air by a factor of {approx}70. The crack initiation and crack growth characteristics of carbon and low-alloy steels in LWR environments are presented. Decreases in fatigue life of these steels in high-dissolved-oxygen water are caused primarily by the effect of environment on growth of short cracks < 100 {micro}m in depth. The material and loading parameters that influence fatigue life in LWR environments are defined. Fatigue life is decreased significantly when five conditions are satisfied simultaneously, viz., applied strain range, service temperature, dissolved oxygen in water, and S content in steel are above a threshold level, and loading strain rate is below a threshold value. Statistical models have been developed for estimating the fatigue life of these steels in LWR environments. The significance of the effect of environment on the current Code design curve is evaluated.

  8. Master curve analysis of the SA508 Gr. 4N Ni-Mo-Cr low alloy steels for reactor pressure vessels

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Ki Hyoung; Wee, Dang Moon [KAIST, Daejeon (Korea, Republic of); Kim, Min Chul; Lee, Bong Sang [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2009-10-15

    Low alloy steels used as Reactor Pressure Vessels (RPVs) materials directly relate to the safety margin and the life span of reactors. Currently, SA508 Gr.3 low alloy steel is generally used for RPV material. But, for larger capacity and long-term durability of RPV, materials that have better properties including strength and toughness are needed. Therefore, tempered martensitic SA508 Gr.4N low alloy steel is considered as a candidate material due to excellent mechanical properties. The fracture toughness loss caused by irradiation embrittlement during reactor operation is one of the important issues for ferritic RPV steels, because the decrease of fracture toughness is directly related to the integrity of RPVs. One reliable and efficient concept to evaluate the fracture toughness of ferritic steels is master curve method. In ASTM E1921, it is clearly mentioned the universal shape of the median toughness-temperature curve for ferritic steels including tempered martensitic steels. However, currently, concerns have arisen regarding the appropriateness of the universal shape in ASTM for the tempered martensitic steels such as Eurofer97. Therefore, it may be necessary to assess the master curve applicability for the tempered martensitic SA508 Gr.4N low alloy steel. In this study, the fracture toughness behavior with temperature of the tempered martensitic SA508 Gr.4N low alloy steels was evaluated using the ASTM E1921 master curve method. And the results were compared with those of the bainitic SA508 Gr.3 low alloy steel. Furthermore, the way to define the fracture toughness behavior of Gr.4N steels well is discussed.

  9. TIG-dressing of High Strength Steel Butt Welded Connections. Part 1 : Weld Toe Geometry and Local Hardness

    NARCIS (Netherlands)

    Van Es, S.H.J.; Kolstein, M.H.; Pijpers, R.J.M.; Bijlaard, F.S.K.

    2014-01-01

    This paper presents the results of extensive measurements on weld toe geometry of as-welded and TIG-dressed butt welded connections in high strength steels S460, S690 and very high strength steels S890 and S1100. Descriptions of the measurement techniques and data analysis are presented. Four weld

  10. TIG-dressing of high strength steel butt welded connections - Part 1: weld toe geometry and local hardness

    NARCIS (Netherlands)

    Es, S.H.J. van; Kolstein, M.H.; Pijpers, R.J.M.; Bijlaard, F.S.K.

    2013-01-01

    This paper presents the results of extensive measurements on weld toe geometry of as-welded and TIG-dressed butt welded connections in high strength steels S460, S690 and very high strength steels S890 and S1100. Descriptions of the measurement techniques and data analysis are presented. Four weld

  11. Properties of Fresh and Hardened High Strength Steel Fibres Reinforced Self-Compacted Concrete

    Directory of Open Access Journals (Sweden)

    Saad Ali Al-Ta'an

    2016-10-01

    Full Text Available Fresh and hardened properties of high strength steel fibrous self-compacted concrete were studied in this investigation. One reference high strength self-compacted concrete mix is used, with five percent (by weight of cement silica fume and eight percent of the cement replaced by limestone powder. Three steel fibres percentages by volume of concrete are used (0.4, 0.8, and 1.2. The used steel fibres were a shelled Harex type with irregular cross-section, equivalent diameter of 0.9278 mm, and 32 mm long. Super plasticizer was used to improve the workability and flow ability of the mixes. The test results showed that the presence of steel fibres decrease the flow ability, and increase the time of spreading, segregation, and passing ability of the fresh concrete. For the fibres percentages used, the fresh properties were within the recommended specifications for the self-compacted concrete. The test results showed an early strength development rate more than that for plain normal concrete due to the presence of the fine materials. As for normal concrete, the test results showed also that the increase in the splitting strength is more than the increase in the compressive strength due to the presence of the steel fibres. The brittle mode of failure of the plain unreinforced specimens changed to a ductile one due to the presence of the steel fibres.

  12. Effects of alloying element contents on the toughness and transition behavior in the SA508 Gr. 4N Ni-Mo-Cr low alloy steels

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Ki Hyoung; Park, Sang Gyu; Wee, Dang Moon [KAIST, Daejeon (Korea, Republic of); Kim, Min Chul; Lee, Bong Sang [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2009-05-15

    Low alloy steels used as materials for reactor pressure vessels (RPVs) determine the safety and the life span of reactors. Currently, SA508 Gr.3 low alloy steel is generally used for RPV materials. But, for larger capacity and long-term durability of the next generation RPVs, materials that have much better properties are needed, such as strength, toughness and irradiation resistance. SA508 Gr.4N low alloy steel shows good mechanical properties due to high Ni and Cr contents in comparison with the currently used reactor pressure vessel steels. Materials for RPVs suffer a decrease of toughness due to an embrittlement of the materials by neutron irradiation, especially in ferritic steels. This toughness loss causes an increase in the transition temperature, and then a brittle fracture could occur. Therefore, for an integrity assessment of low alloy steels as RPVs, an accurate evaluation of the transition behavior is needed, such as fracture and impact toughness. In this study, the toughness and transition behavior of SA 508 Gr.4N low alloy steels, which have different Ni, Cr and Mo, were evaluated in the transition region. And the applicability of the test results for Master-Curve method was assessed. Additionally, differences between influences of alloying elements contents on Charpy impact toughness and fracture toughness were discussed in terms of microstructural features.

  13. An investigation of the properties of conventional and severe shot peened low alloy steel

    Science.gov (United States)

    Quang Trung, Pham; Butler, David Lee; Win Khun, Nay

    2017-07-01

    The effects of the conventional shot peening and severe shot peening process on the mechanical and tribological properties of shot peened AISI 4340 high strength steel were systematically investigated. Compared with the conventional shot peened sample, the ultrafine grain surface layer with a depth of about 20 µm generated by the severe shot peening process can enhance the hardness and wear resistance of the treated material. However, deeper dimples generated by the high media velocity in the severe shot peening process resulted in a higher surface roughness, which is considered as a side effect of this method reducing the fatigue life of the material. Applying a smaller shot size with an appropriate intensity can be used to peen the severe shot peened samples to not only reduce the surface roughness and friction coefficient but also improve the wear resistance for these samples. This work was presented in the shot peening section during ‘The 30th International Conference on Surface Modification Technologies, 2016, Milan, Italy’ (SMT30, ID 61, entitled ‘Comparison of the effects of conventional shot peening and severe shot peening processes on the mechanical and tribological properties of shot peened AISI 4340’) and the authors were encouraged to submit a manuscript to the Materials Research Express journal after adding some nessesary information.

  14. Study on the strength characteristics of High strength concrete with Micro steel fibers

    Science.gov (United States)

    Gowdham, K.; Sumathi, A.; Saravana Raja Mohan, K.

    2017-07-01

    The study of High Strength Concrete (HSC) has become interesting as concrete structures grow taller and larger. The usage of HSC in structures has been increased worldwide and has begun to make an impact in India. Ordinary cementitious materials are weak under tensile loads and fiber reinforced cementitious composites (FRCCs) have been developed to improve this weak point. High Strength concrete containing Alccofine as mineral admixture and reinforced with micro steel fibers were cast and tested to study the mechanical properties. The concrete were designed to have compressive strength of 60 MPa. Mixtures containing 0% and 10% replacement of cement by Alccofine and with 1%, 2% and 3% of micro steel fibers by weight of concrete were prepared. Mixtures incorporating Alccofine with fibers developed marginal increase in strength properties at all curing days when compared to control concrete.

  15. Research on the Optimal Layout of High-strength Steel in the Transmission Tower

    Science.gov (United States)

    Chunming, W. EI.; Tingting, S. U.; Bin, M. A.; Jing, Gong

    In order to research on the arrangement way of high-strength steel in ultrahigh voltage transmission towers, the integrated structure and material multi-objective optimization model of ultrahigh voltage transmission towers was established, and the optimization model is solved by using fast non-dominated sorting genetic algorithm (NSGA-II). Sectional areas and materials of each bar were regarded as the design variables, the structural min-cost was considered as the objective of the economic optimization, and the min-displacement of the control point was regarded as the objective of structural optimization. Based on the software MATLAB, relevant optimization program was programmed to solve the optimization model. The results show, the optimal results can satisfy the structural requirements and reduce the cost of projects, making the arrangement way of high-strength steel way in ultrahigh voltage transmission towers more reasonable and more economical.

  16. Manufacturing of High-Strength and High-Ductility Pearlitic Steel Wires Using Noncircular Drawing Sequence

    Energy Technology Data Exchange (ETDEWEB)

    Baek, Hyun Moo; Joo, Ho Seon; Im, Yong-Taek [KAIST, Daejeon (Korea, Republic of); Hwang, Sun Kwang [KITECH, Cheonan (Korea, Republic of); Son, Il-Heon; Bae, Chul Min [POSCO, Pohang (Korea, Republic of)

    2014-07-15

    In this study, a noncircular drawing (NCD) sequence for manufacturing high-strength and high-ductility pearlitic steel wires was investigated. Multipass NCD was conducted up to the 12th pass at room temperature with two processing routes (defined as the NCDA and NCDB), and compared with the wire drawing (WD). During the torsion test, delamination fracture in the drawn wire was observed in the 10th pass of the WD whereas it was not observed until the 12th pass of the NCDB. From X-ray diffraction, the circular texture component that increases the likelihood of delamination fracture of the drawn wire was rarely observed in the NCDB. Thus, the improved ability of the multipass NCDB to manufacture high-strength pearlitic steel wires with high torsional ductility compared to the WD (by reducing the likelihood of delamination fracture) was demonstrated.

  17. High strength oil palm shell concrete beams reinforced with steel fibres

    OpenAIRE

    Poh-Yap, S.; Johnson-Alengaram, U.; Hung-Mo, K.; Zamin-Jumaat, M.

    2017-01-01

    The utilization of lightweight oil palm shell to produce high strength lightweight sustainable material has led many researchers towards its commercialization as structural concrete. However, the low tensile strength of Oil Palm Shell Concrete (OPSC) has hindered its development. This study aims to enhance the mechanical properties and flexural behaviours of OPSC by the addition of steel fibres of up to 3% by volume, to produce oil palm shell fibre-reinforced concrete (OPSFRC). The experiment...

  18. Effects of boundary characteristics on resistance to temper embrittlement and segregation behavior of Ni-Cr-Mo low alloy steel

    Energy Technology Data Exchange (ETDEWEB)

    Park, Sang-Gyu; Lee, Ki-Hyoung [Nuclear Materials Research Division, Korea Atomic Energy Research Institute, Daedeok-daero 989-111, Yuseong-gu, Daejeon 305-353 (Korea, Republic of); Kim, Min-Chul, E-mail: mckim@kaeri.re.kr [Nuclear Materials Research Division, Korea Atomic Energy Research Institute, Daedeok-daero 989-111, Yuseong-gu, Daejeon 305-353 (Korea, Republic of); Lee, Bong-Sang [Nuclear Materials Research Division, Korea Atomic Energy Research Institute, Daedeok-daero 989-111, Yuseong-gu, Daejeon 305-353 (Korea, Republic of)

    2013-01-20

    SA508 Gr.4N Ni-Cr-Mo low alloy steel has higher strength and fracture toughness than those of commercial SA508 Gr.3 low alloy steel, due to its tempered martensitic microstructure as well as the solid solution effect and its higher contents of Ni and Cr. Hence, several studies have been performed on SA508 Gr.4N for nuclear application. In this study, the effects of microstructure on temper embrittlement and segregation behaviors in Ni-Cr-Mo low alloy steel were evaluated from the viewpoint of grain boundary characteristics. To evaluate the microstructural effect while excluding chemistry effects, the same heat was used but different microstructure samples were prepared by changing the cooling rate after austenitization. The increased volume fraction of martensite reduces the resistance to temper embrittlement, showing an increased transition-temperature shift (TTS) and increased P segregation at prior austenite boundaries. The segregation occurred intensively at prior austenite grain boundaries in tempered martensite, while the segregation occurred simultaneously at both prior austenite boundaries and packet boundaries in tempered bainite. In the EBSD results, most of the packet boundaries in tempered martensite are special boundaries such as N-Ary-Summation 3 coincident site lattice (CSL) boundaries. The differences in P segregation between tempered martensite and tempered bainite are mainly caused by different portions of low energy special boundaries among the sub-grain boundaries. The reduction of temper embrittlement resistance in tempered martensite could be explained by the increased fraction of low energy CSL boundaries, which leads to a concentrated segregation of P at prior austenite grain boundaries.

  19. Analysis of local warm forming of high strength steel using near infrared ray energy

    Science.gov (United States)

    Yang, W. H.; Lee, K.; Lee, E. H.; Yang, D. Y.

    2013-12-01

    The automotive industry has been pressed to satisfy more rigorous fuel efficiency requirements to promote energy conservation, safety features and cost containment. To satisfy this need, high strength steel has been developed and used for many different vehicle parts. The use of high strength steels, however, requires careful analysis and creativity in order to accommodate its relatively high springback behavior. An innovative method, called local warm forming with near infrared ray, has been developed to help promote the use of high strength steels in sheet metal forming. For this method, local regions of the work piece are heated using infrared ray energy, thereby promoting the reduction of springback behavior. In this research, a V-bend test is conducted with DP980. After springback, the bend angles for specimens without local heating are compared to those with local heating. Numerical analysis has been performed using the commercial program, DEFORM-2D. This analysis is carried out with the purpose of understanding how changes to the local stress distribution will affect the springback during the unloading process. The results between experimental and computational approaches are evaluated to assure the accuracy of the simulation. Subsequent numerical simulation studies are performed to explore best practices with respect to thermal boundary conditions, timing, and applicability to the production environment.

  20. Dynamic reverse phase transformation induced high-strain-rate superplasticity in low carbon low alloy steels with commercial potential.

    Science.gov (United States)

    Cao, Wenquan; Huang, Chongxiang; Wang, Chang; Dong, Han; Weng, Yuqing

    2017-08-23

    Superplastic materials are capable of exhibiting large tensile elongation at elevated temperature, which is of great industrial significance because it forms the basis of a fabrication method to produce complex shapes. Superplasticity with elongation larger than 500% has been widely realized in many metals and alloys, but seldomly been succeeded in low carbon low alloy steel, even though it is commercially applied in the largest quantity. Here we report ultrahigh superplastic elongation of 900-1200% in the FeMnAl low carbon steels at high strain rate of 10-2-10-3 s-1. Such high-strain-rate superplasticity was attributed to dynamic austenite reverse phase transformation from a heavily cold rolled ferrite to fine-grained ferrite/austenite duplex microstructure and subsequent limited dynamic grain coarsening, under which a large fraction of high angle boundaries can be resulted for superplastic deformation. It is believed that this finding of the low carbon low alloy steel with ultrahigh superplasticity and relative low cost would remarkably promote the application of superplastic forming technique in automobile, aeronautical, astronautical and other fields.

  1. Effects of LWR coolant environments on fatigue S-N curves for carbon and low-alloy steels

    Energy Technology Data Exchange (ETDEWEB)

    Chopra, O.K.; Shack, W.J.

    1996-06-01

    The ASME Boiler and Pressure Vessel Code provides rules for the construction of nuclear power plant components. Figure I-90 of Appendix I to Section III of the Code specifies fatigue design curves for structural materials. However, the effects of light water reactor (LWR) coolant environments are not explicitly addressed by the Code design curves. Recent test data indicate significant decreases in fatigue lives of carbon and low-alloy steels in LWR environments when five conditions are satisfied simultaneously: applied strain range, temperature, dissolved oxygen in the water, and S content of the steel are above minimum threshold levels, and loading strain rate is below a threshold value. Only moderate decrease in fatigue life is observed when any one of these conditions is not satisfied. This paper presents several methods that have been proposed for evaluating the effects of LWR coolant environments on fatigue S-N curves for carbon and low-alloy steels. Estimations of fatigue lives under actual loading histories are discussed.

  2. Development of a test method for determining the cracking susceptibility of resistance spot welded high strength steel sheets

    OpenAIRE

    Rethmeier, Michael; Suwala, Hubert

    2014-01-01

    In this study a test method for determining the cracking susceptibility of resistance spot welded high strength steel sheets was investigated. The development of a suitable test procedure is based on the External-Loaded Hot Crack Test (PVC-Test). The test modification for resistance spot welding contains a constant tensile force load. The test method for determining the cracking susceptibility was experimentally verified for a high strength steel, a transformation induced plasticity steel (TR...

  3. Analysis of thermal cycles and microstructure of heat affected zone for a low alloy carbon steel pipe under multipass weld

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Tae Woan; Ha, Joon Wook; Kim, Dong Jin; Kim, Jeong Tae [Doosan Heavy Industries and Construction Co., Ltd., Changwon (Korea, Republic of)

    2002-03-01

    The purpose of this study is to analyze thermal cycles and to investigate microstructures of heat affected zones for a low alloy carbon steel pipe under a multipass weld. The commercial finite element code SYSWELD is used to compute thermal cycles during multipass weld. The numerical results such as thermal cycles and size of heat affected zone are compared with those of the experiment and the two results show a good agreement. In addition, the microstructure and hardness and investigated from the weldment in detail. The weakest location is founded at intercritical region near the base metal.

  4. Ductile-Brittle Transition Behavior in Tempered Martensitic SA508 Gr. 4N Ni-Mo-Cr Low Alloy Steels for Reactor Pressure Vessels

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Ki Hyoung; Wee, Dang Moon [KAIST, Daejeon (Korea, Republic of); Kim, Min Chul; Lee, Bong Sang [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2010-05-15

    Reactor pressure vessels (RPVs) operate under severe conditions of elevated temperature, high pressure, and irradiation. Therefore, a combination of sufficient strength, toughness, good weldability, and high irradiation resistance are required for RPV materials. SA508 Gr.4N low alloy steel, which has higher Ni and Cr contents than those of commercial RPV steel, Gr.3 steel, is considered as a candidate material due to its excellent mechanical properties from tempered martensitic microstructure. The ferritic steels such as Gr.3 and Gr.4N low alloy steels reveal a ductile-brittle transition and large scatters in the fracture toughness within a small temperature range. Recently, there are some observations of the steeper transition behavior in the tempered martensitic steels, such as Eurofer97 than the transition behavior of commercial RPV steels. It was also reported that the fracture toughness increased discontinuously when the phase fraction of the tempered martensite was over a critical fraction in the heat affected zones of SA508 Gr.3. Therefore, it may be necessary to evaluate the changes of transition behavior with a microstructure for the tempered martensitic SA508 Gr.4N low alloy steel. In this study, the fracture toughness for SA508 Gr.4N low alloy steels was evaluated from a view point of the temperature dependency with phase fraction of tempered martensite controlled by cooling rate. Additionally, a possible modification of the fracture toughness master curve was proposed and discussed

  5. Hydrogen induced cracking tests of high strength steels and nickel-iron base alloys using the bolt-loaded specimen

    Energy Technology Data Exchange (ETDEWEB)

    Vigilante, G.N.; Underwood, J.H.; Crayon, D.; Tauscher, S.; Sage, T.; Troiano, E. [Army Armament RD and E Center, Watervliet, NY (United States). Benet Labs.

    1997-12-31

    Hydrogen induced cracking tests were conducted on high strength steels and nickel-iron base alloys using the constant displacement bolt-loaded compact specimen. The bolt-loaded specimen was subjected to both acid and electrochemical cell environments in order to produce hydrogen. The materials tested were A723, Maraging 200, PH 13-8 Mo, Alloy 718, Alloy 706, and A286, and ranged in yield strength from 760--1400 MPa. The effects of chemical composition, refinement, heat treatment, and strength on hydrogen induced crack growth rates and thresholds were examined. In general, all high strength steels tested exhibited similar crack growth rates and thresholds were examined. In general, all high strength steels tested exhibited similar crack growth rates and threshold levels. In comparison, the nickel-iron base alloys tested exhibited up to three orders of magnitude lower crack growth rates than the high strength steels tested. It is widely known that high strength steels and nickel base alloys exhibit different crack growth rates, in part, because of their different crystal cell structure. In the high strength steels tested, refinement and heat treatment had some effect on hydrogen induced cracking, though strength was the predominant factor influencing susceptibility to cracking. When the yield strength of one of the high strength steels tested was increased moderately, from 1130 MPa to 1275 MPa, the incubation times decreased by over two orders of magnitude, the crack growth rates increased by an order of magnitude, and the threshold stress intensity was slightly lower.

  6. Prospective high strength steel utilizing TRIP effect; Hentai yuki sosei koka wo riyoshita jisedai kokyodo usukoban

    Energy Technology Data Exchange (ETDEWEB)

    Sakuma, Y.; Kimura, N.; Itami, a.; Hiwatashi, S.; Kawano, O.; Sakata, K. [Nippon Steel Corp., Tokyo (Japan)

    1994-11-29

    The transformation induced plasticity (TRIP) means the large extension of chemically unstable austenitic {gamma} phase when it is transformed into martensite by the addition of dynamic energy. The application of TRIP effect is promising to the auto-body use steel plate because thin stainless steel plates excelling in bulging properties are producible. The present paper explained the enlarging mechanism of elongation, principle of production, examples of production on the actual line, formability, weldability and fatigue durability. Than that of the different conventional steel plates, a better combination of both strength and elongation was recorded through the actual line trial production of cold and hot rolled steel plates which were 590 to 980N/mm{sup 2} in tensile strength. Their apparent superiority in bulging properties was confirmed in the vicinity of plain strain, while their deep drawability was also known to be good through a TZP test. The presently developed steel excelled the conventional high-strength steel in strength at spot welding, while its fatigue strength was higher even than that of the dual-phase steel so far regarded as the best in it. 13 refs., 12 figs., 4 tabs.

  7. On the performance of circular concrete-filled high strength steel columns under axial loading

    Directory of Open Access Journals (Sweden)

    Mohamed Mahmoud El-Heweity

    2012-06-01

    Full Text Available This work presents a numerical study to investigate the performance of circular high-strength steel tubes filled with concrete (CFT under monotonic axial loading. A model is developed to implement the material constitutive relationships and non-linearity. Calibration against previous experimental data shows good agreement. A parametric study is then conducted using the model and compared with codes provisions. Strength and ductility of confined concrete are of primary concern. Variables considered are yield stress of steel tube and column diameter. The assessment of column performance is based on axial load carrying capacities and enhancements of both strength and ductility due to confinement. Two parameters namely strength enhancement factor (Kf and ductility index (μ are clearly defined and introduced for assessment. Results indicate that both concrete strength and ductility of CFT columns are enhanced but to different extents. The ductile behaviors are significantly evident. The increase in yield stress of steel tube has a minimal effect on concrete strength but pronounced effect on concrete ductility. However, reduction in ductility is associated with using high-tensile steel of Grade 70. The overall findings indicate that the use of high-strength tube in CFT columns is not promising. This finding may seriously be considered in seismic design.

  8. Surface characteristics and mechanical properties of high-strength steel wires in corrosive conditions

    Science.gov (United States)

    Xu, Yang; Li, Shunlong; Li, Hui; Yan, Weiming

    2013-04-01

    Cables are always a critical and vulnerable type of structural components in a long-span cable-stayed bridge in normal operation conditions. This paper presents the surface characteristics and mechanical performance of high-strength steel wires in simulated corrosive conditions. Four stress level (0MPa, 300MPa, 400MPa and 500MPa) steel wires were placed under nine different corrosive exposure periods based on the Salt Spray Test Standards ISO 9227:1990. The geometric feathers of the corroded steel wire surface were illustrated by using fractal dimension analysis. The mechanical performance index including yielding strength, ultimate strength and elastic modulus at different periods and stress levels were tested. The uniform and pitting corrosion depth prediction model, strength degradation prediction model as well as the relationship between strength degradation probability distribution and corrosion crack depth would be established in this study.

  9. Segregation Behaviour of Third Generation Advanced High-Strength Mn-Al Steels

    Directory of Open Access Journals (Sweden)

    A. Grajcar

    2012-04-01

    Full Text Available The paper addresses the macro- and microsegregation of alloying elements in the new-developed Mn-Al TRIP steels, which belong to the third generation of advanced high-strength steels (AHSS used in the automotive industry. The segregation behaviour both in the as-cast state and after hot forging was assessed in the macro scale by OES and by EDS measurements in different structural constituents. The structural investigations were carried out using light and scanning electron microscopy. A special attention was paid to the effect of Nb microaddition on the structure and the segregation of alloying elements. The tendency of Mn and Al to macrosegregation was found. It is difficult to remove in Nb-free steels. Microsegregation of Mn and Al between austenite and ferritic structural constituents can be removed.

  10. Effects of thermal aging on microstructures of low alloy steel-Ni base alloy dissimilar metal weld interfaces

    Science.gov (United States)

    Choi, Kyoung Joon; Kim, Jong Jin; Lee, Bong Ho; Bahn, Chi Bum; Kim, Ji Hyun

    2013-10-01

    In this study, the advanced instrumental analysis has been performed to investigate the effect of long-term thermal aging on the microstructural evolution in the fusion boundary region between weld metal and low alloy steel in dissimilar metal welds. A representative dissimilar weld mock-up made of Alloy 690-Alloy 152-A533 Gr. B was fabricated and aged at 450 °C for 2750 h. The micro- and nano-scale characterization were conducted mainly near in a weld root region by using optical microscopy, scanning electron microscopy, transmission electron microscopy, and three dimensional atom probe tomography. It was observed that the weld root was generally divided into several regions including dilution zone in the Ni-base alloy weld metal, fusion boundary, and heat-affected zone in the low alloy steel. A steep gradient was shown in the chemical composition profile across the interface between A533 Gr. B and Alloy 152. The precipitation of carbides was also observed along and near the fusion boundary of as-welded and aged dissimilar metal joints. It was also found that the precipitation of Cr carbides was enhanced by the thermal aging near the fusion boundary.

  11. Investigation of the Failure of Advanced High Strength Steels Heterogeneous Spot Welds

    Directory of Open Access Journals (Sweden)

    Thibaut Huin

    2016-05-01

    Full Text Available Nowadays, environmental regulation encourages carmakers to reduce the global vehicle weight. Steelmakers develop grades with high performance (Advanced High Strength Steels, AHSS and fine steel sheet assemblies are used in car body structures, with an optimized thickness in each part. However, unusual fracture modes are sometimes observed during the mechanical tests of heterogeneous AHSS welds, made of dissimilar steel grades and sheet thicknesses. Weld fractures can occur with a strength lower than expected. This study aims at understanding these fracture mechanisms and focuses on two common steel grades joined by Resistance Spot Welding (RSW: DP600 (a dual phase steel and Usibor®1500 (a martensitic steel. The parameters affecting the failure modes and load bearing capacity are investigated during two common types of tests: the Cross Tension and Tensile Shear tests. The positive effects of heterogeneous welding with respect to the corresponding homogeneous configurations are discussed, as well as the consequences of a so-called Dome failure occurring at the weld nugget boundary.

  12. A numerical study on the mechanical properties and the processing behaviour of composite high strength steels

    Energy Technology Data Exchange (ETDEWEB)

    Muenstermann, Sebastian [RWTH Aachen (Germany). Dept. of Ferrous Metallurgy; Vajragupta, Napat [RWTH Aachen (Germany). Materials Mechanics Group; Weisgerber, Bernadette [ThyssenKrupp Steel Europe AG (Germany). Patent Dept.; Kern, Andreas [ThyssenKrupp Steel Europe AG (Germany). Dept. of Quality Affairs

    2013-06-01

    The demand for lightweight construction in mechanical and civil engineering has strongly promoted the development of high strength steels with excellent damage tolerance. Nowadays, the requirements from mechanical and civil engineering are even more challenging, as gradients in mechanical properties are demanded increasingly often for components that are utilized close to the limit state of load bearing capacity. A metallurgical solution to this demand is given by composite rolling processes. In this process components with different chemical compositions were jointed, which develop after heat treatment special properties. These are actually evaluated in order to verify that structural steels with the desired gradients in mechanical properties can be processed. A numerical study was performed aiming to numerically predict strenght and toughness properties, as well as the procesing behaviour using Finite Element (FE) simulations with damage mechanics approaches. For determination of mechanical properties, simulations of tensile specimen, SENB sample, and a mobile crane have been carried out for different configurations of composite rolled materias out of high strebght structural steels. As a parameter study, both the geometrical and the metallurgical configurations of the composite rolled steels were modified. Thickness of each steel layer and materials configuration have been varied. Like this, a numerical procedure to define optimum tailored configurations of high strenght steels could be established.

  13. Corrosion of Steel in High-Strength Self-Compacting Concrete Exposed to Saline Environment

    Directory of Open Access Journals (Sweden)

    Hana A. Yousif

    2014-01-01

    Full Text Available A research work was carried out to investigate the effectiveness of high-strength self-compacting concrete (SF-R in controlling corrosion of embedded steel. Reinforced concrete cylinders and plain cubes were subjected to 5% NaCl solution. Slump flow, J-ring, V-funnel, compressive strength, electrical resistance, and electrochemical tests were conducted. Corrosion resisting characteristics of steel were examined by monitoring corrosion potential, polarization resistance, corrosion currents, and Tafel plots. The relationship between corrosion current density and corrosion potential was established. Results were compared with characteristics of a grade 40 MPa reference concrete (R and grade 70 MPa conventional self-compacting concrete (SP. Results indicated that at 270 days of exposure, the corrosion currents for steel in SF-R were 63- and 16-fold lower compared to those of steel in R and SP concretes, respectively. This concrete showed a considerable increase in electrical resistance and compressive strength of 96 MPa at 28 days of exposure. Relying on corrosion risk classification based on corrosion current densities and corrosion potentials, the steel in SF-R concrete is definitely in the passive condition. The splendid durability performance of steel in SF-R concrete linked to adorable self-compacting features could furnish numerous opportunities for future structural applications in severe environmental conditions.

  14. Influence of steel fibers on the shear and flexural performance of high-strength concrete beams tested under blast loads

    Science.gov (United States)

    Algassem, O.; Li, Y.; Aoude, H.

    2017-09-01

    This paper presents the results of a study examining the effect of steel fibres on the blast behaviour of high-strength concrete beams. As part of the study, a series of three large-scale beams built with high-strength concrete and steel fibres are tested under simulated blast loading using the shock-tube testing facility at the University of Ottawa. The specimens include two beams built with conventional high-strength concrete (HSC) and one beam built with high-strength concrete and steel fibres (HSFRC). The effect of steel fibres on the blast behaviour is examined by comparing the failure mode, mid-span displacements and, overall blast resistance of the specimens. The results show that the addition of steel fibres in high-strength concrete beams can prevent shear failure and substitute for shear reinforcement if added in sufficient quantity. Moreover, the use of steel fibres improves flexural response under blast loading by reducing displacements and increasing blast capacity. Finally, the provision of steel fibres is found to improve the fragmentation resistance of high-strength concrete under blast loads.

  15. Testing new tribo-systems for sheet metal forming of advanced high strength steels and stainless steels

    DEFF Research Database (Denmark)

    Bay, Niels; Ceron, Ermanno

    2014-01-01

    Testing of new tribo-systems in sheet metal forming has become an important issue due to new legislation, which forces industry to replace current, hazardous lubricants. The present paper summarizes the work done in a recent PhD project at the Technical University of Denmark on the development...... of a methodology for off-line testing of new tribo-systems for advanced high strength steels and stainless steels. The methodology is presented and applied to an industrial case, where different tribo-systems are tested. A universal sheet tribotester has been developed, which can run automatically repetitive...

  16. Influence of different cyclic intercritical heat treatment schedules on the microstructure and mechanical behaviour of a medium carbon low alloy steel

    Directory of Open Access Journals (Sweden)

    K. K. Alaneme

    2013-06-01

    Full Text Available In the present research, the prospect of optimizing high strength and formability in medium carbon low alloy steel via different cyclic intercritical treatment procedures was investigated. Three intercritical treatment schedules (Route A - cyclic intercritical annealing only, Route B - cold rolling followed by cyclic intercritical annealing, and Route C - cyclic cold rolling and intercritical annealing operations performed at 770o C were utilized in this research work. For each treatment route, a maximum of three heating cycles was used. Microstructural examination, hardness measurement and tensile properties evaluation were used as basis to assess the mechanical behaviour of the dual phase structures produced. The results show that for Route A and B, grain refinement and homogeneous distribution of ferrite and martensite was obtained for specimens subjected to two cycles of intercritical annealing. This resulted in peak strength, toughness and hardness in comparison to specimens subjected to one or three cycles of intercritical annealing. For Route C, the same properties were impoverished with increase in intercritical annealing cycles. The best combination of hardness, strength, toughness and strain to fracture was achieved with the use of an initial cold rolling and two cycles of intercritical annealing at 770o C.

  17. Effect of Q&P heat treatment on fine microstructure and mechanical properties of a low-alloy medium-carbon steel

    Science.gov (United States)

    Jafari, Rahim; Kheirandish, Shahram; Mirdamadi, Shamsoddin

    2018-01-01

    The current research investigates the effect of ultrafine microstructure resulted from Quench and Partitioning (Q&P) process on obtaining ultra-high strengths in a low-alloy steel with 4wt.% carbon. The purpose of Q&P heat treatment is to enrich the austenite with carbon by partitioning of carbon from supersaturated martensite to austenite, in order to stabilize it to the room temperature. The microstructure, consequently, is consists of martensite, retained austenite and in some conditions bainite. Two-step Q&P heat treatment with quench and partitioning temperatures equal to 120°C and 300°C respectively were applied to the samples at different times. Mechanical behavior was studied by tensile test. The microstructure of the samples was observed using SEM, and TEM and to quantify the amount of retained austenite X-ray diffraction was used. The retained austenite grain size was estimated to be about 0.5 µm and the highest amount of retained austenite obtained was 10 vol%. All samples showed a yield strength and a tensile strength of above 900MPa and 1500MP respectively. The yield strength increased with increase in partitioning time, whereas tensile strength showed an inverse behavior. The elongation in samples varied from 5% to 9% which seemed to not have a direct connection with the amount of retained austenite, but instead it was related to the ferritic structures formed during partitioning such as coalesced martensite, bainite and tempered martensite.

  18. Springback Prediction and Compensation for a High Strength Steel Side Impact Beam

    Science.gov (United States)

    Dutton, Trevor; Edwards, Richard; Blowey, Andrew

    2005-08-01

    Prediction of formability for sheet metal pressings has advanced to a high state of confidence in recent years. The major challenge is now to predict springback and, moreover, to assist in the design of tooling to correctly compensate for springback. This is particularly the case for materials now being routinely considered for automotive production, such as aluminium and ultra high strength steels, which are prone to greater degrees of springback than traditional mild steels. This paper presents a case study based on the tool design for an ultra high strength steel side impact beam. The forming and springback simulations, carried out using eta/DYNAFORM (based on the LS-DYNA solver), are reported and compared to measurements from the prototype panels. The analysis parameters used in the simulation are presented, and the sensitivity of the results to variation in physical properties is also reviewed. The process of compensating the tools based on the analysis prediction is described; finally, an automated springback compensation method is also applied and the results compared with the final tool design.

  19. Experimental evaluation of the fretting fatigue behavior of high-strength steel monostrands

    DEFF Research Database (Denmark)

    Winkler, Jan; Fischer, Gregor; Georgakis, Christos T.

    2013-01-01

    In this paper, the fretting fatigue behavior of pretensioned high-strength steel monostrands is investigated. A method based on the digital image correlation (DIC) technique was used to quantify the relative movement between individual wires along the length of the monostrand. The experimental data...... indicate that the interwire movement due to transverse deformations is highest at the neutral axis of the monostrand. The results showthat the midspan and the anchorage of the monostrand are the two locationswhere the combination of tensile strains and the interwire friction is the most unfavorable...

  20. Correlation of the thermodynamic calculation and the experimental observation of Ni-Mo-Cr low alloy steel changing Ni, Mo, and Cr contents

    Science.gov (United States)

    Park, Sang-Gyu; Kim, Min-Chul; Lee, Bong-Sang; Wee, Dang-Moon

    2010-12-01

    SA508 Gr.4N Ni-Mo-Cr low alloy steel has improved fracture toughness and strength compared to commercial low alloy steels such as SA508 Gr.3 Mn-Mo-Ni low alloy steel, which has less than 1% Ni. Higher strength and fracture toughness of low alloy steels can be achieved by increasing the Ni and Cr contents. In this study, the effects of the alloying elements of Ni and Cr on the microstructural characteristics and mechanical properties of SA508 Gr.4N Ni-Mo-Cr low alloy steel are evaluated. Changes in the stable phases of SA508 Gr.4N low alloy steel with these alloying elements were evaluated using thermodynamic calculation software. These values were then compared with the observed microstructural results. Additionally, tensile tests and Charpy impact test were carried out to evaluate the mechanical properties. The thermodynamic calculations show that Ni mainly affects the change of the matrix phase of γ and α rather than the carbide phase. Contrary to the Ni effect, Cr and Mo primarily affect the precipitation behavior of the carbide phases of Cr 23C 6, Cr 7C 3 and Mo 2C. In the microscopic observations, the lath martensitic structure becomes finer as the Ni content increases without affecting the carbides. When the Cr content decreases, the Cr carbide becomes unstable and carbide coarsening occurs. Carbide Mo 2C in the form of fine needles were observed in the high-Mo alloy. Greater strength was obtained after additions of Ni and Mo and the transition properties were improved as the Ni and Cr contents increased. These results were correlated with the thermodynamic calculation results.

  1. Correlation of the thermodynamic calculation and the experimental observation of Ni-Mo-Cr low alloy steel changing Ni, Mo, and Cr contents

    Energy Technology Data Exchange (ETDEWEB)

    Park, Sang-Gyu, E-mail: sg121243@kaist.ac.k [Korea Advanced Institute of Science and Technology, 373-1 Guseong-dong, Yuseong-gu, Daejeon 305-701 (Korea, Republic of); Kim, Min-Chul; Lee, Bong-Sang [Korea Atomic Energy Research Institute, 150 Deogjin-dong, Yuseong-gu, Daejeon 305-353 (Korea, Republic of); Wee, Dang-Moon [Korea Advanced Institute of Science and Technology, 373-1 Guseong-dong, Yuseong-gu, Daejeon 305-701 (Korea, Republic of)

    2010-12-15

    SA508 Gr.4N Ni-Mo-Cr low alloy steel has improved fracture toughness and strength compared to commercial low alloy steels such as SA508 Gr.3 Mn-Mo-Ni low alloy steel, which has less than 1% Ni. Higher strength and fracture toughness of low alloy steels can be achieved by increasing the Ni and Cr contents. In this study, the effects of the alloying elements of Ni and Cr on the microstructural characteristics and mechanical properties of SA508 Gr.4N Ni-Mo-Cr low alloy steel are evaluated. Changes in the stable phases of SA508 Gr.4N low alloy steel with these alloying elements were evaluated using thermodynamic calculation software. These values were then compared with the observed microstructural results. Additionally, tensile tests and Charpy impact test were carried out to evaluate the mechanical properties. The thermodynamic calculations show that Ni mainly affects the change of the matrix phase of {gamma} and {alpha} rather than the carbide phase. Contrary to the Ni effect, Cr and Mo primarily affect the precipitation behavior of the carbide phases of Cr{sub 23}C{sub 6}, Cr{sub 7}C{sub 3} and Mo{sub 2}C. In the microscopic observations, the lath martensitic structure becomes finer as the Ni content increases without affecting the carbides. When the Cr content decreases, the Cr carbide becomes unstable and carbide coarsening occurs. Carbide Mo{sub 2}C in the form of fine needles were observed in the high-Mo alloy. Greater strength was obtained after additions of Ni and Mo and the transition properties were improved as the Ni and Cr contents increased. These results were correlated with the thermodynamic calculation results.

  2. High strength oil palm shell concrete beams reinforced with steel fibres

    Directory of Open Access Journals (Sweden)

    S. Poh-Yap

    2017-10-01

    Full Text Available The utilization of lightweight oil palm shell to produce high strength lightweight sustainable material has led many researchers towards its commercialization as structural concrete. However, the low tensile strength of Oil Palm Shell Concrete (OPSC has hindered its development. This study aims to enhance the mechanical properties and flexural behaviours of OPSC by the addition of steel fibres of up to 3% by volume, to produce oil palm shell fibre-reinforced concrete (OPSFRC. The experimental results showed that the steel fibres significantly enhanced the mechanical properties of OPSFRC. The highest compressive strength, splitting tensile and flexural strengths of 55, 11.0 and 18.5 MPa, respectively, were achieved in the OPSFRC mix reinforced with 3% steel fibres. In addition, the flexural beam testing on OPSFRC beams with 3% steel fibres showed that the steel fibre reinforcement up to 3% produced notable increments in the moment capacity and crack resistance of OPSFRC beams, but accompanied by reduction in the ductility.

  3. Experimental investigation of the effect of surface markings on the mechanical integrity of weathering bridge steels : [summary].

    Science.gov (United States)

    2014-11-01

    High-strength low-alloy steel (HSLA) weathering : steels are the conventional choice for fracture-critical members in bridge construction. HSLA : weathering steels offer superior corrosion : resistance, important in Floridas humid and : coastal en...

  4. Anisotropic Hardening Behaviour and Springback of Advanced High-Strength Steels

    Directory of Open Access Journals (Sweden)

    Jaebong Jung

    2017-11-01

    Full Text Available Advanced high-strength steels (AHSSs exhibit large, and sometimes anisotropic, springback recovery after forming. Accurate description of the anisotropic elasto-plastic behaviour of sheet metals is critical for predicting their anisotropic springback behaviour. For some materials, the initial anisotropy is maintained while hardening progresses. However, for other materials, anisotropy changes with hardening. In this work, to account for the evolution of anisotropy of a dual-phase steel, an elastoplastic material constitutive model is developed. In particular, the combined isotropic–kinematic hardening model was modified. Tensile loading–unloading, uniaxial and biaxial tension, and tension–compression tests were conducted along the rolling, diagonal, and transverse directions to measure the anisotropic properties, and the parameters of the proposed constitutive model were determined. For validation, the proposed model was applied to a U-bending process, and the measured springback angles were compared to the predicted ones.

  5. Application of high strength MnMoNi steel to pressure vessels for nuclear power plant

    Energy Technology Data Exchange (ETDEWEB)

    Suzuki, K.; Kurihara, I.; Sasaki, T.; Koyama, Y.; Tanaka, Y. [The Japan Steel Works, Ltd. (Japan)

    1999-07-01

    Recent increase in output of nuclear power plant has been attained by enlargement of major components such as pressure vessels. Such large components have almost reached limit of size from the points of manufacturing capacity and cost in both forgemasters and fabricaters. In order to solve this problem, it must be beneficial to apply design by use of material of higher strength which brings reduction of pressure vessel thickness and weight. The Japan Steel Works, Ltd. (JSW) has many manufacturing experiences of large integrated forgings made from high strength MnMoNi steel with tensile strength level of 620MPa for steam generator (SG) pressure vessel, and has made confirmation tests of its material properties. This paper describes the confirmation test results such as tensile and impact properties, nil-ductility transition temperature (NDT-T), static and dynamic fracture toughness weldability including under clad cracking (UCC) sensitivity and metallurgical factors which influence on such material properties. (orig.)

  6. Application of high strength MnMoNi steel to pressure vessels for nuclear power plant

    Energy Technology Data Exchange (ETDEWEB)

    Suzuki, K. E-mail: koumei_suzuki@jsw.co.jp; Kurihara, I.; Sasaki, T.; Koyoma, Y.; Tanaka, Y

    2001-06-01

    Recent increase in output of nuclear power plant has been attained by enlargement of major components such as pressure vessels. Such large components have almost reached a size limit from the points of manufacturing capacity and cost in both forgemasters and fabricaters. In order to solve this problem, it must be beneficial to apply design by use of material of higher strength, which brings reduction of pressure vessel thickness and weight. The Japan Steel Works Ltd. (JSW) has many manufacturing experiences of large integrated forgings made from high strength MnMoNi steel with tensile strength level of 620 MPa for steam generator (SG) pressure vessel, and has performed confirmation tests of its material properties. This paper describes the confirmation test results such as tensile and impact properties, nil-ductility transition temperature (NDT-T), static and dynamic fracture toughness, weldability including under-clad cracking (UCC) sensitivity, as well as metallurgical factors which influence on such material properties.

  7. Microstructure and Hardness Distribution of Resistance Welded Advanced High Strength Steels

    DEFF Research Database (Denmark)

    Pedersen, Kim Richardt; Harthøj, Anders; Friis, Kasper Leth

    2008-01-01

    In this work a low carbon steel and two high strength steels (DP600 and TRIP700) have been resistance lap welded and the hardness profiles were measured by micro hardness indentation of cross sections of the joint. The resulting microstructure of the weld zone of the DP-DP and TRIP-TRIP joints were...... found to consist of a martensitic structure with a significant increase in hardness. Joints of dissimilar materials mixed completely in the melted region forming a new alloy with a hardness profile lying in between the hardness measured in joints of the similar materials. Furthermore the joints were...... simulated numerically and together with the material carbon equivalent, austenization temperatures and the thermal history the simulations were used to estimate the resulting post weld hardness using the commercial FE code SORPAS. The hardness of the welds of dissimilar materials was estimated...

  8. Modeling of nonlinear elastoplastic behavior after stress reversal for high strength steel

    Science.gov (United States)

    Sumikawa, S.; Ishiwatari, A.; Hiramoto, J.

    2017-09-01

    Material characteristics have significant impact on simulation of sheet metal forming. The accuracy of springback prediction depends on the estimation of strain recovery after die release. It is well known that the experimentally obtained unloading behavior for steel sheets is nonlinear stress-strain relationship, and the response during unloading and reloading shows a hysteresis loop. This behavior should be modeled by a material model and considered in FE-simulations for accurate predictions. In this study, the in-plane stress reversal tests for high strength steel were carried out to observe the elastoplastic behaviors after stress reversal. A material model that considers the nonlinear behavior was newly developed and implemented into the FEM software. The accuracy of springback prediction with the developed material model was validated by the draw bending tests and its springback simulations. The simulations with the developed material model show better agreement with the experimentally measured springback profile as compared to the other material models.

  9. Latest Development and Application of Nb-Bearing High Strength Pipeline Steels

    Science.gov (United States)

    Zhang, Yongqing; Shang, Chengjia; Guo, Aimin; Zheng, Lei; Niu, Tao; Han, Xiulin

    In order to solve the pollution problem emerging in China recently, China's central government is making great efforts to raise the percentage of natural gas consumption in the China's primary energy mix, which needs to construct big pipelines to transport natural gas from the nation's resource-rich western regions to the energy-starved east, as well as import from the Central Asia and Russia. With this mainstream trend, high strength, high toughness, heavy gauge, and large diameter pipeline steels are needed to improve the transportation efficiency. This paper describes the latest progresses in Nb-bearing high strength pipeline steels with regard to metallurgical design, development and application, including X80 coil with a thickness up to 22.0mm, X80 plate with a diameter as much as 1422mm, X80 plate with low-temperature requirements and low-Mn sour service X65 for harsh sour service environments. Moreover, based on widely accepted TMCP and HTP practices with low carbon and Nb micro-alloying design, this paper also investigated some new metallurgical phenomena based on powerful rolling mills and heavy ACC equipment.

  10. Fatigue Properties of the Ultra-High Strength Steel TM210A.

    Science.gov (United States)

    Yin, Guang-Qiang; Kang, Xia; Zhao, Gui-Ping

    2017-09-09

    This paper presents the results of an experiment to investigate the high cycle fatigue properties of the ultra-high strength steel TM210A. A constant amplitude rotating bending fatigue experiment was performed at room temperature at stress ratio R = -1. In order to evaluate the notch effect, the fatigue experiment was carried out upon two sets of specimens, smooth and notched, respectively. In the experiment, the rotating bending fatigue life was tested using the group method, and the rotating bending fatigue limit was tested using the staircase method at 1 × 10⁷ cycles. A double weighted least square method was then used to fit the stress-life (S-N) curve. The S-N curves of the two sets of specimens were obtained and the morphologies of the fractures of the two sets of specimens were observed with scanning electron microscopy (SEM). The results showed that the fatigue limit of the smooth specimen for rotating bending fatigue was 615 MPa; the ratio of the fatigue limit to tensile strength was 0.29, and the cracks initiated at the surface of the smooth specimen; while the fatigue limit of the notched specimen for rotating bending fatigue was 363 MPa, and the cracks initiated at the edge of the notch. The fatigue notch sensitivity index of the ultra-high strength maraging steel TM210A was 0.69.

  11. Analysis of hot forming of a sheet metal component made of advanced high strength steel

    Science.gov (United States)

    Demirkaya, Sinem; Darendeliler, Haluk; Gökler, Mustafa İlhan; Ayhaner, Murat

    2013-05-01

    To provide reduction in weight while maintaining crashworthiness and to decrease the fuel consumption of vehicles, thinner components made of Advanced High Strength Steels (AHSS) are being increasingly used in automotive industry. However, AHSS cannot be formed easily at the room temperature (i.e. cold forming). The alternative process involves heating, hot forming and subsequent quenching. A-pillar upper reinforcement of a vehicle is currently being produced by cold forming of DP600 steel sheet with a thickness of 1.8 mm. In this study, the possible decrease in the thickness of this particular part by using 22MnB5 as appropriate AHSS material and applying this alternative process has been studied. The proposed process involves deep drawing, trimming, heating, sizing, cooling and piercing operations. Both the current production process and the proposed process are analyzed by the finite element method. The die geometry, blank holding forces and the design of the cooling channels for the cooling process are determined numerically. It is shown that the particular part made of 22MnB5 steel sheet with a thickness of 1.2 mm can be successfully produced by applying the proposed process sequence and can be used without sacrificing the crashworthiness. With the use of the 22MnB5 steel with a thickness of 1.2 mm instead of DP600 sheet metal with a thickness of 1.8 mm, the weight is reduced by approximately 33%.

  12. New Insights in the Long-Term Atmospheric Corrosion Mechanisms of Low Alloy Steel Reinforcements of Cultural Heritage Buildings.

    Science.gov (United States)

    Bouchar, Marie; Dillmann, Philippe; Neff, Delphine

    2017-06-19

    Reinforcing clamps made of low alloy steel from the Metz cathedral and corroded outdoors during 500 years were studied by OM, FESEM/EDS, and micro-Raman spectroscopy. The corrosion product layer is constituted of a dual structure. The outer layer is mainly constituted of goethite and lepidocrocite embedding exogenous elements such as Ca and P. The inner layer is mainly constituted of ferrihydrite. The behaviour of the inner layer under conditions simulating the wetting stage of the RH wet/dry atmospheric corrosion cycle was observed by in situ micro-Raman spectroscopy. The disappearance of ferrihydrite near the metal/oxide interface strongly suggests a mechanism of reductive dissolution caused by the oxidation of the metallic substrate and was observed for the first time in situ on an archaeological system.

  13. New Insights in the Long-Term Atmospheric Corrosion Mechanisms of Low Alloy Steel Reinforcements of Cultural Heritage Buildings

    Directory of Open Access Journals (Sweden)

    Marie Bouchar

    2017-06-01

    Full Text Available Reinforcing clamps made of low alloy steel from the Metz cathedral and corroded outdoors during 500 years were studied by OM, FESEM/EDS, and micro-Raman spectroscopy. The corrosion product layer is constituted of a dual structure. The outer layer is mainly constituted of goethite and lepidocrocite embedding exogenous elements such as Ca and P. The inner layer is mainly constituted of ferrihydrite. The behaviour of the inner layer under conditions simulating the wetting stage of the RH wet/dry atmospheric corrosion cycle was observed by in situ micro-Raman spectroscopy. The disappearance of ferrihydrite near the metal/oxide interface strongly suggests a mechanism of reductive dissolution caused by the oxidation of the metallic substrate and was observed for the first time in situ on an archaeological system.

  14. Structural properties of iron phases formed on low alloy steels immersed in sodium chloride-rich solutions

    Energy Technology Data Exchange (ETDEWEB)

    Perez, F.R., E-mail: fredy.perez@upb.edu.c [Grupo de Optica y Espectroscopia, Universidad Pontificia Bolivariana, A. A. 56006, Medellin (Colombia); Grupo de Estado Solido, Universidad de Antioquia, A. A. 1226, Medellin (Colombia); Barrero, C.A.; Arnache, O.; Sanchez, L.C.; Garcia, K.E. [Grupo de Estado Solido, Universidad de Antioquia, A. A. 1226, Medellin (Colombia); Hight Walker, A.R. [Physics Laboratory, National Institute of Standards and Technology (NIST), Gaithersburg, MD 20899 (United States)

    2009-05-01

    Products of corrosion were obtained from low alloy steels submitted to total immersion tests in solutions containing sodium chloride at different concentrations, during seven days. In order to properly characterize the adherent (AR) and the non-adherent rusts (NAR), a methodology including room temperature Moessbauer spectrometry, diffuse reflectance infrared Fourier transform spectroscopy, Raman spectroscopy, scanning electron microscopy and X-ray diffraction was addressed. The techniques showed that the AR samples were composed of non-stoichiometric magnetite, goethite, akaganeite and lepidocrocite. The composition of the NAR samples was the same, but with very small amounts of magnetite. Different cell parameters and mean crystallite sizes were found for all phases presented in AR and the NAR samples. The corrosion rates were higher than 580 mum/y. The ratio of the abundances of goethite to the sum of lepidocrocite, akaganeite and magnetite were less than one.

  15. Delineation of Prior Austenite Grain Boundaries in a Low Alloy High Performance Steel (Preprint)

    Science.gov (United States)

    2017-07-31

    property relationships in steels, since prior austenite grain size plays an important role in defining the microstructural scale of low-temperature...the microstructure-24 property relationships in steels, since prior austenite grain size plays an important role in 25 defining the microstructural...steels [8]. A solution 73 containing 10g CrO3, 50g NaOH, 1.5g picric acid, and 100ml distilled water was also reported to 74 provide significantly

  16. Hot cracking investigation during laser welding of high-strength steels with multi-scale modelling approach

    NARCIS (Netherlands)

    Gao, H.; Agarwal, G.; Amirthalingam, M.; Hermans, M.J.M.

    2017-01-01

    Hot cracking during laser welding of advanced high-strength steels is reported to be a serious problem by automotive manufacturers. In this work, hot cracking susceptibilities of transformation-induced plasticity (TRIP) and dual-phase (DP) steels are studied based on a multi-scale modelling

  17. Experimental study and modelling of the effect of microstructure on friction and wear mechanisms of low alloy steel

    Science.gov (United States)

    Trevisiol, C.; Jourani, A.; Bouvier, S.

    2017-12-01

    Few models are focused on the combined effects of microstructure and roughness on the tribological behavior of materials. Hardness is the material property mainly used in the tribological models which are usually at a macroscopic scale. For a dual-phase steel, experimental and predicted values of friction coefficients and specific wear resistances are compared. The investigated models are declined into two pressure distribution modes between the phases. Friction tests are performed between steel pins composed of a ferrite-martensite dual-phase microstructure against abrasive papers with various abrasive particle sizes ranging from 15 µm to 200 µm. By using heat treatments on a low alloy steel, dual-phase microstructures with various martensite volume fractions, ranging from 45% to 100%, are generated. As martensite volume fraction increases, the experimental and predicted results show that the specific wear resistance increases whereas the friction coefficient decreases. Furthermore, the latter evolutions depend on roughness. For a predominance of abrasive wear mechanisms generated by coarse abrasive particles (~200 µm), the experimental tribological parameters tend to follow the predicted ones associated to the mode characterized by equal pressures between the phases. Then, as the abrasive particle size decreases, abrasive wear mechanisms reduce whereas adhesive wear mechanisms increase and the experimental tribological parameters tend to follow the predicted ones associated to the mode characterized by equal wear rate between the phases.

  18. A fracture mechanics approach for estimating fatigue crack initiation in carbon and low-alloy steels in LWR coolant environments

    Energy Technology Data Exchange (ETDEWEB)

    Park, H. B.; Chopra, O. K.

    2000-04-10

    A fracture mechanics approach for elastic-plastic materials has been used to evaluate the effects of light water reactor (LWR) coolant environments on the fatigue lives of carbon and low-alloy steels. The fatigue life of such steel, defined as the number of cycles required to form an engineering-size crack, i.e., 3-mm deep, is considered to be composed of the growth of (a) microstructurally small cracks and (b) mechanically small cracks. The growth of the latter was characterized in terms of {Delta}J and crack growth rate (da/dN) data in air and LWR environments; in water, the growth rates from long crack tests had to be decreased to match the rates from fatigue S-N data. The growth of microstructurally small cracks was expressed by a modified Hobson relationship in air and by a slip dissolution/oxidation model in water. The crack length for transition from a microstructurally small crack to a mechanically small crack was based on studies on small crack growth. The estimated fatigue S-N curves show good agreement with the experimental data for these steels in air and water environments. At low strain amplitudes, the predicted lives in water can be significantly lower than the experimental values.

  19. Seismic performance of steel reinforced ultra high-strength concrete composite frame joints

    Science.gov (United States)

    Yan, Changwang; Jia, Jinqing

    2010-09-01

    To investigate the seismic performance of a composite frame comprised of steel reinforced ultra high-strength concrete (SRUHSC) columns and steel reinforced concrete (SRC) beams, six interior frame joint specimens were designed and tested under low cyclically lateral load. The effects of the axial load ratio and volumetric stirrup ratio were studied on the characteristics of the frame joint performance including crack pattern, failure mode, ductility, energy dissipation capacity, strength degradation and rigidity degradation. It was found that all joint specimens behaved in a ductile manner with flexural-shear failure in the joint core region while plastic hinges appeared at the beam ends. The ductility and energy absorption capacity of joints increased as the axial load ratio decreased and the volumetric stirrup ratio increased. The displacement ductility coefficient and equivalent damping coefficient of the joints fell between the corresponding coefficients of the steel reinforced concrete (SRC) frame joint and RC frame joint. The axial load ratio and volumetric stirrup ratio have less influence on the strength degradation and more influence on the stiffness degradation. The stiffness of the joint degrades more significantly for a low volumetric stirrup ratio and high axial load ratio. The characteristics obtained from the SRUHSC composite frame joint specimens with better seismic performance may be a useful reference in future engineering applications.

  20. Hydroformability of 980MPa and 1180MPa ultra-high strength ERW steel tubes

    Science.gov (United States)

    Hashimoto, Yuji; Katsumura, Tatsuro; Aratani, Masatoshi; Sonobe, Osamu; Kato, Yasushi

    2013-12-01

    High strength steel tubes have attracted attention as materials for reducing auto body weight. However, there have been few reports on hydroforming using materials with nominal tensile strengths exceeding 980MPa. Therefore, free bulge forming tests and rectangular section bulge forming tests were carried out with electric resistance welded (ERW) tubes having nominal tensile strengths of 980MPa and 1180MPa. These steels are dual-phase steels consisting of martensite and ferrite. In the free bulge forming tests, the limiting bulging ratio (LBR) under axial feeding was 17% for the 980MPa material and 5% for the 1180MPa material. In the rectangular section bulge tests with a bulging ratio of 4%, it was possible to avoid rupture of the 1180MPa material at the heat-affected zone (HAZ) by applying axial feed loading or selecting the proper welded seam position. Under the same rectangular section bulging test conditions, forming of the 980MPa material without defects was possible regardless of the axial feeding condition and selection of the welded seam position.

  1. Nanoscale surface analysis on second generation advanced high strength steel after hot dip galvanizing.

    Science.gov (United States)

    Arndt, M; Duchoslav, J; Preis, K; Samek, L; Stifter, D

    2013-09-01

    Second generation advanced high strength steel is one promising material of choice for modern automotive structural parts because of its outstanding maximal elongation and tensile strength. Nonetheless there is still a lack of corrosion protection for this material due to the fact that cost efficient hot dip galvanizing cannot be applied. The reason for the insufficient coatability with zinc is found in the segregation of manganese to the surface during annealing and the formation of manganese oxides prior coating. This work analyses the structure and chemical composition of the surface oxides on so called nano-TWIP (twinning induced plasticity) steel on the nanoscopic scale after hot dip galvanizing in a simulator with employed analytical methods comprising scanning Auger electron spectroscopy (SAES), energy dispersive X-ray spectroscopy (EDX), and focused ion beam (FIB) for cross section preparation. By the combination of these methods, it was possible to obtain detailed chemical images serving a better understanding which processes exactly occur on the surface of this novel kind of steel and how to promote in the future for this material system galvanic protection.

  2. GRINDABILITY OF SELECTED GRADES OF LOW-ALLOY HIGH-SPEED STEEL

    Directory of Open Access Journals (Sweden)

    Jan Jaworski

    2016-09-01

    Full Text Available In this paper, we presents the results of investigations studied the cutting ability and grindability of selected high-speed steels. We analysed the effect of the austenitization temperature on the grain size, the amount of retained austenite and percentage of retained austenite in HS3-1-1 steel. Furthermore, the investigations concerned on the efficiency of the keyway broaches during the whole period of operation were carried out. It was found that the value of average roughness parameter increases together with increases in the grinding depth. The investigations also show the influence of tempering conditions on the volume of carbide phases in HS3-1-1 steel.

  3. EXPERIMENTAL STUDY ABOUT THE APPLICATIONS OF REINFORCED CONCRETE BRIDGE PIERS WITH HIGH-STRENGTH-STEEL LONGITUDINAL AND HOOP REINFORCEMENT

    Science.gov (United States)

    Sogabe, Naoki; Kitsugi, Katsuhiko; Ibuki, Kazuyuki; Moriyama, Yoichi; Ishiyama, Kazuyuki; Yamanobe, Shinichi; Suda, Kumiko; Watanabe, Yoshimitsu

    The cross-sectional area of reinforced concrete bridge piers and the number of longitudinal reinforcing bars required for bridge piers can be reduced by usin g high-strength reinforcing steel with a yield strength of 685 N/mm2. Reduction in the quantity of materials for bridge pier structures is effective in enhancing constructibility and reducing construction cost because pier foundations can be made smaller. As an example of use of high-strength reinforcing steel in reinforced concrete bridge piers, high-strength blast furnace steel has been used to reinforce tall (about 60 to 120 m) bridge piers made with concrete with a design strength of 50 N/mm2. In this study, verification was made, through a series of structural experiments, with respect to the structural characteristics of concrete piers reinforced with high-strength electric furnace steel. This paper re ports the findings that may help promote the use of high-strength reinforcing steel in reinforced concrete piers.

  4. Gradient twinned 304 stainless steels for high strength and high ductility

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Aiying [School of Materials Science and Engineering, University of Shanghai for Science and Technology, Shanghai (China); Liu, Jiabin; Wang, Hongtao [Institute of Applied Mechanics, Zhejiang University, Hangzhou (China); Lu, Jian, E-mail: jianlu@cityu.edu.hk [Department of Mechanical and Biomedical Engineering, City University of Hong Kong, Hong Kong (China); Wang, Y. Morris, E-mail: ymwang@llnl.gov [Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, CA (United States)

    2016-06-14

    Gradient materials often have attractive mechanical properties that outperform uniform microstructure counterparts. It remains a difficult task to investigate and compare the performance of various gradient microstructures due to the difficulty of fabrication, the wide range of length scales involved, and their respective volume percentage variations. We have investigated four types of gradient microstructures in 304 stainless steels that utilize submicrotwins, nanotwins, nanocrystalline-, ultrafine- and coarse-grains as building blocks. Tensile tests reveal that the gradient microstructure consisting of submicrotwins and nanotwins has a persistent and stable work hardening rate and yields an impressive combination of high strength and high ductility, leading to a toughness that is nearly 50% higher than that of the coarse-grained counterpart. Ex- and in-situ transmission electron microscopy indicates that nanoscale and submicroscale twins help to suppress and limit martensitic phase transformation via the confinement of martensite within the twin lamellar. Twinning and detwinning remain active during tensile deformation and contribute to the work hardening behavior. We discuss the advantageous properties of using submicrotwins as the main load carrier and nanotwins as the strengthening layers over those coarse and nanocrystalline grains. Our work uncovers a new gradient design strategy to help metals and alloys achieve high strength and high ductility.

  5. Influence of Carbide Modifications on the Mechanical Properties of Ultra-High-Strength Stainless Steels

    Science.gov (United States)

    Seo, Joo-Young; Park, Soo-Keun; Kwon, Hoon; Cho, Ki-Sub

    2017-10-01

    The mechanical properties of ultra-high-strength secondary hardened stainless steels with varying Co, V, and C contents have been studied. A reduced-Co alloy based on the chemical composition of Ferrium S53 was made by increasing the V and C content. This changed the M2C-strengthened microstructure to a MC plus M2C-strengthened microstructure, and no deteriorative effects were observed for peak-aged and over-aged samples despite the large reduction in Co content from 14 to 7 wt pct. The mechanical properties according to alloying modification were associated with carbide precipitation kinetics, which was clearly outlined by combining analytical tools including small-angle neutron scattering (SANS) as well as an analytical TEM with computational simulation.

  6. Experimental and Numerical Determination of Hot Forming Limit Curve of Advanced High-Strength Steel

    Science.gov (United States)

    Ma, B. L.; Wan, M.; Liu, Z. G.; Li, X. J.; Wu, X. D.; Diao, K. S.

    2017-07-01

    This paper studied the hot formability of the advanced high-strength steel B1500HS. The hot Nakazima tests were conducted to obtain the forming limit curve (FLC), and the sheet temperatures were recorded to analyze temperature distributions during deformation. Meanwhile, the numerical simulations of hot Nakazima tests were performed to compare with the experimental ones. By utilizing the commercial software, Abaqus, the punch force-displacement curve, sheet temperature distribution at the time of the maximum punch load and temperature path of the necked element were investigated from both of experiments and numerical simulations. The FLCs from experiment and numerical simulation showed a good agreement. The temperature path of the necked element on each FLC specimen was different due to the numerical stretching time and stress state. This study demonstrated the predictive capability of finite element simulation on hot stamping.

  7. Fatigue Behavior of Steel Fiber Reinforced High-Strength Concrete under Different Stress Levels

    Science.gov (United States)

    Zhang, Chong; Gao, Danying; Gu, Zhiqiang

    2017-12-01

    The investigation was conducted to study the fatigue behavior of steel fiber reinforced high-strength concrete (SFRHSC) beams. A series of 5 SFRHSC beams was conducted flexural fatigue tests at different stress level S of 0.5, 0.55, 0.6, 0.7 and 0.8 respectively. Static test was conducted to determine the ultimate static capacity prior to fatigue tests. Fatigue modes and S-N curves were analyzed. Besides, two fatige life prediction model were analyzed and compared. It was found that stress level S significantly influenced the fatigue life of SFRHSC beams and the fatigue behavior of SFRHSC beams was mainly determined by the tensile reinforcement.

  8. DETERMINATION OF HYDROGEN DESORBED THROUGH THERMAL CALORIMETRY IN A HIGH STRENGTH STEEL

    Directory of Open Access Journals (Sweden)

    Carolina A. Asmus

    2014-03-01

    Full Text Available The following study aims to quantify the release activation energy (Ea of hydrogen (H from lattice sites, reversible or irreversible, where the H can be trapped. Moreover, enthalpy changes associated with the main hydrogen (H trapping sites can be analyzed by means of differential scanning calorimetry (DSC. In this technique, the peak temperature measurement is determined at two different heating rates, 3ºC/min y 5ºC/min, from ambient temperature to 500°C. In order to simulate severe conditions of hydrogen income into resulfurized high strength steel, electrolytic permeation tests were performed on test tubes suitable for fatigue tests. Sometimes during charging, H promoters were aggregated to electrolytic solution. Subsequently, the test tubes were subjected to flow cycle fatigue tests. Finally, irreversible trap which anchor more strongly H atoms are MnS inclusions. Its role on hydrogen embrittlement during fatigue tests is conclusive.

  9. Effect of defect length on rolling contact fatigue crack propagation in high strength steel

    Directory of Open Access Journals (Sweden)

    T. Makino

    2015-10-01

    Full Text Available The objective of the present paper is to clarify the effect of defect length in depth direction on rolling contact fatigue (RCF crack propagation in high strength steel. RCF test and synchrotron radiation micro computed tomography (SR micro CT imaging were conducted. In the case of the defect with the 15 m diameter, flaking life decreased with increasing defect length. In a comparison of the CT image and the SEM view, the shapes of defects and the locations of the horizontal cracks were almost the same respectively. The mechanism of RCF crack propagation was discussed by finite element (FE analysis. Defects led to higher tensile residual stress than that without defects in the region where the defect exists. The shear stress range at 0.1 mm in depth on the middle line of the defect and the range of mode II stress intensity factor at the bottom of a vertical crack increased with increasing defect length.

  10. Effect of Welding Consumables on Fatigue Performance of Shielded Metal Arc Welded High Strength, Q&T Steel Joints

    Science.gov (United States)

    Magudeeswaran, G.; Balasubramanian, V.; Madhusudhan Reddy, G.

    2009-02-01

    Quenched and Tempered (Q&T) steels are widely used in the construction of military vehicles due to their high strength-to-weight ratio and high hardness. These steels are prone to hydrogen-induced cracking in the heat affected zone (HAZ) after welding. The use of austenitic stainless steel consumables to weld the above steel was the only remedy because of higher solubility for hydrogen in austenitic phase. Recent studies proved that high nickel steel and low hydrogen ferritic steel consumables can be used to weld Q&T steels, which can give very low hydrogen levels in the weld deposits. In this investigation an attempt has been made to study the effect of welding consumables on high cycle fatigue properties of high strength, Q&T steel joints. Three different consumables namely (i) austenitic stainless steel, (ii) low hydrogen ferritic steel, and (iii) high nickel steel have been used to fabricate the joints by shielded metal arc (SMAW) welding process. The joints fabricated using low hydrogen ferritic steel electrodes showed superior fatigue properties than other joints.

  11. Finite element modelling of chain-die forming for ultra-high strength steel

    Science.gov (United States)

    Majji, Raju; Xiang, Yang; Ding, Scott; Yang, Chunhui

    2017-10-01

    There has been a high demand for weight reduction in automotive vehicles while maintaining passenger safety. A potential steel material to achieve this is Ultra High Strength Steel (UHSS). As a high strength material, it is difficult to be formed with desired profiles using traditional sheet metal forming processes such as Cold Roll Forming. To overcome this problem, a potentially alternative solution is Chain-die Forming (CDF), recently developed. The basic principal of the CDF is to fully combine roll forming and bending processes. The main advantage of this process is the elongated deformation length that significantly increases effective roll radius. This study focuses on identifying issues with the CDF by using CAD modelling, Motion Analysis and Finite Element Analysis (FEA) to devise solutions and construct a more reliable process in an optimal design sense. Some attempts on finite element modelling and simulation of the CDF were conducted using relatively simple models in literature and the research was still not sufficient enough for optimal design of a typical CDF for UHSS. Therefore two numerical models of Chain-die Forming process are developed in this study, including a) one having a set of rolls similar to roll forming but with a large radius, i.e., 20 meters; and b) the other one with dies and punch segments similar to a typical CDF machine. As a case study, to form a 60° channel with single pass was conducted using these two devised models for a comparison. The obtained numerical results clearly show the CDF could generate less residual stress, low strain and small springback of a single pass for the 60° UHSS channel. The design analysis procedure proposed in this study could greatly help the mechanical designers to devise a cost-effective and reliable CDF process for forming UHSS.

  12. Fracture Toughness (K1C evaluation for dual phase medium carbon low alloy steels using circumferential notched tensile (CNT specimens

    Directory of Open Access Journals (Sweden)

    Kenneth Kanayo Alaneme

    2011-01-01

    Full Text Available The fracture behavior of dual phase medium carbon low alloy steels produced using two different chemical compositions (A - 0.34C, 0.75Mn, 0.12Cr, 0.13Ni steel and B - 0.3C, 0.97Mn, 0.15Cr steel was investigated using circumferential notched tensile (CNT specimens. Intercritical treatments were performed on samples with composition A by 1 austenitizing at 860 °C for 1 hour cooling in air, then treating at 770 °C for 30 minutes before oil quenching; 2 austenitizing at 860 °C for 1 hour quenching in oil, then treating at 770 °C for 30 minutes before quenching in oil; and 3 austenitizing at 860 °C for 1 hour, super-cooling to 770 °C and then quenching in oil. Samples of composition B were subjected to intercritical treatment at temperatures of 740, 760, and 780 °C for 30 minutes, followed by quenching rapidly in oil. Tensile testing was then performed on specimens without notches and the CNT specimens. It was observed that the dual phase steel produced from procedure (2 yielded a fine distribution of ferrite and martensite which gave the best combination of tensile properties and fracture toughness for composition A while the dual phase structure produced by treating at 760 °C yielded the best combination of tensile properties and fracture toughness for composition B. The fracture toughness results evaluated from the test were found to be valid (in plain strain condition and a high correlation between the fracture toughness and notch tensile strength was observed. The fracture toughness values were also found to be in close agreement with data available in literature.

  13. Bonding evolution with sintering temperature in low alloyed steels with chromium

    Directory of Open Access Journals (Sweden)

    Fuentes-Pacheco L.

    2009-01-01

    Full Text Available At present, high performance PM steels for automotive applications follow a processing route that comprises die compaction of water-atomized powder, followed by sintering and secondary treatments, and finishing operations. This study examines Cr-alloyed sintered steels with two level of alloying. In chromium-alloyed steels, the surface oxide on the powder is of critical importance for developing the bonding between the particles during sintering. Reduction of this oxide depends mainly on three factors: temperature, dew point of the atmosphere, and carbothermic reduction provided by the added graphite. The transformation of the initial surface oxide evolves sequence as temperature increases during sintering, depending on the oxide composition. Carbothermic reduction is supposed to be the controlling mechanism, even when sintering in hydrogen-containing atmospheres. The effect of carbothermic reduction can be monitored by investigating the behavior of the specimens under tensile testing, and studying the resultant fracture surfaces.

  14. Heat treatment and effects of Cr and Ni in low alloy steel

    Indian Academy of Sciences (India)

    Administrator

    Materials and Metallurgical Engineering Department, Bangladesh University of Engineering and Technology. (BUET), Bangladesh. MS received 1 March 2010; revised 14 February 2011. Abstract. The effects of Cr and Ni on low carbon steel was observed. Undissolved carbide particles refine the austenite grain size.

  15. Mechanical Behavior of DP980 High Strength Steel Under Dynamic Tensile Tests

    Directory of Open Access Journals (Sweden)

    TIAN Wen-yang

    2017-03-01

    Full Text Available The mechanical behavior and fracture modes of DP980 high strength steels were studied by comparing the results of dynamic tensile tests at strain rates from 10-3s-1 to 103s-1. The results show that the strength of DP980 steel remains almost unchanged and the plasticity decreases by 7.5% as the strain rate increasing from quasi-static(10-3s-1 to 100s-1. When the strain rate increases from 100s-1 to 103s-1, the strength keeps increasing, while the plasticity increases by 14% at the strain rate ranging from 100s-1 to 102s-1, but then follows by a decrease of 24.7% in the range of 102s-1 to 103s-1. The strain rate sensitivity coefficient m increases with the increasing of the strain rate. During the plastic deformation, the multiplication reinforcement of dislocation and the motion resistance due to the acceleration of dislocation in ferrite matrix are the main reasons for the strength enhancement. The plastic deformation concentrates in the ferrite, and the microvoids and cracks propagate along the martensite-ferrite interface. In the thickness direction of specimen, the macrographs of fracture are "V" shape cups when strain rate is lower than 101s-1, but the pure sheer shape with 45° to the tensile direction when strain rate is over 101s-1.

  16. Alloy and composition dependence of hydrogen embrittlement susceptibility in high-strength steel fasteners

    Science.gov (United States)

    Brahimi, S. V.; Yue, S.; Sriraman, K. R.

    2017-06-01

    High-strength steel fasteners characterized by tensile strengths above 1100 MPa are often used in critical applications where a failure can have catastrophic consequences. Preventing hydrogen embrittlement (HE) failure is a fundamental concern implicating the entire fastener supply chain. Research is typically conducted under idealized conditions that cannot be translated into know-how prescribed in fastener industry standards and practices. Additionally, inconsistencies and even contradictions in fastener industry standards have led to much confusion and many preventable or misdiagnosed fastener failures. HE susceptibility is a function of the material condition, which is comprehensively described by the metallurgical and mechanical properties. Material strength has a first-order effect on HE susceptibility, which increases significantly above 1200 MPa and is characterized by a ductile-brittle transition. For a given concentration of hydrogen and at equal strength, the critical strength above which the ductile-brittle transition begins can vary due to second-order effects of chemistry, tempering temperature and sub-microstructure. Additionally, non-homogeneity of the metallurgical structure resulting from poorly controlled heat treatment, impurities and non-metallic inclusions can increase HE susceptibility of steel in ways that are measurable but unpredictable. Below 1200 MPa, non-conforming quality is often the root cause of real-life failures. This article is part of the themed issue 'The challenges of hydrogen and metals'.

  17. A new specimen for out-of-plane shear strength of advanced high strength steel sheets

    Science.gov (United States)

    Gu, B.; He, J.; Li, S. H.; Zhao, Y. X.; Li, Y. F.; Zeng, D.; Xia, Z. C.; Lin, Z. Q.

    2017-09-01

    Compared with the conventional steels, “shear fracture” is one of the main issues for advanced high strength steels (AHSS). Due to rolling, anisotropy is an intrinsic property for sheet metals. Not only the plastic responses of sheet metals but also the fracture strengths are orientation dependent. In the small radius forming process, for example, the stretch-bending deformation of sheet metals under small radius condition, the normal stress cannot be neglected. Three-dimensional loading condition constructs complex shear stress states of sheet metals especially the out-of-plane shear stress. The out-of-plane performance must be considered in order to better understand the “shear fracture” phenomenon of AHSS. Compared to in-plane shear test, the out-of-plane shear test is more difficult to carry out due to the severe restriction of the dimensions in the thickness direction. In this paper, a new specimen is presented for out-of-plane shear test. Failure of the specimen occurs in shear between two centrally located notches machined halfway through its thickness from opposing sides. Meanwhile, the finite element (FE) model and possible failure modes of this specimen are investigated in detail. At last, brief experimental results between out-of-plane shear fracture strength and the in-plane shear fracture strength are compared for DP980 sheets.

  18. Hybrid Laser-Arc Welding of the High-Strength Shipbuilding Steels: Equipment and Technology

    Science.gov (United States)

    Turichin, G.; Kuznetsov, M.; Tsibulskiy, I.; Firsova, A.

    Hybrid laser-arc welding (HLAW) allows getting weld joints with thickness up to 35 mm for one pass, provide good quality formation of joints, minimal thermal deformations, the productivity in 10 times more in comparison with arc welding. In addition, replacement arc welding to the HLAW allows economizing filler materials, shielding gas and consumable electricity more than 4 times. Therefore, HLAW is actually technology for basic engineering branches and especially for shipbuilding. The Institute of Laser and Welding Technologies (ILWT) developed laser and hybrid laser-arc welding technologies for different type of steels and alloys including high-strength shipbuilding steels. Also ILWT produced portal and robotic systems for HLAW process realization. Portal system for hybrid laser-arc welding of panels with dimensions 6x6 m using at the manufacturing of flat curvilinear sections in the shipbuilding is depicted in the article. Results of experimental researches of the hybrid laser-arc welding parameters influence on the formation and mechanical properties of weld joint are described at the publication also. Experimental part was made with using of the portal system.

  19. High strength and heat resistant chromium steels for sodium-cooled fast reactors.

    Energy Technology Data Exchange (ETDEWEB)

    Kamal, S.; Grandy, C.; Farmer, M.; Brunsvold, A.

    2004-12-22

    This report provides the results of a preliminary phase of a project supporting the Advanced Nuclear Fuel Cycle Technology Initiative at ANL. The project targets the Generation IV nuclear energy systems, particularly the area of reducing the cost of sodium-cooled fast-reactors by utilizing innovative materials. The main goal of the project is to provide the nuclear heat exchanger designers a simplified means to quantify the cost advantages of the recently developed high strength and heat resistant ferritic steels with 9 to 13% chromium content. The emphasis in the preliminary phase is on two steels that show distinctive advantages and have been proposed as candidate materials for heat exchangers and also for reactor vessels and near-core components of Gen IV reactors. These steels are the 12Cr-2W (HCM12A) and 9Cr-1MoVNb (modified 9Cr-1Mo). When these steels are in tube form, they are referred to in ASTM Standards as T122 and T91, respectively. A simple thermal-hydraulics analytical model of a counter-flow, shell-and-tube, once-through type superheated steam generator is developed to determine the required tube length and tube wall temperature profile. The single-tube model calculations are then extended to cover the following design criteria: (i) ratio of the tube stress due to water/steam pressure to the ASME B&PV Code allowable stress, (ii) ratio of the strain due to through-tube-wall temperature differences to the material fatigue limit, (iii) overall differential thermal expansion between the tube and shell, and (iv) total amount of tube material required for the specified heat exchanger thermal power. Calculations were done for a 292 MW steam generator design with 2200 tubes and a steam exit condition of 457 C and 16 MPa. The calculations were performed with the tubes made of the two advanced ferritic steels, 12Cr-2W and 9Cr-1MoVNb, and of the most commonly used steel, 2 1/4Cr-1Mo. Compared to the 2 1/4Cr-1Mo results, the 12Cr-2W tubes required 29% less

  20. A cohesive zone model to simulate the hydrogen embrittlement effect on a high-strength steel

    Directory of Open Access Journals (Sweden)

    G. Gobbi

    2016-01-01

    Full Text Available The present work aims to model the fracture mechanical behavior of a high-strength low carbon steel, AISI 4130 operating in hydrogen contaminated environment. The study deals with the development of 2D finite element cohesive zone model (CZM reproducing a toughness test. Along the symmetry plane over the crack path of a C(T specimen a zero thickness layer of cohesive elements are implemented in order to simulate the crack propagation. The main feature of this kind of model is the definition of a traction-separation law (TSL that reproduces the constitutive response of the material inside to the cohesive elements. Starting from a TSL calibrated on hydrogen non-contaminated material, the embrittlement effect is simulated by reducing the cohesive energy according to the total hydrogen content including the lattice sites (NILS and the trapped amount. In this perspective, the proposed model consists of three steps of simulations. First step evaluates the hydrostatic pressure. It drives the initial hydrogen concentration assigned in the second step, a mass diffusion analysis, defining in this way the contribution of hydrogen moving across the interstitial lattice sites. The final stress analysis, allows getting the total hydrogen content, including the trapped amount, and evaluating the new crack initiation and propagation due to the hydrogen presence. The model is implemented in both plane strain and plane stress configurations; results are compared in the discussion. From the analyses, it resulted that hydrogen is located only into lattice sites and not in traps, and that the considered steel experiences a high hydrogen susceptibility. By the proposed procedure, the developed numerical model seems a reliable and quick tool able to estimate the mechanical behavior of steels in presence of hydrogen.

  1. Modeling of Austenite Grain Growth During Austenitization in a Low Alloy Steel

    Science.gov (United States)

    Dong, Dingqian; Chen, Fei; Cui, Zhenshan

    2016-01-01

    The main purpose of this work is to develop a pragmatic model to predict austenite grain growth in a nuclear reactor pressure vessel steel. Austenite grain growth kinetics has been investigated under different heating conditions, involving heating temperature, holding time, as well as heating rate. Based on the experimental results, the mathematical model was established by regression analysis. The model predictions present a good agreement with the experimental data. Meanwhile, grain boundary precipitates and pinning effects on grain growth were studied by transmission electron microscopy. It is found that with the increasing of the temperature, the second-phase particles tend to be dissolved and the pinning effects become smaller, which results in a rapid growth of certain large grains with favorable orientation. The results from this study provide the basis for the establishment of large-sized ingot heating specification for SA508-III steel.

  2. Influence of Boron on transformation behavior during continuous cooling of low alloyed steels

    Energy Technology Data Exchange (ETDEWEB)

    Terzic, A., E-mail: Adnan.Terzic@imf.tu-freiberg.de [Technische Universität Bergakademie Freiberg, Institute of Metal Forming, Bernhard-von-Cotta-Str. 4, 09596 Freiberg (Germany); Calcagnotto, M. [Salzgitter Mannesmann Forschung GmbH, Eisenhüttenstr. 99, 38239 Salzgitter (Germany); Guk, S. [Technische Universität Bergakademie Freiberg, Institute of Metal Forming, Bernhard-von-Cotta-Str. 4, 09596 Freiberg (Germany); Schulz, T. [Salzgitter Mannesmann Forschung GmbH, Eisenhüttenstr. 99, 38239 Salzgitter (Germany); Kawalla, R. [Technische Universität Bergakademie Freiberg, Institute of Metal Forming, Bernhard-von-Cotta-Str. 4, 09596 Freiberg (Germany)

    2013-11-01

    Abstracts: The phase transformation behavior during continuous cooling of low-carbon (LC) Boron-treated steels was studied. Furthermore, the influence of combining Boron with Nb or Ti or V on transformation kinetics was investigated. Additions of Boron to LC steels have a strong influence on the ferrite transformation. By adding 30 ppm Boron to a Boron-free reference alloy the suppressing effect on the ferrite transformation is most pronounced, whereas 10 ppm Boron has almost no effect and 50 ppm Boron the same effect as 30 ppm Boron. Thereby the critical Boron concentration for transformation kinetics in this alloying concept is 30 ppm. The combination of Boron with Ti shifts the phase fields to shorter times and increase the ferrite start temperature, whereas the combination of B+V and B+Nb only affects the ferrite start temperature. Hardness values are mostly influenced by the presence of Boron and strongly depend on the cooling rate.

  3. Phenomenon of low-alloy steel parametrization transformation at cyclic loading in low-cyclic area

    Science.gov (United States)

    Shipachev, A. M.; Nazarova, M. N.

    2017-10-01

    Following the results of measurements of hardness, magnetizing force and the rate of ultrasonic longitudinal waves of 09G2S steel samples at various cyclic operating time values, there is a phenomenon of transformation from the normal law of speed distribution of these parameters in power-mode distribution. It shows the submission of the behavior of metal as a complex system to the theory of the self-organized criticality.

  4. Influence of steel fibres on the blast response of normal-strength and high-strength reinforced concrete columns

    Science.gov (United States)

    Hammoud, A.; Aoude, H.

    2017-09-01

    This paper examines the influence of steel fibres on the blast performance of normal-strength concrete and high-strength concrete columns. As part of the study, four normal-strength and high-strength concrete columns built with and without steel fibres are tested under simulated blast loads using the shock-tube facility at the University of Ottawa. The specimens include two columns built with plain concrete and two columns built with steel fibre-reinforced concrete. The results show that the addition of steel fibres in reinforced concrete columns leads to important enhancements in blast performance, with improved control of mid-span displacements at equivalent blasts and increased damage tolerance.

  5. Carbon Equivalent (Pcm) Limits for Thick Carbon and Low Alloy Steels

    Science.gov (United States)

    2000-04-04

    by the BOF practice. The BOF is a tiltable vessel lined with basic refractory material. It is charged with a mixture of 65-75% molten pig iron and...That is, the scrap steel is added to prevent the temperature of the molten pool from exceeding 1650o C and causing excessive refractory erosion. Since...amount of each ingredient used for a particular heat. A typical heat of molten metal which weighs approximately 80 tons is then poured into a ladle for

  6. Influence of tempered microstructures on the transformation behaviour of cold deformed and intercritically annealed medium carbon low alloy steel

    Directory of Open Access Journals (Sweden)

    Kenneth Kanayo Alaneme

    2010-06-01

    Full Text Available This research is focused on understanding the role of microstructural variables and processing parameters in obtaining optimised dual phase structures in medium carbon low alloy steels. Tempered Martensite structures produced at 300, 500, and 650 °C, were cold rolled to varied degrees ranging from 20 to 80% deformation. Intercritical annealing was then performed at 740, 760, and 780 °C for various time duration ranging from 60 seconds to 60 minutes before quenching in water. The transformation behaviour was studied with the aid of optical microscopy and hardness curves. From the results, it is observed that microstructural condition, deformation, and intercritical temperatures influenced the chronological order of the competing stress relaxation and decomposition phase reactions which interfered with the rate of the expected α → γ transformation. The three unique transformation trends observed are systematically analyzed. It was also observed that the 300 and 500 °C tempered initial microstructures were unsuitable for the production of dual structures with optimized strength characteristics.

  7. Effect of Temperature on the Toughness of Locally Manufactured Low Alloy Steel SUP9 Used for Manufacturing Leaf Springs

    Directory of Open Access Journals (Sweden)

    Muhammad Ishaque Abro

    2011-10-01

    Full Text Available The effect of heat treatment on locally manufactured low alloy steel grade SUP9 most frequently used in making leaf springs for automobiles was studied. While for determination of toughness and hardness Charpy impact testing machine and Rockwell hardness tester were used. The cryogenic test temperatures were achieved by soaking the samples in liquid nitrogen and temperature was measured using digital thermometer capable of reading the temperature from -40-200oC. Hardening, tempering and austempering treatments were conducted using muffle furnace and salt bath furnace. After heat treatment samples were quenched in oil. The results of present work confirmed that toughness and hardness are inversely related with each other and are highly dependent on the type of heat treatment employed. Highest toughness was measured after austempering at 450oC. Effect of test temperature revealed that toughness of the samples increased significantly with decreasing temperature. DBTT (Ductile to Brittle Transition Temperature of the austempered samples was observed at -10oC, whereas, that of tempered samples could not be determined. Based on the test results authors wish to recommend the 600oC tempering temperature in place of 450oC where normally tempering is practiced in Alwin industry Karachi during manufacturing of leaf spring.

  8. The small punch assessment of toughness losses in low alloy steels

    Energy Technology Data Exchange (ETDEWEB)

    Bulloch, J.H. [ESB, Power Generation, Dublin (Ireland)

    1998-12-31

    The presentation deals at length with the relationship between the Small Punch, SP, test transition temperature Tsp, behaviour and those displayed by the conventional Charpy Fracture Appearance Transition Temperature, FATT, obtained from large test specimens. Essentially it was demonstrated that the total test temperature range trends could reasonably be described by a non-linear expression such as FATT varied inversely with the square of the Tsp. Finally when the Tsp against FATT trends were separated into different steel classes an encouraging picture emerged inasmuch that a reasonable amount of data exhibited good agreement with the predicted effects of grain size. Fractographic details were also discussed and strong effects of strain or loading rates were identified. (orig.) 19 refs.

  9. Structure-property relation in a quenched-partitioned low alloy steel involving bainite transformation

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Haoran [Beijing Jiaotong University, School of Mechanical, Electronic and Control Engineering, Material Science & Engineering Research Center, Beijing 100044 (China); Gao, Guhui, E-mail: gaogh@bjtu.edu.cn [Beijing Jiaotong University, School of Mechanical, Electronic and Control Engineering, Material Science & Engineering Research Center, Beijing 100044 (China); Gui, Xiaolu [Beijing Jiaotong University, School of Mechanical, Electronic and Control Engineering, Material Science & Engineering Research Center, Beijing 100044 (China); Misra, R.D.K., E-mail: dmisra2@utep.edu [Laboratory for Excellence in Advanced Steel Research, Department of Metallurgical and Materials Engineering, University of Texas at El Paso, TX 79968-0520 (United States); Bai, Bingzhe [Tsinghua University, Key Laboratory of Advanced Material, School of Material Science & Engineering, Beijing 100084 (China)

    2016-06-14

    The impact of bainite transformation during initial quenching and partitioning steps on the microstructural evolution was studied in a Fe-0.4C-2.0Mn-1.7Si-0.4Cr (wt%) steel. By optimizing quenching cooling rate and partitioning time, the final microstructure comprised of initial-quenched bainite, carbon-depleted martensite, bainite formed during partitioning, and final-quenched martensite, together with retained austenite. High volume fraction of retained austenite with desired carbon-content was obtained by prolonging the partitioning time to 2700 s The initial-quenched bainite, bainite formed during partitioning, and martensite provided carbon atoms to austenite, leading to the formation of retained austenite with different degree of stability. Consequently, a good combination of strength and elongation (ultimate tensile strength: 1688 MPa, total elongation: 25.2%) was obtained.

  10. Effects of postweld heat treatment on the dissimilar weldments of SA508 Gr. 4N Ni-Mo-Cr low alloy steels

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Hong Eun; Lee, Chang Hee [Hanyang University, Seoul (Korea, Republic of); Kim, Min Chul; Lee, Ho Jin; Kim, Keong Ho [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Jung, In Chul; Byeon, Jin Gwi [Doosan HEAVY Industries and Construction, Seoul (Korea, Republic of)

    2009-10-15

    Low alloy steels are generally employed in reactor pressure vessels (RPVs) of nuclear power plants. SA508 Gr.4N Ni-Mo-Cr low alloy steel has been studied as candidate materials for RPVs because it has excellent mechanical properties such as strength and toughness due to higher Ni and Cr contents compared with SA508 Gr.3 commercial RPV steel. In order to improve corrosion resistance of inner-wall of RPV, it is necessary to be coated by clad-welding with austenitic stainless steels such as 308L and 309L. PWHT of such dissimilar weldments results in the formation of a soft region near the weld interface on the low Cr side, and hard zone on the high Cr side of the weldment. The hardness change of weldments by formation of these characteristic zones affected overall safety margin and integrity property of RPV. In this study, effects of post-weld heat treatment (PWHT) on the microstructural and mechanical properties of dissimilar weldment between SA508 Gr.4N steel and austenitic stainless steel have been studied. The changes in microstructure, hardness and composition profiles across the weld interface were studied in detail. And, those results were compared with weldment in SA508 Gr.3 steel.

  11. Microstructure, Composition, and Impact Toughness Across the Fusion Line of High-Strength Bainitic Steel Weldments

    Science.gov (United States)

    Lan, Liangyun; Kong, Xiangwei; Chang, Zhiyuan; Qiu, Chunlin; Zhao, Dewen

    2017-09-01

    This paper analyzed the evolution of microstructure, composition, and impact toughness across the fusion line of high-strength bainitic steel weldments with different heat inputs. The main purpose was to develop a convenient method to evaluate the HAZ toughness quickly. The compositions of HAZ were insensitive to higher contents of alloy elements ( e.g., Ni, Mo) in the weld metal because their diffusion distance is very short into the HAZ. The weld metal contained predominantly acicular ferrite at any a heat input, whereas the main microstructures in the HAZ changed from lath martensite/bainite to upper bainite with the increasing heat input. The evolution of HAZ toughness in relation to microstructural changes can be revealed clearly combined with the impact load curve and fracture morphology, although the results of impact tests do not show an obvious change with heat input because the position of Charpy V notch contains the weld metal, HAZ as well as a part of base metal. As a result, based on the bead-on-plate welding tests, the welding parameter affecting the HAZ toughness can be evaluated rapidly.

  12. Experimental investigation of piercing of high-strength steels within a critical range of slant angle

    Science.gov (United States)

    Senn, S.; Liewald, M.

    2017-09-01

    Deep drawn parts often do have complex designs and, therefore, must be trimmed or punched subsequently in a second stage. Due to the complex part geometry, most punching areas do reveal critical slant angle (angle between part surface and ram movement direction) different to perpendicular direction. Piercing within a critical range of slant angle may lead to severe damage of the cutting tool. Consequently, expensive cam units are required to transform the ram moving direction in order to perform the piercing process perpendicularly to the local part surface. For modern sheet metals, however, the described critical angle of attack has not been investigated adequately until now. Therefore, cam units are used in cases in which regular piercing with high slant angle wouldn’t be possible. Purpose of this study is to investigate influencing factors and their effect on punch damage during piercing of high strength steels with slant angles. Therefore, a modular shearing tool was designed, which allows to simply switch die parts to vary cutting clearance and cutting angle. The target size of the study is to measure the lateral deviation of the punch which is monitored by an eddy current sensor. The sensor is located in the downholder and measures the lateral punch deviation in-line during manufacturing. The deviation is mainly influenced by slant angle of workpiece surface. In relation to slang angle and sheet thickness the clearance has a small influence on the measured punch deflection.

  13. The strain-rate sensitivity of high-strength high-toughness steels.

    Energy Technology Data Exchange (ETDEWEB)

    Dilmore, M.F. (AFRL/MNMW, Eglin AFB, FL); Crenshaw, Thomas B.; Boyce, Brad Lee

    2006-01-01

    The present study examines the strain-rate sensitivity of four high strength, high-toughness alloys at strain rates ranging from 0.0002 s-1 to 200 s-1: Aermet 100, a modified 4340, modified HP9-4-20, and a recently developed Eglin AFB steel alloy, ES-1c. A refined dynamic servohydraulic method was used to perform tensile tests over this entire range. Each of these alloys exhibit only modest strain-rate sensitivity. Specifically, the strain-rate sensitivity exponent m, is found to be in the range of 0.004-0.007 depending on the alloy. This corresponds to a {approx}10% increase in the yield strength over the 7-orders of magnitude change in strain-rate. Interestingly, while three of the alloys showed a concominant {approx}3-10% drop in their ductility with increasing strain-rate, the ES1-c alloy actually exhibited a 25% increase in ductility with increasing strain-rate. Fractography suggests the possibility that at higher strain-rates ES-1c evolves towards a more ductile dimple fracture mode associated with microvoid coalescence.

  14. Numerical and Experimental Investigation into Hot Forming of Ultra High Strength Steel Sheet

    Science.gov (United States)

    Liu, Hongsheng; Liu, Wei; Bao, Jun; Xing, Zhongwen; Song, Baoyu; Lei, Chengxi

    2011-02-01

    Hot forming of ultra high strength steel (UHSS) sheet metal grade 22MnB5 boron for channel components using water cooling is studied on a laboratory scale. After hot forming, the different microstructures such as martensite, bainite, and pearlite in formed component are produced, which are closely related with mechanical properties of formed component. The effect of forming start temperature and the contact state between blank and die on the microstructure evolution is investigated. In addition, the effect of processing parameters, such as forming start temperature and blank holder force (BHF), on the final quality of component, i.e., springback, that happens after hot forming of UHSS is investigated. It can be concluded that the forming start temperature has a significant effect on the final mechanical properties of formed components. The effect of forming start temperature on springback is examined in detail under a wide range of operating conditions. The higher the BHF and the forming start temperature, the lower is the springback after hot forming. Furthermore, thermo-mechanically coupled finite element analysis model encompassing heating of sheet blank, forming and quenching are developed for hot forming process. The stress distributions on sheet blank under different conditions during hot forming are compared to gain a fundamental understanding of the mechanism of springback. Comparisons show that numerical simulation results have good agreement with experimental results.

  15. Setting Mechanical Properties of High Strength Steels for Rapid Hot Forming Processes.

    Science.gov (United States)

    Löbbe, Christian; Hering, Oliver; Hiegemann, Lars; Tekkaya, A Erman

    2016-03-25

    Hot stamping of sheet metal is an established method for the manufacturing of light weight products with tailored properties. However, the generally-applied continuous roller furnace manifests two crucial disadvantages: the overall process time is long and a local setting of mechanical properties is only feasible through special cooling techniques. Hot forming with rapid heating directly before shaping is a new approach, which not only reduces the thermal intervention in the zones of critical formability and requested properties, but also allows the processing of an advantageous microstructure characterized by less grain growth, additional fractions (e.g., retained austenite), and undissolved carbides. Since the austenitization and homogenization process is strongly dependent on the microstructure constitution, the general applicability for the process relevant parameters is unknown. Thus, different austenitization parameters are analyzed for the conventional high strength steels 22MnB5, Docol 1400M, and DP1000 in respect of the mechanical properties. In order to characterize the resulting microstructure, the light optical and scanning electron microscopy, micro and macro hardness measurements, and the X-ray diffraction are conducted subsequent to tensile tests. The investigation proves not only the feasibility to adjust the strength and ductility flexibly, unique microstructures are also observed and the governing mechanisms are clarified.

  16. An evaluation of the using possibilities of the carbonitrided simple steels instead of carburized low alloy steels (wear properties)

    Science.gov (United States)

    Karamiş, M. B.; İpek, R.

    1997-09-01

    In this study, the wear behaviour of carburized and carbonitrided AISI 1020 and 5115 steels, widely used in industry, were investigated. The surface properties, microstructures, hardness distributions and wear behaviour of the treated steels were determined as well as the wear characteristics and weight losses of the treated samples as a function of wear test durations and loads. The results indicated that the surface of carbonitrided steel have ɛ-carbonitride compound layer and diffusion zone with chromium iron carbide (Cr, Fe)7C3, chromium carbide nitride (Cr62C3 · 5N0.3), chromium nitride (Cr2N), [Cr, Fe(2N1...x)] and Fe2N phases. The surface hardness and wear resistance of the carbonitrided samples are higher than those of the carburized samples. The carbonitrided 5115 steel has the highest wear resistance followed by carburized 5115, carbonitrided 1020 and carburized 1020 respectively.

  17. Control of Softening Processes in the Heat-Affected Zone During Welding of High-Strength Steels

    Science.gov (United States)

    Efimenko, L. A.; Kapustin, O. E.; Ramus', A. A.; Ramus', R. O.

    2016-11-01

    The hardness and the structure of the heat-affected zone (HAZ) under welding of tube steels of strength category K60 - K70 are studied. The steels are treated by regimes imitating the thermal cycles of different welding processes applied to tubes starting with manual arc welding and ending with energy-intensive automatic submerged-arc welding. The welding modes causing maximum decrease in the hardness of HAZ regions are determined. The conditions preventing softening under one-pass and multipass welding of high-strength steels are presented.

  18. The environmentally-assisted cracking behaviour in the transition region of nickel-base alloy/low-alloy steel dissimilar weld joints under simulated BWR conditions

    Energy Technology Data Exchange (ETDEWEB)

    Ritter, S.; Seifert, H.P.; Leber, H.J. [Paul Scherrer Institute, Nuclear Energy and Safety Research Department, Lab for Nuclear Materials, 5232 Villigen PSI (Switzerland)

    2011-07-01

    The stress corrosion cracking (SCC) behaviour perpendicular to the fusion line in the transition region between the Alloy 182 nickel-base weld metal and the adjacent low-alloy reactor pressure vessel (RPV) steel of simulated dissimilar metal weld joints was investigated under boiling water reactor normal water chemistry conditions at different stress intensities and chloride concentrations. A special emphasis was placed to the question whether a fast growing inter-dendritic SCC crack in the highly susceptible Alloy 182 weld metal can easily cross the fusion line and significantly propagate into the adjacent low-alloy RPV steel. Cessation of inter-dendritic stress corrosion crack growth was observed in high-purity or sulphate-containing oxygenated water under periodical partial unloading or constant loading conditions with stress intensity factors below 60 MPa-m{sup 1/2} for those parts of the crack front, which reached the fusion line. In chloride containing water, on the other hand, the inter-dendritic stress corrosion crack in the Alloy 182 weld metal very easily crossed the fusion line and further propagated with a very high growth rate as a transgranular crack into the heat-affected zone and base material of the adjacent low-alloy steel. (authors)

  19. submitter Physical Properties of a High-Strength Austenitic Stainless Steel for the Precompression Structure of the ITER Central Solenoid

    CERN Document Server

    Sgobba, Stefano; Arauzo, Ana; Roussel, Pascal; Libeyre, Paul

    2016-01-01

    The ITER central solenoid (CS) consists of six independent coils kept together by a precompression support structure that must react vertical tensile loads and provide sufficient preload to maintain coil-to-coil contact when the solenoid is energized. The CS precompression system includes tie plates, lower and upper key blocks, load distribution and isolation plates and other attachment, support and insulating hardware. The tie plates operating at 4 K are manufactured starting from forgings in a high-strength austenitic stainless steel (FXM-19) with a stringent specification. Moreover, forged components for the lower and upper key blocks have to be provided in the same FXM-19 grade with comparably strict requirements. FXM-19 is a high-nitrogen austenitic stainless steel, featuring high strength and toughness, ready weldability, and forgeability. It features as well higher integral thermal contraction down to 4 K compared with the very high Mn steel grade selected for the CS coil jackets, hence providing an ad...

  20. The Effects of Steel Fibre on the Mechanical Strength and Durability of Steel Fibre Reinforced High Strength Concrete (SFRHSC Subjected to Normal and Hygrothermal Curing

    Directory of Open Access Journals (Sweden)

    Velayutham G.

    2014-03-01

    Full Text Available This paper presents the experimental investigation into the mechanical strength and durability of steel fibre high strength concrete (SFHSC. In the experimental investigation, the properties of the steel fibre high strength concrete were assessed through two types of curing regimes, the normal water curing and the hygrothermal curing treatment, with the results of the tests being taken at 7 days and 7 days + 24 hours. The steel fibres were added at volume fractions of 0.5%, 1.0%, 1.5%, 2.0% and 3.0%. The tests that were performed for the mechanical strength and durability were the compressive and flexural strength test, the modulus of elasticity test, the ultrasonic pulse velocity test, the water absorption test, the air permeability test and the porosity test. The compressive and flexural strength of the steel fibre high strength concrete reached their maximum of 70.7 MPa and 11.45 MPa, respectively during normal curing for the 3.0% volume fraction of steel fibre. The experimental results of this study indicate that the inclusion of steel fibres enhances the mechanical strength of high strength concrete cured in normal water curing as compared to the hygrothermal curing treatment.

  1. Development of Appropriate Spot Welding Practice for Advanced High Strength Steels (TRP 0114)

    Energy Technology Data Exchange (ETDEWEB)

    Brian Girvin; Warren Peterson; Jerry Gould

    2004-09-17

    This program evaluated the effects of common manufacturing variables on spike-tempering effectiveness. The investigation used design-of-experiment (DOE) techniques, and examined both dual-phase and martensitic grades of high-strength steels (HSS). The specific grades chosen for this project were: Dual-phase (DP) 600, galvannealed (GA), 1.55 mm (DP) 600; Dual-phase (DP) 980 (uncoated), 1.55 mm (DP) 980; and Martensitic (M) 1300, 1.55 mm (M) 1300. Common manufacturing conditions of interest included tempering practice (quench and temper time), button size, simulated part fitup (sheet angular misalignment and fitup), and electrode wear (increased electrode face diameter). All of these conditions were evaluated against mechanical performance (static and dynamic tensile shear). Weld hardness data was also used to examine correlations between mechanical performance and the degree of tempering. Mechanical performance data was used to develop empirical models. The models were used to examine the robustness of weld strength and toughness to the selected processing conditions. This was done using standard EWI techniques. Graphical representations of robustness were then coupled with metallographic data to relate mechanical properties to the effectiveness of spike tempering. Mechanical properties for all three materials were relatively robust to variation in tempering. Major deviations in mechanical properties were caused by degradation of the weld itself. This was supported by a lack of correlation between hardness data and mechanical results. Small button sizes and large electrode face diameters (worn electrodes) produced large reductions in both static and dynamic strength levels when compared to standard production setups. Dynamic strength was further degraded by edge-located welds.

  2. Integrated Computational Materials Engineering Development of Advanced High Strength Steel for Lightweight Vehicles

    Energy Technology Data Exchange (ETDEWEB)

    Hector, Jr., Louis G. [General Motors, Warren, MI (United States); McCarty, Eric D. [United States Automotive Materials Partnership LLC (USAMP), Southfield, MI (United States)

    2017-07-31

    The goal of the ICME 3GAHSS project was to successfully demonstrate the applicability of Integrated Computational Materials Engineering (ICME) for the development and deployment of third generation advanced high strength steels (3GAHSS) for immediate weight reduction in passenger vehicles. The ICME approach integrated results from well-established computational and experimental methodologies to develop a suite of material constitutive models (deformation and failure), manufacturing process and performance simulation modules, a properties database, as well as the computational environment linking them together for both performance prediction and material optimization. This is the Final Report for the ICME 3GAHSS project, which achieved the fol-lowing objectives: 1) Developed a 3GAHSS ICME model, which includes atomistic, crystal plasticity, state variable and forming models. The 3GAHSS model was implemented in commercially available LS-DYNA and a user guide was developed to facilitate use of the model. 2) Developed and produced two 3GAHSS alloys using two different chemistries and manufacturing processes, for use in calibrating and validating the 3GAHSS ICME Model. 3) Optimized the design of an automotive subassembly by substituting 3GAHSS for AHSS yielding a design that met or exceeded all baseline performance requirements with a 30% mass savings. A technical cost model was also developed to estimate the cost per pound of weight saved when substituting 3GAHSS for AHSS. The project demonstrated the potential for 3GAHSS to achieve up to 30% weight savings in an automotive structure at a cost penalty of up to $0.32 to $1.26 per pound of weight saved. The 3GAHSS ICME Model enables the user to design 3GAHSS to desired mechanical properties in terms of strength and ductility.

  3. Modeling and FE Simulation of Quenchable High Strength Steels Sheet Metal Hot Forming Process

    Science.gov (United States)

    Liu, Hongsheng; Bao, Jun; Xing, Zhongwen; Zhang, Dejin; Song, Baoyu; Lei, Chengxi

    2011-08-01

    High strength steel (HSS) sheet metal hot forming process is investigated by means of numerical simulations. With regard to a reliable numerical process design, the knowledge of the thermal and thermo-mechanical properties is essential. In this article, tensile tests are performed to examine the flow stress of the material HSS 22MnB5 at different strains, strain rates, and temperatures. Constitutive model based on phenomenological approach is developed to describe the thermo-mechanical properties of the material 22MnB5 by fitting the experimental data. A 2D coupled thermo-mechanical finite element (FE) model is developed to simulate the HSS sheet metal hot forming process for U-channel part. The ABAQUS/explicit model is used conduct the hot forming stage simulations, and ABAQUS/implicit model is used for accurately predicting the springback which happens at the end of hot forming stage. Material modeling and FE numerical simulations are carried out to investigate the effect of the processing parameters on the hot forming process. The processing parameters have significant influence on the microstructure of U-channel part. The springback after hot forming stage is the main factor impairing the shape precision of hot-formed part. The mechanism of springback is advanced and verified through numerical simulations and tensile loading-unloading tests. Creep strain is found in the tensile loading-unloading test under isothermal condition and has a distinct effect on springback. According to the numerical and experimental results, it can be concluded that springback is mainly caused by different cooling rats and the nonhomogengeous shrink of material during hot forming process, the creep strain is the main factor influencing the amount of the springback.

  4. Microstructure and Property of Mn-Nb-B Low Carbon Bainite High Strength Steel Under Ultra-fast Cooling

    Directory of Open Access Journals (Sweden)

    WANG Bing-xing

    2016-07-01

    Full Text Available Using the Mn-Nb-B low carbon bainite high strength steel with the reducing production technology as the research target, the deformation behavior and phase transformation behavior were studied by the thermal simulation testing machine. Combining with the characteristics of the medium and heavy plate production line, the controlled rolling and controlled cooling technology based on ultra-fast cooling were designed to produce low cost high strength construction machinery steel with superior comprehensive mechanical properties. The strengthening mechanisms such as grain refinement strengthening, precipitation strengthening are effective to produce the Mn-Nb-B low carbon bainite high strength steel. The yield strength and tensile strength of the product reach to 678MPa and 756 MPa respectively, the elongation A50 is 33% and the impact energy at -20℃ is 261J. The microstructure of the steel is composed of granular bainite, acicular ferrite and lath bainite. A large number of fine, point, granular M/A constituents and dislocation structures dispersively distributed inside the matrix, and also tiny and dispersed (Nb,Ti (C,N precipitates are observed by transmission electron microscopy.

  5. Comparison on Mechanical Properties of SA508 Gr.3 Cl.1, Cl.2, and Gr.4N Low Alloy Steels for Pressure Vessels

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Min-Chul; Park, Sang-Gyu; Lee, Bong-Sang [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Lee, Ki-Hyoung [Korea Institute of Nuclear Safety, Daejeon (Korea, Republic of)

    2014-10-15

    In this study, microstructure and mechanical properties of SA508 Gr.3 Cl. 1, Cl.2, and Gr.4N low alloy steels are characterized to compare their properties. To evaluate the fracture toughness in the transition region, the master curve method according to ASTM E1921 was adopted in the cleavage transition region. Tensile tests and Charpy impact tests were also performed to evaluate the mechanical properties, and a microstructural investigation was carried out. The microstructure and mechanical properties of SA508 Gr.3 Cl.1, Cl2 and Gr.4N low alloy steels were characterized.. The predominant microstructure of SA508 Gr.4N model alloy is tempered martensite, while SA508 Gr.3 Cl.1 and Cl.2 steels show a typical tempered upper bainitic structure. SA508 Gr. 4N model alloy shows the best strength and transition behavior among the three SA508 steels. SA508 Gr.3 Cl.2 steel also has quite good strength, but there is a loss of toughness.

  6. Development of Low Carbon Niobium Bearing High Strength F-B Dual Phase Steel with High Hole Expansion Property

    Science.gov (United States)

    Zhang, Lin; Xia, Ming-sheng; Xiong, Zi-liu; Du, Yan-bing; Qiao, Zhi-ming; Zhang, Hong-bo

    In the study a low carbon niobium bearing high strength F-B dual phase automobile steel with high hole expansion property has been investigated. Steels of different chemical composition have been investigated by simulation experiments of controlled rolling and cooling process to study the influences of chemical elements, especially for C,Nb and Ti, and cooling pattern on the mechanical properties, flangeability and microstructure of strips. So-called 3-stages cooling pattern was adopted in simulation experiments, combining ultra fast cooling in first stage, air cooling in middle stage and fast cooling in the last stage, and at the end of run-out table the temperature of rolled pieces drop to below Bs point. Optical microstructure and SEM morphology have been observed. Results indicate that it is possible to obtain dual phase microstructure of polygonal ferrite plus bainite in adopting 3-stages cooling pattern. The low temperature coiling method using 3-step controlled cooling pattern after hot rolling is effective to produce low carbon Nb bearing steel with high balance of strength-ductility-flangeability, in addition, higher carbon content of steel tend to be detrimental to flangeability of steel, due to much carbide precipitation at ferrite boundary. Based on the results of simulation experiments mill trial has been carried out and hot rolled high strength steel with tensile strength higher as 600Mpa and hole expansion ratio higher as 100% has been developed successfully.

  7. Microstructure Control of Fire-resistant, Low-alloy Steel; An in-situ 3D X-ray Diffraction and A Small-angle X-ray Scattering Study

    NARCIS (Netherlands)

    Dere, E.G.

    2013-01-01

    The research presented in this thesis aims at deepening our understanding of the formation of the microstructure of steel during thermal processing in order to control the microstructure and thereby improve the fire-resistance of low-alloy steel. The strength of steel decreases during a fire mainly

  8. Microstructure Control of Fire-resistant, Low-alloy Steel; An in-situ 3D X-ray Diffraction and A Small-angle X-ray Scattering Study

    NARCIS (Netherlands)

    Sietsma, J.; Offerman, S.E.; Dere, E.G.

    The research presented in this thesis aims at deepening our understanding of the formation of the microstructure of steel during thermal processing in order to control the microstructure and thereby improve the fire-resistance of low-alloy steel. The strength of steel decreases during a fire mainly

  9. Fatigue strain-life behavior of carbon and low-alloy steels, austenitic stainless steels, and Alloy 600 in LWR environments

    Energy Technology Data Exchange (ETDEWEB)

    Keisler, J.; Chopra, O.K.; Shack, W.J. [Argonne National Lab., IL (United States)

    1995-08-01

    The existing fatigue strain vs. life (S-N) data, foreign and domestic, for carbon and low-alloy steels, austenitic stainless steels, and Alloy 600 used in the construction of nuclear power plant components have been compiled and categorized according to material, loading, and environmental conditions. Statistical models have been developed for estimating the effects of the various service conditions on the fatigue life of these materials. The results of a rigorous statistical analysis have been used to estimate the probability of initiating a fatigue crack. Data in the literature were reviewed to evaluate the effects of size, geometry, and surface finish of a component on its fatigue life. The fatigue S-N curves for components have been determined by adjusting the probability distribution curves for smooth test specimens for the effect of mean stress and applying design margins to account for the uncertainties due to component size/geometry and surface finish. The significance of the effect of environment on the current Code design curve and on the proposed interim design curves published in NUREG/CR-5999 is discussed. Estimations of the probability of fatigue cracking in sample components from BWRs and PWRs are presented.

  10. Influence of mill scale and rust layer on the corrosion resistance of low-alloy steel in simulated concrete pore solution

    Science.gov (United States)

    Shi, Jin-jie; Ming, Jing

    2017-01-01

    Electrochemical impedance spectroscopy, cyclic potentiodynamic polarization measurements, and scanning electron microscopy in conjunction with energy-dispersive X-ray spectroscopy were used to investigate the influence of mill scale and rust layer on the passivation capability and chloride-induced corrosion behaviors of conventional low-carbon (LC) steel and low-alloy (LA) steel in simulated concrete pore solution. The results show that mill scale exerts different influences on the corrosion resistance of both steels at various electrochemical stages. We propose that the high long-term corrosion resistance of LA steel is mainly achieved through the synergistic effect of a gradually formed compact, adherent and well-distributed Cr-enriched inner rust layer and the physical barrier protection effect of mill scale.

  11. Laser-Assisted Sheet Metal Working of High Strength Steels in Serial Production

    Science.gov (United States)

    Brecher, Christian; Emonts, Michael; Eckert, Markus

    Within the sheet metal working industry the demand for thinner sheet materials with very high strength is growing due to the increasing need to save energy and a responsible use of natural resources. The high strength and the low ductility restricts using state of art technology to sheer, bend, emboss or deep draw parts with the needed complexity and quality. The Fraunhofer IPT developed a combination of laser-assisted preheating and conventional punching to a new hybrid technology which allows to shear, bend, emboss and draw high strength materials with a high quality and complexity in a serial production.

  12. Fracture Profile and Crack Propagation of Ultra-High Strength Hot-Stamped Boron Steel During Mechanical Trimming Process

    Science.gov (United States)

    Han, Xianhong; Yang, Kun; Chen, Sisi; Chen, Jun

    2015-10-01

    Mechanical trimming process for ultra-high strength boron steel after hot stamping was carried out in this study. Shear and tensile tests were designed to analyze the influences of stress state on the fracture mode; trimmed fracture surface and profile were observed and compared to other commonly used steels such as DP980 and Q235 etc.; the crack propagation during trimming process was studied through step-by-step tests. The observation and analysis reveal that the fracture mode of hot-stamped boron steel is highly related to the stress state, it belongs to cleavage fracture on low stress triaxiality but dimple fracture on high stress triaxiality. Such phenomenon is reflected in the trimming process, during which the stress state changes from shear-dominated state to tensile-dominated state. In addition, the burnish zone of trimmed boron steel is much smaller than other high strength steels, and the profile of cutting surface shows an `S'-like shape which is destructive to the trimming tool. Moreover, during the trimming process, most martensite laths near the cutting edge are stretched and rotated markedly to the direction of the shear band, and the main crack expands along those grain boundaries, which may penetrate through a few martensite laths and form small crack branches.

  13. Experimental and numerical determination of thermal forming limit diagrams (TFLD) of high strength steel 22MnB5

    Science.gov (United States)

    Shi, D. Y.; Ying, L.; Hu, P.; Lu, J. D.; Zhao, X.; Liu, W. Q.

    2013-05-01

    High strength steel components are increasingly being considered for use in vehicle structures due to the potential for higher strength to weight ratio, fuel economy improvement and emission reduction. However, high strength steel's poor ductility at room temperature requires sheet forming to be carried out in hot forming method. The Thermal Forming Limit Diagram (TFLD) is an important primary criterion to determine how close the sheet metal is to tearing when it is formed into a product shape in hot forming process. In this work, an efficient experimental set-up named TFLD 300 which is based on Nakajima test has been developed. Several experiments for hot forming limits of high strength steel 22MnB5 were performed and the forming limit curves at different temperatures are obtained. Then the three-dimensional TFLD which considers temperature history and strain path is constructed. As an evaluation criterion for formability, the three-dimensional TFLD is introduced into KMAS (King Mesh Analysis System), which is independently developed commercial CAE software and can be used for hot forming simulation. Subsequently, a typical B-pillar's hot forming process with varying process conditions have been simulated by using the KMAS software. And the corresponding experiment results confirm that the KMAS software and three-dimensional TFLD can accurately predict the fracture of sheet metal in hot forming.

  14. Behavior of steel fiber high strength concrete under impact of projectiles

    Directory of Open Access Journals (Sweden)

    Cánovas, M. F.

    2012-09-01

    Full Text Available This paper presents the results of the investigation carried out by the authors about the behavior of 80 MPa characteristic compression strength concrete reinforced with different amount of high carbon content steel fiber, submit to impact of different caliber projectiles, determining the thickness of this type of concrete walls needs to prevent no perforation, as well as the maximum penetration to reach into them, so that in the event of no perforation and only penetration, "scabbing" phenomena does not take place on the rear surface of the wall. Prior to ballistic testing was necessary to design the high-strength concrete with specific mechanical properties, especially those related to ductility, since these special concrete must absorb the high energy of projectiles and also the shock waves that accompany them.Este trabajo presenta los resultados de la investigación llevada a cabo por los autores sobre el comportamiento de hormigón de 80 MPa de resistencia característica a compresión reforzado con diferentes cuantías de fibras de acero de alto contenido en carbono sometido al impacto de proyectiles de distintos calibres, determinando el espesor de muros de este tipo de hormigón que sería preciso disponer para impedir su perforación por dichos proyectiles, así como los valores máximos de penetración, para que en el caso de no producirse perforación y sólo penetración, no se genera cráter, “scabbing”, en el trasdós de los mismos. Previamente a los ensayos balísticos fue preciso diseñar los hormigones para que, presentaran determinadas características mecánicas, especialmente las relacionadas con la ductilidad, dado que estos hormigones especiales deben absorber la elevada energía que le transmiten los proyectiles y las ondas de choque que los acompañan.

  15. Laser-Assisted Sheet Metal Working of High Strength Steels in Serial Production

    OpenAIRE

    Brecher, Christian; Emonts, Michael; Eckert, Markus

    2011-01-01

    Within the sheet metal working industry the demand for thinner sheet materials with very high strength is growing due to the increasing need to save energy and a responsible use of natural resources. The high strength and the low ductility restricts using state of art technology to sheer, bend, emboss or deep draw parts with the needed complexity and quality. The Fraunhofer IPT developed a combination of laser-assisted preheating and conventional punching to a new hybrid technology which allo...

  16. Effect of Loading Rate on the Deformation Behavior of SA508 Gr.1a Low Alloy Steel and TP316 Stainless Steel Pipe Materials at RT and 316℃

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jin Weon; Choi, Myung Rak [Chosun University, Gwangju (Korea, Republic of)

    2015-04-15

    This study conducted tensile tests on SA508 Gr.1a low alloy steel and SA312 TP316 stainless steel piping materials under various strain rates at room temperature (RT) and 316°C to investigate the effects of loading rate on the deformation behavior of nuclear piping materials. At RT, the deformation behavior for both pipe materials showed a typical loading rate dependence, i.e., the strength increased and the ductility decreased as the loading rate increased. At 316°C, however, the strength and elongation of SA508 Gr.1a low alloy steel decreased as the loading rate increased, and its reduction of area non-linearly varied with the loading rate. For SA312 TP316 stainless steel, the strength, elongation, and reduction of area at 316°C were almost the same regardless of the loading rate. At both temperatures, the strain hardening capacity was nearly independent of the loading rate for SA508 Gr.1a low alloy steel, while it decreased with increasing loading rate for SA312 TP316 stainless steel.

  17. Pitting corrosion resistance and bond strength of stainless steel overlay by friction surfacing on high strength low alloy steel

    OpenAIRE

    Amit Kumar Singh; G. Madhusudhan Reddy; K. Srinivas Rao

    2015-01-01

    Surface modification is essential for improving the service properties of components. Cladding is one of the most widely employed methods of surface modification. Friction surfacing is a candidate process for depositing the corrosion resistant coatings. Being a solid state process, it offers several advantages over conventional fusion based surfacing process. The aim of this work is to identify the relationship between the input variables and the process response and develop the predictive mo...

  18. Effects of Phase Fraction on Temperature Dependency of Fracture Toughness in Transition Temperature Region in SA508 Gr. 4N Ni-Mo-Cr Low Alloy Steels

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Ki Hyoung; Wee, Dang Moon [Korea Advanced Institute of Science and Technology, Daejeon (Korea, Republic of); Kim, Min Chul; Lee, Bong Sang [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2010-10-15

    The Reactor Pressure Vessel (RPV) is the main component in determining the lifetime of nuclear power plants because it is subject to the aging phenomenon of irradiation embrittlement and there is no practical method for replacing that component. For materials used for the RPV, sufficient strength and toughness are required to prevent failure against the severe operating conditions and the aging degradation of materials. SA508 Gr.4N Ni-Mo-Cr low alloy steel, in which Ni and Cr contents are higher than in conventional RPV steels, may be a promising RPV material with the improved strength and toughness from its tempered martensitic microstructure. Wallin observed that the temperature dependency of fracture toughness is not sensitive to the chemical composition, heat treatment, and irradiation for ferritic steels. This result led to the concept of a universal shape in the median toughness-temperature curve for all 'ferritic steels'. However, there are some doubts about the universal shape in the ASTM master curve for the tempered martensitic steels, such as Eurofer97. It was also reported that the fracture toughness increased discontinuously when the phase fraction of the tempered martensite was over a critical fraction in the heat affected zones of SA508 Gr.3. Therefore, it may be necessary to evaluate the changes of transition behavior with microstructures of steel. In this study, the effects phase fraction of tempered martensite controlled by a cooling rate on the transition behavior of SA508 Gr.4N low alloy steels was evaluated. Additionally, the relationship between the variations of yield strength with the temperature and fracture stress in a local approach was discussed

  19. Crack growth behaviour of low alloy steels for pressure boundary components under transient light water reactor operating conditions (CASTOC)

    Energy Technology Data Exchange (ETDEWEB)

    Foehl, J.; Weissenberg, T. [Materialpruefungsanstalt, Univ. Stuttgart (Germany); Gomez-Briceno, D.; Lapena, J. [Centro de Investigaciones Energeticas, Medioambientales y Tecnologicas (CIEMAT) (Spain); Ernestova, M.; Zamboch, M. [Nuclear Research Inst. (NRI) (Czech Republic); Seifert, H.P.; Ritter, S. [Paul Scherrer Inst. (PSI) (Switzerland); Roth, A.; Devrient, B. [Framatome ANP GmbH (F ANP) (Germany); Ehrnsten, U. [Technical Research Centre of Finland (VTT) (Finland)

    2004-07-01

    The CASTOC project addresses environmentally assisted cracking (EAC) phenomena in low alloy steels used for pressure boundary components in both Western type boiling water reactors (BWR) and Russian type pressurised water reactors (VVER). It comprises the four work packages (WP): inter-laboratory comparison test (WP1); EAC behaviour under static load (WP2), EAC behaviour under cyclic load and load transients (WP3); evaluation of the results with regard to their relevance for components in practice (WP4). The use of sophisticated test facilities and measurement techniques for the on-line detection of crack advances have provided a more detailed understanding of the mechanisms of environmentally assisted cracking and provided quantitative data of crack growth rates as a function of loading events and time, respectively. The effect of several major parameters controlling EAC was investigated with particular emphasis on the transferability of the results to components in service. The obtained crack growth rate data were reflected on literature data and on commonly applied prediction curves as presented in the appropriate Code. At relevant stress intensity factors it could be shown that immediate cessation of growing cracks occurs after changing from cyclic to static load in high purity oxygenated BWR water and oxygen-free VVER water corresponding to steady state operation conditions. Susceptibility to environmentally assisted cracking under static load was observed for a heat affected zone material in oxygenated high purity water and also in base materials during a chloride transient representing BWR water condition below Action Level 1 of the EPRI Water Chemistry Guidelines according to the lectrical conductivity of the water but in the range of Action Level 2 according to the content of chlorides. Time based crack growth was also observed in one Russian type base material in oxygenated VVER water and in one Western type base material in oxygenated high purity BWR

  20. EIS Behavior of Experimental High-Strength Steel in Near-Neutral pH and Load Conditions

    Science.gov (United States)

    Barraza-Fierro, Jesus Israel; Serna-Barquera, Sergio Alonso; Campillo-Illanes, Bernardo Fabian; Castaneda, Homero

    2017-04-01

    Two thermomechanical heat treatments were applied to a high-strength low carbon steel with an experimental chemical composition, and as a result two different microstructures were obtained. Steel A had a ferritic microstructure, and steel B had a bainitic-martensitic one. The corrosion behavior was reviewed at long times in samples without load by means of Electrochemical Impedance Spectroscopy (EIS) in a near-neutral pH (NNpH) environment. The results showed that the quantity and adherence of corrosion products on the sample surface at long times are different. Hence, the impedance was higher for steel B. Slow strain rate testing (SSRT) was applied to tempered samples of the two steels at 473 K, 673 K, and 873 K (200 °C, 400 °C, and 600 °C), and the corrosion behavior was acquired using EIS at the same time as the SSRT in NNpH conditions. This is a novel result because the tension samples were not electrically isolated from the rest of the load frame. The impedance for the ferritic steel was higher than the bainitic-martensitic one, while it slightly decreased for both steel over time. Tempering improved the corrosion resistance for steel A, while it was not modified for steel B. The corrosion behavior could be associated with the susceptibility of these steels to stress corrosion cracking. A transmission line model was proposed to show qualitatively the corrosion behavior of a crack in the steel, if there is a potential profile inside the crack. A hypothetical potential profile was acquired as well as different impedance behaviors based on electrochemical variables.

  1. Hydrogen diffusion and effect on degradation in welded microstructures of creep-resistant low-alloyed steels

    Energy Technology Data Exchange (ETDEWEB)

    Rhode, Michael

    2016-04-04

    The main challenge for the future is to further increase the power plant thermal efficiency independent of the type of power plant concept, i.e. fossil-fired or nuclear power plant, where the material selection can directly affect reduction of CO{sub 2} emissions. In power plant design, welding is the most applied manufacturing technique in component construction. The necessary weld heat input causes metallurgical changes and phase transitions in the heat affected zone (HAZ) of the base materials and in the deposited weld metal. The weld joint can absorb hydrogen during welding or in later service - This absorption can cause degradation of mechanical properties of the materials, and in certain loading conditions, hydrogen-assisted cold cracks can occur. This cracking phenomenon can appear time delayed due to the temperature dependency of the hydrogen diffusion and the presence of a ''critical'' hydrogen concentration. Additionally, each specific weld microstructure shows a certain hydrogen diffusion and solubility that contribute to susceptibility of the cracking phenomenon. Therefore hydrogen cannot be neglected as possible failure effect, which was identified recently in the case of T24 creep-resistant tube-to-tube weld joints. It is necessary to identify and assess the hydrogen effect in weld joints of low-alloyed steel grades for to improve further early detection of possible failures. For each specific weld joint microstructure, it is necessary to separate the interdependencies between mechanical load and the hydrogen concentration. The diffusivity and solubility must be considered to identify hydrogen quantities in the material at any given time. In this case, the effects of mechanical loading were dealt with independently. For the characterization of the mechanical properties, hydrogen charged tensile specimens were investigated for the base materials and thermally simulated HAZ microstructures. The hydrogen diffusion was characterized

  2. Effects of Nitrogen Content on the HAZ Softening of Ti-Containing High Strength Steels Manufactured by Accelerated Cooling

    Energy Technology Data Exchange (ETDEWEB)

    Bang, Kook-soo; Jung, Ho-shin; Park, Chan [Pukyong National University, Busan (Korea, Republic of)

    2017-03-15

    The effects of nitrogen content on the HAZ softening of Ti-containing high strength steels manufactured by accelerating cooling were investigated and interpreted in terms of the microstructures in the softening zone. Regardless of their content, all of the steels investigated showed a softened zone 9-10 mm wide. The minimum hardness in the zone, however, was different, with lower hardness in the higher nitrogen content steel. Microstructural observations of the steel showed that the amount of soft ferrite was increased in the zone with an increase of nitrogen content of the steel, suggesting that microstructural evolution in the HAZ is influenced by the nitrogen content. Measurements of TiN particles showed that the degree of particles coarsening in the HAZ was lower in the higher nitrogen content steel. Therefore, it is believed that finer TiN particles in the HAZ inhibit austenite grain growth more effectively, and lead to an accelerated ferrite transformation in higher nitrogen content steel, resulting in a higher amount of soft ferrite microstructure in the softened zone.

  3. The role of water chemistry for environmentally assisted cracking in low-alloy reactor pressure vessel and piping steels under boiling reactor conditions

    Energy Technology Data Exchange (ETDEWEB)

    Seifert, H.-P.; Ritter, S

    2005-07-01

    The environmentally assisted initiation and propagation of cracks in structural materials is one of the most important degradation and ageing mechanisms in light water reactors (LWR) and may seriously affect plant availability and economics. In the first part of this paper a short general introduction on environmentally assisted cracking (EAC) and its significance for LWR is given. Then the important role of water chemistry control in reducing the EAC risk in LWR is illustrated by current research results about the effect of chloride transients and hydrogen water chemistry on the EAC crack growth behaviour of low-alloy reactor pressure vessel and piping steels under boiling water reactor conditions. (author)

  4. Hydrogen induced cold cracking studies on armour grade high strength, quenched and tempered steel weldments

    Energy Technology Data Exchange (ETDEWEB)

    Magudeeswaran, G.; Balasubramanian, V. [Centre for Materials Joining Research (CEMAJOR), Department of Manufacturing Engineering, Annamalai University, Annamalai Nagar 608 002, Tamil Nadu (India); Madhusudhan Reddy, G. [Metal Joining Section, Defence Metallurgical Research Laboratory (DMRL), Kanchanbagh (P.O.) Hyderabad 560 058 Andhra Pradesh (India)

    2008-04-15

    Quenched and tempered (Q and T) steels are prone to hydrogen induced cracking (HIC) in the heat affected zone after welding. The use of austenitic stainless steel (ASS) consumables to weld the above steel was the only available remedy because of higher solubility for hydrogen in austenitic phase. The use of stainless steel consumables for a non-stainless steel base metal is not economical. Hence, alternate consumables for welding Q and T steels and their vulnerability to HIC need to be explored. Recent studies proved that low hydrogen ferritic (LHF) steel consumables can be used to weld Q and T steels, which can give very low hydrogen levels in the weld deposits. In this investigation an attempt has been made to study the influence of welding consumables and welding processes on hydrogen induced cold cracking of armour grade Q and T steel welds by implant testing. Shielded metal arc welding (SMAW) and flux cored arc welding (FCAW) processes were used for making welds using ASS and LHF welding consumables. ASS welds made using FCAW process offered a higher resistance to HIC than all other welds considered in this investigation. (author)

  5. An investigation of laser cutting quality of 22MnB5 ultra high strength steel using response surface methodology

    Science.gov (United States)

    Tahir, Abdul Fattah Mohd; Aqida, Syarifah Nur

    2017-07-01

    In hot press forming, changes of mechanical properties in boron steel blanks have been a setback in trimming the final shape components. This paper presents investigation of kerf width and heat affected zone (HAZ) of ultra high strength 22MnB5 steel cutting. Sample cutting was conducted using a 4 kW Carbon Dioxide (CO2) laser machine with 10.6 μm wavelength with the laser spot size of 0.2 mm. A response surface methodology (RSM) using three level Box-Behnken design of experiment was developed with three factors of peak power, cutting speed and duty cycle. The parameters were optimised for minimum kerf width and HAZ formation. Optical evaluation using MITUTOYO TM 505 were conducted to measure the kerf width and HAZ region. From the findings, laser duty cycle was crucial to determine cutting quality of ultra-high strength steel; followed by cutting speed and laser power. Meanwhile, low power intensity with continuous wave contributes the narrowest kerf width formation and least HAZ region.

  6. Use of Niobium High Strength Steels with 450 MPA Yield Strength for Construction

    Science.gov (United States)

    Silvestre, Leonardo; Langenberg, Peter; Amaral, Thiago; Carboni, Marcelo; Meira, Marcos; Jordão, Alexandre

    This paper presents an actual case of a new industrial building at CBMM's plant in Araxá, Brazil as an example of lean design using microalloyed steels. The structure consists mostly of microalloyed ASTM A572 steel grades 65 and 50 instead of the conventional carbon manganese ASTM A36 steel. The application of grade 65 with more than 450 MPa of yield strength is an innovative solution for this type of construction in South America. A complete welding evaluation performed on the low carbon, niobium microalloyed grade 65 steel showed the welding properties and benefits. Niobium's effect of increasing strength and toughness simultaneously resulted in relevant savings in total steel consumption for the project. The paper also quantifies the expected savings in costs, energy and carbon dioxide emissions.

  7. Experimental investigation of the effect of surface markings on the mechanical integrity of weathering bridge steels.

    Science.gov (United States)

    2014-11-01

    High-strength low-alloy (HSLA) weathering steels are the conventional material used for non-redundant fracture-critical members in bridge construction. Guidelines have been put in place by state : Departments of Transportation (DOTs) to prevent mater...

  8. Effect of thermal and thermo-mechanical cycling on the boron segregation behavior in the coarse-grained heat-affected zone of low-alloy steel

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Sanghoon; Kang, Yongjoon; Lee, Changhee, E-mail: chlee@hanyang.ac.kr

    2016-06-15

    The boron segregation behavior in the coarse-grained heat-affected zone (CGHAZ) of 10 ppm boron-added low-alloy steel during the welding cycle was investigated by taking the changes in the microstructure and hardness into account. Various CGHAZs were simulated with a Gleeble system as a function of the heat input and external stress, and the boron segregation behavior was analyzed by secondary ion mass spectrometry (SIMS) and particle tracking autoradiography (PTA). The segregation of boron was found to initially increase, and then decrease with an increase in the heat input. This is believed to be due to the back-diffusion of boron with an increase in the exposure time at high temperature after non-equilibrium grain boundary segregation. The grain boundary segregation of boron could be decreased by an external stress applied during the welding cycle. Such behavior may be due to an increase in the grain boundary area as a result of the grain size reduction induced by the external stress. - Highlights: • Boron segregation behavior in the CGHAZ of low-alloy steel during a welding cycle was investigated. • Various CGHAZs were simulated with a Gleeble system as a function of the heat input and external stress. • Boron segregation behavior was analyzed using SIMS and PTA techniques.

  9. Effect of Temperature on the Galvanic Corrosion of Cu-Ni Alloy/High Strength Steel in Seawater

    Directory of Open Access Journals (Sweden)

    Wang Chun Li

    2016-01-01

    Full Text Available The galvanic corrosion behavior of Cu-Ni Alloy(B10/high strength steel (921A has been studied using a zero-resistance ammeter (ZRA in seawater at different temperatures. As well as it was systemically investigated by weight loss measurements, electrochemical methods and scanning electron microscope.Results showed 921A acts as the anode and B10 act as the cathodes. The effect of temperature on the galvanic corrosion is important, the corrosion rate became higher with the temperature increased.

  10. Development and application of super heavy gauge high-strength structural steel for high-rise buildings

    Science.gov (United States)

    Gu, Linhao Gu; Lu, Shiping; Liu, Chunming; Liu, Jingang; Zhang, Suyuan; Chu, Rensheng; Ma, Changwen

    2017-09-01

    This paper presents development of 130mm S460G1-Z35 by using low carbon Nb-Ni-Mo-V-Ti micro-alloying design and two-stage rolling, quenching and tempering process. For the super heavy gauge high-strength structural steel, the yield strength is higher than 450MPa, the tensile strength is higher than 550MPa, the elongation is greater than 20%, the low temperature(-40) impact energy value is not less than 250J, the z-direction section shrinkage is more than 65%, and the welding performance is good. The plate are successfully applied to the engineering construction of the city of dreams in Macau.

  11. Microstructure evolution in high strength steel for power plant application - Microscopy and modelling

    Energy Technology Data Exchange (ETDEWEB)

    Korcakova, L.

    2002-08-01

    The aim of the work presented in this thesis was to characterise and model microstructure development of 9-12%Cr steels during creep exposure or isothermal ageing at elevated temperatures. 9-12%Cr steels alloyed with W and/or Mo are applied for high-temperature components in advanced fossil-fired power plants because of their superior creep performance. Addition of Mo and W induces precipitation of intermetallic Laves phase during long-term exposure at service temperatures around 600 deg C. The main part of the experimental work focuses on growth and coarsening of Laves phase in 9-12%Cr steels. Laves phase was investigated in three steels with different levels of Cr and W after creep testing or isothermal ageing at 600 deg C or 650 deg C up to 59,000 h. The steels chosen for the investigations were the well-established P92 and P122, which exhibited very stable creep behaviour and the test alloy FN5, which shows breakdown in creep properties during the first 10,000 h of creep exposure. A new scanning electron microscopy (SEM) method for quantification of Laves phase was developed. The method allows discrimination of Laves phase partides from M{sub 22}C{sub 6} carbides based on a difference in their atomic number contrast. The investigations showed that Laves phase in steel P92 and P122 precipitates during creep exposure or isothermal ageing. In steel FN5 two populations of Laves phase partides exist, where one is present after final heat treatment and the second develops during creep exposure. Laves phase in steel P122 was observed to grow faster than in steel P92 and FN5. The final size of Laves phase in steel P122 is smaller than in steel P92 and FN5. M{sub 23}C6 carbides and MX carbo-nitrides were investigated in a sample crept at 600 deg C for 59,000 h using energy filtered transmission electron microscopy (EFTEM). Both partide types were found to be very stable also after long exposure times. Furthermore, transmission electron microscopy (TEM) investigations of

  12. Microstructure evolution in high strength steel for power plant application: microscopy and modelling

    Energy Technology Data Exchange (ETDEWEB)

    Korcakova, L.

    2002-08-01

    The aim of the work presented in this thesis was to characterise and model microstructure development of 9-12%Cr steels during creep exposure or isothermal ageing at elevated temperatures. 9-12%Cr steels alloyed with W and/or Mo are applied for high-temperature components in advanced fossil-fired power plants because of their superior creep performance. Addition of Mo and W induces precipitation of intermetallic Laves phase during long-term exposure at service temperatures around 600 deg. C. The main part of the experimental work focuses on growth and coarsening of Laves phase in 9-12%Cr steels. Laves phase was investigated in three steels with different levels of Cr and W after creep testing or isothermal ageing at 600 deg. C or 650 deg. C up to 59,000 h. The steels chosen for the investigations were the well-established P92 and P122, which exhibited very stable creep behaviour and the test alloy FN5, which shows breakdown in creep properties during the first 10,000 h of creep exposure. A new scanning electron microscopy (SEM) method for quantification of Laves phase was developed. The method allows discrimination of Laves phase particles from M{sub 23}C{sub 6} carbides based on a difference in their atomic number contrast. The investigations showed that Laves phase in steel P92 and P122 precipitates during creep exposure or isothermal ageing. In steel FN5 two populations of Laves phase particles exist, where one is present after final heat treatment and the second develops during creep exposure. Laves phase in steel P122 was observed to grow faster than in steel P92 and FN5. The final size of Laves phase in steel P122 is smaller than in steel P92 and FN5. M{sub 23}C{sub 6} carbides and MX carbo-nitrides were investigated in a sample crept at 600 deg. deg. for 59,000 h using energy filtered transmission electron microscopy (EFTEM). Both particle types were found to be very stable also after long exposure times. Furthermore, transmission electron microscopy (TEM

  13. Development of Advanced High Strength Steel for Improved Vehicle Safety, Fuel Efficiency and CO2 Emission

    Science.gov (United States)

    Kumar, Satendra; Singhai, Mrigandra; Desai, Rahul; Sam, Srimanta; Patra, Pradip Kumar

    2016-10-01

    Global warming and green house gas emissions are the major issues worldwide and their impacts are clearly visible as a record high temperatures, rising sea, and severe `flooding and droughts'. Motor vehicles considered as a major contributor on global warming due to its green house gas emissions. Hence, the automobile industries are under tremendous pressure from government and society to reduce green house gas emission to maximum possible extent. In present work, Dual Phase steel with boron as microalloying is manufactured using thermo-mechanical treatment during hot rolling. Dual phase steel with boron microalloying improved strength by near about 200 MPa than dual phase steel without boron. The boron added dual phase steel can be used for manufacturing stronger and a lighter vehicle which is expected to perform positively on green house gas emissions. The corrosion resistance behavior is also improved with boron addition which would further increase the life cycle of the vehicle even under corrosive atmosphere.

  14. Effect of Nb on hydrogen-induced delayed fracture in high strength hot stamping steels

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Shiqi [School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China); College of Mechanical Engineering, Yangtze University, Jingzhou 434023 (China); Huang, Yunhua, E-mail: huangyh@mater.ustb.edu.cn [School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Sun, Bintang, E-mail: bingtangsun@ustb.edu.cn [School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Liao, Qingliang [School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Lu, Hongzhou [CITIC Metal Co. Ltd., Room 1901, Capital Mansion 6, Xin Yuan Nanlu, Chaoyang District, Beijing 100004 (China); The School of Resources and Environmental Engineering, East China University of Science and Technology, Meilong road 130, Xujiahui District, Shanghai 200237 (China); Jian, Bian [Niobium Tech Asia, 068898 Singapore (Singapore); Mohrbacher, Hardy [NiobelCon bvba, 2970 Schilde (Belgium); Zhang, Wei; Guo, Aimin [CITIC Metal Co. Ltd., Room 1901, Capital Mansion 6, Xin Yuan Nanlu, Chaoyang District, Beijing 100004 (China); Zhang, Yue [School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China); The State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083 (China)

    2015-02-25

    The effect of Nb addition (0.022, 0.053, 0.078 wt%) on the hydrogen-induced delayed fracture resistance of 22MnB5 was studied by constant load test and electrochemical hydrogen permeation method. It is shown that the appropriate addition of Nb is beneficial to the improvement of the delayed fracture resistance of tested steel, especially when the steel contains high concentration of hydrogen, and the maximum delayed fracture resistance is obtained at a Nb content of 0.053%.The result of hydrogen permeation test shows that the diffusion coefficient of hydrogen in the steel containing niobium is lower than that in steel without niobium, which indicates that it is harder for hydrogen in the steels containing niobium to diffuse and aggregate. In addition, the reason for Nb improving the delayed fracture resistance of steels is discussed from two aspects: hydrogen trap effect and grain refinement effect. The analysis shows that the main reason leading to the improvement of the delayed fracture resistance is the hydrogen trapping effect of NbC while the grain refinement effect of Nb(C,N) secondary.

  15. Characterization of transition behavior in SA508 Gr.4N Ni-Cr-Mo low alloy steels with microstructural alteration by Ni and Cr contents

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Ki-Hyoung; Park, Sang-gyu [Department of Materials Science and Engineering, KAIST, Daejeon 305-701 (Korea, Republic of); Nuclear Materials Research Division, KAERI, Daejeon 305-353 (Korea, Republic of); Kim, Min-Chul, E-mail: mckim@kaeri.re.kr [Nuclear Materials Research Division, KAERI, Daejeon 305-353 (Korea, Republic of); Lee, Bong-Sang [Nuclear Materials Research Division, KAERI, Daejeon 305-353 (Korea, Republic of); Wee, Dang-Moon [Department of Materials Science and Engineering, KAIST, Daejeon 305-701 (Korea, Republic of)

    2011-11-25

    Highlights: {yields} We offer information for determining optimum alloying contents of SA508 Gr.4N steel. {yields} This study shows improvement of toughness with increasing Ni and Cr contents. {yields} Ni content is more effective on the impact toughness than on the fracture toughness. {yields} Cr content is more effective on the fracture toughness. {yields} We offer detailed information on relationship between toughness and microstructure. - Abstract: SA508 Gr.4N Ni-Cr-Mo low alloy steel, in which Ni and Cr contents are higher than in commercial reactor pressure vessel (RPV) steels, may be a candidate RPV material with the improved strength and toughness due to its tempered martensitic microstructure. This study aims at assessing the effects of microstructural factors with alloying element contents on the transition properties of Ni-Cr-Mo low alloy steels. Model alloys with different Ni and Cr contents were fabricated and their Charpy impact toughness and fracture toughness were examined in the transition region according to ASTM E23 and E1921 standard procedures, respectively. The test results showed extensive improvements of both impact toughness and fracture toughness with increasing Ni and Cr contents. However, Ni content was more effective on the impact toughness than on the fracture toughness, while Cr content was more effective on the fracture toughness. In order to identify a difference in effects of alloying elements contents on the fracture toughness and impact toughness, the relations between the transition properties and the scale of the microstructural features such as packets and carbides are discussed in detail.

  16. Surface Oxidation of the High-Strength Steels Electrodeposited with Cu or Fe and the Resultant Defect Formation in Their Coating during the Following Galvanizing and Galvannealing Processes

    Science.gov (United States)

    Choi, Yun-Il; Beom, Won-Jin; Park, Chan-Jin; Paik, Doojin; Hong, Moon-Hi

    2010-12-01

    This study examined the surface oxidation of high-strength steels electrodeposited with Cu or Fe and the resultant defect formation in their coating during the following galvanizing and galvannealing processes. The high-strength steels were coated with an Cu or Fe layer by the electroplating method. Then, the coated steels were annealed in a reducing atmosphere, dipped in a molten zinc, and finally transformed into galvannealed steels through the galvannealing process. The formation of Si and Mn oxides on the surface of the high-strength steel was effectively suppressed, and the density of surface defects on the galvanized steel was significantly reduced by the pre-electrodeposition of Cu and Fe. This effect was more prominent for the steels electrodeposited at higher cathodic current densities. The finer electrodeposit layer formed at higher cathodic current density on the steels enabled the suppression of partial surface oxidation by Mn or Si and better wetting of Zn on the surface of the steels in the following galvanizing process. Furthermore, the pre-electrodeposited steels exhibited a smoother surface without surface cracks after the galvannealing process compared with the untreated steel. The diffusion of Fe and Zn in the Zn coating layer in the pre-electrodeposited steels appears to occur more uniformly during the galvannealing process due to the low density of surface defects induced by oxides.

  17. Control of Hydrogen Environment Embrittlement of Ultra-High Strength Steel for Naval Application

    Science.gov (United States)

    2005-07-01

    to the log da/dt vs. l/T data. Speidel reported simple Arrhenius behavior for lower strength Nimonic 105 (Cyys = 825 MPa) for 0°C < T < 100°C (Speidel...HYDROGEN ASSISTED CRACKING OF HIGH STRENGTH ALLOYS Richard P. Gangloff August. 2003 Page 115 of 194 L (a) R250 nm 250 nm SL (b) R Figure 43: Matching...34Hydrogen in Metals", Eds., I.M. Bernstein and A.W. Thompson, ASM International, Materials Park, OH, 1974, pp. 115 -147. W.W. Gerberich, Y.T. Chen and C

  18. Assessment of the Critical Parameters Influencing the Edge Stretchability of Advanced High-Strength Steel Sheet

    Science.gov (United States)

    Pathak, N.; Butcher, C.; Worswick, M.

    2016-11-01

    The edge formability of ferritic-martensitic DP (dual-phase) and ferritic-bainitic CP (complex-phase) steels was evaluated using a hole expansion test for different edge conditions. Hole expansion tests involving the standard conical punch as well as a custom flat punch were performed to investigate formability when the hole is expanded out-of-plane (conical punch) and in-plane using the flat punch. A range of edge conditions were considered, in order to isolate the influence of a range of factors thought to influence edge formability. The results demonstrate that work hardening and void damage at the sheared edge govern formability, while the sheared surface quality plays a minor or secondary role. A comparison of the edge stretching limits of DP and CP steels demonstrates the advantages of a ferritic-bainitic microstructure for forming operations with severe local deformation as in a stretch-flanging operation. A comparison of a traditional DP780 steel with a CP steel of similar strength showed that the edge stretching limit of the CP steel was three times larger than that of the DP780.

  19. Dissimilar Arc Welding of Advanced High-Strength Car-Body Steel Sheets

    Science.gov (United States)

    Russo Spena, P.; D'Aiuto, F.; Matteis, P.; Scavino, G.

    2014-11-01

    A widespread usage of new advanced TWIP steel grades for the fabrication of car-body parts is conditional on the employment of appropriate welding methods, especially if dissimilar welding must be performed with other automotive steel grades. Therefore, the microstructural features and the mechanical response of dissimilar butt weld seams of TWIP and 22MnB5 steel sheets after metal-active-gas arc welding are examined. The microstructural and mechanical characterization of the welded joints was carried out by optical metallography, microhardness and tensile testing, and fractographic examination. The heat-affected zone on the TWIP side was fully austenitic and the only detectable effect was grain coarsening, while on the 22MnB5 side it exhibited newly formed martensite and tempered martensite. The welded tensile specimens exhibited a much larger deformation on the TWIP steel side than on the 22MnB5. The fracture generally occurred at the interface between the fusion zone and the heat-affected zones, with the fractures surfaces being predominantly ductile. The ultimate tensile strength of the butt joints was about 25% lower than that of the TWIP steel.

  20. Hydrogen adsorption and diffusion, and subcritical-crack growth in high strength steels and nickel base alloys

    Science.gov (United States)

    Wei, R. P.; Klier, K.; Simmons, G. W.; Chornet, E.

    1973-01-01

    Embrittlement, or the enhancement of crack growth by gaseous hydrogen in high strength alloys, is of primary interest in selecting alloys for various components in the space shuttle. Embrittlement is known to occur at hydrogen gas pressures ranging from fractions to several hundred atmospheres, and is most severe in the case of martensitic high strength steels. Kinetic information on subcritical crack growth in gaseous hydrogen is sparse at this time. Corroborative information on hydrogen adsorption and diffusion is inadequate to permit a clear determination of the rate controlling process and possible mechanism in hydrogen enhanced crack growth, and for estimating behavior over a range of temperatures and pressures. Therefore, coordinated studies of the kinetics of crack growth, and adsorption and diffusion of hydrogen, using identical materials, have been initiated. Comparable conditions of temperature and pressure will be used in the chemical and mechanical experiments. Inconel 718 alloy and 18Ni(200) maraging steel have been selected for these studies. Results from these studies are expected to provide not only a better understanding of the gaseous hydrogen embrittlement phenomenon itself, but also fundamental information on hydrogen adsorption and diffusion, and crack growth information that can be used directly for design.

  1. Effect of microstructure on the fracture response of advanced high strength steels

    Science.gov (United States)

    Taylor, Mark David

    The effect of constituent hardness on formability performance for higher-strength dual phase (DP) steels was evaluated. A commercially-produced DP steel with 1080 MPa ultimate tensile strength (UTS) was processed to create eight additional constituent hardness conditions by tempering and cold-rolling, processes that primarily affected constituent hardness properties. Using nanoindentation, ferrite and martensite hardness values for the nine conditions of the DP steel (as-received, four as-tempered, four temper cold-rolled) provided a range of hardness values to evaluate formability performance. Formability performance for the nine steel conditions was evaluated using tensile and hole expansion testing. A decrease in martensite/ferrite hardness ratio corresponded to an increase in hole expansion ratio (HER), and an increase in yield strength (YS). A lower hardness ratio (increased similarity of ferrite and martensite hardness) was interpreted to increase strain-sharing between ferrite and martensite, which suppressed plastic strain localization to higher stresses for the case of YS, and to higher formability limits for the case of HER. A lower hardness ratio corresponded to a decrease in work-hardening, and was interpreted to be caused by the suppression of strain localization in ferrite. Multiple studies from literature correlated HER to tensile properties, and the nine steel conditions produced consistent trends with the data reported in each study, confirming the experimental HER and tensile properties obtained in the current study are consistent with literature. The microstructural response to plastic deformation was evaluated using two DP steels with equivalent UTS and different hardness ratios. Nanoindentation analyses on tensile specimens deformed to the UTS revealed a greater increase in ferrite hardness for the higher hardness ratio steel, interpreted to be caused by the greater amount of work hardening. EBSD crystallographic orientation maps for the two DP

  2. Investigation of the hot ductility of a high-strength boron steel

    Energy Technology Data Exchange (ETDEWEB)

    Güler, Hande, E-mail: handeguler@uludag.edu.tr; Ertan, Rukiye; Özcan, Reşat

    2014-07-01

    In this study, the high-temperature ductility behaviour of an Al–Si-coated 22MnB5 sheet was investigated. The mechanical properties of Al–Si-coated 22MnB5 boron steel were examined via hot tensile tests performed at temperatures ranging from 400 to 900 °C at a strain rate of 0.083 s{sup −1}. The deformation and fracture mechanisms under hot tensile testing were considered in relation to the testing data and to the fracture-surface observations performed via SEM. The hot ductility of the tested boron steel was observed as a function of increasing temperature and the Al–Si-coated 22MnB5 boron steel exhibited a ductility loss at 700 °C.

  3. ACCELERATED CARBONATION OF STEEL SLAG COMPACTS: DEVELOPMENT OF HIGH STRENGTH CONSTRUCTION MATERIALS

    Directory of Open Access Journals (Sweden)

    Mieke eQuaghebeur

    2015-12-01

    Full Text Available Mineral carbonation involves the capture and storage of carbon dioxide in carbonate minerals. Mineral carbonation presents opportunities for the recycling of steel slags and other alkaline residues that are currently landfilled. The Carbstone process was initially developed to transform non-hydraulic steel slags (stainless steel slag and basic oxygen furnace slags in high quality construction materials. The process makes use of accelerated mineral carbonation by treating different types of steel slags with CO2 at elevated pressure (up to 2 MPa and temperatures (20 to 140°C. For stainless steel slags raising the temperature from 20 to 140°C had a positive effect on the CO2 uptake, strength development and the environmental properties (i.e. leaching of Cr and Mo of the carbonated slag compacts. For BOF slags raising the temperature was not beneficial for the carbonation process. Elevated CO2 pressure and CO2 concentration of the feed gas had a positive effect on the CO2 uptake and strength development for both types of steel slags. In addition also the compaction force had a positive effect on the strength development. The carbonates that are produced in-situ during the carbonation reaction act as a binder, cementing the slag particles together. The carbonated compacts (Carbstones have technical properties that are equivalent to conventional concrete products. An additional advantage is that the carbonated materials sequester 100 to 150 g CO2/kg slag. The technology was developed on lab scale by optimisation of process parameters with regard to compressive strength development, CO2 uptake and environmental properties of the carbonated construction materials. The Carbstone technology was validated using (semi-industrial equipment and process conditions.

  4. Corrosion and Fatigue Behavior of High-Strength Steel Treated with a Zn-Alloy Thermo-diffusion Coating

    Science.gov (United States)

    Mulligan, C. P.; Vigilante, G. N.; Cannon, J. J.

    2017-09-01

    High and low cycle fatigue tests were conducted on high-strength steel using four-point bending. The materials tested were ASTM A723 steel in the as-machined condition, grit-blasted condition, MIL-DTL-16232 heavy manganese phosphate-coated condition, and ASTM A1059 Zn-alloy thermo-diffusion coated (Zn-TDC). The ASTM A723 steel base material exhibits a yield strength of 1000 MPa. The effects of the surface treatments versus uncoated steel were examined. The fatigue life of the Zn-TDC specimens was generally reduced on as-coated specimens versus uncoated or phosphate-coated specimens. Several mechanisms are examined including the role of compressive residual stress relief with the Zn-TDC process as well as fatigue crack initiation from the hardened Zn-Fe alloy surface layer produced in the gas-metal reaction. Additionally, the effects of corrosion pitting on the fatigue life of coated specimens are explored as the Zn-TDC specimens exhibit significantly improved corrosion resistance over phosphate-coated and oiled specimens.

  5. A new integration of hot pressing and carbon partition process to produce high strength steel components with better toughness

    Directory of Open Access Journals (Sweden)

    Zhang Shi-hong

    2015-01-01

    Full Text Available A novel one step method for hot pressing and quench & partition (Q&P integration – hot Pressing-dynamic partitioning (HP-DP process is presented, which can be processed by regular hot pressing equipment and process. The HP-DP formed steel is an upgrade of the existing hot pressed steel especially suitable for making high strength components with superior crashworthiness due to better toughness. Corresponding steel sheet based on conventional 22MnB5 is designed and prepared. After that, the physical simulation experiments for HP-DP are carried out on thermal-mechanical simulator. Microstructure of the steel subjected to HP-DP treatment, with a typical Q&P treated feature, is mainly composed of initial quenched martensite phase, final quenched martensite phase and retained austenite phase, which indicate the occurrence of carbon diffusion concomitantly with martensite transformation. Compared with conventional hot pressed samples, the HP-DP samples show both better tensile property especially elongation and impact energy absorption ability. The effect of HP-DP parameters on the stability of retained austenite and mechanical property is also discussed. The paper illustrates the promising application potential of the HP-DP process.

  6. Corrosion and Fatigue Behavior of High-Strength Steel Treated with a Zn-Alloy Thermo-diffusion Coating

    Science.gov (United States)

    Mulligan, C. P.; Vigilante, G. N.; Cannon, J. J.

    2017-11-01

    High and low cycle fatigue tests were conducted on high-strength steel using four-point bending. The materials tested were ASTM A723 steel in the as-machined condition, grit-blasted condition, MIL-DTL-16232 heavy manganese phosphate-coated condition, and ASTM A1059 Zn-alloy thermo-diffusion coated (Zn-TDC). The ASTM A723 steel base material exhibits a yield strength of 1000 MPa. The effects of the surface treatments versus uncoated steel were examined. The fatigue life of the Zn-TDC specimens was generally reduced on as-coated specimens versus uncoated or phosphate-coated specimens. Several mechanisms are examined including the role of compressive residual stress relief with the Zn-TDC process as well as fatigue crack initiation from the hardened Zn-Fe alloy surface layer produced in the gas-metal reaction. Additionally, the effects of corrosion pitting on the fatigue life of coated specimens are explored as the Zn-TDC specimens exhibit significantly improved corrosion resistance over phosphate-coated and oiled specimens.

  7. Elemental segregation during resistance spot welding of boron containing advanced high strength steels

    NARCIS (Netherlands)

    Amirthalingam, M.; Van der Aa, E.M.; Kwakernaak, C.; Hermans, M.J.M.; Richardson, I.M.

    2015-01-01

    The partitioning behaviour of carbon, phosphorous and boron during the solidification of a resistance spot weld pool was studied using experimental simulations and a phase field model. Steels with varying carbon, phosphorous and boron contents were designed and subjected to a range of resistant spot

  8. Effect of steel fibers on plastic shrinkage cracking of normal and high strength concretes

    Directory of Open Access Journals (Sweden)

    Özgür Eren

    2010-06-01

    Full Text Available Naturally concrete shrinks when it is subjected to a drying environment. If this shrinkage is restrained, tensile stresses develop and concrete may crack. Plastic shrinkage cracks are especially harmful on slabs. One of the methods to reduce the adverse effects of shrinkage cracking of concrete is by reinforcing concrete with short randomly distributed fibers. The main objective of this study was to investigate the effect of fiber volume and aspect ratio of hooked steel fibers on plastic shrinkage cracking behavior together with some other properties of concrete. In this research two different compressive strength levels namely 56 and 73 MPa were studied. Concretes were produced by adding steel fibers of 3 different volumes of 3 different aspect ratios. From this research study, it is observed that steel fibers can significantly reduce plastic shrinkage cracking behavior of concretes. On the other hand, it was observed that these steel fibers can adversely affect some other properties of concrete during fresh and hardened states.

  9. Development of High Strength and High Toughness Steels for Reactor Vessel and Surgeline Pipe

    Energy Technology Data Exchange (ETDEWEB)

    Lee, B. S.; Kim, M. C.; Yoon, J. H.; Kim, K. B.; Choi, K. J.; Cho, H. D.

    2010-07-15

    In addition to evaluating the effects of alloying elements, heat treatment conditions, weldability and neutron irradiation behavior were evaluated with 15 types of SA508 Gr.4N model alloys for reactor pressure vessel. The maximum yield strength of 630MPa were obtained by controlling chemical compositions and heat treatment conditions. Model alloys also showed excellent impact toughness and fracture toughness. The microstructure and mechanical properties of weld heat affected zone were evaluated by using simulated specimens and the effects of post weld heat treatment conditions were also investigated. Neutron irradiation behavior at high fluence level were characterized and then compared with commercial reactor pressure vessel steel. The value of transition temperature shift(TTS) was 22 .deg. C at 6.4x10{sup 19} n/cm{sup 2} which is similar to commercial RPV steel. However, its toughness after irradiation is much better than that of unirradiated commercial RPV steel due to the superior initial toughness. Leak-before-break(LBB) properties of type 316 stainless steel model alloys and their welds for surge line were evaluated as well as microstructure and mechanical properties. Tensile tests and J-R fracture resistance tests were carried out at RT and 316 .deg. C. The model alloys showed good tensile strength over standard value, except type 316L which has lower C/N. In the LBB safety analysis result, all of type 316 model alloys have higher allowable load than that of OPR1000 surge line

  10. Corrosion resistance of Zn-Co-Fe alloy coatings on high strength steel

    NARCIS (Netherlands)

    Lodhi, Z.F.; Mol, J.M.C.; Hovestad, A.; Hoen-Velterop, L. 't; Terryn, H.; Wit, J.H.W.de

    2009-01-01

    The corrosion properties of electrodeposited zinc-cobalt-iron (Zn-Co-Fe) alloys (up to 40 wt.% Co and 1 wt.% Fe) on steel were studied by using various electrochemical techniques and compared with zinc (Zn) and cadmium (Cd) coatings in 3.5% NaCl solution. It was found that with an increase in Co

  11. Effect of Ultra-Fast Cooling on Microstructure and Properties of High Strength Steel for Shipbuilding

    Science.gov (United States)

    Zhou, Cheng; Ye, Qibin; Yan, Ling

    The effect of ultra-fast cooling(UFC) and conventional accelerated cooling(AcC) on the mechanical properties and microstructure of controlled rolled AH32 grade steel plates on industrial scale were compared using tensile test, Charpy impact test, welding thermal simulation, and microscopic analysis. The results show that the properties of the plate produced by UFC are improved considerably comparing to that by AcC. The yield strength is increased with 54 MPa without deterioration in the ductility and the impact energy is improved to more than 260 J at -60 °C with much lower ductile-to-brittle transition temperature(DBTT). The ferrite grain size is refined to ASTM No. 11.5 in the UFC steel with uniform microstructure throughout the thickness direction, while that of the AcC steel is ASTM No. 9.5. The analysis of nucleation kinetics of α-ferrite indicates that the microstructure is refined due to the increased nucleation rate of α-ferrite by much lower γ→α transition temperature through the UFC process. The Hall-Petch effect is quantified for the improvement of the strength and toughness of the UFC steel attributed to the grain refinement.

  12. The effect of low temperatures on the fatigue of high-strength structural grade steels

    NARCIS (Netherlands)

    Walters, C.L.

    2014-01-01

    It is well-known that for fracture, ferritic steels undergo a sudden transition from ductile behavior at higher temperatures to brittle cleavage failure at lower temperatures. However, this phenomenon has not received much attention in the literature on fatigue. The so-called Fatigue Ductile-Brittle

  13. Hydrogen uptake and diffusion in welds of high-strength steels; Wasserstoffaufnahme und -diffusion in Schweissnahtgefuegen hochfester Staehle

    Energy Technology Data Exchange (ETDEWEB)

    Seeger, D.M.

    2005-07-01

    case depending on chemical composition and on the heat control. Additionally, the hydrogen diffusion and uptake in welded microstructures of ultra-high strength fine-grained structural steels was examined. (orig.)

  14. Hydrogen Environment Assisted Cracking of Modern Ultra-High Strength Martensitic Steels

    Science.gov (United States)

    Pioszak, Greger L.; Gangloff, Richard P.

    2017-09-01

    Martensitic steels (Aermet®100, Ferrium®M54™, Ferrium®S53®, and experimental CrNiMoWV at ultra-high yield strength of 1550 to 1725 MPa) similarly resist hydrogen environment assisted cracking (HEAC) in aqueous NaCl. Cracking is transgranular, ascribed to increased steel purity and rare earth addition compared to intergranular HEAC in highly susceptible 300M. Nano-scale precipitates ((Mo,Cr)2C and (W,V)C) reduce H diffusivity and the K-independent Stage II growth rate by 2 to 3 orders of magnitude compared to 300M. However, threshold K TH is similarly low (8 to 15 MPa√m) for each steel at highly cathodic and open circuit potentials. Transgranular HEAC likely occurs along martensite packet and {110}α'-block interfaces, speculatively governed by localized plasticity and H decohesion. Martensitic transformation produces coincident site lattice interfaces; however, a connected random boundary network persists in 3D to negate interface engineering. The modern steels are near-immune to HEAC when mildly cathodically polarized, attributed to minimal crack tip H production and uptake. Neither reduced Co and Ni in M54 and CrNiMoWV nor increased Cr in S53 broadly degrade HEAC resistance compared to baseline AM100. The latter suggests that crack passivity dominates acidification to widen the polarization window for HEAC resistance. Decohesion models predict the applied potential dependencies of K TH and d a/d t II with a single-adjustable parameter, affirming the importance of steel purity and trap sensitive H diffusivity.

  15. The microstructural evolution and elemental distribution of a 3rd generation 1 GPa advanced high strength steel during double pulse resistance spot welding

    NARCIS (Netherlands)

    Eftekharimilani, P.; van der Aa, EM; Hermans, M.J.M.; Richardson, I.M.

    2017-01-01

    This paper presents the effects of double pulse resistance spot welding (RSW) on the microstructural evolution, elemental distribution and mechanical properties of a 3rd generation 1 GPa advanced high strength steel (AHSS). In order to investigate the effect of double pulsing, the steel was exposed

  16. Characterization of Precipitation Behavior and Fracture Toughness along Thickness Direction in SA508 Gr.3 Mn-Mo-Ni low alloy steels

    Energy Technology Data Exchange (ETDEWEB)

    Song, Jaemin; Kim, Min-Chul; Hong, Seokmin; Lee, Bong-Sang [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2015-10-15

    SA 508 Gr.3 Mn-Mo-Ni low alloy steel forgings thicker than 200 mm are used for reactor pressure vessels in nuclear power plants. The cooling rate difference along the thickness direction during the quenching process causes variation in the microstructure and mechanical properties. The microstructural variation and its influence on the fracture toughness of RPV steels were investigated in this study. The cleavage fracture toughness in the transition region were evaluated with the ASTM E1921 master curve method for samples at different locations from the inner surface to the center thickness of the RPV steel. The microstructural features, such as the area fraction, and the size and distribution of precipitates were quantitatively evaluated at each sampling position. Microstructure observations showed that at near the surface position, bainite laths are finer, and furthermore, the carbides are smaller and homogeneously distributed. The fracture toughness at the surface was better than those at deeper positions. The reference temperature T{sub 0} showed a linear relationship with the area fraction of the carbides bigger than a certain critical size. It is concluded that the size of the precipitates caused by the cooling rate gradient may have a dominant role in controlling the cleavage fracture toughness variation along the thickness direction for a very thick RPV steel.

  17. Optimum Design and Development of High Strength and Toughness Welding Wire for Pipeline Steel

    Science.gov (United States)

    Chen, Cuixin; Xue, Haitao; Yin, Fuxing; Peng, Huifen; Zhi, Lei; Wang, Sixu

    Pipeline steel with higher strength(>800MPa) has been gradually used in recent years, so how to achieve good match of base metal and weld deposit is very important for its practical application. Based on the alloy system of 0.02-0.04%C, 2.0%Mn and 0.5%Si, four different kinds of welding wires were designed and produced. The effects of alloy elements on phase transformation and mechanical properties were analyzed. Experimental results show that the designed steels with the addition of 2-4% Ni+Cr+Mo and 800MPa) and good elongation (>15%). The microstructure of deposits metal is mainly composed of granular bainite and M-A constituents with the mean size of 0.2-07μm are dispersed on ferritic matrix. The deposited metals have good match of strength (>800MPa) and impact toughness (>130J) which well meet the requirement of pipeline welding.

  18. Control of Hydrogen Embrittlement in High Strength Steel Using Special Designed Welding Wire

    Science.gov (United States)

    2016-03-01

    microstructure 4. A low near ambient temperature is reached. • All four factor must be simultaneously present 3 Mitigating HIC and Improving Weld Fatigue...Performance Through Weld Residual Stress Control UNCLASIFIED:DISTRIBUTION A. Approved for public release: distribution unlimited. Click to edit Master...title style 4 • Welding of Armor Steels favors all these conditions for HIC • Hydrogen Present in Sufficient Degree – Derived from moisture in the

  19. Effect of steel fibers on plastic shrinkage cracking of normal and high strength concretes

    OpenAIRE

    Özgür Eren; Khaled Marar

    2011-01-01

    Naturally concrete shrinks when it is subjected to a drying environment. If this shrinkage is restrained, tensile stresses develop and concrete may crack. Plastic shrinkage cracks are especially harmful on slabs. One of the methods to reduce the adverse effects of shrinkage cracking of concrete is by reinforcing concrete with short randomly distributed fibers. The main objective of this study was to investigate the effect of fiber volume and aspect ratio of hooked steel fibers on plastic shri...

  20. P/M Processing of Rare Earth Modified High Strength Steels.

    Science.gov (United States)

    1980-12-01

    poder of Hat 971(0.43%Ce) 164 * - ’-’ ~ ~ ~ --- (a) Magnification, 10OX (b) Magnification, 100OX Figure 6. SEM photographs of hydrogen gas atomized...earth elements was made by the RSR atomization process at Pratt & Whitney Aircraft, Government Products Division , while another RSR heat of 4340...powders with characteristics similar to RSR powders, This process was developed by Universal-Cyclops Specialty Steel Division , Cyclops Corporation, as

  1. Light weight and high strength materials made of recycled steel and aluminum

    Science.gov (United States)

    Nounezi, Thomas

    Recycling has proven not only to address today's economical, environmental and social issues, but also to be imperative for the sustainability of human technology. The current thesis has investigated the feasibility of a new philosophy for Recycling (Alloying-Recycling) using steel 1020 and aluminum 6061T6. The study was limited to the metallurgical aspects only and has highlighted the potential of recycled alloys made of recycled aluminum and steel to exhibit substantially increased wear resistance and strength-to-weight ratio as compared to initial primary materials. Three alloy-mixtures are considered: TN3 (5wt% 1020 +95wt% 6061T6); TN5 (0.7wt% 1020 + 99.3wt% 6061T6); and TN4 (10wt% 6061T6 + 90wt% 1020). A Tucker induction power supply system (3kW; 135-400 kHz) is used to melt the alloy mixtures for casting in graphite crucibles. Heat treatment of the cast samples is done using a radiation box furnace. Microscopy, Vickers hardness and pin-on-disc abrasive wear tests are performed. Casting destroyed the initial microstructures of the alloys leading to a hardness reduction in the as-cast and solution heat-treated aluminum rich samples to 60 Hv from 140 Hv. Ageing slightly increased the hardness of the cast samples and provided a wear resistance two times higher than that of the initial 6061T6 material. On the steel rich side, the hardness of the as-cast TN4 was 480 Hv, which is more than twice as high as the initial hardness of steel 1020 of 202 Hv; this hints to strong internal and residual stress, probably martensite formation during fast cooling following casting. Solution heat treatment lowered the hardness to the original value of steel 1020, but provided about ten (10) times higher wear resistance; this suggests higher ductility and toughness of normalised TN4 as compared to 1020. In addition, TN4 exhibits about 25% weight reduction as compared to 1020. The actual recycling process and the effect of non-metallic impurities shall be investigated in future

  2. Hybrid laser-gas metal arc welding (GMAW) of high strength steel gas transmission pipelines

    Energy Technology Data Exchange (ETDEWEB)

    Harris, Ian D.; Norfolk, Mark I. [Edison Welding Institute (EWI), Columbus, Ohio (United States)

    2009-07-01

    Hybrid Laser/arc welding process (HLAW) can complete 5G welds, assure weld soundness, material properties, and an acceptable geometric profile. Combining new lasers and pulsed gas metal arc welding (GMAW-P) has led to important innovations in the HLAW process, increasing travel speed for successful root pass welding. High power Yb fiber lasers allow a 10 kW laser to be built the size of a refrigerator, allowing portability for use on the pipeline right-of-way. The objective was to develop and apply an innovative HLAW system for mechanized welding of high strength, high integrity, pipelines and develop 5G welding procedures for X80 and X100 pipe, including mechanical testing to API 1104. A cost-matched JIP developed a prototype HLAW head based on a commercially available bug and band system (CRC-Evans P450). Under the US Department of Transportation (DOT) project, the subject of this paper, the system was used to advance pipeline girth welding productivity. External hybrid root pass welding achieved full penetration welds with a 4-mm root at a travel speed of 2.3-m/min. Welds were made 'double down' using laser powers up to 10 kW and travel speeds up to 3-m/min. The final objective of the project was to demonstrate the hybrid LBW/GMAW system under simulated field conditions. (author)

  3. Quantification of elemental segregation to lath and grain boundaries in low-alloy steel by STEM X-ray mapping combined with the zeta-factor method

    CERN Document Server

    Watanabe, M

    2003-01-01

    Elemental segregation to two types of boundaries in a low-alloy steel were studied by X-ray mapping using scanning transmission electron microscopy (STEM). To quantify the acquired X-ray maps, the zeta-factor method was applied, and then the compositional maps and the thickness map were obtained. Based on these quantified maps, further information about the analytical sensitivity of solute-element detection and the spatial resolution of segregation analysis were extracted. Furthermore, maps of the number of excess atoms on the boundary were also calculated from the compositional and thickness maps. It was concluded that Cr, Ni and Mo are co-segregated on the prior-austenite grain boundary and only Ni was segregated on the lath boundary. (orig.)

  4. In situ Raman spectroscopic analysis of surface oxide films on Ni-base alloy/low alloy steel dissimilar metal weld interfaces in high-temperature water

    Science.gov (United States)

    Kim, Jongjin; Choi, Kyung Joon; Bahn, Chi Bum; Kim, Ji Hyun

    2014-06-01

    In situ Raman spectroscopy has been applied to analyze the surface oxide films formed on dissimilar metal weld (DMW) interfaces of nickel-base alloy/low alloy steel under hydrogenated high-temperature water condition. For the analysis of the oxide films under high temperature/pressure aqueous conditions, an in situ Raman spectroscopy system was developed by constructing a hydrothermal cell where the entire optics including the excitation laser and the Raman light collection system were located at the nearest position to the specimen by means of immersion optics. In situ Raman spectra of the DMW interfaces were collected in hydrogenated water condition at different temperatures up to 300 °C. The measured in situ Raman spectra showed peaks of Cr2O3, NiCr2O4 and Fe3O4 at the DMW interface. It is considered that differences in the oxide chemistry originated from the chemical element distribution inside of the DMW interface region.

  5. Production and construction technology of C100 high strength concrete filled steel tube

    Science.gov (United States)

    Wu, Yanli; Sun, Jinlin; Yin, Suhua; Liu, Yu

    2017-10-01

    In this paper, the effect of the amount of cement, water cement ratio and sand ratio on compressive strength of C100 concrete was studied. The optimum mix ratio was applied to the concrete filled steel tube for the construction of Shenyang Huangchao Wanxin mansion. The results show that the increase of amount of cement, water cement ratio can improve the compressive strength of C100 concrete but increased first and then decreased with the increase of sand ratio. The compressive strength of C100 concrete can reach 110MPa with the amount of cement 600kg/m3, sand ratio 40% and water cement ratio 0.25.

  6. Creep and microstructural processes in a low-alloy 2.25%Cr1.6%W steel (ASTM Grade 23)

    Energy Technology Data Exchange (ETDEWEB)

    Kucharova, K. [Institute of Physics of Materials, Academy of Sciences of the Czech Republic, CZ-616 62 Brno (Czech Republic); Sklenicka, V., E-mail: sklen@ipm.cz [Institute of Physics of Materials, Academy of Sciences of the Czech Republic, CZ-616 62 Brno (Czech Republic); CEITEC — IPM, Institute of Physics of Materials, Academy of Sciences of the Czech Republic, CZ-616 62 Brno (Czech Republic); Kvapilova, M.; Svoboda, M. [Institute of Physics of Materials, Academy of Sciences of the Czech Republic, CZ-616 62 Brno (Czech Republic); CEITEC — IPM, Institute of Physics of Materials, Academy of Sciences of the Czech Republic, CZ-616 62 Brno (Czech Republic)

    2015-11-15

    A low-alloy 2.25%Cr1%Mo steel (ASTM Grade 22) has been greatly improved by the substitution of almost all of the 1%Mo by 1.6%W. The improved material has been standardized as P/T23 steel (Fe–2.25Cr–1.6W–0.25V–0.05Nb–0.07C). The present investigation was conducted on T23 steel in an effort to obtain a more complete description and understanding of the role of the microstructural evolution and deformation processes in high-temperature creep. Constant load tensile creep tests were carried out in an argon atmosphere in the temperature range 500–650 °C at stresses ranging from 50 to 400 MPa. It was found that the diffusion in the matrix lattice is the creep-rate controlling process. The results of an extensive transmission electron microscopy (TEM) analysis programme to investigate microstructure evolution as a function of temperature are described and compared with the thermodynamic calculations using the software package Thermo-Calc. The significant creep-strength drop of T23 steel after long-term creep exposures can be explained by the decrease in dislocation hardening, precipitation hardening and solid solution hardening due to the instability of the microstructure at high temperature. - Highlights: • The constant load creep tests of T23 steel were carried out at 500–650 °C. • The stress exponents of the creep rate correspond to power law (dislocation) creep. • Diffusion in the matrix lattice is the creep-rate controlling process. • The microstructure instability is the main creep degradation process in T23 steel.

  7. Forta FDX 27 - duplex stainless steel for high strength gasket plate heat exchangers

    Science.gov (United States)

    Groth, A.; Schedin, E.; Sun, CC; He, Hailan; Guan, Li

    2017-09-01

    Outokumpu has developed a new duplex stainless steel with improved formability compared to other duplex grades. The so-called Forta FDX grades allows the utilization of duplex grades in more forming intensive products previously not possible and at the same time benefit from other duplex stainless steel properties for increased application performance. In this paper a Gasket Plate Heat Exchanger (GPHE) plate is formed with the new duplex grade Forta FDX 27 and compared to the baseline grade Supra 316L/4404. Detailed material characterization, strain measurements and Finite Element Analysis (FEA) were performed to further investigate the case. Small differences in measured strain distribution between Forta FDX 27 and Supra 316L/4404 were found after the stamping operation for both material grades and for the same design feature. Strain measurements showed reasonable agreement between measured experimental results and the numerical simulation for Forta FDX 27. Additionally, FEA predicts an improvement of the final strength of the product up to 30 % at the final configuration by using Forta FDX 27 instead of Supra 316L/4404.

  8. Low cycle notched fatigue behavior and life predictions of A723 high strength steels

    Energy Technology Data Exchange (ETDEWEB)

    Troiano, E.; Underwood, J.H.; Crayon, D. [Army Armament Research, Development and Engineering Center, Watervliet, NY (United States). Benet Labs.

    1995-12-31

    Two types of ASTM A723 steels have been investigated for their low cycle fatigue behavior. Specimens were tested in four-point bending, both with and without notches, and the measured fatigue lives were compared with those predicted by Neubers notch analysis, and standard fracture mechanics life prediction techniques. Comparison of measured and predicted lives indicate that the elastic/plastic Neuber analysis under predicts the measured fatigue life by as much as 67% at large strains, and becomes a better predictor of life as the applied strains decrease. The elastic Neubers analysis also under predicts the measured fatigue lives by 45% at large applied strains, but seems to accurately predict lives at reversals to failure greater than 100. The fracture mechanics approach assumes elastic stresses at the crack tip, and predicts lives within 30% over the full range of strains investigated. The results show that the Neuber notch analysis is not as good an indicator of the low cycle fatigue behavior of A723 steels as is the fracture mechanics life prediction techniques. As the life cycles to failure decreases, the Neubers analysis predicts lives that are two to three times more conservative than those experimentally measured.

  9. Hydrogen-induced cold cracking in heat-affected zone of low-carbon high-strength steel

    Science.gov (United States)

    Lan, Liangyun; Kong, Xiangwei; Hu, Zhiyong; Qiu, Chunlin

    2014-12-01

    The Y-groove cracking test by submerged arc welding was employed to study the susceptibility of a low-carbon high-strength steel to hydrogen-induced cold cracking (HICC). The morphology of hydrogen cracks was observed using an electron probe microscope. The results showed that the heat-affected zone (HAZ) has a higher susceptibility to HICC than the weld metal and that increasing heat input can improve the HICC resistance of the weldment. The intergranular microcracking is the main HICC mode at the lowest heat input condition, accompanied with some transgranular microcracks attached to complex inclusions. In combination with phase transformation behaviour in sub-zones, the effect of the phase transformation sequence is proposed to try to illustrate the fact that the fine-grained HAZ has higher probability of hydrogen cracking than the coarse-grained HAZ owing to the occurrence of hydrogen enrichment in the fine-grained HAZ after the transformation.

  10. Evaluation of base material and welded joints designated for membrane wall components made from low-alloy steels in large boilermaker conditions

    Energy Technology Data Exchange (ETDEWEB)

    Dobrzanski, Janusz; Zielinski, Adam [Institute for Ferrous Metallurgy, Gliwice (Poland); Pasternak, Jerzy [Boiler Engineering Company RAFAKO S.A., Raciborz (Poland)

    2010-07-01

    Supercritical operating parameters of lower emission power units require novel creep resisting steels. Therefore, this paper constains selected information, results of collectors made from the new low-alloy bainitic creep-resistant steels as 7CrWVNb9-6(P23) and 7CrMoVTiB10-10(P24) performed in large boilermaker conditions. The research and implementation process includes: - evaluation, comparison of requested properties of base material and welded joints as tensile strength, impact strength and technological properties, - destructive examinations with evaluation of welded joints and HAZ structure and hardness distribution, - evaluation of creep resistance properties and structure stability after heat treatments and again process of base material, HAZ and welded joints, - influence of manufacturing process in large boilermaker conditions and after simulated operation. A new creep-resistant steels to be used, in order to comply with the operational requirements, as to assure the appropriate reliability and safety of the boiler equipment in operation process. (orig.)

  11. A Crystal Plasticity Approach for Shear Banding in Hot Rolled High-Strength Steels

    Science.gov (United States)

    Lindroos, Matti; Laukkanen, Anssi; Kuokkala, Veli-Tapani

    2017-11-01

    A crystal plasticity approach with a phenomenological shear banding mechanism incorporated in a conventional dislocation crystal plasticity model is presented. In the developed framework, the hardening and softening relations are considered both within and between the deformation mechanisms. The study aims to increase the understanding of the importance of hot rolling texture to the shear banding propensity in martensitic steels. In the single crystal simulations performed for selected common rolling textures, it was found that shear band activation and the magnitude of softening are dependent on the initial orientation of the crystal. In general, softening-related shear banding in single crystals was shown to be well reproduced by the model at high plastic strains and high strain rates.

  12. European column buckling curves and finite element modelling including high strength steels

    DEFF Research Database (Denmark)

    Jönsson, Jeppe; Stan, Tudor-Cristian

    2017-01-01

    Eurocode allows for finite element modelling of plated steel structures, however the information in the code on how to perform the analysis or what assumptions to make is quite sparse. The present paper investigates the deterministic modelling of flexural column buckling using plane shell elements...... in advanced non-linear finite element analysis (GMNIA) with the goal of being able to reestablish the European buckling curves. A short comprehensive historical review is given on the development of the European buckling curves and the related assumptions made with respect to deterministic modelling of column...... deterministic analysis can be performed based on given magnitudes of characteristic yield stress, material stress–strain relationship, and given characteristic values for imperfections and residual stresses. The magnitude of imperfections and residual stresses are discussed as well as how the use of equivalent...

  13. Precipitation of aluminum nitride in a high strength maraging steel with low nitrogen content

    Energy Technology Data Exchange (ETDEWEB)

    Jeanmaire, G., E-mail: guillaume.jeanmaire@univ-lorraine.fr [Institut Jean Lamour, UMR 7198 CNRS-Université de Lorraine, 54011 Nancy Cedex (France); Aubert and Duval, BP1, 63770 Les Ancizes (France); Dehmas, M.; Redjaïmia, A. [Institut Jean Lamour, UMR 7198 CNRS-Université de Lorraine, 54011 Nancy Cedex (France); Puech, S. [Aubert and Duval, BP1, 63770 Les Ancizes (France); Fribourg, G. [Snecma Gennevilliers, 171 Boulevard de Valmy-BP 31, 92702 Colombes (France)

    2014-12-15

    In the present work, aluminum nitride (AlN) precipitation was investigated in a X23NiCoCrMoAl13-6-3 maraging steel with low nitrogen content (wt.% N = 5.5 ppm). A reliable and robust automatic method by scanning electron microscopy observations coupled with energy dispersive X-ray spectroscopy was developed for the quantification of AlN precipitates. The first stage was to identify the solvus temperature and to develop a heat treatment able to dissolve the AlN precipitates. The experimental determination of equilibrium conditions and solvus temperature show good agreement with ThermoCalc® simulation. Then, from this AlN-free state, the cooling rate, isothermal holding time and temperature were the subject of an intensive investigation in the austenite region of this maraging steel. In spite of the high temperatures used during heat treatments, the growth kinetic of the largest AlN precipitates (> 1 μm) is slow. The cooling rate has a major effect on the size and the number density of AlN due to a higher driving force for nucleation at low temperatures. At last, quenching prior to isothermal annealing at high temperatures leads to fine and dense AlN precipitation, resulting from the martensite to austenite transformation. Experimental results will be discussed and compared with kinetic data obtained with the mobility database MobFe2 implemented in Dictra® software. - Highlights: • Slow dissolution kinetic of AlN precipitates due to both their large size and small chemical driving force • Significant effects of cooling rate prior isothermal heat treatment, holding time and temperature on AlN precipitation • Size of AlN precipitates can be reduced by quenching prior isothermal holding. • Fine precipitation of AlN related to the α → γ transformation.

  14. Microstructure Characterization of Fiber Laser Welds of S690QL High-Strength Steels

    Science.gov (United States)

    Li, Baoming; Xu, Peiquan; Lu, Fenggui; Gong, Hongying; Cui, Haichao; Liu, Chuangen

    2018-02-01

    The use of fiber laser welding to join S690QL steels has attracted interest in the field of construction and assembly. Herein, 13-mm-thick S690QL welded joints were obtained without filler materials using the fiber laser. The as-welded microstructures and the impact energies of the joints were characterized and measured using electron microscopy in conjunction with high-resolution transmission electron images, X-ray diffraction, and impact tests. The results indicated that a single-sided welding technique could be used to join S690QL steels up to a thickness of 12 mm (fail to fuse the joint in the root) when the laser power is equal to 12 kW (scan speed 1 m/min). Double-side welding technique allows better weld penetration and better control of heat distribution. Observation of the samples showed that the fusion zone exhibited bainitic and martensitic microstructures with increased amounts of martensites (Ms) compared with the base materials. Also, the grains in the fusion zone increased in coarseness as the heat input was increased. The fusion zone exhibited increased hardness (397 HV0.2) while exhibiting a simultaneous decrease in the impact toughness. The maximum impact energy value of 26 J was obtained from the single-side-welded sample, which is greater than those obtained from the double-side-welded samples (maximum of 18 J). Many more dislocations and plastic deformations were found in the fusion zone than the heat-affected zone in the joint, which hardened the joints and lowered the impact toughness. The microstructures characterized by FTEM-energy-dispersive X-ray spectrometer also exhibited laths of M, as well as stacking faults and dislocations featuring high-density, interfacial structure ledges that occur between the high-angle grain boundaries and the M and bainite.

  15. Advanced High Strength Steels: Improved Properties by Design of Textures and Microstructures

    Science.gov (United States)

    Kestens, Leo A. I.; De Knijf, Dorien; Castro Cerda, Felipe; Petrov, Roumen H.

    2017-07-01

    Texture and microstructure formation during annealing of a 75% cold rolled AHS steel, reheated at a rate of 10°C/s to ∼3000°C/s were studied with the purpose to investigate the interaction between the recrystallization and the austenite formation as well as the possibility of grain refinement. It was found that at ultra-high heating rates, the bcc-fcc phase transformation starts before the completion of recrystallization and the deformation texture is partially retained in the samples after annealing. The crystallographic texture observed in the martensitic phase, which is the product of intercritical austenite transformation in as-quenched samples, i.e., after the double α-γ-α’ transformation, is similar to the initial cold rolling texture, which is an indication for the texture memory effect. After ultra-fast reheating with average reheating rates of 1000°C/s and higher, a significant grain refinement was observed with an average calculated ferrite grain diameter of ∼2 μm. The obtained final ferrite grain size depends significantly on both the reheating temperature and the heating rate. The same effect is observed in 75% cold rolled quenching and partitioning steels for heating rates of 400°C/s, 800°C/s and 1000°C/s. In both cases the combination of fine grains, and weak RD/ND-fiber textures produce an increase of strength and ductility compared to material annealed using a conventional heating rate of ∼10°C/s.

  16. Influence of the thermodynamic parameters on the temper embrittlement of SA508 Gr.4N Ni-Cr-Mo low alloy steel with variation of Ni, Cr and Mn contents

    Science.gov (United States)

    Park, Sang-Gyu; Lee, Ki-Hyoung; Min, Ki-Deuk; Kim, Min-Chul; Lee, Bong-Sang

    2012-07-01

    It is well known that SA508 Gr.4N low alloy steel offers improved fracture toughness and strength compared to commercial low alloy steels such as SA508 Gr.3 Mn-Mo-Ni low alloy steel. In this study, the effects of Cr, Mn, and Ni on temper embrittlement in SA508 Gr.4N low alloy steel were evaluated from the viewpoint of thermodynamic parameters such as P diffusivity and C activity. The changes of the ductile-brittle transition temperatures before and after aging were correlated with varying alloying element content, and the diffusivity of P and the activity of C were calculated and correlated with the transition behaviors. The addition of Ni, Cr, and Mn reduce the resistance to temper embrittlement, showing increased Transition-Temperature Shift (TTS) and an increased fraction of intergranular fracture. Although the diffusivity of P is changed by the addition of alloying elements, it does not considerably affect the temper embrittlement. The Mn and Cr content in the matrix significantly reduce the C activity, with showing an inversely proportional relationship to TTS. The change of susceptibility to temper embrittlement caused by Cr and Mn addition could be explained by the variation of C activity. Unlike Cr and Mn, Ni has little effect on the temper embrittlement and C activity.

  17. Influence of the thermodynamic parameters on the temper embrittlement of SA508 Gr.4N Ni-Cr-Mo low alloy steel with variation of Ni, Cr and Mn contents

    Energy Technology Data Exchange (ETDEWEB)

    Park, Sang-Gyu; Lee, Ki-Hyoung [Nuclear Materials Research Division, Korea Atomic Energy Research Institute, 150-1 Deogjin-dong, Yuseong-gu, Daejeon 305-353 (Korea, Republic of); Min, Ki-Deuk [Division of Material Science and Engineering, Hanyang University, 17 Haengdang-dong, Seongdong-gu, Seoul 133-791 (Korea, Republic of); Kim, Min-Chul, E-mail: mckim@kaeri.re.kr [Nuclear Materials Research Division, Korea Atomic Energy Research Institute, 150-1 Deogjin-dong, Yuseong-gu, Daejeon 305-353 (Korea, Republic of); Lee, Bong-Sang [Nuclear Materials Research Division, Korea Atomic Energy Research Institute, 150-1 Deogjin-dong, Yuseong-gu, Daejeon 305-353 (Korea, Republic of)

    2012-07-15

    It is well known that SA508 Gr.4N low alloy steel offers improved fracture toughness and strength compared to commercial low alloy steels such as SA508 Gr.3 Mn-Mo-Ni low alloy steel. In this study, the effects of Cr, Mn, and Ni on temper embrittlement in SA508 Gr.4N low alloy steel were evaluated from the viewpoint of thermodynamic parameters such as P diffusivity and C activity. The changes of the ductile-brittle transition temperatures before and after aging were correlated with varying alloying element content, and the diffusivity of P and the activity of C were calculated and correlated with the transition behaviors. The addition of Ni, Cr, and Mn reduce the resistance to temper embrittlement, showing increased Transition-Temperature Shift (TTS) and an increased fraction of intergranular fracture. Although the diffusivity of P is changed by the addition of alloying elements, it does not considerably affect the temper embrittlement. The Mn and Cr content in the matrix significantly reduce the C activity, with showing an inversely proportional relationship to TTS. The change of susceptibility to temper embrittlement caused by Cr and Mn addition could be explained by the variation of C activity. Unlike Cr and Mn, Ni has little effect on the temper embrittlement and C activity.

  18. Performance optimization and computational design of ultra-high strength gear steels

    Science.gov (United States)

    Tiemens, Benjamin Lee

    Rising power density requirements in transmission gear applications are swiftly outpacing gear redesign alone and will ultimately depend on better materials. Ni-Co secondary hardening steels show great promise for these applications due to their optimized combination of strength and toughness. The commercially available secondary hardening alloys GearMet RTM C61 and C67 have already demonstrated promising contact fatigue resistance, however bending fatigue is anticipated to be the primary failure mode limiting high power density gear applications. Single tooth bending fatigue testing was therefore completed on C61 and C67 spur gears to both assess the optimized performance of these alloys as well as identify defect populations currently limiting further advances. The resultant best-practice C61 spur gears in a shot peened and isotropic superfinished condition outperformed the top-ranking premium gear steel, demonstrating an approximate 15% improvement in bending fatigue endurance limit. Fatigue failures limiting further bending fatigue performance were identified to primarily initiate at three defect classes: shot peening-induced surface damage, subsurface inter-granular cleavage facets and Al2O3 and La2O2S inclusions. C67 spur gears did not show increased performance despite elevated surface hardness levels due to the inability of current shot peening practices to achieve maximum compressive stress in ultra-high hardness materials. In an effort to reduce the material cost of these alloys through minimization/elimination of cobalt alloying additions, BCC Cu precipitation was incorporated to offset ensuing losses in temper resistance by providing additional heterogeneous nucleation sites for the M2C strengthening dispersion. Fifty-pound experimental heats were made of four designed compositions. Peak hardness levels achieved during tempering fell on average 200 VHN short of the 900 VHN designed surface hardness. 3-dimensional local electrode atom probe (LEAP

  19. A Study of the Influence of Thermomechanical Controlled Processing on the Microstructure of Bainite in High Strength Plate Steel

    Science.gov (United States)

    Liang, Xiaojun; DeArdo, Anthony J.

    2014-10-01

    Steels with compositions that are hot rolled and cooled to exhibit high strength and good toughness often require a bainitic microstructure. This is especially true for plate steels for linepipe applications where strengths in excess of 690 MPa (100 ksi) are needed in thicknesses between approximately 6 and 30 mm. To ensure adequate strength and toughness, the steels should have adequate hardenability (C. E. >0.50 and Pcm >0.20), and are thermomechanically controlled processed, i.e., controlled rolled, followed by interrupted direct quenching to below the Bs temperature of the pancaked austenite. Bainite formed in this way can be defined as a polyphase mixture comprised a matrix phase of bainitic ferrite plus a higher carbon second phase or micro-constituent which can be martensite, retained austenite, or cementite, depending on circumstances. This second feature is predominately martensite in IDQ steels. Unlike pearlite, where the ferrite and cementite form cooperatively at the same moving interface, the bainitic ferrite and MA form in sequence with falling temperature below the Bs temperature or with increasing isothermal holding time. Several studies have found that the mechanical properties may vary strongly for different types of bainite, i.e., different forms of bainitic ferrite and/or MA. Thermomechanical controlled processing (TMCP) has been shown to be an important way to control the microstructure and mechanical properties in low carbon, high strength steel. This is especially true in the case of bainite formation, where the complexity of the austenite-bainite transformation makes its control through disciplined processing especially important. In this study, a low carbon, high manganese steel containing niobium was investigated to better understand the effects of austenite conditioning and cooling rates on the bainitic phase transformation, i.e., the formation of bainitic ferrite plus MA. Specimens were compared after transformation from recrystallized

  20. The mechanical properties and microstructures of vanadium bearing high strength dual phase steels processed with continuous galvanizing line simulations

    Science.gov (United States)

    Gong, Yu

    For galvanized or galvannealed steels to be commercially successful, they must exhibit several attributes: (i) easy and inexpensive processing in the hot mill, cold mill and on the coating line, (ii) high strength with good formability and spot weldability, and (iii) good corrosion resistance. At the beginning of this thesis, compositions with a common base but containing various additions of V or Nb with or without high N were designed and subjected to Gleeble simulations of different galvanizing(GI), galvannealing(GA) and supercooling processing. The results revealed the phase balance was strongly influenced by the different microalloying additions, while the strengths of each phase were somewhat less affected. Our research revealed that the amount of austenite formed during intercritical annealing can be strongly influenced by the annealing temperature and the pre-annealing conditions of the hot band (coiling temperature) and cold band (% cold reduction). In the late part of this thesis, the base composition was a low carbon steel which would exhibit good spot weldability. To this steel were added two levels of Cr and Mo for strengthening the ferrite and increasing the hardenability of intercritically formed austenite. Also, these steels were produced with and without the addition of vanadium in an effort to further increase the strength. Since earlier studies revealed a relationship between the nature of the starting cold rolled microstructure and the response to CGL processing, the variables of hot band coiling temperature and level of cold reduction prior to annealing were also studied. Finally, in an effort to increase strength and ductility of both the final sheet (general formability) and the sheared edges of cold punched holes (local formability), a new thermal path was developed that replaced the conventional GI ferrite-martensite microstructure with a new ferrite-martensite-tempered martensite and retained austenite microstructure. The new

  1. Temperature-dependent yield criterion for high strength steel sheets under warm-forming conditions

    Directory of Open Access Journals (Sweden)

    Cai Zhengyang

    2015-01-01

    Full Text Available In this paper, uniaxial and biaxial tensile tests with cruciform specimens were conducted to investigate the deformation behaviour of dual phase steel sheet with a tensile strength of 590 MPa (DP590 under evaluated warm-forming temperatures (20–190 ∘C. Detailed analyses were then carried out to obtain the corresponding experimental yield loci. For the purpose of describing the temperature-dependent yield behaviour of DP590 appropriately, the Yld2000–2d yield function with temperature-dependent exponent was proposed. The identification procedures of the introduced parameters were then proposed based on Levenberg-Marquardt optimization algorithm. Afterwards, the proposed model was implemented into ABAQUS as user subroutine VUMAT with NICE (Next Increment Corrects Error explicit integration scheme. The numerical simulations of biaxial tensile tests were then conducted to confirm the validity of the proposed model. It could be concluded that the flexibility and accuracy of the proposed model guarantee the applicability in warm-forming applications.

  2. Ductility of Advanced High-Strength Steel in the Presence of a Sheared Edge

    Science.gov (United States)

    Ruggles, Tim; Cluff, Stephen; Miles, Michael; Fullwood, David; Daniels, Craig; Avila, Alex; Chen, Ming

    2016-07-01

    The ductility of dual-phase (DP) 980 and transformation-induced plasticity (TRIP) assisted bainitic ferritic (TBF) 980 steels was studied in the presence of a sheared edge. Specimens were tested in uniaxial tension in a standard test frame as well as in situ in the scanning electron microscope (SEM). Incremental tensile straining was done in the SEM with images taken at each strain increment. Then digital image correlation (DIC) was used to compute the effective strain at the level of the individual phases in the microstructure. Shear banding across multiple phases was seen in strained TBF specimens, while the DP specimens exhibited more of a patchwork strain pattern, with high strains concentrated in ferrite and low strains observed in the martensite. Two-point statistics were applied to the strain data from the DIC work and the corresponding microstructure images to evaluate the effect of phase hardness on localization and fracture. It was observed that the DP 980 material had a greater tendency for localization around hard phases compared to the TBF 980. This at least partially explains the greater ductility of the TBF material, especially in specimens where a sheared edge was present.

  3. Measurement of fatigue accumulation in high-strength steels by microstructural examination

    Science.gov (United States)

    Nakagawa, Y. G.; Yoshizawa, H.; Lapides, M. E.

    1990-07-01

    Fatigue test bars fabricated from an SA508 class 3 low-carbon steel plate were cyclically deformed at 300 °C (constant low-cycle fatigue, total strain range Δɛ = 0.78 pct and 0.48 pct) to crack initiation (100 pct cumulative damage, CD) and to the factors 75, 50, and 25 pct CD. The test bars were cut perpendicular to the stress axis at the center of the gage length. The X-ray diffraction line-broadening (XRD) was performed on the cross sections created by the cuts. Thin foils (˜0.1-μm thick) were prepared from each cross section and used for the transmission electron microscope (TEM) and selected area diffraction (SAD) study. The half-value line breadth change measured by the XRD increased with the CD increase up to 50 pct, beyond which a significant reduction was observed for the 75 and 100 pct CD sample regardless of the incident X-ray beam angle. By the TEM, the undamaged material (0 pct CD) was characterized by high-angle boundaries, small carbide precipitates, and dislocation cell networks in grains. These characteristics did not show any appreciable changes in all of the samples with fatigue damage of the respective levels. Micro-orientation changes of the dislocation cells studied by the SAD of the foils and a statistical data analysis clearly demonstrated that the mean orientation difference in the cells and its standard deviation increased gradually as the CD increased.

  4. Twin-spot laser welding of advanced high-strength multiphase microstructure steel

    Science.gov (United States)

    Grajcar, Adam; Morawiec, Mateusz; Różański, Maciej; Stano, Sebastian

    2017-07-01

    The study addresses the results concerning the laser welding of TRIP (TRansformation Induced Plasticity) steel using a beam focused at two spots (also referred to as twin-spot laser welding). The analysis involved the effect of variable welding thermal cycles on the properties and microstructure of welded joints. The tests were performed using a linear energy of 0.048 and 0.060 kJ/mm and the laser beam power distribution of 50%:50%, 60%:40% and 70%:30%. The tests also involved welding performed using a linear energy of 0.150 kJ/mm and the laser beam power distribution of 70%:30%. In addition, the research included observations of the microstructure of the fusion zone, heat affected zone and the transition zone using light microscopy and scanning electron microscopy. The fusion zone was composed of blocky-lath martensite whereas the HAZ (heat-affected zone) was characterised by the lath microstructure containing martensite, bainite and retained austenite. The distribution of twin-spot laser beam power significantly affected the microstructure and hardness profiles of welded joints. The highest hardness (480-505 HV), regardless of welding variants used, was observed in the HAZ.

  5. Corrosion Behavior of Metal Active Gas Welded Joints of a High-Strength Steel for Automotive Application

    Science.gov (United States)

    Garcia, Mainã Portella; Mantovani, Gerson Luiz; Vasant Kumar, R.; Antunes, Renato Altobelli

    2017-10-01

    In this work, the corrosion behavior of metal active gas-welded joints of a high-strength steel with tensile yield strength of 900 MPa was investigated. The welded joints were obtained using two different heat inputs. The corrosion behavior has been studied in a 3.5 wt.% NaCl aqueous solution using electrochemical impedance spectroscopy and potentiodynamic polarization tests. Optical microscopy images, scanning electron microscopy and transmission electron microscopy with energy-dispersive x-ray revealed different microstructural features in the heat-affected zone (HAZ) and the weld metal (WM). Before and after the corrosion process, the sample was evaluated by confocal laser scanning microscopy to measure the depth difference between HAZ and WM. The results showed that the heat input did not play an important role on corrosion behavior of HSLA steel. The anodic and cathodic areas of the welded joints could be associated with depth differences. The HAZ was found to be the anodic area, while the WM was cathodic with respect to the HAZ. The corrosion behavior was related to the amount and orientation nature of carbides in the HAZ. The microstructure of the HAZ consisted of martensite and bainite, whereas acicular ferrite was observed in the weld metal.

  6. Reason for high strength and good ductility in dual phase steels composed of soft ferrite and hard martensite

    Science.gov (United States)

    Terada, Daisuke; Ikeda, Gosuke; Park, Myeong-heom; Shibata, Akinobu; Tsuji, Nobuhiro

    2017-07-01

    Dual phase (DP) steels in which the microstructures are composed of a soft ferrite phase and a hard martensite phase are known to show good strain-hardening, high strength and large elongation, but reasons for their superior mechanical properties are still unclear. In the present study, two types of DP structures, having either networked martensite or isolated martensite were fabricated in a low-carbon steel by different heat treatment routes, and their tensile deformation behavior was analyzed using the digital image correlation (DIC) technique. It was revealed that the DP specimens having networked martensite microstructures showed a better strength-ductility balance than the DP specimens with isolated martensite structures. The microscopic DIC analysis of identical areas showed that the strain distribution within the DP microstructures was not uniform and the plastic strain was localized in soft ferrite grains. The strain localized regions tended to detour around hard martensite but eventually propagated across the martensite. It was found also from the DIC analysis that the degree of strain partitioning between ferrite and martensite in the networked DP structure was lower than that in the isolated DP structure. The deformation became more homogeneous when the hard phase (martensite) was connected to form a network structure, which could be one of the reasons for the better strength-ductility balance in the networked DP structure compared to that in the isolated DP structure.

  7. Experimental and Numerical Investigations of Applying Tip-bottomed Tool for Bending Advanced Ultra-high Strength Steel Sheet

    Science.gov (United States)

    Mitsomwang, Pusit; Borrisutthekul, Rattana; Klaiw-awoot, Ken; Pattalung, Aran

    2017-09-01

    This research was carried out aiming to investigate the application of a tip-bottomed tool for bending an advanced ultra-high strength steel sheet. The V-die bending experiment of a dual phase steel (DP980) sheet which had a thickness of 1.6 mm was executed using a conventional bending and a tip-bottomed punches. Experimental results revealed that the springback of the bent worksheet in the case of the tip-bottomed punch was less than that of the conventional punch case. To further discuss bending characteristics, a finite element (FE) model was developed and used to simulate the bending of the worksheet. From the FE analysis, it was found that the application of the tip-bottomed punch contributed the plastic deformation to occur at the bending region. Consequently, the springback of the worksheet reduced. In addition, the width of the punch tip was found to affect the deformation at the bending region and determined the springback of the bent worksheet. Moreover, the use of the tip-bottomed punch resulted in the apparent increase of the surface hardness of the bent worksheet, compared to the bending with the conventional punch.

  8. Corrosion Behavior of Metal Active Gas Welded Joints of a High-Strength Steel for Automotive Application

    Science.gov (United States)

    Garcia, Mainã Portella; Mantovani, Gerson Luiz; Vasant Kumar, R.; Antunes, Renato Altobelli

    2017-09-01

    In this work, the corrosion behavior of metal active gas-welded joints of a high-strength steel with tensile yield strength of 900 MPa was investigated. The welded joints were obtained using two different heat inputs. The corrosion behavior has been studied in a 3.5 wt.% NaCl aqueous solution using electrochemical impedance spectroscopy and potentiodynamic polarization tests. Optical microscopy images, scanning electron microscopy and transmission electron microscopy with energy-dispersive x-ray revealed different microstructural features in the heat-affected zone (HAZ) and the weld metal (WM). Before and after the corrosion process, the sample was evaluated by confocal laser scanning microscopy to measure the depth difference between HAZ and WM. The results showed that the heat input did not play an important role on corrosion behavior of HSLA steel. The anodic and cathodic areas of the welded joints could be associated with depth differences. The HAZ was found to be the anodic area, while the WM was cathodic with respect to the HAZ. The corrosion behavior was related to the amount and orientation nature of carbides in the HAZ. The microstructure of the HAZ consisted of martensite and bainite, whereas acicular ferrite was observed in the weld metal.

  9. Investigation of Clusters in Medium Carbon Secondary Hardening Ultra-high-strength Steel After Hardening and Aging Treatments

    Science.gov (United States)

    Veerababu, R.; Balamuralikrishnan, R.; Muraleedharan, K.; Srinivas, M.

    2015-06-01

    Clusters, containing between 10 and 1000 atoms, have been investigated in a martensitic secondary hardening ultra-high-strength steel austenitized at 1173 K (900 °C) for 1 hour and tempered at either 768 K or 783 K (495 °C or 510 °C) for 4 or 8 hours using 3D atom probe. The presence of clusters was unambiguously established by comparing the observed spatial distribution of the different alloying elements against the corresponding distribution expected for a random solid solution. Maximum separation envelope method has been used for delineating the clusters from the surrounding "matrix." Statistical analysis was used extensively for size and composition analyses of the clusters. The clusters were found to constitute a significant fraction accounting for between 1.14 and 2.53 vol pct of the microstructure. On the average, the clusters in the 783 K (510 °C) tempered sample were coarser by ~65 pct, with an average diameter of 2.26 nm, relative to the other samples. In all samples, about 85 to 90 pct of the clusters have size less than 2 nm. The percentage frequency histograms for carbon content of the clusters in 768 K and 783 K (495 °C and 510 °C) tempered samples revealed that the distribution shifts toward higher carbon content when the tempering temperature is higher. It is likely that the presence of these clusters exerts considerable influence on the strength and fracture toughness of the steel.

  10. Low friction and high strength of 316L stainless steel tubing for biomedical applications.

    Science.gov (United States)

    Amanov, Auezhan; Lee, Soo-Wohn; Pyun, Young-Sik

    2017-02-01

    We propose herein a nondestructive surface modification technique called ultrasonic nanocrystalline surface modification (UNSM) to increase the strength and to improve the tribological performance of 316L stainless steel (SS) tubing. Nanocrystallization along nearly the complete tube thickness of 200μm was achieved by UNSM technique that was confirmed by electron backscatter diffraction (EBSD). Nano-hardness of the untreated and UNSM-treated specimens was measured using a nanoindentation. Results revealed that a substantial increase in hardness was obtained for the UNSM-treated specimen that may be attributed to the nanocrystallization and refined grains. Stress-strain behavior of the untreated and UNSM-treated specimens was assessed by a 3-point bending test. It was found that the UNSM-treated specimen exhibited a much higher strength than that of the untreated specimen. In addition, the tribological behavior of the untreated and UNSM-treated specimens with an outer diameter (OD) of 1.6mm and an inner diameter (ID) of 1.2mm was investigated using a cylinder-on-cylinder (crossed tubes of equal radius) tribo-tester against itself under dry conditions at ambient temperature. The friction coefficient and wear resistance of the UNSM-treated specimen were remarkably improved compared to that of the untreated specimen. The significant increase in hardness after UNSM treatment is responsible for the improved friction coefficient and wear resistance of the tubing. Thus, the UNSM technique was found to be beneficial to improving the mechanical and tribological properties of 316L SS tubing for various potential biomedical applications, in particular for coronary artery stents. Copyright © 2016 Elsevier B.V. All rights reserved.

  11. The effect of chloride on general corrosion and crack initiation of low-alloy steels in oxygenated high-temperature water

    Energy Technology Data Exchange (ETDEWEB)

    Herbst, Matthias; Roth, Armin [AREVA NP GmbH, Erlangen (Germany); Widera, Martin [RWE Power AG, Essen (Germany); Kuester, Karin; Huettner, Frank [Vattenfall Europe Nuclear Energy GmbH, Hamburg (Germany); Nowak, Erika [E.ON Kernkraft GmbH, Hannover (Germany)

    2012-07-01

    The effect of chloride on the general corrosion and its potential impact on EAC crack initiation of low-alloy steel (German reactor pressure vessel steel 22 NiMoCr 3 7) in oxygenated high-temperature water were investigated. The general corrosion behavior was analyzed by exposure tests with either permanently increased chloride concentration levels or temporary chloride transients. The potential effect on EAC crack initiation was analyzed with pre-strained C-ring specimens and in SSRT (CERT) tests with slowly rising strain. Both kinds of tests were performed under simulated BWR conditions and with different chloride levels. The chloride concentrations of 5 to 50 ppb were chosen according to the action levels of the German water chemistry guideline for the reactor coolant of BWRs (VGB R401J, 2006). In all exposure tests, none of the pre-strained C-ring specimens showed crack initiation during up to 1000 hours of exposure time with up to 50 ppb chloride. Investigations of the oxide layer thickness after immersion testing revealed a decrease with increasing chloride concentration. As shown by post-test chemical analysis of the oxide layer composition by TOF-SIMS, this effect is most likely primarily due to adsorption of chloride on the oxide layer surface, since only very limited penetration of chloride into the oxide was detected. In contrast to the tests with C-ring specimens, where no crack initiation occurred, slightly accelerated crack initiation at lower elongation levels was observed at increasing chloride concentrations in SSRT tests under simulated BWR conditions using actively loaded specimens. In addition, SSRT specimens that were cyclically loaded at the oxide fracture elongation level were used to generate a continuous, exposure of bare metal to the environment by repeated fracture of the oxide. This loading pattern did not cause crack initiation at all chloride concentrations applied (up to 50 ppb). From these results, it may be concluded that at least

  12. 76 FR 31938 - Certain Hot-Rolled Carbon Steel Flat Products From India: Notice of Preliminary Results of 2009...

    Science.gov (United States)

    2011-06-02

    ....50 percent of aluminum, or 1.25 percent of chromium, or 0.30 percent of cobalt, or 0.40 percent of..., high-strength low-alloy (``HSLA'') steels, and the substrate for motor lamination steels. IF steels are... are recognized as steels with micro-alloying levels of elements such as chromium, copper, niobium...

  13. The investigation of the deformation wave hardening effect on the strength of the medium and low alloy steels

    Science.gov (United States)

    Kirichek, A. V.; Barinov, S. V.; Yashin, A. V.; Kolontsov, S. E.

    2017-02-01

    The article presents the data on the effect of wave deformation hardening on the strength of the 45, 40X and 35 HGSA steel. To improve the strength of these steels, it is proposed to create structured areas consisting of alternating solid and viscous-plastic sections in their surface layer. The evenness of arrangement of the sections is characterized by the overlap factor. The studies found that wave deformation treatment of the samples, made of the 45, 40X 35HGSA steel, made it possible to increase the tensile strength by 8, 4.2 and 13%, the values of elastic deformations - by 37, 81 and 51% during their hardening with overlapping coefficients 0.7; 0.9 and 0.7, respectively.

  14. Morphology, crystallography, and crack paths of tempered lath martensite in a medium-carbon low-alloy steel

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Chengduo [School of Material Science and Engineering, Zhengzhou University, 100 Science Avenue, Zhengzhou, Henan 450001 (China); Qiu, Hai; Kimura, Yuuji; Inoue, Tadanobu [Research Center for Strategic Materials, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba 305-0047 (Japan)

    2016-07-04

    The tempered lath martensite and its crack propagation have significant influence on the ductility and toughness of the warm tempformed medium-carbon steel. The martensitic microstructures of these medium-carbon steels are transformed from twinned austenite and the orientation relationship of lath martensite (α′) with prior austenite (γ) is distinctive. In the present paper we investigate the microstructure and fracture mode of a quenched and tempered 0.4%C-2%Si-1%Cr-1%Mo steel using electron backscatter diffraction technique. The results showed that the orientation relationship between γ and α′ is Greninger-Troiano (G-T) relationship. A single γ grain was divided into 4 packets and each packet was subdivided into 3 blocks. The misorientation angles between adjacent blocks were ~54.3° or ~60.0° in a packet. Most γ grains were twins sharing a {111}{sub γ} plane. There were 7 packets in a twinned γ grain and the twin boundaries were in a special packet. Besides the common packet, there were three packets in each twin. Being different from the cleavage fracture along the {001} planes in conventional martensitic steels, both cleavage and intergranular cracks were present in our medium-carbon steel. The former was in the larger blocks and it propagated along the {001}, {011}, and {112} planes. The latter propagated along the block, packet, or prior austenite boundaries. The intergranular cracks were generally in the fine block region. These results suggested that the block size is the key factor in controlling the brittle fracture mode of lath martensitic steel.

  15. Alloying effect of copper on the corrosion properties of low-alloy steel for flue gas desulfurization system

    Science.gov (United States)

    Kim, Seon-Hong; Park, Sun-Ah; Kim, Jung-Gu; Shin, Kee-Sam; He, Yinsheng

    2015-03-01

    The alloying effect of Cu for a flue gas desulfurization materials was investigated using the electrochemical methods in the modified green death solution and the surface analyses. The test results demonstrated that the densely formed rust layer with high metallic Cu content improves the corrosion resistance of Cu-containing steel in the flue gas desulfurization (FGD) environment. The rust layer on the surface of the 0.02 wt% Cu steel, which has an insufficient Cu content, was less protective than others. The 0.05 wt% Cu steel represented the highest corrosion resistance due to the formation of the densely formed rust layer with optimum Cu content. Because the free standing Cu2S precipitates had the insoluble characteristic in highly acidic solution, it produced the relatively porous Cu-enriched layer on the 0.08 wt% Cu steel surface. From these phenomena, the corrosion resistance of specimen decreased as the Cu content of specimen increased from 0.05 wt% to 0.08 wt%.

  16. Effect of High Cl- Environment on Stress Corrosion Cracking Behavior of M152 and 17-4PH High-strength Steels

    Directory of Open Access Journals (Sweden)

    WU Wei

    2018-02-01

    Full Text Available The stress corrosion cracking (SCC behavior and mechanism of M152 and 17-4PH high-strength steels in high Cl- environment were studied through neutral salt spray test and slow strain rate tensile (SSRT test. The result shows that M152 and 17-4PH steels exhibit a certain sensitivity to SCC in Cl- environment, elongations of them both decrease with the increasing time of early neutral salt spray test, and the SCC sensitivity gradually increases. Comparing the fracture morphology with lateral crack through SEM, it can be found that the fracture mechanism of M152 and 17-4PH high-strength steels converts ductile fracture to brittle fracture as the extension of neutral salt spray test time. The synergistic effect of anodic dissolution (AD and hydrogen embrittlement (HE result in the occurrence of SCC in high Cl- environment, and Cl- can promote the AD process. Due to the obvious effect of HE, 17-4PH steel has higher SCC sensitivity than M152 steel with the same time of early neutral salt spray test. 17-4PH high-strength steel is more prone to SCC than M152 in high Cl- environment.

  17. Microstructural and microanalysis investigations of bond titanium grade1/low alloy steel st52-3N obtained by explosive welding

    Energy Technology Data Exchange (ETDEWEB)

    Gloc, Michal, E-mail: michalgloc@wp.pl [Warsaw University of Technology, Faculty of Materials Science and Engineering (Poland); Wachowski, Marcin [Military University of Technology in Warsaw, Faculty of Mechanical Engineering (Poland); Plocinski, Tomasz; Kurzydlowski, Krzysztof Jan [Warsaw University of Technology, Faculty of Materials Science and Engineering (Poland)

    2016-06-25

    Explosive welding is a solid state welding process that is used for the metallurgical joining of two or more dissimilar metals. In this process, forces of controlled detonations are utilized to accelerate one metal plate into another. As a result, an atomic bond is created. It is considered as a cold-welding process since it allows metals to be joined without losing their pre-bonding properties. The metal plates are joined under the influence of very high pressure which causes local plastic deformation and grain refining at the bond interface. Moreover, between the parent and flyer plate some local melting zones are formed. The explosively cladded steel plates are used in the chemical, petrochemical and nuclear industry due to their good corrosion resistance and mechanical properties. In this work, microstructural and chemical analyses of clad plates obtained by the explosive method are presented. The clad plates studied were made of titanium grade 1 explosively bonded with a thin layer of st52-3N low alloy steel. The microstructure was evaluated using light (LM) and scanning electron microscopes (SEM), while chemical composition was assessed using energy dispersive spectroscopy (EDS). It was found that the bond area had different microstructure, chemical composition and microhardness than the bonded materials. In the junction between the base steel and the cladding, a strongly defected transient zone with altered chemical composition in comparison with the bonded metals was revealed. - Highlights: • Explosive welding as an effective method for joining similar or dissimilar metals. • Slip brands, elongated grains and twins correlated with high plastic deformations. • Investigations of the local melted zones, formed at the interface of the clads. • Mechanical properties connected with microstructural changes and deformation.

  18. Investigations of Temperatures of Phase Transformations of Low-Alloyed Reinforcing Steel within the Heat Treatment Temperature Range

    Directory of Open Access Journals (Sweden)

    Kargul T.

    2017-06-01

    Full Text Available The paper presents the results of DSC analysis of steel B500SP produced in the process of continuous casting, which is intended for the production reinforcement rods with high ductility. Studies were carried out in the temperature range below 1000°C in a protective atmosphere of helium during samples heating program. The main objective of the study was to determine the temperature range of austenite structure formation during heating. As a result of performed experiments: Ac1s, Ac1f – temperatures of the beginning and finish of the eutectoid transformation, Ac2 – Curie temperature of the ferrite magnetic transformation and the temperature Ac3 of transformation of proeutectoid ferrite into austenite were elaborated. Experimental determination of phase transformations temperatures of steel B500SP has great importance for production technology of reinforcement rods, because good mechanical properties of rods are formed by the special thermal treatment in Tempcore process.

  19. A study and development of technology for surface induction hardening of railroad rails from low-alloy steel

    Science.gov (United States)

    Degtyarev, S. I.; Skoblo, T. S.; Sapozhnikov, V. E.

    1998-12-01

    A technology of heat treatment of railroad rails using induction heating has been developed and installed in the Azovstal' metallurgical works. It provides the requisite combination of properties in the metal of rail heads. However, the metal of the web and the bottom of the rails remains in the initial (unhardened) state. Under severe operational conditions (small-radius curves, high axial loads, and composite configuration of the road) the wear resistance of the head and the structural strength of the web and the bottom not hardened in the plant have to be increased. The properties of the rail steel can be improved by alloying it using the most effective and available elements. Currently, in Ukraine this is manganese. The present paper is devoted to the effect of manganese additives on the phase transformations in induction hardening and the specific features of the formed structure and properties of the rail steel. Optimum parameters for heat treatment of rails are recommended.

  20. Use of Extracted Green Inhibitors as a Friendly Choice in Corrosion Protection of Low Alloy Carbon Steel

    Directory of Open Access Journals (Sweden)

    Jano, A.

    2012-11-01

    Full Text Available Mitigation of corrosion impact on environment is an important step in environmental protection. Use of environmentally friendly corrosion protection methods is very important. It is smart to choose cheap and safe to handle compounds as corrosion inhibitors. The use of green inhibitors (extracted inexpensively, from the seed endosperm of some Leguminosae plants, and investigation of their efficiency in corrosion protection is the aim of this study. As green inhibitor one kind of polysaccharides (galactomannan from locust bean gum (also known as carob gum, carob bean gum extracted from the seed of carob tree is used. Corrosion protection efficiency of these extracted green inhibitors was tested for carbon steel marked as: steel 39, steel 44, and iron B 500 (usually applied as reinforcing bars to concrete. Sulfuric acid solution in the presence of chloride ions was used as corrosion media. The composition of corrosion acid media used was 1 mol L-1 H2SO4 and 10-3 mol L-1 Cl- (in the form of NaCl. Electrochemical techniques such as potentiodynamic polarization methods were used for inhibitor efficiency testing.

  1. Modeling of the hot flow behavior of advanced ultra-high strength steels (A-UHSS) microalloyed with boron

    Energy Technology Data Exchange (ETDEWEB)

    Mejía, I., E-mail: imejia@umich.mx [Instituto de Investigaciones Metalúrgicas, Universidad Michoacana de San Nicolás de Hidalgo, Edificio “U”, Ciudad Universitaria, 58066 Morelia, Michoacán (Mexico); Altamirano, G.; Bedolla-Jacuinde, A. [Instituto de Investigaciones Metalúrgicas, Universidad Michoacana de San Nicolás de Hidalgo, Edificio “U”, Ciudad Universitaria, 58066 Morelia, Michoacán (Mexico); Cabrera, J.M. [Departament de Ciència dels Materials i Enginyeria Metallúrgica, ETSEIB – Universitat Politècnica de Catalunya, Av. Diagonal 647, 08028 Barcelona (Spain); Fundació CTM Centre Tecnològic, Av. de las Bases de Manresa, 1, 08240 Manresa (Spain)

    2014-07-29

    In this research work, modeling of the hot flow behavior was carried out in a low carbon advanced ultra-high strength steels (A-UHSS) microalloyed with different amounts of boron (14, 33, 82, 126 and 214 ppm). For this purpose, experimental stress–strain data of uniaxial hot-compression tests over a wide range of temperatures (1223, 1273, 1323 and 1373 K (950, 1000, 1050 and 1100 °C)) and strain rates (10{sup −3}, 10{sup −2} and 10{sup −1} s{sup −1}) were used. The stress–strain relationships as a function of temperature and strain rate were successfully described on the basis of the approach proposed by Estrin, Mecking, and Bergström, together with the classical Avrami equation and the conventional hyperbolic sine function. The analysis of the modeling parameters of the hot flow curves shows that boron additions to A-UHSS play a major role in softening mechanisms rather than on hardening. The peak stress (σ{sub p}) and steady-state stress (σ{sub ss}) values show a decreasing trend with increasing boron content, which indicates that boron additions promote a solid solution softening effect additional to that produced by DRX. The time for 50% recrystallization (t{sub 50%}) tends to increase with boron additions, revealing that boron additions cause a delay of the DRX kinetics during hot deformation. Similarly, the presence of boron in the steel decreases the apparent activation energy for recrystallization (Q{sub t}), indicating that boron additions accelerate the onset of DRX. The constitutive equations developed in this way provided an excellent description of the experimental hot flow curves.

  2. Temperature and Material Flow Prediction in Friction-Stir Spot Welding of Advanced High-Strength Steel

    Energy Technology Data Exchange (ETDEWEB)

    Miles, Michael; Karki, U.; Hovanski, Yuri

    2014-10-01

    Friction-stir spot welding (FSSW) has been shown to be capable of joining advanced high-strength steel, with its flexibility in controlling the heat of welding and the resulting microstructure of the joint. This makes FSSW a potential alternative to resistance spot welding if tool life is sufficiently high, and if machine spindle loads are sufficiently low that the process can be implemented on an industrial robot. Robots for spot welding can typically sustain vertical loads of about 8 kN, but FSSW at tool speeds of less than 3000 rpm cause loads that are too high, in the range of 11–14 kN. Therefore, in the current work, tool speeds of 5000 rpm were employed to generate heat more quickly and to reduce welding loads to acceptable levels. Si3N4 tools were used for the welding experiments on 1.2-mm DP 980 steel. The FSSW process was modeled with a finite element approach using the Forge* software. An updated Lagrangian scheme with explicit time integration was employed to predict the flow of the sheet material, subjected to boundary conditions of a rotating tool and a fixed backing plate. Material flow was calculated from a velocity field that is two-dimensional, but heat generated by friction was computed by a novel approach, where the rotational velocity component imparted to the sheet by the tool surface was included in the thermal boundary conditions. An isotropic, viscoplastic Norton-Hoff law was used to compute the material flow stress as a function of strain, strain rate, and temperature. The model predicted welding temperatures to within percent, and the position of the joint interface to within 10 percent, of the experimental results.

  3. Temperature and Material Flow Prediction in Friction-Stir Spot Welding of Advanced High-Strength Steel

    Science.gov (United States)

    Miles, M.; Karki, U.; Hovanski, Y.

    2014-10-01

    Friction-stir spot welding (FSSW) has been shown to be capable of joining advanced high-strength steel, with its flexibility in controlling the heat of welding and the resulting microstructure of the joint. This makes FSSW a potential alternative to resistance spot welding if tool life is sufficiently high, and if machine spindle loads are sufficiently low that the process can be implemented on an industrial robot. Robots for spot welding can typically sustain vertical loads of about 8 kN, but FSSW at tool speeds of less than 3000 rpm cause loads that are too high, in the range of 11-14 kN. Therefore, in the current work, tool speeds of 5000 rpm were employed to generate heat more quickly and to reduce welding loads to acceptable levels. Si3N4 tools were used for the welding experiments on 1.2-mm DP 980 steel. The FSSW process was modeled with a finite element approach using the Forge® software. An updated Lagrangian scheme with explicit time integration was employed to predict the flow of the sheet material, subjected to boundary conditions of a rotating tool and a fixed backing plate. Material flow was calculated from a velocity field that is two-dimensional, but heat generated by friction was computed by a novel approach, where the rotational velocity component imparted to the sheet by the tool surface was included in the thermal boundary conditions. An isotropic, viscoplastic Norton-Hoff law was used to compute the material flow stress as a function of strain, strain rate, and temperature. The model predicted welding temperatures to within 4%, and the position of the joint interface to within 10%, of the experimental results.

  4. Characterization of Stress Corrosion Cracking at the Welded Region of High Strength Steel using Acoustic Emission Method

    Energy Technology Data Exchange (ETDEWEB)

    Na, Eui Gyun [Kunsan University, Kunsan (Korea, Republic of); Kim, Hoon [Yosu National University, Yeosu (Korea, Republic of)

    2003-06-15

    This study is to evaluate the characteristics of SCC at the welded region of high strength steel using acoustic emission(AE) method. Specimens were loaded by a slow strain rate method in synthetic seawater and the damage process was monitored simultaneously by AE method. Corrosive environment was controlled using the potentiostat, in which -0.8V and -1.1V were applied to the specimens. In the case of one-pass weldment subjected to -0.8V, much more AE counts were detected compared with the PWHT specimen. It was verified through the cumulative counts that coalescence of micro cracks and cracks for the one pass weldment with -0.8V were mostly detected. In case of the one pass weldment subjected to -1.1V, time to failure became shorter and AE counts were produced considerably as compared with that of the two pass weldment. It was shown that AE counts and range of AE amplitude have close relations with the number and size as well as width of the cracks which were formed during the SCC

  5. Optimizing Cutting Conditions for Minimum Surface Roughness in Face Milling of High Strength Steel Using Carbide Inserts

    Directory of Open Access Journals (Sweden)

    Adel Taha Abbas

    2016-01-01

    Full Text Available A full factorial design technique is used to investigate the effect of machining parameters, namely, spindle speed (N, depth of cut (ap, and table feed rate (Vf, on the obtained surface roughness (Ra and Rt during face milling operation of high strength steel. A second-order regression model was built using least squares method depending on the factorial design results to approximate a mathematical relationship between the surface roughness and the studied process parameters. Analysis of variance was conducted to estimate the significance of each factor and interaction with respect to the surface roughness. For Ra, the results show that spindle speed, depth of cut, and table feed rate have a significant effect on the surface roughness in both linear and quadratic terms. There is also an interaction between depth of cut and feed rate. It also appears that feed rate has the greatest effect on the data variation followed by depth of cut. For Rt, the results show that the table feed rate is the most effective factor followed by the depth of cut, while the spindle speed had a significant small effect only in its quadratic term. The conditions of minimum Ra and Rt are identified through least square optimization. Moreover, multiobjective optimization for minimizing Ra and maximizing metal removal rate Q is conducted and the results are presented.

  6. Deformation and Recrystallization Behavior of the Cast Structure in Large Size, High Strength Steel Ingots: Experimentation and Modeling

    Science.gov (United States)

    Chadha, K.; Shahriari, D.; Tremblay, R.; Bhattacharjee, P. P.; Jahazi, M.

    2017-09-01

    Constitutive modeling of the ingot breakdown process of large size ingots of high strength steel was carried out through comprehensive thermomechanical processing using Gleeble 3800® thermomechanical simulator, finite element modeling (FEM), optical and electron back scatter diffraction (EBSD). For this purpose, hot compression tests in the range of 1473 K to 1323 K (1200 °C to 1050 °C) and strain rates of 0.25 to 2 s-1 were carried out. The stress-strain curves describing the deformation behavior of the dendritic microstructure of the cast ingot were analyzed in terms of the Arrhenius and Hansel-Spittel models which were implemented in Forge NxT 1.0® FEM software. The results indicated that the Arrhenius model was more reliable in predicting microstructure evolution of the as-cast structure during ingot breakdown, particularly the occurrence of dynamic recrystallization (DRX) process which was a vital parameter in estimating the optimum loads for forming of large size components. The accuracy and reliability of both models were compared in terms of correlation coefficient (R) and the average absolute relative error (ARRE).

  7. Effect of the Leveling Conditions on Residual Stress Evolution of Hot Rolled High Strength Steels for Cold Forming

    Science.gov (United States)

    Park, Keecheol; Oh, Kyungsuk

    2017-09-01

    In order to investigate the effect of leveling conditions on residual stress evolution during the leveling process of hot rolled high strength steels, the in-plane residual stresses of sheet processed under controlled conditions at skin-pass mill and levelers were measured by cutting method. The residual stress was localized near the edge of sheet. As the thickness of sheet was increased, the residual stress occurred region was expanded. The magnitude of residual stress within the sheet was reduced as increasing the deformation occurred during the leveling process. But the residual stress itself was not removed completely. The magnitude of camber occurred at cut plate was able to be predicted by the residual stress distribution. A numerical algorithm was developed for analysing the effect of leveling conditions on residual stress. It was able to implement the effect of plastic deformation in leveling, tension, work roll bending, and initial state of sheet (residual stress and curl distribution). The validity of simulated results was verified from comparison with the experimentally measured residual stress and curl in a sheet.

  8. Investigation of the Hot-Stamping Process for Advanced High-Strength Steel Sheet by Numerical Simulation

    Science.gov (United States)

    Liu, H. S.; Xing, Z. W.; Bao, J.; Song, B. Y.

    2010-04-01

    Hot forming is a new way to manufacture complex-shaped components of advanced high-strength steel (AHSS) sheet with a minimum of spring-back. Numerical simulation is an effective way to examine the hot-forming process, particularly to determine thermal and thermo-mechanical characteristics and their dependencies on temperature, strain and strain rate. The flow behavior of the 22MnB5 AHSS is investigated through hot tensile tests. A 3D finite element (FE) model of hot-stamping process for the [InlineMediaObject not available: see fulltext.] shaped part is built under the ABAQUS/Explicit environment based on the solutions of several key problems, such as treatment of contact between blank and tools, determination of material characteristics and meshing, etc. Numerical simulation is carried out to investigate the influence of blank holder force (BHF) and die gap on the hot-forming process for the [InlineMediaObject not available: see fulltext.] shaped part. Numerical results show the FE model is effective in simulation of hot-forming process. Large BHF reduces the amount of spring-back and improves the contact of flange with tools while avoiding cracking of stamped part. Die gap has a considerable influence on the distribution of temperature on side walls; the larger the die gap, higher is the temperature on the sidewall of [InlineMediaObject not available: see fulltext.] shaped part.

  9. Prediction Model of Cutting Parameters for Turning High Strength Steel Grade-H: Comparative Study of Regression Model versus ANFIS

    Directory of Open Access Journals (Sweden)

    Adel T. Abbas

    2017-01-01

    Full Text Available The Grade-H high strength steel is used in the manufacturing of many civilian and military products. The procedures of manufacturing these parts have several turning operations. The key factors for the manufacturing of these parts are the accuracy, surface roughness (Ra, and material removal rate (MRR. The production line of these parts contains many CNC turning machines to get good accuracy and repeatability. The manufacturing engineer should fulfill the required surface roughness value according to the design drawing from first trail (otherwise these parts will be rejected as well as keeping his eye on maximum metal removal rate. The rejection of these parts at any processing stage will represent huge problems to any factory because the processing and raw material of these parts are very expensive. In this paper the artificial neural network was used for predicting the surface roughness for different cutting parameters in CNC turning operations. These parameters were investigated to get the minimum surface roughness. In addition, a mathematical model for surface roughness was obtained from the experimental data using a regression analysis method. The experimental data are then compared with both the regression analysis results and ANFIS (Adaptive Network-based Fuzzy Inference System estimations.

  10. Research on the Cross Section Precision of High-strength Steel Tube with Rectangular Section in Rotary Draw Bending

    Science.gov (United States)

    Yang, Hongliang; Zhao, Hao; Xing, Zhongwen

    2017-11-01

    For the demand of energy conservation and security improvement, high-strength steel (HSS) is increasingly being used to produce safety related automotive components. However, cross-section distortion occurs easily in bending of HSS tube with rectangular section (RS), affecting the forming precision. HSS BR1500HS tube by rotary draw bending is taken as the study object and a description method of cross-section distortion is proposed in this paper. The influence on cross-section precision of geometric parameters including cross-section position, thickness of tube, bend radius etc. are studied by experiment. Besides, simulation of the rotary draw bending of HSS tube with rectangular section by ABAQUS are carried out and compared to the experiment. The results by simulation agree well with the experiment and show that the cross-section is approximately trapezoidal after distortion; the maximum of distortion exists at 45 ∼ 60° of the bending direction; and the absolute and relative distortion values increase with the decreasing of tube thickness or bending radius. Therefore, the results can provide a reference for the design of geometric parameters of HSS tube with rectangular section in rotary draw bending.

  11. The Influence of Austenite Grain Size on the Mechanical Properties of Low-Alloy Steel with Boron

    Directory of Open Access Journals (Sweden)

    Beata Białobrzeska

    2017-01-01

    Full Text Available This study forms part of the current research on modern steel groups with higher resistance to abrasive wear. In order to reduce the intensity of wear processes, and also to minimize their impact, the immediate priority seems to be a search for a correlation between the chemical composition and structure of these materials and their properties. In this paper, the correlation between prior austenite grain size, martensite packets and the mechanical properties were researched. The growth of austenite grains is an important factor in the analysis of the microstructure, as the grain size has an effect on the kinetics of phase transformation. The microstructure, however, is closely related to the mechanical properties of the material such as yield strength, tensile strength, elongation and impact strength, as well as morphology of occurred fracture. During the study, the mechanical properties were tested and a tendency to brittle fracture was analysed. The studies show big differences of the analysed parameters depending on the applied heat treatment, which should provide guidance to users to specific applications of this type of steel.

  12. Study of Secondary Phase Particle Dissolution and Austenite Grain Growth on Heating Fine-Grained High-Strength IF-Steel

    Science.gov (United States)

    Jia, Hong-bin; Zhang, Hong-mei; Sun, Cheng-qian

    2016-09-01

    Dissolution of particles of second phase and growth of austenite grains in high-strength fine-grained IF-steel (0.0057% C, 0.0023% N) on heating is studied. Metallographic analysis of flat steel specimens cut from plates prepared by hot and cold rolling is performed. Steel structure is studied after holding for 10 - 60 min at different temperatures and water quenching. The quenching parameters at which the microalloying elements (Ti, Nb) dissolve completely with retention of fine-grained austenite are determined. Amathematical model of austenite grain growth is developed by nonlinear regression analysis of experimental data.

  13. Combined Effect of Hydrogen and Dynamic Strain Aging on Low Cycle Fatigue Behaviors of SA508 Gr.1a Low Alloy Steels in 310 .deg. C Deoxygenated Water

    Energy Technology Data Exchange (ETDEWEB)

    Jang, Hun; Kim, Jeong Hyeon; Jang, Chang Heui [KAIST, Daejeon (Korea, Republic of); Kim, Tae Soon [Korea Hydro and Nuclear Power Co., Daejeon (Korea, Republic of)

    2011-05-15

    Significant reduction of fatigue life of structural materials in nuclear power plants is one of the issues of considerable significance to maintain superior integrity throughout their service life. From extensive studies, hydrogen induced cracking (HIC) is widely accepted mechanisms for reduction of fatigue life of low alloy steels (LAS) used as structural materials. Some of authors reported that hydrogen content in reactor pressure vessel could reach 2 {approx} 5 ppm during reactor operation. Hydrogen was resulted from corrosion reaction at the metal surface or crack tip in water. In addition, it has been reported that LAS is susceptible material for dynamic strain aging (DSA) in PWR environment at specific strain rate. Therefore, it is possible that the synergism between DSA and hydrogen might induce more significant LCF damage in PWR environment. In this regard, combined effect of DSA and hydrogen was investigated in this study. For that, LCF tests of SA508 Gr.1a LAS in various environments and tensile tests of hydrogen charged (H charged) samples in DSA range were conducted

  14. Analysis of the master curve approach on the fracture toughness properties of SA508 Gr.4N Ni-Mo-Cr low alloy steels for reactor pressure vessels

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Ki-Hyoung, E-mail: shirimp@kaist.ac.kr [Department of Materials Science and Engineering, KAIST, Daejeon 305-701 (Korea, Republic of); Kim, Min-Chul; Lee, Bong-Sang [Nuclear Materials Research Division, KAERI, Daejeon 305-353 (Korea, Republic of); Wee, Dang-Moon [Department of Materials Science and Engineering, KAIST, Daejeon 305-701 (Korea, Republic of)

    2010-06-15

    This study aims at assessing the fracture toughness behavior of tempered martensitic Ni-Mo-Cr low alloy steels for reactor pressure vessels in a transition temperature region using a master curve approach. The fracture toughness tests for model alloys with various chemical compositions were carried out following ASTM E1921-08. The microstructures, tensile properties, and Charpy impact toughness were also evaluated. Alloying elements such as Ni, Cr, and Mo affected the mechanical properties of alloys from changes in the phase fraction and precipitation behavior. In the fracture toughness test results, the data sets showed a deviation from the median curve and a smaller scatter than that of the prediction of the ASTM standard, especially in the lower transition region. The exponential parameter of the master curve equation was adjusted by an exponential fitting to data sets for expressing well the temperature dependency of the fracture toughness. The adjusted parameter provided good agreement for data distribution and the independence of T{sub 0} from test temperatures through an overall temperature range in contrast with the results from the standard master curve.

  15. In situ Raman spectroscopic analysis of surface oxide films on Ni-base alloy/low alloy steel dissimilar metal weld interfaces in high-temperature water

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jongjin; Choi, Kyung Joon [School of Mechanical and Nuclear Engineering, Ulsan National Institute of Science and Technology (UNIST), 100 Banyeon-ri, Eonyang-eup, Ulju-gun, Ulsan 689-798 (Korea, Republic of); Bahn, Chi Bum [School of Mechanical Engineering, Pusan National University 2, 63-gil, Geumjeong-Gu, Pusan 609-735 (Korea, Republic of); Kim, Ji Hyun, E-mail: kimjh@unist.ac.kr [School of Mechanical and Nuclear Engineering, Ulsan National Institute of Science and Technology (UNIST), 100 Banyeon-ri, Eonyang-eup, Ulju-gun, Ulsan 689-798 (Korea, Republic of)

    2014-06-01

    In situ Raman spectroscopy has been applied to analyze the surface oxide films formed on dissimilar metal weld (DMW) interfaces of nickel-base alloy/low alloy steel under hydrogenated high-temperature water condition. For the analysis of the oxide films under high temperature/pressure aqueous conditions, an in situ Raman spectroscopy system was developed by constructing a hydrothermal cell where the entire optics including the excitation laser and the Raman light collection system were located at the nearest position to the specimen by means of immersion optics. In situ Raman spectra of the DMW interfaces were collected in hydrogenated water condition at different temperatures up to 300 °C. The measured in situ Raman spectra showed peaks of Cr{sub 2}O{sub 3}, NiCr{sub 2}O{sub 4} and Fe{sub 3}O{sub 4} at the DMW interface. It is considered that differences in the oxide chemistry originated from the chemical element distribution inside of the DMW interface region.

  16. The effects of temperature and aeration on the corrosion of A508III low alloy steel in boric acid solutions at 25–95 °C

    Energy Technology Data Exchange (ETDEWEB)

    Xiao, Qian [Institute of Materials Science, School of Materials Science and Engineering, Shanghai University, Mailbox 269, 149 Yanchang Road, Shanghai, 200072 (China); State Key Laboratory of Advanced Special Steel, Shanghai University, 149 Yanchang Road, Shanghai, 200072 (China); Lu, Zhanpeng, E-mail: zplu@t.shu.edu.cn [Institute of Materials Science, School of Materials Science and Engineering, Shanghai University, Mailbox 269, 149 Yanchang Road, Shanghai, 200072 (China); State Key Laboratory of Advanced Special Steel, Shanghai University, 149 Yanchang Road, Shanghai, 200072 (China); Shanghai Key Laboratory of Advanced Ferrometallurgy, Shanghai University, 149 Yanchang Road, Shanghai, 200072 (China); Chen, Junjie [Institute of Materials Science, School of Materials Science and Engineering, Shanghai University, Mailbox 269, 149 Yanchang Road, Shanghai, 200072 (China); State Key Laboratory of Advanced Special Steel, Shanghai University, 149 Yanchang Road, Shanghai, 200072 (China); Yao, Meiyi [Institute of Materials Science, School of Materials Science and Engineering, Shanghai University, Mailbox 269, 149 Yanchang Road, Shanghai, 200072 (China); State Key Laboratory of Advanced Special Steel, Shanghai University, 149 Yanchang Road, Shanghai, 200072 (China); Shanghai Key Laboratory of Advanced Ferrometallurgy, Shanghai University, 149 Yanchang Road, Shanghai, 200072 (China); Chen, Zhen; Ejaz, Ahsan [Institute of Materials Science, School of Materials Science and Engineering, Shanghai University, Mailbox 269, 149 Yanchang Road, Shanghai, 200072 (China)

    2016-11-15

    The effects of temperature, solution composition and dissolved oxygen on the corrosion rate and electrochemical behavior of an A508III low alloy steel in boric acid solution with lithium hydroxide at 25–95 °C are investigated. In aerated solutions, increasing the boric acid concentration increases the corrosion rate and the anodic current density. The corrosion rate in deaerated solutions increases with increasing temperature. A corrosion rate peak value is found at approximately 75 °C in aerated solutions. Increasing temperature increases the oxygen diffusion coefficient, decreases the dissolved oxygen concentration, accelerates the hydrogen evolution reaction, and accelerates both the active dissolution and the film forming reactions. Increasing dissolved oxygen concentration does not significantly affect the corrosion rate at 50 and 60 °C, increases the corrosion rate at 70 and 80 °C, and decreases the corrosion rate at 87.5 and 95 °C in a high concentration boric acid solution with lithium hydroxide. - Highlights: • Effects of temperature on the corrosion of LAS in simulated PWR water are studied. • Increase of corrosion rate with increasing temperature in deaerated solution is observed. • Corrosion rate peaks at approximately 75 °C in aerated solution. • Deaeration decreases the corrosion rate in concentrated PWR water at 70–80 °C. • Deaeration increases the corrosion rate in concentrated PWR water at 87.5–95 °C.

  17. The effects of temperature and aeration on the corrosion of A508III low alloy steel in boric acid solutions at 25-95 °C

    Science.gov (United States)

    Xiao, Qian; Lu, Zhanpeng; Chen, Junjie; Yao, Meiyi; Chen, Zhen; Ejaz, Ahsan

    2016-11-01

    The effects of temperature, solution composition and dissolved oxygen on the corrosion rate and electrochemical behavior of an A508III low alloy steel in boric acid solution with lithium hydroxide at 25-95 °C are investigated. In aerated solutions, increasing the boric acid concentration increases the corrosion rate and the anodic current density. The corrosion rate in deaerated solutions increases with increasing temperature. A corrosion rate peak value is found at approximately 75 °C in aerated solutions. Increasing temperature increases the oxygen diffusion coefficient, decreases the dissolved oxygen concentration, accelerates the hydrogen evolution reaction, and accelerates both the active dissolution and the film forming reactions. Increasing dissolved oxygen concentration does not significantly affect the corrosion rate at 50 and 60 °C, increases the corrosion rate at 70 and 80 °C, and decreases the corrosion rate at 87.5 and 95 °C in a high concentration boric acid solution with lithium hydroxide.

  18. Precision Measurement and Modeling of Quenching-Tempering Distortion in Low-Alloy Steel Components with Internal Threads

    Science.gov (United States)

    Nie, Zhenguo; Wang, Gang; Lin, Yongliang; Rong, Yiming (Kevin)

    2015-12-01

    Distortion resulting from heat treatment may cause serious problems for precision parts. A precision component made from 30CrNi3Mo steel with internal threads distorts slightly after quenching-tempering treatment. Such a small distortion results in serious difficulties in the subsequent assembly process. The distortion of the internal thread was measured using semi-destructive testing with video measuring system. Periodic wavy distortions emerged in the internal threads after heat treatment. Then both XRD analysis and hardness testing were conducted. A numerical simulation of the complete quenching-tempering process was conducted by DANTE, which is a set of user subroutines that link into the ABAQUS/STD solver. The results from the simulations are in good agreement with the measurement in distortion, microstructure field, and hardness. The effects of the technological parameters including quenchant, immersion orientation, and grooves were discussed on the basis of the simulation results. Finally, strategies to significantly decrease distortion and residual stress are proposed.

  19. Effect of neutron irradiation on magnetic properties in the low alloy Ni-Mo steel SA508-3

    Science.gov (United States)

    Park, D. G.; Kim, C. G.; Kim, H. C.; Hong, J. H.; Kim, I. S.

    1997-04-01

    The B-H hysteresis loop and Barkhausen noise have been measured in the neutron irradiated SA508 steel of 45 μm thickness. The coercive force of B-H loop showed a slow change up to a neutron dose of 1014 n/cm2 and increased by 15.4% for a 1016 n/cm2 dose sample compared with that of the unirradiated one, related to the domain wall motion hindered by the increased defects. However, the amplitude of Barkhausen noise reflecting the wall motion decreased slowly up to 1014 n/cm2 irradiation, followed by a rapid decrease of 37.5% at 1016 n/cm2.

  20. Effect of high-temperature water and hydrogen on the fracture behavior of a low-alloy reactor pressure vessel steel

    Energy Technology Data Exchange (ETDEWEB)

    Roychowdhury, S., E-mail: sroy27@gmail.com [Paul Scherrer Institut, Nuclear Energy and Safety Research Department, Laboratory for Nuclear Materials, 5232 Villigen, PSI (Switzerland); Materials Processing & Corrosion Engineering Division, Mod-Lab, D-Block, Bhabha Atomic Research Centre, Mumbai 400085 (India); Seifert, H.-P.; Spätig, P.; Que, Z. [Paul Scherrer Institut, Nuclear Energy and Safety Research Department, Laboratory for Nuclear Materials, 5232 Villigen, PSI (Switzerland)

    2016-09-15

    Structural integrity of reactor pressure vessels (RPV) is critical for safety and lifetime. Possible degradation of fracture resistance of RPV steel due to exposure to coolant and hydrogen is a concern. In this study tensile and elastic-plastic fracture mechanics (EPFM) tests in air (hydrogen pre-charged) and EFPM tests in hydrogenated/oxygenated high-temperature water (HTW) was done, using a low-alloy RPV steel. 2–5 wppm hydrogen caused embrittlement in air tensile tests at room temperature (25 °C) and at 288 °C, effects being more significant at 25 °C and in simulated weld coarse grain heat affected zone material. Embrittlement at 288 °C is strain rate dependent and is due to localized plastic deformation. Hydrogen pre-charging/HTW exposure did not deteriorate the fracture resistance at 288 °C in base metal, for investigated loading rate range. Clear change in fracture morphology and deformation structures was observed, similar to that after air tests with hydrogen. - Highlights: • Hydrogen content, microstructure of LAS, and strain rate affects tensile properties at 288 °C. • Strength affects hydrogen embrittlement susceptibility to a greater extent than grain size. • Hydrogen in LAS leads to strain localization and restricts cross-slip at 288 °C. • Possible hydrogen pickup due to exposure to 288 °C water alters fracture surface appearance without affecting fracture toughness in bainitic base material. • Simulated weld heat affected zone microstructure shows unstable crack propagation in 288 °C water.

  1. Metadynamic recrystallization in C steels

    Indian Academy of Sciences (India)

    Unknown

    eds) C M Sellars and G J Davies. (London: The Metals Society) pp 3–15. Tamura I, Ouchi C, Tanaka T and Sekine H 1988 Thermo- mechanical processing of high strength low alloy steels. (London: Butterworths Publications) pp 49–53.

  2. Niobium Solar Mobile Project — High Strength Niobium Microalloyed Steel as a Solution to Improve Electric Super Scooter and Motorcycle Performance

    Science.gov (United States)

    Richards, Terry; Kauppi, Erik; Flanagan, Lauren; Ribeio, Eduardo A. A. G.; Nogueira, Marcos A. Stuart; McCourtney, Ian

    This paper presents the advantages of replacing mild steel with high strength niobium microalloyed steel in the structure of Electric Super Scooters, Electric Cargo Motorcycles and Solar Charging Stations. The Mini-Fleet-in-a-Box concept was developed by Current Motor to guarantee mobility, efficiency and solar generated electricity. With the adoption of niobium microalloyed high strength steel for more than 90% of the Super Scooter and Motorcycle structures, it was possible to redesign the frame, resulting in a 31% weight reduction and a very modern and functional body. Together with a new powertrain, these changes were responsible for increasing Motorcycle autonomy by more than 15%, depending on average speed. The new frame design reduced the number of high strain points in the frame, increasing the safety of the project. The Solar Charging Station was built using the container concept and designed with high strength niobium microalloyed steel, which resulted in a weight reduction of 25%. CBMM's facility in Araxá, Brazil was selected in the second half of 2013 as the demonstration site to test the efficiency of the Super Scooter and Solar Charging Station. Each Super Scooter has run more than 2,000 km maintenance-free with an autonomy of more than 100 km per charge.

  3. Resistance of Some Steels to Stress Corrosion Cracking

    Science.gov (United States)

    Humphries, T. S.; Nelson, E. E.

    1982-01-01

    Evaluations of stress-corrosion cracking resistance of five high-strength low-alloy steels described in report now available. Steels were heat-treated to various tensile strengths and found to be highly resistant to stress-corrosion cracking.

  4. Fabricating interstitial-free steel with simultaneous high strength and good ductility with homogeneous layer and lamella structure

    DEFF Research Database (Denmark)

    Zhang, Ling; Chen, Zhen-Zhe; Wang, Yuhui

    2017-01-01

    Annealed interstitial-free steel (IF steel) and deformed IF steel sheets were stacked alternatively into multi-layers to produce laminated IF steel through thermal-mechanical processing. After proper processing, a yield strength of 500 MPa, an ultimate tensile strength of 600 MPa (comparable...

  5. 77 FR 263 - Certain Cut-To-Length Carbon-Quality Steel Plate From Italy and Japan: Revocation of Antidumping...

    Science.gov (United States)

    2012-01-04

    ... plastic or other non-metallic substances are included within the scope. Also, specifically included in the scope are high strength, low alloy (``HSLA'') steels. HSLA steels are recognized as steels with micro..., varnished or coated with plastic or other non-metallic substances; (2) SAE grades (formerly AISI grades) of...

  6. Conservation Research and Development/ New Ultra-Low Carbon High Strength Steels with Improved Bake Hardenability for Enhanced Stretch Formability and Dent Resistance

    Energy Technology Data Exchange (ETDEWEB)

    Anthony J. DeArdo; C. Isaac Garcia

    2003-12-15

    Conservation Research and Development/New Ultra-Low Carbon High Strength Steels with Improved Bake Hardenability for Enhanced Stretch Formability and Dent Resistance. The experimental work can be divided into four phases. In each phase, the materials were received or designed, processed and tested, to evaluate the BH increment or response, as a function of compositions and processing conditions. Microstructural characterization by various techniques was performed in order to gain insights into the mechanisms of flow stress increment by bake hardening.

  7. Principles and Application of Magnetic Rubber Testing for Crack Detection in High-Strength Steel Components: II. Residual-Field Inspection

    Science.gov (United States)

    2014-12-01

    ABSTRACT Since its introduction in the 1970s, magnetic rubber testing ( MRT ) has been used successfully to inspect critical high-strength steel...aerospace components for surface-breaking fatigue cracks. In the residual-field variant of MRT , inspections are performed following the application...geometries, residual-field MRT is capable of reliable detection of cracks as small as 0.43 mm (0.017 inch) in surface length. However, for other conditions

  8. Principles and Application of Magnetic Rubber Testing for Crack Detection in High-Strength Steel Components: I. Active-Field Inspection

    Science.gov (United States)

    2014-12-01

    ABSTRACT Magnetic rubber testing ( MRT ) is a sensitive non-destructive inspection technique, capable of detecting cracks as small as 0.5 mm (0.020...inch) in length with high reliability. Since its introduction in the 1970s, MRT has been successfully used to inspect high-strength steel aerospace...components for surface-breaking fatigue cracks. However, despite its widespread use and apparent simplicity, the underpinning science of MRT is not

  9. Effect of Welding Thermal Cycles on Microstructure and Mechanical Properties of Simulated Heat Affected Zone for a Weldox 1300 Ultra-High Strength Alloy Steel

    Directory of Open Access Journals (Sweden)

    Węglowski M. St.

    2016-03-01

    Full Text Available In the present study, the investigation of weldability of ultra-high strength steel has been presented. The thermal simulated samples were used to investigate the effect of welding cooling time t8/5 on microstructure and mechanical properties of heat affected zone (HAZ for a Weldox 1300 ultra-high strength steel. In the frame of these investigation the microstructure was studied by light and transmission electron microscopies. Mechanical properties of parent material were analysed by tensile, impact and hardness tests. In details the influence of cooling time in the range of 2,5 ÷ 300 sec. on hardness, impact toughness and microstructure of simulated HAZ was studied by using welding thermal simulation test. The microstructure of ultra-high strength steel is mainly composed of tempered martensite. The results show that the impact toughness and hardness decrease with increase of t8/5 under condition of a single thermal cycle in simulated HAZ. The increase of cooling time to 300 s causes that the microstructure consists of ferrite and bainite mixture. Lower hardness, for t8/5 ≥ 60 s indicated that low risk of cold cracking in HAZ for longer cooling time, exists.

  10. Corrosion inhibition in 2.0 M sulfuric acid solutions of high strength maraging steel by aminophenyl tetrazole as a corrosion inhibitor

    Energy Technology Data Exchange (ETDEWEB)

    Sherif, El-Sayed M., E-mail: emsherif@gmail.com [Center of Excellence for Research in Engineering Materials (CEREM), Advanced Manufacturing Institute, King Saud University, PO. Box 800, Al-Riyadh 11421 (Saudi Arabia); National Research Centre (NRC), Electrochemistry and Corrosion Laboratory, Department of Physical Chemistry, National Research Centre (NRC), Dokki, 12622 Cairo (Egypt)

    2014-02-15

    The corrosion of high strength maraging steel after varied immersion times in concentrated solution, 2.0 M, of sulfuric acid has been investigated. The work was also extended to study the effect of 5-(3-aminophenyl)-tetrazole (APTA) on the inhibition of the steel corrosion. The study has been carried out using electrochemical impedance spectroscopy (EIS), potentiodynamic polarization and scanning electron microscope (SEM) along with energy dispersive X-ray analyzer (EDX) investigations. EIS spectra showed that the corrosion and polarization resistances decrease with increasing the immersion time of the steel before measurement and increase in the presence of APTA and the increase of its concentration. Polarization data agreed with the EIS measurements and indicated that the increase of immersion time increases the corrosion of steel by increasing its corrosion current and corrosion rate and lowering its polarization resistance. On the other hand, the addition of APTA and the increase of its concentration minimized the corrosion of steel through decreasing the corrosion current and corrosion rate and increasing the polarization resistance at all exposure test periods. SEM and EDX investigations confirmed that the inhibition of the maraging steel in the 2.0 M H{sub 2}SO{sub 4} solutions is achieved via the adsorption of the APTA molecules onto the steel protecting its surface from being dissolved easily.

  11. An inverse approach for the geometry prediction of sheet-metal parts with embossings made of high- and ultra-high strength steels

    Science.gov (United States)

    Stahl, J.; Tröber, P.; Feistle, M.; Golle, R.; Volk, W.

    2017-09-01

    Embossing or offsetting is a shear forming process closely related to fineblanking. It is mainly used for the manufacturing of functional geometry features like alignment pins on brake calipers or gears of seat adjustments. To achieve weight reduction, a trend towards the usage of high- and ultra-high-strength steels can be observed. Especially in embossing, the lack of knowledge for these grades evokes challenges in part design due to the higher springback and the different forming behaviour which greatly influence the characteristics of the formed geometry. Furthermore, Finite-Element simulations for geometry prediction are not yet able to achieve satisfying results due to the challenging material testing of the sheet-metal material. To address this problem, a novel method for the geometry prediction of sheet-metal parts with embossings made of high- and ultra-high-strength steels is proposed and demonstrated on the mild steels HSM 355 and HLB 22 as well as the high-strength steels HSM 700 HD and StrenX 700 MC plus. The method is based on the experimental identification of simple embossing geometries. Especially the die-roll was in the focus of interest, as it reduces the area available for functional features. A routine for the determination of the die-roll using the second derivative of the surface profile was implemented. The material model is subsequently calculated by an inverse algorithm. Furthermore, the dependency between the part’s geometry and the flow curve was investigated to reduce the calculation time. It is shown, that it is possible to determine a material model, which is capable of predicting the geometry of a part with an embossing for different materials and process parameters.

  12. The Development and Microstructure Analysis of High Strength Steel Plate NVE36 for Large Heat Input Welding

    Science.gov (United States)

    Peng, Zhang; Liangfa, Xie; Ming, Wei; Jianli, Li

    In the shipbuilding industry, the welding efficiency of the ship plate not only has a great effect on the construction cost of the ship, but also affects the construction speed and determines the delivery cycle. The steel plate used for large heat input welding was developed sufficiently. In this paper, the composition of the steel with a small amount of Nb, Ti and large amount of Mn had been designed in micro-alloyed route. The content of C and the carbon equivalent were also designed to a low level. The technology of oxide metallurgy was used during the smelting process of the steel. The rolling technology of TMCP was controlled at a low rolling temperature and ultra-fast cooling technology was used, for the purpose of controlling the transformation of the microstructure. The microstructure of the steel plate was controlled to be the mixed microstructure of low carbon bainite and ferrite. Large amount of oxide particles dispersed in the microstructure of steel, which had a positive effects on the mechanical property and welding performance of the steel. The mechanical property of the steel plate was excellent and the value of longitudinal Akv at -60 °C is more than 200 J. The toughness of WM and HAZ were excellent after the steel plate was welded with a large heat input of 100-250 kJ/cm. The steel plate processed by mentioned above can meet the requirement of large heat input welding.

  13. Experimental evaluation of tool wear throughout a continuous stroke blanking process of quenched 22MnB5 ultra-high-strength steel

    Science.gov (United States)

    Vogt, S.; Neumayer, F. F.; Serkyov, I.; Jesner, G.; Kelsch, R.; Geile, M.; Sommer, A.; Golle, R.; Volk, W.

    2017-09-01

    Steel is the most common material used in vehicles’ chassis, which makes its research an important topic for the automotive industry. Recently developed ultra-high-strength steels (UHSS) provide extreme tensile strength up to 1,500 MPa and combine great crashworthiness with good weight reduction potential. However, in order to reach the final shape of sheet metal parts additional cutting steps such as trimming and piercing are often required. The final trimming of quenched metal sheets presents a huge challenge to a conventional process, mainly because of the required extreme cutting force. The high cutting impact, due to the materials’ brittleness, causes excessive tool wear or even sudden tool failure. Therefore, a laser is commonly used for the cutting process, which is time and energy consuming. The purpose of this paper is to demonstrate the capability of a conventional blanking tool design in a continuous stroke piercing process using boron steel 22MnB5 sheets. Two different types of tool steel were tested for their suitability as active cutting elements: electro-slag remelted (ESR) cold work tool steel Bohler K340 ISODUR and powder-metallurgic (PM) high speed steel Bohler S390 MICROCLEAN. A FEM study provided information about an optimized punch design, which withstands buckling under high cutting forces. The wear behaviour of the process was assessed by the tool wear of the active cutting elements as well as the quality of cut surfaces.

  14. Predicting the drying shrinkage behavior of high strength portland cement mortar under the combined influence of fine aggregate and steel micro fiber

    Directory of Open Access Journals (Sweden)

    Zhengqi Li

    2017-03-01

    Full Text Available The workability, 28-day compressive strength and free drying shrinkage of a very high strength (121-142 MPa steel micro fiber reinforced portland cement mortar were studied under a combined influence of fine aggregate content and fiber content. The test results showed that an increase in the fine aggregate content resulted in decreases in the workability, 28-day compressive strength and drying shrinkage of mortar at a fixed fiber content. An increase in the fiber content resulted in decreases in the workability and drying shrinkage of mortar, but an increase in the 28-day compressive strength of mortar at a fixed fine aggregate content. The modified Gardner model most accurately predicted the drying shrinkage development of the high strength mortars, followed by the Ross model and the ACI 209R-92 model. The Gardner model gave the least accurate prediction for it was developed based on a database of normal strength concrete.

  15. The effect of long term exposition at 540 °C on the empirical correlations for determination of mechanical properties of low alloy CrMoV steel from the results of Small Punch tests

    Directory of Open Access Journals (Sweden)

    Ondřej Dorazil

    2016-03-01

    Full Text Available The present paper describes the effect of long term exposure at 540 °C on the empirical correlations for determination of yield strength, tensile strength and FATT of 14MoV6-3 low alloy steel. Empirical correlations obtained for the pipe in as received state were compared with the results of standardized tensile, impact and Small Punch tests carried out on the testing materials cut of the three pipes of significantly different metallurgical quality and time of exposure at 540 °C.

  16. Sodium alginate: A promising biopolymer for corrosion protection of API X60 high strength carbon steel in saline medium.

    Science.gov (United States)

    Obot, I B; Onyeachu, Ikenna B; Kumar, A Madhan

    2017-12-15

    Sodium alginate (SA), a polysaccharide biopolymer, has been studied as an effective inhibitor against the corrosion of API X60 steel in neutral 3.5% NaCl using gravimetric and electrochemical techniques (OCP, EIS and EFM). The inhibition efficiency of the SA increased with concentration but was lower at higher temperature (70°C). Electrochemical measurements showed that the SA shifted the steel corrosion potential to more positive value and reduced the kinetics of corrosion by forming an adsorbed layer which mitigated the steel surface wetting, based on contact angle measurement. SEM-EDAX was used to confirm the inhibition of SA on API X60 steel surfaces. The SA adsorbs on the steel surface through a physisorption mechanism using its carboxylate oxygen according to UV-vis and ATR-IR measurements, respectively. This phenomena result in decreased localized pitting corrosion of the API X60 steel in 3.5% NaCl solution. Theoretical results using quantum chemical calculations and Monte Carlo simulations provide further atomic level insights into the interaction of SA with steel surface. Copyright © 2017 Elsevier Ltd. All rights reserved.

  17. CORRELATION BETWEEN HARDNESS AND TENSILE PROPERTIES IN ULTRA-HIGH STRENGTH DUAL PHASE STEELS – SHORT COMMUNICATION

    Directory of Open Access Journals (Sweden)

    Martin Gaško

    2012-02-01

    Full Text Available The possibility to predict yield strength, strength limit, fatigue live estimation as well as other mechanical properties depending on values of materials hardness is commonly known and it is often used in practice. The main aim of this contribution is to review the possibilities of application of correlation relationships between hardness and ultimate tensile strength of steel sheets in various structural states. The experiments were performed on advanced steels with structure which is composed from ferrite and martensite (dual phase steels.

  18. CORRELATION BETWEEN HARDNESS AND TENSILE PROPERTIES IN ULTRA-HIGH STRENGTH DUAL PHASE STEELS ��� SHORT COMMUNICATION

    Directory of Open Access Journals (Sweden)

    Gejza Rosenberg

    2011-11-01

    Full Text Available The possibility to predict yield strength, strength limit, fatigue live estimation as well as other mechanical properties depending on values of materials hardness is commonly known and it is often used in practice. The main aim of this contribution is to review the possibilities of application of correlation relationships between hardness and ultimate tensile strength of steel sheets in various structural states. The experiments were performed on advanced steels with structure which is composed from ferrite and martensite (dual phase steels.

  19. Microstructural Characterization and Mechanical Properties of Electron Beam Welded Joint of High Strength Steel Grade S690QL

    Directory of Open Access Journals (Sweden)

    Błacha S.

    2016-06-01

    Full Text Available In the paper the results of metallographic examination and mechanical properties of electron beam welded joint of quenched and tempered steel grade S690QL are presented. Metallographic examination revealed that the concentrated electron beam significantly affect the changes of microstructure in the steel. Parent material as a delivered condition (quenched and tempered had a bainitic-martensitic microstructure at hardness about 290 HV0.5. After welding, the microstructure of heat affected zone is composed mainly of martensite (in the vicinity of the fusion line of hardness 420 HV0.5. It should be noted, however, that the microstructure of steel in the heat affected zone varies with the distance from the fusion line. The observed microstructural changes were in accordance with the CCT-S transformation diagram for the examined steel.

  20. Hydrogen adsorption and diffusion, and subcritical-crack growth in high-strength steels and nickel base alloys

    Science.gov (United States)

    Wei, R. P.; Klier, K.; Simmons, G. W.

    1974-01-01

    Coordinated studies of the kinetics of crack growth and of hydrogen adsorption and diffusion were initiated to develop information that is needed for a clearer determination of the rate controlling process and possible mechanism for hydrogen enhanced crack growth, and for estimating behavior over a range of temperatures and pressures. Inconel 718 alloy and 18Ni(200) maraging steel were selected for these studies. 18Ni(250) maraging steel, 316 stainless steel, and iron single crystal of (111) orientation were also included in the chemistry studies. Crack growth data on 18Ni(250) maraging steel from another program are included for comparison. No sustained-load crack growth was observed for the Inconel 718 alloy in gaseous hydrogen. Gaseous hydrogen assisted crack growth in the 18Ni maraging steels were characterized by K-independent (Stage 2) extension over a wide range of hydrogen pressures (86 to 2000 torr or 12 kN/m2 to 266 kN/m2) and test temperatures (-60 C to +100 C). The higher strength 18Ni(250) maraging steel was more susceptible than the lower strength 200 grade. A transition temperature was observed, above which crack growth rates became diminishingly small.

  1. Microstructural, mechanical and tribological investigation of 30CrMnSiNi2A ultra-high strength steel under various tempering temperatures

    Science.gov (United States)

    Arslan Hafeez, Muhammad; Farooq, Ameeq

    2018-01-01

    The aim of the research was to investigate the variation in microstructural, mechanical and tribological characteristics of 30CrMnSiNi2A ultra-high strength steel as a function of tempering temperatures. Steel was quenched at 880 °C and tempered at five different tempering temperatures ranging from 250 °C to 650 °C. Optical microscopy and pin on disc tribometer was used to evaluate the microstructural and wear properties. Results show that characteristics of 30CrMnSiNi2A are highly sensitive to tempering temperatures. Lathe and plate shaped martensite obtained by quenching transform first into ε-carbide, second cementite, third coarsened and spheroidized cementite and finally into recovered ferrite and austenite. Hardness, tensile and yield strengths decreased while elongation increased with tempering temperatures. On the other hand, wear rate first markedly decreased and then increased. Optimum amalgamation of characteristics was achieved at 350 °C.

  2. Effect of Cooling Rate on Microstructure and Centerline Segregation of a High-Strength Steel for Shipbuilding

    Science.gov (United States)

    Ye, Qibin; Liu, Zhenyu; Wang, Guodong

    Ultra-fast cooling (UFC) has been increasingly applied in industry, but accompanying with great changes of rolling strategy. It is therefore of importance to evaluate the characteristics of steels produced by UFC as compared to those processed by conventional accelerated cooling (ACQ. The present study examines the microstructure through thickness and centerline segregation of solute elements between UFC and ACC steels, both of which were rolled at a final rolling temperature at around non-recrystallized temperature. UFC steel showed the pronounced microstructural transition from lath-type bainite with Widmanstätten ferrite at subsurface to acicular ferrite in an average size of 5 µm dispersed with degenerate pearlite in the interior. In contrast, ACC steel had the homogeneous microstructure through the thickness, which was distinguished with coarser polygonal ferrite grains and pearlite nodules. Moreover, the centerline segregation was significantly suppressed by applying UFC at a higher cooling rate of 40 K/s compared to 17K/s for ACC steel. The significant differences in the microstructure and centerline segregation caused by various cooling rate is discussed from the view of γ→α transformation.

  3. Research and Service Experience with Environmentally-Assisted Cracking in Carbon and Low-Alloy Steels in High-Temperature Water

    Energy Technology Data Exchange (ETDEWEB)

    Seifert, Hans-Peter; Ritter, Stefan [Paul Scherrer Inst., Laboratory for Materials Behaviour, Villigen (Switzerland). Nuclear Energy and Safety Research Dept.

    2005-11-15

    The most relevant aspects of research and service experience with environmentally-assisted cracking (EAC) of carbon (C) and low-alloy steels (LAS) in high-temperature (HT) water are reviewed, with special emphasis on the primary pressure boundary components of boiling water reactors (BWRs). The main factors controlling the susceptibility to EAC under light water reactor (LWR) conditions are discussed with respect to crack initiation and crack growth. The adequacy and conservatism of the current BWRVIP-60 stress corrosion cracking (SCC) disposition lines (DLs), ASME III fatigue design curves, and ASME XI reference fatigue crack growth curves, as well as of the GE EAC crack growth model are evaluated in the context of recent research results. The operating experience is summarized and compared to the experimental/mechanistic background knowledge. Finally, open questions and possible topics for further research are identified. Laboratory investigations revealed significant effects of simulated reactor environments on fatigue crack initiation/growth, as well as the possibility of SCC crack growth for certain specific critical combinations of environmental, material and loading parameters. During the last three decades, the major factors of influence and EAC susceptibility conditions have been readily identified. Most parameter effects on EAC initiation and growth are adequately known with acceptable reproducibility and reasonably understood by mechanistic models. Tools for incorporating environmental effects in ASME III fatigue design curves have been developed/qualified and should be applied in spite of the high degree of conservatism in fatigue evaluation procedures. The BWRVIP-60 SCC DLs and ASME XI reference fatigue crack growth curves are usually conservative and adequate under most BWR operation circumstances. The operating experience of C and LAS primary pressure-boundary components in LWRs is very good worldwide. However, isolated instances of EAC have occurred

  4. A two-parameter model to predict fatigue life of high-strength steels in a very high cycle fatigue regime

    Science.gov (United States)

    Sun, Chengqi; Liu, Xiaolong; Hong, Youshi

    2015-06-01

    In this paper, ultrasonic (20 kHz) fatigue tests were performed on specimens of a high-strength steel in very high cycle fatigue (VHCF) regime. Experimental results showed that for most tested specimens failed in a VHCF regime, a fatigue crack originated from the interior of specimen with a fish-eye pattern, which contained a fine granular area (FGA) centered by an inclusion as the crack origin. Then, a two-parameter model is proposed to predict the fatigue life of high-strength steels with fish-eye mode failure in a VHCF regime, which takes into account the inclusion size and the FGA size. The model was verified by the data of present experiments and those in the literature. Furthermore, an analytic formula was obtained for estimating the equivalent crack growth rate within the FGA. The results also indicated that the stress intensity factor range at the front of the FGA varies within a small range, which is irrespective of stress amplitude and fatigue life.

  5. Optimization of quenching process in hot press forming of 22MnB5 steel for high strength properties for publication in

    Science.gov (United States)

    Aziz, Nuraini; Aqida, S. N.

    2013-12-01

    This paper presents hot press forming of 22MnB5 steel blanks for high strength automotive components. The hot press forming was performed using Schenck press PEZ0673 machine with maximum press force of 1000 kN. Samples were square 22MnB5 blanks, of 50 × 60 mm dimension. A high temperature furnace was used to heat up the blanks to austenite temperature of 950°C. Samples were held at the austenite temperature prior to forming and quenching process. Three independent controlled parameters were cooling water temperature, press holding time and flow rate of water. Pressed samples were characterized for metallographic study, hardness properties and tensile properties. Metallographic study was conducted using Meiji optical microscope. Hardness was measured using Vickers indenter with load 1000gf. From metallographic study, the hot pressed 22MnB5 boron steel samples produced lath martensitic microstructure. Hardness of hot pressed samples increased with decreasing cooling time. The yield strength and the ultimate tensile strength of samples after hot forming were between 1546 and 1923 N/mm2. These findings were important to design tailored ultra-high strength in automotive components at different process parameter settings.

  6. Development of low-temperature high-strength integral steel castings for offshore construction by casting process engineering

    Directory of Open Access Journals (Sweden)

    Lim Sang-Sub

    2014-12-01

    Full Text Available In casting steels for offshore construction, manufacturing integral casted structures to prevent fatigue cracks in the stress raisers is superior to using welded structures. Here, mold design and casting analysis were conducted for integral casting steel. The laminar flow of molten metal was analyzed and distributions of hot spots and porosities were studied. A prototype was subsequently produced, and air vents were designed to improve the surface defects caused by the release of gas. A radiographic test revealed no internal defects inside the casted steel. Evaluating the chemical and mechanical properties of specimens sampled from the product revealed that target values were quantitatively satisfied. To assess weldability in consideration of repair welding, the product was machined with grooves and welded, after which the mechanical properties of hardness as well as tensile, impact, and bending strengths were evaluated. No substantive differences were found in the mechanical properties before and after welding.

  7. Effect of nano-particulate sol-gel coatings on the oxidation resistance of high-strength steel alloys during the press-hardening process

    Energy Technology Data Exchange (ETDEWEB)

    Yekehtaz, M.; Benfer, S.; Fuerbeth, W. [DECHEMA-Forschungsinstitut, Theodor-Heuss-Allee 25, D-60486 Frankfurt am Main (Germany); Klesen, C.; Bleck, W. [Institut fuer Eisenhuettenkunde der RWTH Aachen, Intzestrasse 1, D-52072 Aachen (Germany)

    2012-10-15

    The need for lighter constructional materials in automotive industries has increased the use of high-strength steel alloys. To enhance passenger's safety press hardening may be applied to steel parts. However, as the steel parts are heated up to 950 C during this process they have to be protected by some kind of coating against the intense oxide formation usually taking place. As the coating systems used so far all have certain disadvantages in this work the ability of nano-particulate thin coatings obtained by the sol-gel process to improve the oxidation resistance of 22MnB5 steel is investigated. The coatings obtained from three sols containing lithium aluminum silicate and potassium aluminum silicate showed the best performance against oxidation. The structural properties of the coating materials were characterized using different methods like XRD and differential thermal analysis. Comparison of the oxidation rate constants proved the ability of the coatings to protect against oxidation at temperatures up to 800 C. Press-hardening experiments in combination with investigations on the thermal shock resistance of the coated samples also showed the ability of the coatings to stay intact during press hardening with only slight spalling of the coatings in the bending areas. The absence of any secondary intermetallic phases and layer residues during laser beam welding experiments on coated samples proves the suitability of the nano-particulate coatings for further industrial processing. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  8. Caracterização microestrutural de soldas dissimilares dos aços ASTM A-508 e AISI 316L Characterization of dissimilar metal weld between low alloy steel ASTM A-508 and 316L stainless steel

    Directory of Open Access Journals (Sweden)

    Luciana Iglésias Lourenço Lima

    2010-06-01

    Full Text Available As soldas dissimilares (dissimilar metal welds - DMWs são utilizadas em diversos segmentos da indústria. No caso específico de usinas nucleares, tais soldas são necessárias para conectar tubulações de aço inoxidável com componentes fabricados em aços baixa liga. Os materiais de adição mais utilizados neste tipo de solda são as ligas de níquel 82 e 182. Este trabalho consistiu na soldagem de uma junta dissimilar de aço baixa liga ASTM A-508 G3 e aço inoxidável austenítico AISI 316L utilizando as ligas de níquel 82 e 182 como metais de adição. A soldagem foi realizada manualmente empregando os processos de soldagem ao arco SMAW (Shielded Metal Arc Welding e GTAW (Gas Tungsten Arc Welding. Os corpos de prova foram caracterizados microestruturalmente utilizando-se microscópio óptico e microscópio eletrônico de varredura com microanálise por dispersão de energia de raios X (EDS e ensaios de microdureza Vickers. Observou-se uma microestrutura constituída de dendritas de austenita com a presença de precipitados com formas e dimensões definidas pelo aporte térmico e pela direção de soldagem. Não houve variação significativa da dureza ao longo da junta soldada, demonstrando a adequação dos parâmetros de soldagem utilizados.The dissimilar metal welds (DMWs are used in several areas of the industries. In the nuclear power plant, this weld using nickel alloy welding wires is used to connect stainless steel pipes to low alloy steel components on the reactor pressured vessels. The filler materials commonly used in this type of weld are nickel alloys 82 and 182.. In this study, dissimilar metal welds composed of low alloy steel ASTM A-508 G3, nickel alloys 82 e 182 as weld metals, and austenitic stainless steel AISI 316L were prepared by manual shielded metal arc welding (SMAW and gas tungsten arc welding techniques (GTAW. Samples were microstructural characterized by optical microscopy and scanning electron microscopy

  9. Microstructural and Mechanical Characterization of Electron Beam Welded Joints of High Strength S960QL and Weldox 1300 Steel Grades

    Directory of Open Access Journals (Sweden)

    Błacha S.

    2017-06-01

    Full Text Available The paper shows the results of metallographic examination and mechanical properties of electron beam welded joints of quenched and tempered S960QL and Weldox 1300 steel grades. The aim of this study was to examine the feasibility of producing good quality electron beam welded joints without filler material.

  10. Reduction of Residual Stress and Distortion in HY100 and HY130 High Strength Steels During Welding

    Science.gov (United States)

    1989-06-01

    run of ,our office and for being the best advisor a student could have. To the Laboratory for Nuclear Science in Building 20 for cutting our test pieces...stress from previous experiments and calculated values. 50 Data from "Predicted Res Sress MS" Low Carbon Steel (GMA) 3𔃺 0- Calculated S20 4- Experiment

  11. The investigation of applicability of the Hollomon-Jaffe equation on tempering the HSLA steel

    OpenAIRE

    A. Patarić; Mihailović, M.; Z. Gulišija; Z. Janjušević

    2009-01-01

    High strength low-alloyed (HSLA) Cr-Mn-Si steels belong to a group of steels that can reach their full mechanical properties after quenching and tempering. Those properties depend both on the temperature and time of tempering. Knowing the tempering parameters, it is possible to reach the desired properties of the treated steel. Some results on investigating the Hollomon-Jaffe equation (in parametric form) application for tempering of HSLA steel, are shown in this paper. The experiments were p...

  12. High-throughput design of low-activation, high-strength creep-resistant steels for nuclear-reactor applications

    Energy Technology Data Exchange (ETDEWEB)

    Lu, Qi; Zwaag, Sybrand van der [Novel Aerospace Materials Group, Faculty of Aerospace Engineering, Delft University of Technology, Kluyverweg 1, 2629 HS, Delft (Netherlands); Xu, Wei, E-mail: xuwei@ral.neu.edu.cn [State Key Laboratory of Rolling and Automation, Northeastern University, 110819, Shenyang (China); Novel Aerospace Materials Group, Faculty of Aerospace Engineering, Delft University of Technology, Kluyverweg 1, 2629 HS, Delft (Netherlands)

    2016-02-15

    Reduced-activation ferritic/martensitic steels are prime candidate materials for structural applications in nuclear power reactors. However, their creep strength is much lower than that of creep-resistant steel developed for conventional fossil-fired power plants as alloying elements with a high neutron activation cannot be used. To improve the creep strength and to maintain a low activation, a high-throughput computational alloy design model coupling thermodynamics, precipitate-coarsening kinetics and an optimization genetic algorithm, is developed. Twelve relevant alloying elements with either low or high activation are considered simultaneously. The activity levels at 0–10 year after the end of irradiation are taken as optimization parameter. The creep-strength values (after exposure for 10 years at 650 °C) are estimated on the basis of the solid-solution strengthening and the precipitation hardening (taking into account precipitate coarsening). Potential alloy compositions leading to a high austenite fraction or a high percentage of undesirable second phase particles are rejected automatically in the optimization cycle. The newly identified alloys have a much higher precipitation hardening and solid-solution strengthening at the same activity level as existing reduced-activation ferritic/martensitic steels.

  13. Improvement of the galvanized coating quality of high strength dual phase steels by pre-electroplating nickel layer

    Energy Technology Data Exchange (ETDEWEB)

    Zhong, N. [Institute of Marine Materials Science and Engineering, Shanghai Maritime University, Shanghai 200135 (China); Zhang, K. [Institute of Concrete Pumps Machinery R and D, Sany Heavy Industry Co., Ltd. 410100 (China); Li, J. [Baoshan Iron and Steel Co., Ltd, Shanghai 201900 (China); Hu, W.B. [State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, Shanghai 200240 (China)

    2011-03-15

    Galvanized dual phase steel sheets are used extensively in the industrial applications because of their excellent mechanical properties and superior corrosion resistance, but the segregation of alloying elements and the formation of oxides on the steel surface often have a deleterious effect on coating adhesion during the galvanizing process. In order to improve the coating quality, a nickel layer was pre-electroplated on the steel substrate before galvanizing and it's found that there is an improvement in the coating quality. The coating microstructures were investigated by scanning electron microscopy together with energy dispersive X-ray spectroscope, glow discharge optical emission spectroscope and X-ray diffractions. The experimental results show that the compact Ni{sub 3}Zn{sub 22} intermetallic layer formed at the zinc/nickel interface during the galvanizing process, prohibiting the nucleation and the growth of the {zeta}-Zn phase layer and resulting in the improvement of the zinc coating adhesion. (Copyright copyright 2011 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)

  14. Microgalvanic corrosion of laser-welded HSLA steels

    NARCIS (Netherlands)

    De Wit, J.H.; Looi, Y.M.

    Laser welding of galvanized high strength low alloy (HSLA) steels leads to the evaporation of zinc at the weld and the formation of a heat-affected-zone (HAZ). High heat input due to welding generates macro galvanic coupling between the weld and the parent metal as well as micro galvanic corrosion

  15. Microgalvanic corrosion of laser-welded HSLA steels

    NARCIS (Netherlands)

    Looi, Y.M.

    2008-01-01

    Laser welding of galvanized high strength low alloy (HSLA) steels leads to the evaporation of zinc at the weld and the formation of a heat-affected-zone (HAZ). High heat input due to welding generates macro galvanic coupling between the weld and the parent metal as well as micro galvanic corrosion

  16. Austenite stabilization and high strength-elongation product of a low silicon aluminum-free hot-rolled directly quenched and dynamically partitioned steel

    Energy Technology Data Exchange (ETDEWEB)

    Tan, Xiao-Dong [State Key Laboratory of Rolling and Automation, Northeastern University, Shenyang 110819 (China); Xu, Yun-Bo, E-mail: yunbo_xu@126.com [State Key Laboratory of Rolling and Automation, Northeastern University, Shenyang 110819 (China); Yang, Xiao-Long; Hu, Zhi-Ping; Peng, Fei [State Key Laboratory of Rolling and Automation, Northeastern University, Shenyang 110819 (China); Ju, Xiao-Wei [Ceri Long Product Co., Ltd., Beijing 100176 (China); Wu, Di [State Key Laboratory of Rolling and Automation, Northeastern University, Shenyang 110819 (China)

    2015-06-15

    Microstructures composed of lath martensite and retained austenite with volume fraction between 8.0 vol.% and 12.0 vol.% were obtained in a low-C low-Si Al-free steel through hot-rolling direct quenching and dynamical partitioning (HDQ&DP) processes. The austenite stabilization mechanism in the low-C low-Si Al-free steel under the special dynamical partitioning processes is investigated by analyzing the carbon partition behavior from martensite to austenite and the carbide precipitation-coarsening behavior in martensite laths combining with the possible hot rolling deformation inheritance. Results show that the satisfying retained austenite amount in currently studied low-Si Al-free HDQ&DP steel is caused by the high-efficiency carbon enrichment in the 30–80 nm thick regions of austenite near the interfaces in the hot-rolled ultra-fast cooled structure and the avoidance of serious carbides coarsening during the continuous cooling procedures. The excellent strength-elongation product reaching up to 26,000 MPa% shows that the involved HDQ&DP process is a promising method to develop a new generation of advanced high strength steel. - Highlights: • HDQ&DP processes were applied to a low-C low-Si Al-free steel. • Effective partitioning time during the continuous cooling processes is 1–220 s. • Retained austenite with volume fraction between 8.0 vol. % and 12.0 vol. % has been obtained. • The special austenite stabilization mechanism has been expounded.

  17. Development and characterization of high strength impact resistant Fe-Mn-(Al-, Si) TRIP/TWIP steels

    Energy Technology Data Exchange (ETDEWEB)

    Bruex, U.; Frommeyer, G. [Dept. of Materials Technology, Max-Planck-Inst. fuer Eisenforschung, Duesseldorf (Germany); Graessel, O. [Pierburg AG, Neuss (Germany); Meyer, L.W.; Weise, A. [Lehrstuhl Werkstoffe des Maschinenbaus, TU Chemnitz, Chemnitz (Germany)

    2002-07-01

    Iron manganese steels with Mn mass contents of 15 to 30% exhibit microstructural related superior ductility and extraordinary strengthening behaviour during plastic deformation, which strongly depends on the Mn content. This influences the austenite stability and stacking fault energy {gamma}{sub fcc} and shows a great impact on the microstructure to be developed under certain stress state or during severe plastic deformation. At medium Mn mass contents (15 to 20%) the martensitic {gamma}-{epsilon}-{alpha}' phase transformation plays an important role in the deformation mechanisms of the TRIP effect in addition to dislocation glide. With increasing Mn mass content large elongation is favoured by intensive twinning formation. The mechanical properties of plain iron manganese alloys are strongly influenced by the alloying elements, Al and Si. Alloying with Al increases the stacking fault energy and therefore strongly suppresses the martensitic {gamma}-{epsilon} transformation, while Si sustains the {gamma}-{epsilon} transformation by decreasing the stacking fault energy {gamma}{sub fcc}. The {gamma}-{epsilon} phase transformation takes place in Fe-Mn-X alloys with {gamma}{sub fcc} {<=} 20 mJm{sup -2}. The developed light weight high manganese TRIP and TWIP (twinning induced plasticity) steels exhibit high ultimate tensile strength (600 to 1100 MPa) and extremely large elongation of 60 to 95% even at high strain rates of {epsilon}= 10{sup 3} s{sup -1}. Particularly due to the advanced specific energy absorption of TRIP and TWIP steels compared to conventional deep drawing steels high dynamic tensile and compression tests were carried out in order to investigate the change in the microstructure under near crash conditions. Tensile and compression tests of iron manganese alloys with varying Mn content were performed at different temperatures and strain rates. The resulting formation of {gamma} twins, {alpha}'- and {epsilon} martensite by plastic deformation

  18. On modelling of shear fracture in deep drawing of a high-strength dual-phase sheet steel

    Science.gov (United States)

    Behrens, B.-A.; Bonk, C.; Peshekhodov, I.

    2017-09-01

    The paper presents application of fracture behaviour characterisation results of a dual-phase sheet steel DP600 to an FEA of its deep-drawing for shear fracture prediction. The characterisation results were obtained with the help of a characterisation method based on a tensile test on a novel butterfly specimen and published previously by the authors. The aim of the present paper is to evaluate that characterisation method on a deep-drawing process. Based on the previous results of the authors, the fracture behaviour is modelled here with the help of the modified Mohr-Coloumb fracture model. The obtained FEA results reveal that shear fracture of the studied material is predicted too early by the used MMC fracture model. A novel adjustment of the model is proposed yielding infinitely high fracture strains at strongly pressure-superimposed stress states. As it is often the case in the state-of-the-art fracture characterisation of high-strenght sheet steels, such stress states were not tested during the previously performed fracture characterisation but occur during the studied deep drawing process. With the help of the adjusted MMC fracture model, it is possible to predict the crack initiation moment very accurately and the crack initiation location sufficiently accurately.

  19. Low alloy steels that minimize the hydrogen-carbide reaction. Final technical report, October 1, 1978-September 30, 1979. Part I

    Energy Technology Data Exchange (ETDEWEB)

    Kar, R. J.; Parker, E. R.; Zackay, V. F.

    1979-01-01

    This report presents results obtained during the first year of a research program to investigate important metallurgical parameters that control the reactions of hydrogen with carbides in steels. Preliminary work included a detailed literature review of th phenomenon of decarburization and methane bubble formation in steels and a suitable experimental technique for investigating hydrogen attack in laboratory conditions was established. Detailed microstructural-mechanical property evaluations were carried out on two series of alloys; the first was based on a plain carbon steel to which binary and ternary alloy additions were made to vary the carbide structure and morphology and assess these effects on the observed hydrogen attack resistance. The second group of steels consisted of commercial Mn-Mo-Ni (A 533 B) and Cr-Mo (A 542 type) steels and their alloy modifications, with a view towards developing steels with improved hydrogen attack resistance.

  20. Simulations of local mechanical fields. Application to the ductile/brittle transition in low alloy steels; Simulations des champs mecaniques locaux. Applications a la transition ductile / fragile dans les aciers faiblement allies

    Energy Technology Data Exchange (ETDEWEB)

    Libert, M.; Rey, C. [Ecole Centrale de Paris, Lab. MSSMat, 92 - Chatenay Malabry (France); Libert, M.; Marini, B. [CEA Saclay, Dept. des Materiaux pour le Nucleaire (DEN/SAC/DMN/SRMA), 91 - Gif sur Yvette (France)

    2006-07-01

    The objective of this study is to take into account the effect of plasticity mechanisms on the ductile/brittle transition in low alloy steels of PWR reactor vessels. A crystalline plasticity model, describing the effect of temperature on the behaviour, has been implemented in a large transformation frame. The material parameters of the model have been determined experimentally and from mechanical tests using an inverse method. Simulations of polycrystalline aggregates have been performed with imposed triaxiality. The study of local heterogeneities shows that the distribution of main stress can be modeled using a distribution of extreme values of first species (Gumbel) and that the parameters of this distribution can be simply described as a function of {sigma}{sub mises} (the average equivalent stress) and T (temperature). This approach will allow to introduce the effect of these heterogeneities in a local approach criterion of rupture. (J.S.)

  1. Research on rapid-cooling press hardening process and its effect for formability of ultra high strength steel

    Science.gov (United States)

    Ying, L.; Hu, P.; Zhao, X.; Shi, D. Y.; Dai, M. H.; Yu, H. Y.; Chang, Y.

    2013-05-01

    In this study, a new rapid-cooling process in press hardening based on theoretical analysis, experimental test and optimal formability simulation were investigated for improving formability and obdurability of 22MnB5 boron steel. A series of non-isothermal flow behaviors in different plastic strain rates from 0.001s-1 to 0.1s-1 was investigated by thermal-mechanical uniaxial tensile tests. Furthermore, martensite transformation measurement was also involved in the temperature range from 600° to 800°. According to an interrelated Norton-Hoff constitutive model was developed to describe the complicated thermal-mechanical-phase transformation couple model, a typical deep drawing box used to simulate formability so as to compare with actual press hardening experiments used by the self-developed multi-field coupled static-explicit FE software KMAS and dynamic-explicit commercial software LS-DYNA respectively. The results showed the rapid-cooling process indicate the validity and efficiency of meeting the forming performance characteristics and the optimal process which temperature range from 650°C˜700°C can contribute to improve formability of press hardening manufacture.

  2. A Modified Constitutive Model for Tensile Flow Behaviors of BR1500HS Ultra-High-Strength Steel at Medium and Low Temperature Regions

    Science.gov (United States)

    Zhao, Jun; Quan, Guo-Zheng; Pan, Jia; Wang, Xuan; Wu, Dong-Sen; Xia, Yu-Feng

    2018-01-01

    Constitutive model of materials is one of the most requisite mathematical model in the finite element analysis, which describes the relationships of flow behaviors with strain, strain rate and temperature. In order to construct such constitutive relationships of ultra-high-strength BR1500HS steel at medium and low temperature regions, the true stress-strain data over a wide temperature range of 293-873 K and strain rate range of 0.01-10 s-1 were collected from a series of isothermal uniaxial tensile tests. The experimental results show that stress-strain relationships are highly non-linear and susceptible to three parameters involving temperature, strain and strain rate. By considering the impacts of strain rate and temperature on strain hardening, a modified constitutive model based on Johnson-Cook model was proposed to characterize flow behaviors in medium and low temperature ranges. The predictability of the improved model was also evaluated by the relative error (W(%)), correlation coefficient (R) and average absolute relative error (AARE). The R-value and AARE-value for modified constitutive model at medium and low temperature regions are 0.9915 & 1.56 % and 0.9570 & 5.39 %, respectively, which indicates that the modified constitutive model can precisely estimate the flow behaviors for BR1500HS steel in the medium and low temperature regions.

  3. Microstructural evolution and mechanical properties of a novel FeCrNiBSi advanced high-strength steel: Slow, accelerated and fast casting cooling rates

    Energy Technology Data Exchange (ETDEWEB)

    Askari-Paykani, Mohsen; Shahverdi, Hamid Reza, E-mail: shahverdi@modares.ac.ir; Miresmaeili, Reza

    2016-06-21

    In the current work, three different solidification routes and a two-step heat treatment process were applied to a novel FeCrNiBSi alloy system to introduce a new candidate for advanced high-strength steels. The evolution of the microstructure after solidification, heat treatment, and tensile deformation was characterized using optical and electron microscopy techniques, as well as hardness and room temperature uniaxial tensile tests. The effects of the different solidification routes and heat treatment parameters on the deformation and fracture mechanisms of this steel are discussed. Grain refinement, precipitation hardening, and solid solution as a result of the fast casting cooling rate led to an increase in strength at improved ductility. This result can be explained partly by the less severe stress/strain partitioning at the matrix grain/M{sub 2}B interfaces and better interface cohesion. Moreover, the stress/strain partitioning characteristics between the matrix grains and M{sub 2}B led to a higher initial strain hardening rate. The fast casting cooling rate further promoted ductile fracture mechanisms, which is a result of increased cleavage fracture stress. The higher casting cooling rate and two-step heat treatment resulted in a strong increase in formability index, from 8 GPa% to 24 GPa%, at which the mechanical properties occupy the TRIP envelope. Heat treatment of the fast-cooling specimens led to a small reduction in yield and tensile strength and 22% total elongation percentage improvement (from 10% to 32%).

  4. Modeling the Hot Tensile Flow Behaviors at Ultra-High-Strength Steel and Construction of Three-Dimensional Continuous Interaction Space for Forming Parameters

    Science.gov (United States)

    Quan, Guo-zheng; Zhan, Zong-yang; Wang, Tong; Xia, Yu-feng

    2017-01-01

    The response of true stress to strain rate, temperature and strain is a complex three-dimensional (3D) issue, and the accurate description of such constitutive relationships significantly contributes to the optimum process design. To obtain the true stress-strain data of ultra-high-strength steel, BR1500HS, a series of isothermal hot tensile tests were conducted in a wide temperature range of 973-1,123 K and a strain rate range of 0.01-10 s-1 on a Gleeble 3800 testing machine. Then the constitutive relationships were modeled by an optimally constructed and well-trained backpropagation artificial neural network (BP-ANN). The evaluation of BP-ANN model revealed that it has admirable performance in characterizing and predicting the flow behaviors of BR1500HS. A comparison on improved Arrhenius-type constitutive equation and BP-ANN model shows that the latter has higher accuracy. Consequently, the developed BP-ANN model was used to predict abundant stress-strain data beyond the limited experimental conditions. Then a 3D continuous interaction space for temperature, strain rate, strain and stress was constructed based on these predicted data. The developed 3D continuous interaction space for hot working parameters contributes to fully revealing the intrinsic relationships of BR1500HS steel.

  5. Springback Compensation in Cold Forming Process for High Strength Steel / Kompensacja sprężynowania w procesie formowania stali na zimno

    Directory of Open Access Journals (Sweden)

    Bałon P.

    2015-12-01

    Full Text Available Process of metal forming in automotive parts construction becomes more and more demanding due to tightened up tolerance and trials to realize very complex and in many cases unworkable design in mass production. Moreover it is required to cut and limit costs of die production and simultaneously keep high quality. Furthermore, construction elements are more often produced from materials which belong to High Strength Steel or Ultra High Strength Steel. Application of this kind of materials considerably reduces construction mass due to high durability. Nevertheless, it results in appearance of springback effect. Springback value depends mainly on used material as well as part geometry and in extreme cases deviation value from target part might reach in some areas high level. Reduction of implementation time, development of metal components and greater restrictions about designing and producing stamping tools generate extra costs. Designing of dies requires using of appropriate Finite Element Method software to make them more economic and less time-consuming. Therefore analysis of forming process alone is not enough to be taken into account. During the design process it is needed to include the die compensation to reach optimized blank sheet. Prediction of springback effect by tryout method and then correction of deviation is difficult arduous and painstaking. Virtual compensation methods make it possible to receive precise result in a short time. This way gives a huge economic advantage eliminating useless milling and allows to produce of die just in time. Optimization process can relate to individual operation as well as take into consideration intermediate stages in the final result, at the same time increasing the accuracy. Die compensation with software application was experimentally verified by prototype die. Quality requirements regarding products of sheet stamping process are very high due to the technologies of automatic assembly of formed

  6. Development of High-Strength Bulk Ultrafine-Grained Low Carbon Steel Produced by Equal-Channel Angular Pressing

    Science.gov (United States)

    Singh, Raj Bahadur; Mukhopadhyay, N. K.; Sastry, G. V. S.; Manna, R.

    2017-11-01

    Low carbon steel (LCS) workpieces have been deformed by equal-channel angular pressing (ECAP) at a large equivalent strain of 16.8 at room temperature. The mechanisms of microstructural refinement, strengthening, hardening, and fracture behavior are investigated. LCS becomes refined by a sequence of mechanisms of elongation of grains, splitting of elongated grains to bands at low strain, subdivision of bands to cells at intermediate strain, elongation of bands to ribbon grains, and breaking of ribbons to near-equiaxed grains at a high strain level. ECAP of LCS at ɛ vm = 16.8 refines the material to near-equiaxed grains of size 0.2 µm having a high-angle grain boundary fraction of 82.4 pct and average misorientation angle of 40.8 deg. The ultrafine-grained (UFG) LCS contains a dislocation density of 1.7 × 1015 m2. In the initial passes of ECAP, the yield and tensile strengths increase rapidly due to rapid grain refinement, reduction in domain size, and increase in dislocation density. At high strain levels, strengthening can be attributed to a combination of grain refinement, dissolution of cementite in the ferrite matrix, and increase in misorientation angle. At ɛ vm = 16.8, the ultimate tensile strength (UTS) reaches >1000 MPa with a consequent drop in ductility to ≈10.6 pct. Reduction in ductility is found to be due to high dislocation density, high stored energy in the matrix, and occurrence of nonequilibrium grain boundaries. The LCS at low equivalent strain fails by ductile fracture. The dimple size and its volume fraction decrease, but their number density and stored energy increase with increasing equivalent strain. Beyond a critical equivalent strain of 9, the material fails by ductile-brittle fracture. At ɛ vm = 16.8, equal-channel angular pressed UFG LCS fails mainly by cleavage fracture.

  7. Effect of alloy elements on the anti-corrosion properties of low alloy ...

    Indian Academy of Sciences (India)

    Home; Journals; Bulletin of Materials Science; Volume 23; Issue 3. Effect of alloy elements on the anti-corrosion properties of low alloy steel ... Effect of alloy elements on corrosion of low alloy steel was studied under simulated offshore conditions. The results showed that the elements Cu, P, Mo, W, V had evident effect on ...

  8. ``Global and local approaches of fracture in the ductile to brittle regime of a low alloy steel``; ``Approches globale et locale de la rupture dans le domaine de transition fragile-ductile d`un acier faiblement allie``

    Energy Technology Data Exchange (ETDEWEB)

    Renevey, S

    1998-12-31

    The study is a contribution to the prediction of flow fracture toughness of low alloy steel and to a better knowledge of fracture behavior in the ductile to brittle transition region. Experiments were performed on a nozzle cut-off from a pressurized water reactor vessel made of steels A508C13 type steel. Axisymmetrical notched specimens were tested to study the fracture onset in a volume element while pre-cracked specimens were used to investigate cleavage fracture after stable crack growth. Systematic observations of fracture surfaces showed manganese sulfide inclusions (MnS) at cleavage sites or in the vicinity. The experimental results were used for modelling by the local approach to fracture. In a volume element the fracture is described by an original probabilistic model. This model is based on volume fraction distributions of MnS inclusions gathered in clusters and on the assumption of a competition without interaction between ductile and cleavage fracture modes. This model was applied to pre-cracked specimens (CT specimens). It is able to describe the scatter in the toughness after a small stable crack growth if a temperature effect on the cleavage stress is assumed. So, the modelling is able to give a lower bound of fracture toughness as a function of temperature. (author) 100 refs.

  9. Carbon Redistribution and Carbide Precipitation in a High-Strength Low-Carbon HSLA-115 Steel Studied on a Nanoscale by Atom Probe Tomography

    Science.gov (United States)

    Jain, Divya; Isheim, Dieter; Seidman, David N.

    2017-07-01

    HSLA-115 is a newly developed Cu-bearing high-strength low-carbon martensitic steel for use in Naval structural applications. This research provides, for the first time, a comprehensive compositional analysis of carbon redistribution and associated complex phase transformations in an isothermal aging study of HSLA-115 at 823 K (550 °C). Specifically, we characterize carbon segregation at lath boundaries, grain-refining niobium carbonitrides, cementite, and secondary hardening M2C carbides, in addition to copper precipitation, by 3D atom probe tomography (APT). Segregation of carbon (3 to 6 at. pct C) is observed at martensitic lath boundaries in the as-quenched and 0.12-hour aged microstructures. On further aging, carbon redistributes itself forming cementite and M2C carbides. Niobium carbonitride precipitates do not dissolve during the austenitizing treatment and are inherited in the as-quenched and aged microstructures; these are characterized along with cementite by synchrotron X-ray diffraction and APT. Sub-nanometer-sized M2C carbide precipitates are observed after the formation of Cu precipitates, co-located with the latter, indicating heterogeneous nucleation of M2C. The temporal evolution of the composition and morphology of M2C carbides at 823 K (550 °C) is described using APT; their precipitation kinetics is intertwined with Cu precipitates, affecting the bulk mechanical properties of HSLA-115. Phase compositions determined by APT are compared with computed compositions at thermodynamic equilibrium using ThermoCalc.

  10. Correlation Between Microstructure and Low-Temperature Impact Toughness of Simulated Reheated Zones in the Multi-pass Weld Metal of High-Strength Steel

    Science.gov (United States)

    Kang, Yongjoon; Park, Gitae; Jeong, Seonghoon; Lee, Changhee

    2018-01-01

    A large fraction of reheated weld metal is formed during multi-pass welding, which significantly affects the mechanical properties (especially toughness) of welded structures. In this study, the low-temperature toughness of the simulated reheated zone in multi-pass weld metal was evaluated and compared to that of the as-deposited zone using microstructural analyses. Two kinds of high-strength steel welds with different hardenabilities were produced by single-pass, bead-in-groove welding, and both welds were thermally cycled to peak temperatures above Ac3 using a Gleeble simulator. When the weld metals were reheated, their toughness deteriorated in response to the increase in the fraction of detrimental microstructural components, i.e., grain boundary ferrite and coalesced bainite in the weld metals with low and high hardenabilities, respectively. In addition, toughness deterioration occurred in conjunction with an increase in the effective grain size, which was attributed to the decrease in nucleation probability of acicular ferrite; the main cause for this decrease changed depending on the hardenability of the weld metal.

  11. Carbon Redistribution and Carbide Precipitation in a High-Strength Low-Carbon HSLA-115 Steel Studied on a Nanoscale by Atom Probe Tomography

    Energy Technology Data Exchange (ETDEWEB)

    Jain, Divya; Isheim, Dieter; Seidman, David N. (NWU)

    2017-05-09

    HSLA-115 is a newly developed Cu-bearing high-strength low-carbon martensitic steel for use in Naval structural applications. This research provides, for the first time, a comprehensive compositional analysis of carbon redistribution and associated complex phase transformations in an isothermal aging study of HSLA-115 at 823 K (550 °C). Specifically, we characterize carbon segregation at lath boundaries, grain-refining niobium carbonitrides, cementite, and secondary hardening M2C carbides, in addition to copper precipitation, by 3D atom probe tomography (APT). Segregation of carbon (3 to 6 at. pct C) is observed at martensitic lath boundaries in the as-quenched and 0.12-hour aged microstructures. On further aging, carbon redistributes itself forming cementite and M2C carbides. Niobium carbonitride precipitates do not dissolve during the austenitizing treatment and are inherited in the as-quenched and aged microstructures; these are characterized along with cementite by synchrotron X-ray diffraction and APT. Sub-nanometer-sized M2C carbide precipitates are observed after the formation of Cu precipitates, co-located with the latter, indicating heterogeneous nucleation of M2C. The temporal evolution of the composition and morphology of M2C carbides at 823 K (550 °C) is described using APT; their precipitation kinetics is intertwined with Cu precipitates, affecting the bulk mechanical properties of HSLA-115. Phase compositions determined by APT are compared with computed compositions at thermodynamic equilibrium using ThermoCalc.

  12. Initiation of cleavage in a low alloy steel: effect of a ductile damage localized around inclusions; Declenchement du clivage dans un acier faiblement allie: role de l'endommagement ductile localise autour des inclusions

    Energy Technology Data Exchange (ETDEWEB)

    Carassou, S

    2000-07-01

    The fracture mechanism in a low alloy steel, used in the pressurised water reactor vessel, has been studied in the ductile to brittle transition temperature range. We used the local approach of fracture in conjunction with both fractographic observations and numerical simulations. Previous studies suggested the onset of cleavage to be favoured by the presence of nearby manganese sulphide (MnS) clusters: the ductile damaged zone localised inside a cluster increases the stress around it, and so contribute to the triggering of cleavage due to nearby classical sites, like carbides. The experimental study of size dependence and anisotropy on the global fracture behaviour, together with fractographic observations, give here the proof of the influence of MnS clusters on the onset of cleavage in this steel. Fracture behaviour of pre-cracked specimens tested in the transition regime has then been simulated, by three dimensional finite element method computations. Ductile tearing process preceding the cleavage onset at those temperatures regime was well reproduced by the Rousselier's model. Failure probabilities, related to given stress states, has been given by post-processor calculations, using a probabilistic model based on the specific cleavage fracture process. Fracture toughness scatter of the steel, tested in the transition regime, is then well reproduced by those calculations. However, the critical cleavage stress of an elementary volume, that scales for the fracture process, is still assumed to be temperature dependant. Numerical simulations of the local fracture process suggest that this temperature effect can partly be explained by the temperature dependant decrease of the stress amplification due to the MnS clusters. (author)

  13. Electrochemical frequency modulation and inductively coupled plasma atomic emission spectroscopy methods for monitoring corrosion rates and inhibition of low alloy steel corrosion in HCl solutions and a test for validity of the Tafel extrapolation method

    Energy Technology Data Exchange (ETDEWEB)

    Amin, Mohammed A. [Chemistry Department, Faculty of Science, Ain Shams University, Al-Khalefah Al-Maamoon St., Abbassia, Cairo 11566 (Egypt)], E-mail: maaismail@yahoo.com; Abd El Rehim, Sayed S. [Chemistry Department, Faculty of Science, Ain Shams University, Al-Khalefah Al-Maamoon St., Abbassia, Cairo 11566 (Egypt); Abdel-Fatah, Hesham T.M. [Central Chemical Laboratories, Egyptian Electricity Holding Company, Sabtia, Cairo (Egypt)

    2009-04-15

    The inhibition effect of glycine (Gly) towards the corrosion of low alloy steel ASTM A213 grade T22 boiler steel was studied in aerated stagnant 0.50 M HCl solutions in the temperature range 20-60 deg. C using potentiodynamic polarization (Tafel polarization and linear polarization) and impedance techniques, complemented with scanning electron microscope (SEM) and energy dispersive X-ray (EDX). Electrochemical frequency modulation (EFM), a non-destructive corrosion measurement technique that can directly give values of corrosion current without prior knowledge of Tafel constants, is also presented here. Experimental corrosion rates determined by the Tafel extrapolation method are compared with corrosion rates obtained by electrochemical, namely EFM technique, and chemical (i.e., non-electrochemical) method for steel in HCl. The chemical method of confirmation of the corrosion rates involved determination of the dissolved cation, using ICP-AES (inductively coupled plasma atomic emission spectrometry) method of analysis. Corrosion rates (in mm y{sup -1}) obtained from the electrochemical (Tafel extrapolation and EFM) and the chemical method, ICP, are in a good agreement. Polarization studies have shown that Gly is a good 'green', mixed-type inhibitor with cathodic predominance. The inhibition process was attributed to the formation of an adsorbed film on the metal surface that protects the metal against corrosive agents. Scanning electron microscopy (SEM) and energy dispersion X-ray (EDX) examinations of the electrode surface confirmed the existence of such an adsorbed film. The inhibition efficiency increases with increase in Gly concentration, while it decreases with solution temperature. Temkin isotherm is successfully applied to describe the adsorption process. Thermodynamic functions for the adsorption process were determined.

  14. 76 FR 2344 - Certain Hot-Rolled Carbon Steel Flat Products From India: Notice of Preliminary Results of...

    Science.gov (United States)

    2011-01-13

    ..., or 1.25 percent of chromium, or 0.30 percent of cobalt, or 0.40 percent of lead, or 1.25 percent of... stabilized (commonly referred to as interstitial-free (``IF'')) steels, high-strength low-alloy (``HSLA... with micro-alloying levels of elements such as chromium, copper, niobium, vanadium, and molybdenum. The...

  15. Development of low-temperature galvanizing and its application for corrosion protection of high-strength steels; Entwicklung einer niedrigschmelzenden Legierung und deren Applikation zum Korrosionsschutz hochfester Staehle

    Energy Technology Data Exchange (ETDEWEB)

    Wielage, B.; Lampke, T.; Steinhaeuser, S. [Technische Universitaet Chemnitz (Germany). Institut fuer Werkstoffwissenschaft und Werkstofftechnik; Strobel, C. [Fachhochschule Ingolstadt (Germany); Merklinger, V.

    2008-12-15

    Apart from reliability and quality, vehicle safety and cost efficiency are the decisive criteria for automobile manufacturers. Corrosion protection plays a decisive role because it increases the service life. The ultra-high-strength steels are materials which exhibit high lightweight potential as well as a very good energy absorption capacity because of their mechanical properties. In connection with the possibility of hot forming, they are predestined for the fabrication of complicated, load-compatible shapes in the crash-relevant frame and body construction. The application of these steel qualities has been carried out in structural parts which are protected from corrosion by a hot-dip coat of FeAl7 - the so-called Usibor. However, at the moment there is no ready-for-production solution for later corrosion protection of already hot-formed parts. Therefore, a corrosion protection system on the basis of conventional low-temperature galvanizing processes has been developed and utilized. First, the softening behavior of the highly-resistant 22MnB5 substrate was analyzed. Afterwards, a galvanizing system was developed and applied. The corrosion protection coatings were characterized with regard to their structure and corrosion protection potential. As a result, a significant improvement of the corrosion behaviour has occurred. (Abstract Copyright [2008], Wiley Periodicals, Inc.) [German] Neben Zuverlaessigkeit und Qualitaet sind vor allem Fahrzeugsicherheit und Wirtschaftlichkeit entscheidende Kriterien fuer den Automobilhersteller. Der Korrosionsschutz spielt dabei eine herausragende Rolle, da hierdurch die Lebens- und Gebrauchsdauer erhoeht wird. Mit der Bereitstellung hoechstfester Stahlqualitaeten stehen Werkstoffe zur Verfuegung, die auf Grund ihrer mechanischen Eigenschaften ein hohes Leichtbaupotenzial sowie ein sehr gutes Energieabsorptionsvermoegen aufweisen. In Verbindung mit der Moeglichkeit der Warmformgebung sind sie damit praedestiniert fuer die

  16. Effect of solute grain boundary segregation and hardness on the ductile-to-brittle transition for a Cr-Mo low-alloy steel

    Energy Technology Data Exchange (ETDEWEB)

    Shen, D.-D. [School of Materials and Metallurgy, Wuhan University of Science and Technology, Wuhan 430081 (China); Song, S.-H. [Division of Materials Science and Engineering, Shenzhen Graduate School, Harbin Institute of Technology, Shenzhen University Town, Xili, Shenzhen 518055 (China)]. E-mail: shsonguk@yahoo.co.uk; Yuan, Z.-X. [School of Materials and Metallurgy, Wuhan University of Science and Technology, Wuhan 430081 (China); Weng, L.-Q. [Division of Materials Science and Engineering, Shenzhen Graduate School, Harbin Institute of Technology, Shenzhen University Town, Xili, Shenzhen 518055 (China)

    2005-03-15

    Combined solute grain boundary segregation and hardness effect on the ductile-to-brittle transition is examined for a P-doped 2.25Cr-1Mo steel by means of Auger electron spectroscopy (AES) in conjunction with hardness measurements, Charpy impact tests and scanning electron microscopy (SEM). During ageing at 540 deg. C after water quenching from 980 deg. C, the segregation of phosphorus, molybdenum and chromium increases and the hardness decreases with increasing ageing time. The ductile-to-brittle transition temperature (DBTT) increases with increasing phosphorus segregation and decreases with decreasing hardness. The phosphorus segregation effect is dominant until 100 h ageing and after that the hardness effect becomes dominant, making the DBTT decrease with further increasing ageing time although the segregation of phosphorus still increases strongly. The segregation of molybdenum has some effect on the DBTT decrease.

  17. Annealing for plant life management: hardness, tensile and Charpy toughness properties of irradiated, annealed and re-irradiated mock-up low alloy nuclear pressure vessel steel

    Energy Technology Data Exchange (ETDEWEB)

    Tipping, Philip; Cripps, Robin (Paul Scherrer Inst. (PSI), Villigen (Switzerland))

    1994-01-01

    Hardness, tensile and Charpy properties of an irradiated (I) and irradiated-annealed-reirradiated (IAR) mock-up pressure vessel steel are presented. Spectrum tailored pressurized light water reactor (PWR) irradiation at 290[sup o]C by fast neutrons up to nominal fluences of 5 x 10[sup 19]/cm[sup 2] (E [>=] 1 MeV) in a swimming pool type reactor caused the hardness, tensile yield stress and tensile strength to increase. Embrittlement also occurred as indicated by Charpy toughness tests. The optimum annealing heat treatment for the main program was determined using isochronal and isothermal runs on the material and measuring the Vickers microhardness. The response to an intermediate annealing treatment (460[sup o]C for 18 h), when 50% of the target fluence has been reached and then irradiating to the required end fluence (IAR condition) was then monitored further by Charpy and tensile mechanical properties. Annealing was beneficial in mitigating overall hardening or embrittlement effects. The rate of re-embrittlement after annealing and re-irradiating was no faster than when no annealing had been performed. Annealing temperatures below 440[sup o]C were indicated as requiring relatively long times, i.e. [>=] 168 h to achieve some reduction in radiation induced hardness for example. (Author).

  18. Effect of the detector dead-time uncertainty on the analytical result of minor elements in low-alloy steel by isotope dilution/ICP sector field mass spectrometry.

    Science.gov (United States)

    Nonose, Naoko; Hioki, Akiharu; Chiba, Koichi

    2014-01-01

    In the present study the effects of the detector dead-time and its uncertainties on the accuracy and uncertainty of isotope dilution mass spectrometry (IDMS) were considered through an interlaboratory study on the analysis of low-alloy steel by using an ICP-sector field mass spectrometer. Also, an optimized mixing ratio of the sample and the spike to obtain highly precise results was theoretically and experimentally investigated. The detector dead-time used in the interlaboratory study showed a negative value. However, it less affected the trueness of the analytical result if the dead-time correction for the measured isotope ratio was done properly. As many researchers have pointed out, the detector dead-time showed a clear mass dependence. Therefore, it is desirable to check the dead-time in every target element by using assay standards or isotopic standards, which would lead to an accurate result even if the detector dead-time is a negative value. On the other hand, the effect of the uncertainty of the detector dead-time can be minimized when both isotope ratios and ICP-MS signals of the [sample + spike] blend in IDMS are equal to those of [spike + assay standard] in reverse IDMS. From standpoints of error magnification theory and the precision of the isotope ratio measurement, an optimized isotope ratio of the sample-spike blend would be 1.0 for an element with a large difference in ten times and more between the atomic fractions of two isotopes used for IDMS. In the case of an element with no significant difference between the atomic fractions of two isotopes, an optimized isotope ratio can be calculated by a formula expressed as a function of the atomic fractions of the sample and the spike as well as the signal of ICP-MS.

  19. Influence of non-metallic second phases on fatigue behaviour of high strength steel components; Efecto de segundas fases no metalicas sobre el comportamiento a fatiga de componentes de acero con elevadas solicitaciones

    Energy Technology Data Exchange (ETDEWEB)

    Gonzalez, L.; Elvira, R.; Garcia de Andoin, A.; Pizarro, R.; Bertrand, C.

    2005-07-01

    To assess the real effect of the inclusion type on fatigue life of ultra clean high strength steels mechanical components made of 100Cr6 steel were fatigue tested and fracture surfaces analysed to determine the origin of fatigue cracks.Two heats proceedings from different steelmaking routes were taken for the tests. The material were forged into ring shape components which were fatigue tested under compression-compression loads. Failures were analysed by SFEM (Scanning field Emission Microscopy), proving that most of failures at high loads were originated by manganese sulphides of small size (10-70 micros), while less than 40% of all fatigue cracks due to inclusions were caused by titanium carbonitrides and hard oxides. It has been demonstrated that once number and size of hard inclusions have been reduced, the hazardous effect of oxides and carbonitrides on the fatigue life decreases also. However, softer inclusions as manganese sulphides, currently considered as less hazardous, play a more relevant role as direct cause of fatigue failure and they should be taken into account in a deeper way in order to balance both machinability and fatigue life requirements in high strength steel components. (Author) 11 refs.

  20. Application of the S690QL class steels in responsible welded structures

    Directory of Open Access Journals (Sweden)

    Dušan Arsić

    2013-12-01

    Full Text Available In this paper are considered the most important properties of a special class of high strength steels S690QL, which can be classified into the group of special low alloyed steels. The high strength steels belong into a group of high quality steels. They possess exceptional mechanical properties, especially tensile strength and toughness. Those favorable properties are being achieved by application of special procedures of thermo-mechanical processing and simultaneous alloying with adequate elements. The advantages that the S690QL steels have with respect to other steels are being presented here. However, possibilities for application of those steels in responsible welded structures are limited due to their only relatively good weldability.  The special procedures for improving it are discussed here, primarily preheating, controlled heat input during welding and additional heat treatment of the welded joint.

  1. A comparative evaluation of microstructural and mechanical behavior of fiber laser beam and tungsten inert gas dissimilar ultra high strength steel welds

    Directory of Open Access Journals (Sweden)

    Jaiteerth R. Joshi

    2016-12-01

    Full Text Available The influence of different welding processes on the mechanical properties and the corresponding variation in the microstructural features have been investigated for the dissimilar weldments of 18% Ni maraging steel 250 and AISI 4130 steel. The weld joints are realized through two different fusion welding processes, tungsten inert arc welding (TIG and laser beam welding (LBW, in this study. The dissimilar steel welds were characterized through optical microstructures, microhardness survey across the weldment and evaluation of tensile properties. The fiber laser beam welds have demonstrated superior mechanical properties and reduced heat affected zone as compared to the TIG weldments.

  2. Study and numerical analysis on formability of quenching and partitioning steel sheets of auto-body

    Science.gov (United States)

    Hu, Xing; Liu, Yifan; Zhu, Lin

    2013-05-01

    Advanced high strength steel is the basic structure material for lightweight design and safety enhancement for automobile industry. Quenching and partitioning steel is a recently developed kind of low carbon and low alloy material with retained Austenite for the requirements of both high strength and high ductility. This paper focuses on the formability of a hinge pillar for some car under numerical modelling analysis. The results show that QP980 has an equal elongation comparing with DP590. Moreover, the numerical modelling results of QP980 are more sensitive to the selection of yielding equation comparing with DP590.

  3. Evaluation of essential work of fracture in a dual phase high strength steel sheet; Evaluacion del trabajo esencial de fractura en chapa de un acero de alta resistencia de fase dual

    Energy Technology Data Exchange (ETDEWEB)

    Gutierrez, D.; Perez, L. I.; Lara, A.; Casellas, D.; Prado, J. M.

    2013-03-01

    Fracture toughness of advanced high strength steels (AHSS), can be used to optimize crash behavior of structural components. However it cannot be readily measured in metal sheet because of the sheet thickness. In this work, the Essential Work of Fracture (EWF) methodology is proposed to evaluate the fracture toughness of metal sheets. It has been successfully applied in polymers films and some metal sheets. However, their information about the applicability of this methodology to AHSS is relatively scarce. In the present work the fracture toughness of a Dual Phase (strength of 800 MPa) and drawing steel sheets has been measured by means of the EWF. The results show that the test requirements are met and also show the clear influence of notch radii on the measured values, specially for the AHSS grade. Thus, the EWF is postulated as a methodology to evaluate the fracture toughness in AHSS sheets. (Author) 18 refs.

  4. High strength alloys

    Energy Technology Data Exchange (ETDEWEB)

    Maziasz, Phillip James; Shingledecker, John Paul; Santella, Michael Leonard; Schneibel, Joachim Hugo; Sikka, Vinod Kumar; Vinegar, Harold J.; John, Randy Carl; Kim, Dong Sub

    2012-06-05

    High strength metal alloys are described herein. At least one composition of a metal alloy includes chromium, nickel, copper, manganese, silicon, niobium, tungsten and iron. System, methods, and heaters that include the high strength metal alloys are described herein. At least one heater system may include a canister at least partially made from material containing at least one of the metal alloys. At least one system for heating a subterranean formation may include a tublar that is at least partially made from a material containing at least one of the metal alloys.

  5. High strength alloys

    Energy Technology Data Exchange (ETDEWEB)

    Maziasz, Phillip James [Oak Ridge, TN; Shingledecker, John Paul [Knoxville, TN; Santella, Michael Leonard [Knoxville, TN; Schneibel, Joachim Hugo [Knoxville, TN; Sikka, Vinod Kumar [Oak Ridge, TN; Vinegar, Harold J [Bellaire, TX; John, Randy Carl [Houston, TX; Kim, Dong Sub [Sugar Land, TX

    2010-08-31

    High strength metal alloys are described herein. At least one composition of a metal alloy includes chromium, nickel, copper, manganese, silicon, niobium, tungsten and iron. System, methods, and heaters that include the high strength metal alloys are described herein. At least one heater system may include a canister at least partially made from material containing at least one of the metal alloys. At least one system for heating a subterranean formation may include a tubular that is at least partially made from a material containing at least one of the metal alloys.

  6. Effect of microstructure on fatigue behavior of advanced high strength steels produced by quenching and partitioning and the role of retained austenite

    Energy Technology Data Exchange (ETDEWEB)

    Diego-Calderón, I. de, E-mail: irenedediego.calderon@imdea.org [IMDEA Materials Institute, Calle Eric Kandel 2, 28906 Getafe, Madrid (Spain); Rodriguez-Calvillo, P. [Fundació CTM Centre Tecnològic, Plaza de la Ciencia 2, 08243 Manresa (Spain); Departamento de Ciencia de los Materiales e Ingeniería Metalúrgica, Universitat Politècnica de Catalunya, Av. Diagonal 647, 08028 Barcelona (Spain); Lara, A. [Fundació CTM Centre Tecnològic, Plaza de la Ciencia 2, 08243 Manresa (Spain); Molina-Aldareguia, J.M. [IMDEA Materials Institute, Calle Eric Kandel 2, 28906 Getafe, Madrid (Spain); Petrov, R.H. [Department of Materials Science and Engineering, Ghent University, Technologiepark 903, B-9052 Zwijnaarde (Ghent) (Belgium); Department of Materials Science and Engineering, Delft University of Technology, 2628 CD Delft (Netherlands); De Knijf, D. [Department of Materials Science and Engineering, Ghent University, Technologiepark 903, B-9052 Zwijnaarde (Ghent) (Belgium); Sabirov, I. [IMDEA Materials Institute, Calle Eric Kandel 2, 28906 Getafe, Madrid (Spain)

    2015-08-12

    Despite the significant body of research on mechanical properties of quenched and partitioned (Q&P) steels, their fatigue behavior has not been investigated. This work focuses on the effect of microstructure on high cycle fatigue of Q&P steels and microstructural evolution during cyclic loading. It is demonstrated that increased content of retained austenite (RA) improves fatigue limit of Q&P steels that is related to delay of crack propagation due to austenite–martensite phase transformation. Increasing stress amplitude promotes austenite–martensite phase transformation during cycling loading. It is shown that size and crystallographic orientation of RA are the main factors determining its stability, whereas its shape and spatial distribution do not seem to affect it significantly. Fatigue crack initiation during fatigue testing with high stress amplitudes occurs by intergranular cracking, whereas transgranular cracking controls fatigue crack initiation during cycling loading with lower stress amplitudes. Transgranular crack propagation dominates in the second stage of fatigue at all stress amplitudes. The final stage of fatigue is also not affected by the stress amplitude. It is suggested that fatigue life of Q&P steels can be enhanced via improvement of strength of grain/interphase boundaries.

  7. Interfacial Reaction Characteristics and Mechanical Properties of Welding-brazing Bonding Between AZ31B Magnesium Alloy and PRO500 Ultra-high Strength Steel

    Directory of Open Access Journals (Sweden)

    CHEN Jian-hua

    2017-11-01

    Full Text Available Experiments were carried out with TIG welding-brazing of AZ31B magnesium alloy to PRO500 steel using TIG arc as heat source. The interfacial reaction characteristics and mechanical properties of the welding-brazing bonding were investigated. The results show that an effective bonding is achieved between AZ31B magnesium alloy and PRO500 steel by using TIG welding-brazing method. Some spontaneous oxidation reactions result in the formation of a transition zone containing AlFe3 phase with rich oxide. The micro-hardness value of the interfacial transition zone is between that of the AZ31B and the PRO500. Temper softening zone appears due to the welding thermal cycle nearby the bonding position in the interface. A higher heat input makes an increase of the brittle phases and leads to an obvious decrease of the bonding strength.

  8. Effect of Boron on the Strength and Toughness of Direct-Quenched Low-Carbon Niobium Bearing Ultra-High-Strength Martensitic Steel

    Science.gov (United States)

    Hannula, Jaakko; Kömi, Jukka; Porter, David A.; Somani, Mahesh C.; Kaijalainen, Antti; Suikkanen, Pasi; Yang, Jer-Ren; Tsai, Shao-Pu

    2017-11-01

    The effect of boron on the microstructures and mechanical properties of laboratory-control-rolled and direct-quenched 6-mm-thick steels containing 0.08 wt pct C and 0.02 wt pct Nb were studied. The boron contents were 24 ppm and a residual amount of 4 ppm. Two different finish rolling temperatures (FRTs) of 1093 K and 1193 K (820 °C and 920 °C) were used in the hot rolling trials to obtain different levels of pancaked austenite prior to DQ. Continuous cooling transformation (CCT) diagrams were constructed to reveal the effect of boron on the transformation behavior of these steels. Microstructural characterization was carried out using various microscopy techniques, such as light optical microscopy (LOM) and scanning electron microscopy-electron backscatter diffraction (SEM-EBSD). The resultant microstructures after hot rolling were mixtures of autotempered martensite and lower bainite (LB), having yield strengths in the range 918 to 1067 MPa with total elongations to fracture higher than 10 pct. The lower FRT of 1093 K (820 °C) produced better combinations of strength and toughness as a consequence of a higher degree of pancaking in the austenite. Removal of boron lowered the 34 J/cm2 Charpy-V impact toughness transition temperature from 206 K to 158 K (-67 °C to -115 °C) when the finishing rolling temperature of 1093 K (820 °C) was used without any loss in the strength values compared to the boron-bearing steel. This was due to the finer and more uniform grain structure in the boron-free steel. Contrary to expectations, the difference was not caused by the formation of borocarbide precipitates, as verified by transmission electron microscopy (TEM) investigations, but through the grain coarsening effect of boron.

  9. Creep properties and simulation of weld repaired low alloy heat resistant CrMo and Mo steels at 540 deg C. Sub project 1 - Ex-serviced parent metal and virgin weld metals

    Energy Technology Data Exchange (ETDEWEB)

    Rui Wu; Storesund, Jan; Borggreen, Kjeld; Weilin Zang

    2006-10-15

    Many existing power generating and process plants, where low alloy heat resistant CrMo(V) steels are extensively used for critical components, have exceeded their design lifetime of usually 100,000 hours. Assessment of residual lifetime and extension of economic life by weld repair have become increasingly important and attractive. This project aims at i) performing weld repair and determining the degree of mismatching, ii) evaluating the creep properties of weld repairs, iii) analysing creep behaviour of weld repair and providing necessary data for further reliable simulations of weld repair creep behaviour in long term service, and iv), simulating and assessing lifetime and creep damage evolution of weld repair. Weld repair using 10 CrMo 9 10, 13 CrMo 4 4 and 15 Mo 3 consumables has been carried out in a service-exposed 10 CrMo 9 10 pipe. Creep specimens have been extracted from the service-exposed 10 CrMo 9 10 parent metal (PM), from the virgin 10 CrMo 9 10 weld metal (WM), from the virgin 13 CrMo 4 4 WM as well as from the virgin 15 Mo 3 WM. Iso-thermal uniaxial creep tests have been performed at 540 deg C in air. Pre- and post-metallography are carried out on the selected samples. FEM simulations using obtained creep data are executed. Pre-test metallography shows normal and acceptable weld repairs at given welding conditions. Creep tests demonstrate that the virgin 10 CrMo 9 10, 13 CrMo 4 4 and 15 Mo 3 WMs have apparently longer creep lifetime than the service-exposed CrMo 9 10 PM at higher stresses than 110 MPa. Among the weld metals, the longest creep lifetime is found in 10 CrMo 9 10. Higher creep strength and lower creep strain rate in the weld metals indicate an overmatch weld. At 95 MPa, however, lifetime of 13 CrMo 4 4 WM is surprisingly short (factors which may shorten lifetime are discussed and one more test will start to verify creep strength at low stress) and tests are still running for other two weld metals. More results regarding low stress

  10. In-Situ Synchrotron X-ray Diffraction Studies on Effects of Plastic and Elastic Loading on bcc Phase Transformations of a 3rd Generation 1 GPa Advanced High Strength Steel

    Science.gov (United States)

    Eftekharimilani, P.; Huizenga, R. M.; Kim, B.; Bernasconi, A.; Hermans, M. J. M.

    2018-01-01

    In this paper, we describe the effects of mechanical loading on bcc-to-bcc phase transformations of an Advanced High Strength Steel during cooling. In-situ synchrotron diffraction was employed to measure time-temperature-load diffraction patterns. Calculations were made of the volume fractions of the phases, the transformation kinetics, and the austenite lattice parameter during cooling and simultaneous loading. In addition, volume fractions and lattice parameters of retained austenite at room temperature under different loading conditions were obtained. The results show that applying a load during cooling of the fcc phase significantly increases the volume fraction of a bcc phase before the start of the martensitic transformation. The kinetics of phase transformations were affected by the applied loads. The volume fraction and lattice parameter of retained austenite at room temperature vary in different samples and the highest retained austenite and the largest lattice parameter were obtained in the sample subjected to the highest load.

  11. The Effects of Finish Rolling Temperature and Niobium Microalloying on the Microstructure and Properties of a Direct Quenched High-Strength Steel

    Directory of Open Access Journals (Sweden)

    Kaijalainen A.

    2017-06-01

    Full Text Available This paper comprehends the effects of finish rolling temperature (FRT and Nb-microalloying on the microstructural evolution and resultant properties of a low carbon direct quenched steel in the yield strength category of ≥900 MPa. Results indicate that a decrease in FRT close to Ar3 temperature significantly influenced the microstructure following phase transformation, especially at the subsurface (~50-400 μm of the rolled strip. On decreasing the FRT, the subsurface microstructure revealed a fine mixture of ferrite and bainite obviously as a result of strain-induced transformation, whereas the structure at the centreline remained essentially martensitic. Further, Nb-microalloying promoted the formation of ferrite and bainite even at higher FRTs, thus influencing the mechanical properties. The microstructures of the hot-rolled strips were further corroborated with the aid of CCT diagrams.

  12. Microstructure and fatigue resistance of high strength dual phase steel welded with gas metal arc welding and plasma arc welding processes

    Science.gov (United States)

    Ahiale, Godwin Kwame; Oh, Yong-Jun; Choi, Won-Doo; Lee, Kwang-Bok; Jung, Jae-Gyu; Nam, Soo Woo

    2013-09-01

    This study presents the microstructure and high cycle fatigue performance of lap shear joints of dual phase steel (DP590) welded using gas metal arc welding (GMAW) and plasma arc welding (PAW) processes. High cycle fatigue tests were conducted on single and double lap joints under a load ratio of 0.1 and a frequency of 20 Hz. In order to establish a basis for comparison, both weldments were fabricated to have the same weld depth in the plate thickness. The PAW specimens exhibited a higher fatigue life, a gentle S-N slope, and a higher fatigue limit than the GMAW specimens. The improvement in the fatigue life of the PAW specimens was primarily attributed to the geometry effect that exhibited lower and wider beads resulting in a lower stress concentration at the weld toe where cracks initiate and propagate. Furthermore, the microstructural constituents in the heat-affected zone (HAZ) of the PAW specimens contributed to the improvement. The higher volume fraction of acicular ferrite in the HAZ beneath the weld toe enhanced the PAW specimen's resistance to fatigue crack growth. The double lap joints displayed a higher fatigue life than the single lap joints without changing the S-N slope.

  13. An Experimental Investigation on the Effect of Addition of Ternary Blend on the Mix Design Characteristics of High Strength Concrete using Steel Fibre

    Science.gov (United States)

    Sinha, Deepa A., Dr; Verma, A. K., Dr

    2017-08-01

    This paper presents the results of M60 grade of concrete. M60 grade of concrete is achieved by maximum density technique. Concrete is brittle and weak in tension and develops cracks during curing and due to thermal expansion / contraction over a period ot time. Thus the effect of addition of 1% steel fibre is studied. For ages, concrete has been one of the widely used materials for construction. When cement is manufactured, every one ton of cement produces around one ton of carbon dioxide leading to global warming and also as natural resources are finishing, so use of supplementary cementitious material like alccofine and flyash is used as partial replacement of cement is considered. The effect of binary and ternary blend on the strength characteristics is studied. The results indicate that the concrete made with alccofine and flyash generally show excellent fresh and hardened properties. The ternary system that is Portland cement-fly ash-Alccofine concrete was found to increase the strength of concrete when compared to concrete made with Portland cement or even from Portland cement and fly ash.

  14. Behaviour of high-strength concrete incorporating ground ...

    African Journals Online (AJOL)

    of tests were carried out on concrete incorporating Ground Granulated Blast Furnace Slag (GGBFS) of “Mittal steel Annaba” (Algeria) ... Keywords: High strength concrete- fillers- high-temperature- polypropylene fibres- Ground granulated. Furnace Slag ..... hybrid fibre reinforced high strength concrete after heat exposition ...

  15. Laser-Beam Welding Impact on the Deformation Properties of Stainless Steels When Used for Automotive Applications

    Directory of Open Access Journals (Sweden)

    Evin Emil

    2016-09-01

    Full Text Available Materials other than standard and advanced high strength steels are remarkable for the thin-walled structures of the car-body in recent years in order to safety enhancement, weight and emission reduction, corrosion resistance improvement. Thus, there are presented in the paper the deformation properties of laser welded austenitic AISI 304 and ferritic AISI 430 stainless steels compared to these one measured for the high strength low alloyed steel H220PD. The properties were researched by tensile test and 3-point bending test with fixed ends on specimens made of basic material and laser welded one. The specimens were welded by solid state fiber laser YLS-5000 in longitudinal direction (the load direction. The deformation properties such as strength, stiffness and deformation work were evaluated and compared. The strength and stiffness were calculated from tensile test results and the deformation work was calculated from both, tensile test and 3-point bending test results. There has been found only minor effect of laser welding to the deformation properties for high strength low alloyed steel H220PD and austenitic stainless steel AISI 304. Otherwise, the laser welding strongly influenced the deformation work of the ferritic stainless steel AISI 430 as well as the elongation at tensile test.

  16. High Strength-High Ductility Combination Ultrafine-Grained Dual-Phase Steels Through Introduction of High Degree of Strain at Room Temperature Followed by Ultrarapid Heating During Continuous Annealing of a Nb-Microalloyed Steel

    Science.gov (United States)

    Deng, Yonggang; Di, Hongshuang; Hu, Meiyuan; Zhang, Jiecen; Misra, R. D. K.

    2017-07-01

    Ultrafine-grained dual-phase (UFG-DP) steel consisting of ferrite (1.2 μm) and martensite (1 μm) was uniquely processed via combination of hot rolling, cold rolling and continuous annealing of a low-carbon Nb-microalloyed steel. Room temperature tensile properties were evaluated and fracture mechanisms studied and compared to the coarse-grained (CG) counterpart. In contrast to the CG-DP steel, UFG-DP had 12.7% higher ultimate tensile strength and 10.7% greater uniform elongation. This is partly attributed to the increase in the initial strain-hardening rate, decrease in nanohardness ratio of martensite and ferrite. Moreover, a decreasing number of ferrite grains with {001} orientation increased the cleavage fracture stress and increased the crack initiation threshold stress with consequent improvement in ductility UFG-DP steel.

  17. Effect of alloy elements on the anti-corrosion properties of low alloy ...

    Indian Academy of Sciences (India)

    Unknown

    Abstract. Effect of alloy elements on corrosion of low alloy steel was studied under simulated offshore condi- tions. The results showed that the elements Cu, P, Mo, W, V had evident effect on corrosion resistance in the atmosphere zone; Cu, P, V, Mo in the splash zone and Cr, Al, Mo in the submerged zone. Keywords.

  18. Cadmium Alternatives for High-Strength Steel

    Science.gov (United States)

    2011-09-22

    the course of 30 years and most recently processed in Europe at Aluminal Corporation. The process was licensed in the United States to AlumiPlate...30 years and licensed in 1995 in the United States to AlumiPlate, Inc. In Europe, the company Aluminal GmbH & Co. was the manufacturer for the...free from blisters, pits, nodules, burning, contaminants, excessive powder and other apparent defects MIL-STD-870; AMS-QQ-P-416 Throwing Power

  19. Development of a new low alloy steel for high pressure low pressure mono-block steam turbine rotor. Koteiatsu ittai gata joki turbine rotor yo shin tainetsu ko 2 1/4 Cr-Mo-V ko no kaihatsu

    Energy Technology Data Exchange (ETDEWEB)

    Tsuji, I.; Matsuo, A. (Mitsubishi Heavy Industries, Ltd., Tokyo (Japan). Takasago Technical Inst. Mitsubishi Heavy Industries, Ltd., Tokyo (Japan). Takasago Machinary Works)

    1990-07-01

    The compound power plant, combination of a steam turbine and a gas turbine, is drawing public attention from the viewpoints of energy saving and economy, and in this connection, high pressure-low pressure mono-block steam turbines are being adopted. In addition, high pressure-low pressure mono-block type turbines are also adopted for the conventional intermediate capacity steam turbines and their output is increasing. One of the material technologies capable for responding the above requirements is to develop the economical steam turbine rotor material which has the high temperature strength at the same level as the conventional high pressure rotor material, 1CrMoV steel on the high pressure side and on the low pressure side, excellent strength and toughness at the room temperature even if it becomes larger than the conventional rotor material. In this article, is reported the development of 2 {1/4} CrMoV steel which was made with reference to the conventional rotor material, 1CrMoV steel and the conventional boiler material, 2 {1/4} CrMoV steel. As the results of various experiments carried out on this new material, it was ascertained that this steel maintained its good toughness even for a large rotor of 2000mm in diameter made thereof and showed sufficient proof stress on both high and low pressure sides. 14 refs., 16 figs., 3 tabs.

  20. Electrochemical corrosion behavior of X52 and X60 steels in carbon dioxide containing saltwater solution

    OpenAIRE

    Rihan Omar Rihan

    2012-01-01

    X52 and X60 high strength low alloy (HSLA) steels are widely used in the construction of petroleum pipelines. This paper discusses the corrosion resistance of X52 and X60 steels in CO2 containing saltwater at pH 4.4 and 50 ºC. A circulating flow loop system inside an autoclave was used for conducting the experimental work. The rotating impeller speed was 2000 rpm. The corrosion rate was monitored using in situ electrochemical methods such as potentiodynamic sweep, linear polarization resistan...

  1. Intergranular brittle fracture of a low alloy steel induced by grain boundary segregation of impurities: influence of the microstructure; Rupture intergranulaire fragile d'un acier faiblement allie induite par la segregation d'impuretes aux joints de grains: influence de la microstructure

    Energy Technology Data Exchange (ETDEWEB)

    Raoul, St

    1999-07-01

    The study contributes to improve the comprehension of intergranular embrittlement induced by the phosphorus segregation along prior austenitic grain boundaries of low alloy steels used in pressurized power reactor vessel. A part of this study was performed using a A533 steel which contains chemical fluctuations (ghost lines) with two intensities. Axi-symmetrically notched specimens were tested and intergranular brittle de-cohesions were observed in the ghost lines. The fracture initiation sites observed on fracture surfaces were identified as MnS inclusions. A bimodal statistic obtained in a probabilistic model of the fracture is explained by the double population of ghost lines' intensities. A metallurgical study was performed on the same class of steel by studying the influence of the microstructure on the susceptibility to temper embrittlement. Brittle fracture properties of such microstructures obtained by dilatometric experiments were tested on sub-sized specimens to measure the V-notched fracture toughness. Fraction areas of brittle fracture modes were determined on surface fractures. A transition of the fracture mode with the microstructure is observed. It is shown that tempered microstructures of martensite and lower bainite are more susceptible to intergranular embrittlement than tempered upper bainitic microstructure. The intergranular fracture is the most brittle mode. The analysis of crystalline mis-orientations shows a grain boundary structure appreciably more coherent for tempered microstructures of martensite and lower bainite. The higher density of randomgrain boundaries is susceptible to drag the phosphorus in the upper bainitic matrix and to make the quantity of free phosphorus decreasing. Microstructure observations show a difference in the size and the spatial distribution of carbides, essentially cementite, between tempered martensite and upper bainite. It can explain the bigger susceptibility of this last microstructure to cleavage mode

  2. Development of structural steels for nuclear application

    Energy Technology Data Exchange (ETDEWEB)

    Hong, Jun Hwa; Chi, S. H.; Ryu, W. S.; Lee, B. S.; Kim, D. H.; Kim, J. H.; Oh, Y. J.; Byun, T. S.; Yoon, J. H.; Park, D. K.; Oh, J. M.; Cho, H. D.; Kim, H.; Kim, H. D.; Kang, S. S.; Kim, J. W.; Ahn, S. B.

    1997-08-01

    To established the bases of nuclear structural material technologies, this study was focused on the localization and improvement of nuclear structural steels, the production of material property data, and technology developments for integrity evaluation. The important test and analysis technologies for material integrity assessment were developed, and the materials properties of the pressure vessel steels were evaluated systematically on the basis of those technologies, they are microstructural characteristics, tensile and indentation deformation properties, impact properties, and static and dynamic fracture toughness, fatigue and corrosion fatigue etc. Irradiation tests in the research reactors were prepared or completed to obtain the mechanical properties of irradiated materials. The improvement of low alloy steel was also attempted through the comparative study on the manufacturing processes, computer assisted alloy and process design, and application of the inter critical heat treatment. On the other hand, type 304 stainless steels for reactor internals were developed and tested successfully. High strength type 316LN stainless steels for reactor internals were developed and the microstructural characteristics, corrosion resistance, mechanical properties at high temperatures, low cycle fatigue property etc. were tested and analyzed in the view point of the effect of nitrogen. Type 347 stainless steels with high corrosion resistance and toughness for pipings and tubes and low-activated Cr-Mn steels were also developed and their basic properties were evaluated. Finally, the martensitic stainless steels for turbine blade were developed and tests. (author). 242 refs., 100 tabs., 304 figs.

  3. Study on the correlation of toughness with chemical composition and tensile test results in microalloyed API pipeline steels

    Directory of Open Access Journals (Sweden)

    Pouraliakbar H.

    2015-01-01

    Full Text Available In this investigation, an artificial neural network model with feed forward topology and back propagation algorithm was developed to predict the toughness (area underneath of stress-strain curve of high strength low alloy steels. The inputs of the neural network included the weight percentage of 15 alloying elements and the tensile test results such as yield strength, ultimate tensile strength and elongation. Developing the model, 118 different steels from API X52 to X70 grades were used. The developed model was validated with 26 other steels from the data set that were not used for the model development. Additionally, the model was also employed to predict the toughness of 26 newly tested steels. The predicted values were in very good agreement with the measured ones indicating that the developed model was very accurate and had the great ability for predicting the toughness of pipeline steels.

  4. The influence of molybdenum on stress corrosion in Ultra Low Carbon Steels with copper addition

    Directory of Open Access Journals (Sweden)

    M. Mazur

    2010-07-01

    Full Text Available The influence of molybdenum content on the process of stress corrosion of ultra-low carbon structural steels with the addition of copper HSLA (High Strength Low Alloy was analyzed. The study was conducted for steels after heat treatment consisting of quenching andfollowing tempering at 600°C and it was obtained microstructure of the tempered martensite laths with copper precipitates and the phaseLaves Fe2Mo type. It was found strong influence of Laves phase precipitate on the grain boundaries of retained austenite on rate anddevelopment of stress corrosion processes. The lowest corrosion resistance was obtained for W3 steel characterized by high contents ofmolybdenum (2.94% Mo which should be connected with the intensity precipitate processes of Fe2Mo phase. For steels W1 and W2which contents molybdenum equals 1.02% and 1.88%, respectively were obtained similar courses of corrosive cracking.

  5. Experimental and numerical studies of the effect of plasticity mechanisms on the brittle rupture by cleavage in low alloy steels; Etudes experimentale et numerique de l'effet des mecanismes de plasticite sur la rupture fragile par clivage dans les aciers faiblement allies

    Energy Technology Data Exchange (ETDEWEB)

    Libert, M

    2007-09-15

    It is indispensable to guarantee the integrity of PWR reactor vessels during an accidental running: in this context, the understanding and the modelling of the mechanisms of brittle rupture of steels are decisive elements of the complicated estimation of the service life of reactor vessels. The models of local approach of rupture by cleavage are one of the main tools of anticipation of the tensile strength of low alloy steels. In this work, the effect of the stresses heterogeneities in a local criteria of initiation of cleavage has been taken into account. The results of the microstructure calculations are used for proposing a statistical description of the local stresses distribution evolution. This statistical approach allows to propose a local approach model of the rupture depending both of the mechanical heterogeneities and of the sizes distributions of the defects. The behaviour of the material and its evolution are characterized at the microscopic and macroscopic scales in the temperature range [25 C, -196 C]. Simple tensile tests, velocity and temperature rises tests and toughness tests have been carried out. A micro-mechanical behaviour model describing the plastic behaviour below the transition temperature T{sub a} has been proposed. The behaviour law is based on the deformation mechanisms described in bibliography and identified by an inverse method from mechanical tests. The TEM observations and the characterization of the behaviour thermally activated allow to determine several parameters of the model. Simulations are carried out in order to model the main stress distributions {sigma}{sub 1} in two bainite microstructures corresponding to the elementary volume of the local approach of the rupture. The temperature and the triaxiality effects on the evolutions of the heterogeneities is characterized. A distribution function describing the distribution of the local values of {sigma}{sub 1} in terms of the main and equivalent mean stresses {sigma}{sub 1

  6. Mechanical And Microstructural Evaluation Of A Wear Resistant Steel; Avaliacao mecanica e microestrutural de um aco resistente ao desgaste

    Energy Technology Data Exchange (ETDEWEB)

    Santos, F.L.F. dos; Vieira, A.G.; Correa, E.C.S.; Pinheiro, I.P., E-mail: falletti@hotmail.co [Centro Federal de Educacao Tecnologica de Minas Gerais (CEFET/MG), Belo Horizonte, MG (Brazil). Dept. de Engenharia de Materiais

    2010-07-01

    In the present work, the analysis of the mechanical properties and the microstructural features of a high strength low alloy steel, containing chromium, molybdenum and boron, subjected to different heat treatments, was conducted. After austenitizing at 910 deg C for 10 minutes, three operations were carried out: oil quenching, oil quenching followed by tempering at 200 deg C for 120 minutes and austempering at 400 deg C for 5 minutes followed by water cooling. The analysis was performed through tensile and hardness tests, optical microscopy and X-ray diffraction. The bainitic structure led to high strength and toughness, both essential mechanical properties for wear resistant steels. The occurrence of allotriomorphic ferrite and retained austenite in the samples also increased the wear resistance. This phenomenon is related to the fact that both structures are able to be deformed and, in the case of the retained austenite, the transformation induced plasticity TRIP effect may take place as the material is used. (author)

  7. High strength fibre reinforced concrete : Static and fatigue behaviour in bending

    NARCIS (Netherlands)

    Lappa, E.S.

    2007-01-01

    Recently, a number of high strength and ultra high strength steel fibre concretes have been developed. Since these materials seem very suitable for structures that might be prone to fatigue failure, such as bridge decks, the understanding of the static and fatigue bending behaviour is vital. In

  8. Construction and assembly of pipelines using API 5L grade X80 tubes - considerations to be observed with high-strength steels; Construcao e montagem de dutos terrestres utilizando tubos API 5L Gr. X80

    Energy Technology Data Exchange (ETDEWEB)

    Oliveira, Ailton C. de; Rabello, Jose Mauricio B. [PETROBRAS S.A., Rio de Janeiro, RJ (Brazil)

    2005-07-01

    The use of line pipes API 5L Grade X80, at the point of view of designer allows: reduction of wall thickness and pipe weight or increase of design pressure. In the pipeline construction point of view, the use of line pipes API 5L Grade X80 provide some advantages, however some difficulties must be expected in several stages of the construction and assembly. The implications in cost, productivity, inspection and integrity, with the application of these high resistance steels, complying with PETROBRAS Standard N - 464 Construcao, Montagem e Condicionamento de Dutos Terrestres (Rev. H - 2004 Dec) and the experience consolidated in pipelines construction abroad were presented. At the design stage, a comparison between pipelines designed using API 5L-X70 and API 5L-X80 was carried out approaching the aspects of variation of thickness, pressure design and design factor. An evaluation of the expected gains when choosing API 5L Grade X80 steels were done, regarding reduction of costs and pipe weight. Regarding API 5L-X80 pipe fabrication, the obtained results were reported, proving that this aspect was already overcome, showing the viability of its production in Brazil. Difficulties were detected regarding construction and assembly stage and showing the need of revision of PETROBRAS standard N-464. (author)

  9. Reduction of the Early Autogenous Shrinkage of High Strength Concrete

    Directory of Open Access Journals (Sweden)

    Drago Saje

    2015-01-01

    Full Text Available The results of a laboratory investigation on the early autogenous shrinkage of high strength concrete, and the possibilities of its reduction, are presented. Such concrete demonstrates significant autogenous shrinkage, which should, however, be limited in the early stages of its development in order to prevent the occurrence of cracks and/or drop in the load-carrying capacity of concrete structures. The following possibilities for reducing autogenous shrinkage were investigated: the use of low-heat cement, a shrinkage-reducing admixture, steel fibres, premoistened polypropylene fibres, and presoaked lightweight aggregate. In the case of the use of presoaked natural lightweight aggregate, with a fraction from 2 to 4 mm, the early autogenous shrinkage of one-day-old high strength concrete decreased by about 90%, with no change to the concrete's compressive strength in comparison with that of the reference concrete.

  10. Stress corrosion cracking of several high strength ferrous and nickel alloys

    Science.gov (United States)

    Nelson, E. E.

    1971-01-01

    The stress corrosion cracking resistance of several high strength ferrous and nickel base alloys has been determined in a sodium chloride solution. Results indicate that under these test conditions Multiphase MP35N, Unitemp L605, Inconel 718, Carpenter 20Cb and 20Cb-3 are highly resistant to stress corrosion cracking. AISI 410 and 431 stainless steels, 18 Ni maraging steel (250 grade) and AISI 4130 steel are susceptible to stress corrosion cracking under some conditions.

  11. 1998 Annual Study Report. Standardization of methods for evaluating characteristics of high-strength, large-diameter steel pipes for superhigh-pressure natural gas pipelines; 1998 nendo seika hokokusho. Chokoatsu tennen gas pipeline yo kokyodo daikei kokan no tokusei hoho no hyojunka

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1999-03-01

    The pipelines for safely transmitting superhigh-pressure natural gas should have excellent characteristics. The steel pipe is required to have a sufficient toughness, more concretely Charpy impact-absorbing energy, to prevent propagating shear fracture characteristic of natural gas pipelines. Recently, the natural gas pipeline is increasingly required to have higher design pressures (15 Mpa or higher) and grade (X80 or higher). In order to develop the techniques for simulating crack propagation in the propagating shear fracture of natural gas pipe lines as part of the programs to cope with these trends, the 1998 efforts were directed to reviewing the research results obtained so far and analysis of the problems to be solved and tasks to be taken, based on which the analytical procedure for gas releasing phenomena during the fracture process was basically developed, the material characteristic data were collected by the laboratory scale toughness tests, and the preliminary tests with rupture disks were conducted to verify the above analytical procedure. These efforts have established the bases for evaluating the characteristics of high-strength, large-diameter steel pipes in the light of safety against fracture, and greatly advanced the program towards the final target of developing the international specification drafts for toughness. (NEDO)

  12. Microstructure and Failure Analysis of Flash Butt Welded HSLA 590CL Steel Joints in Wheel Rims

    Science.gov (United States)

    Lu, Ping; Xu, Zhixin; Shu, Yang; Ma, Feng

    2017-02-01

    The aim of the present investigation was to evaluate the microstructures, mechanical properties and failure behavior of flash butt welded high strength low alloy 590CL steel joints. Acicular ferrite, Widmanstatten ferrite and granular bainite were observed in the weld. The micro-hardness values of the welded joints varied between 250 HV and 310 HV. The tensile strength of the welded joints met the strength standard of the wheel steel. The Charpy V-notch impact absorbing energy of the welded joints was higher than the base metal, and the impact fracture of the welded joints was composed of shearing and equiaxed dimples. The fracture mode of the wheel rim in the flaring and expanding process was brittle fracture and ductile fracture, respectively. A limited deviation was found in the terminal of the crack for the wheel in the flaring process. A transition from the weld to the Heat Affected Zone was observed for the wheel in the expanding process.

  13. ABRASION RESISTANCE ESTIMATION OF HIGH STRENGTH CONCRETE

    Directory of Open Access Journals (Sweden)

    Şemsi YAZICI

    2007-01-01

    Full Text Available This study gives the results of a laboratory investigation undertaken to determine the relationship between mechanical properties (compressive and flexural strengths and abrasion resistance of 65-85 MPa high strength concretes incorporating silica fume, fly ash and silica fume-fly ash mixtures as supplementary cementing materials. A series of six different concrete mixtures including a control high strength concrete mixture (C1, and five high strength concrete mixtures (C2, C3, C4, C5, C6 incorporating supplementary cementing materials, were manufactured. The compressive strength, flexural strength, and abrasion resistance were determined for each mixture at 28-days. Mathematical expressions were suggested to estimate the abrasion resistance of concrete regarding their compressive strength and flexural strength.

  14. Corrosion Assessment Guidance for High Strength Steels (Phase 1)

    Science.gov (United States)

    2009-08-01

    The continuing worldwide demand for natural gas presents major challenges to pipeline operators. There is increasing need to construct long distance, high capacity transmission pipelines, particularly in the more remote areas of Arctic North America,...

  15. Hydrogen Assisted Cracking of High Strength Steel Welds

    Science.gov (United States)

    1988-05-01

    AG . 69 floveof Shieldin~ga % i.* *i • f, s’ eiettrode gop3.5mm 9 ti ’s I *eloirrae~ gap 1.2 3𔃿f’. - apa 71.. 6- ID , --- A - - -- - - 10 12 I 1 18...Institute of Technology, Metallurgical and Materials Engineering Department, Chicago, IL 60616 1 ATTN: Dr. Norma ’ Breyer Director, U.S. Army Materials

  16. Navy High-Strength Steel Corrosion-Fatigue Modeling Program

    Science.gov (United States)

    2006-10-01

    For elastic-plastic materials additional coefficients can be formula- based: the yield strength, the Ramberg - Osgood parameters, etc. The formulae...analysis codes having three different solution techniques (h-version finite element analy- sis in ABAQUS , p-version finite element analysis in StressCheck...inches] St re ss C on ce nt ra tio n Fa ct or ABAQUS BEASY StressCheck D=0.0625” D=0.25” D=1.0” Figure 5.2.5-1. Analysis Results of Various

  17. Durability improvement assessment in different high strength ...

    Indian Academy of Sciences (India)

    This paper provides an insight into a new biotechnological method based on calcite precipitation for achieving high strength bio-concrete durability. It is very clear that mineral precipitation has the potential to enhance construction material resistance towards degradation procedures. The appropriate microbial cell ...

  18. Laser-ultrasonic absorption measurements in low carbon steels

    Energy Technology Data Exchange (ETDEWEB)

    Moreau, A.; Lord, M.; Levesque, D.; Dubois, M.; Bussiere, J.F. [Institut des Materiaux Industriels, Boucherville, Que. (Canada)

    2000-09-28

    We have refined the contactless laser-ultrasound reverberation technique to measure ultrasonic absorption on small metallic samples. In this technique, a sample is supported by a holder which is ultrasonically decoupled from the sample. A pulsed laser is used to generate an acoustic pulse. After the pulse has mode converted and scattered sufficiently to fully insonify the sample, the decrease in the noise-like ultrasonic signal is recorded as a function of time using a laser-interferometer. A joint time-frequency analysis technique is used to extract an absorption spectrum from the signal. In this paper, the technique is demonstrated in a frequency bandwidth ranging from 1 to 7 MHz, and in a dynamic range of 0.003 to 0.3 dB {mu}s{sup -1}. Measurements made on samples of three low-carbon steel grades, namely ultra low carbon (ULC), low carbon (LC), and high strength, low-alloy steels (HSLA), clearly show that ultrasonic absorption varies with steel grade. The technique was utilized to study the effect of a magnetic field on the ultrasonic absorption of an annealed ultra low carbon steel sample. It was found that magnetoelastic effects are responsible for a large fraction of the total absorption. (orig.)

  19. Effect of V and N on the microstructure evolution during continuous casting of steel

    Science.gov (United States)

    Santillana, B.; Eskin, D. G.; Boom, R.; Katgerman, L.

    2012-01-01

    Low Carbon (LC) steel is not expected to be sensitive to hot tearing and/or cracking while microalloyed steels are known for their high cracking sensitivity during continuous casting. Experience of the Direct Sheet Plant caster at Tata Steel in Ijmuiden (the Netherlands), seems to contradict this statement. It is observed that a LC steel grade has a high risk of cracking alias hot tearing, while a High Strength Low Alloyed (HSLA) steel has a very low cracking occurrence. Another HSLA steel grade, with a similar composition but less N and V is however very sensitive to hot tearing. An extreme crack results in a breakout. A previous statistical analysis of the breakout occurrence reveals a one and a half times higher possibility of a breakout for the HSLA grade compared to the LC grade. HSLA with extra N, V shows a four times smaller possibility of breakout than LC. This study assigns the unexpected effect of the chemical composition on the hot tearing sensitivity to the role of some alloying elements such as V and N as structure refiners.

  20. Experimental Investigation of the Fracture Behaviour of Reinforced Ultra High Strength Concrete

    DEFF Research Database (Denmark)

    Ulfkjær, J. P.; Henriksen, M. S.; Aarup, B.

    the structural behaviour of a very high strength cement based material with and without steel fibres is investigated. A simple structural geometry has been tested, namely a beam subjected to three point bending. The results shows that the increase of ductility of the material also gives a more ductile behaviour...

  1. Experiments and fracture modeling of high-strength pipelines for high and low stress triaxialities

    NARCIS (Netherlands)

    Walters, C.L.; Kofiani, K.; Nonn, A.; Wierzbicki, T.; Kalwa, C.

    2012-01-01

    This paper provides results from a comprehensive study on mechanical characterization of high-strength pipeline steel, grade X100 using experimental and numerical methods. The material was characterized for anisotropic plasticity, fracture initiation for various states of stress, (pre-cracked)

  2. Initiation fracture toughness of HSLA steel through automatic measurement of stretch zone

    Energy Technology Data Exchange (ETDEWEB)

    Tarafder, M.; Swati Dey; Dash, B.; Sivaprasad, S.; Tarafder, S. [National Metallurgical Laboratory, Jamshedpur (India)

    2004-12-15

    Stretch zones are formed due to crack tip blunting in ductile materials before the initiation of a crack. Using special edge detection filters, an automatic measurement procedure based on image analysis (IA) for estimating stretch zone dimensions has been proposed. The in house developed software based on the proposed technique requires only fractographic images to automatically define stretch zone boundaries. Employing the proposed technique, stretch zone measurements were carried out on a high strength low alloy (HSLA) steel. The initiation fracture toughness of this HSLA steel has been estimated using these stretch zone dimensions. A comparison of measured stretch zone dimensions with the crack tip blunting region of the fracture resistance curve revealed that the blunting behaviour is non-linear and the data range normally considered for constructing the blunting line is inadequate to represent this non-linearity for these steels. Prediction of initiation fracture toughness (J{sub i}) in high strength, high toughness materials therefore requires blunting line estimation from a modified data range. An upper bound blunting line data range is proposed for accurate prediction of {delta}a{sub cr} (SZW) and J{sub i}. The results of this study indicate that the IA technique can be used effectively for accurate determination of SZW, SZD, J{sub i}, and J{sub Q}. It is also noted that for materials with non-linear blunting behaviour, SZW is a better parameter than SZD for predicting J{sub i} and J{sub Q}. (author)

  3. High Strength and High Modulus Electrospun Nanofibers

    OpenAIRE

    Jian Yao; Cees W. M. Bastiaansen; Ton Peijs

    2014-01-01

    Electrospinning is a rapidly growing polymer processing technology as it provides a viable and simple method to create ultra-fine continuous fibers. This paper presents an in-depth review of the mechanical properties of electrospun fibers and particularly focuses on methodologies to generate high strength and high modulus nanofibers. As such, it aims to provide some guidance to future research activities in the area of high performance electrospun fibers.

  4. Effect of Hybrid Fibers on the Mechanical Properties of High Strength Concrete

    Directory of Open Access Journals (Sweden)

    Hamid H. Hussein, Saeed K. Rejeb Hayder T. Abd

    2014-04-01

    Full Text Available In this study, high strength concrete of 75 MPa compressive strength was investigated. The experimental program was designed to study the effect of fibers and hybrid fibers (steel and polypropylene fibers on the fresh (workability and wet density and hardened properties (compressive strength, splitting strength, flexural strength and dry density of high strength concrete. Results show that decreases in slump flow of all concrete mixtures containing steel, polypropylene and hybrid fibers compared with control mix (0% fiber. Hybrid high strength concrete with steel and polypropylene fibers showed superior compressive, splitting, flexural strengths over the others concrete without or with single fibers content. The test results indicate that the maximum increase in compressive and flexural strengths are obtains with the hybridization ratio (70%steel + 30% polypropylene and were equal to 14.54% and 23.34% respectively, compared with the control mix. While, the maximum increase in splitting tensile strength with (100% steel fiber + 0 polypropylene is 21.19%. 

  5. Effects of Welding Heat Input on Microstructure and Electrochemical Behavior of Flux-Cored Arc-Welded Q690 HSLA Steel

    Directory of Open Access Journals (Sweden)

    Kai Wang

    2018-01-01

    Full Text Available In this work, the weld metal (WM for the Q690 high-strength low-alloy (HSLA steel was prepared through flux-cored arc welding (FCAW at 10 kJ/cm and 20 kJ/cm heat inputs. The effect of welding heat input on the relationship between the microstructural factors and the electrochemical behavior of the FCAW Q690 steel was studied. Due to the fine grain and acicular ferrite affected by the 10 kJ/cm low heat input, the WM presented similar electrochemical behavior to the Q690 base metal, which would minimize the risk of galvanic corrosion. Also, at 20 kJ/cm of high welding heat input, the WM with higher-sized bainite structure was prone to galvanic corrosion risk minimization.

  6. Interfacial (Fiber-matrix) Properties of High-strength Mortar (150 MPa) from Fiber Pullout

    DEFF Research Database (Denmark)

    Shannag, M.J.; Brincker, Rune; Hansen, Will

    1996-01-01

     The steel fiber-matrix properties of high-strength mortar (150 MPa), such as DSP (densified small particle), are obtained and compared to an ordinary strength mortar (40 MPa) using a specially designed fiber pullout apparatus. A new method for estimating the debonding energy of the interfacial z...... DSP mortar has significantly improved interfacial properties compared to ordinary strength mortar. These results are important in the understanding of the role of steel fibers in improving the tensile properties of high-strength, brittle, cement-matrix composites....... The steel fiber-matrix properties of high-strength mortar (150 MPa), such as DSP (densified small particle), are obtained and compared to an ordinary strength mortar (40 MPa) using a specially designed fiber pullout apparatus. A new method for estimating the debonding energy of the interfacial...... zone from the experimental pullout curve is presented. The method is used to separate the areas under the pullout curve corresponding to debonding and friction. The predictions are compared to other methods in the literature. The proposed method seems to provide less variations in the results. The high-strength...

  7. Effects of thermal aging on microstructures of low alloy steel–Ni base alloy dissimilar metal weld interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Kyoung Joon; Kim, Jong Jin [Interdisciplinary School of Green Energy, Ulsan National Institute of Science and Technology (UNIST), 100 Banyeon-ri, Eonyang-eup, Ulju-gun, Ulsan 689-798 (Korea, Republic of); Lee, Bong Ho [National Center for Nanomaterials Technology (NCNT), Pohang University of Science and Technology (POSTECH), 77 Cheongam-ro, Nam-gu, Pohang, Gyeongbuk 790-784 (Korea, Republic of); Bahn, Chi Bum [Argonne National Laboratory, 9700 S. Cass Ave, Lemont, IL 60439 (United States); Kim, Ji Hyun, E-mail: kimjh@unist.ac.kr [Interdisciplinary School of Green Energy, Ulsan National Institute of Science and Technology (UNIST), 100 Banyeon-ri, Eonyang-eup, Ulju-gun, Ulsan 689-798 (Korea, Republic of)

    2013-10-15

    In this study, the advanced instrumental analysis has been performed to investigate the effect of long-term thermal aging on the microstructural evolution in the fusion boundary region between weld metal and low alloy steel in dissimilar metal welds. A representative dissimilar weld mock-up made of Alloy 690-Alloy 152-A533 Gr. B was fabricated and aged at 450 °C for 2750 h. The micro- and nano-scale characterization were conducted mainly near in a weld root region by using optical microscopy, scanning electron microscopy, transmission electron microscopy, and three dimensional atom probe tomography. It was observed that the weld root was generally divided into several regions including dilution zone in the Ni-base alloy weld metal, fusion boundary, and heat-affected zone in the low alloy steel. A steep gradient was shown in the chemical composition profile across the interface between A533 Gr. B and Alloy 152. The precipitation of carbides was also observed along and near the fusion boundary of as-welded and aged dissimilar metal joints. It was also found that the precipitation of Cr carbides was enhanced by the thermal aging near the fusion boundary.

  8. High-strength mineralized collagen artificial bone

    Science.gov (United States)

    Qiu, Zhi-Ye; Tao, Chun-Sheng; Cui, Helen; Wang, Chang-Ming; Cui, Fu-Zhai

    2014-03-01

    Mineralized collagen (MC) is a biomimetic material that mimics natural bone matrix in terms of both chemical composition and microstructure. The biomimetic MC possesses good biocompatibility and osteogenic activity, and is capable of guiding bone regeneration as being used for bone defect repair. However, mechanical strength of existing MC artificial bone is too low to provide effective support at human load-bearing sites, so it can only be used for the repair at non-load-bearing sites, such as bone defect filling, bone graft augmentation, and so on. In the present study, a high strength MC artificial bone material was developed by using collagen as the template for the biomimetic mineralization of the calcium phosphate, and then followed by a cold compression molding process with a certain pressure. The appearance and density of the dense MC were similar to those of natural cortical bone, and the phase composition was in conformity with that of animal's cortical bone demonstrated by XRD. Mechanical properties were tested and results showed that the compressive strength was comparable to human cortical bone, while the compressive modulus was as low as human cancellous bone. Such high strength was able to provide effective mechanical support for bone defect repair at human load-bearing sites, and the low compressive modulus can help avoid stress shielding in the application of bone regeneration. Both in vitro cell experiments and in vivo implantation assay demonstrated good biocompatibility of the material, and in vivo stability evaluation indicated that this high-strength MC artificial bone could provide long-term effective mechanical support at human load-bearing sites.

  9. The investigation of applicability of the Hollomon-Jaffe equation on tempering the HSLA steel

    Directory of Open Access Journals (Sweden)

    A. Patarić

    2009-09-01

    Full Text Available High strength low-alloyed (HSLA Cr-Mn-Si steels belong to a group of steels that can reach their full mechanical properties after quenching and tempering. Those properties depend both on the temperature and time of tempering. Knowing the tempering parameters, it is possible to reach the desired properties of the treated steel. Some results on investigating the Hollomon-Jaffe equation (in parametric form application for tempering of HSLA steel, are shown in this paper. The experiments were performed in real production conditions, using a standard material. The quenching was performed at 870 C, the heating period was always 30 min, with subsequent cooling into the oil bath. The tempering was carried out in temperature range from 480 to 680 C, while tempering time varied from 15 min to 24 h. The degree of tempering is referred through the hardness values changing. The experimental results have shown a pretty well agreement to tempering parameters, included in Hollomon- -Jaffe equation, for this kind of HSLA steel.

  10. Steel Alloy Hot Roll Simulations and Through-Thickness Variation Using Dislocation Density-Based Modeling

    Science.gov (United States)

    Jansen Van Rensburg, G. J.; Kok, S.; Wilke, D. N.

    2017-10-01

    Different roll pass reduction schedules have different effects on the through-thickness properties of hot-rolled metal slabs. In order to assess or improve a reduction schedule using the finite element method, a material model is required that captures the relevant deformation mechanisms and physics. The model should also report relevant field quantities to assess variations in material state through the thickness of a simulated rolled metal slab. In this paper, a dislocation density-based material model with recrystallization is presented and calibrated on the material response of a high-strength low-alloy steel. The model has the ability to replicate and predict material response to a fair degree thanks to the physically motivated mechanisms it is built on. An example study is also presented to illustrate the possible effect different reduction schedules could have on the through-thickness material state and the ability to assess these effects based on finite element simulations.

  11. Prediction of Forming Limit Curves from Hardness for Steels

    Science.gov (United States)

    Pavlina, Erik J.; Van Tyne, Chester J.

    2016-08-01

    This paper presents a method for predicting the strain-based forming limit curve (FLC) for steels using hardness. The stretching side (positive minor strain component) of the FLC was calculated by using a Marciniak-Kuczyński model with a non-quadratic yield function, while the drawing side (negative minor strain component) of the FLC was predicted based on the relationship between the major and minor critical strains, in accordance with the theory of maximum sheet tension for local necking. The requisite parameter that describes the plastic flow behavior (in this case, the strain hardening exponent) was calculated, based on correlations with the measured microhardness. Additionally, the strain rate sensitivity was considered in the model by using a newly developed empirical correlation between hardness and strain rate sensitivity. This hardness-based model was used to predict FLCs that demonstrate good agreement with experimental FLCs of a high-strength low-alloy steel and a dual-phase steel. Equations are provided that enable the calculation of the FLC from given hardness values for different severities of the material inhomogeneity.

  12. Superplasticity of low carbon HSLA steel during bainite transformation. Teitanso teigokinko no beinaito hentai ni okeru chososei kyodo

    Energy Technology Data Exchange (ETDEWEB)

    Nakajima, H.; Yamamoto, S.; Miyaji, H.; Furubayashi, E. (National Research Inst. for Metals, Tsukuba, Ibaraki (Japan))

    1993-12-01

    Recently, the development of high strength low alloy steel (HSLA steel) of untempered type is advanced by using the comparatively high strength and excellent tenacity of the bainite or martensite of carbon remained being transformed. In the present researches, the superplasticity during the bainite transformation due to the continuous cooling and changes of the structure as well as the mechanical properties due to the superplastic deformation are examined with the samples of Mn-Cr-Mo system HSLA steel. The results obtained therefrom are shown as follows. The temperatre range of B[sub S] and bainite transformation is moving to the higher temperature side along with the increasing of the applied stress when it is over 60 MPa. The bainitic structure is composed of the mixture lath-like bainitic ferrite and granular bainitic ferrite in the use of having no applied stress, while the percentage of the latter increases simultaneously with the increasing of the applied stress. Transformation superplastic strain is increasing together with the increasing of the applied stress, and its increasing is over the linear function when the applied stress is above about 50 MPa. 22 refs., 9 figs., 2 tabs.

  13. High strength air-dried aerogels

    Science.gov (United States)

    Coronado, Paul R.; Satcher, Jr., Joe H.

    2012-11-06

    A method for the preparation of high strength air-dried organic aerogels. The method involves the sol-gel polymerization of organic gel precursors, such as resorcinol with formaldehyde (RF) in aqueous solvents with R/C ratios greater than about 1000 and R/F ratios less than about 1:2.1. Using a procedure analogous to the preparation of resorcinol-formaldehyde (RF) aerogels, this approach generates wet gels that can be air dried at ambient temperatures and pressures. The method significantly reduces the time and/or energy required to produce a dried aerogel compared to conventional methods using either supercritical solvent extraction. The air dried gel exhibits typically less than 5% shrinkage.

  14. Plastic collapse load of corroded steel plates

    Indian Academy of Sciences (India)

    ple, Bruneau & Zahrai (1997) and Zuraski & Johnson (1990) have studied fatigue strength of corroded steel specimens taken from aged bridges. Chen et al (2005) have studied mechani- cal properties of low alloy steels in chloride solution. Some research works were also done on structural integrity of aged structures.

  15. Microstructure, Hardness, and Residual Stress Distributions in T-Joint Weld of HSLA S500MC Steel

    Science.gov (United States)

    Frih, Intissar; Montay, Guillaume; Adragna, Pierre-Antoine

    2017-03-01

    This paper investigates the characterization of the microstructure, hardness, and residual stress distributions of MIG-welded high-strength low-alloy S500MC steel. The T-joint weld for 10-mm-thick plates was joined using a two passes MIG welding technology. The contour method was performed to measure longitudinal welding residual stress. The obtained results highlighted a good correlation between the metallurgical phase constituents and hardness distribution within the weld zones. In fact, the presence of bainite and smaller ferrite grain size in the weld-fusion zone might be the reason for the highest hardness measured in this region. A similar trend of the residual stress and hardness distributions was also obtained.

  16. Comprehensive Understanding of Ductility Loss Mechanisms in Various Steels with External and Internal Hydrogen

    Science.gov (United States)

    Takakuwa, Osamu; Yamabe, Junichiro; Matsunaga, Hisao; Furuya, Yoshiyuki; Matsuoka, Saburo

    2017-11-01

    Hydrogen-induced ductility loss and related fracture morphologies are comprehensively discussed in consideration of the hydrogen distribution in a specimen with external and internal hydrogen by using 300-series austenitic stainless steels (Types 304, 316, 316L), high-strength austenitic stainless steels (HP160, XM-19), precipitation-hardened iron-based super alloy (A286), low-alloy Cr-Mo steel (JIS-SCM435), and low-carbon steel (JIS-SM490B). External hydrogen is realized by a non-charged specimen tested in high-pressure gaseous hydrogen, and internal hydrogen is realized by a hydrogen-charged specimen tested in air or inert gas. Fracture morphologies obtained by slow-strain-rate tensile tests (SSRT) of the materials with external or internal hydrogen could be comprehensively categorized into five types: hydrogen-induced successive crack growth, ordinary void formation, small-sized void formation related to the void sheet, large-sized void formation, and facet formation. The mechanisms of hydrogen embrittlement are broadly classified into hydrogen-enhanced decohesion (HEDE) and hydrogen-enhanced localized plasticity (HELP). In the HEDE model, hydrogen weakens interatomic bonds, whereas in the HELP model, hydrogen enhances localized slip deformations. Although various fracture morphologies are produced by external or internal hydrogen, these morphologies can be explained by the HELP model rather than by the HEDE model.

  17. Effect of Microstructure on Torsional Fatigue Endurance of Martensitic Carbon Steel

    National Research Council Canada - National Science Library

    TOYODA, Shunsuke; ISHIGURO, Yasuhide; KAWABATA, Yoshikazu; SAKATA, Kei; SATO, Akio; SAKAI, Jun'ichi

    2009-01-01

    The microstructural influence of martensitic carbon steel on torsional fatigue endurance was investigated, taking into consideration the application of high strength steel electric resistance welded (ERW...

  18. Estudo comparativo de metais de solda de aço de alta resistência obtidos pelos processos eletrodo revestido e arame tubular para aplicação em equipamentos de amarração offshore Comparative study of high strength steel weld metals obtained by the SMAW and FCAW processes for offshore applications and mooring chains

    Directory of Open Access Journals (Sweden)

    Humberto N. Farneze

    2009-06-01

    Full Text Available Realizou-se um estudo comparativo entre os processos eletrodo revestido e arame tubular, considerando-se as propriedades mecânicas e microestruturais de metais de solda de aço de alta resistência, nas condições de como soldado e com tratamento térmico de alívio de tensões (TTAT. Os resultados mostram que os procedimentos adotados para soldagem com arame tubular e eletrodos revestidos possibilitaram obter níveis de resistência mecânica satisfatórios, com exceção do valor de alongamento percentual para o arame tubular, na condição de como soldado. Os ensaios de impacto mostram que ambos os metais de solda apresentam tenacidade ao impacto satisfatória, tanto na condição de como soldado quanto na de TTAT, observando-se que, para o arame tubular, a tenacidade ao impacto é inferior a do eletrodo revestido em ambas as condições, situando-se próximo ao limite do critério de aceitação aplicado de 50 joules a 0ºC, na condição de TTAT. Verificou-se que a produtividade propiciada pelo processo arame tubular foi aproximadamente duas vezes superior ao processo eletrodo revestido. Desta forma, a vantagem inerente ao processo arame tubular deve ser complementada pela consideração do conjunto das propriedades mecânicas obtidas, orientando a seleção adequada do processo de soldagem em particular para aplicação em equipamentos que operam sob condições de fadiga.A comparative study of FCAW and SMAW processes was performed considering the mechanical and microstructural properties of high strength steel weld metals in the as welded and post weld heat treated (PWHT conditions. The results showed that the welding procedures adopted for FCAW and SMAW processes produced satisfactory mechanical properties levels with exception of the percentage elongation for FCAW in the as welded condition. The impact test results show that both weld metals had good impact toughness in the as welded and PWHT conditions. It was observed that the FCAW

  19. Ballistic Characterization Of A Typical Military Steel Helmet

    Directory of Open Access Journals (Sweden)

    Mohamed Ali Maher

    2017-08-01

    Full Text Available In this study the ballistic limit of a steel helmet against a FMJ 919 mm caliber bullet is estimated. The helmet model is the typical polish helmet wz.31.The helmet material showed high strength low alloy steel material of 0.28 carbon content and 9.125 kgm2 areal density. The tensile test according to ASTM E8 showed a tensile strength of 1236.4 MPa .The average hardness value was about HV550. First shooting experiment has been executed using a 9 mm pistol based on 350 ms muzzle velocity at 5m against the simply supported helmet complete penetrations rose in this test were in the form of cracks on the helmet surface and partial penetrations were in the form of craters on the surface whose largest diameter and depth were 43 mm and 20.2 mm consequently .The second experiment was on a rifled gun arrangement 13 bullets of 919 mm caliber were shot on the examined simply supported steel helmet at a zero obliquity angle at different velocities to determine the ballistic limit velocity V50 according to MIL-STD-662F. Three major outcomes were revealed 1 the value V50 which found to be about 390 ms is higher than the one found in literature 360 ms German steel helmet model 1A1. 2 The smallest the standard deviation of the mixed results zone data the most accurate the ballistic limit is. 3Similar to the performance of blunt-ended projectiles impacting overmatching targets tD near 11 or larger It was found that the dominating failure mode of the steel helmet stuck by a hemispherical-nose projectile was plugging mode despite of having tD ratio of about 19 undermatching.

  20. Alternatives to steel grid decks - phase II.

    Science.gov (United States)

    2012-09-01

    The primary objective of this research project was to investigate alternatives to open grid steel decks for movable bridges. Three alternative deck systems, including aluminum deck, ultra-high performance concrete (UHPC)-high-strength steel (HSS) dec...