Butt Welding of 2205/X65 Bimetallic Sheet and Study on the Inhomogeneity of the Properties of the Welded Joint

Science.gov (United States)

Gou, Ning-Nian; Zhang, Jian-Xun; Wang, Jian-Long; Bi, Zong-Yue

2017-04-01

The explosively welded 2205 duplex stainless steel/X65 pipe steel bimetallic sheets were butt jointed by multilayer and multi-pass welding (gas tungsten arc welding for the flyer and gas metal arc welding for the transition and parent layers of the bimetallic sheets). The microstructure and mechanical properties of the welded joint were investigated. The results showed that in the thickness direction, microstructure and mechanical properties of the welded joint exhibited obvious inhomogeneity. The microstructures of parent filler layers consisted of acicular ferrite, widmanstatten ferrite, and a small amount of blocky ferrite. The microstructure of the transition layer and flyer layer consisted of both austenite and ferrite structures; however, the transition layer of weld had a higher volume fraction of austenite. The results of the microhardness test showed that in both weld metal (WM) and heat-affected zone (HAZ) of the parent filler layers, the average hardness decreased with the increasing (from parent filler layer 1 to parent filler layer 3) welding heat input. The results of hardness test also indicated that the hardness of the WM and the HAZ for the flyer and transition layers was equivalent. The tensile test combined with Digital Specklegram Processing Technology demonstrated that the fracturing of the welded joint started at the HAZ of the flyer, and then the fracture grew toward the base metal of the parent flyer near the parent HAZ. The stratified impact test at -5 °C showed that the WM and HAZ of the flyer exhibited lower impact toughness, and the fracture mode was ductile and brittle mixed fracture.

Verification of Strength of the Welded Joints by using of the Aramis Video System

Directory of Open Access Journals (Sweden)

Pała Tadeusz

2017-03-01

Full Text Available In the paper are presented the results of strength analysis for the two types of the welded joints made according to conventional and laser technologies of high-strength steel S960QC. The hardness distributions, tensile properties and fracture toughness were determined for the weld material and heat affect zone material for both types of the welded joints. Tests results shown on advantage the laser welded joints in comparison to the convention ones. Tensile properties and fracture toughness in all areas of the laser joints have a higher level than in the conventional one. The heat affect zone of the conventional welded joints is a weakness area, where the tensile properties are lower in comparison to the base material. Verification of the tensile tests, which carried out by using the Aramis video system, confirmed this assumption. The highest level of strains was observed in HAZ material and the destruction process occurred also in HAZ of the conventional welded joint.

Microstructure of friction stir welded joints of 2017A aluminium alloy sheets.

Science.gov (United States)

Mroczka, K; Dutkiewicz, J; Pietras, A

2010-03-01

The present study examines a friction stir welded 2017A aluminium alloy. Transmission electron microscope investigations of the weld nugget revealed the average grain size of 5 microm, moderate density of dislocations as well as the presence of nanometric precipitates located mostly in grains interiors. Scanning electron microscope observations of fractures showed the presence of ductile fracture in the region of the weld nugget with brittle precipitates in the lower part. The microhardness analysis performed on the cross-section of the joints showed fairly small changes; however, after the artificial ageing process an increase in hardness was observed. The change of the joint hardness subject to the ageing process indicates partial supersaturation in the material during friction stir welding and higher precipitation hardening of the joint.

Electrostimulated recovery of welded joint durability: experiment and model

International Nuclear Information System (INIS)

Semakin, E.V.; Chirakadze, D.Z.; Tsellermaer, V.Ya.; Gromov, V.E.; Sosnin, O.V.

1997-01-01

The possibility to increase the durability of welded joints operating under conditions of low cycle fatigue is shown to be brought about using electric current pulses. Experimental method of recovery of operational capability is demonstrated on welded joints of tool steels R6M5 and 40Kh/ The onset of critical stage of fatigue in the welded joint was determined by ultrasonic testing. Then the specimens were treated with 20 Hz electric pulses with amplitude of 250 MA/M 2 for 100 μs. Such treatment resulted in an increase of time to fracture. The phenomenological model of the process is proposed

Research on fatigue behavior and residual stress of large-scale cruciform welding joint with groove

International Nuclear Information System (INIS)

Zhao, Xiaohui; Liu, Yu; Liu, Yong; Gao, Yuan

2014-01-01

Highlights: • The fatigue behavior of the large-scale cruciform welding joint with groove was studied. • The longitudinal residual stress of the large-scale cruciform welding joint was tested by contour method. • The fatigue fracture mechanism of the large-scale cruciform welding joint with groove was analyzed. - Abstract: Fatigue fracture behavior of the 30 mm thick Q460C-Z steel cruciform welded joint with groove was investigated. The fatigue test results indicated that fatigue strength of 30 mm thick Q460C-Z steel cruciform welded joint with groove can reach fatigue level of 80 MPa (FAT80). Fatigue crack source of the failure specimen initiated from weld toe. Meanwhile, the microcrack was also found in the fusion zones of the fatigue failure specimen, which was caused by weld quality and weld metal integrity resulting from the multi-pass welds. Two-dimensional map of the longitudinal residual stress of 30 mm thick Q460C-Z steel cruciform welded joint with groove was obtained by using the contour method. The stress nephogram of Two-dimensional map indicated that longitudinal residual stress in the welding center is the largest

Modeling of the fracture behavior of spot welds using advanced micro-mechanical damage models

International Nuclear Information System (INIS)

Sommer, Silke

2010-01-01

This paper presents the modeling of deformation and fracture behavior of resistance spot welded joints in DP600 steel sheets. Spot welding is still the most commonly used joining technique in automotive engineering. In overloading situations like crash joints are often the weakest link in a structure. For those reasons, crash simulations need reliable and applicable tools to predict the load bearing capacity of spot welded components. Two series of component tests with different spot weld diameters have shown that the diameter of the weld nugget is the main influencing factor affecting fracture mode (interfacial or pull-out fracture), load bearing capacity and energy absorption. In order to find a correlation between nugget diameter, load bearing capacity and fracture mode, the spot welds are simulated with detailed finite element models containing base metal, heat affected zone and weld metal in lap-shear loading conditions. The change in fracture mode from interfacial to pull-out or peel-out fracture with growing nugget diameter under lap-shear loading was successfully modeled using the Gologanu-Leblond model in combination with the fracture criteria of Thomason and Embury. A small nugget diameter is identified to be the main cause for interfacial fracture. In good agreement with experimental observations, the calculated pull-out fracture initiates in the base metal at the boundary to the heat affected zone.

Welded joint properties of steel 2.25Cr1MoNiNb

International Nuclear Information System (INIS)

Gladis, R.; Ivanek, J.; Gottwald, M.

1981-01-01

Welded joints of steel 08Cr2.25Mo1NiNb for fast reactor steam generators made using manual arc welding with electrodes of identical compositions attain short-term mechanical properties and times to fracture when creep tested that match those of the base material. The reduction of the carbidic phase content in the steel and the welded joint metal did not adversely affect the tensile properties of the welded joint while increasing notch toughness of the heat-affected zone. Reduced carbon and niobium contents in the steel and the welded joint resulted in significant reduction in the proportion of carbidic eutectic particles in both the heat-affected zone and the weld metal. (Ha)

Effect of yield stress matching on ductile fracture behavior of girth welds for X line pipe

Energy Technology Data Exchange (ETDEWEB)

Motohashi, Hiroyuki; Hagiwara, Naoto [Tokyo Gas Co., Ltd. (Japan)

2005-07-01

This paper describes the effects of yield stress matching on the ductile fracture behavior of girth welded joints for X linepipes. Three welded joints were made on an X line pipe using several consumables to obtain about a 20% overmatched, even matched and about a 20% under matched weld metal. For these three welded joints, curved wide plate tensile tests were then conducted with a surface notch in the weld metal. To determine the ductile crack initiation from the surface notch, these tests employed a direct-current electric potential (d-c E P) method. Crack opening displacement, gauge length strain and local strain adjacent to the surface notch were also measured. The ductile crack initiation was successfully detected using the d-c E P method. The yield stress matching significantly affected the ductile crack initiation and fracture behavior, that is, the overmatched welded joint had a higher resistance to ductile fracture than that of the under matched welded joint. The allowable strength matching level was determined from the relationship between the strength matching and the gauge length strain at the ductile crack initiation detected using the d-c E P method. (author)

Microstructure and Fatigue Properties of Laser Welded DP590 Dual-Phase Steel Joints

Science.gov (United States)

Xie, Chaojie; Yang, Shanglei; Liu, Haobo; Zhang, Qi; Cao, Yaming; Wang, Yuan

2017-08-01

In this paper, cold-rolled DP590 dual-phase steel sheets with 1.5 mm thickness were butt-welded by a fiber laser, and the evolution and effect on microhardness, tensile property and fatigue property of the welded joint microstructure were studied. The results showed that the base metal is composed of ferrite and martensite, with the martensite dispersed in the ferrite matrix in an island manner. The microstructure of the weld zone was lath-shaped martensite that can be refined further by increasing the welding speed, while the heat-affected zone was composed of ferrite and tempered martensite. The microhardness increased with increasing welding speed, and the hardness reached its highest value—393.8 HV—when the welding speed was 5 m/min. Static tensile fracture of the welded joints always occurred in the base metal, and the elongation at break was more than 16%. The conditional fatigue limits of the base metal and the weld joints were 354.2 and 233.6 MPa, respectively, under tension-tension fatigue tests with a stress rate of 0.1. After observation of the fatigue fracture morphology, it was evident that the fatigue crack of the base metal had sprouted into the surface pits and that its expansion would be accelerated under the action of a secondary crack. The fatigue source of the welded joint was generated in the weld zone and expanded along the martensite, forming a large number of fatigue striations. Transient breaking, which occurred in the heat-affected zone of the joint as a result of the formation of a large number of dimples, reflected the obvious characteristics of ductile fracture.

Origin of unusual fracture in stirred zone for friction stir welded 2198-T8 Al-Li alloy joints

Energy Technology Data Exchange (ETDEWEB)

Tao, Y. [Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Ni, D.R., E-mail: drni@imr.ac.cn [Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China); Xiao, B.L.; Ma, Z.Y. [Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China); Wu, W.; Zhang, R.X. [AVIC Beijing Aeronautical Manufacturing Technology Research Institute, Beijing 100024 (China); Zeng, Y.S., E-mail: yszeng@hotmail.com [AVIC Beijing Aeronautical Manufacturing Technology Research Institute, Beijing 100024 (China)

2017-05-02

Friction stir welded (FSW) joints of conventional precipitation-hardened aluminum alloys usually fracture in the lowest hardness zone (LHZ) during tension testing. However, all of the FSW joints of a 2198-T8 Al-Li alloy fractured in the stirred zone (SZ) instead of the LHZ with the welding parameters of 800 rpm-200 mm/min and 1600 rpm-200 mm/min under the condition that no welding defects existed in the SZ. The experiment results revealed that lazy S was not the dominant factor resulting in the unusual fracture. The SZ consisted of three subzones, i.e., the shoulder-affected zone, the pin-affected zone, and the transition zone between them. While the former two zones were characterized by fine and equiaxed recrystallized grains, incompletely dynamically recrystallized microstructure containing coarse elongated non-recrystallized grains was observed in the transition zone. The transition zone exhibited the lowest average Taylor factor in the SZ, resulting in a region that was crystallographically weak. Furthermore, obvious lithium segregation at grain boundaries was observed in the transition zone via time-of-flight secondary ion mass spectroscopy analysis, but not in the shoulder-affected zone or the pin-affected zone. The combined actions of both the two factors resulted in the appearance of preferential intergranular fracture in the transition zone and eventually caused the failure in the SZ. The lithium segregation at grain boundaries in the transition zone was closely associated with both the segregation in the base material and the partially dynamically recrystallized microstructure resulting from the inhomogeneous plastic deformation in the SZ.

Origin of unusual fracture in stirred zone for friction stir welded 2198-T8 Al-Li alloy joints

International Nuclear Information System (INIS)

Tao, Y.; Ni, D.R.; Xiao, B.L.; Ma, Z.Y.; Wu, W.; Zhang, R.X.; Zeng, Y.S.

2017-01-01

Friction stir welded (FSW) joints of conventional precipitation-hardened aluminum alloys usually fracture in the lowest hardness zone (LHZ) during tension testing. However, all of the FSW joints of a 2198-T8 Al-Li alloy fractured in the stirred zone (SZ) instead of the LHZ with the welding parameters of 800 rpm-200 mm/min and 1600 rpm-200 mm/min under the condition that no welding defects existed in the SZ. The experiment results revealed that lazy S was not the dominant factor resulting in the unusual fracture. The SZ consisted of three subzones, i.e., the shoulder-affected zone, the pin-affected zone, and the transition zone between them. While the former two zones were characterized by fine and equiaxed recrystallized grains, incompletely dynamically recrystallized microstructure containing coarse elongated non-recrystallized grains was observed in the transition zone. The transition zone exhibited the lowest average Taylor factor in the SZ, resulting in a region that was crystallographically weak. Furthermore, obvious lithium segregation at grain boundaries was observed in the transition zone via time-of-flight secondary ion mass spectroscopy analysis, but not in the shoulder-affected zone or the pin-affected zone. The combined actions of both the two factors resulted in the appearance of preferential intergranular fracture in the transition zone and eventually caused the failure in the SZ. The lithium segregation at grain boundaries in the transition zone was closely associated with both the segregation in the base material and the partially dynamically recrystallized microstructure resulting from the inhomogeneous plastic deformation in the SZ.

Numerical Simulation of Tension Properties for Al-Cu Alloy Friction Stir-Welded Joints with GTN Damage Model

Science.gov (United States)

Sun, Guo-Qin; Sun, Feng-Yang; Cao, Fang-Li; Chen, Shu-Jun; Barkey, Mark E.

2015-11-01

The numerical simulation of tensile fracture behavior on Al-Cu alloy friction stir-welded joint was performed with the Gurson-Tvergaard-Needleman (GTN) damage model. The parameters of the GTN model were studied in each region of the friction stir-welded joint by means of inverse identification. Based on the obtained parameters, the finite element model of the welded joint was built to predict the fracture behavior and tension properties. Good agreement can be found between the numerical and experimental results in the location of the tensile fracture and the mechanical properties.

Evaluation of local deformation behavior accompanying fatigue damage in F82H welded joint specimens by using digital image correlation

International Nuclear Information System (INIS)

Nakata, Toshiya; Tanigawa, Hiroyasu

2012-01-01

Highlights: ► In tensile, the TIG welded joint material was concentrated in the THAZ. ► In tensile, fracture occurred at the point where the axial strain converged. ► In fatigue, fracture occurred at the point where the Max. shear strain converged. ► Many macrocracks and cavities formed in the FGHAZ and THAZ of the cross section. - Abstract: By using digital image correlation, the deformation behaviors of local domains of F82H joint specimens welded using tungsten inert gas (TIG) and electron beam (EB) welding were evaluated during tensile and fatigue testing. In the tensile test specimens, the tensile strength decreased in the TIG-welded joints, and ductility decreased in both the EB- and TIG-welded joints. Because axial strain increased in the tempered heat-affected zone (HAZ) and led to the fracture of the TIG-welded joint, the strength was considered to have decreased because of welding. In fatigue testing, the number of cycles to fracture for the welded joint decreased to less than 40–60% of that for the base metal. For both fracture specimens, the largest value of shear strain was observed in the region approximately between the fine-grained HAZ and tempered HAZ; this shear strain ultimately led to fracture. Cavities and macrocracks were observed in the fine-grained HAZ and tempered HAZ in the cross sections of the fracture specimens, and geometrical damage possibly resulted in the reduction of fatigue lifetime.

Load-Displacement Curves of Spot Welded, Bonded, and Weld-Bonded Joints for Dissimilar Materials and Thickness

Directory of Open Access Journals (Sweden)

E.A. Al-Bahkali

2011-12-01

Full Text Available Three-dimensional finite element models of spot welded, bonded and weld-bonded joints are developed using ABAQUS software. Each model consists of two strips with dissimilar materials and thickness and is subjected to an axial loading. The bonded and weld-bonded joints have specific adhesive thickness. A detailed experimental plan to define many properties and quantities such as, the elastic - plastic properties, modulus of elasticity, fracture limit, and properties of the nugget and heat affected zones are carried out. Experiments include standard testing of the base metal, the adhesive, the nugget and heat affected zone. They also include employing the indentation techniques, and ductile fracture limits criteria, using the special notch tests. Complete load-displacement curves are obtained for all joining models and a comparison is made to determine the best combination.

Creep deformation behavior of weld metal and heat affected zone on 316FR steel thick plate welded joint

International Nuclear Information System (INIS)

Hongo, Hiromichi; Yamazaki, Masayoshi; Watanabe, Takashi; Kinugawa, Junichi; Tanabe, Tatsuhiko; Monma, Yoshio; Nakazawa, Takanori

1999-01-01

Using hot-rolled 316FR stainless plate (50 mm thick) and 16Cr-8Ni-2Mo filler wire, a narrow-gap welded joint was prepared by GTAW (gas tungsten arc welding) process. In addition to conventional round bar specimens of base metals and weld metal, full-thickness joint specimens were prepared for creep test. Creep tests were conducted at 550degC in order to examine creep deformation and rupture behavior in the weld metal of the welded joint. Creep strain distribution on the surface of the joint specimen was measured by moire interferometry. In the welded joint, creep strength of the weld metal zone apart from the surface was larger than that in the vicinity of the surface due to repeating heat cycles during welding. Creep strain and creep rate within the HAZ adjacent to the weld metal zone were smaller than those within the base metal zone. Creep rate of the weld metal zone in the welded joint was smaller than that of the weld metal specimen due to the restraint of the hardened HAZ adjacent to the zone. The full-thickness welded joint specimens showed longer lives than weld metal specimens, though the lives of the latter was shorter than those of the base metal (undermatching). In the full-thickness welded joint specimen, crack started from the last pass layer of the weld metal zone and fracture occurred at the zone. From the results mentioned above, in order to evaluate the creep properties of the welded joint correctly, it is necessary to conduct the creep test using the full-thickness welded joint specimen which includes the weakest zones of the weld metal, the front and back sides of the plate. (author)

The characteristic investigation on narrow-gap TIG weld joint of heavy wall austenitic stainless steel pipe

International Nuclear Information System (INIS)

Shim, Deog Nam; Jung, In Cheol

2003-01-01

Although Gas Tungsten Arc Welding (GTAW or TIG welding) is considered as high quality and precision welding process, it also has demerit of low melting rate. Narrow-gap TIG welding which has narrow joint width reduces the groove volume remarkably, so it could be shorten the welding time and decrease the overall shrinkage in heavy wall pipe welding. Generally narrow-gap TIG welding is used as orbital welding process, it is important to select the optimum conditions for the automatic control welding. This paper looks at the application and metallurgical properties on narrow-gap TIG welding joint of heavy wall large austenitic stainless steel pipe to determine the deposition efficiency, the resultant shrinkage and fracture toughness. The fracture toughness depends slightly on the welding heat input

Joint properties of dissimilar Al6061-T6 aluminum alloy/Ti–6%Al–4%V titanium alloy by gas tungsten arc welding assisted hybrid friction stir welding

International Nuclear Information System (INIS)

Bang, HanSur; Bang, HeeSeon; Song, HyunJong; Joo, SungMin

2013-01-01

Highlights: • Hybrid friction stir welding for Al alloy and Ti alloy joint has been carried out. • Mechanical strength of dissimilar joint by HFSW and FSW has been compared. • Microstructure of dissimilar joint by HFSW and FSW has been compared. - Abstract: Hybrid friction stir butt welding of Al6061-T6 aluminum alloy plate to Ti–6%Al–4%V titanium alloy plate with satisfactory acceptable joint strength was successfully achieved using preceding gas tungsten arc welding (GTAW) preheating heat source of the Ti alloy plate surface. Hybrid friction stir welding (HFSW) joints were welded completely without any unwelded zone resulting from smooth material flow by equally distributed temperature both in Al alloy side and Ti alloy side using GTAW assistance for preheating the Ti alloy plate unlike friction stir welding (FSW) joints. The ultimate tensile strength was approximately 91% in HFSW welds by that of the Al alloy base metal, which was 24% higher than that of FSW welds without GTAW under same welding condition. Notably, it was found that elongation in HFSW welds increased significantly compared with that of FSW welds, which resulted in improved joint strength. The ductile fracture was the main fracture mode in tensile test of HFSW welds

Microstructural Evolution and Fracture Behavior of Friction-Stir-Welded Al-Cu Laminated Composites

Science.gov (United States)

Beygi, R.; Kazeminezhad, Mohsen; Kokabi, A. H.

2014-01-01

In this study, we attempt to characterize the microstructural evolution during friction stir butt welding of Al-Cu-laminated composites and its effect on the fracture behavior of the joint. Emphasis is on the material flow and particle distribution in the stir zone. For this purpose, optical microscopy and scanning electron microscopy (SEM) images, energy-dispersive spectroscopy EDS and XRD analyses, hardness measurements, and tensile tests are carried out on the joints. It is shown that intermetallic compounds exist in lamellas of banding structure formed in the advancing side of the welds. In samples welded from the Cu side, the banding structure in the advancing side and the hook formation in the retreating side determine the fracture behavior of the joint. In samples welded from the Al side, a defect is formed in the advancing side of the weld, which is attributed to insufficient material flow. It is concluded that the contact surface of the laminate (Al or Cu) with the shoulder of the FSW tool influences the material flow and microstructure of welds.

Strength of joints made of BT16 alloy produced by diffusion welding

International Nuclear Information System (INIS)

Kazakov, N.F.; Mashkova, N.A.; Varyanitsa, V.Yu.; Ermakova, N.V.; Fedorova, O.V.

1984-01-01

Strength characteristics of samples prepared by diffusion welding have been estimated for determination of optimum conditions for producing welded joints. It is shown that the joint strength ultimate plasticity and character of the joint fracture should be necessarily taken into accoUnt for choice of the optimum welding regime of homogeneous materials. The following regime is optimum for the titanium VT16 alloy: 1170 K welding temperature, 2 h duration of hold-up at the maximum temperature; 8 MPa pressure. A necessity of recrystallization annealing after welding is demonstrated. The annealing regime is as follows: 1070 K temperature; 60 min hold-up time. This treatment permits to reduce the grain size from the first point to the eighth one

Damage tolerance reliability analysis of automotive spot-welded joints

International Nuclear Information System (INIS)

Mahadevan, Sankaran; Ni Kan

2003-01-01

This paper develops a damage tolerance reliability analysis methodology for automotive spot-welded joints under multi-axial and variable amplitude loading history. The total fatigue life of a spot weld is divided into two parts, crack initiation and crack propagation. The multi-axial loading history is obtained from transient response finite element analysis of a vehicle model. A three-dimensional finite element model of a simplified joint with four spot welds is developed for static stress/strain analysis. A probabilistic Miner's rule is combined with a randomized strain-life curve family and the stress/strain analysis result to develop a strain-based probabilistic fatigue crack initiation life prediction for spot welds. Afterwards, the fatigue crack inside the base material sheet is modeled as a surface crack. Then a probabilistic crack growth model is combined with the stress analysis result to develop a probabilistic fatigue crack growth life prediction for spot welds. Both methods are implemented with MSC/NASTRAN and MSC/FATIGUE software, and are useful for reliability assessment of automotive spot-welded joints against fatigue and fracture

Study on the application of 50 mm thick welded joints without PWHT for containment vessels

Energy Technology Data Exchange (ETDEWEB)

Watanabe, Nozomu; Sakai, Yoshiyuki; Hayashi, Kazutoshi; Higashikubo, Tomohiro (Mitsubishi Heavy Industries. Ltd., Kobe Shipyard and Machinery Works (Japan)); Iida, Kunihiro (Shibaura Inst. of Tech., Dept. of Mechanical Engineering, Tokyo (Japan)); Satou, Masanobu (Mitsubishi Heavy Industries. Ltd., Tkasago Research and Development Center (Japan))

1992-01-01

In order to investigate the propriety of the use of 50 mm thick SGV480 carbon steel which is equivalent to ASTM A516 Gr. 70 without post weld heat treatment for containment vessels, the authors have certified the basic properties of base metal and welded joints of 50 mm thick SGV480 steel plates. The results showed that fracture thoughness of welded joints is high without PWHT and the steel is safe enough without PWHT against embrittlement fracture under the operating conditions. (orig.).

Study on the application of 50 mm thick welded joints without PWHT for containment vessels

International Nuclear Information System (INIS)

Watanabe, Nozomu; Sakai, Yoshiyuki; Hayashi, Kazutoshi; Higashikubo, Tomohiro; Iida, Kunihiro; Satou, Masanobu

1992-01-01

In order to investigate the propriety of the use of 50 mm thick SGV480 carbon steel which is equivalent to ASTM A516 Gr. 70 without post weld heat treatment for containment vessels, the authors have certified the basic properties of base metal and welded joints of 50 mm thick SGV480 steel plates. The results showed that fracture thoughness of welded joints is high without PWHT and the steel is safe enough without PWHT against embrittlement fracture under the operating conditions. (orig.)

A comparative study of the microstructure and properties of 800 MPa microalloyed C-Mn steel welded joints by laser and gas metal arc welding

Energy Technology Data Exchange (ETDEWEB)

Sun, Qian [The State Key Laboratory of Rolling and Automation of Northeastern University, Shenyang 110819 (China); Di, Hong-Shuang, E-mail: hongshuangdi_ral@126.com [The State Key Laboratory of Rolling and Automation of Northeastern University, Shenyang 110819 (China); Li, Jun-Chen [The State Key Laboratory of Rolling and Automation of Northeastern University, Shenyang 110819 (China); Wu, Bao-Qiang [National Key Laboratory for Precision Hot Processing of Metals, Harbin Institute of Technology, Harbin 150001 (China); Misra, R.D.K. [Laboratory for Excellence in Advanced Steel Research, Department of Metallurgical, Material and Biomedical Engineering, University of Texas at El Paso, TX 79968 (United States)

2016-07-04

The differences in microstructure and mechanical properties of laser beam welded (LBW) and gas metal arc welded (GMAW) joints of 800 MPa grade Nb-Ti-Mo microalloyed C-Mn steel of 5 mm thickness were studied. The study suggested that the microstructure in welded seam (WS) of GMAW was acicular ferrite and fine grained ferrite, whereas lath martensite (LM) was obtained in WS of LBW, where inclusions were finer and did not act as nucleation sites for acicular ferrite. The microstructure of coarse-grained HAZ (CGHAZ) obtained using the two welding methods was LM and granular bainite (GB), respectively. The original austenite grain size in CGHAZ of LBW was 1/3 of GMAW. The microstructure of fine-grained HAZ and mixed-grained HAZ using the two welding methods was ferrite and M-A constituents, while that of LBW was significantly fine. The hardness of LBW welded joints was higher than the base metal (BM), which was the initiation site for tensile fracture. The tensile fracture location of GMAW welded joints was in WS. The impact toughness of LBW welded joints was excellent and the impact absorption energy was similar to BM.

Fracture toughness and crack growth resistance of pressure vessel plate and weld metal steels

International Nuclear Information System (INIS)

Moskovic, R.

1988-01-01

Compact tension specimens were used to measure the initiation fracture toughness and crack growth resistance of pressure vessel steel plates and submerged arc weld metal. Plate test specimens were manufactured from four different casts of steel comprising: aluminium killed C-Mn-Mo-Cu and C-Mn steel and two silicon killed C-Mn steels. Unionmelt No. 2 weld metal test specimens were extracted from welds of double V butt geometry having either the C-Mn-Mo-Cu steel (three weld joints) or one particular silicon killed C-Mn steel (two weld joints) as parent plate. A multiple specimen test technique was used to obtain crack growth data which were analysed by simple linear regression to determine the crack growth resistance lines and to derive the initiation fracture toughness values for each test temperature. These regression lines were highly scattered with respect to temperature and it was very difficult to determine precisely the temperature dependence of the initiation fracture toughness and crack growth resistance. The data were re-analysed, using a multiple linear regression method, to obtain a relationship between the materials' crack growth resistance and toughness, and the principal independent variables (temperature, crack growth, weld joint code and strain ageing). (author)

Virtual Welded-Joint Design Integrating Advanced Materials and Processing Technologies

Energy Technology Data Exchange (ETDEWEB)

Yang, Z.; Dong, P.; Liu, S.; Babu, S.; Olson, G.; DebRoy, T.

2005-04-15

The primary goal of this project is to increase the fatigue life of a welded-joint by 10 times and to reduce energy use by 25% through product performance and productivity improvements using an integrated modeling approach. The fatigue strength of a welded-joint is currently the bottleneck to design high performance and lightweight welded structures using advanced materials such as high strength steels. In order to achieve high fatigue strength in a welded-joint it is necessary to manage the weld bead shape for lower stress concentration, produce preferable residual stress distribution, and obtain the desired microstructure for improved material toughness and strength. This is a systems challenge that requires the optimization of the welding process, the welding consumable, the base material, as well as the structure design. The concept of virtual welded-joint design has been proposed and established in this project. The goal of virtual welded-joint design is to develop a thorough procedure to predict the relationship of welding process, microstructure, property, residual stress, and the ultimate weld fatigue strength by a systematic modeling approach. The systematic approach combines five sub-models: weld thermal-fluid model, weld microstructure model, weld material property model, weld residual stress model, and weld fatigue model. The systematic approach is thus based on interdisciplinary applied sciences including heat transfer, computational fluid dynamics, materials science, engineering mechanics, and material fracture mechanics. The sub-models are based on existing models with further development. The results from modeling have been validated with critical experiments. The systematic modeling approach has been used to design high fatigue resistant welds considering the combined effects of weld bead geometry, residual stress, microstructure, and material property. In particular, a special welding wire has been developed in this project to introduce

Microstructure and mechanical properties of resistance upset butt welded 304 austenitic stainless steel joints

International Nuclear Information System (INIS)

Sharifitabar, M.; Halvaee, A.; Khorshahian, S.

2011-01-01

Graphical abstract: Three different microstructural zones formed at different distances from the joint interface in resistance upset butt welding of 304 austenitic stainless steel. Highlights: → Evaluation of microstructure in resistance upset welding of 304 stainless steel. → Evaluation of welding parameters effects on mechanical properties of the joint. → Introducing the optimum welding condition for joining stainless steel bars. -- Abstract: Resistance upset welding (UW) is a widely used process for joining metal parts. In this process, current, time and upset pressure are three parameters that affect the quality of welded products. In the present research, resistance upset butt welding of 304 austenitic stainless steel and effect of welding power and upset pressure on microstructure, tensile strength and fatigue life of the joint were investigated. Microstructure of welds were studied using scanning electron microscopy (SEM). X-ray diffraction (XRD) analysis was used to distinguish the phase(s) that formed at the joint interface and in heat affected zone (HAZ). Energy dispersive spectroscopy (EDS) linked to the SEM was used to determine chemical composition of phases formed at the joint interface. Fatigue tests were performed using a pull-push fatigue test machine and the fatigue properties were analyzed drawing stress-number of cycles to failure (S-N) curves. Also tensile strength tests were performed. Finally tensile and fatigue fracture surfaces were studied by SEM. Results showed that there were three different microstructural zones at different distances from the joint interface and delta ferrite phase has formed in these regions. There was no precipitation of chromium carbide at the joint interface and in the HAZ. Tensile and fatigue strengths of the joint decreased with welding power. Increasing of upset pressure has also considerable influence on tensile strength of the joint. Fractography of fractured samples showed that formation of hot spots at

A Probabilistic Damage Tolerance Concept for Welded Joints

DEFF Research Database (Denmark)

Lassen, T.; Sørensen, John Dalsgaard

2002-01-01

The first part of this paper presented the required statistics and stochastic models for reliability analysis of the fatigue fracture of welded plate joints. This present Part 2 suggests a probabilistic damage tolerance supplement to the design S–N curves for welded joints. The goal is to provide......) will have the same reliability level for the same FDF. This is true at the end of TSL and at earlier stages, i.e. fractions of TSL. The absolute value of TSL is immaterial for a given FDF. In the case of in-service inspection, the inspection interval is also given without dimensions as a fraction of TSL...

Fracture toughness of stainless steel welds

International Nuclear Information System (INIS)

Mills, W.J.

1985-11-01

The effects of temperature, composition and weld-process variations on the fracture toughness behavior for Types 308 and 16-8-2 stainless steel (SS) welds were examined using the multiple-specimen J/sub R/-curve procedure. Fracture characteristics were found to be dependent on temperature and weld process but not on filler material. Gas-tungsten-arc (GTA) welds exhibited the highest fracture toughness, a shielded metal-arc (SMA) weld exhibited an intermediate toughness and submerged-arc (SA) welds yielded the lowest toughness. Minimum-expected fracture properties were defined from lower-bound J/sub c/ and tearing modulus values generated here and in previous studies. Fractographic examination revealed that microvoid coalescence was the operative fracture mechanism for all welds. Second phase particles of manganese silicide were found to be detrimental to the ductile fracture behavior because they separated from the matrix during the initial stages of plastic straining. In SA welds, the high density of inclusions resulting from silicon pickup from the flux promoted premature dimple rupture. The weld produced by the SMA process contained substantially less manganese silicide, while GTA welds contained no silicide inclusions. Delta ferrite particles present in all welds were substantially more resistant to local failure than the silicide phase. In welds containing little or no manganese silicide, delta ferrite particles initiated microvoid coalescence but only after extensive plastic straining

Effect of technological procedures on the crack resistance of nickel alloy welded joints under heat treatment

International Nuclear Information System (INIS)

Bagdasarov, Yu.S.; Sorokin, L.I.; Yakushin, B.F.; Moryashchev, S.F.

1983-01-01

Comparison of the efficiency of some technological procedures directed to the increase of crack resistance of KhN50MBKTYUR (EhP99) alloy welded joints under heat treatment was conducted. Welded joints were manufactured by the methods of electron beam welding, laser welding, automatic argon-arc welding. The latter was conducted by conventional technology as well as with electromagnetic mixing of liquid metal of welding bath, with compulsory cooling of weld matal, with pulse arc. It is shown that the high fracture resistance of welded joints, manufactured by electron beam and laser welding is achieved by combination of high mechanical properties of heat affected zone metal and reduced elastic potential energy margin of residual welding stresses (as compared to argon-arc welding)

Microstructures of a welded joint using an irradiated wrapper tube

International Nuclear Information System (INIS)

Hamada, S.; Watanabe, K.; Hishinuma, A.; Takahashi, I.; Kikuchi, T.

1993-01-01

The behavior of helium in welded joint fabricated using tungsten inert gas (TIG) welding process for a type 316 stainless steel wrapper tube irradiated in a fast reactor was investigated. The wrapper tube was irradiated to (1.5 - 4.2) x 10 26 n/m 2 (helium level of 3 to 9 appm) at 395 - 410 degrees C. All welded joints fractured in the heat-affected zone (HAZ). The microstructures of each portion of the base metal, the HAZ and the fusion zone in a welded joint were examined through a transmission electron microscope. Small helium bubbles were observed in number density of 2 x 10 20 m -3 in the matrix and rarely found on the grain boundaries of the base metal. In the HAZ, small and large helium bubbles mixed and lined up along the grain boundaries. In particular, some of them elongated along the grain boundary. In the matrix of the fusion zone, delta-ferrite phases and unresolved carbides were scattered. Large cavities were attached to these precipitates and also occurred along grain boundaries. These results suggest that the failure in the HAZ of welded joints is attributed to the preferential growth and coalescence of helium bubbles in the grain boundaries of the HAZ caused by weld heat input and stress during welding

Microstructure and mechanical properties of weld-bonded and resistance spot welded magnesium-to-steel dissimilar joints

International Nuclear Information System (INIS)

Xu, W.; Chen, D.L.; Liu, L.; Mori, H.; Zhou, Y.

2012-01-01

Highlights: ► Adhesive reduces shrinkage porosity and stress concentration around the weld nugget. ► Adhesive promotes the formation of intermetallic compounds during weld bonding. ► In Mg/steel joints fusion zone appears only at the Mg side with dendritic structures. ► Weld-bonded Mg/steel joints are considerably stronger than RSW Mg/steel joints. ► Fatigue strength is three-fold higher for weld-bonded joints than for RSW joints. - Abstract: The aim of this study was to evaluate microstructures, tensile and fatigue properties of weld-bonded (WB) magnesium-to-magnesium (Mg/Mg) similar joints and magnesium-to-steel (Mg/steel) dissimilar joints, in comparison with resistance spot welded (RSW) Mg/steel dissimilar joints. In the WB Mg/Mg joints, equiaxed dendritic and divorced eutectic structures formed in the fusion zone (FZ). In the dissimilar joints of RSW and WB Mg/steel, FZ appeared only at Mg side with equiaxed and columnar dendrites. At steel side no microstructure changed in the WB Mg/steel joints, while the microstructure in the RSW Mg/steel joints consisted of lath martensite, bainite, pearlite and retained austenite leading to an increased microhardness. The relatively low cooling rate suppressed the formation of shrinkage porosity but promoted the formation of MgZn 2 and Mg 7 Zn 3 in the WB Mg/steel joints. The added adhesive layer diminished stress concentration around the weld nugget. Both WB Mg/Mg and Mg/steel joints were significantly stronger than RSW Mg/steel joints in terms of the maximum tensile shear load and energy absorption, which also increased with increasing strain rate. Fatigue strength was three-fold higher for WB Mg/Mg and Mg/steel joints than for RSW Mg/steel joints. Fatigue failure in the RSW Mg/steel joints occurred from the heat-affected zone near the notch root at lower load levels, and in the mode of interfacial fracture at higher load levels, while it occurred in the Mg base metal at a maximum cyclic load up to ∼10 kN in

Microstructure and failure mechanisms of refill friction stir spot welded 7075-T6 aluminum alloy joints

International Nuclear Information System (INIS)

Shen, Zhikang; Yang, Xinqi; Zhang, Zhaohua; Cui, Lei; Li, Tielong

2013-01-01

Highlights: ► There is a correlation between the void in the weld and the joint strength. ► The preferable mechanical properties can be obtained by lowering rotational speed. ► The alclad has an adverse effect on the mechanical properties. -- Abstract: In this paper, the microstructure and mechanical properties of 7075-T6 aluminum alloy joints joined by refill friction stir spot welding (RFSSW) were investigated. The keyhole was refilled successfully, and the microstructure of the weld exhibited variations in the grain sizes in the width and the thickness directions. There existed defects (hook, voids, bonding ligament, etc.) associated to the material flow in the weld. Mechanical properties of the joint have been investigated in terms of hardness and tensile/shear and cross-tension test, and the fracture mechanisms were observed by SEM (scanning electron microscope). The hardness profile of the weld exhibited a W-shaped appearance in the macroscopic level, which reached the minimum at the boundary of the sleeve and the clamping ring. The variation laws between tensile/shear and cross-tension strength and processing parameters were rather complicated. The void in the weld played an important role in determining the strength of the joint. On the whole, the preferable strength can be obtained at lower rotational speed. Shear fracture mode was observed under tensile–shear loadings, and nugget debonding, plug type fracture (on the upper sheet) and plug type fracture (on the lower sheet) modes were observed under cross-tension loadings. It was also observed that the main feature affecting the mechanical properties of the joint is the alclad between the upper and lower sheets and the connecting qualities between the stir zone and thermo-mechanically affected zone.

Microstructure and mechanical properties of China low activation martensitic steel joint by TIG multi-pass welding with a new filler wire

Science.gov (United States)

Huang, Bo; Zhang, Junyu; Wu, Qingsheng

2017-07-01

Tungsten Inner Gas (TIG) welding is employed for joining of China low activation martensitic (CLAM) steel. A new filler wire was proposed, and the investigation on welding with various heat input and welding passes were conducted to lower the tendency towards the residual of δ ferrite in the joint. With the optimized welding parameters, a butt joint by multi-pass welding with the new filler wire was prepared to investigate the microstructure and mechanical properties. The microstructure of the joint was observed by optical microscope (OM) and scanning electron microscope (SEM). The hardness, Charpy impact and tensile tests of the joint were implemented at room temperature (25 °C). The results revealed that almost full martensite free from ferrite in the joints were obtained by multipass welding with the heat input of 2.26 kJ/mm. A certain degree of softening occurred at the heat affected zone of the joint according to the results of tensile and hardness tests. The as welded joints showed brittle fracture in the impact tests. However, the joints showed toughness fracture after tempering and relatively better comprehensive performance were achieved when the joints were tempered at 740 °C for 2 h.

Interface and properties of the friction stir welded joints of titanium alloy Ti6Al4V with aluminum alloy 6061

International Nuclear Information System (INIS)

Wu, Aiping; Song, Zhihua; Nakata, Kazuhiro; Liao, Jinsun; Zhou, Li

2015-01-01

Highlights: • Friction stir butt welding of titanium alloy Ti6Al4V and aluminum alloy A6061-T6. • Welding parameters affect interfacial microstructure of the joint. • Welding parameters affect the mechanical property of joint and fracture position. • Joining mechanism of Ti6Al4V/A6061 dissimilar alloys by FSW is investigated. - Abstract: Titanium alloy Ti6Al4V and aluminum alloy 6061 dissimilar material joints were made with friction stir welding (FSW) method. The effects of welding parameters, including the stir pin position, the rotating rate and the travel speed of the tool, on the interface and the properties of the joints were investigated. The macrostructure of the joints and the fracture surfaces of the tensile test were observed with optical microscope and scanning electron microscope (SEM). The interface reaction layer was investigated with transmission electron microscopy (TEM). The factors affecting the mechanical properties of the joints were discussed. The results indicated that the tensile strength of the joints and the fracture location are mainly dependent on the rotating rate, and the interface and intermetallic compound (IMC) layer are the governing factor. There is a continuous 100 nm thick TiAl 3 IMC at the interface when the rotating rate is 750 rpm. When the welding parameters were appropriate, the joints fractured in the thermo-mechanically affected zone (TMAZ) and the heat affected zone (HAZ) of the aluminum alloy and the strength of the joints could reach 215 MPa, 68% of the aluminum base material strength, as well as the joint could endure large plastic deformation

Effects of local mechanical and fracture properties on LBB behavior of a dissimilar metal welded joint in nuclear power plants

Energy Technology Data Exchange (ETDEWEB)

Du, L.Y.; Wang, G.Z., E-mail: gzwang@ecust.edu.cn; Xuan, F.Z.; Tu, S.T.

2013-12-15

Highlights: • Effect of local mechanical and fracture properties on LBB behavior were investigated. • Considering local mechanical properties leads to slightly high LBB curve. • Use of fracture resistance of base or weld will produce non-conservative LBB result. • Local fracture properties of interface region cannot be ignored in LBB analysis. - Abstract: In this paper, three-dimensional finite element models with and without considering local mechanical properties were built for a dissimilar metal welded joint (DMWJ) connected the safe end to pipe-nozzle of a reactor pressure vessel. The inner circumferential surface cracks were postulated at the interface of A508 steel and buttering Alloy52Mb. Based on the elastic–plastic fracture mechanics theory of J-integral, the crack growth stability was analyzed. The effects of the local mechanical and fracture resistance properties on LBB behavior were investigated. The results show that considering local mechanical properties leads to slightly high LBB curve. For the A508/Alloy52Mb interface region cracks in the DMWJ, if the fracture resistance curve of base metal A508 or the buttering Alloy52Mb is used, the non-conservative (unsafe) LBB assessment result will be produced. With increasing the applied bending moment, the degree of un-conservatism in LBB behavior becomes large. Therefore, to obtain accurate LBB assessment results, the local fracture resistance properties of the interface region should be used.

Effect of friction stir lap welding conditions on joint strength of aluminium alloy 6060

International Nuclear Information System (INIS)

Yazdanian, S; Chen, Z W

2009-01-01

Strength of lap joints made by friction stir welding (FSW) depends strongly on how material flows forming the weld nugget zone during FSW and also on how the joint is loaded during testing. Understanding of this processing-property relationship is currently inadequate. In this study, the effects of pin length, welding speed and rotation rate on weld strength using aluminium alloy 6060 were investigated. It has been found that the pin length needed to be slightly greater than the thickness of the sheet for an adequate joint to be established. However, further increase in pin length did not benefit the joint strength. The major factor affecting joint strength has been found to be the rotation speed. An increase in rotation speed resulted in lowering the joint strength. Various modes of fracture have been observed and these modes relate to the degree of hooking and softening. Explanation of how the speed values relate to heat input and material flow and then to the joint strength is given.

Microstructure and mechanical properties of China low activation martensitic steel joint by TIG multi-pass welding with a new filler wire

Energy Technology Data Exchange (ETDEWEB)

Huang, Bo [Key Laboratory of Neutronics and Radiation Safety, Institute of Nuclear Energy Safety Technology, Chinese Academy of Sciences, Hefei, Anhui, 230031 (China); Zhang, Junyu [Key Laboratory of Neutronics and Radiation Safety, Institute of Nuclear Energy Safety Technology, Chinese Academy of Sciences, Hefei, Anhui, 230031 (China); University of Science and Technology of China, Hefei, Anhui, 230027 (China); Wu, Qingsheng, E-mail: qingsheng.wu@fds.org.cn [Key Laboratory of Neutronics and Radiation Safety, Institute of Nuclear Energy Safety Technology, Chinese Academy of Sciences, Hefei, Anhui, 230031 (China)

2017-07-15

Tungsten Inner Gas (TIG) welding is employed for joining of China low activation martensitic (CLAM) steel. A new filler wire was proposed, and the investigation on welding with various heat input and welding passes were conducted to lower the tendency towards the residual of δ ferrite in the joint. With the optimized welding parameters, a butt joint by multi-pass welding with the new filler wire was prepared to investigate the microstructure and mechanical properties. The microstructure of the joint was observed by optical microscope (OM) and scanning electron microscope (SEM). The hardness, Charpy impact and tensile tests of the joint were implemented at room temperature (25 °C). The results revealed that almost full martensite free from ferrite in the joints were obtained by multipass welding with the heat input of 2.26 kJ/mm. A certain degree of softening occurred at the heat affected zone of the joint according to the results of tensile and hardness tests. The as welded joints showed brittle fracture in the impact tests. However, the joints showed toughness fracture after tempering and relatively better comprehensive performance were achieved when the joints were tempered at 740 °C for 2 h. - Highlights: •A new filler material was proposed to control ferrite content in CLAM weld metal. •Heat input affected ferrite content through influencing cooling rate during welding. •Multipass welding was a promising way to eliminate the ferrite in the weld.

Friction Stir Welding of Al-Cu Bilayer Sheet by Tapered Threaded Pin: Microstructure, Material Flow, and Fracture Behavior

Science.gov (United States)

Beygi, R.; Kazeminezhad, M.; Kokabi, A. H.; Loureiro, A.

2015-06-01

The fracture behavior and intermetallic formation are investigated after friction stir welding of Al-Cu bilayer sheets performed by tapered threaded pin. To do so, temperature, axial load, and torque measurements during welding, and also SEM and XRD analyses and tensile tests on the welds are carried out. These observations show that during welding from Cu side, higher axial load and temperature lead to formation of different kinds of Al-Cu intermetallics such as Al2Cu, AlCu, and Al4Cu9. Also, existence of Al(Cu)-Al2Cu eutectic structures, demonstrates liquation during welding. The presence of these intermetallics leads to highly brittle fracture and low strength of the joints. In samples welded from Al side, lower axial load and temperature are developed during welding and no intermetallic compound is observed which results in higher strength and ductility of the joints in comparison with those welded from Cu side.

Effects of different brazing and welding methods on the fracture load of various orthodontic joining configurations.

Science.gov (United States)

Bock, Jens J; Bailly, Jacqueline; Fuhrmann, Robert A

2009-06-01

The aim of this study was to compare the fracture load of different joints made by conventional brazing, tungston inert gas (TIG) and laser welding. Six standardized joining configurations of spring hard quality orthodontic wire were investigated: end-to-end, round, cross, 3 mm length, 9 mm length and 6.5 mm to orthodontic band. The joints were made by five different methods: brazing with universal silver solder, two TIG and two laser welding devices. The fracture loads were measured with a universal testing machine (Zwick 005). Data were analysed with the Mann-Whitney-Wilcoxon and Kruskal-Wallis tests. The significance level was set at Pwelding (Pwelding (826 N). No differences between the various TIG or laser welding devices were demonstrated, although it was not possible to join an orthodontic wire to an orthodontic band using TIG welding. For orthodontic purposes laser and TIG welding are solder free alternatives. TIG welding and laser welding showed similar results. The laser technique is an expensive, but sophisticated and simple method.

Low-temperature cyclic cracking resistance of Fe-Cr-Ni and Fe-Cr-Mn steels welded joints

International Nuclear Information System (INIS)

Ostash, O.P.; Zhmur-Klimenko, V.T.; Yarema, S.Ya.; Yushchenko, K.A.; Strok, L.P.; Belotserkovets, V.I.

1983-01-01

Results of further investigations into regularities of development of low-temperature fatigue fracture of welded oints in 07Kh13G20AN4 steel are presented, they are compared with analogous data traditional cryogenic 0Kh18N10T and 03Kh13AG19 steels. Welded joints have been prepared by means of automatic V-like level arc Welding of plates; 0Kh18N10T and 07Kh13G20AN4 steels have been welded by means of sv-04Kh19N9 wire, 03Kh13AG19 steel-by means of sv-07Kh13AG19 wire. Tests at almost zero (asymmetry coefficient R=0.05) cycle of extension at 15-20 Hz frequency have been conducted on 5 mm thick disk samples at 20 deg C and - 160 deg C according to the given methods. It is shown that by cyclic crack resistance of welded joint zones of 0Kh18N10T steel and chromium-manganese steels at normal temperature the 07Kh13G20AN4 steel exceeds 0Kh18N10T steel, at low temperature it yields to 0Kh18N10T only by fracture toughness of heat affected zones HAZ and weld metal (ne). 07Kh13G20AN4 steel and its welded joints as most hardened and cheap may be a good substituent for 0Kh18N10T steel. Optimization of WM alloying for increase of its cyclic fracture toughness at cryogenic temperatures is necessary

Microstructural characterization of welded zone for Fe{sub 3}Al/Q235 fusion-bonded joint

Energy Technology Data Exchange (ETDEWEB)

Ma Haijun [Key Lab of Liquid Structure and Heredity of Materials, Ministry of Education, Shandong University, Jinan 250061, Shandong Province, Jing Shi Road 73, Shandong (China)], E-mail: hjma123@mail.sdu.edu.cn; Li Yajiang [Key Lab of Liquid Structure and Heredity of Materials, Ministry of Education, Shandong University, Jinan 250061, Shandong Province, Jing Shi Road 73, Shandong (China); Material Science Department, Bauman Moscow State Technical University, Moscow 105005 (Russian Federation); Puchkov, U.A. [Material Science Department, Bauman Moscow State Technical University, Moscow 105005 (Russian Federation); Wang Juan [Key Lab of Liquid Structure and Heredity of Materials, Ministry of Education, Shandong University, Jinan 250061, Shandong Province, Jing Shi Road 73, Shandong (China)

2008-12-20

The microstructural characterization of Fe{sub 3}Al/Q235 welded zone were analysed to investigate the welding behavior of Fe{sub 3}Al intermetallic. The results indicated that a crack-free Fe{sub 3}Al/Q235 joint was obtained when Cr25-Ni13 alloy was adopted as the filler metal. The microstructure of the welded zone presented different morphology due to the severe fluctuation of Al, Ni, Mn and Cr elements near the fusion zone. The fish-bone like structures in Q235 side fusion zone were composed of {alpha}-Fe(Cr, Al, Ni) solid solutions. Fe{sub 3}Al/Q235 joint fractured in the Fe{sub 3}Al HAZ, and shear strength of 533.33 MPa was achieved. The fracture mode of Fe{sub 3}Al side fracture surface was mainly transgranular cleavage, occured along [1 1 1] orientation on {l_brace}1 1 0{r_brace} planes. And the Q235 side fracture surface was in intergranular and quasi-cleavage mode. The phase relations of {gamma} and {alpha} in Fe{sub 3}Al side fusion zone, constituent of lower bainite in the weld and the Fe{sub 3}Al ordered transformation in HAZ were also determined.

Effect of nickel content on mechanical properties and fracture toughness of weld metal of WWER-1000 reactor vessel welded joints

International Nuclear Information System (INIS)

Zubchenko, A.S.; Vasilchenko, G.S.; Starchenko, E.G.; Nosov, S.I.

2004-01-01

Welding of WWER-1000 reactor vessel of steel 15X2HMPHIA is performed using the C B -12X2H2MAA wire and PHI-16 or PHI-16A flux. Nickel content in the weld metal usually lays within the limits 1.2-1.9%. The experimental data is shown on the weld metal with the nickel contents 1.28-2.45% after irradiation with fluence up to 260.10 22 n/m 2 at energy more than 0.5 MEV. The embrittlement was measured by shift of critical brittleness temperature. Has appeared, that the weld metal with the low nickel content is the least responsive to irradiation embrittlement. The mechanical properties and fracture toughness of the weld metal with the contents of a nickel less than 1.3% are studied. Specimens CT-1T are tested, the 'master-curve', and its confidence bounds with probability of destruction 5 and 95% is built. 'Master-curve' in the specified confidence interval is affirmed by CT-4T specimens test data. Is shown, that the mechanical properties and fracture toughness of the weld metal with the contents of nickel less than 1.3% satisfy the normative requirements

Development of fatigue resistance evaluation method for socket-weld-jointed pipes

International Nuclear Information System (INIS)

Noguchi, Shinji; Shibayama, Motoaki; Iwata, Masazumi; Matsuura, Masayuki

2003-01-01

Vent line, drain line and sampling line in nuclear power station have many socket welded-joints made of austenitic stainless steel. Their slenderness and stagnation yield some potential of vibration-induced cracking and stress corrosion cracking. For the joints under vibration, the authors firstly elucidated their welding-defect-related fatigue strength by using fracture mechanics. It could define the allowable sets of stress amplitude and defect size. Secondly, authors developed an ultra-sonic detecting apparatus by using a focus-type probe and its programmed crawl on socket part. The authors finally measured the stress amplitude and frequency by sticking strain gage on suspected joints, then evaluated the fatigue resistance of the joints. For more efficient procedure, the method of stress amplitude analysis through vibration measurement is being developed. (author)

In Situ SEM Observations of Fracture Behavior of Laser Welded-Brazed Al/Steel Dissimilar Joint

Science.gov (United States)

Xia, Hongbo; Tan, Caiwang; Li, Liqun; Ma, Ninshu

2018-03-01

Laser welding-brazing of 6061-T6 aluminum alloy to DP590 dual-phase steel with Al-Si12 flux-cored filler wire was performed. The microstructure at the brazing interface was characterized. Fracture behavior was observed and analyzed by in situ scanning electron microscope. The microstructure of the brazing interface showed that inhomogeneous intermetallic compounds formed along the thickness direction, which had a great influence on the crack initiation and propagation. In the top region, the reaction layer at the interface consisted of scattered needle-like Fe(Al,Si)3 and serration-shaped Fe1.8Al7.2Si. In the middle region, the compound at the interface was only serration-shaped Fe1.8Al7.2Si. In the bottom region, the interface was composed of lamellar-shaped Fe1.8Al7.2Si. The cracks were first detected in the bottom region and propagated from bottom to top along the interface. At the bottom region, the crack initiated and propagated along the Fe1.8Al7.2Si/weld seam interface during the in situ tensile test. When the crack propagated into the middle region, a deflection of crack propagation appeared. The crack first propagated along the steel/Fe1.8Al7.2Si interface and then moved along the weld seam until the failure of the joint. The tensile strength of the joint was 146.5 MPa. Some micro-cracks were detected at Fe(Al,Si)3 and the interface between the steel substrate and Fe(Al,Si)3 in the top region while the interface was still connected.

Effect of welding processes and joint configuration on the residual stresses and distortion in type 316 LN stainless steel weld joints

International Nuclear Information System (INIS)

Vasantharaja, P.; Vasudevan, M.; Palanichamy, P.

2012-01-01

Fabrication by welding introduces significant residual stresses in the welded structure/component due to non-uniform heat distribution during heating and cooling cycle. To control, reduce, or beneficially redistribute the residual stresses in weld joints, the stress distribution needs to be known. In the present study, weld joints of 16 mm thick 316LN stainless steel were made by multi-pass TIG, A-TIG welding and combination of TIG and A-TIG welding processes with various joint configurations. While V-groove edge preparation was required for making multi-pass TIG weld joint, square-edge preparation was sufficient for making A-TIG weld joint. Ultrasonic nondestructive technique based on the critically refracted longitudinal waves (LCR waves) has been used for the quantitative surface/sub-surface residual stress measurements in the weld joints. Distortion measurements were carried out before and after welding using height gauge. A-TIG weld joint was found to exhibit significant reduction in tensile residual stresses and distortion in comparison to that of other joints. (author)

Metallurgical and mechanical examinations of steel–copper joints arc welded using bronze and nickel-base superalloy filler materials

International Nuclear Information System (INIS)

Velu, M.; Bhat, Sunil

2013-01-01

Highlights: ► Optical and scanning electron microscopy show defect free weld interfaces. ► Energy dispersive spectroscopy shows low dilution level of the weld by Fe. ► XRD studies show no brittle intermetallic phases in the weld interfaces. ► Weld interfaces did not fail during tensile, transverse bending and impact tests. ► The joint exhibits superior strength properties than that of bronze filler. - Abstract: The paper presents metallurgical and mechanical examinations of joints between dissimilar metals viz. copper (UNSC11000) and alloy steel (En31) obtained by Shielded Metal Arc Welding (SMAW) using two different filler materials, bronze and nickel-base super alloy. The weld bead of the joint with bronze-filler displayed porosity, while that with nickel-filler did not. In tension tests, the weldments with bronze-filler fractured in the centre of the weld, while those with nickel-filler fractured in the heat affected zone (HAZ) of copper. Since the latter exhibited higher strength than the former, all the major tests were undertaken over the joints with nickel-filler alone. Scanning Electron Microscopy (SEM) coupled with Energy Dispersive Spectroscopy (EDS) indicated corrugated weld interfaces and favorable elemental diffusions across them. X-ray diffraction (XRD) studies around the weld interfaces did not reveal any detrimental intermetallic compounds. Transverse bending tests showed that flexural strengths of the weldments were higher than the tensile strengths. Transverse side bend tests confirmed good ductility of the joints. Shear strength of the weld-interface (Cu–Ni or Ni–steel) was higher than the yield strength of weaker metal. Microhardness and Charpy impact values were measured at all the important zones across the weldment

Effect of nickel content on mechanical properties and fracture toughness of weld metal of WWER-1000 reactor vessel welded joints

Energy Technology Data Exchange (ETDEWEB)

Zubchenko, A.S.; Vasilchenko, G.S.; Starchenko, E.G.; Nosov, S.I

2004-08-01

Welding of WWER-1000 reactor vessel of steel 15X2HMPHIA is performed using the C{sub B}-12X2H2MAA wire and PHI-16 or PHI-16A flux. Nickel content in the weld metal usually lays within the limits 1.2-1.9%. The experimental data is shown on the weld metal with the nickel contents 1.28-2.45% after irradiation with fluence up to 260.10{sup 22}n/m{sup 2} at energy more than 0.5 MEV. The embrittlement was measured by shift of critical brittleness temperature. Has appeared, that the weld metal with the low nickel content is the least responsive to irradiation embrittlement. The mechanical properties and fracture toughness of the weld metal with the contents of a nickel less than 1.3% are studied. Specimens CT-1T are tested, the 'master-curve', and its confidence bounds with probability of destruction 5 and 95% is built. 'Master-curve' in the specified confidence interval is affirmed by CT-4T specimens test data. Is shown, that the mechanical properties and fracture toughness of the weld metal with the contents of nickel less than 1.3% satisfy the normative requirements.

Characteristics of AZ31 Mg alloy joint using automatic TIG welding

Science.gov (United States)

Liu, Hong-tao; Zhou, Ji-xue; Zhao, Dong-qing; Liu, Yun-teng; Wu, Jian-hua; Yang, Yuan-sheng; Ma, Bai-chang; Zhuang, Hai-hua

2017-01-01

The automatic tungsten-inert gas welding (ATIGW) of AZ31 Mg alloys was performed using a six-axis robot. The evolution of the microstructure and texture of the AZ31 auto-welded joints was studied by optical microscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and electron backscatter diffraction. The ATIGW process resulted in coarse recrystallized grains in the heat affected zone (HAZ) and epitaxial growth of columnar grains in the fusion zone (FZ). Substantial changes of texture between the base material (BM) and the FZ were detected. The {0002} basal plane in the BM was largely parallel to the sheet rolling plane, whereas the c-axis of the crystal lattice in the FZ inclined approximately 25° with respect to the welding direction. The maximum pole density increased from 9.45 in the BM to 12.9 in the FZ. The microhardness distribution, tensile properties, and fracture features of the AZ31 auto-welded joints were also investigated.

Microstructures and mechanical properties of magnesium alloy and stainless steel weld-joint made by friction stir lap welding

International Nuclear Information System (INIS)

Wei, Yanni; Li, Jinglong; Xiong, Jiangtao; Huang, Fu; Zhang, Fusheng

2012-01-01

Highlights: → Friction stir lap welding technology with cutting pin was successfully employed to form lap joint of magnesium and steel. → The cutting pin made the lower steel participate in deformation and the interface was no longer flat. → A saw-toothed structure formed due to a mechanical mixing of the magnesium and steel was found at the interface. → A high-strength joint was produced which fractured in the magnesium side. -- Abstract: Friction stir lap welding was conducted on soft/hard metals. A welding tool was designed with a cutting pin of rotary burr made of tungsten carbide, which makes the stirring pin possible to penetrate and cut the surface layer of the hard metal. Magnesium alloy AZ31 and stainless steel SUS302 were chosen as soft/hard base metals. The structures of the joining interface were analyzed by scanning electron microscopy (SEM). The joining strength was evaluated by tensile shear test. The results showed that flower-like interfacial morphologies were presented with steel flashes and scraps, which formed bonding mechanisms of nail effect by long steel flashes, zipper effect by saw-tooth structure and metallurgical bonding. The shear strength of the lap joint falls around the shear strength of butt joint of friction stir welded magnesium alloy.

Microstructures and mechanical properties of welded joints of novel 3Cr pipeline steel using an inhouse and two commercial welding wires

International Nuclear Information System (INIS)

Zhu, Jinyang; Xu, Lining; Chang, Wei; Hu, Lihua; Lu, Minxu

2014-01-01

Highlights: • Weldability of novel 3Cr pipeline steel was investigated using two commercial and an inhouse welding wires. • Mechanical properties were measured and microstructure characteristics were observed. • Fracture positions of tensile test just corresponded to the minimum hardness region of the joints. • The inhouse wire R01 can provide the highest cost-performance ratio. - Abstract: The welded joints of the novel 3Cr pipeline steel were fabricated via the gas tungsten arc welding (GTAW) technique using an inhouse welding wire labeled as R01 and two kinds of commercial wires (H08Cr3MoMnA and TGS-2CML). Microhardness, impact toughness and tensile properties of the joints were measured, and microstructure characteristics were observed by scanning electron microscopy (SEM). The results show that under selected welding procedure, the joints of R01 can achieve quite good mechanical properties without preheating and post weld heat treatment (PWHT). After thermal refining, elongation (15.2%) doubled and met the DNV-OS-F101 standard. For low carbon or super low carbon pipeline steels such as 3Cr steel, the revised formula with the carbon applicable coefficient (A(c)) was quite good for predicting the maximum hardness in heat affected zone (HAZ). Compared with these two selected commercial wires, the inhouse welding wire R01 can provide the highest cost-performance ratio

Variant selection of martensites in steel welded joints with low transformation temperature weld metals

International Nuclear Information System (INIS)

Takahashi, Masaru; Yasuda, Hiroyuki Y.

2013-01-01

Highlights: ► We examined the variant selection of martensites in the weld metals. ► We also measured the residual stress developed in the butt and box welded joints. ► 24 martensite variants were randomly selected in the butt welded joint. ► High tensile residual stress in the box welded joint led to the strong variant selection. ► We discussed the rule of the variant selection focusing on the residual stress. -- Abstract: Martensitic transformation behavior in steel welded joints with low transformation temperature weld (LTTW) metal was examined focusing on the variant selection of martensites. The butt and box welded joints were prepared with LTTW metals and 980 MPa grade high strength steels. The residual stress of the welded joints, which was measured by a neutron diffraction technique, was effectively reduced by the expansion of the LTTW metals by the martensitic transformation during cooling after the welding process. In the LTTW metals, the retained austenite and martensite phases have the Kurdjumov–Sachs (K–S) orientation relationship. The variant selection of the martensites in the LTTW metals depended strongly on the type of welded joints. In the butt welded joint, 24 K–S variants were almost randomly selected while a few variants were preferentially chosen in the box welded joint. This suggests that the high residual stress developed in the box welded joint accelerated the formation of specific variants during the cooling process, in contrast to the butt welded joint with low residual stress

Effect of Al-Si Coating on Weld Microstructure and Properties of 22MnB5 Steel Joints for Hot Stamping

Science.gov (United States)

Lin, Wenhu; Li, Fang; Wu, Dongsheng; Chen, Xiaoguan; Hua, Xueming; Pan, Hua

2018-03-01

22MnB5 hot stamping steels are gradually being used in tailor-welded blank applications. In this experiment, 1-mm-thick Al-Si coated and de-coated 22MnB5 steels were laser-welded and then hot-stamped. The chemical compositions, solidification process, microstructure and mechanical properties were investigated to reveal the effect of Al-Si coating and heat treatment. In the welded condition, the coated joints had an Al content of approximately 2.5 wt.% in the fusion zone and the de-coated joints had 0.5 wt.% Al. The aluminum promoted the δ-ferrite formation as the skeletal structure during solidification. In the high-aluminum weld, the microstructure consisted of martensite and long and band-like δ-ferrite. Meanwhile, the low-aluminum weld was full of lath martensite. After the hot stamping process, the δ-ferrite fraction increased from 10 to 24% in the coated joints and the lath martensite became finer in the de-coated joints. The tensile strengths of the coated joints or de-coated joints were similar to that before hot stamping, but the strength of the coated joints was reduced heavily after hot stamping compared to the de-coated joints and base material. The effect of δ-ferrite on the tensile properties became stronger when the fusion zone was soft and deformed first in the hot-stamped specimens. The coated weld showed a brittle fracture surface with many cleavage planes, and the de-coated weld showed a ductile fracture surface with many dimples in hot-stamped conditions.

Improved Formula for the Stress Intensity Factor of Semi-Elliptical Surface Cracks in Welded Joints under Bending Stress

Science.gov (United States)

Peng, Yang; Wu, Chao; Zheng, Yifu; Dong, Jun

2017-01-01

Welded joints are prone to fatigue cracking with the existence of welding defects and bending stress. Fracture mechanics is a useful approach in which the fatigue life of the welded joint can be predicted. The key challenge of such predictions using fracture mechanics is how to accurately calculate the stress intensity factor (SIF). An empirical formula for calculating the SIF of welded joints under bending stress was developed by Baik, Yamada and Ishikawa based on the hybrid method. However, when calculating the SIF of a semi-elliptical crack, this study found that the accuracy of the Baik-Yamada formula was poor when comparing the benchmark results, experimental data and numerical results. The reasons for the reduced accuracy of the Baik-Yamada formula were identified and discussed in this paper. Furthermore, a new correction factor was developed and added to the Baik-Yamada formula by using theoretical analysis and numerical regression. Finally, the predictions using the modified Baik-Yamada formula were compared with the benchmark results, experimental data and numerical results. It was found that the accuracy of the modified Baik-Yamada formula was greatly improved. Therefore, it is proposed that this modified formula is used to conveniently and accurately calculate the SIF of semi-elliptical cracks in welded joints under bending stress. PMID:28772527

Forming Completely Penetrated Welded T-joints when Pulsed Arc Welding

Science.gov (United States)

Krampit, N. Yu; Krampit, M. A.; Sapozhkov, A. S.

2016-04-01

The paper is focused on revealing the influence of welding parameters on weld formation when pulsed arc welding. As an experimental sample a T-joint over 10 mm was selected. Welding was carried out in flat position, which required no edge preparation but provided mono-directional guaranteed root penetration. The following parameters of welding were subjected to investigation: gap in the joint, wire feed rate and incline angles of the torch along and across the weld axis. Technological recommendations have been made with respect to pulsed arc welding; the cost price of product manufacturing can be reduced on their basis due to reduction of labor input required by machining, lowering consumption of welding materials and electric power.

Mechanical properties of welded joints of duplex steels

International Nuclear Information System (INIS)

Kawiak, M.; Nowacki, J.

2003-01-01

The paper presents the study results of mechanical properties of duplex steels UNS S31803 welded joints as well as duplex and NV A36 steels welded joints. They have ben welded by FCAW method in CO 2 using FCW 2205-H flux-cored wire. The joints have been subjected: tensile tests, impact tests, bending tests, hardness tests and metallographic investigations. The influence of welding parameters and mechanical properties of the joints was appreciated. The welding method assured high tensile strength of the joints (approximately 770 MPa) and high impact strength of the welds (approximately 770 J). All samples were broken outside of welds. (author)

On the effect of niobium on the properties of welded joints in the 2.25% Cr-1% Mo type steel with nickel and niobium additions

International Nuclear Information System (INIS)

Matusek, P.; Gladis, R.; Walder, V.

The effects were studied of the chemical composition of the base material and of welding parameters on the properties of welded joints of steel 08Cr2.25Mo1NiNb for fast reactor steam generators. Welding was done using Boehler-Fox electrodes and electrodes developed in Czechoslovakia. Testing revealed that the welded joint hardened and embrittled depending on the content of free niobium. The occurrence of eutectic formation of a general composition of Nbsub(m)Xsub(n) and possible of the Fe 2 Nb phase was considered to be one of the possible unfavourable microstructural factor which affects the mechanical properties of the thermally affected zone. The effect of the cooling rate Δtausub(8/5), ie., the effect of welding technologies was also found to be a function of the free niobium content. The results of welded joint creep to the fracture showed that until the 2x10 4 fracture time no negative effect of the welding cycle on the welded joint refractoriness was found. (B.S.)

Microstructure evolution of Al/Mg butt joints welded by gas tungsten arc with Zn filler metal

International Nuclear Information System (INIS)

Liu Fei; Zhang Zhaodong; Liu Liming

2012-01-01

Based on the idea of alloying welding seam, Gas tungsten arc welding method with pure Zn filler metal was chosen to join Mg alloy and Al alloy. The microstructures, phases, element distribution and fracture morphology of welding seams were examined. The results indicate that there was a transitional zone in the width of 80–100 μm between the Mg alloy substrate and fusion zone. The fusion zone was mainly composed of MgZn 2 , Zn-based solid solution and Al-based solid solution. The welding seam presented distinct morphology in different location owning to the quite high cooling rate of the molten pool. The addition of Zn metal could prevent the formation of Mg–Al intermetallics and form the alloyed welding seam during welding. Therefore, the tensile strengths of joints have been significantly improved compared with those of gas tungsten arc welded joints without Zn metal added. Highlights: ► Mg alloy AZ31B and Al alloy 6061 are welded successfully. ► Zinc wire is employed as a filler metal to form the alloyed welding seam. ► An alloyed welding seam is benefit for improving of the joint tensile strength.

Microstructure and Mechanical Properties of Ultrasonic Spot Welded Mg/Al Alloy Dissimilar Joints

Directory of Open Access Journals (Sweden)

He Peng

2018-04-01

Full Text Available Lightweight structural applications of magnesium and aluminum alloys inevitably necessitate welding and joining, especially dissimilar welding between these alloys. The objective of this study was to examine the feasibility of joining ZEK100 Mg alloy to Al6022 alloy via ultrasonic spot welding, focusing on effects of welding energy. An interface diffusion layer consisting of α-Mg and Al12Mg17 eutectic structure was observed to form, with its thickness increased from ~0.5 µm to ~30 µm with increasing welding energy from 500 J to 2000 J. The tensile lap shear peak load or strength and critical stress intensity of the welded joints first increased and then decreased with increasing welding energy, with their peak values achieved at 750 J. Fatigue life of the joints made at 750 J and 2000 J was equivalent at the lower cyclic loading levels, while it was longer for the joints made at 750 J at the higher cyclic loading levels. Fatigue fracture mode changed from interfacial failure to mainly transverse-through-thickness crack growth with decreasing cyclic loading level, which corresponded well to the bi-linear characteristic of S-N curves. Crack initiation basically occurred at the weld nugget border and at the interface between the two sheets, which can be understood via a theoretical stress analysis.

Effects of welding parameters on friction stir spot welding of high density polyethylene sheets

International Nuclear Information System (INIS)

Bilici, Mustafa Kemal; Yukler, Ahmet Irfan

2012-01-01

Graphical abstract: (a) Schematic illustration of the cross section of a friction stir spot weld and (b) Geometry of the weld bonded area, x: nugget thickness and y: the thickness of the upper sheet. Highlights: → Welding parameters affect the FSSW nugget formation and the strength of the joint. → Melting of polyethylene occurred in the vicinity of the tool pin. → The joint that fractures with a pull nugget failure mode has a higher strength. -- Abstract: Friction stir spot welding parameters affect the weld strength of thermoplastics, such as high density polyethylene (HDPE) sheets. The effects of the welding parameters on static strength of friction stir spot welds of high density polyethylene sheets were investigated. For maximizing the weld strength, the selection of welding parameters is very important. In lap-shear tests two fracture modes were observed; cross nugget failure and pull nugget failure. The tool rotational speed, tool plunge depth and dwell time were determined to be important in the joint formation and its strength. The joint which had a better strength fails with a pull nugget failure morphology. Weld cross section image analysis of the joints were done with a video spectral comparator. The plunge rate of the tool was determined to have a negligible effect on friction stir spot welding.

Recent Corrosion Research Trends in Weld Joints

International Nuclear Information System (INIS)

Kim, Hwan Tae; Kil, Sang Cheol; Hwang, Woon Suk

2007-01-01

The increasing interest in the corrosion properties of weld joints in the corrosive environment is placing stringent demands on the manufacturing techniques and performance requirements, and the manufacture employs the high quality and efficiency welding process to produce welds. Welding plays an important role in the fabrication of chemical plants, nuclear power plant, ship construction, and this has led to an increasing attention to the corrosion resistant weld joints. This paper covers recent technical trends of welding technologies for corrosion resistance properties including the COMPENDEX DB analysis of welding materials, welding process, and welding fabrications

Corrosion resistance of «tube – tubesheet» weld joint obtained by friction welding

Directory of Open Access Journals (Sweden)

RIZVANOV Rif Garifovich

2017-08-01

Full Text Available Shell-and-tube heat exchangers are widely applied for implementation of various processes at ventures of fuel and energy complex. Cost of production and reliability of heat exchangers of this type is to a wide extent determined by corresponding characteristics of tube bundle, «tube – tubesheet» is its typical joint in particular when welding operations are used in order to attach tubes to tubesheet in addition to expansion. When manufacturing such equipment of heat-resistant chrome-bearing or chromium-molybdenum steels including steel 15H5M, the process of fixed joint manufacturing gets significantly more complicated and costly due to the necessity to use thermal treatment before, during and after welding (this problem is particularly applicable for manufacturing of large-size equipment. One of the options to exclude thermal treatment from manufacturing process is to use «non-arc» welding methods – laser welding, explosion welding as well as friction welding. Use of each of the welding methods mentioned above during production of heat-exchange equipment has its process challenges and peculiarities. This article gives a comparative analysis of weld structure and distribution of electrode potentials of welded joints and parent metal of the joints simulating welding of tube to tubesheet of steel 15H5M using the following welding methods: shielded manual arc welding, tungsten-arc inert-gas welding and friction welding. Comparative analysis of macro- and microstructures of specific zones of the studied welded joints showed that the joints produced by arc welding methods do not exhibit evident inhomogeneity of the structure after application of thermal treatment which is explained by the correctness of thermal treatment. Joints obtained via friction welding are characterized by structural inhomogeneity of the welded joint zone metal microstructure. The ultra-fine-grained structure obtained as a result of friction welding makes it possible to

Welding technology transfer task/laser based weld joint tracking system for compressor girth welds

Science.gov (United States)

Looney, Alan

1991-01-01

Sensors to control and monitor welding operations are currently being developed at Marshall Space Flight Center. The laser based weld bead profiler/torch rotation sensor was modified to provide a weld joint tracking system for compressor girth welds. The tracking system features a precision laser based vision sensor, automated two-axis machine motion, and an industrial PC controller. The system benefits are elimination of weld repairs caused by joint tracking errors which reduces manufacturing costs and increases production output, simplification of tooling, and free costly manufacturing floor space.

Fracture assessment for a dissimilar metal weld of low alloy steel and Ni-base alloy

Energy Technology Data Exchange (ETDEWEB)

Ogawa, Takuya, E-mail: takuya4.ogawa@toshiba.co.jp [Toshiba Corporation Power Systems Company, Power and Industrial Systems Research and Development Center, 8, Shinsugita-cho, Isogo-ku, Yokohama 235-8523 (Japan); Itatani, Masao; Saito, Toshiyuki; Hayashi, Takahiro; Narazaki, Chihiro; Tsuchihashi, Kentaro [Toshiba Corporation Power Systems Company, Power and Industrial Systems Research and Development Center, 8, Shinsugita-cho, Isogo-ku, Yokohama 235-8523 (Japan)

2012-02-15

Recently, instances of SCC in Ni-base alloy weld metal of light water reactor components have been reported. Despite the possibility of propagation of SCC crack to the fusion line between low alloy steel (LAS) of pressure vessel and Ni-base alloy of internal structure, a fracture assessment method of dissimilar metal welded joint has not been established. The objective of this study is to investigate a fracture mode of dissimilar metal weld of LAS and Ni-base alloy for development of a fracture assessment method for dissimilar metal weld. Fracture tests were conducted using two types of dissimilar metal weld test plates with semi-elliptical surface crack. In one of the test plates, the fusion line lies around the surface points of the surface crack and the crack tips at the surface points have intruded into LAS. Material ahead of the crack tip at the deepest point is Ni-base alloy. In the other, the fusion line lies around the deepest point of the surface crack and the crack tip at the deepest point has intruded into LAS. Material ahead of the crack tip at the deepest point is LAS. The results of fracture tests using the former type of test plate reveal that the collapse load considering the proportion of ligament area of each material gives a good estimation for fracture load. That is, fracture assessment based on plastic collapse mode is applicable to the former type of test plate. It is also understood that a fracture assessment method based on the elastic-plastic fracture mode is suitable for the latter type of test plate.

Properties of welded joints in laser welding of aeronautic aluminum-lithium alloys

Science.gov (United States)

Malikov, A. G.; Orishich, A. M.

2017-01-01

The work presents the experimental investigation of the laser welding of the aluminum-lithium alloys (system Al-Mg-Li) and aluminum alloy (system Al-Cu-Li) doped with Sc. The influence of the nano-structuring of the surface layer welded joint by the cold plastic deformation method on the strength properties of the welded joint is determined. It is founded that, regarding the deformation degree over the thickness, the varying value of the welded joint strength is different for these aluminum alloys.

Study of local-zone microstructure, strength and fracture toughness of hybrid laser-metal-inert-gas-welded A7N01 aluminum alloy joint

Energy Technology Data Exchange (ETDEWEB)

Wang, Xiaomin, E-mail: xmwang991011@163.com [School of Life Science and Engineering, Southwest Jiaotong University, Chengdu 610031, Sichuan (China); Li, Bo [School of Materials Science and Engineering, Southwest Jiaotong University, Chengdu 610031, Sichuan (China); Li, Mingxing; Huang, Cui [School of Life Science and Engineering, Southwest Jiaotong University, Chengdu 610031, Sichuan (China); Chen, Hui [School of Materials Science and Engineering, Southwest Jiaotong University, Chengdu 610031, Sichuan (China)

2017-03-14

Mechanical properties of hybrid laser-metal-inert-gas-welded A7N01-T5 aluminum alloy joints were studied by using local samples that were extracted from the base metal (BM), heat-affected zone (HAZ), and fusion zone (FZ) of the joint to investigate the triangular relationship of microstructure, strength and fracture toughness of the local zones. The BM had the highest yield strength, ultimate tensile strength (UTS) and lowest elongation, which contrasts with the FZ. The yield strength of the HAZ is lower than that of the BM, whereas its UTS is very close to that of the BM, and its elongation is higher than that of the BM. The fracture toughness of the three local zones decreased as HAZ>BM>FZ. To analyze differences in local mechanical behavior, the detailed microstructure of the three local zones was studied by optical microscopy and electron backscattered diffraction, whereas the fracture surface and precipitation were studied by scanning and transmission electron microscopy. The variation of grain size, especially the morphology and distribution of strengthening phase in HAZ in welding process is the key factor that leads to its different mechanical properties from that of BM, which can be elucidated by different dislocation mechanism, sheared mechanism or Orowan mechanism. The as-cast microstructure and second-phase particles that segregate between dendritic branches provide the FZ with the lowest yield strength and UTS. The factors including area fraction of the precipitates, the difference of strength between the matrix and the grain boundaries, the precipitate-free zone along grain boundaries, as well as the grain boundaries angle are taken into account to explain the difference of fracture toughness among BM, HAZ and FZ, and their fracture modes.

Study of susceptibility to hydrogen embrittlement of welded joints of large WWER reactor vessels at different temperatures

International Nuclear Information System (INIS)

Mazel', R.E.; Kuznetsova, T.P.; Grinenko, V.G.; Sapronova, M.N.

1977-01-01

The effect is studied of hydrogen and a coolant of WWER on the susceptibility to brittle fracture of welded joints from steels 15Kh2MFA and 15Kh2NMFA obtained by automatic submerged arc welding with the use of the welding materials of different purity. The effect of hydrogen (concentration range 0.5-7.5 cm 3 /100 g, testing temperatures 20, 70 and 325 deg C) and the coolant (pressures up to 120 atm, temperatures 20-350 deg C) have been estimated by the fracture work during static bending tests. It is shown that the purification of the welding materials enhances the fracture properties by about a factor of 2. Hydrogenation results in a sharp drop (by about a factor of 3) of the fracture work. The increased testing temperature (up to 325 deg C) is accompanied by disappearance of the effect of hydrogen embrittlement, which is explained by an increase in the diffusion mobility of atomic hydrogen. Under the action of the coolant the fracture work shows a two-fold decrease, while the pressure being increased up to 100 atm leads to greater fracture work decrease

Fracture Mechanics Approach to X-Ray Diffraction Method for Spot Welded Lap Joint Structure of Rolled Steel Considered Residual Stress

International Nuclear Information System (INIS)

Baek, Seung Yeb; Bae, Dong Ho

2011-01-01

Cold and hot-rolled carbon steel sheets are commonly used in railroad cars or commercial vehicles such as the automobile. The sheets used in these applications are mainly fabricated by spot welding, which is a type of electric resistance welding. However, the fatigue strength of a spot-welded joint is lower than that of the base metal because of high stress concentration at the nugget edge of the spot-welded part. In particular, the fatigue strength of the joint is influenced by not only geometrical and mechanical factors but also the welding conditions for the spot-welded joint. Therefore, there is a need for establishing a reasonable criterion for a long-life design for spot-welded structures. In this thesis, ΔP-N f relation curves have been used to determine a long-life fatigue-design criterion for thin-sheet structures. However, as these curves vary under the influence of welding conditions, mechanical conditions, geometrical factors, etc. It is very difficult to systematically determine a fatigue-design criterion on the basis of these curves. Therefore, in order to eliminate such problems, the welding residual stresses generated during welding and the stress distributions around the weld generated by external forces were numerically and experimentally analyzed on the basis of the results, reassessed fatigue strength of gas welded joints

A Comparative Study of Fracture Toughness at Cryogenic Temperature of Austenitic Stainless Steel Welds

Science.gov (United States)

Aviles Santillana, I.; Boyer, C.; Fernandez Pison, P.; Foussat, A.; Langeslag, S. A. E.; Perez Fontenla, A. T.; Ruiz Navas, E. M.; Sgobba, S.

2018-03-01

The ITER magnet system is based on the "cable-in-conduit" conductor (CICC) concept, which consists of stainless steel jackets filled with superconducting strands. The jackets provide high strength, limited fatigue crack growth rate and fracture toughness properties to counteract the high stress imposed by, among others, electromagnetic loads at cryogenic temperature. Austenitic nitrogen-strengthened stainless steels have been chosen as base material for the jackets of the central solenoid and the toroidal field system, for which an extensive set of cryogenic mechanical property data are readily available. However, little is published for their welded joints, and their specific performance when considering different combinations of parent and filler metals. Moreover, the impact of post-weld heat treatments that are required for Nb3Sn formation is not extensively treated. Welds are frequently responsible for cracks initiated and propagated by fatigue during service, causing structural failure. It becomes thus essential to select the most suitable combination of parent and filler material and to assess their performance in terms of strength and crack propagation at operation conditions. An extensive test campaign has been conducted at 7 K comparing tungsten inert gas (TIG) welds using two fillers adapted to cryogenic service, EN 1.4453 and JK2LB, applied to two different base metals, AISI 316L and 316LN. A large set of fracture toughness data are presented, and the detrimental effect on fracture toughness of post-weld heat treatments (unavoidable for some of the components) is demonstrated. In this study, austenitic stainless steel TIG welds with various filler metals have undergone a comprehensive fracture mechanics characterization at 7 K. These results are directly exploitable and contribute to the cryogenic fracture mechanics properties database of the ITER magnet system. Additionally, a correlation between the impact in fracture toughness and microstructure

Effect of Post Weld Heat Treatment on Microstructure and Mechanical Properties of Submerged Friction Stir Welded 7A04 Aluminum Alloy

Directory of Open Access Journals (Sweden)

HAO Ya-xin

2016-06-01

Full Text Available 7A04 aluminum alloy plate was jointed by submerged friction stir welding(SFSW, and welded joints were treated (Post Weld Heat Treatment, PWHT, and the effect of post weld heat treatment on the microstructure and mechanical properties in SFSW was investigated. The results show that PWHT joints exhibit dispersively distributed fine precipitates phase morphology, are significantly superior than the feature of the small amount of precipitates with dispersed distribution in SFSW joints. Compared with SFSW joints, the mechanical properties of joints are improved significantly by PWHT. The average hardness of the weld joints nugget zone is increased by 39.7HV, and the tensile strength is increased by 67MPa, reaches 96.1% of the base material, strain hardening capacity of the joints is also enhanced, the tensile fracture exhibits mixed fracture feature of microporous polymerization and cleavage.

Microstructure Evolution and Mechanical Properties of Underwater Dry and Local Dry Cavity Welded Joints of 690 MPa Grade High Strength Steel.

Science.gov (United States)

Shi, Yonghua; Sun, Kun; Cui, Shuwan; Zeng, Min; Yi, Jianglong; Shen, Xiaoqin; Yi, Yaoyong

2018-01-22

Q690E high strength low alloy (HSLA) steel plays an important role in offshore structures. In addition, underwater local cavity welding (ULCW) technique was widely used to repair important offshore constructions. However, the high cooling rate of ULCW joints results in bad welding quality compared with underwater dry welding (UDW) joints. Q690E high strength low alloy steels were welded by multi-pass UDW and ULCW techniques, to study the microstructural evolution and mechanical properties of underwater welded joints. The microstructure and fracture morphology of welded joints were observed by scanning electron microscope and optical microscope. The elemental distribution in the microstructure was determined with an Electron Probe Microanalyzer. The results indicated that the microstructure of both two welded joints was similar. However, martensite and martensite-austenite components were significantly different with different underwater welding methods such that the micro-hardness of the HAZ and FZ in the ULCW specimen was higher than that of the corresponding regions in UDW joint. The yield strength and ultimate tensile strength of the ULCW specimen are 109 MPa lower and 77 MPa lower, respectively, than those of the UDW joint. The impact toughness of the UDW joint was superior to those of the ULCW joint.

Microstructure Evolution and Mechanical Properties of Underwater Dry and Local Dry Cavity Welded Joints of 690 MPa Grade High Strength Steel

Science.gov (United States)

Sun, Kun; Cui, Shuwan; Zeng, Min; Yi, Jianglong; Shen, Xiaoqin; Yi, Yaoyong

2018-01-01

Q690E high strength low alloy (HSLA) steel plays an important role in offshore structures. In addition, underwater local cavity welding (ULCW) technique was widely used to repair important offshore constructions. However, the high cooling rate of ULCW joints results in bad welding quality compared with underwater dry welding (UDW) joints. Q690E high strength low alloy steels were welded by multi-pass UDW and ULCW techniques, to study the microstructural evolution and mechanical properties of underwater welded joints. The microstructure and fracture morphology of welded joints were observed by scanning electron microscope and optical microscope. The elemental distribution in the microstructure was determined with an Electron Probe Microanalyzer. The results indicated that the microstructure of both two welded joints was similar. However, martensite and martensite-austenite components were significantly different with different underwater welding methods such that the micro-hardness of the HAZ and FZ in the ULCW specimen was higher than that of the corresponding regions in UDW joint. The yield strength and ultimate tensile strength of the ULCW specimen are 109 MPa lower and 77 MPa lower, respectively, than those of the UDW joint. The impact toughness of the UDW joint was superior to those of the ULCW joint. PMID:29361743

Welded joints integrity analysis and optimization for fiber laser welding of dissimilar materials

Science.gov (United States)

Ai, Yuewei; Shao, Xinyu; Jiang, Ping; Li, Peigen; Liu, Yang; Liu, Wei

2016-11-01

Dissimilar materials welded joints provide many advantages in power, automotive, chemical, and spacecraft industries. The weld bead integrity which is determined by process parameters plays a significant role in the welding quality during the fiber laser welding (FLW) of dissimilar materials. In this paper, an optimization method by taking the integrity of the weld bead and weld area into consideration is proposed for FLW of dissimilar materials, the low carbon steel and stainless steel. The relationships between the weld bead integrity and process parameters are developed by the genetic algorithm optimized back propagation neural network (GA-BPNN). The particle swarm optimization (PSO) algorithm is taken for optimizing the predicted outputs from GA-BPNN for the objective. Through the optimization process, the desired weld bead with good integrity and minimum weld area are obtained and the corresponding microstructure and microhardness are excellent. The mechanical properties of the optimized joints are greatly improved compared with that of the un-optimized welded joints. Moreover, the effects of significant factors are analyzed based on the statistical approach and the laser power (LP) is identified as the most significant factor on the weld bead integrity and weld area. The results indicate that the proposed method is effective for improving the reliability and stability of welded joints in the practical production.

Creep behavior evaluation of welded joint

International Nuclear Information System (INIS)

Susei, Shuzo; Matsui, Shigetomo; Mori, Eisuke; Shimizu, Shigeki; Satoh, Keisuke.

1980-01-01

In the creep design of high temperature structural elements, it is necessary to grasp the creep performance of joints as a whole, paying attention to the essential lack of uniformity between the material qualities of parent metals and welds. In this study, the factors controlling the creep performance of butt welded joints were investigated theoretically, when they were subjected to lateral tension and longitudinal tension. It was clarified that the rupture time in the case of laterally pulled joints was determined by the ratio of the creep rupture times of weld metals and parent metals, and the rupture time in the case of longitudinally pulled joints was determined by the ratio of the creep rupture times and the ratio of the creep strain rates of weld metals and parent metals. Moreover, when the joints of the former ratio less than 1 and the latter ratio larger than 1 were investigated experimentally, the rupture time in the case of laterally pulled joints was affected by the relative thickness, and when the relative thickness was large, the theoretical and the experimental values coincided, but the relative thickness was small, the theoretical values gave the evaluation on safe side as compared with the experimental values due to the effect of restricting deformation. In the case of longitudinally pulled joints, the theoretical and the experimental values coincided relatively well. The diagram of classifying the creep performance of welded joints was proposed. (Kako, I.)

Friction stir spot welding of dissimilar aluminium alloys

International Nuclear Information System (INIS)

Bozkurt, Yahya

2016-01-01

Friction stir spot welding (FSSW) has been proposed as an effective technology to spot weld the so-called “difficult to be welded” metal alloys such as thin sheets aluminum alloys and dissimilar materials. FSSW is derived from friction stir welding technology, its principle benefit being low cost joining, lower welding temperature and shorter welding time than conventional welding methods. In this study, dissimilar AlMg 3 and AlCu 4 Mg 1 aluminium alloy plates were FSSWed by offsetting the low strength sheet on upper side of the weld. The effects of tool rotation speed on the microstructure, lap shear fracture load (LSFL), microhardness and fracture features of the weld are investigated by constant welding parameters. The maximum LSFL was obtained by increasing the tool rotational speed. However, the joints exhibited pull-out nugget fracture mode under lap shear tensile testing conditions. The largest completely bonded zone was observed as 5.86 mm which was narrower at the opposite position of the joint. Key words: friction stir spot welding, aluminium alloys, mechanical properties, dissimilar joint, welding parameters

Effect of water-cooling treatment times on properties of friction stir welded joints of 7N01-T4 aluminum alloy

Science.gov (United States)

Zhang, T. H.; Wang, Y.; Fang, X. F.; Liang, P.; Zhao, Y.; Li, Y. H.; Liu, X. M.

2018-02-01

Due to the deformation caused by residual stress in the welding process, welded components need treatment to reduce welding distortion. In this paper, several different times of flame-heating and water-cooling treatment were subjected to the friction stir welding joints of 15mm thick 7N01P-T4 aluminum alloy sheets to study the microstructure variation of friction stir welding joints of 7N01P-T4 aluminum alloy, and to analyze the effect on micro-hardness, tensile and fracture mechanical properties. This investigation will be helpful to optimize treatment methods and provide instruction on industrial production.

Equivalent CTOD concept based on the local approach and its application to fracture performance evaluation of welded joints; Local approach ni motozuku toka CTOD gainen no teian to tsugite hakai seino hyoka eno oyo

Energy Technology Data Exchange (ETDEWEB)

Ohata, M.; Minami, F.; Toyoda, M. [Osaka University, Osaka (Japan). Faculty of Engineering; Tanaka, T.; Arimochi, K. [Sumitomo Metal Industries, Ltd., Osaka (Japan); Glover, A. [Nova Gas Transmission Ltd., Calgary (Canada); North, T. [University of Toronto (Canada)

1996-12-31

A proposal was given on an equivalent crack tip opening displacement (CTOD) concept which relates quantitatively fracture performance of a structural member with the result of a three-point bending CTOD test via the Weibull stress based on a local approach. The equivalent CTOD is defined as a CTOD in which a three-point CTOD test piece and a structural member provide the same Weibull stress. Experimental and analytical discussions were performed on X80 steel welded joints. Effectiveness of the equivalent CTOD concept was verified from the fact that the fracture performance in welded joints with a large width estimated from the result of the three-point bending CTOD test using the equivalent CTOD concept showed good correspondence with the fracture performance obtained in the experiments. On the other hand, the result of estimation using the conventional CTOD concept is considerably smaller than measurements. As an application of the equivalent CTOD concept, a new determination procedure was introduced on required fracture tenacity to ensure deformation performance required on structural elements. The required CTOD value shows a trend that the smaller the ratio of yield stress of the welded metals to that in the base material, the greater the required CTOD grows. 16 refs., 19 figs., 3 tabs.

Equivalent CTOD concept based on the local approach and its application to fracture performance evaluation of welded joints; Local approach ni motozuku toka CTOD gainen no teian to tsugite hakai seino hyoka eno oyo

Energy Technology Data Exchange (ETDEWEB)

Ohata, M; Minami, F; Toyoda, M [Osaka University, Osaka (Japan). Faculty of Engineering; Tanaka, T; Arimochi, K [Sumitomo Metal Industries, Ltd., Osaka (Japan); Glover, A [Nova Gas Transmission Ltd., Calgary (Canada); North, T [University of Toronto (Canada)

1997-12-31

A proposal was given on an equivalent crack tip opening displacement (CTOD) concept which relates quantitatively fracture performance of a structural member with the result of a three-point bending CTOD test via the Weibull stress based on a local approach. The equivalent CTOD is defined as a CTOD in which a three-point CTOD test piece and a structural member provide the same Weibull stress. Experimental and analytical discussions were performed on X80 steel welded joints. Effectiveness of the equivalent CTOD concept was verified from the fact that the fracture performance in welded joints with a large width estimated from the result of the three-point bending CTOD test using the equivalent CTOD concept showed good correspondence with the fracture performance obtained in the experiments. On the other hand, the result of estimation using the conventional CTOD concept is considerably smaller than measurements. As an application of the equivalent CTOD concept, a new determination procedure was introduced on required fracture tenacity to ensure deformation performance required on structural elements. The required CTOD value shows a trend that the smaller the ratio of yield stress of the welded metals to that in the base material, the greater the required CTOD grows. 16 refs., 19 figs., 3 tabs.

The technology and welding joint properties of hybrid laser-tig welding on thick plate

Science.gov (United States)

Shenghai, Zhang; Yifu, Shen; Huijuan, Qiu

2013-06-01

The technologies of autogenous laser welding and hybrid laser-TIG welding are used on thick plate of high strength lower alloy structural steel 10CrNiMnMoV in this article. The unique advantages of hybrid laser-TIG welding is summarized by comparing and analyzing the process parameters and welding joints of autogenous laser welding laser welding and hybrid laser-TIG welding. With the optimal process parameters of hybrid welding, the good welding joint without visible flaws can be obtained and its mechanical properties are tested according to industry standards. The results show that the hybrid welding technology has certain advantages and possibility in welding thick plates. It can reduce the demands of laser power, and it is significant for lowering the aspect ratio of weld during hybrid welding, so the gas in the molten pool can rise and escape easily while welding thick plates. Therefore, the pores forming tendency decreases. At the same time, hybrid welding enhances welding speed, and optimizes the energy input. The transition and grain size of the microstructure of hybrid welding joint is better and its hardness is higher than base material. Furthermore, its tensile strength and impact toughness is as good as base material. Consequently, the hybrid welding joint can meet the industry needs completely.

Fracture toughness of a welded super duplex stainless steel

Energy Technology Data Exchange (ETDEWEB)

Pilhagen, Johan, E-mail: pilhagen@kth.se [Department of Materials Science and Engineering, KTH Royal Institute of Technology, Stockholm (Sweden); Sieurin, Henrik [Scania CV AB, Södertälje (Sweden); Sandström, Rolf [Department of Materials Science and Engineering, KTH Royal Institute of Technology, Stockholm (Sweden)

2014-06-01

Fracture toughness testing was conducted on standard single-edge notched bend bar specimens of base and weld metal. The material was the SAF 2906 super duplex stainless steel. The aim was to evaluate the susceptibility for brittle failure at sub-zero temperatures for the base and weld metal. The base metal was tested between −103 and −60 °C and was evaluated according to the crack-tip opening displacement method. The fracture event at and below −80 °C can be described as ductile until critical cleavage initiation occurs, which caused unstable failure of the specimen. The welding method used was submerged arc welding with a 7 wt% nickel filler metal. The welded specimens were post-weld heat treated (PWHT) at 1100 °C for 20 min and then quenched. Energy-dispersive X-ray spectroscopy analysis showed that during PWHT substitutional element partitioning occurred which resulted in decreased nickel content in the ferrite. The PWHT weld metal specimens were tested at −72 °C. The fracture sequence was critical cleavage fracture initiation after minor crack-tip blunting and ductile fracture.

Protection of welded joints against corrosion degradation

Directory of Open Access Journals (Sweden)

Jiří Votava

2013-01-01

Full Text Available Welded joints form an integral part of steel constructions. Welded joints are undetachable joints, which are however subjects of corrosion processes. The internal energy increases during the fusion welding especially in the heat affected places around the welded joint, which become initiating spot of corrosion degradation.The aim of the experiment is to put a welded joint produced by the MAG method to a test of corrosion degradation under the conditions of the norm ČSN ISO 9227 (salt-spray test. Organic and inorganic anticorrosion protections were applied on welded beads. First of all, there were prepared welded beads using the method MAG; secondly, metallographical analyses of welded metal, heat affected places and base material were processed. Further, microhardness as well as analysis of chemical composition using the EDS microscope were analysed. Based on a current trend in anticorrosion protections, there were chosen three types of protective coatings. First protective system was a double-layer synthetic system, where the base layer is formed by paint Pragroprimer S2000 and the upper layer by finishing paint Industrol S 2013. Second protective system is a duplex system formed by a combination of a base zinc coating with Zinorex paint. The last protective system was formed by zinc dipping only. Corrosion resistance of the individual tested samples was evaluated based on degradation of protective coating. The corrosion origin as well as the corrosion process were observed, the main criteria was the observation of welded bead.

Fatigue strength of socket welded pipe joint

International Nuclear Information System (INIS)

Iida, K.; Matsuda, F.; Sato, M.; Higuchi, M.; Nakagawa, A.

1994-01-01

Fully reversed four point bending fatigue tests were carried out of small diameter socket welded joints made of carbon steels. Experimental parameters are pipe diameter, thickness of pipe and socket wall, throat depth and shape of fillet welds, slip-on and diametral gaps in the socket welding, lack of penetration at the root of fillet welds, and peening of fillet welds. In most cases a fatigue crack started from the root of the fillet, but in the case of higher stress amplitude, it tended to start from the toe of fillet. The standard socket welded joint of 50 mm diameter showed relatively low fatigue strength, 46 MPa in stress amplitude at the 10 7 cycles failure life. This value corresponds to about 1/5 of that of the smoothed base metal specimens in axial fatigue. The fatigue strength showed decrease with increasing pipe diameter, and increase with increasing the thickness of pipe and socket wall. The effects of throat depth and shape of fillet welds on fatigue strength were not significant. Contrary to the expectation, the fatigue strength of the socket welded joint without slip-on gap is higher than that of the joint with the normal gap. A lack of penetration at the root deleteriously reduced fatigue strength, showing 14 MPa in stress amplitude at the 10 7 cycles failure life for the 50 mm diameter socket joint. (orig.)

Fatigue crack growth in welded joints in seawater

Energy Technology Data Exchange (ETDEWEB)

Lambert, S.B.

1988-01-01

A pipe-to-plate specimen has been developed to study the influence of seawater on the fatigue behaviour of welded tubular joints. DC potential drop techniques have been used to detect fatigue crack initiation, and to monitor the subsequent growth of fatigue cracks. Results for three specimens, tested in air are compared with similar data for tubular and T-plate joints. These comparisons indicate that the pipe/plate is a reasonable model of a tubular joint. Testing was performed on a further six specimens in artificial seawater; two each with free corrosion, optimum cathodic protection, and cathodic overprotection. Fatigue life reduction factors compared with corresponding tests in air were 1.8 and 2.8 for free corrosion, 1.7 and 1.1 with cathodic protection, and 4.2 and 3.3 with cathodic over-protection. These fatigue life reduction factors were comparable to results on T-plate specimens, and were strongly dependent on crack shape development. Linear elastic fracture mechanics techniques appear suitable for the calculation of fatigue crack propagation life. Three approximate solution techniques for crack tip stress intensity factors show reasonable agreement with experimentally derived values. It is recommended that forcing functions be used to model crack aspect ratio development in welded joints. Such forcing functions are influenced by the initial stress distribution and the environment. 207 refs., 192 figs., 22 tabs.

Fracture toughness of partially welded joints of SUS316 stainless steel at 4 K by large bend tests

International Nuclear Information System (INIS)

Nishimura, A.; Tobler, R.L.; Tamura, H.; Imagawa, S.; Mito, T.; Yamamoto, J.; Motojima, O.; Takahashi, H.; Suzuki, S.

1996-01-01

Austenitic stainless steels in relatively thick sections are specified in support structure designs for huge superconducting magnets in fusion energy machines such as the Large Helical Device (LHD). In the LHD under construction at the National Institute for Fusion Science (NIFS) in Japan, partial welding of SUS 316 stainless steel is employed to fabricate the 100-mm thick coil can and coil support structures. Partial welding lowers the heat input and reduces residual deformation after welding. The main disadvantage is that a sizable crack-like defect remains embedded in the unwelded portion of the primary structural component. Here, SUS 316 stainless steel bars were partially welded and tested in 3-point bending to evaluate the effect of natural cracks on fusion zone toughness at 4 K. The specimens had a cross-section 87.5 mm x 175 mm and were fractured in liquid helium using a 10 MN cryogenic mechanical testing machine. In two tests, unstable fracture occurred at maximum load and at critical stress intensity factors K max = 227 and 228 MPa√m. Results indicate a high resistance to fracture initiation but no stable tearing. Therefore, no resistance to crack propagation may exist in a fusion zone at a weld root under cryogenic temperature

Spot weld arrangement effects on the fatigue behavior of multi-spot welded joints

International Nuclear Information System (INIS)

Hassanifard, Soran; Zehsaz, Mohammad; Esmaeili, Firooz

2011-01-01

In the present study, the effects of spot weld arrangements in multi-spot welded joints on the fatigue behavior of the joints are studied. Three different four-spot welded joints are considered: one-row four-spot parallel to the loading direction, one-row four-spot perpendicular to the loading direction and two-row four-spot weld specimens. The experimental fatigue test results reveal that the differences between the fatigue lives of three spot welded types in the low cycle regime are more considerable than those in the high cycle regime. However, all kinds of spot weld specimens have similar fatigue strength when approaching a million cycles. A non-linear finite element analysis is performed to obtain the relative stress gradients, effective distances and notch strength reduction factors based on the volumetric approach. The work here shows that the volumetric approach does a very good job in predicting the fatigue life of the multi-spot welded joints

Fatigue properties of dissimilar metal laser welded lap joints

Science.gov (United States)

Dinsley, Christopher Paul

This work involves laser welding austenitic and duplex stainless steel to zinc-coated mild steel, more specifically 1.2mm V1437, which is a Volvo Truck Coiporation rephosphorised mild steel. The work investigates both tensile and lap shear properties of similar and dissimilar metal laser welded butt and lap joints, with the majority of the investigation concentrating on the fatigue properties of dissimilar metal laser welded lap joints. The problems encountered when laser welding zinc-coated steel are addressed and overcome with regard to dissimilar metal lap joints with stainless steel. The result being the production of a set of guidelines for laser welding stainless steel to zinc-coated mild steel. The stages of laser welded lap joint fatigue life are defined and the factors affecting dissimilar metal laser welded lap joint fatigue properties are analysed and determined; the findings suggesting that dissimilar metal lap joint fatigue properties are primarily controlled by the local stress at the internal lap face and the early crack growth rate of the material at the internal lap face. The lap joint rotation, in turn, is controlled by sheet thickness, weld width and interfacial gap. Laser welded lap joint fatigue properties are found to be independent of base material properties, allowing dissimilar metal lap joints to be produced without fatigue failure occurring preferentially in the weaker parent material, irrespective of large base material property differences. The effects of Marangoni flow on the compositions of the laser weld beads are experimentally characterised. The results providing definite proof of the stirring mechanism within the weld pool through the use of speeds maps for chromium and nickel. Keywords: Laser welding, dissimilar metal, Zinc-coated mild steel, Austenitic stainless steel, Duplex stainless steel, Fatigue, Lap joint rotation, Automotive.

Rotary friction welding of dissimilar joints and bonding interface characterization by EDX and XPS

Energy Technology Data Exchange (ETDEWEB)

Alves, Eder Paduan; Dollinger, Christian Avila [Instituto de Aeronautica e Espaco (IAE), Sao Jose dos Campos, SP (Brazil); Marcuzzo, Jossano Saldanha; Baldan, Mauricio Ribeiro; Toledo, Rafael Cardoso; Piorino Neto, Francisco; An, Chen Ying, E-mail: eder.padua@yahoo.com.br [Instituto Nacional de Pesquisas Espaciais (INPE), Sao Jose dos Campos, SP (Brazil)

2016-07-01

Full text: Welding of dissimilar materials has been a challenge to engineering. The study and development of new union processes that meet the requirements of projects in the aerospace, nuclear and aviation sector are of great importance to the scientific and productive means. The Rotary friction welding process (RFW) is a process of union that occurs in the solid state, without occurrence of fusion between the parties, and that have like the main bonding mechanisms the diffusion and mechanical mixture. This work has as objective the obtaining of dissimilar joints involving AA 6351-T6 alloy and stainless steel AISI 304l for applications in the aerospace area. The joints obtained by RFW who had procedures and qualified welding process have undergone the techniques of Energy Dispersive X-Ray Spectroscopy (EDX) and X-Ray Photoelectron Spectroscopy (XPS) for analysis of the bonding interface. Were obtained joints with superior mechanical properties the AA 6351-T6 alloy, with the fracture occurring in aluminum away from the bonding interface. The analyses carried out by EDX and XPS have shown the occurrence of interdiffusion among the main elements of the materials involved. The Rotary friction welding process proved to be a great method for obtaining of joints between dissimilar materials that are not possible by fusion welding processes. (author)

Rotary friction welding of dissimilar joints and bonding interface characterization by EDX and XPS

International Nuclear Information System (INIS)

Alves, Eder Paduan; Dollinger, Christian Avila; Marcuzzo, Jossano Saldanha; Baldan, Mauricio Ribeiro; Toledo, Rafael Cardoso; Piorino Neto, Francisco; An, Chen Ying

2016-01-01

Full text: Welding of dissimilar materials has been a challenge to engineering. The study and development of new union processes that meet the requirements of projects in the aerospace, nuclear and aviation sector are of great importance to the scientific and productive means. The Rotary friction welding process (RFW) is a process of union that occurs in the solid state, without occurrence of fusion between the parties, and that have like the main bonding mechanisms the diffusion and mechanical mixture. This work has as objective the obtaining of dissimilar joints involving AA 6351-T6 alloy and stainless steel AISI 304l for applications in the aerospace area. The joints obtained by RFW who had procedures and qualified welding process have undergone the techniques of Energy Dispersive X-Ray Spectroscopy (EDX) and X-Ray Photoelectron Spectroscopy (XPS) for analysis of the bonding interface. Were obtained joints with superior mechanical properties the AA 6351-T6 alloy, with the fracture occurring in aluminum away from the bonding interface. The analyses carried out by EDX and XPS have shown the occurrence of interdiffusion among the main elements of the materials involved. The Rotary friction welding process proved to be a great method for obtaining of joints between dissimilar materials that are not possible by fusion welding processes. (author)

Effect of welding processes on the impression creep resistance of type 316 LN stainless steel weld joints

International Nuclear Information System (INIS)

Vasudevan, M.; Vasantharaja, P.; Sisira, P.; Divya, K.; Ganesh Sundara Raman, S.

2016-01-01

Type 316 LN stainless steel is the major structural material used in the construction of fast breeder reactors. Activated Tungsten Inert Gas (A-TIG) welding , a variant of the TIG welding process has been found to enhance the depth of penetration significantly during autogenous welding and also found to enhance the creep rupture life in stainless steels. The present study aims at comparing the effect of TIG and A-TIG welding processes on the impression creep resistance of type 316 LN stainless steel base metal, fusion zone and heat affected zone (HAZ) of weld joints. Optical and TEM have been used to correlate the microstructures with the observed creep rates of various zones of the weld joints. Finer microstructure and higher ferrite content was observed in the TIG weld joint fusion zone. Coarser grain structure was observed in the HAZ of the weld joints. Impression creep rate of A-TIG weld joint fusion zone was almost equal to that of the base metal and lower than that of the TIG weld joint fusion zone. A-TIG weld joint HAZ was found to have lower creep rate compared to that of conventional TIG weld joint HAZ due to higher grain size. HAZ of the both the weld joints exhibited lower creep rate than the base metal. (author)

Effects of strength mis-matching on the fracture behavior of nuclear pressure steel A508-III welded joint

Energy Technology Data Exchange (ETDEWEB)

Zhu Zhengqiang [School of Material Science and Technology, Shanghai Jiaotong University, 1954 Huashan Road, Shanghai 200030 (China)]. E-mail: zhuzhq01@sjtu.edu.cn; Jing Hongyang [School of Material Science and Technology, Tianjin University, Tianjin 300072 (China); Ge Jingguo [School of Material Science and Technology, Shanghai Jiaotong University, 1954 Huashan Road, Shanghai 200030 (China); Chen Ligong [School of Material Science and Technology, Shanghai Jiaotong University, 1954 Huashan Road, Shanghai 200030 (China)

2005-01-15

In this paper, according to the nuclear pressure steel A508-III, the effect of strength mis-matching on the fracture behavior was analyzed by fracture mechanics test and the crack tip stress field of three-point bend specimen was analyzed by using finite element analysis method (FEM). The fracture of heat-affected zone (HAZ) was emphasized especially. The results of FEM show that if the under-matching weld was used, the opening stress and stress triaxiality in the vicinity of crack tip would increase for weld-crack specimen, and would reduce for HAZ-crack specimen. This tendency was confirmed by the test results.

Study on the Size Effects of H-Shaped Fusion Zone of Fiber Laser Welded AZ31 Joint

Directory of Open Access Journals (Sweden)

Guang-Feng Lu

2018-03-01

Full Text Available There are two kinds of typical cross-section profiles for the fusion zone (FZ of a laser welded thin section joint, i.e., a V-shaped cross-section and an H-shaped cross-section. Previous researches indicated that tensile strength of the V-shaped joint was lower than that of the H-shaped one due to the greater heterogeneity of strain distribution on the V-shaped joint during tensile process. In this work, impacts of the aspect ratio of FZ on the mechanical properties of laser welded thin section joints with an H-shaped cross-section profile were investigated. Welding conditions corresponding to two typical H-shaped joints (i.e., Wnarrower with a narrower FZ, and Wwider with a wider FZ were decided through a laser welding orthogonal experimental plan. Then, the microstructure and properties of both joints were examined and compared. The results show that the tensile strength of joint Wnarrower and joint Wwider was about 72% and 80.9% that of the base metal, respectively. Both joints fractured in the FZ during tensile processes. The low-cycle fatigue life of the base metal, the joint Wnarrower and the joint Wwider were 3377.5 cycles, 2825 cycles and 3155.3 cycles, respectively. By using high-speed imaging, it was found that the fatigue crack of joint Wnarrower initiated and propagated inside the fusion zone, while the fatigue crack of the joint Wwider initiated at the edge of the base metal and propagated for a distance within the base metal before entering into the fusion zone. This work promoted our understanding about the influence of the weld bead shape on the properties of laser welded thin section joints.

Creep damage evaluation of low alloy steel weld joint by small punch creep testing

International Nuclear Information System (INIS)

Nishioka, Tomoya; Sawaragi, Yoshiatsu; Uemura, Hiromi

2013-01-01

The effect of sampling location on SPC (Small Punch Creep) tests were investigated for weld joints to establish evaluation method of Type IV creep behavior. The SPC specimen shape was 10mm diameter and 0.5mm thick round disc prepared from weld joints of 2.25Cr-1Mo low alloy steel. It was found that the center of SPC specimen should be 2mm apart from the weld interface as the recommended sampling location. Creep damage was imposed for large weld joint specimens by axial creep loading at 620degC, 52MPa with the interrupted time fraction of 0.34, 0.45, 0.64 and 0.82.SPC samples were prepared from those damaged specimens following the recommended way described in this paper. Among the various SPC tests conducted, good relationships were found for the test condition of 625degC, 200N. Namely, good relationships were obtained both between minimum deflection rate and creep life fraction, and between rupture time and creep life fraction. Consequently, creep life assessment of Type IV fracture by SPC tests could be well conducted using the sampling location and the test condition recommended in this paper. (author)

Characteristics of welded joints of nuclear reactor interest

International Nuclear Information System (INIS)

1978-01-01

The main propose of this work, was the determination of the optical conditions for obtaining welded joints of stainless steel, the quality control of joints obtained by destructive and non-destructive essays, as well as, the first specific essays of fluence and fatigue of the base metals employed. All tests performed in the base metals are very important from the joint of view that the comparison between results obtained with base metals and welded joints allows a the evaluation of the efficiency of the welded joints. (author) [pt

Role of butter layer in low-cycle fatigue behavior of modified 9Cr and CrMoV dissimilar rotor welded joint

International Nuclear Information System (INIS)

Wu, Qingjun; Lu, Fenggui; Cui, Haichao; Liu, Xia; Wang, Peng; Tang, Xinhua

2014-01-01

Highlights: • Modified 9Cr–CrMoV dissimilar turbine rotor was successfully welded by NG-SAW. • LCF properties of both welded joints were approximate at smaller strain amplitude. • Tempered martensite with amounts of carbides in HAZ contributed to weakest zones. • Matched BL determined LCF properties of whole joint for dissimilar welded rotor. - Abstract: The present work aims at studying the role of butter layer (BL) in low-cycle fatigue (LCF) behavior of modified 9Cr steel and CrMoV steel dissimilar welded joint. The significant difference of the chemical composition of base metals (BMs) makes it a challenge to achieve sound welded joint. Therefore, buttering was considered to obtain a transition layer between the dissimilar steels. The LCF tests of two kinds of specimens without and with butter layer were performed applying strain-controlled cyclic load with different axial strain amplitudes. The test results indicated that the number of cycles at higher strain amplitudes of welded joint without butter layer was greatly higher than that of the joint with butter layer, while the fatigue lifetime to crack initiation (2N f ) became closer to each other at low and middle strain amplitudes. The failure was in the tempered heat affected zone (HAZ) at the CrMoV side for specimens without BL, while the fracture occurred at the tempered HAZ in the BL for specimens with BL. The microstructure details of BM, BL, HAZ and weld metals (WMs) were revealed by optical microscopy (OM). It was found that the tempered martensite was major microstructure for welded joint and much more carbides were observed in tempered HAZ than other parts due to the repeated tempering. Microhardness test indicated a softest zone existing tempered HAZ of BL and also there was a softer zone in tempered HAZ at the CrMoV side due to repeated tempering during welding and post weld heat treatment (PWHT). And scanning electron microscopy (SEM) was applied to observe the fractography. It was

The characteristics of welded joints for air conditioning application

Science.gov (United States)

Weglowski, M. St.; Weglowska, A.; Miara, D.; Kwiecinski, K.; Błacha, S.; Dworak, J.; Rykala, J.; Pikula, J.; Ziobro, G.; Szafron, A.; Zimierska-Nowak, P.; Richert, M.; Noga, P.

2017-10-01

In the paper the results of metallographic examination of welded joints for air-conditioning elements are presented. The European directives 2006/40/EC on the greenhouse gasses elimination demand to stop using traditional refrigerant and to change it to R744 (CO2) medium in air conditioning installation. The R744 refrigerant is environmental friendly medium if compared with standard solution such as R12, R134a or R1234yf and safer for passengers than R1234yf. The non-standard thermodynamic parameters of the R744 which translate into high pressure and high temperature require specific materials to develop the shape and to specify the technology of manufacturing for the particular elements of the conduits and moreover the technologies of joining for the whole structure, which would meet the exploitation requirements of the new air-conditioning system. To produce the test welded joints of stainless steels four different joining technologies were applied: laser welding, plasma welding, electron beam welding as well as high speed rotation welding. This paper describes the influence of the selected welding process on the macrostructure and microstructure of welded joints of AISI 304 and AISI 316L steels. The results indicated that plasma welding laser welding and electron beam welding technologies guaranty the proper quality of welded joints and can be used for the air conditioning application in automotive industry. However, high speed rotation welding not guarantee the good quality of welded joints and cannot be used for above application.

STUDY AND ANALYSIS OF THE EFFECT OF WELDING PROCESS ON DISTORTION WITH 304L STAINLESS STEEL WELD JOINTS

OpenAIRE

Dhananjay Kumar*, Dharamvir mangal

2017-01-01

The effect of welding process on the distortion with 304L stainless steel 12thk weld joints made by TIG (tungsten inert gas) and SMAW (Shielded metal arc welding) welding process involving different type joint configuration have been studied. The joint configurations employed were double V-groove edge preparation for double side SMAW welding and square – butt preparation for double side TIG welding. All weld joints passed by radiographic. Distortion measurements were carried out using height ...

Abnormal microstructure in the weld zone of linear friction welded Ti–6.5Al–3.5Mo–1.5Zr–0.3Si titanium alloy joint and its influence on joint properties

Energy Technology Data Exchange (ETDEWEB)

Li, Wenya, E-mail: liwy@nwpu.edu.cn [State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi' an 710072 (China); Suo, Juandi; Ma, Tiejun; Feng, Yan [State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi' an 710072 (China); Kim, KeeHyun [School of Metallurgy and Materials, University of Birmingham, Edgbaston, Birmingham B15 2TT (United Kingdom)

2014-04-01

A detailed investigation on an unexpected abnormal microstructure formed near the weld line in the linear friction welded Ti–6.5Al–3.5Mo–1.5Zr–0.3Si titanium alloy joint had been performed. Microstructure observations with the help of optical microscope, electron backscatter diffraction and transmission electron microscope with an energy dispersive X-ray spectroscopy were conducted to determine the compositions and phases near the weld line. The results indicate that the abnormal microstructure may be obtained at a low friction pressure and consists of α phase in the form of spherical particles. Tensile strength and fracture characteristics were also examined to clarify the influence of α grains. It is found that the tensile strength is only about 49% of the parent material. The explanation to the formation of spherical α is that lamellar α breaks up, spheroidizes and coalesces to form bigger particles by squeezing out the softer intergranular β phase. The effect of post-weld heat treatment (PWHT) was also investigated to optimize the joint microstructure and mechanical properties. The results suggest that the defects still exist after PWHT, and consequently the appropriate process parameters should be used to achieve a good weld.

Friction stir scribe welding technique for dissimilar joining of aluminium and galvanised steel

Energy Technology Data Exchange (ETDEWEB)

Wang, Tianhao [Center for Friction Stir Processing, Department of Materials Science and Engineering, University of North Texas, Denton, TX, USA; Sidhar, Harpreet [Center for Friction Stir Processing, Department of Materials Science and Engineering, University of North Texas, Denton, TX, USA; Mishra, Rajiv S. [Center for Friction Stir Processing, Department of Materials Science and Engineering, University of North Texas, Denton, TX, USA; Hovanski, Yuri [Pacific Northwest National Laboratory, Energy Materials and Manufacturing, Richland, WA, USA; Upadhyay, Piyush [Pacific Northwest National Laboratory, Energy Materials and Manufacturing, Richland, WA, USA; Carlson, Blair [General Motors Technical Center, Warren, MI, USA

2017-10-04

Friction stir scribe technology, a derivative of friction stir welding, was applied for the dissimilar lap welding of an aluminum alloy and galvanized mild steel sheets. During the process, the rotating tool with a cobalt steel scribe first penetrated the top material — aluminum — and then the scribe cut the bottom material — steel. The steel was displaced into the upper material to produce a characteristic hook feature. Lap welds were shear tested, and their fracture paths were studied. Welding parameters affected the welding features including hook height, which turned out to be highly related to fracture position. Therefore, in this paper, the relationships among welding parameters, hook height, joint strength and fracture position are presented. In addition, influence of zinc coating on joint strength was also studied. Keywords: friction stir scribe technology; dissimilar material welding; zinc coating; hook height; joint strength; fracture position

Environmental Degradation of Dissimilar Austenitic 316L and Duplex 2205 Stainless Steels Welded Joints

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Topolska S.

2017-12-01

Full Text Available The paper describes structure and properties of dissimilar stainless steels welded joints between duplex 2205 and austenitic 316L steels. Investigations were focused on environmentally assisted cracking of welded joints. The susceptibility to stress corrosion cracking (SCC and hydrogen embrittlement was determined in slow strain rate tests (SSRT with the strain rate of 2.2 × 10−6 s−1. Chloride-inducted SCC was determined in the 35% boiling water solution of MgCl2 environment at 125°C. Hydrogen assisted SCC tests were performed in synthetic sea water under cathodic polarization condition. It was shown that place of the lowest resistance to chloride stress corrosion cracking is heat affected zone at duplex steel side of dissimilar joins. That phenomenon was connected with undesirable structure of HAZ comprising of large fractions of ferrite grains with acicular austenite phase. Hydrogen assisted SCC tests showed significant reduction in ductility of duplex 2205 steel while austenitic 316L steel remains almost immune to degradation processes. SSR tests of dissimilar welded joints revealed a fracture in the area of austenitic steel.

Creep rupture behavior of 9Cr–1.8W–0.5Mo–VNb (ASME grade 92) ferritic steel weld joint

Energy Technology Data Exchange (ETDEWEB)

Sakthivel, T., E-mail: tsakthivel@igcar.gov.in; Vasudevan, M.; Laha, K., E-mail: laha@igcar.gov.in; Parameswaran, P.; Chandravathi, K.S.; Panneer Selvi, S.; Maduraimuthu, V.; Mathew, M.D.

2014-01-03

Creep rupture behavior of 9Cr–1.8W–0.5Mo–VNb (ASME grade 92) ferritic steel weld joint fabricated by activated TIG (A-TIG) welding process have been investigated at 923 K over a stress range of 80–150 MPa. The weld joint was comprise of fusion zone, heat affected zone (HAZ) and base metal. The HAZ consisted of coarse prior-austenite grain (CGHAZ), fine prior-austenite grain (FGHAZ) and intercritical (ICHAZ) regions in an order away from the fusion zone to base metal. A hardness trough was observed at the outer edge of HAZ of the weld joint. TEM investigation revealed the presence of coarse M{sub 23}C{sub 6} precipitates and recovery of martensite lath structure into subgrain in the ICHAZ of the weld joint, leading to the hardness trough. The weld joint exhibited lower creep rupture lives than the base metal at relatively lower stresses. Creep rupture failure location of the weld joint was found to shift with applied stress. At high stresses fracture occurred in the base metal, whereas failure location shifted to FGHAZ at lower stresses with significant decrease in rupture ductility. SEM investigation of the creep ruptured specimens revealed precipitation of Laves phase across the joint, more extensively in the FGHAZ. On creep exposure, the hardness trough was found to shift from the ICHAZ to FGHAZ. Extensive creep cavitation was observed in the FGHAZ and was accompanied with the Laves phase, leading to the premature type IV failure of the steel weld joint at the FGHAZ.

Structure of Fe-Ni-Cr steel welded joints

International Nuclear Information System (INIS)

Bratukhin, A.G.; Maslenkov, S.B.; Logunov, A.V.

1993-01-01

Properties of a welded joint depend on the structure of metal of the joint and near the joint areas subjected to thermal effect in the process of welding. The well-known phenomena, accompanying the welding (grain growth in near the joint area, intergrain slip, stressed state related to crystallization and rapid cooling), as well as certain other processes, which have been insufficiently studied either due to their poor pronouncement or owing to imperfection of the equipment and methods employed, were analyzed, as applied to stainless hihg-strength Fe-Ni-Cr steels

Influence of Friction Stir Welding on Mechanical Properties of Butt Joints of AZ61 Magnesium Alloy

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Seung-Ju Sun

2017-01-01

Full Text Available In this study, the effect of heat input on the mechanical properties and fracture behaviors of AZ61 magnesium alloy joints has been studied. Magnesium alloy AZ61 plates with thickness of 5 mm were welded at different ratios of tool rotational speed to welding speed (ω/ν. The average ultimate tensile strength of all weld conditions satisfying a ω/ν ratio of 3 reached 100% of the strength of the base material. Fractures occurred at the interface between the thermomechanical affected zone at advancing side and the stir zone in all welded specimens. From the scanning electron microscope and electron backscatter diffraction analysis, it was determined that the interface between the thermomechanical affected zone and the stir zone, which is the region where the grain orientation changes, was the weakest part; the advancing side region was relatively weaker than the retreating side region because the grain orientation change occurred more dramatically in the advancing side region.

Evaluation of weld joints properties of 60mm thick AISI 316L for fusion reactor vacuum vessel by TIG and EB welding processes

International Nuclear Information System (INIS)

Buddu, Ramesh Kutner

2016-01-01

The present paper is focussed on the NDT examination procedures, evaluated mechanical properties; microstructure details investigated on the different welding process of Multipass TIG process (64 passes) and electron beam welding (two pass) of the AISI SS316LN plates. The characterization of mechanical properties (Tensile, Bend, Hardness and Impact) and detailed microstructure analysis have been discussed in this paper. Mechanical properties in both conditions shown higher joint efficiencies. Bend tests shown the good quality of weld and ductility behavior of the joining process. Hardening is observed in both the samples for welded zone and HAZ compared to base metal. Impact fracture results revealed the poor toughness properties for the WZ compared to HAZ and BM samples in both the cases

Texture, microstructure, and fractal features of the low-cycle fatigue failure of the metal in pipeline welded joints

Science.gov (United States)

Usov, V. V.; Gopkalo, E. E.; Shkatulyak, N. M.; Gopkalo, A. P.; Cherneva, T. S.

2015-09-01

Crystallographic texture and fracture features are studied after low-cycle fatigue tests of laboratory specimens cut from the base metal and the characteristic zones of a welded joint in a pipeline after its longterm operation. The fractal dimensions of fracture surfaces are determined. The fractal dimension is shown to increase during the transition from ductile to quasi-brittle fracture, and a relation between the fractal dimension of a fracture surface and the fatigue life of the specimen is found.

Microstructure and Strain Rate-Dependent Tensile Deformation Behavior of Fiber Laser-Welded Butt Joints of Dual-Phase Steels

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Liu, Yang; Dong, Danyang; Han, Zhiqiang; Yang, Zhibin; Wang, Lu; Dong, Qingwei

2018-05-01

The microstructure and tensile deformation behavior of the fiber laser-welded similar and dissimilar dual-phase (DP) steel joints over a wide range of strain rates from 10-3 to 103 s-1 were investigated for the further applications on the lightweight design of vehicles. The high strain rate dynamic tensile deformation process and full-field strain distribution of the base metals and welded joints were examined using the digital image correlation method and high-speed photography. The strain rate effects on the stress-strain responses, tensile properties, deformation, and fracture behavior of the investigated materials were analyzed. The yield stress (YS) and ultimate tensile strength (UTS) of the dissimilar DP780/DP980 welded joints were lying in-between those of the DP780 and DP980 base metals, and all materials exhibited positive strain rate dependence on the YS and UTS. Owing to the microstructure heterogeneity, the welded joints showed relatively lower ductility in terms of total elongation (TE) than those of the corresponding base metals. The strain localization started before the maximum load was reached, and the strain localization occurred earlier during the whole deformation process with increasing strain rate. As for the dissimilar welded joint, the strain localization tended to occur in the vicinity of the lowest hardness value across the welded joint, which was in the subcritical HAZ at the DP780 side. As the strain rate increased, the typical ductile failure characteristic of the investigated materials did not change.

Microstructure and Strain Rate-Dependent Tensile Deformation Behavior of Fiber Laser-Welded Butt Joints of Dual-Phase Steels

Science.gov (United States)

Liu, Yang; Dong, Danyang; Han, Zhiqiang; Yang, Zhibin; Wang, Lu; Dong, Qingwei

2018-04-01

The microstructure and tensile deformation behavior of the fiber laser-welded similar and dissimilar dual-phase (DP) steel joints over a wide range of strain rates from 10-3 to 103 s-1 were investigated for the further applications on the lightweight design of vehicles. The high strain rate dynamic tensile deformation process and full-field strain distribution of the base metals and welded joints were examined using the digital image correlation method and high-speed photography. The strain rate effects on the stress-strain responses, tensile properties, deformation, and fracture behavior of the investigated materials were analyzed. The yield stress (YS) and ultimate tensile strength (UTS) of the dissimilar DP780/DP980 welded joints were lying in-between those of the DP780 and DP980 base metals, and all materials exhibited positive strain rate dependence on the YS and UTS. Owing to the microstructure heterogeneity, the welded joints showed relatively lower ductility in terms of total elongation (TE) than those of the corresponding base metals. The strain localization started before the maximum load was reached, and the strain localization occurred earlier during the whole deformation process with increasing strain rate. As for the dissimilar welded joint, the strain localization tended to occur in the vicinity of the lowest hardness value across the welded joint, which was in the subcritical HAZ at the DP780 side. As the strain rate increased, the typical ductile failure characteristic of the investigated materials did not change.

Tensile Properties of Friction Stir Welded Joints of AA 2024-T6 Alloy at Different Welding Speeds

Science.gov (United States)

Avula, Dhananjayulu; Devuri, Venkateswarlu; Cheepu, Muralimohan; Dwivedi, Dheerendra Kumar

2018-03-01

The influence of welding speed on the friction stir welded joint properties of hardness, tensile properties, defects and microstructure characterization are studied in the present study. The friction stir welding was conducted on AA2014-T6 heat treated alloy with 5 mm thickness plate in butt joint configuration. The welding speed was varied from 8 mm/min to 120 mm/min at the fixed travel speed and load conditions. It is observed that the welding speeds at higher rate with wide range can be possible to weld this alloy at higher rates of tool revolution suggesting that the inherent capability of friction stir welding technique for aluminum 2014 alloys. The strength of the joints gradually increases with enhancing of welding speed. The micro structural observations exhibited the formation of equiaxed grains in the stir zone and slightly in the thermo-mechanically affected zone. In addition, the size of the grains decreases with increase in welding speed owing to the presence of low heat input. Hence the hardness of the joints slightly increased in the stir zones over the other zones of the weld nugget. The joint strength initially increases with the welding speed and starts to decreases after reaching to the maximum value. The relationship between the welding conditions and friction stir welded joint properties has been discussed.

Degradation Processes of Al-Zn Welded Joints

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Jiří Votava

2014-01-01

Full Text Available Welding of metal materials belongs to non-demountable joints. Current trend especially in an automotive industry is to join materials with a different melting temperature. Most of all, there are dural profiles with ferrite or austenite steel. The reason for this is the effort to lower the weight of the whole construction and at the same time preserve sufficient mechanical characteristics. However, there is a big risk of different electrical potentials of both of these metals in this type of non-demountable joints. The experimental part of this paper brings evaluation of mechanical-corrosion processes of overlapped joints produced by the CMT (cold metal transfer method. The base material for weld bead is dural sheet AlMg3 and dural sheet with a surface treatment aluzinc DX51D+AZ 150. Material AlSi5 in the form of a wire was used as an additional material for a welding bath. Method CMT was used in order to create a weld bead. Initial analysis of weld bead was done visually using a binocular microscope. Further, a metallographic analysis of weld bead and base material was processed. The aim was to identify the heat affected area around the welded joint. Microhardness of intermetallic aluminium phases was measured, after the identification of intermetallic phases a chemical analysis EDS was processed. Prepared samples underwent corrosion degradation in a salt spray environment in compliance with the norm ČSN EN ISO 9227. Visual and metallographic evaluation of the individual samples was processed after every week of exposition to the salt spray environment. The goal of this experiment was to record the initial impulse of galvanic corrosion which consists in corrosion degradation in the area of welded joint.

Thermographic Analysis of Stress Distribution in Welded Joints

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Domazet Ž.

2010-06-01

Full Text Available The fatigue life prediction of welded joints based on S-N curves in conjunction with nominal stresses generally is not reliable. Stress distribution in welded area affected by geometrical inhomogeneity, irregular welded surface and weld toe radius is quite complex, so the local (structural stress concept is accepted in recent papers. The aim of this paper is to determine the stress distribution in plate type aluminum welded joints, to analyze the reliability of TSA (Thermal Stress Analysis in this kind of investigations, and to obtain numerical values for stress concentration factors for practical use. Stress distribution in aluminum butt and fillet welded joints is determined by using the three different methods: strain gauges measurement, thermal stress analysis and FEM. Obtained results show good agreement - the TSA mutually confirmed the FEM model and stresses measured by strain gauges. According to obtained results, it may be stated that TSA, as a relatively new measurement technique may in the future become a standard tool for the experimental investigation of stress concentration and fatigue in welded joints that can help to develop more accurate numerical tools for fatigue life prediction.

Thermographic Analysis of Stress Distribution in Welded Joints

Science.gov (United States)

Piršić, T.; Krstulović Opara, L.; Domazet, Ž.

2010-06-01

The fatigue life prediction of welded joints based on S-N curves in conjunction with nominal stresses generally is not reliable. Stress distribution in welded area affected by geometrical inhomogeneity, irregular welded surface and weld toe radius is quite complex, so the local (structural) stress concept is accepted in recent papers. The aim of this paper is to determine the stress distribution in plate type aluminum welded joints, to analyze the reliability of TSA (Thermal Stress Analysis) in this kind of investigations, and to obtain numerical values for stress concentration factors for practical use. Stress distribution in aluminum butt and fillet welded joints is determined by using the three different methods: strain gauges measurement, thermal stress analysis and FEM. Obtained results show good agreement - the TSA mutually confirmed the FEM model and stresses measured by strain gauges. According to obtained results, it may be stated that TSA, as a relatively new measurement technique may in the future become a standard tool for the experimental investigation of stress concentration and fatigue in welded joints that can help to develop more accurate numerical tools for fatigue life prediction.

The effects of alloying elements on microstructures and mechanical properties of tungsten inert gas welded AZ80 magnesium alloys joint

Science.gov (United States)

Li, Hui; Zhang, Jiansheng; Ding, Rongrong

2017-11-01

The effects of alloying elements on the macrostructures, microstructures and tensile strength of AZ80 Mg alloy weldments were studied in the present study. The results indicate that with the decrease of Al element content of filler wire, the welding defects of seam are gradually eliminated and the β-Mg17Al12 phases at α-Mg boundaries are refined and become discontinuous, which are beneficial to the improvement of tensile strength. With AZ31 Mg alloy filler wire, the maximum tensile strength of AZ80 weldment is 220 MPa and fracture occurs at the welding seam of joint. It is experimentally proved that robust AZ80 Mg alloy joints can be obtained by tungsten inert gas (TIG) welding process with AZ31 Mg alloy filler wire. However, further study is required to improve the microstructures and reduce welding defects of joint in order to further improve the joining strength of AZ80 Mg alloy joint.

Ductile fracture of two-phase welds under 77K. [Steel-EhP810, steel-EhP666, steel-08Kh18N10T, steel-EhP659-VI, steel-chP810

Energy Technology Data Exchange (ETDEWEB)

Yushchenko, K.A.; Voronin, S.A.; Pustovit, A.I.; Shavel' , A.V.

The effect of the type of welding and fillers on crack resistance of welded joints high-strength steel EhP810 and its various compounds with steels EhP666, 08Kh18N10T has been studied. For the welding of steel EhP810 with steels EhP810, EhP666, 08Kh18N10T electron-beam, automatic, argon tungsten arc with non-consumable electrode with various fillers, as well as argon metal-arc welding with consumable electrode, were used. It is shown, that for a joint, made by electron-beam welding, parameters sigmasub(u), Ksub(IcJ), KCV are higher than for a joint of a similar phase structure made using filler wire EhP659-VI. It is explained by the fact, that during electron-beam welding joint metal refining takes place, which removes gases. In welded joints of chP810 steel, having joints with austenitic structure, characteristic of crack resistance Ssub(c) increases by more than 0.2 mm in contrast to two-phase joints, which conventional yield strength at 77 K exceeds 1000 MPa. It is worth mentioning, that for other classes of steels formation of two-phase structure of joint increases welded joint resistance to brittle fracture. It is possible to obtain the required structure of joint with assigned level of resistance to brittle fracture by means of the use of different fillers, optimum and welding procedure, regulating the part of the basic metal in joint content.

Reproducibility of pop-ins in laboratory testing of welded joints

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Berejnoi C.

2000-01-01

Full Text Available The pop-in phenomenon, quite common in fracture mechanics tests of welded joints, corresponds to a brittle crack initiation grown from a local brittle zone (LBZ that is arrested in reaching the higher toughness material that surrounds this LBZ. A methodology to obtain a high percentage of pop-in occurrence in laboratory testing is necessary to study the pop-in significance. Such a method is introduced in this work and includes the consumable combination and welding procedures for the SMAW welding process to generate artificial LBZ. In order to find out the influence of the loading state upon the pop-in phenomenon, laboratory CTOD tests were performed using two specimen configurations: some single edge-notched specimens were loaded on a three-point bending (SE(B fixture while others were tested in tensile load (SE(T. A higher frequency of pop-in occurrence was observed in the SE(B geometry.

The effect of controlled shot peening on fusion welded joints

International Nuclear Information System (INIS)

Lah, Nur Azida Che; Ali, Aidy; Ismail, Napsiah; Chai, Lim Poon; Mohamed, Abdul Aziz

2010-01-01

This work examines the effect of controlled shot peening (CSP) treatment on the fatigue strength of an ASTM A516 grade 70 carbon steel welded joint. Metallurgical modifications, hardness, elemental compositions, and internal discontinuities, such as porosity, inclusions, lack of penetration, and undercut found in treated and untreated fusion welded joints, were characterized. The fatigue results of as-welded and peened skimmed joints were compared. It was observed that the effect of the CSP and skimming processes improved the fatigue life of the fusion weld by 50% on MMA-welded, 63% on MIG-welded, and 60% on TIG-welded samples.

Residual stress reduction in the penetration nozzle weld joint by overlay welding

International Nuclear Information System (INIS)

Jiang, Wenchun; Luo, Yun; Wang, B.Y.; Tu, S.T.; Gong, J.M.

2014-01-01

Highlights: • Residual stress reduction in penetration weld nozzle by overlay welding was studied. • The overlay weld can decrease the residual stress in the weld root. • Long overlay welding is proposed in the actual welding. • Overlay weld to decrease residual stress is more suitable for thin nozzle. - Abstract: Stress corrosion cracking (SCC) in the penetration nozzle weld joint endangers the structural reliability of pressure vessels in nuclear and chemical industries. How to decrease the residual stress is very critical to ensure the structure integrity. In this paper, a new method, which uses overlay welding on the inner surface of nozzle, is proposed to decrease the residual stresses in the penetration joint. Finite element simulation is used to study the change of weld residual stresses before and after overlay welding. It reveals that this method can mainly decrease the residual stress in the weld root. Before overlay welding, large tensile residual stresses are generated in the weld root. After overlay weld, the tensile hoop stress in weld root has been decreased about 45%, and the radial stress has been decreased to compressive stress, which is helpful to decrease the susceptibility to SCC. With the increase of overlay welding length, the residual stress in weld root has been greatly decreased, and thus the long overlay welding is proposed in the actual welding. It also finds that this method is more suitable for thin nozzle rather than thick nozzle

Finite element analysis for the initiation of lamellar tearing in welded joints

International Nuclear Information System (INIS)

Krieg, R.D.; Thomas, R.K.

1980-01-01

A numerical procedure using the finite element method is presented for predicting the initiation of lamellar tearing in fillet welded T-joints commonly employed in large structures. Starting with a prescribed geometry, the welding process is approximated by a known time-dependent volumetric heat source which simulates the arc heating and deposition of liquid metal. The transient nonlinear thermal and stress problems are then solved using finite element computer codes. Results of the elastic-plastic stress analysis are presented showing a predicted region of incipient lamellar tearing based on a ductile fracture theory which qualitatively agrees with the size and location of tears typically observed in photomicrographs. Additional insight into post failure crack length and stability is presented based on a simplified linear elastic fracture mechanics approach. Although the analysis procedure shows signs of promise, several weak points in the model are pointed out which must be improved before lamellar tearing can be quantified in an approach of this general type

Effect of Welding Processes on the Microstructure, Mechanical Properties and Residual Stresses of Plain 9Cr-1Mo Steel Weld Joints

Science.gov (United States)

Nagaraju, S.; Vasantharaja, P.; Brahadees, G.; Vasudevan, M.; Mahadevan, S.

2017-12-01

9Cr-1Mo steel designated as P9 is widely used in the construction of power plants and high-temperature applications. It is chosen for fabricating hexcan fuel subassembly wrapper components of fast breeder reactors. Arc welding processes are generally used for fabricating 9Cr-1Mo steel weld joints. A-TIG welding process is increasingly being adopted by the industries. In the present study, shielded metal arc (SMA), tungsten inert gas (TIG) and A-TIG welding processes are used for fabricating the 9Cr-1Mo steel weld joints of 10 mm thickness. Effect of the above welding processes on the microstructure evolution, mechanical properties and residual stresses of the weld joints has been studied in detail. All the three weld joints exhibited comparable strength and ductility values. 9Cr-1Mo steel weld joint fabricated by SMAW process exhibited lower impact toughness values caused by coarser grain size and inclusions. 9Cr-1Mo steel weld joint fabricated by TIG welding exhibited higher toughness due to finer grain size, while the weld joint fabricated by A-TIG welding process exhibited adequate toughness values. SMA steel weld joint exhibited compressive residual stresses in the weld metal and HAZ, while TIG and A-TIG weld joint exhibited tensile residual stresses in the weld metal and HAZ.

Effect of Mg and Cu on mechanical properties of high-strength welded joints of aluminum alloys obtained by laser welding

Science.gov (United States)

Annin, B. D.; Fomin, V. M.; Karpov, E. V.; Malikov, A. G.; Orishich, A. M.

2017-09-01

Results of experimental investigations of welded joints of high-strength aluminum-lithium alloys of the Al-Cu-Li and Al-Mg-Li systems are reported. The welded joints are obtained by means of laser welding and are subjected to various types of processing for obtaining high-strength welded joints. A microstructural analysis is performed. The phase composition and mechanical properties of the welded joints before and after heat treatment are studied. It is found that combined heat treatment of the welded joint (annealing, quenching, and artificial ageing) increases the joint strength, but appreciably decreases the alloy strength outside the region thermally affected by the welding process.

The Effect of Weld Reinforcement and Post-Welding Cooling Cycles on Fatigue Strength of Butt-Welded Joints under Cyclic Tensile Loading.

Science.gov (United States)

Araque, Oscar; Arzola, Nelson; Hernández, Edgar

2018-04-12

This research deals with the fatigue behavior of butt-welded joints, by considering the geometry and post-welding cooling cycles, as a result of cooling in quiet air and immersed in water. ASTM A-36 HR structural steel was used as the base metal for the shielded metal arc welding (SMAW) process with welding electrode E6013. The welding reinforcement was 1 mm and 3 mm, respectively; axial fatigue tests were carried out to determine the life and behavior in cracks propagation of the tested welded joints, mechanical characterization tests of properties in welded joints such as microhardness, Charpy impact test and metallographic analysis were carried out. The latter were used as input for the analysis by finite elements which influence the initiation and propagation of cracks and the evaluation of stress intensity factors (SIF). The latter led to obtaining the crack propagation rate and the geometric factor. The tested specimens were analyzed, by taking photographs of the cracks at its beginning in order to make a count of the marks at the origin of the crack. From the results obtained and the marks count, the fatigue crack growth rate and the influence of the cooling media on the life of the welded joint are validated, according to the experimental results. It can be concluded that the welded joints with a higher weld reinforcement have a shorter fatigue life. This is due to the stress concentration that occurs in the vicinity of the weld toe.

A Neural Network Approach for GMA Butt Joint Welding

DEFF Research Database (Denmark)

Christensen, Kim Hardam; Sørensen, Torben

2003-01-01

This paper describes the application of the neural network technology for gas metal arc welding (GMAW) control. A system has been developed for modeling and online adjustment of welding parameters, appropriate to guarantee a certain degree of quality in the field of butt joint welding with full...... penetration, when the gap width is varying during the welding process. The process modeling to facilitate the mapping from joint geometry and reference weld quality to significant welding parameters has been based on a multi-layer feed-forward network. The Levenberg-Marquardt algorithm for non-linear least...

A Neural Network Approach for GMA Butt Joint Welding

DEFF Research Database (Denmark)

Christensen, Kim Hardam; Sørensen, Torben

2003-01-01

penetration, when the gap width is varying during the welding process. The process modeling to facilitate the mapping from joint geometry and reference weld quality to significant welding parameters has been based on a multi-layer feed-forward network. The Levenberg-Marquardt algorithm for non-linear least......This paper describes the application of the neural network technology for gas metal arc welding (GMAW) control. A system has been developed for modeling and online adjustment of welding parameters, appropriate to guarantee a certain degree of quality in the field of butt joint welding with full...

Tool geometry, rotation and travel speeds effects on the properties of dissimilar magnesium/aluminum friction stir welded lap joints

International Nuclear Information System (INIS)

Mohammadi, J.; Behnamian, Y.; Mostafaei, A.; Gerlich, A.P.

2015-01-01

Highlights: • Tool geometry, rotation and travel speeds show great effect on the microstructure stability of FSW joint. • Increasing rotation and travel speeds resulted in increasing the tensile strength and ductility of the joints. • Better intermixing between Al/Mg alloys was obtained by tapered threaded pin. • A mechanical interlocking mechanism proposed for higher ductility and superior tensile properties in FSW joints. - Abstract: Lap joint friction stir welding (FSW) between dissimilar AZ31B and Al 6061 alloys sheets was conducted using various welding parameters including tool geometry, rotation and travel speeds. Tapered threaded pin and tapered pin tools were applied to fabricate FSW joints, using different rotation and travel speeds. Metallurgical investigations including X-ray diffraction pattern (XRD), optical microscopy images (OM), scanning electron microscopy equipped with an energy-dispersive X-ray spectroscopy (SEM–EDS) and electron probe microanalysis (EPMA) were used to characterize joints microstructures made with different welding parameters. Intermetallic phases were detected in the weld zone (WZ). Various microstructures were observed in the stir zone which can be attributed to using different travel and rotation speeds. Mechanical evaluation including lap shear fracture load test and microhardness measurements indicated that by simultaneously increasing the tool rotation and travel speeds, the joint tensile strength and ductility reached a maximum value. Microhardness studies and extracted results from stress–strain curves indicated that mechanical properties were affected by FSW process. Furthermore, phase analyses by XRD indicated the presence of intermetallic compounds in the weld zone. Finally, in the Al/Mg dissimilar weld, fractography studies showed that intermetallic compounds formation in the weld zone had an influence on the failure mode

Effect of Multipass TIG and Activated TIG Welding Process on the Thermo-Mechanical Behavior of 316LN Stainless Steel Weld Joints

Science.gov (United States)

Ganesh, K. C.; Balasubramanian, K. R.; Vasudevan, M.; Vasantharaja, P.; Chandrasekhar, N.

2016-04-01

The primary objective of this work was to develop a finite element model to predict the thermo-mechanical behavior of an activated tungsten inert gas (ATIG)-welded joint. The ATIG-welded joint was fabricated using 10 mm thickness of 316LN stainless steel plates in a single pass. To distinguish the merits of ATIG welding process, it was compared with manual multipass tungsten inert gas (MPTIG)-welded joint. The ATIG-welded joint was fabricated with square butt edge configuration using an activating flux developed in-house. The MPTIG-welded joint was fabricated in thirteen passes with V-groove edge configuration. The finite element model was developed to predict the transient temperature, residual stress, and distortion of the welded joints. Also, microhardness, impact toughness, tensile strength, ferrite measurement, and microstructure were characterized. Since most of the recent publications of ATIG-welded joint was focused on the molten weld pool dynamics, this research work gives an insight on the thermo-mechanical behavior of ATIG-welded joint over MPTIG-welded joint.

Effect of joint design on ballistic performance of quenched and tempered steel welded joints

International Nuclear Information System (INIS)

Balakrishnan, M.; Balasubramanian, V.; Madhusudhan Reddy, G.

2014-01-01

Highlights: • Traditional usage of austenitic stainless steel filler for armour steel welding shows poor ballistic performance. • Earlier efforts show dubious success on ballistic resistance of armour steel joints. • Comparative evaluation of equal/unequal joint design on ballistic performance. • Effect of joint design covers the main aspects of successful bullet stoppage. - Abstract: A study was carried out to evaluate the effect of joint design on ballistic performance of armour grade quenched and tempered steel welded joints. Equal double Vee and unequal double Vee joint configuration were considered in this study. Targets were fabricated using 4 mm thick tungsten carbide hardfaced middle layer; above and below which austenitic stainless steel layers were deposited on both sides of the hardfaced interlayer in both joint configurations. Shielded metal arc welding process was used to deposit for all layers. The fabricated targets were evaluated for its ballistic performance and the results were compared in terms of depth of penetration on weld metal. From the ballistic test results, it was observed that both the targets successfully stopped the bullet penetration at weld center line. Of the two targets, the target made with unequal double Vee joint configuration offered maximum resistance to the bullet penetration at weld metal location without any bulge at the rear side. The higher volume of austenitic stainless steel front layer and the presence of hardfaced interlayer after some depth of soft austenitic stainless steel front layer is the primary reason for the superior ballistic performance of this joint

The effect of axial external magnetic field on tungsten inert gas welding of magnesium alloy

Science.gov (United States)

Li, Caixia; Zhang, Xiaofeng; Wang, Jing

2018-04-01

The influences of axial external magnetic field on the microstructure and mechanical property of the AZ31 magnesium (Mg) alloy joints were studied. The microstructure of Mg alloy joint consisted of the weld seam, heat affected zone and base metal zone. The average grain size of weld seam welded with magnetic field is 39 μm, which is 38% smaller than that of the joint welded with absence of magnetic field. And the microhardness of weld seam increases with the help of magnetic field treatment, owing to the coarse grain refinement. With coil current of 2.0A, the maximum mechanical property of joint increases 6.7% to 255 MPa over the specimen without magnetic field treatment. Furthermore, fracture location is near heat affected area and the fracture surface is characterized with ductile fracture.

Prediction of mechanical properties in friction stir welds of pure copper

International Nuclear Information System (INIS)

Heidarzadeh, A.; Saeid, T.

2013-01-01

Highlights: • Range of parameters for defect-free friction stir welded pure copper was reached. • Models were developed for predicting UTS, TE and hardness of pure copper joints. • Analysis of variance was used to validate the developed models. • Effect of welding parameters on mechanical behavior of welded joints was explored. • The microstructure and fracture surface of welded joints were investigated. - Abstract: This research was carried out to predict the mechanical properties of friction stir welded pure copper joints. Response surface methodology based on a central composite rotatable design with three parameters, five levels, and 20 runs, was used to conduct the experiments and to develop the mathematical regression model by using of Design-Expert software. The three welding parameters considered were rotational speed, welding speed, and axial force. Analysis of variance was applied to validate the predicted models. Microstructural characterization and fractography of joints were examined using optical and scanning electron microscopes. Also, the effects of the welding parameters on mechanical properties of friction stir welded joints were analyzed in detail. The results showed that the developed models were reasonably accurate. The increase in welding parameters resulted in increasing of tensile strength of the joints up to a maximum value. Elongation percent of the joints increased with increase of rotational speed and axial force, but decreased by increasing of welding speed, continuously. In addition, hardness of the joints decreased with increase of rotational speed and axial force, but increased by increasing of welding speed. The joints welded at higher heat input conditions revealed more ductility fracture mode

Microstructure development of welding joints in high Cr ferritic steels

Energy Technology Data Exchange (ETDEWEB)

Kubushiro, Keiji; Takahashi, Satoshi; Morishima, Keiko [IHI Corporation (Japan). Research Lab.

2010-07-01

Creep failure in high Cr ferritic steels welding joints are Type IV failure. Type IV-failure was ruptured in fine grained region of heat affected zone, microstructure and phase transformation process at welding in fine grained region were very important to clarify. Microstructure difference of heat affected zone was investigated in Gr.91, Gr.92, Gr.122 welding joint. The fraction of 60 degree block boundary, packet boundary, random boundary (including prior gamma boundary) length was compared in three ferritic steels by EBSP(Electron Backscatter Diffraction Pattern) analysis. HAZ was almost fully martensite phase in Gr.122 weld joint. On the other hand, HAZ in Gr.91 welding joint were some equiaxial grain and martensite structure. (orig.)

Studies on mechanical properties, microstructure and fracture morphology details of laser beam welded thick SS304L plates for fusion reactor applications

Energy Technology Data Exchange (ETDEWEB)

Buddu, Ramesh Kumar, E-mail: buddu@ipr.res.in [Fusion Reactor Materials Development and Characterization Division, Institute for Plasma Research, Bhat, Gandhinagar 382428 (India); Chauhan, N.; Raole, P.M. [Fusion Reactor Materials Development and Characterization Division, Institute for Plasma Research, Bhat, Gandhinagar 382428 (India); Natu, Harshad [Magod Laser Machining Pvt. Ltd, Jigani, Bengaluru 560105 (India)

2015-06-15

Highlights: • CO{sub 2} laser welding of 8 mm thick SS304L plates has been carried out and full penetration welds fabricated and characterized for mechanical properties and microstructure details. • Welded samples have shown tensile properties comparable to base indicating good weld quality joints. • Impact fracture tests of weld zone and heat affected zone samples have shown poor toughness compared to the base metal. • SEM analysis of fracture samples of tensile and impact specimens indicated the complex microstructure features in weld zone and combined ductile and brittle fracture features. • Combined features of dendrite and cellular structures are observed in weld microstructures with narrow HAZ and delta ferrite is found in the welds and further confirmed by higher Ferrite Number data. - Abstract: Austenitic stainless steel is widely used structural material for the fabrication of the fusion reactor components. Laser welding is high power density process which offers several advantages over the other conventional processes like Tungsten Inert Gas welding. The features like low distortion, narrow heat affected zone, deep penetration in single pass, good mechanical properties are some of the advantages of laser welding process. The laser weld process parameters optimization has several challenges in terms of overcoming the weld defects like voids due to lack of penetration over depth, undercuts and porosity. The present paper reports the studies carried out with CO{sub 2} laser welding of 8 mm thick austenitic stainless steel SS304L plates and their characterization of mechanical properties, microstructure and fracture morphology details. The weld process parameter optimization towards defect free welds with full penetration welding has been carried out. The welded samples have shown tensile properties comparable to base metal, bend tests are successfully passed. The hardness measurements have shown slightly higher for weld zone compared to base metal

Studies on mechanical properties, microstructure and fracture morphology details of laser beam welded thick SS304L plates for fusion reactor applications

International Nuclear Information System (INIS)

Buddu, Ramesh Kumar; Chauhan, N.; Raole, P.M.; Natu, Harshad

2015-01-01

Highlights: • CO 2 laser welding of 8 mm thick SS304L plates has been carried out and full penetration welds fabricated and characterized for mechanical properties and microstructure details. • Welded samples have shown tensile properties comparable to base indicating good weld quality joints. • Impact fracture tests of weld zone and heat affected zone samples have shown poor toughness compared to the base metal. • SEM analysis of fracture samples of tensile and impact specimens indicated the complex microstructure features in weld zone and combined ductile and brittle fracture features. • Combined features of dendrite and cellular structures are observed in weld microstructures with narrow HAZ and delta ferrite is found in the welds and further confirmed by higher Ferrite Number data. - Abstract: Austenitic stainless steel is widely used structural material for the fabrication of the fusion reactor components. Laser welding is high power density process which offers several advantages over the other conventional processes like Tungsten Inert Gas welding. The features like low distortion, narrow heat affected zone, deep penetration in single pass, good mechanical properties are some of the advantages of laser welding process. The laser weld process parameters optimization has several challenges in terms of overcoming the weld defects like voids due to lack of penetration over depth, undercuts and porosity. The present paper reports the studies carried out with CO 2 laser welding of 8 mm thick austenitic stainless steel SS304L plates and their characterization of mechanical properties, microstructure and fracture morphology details. The weld process parameter optimization towards defect free welds with full penetration welding has been carried out. The welded samples have shown tensile properties comparable to base metal, bend tests are successfully passed. The hardness measurements have shown slightly higher for weld zone compared to base metal and the

Effects of Heat Input on the Mechanical and Metallurgical Characteristics of Tig Welded Incoloy 800Ht Joints

Directory of Open Access Journals (Sweden)

Kumar S. Arun

2017-09-01

Full Text Available This study focuses on the effect of heat input on the quality characteristics of tungsten inert arc gas welded incoloy 800HT joints using inconel-82 filler wire. Butt welding was done on specimens with four different heat inputs by varying the process parameters like welding current and speed. The result indicated that higher heat input levels has led to the formation of coarser grain structure, reduced mechanical properties and sensitization issues on the weldments. The formation of titanium nitrides provided resistance to fracture and increased the tensile strength of the joints at high temperatures. Further aging was done on the welded sample at a temperature of 750°C for 500 hours and the metallographic result showed formation of carbides along the grain boundaries in a chain of discrete and globular form which increased the hardness of the material. The formation of spinel NiCr2O4 provided oxidation resistance to the material during elevated temperature service.

Effect of post-weld aging treatment on mechanical properties of Tungsten Inert Gas welded low thickness 7075 aluminium alloy joints

International Nuclear Information System (INIS)

Temmar, M.; Hadji, M.; Sahraoui, T.

2011-01-01

Highlights: → The effects of post-weld aging treatment on the properties of joints is studied. → The post-weld aging treatment increases the tensile strength of TIG welded joints. → The strengthening is due to a balance of dissolution, reversion and precipitation. → Simple post-weld aging at 140 o C enhances the properties of the welded joints. -- Abstract: This paper reports the influence of post-weld aging treatment on the microstructure, tensile strength, hardness and Charpy impact energy of weld joints low thickness 7075 T6 aluminium alloy welded by Tungsten Inert Gas (TIG). Hot cracking occurs in aluminium welds when high levels of thermal stress and solidification shrinkage are present while the weld is undergoing various degrees of solidification. Weld fusion zones typically exhibit microstructure modifications because of the thermal conditions during weld metal solidification. This often results in low weld mechanical properties and low resistance to hot cracking. It has been observed that the mechanical properties are very sensitive to microstructure of weld metal. Simple post-weld aging treatment at 140 o C applied to the joints is found to be beneficial to enhance the mechanical properties of the welded joints. Correlations between microstructures and mechanical properties were discussed.

Microstructure and toughness of ferritic weld metal of hyperbaric welded joints

International Nuclear Information System (INIS)

Mueller, L.

1988-01-01

In the present work ferritic weld metals of hyperbaric MIG/MAG welds with pressures up to 100 bar were examined. As a result of the pressure, interactions with the shielding gas, the filler metal as well as with the welding parameters had to be expected and were consequently included in the analysis. Investigation was focused on the influence of these parameters on the chemical composition of the weld metals, the microstructure and toughness behaviour, including fracture mechanics test. Using quantitative microstructural analysis as well as fractography a correlation between microstructure and toughness has been shown. (orig.) [de

Identifying Combination of Friction Stir Welding Parameters to Maximize Strength of Lap Joints of AA2014-T6 Aluminum Alloy

Directory of Open Access Journals (Sweden)

Rajendrana C.

2017-01-01

Full Text Available AA2014 aluminum alloy (Al-Cu alloy has been widely utilized in fabrication of lightweight structures like aircraft structures, demanding high strength to weight ratio and good corrosion resistance. The fusion welding of these alloys will lead to solidification problems such as hot cracking. Friction stir welding is a new solid state welding process, in which the material being welded does not melt and recast. Lot of research works have been carried out by many researchers to optimize process parameters and establish empirical relationships to predict tensile strength of friction stir welded butt joints of aluminum alloys. However, very few investigations have been carried out on friction stir welded lap joints of aluminum alloys. Hence, in this investigation, an attempt has been made to optimize friction stir lap welding (FSLW parameters to attain maximum tensile strength using statistical tools such as design of experiment (DoE, analysis of variance (ANOVA, response graph and contour plots. By this method, it is found that maximum tensile shear fracture load of 12.76 kN can be achieved if a joint is made using tool rotational speed of 900 rpm, welding speed of 110 mm/min, tool shoulder diameter of 12 mm and tool tilt angle of 1.5°.

Tensile Properties of Under-Matched Weld Joints for 950 MPa Steel.

Science.gov (United States)

Yamamoto, Kouji; Arakawa, Toshiaki; Akazawa, Nobuki; Yamamoto, Kousei; Matsuo, Hiroki; Nakagara, Kiyoyuki; Suita, Yoshikazu

In welding of 950 MPa-class high tensile strength steel, preheating is crucial in order to avoid cold cracks, which, however, eventually increases welding deformations. One way to decrease welding deformations is lowering preheating temperature by using under-matched weld metal. Toyota and others clarify that although breaking elongation can decrease due to plastic constraint effect under certain conditions, static tensile of under-matched weld joints is comparable to that of base metal. However, there has still been no report about joint static tensile of under-matched weld joints applied to 950 MPa-class high tensile strength steel. In this study, we aim to research tensile strength and fatigue strength of under-matched weld joints applied to 950 MPa-class high tensile steel.

Phased array ultrasonic testing of dissimilar metal pipe weld joints

International Nuclear Information System (INIS)

Rajeev, J.; Sankaranarayanan, R.; Sharma, Govind K; Joseph, A.; Purnachandra Rao, B.

2015-01-01

Dissimilar metal weld (DMW) joints made of stainless steel and ferritic steel is used in nuclear industries as well as oil and gas industries. These joints are prone to frequent failures which makes the non-destructive testing of dissimilar metal weld joints utmost important for reliable and safe operation of nuclear power plants and oil and gas industries. Ultrasonic inspection of dissimilar metal weld joints is still challenging due to the inherent anisotropic and highly scattering nature. Phased array ultrasonic testing (PAUT) is an advanced technique and its capability has not been fully explored for the inspection of dissimilar metal welds

Friction stir welding joint of dissimilar materials between AZ31B magnesium and 6061 aluminum alloys: Microstructure studies and mechanical characterizations

Energy Technology Data Exchange (ETDEWEB)

Mohammadi, J. [Department of Materials Science and Engineering, Science and Research Branch, Islamic Azad University, Tehran 141554933 (Iran, Islamic Republic of); Behnamian, Y. [Department of Chemical and Materials Engineering, University of Alberta, Edmonton, Alberta T6G 2V4 (Canada); Mostafaei, A., E-mail: amir.mostafaei@gmail.com [Young Researchers and Elites Club, Tehran North Branch, Islamic Azad University, Tehran (Iran, Islamic Republic of); Izadi, H. [Department of Chemical and Materials Engineering, University of Alberta, Edmonton, Alberta T6G 2V4 (Canada); Saeid, T. [Faculty of Materials Engineering, Sahand University of Technology, Tabriz 513351996 (Iran, Islamic Republic of); Kokabi, A.H. [Department of Materials Science and Engineering, Sharif University of Technology, Tehran 113659466 (Iran, Islamic Republic of); Gerlich, A.P., E-mail: adrian.gerlich@uwaterloo.ca [Department of Mechanical and Mechatronics Engineering, University of Waterloo, Waterloo, Ontario N2L 3G1 (Canada)

2015-03-15

Friction stir welding is an efficient manufacturing method for joining dissimilar alloys, which can dramatically reduce grain sizes and offer high mechanical joint efficiency. Lap FSW joints between dissimilar AZ31B and Al 6061 alloy sheets were made at various tool rotation and travel speeds. Rotation and travel speeds varied between 560–1400 r/min and 16–40 mm/min respectively, where the ratio between these parameters was such that nearly constant pitch distances were applied during welding. X-ray diffraction pattern (XRD), optical microscopy images (OM), electron probe microanalysis (EPMA) and scanning electron microscopy equipped with an energy-dispersive X-ray spectroscopy (SEM-EDS) were used to investigate the microstructures of the joints welded. Intermetallic phases including Al{sub 12}Mg{sub 17} (γ) and Al{sub 3}Mg{sub 2} (β) were detected in the weld zone (WZ). For different tool rotation speeds, the morphology of the microstructure in the stir zone changed significantly with travel speed. Lap shear tensile test results indicated that by simultaneously increasing the tool rotation and travel speeds to 1400 r/min and 40 mm/min, the joint tensile strength and ductility reached a maximum. Microhardness measurements and tensile stress–strain curves indicated that mechanical properties were affected by FSW parameters and mainly depended on the formation of intermetallic compounds in the weld zone. In addition, a debonding failure mode in the Al/Mg dissimilar weld nugget was investigated by SEM and surface fracture studies indicated that the presence of intermetallic compounds in the weld zone controlled the failure mode. XRD analysis of the fracture surface indicated the presence of brittle intermetallic compounds including Al{sub 12}Mg{sub 17} (γ) and Al{sub 3}Mg{sub 2} (β). - Highlights: • Dissimilar Al/Mg joint was obtained by lap friction stir welding technique. • Effect of rotation and travel speeds on the formation of intermetallic

Friction stir welding joint of dissimilar materials between AZ31B magnesium and 6061 aluminum alloys: Microstructure studies and mechanical characterizations

International Nuclear Information System (INIS)

Mohammadi, J.; Behnamian, Y.; Mostafaei, A.; Izadi, H.; Saeid, T.; Kokabi, A.H.; Gerlich, A.P.

2015-01-01

Friction stir welding is an efficient manufacturing method for joining dissimilar alloys, which can dramatically reduce grain sizes and offer high mechanical joint efficiency. Lap FSW joints between dissimilar AZ31B and Al 6061 alloy sheets were made at various tool rotation and travel speeds. Rotation and travel speeds varied between 560–1400 r/min and 16–40 mm/min respectively, where the ratio between these parameters was such that nearly constant pitch distances were applied during welding. X-ray diffraction pattern (XRD), optical microscopy images (OM), electron probe microanalysis (EPMA) and scanning electron microscopy equipped with an energy-dispersive X-ray spectroscopy (SEM-EDS) were used to investigate the microstructures of the joints welded. Intermetallic phases including Al 12 Mg 17 (γ) and Al 3 Mg 2 (β) were detected in the weld zone (WZ). For different tool rotation speeds, the morphology of the microstructure in the stir zone changed significantly with travel speed. Lap shear tensile test results indicated that by simultaneously increasing the tool rotation and travel speeds to 1400 r/min and 40 mm/min, the joint tensile strength and ductility reached a maximum. Microhardness measurements and tensile stress–strain curves indicated that mechanical properties were affected by FSW parameters and mainly depended on the formation of intermetallic compounds in the weld zone. In addition, a debonding failure mode in the Al/Mg dissimilar weld nugget was investigated by SEM and surface fracture studies indicated that the presence of intermetallic compounds in the weld zone controlled the failure mode. XRD analysis of the fracture surface indicated the presence of brittle intermetallic compounds including Al 12 Mg 17 (γ) and Al 3 Mg 2 (β). - Highlights: • Dissimilar Al/Mg joint was obtained by lap friction stir welding technique. • Effect of rotation and travel speeds on the formation of intermetallic compounds • Microstructure and chemical

Characterisation of girth pipe weld for primary heat transport system of pressurised heavy water reactors

International Nuclear Information System (INIS)

Singh, P.K.; Vaze, K.K.; Kushwaha, H.S.

2002-01-01

The weld and heat affected zone (HAZ) associated with the girth weld are most vulnerable regions of the piping system. The different regions of the weld joint such as the weld metal, HAZ and base metal lead to heterogeneous mechanical and metallurgical properties of the joints. Due to their different metallurgical and mechanical properties, the amounts of damage produced in these regions are different when the component is subjected to service condition. Thus, it is imperative to know the characteristics of these regions of a pipe weld in order to identify the weakest zone for safe designing of high energy piping components. In view of this necessity the present study has been planned to carry out complete characterisation of the weld joint of SA 333 Gr.6 steel pipe, in terms of its metallurgical, mechanical and fracture properties. The mechanical and fracture mechanics properties of the base metal, weld deposit and HAZ have been compared and correlated with reference to their microstructures. Weld joints of SA 333 Gr.6 steel pipe have been prepared by using GTAW root pass and SMAW filling of V-grove as per recommended welding procedure specifications (WPS) conforming to ASME Sec IX commonly used to fabricate nuclear piping system components. The emphasis of the study is to characterise base, weld and HAZ of the pipe weld in terms of chemical, metallurgical, mechanical and fracture mechanics properties. The fracture toughness behaviour of the welds and HAZ has been characterised by J-integral parameters. The fatigue crack growth rate has been characterised by Paris Law. Stretched zone width (SZW) has been measured under SEM to evaluate initiation fracture toughness. The estimated initiation fracture toughness based on SZW and blunting line given by EGF recommendation have been compared. The fracture mechanics properties of base, weld and HAZ has been determined and compared. The fracture mechanics properties of the weld and HAZ have been correlated to their

Measuring and Modeling Flow in Welded Fractured Tuffs

International Nuclear Information System (INIS)

R. Salve; C. Doughty; J.S. Wang

2001-01-01

We have carried out a series of in situ liquid-release experiments in conjunction with a numerical modeling study to examine the effect of the rock matrix on liquid flow and transport occurring primarily through the fracture network. Field experiments were conducted in the highly fractured Topopah Spring welded tuff at a site accessed from the Exploratory Studies Facility (ESFS), an underground laboratory in the unsaturated zone at Yucca Mountain, Nevada. During the experiment, wetting-front movement, flow-field evolution, and drainage of fracture flow paths were evaluated. Modeling was used to aid in experimental design, predict experimental results, and study the physical processes accompanying liquid flow through unsaturated fractured welded tuff. Field experiments and modeling suggest that it may not be sufficient to conceptualize the fractured tuff as consisting of a single network of high-permeability fractures embedded in a low-permeability matrix. The need to include a secondary fracture network is demonstrated by comparison to the liquid flow observed in the field

Fracture toughness evaluation of a low upper-shelf weld metal from the Midland Reactor using the master curve

International Nuclear Information System (INIS)

McCabe, D.E.; Sokolov, M.A.; Nanstad, R.K.

1997-01-01

The primary objective of the Heavy-Section Steel Irradiation (HSSI) Program Tenth Irradiation Series was to develop a fracture mechanics evaluation of weld metal WF-70, which was taken from the beltline and nozzle course girth weld joints of the Midland Reactor vessel. This material became available when Consumers Power Company of Midland, Michigan, decided to abort plans to operate their nuclear power plant. WF-70 is classified as a low upper-shelf steel primarily due to the Linde 80 flux that was used in the submerged-arc welding process. The master curve concept is introduced to model the transition range fracture toughness when the toughness is quantified in terms of K Jc values. K Jc is an elastic-plastic stress intensity factor calculated by conversion from J c ; i.e., J-integral at onset of cleavage instability

Defect features, texture and mechanical properties of friction stir welded lap joints of 2A97 Al-Li alloy thin sheets

Energy Technology Data Exchange (ETDEWEB)

Chen, Haiyan [State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi' an 710072 (China); Shaanxi Key Laboratory of Friction Welding Technologies, Northwestern Polytechnical University, Xi' an 710072 (China); Fu, Li, E-mail: fuli@nwpu.edu.cn [State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi' an 710072 (China); Shaanxi Key Laboratory of Friction Welding Technologies, Northwestern Polytechnical University, Xi' an 710072 (China); Liang, Pei; Liu, Fenjun [Shaanxi Key Laboratory of Friction Welding Technologies, Northwestern Polytechnical University, Xi' an 710072 (China)

2017-03-15

1.4 mm 2A97 Al-Li alloy thin sheets were welded by friction stir lap welding using the stirring tools with different pin length at different rotational speeds. The influence of pin length and rotational speed on the defect features and mechanical properties of lap joints were investigated in detail. Microstructure observation shows that the hook defect geometry and size mainly varies with the pin length instead of the rotational speed. The size of hook defects on both the advancing side (AS) and the retreating side (RS) increased with increasing the pin length, leading to the effective sheet thickness decreased accordingly. Electron backscatter diffraction analysis reveals that the weld zones, especially the nugget zone (NZ), have the much lower texture intensity than the base metal. Some new texture components are formed in the thermo-mechanical affected zone (TMAZ) and the NZ of joint. Lap shear test results show that the failure load of joints generally decreases with increasing the pin length and the rotational speed. The joints failed during the lap shear tests at three locations: the lap interface, the RS of the top sheet and the AS of the bottom sheet. The fracture locations are mainly determined by the hook defects. - Highlights: • Hook defect size mainly varies with the pin length of stirring tool. • The proportion of LAGBs and substructured grains increases from NZ to TMAZ. • Weld zones, especially the NZ, have the much lower texture intensity than the BM. • Lap shear failure load and fracture location of joints is relative to the hook defects.

Defect features, texture and mechanical properties of friction stir welded lap joints of 2A97 Al-Li alloy thin sheets

International Nuclear Information System (INIS)

Chen, Haiyan; Fu, Li; Liang, Pei; Liu, Fenjun

2017-01-01

1.4 mm 2A97 Al-Li alloy thin sheets were welded by friction stir lap welding using the stirring tools with different pin length at different rotational speeds. The influence of pin length and rotational speed on the defect features and mechanical properties of lap joints were investigated in detail. Microstructure observation shows that the hook defect geometry and size mainly varies with the pin length instead of the rotational speed. The size of hook defects on both the advancing side (AS) and the retreating side (RS) increased with increasing the pin length, leading to the effective sheet thickness decreased accordingly. Electron backscatter diffraction analysis reveals that the weld zones, especially the nugget zone (NZ), have the much lower texture intensity than the base metal. Some new texture components are formed in the thermo-mechanical affected zone (TMAZ) and the NZ of joint. Lap shear test results show that the failure load of joints generally decreases with increasing the pin length and the rotational speed. The joints failed during the lap shear tests at three locations: the lap interface, the RS of the top sheet and the AS of the bottom sheet. The fracture locations are mainly determined by the hook defects. - Highlights: • Hook defect size mainly varies with the pin length of stirring tool. • The proportion of LAGBs and substructured grains increases from NZ to TMAZ. • Weld zones, especially the NZ, have the much lower texture intensity than the BM. • Lap shear failure load and fracture location of joints is relative to the hook defects.

Enhancement of mechanical properties and failure mechanism of electron beam welded 300M ultrahigh strength steel joints

International Nuclear Information System (INIS)

Zhang, Guodong; Yang, Xinqi; He, Xinlong; Li, Jinwei; Hu, Haichao

2013-01-01

Highlights: ► Normalizing at 970 °C plus quenching and tempering cannot refine the columnar grains. ► Ductility and toughness of conventional quenched and tempered joint are very low. ► An optimum combination of strength and ductility was obtained for the welded joints. ► Intergranular cracked columnar dendritic grains were found on the fracture surface. -- Abstract: In this study, four post-weld heat treatment (PWHT) schedules were selected to enhance the mechanical properties of electron beam welded 300M ultrahigh strength steel joints. The microstructure, mechanical properties and fractography of specimens under the four post-weld heat treatment (PWHT) conditions were investigated and also compared with the base metal (BM) specimens treated by conventional quenching and tempering (QT). Results of macro and microstructures indicate that all of the four PWHT procedures did not eliminate the coarse columnar dendritic grains in weld metal (WM). Whereas, the morphology of the weld centerline and the boundaries of the columnar dendritic grains in WM of weld joint specimens subjected to the PWHT procedure of normalizing at 970 °C for 1 h followed by conventional quenching and tempering (W-N2QT) are indistinct. The width of martensite lath in WM of W-N2QT is narrower than that of specimens subjected to other PWHT procedures. Experimental results indicate that the ductility and toughness of conventional quenched and tempered joints are very low compared with the BM specimens treated by conventional QT. However, the strength and impact toughness of the W-N2QT specimens are superior to those of the BM specimen treated by conventional QT, and the ductility is only slightly inferior to that of the latter.

Influence of joint line remnant on crack paths under static and fatigue loadings in friction stir welded Al-Mg-Sc alloy

Directory of Open Access Journals (Sweden)

Y. Besel

2016-01-01

Full Text Available The influence of the joint line remnant (JLR on tensile and fatigue fracture behaviour has been investigated in a friction stir welded Al-Mg-Sc alloy. JLR is one of the microstructural features formed in friction stir welds depending on welding conditions and alloy systems. It is attributed to initial oxide layer on butting surfaces to be welded. In this study, two different tool travel speeds were used. JLR was formed in both welds but its spatial distribution was different depending on the tool travel speeds. Under the tensile test, the weld with the higher heat input fractured partially along JLR, since strong microstructural inhomogeneity existed in the vicinity of JLR in this weld and JLR had weak bonding. Resultantly, the mechanical properties of this weld were deteriorated compared with the other weld. Fatigue crack initiation was not affected by the existence of JLR in all welds. But the crack propagated preferentially along JLR in the weld of the higher heat input, when it initiated on the retreating side. Consequently, such crack propagation behaviour along JLR could bring about shorter fatigue lives in larger components in which crack growth phase is dominant.

Structure and mechanical properties of Cresco-Ti laser-welded joints and stress analyses using finite element models of fixed distal extension and fixed partial prosthetic designs.

Science.gov (United States)

Uysal, Hakan; Kurtoglu, Cem; Gurbuz, Riza; Tutuncu, Naki

2005-03-01

The Cresco-Ti System uses a laser-welded process that provides an efficient technique to achieve passive fit frameworks. However, mechanical behavior of the laser-welded joint under biomechanical stress factors has not been demonstrated. This study describes the effect of Cresco-Ti laser-welding conditions on the material properties of the welded specimen and analyzes stresses on the weld joint through 3-dimensional finite element models (3-D FEM) of implant-supported fixed dentures with cantilever extensions and fixed partial denture designs. Twenty Grade III (ASTM B348) commercially pure titanium specimens were machine-milled to the dimensions described in the EN10002-1 tensile test standard and divided into test (n = 10) and control (n = 10) groups. The test specimens were sectioned and laser-welded. All specimens were subjected to tensile testing to determine yield strength (YS), ultimate tensile strength (UTS), and percent elongation (PE). The Knoop micro-indentation test was performed to determine the hardness of all specimens. On welded specimens, the hardness test was performed at the welded surface. Data were analyzed with the Mann-Whitney U test and Student's t test (alpha=.05). Fracture surfaces were examined by scanning electron microscopy to characterize the mode of fracture and identify defects due to welding. Three-dimensional FEMs were created that simulated a fixed denture with cantilever extensions supported by 5 implants (M1) and a fixed partial denture supported by 2 implants (M2), 1 of which was angled 30 degrees mesio-axially. An oblique load of 400 N with 15 degrees lingual-axial inclinations was applied to both models at various locations. Test specimens fractured between the weld and the parent material. No porosities were observed on the fractured surfaces. Mean values for YS, UTS, PE, and Knoop hardness were 428 +/- 88 MPa, 574 +/- 113 MPa, 11.2 +/- 0.4%, 270 +/- 17 KHN, respectively, for the control group and 642 +/- 2 MPa, 772 +/- 72

High-cycle fatigue properties of small-bore socket-welded pipe joint

International Nuclear Information System (INIS)

Maekawa, Akira; Noda, Michiyasu; Suzuki, Michiaki

2009-01-01

Piping and equipment in nuclear power plants are structures including many welded joints. Reliability of welded joints is one of high-priority issues to improve the safety of nuclear power plants. However, occurrence of fatigue failures in small-bore socket-welded pipe joints by high-cycle vibrations is still reported. In this study, fatigue experiments on a socket-welded joint of austenitic stainless steel pipe was conducted under excitation conditions similar to those in actual plants to investigate vibration characteristics and fatigue strength. It was found that the natural frequency of pipe with socket-welded joint gradually decreased as fatigue damage developed, according to the Miner rule for fatigue life evaluation. The results indicate that the fatigue life of the welded pipe joint could be estimated by monitoring the decreasing ratio of the natural frequency of the pipe. The evaluation of decreasing ratio of the natural frequency in addition to fatigue damage evaluation by the Miner rule could enhance the accuracy of fatigue life evaluation. (author)

Numerical/experimental research on welded joints in aluminium truss girders

NARCIS (Netherlands)

van Hove, B.W.E.M.; Soetens, F.; Mazzolani, F.M.; Bellucci, F.; Faggiano, B.; Squillace, A.

2016-01-01

Welded joints in a 30 meter span aluminium truss girder were investigated numerically and experimentally. Since aluminium design rules for welded K-and N-joints in CHS truss girders were lacking the joints were checked using steel design rules. Calculations showed that the N-joints were governing

Properties of simulated welded joints of Cr-Mo steel following heat treatment in intercritical temperature range

International Nuclear Information System (INIS)

Sabun, L.B.; Vornovitskij, I.N.; Lukicheva, S.V.; Melamed, S.Eh.

1975-01-01

The parameters are determined of the welded joints heat treatment which permit to shorten the holp-up period due to the accelerating the process of the weld-stress release and the diffusion of carbon and alloying elements resulting in the equilibration of the weld metal chemical composition. The properties of an imitated welded joint of the 15KHM steel have been studied after various modes of heat treatment. The critical points are 740 and 875 deg C. The mechanical properties determination and the study of the strain hardening process are carried out with a high-temperature metallography plant. The modes of a low-temperature tempering and incomplete annealing are investigated within an intercritical range at temperatures of 750 to 780 deg C and a hold-up periods of to five minutes with a consecutive cooling in air or with the furnace respectively. The results of the studies have shown that with the decrease in the heat treatment temperature the strength, plasticity and also hardness of the welded joint zones prove to be to the standard of a sample treated conforming to the high tempering mode. In case of an incomplete annealing (770 to 780 deg C) the strength of the welded joint is maintained to the standard of the strength obtained at the high tempering, and the relative elongation value increases considerably at all the hold-up periods investigated. The strain-hardening process for the low-temperature normalizing and high tempering proceeds approximately equally. The fracture occurs at the deformation of 30 to 35% in microvolume, the relative elongation in that case being 12 to 13%

Modeling and design of energy concentrating laser weld joints

Energy Technology Data Exchange (ETDEWEB)

Milewski, J.O. [Los Alamos National Lab., NM (United States); Sklar, E. [OptiCad Corp., Santa Fe, NM (United States)

1997-04-01

The application of lasers for welding and joining has increased steadily over the past decade with the advent of high powered industrial laser systems. Attributes such as high energy density and precise focusing allow high speed processing of precision assemblies. Other characteristics of the process such as poor coupling of energy due to highly reflective materials and instabilities associated with deep penetration keyhole mode welding remain as process limitations and challenges to be overcome. Reflective loss of laser energy impinging on metal surfaces can in some cases exceed ninety five percent, thus making the process extremely inefficient. Enhanced coupling of the laser beam can occur when high energy densities approach the vaporization point of the materials and form a keyhole feature which can trap laser energy and enhance melting and process efficiency. The extreme temperature, pressure and fluid flow dynamics of the keyhole make control of the process difficult in this melting regime. The authors design and model weld joints which through reflective propagation and concentration of the laser beam energy significantly enhance the melting process and weld morphology. A three dimensional computer based geometric optical model is used to describe the key laser parameters and joint geometry. Ray tracing is used to compute the location and intensity of energy absorption within the weld joint. Comparison with experimentation shows good correlation of energy concentration within the model to actual weld profiles. The effect of energy concentration within various joint geometry is described. This method for extending the design of the laser system to include the weld joint allows the evaluation and selection of laser parameters such as lens and focal position for process optimization. The design of narrow gap joints which function as energy concentrators is described. The enhanced laser welding of aluminum without keyhole formation has been demonstrated.

Project of integrity assessment of flawed components with structural discontinuity (IAF). Data book for residual stress analysis in weld joint. Analysis model of dissimilar metal weld joint applied post weld heat treatment (PWHT)

International Nuclear Information System (INIS)

2012-12-01

The project of Integrity Assessment of Flawed Components with Structural Discontinuity (IAF) was entrusted to Japan Power Engineering and Inspection Corporation (JAPEIC) from Nuclear and Industrial Safety Agency (NISA) and started from FY 2001. And then, it was taken over to Japan Nuclear Energy Safety Organization (JNES) which was established in October 2003 and carried out until FY 2007. In the IAF project, weld joints between nickel based alloys and low alloy steels around penetrations in reactor vessel, safe-end of nozzles and shroud supports were selected from among components and pipe arrangements in nuclear power plants, where high residual stresses were generated due to welding and complex structure. Residual stresses around of the weld joints were estimated by finite element analysis method (FEM) with a general modeling method, then the reasonability and the conservativeness was evaluated. In addition, for postulated surface crack of stress corrosion cracking (SCC), a simple calculation method of stress intensity factor (K) required to estimate the crack growth was proposed and the effectiveness was confirmed. JNES compiled results of the IAF project into Data Books of Residual Stress Analysis of Weld Joint, and Data Book of Simplified Stress Intensity Factor Calculation for Penetration of Reactor as typical Structure Discontinuity, respectively. Data Books of Residual Stress Analysis in Weld Joint. 1. Butt Weld Joint of Small Diameter Cylinder (4B Sch40) (JNES-RE-2012-0005), 2. Dissimilar Metal Weld Joint in Safe End (One-Side Groove Joint (JNES-RE-2012-0006), 3. Dissimilar Metal Weld Joint in Safe End (Large Diameter Both-Side Groove Joint) (JNES-RE-2012-0007), 4. Weld Joint around Penetrations in Reactor Vessel (Insert Joint) (JNES-RE-2012-0008), 5. Weld Joint in Shroud Support (H8, H9, H10 and H11 Welds) (JNES-RE-2012-0009), 6. Analysis Model of Dissimilar Metal Weld Joint Applied Post Weld Heat Treatment (PWHT) (JNES-RE-2012-0010). Data Book of

Mechanical strength and analysis of fracture of titanium joining submitted to laser and tig welding

Directory of Open Access Journals (Sweden)

Ana Cláudia Gabrielli Piveta

2012-12-01

Full Text Available This study compared the tensile strength and fracture mechanism of tungsten inert gas (TIG welds in cylindrical rods of commercially pure titanium (cp Ti with those of laser welds and intact samples. Thirty dumbbell-shaped samples were developed by using brass rods as patterns. The samples were invested in casings, subjected to thermal cycles, and positioned in a plasma arc welding machine under argon atmosphere and vacuum, and titanium was injected under vacuum/pressure. The samples were X-rayed to detect possible welding flaws and randomly assigned to three groups to test the tensile strength and the fracture mechanism: intact, laser welding, and TIG welding. The tensile test results were investigated using ANOVA, which indicated that the samples were statistically similar. The fracture analysis showed that the cpTi samples subjected to laser welding exhibited brittle fracture and those subjected to TIG welding exhibited mixed brittle/ductile fracture with a predominance of ductile fracture with the presence of microcavities and cleavage areas. Intact samples presented the characteristic straightening in the fracture areas, indicating the ductility of the material.

Micromechanical and internal discontinuity aspects in fusion welded joints

International Nuclear Information System (INIS)

Nur Azida Che Lah; Aidy Ali

2009-01-01

Full text: This paper deals with characterization of macrostructure, microstructure, hardness, elemental compositions and internal discontinuities of ASTM A516 grade 70 fusion welded joints. The welded joints of ASTM A516 grade 70 carbon steel, which are widely used in pressure vessel fabrication were prepared using welding procedures of Manual Metal Arc (MMA), Metal Inert Gas (MIG) and Tungsten Inert Gas (TIG). Local microstructural condition and elemental composition of the welds were characterised using scanning electron microscopy (SEM) in association with energy dispersive X-ray (EDX). Radiography testing was applied to study the common internal weld defects. This comprehensive information provides a practical guide in order to determine the most adequate welding procedure and assisting in understanding the behaviour of the weld zones. (author)

The Investigation of Structure Heterogeneous Joint Welds in Pipelines

Directory of Open Access Journals (Sweden)

Lyubimova Lyudmila

2016-01-01

Full Text Available Welding joints of dissimilar steels don’t withstand design life. One of the important causes of premature destructions can be the acceleration of steel structural degradation due to cyclic mechanical and thermal gradients. Two zones of tube from steel 12H18N9T, exhibiting the structural instability at early stages of the decomposition of a supersaturated solid austenite solution, were subjected to investigation. Methods of x-ray spectral and structure analysis, micro hardnessmetry were applied for the research. Made the following conclusions, inside and outside tube wall surfaces of hazardous zones in welding joint have different technological and resource characteristics. The microhardness very sensitive to changes of metal structure and can be regarded as integral characteristic of strength and ductility. The welding processes are responsible for the further fibering of tube wall structure, they impact to the characteristics of hot-resistance and long-term strength due to development of ring cracks in the welding joint of pipeline. The monitoring of microhardness and structural phase conversions can be used for control by changes of mechanical properties in result of post welding and reductive heat treatment of welding joints.

Creep damage behaviour of modified 9Cr-1Mo steel weld joints

International Nuclear Information System (INIS)

Sakthivel, T.; Laha, K.; Vasudevan, M.; Panneer Selvi, S.

2016-01-01

Creep deformation and rupture behaviour of modified 9Cr-1Mo steel weld joints fabricated by single-pass activated TIG (A-TIG) and shielded metal arc welding (SMAW) processes have been investigated at 923 K over a stress range of 50 to 110 MPa after post weld heat treatment (PWHT). The weld joints exhibited significantly lower creep rupture lives than the base metal at lower applied stresses. Creep rupture location of the weld joints were found to occur in the ICHAZ. An extensive localized creep deformation, coarsening of M 23 C 6 precipitates in the ICHAZ with creep exposure led to the premature type IV failure of the joints. The coarsening of M 23 C 6 precipitates was extensive in the mid-section of the ICHAZ than the sub-surface of the joints, and was more predominant in the SMAW joint. While A-TIG weld joint exhibited reduced creep cavitation and coarsening of M 23 C 6 precipitates due to lower deformation constraints by adjacent regions in the ICHAZ. Hence, A-TIG weld joint exhibited higher creep rupture life than the SMAW joint. (author)

Effect of weld spacing on microstructure and mechanical properties of CLAM electron beam welding joints

Energy Technology Data Exchange (ETDEWEB)

Zhai, Yutao; Huang, Bo, E-mail: aufa0007@163.com; Zhang, Junyu; Zhang, Baoren; Liu, Shaojun; Huang, Qunying

2016-11-15

Highlights: • The welded joints of CLAM steel with different weld spacings have been fabricated with electron beam welding, and a simplified model of CLAM sheet was proposed. • The microstructure and mechanical properties such as microhardness, impact and tensile were investigated at different welding spacing for both conditions of as-welded and post weld heat treatment (PWHT). • The effect of the welding thermal cycle was significantly when the weld spacings were smaller than 4 mm. • When the weld spacing was small enough, the original microstructures would be fragmented with the high heat input. - Abstract: China low activation martensitic (CLAM) steel has been chosen as the primary structural material in the designs of dual function lithium-lead (DFLL) blanket for fusion reactors, China helium cooled ceramic breeder (HCCB) test blanket module (TBM) for ITER and China fusion engineering test reactor (CFETR) blanket. The cooling components of the blankets are designed with high density cooling channels (HDCCs) to remove the high nuclear thermal effectively. Hence, the welding spacing among the channels are small. In this paper, the welded joints of CLAM steel with different weld spacings have been fabricated with electron beam welding (EBW). The weld spacing was designed to be 2 mm, 3 mm, 4 mm, 6 mm and 8 mm. The microstructure and mechanical properties such as microhardness, impact and tensile were investigated at different welding spacing for both conditions of as-welded and post weld heat treatment (PWHT). The PWHT is tempering at 740 °C for 120 min. The results showed that the grain size in the heat affected zone (HAZ) increased with the increasing weld spacing, and the joint with small weld spacing had a better performance after PWHT. This work would give useful guidance to improve the preparation of the cooling components of blanket.

Estimation of creep life of thick welded joints using a simple model. Creep characteristics in thick welded joint and their improvements. 2

International Nuclear Information System (INIS)

Nakacho, Keiji; Yamazaki, Masayoshi

2001-01-01

The information of the creep behavior of the thick welded joint is very important to secure the safety of the elevated temperature vessels like the nuclear reactors. The creep behavior of the thick welded point is very complex, thence it is difficult to practice the experiment or the theoretical analysis. A simple accurate model for theoretical analysis was developed in the first study. The simple model is constructed of several one-dimensional finite elements which can analyze three-dimensional creep behavior under a assumption. The model is easy to treat, and needs only a little labor and computation time to simulate the creep curve and local strain of the thick welded joint. In this second study, the capability of the model is expanded to estimate the creep life of the thick welded joint. New model can easily estimate the time of the rupture of the thick welded joint. It is verified comparing the result with the experimental one that the model can accurately predict the creep life. The histories of the local strains to the rupture time may be observed in the simulation by using the model. The information will be useful to improve the creep characteristics of the joints. (author)

Research on Microstructure and Properties of Welded Joint of High Strength Steel

Science.gov (United States)

Zhu, Pengxiao; Li, Yi; Chen, Bo; Ma, Xuejiao; Zhang, Dongya; Tang, Cai

2018-01-01

BS960 steel plates were welded by Laser-MAG and MAG. The microstructure and properties of the welded joints were investigated by optical microscope, micro-hardness tester, universal tensile testing machine, impact tester, scanning electron microscope (SEM) and fatigue tester. By a series of experiments, the following results were obtained: The grain size of the coarse grain zone with Laser-MAG welded joint is 20μm, and that with MAG welded joint is about 32μm, both of the fine grain region are composed of fine lath martensite and granular bainite; the width of the heat affected region with Laser-MAG is lower than that with MAG. The strength and impact energy of welded joints with Laser-MAG is higher than that with MAG. The conditioned fatigue limit of welded joint with Laser-MAG is 280MPa; however, the conditioned fatigue limit of welded joint with MAG is 250MPa.

Effect of Shielding Gas on the Properties of AW 5083 Aluminum Alloy Laser Weld Joints

Science.gov (United States)

Vyskoč, Maroš; Sahul, Miroslav; Sahul, Martin

2018-04-01

The paper deals with the evaluation of the shielding gas influence on the properties of AW 5083 aluminum alloy weld joints produced with disk laser. Butt weld joints were produced under different shielding gas types, namely Ar, He, Ar + 5 vol.% He, Ar + 30 vol.% He and without shielding weld pool. Light and electron microscopy, computed tomography, microhardness measurements and tensile testing were used for evaluation of weld joint properties. He-shielded weld joints were the narrowest ones. On the other hand, Ar-shielded weld joints exhibited largest weld width. The choice of shielding gas had significant influence on the porosity level of welds. The lowest porosity was observed in weld joint produced in Ar with the addition of 5 vol.% He shielding atmosphere (only 0.03%), while the highest level of porosity was detected in weld joint produced in pure He (0.24%). Except unshielded aluminum alloy weld joint, the lowest tensile strength was recorded in He-shielded weld joints. On the contrary, the highest average microhardness was measured in He-shielded weld joints.

The influence of radiation on the properties of welds and joints

International Nuclear Information System (INIS)

Tavassoli, A.A.

1987-01-01

The effect of radiation on mechanical properties of candidate structural materials for the first wall and breeder blanket of fusion reactors is reviewed. The accent is placed on austenitic stainless steel type 316L and its weld metals and design parameters considered are similar to those currently specified for the Next European Torus, namely, irradiation doses ≤ 15 dpa, temperatures ≤ 400 0 C, number of pulse cycles = 10 5 and hold times ≤ 15 mn. The effect of irradiation on other materials, including austenitic stainless steel type 304L, weld metal type 308L and ferritic/martensitic steels (9-12% Cr - Mo), as well as other service conditions such as temperatures as high as 550 0 C are also briefly discussed. The data collected and presented in this review are those usually measured, before and after irradiation, through tensile, impact toughness, fracture toughness, fatigue, creep-fatigue and fatigue crack propagation testing. In each case the influence of irradiation parameters on the observed changes are discussed and relative conclusions are drawn. The most important observation made is the lack of medium dose irradiation data on the weld metal and in particular on the electron beam welded joints

The effect of advanced ultrasonic forging on fatigue fracture mechanisms of welded Ti-6A1-4V alloy

Science.gov (United States)

Smirnova, A.; Pochivalov, Yu.; Panin, V.; Panin, S.; Eremin, A.; Gorbunov, A.

2017-12-01

The current study is devoted to application of advanced postwelding ultrasonic forging to joints formed by laser welding of Ti-6A1-4V alloy in order to enhance their mechanical properties and fatigue durability. Low cycle fatigue tests were performed via digital image correlation technique used to obtain strain fields and in situ characterization of deformation, crack growth and fracture. Fracture surfaces were studied by SEM analysis accompanied with calculation of fracture patterns percentage. The fatigue tests demonstrate the high increase in the number of cycles until fracture (from 17 000 to 32 000 cycles) which could be explained by high ductility of welded material after treatment. This leads to lower fatigue crack growth rate due to higher energy dissipation. The obtained effect is attributable only for small cracks on micro-/mesoscales and fails to play a significant role for macro cracks.

Dependence of fracture toughness of molybdenum laser welds on processing parameters and in-situ oxygen gettering

International Nuclear Information System (INIS)

Pope, L.E.; Jellison, J.L.

1980-01-01

Fracture toughness properties have been determined for laser welds in different grades of molybdenum. The fracture toughness of welds in sintered molybdenum was consistently less than the fracture toughness of welds in vacuum arc remelted molybdenum. These differences cannot be attributed to oxygen content, since the oxygen level was nominally the same for all grades of molybdenum examined in this program. Alloy additions of titanium by means of physically deposited coatings significantly improved the fracture toughness of welds in sintered molybdenum, whereas titanium additions to welds in vacuum arc remelted molybdenum decreased the fracture toughness slightly. Pulsed laser welds exhibited fine columnar structures and, in the case of sintered molybdenum, superior fracture toughness when compared with continuous wave laser welds. 6 figures, 3 tables

A study of fatigue life distribution of butt-welded joints

International Nuclear Information System (INIS)

Sakai, Tatsuo; Fujitani, Keizo; Kikuchi, Toshiro; Tanaka, Takao.

1981-01-01

Various kinds of welded joints are being used in many structures such as ships, bridges and constructions. It is important in reliability analysis of such structures to clarify the statistical fatigue property of the welded joints. In this study, fatigue tests were carried out on the butt-welded joints of SM50A steel and a theoretical interpretation on the fatigue life distribution was attempted, assuming that a butt-welded joint is composed of a number of sliced specimens with different fatigue strengths. Main results obtained are summarized as follows; (1) The median crack initiation life of the butt-welded joint specimens coincided with that of the sliced specimens, when the crack initiation was defined by a 0.2 mm crack in the sliced specimens or the equivalent state of stress intensity factor in the joint specimens. (2) The distribution of crack initiation lives of the butt-welded joints can be theoretically derived by combining the concept of extreme distribution and the distribution model on the number of fatigue cracks. The theoretical distribution of crack initiation lives of the joints is in good agreement with the general trend of the experimental results. (3) If the distribution of crack initiation lives and the crack growth law are given experimentally, one can obtain analytically the distribution of final fatigue lives. The fatigue life distribution of the sliced specimens can be explained by the theory established in this study. (author)

Fracture toughness of austenitic stainless steel weld metal at 4 K

International Nuclear Information System (INIS)

Goodwin, G.M.

1984-08-01

Selection of the welding processess and weld filler metals for fabrication of a large toroidal superconducting magnet is described. Data available in the literature are collected and compared with data generated in this study for three welding processes, shielded metal arc (SMA), gas tungsten arc (GTA), and flux cored arc (FCA) welds had the highest fracture toughness as measured by K/sub Ic/ estimated from J/sub Ic/. The SMA and FCA welds had about the same toughness, below the GTA values but above the average from the literature. The fracture mode for all three processes was typified by ductile dimples. The fracture morphology of the FCA weld specimens was influenced by the solidification substructure, and small particles were found to be nucleation sites for void formation, especially for the GTA welds. All three welding processes were deemed adequate for the intended service and were used to fabricate the large magnet. A trunnion-type turning fixture eliminated the need for welding in the vertical and overhead positions. The GTA process was used for all root passes, and the horizontal welds were filled by the SMA process. Over 80% of the welds were done in the flat position with the FCA process, and its high deposition rate and ease of operation are credited with contributing greatly to the success of the effort

Structural integrity and fatigue crack propagation life assessment of welded and weld-repaired structures

Science.gov (United States)

Alam, Mohammad Shah

2005-11-01

Structural integrity is the science and technology of the margin between safety and disaster. Proper evaluation of the structural integrity and fatigue life of any structure (aircraft, ship, railways, bridges, gas and oil transmission pipelines, etc.) is important to ensure the public safety, environmental protection, and economical consideration. Catastrophic failure of any structure can be avoided if structural integrity is assessed and necessary precaution is taken appropriately. Structural integrity includes tasks in many areas, such as structural analysis, failure analysis, nondestructive testing, corrosion, fatigue and creep analysis, metallurgy and materials, fracture mechanics, fatigue life assessment, welding metallurgy, development of repairing technologies, structural monitoring and instrumentation etc. In this research fatigue life assessment of welded and weld-repaired joints is studied both in numerically and experimentally. A new approach for the simulation of fatigue crack growth in two elastic materials has been developed and specifically, the concept has been applied to butt-welded joint in a straight plate and in tubular joints. In the proposed method, the formation of new surface is represented by an interface element based on the interface potential energy. This method overcomes the limitation of crack growth at an artificial rate of one element length per cycle. In this method the crack propagates only when the applied load reaches the critical bonding strength. The predicted results compares well with experimental results. The Gas Metal Arc welding processes has been simulated to predict post-weld distortion, residual stresses and development of restraining forces in a butt-welded joint. The effect of welding defects and bi-axial interaction of a circular porosity and a solidification crack on fatigue crack propagation life of butt-welded joints has also been investigated. After a weld has been repaired, the specimen was tested in a universal

Effect of boundary conditions on the strength and deformability of replicas of natural fractures in welded tuff

International Nuclear Information System (INIS)

Wibowo, J.; Amadei, B.; Sture, S.; Robertson, A.B.

1993-09-01

Four series of cyclic direct-shear experiments were conducted on several replicas of three natural fractures and a tensile fracture of welded tuff from Yucca Mountain. The objective of these tests was to examine the effect of cyclic loading on joint shear behavior under different boundary conditions. The shear tests were performed under either different levels of constant normal load ranging between 0.6 and 25.6 kips (2.7 and 113.9 kN) or constant normal stiffness ranging between 14.8 and 187.5 kips/in (25.9 and 328.1 kn/cm) . Bach test in the two categories consisted of five cycles of forward and reverse shear. Normal compression tests were also performed both before and after each shear experiment to measure changes in joint normal deformability. In order to quantify fracture surface damage during shear, fracture-surface fractal dimensions were obtained from measurements before and after shear

The Effect of Welding Energy on the Microstructural and Mechanical Properties of Ultrasonic-Welded Copper Joints

Science.gov (United States)

Yang, Jingwei; Cao, Biao; Lu, Qinghua

2017-01-01

The effects of welding energy on the mechanical and microstructural characteristics of ultrasonic-welded pure copper plates were investigated. Complex dynamic recrystallization and grain growth occurred inside the weld zone during ultrasonic welding. At a low welding energy, a thin band of straight weld interfaces was observed and had an ultra-fine grain structure. With an increase in welding energy, the weld interface progressively changed from flat to sinusoidal, and eventually turned into a convoluted wavy pattern, bearing similarities to shear instabilities, as observed in fluid dynamics. The lap shear load of the joints initially increased and then remained stable as the welding energy increased. The tensile characteristics of the joints significantly depended on the development of plastic deformation at the interface. The influence of the microstructure on the hardness was also discussed. PMID:28772553

The effect of aging treatment on the high temperature fatigue strength and fatigue fracture behaviour of friction welded domestic heat resisting steels (SUH3-SUS303)

International Nuclear Information System (INIS)

Lee, K.Y.; Oh, S.K.; Kim, H.J.

1981-01-01

In this study the experiment was carried out as the high temperature rotary bending fatigue testing under the condition of 700 0 C high temperature to the friction welded domestic heat resisting steels, SUH3-SUS303, which were 10 hr., 100 hr. aging heat treated at 700 0 C after solution treatment 1 hr. at 1060 0 C for the purpose of observing the effects of the high temperature fatigue strength and fatigue fracture behaviours as well as with various mechanical properties of welded joints. The results obtained are summarized as follows: 1) Through mechanical tests and microstructural examinations, the determined optimum welding conditions, rotating speed 2420 rpm, heating pressure 8 kg/mm 2 , upsetting pressure 22 kg/mm 2 , the amount of total upset 7 mm (heating time 3 sec and upsetting time 2 sec) were satisfied. 2) The solution treated material SUH3, SUS303 and SUH3-SUS303, have the highest inclination gradiant on S-N curve due to the high temperature fatigue testing for long time at 700 0 C. 3) The optimum aging time of friction welded SUH3-SUS303, has been recognized near the 10 hr. at 700 0 C after the solution treatment of 1 hr. at 1060 0 C. 4) The high temperature fatigue limits of aging treated materials were compared with those of raw material according to the extender of aging time, on 10 hr. aging, fatigue limits were increased by SUH3 75.4%, SUS303 28.5%, friction welded joints SUH3-SUS303 44.2% and 100 hr. aging the rate were 64.9%, 30.4% and 36.6% respectively. 5) The fatigue fractures occurred at the side of the base metal SUS303 of the friction welded joints SUH3-SUS303 and it is difficult to find out fractures at the friction welding interfaces. 6) The cracking mode of SUS303, SUH3-SUS303 is intergranular in any case, but SUH3 is fractured by transgranular cracking. (author)

A novel weld seam detection method for space weld seam of narrow butt joint in laser welding

Science.gov (United States)

Shao, Wen Jun; Huang, Yu; Zhang, Yong

2018-02-01

Structured light measurement is widely used for weld seam detection owing to its high measurement precision and robust. However, there is nearly no geometrical deformation of the stripe projected onto weld face, whose seam width is less than 0.1 mm and without misalignment. So, it's very difficult to ensure an exact retrieval of the seam feature. This issue is raised as laser welding for butt joint of thin metal plate is widely applied. Moreover, measurement for the seam width, seam center and the normal vector of the weld face at the same time during welding process is of great importance to the welding quality but rarely reported. Consequently, a seam measurement method based on vision sensor for space weld seam of narrow butt joint is proposed in this article. Three laser stripes with different wave length are project on the weldment, in which two red laser stripes are designed and used to measure the three dimensional profile of the weld face by the principle of optical triangulation, and the third green laser stripe is used as light source to measure the edge and the centerline of the seam by the principle of passive vision sensor. The corresponding image process algorithm is proposed to extract the centerline of the red laser stripes as well as the seam feature. All these three laser stripes are captured and processed in a single image so that the three dimensional position of the space weld seam can be obtained simultaneously. Finally, the result of experiment reveals that the proposed method can meet the precision demand of space narrow butt joint.

Materials participation in welded joints manufacturing

Science.gov (United States)

Ghenghea, L. D.

2016-08-01

Management of materials dilution to form a joint with higher features asked by complex metallic structures is a problem that took attention and efforts of welding processes researchers and this communication will give a little contribution presenting some scientific and experimental results of dilution processes studied by Welding Research Group from Iasi, Romania, TCM Department. Liquid state welding processes have a strong dependence related to dilution of base and filler materials, the most important are for automatic joining using welding. The paper presents a review of some scientific works already published and their contributions, results of dilution coefficient evaluation using weighing, graphics and software applied for shielded metal arc welding process. Paper results could be used for welders’ qualification, welding procedure specification and other welding processes researchers’ activities. The results of Welding Research Group from Iasi, Romania, TCM Department, show dilution coefficient values between 20-30 % of base material and 70-80 % of filler material for studied welding process.

Thermal-deformation effect of welding on A 1 reactor pressure vessel weld joints properties and state of stress

International Nuclear Information System (INIS)

Becka, J.; Kupka, I.

1976-01-01

The methods are compared of electroslag welding and of arc welding with a view to their possible application in welding the Bohunice A-1 reactor pressure vessel. Considered are the thermal deformation effects of welding on the physical properties and the stress present in welded joints. For testing, plates were used having the dimensions of 1100x2300x200 mm and rings with 4820 mm outer diameter, 1800 mm height and 170 mm thickness made of steel CSN 413O30 modified with Ni, Al+Ti. The deformation effect of welding on the residual surface and triaxial stress, the specific stored energy, the initiation temperature of brittle crack and the critical size of the initiation defect corresponding to the thermal deformation effect of welding were determined. It was found that for electroslag welding, there is a low probability of crack formation in the joints, a low level of residual stress and a low level of specific stored energy in a relatively wide joint zone. For arc welding there is a considerable probability of defect formation in the vicinity of the sharp boundary of the joint, a high level of the triaxial state of stress in the tensile region, and a high level of specific stored energy concentrated in the narrow zone of weld joints. The recommended thermal process is given for welding pressure vessels made of the CSN 413030 steel modified with Ni, Al+Ti, and 150 to 200 mm in thickness. (J.P.)

Experimental assessment of the influence of welding process parameters on Lamb wave transmission across ultrasonically welded thermoplastic composite joints

Science.gov (United States)

Ochôa, Pedro; Fernandez Villegas, Irene; Groves, Roger M.; Benedictus, Rinze

2018-01-01

One of the advantages of thermoplastic composites relative to their thermoset counterparts is the possibility of assembling components through welding. Ultrasonic welding in particular is very promising for industrialization. However, uncertainty in the fatigue and fracture behaviour of composites is still an obstacle to the full utilisation of these materials. Health monitoring is then of vital importance, and Lamb wave techniques have been widely recognised as some of the most promising approaches for that end. This paper presents the first experimental study about the influence of welding travel on the transmission of Lamb waves across ultrasonically welded thermoplastic composite joints in single-lap configuration. The main aim of this research is to start to understand how guided waves interact with the internal structure of ultrasonic welds, so that benign, manufacturing-related structural features can be distinguished from damaging ones in signal interpretation. The power transmission coefficient and the correlation coefficient proved to be suitable for analysing the wave propagation phenomena, allowing quantitative identification of small variations of weld-line thickness and intermolecular diffusion at the weld interface. The conclusions are used to develop a tentative damage detection criterion which can later on assist the design of a Lamb wave based structural health monitoring system for thermoplastic composite structures. The Lamb wave test results are backed up by phased-array inspections, which also provide some extra insight on the internal structure of ultrasonic welds.

Plastic fracture toughness of austenitic welding connection for Ver-1000 nuclear reactor piping of 300-350 mm diameter

International Nuclear Information System (INIS)

Vasil'chenko, G.S.; Dragunov, Yu.G.; Kabelevskij, M.G.; Kazantsev, A.G.; Kunavin, S.A.; Merinov, G.N.; Sokov, L.M.

2000-01-01

The outside welding technology for circular welds in a pearlitic tube using austenitic welding wire materials is developed and applied in manufacturing pipelines of CPP and ECC. Mechanical properties and fracture toughness of austenitic welded joints in pearlitic tubes are determined to substantiate by calculation the practicality of the leakage prior to failure concept. The work is accomplished on experimental tube manufactured by hand arc welding. When manufactured the tube is cut into 5 rings. From the rings the tensile specimens are cut for testing at 20 and 350 deg C as well as Charpy V-notch impact specimens and compact specimens ST-1T. It is shown that the materials of the experimental tube meet the standard requirements. Only axial specimens cut across the weld are not in conformity with the requirements for specific elongation [ru

Mechanical behaviour of Astm A 297 grade Hp joints welded using different processes

International Nuclear Information System (INIS)

Emygdio, Paulo Roberto Oliveira; Zeemann, Annelise; Almeida, Luiz Henrique de

1996-01-01

The influence of different arc welding processes on mechanical behaviour was studied for cast heat resistant stainless steel welded joints, in the as welded conditions. ASTM A 297 grade HP with niobium and niobium/titanium additions were welded following three different welding procedures, using shielded metal arc welding gas tungsten arc welding and plasma arc welding, in six welded joints. The welded joint mechanical behaviour was evaluated by ambient temperature and 870 deg C tensile tests; and creep tests at 900 deg C and 50 MPa. Mechanical test results showed that the welding procedure qualification following welding codes is not suitable for high temperature service applications. (author)

Reliability and durability of the 12Kh1MF steel tubes of electroslag remelting and their welded joints

International Nuclear Information System (INIS)

Lanskaya, K.A.; Kulikova, L.V.; Mazel', R.E.; Khromchenko, F.A.; Strizhenova, V.F.

1978-01-01

Results of investigating the positive effect of electrolag remelting (ESR) on the properties of the base metal and welded joint of the 12Kh1MF steel steam pipes with the aim of increasing their durability up to 20,000 hrs, are presented. To estimate the quality and properties of tube billet metal, microstructure, content and nature of nonmetallic inclusions, content of gases, austenite grain size, austenite transformations during continuous cooling, metal ductility, mechanical properties at different temperatures and heat resisting properties, have been investigated. It is established, that the base metal in tubes of electroslag remelting possess higher heat resistance, while welded joints besides, have high deformability and resistance to brittle fracture

Effects of residual stress on fatigue strength of small diameter welded pipe joint

International Nuclear Information System (INIS)

Yamashita, Tetsuo; Hattori, Takahiro; Nomoto, Toshiharu; Iida, Kunihiro; Sato, Masanobu

1996-01-01

A power plant consists of many welded components, therefore, it is essential in establishing the reliability of the power plant to maintain the reliability of all welded components. The fatigue failure caused by mechanical vibrations of small diameter welded joints, which is represented by socket welded joints, is one of the major causes of trouble for the welded parts of the power plant. Here, bending fatigue tests were conducted to investigate the fatigue strength of small diameter socket welded pipe joints. In the most cases of large diameter socket joints, a fatigue crack started from the root of the fillet weld though the stress amplitude at the root was smaller than that at the toe of fillet weld. Additionally, the fatigue strength was affected by the weld bead sequence. The residual stress was considered to be one of the important parameters governing fatigue strength, therefore, its effects were investigated. In several types of pipe joints, the local stress and residual stress distributions were calculated by finite element analysis. The residual stresses were compressive at the toe and tensile at the root of the socket welded joints. Based on these results, the effects of residual stresses on the fatigue strength are discussed for small diameter welded pipe joints in the present work

Residual stress relief in MAG welded joints of dissimilar steels

International Nuclear Information System (INIS)

Seodek, P.; Brozda, J.; Wang, L.; Withers, P.J.

2003-01-01

This paper addresses the relief of residual stress in welded joints between austenitic and non-alloyed ferritic-pearlitic steels. A series of similar and dissimilar steel joints based on the 18G2A (ferritic-pearlitic) and 1H18N10T (austenitic) steels were produced, some of which were stress relieved by annealing and some by mechanical prestressing. For the as-welded and stress relieved test joints the residual stresses were measured by trepanning. To aid the interpretation of these results, 2D plane stress finite element analysis has been performed to simulate the residual stress relieving methods. Analysis of the results has shown that thermal stress relieving of welded joints between dissimilar steels is not effective and may even increase residual stresses, due to the considerable difference in thermal expansion of the joined steels. It was found that, for the loads imposed, the effectiveness of the mechanical stress relieving of dissimilar steel welded joints was much lower than that of similar steel joints

Weld Joint Design for SFR Metallic Fuel Element Closures

Energy Technology Data Exchange (ETDEWEB)

Lee, Jung Won; Kim, Soo Sung; Woo, Yoon Myeng; Kim, Hyung Tae; Kim, Ki Hwan; Yoon, Kyung Ho [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

2014-05-15

The sodium-cooled fast reactor (SFR) system is among the six systems selected for Gen-IV promising systems and expected to become available for commercial introduction around 2030. In Korea, the R and D on SFR has been begun since 1997, as one of the national long-term nuclear R and D programs. The international collaborative research is under way on fuel developments within Advanced Fuel Project for Gen-IV SFR with the closed fuel cycle of full actinide recycling, while TRU bearing metallic fuel, U-TRU-Zr alloy fuel, was selected and is being developed. For the fabrication of SFR metallic fuel elements, the endplug welding is a crucial process. The sealing of endplug to cladding tube should be hermetically perfect to prevent a leakage of fission gases and to maintain a good reactor performance. In this study, the joint designs for endplug welding were investigated. For the irradiation test of SFR metallic fuel element, the TIG welding technique was adopted and the welding joint design was developed based on the welding conditions and parameters established. In order to make SFR metallic fuel elements, the weld joint design was developed based on the TIG welding technique.

The behavior of welded joint in steel pipe members under monotonic and cyclic loading

International Nuclear Information System (INIS)

Chang, Kyong-Ho; Jang, Gab-Chul; Shin, Young-Eui; Han, Jung-Guen; Kim, Jong-Min

2006-01-01

Most steel pipe members are joined by welding. The residual stress and weld metal in a welded joint have the influence on the behavior of steel pipes. Therefore, to accurately predict the behavior of steel pipes with a welded joint, the influence of welding residual stress and weld metal on the behavior of steel pipe must be investigated. In this paper, the residual stress of steel pipes with a welded joint was investigated by using a three-dimensional non-steady heat conduction analysis and a three-dimensional thermal elastic-plastic analysis. Based on the results of monotonic and cyclic loading tests, a hysteresis model for weld metal was formulated. The hysteresis model was proposed by the authors and applied to a three-dimensional finite elements analysis. To investigate the influence of a welded joint in steel pipes under monotonic and cyclic loading, three-dimensional finite elements analysis considering the proposed model and residual stress was carried out. The influence of a welded joint on the behavior of steel pipe members was investigated by comparing the analytical result both steel pipe with a welded joint and that without a welded joint

Grinding assembly, grinding apparatus, weld joint defect repair system, and methods

Science.gov (United States)

Larsen, Eric D.; Watkins, Arthur D.; Bitsoi, Rodney J.; Pace, David P.

2005-09-27

A grinding assembly for grinding a weld joint of a workpiece includes a grinder apparatus, a grinder apparatus includes a grinding wheel configured to grind the weld joint, a member configured to receive the grinding wheel, the member being configured to be removably attached to the grinder apparatus, and a sensor assembly configured to detect a contact between the grinding wheel and the workpiece. The grinding assembly also includes a processing circuitry in communication with the grinder apparatus and configured to control operations of the grinder apparatus, the processing circuitry configured to receive weld defect information of the weld joint from an inspection assembly to create a contour grinding profile to grind the weld joint in a predetermined shape based on the received weld defect information, and a manipulator having an end configured to carry the grinder apparatus, the manipulator further configured to operate in multiple dimensions.

Visualization of Spot- welding Resistance

Directory of Open Access Journals (Sweden)

Michal Černý

2016-01-01

Full Text Available This contribution devotes to monitoring of processes running during joining of steel sheets by incadescent so called point welding using non-destructive trial method – acoustic emission (AE. The joining process is detailed described within experimental measuring from the point of view of metallurgic effects runnig during weld creation (records obtained by means of AE method. It takes into consideration quality of joined steels within welding data of steel producer. Steel welding (determined by chemical composition during mechanical verification and firmness of welds consider results of measurement AE and fracture effect of point joints. The measurement also demonstrates conclusion about connection of metallurgic processes with material wave effects (AE measurement and their impact on firmness of joint at steel with guaranteed welding, difficult welding and at their potential combination.

Microstructure characteristics and temperature-dependent high cycle fatigue behavior of advanced 9% Cr/CrMoV dissimilarly welded joint

International Nuclear Information System (INIS)

Wu, Qingjun; Lu, Fenggui; Cui, Haichao; Ding, Yuming; Liu, Xia; Gao, Yulai

2014-01-01

Advanced 9% Cr and CrMoV steels chosen as candidate materials are first welded by narrow-gap submerged arc welding (NG-SAW) to fabricate the heavy section rotor. The present work focuses on studying the high-cycle fatigue (HCF) behavior of advanced 9% Cr/CrMoV dissimilarly welded joint at different temperatures. Conditional fatigue strength of this dissimilarly welded joint was obtained by HCF tests at room temperature (RT), 400 °C and 470 °C. It was observed that the failure occurred at the side of CrMoV base metal (BM), weld metal (WM) and heat affected zone (HAZ) of CrMoV side over 5×10 7 cycles for the specimens tested at RT, 400 °C and 470 °C. The detailed microstructures of BMs, WMs and HAZs as well as fracture appearance were observed by optical microscopy (OM) and scanning electron microscopy (SEM). Precipitation and aggregation of carbides along the grain boundaries were clearly detected with the increase of temperature, which brought a negative effect on the fatigue properties. It is interesting to note that the inclusion size leading to crack initiation became smaller for the HCF test at higher temperature. Therefore, reduction in the inclusion size in a welded joint helps to improve the HCF performance at high temperature

Microstructure characteristics and temperature-dependent high cycle fatigue behavior of advanced 9% Cr/CrMoV dissimilarly welded joint

Energy Technology Data Exchange (ETDEWEB)

Wu, Qingjun [Shanghai Key Laboratory of Materials Laser Processing and Modification, Shanghai Jiao Tong University, Shanghai 200240 (China); Lu, Fenggui, E-mail: Lfg119@sjtu.edu.cn [Shanghai Key Laboratory of Materials Laser Processing and Modification, Shanghai Jiao Tong University, Shanghai 200240 (China); Shanghai Key Laboratory of Modern Metallurgy and Materials Processing, Shanghai University, Shanghai 200072 (China); Cui, Haichao [Shanghai Key Laboratory of Materials Laser Processing and Modification, Shanghai Jiao Tong University, Shanghai 200240 (China); Ding, Yuming; Liu, Xia [Shanghai Turbine Plant of Shanghai Electric Power Generation Equipment Co. Ltd., Shanghai 200240 (China); Gao, Yulai, E-mail: ylgao@shu.edu.cn [Shanghai Key Laboratory of Modern Metallurgy and Materials Processing, Shanghai University, Shanghai 200072 (China)

2014-10-06

Advanced 9% Cr and CrMoV steels chosen as candidate materials are first welded by narrow-gap submerged arc welding (NG-SAW) to fabricate the heavy section rotor. The present work focuses on studying the high-cycle fatigue (HCF) behavior of advanced 9% Cr/CrMoV dissimilarly welded joint at different temperatures. Conditional fatigue strength of this dissimilarly welded joint was obtained by HCF tests at room temperature (RT), 400 °C and 470 °C. It was observed that the failure occurred at the side of CrMoV base metal (BM), weld metal (WM) and heat affected zone (HAZ) of CrMoV side over 5×10{sup 7} cycles for the specimens tested at RT, 400 °C and 470 °C. The detailed microstructures of BMs, WMs and HAZs as well as fracture appearance were observed by optical microscopy (OM) and scanning electron microscopy (SEM). Precipitation and aggregation of carbides along the grain boundaries were clearly detected with the increase of temperature, which brought a negative effect on the fatigue properties. It is interesting to note that the inclusion size leading to crack initiation became smaller for the HCF test at higher temperature. Therefore, reduction in the inclusion size in a welded joint helps to improve the HCF performance at high temperature.

Effects of solidified microstructures on J-R fracture resistances of the surge line pipe welds

International Nuclear Information System (INIS)

Youn, J. H.; Lee, B. S.; Yoo, W.

2003-01-01

The cause of the difference in J-R fracture resistances of AISI Type 347 GTAW welds which had almost same amounts of chromium carbides were investigated by the microstructural observations. As a result, the difference in the fracture resistances with the morphologies of the retained δ-ferrites in Type 347 welds were observed. The fracture resistance of the weld which had mostly vermicular type δ-ferrites was inferior to the weld which has lacy and acicular mixed type δ-ferrites. Therefore, it was deduced that the morphology of δ-ferrites affected the J-R fracture resistances of Type 347 welds

Thermomechanical treatment of welded joints of aluminum-lithium alloys modified by scandium

Science.gov (United States)

Malikov, A. G.

2017-12-01

At present, the aeronautical equipment manufacture involves up-to-date high-strength aluminum alloys of decreased density resulting from the lithium admixture. Various technologies of fusible welding of these alloys are being developed. The paper presents experimental investigations of the optimization of the laser welding of aluminum alloys with the scandium-modified welded joint after thermomechanical treatment. The effect of scandium on the micro- and macrostructure is studied along with strength characteristics of the welded joint. It is found that thermomechanical treatment allows us to obtain the strength of the welded joint 0.89 for the Al-Mg-Li system and 0.99 for the Al-Cu-Li system with the welded joint modified by scandium in comparison with the base alloy after treatment.

Ultrasonic Welding of Thermoplastic Composite Coupons for Mechanical Characterization of Welded Joints through Single Lap Shear Testing.

Science.gov (United States)

Villegas, Irene F; Palardy, Genevieve

2016-02-11

This paper presents a novel straightforward method for ultrasonic welding of thermoplastic-composite coupons in optimum processing conditions. The ultrasonic welding process described in this paper is based on three main pillars. Firstly, flat energy directors are used for preferential heat generation at the joining interface during the welding process. A flat energy director is a neat thermoplastic resin film that is placed between the parts to be joined prior to the welding process and heats up preferentially owing to its lower compressive stiffness relative to the composite substrates. Consequently, flat energy directors provide a simple solution that does not require molding of resin protrusions on the surfaces of the composite substrates, as opposed to ultrasonic welding of unreinforced plastics. Secondly, the process data provided by the ultrasonic welder is used to rapidly define the optimum welding parameters for any thermoplastic composite material combination. Thirdly, displacement control is used in the welding process to ensure consistent quality of the welded joints. According to this method, thermoplastic-composite flat coupons are individually welded in a single lap configuration. Mechanical testing of the welded coupons allows determining the apparent lap shear strength of the joints, which is one of the properties most commonly used to quantify the strength of thermoplastic composite welded joints.

Creep rupture strength of activated-TIG welded 316L(N) stainless steel

International Nuclear Information System (INIS)

Sakthivel, T.; Vasudevan, M.; Laha, K.; Parameswaran, P.; Chandravathi, K.S.; Mathew, M.D.; Bhaduri, A.K.

2011-01-01

316L(N) stainless steel plates were joined using activated-tungsten inert gas (A-TIG) welding and conventional TIG welding process. Creep rupture behavior of 316L(N) base metal, and weld joints made by A-TIG and conventional TIG welding process were investigated at 923 K over a stress range of 160-280 MPa. Creep test results showed that the enhancement in creep rupture strength of weld joint fabricated by A-TIG welding process over conventional TIG welding process. Both the weld joints fractured in the weld metal. Microstructural observation showed lower δ-ferrite content, alignment of columnar grain with δ-ferrite along applied stress direction and less strength disparity between columnar and equiaxed grains of weld metal in A-TIG joint than in MP-TIG joint. These had been attributed to initiate less creep cavitation in weld metal of A-TIG joint leading to improvement in creep rupture strength.

Creep rupture strength of activated-TIG welded 316L(N) stainless steel

Science.gov (United States)

Sakthivel, T.; Vasudevan, M.; Laha, K.; Parameswaran, P.; Chandravathi, K. S.; Mathew, M. D.; Bhaduri, A. K.

2011-06-01

316L(N) stainless steel plates were joined using activated-tungsten inert gas (A-TIG) welding and conventional TIG welding process. Creep rupture behavior of 316L(N) base metal, and weld joints made by A-TIG and conventional TIG welding process were investigated at 923 K over a stress range of 160-280 MPa. Creep test results showed that the enhancement in creep rupture strength of weld joint fabricated by A-TIG welding process over conventional TIG welding process. Both the weld joints fractured in the weld metal. Microstructural observation showed lower δ-ferrite content, alignment of columnar grain with δ-ferrite along applied stress direction and less strength disparity between columnar and equiaxed grains of weld metal in A-TIG joint than in MP-TIG joint. These had been attributed to initiate less creep cavitation in weld metal of A-TIG joint leading to improvement in creep rupture strength.

Creep rupture strength of activated-TIG welded 316L(N) stainless steel

Energy Technology Data Exchange (ETDEWEB)

Sakthivel, T., E-mail: tsakthivel@igcar.gov.in [Metallurgy and Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102 (India); Vasudevan, M.; Laha, K.; Parameswaran, P.; Chandravathi, K.S.; Mathew, M.D.; Bhaduri, A.K. [Metallurgy and Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102 (India)

2011-06-01

316L(N) stainless steel plates were joined using activated-tungsten inert gas (A-TIG) welding and conventional TIG welding process. Creep rupture behavior of 316L(N) base metal, and weld joints made by A-TIG and conventional TIG welding process were investigated at 923 K over a stress range of 160-280 MPa. Creep test results showed that the enhancement in creep rupture strength of weld joint fabricated by A-TIG welding process over conventional TIG welding process. Both the weld joints fractured in the weld metal. Microstructural observation showed lower {delta}-ferrite content, alignment of columnar grain with {delta}-ferrite along applied stress direction and less strength disparity between columnar and equiaxed grains of weld metal in A-TIG joint than in MP-TIG joint. These had been attributed to initiate less creep cavitation in weld metal of A-TIG joint leading to improvement in creep rupture strength.

Laser welding of NiTi shape memory alloy: Comparison of the similar and dissimilar joints to AISI 304 stainless steel

Science.gov (United States)

Mirshekari, G. R.; Saatchi, A.; Kermanpur, A.; Sadrnezhaad, S. K.

2013-12-01

The unique properties of NiTi alloy, such as its shape memory effect, super-elasticity and biocompatibility, make it ideal material for various applications such as aerospace, micro-electronics and medical device. In order to meet the requirement of increasing applications, great attention has been given to joining of this material to itself and to other materials during past few years. Laser welding has been known as a suitable joining technique for NiTi shape memory alloy. Hence, in this work, a comparative study on laser welding of NiTi wire to itself and to AISI 304 austenitic stainless steel wire has been made. Microstructures, mechanical properties and fracture morphologies of the laser joints were investigated using optical microscopy, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction analysis (XRD), Vickers microhardness (HV0.2) and tensile testing techniques. The results showed that the NiTi-NiTi laser joint reached about 63% of the ultimate tensile strength of the as-received NiTi wire (i.e. 835 MPa) with rupture strain of about 16%. This joint also enabled the possibility to benefit from the pseudo-elastic properties of the NiTi component. However, tensile strength and ductility decreased significantly after dissimilar laser welding of NiTi to stainless steel due to the formation of brittle intermetallic compounds in the weld zone during laser welding. Therefore, a suitable modification process is required for improvement of the joint properties of the dissimilar welded wires.

Metallurgical and mechanical characterization of a submerged arc welded joint in a 316 type stainless steel

International Nuclear Information System (INIS)

Piatti, G.; Vedani, M.

1990-01-01

The tensile (deformation and fracture) behaviour of a multipass submerged arc welded joint Type 316 stainless steel is investigated by tests at room temperature and at 400 0 C on all-weld metal and transverse to weld (composite) specimens as well as by microstructural and compositional analyses (optical, scanning electron and transmission electron microscopy). The as-deposited metal is characterised by a systematic variation in the tensile properties across the thickness with the higher strength and the lower ductility in the weld centre. These variations are related to material variability (mainly in dislocation density) because of local dissimilarities in thermal and mechanical histories occurring during the welding process. However, the material variability in the fusion zone, although important is not so large in the present weld and it does not influence the tensile properties of the weld as a whole. Moreover, the tensile behaviour concerning the transverse to weld specimens is characterized by a supporting effect from the higher yield strength material zone (fusion zone) to the lower yield strength material zone (parent metal) justified by the different contribution of the parent metal and of the weld-deposit metal to the integral plastic strain of the specimens. (author)

Technology of Welding Joints Mixed with Duplex Steel

Directory of Open Access Journals (Sweden)

Słania J.

2016-03-01

Full Text Available Results of the examinations of sample plates of mixed joints with the duplex steel were discussed. Examinations were taken on the sample plates of mixed joints of sheet plates type P355NL1 and X2CrNiMoN22-5-3 welded by the flux-cored wire DW-329A by the Kobelco company of the following category T 22 9 3 NL RC/M3 in the gas shroud M21 (Ar+18%CO2 (plate no.1, and nickel covered electrodes E Ni 6082 by the Böhler company (plate no. 2. Results of the side bend test of welded joint, transverse tensile test, stretching of the weld metal, impact strength, micro and macroscopic metallographic examinations, and measurements of the delta ferrite content were presented.

Formed electroslag welded joint from austenitic steel 18/10 CrNi

International Nuclear Information System (INIS)

Jilek, L.; Kusak, L.; Martinak, A.

1987-01-01

The electroslag welded joint from titanium stabilized steel 18/10 CrNi of 150 mm in thickness showed positive results for both nondestructive and destructive testing. Czechoslovak flux VUZ-4F and the optimized welding mode were completely proven. The weldment was subject to deformation by forging with a removal of 20 to 50% and to bending deformation. A 40% to 50% deformation was necessary for breaking the coarse-grain casting structure. The bending deformation resulted in breaking the coarse-grain casting structure in the entire cross-section, it was, however, only acting in a narrow band corresponding to the largest curvature. At the same time, the heat affected zone decayed. Following heat treatment, especially forming, the delta ferrite content in the weld metal decreased, the mechanical properties of the weld metal and the welded joint following welding and heat treatment showed a relatively large scatter. Forming reduced the scatter and improved plastic properties. Machining within 40 and 50% resulted in good echogenicity of the welded joint in ultrasound testing. The welded joint showed equal properties as the base material of the weldment. (author). 15 figs., 2 tabs., 16 refs

Optimum welding condition of 2017 aluminum similar alloy friction welded joints

Energy Technology Data Exchange (ETDEWEB)

Tsujino R.; Ochi, H. [Osaka Inst. of Tech., Osaka (Japan); Morikawa, K. [Osaka Sangyo Univ., Osaka (Japan); Yamaguchi, H.; Ogawa, K. [Osaka Prefecture Univ., Osaka (Japan); Fujishiro, Y.; Yoshida, M. [Sumitomo Metal Technology Ltd., Hyogo (Japan)

2002-07-01

Usefulness of the statistical analysis for judging optimization of the friction welding conditions was investigated by using 2017 aluminum similar alloy, where many samples under fixed welding conditions were friction welded and analyzed statistically. In general, selection of the optimum friction welding conditions for similar materials is easy. However, it was not always the case for 2017 aluminum alloy. For optimum friction welding conditions of this material, it is necessary to apply relatively larger upset pressure to obtain high friction heating. Joint efficiencies obtained under the optimum friction welding conditions showed large shape parameter (m value) of Weibull distribution as well as in the dissimilar materials previously reported. The m value calculated on the small number of data can be substituted for m value on the 30 data. Therefore, m value is useful for practical use in the factory for assuming the propriety of the friction welding conditions. (orig.)

Electrochemical heterogeneity and corrosion resistance of a welded titanium-zirconium joint

International Nuclear Information System (INIS)

Polyakov, S.G.; Goncharov, A.B.; Onoprienko, L.M.; Smiyan, O.D.

1992-01-01

The electrochemical behavior and corrosion resistance of various welded joints of zirconium alloy N-2.5 with commercial titanium VT1 made by the argon-arc method are studied. Electrochemical heterogeneity is studied by measuring the distribution of potentials over the surface, galvanic currents, and recording of polarization curves for different zones of a welded joint in 5% sulfuric acid solution at 340 K. It is established that electrochemical heterogeneity of the zones of an N-2.5 + VT1 welded joint leads to acceleration of the cathodic process in a welded joint and the anodic process along the fusion line from the titanium direction where the greatest hydrogenation of the metal and corrosion damage is correspondingly observed

Research of the Resistance of Contact Welding Joint of R65 Type Rail

Directory of Open Access Journals (Sweden)

Kęstutis Dauskurdis

2015-03-01

Full Text Available In the article the R65 type rail joints that were welded by resistance welding are analysed. Survey methodology of the research consists of the following parts: visual inspection of welded joint, ultrasonic rail inspection, hardness test of upper part of the rail, fusion area research, the measurement hardness test of heat-softened area, the measurement microhardness test, microstructure research of the welded joint, impact strength experiments, chemical analysis of welded joint, wheel-rail interaction research using the finite element method (FEM. The results of the research are analysed and the quality of weld is evaluated. The conclusion is based on the results of this research.

Tensile behavior of dissimilar friction stir welded joints of aluminium alloys

International Nuclear Information System (INIS)

Shanmuga Sundaram, N.; Murugan, N.

2010-01-01

The heat treatable aluminium alloy AA2024 is used extensively in the aircraft industry because of its high strength to weight ratio and good ductility. The non-heat treatable aluminium alloy AA5083 possesses medium strength and high ductility and used typically in structural applications, marine, and automotive industries. When compared to fusion welding processes, friction stir welding (FSW) process is an emerging solid state joining process which is best suitable for joining these alloys. The friction stir welding parameters such as tool pin profile, tool rotational speed, welding speed, and tool axial force influence the mechanical properties of the FS welded joints significantly. Dissimilar FS welded joints are fabricated using five different tool pin profiles. Central composite design with four parameters, five levels, and 31 runs is used to conduct the experiments and response surface method (RSM) is employed to develop the model. Mathematical regression models are developed to predict the ultimate tensile strength (UTS) and tensile elongation (TE) of the dissimilar friction stir welded joints of aluminium alloys 2024-T6 and 5083-H321, and they are validated. The effects of the above process parameters and tool pin profile on tensile strength and tensile elongation of dissimilar friction stir welded joints are analysed in detail. Joints fabricated using Tapered Hexagon tool pin profile have the highest tensile strength and tensile elongation, whereas the Straight Cylinder tool pin profile have the lowest tensile strength and tensile elongation. The results are useful to have a better understanding of the effects of process parameters, to fabricate the joints with desired tensile properties, and to automate the FS welding process.

Process for quality assurance of welded joints for electrical resistance point welding

International Nuclear Information System (INIS)

Schaefer, R.; Singh, S.

1977-01-01

In order to guarantee the reproducibility of welded joints of even quality (above all in the metal working industry), it is proposed that before starting resistance point welding, a preheating current should be allowed to flow at the site of the weld. A given reduction of the total resistance at the site of the weld should effect the time when the preheating current is switched over to welding current. This value is always predetermined empirically. Further possibilities of controlling the welding process are described, where the measurement of thermal expansion of the parts is used. A standard welding time is given. The rated course of electrode movement during the process can be predicted and a running comparison of nominal and actual values can be carried out. (RW) [de

Study of Laser Welding of HCT600X Dual Phase Steels

Directory of Open Access Journals (Sweden)

Švec Pavol

2014-12-01

Full Text Available The effects of beam power and welding speed on microstructure, microhardnes and tensile strength of HCT600X laser welded steel sheets were evaluated. The welding parameters influenced both the width and the microstructure of the fusion zone and heat affected zone. The welding process has no effect on tensile strength of joints which achieved the strength of base metal and all joints fractured in the base metal.

Assessment of Stress Corrosion Cracking Resistance of Activated Tungsten Inert Gas-Welded Duplex Stainless Steel Joints

Science.gov (United States)

Alwin, B.; Lakshminarayanan, A. K.; Vasudevan, M.; Vasantharaja, P.

2017-12-01

The stress corrosion cracking behavior of duplex stainless steel (DSS) weld joint largely depends on the ferrite-austenite phase microstructure balance. This phase balance is decided by the welding process used, heat input, welding conditions and the weld metal chemistry. In this investigation, the influence of activated tungsten inert gas (ATIG) and tungsten inert gas (TIG) welding processes on the stress corrosion cracking (SCC) resistance of DSS joints was evaluated and compared. Boiling magnesium chloride (45 wt.%) environment maintained at 155 °C was used. The microstructure and ferrite content of different weld zones are correlated with the outcome of sustained load, SCC test. Irrespective of the welding processes used, SCC resistance of weld joints was inferior to that of the base metal. However, ATIG weld joint exhibited superior resistance to SCC than the TIG weld joint. The crack initiation and final failure were in the weld metal for the ATIG weld joint; they were in the heat-affected zone for the TIG weld joint.

Fracture mechanics evaluation of heavy welded structures

International Nuclear Information System (INIS)

Sprung, I.; Ericksson, C.W.; Zilberstein, V.A.

1982-01-01

This paper describes some applications of nondestructive examination (NDE) and engineering fracture mechanics to evaluation of flaws in heavy welded structures. The paper discusses not only widely recognized linear elastic fracture mechanics (LEFM) analysis, but also methods of the elastic-plastic fracture mechanics (EPFM), such as COD, J-integral, and Failure Assessment Diagram. Examples are given to highlight the importance of interaction between specialists providing input and the specialists performing the analysis. The paper points out that the critical parameters for as-welded structures when calculated by these methods are conservative since they are based on two pessimistic assumptions: that the magnitude of residual stress is always at the yield strength level, and that the residual stress always acts in the same direction as the applied (mechanical) stress. The suggestion is made that it would be prudent to use the COD or the FAD design curves for a conservative design. The appendix examines a J-design curve modified to include residual stresses

Development of liquid-nitrogen-cooling friction stir spot welding for AZ31 magnesium alloy joints

Science.gov (United States)

Wu, Dong; Shen, Jun; Zhou, Meng-bing; Cheng, Liang; Sang, Jia-xing

2017-10-01

A liquid-nitrogen-cooling friction stir spot welding (C-FSSW) technology was developed for welding AZ31 magnesium alloy sheets. The liquid-nitrogen cooling degraded the deformability of the welded materials such that the width of interfacial cracks increased with increasing cooling time. The grain size of the stirred zone (SZ) and the heat-affected zone (HAZ) of the C-FSSW-welded joints decreased, whereas that of the thermomechanically affected zone (TMAZ) increased with increasing cooling time. The maximum tensile shear load of the C-FSSW-welded joints welded with a cooling time of 5 or 7 s was larger than that of the friction stir spot welding (FSSW)-welded joint, and the tensile shear load decreased with increasing cooling time. The microhardness of the C-FSSW-welded joints was greater than that of the FSSW-welded joint. Moreover, the microhardness of the SZ and the HAZ of the C-FSSW-welded joints increased, whereas that of the TMAZ decreased, with increasing cooling time.

Microstructure and Mechanical Properties of an Ultrasonic Spot Welded Aluminum Alloy: The Effect of Welding Energy

Directory of Open Access Journals (Sweden)

He Peng

2017-04-01

Full Text Available The aim of this study is to evaluate the microstructures, tensile lap shear strength, and fatigue resistance of 6022-T43 aluminum alloy joints welded via a solid-state welding technique–ultrasonic spot welding (USW–at different energy levels. An ultra-fine necklace-like equiaxed grain structure is observed along the weld line due to the occurrence of dynamic crystallization, with smaller grain sizes at lower levels of welding energy. The tensile lap shear strength, failure energy, and critical stress intensity of the welded joints first increase, reach their maximum values, and then decrease with increasing welding energy. The tensile lap shear failure mode changes from interfacial fracture at lower energy levels, to nugget pull-out at intermediate optimal energy levels, and to transverse through-thickness (TTT crack growth at higher energy levels. The fatigue life is longer for the joints welded at an energy of 1400 J than 2000 J at higher cyclic loading levels. The fatigue failure mode changes from nugget pull-out to TTT crack growth with decreasing cyclic loading for the joints welded at 1400 J, while TTT crack growth mode remains at all cyclic loading levels for the joints welded at 2000 J. Fatigue crack basically initiates from the nugget edge, and propagates with “river-flow” patterns and characteristic fatigue striations.

Investigation on edge joints of Inconel 625 sheets processed with laser welding

Science.gov (United States)

Caiazzo, F.; Alfieri, V.; Cardaropoli, F.; Sergi, V.

2017-08-01

Laser welding of Inconel 625 edge joint beads in square groove configuration was investigated. The use of different weld geometries in new aerospace solutions explains research on edge joints. A structured plan was carried out in order to characterize the process defining the influence of laser power and welding speed and to study possible interactions among the governing factors. As weld pool protection is crucial in order to obtain sound joints when processing superalloys, a special glove box for gas supply was designed to upgrade the welding head. Welded joints were characterized referring to bead profile, microstructure and X-rays. It was found that heat input plays an important role as it affects welding stability, porosity content and bead shape. Results suggest operating with low values of heat input to reduce porosity and guarantee stable bead conformation. Furthermore, a decrease in the grain size has been observed as a consequence of decreasing heat input.

Influence of scandium on the microstructure and strength properties of the welded joint at the laser welding of aluminum-lithium alloys

Science.gov (United States)

Malikov, A. G.; Golyshev, A. A.; Ivanova, M. Yu.

2017-10-01

Today, aeronautical equipment manufacture involves up-to-date high-strength aluminum alloys of decreased density resulting from lithium admixture. Various technologies of fusible welding of these alloys are being developed. Serious demands are imposed to the welded joints of aluminum alloys in respect to their strength characteristics. The paper presents experimental investigations of the optimization of the laser welding of aluminum alloys with the scandium-modified welded joint. The effect of scandium on the micro-and macro-structure has been studied as well as the strength characteristics of the welded joint. It has been found that scandium under in the laser welding process increases the welded joint elasticity for the system Al-Mg-Li, aluminum alloy 1420 by 20 %, and almost doubles the same for the system Al-Cu-Li, aluminum alloy 1441.

Microstructure and mechanical properties of the TIG welded joints of fusion CLAM steel

Energy Technology Data Exchange (ETDEWEB)

Jiang Zhizhong, E-mail: zhizhongjiang2006@yahoo.com.c [School of Materials Science and Engineering, University of Science and Technology Beijing, Xueyuan Road, Beijing 100083 (China); Ren Litian; Huang Jihua; Ju Xin; Wu Huibin [School of Materials Science and Engineering, University of Science and Technology Beijing, Xueyuan Road, Beijing 100083 (China); Huang Qunying; Wu Yican [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei, Anhui 230031 (China)

2010-12-15

The CLAM steel plates were butt-welded through manual tungsten inert gas welding (TIG) process, and the following post-welding heat treatment (PWHT) at 740 {sup o}C for 1 h. The microstructure and mechanical properties of the welded joints were measured. The results show that both hardening and softening occur in the weld joints before PWHT, but the hardening is not removed completely in the weld metal and the fusion zone after PWHT. In as-welded condition, the microstructure of the weld metal is coarse lath martensite, and softened zone in heat-affected zone (HAZ) consists of a mixture of tempered martensite and ferrite. After PWHT, a lot of carbides precipitate at all zones in weld joints. The microstructure of softened zone transforms to tempered sorbite. Tensile strength of the weld metal is higher than that of HAZ and base metal regardless of PWHT. However, the weld metal has poor toughness without PWHT. The impact energy of the weld metal after PWHT reaches almost the same level as the base metal. So it is concluded that microstructure and mechanical properties of the CLAM steel welded joints can be improved by a reasonable PWHT.

A comparative study of laser beam welding and laser-MIG hybrid welding of Ti-Al-Zr-Fe titanium alloy

International Nuclear Information System (INIS)

Li Ruifeng; Li Zhuguo; Zhu Yanyan; Rong Lei

2011-01-01

Research highlights: → Ti-Al-Zr-Fe titanium alloy sheets were welded by LBW and LAMIG methods. → LAMIG welded joints have better combination of strength and ductility. → LAMIG welding is proved to be feasible for the production of titanium sheet joints. - Abstract: Ti-Al-Zr-Fe titanium alloy sheets with thickness of 4 mm were welded using laser beam welding (LBW) and laser-MIG hybrid welding (LAMIG) methods. To investigate the influence of the methods difference on the joint properties, optical microscope observation, microhardness measurement and mechanical tests were conducted. Experimental results show that the sheets can be welded at a high speed of 1.8 m/min and power of 8 kW, with no defects such as, surface oxidation, porosity, cracks and lack of penetration in the welding seam. In addition, all tensile test specimens fractured at the parent metal. Compared with the LBW, the LAMIG welding method can produce joints with higher ductility, due to the improvement of seam formation and lower microhardness by employing a low strength TA-10 welding wire. It can be concluded that LAMIG is much more feasible for welding the Ti-Al-Zr-Fe titanium alloy sheets.

The Microstructure and Pitting Resistance of Weld Joints of 2205 Duplex Stainless Steel

Science.gov (United States)

Wu, Mingfang; Liu, Fei; Pu, Juan; Anderson, Neil E.; Li, Leijun; Liu, Dashuang

2017-11-01

2205 duplex stainless steel (DSS) was welded by submerged arc welding. The effects of both heat input and groove type on the ferrite/austenite ratio and elemental diffusion of weld joints were investigated. The relationships among welding joint preparation, ferrite/austenite ratio, elemental diffusion, and pitting corrosion resistance of weld joints were analyzed. When the Ni content of the weld wire deposit was at minimum 2-4% higher than that of 2205 DSS base metal, the desired ratio of ferrite/austenite and elemental partitioning between the austenite and ferrite phases were obtained. While the pitting sensitivity of weld metal was higher than that of base metal, the self-healing capability of the passive film of weld metal was better than that of the base metal when a single V-type groove was used. Furthermore, the heat input should be carefully controlled since pitting corrosion occurred readily in the coarse-grained heat-affected zone near the fusion line of welded joints.

Modeling and validation of multiple joint reflections for ultra- narrow gap laser welding

Energy Technology Data Exchange (ETDEWEB)

Milewski, J.; Keel, G. [Los Alamos National Lab., NM (United States); Sklar, E. [Opticad Corp., Santa Fe, New Mexico (United States)

1995-12-01

The effects of multiple internal reflections within a laser weld joint as a function of joint geometry and processing conditions have been characterized. A computer model utilizing optical ray tracing is used to predict the reflective propagation of laser beam energy focused into the narrow gap of a metal joint for the purpose of predicting the location of melting and coalescence which form the weld. The model allows quantitative analysis of the effects of changes to joint geometry, laser design, materials and processing variables. This analysis method is proposed as a way to enhance process efficiency and design laser welds which display deep penetration and high depth to width aspect ratios, reduced occurrence of defects and enhanced melting. Of particular interest to laser welding is the enhancement of energy coupling to highly reflective materials. The weld joint is designed to act as an optical element which propagates and concentrates the laser energy deep within the joint to be welded. Experimentation has shown that it is possible to produce welds using multiple passes to achieve deep penetration and high depth to width aspect ratios without the use of filler material. The enhanced laser melting and welding of aluminum has been demonstrated. Optimization through modeling and experimental validation has resulted in the development of a laser welding process variant we refer to as Ultra-Narrow Gap Laser Welding.

Tensile Test of Welding Joint Parts for a Plate-type Fuel Assembly

Energy Technology Data Exchange (ETDEWEB)

Yoon, K. H.; Kim, J. Y.; Kim, H. J.; Yim, J. S. [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

2013-05-15

The tensile tests were performed using an INSTRON 4505 (universal tensile) testing machine. These welding joints are composed of two parts for the soundness of the fuel assembly; one is the side plate with a fixing bar and the other is a side plate with an end fitting. These two joint parts are fabricated by TIG welding method. The tensile tests of the welding joints of a plate-type FA are executed by a tensile test. The fixture configurations for the specimen are very important to obtain the strict test results. The maximum strength has an approximately linear correlation with the unit bonding length of the welding joints. In spite of these results, the maximum strengths of the welding joints are satisfied according to the minimum requirement. These tensile tests of the joint parts for a plate-type fuel assembly (FA) have to be executed to evaluate the structural strength. For the tensile test, the joint parts of a FA used in the test are made of aluminum alloy (Al6061-T6)

Tensile Test of Welding Joint Parts for a Plate-type Fuel Assembly

International Nuclear Information System (INIS)

Yoon, K. H.; Kim, J. Y.; Kim, H. J.; Yim, J. S.

2013-01-01

The tensile tests were performed using an INSTRON 4505 (universal tensile) testing machine. These welding joints are composed of two parts for the soundness of the fuel assembly; one is the side plate with a fixing bar and the other is a side plate with an end fitting. These two joint parts are fabricated by TIG welding method. The tensile tests of the welding joints of a plate-type FA are executed by a tensile test. The fixture configurations for the specimen are very important to obtain the strict test results. The maximum strength has an approximately linear correlation with the unit bonding length of the welding joints. In spite of these results, the maximum strengths of the welding joints are satisfied according to the minimum requirement. These tensile tests of the joint parts for a plate-type fuel assembly (FA) have to be executed to evaluate the structural strength. For the tensile test, the joint parts of a FA used in the test are made of aluminum alloy (Al6061-T6)

Tensile strength and fatigue strength of 6061 aluminum alloy friction welded joints

Energy Technology Data Exchange (ETDEWEB)

Ochi, H.; Tsujino, R. [Osaka Inst. of Tech., Asahi-ku Osaka (Japan); Sawai, T. [Osaka Sangyo Univ., Daito (Japan); Yamamoto, Y. [Setsunan Univ., Neyagawa (Japan); Ogawa, K. [Osaka Prefecture Univ., Sakai (Japan); Suga, Y. [Keio Univ., Kohoku-ku, Yokohama (Japan)

2002-07-01

Friction welding of 6061 aluminum alloy was carried out in order to examine the relationship between deformation heat input in the upset stage and joint performance. The joint performance was evaluated by tensile testing and fatigue testing. Stabilized tensile strength was obtained when the deformation heat input in the upset stage exceeded 200 J/s. Weld condition at the weld interface and the width of softened area affected fatigue strength more than tensile strength. That is, when the weld condition at the weld interface is good and the softened area is wide, fatigue strength increases. On the other hand, when the weld condition at the weld interface is good and the softened area is narrow, and when the weld condition at the weld interface is somewhat poor in spite of the wide softened area, fatigue strength decreases. The fatigue limit obtained by the fatigue testing revealed that, when the deformation heat input in the upset stage exceeded a certain value, sound joints could be produced. (orig.)

Effect of Thermal Aging and Test Temperatures on Fracture Toughness of SS 316(N) Welds

Science.gov (United States)

Dutt, B. Shashank; Babu, M. Nani; Shanthi, G.; Moitra, A.; Sasikala, G.

2018-03-01

The effect of thermal aging and test temperatures on fracture toughness (J 0.2) of SS 316(N) weld material has been studied based on J-R curve evaluations. The aging of the welds was carried out at temperatures 370, 475 and 550 °C and for durations varying from 1000 to 20,000 h. The fracture toughness (J-R curve) tests were carried out at 380 and 550 °C for specimens after all aging conditions, including as-weld condition. The initiation fracture toughness (J 0.2) of the SS 316(N) weld material has shown degradation after 20,000-h aging durations and is reflected in all the test temperatures and aging temperatures. The fracture toughness after different aging conditions and test temperatures, including as-weld condition, was higher than the minimum specified value for this class of welds.

Mechanical Properties and Microstructure of Dissimilar Material Welded Joints

Directory of Open Access Journals (Sweden)

Ziewiec A.

2014-10-01

Full Text Available The paper presents results of the mechanical testing and the microstructure analysis of dissimilar welded joint of the R350HT steel and the high-manganese (Hadfield cast steel using Cr-Ni cast steel spacer. The simulation tests of the welded joint surface deformation were carried out. The macroscopic and microscopic investigation were made using light microscopy (LM and scanning electron microscopy (SEM. Content of the magnetic phase was measured using magnetoscope. The quantitative metallographic investigation was used for assessment of ferrite and martensite contents and X-ray diffraction phase analysis was carried out. The results showed that during cooling of the spacer after welding, the transformation of metastable austenite into martensite proceeded. In addition to work hardening, the phase transformation of austenite into martensite occurs during the process of the superficial deformation of the spacer while simulated exploitation. This leads to a substantial increase of hardness, and at the same time, causes the increase of wear resistance of the welded joints of crossovers.

Subminiature eddy-current transducers designed to study welded joints of titanium alloys

Science.gov (United States)

Malikov, V. N.; Dmitriev, S. F.; Katasonov, A. O.; Sagalakov, A. M.; Ishkov, A. V.

2017-12-01

Eddy current transducers (ECT) are used to construct a sensor for investigating titanium sheets connected by a welded joint. The paper provides key technical information about the eddy current transducer used and describes the procedure of measurements that makes it possible to control defects in welded joints of titanium alloys. It is capable of automatically changing the filtering cutoff frequency and operating frequency of the device. Experiments were conducted on welded VT1-0 titanium plates. The paper contains the results of these measurements. The dependence data facilitates the assessment of the quality of the welded joints and helps make an educated conclusion about welding quality.

Characterization of electromagnetic pulse welding joints for advanced steels (ODS) welding applications

International Nuclear Information System (INIS)

Buddu, Ramesh Kumar; Shaikh, Shamsuddin; Raole, P.M.; Sarkar, B.

2015-01-01

Advanced fusion reactors structural materials (like in case of TBM and, first wall components) have several operation challenges due to the demanding high temperature exposure conditions (∼800°C) and low neutron radiation effects. The present paper reports the preliminary case studies carried out on steel and copper EMP joints and their properties characterization towards establishing this technology for ODS alloys. The EMP joints in form of tubes are fabricated and tested (typical process parameters ∼ Voltage 25 kV, Current ∼600-800 kA, Max. energy ∼ 50 kJ, and 50 sec duty cycle as major process parameters). The weld joints are further characterized by X-ray radiography and found that there were no measureable defects/discontinuities across the weld interface. This indicates the good process of joining and acceptable. Characterization studies like microstructure, interface grain orientation features, deformation, hardness has been carried out. SEM studies also carried to check the interface status and some interesting features of discontinuities are observed which are not exclusively revealed by radiography tests. Hardness survey also revealed that there is no much variation in the both parent materials as well at weld zone indicating the no hardening affects like in arc/beam weld process. EMP joining has potential features for the joining requirements of ODS kind typical metallurgical requirements

Hydrogen effects in duplex stainless steel welded joints - electrochemical studies

Science.gov (United States)

Michalska, J.; Łabanowski, J.; Ćwiek, J.

2012-05-01

In this work results on the influence of hydrogen on passivity and corrosion resistance of 2205 duplex stainless steel (DSS) welded joints are described. The results were discussed by taking into account three different areas on the welded joint: weld metal (WM), heat-affected zone (HAZ) and parent metal. The corrosion resistance was qualified with the polarization curves registered in a synthetic sea water. The conclusion is that, hydrogen may seriously deteriorate the passive film stability and corrosion resistance to pitting of 2205 DSS welded joints. The presence of hydrogen in passive films increases corrosion current density and decreases the potential of the film breakdown. It was also found that degree of susceptibility to hydrogen degradation was dependent on the hydrogen charging conditions. WM region has been revealed as the most sensitive to hydrogen action.

Resistance to corrosion fatigue fracture in heat resistant steels and their welded joints

International Nuclear Information System (INIS)

Timofeev, B.T.; Fedorova, V.A.; Zvezdin, Yu.I.; Vajner, L.A.; Filatov, V.M.

1987-01-01

Experimental data on cyclic crack resistance of heat-resistant steels and their welded joints employed for production of the reactor bodies are for the first time generalized and systematized. The formula is suggested accounting for surface and inner defects to calculate the fatigue crack growth in the process of operation. This formula for surface defects regards also the effect of the corrosion factor. Mechanisms of the reactor water effect on the fatigue crack growth rate are considered as well as a combined effect of radiation and corrosive medium on this characteristic

Fatigue behaviour of friction welded medium carbon steel and austenitic stainless steel dissimilar joints

International Nuclear Information System (INIS)

Paventhan, R.; Lakshminarayanan, P.R.; Balasubramanian, V.

2011-01-01

Research highlights: → Fusion welding of dissimilar metals is a problem due to difference in properties. → Solid state welding process such as friction welding is a solution for the above problem. → Fatigue life of friction welded carbon steel and stainless steel joints are evaluated. → Effect of notch on the fatigue life of friction welded dissimilar joints is reported. → Formation of intermetallic is responsible for reduction in fatigue life of dissimilar joints. -- Abstract: This paper reports the fatigue behaviour of friction welded medium carbon steel-austenitic stainless steel (MCS-ASS) dissimilar joints. Commercial grade medium carbon steel rods of 12 mm diameter and AISI 304 grade austenitic stainless steel rods of 12 mm diameter were used to fabricate the joints. A constant speed, continuous drive friction welding machine was used to fabricate the joints. Fatigue life of the joints was evaluated conducting the experiments using rotary bending fatigue testing machine (R = -1). Applied stress vs. number of cycles to failure (S-N) curve was plotted for unnotched and notched specimens. Basquin constants, fatigue strength, fatigue notch factor and notch sensitivity factor were evaluated for the dissimilar joints. Fatigue strength of the joints is correlated with microstructure, microhardness and tensile properties of the joints.

Determination of Ductile Tearing Resistance Curve in Weld Joints

International Nuclear Information System (INIS)

Marie, S.; Gilles, P.; Ould, P.

2010-01-01

Steels present in the ductile domain a tearing resistance which increase with the crack propagation up to the failure. This ductile tearing resistance is in general characterised with curves giving the variation of a global parameter (opening displacement at the crack tip delta, integral J) versus the crack extension Delta a. These global approaches depend more or less on the specimen geometry and on the type of the imposed loading. Local approaches based on the description of the ductile tearing mechanisms provide reliable solution to the transferability problem (from the lab specimen to the component) but are complex and costly to use and are not codified. These problems get worse in the case of a weld joint where no standard is available for the measurement of their ductile tearing resistance. But the welded joints are often the weak point of the structure because of greater risk of defects, the heterogeneity of the microstructure of the weld, deformation along the interface between two materials with different yield stress (mismatch).... After briefly recalling the problems of transferability of the ductile tearing resistance curves obtained on lab specimen to the case of components, this article identifies the factors complicating the determination of the toughness in the welded joints and gives recommendations for the experimental determination of ductile tearing resistance curves of welded joints

Fracture toughness testing of pipeline girth welds

Energy Technology Data Exchange (ETDEWEB)

Shen, G.; Gianetto, J.A.; Bouchard, R.; Bowker, J.T.; Tyson, W.R.

2005-06-01

This paper reviewed the fracture toughness test standards for pipeline girth welds outlined in CSA Z662-03, Annex K as well as the referenced testing standards BS 7448 and ASTM Standard E 1290. The requirements outlined in API 1104, appendix A were also reviewed given its application throughout the world. Crack tip opening displacement (CTOD) tests were conducted on a manual shielded-metal-arc weld (SMAW) that was prepared in a high strength X80 pipeline steel. Another girth weld test consisted of a mechanized gas metal arc weld (GMAW), but only the results for the SMAW were presented in this paper. Two tensile specimens were machined parallel to the pipe axis from the base metal of the X80 pipe used in preparing the pipeline girth welds. The tensile specimens from the pipe base metal and weld metal were tested at 20 degrees C. The yield strength at the CTOD test temperature was estimated by using the yield strength-temperature relationship given in BS 7448. The experimental results obtained by applying the two testing standards were compared. The intent was to identify the differences between these two standards and their influence on test results. The authors discussed critical issues for the fracture toughness tests, such as weld position and notch orientation, circumferential sampling location, residual stress and its modification, crack length measurement and the equations used to evaluate CTOD. The variation of strength and toughness with clock position around the circumference of the girth welds was also discussed. It was concluded that for a high-strength material, local compression may be needed to create a uniform fatigue crack front. For deep-cracked specimens, the maximum allowable difference of the measured fatigue crack length varies significantly between ASTM E 1290-02 and BS 7448 by a factor of about 1 to 3 for ASTM E 1290 and 3 to 15 for BS 7448. The CTOD calculated according to ASTM E 1290-02 and according to BS 7448 can also differ substantially

Improvement in properties of welded joints of titanium alloy VT22 by thermocyclic treatment

International Nuclear Information System (INIS)

Lyasotskaya, V.S.; Kulikov, F.R.; Kirillov, Yu.G.; Ravdonikas, N.Yu.

1983-01-01

The results of investigations of the thermocyclic treatment (TCT) effect on the structure and properties of butt welded joints of tubes (with external diameter 180 mm and wall thickness 20-25 mm) of the VT22 alloy are presented. Welded joints have been obtained by means of multipassing automatic argon-arc (ARAW) and electron-beam (ELB) welding. It is shown that TCT of welded joints of the VT22 alloy results in formation in all zones of substructure with disperse precipitations of α-phase which is analogous to the structure of near welded seam zone metal immediately after welding. As a result of TCT and subsequent TT of welded joints poligonization and recrystallization processes of α- and #betta#-phases, changes in parameters of structural components and thin phase structure take place. TCT with strengthening TT or annealing leads to strength increase, while TCT with annealing besides that improves placticity and impact strength of the VT22 alloy welded joints

Probability-based assessment and maintenance of welded joints damaged by fatigue

International Nuclear Information System (INIS)

Cremona, C.; Lukic, M.

1998-01-01

This paper presents a probabilistic reliability assessment procedure for steel components damaged by fatigue. The study combines the structural reliability theory with a maintenance strategy. The fatigue assessment model is based on a modelisation of the fatigue phenomenon issued from the principles of fracture mechanics theory. The safety margin includes the crack growth propagation and allows to treat fatigue damage in a general manner. Damaging cycles and non damaging cycles are distinguished. The sensitivity study of the different parameters shows that some variables can be taken as deterministic. Applications are made on a welded joint 'stiffener/bottom-plate' of a typical steel bridge. The model is then used for taking into account inspection results. Non destructive inspection (NDI) techniques are also used for updating failure probabilities. The results show their ability to be inserted in a maintenance strategy for optimizing the next inspection time. This has led to define cost functions related to the total maintenance cost; this cost is then minimized for determining the optimal next inspection time. An example of welded joint cracked by fatigue highlights the different concepts. The approach presented in the paper is not only restrained to fatigue problems, but can be applied to a wide variety of degrading phenomena. (orig.)

Stress indices for girth welded joints, including radial weld shrinkage, mismatch and tapered-wall transitions

International Nuclear Information System (INIS)

Rodabaugh, E.C.; Moore, S.E.

1978-09-01

A review is presented of B, C and K stress indices used in the ASME Nuclear Power Plant Code for girth butt welds and girth fillet welds. Theoretical stresses are presented to aid in evaluating C-indices. Fatigue test data are presented to aid in evaluating K-indices and CK-products. A limit load theory is presented to aid in evaluating B-indices. As a result of this review, recommendations are made for changes in the ASME Code. A major part of this consists of presenting definitions for girth welded joints and transitions and appropriate stress indices for those joints

Effect of welding process on the microstructure and properties of dissimilar weld joints between low alloy steel and duplex stainless steel

Science.gov (United States)

Wang, Jing; Lu, Min-xu; Zhang, Lei; Chang, Wei; Xu, Li-ning; Hu, Li-hua

2012-06-01

To obtain high-quality dissimilar weld joints, the processes of metal inert gas (MIG) welding and tungsten inert gas (TIG) welding for duplex stainless steel (DSS) and low alloy steel were compared in this paper. The microstructure and corrosion morphology of dissimilar weld joints were observed by scanning electron microscopy (SEM); the chemical compositions in different zones were detected by energy-dispersive spectroscopy (EDS); the mechanical properties were measured by microhardness test, tensile test, and impact test; the corrosion behavior was evaluated by polarization curves. Obvious concentration gradients of Ni and Cr exist between the fusion boundary and the type II boundary, where the hardness is much higher. The impact toughness of weld metal by MIG welding is higher than that by TIG welding. The corrosion current density of TIG weld metal is higher than that of MIG weld metal in a 3.5wt% NaCl solution. Galvanic corrosion happens between low alloy steel and weld metal, revealing the weakness of low alloy steel in industrial service. The quality of joints produced by MIG welding is better than that by TIG welding in mechanical performance and corrosion resistance. MIG welding with the filler metal ER2009 is the suitable welding process for dissimilar metals jointing between UNS S31803 duplex stainless steel and low alloy steel in practical application.

Improving Joint Formation and Tensile Properties of Dissimilar Friction Stir Welding of Aluminum and Magnesium Alloys by Solving the Pin Adhesion Problem

Science.gov (United States)

Liu, Zhenlei; Ji, Shude; Meng, Xiangchen

2018-03-01

Friction stir welding (FSW), as a solid-state welding technology invented by TWI in 1991, has potential to join dissimilar Al/Mg alloys. In this study, the pin adhesion phenomenon affecting joint quality during FSW of 6061-T6 aluminum and AZ31B magnesium alloys was investigated. The adhesion phenomenon induced by higher heat input easily transformed the tapered-and-screwed pin into a tapered pin, which greatly reduced the tool's ability to drive the plasticized materials and further deteriorated joint formation. Under the condition without the pin adhesion, the complex intercalated interlayer at the bottom of stir zone was beneficial to mechanical interlocking of Al/Mg alloys, improving tensile properties. However, the formation of intermetallic compounds was still the main reason of the joint fracture, significantly deteriorating tensile properties. Under the welding speed of 60 mm/min without the pin adhesion phenomenon, the maximum tensile strength of 107 MPa and elongation of 1.2% were achieved.

Microstructure evolution in dissimilar AA6060/copper friction stir welded joints

Science.gov (United States)

Kalashnikova, T. A.; Shvedov, M. A.; Vasilyev, P. A.

2017-12-01

Friction stir welding process has been applied for making a dissimilar copper/aluminum alloy joint. The grain microstructure and mechanical properties of the obtained joint were studied. The structure of the cross-section of the FSW compound was analyzed. The microstructural evolution of the joint was examined using optical microscopy. The mechanical properties of the intermetallic particles were evaluated by measuring the microhardness according to the Vickers method. The microhardness of the intermetallic particles was by a factor of 4 lower than that of the particles obtained by fusion welding. The results of the investigations enable using friction stir welding for making dissimilar joints.

Comparison of welding induced residual stresses austenitic and ferritic steel weld joints

International Nuclear Information System (INIS)

Rajkumar, K.V.; Arun Kumar, S.; Mahadevan, S.; Manojkumar, R.; Rao, B. Purna Chandra; Albert, Shaju K.; Murugan, S.

2015-01-01

X-ray diffraction (XRD) is a well established technique for measurement of residual stresses in components and is being widely used. In XRD technique, the distance between the crystallographic planes (d spacing) is measured from peak position (2è) at various ø angles, where ø is the angle between the normal to the sample and the bisector of the incident and diffracted beam. From the slope of sin2ø vs. d spacing plot, the residual stresses are arrived by assuming a plane stress model. Welding induced residual stresses is of high importance as it is a major cause of failure in components. Surface compressive stresses improve the fatigue strength, whereas tensile residual stresses tend to decrease the fatigue strength. The present study compares the residual stresses that develop in 3 mm thick SS 316 and P91 TIG weld joints using the XRD technique. This study is aimed at understanding the influence of shrinkage during cooling and the effect of phase transformation induced volume changes on residual stress development in these two steels. While the first effect is predominant in the SS 316 weld, both the effects are present in the P91 welds. Stress measurements on SS 316 and P91 were carried out using Cr Kâ (λ-2.0840 Å) and Cr Ká (λ-2.2896 Å) radiations respectively. Typical 'M' type stress profile was observed across the weld centre line in both the welds. The variation and similarities between the longitudinal stress profiles observed in these two weld joints would be discussed. (author)

Comparative estimation of the properties of heat resisting nickel alloy welded joints made by electron-beam and arc welding

International Nuclear Information System (INIS)

Morochko, V.P.; Sorokin, L.I.; Yakushin, B.F.; Moryakov, V.F.

1977-01-01

As compared to argon arc welding of refractory nickel alloys at 15 m/hour rate, electron beam welding decreases energy consumption per unit length (from 4300 to 2070 cal/cm), the weld area (from 108 to 24 mm 2 ), and the length of the thermal effect zone (from 0.9-1.8 to 0.4-0.8 mm). Electron beam welding also provides for better resistance to hot cracking in the weld metal and in the near-weld zone, as compared to automatic argon arc welding and manual welding with addition of the basic metal. However, this advantage is observed only at welding rates less than 45 m/hour. Electron beam welded joints of refractory nickel alloys with intermetallide reinforcement have higher strength, plasticity and impact strength, and lower scattering of these properties than arc welded joints

Strain rate dependent deformation and failure behavior of laser welded DP780 steel joint under dynamic tensile loading

International Nuclear Information System (INIS)

Liu, Yang; Dong, Danyang; Wang, Lei; Chu, Xi; Wang, Pengfei; Jin, Mengmeng

2015-01-01

Laser welded DP steel joints are used widely in the automotive industry for weight reduction. Understanding the deformation and fracture behavior of the base metal (BM) and its welded joint (WJ), especially at high strain rates, is critical for the design of vehicle structures. This paper is concerned with the effects of strain rate on the tensile properties, deformation and fracture behavior of the laser welded DP780 steel joint. Quasi-static and dynamic tensile tests were performed on the WJ and BM of the DP780 steel using an electromechanical universal testing machine and a high-speed tensile testing machine over a wide range of strain rate (0.0001–1142 s −1 ). The microstructure change and microhardness distribution of the DP780 steel after laser welding were examined. Digital image correlation (DIC) and high-speed photography were employed for the strain measurement of the DP780 WJ during dynamic tensile tests. The DP780 WJ is a heterogeneous structure with hardening in fusion zone (FZ) and inner heat-affected zone (HAZ), and softening in outer HAZ. The DP780 BM and WJ exhibit positive strain rate dependence on the YS and UTS, which is smaller at lower strain rates and becomes larger with increasing strain rate, while ductility in terms of total elongation (TE) tends to increase under dynamic loading. Laser welding leads to an overall reduction in the ductility of the DP780 steel. However, the WJ exhibits a similar changing trend of the ductility to that of the BM with respect to the strain rate over the whole strain rate range. As for the DP780 WJ, the distance of tensile failure location from the weld centerline decreases with increasing strain rate. The typical ductile failure characteristics of the DP780 BM and WJ do not change with increasing strain rate. DIC measurements reveal that the strain localization starts even before the maximum load is attained in the DP780 WJ and gradual transition from uniform strains to severely localized strains occurs

Strain rate dependent deformation and failure behavior of laser welded DP780 steel joint under dynamic tensile loading

Energy Technology Data Exchange (ETDEWEB)

Liu, Yang, E-mail: liuyang@mail.neu.edu.cn [Key Laboratory for Anisotropy and Texture of Materials, Ministry of Education, Northeastern University, Shenyang 110819 (China); Dong, Danyang, E-mail: dongdanyang@mail.neu.edu.cn [College of Science, Northeastern University, Shenyang 110819 (China); Wang, Lei, E-mail: wanglei@mail.neu.edu.cn [Key Laboratory for Anisotropy and Texture of Materials, Ministry of Education, Northeastern University, Shenyang 110819 (China); Chu, Xi, E-mail: chuxi.ok@163.com [College of Science, Northeastern University, Shenyang 110819 (China); Wang, Pengfei, E-mail: wpf1963871400@163.com [College of Science, Northeastern University, Shenyang 110819 (China); Jin, Mengmeng, E-mail: 24401878@163.com [College of Science, Northeastern University, Shenyang 110819 (China)

2015-03-11

Laser welded DP steel joints are used widely in the automotive industry for weight reduction. Understanding the deformation and fracture behavior of the base metal (BM) and its welded joint (WJ), especially at high strain rates, is critical for the design of vehicle structures. This paper is concerned with the effects of strain rate on the tensile properties, deformation and fracture behavior of the laser welded DP780 steel joint. Quasi-static and dynamic tensile tests were performed on the WJ and BM of the DP780 steel using an electromechanical universal testing machine and a high-speed tensile testing machine over a wide range of strain rate (0.0001–1142 s{sup −1}). The microstructure change and microhardness distribution of the DP780 steel after laser welding were examined. Digital image correlation (DIC) and high-speed photography were employed for the strain measurement of the DP780 WJ during dynamic tensile tests. The DP780 WJ is a heterogeneous structure with hardening in fusion zone (FZ) and inner heat-affected zone (HAZ), and softening in outer HAZ. The DP780 BM and WJ exhibit positive strain rate dependence on the YS and UTS, which is smaller at lower strain rates and becomes larger with increasing strain rate, while ductility in terms of total elongation (TE) tends to increase under dynamic loading. Laser welding leads to an overall reduction in the ductility of the DP780 steel. However, the WJ exhibits a similar changing trend of the ductility to that of the BM with respect to the strain rate over the whole strain rate range. As for the DP780 WJ, the distance of tensile failure location from the weld centerline decreases with increasing strain rate. The typical ductile failure characteristics of the DP780 BM and WJ do not change with increasing strain rate. DIC measurements reveal that the strain localization starts even before the maximum load is attained in the DP780 WJ and gradual transition from uniform strains to severely localized strains

Limit load solution for electron beam welded joints with single edge weld center crack in tension

Science.gov (United States)

Lu, Wei; Shi, Yaowu; Li, Xiaoyan; Lei, Yongping

2012-05-01

Limit loads are widely studied and several limit load solutions are proposed to some typical geometry of weldments. However, there are no limit load solutions exist for the single edge crack weldments in tension (SEC(T)), which is also a typical geometry in fracture analysis. The mis-matching limit load for thick plate with SEC(T) are investigated and the special limit load solutions are proposed based on the available mis-matching limit load solutions and systematic finite element analyses. The real weld configurations are simplified as a strip, and different weld strength mis-matching ratio M, crack depth/width ratio a/ W and weld width 2H are in consideration. As a result, it is found that there exists excellent agreement between the limit load solutions and the FE results for almost all the mis-matching ration M, a/ W and ligament-to-weld width ratio ( W-a)/ H. Moreover, useful recommendations are given for evaluating the limit loads of the EBW structure with SEC(T). For the EBW joints with SEC(T), the mis-matching limit loads can be obtained assuming that the components are wholly made of base metal, when M changing from 1.6 to 0.6. When M decreasing to 0.4, the mis-matching limit loads can be obtained assuming that the components are wholly made of base metal only for large value of ( W-a)/ H. The recommendations may be useful for evaluating the limit loads of the EBW structures with SEC(T). The engineering simplifications are given for assessing the limit loads of electron beam welded structure with SEC(T).

Effect of tool rotational speed and penetration depth on dissimilar aluminum alloys friction stir spot welds

Directory of Open Access Journals (Sweden)

Joaquín M. Piccini

2017-03-01

Full Text Available In the last years, the automotive industry is looking for the use of aluminum parts in replace of steel parts in order to reduce the vehicles weight. These parts have to be joined, for instance, by welding processes. The more common welding process in the automotive industry is the Resistance Spot Welding (RSW technique. However, RSW of aluminum alloys has many disadvantages. Regarding this situation, a variant of the Friction Stir Welding process called Friction Stir Spot Welding (FSSW has been developed, showing a strong impact in welding of aluminum alloys and dissimilar materials in thin sheets. Process parameters affect the characteristics of the welded joints. However, the information available on this topic is scarce, particularly for dissimilar joints and thin sheets. The aim of this work was to study the effect of the rotational speed and the tool penetration depth on the characteristics of dissimilar FSS welded joints. Defects free joints have been achieved with higher mechanical properties than the ones reported. The maximum fracture load was 5800 N. It was observed that the effective joint length of the welded spots increased with the tool penetration depth, meanwhile the fracture load increased and then decreased. Finally, welding at 1200 RPM produced welded joints with lower mechanical properties than the ones achieved at 680 and 903 RPM.

Microstructure examination and microhardness of friction stir welded joint of (AA7020-O after PWHT

Directory of Open Access Journals (Sweden)

Ghada M.F. Essa

2018-04-01

Full Text Available This paper studies the microstructure and microhardness of the welded joints of the annealed aluminum alloy AA7020-O produced by friction stir welding (FSW technique. The material was applied to post weld heat treatment (solution treatment and artificially aged, T6. The traverse speed and the rotational speed are the most important process parameters of FSW, and have great influence on the heat input of the welding operation which governs the welded joints quality. To investigate their effect, the welding operation was performed using three traverse speeds, 20, 40 and 60 mm/s with two rotational speeds of 1125 and 1400 rpm, and other welding parameters were kept constant to produce comparable joints. It was found that the two rotational speeds are accepted with lower traverse speeds to produce sound joints. Microstructure of the welded joints was significantly affected by the FSW process parameters, and slight effect was reported for the grain size. Microhardness examination showed high weld joint quality with respect to the base metal hardness, which proves the reprecipitation of the hardening phase in the weld zone. The microhardness profile was strongly dependant on the rotational speed, and the average values of the joints hardness have increased with the decrease in the rotational speed, where it have been slightly affected by the welding speed. Keywords: Friction stir welding, Aluminum alloy, Mechanical properties, Microstructures

Properties of Friction Welding of Dissimilar Metals WCu-Cu Weld for Electrical Contact Device

Energy Technology Data Exchange (ETDEWEB)

An, Y. H.; Yoon, G. G. [Korea Electrotechnology Research Institute (Korea); Min, T. K. [Chungnam National University (Korea); Han, B. S. [Chonbuk National University (Korea)

2000-04-01

A copper-tungsten sintered alloy(WCu) has been friction-welded to a tough pitch copper (Cu) in order to investigate friction weldability. The maximum tensile strength of the WCu-Cu friction welded joints had up to 96% of those of the Cu base metal under the condition of friction time 0.6sec, friction pressure 45MPa, upset pressure 125MPa and upset time 5.0sec. And it is confirmed that the tensile strength of friction welded joints are influenced highly by upset pressure rather than friction time. And it is considered that mixed layer was formed in the Cu adjacent side to the weld interface, W particles included in mixed layer induced fracture in the Cu adjacent side to the weld interface and also, thickness of mixed layer was reduced as upset pressure increase. (author). refs., figs., tabs.

Creep properties of EB welded joint on Hastelloy X

International Nuclear Information System (INIS)

Arata, Yoshiaki; Susei, Shuzo; Shimizu, Shigeki; Satoh, Keisuke; Nagai, Hiroyoshi.

1980-01-01

In order to clarify the creep properties of EB welds on Hastelloy X which is one of the candidate alloys for components of VHTR, creep tests on EB weld metal and welded joint were carried out. The results were discussed in comparison with those of base metal and TIG welds. Further, EB welds were evaluated from the standpoint of high temperature structural design. The results obtained are summarized as follows. 1) Both creep rupture strengths of EB weld metal and EB welded joint are almost equal to that of base metal, but those of TIG welds are lower than base metal. As for the secondary creep rate, EB weld metal is higher and TIG weld metal is lower than base metal. As for the time to onset of tertiary creep, no remarkable difference among base metal, EB weld metal and TIG weld metal is observed. 2) In case of EB weld metal, although anisotropy is slightly observed, the ductility is same or more as compared with base metal. In case of TIG weld metal, on the contrary, anisotropy is not observed and the ductility is essentially low. 3) Such rupture morphology of EB weld metal as appears to have resulted from interconnection of voids which occurred at grain boundary is similar to base metal. In case of TIG weld metal, however, many cracks with sharp tips are observed at grain boundary, and the rupture appears to have occurred in brittle by propagation and connection of the cracks. 4) It can be said from the standpoint of high temperature structural design that EB welding is very suitable to welding for structure where creep effects are significant, because both of the creep ductility and the rupture strength are almost equal to those of base metal. (author)

Welding of Aluminum Alloys to Steels: An Overview

Science.gov (United States)

2013-08-01

and deformations are a few examples of the unwanted consequences which somehow would lead to brittle fracture, fatigue fracture, shape instability...was made under the copper tips of the spot welding machine. The fatigue results showed higher fatigue strength of the joints with transition layer...kHz ultrasonic butt welding system with a vibration source applying eight bolt-clamped Langevin type PZT transducers and a 50 kW static induction

Modelling of damage development and ductile failure in welded joints

DEFF Research Database (Denmark)

Nielsen, Kim Lau

, a study of the damage development in Resistance SpotWelded joints, when subject to the commonly used static shear-lab or cross-tension testing techniques, has been carried out ([P3]-[P6]). The focus in thesis is on the Advanced High Strength Steels, Dual-Phase 600, which is used in for example......This thesis focuses on numerical analysis of damage development and ductile failure in welded joints. Two types of welds are investigated here. First, a study of the localization of plastic flow and failure in aluminum sheets, welded by the relatively new Friction Stir (FS) Welding method, has been...... conducted ([P1], [P2], [P7]-[P9]). The focus in the thesis is on FS-welded 2xxx and 6xxx series of aluminum alloys, which are attractive, for example, to the aerospace industry, since the 2024 aluminum in particular, is typically classified as un-weldable by conventional fusion welding techniques. Secondly...

Microstructural Characteristics and Mechanical Properties of an Electron Beam-Welded Ti/Cu/Ni Joint

Science.gov (United States)

Zhang, Feng; Wang, Ting; Jiang, Siyuan; Zhang, Binggang; Feng, Jicai

2018-05-01

Electron beam welding experiments of TA15 titanium alloy to GH600 nickel superalloy with and without a copper sheet interlayer were carried out. Surface appearance, microstructure and phase constitution of the joint were examined by optical microscopy, scanning electron microscopy and x-ray diffraction analysis. Mechanical properties of Ti/Ni and Ti/Cu/Ni joint were evaluated based on tensile strength and microhardness tests. The results showed that cracking occurred in Ti/Ni electron beam weldment for the formation of brittle Ni-Ti intermetallics, while a crack-free electron beam-welded Ti/Ni joint can be obtained by using a copper sheet as filler metal. The addition of copper into the weld affected the welding metallurgical process of the electron beam-welded Ti/Ni joint significantly and was helpful for restraining the formation of Ti-Ni intermetallics in Ti/Ni joint. The microstructure of the weld was mainly characterized by a copper-based solid solution and Ti-Cu interfacial intermetallic compounds. Ti-Ni intermetallic compounds were almost entirely suppressed. The hardness of the weld zone was significantly lower than that of Ti/Ni joint, and the tensile strength of the joint can be up to 282 MPa.

Microstructural characterizations and mechanical properties in underwater friction stir welding of aluminum and magnesium dissimilar alloys

International Nuclear Information System (INIS)

Zhao, Yong; Lu, Zhengping; Yan, Keng; Huang, Linzhao

2015-01-01

Highlights: • Aluminum and magnesium alloys were joined by underwater friction stir welding. • Underwater FSW was conducted to improve properties of joint with lower heat input. • Microstructures and mechanical properties of dissimilar joint were investigated. • Intermetallic compounds developed in the fracture interface were analyzed. • Fracture features of the tensile samples were analyzed. - Abstract: Formation of intermetallic compounds in the stir zone of dissimilar welds affects the mechanical properties of the joints significantly. In order to reduce heat input and control the amount and morphological characteristics of brittle intermetallic compounds underwater friction stir welding of 6013 Al alloy and AZ31 Mg alloy was carried out. Microstructures, mechanical properties, elements distribution, and the fracture surface of the joints were analyzed by optical microscopy, scanning electron microscopy and energy dispersive X-ray spectroscopy, etc. The result shows that sound dissimilar joint with good mechanical properties can be obtained by underwater friction stir welding. Al and Mg alloys were stirred together and undergone the process of recrystallization, forming complex intercalated flow patterns in the stir zone. Tensile strength of the dissimilar joint was up to 152.3 MPa. Maximum hardness (142HV) appeared in the middle of the centerline of the specimen. Intermetallic compounds layer consisting of Al 3 Mg 2 and Mg 17 Al 12 formed in the Al/Mg interface and resulted in the fracture of the joint

Quantitative metal magnetic memory reliability modeling for welded joints

Science.gov (United States)

Xing, Haiyan; Dang, Yongbin; Wang, Ben; Leng, Jiancheng

2016-03-01

Metal magnetic memory(MMM) testing has been widely used to detect welded joints. However, load levels, environmental magnetic field, and measurement noises make the MMM data dispersive and bring difficulty to quantitative evaluation. In order to promote the development of quantitative MMM reliability assessment, a new MMM model is presented for welded joints. Steel Q235 welded specimens are tested along the longitudinal and horizontal lines by TSC-2M-8 instrument in the tensile fatigue experiments. The X-ray testing is carried out synchronously to verify the MMM results. It is found that MMM testing can detect the hidden crack earlier than X-ray testing. Moreover, the MMM gradient vector sum K vs is sensitive to the damage degree, especially at early and hidden damage stages. Considering the dispersion of MMM data, the K vs statistical law is investigated, which shows that K vs obeys Gaussian distribution. So K vs is the suitable MMM parameter to establish reliability model of welded joints. At last, the original quantitative MMM reliability model is first presented based on the improved stress strength interference theory. It is shown that the reliability degree R gradually decreases with the decreasing of the residual life ratio T, and the maximal error between prediction reliability degree R 1 and verification reliability degree R 2 is 9.15%. This presented method provides a novel tool of reliability testing and evaluating in practical engineering for welded joints.

Behaviour under fatigue of AISI 304-L stainless steel welded joints

International Nuclear Information System (INIS)

Scal, M.W.; Joia, C.J.B.M.; Sousa e Silva, A.S. de

1979-01-01

The fatigue behaviour at room temperature of AISI-304-L stainless steel welded joints obtained by two distinct welding methods was studied. The results obtained were compared to those characteristic of the base metal. The welded joint fatigue samples were rectified in order to eliminate the effect of the welded seam geometry. It was concluded that the mechanisms of fatigue crack start in this case is commanded by the austenitic matrix, there being no influence of the delta ferrite rate and distribution present at the melted zone. (Author) [pt

Microstructure and mechanical properties of resistance-spot-welded joints for A5052 aluminum alloy and DP 600 steel

Energy Technology Data Exchange (ETDEWEB)

Chen, Jianbin [College of Automotive Collaborative Innovation Center, Chongqing University, No. 174, Shazheng Street, Shapingba District, Chongqing 400044 (China); Yuan, Xinjian, E-mail: xinjianyuan@yahoo.com [College of Materials Science and Engineering, Chongqing University, No. 174, Shazheng Street, Shapingba District, Chongqing 400044 (China); Hu, Zhan; Sun, Changzheng; Zhang, Yanxin; Zhang, Yuxuan [College of Materials Science and Engineering, Chongqing University, No. 174, Shazheng Street, Shapingba District, Chongqing 400044 (China)

2016-10-15

The microstructure and mechanical properties of resistance-spot-welded A5052 aluminum alloy and DP 600 dual-phase steel joint were studied. The fusion zone (FZ) and heat-affected zone (HAZ) of DP 600 exhibited lath martensite and ferrite-martensite structures, respectively. The microstructure of FZ and HAZ in the A5052 side was composed of cellular crystals and the boundary region of FZ exhibited a columnar crystal morphology. A Fe{sub 2}Al{sub 5} intermetallic compound (IMC) layer with 3.3 μm thickness was found adjacent to the DP 600 side, whereas a needle-shaped Fe{sub 4}Al{sub 13} IMC layer with length of 0.67 μm to 15.8 μm was found adjacent to the aluminum alloy side. The maximum tensile shear load of the A5052/DP 600 joint was 5.5 KN, with a corresponding molten nugget diameter of 6.3 mm. The fracture morphology of the optimized A5052/DP 600 joint was mainly an elongated dimple fracture accompanied by cleavage fracture. - Highlights: •A5052 and DP 600 with large gaps in properties were investigated by RSW. •The microstructures of RSW joints in DP 600/A5052 were examined detailedly. •The micro/macro-characteristics and strength relations of joints were analyzed.

The interface microstructure, mechanical properties and corrosion resistance of dissimilar joints during multipass laser welding for nuclear power plants

Science.gov (United States)

Li, Gang; Lu, Xiaofeng; Zhu, Xiaolei; Huang, Jian; Liu, Luwei; Wu, Yixiong

2018-05-01

This study presents the interface microstructure, mechanical properties and corrosion resistance of dissimilar joints between Inconel 52M overlays and 316L stainless steel during multipass laser welding for nuclear power plants. The results indicate that the microstructure at the interface beside 316L stainless steel consists of cellular with the width of 30-40 μm, which also exhibits numerous Cr and Mo-rich precipitates like flocculent structure and in chains along grain boundaries as a mixed chemical solution for etching. Many dendritic structure with local melting characteristics and Nb-rich precipitates are exhibited at the interface beside Inconel 52M overlays. Such Nb-rich precipitates at the interface beside Inconel 52M overlays deteriorate the tensile strength and toughness of dissimilar joints at room temperature. The tensile strength of 316L stainless steel at 350 °C significantly decreases with the result that dissimilar joints are fractured in 316L stainless steel. The correlation between corrosion behavior and microstructure of weld metals is also discussed. The difference in high corrosion potential between Nb-rich precipitates and the matrix could result in establishing effective galvanic couples, and thus accelerating the corrosion of weld metals.

Detection and measurement of fatigue cracks in welded joints

International Nuclear Information System (INIS)

Smith, F.C.

1985-01-01

A direct current potential drop system was developed for the detection and measurement of very small fatigue cracks that grow from the toes of welds. Measurement of crack growth less than 0.01 mm and of crack growth rates less than 10 -10 m/cycle, even for cracks less than 1.0 mm deep, is made possible by using a high stability measurement apparatus and an adjustment based on initial conditions. Thus far, the measurement system has successfully examined several aspects of fatigue in welded elements. Crack growth results justified the use of a linear elastic expression for the stress intensity factor and provided an evaluation of a growth law which includes the threshold stress intensity factor. Needle peening fillet welded joints did not change the small proportion of crack initiation life to total fatigue life observed for untreated (not improved) welded joints. However, the measurement system demonstrated that needle peening retarded crack growth rates up to 1 mm depth below the weld toe

Microstructure and dynamic tensile behavior of DP600 dual phase steel joint by laser welding

Energy Technology Data Exchange (ETDEWEB)

Dong, Danyang, E-mail: dongdanyang@mail.neu.edu.cn [College of Science, Northeastern University, No. 11, Lane 3, WenHua Road, HePing District, Shenyang 110819 (China); Liu, Yang, E-mail: liuyang@mail.neu.edu.cn [Key Laboratory for Anisotropy and Texture of Materials, Ministry of Education, Northeastern University, Shenyang 110819 (China); Yang, Yuling, E-mail: yulingyang@mail.neu.edu.cn [College of Science, Northeastern University, No. 11, Lane 3, WenHua Road, HePing District, Shenyang 110819 (China); Li, Jinfeng, E-mail: lijinfengboda@163.com [College of Science, Northeastern University, No. 11, Lane 3, WenHua Road, HePing District, Shenyang 110819 (China); Ma, Min, E-mail: sharon6789@163.com [College of Science, Northeastern University, No. 11, Lane 3, WenHua Road, HePing District, Shenyang 110819 (China); Jiang, Tao, E-mail: tao.jiang906@yahoo.com [College of Science, Northeastern University, No. 11, Lane 3, WenHua Road, HePing District, Shenyang 110819 (China)

2014-01-31

Dual phase (DP) steels have been widely used in the automotive industry to reduce vehicle weight and improve car safety. In such applications welding and joining have to be involved, which would lead to a localized change of the microstructure and property, and create potential safety and reliable issues under dynamic loading. The aim of the present study is to examine the rate-dependent mechanical properties, deformation and fracture behavior of DP600 steel and its welded joint (WJ) produced by Nd:YAG laser welding over a wide range of strain rates (0.001–1133 s{sup −1}). Laser welding results in not only significant microhardness increase in the fusion zone (FZ) and inner heat-affected zone (HAZ), but also the formation of a softened zone in the outer HAZ. The yield strength (YS) of the DP600 steel increases and the ultimate tensile strength (UTS) remains almost unchanged, but the ductility decreases after welding. The DP600 base metal (BM) and WJ are of positive strain rate sensitivity and show similar stress–strain response at all studied strain rates. The enhanced ductility at strain rates ranging from 1 to 100 s{sup −1} is attributed to the retardation of the propagation of plastic strain localization due to the positive strain rate sensitivity and the thermal softening caused by deformation induced adiabatic temperature rise during dynamic tensile deformation. The tensile failure occurs in the inner HAZ of the joint and the distance of failure location from the weld centerline decreases with increasing strain rate. The mechanism for the changing failure location can be related to the different strain rate dependence of the plastic deformation behavior of the microstructures in various regions across the joint. The DP600 WJ absorbs more energy over the whole measured strain rates than that of the BM due to the higher strength at the same strain when the deformation only up to 10% is considered.

Improved design bases of welded joints in seawater

DEFF Research Database (Denmark)

Ólafsson, Ólafur Magnús

The presented work aims to investigate and establish a precise, thorough and detailed database from series of experimental testing of submerged arc welded, SAW, specimens of various thicknesses typically applied in offshore structures and foundations. Additionally, the testing was performed in two...... environment on fatigue resistance. Furthermore, novelty 25 mm thick steel laser-hybrid welded specimens in the as welded condition were subjected to experimental testing. A fatigue resistance S-Ncurve was established for the laser hybrid welded joints in addition to a more detailed analysis. The laser hybrid...... different environments, i.e. under in-air conditions and in a corrosion environment. Welded structures of all sizes and shapes exhibit fatigue failure primarily in the welded region, rather than in the base material, due to imperfections and flaws relating to the welding procedure. The welded region has...

Impression creep behaviour of Mod. 9Cr-1Mo steel weld joints

International Nuclear Information System (INIS)

Ridhin Raj, V.R.; Kottda, Ravi Sankar; Kamaraj, M.; Maduraimuthu, V.M.; Vasudevan, M.

2016-01-01

P91 steel (9Cr-1Mo) steel is extensively used in power plants for super heater coils, headers and steam piping. The aim of the present work is to study the creep behaviour of different zones of A-TIG weld joint using impression creep technique and compare it with that of the TIG weld joint. P91 steel weld joints were made by A-TIG welding without using any filler material and multi-pass TIG welding is done using ER90S-B9 filler rods. Welds were subjected to post-weld heat treatment (PWHT). Impression creep tests were carried out at 650 °C on the base metal, weld metal and HAZ regions. Optical Microscope and TEM were used to correlate microstructures with observed creep rates. The FGHAZ showed significantly higher impression creep rate compared to that of the base metal and weld metal. Fine grain size and relatively coarser M 23 C 6 carbide particles are responsible for higher creep rate. The impression creep rate of A-TIG weld metal and coarse grain HAZ was found to be lower than that of base metal. This is attributed to the higher grain size in weld metal and coarse HAZ attributed to the higher grain size in weld metal and to the higher peak temperature observed during A-TIG welding. (author)

Microstructural characteristics of the laser welded joint of ITER correction coil sub case

Energy Technology Data Exchange (ETDEWEB)

Fang, Chao, E-mail: fangchao@ipp.ac.cn [ASIPP, Shushan Hu Road 350, Hefei, Anhui 230031 (China); Lappeenranta University of Technology, Skinnarilankatu 34, 53850 Lappeenranta (Finland); Song, Yuntao; Wei, Jing; Xin, Jijun [ASIPP, Shushan Hu Road 350, Hefei, Anhui 230031 (China); Wu, Huapeng; Handroos, Hekki; Salminen, Antti [Lappeenranta University of Technology, Skinnarilankatu 34, 53850 Lappeenranta (Finland); Li, Hongwei [ITER China, 15B Fuxing Road, Beijing 100862 (China); Libeyre, Paul; Dolgetta, Nello [ITER Organization, Route de Vinon sur Verdon, 13115 St Paul lez Durance (France)

2015-10-15

Highlights: • The multi-pass laser welding was developed for the ITER CC case manufacture. • The laser welding procedure was studied and optimized. • The microstructural characteristic of the welded joint was discussed. - Abstract: The ITER correction coil (CC) case reinforces the winding packs against the electromagnetic loads, minimizes stresses and deformations to the winding pack. The cases are made of high strength and high toughness austenitic stainless steel (316LN) hot rolled heavy plate and have a thickness of 20 mm. Considering the small cross-section and large dimensions of the case, deformation of the case when welding becomes a challenge in the case manufacturing. Therefore, laser welding was developed as the main welding technology for manufacturing. In this paper, multi-pass laser welding technology is used, the laser weldability of a 20 mm thick 316LN austenitic stainless steel plate is studied and the microstructure of the welded joint is analyzed. The welding experiment used an YLS-6000 fiber laser (IPG) and weld filler of 316LMn to match the base metal was used. The result shows that the welded joint has no obvious surface and internal defects based on the optimized welding parameters. The weld joint have a fine austenite microstructure and display columnar dendrites and cellular grains with strong directional characteristics. No apparent heat affected zone is observed and approximately 2 μm an austenite microstructure of the fusion line is clearly presented.

Microstructural characteristics of the laser welded joint of ITER correction coil sub case

International Nuclear Information System (INIS)

Fang, Chao; Song, Yuntao; Wei, Jing; Xin, Jijun; Wu, Huapeng; Handroos, Hekki; Salminen, Antti; Li, Hongwei; Libeyre, Paul; Dolgetta, Nello

2015-01-01

Highlights: • The multi-pass laser welding was developed for the ITER CC case manufacture. • The laser welding procedure was studied and optimized. • The microstructural characteristic of the welded joint was discussed. - Abstract: The ITER correction coil (CC) case reinforces the winding packs against the electromagnetic loads, minimizes stresses and deformations to the winding pack. The cases are made of high strength and high toughness austenitic stainless steel (316LN) hot rolled heavy plate and have a thickness of 20 mm. Considering the small cross-section and large dimensions of the case, deformation of the case when welding becomes a challenge in the case manufacturing. Therefore, laser welding was developed as the main welding technology for manufacturing. In this paper, multi-pass laser welding technology is used, the laser weldability of a 20 mm thick 316LN austenitic stainless steel plate is studied and the microstructure of the welded joint is analyzed. The welding experiment used an YLS-6000 fiber laser (IPG) and weld filler of 316LMn to match the base metal was used. The result shows that the welded joint has no obvious surface and internal defects based on the optimized welding parameters. The weld joint have a fine austenite microstructure and display columnar dendrites and cellular grains with strong directional characteristics. No apparent heat affected zone is observed and approximately 2 μm an austenite microstructure of the fusion line is clearly presented.

Prediction of retained residual stresses in laboratory fracture mechanics specimens extracted from welded components

International Nuclear Information System (INIS)

Hurlston, R.G.; Sherry, A.H.; James, P.; Sharples, J.K.

2015-01-01

The measurement of weld material fracture toughness properties is important for the structural integrity assessment of engineering components. However, welds can contain high levels of residual stress and these can be retained in fracture mechanics specimens, particularly when machined from non-stress relieved welds. Retained residual stresses can make the measurement of valid fracture toughness properties difficult. This paper describes the results of analytical work undertaken to investigate factors that can influence the magnitude and distribution of residual stresses retained in fracture mechanics specimen blanks extracted from as-welded ferritic and austenitic stainless steel plates. The results indicate that significant levels of residual stress can be retained in specimen blanks prior to notching, and that the magnitude and distribution of stress is dependent upon material properties, specimen geometry and size, and extraction location through the thickness of the weld. Finite element modelling is shown to provide a useful approach for estimating the level and distributions of retained residual stresses. A new stress partitioning approach has been developed to estimate retained stress levels and results compare favourably with FE analysis and available experimental data. The approach can help guide the selection of specimen geometry and machining strategies to minimise the level of residual stresses retained in fracture mechanics specimen blanks extracted from non stress-relieved welds and thus improve the measurement of weld fracture toughness properties. - Highlights: • A simplified method for generating realistic weld residual stresses has been developed. • It has been shown that significant levels of residual stress can be retained within laboratory fracture mechanics specimens. • The level and distribution is dependant upon material, specimen type, specimen size and extraction location. • A method has been developed to allow estimates of the

First industrial application of MAG STT welding with auto adaptative joint control

International Nuclear Information System (INIS)

Tran Tien, Thong

2006-01-01

The Welding Institute has participated to an extraordinary plan: the manufacture of the new LHC (Large Hadron Collider) particles accelerator in a circular tunnel of 27 km of circumference, at the European laboratory for particles physics (CERN) located at the Franco-Swiss frontier. The LHC dipolar magnets wires constituted in semi-cylinders of 15 m length in 316 LN, thickness 10 mm, are assembled in horizontal-vertical position. The Welding Institute has developed a software allowing to implement the auto-adaptative welding with follow of laser joint, using the MAG STT (Surface Tension Transfer) process. The modeling of welding laws connected with the strategy of joints filling runs (in multi-passes), absorb the physical tolerances of the preparation (clearance, poor alignment, root of joint...) and this in welding dynamical condition. (O.M.)

Investigation on Microstructure and Impact Toughness of Different Zones in Duplex Stainless Steel Welding Joint

Science.gov (United States)

Zhang, Zhiqiang; Jing, Hongyang; Xu, Lianyong; Han, Yongdian; Li, Guolu; Zhao, Lei

2017-01-01

This paper investigated on microstructure and impact toughness of different zones in duplex stainless steel welding joint. High-temperature heat-affected zone (HTHAZ) contained coarse ferrite grains and secondary precipitates such as secondary austenite, Cr2N, and sigma. Intergranular secondary austenite was prone to precipitation in low-temperature heat-affected zone (LTHAZ). Both in weld metal (WM) and in HTHAZ, the austenite consisted of different primary and secondary austenite. The ferrite grains in base metal (BM) presented typical rolling texture, while the austenite grains showed random orientation. Both in the HTHAZ and in the LTHAZ, the ferrite grains maintained same texture as the ferrite in the BM. The secondary austenite had higher Ni but lower Cr and Mo than the primary austenite. Furthermore, the WM exhibited the highest toughness because of sufficient ductile austenite and unapparent ferrite texture. The HTHAZ had the lowest toughness because of insufficient austenite formation in addition to brittle sigma and Cr2N precipitation. The LTHAZ toughness was higher than the BM due to secondary austenite precipitation. In addition, the WM fracture was dominated by the dimple, while the cleavage was main fracture mode of the HTHAZ. Both BM and LTHAZ exhibited a mixed fracture mode of the dimple and quasi-cleavage.

Fatigue of welded joint in a stainless steel AISI 304 L

International Nuclear Information System (INIS)

Kuromoto, N.K.; Guimaraes, A.S.; Miranda, P.E.V. de

1986-01-01

The flexion fatigue behavior for the base metal and welded joint of an AISI 304 L stainless steel type, used in the Angra-1 reactor, was determined. An automatic welding process was used with improved procedures in order to assure better welding metallurgy. Fatigue tests samples reinforcements were done to allow the evaluation of metallurgical variables, specially the role played by delta ferrite. The resulting welded joint showed better fatigue life than the base metal. Delta ferrite was found to play an important role on the initiation and propagation processes of the fatigue cracks. (Author) [pt

Effects Of Welding On The Fatigue Behaviour Of Commercial Aluminum AA-1100 Joints

Science.gov (United States)

Uthayakumar, M.; Balasubramanian, V.; Rani, Ahmad Majdi Abdul; Hadzima, Branislav

2018-04-01

Friction Stir Welding (FSW) is an budding solid state welding process, which is frequently used for joining aluminum alloys where materials can be joined without melt and recast. Therefore, when welding alloys through FSW the phase transformations occurs will be in the solid state form. The present work is aimed in evaluating the fatigue life of friction stir welded commercial grade aluminum alloy joints. The commercial grade AA1100 aluminum alloy of 12mm thickness plate is welded and the specimens are tested using a rotary beam fatigue testing machine at different stress levels. The stress versus number of cycles (S-N) curves was plotted using the data points. The Fatigue life of tungsten inert gas (TIG) and metal inert gas (MIG) welded joints was compared. The fatigue life of the weld joints was interrelated with the tensile properties, microstructure and micro hardness properties. The effects of the notches and welding processes are evaluated and reported.

Creep properties and microstructure evaluation of weld joint of the pipe made of P92 steel

Energy Technology Data Exchange (ETDEWEB)

Kasl, Josef; Jandova, Dagmar; Chvostova, Eva [SKODA VYZKUM s.r.o., Plzen (Czech Republic); Folkova, Eva [SKODA POWER a.s., Plzen (Czech Republic)

2010-07-01

One-side weld joint of W type was prepared from P92 type steel using GTAW and SMAW method. Creep test to the rupture of smooth cross-weld samples has been carried out at temperatures ranging from 575 to 650 C and at stresses from 70 to 240 MPa. Fractographic analysis, hardness measurement and detailed study of submicrostructure have been performed using light, scanning and transmission electron microscopy. Changes of microstructure were correlated with the creep strength. Increase in size of secondary phases and cavities formation were evident after creep tests at temperatures above 575 C. Voids were concentrated in the fine prior austenite grain heat affected zones, where fracture occurred. In addition, a sporadic occurrence of individual cavities was found out in the base material and the weld metal after tests at 625 and 650 C. During creep exposures at temperatures above 600 C Laves phase precipitated. (orig.)

An experimental study on fracture toughness of resistance spot welded galvanized and ungalvanized DP 450 steel sheets used in automotive body

Directory of Open Access Journals (Sweden)

Sevim, Ibrahim

2016-09-01

Full Text Available The purpose of this study is to determine fracture toughness of Resistance Spot Welded (RSW Dual Phase (DP steels. RSW of galvanized and ungalvanized DP 450 steel sheets was carried out on spot welding machine. Fracture toughness of RSW joints of galvanized and ungalvanized DP 450 steel sheets was calculated from tensile-shear tests. New empirical equations were developed using Least Squares Method (LSM between energy release rate, fracture toughness and critical crack size depending on the relationship between hardness and fracture toughness values. Results indicated that fracture toughness of joints welded by using RSW increased exponentially while the hardness decreased. In addition, fracture toughness and energy release rate of RSW galvanized DP 450 steel sheets were lower compared to RSW ungalvanized DP 450 steel sheets which had approximately the same hardness.El objetivo de este estudio es determinar la tenacidad de fractura de los aceros dual (DP soldados por puntos de resistencia (RSW. En la máquina de soldadura por puntos se realizó la soldadura de láminas de acero DP 450 galvanizado y sin galvanizar. A partir de los ensayos de tracción-cizallamiento, se calculó la tenacidad a la fractura de las uniones del acero DP 450 galvanizado y sin galvanizar. Aplicando el método de mínimos cuadrados (LSM se desarrollaron nuevas ecuaciones empíricas entre el porcentaje de energía liberada, la tenacidad de fractura y el tamaño de grieta crítica en función de la relación entre los valores de tenacidad de fractura y de dureza. Los resultados indicaron que la tenacidad de fractura de las uniones soldadas por RSW aumentó exponencialmente, mientras que la dureza disminuyó. Además, el porcentaje de energía liberada de las láminas de acero DP 450 galvanizadas y soldadas fueron menores que en el caso de las láminas sin galvanizar a valores iguales de dureza.

Evaluation of mechanical vibration effect on the residual stresses levels in steel welded joints using an Interface Matlab based on Norm API 579

Directory of Open Access Journals (Sweden)

R Rodrigues

2016-10-01

Full Text Available Nowadays with the high growth of petrochemical welding technology a great development due to high manufacturing offshore structures, storage tanks of petroleum, boilers and pressure vessels for refining plants have been done. Due to various metallurgical changes and restrictions to contraction and expansion undergone by materials when subjected to welding thermal cycle, internal stresses are generated in welded joint which are nominated residual stresses. It is generally undesirable because it can lead to several problems, such as cracks, cold stress fracture, stress corrosion, among others. Although several studies involving residual stresses have been developed in recent years, few information about the variation of the residual stresses level in welded joints when subjected to stress relief treatment by mechanical vibration have been done. Likewise, there are few information related to the comparison between the degree of efficiency by using the post-weld heat treatment and those treatment. Therefore, the goal of this work was to apply the relieve residual stresses treatment by mechanical vibration in steel welded joints used in oil industry, and compare the results with those obtained by post heat treatment and evaluate the efficiency level of this technique In addition, this works also hope to contribute for a better understanding of this technique and to find which parameters have a greater influence on the results.

Non-linear imaging condition to image fractures as non-welded interfaces

NARCIS (Netherlands)

Minato, S.; Ghose, R.

2014-01-01

Hydraulic properties of a fractured reservoir are often controlled by large fractures. In order to seismically detect and characterize them, a high-resolution imaging method is necessary. We apply a non-linear imaging condition to image fractures, considered as non-welded interfaces. We derive the

Effect of laser beam position on mechanical properties of F82H/SUS316L butt-joint welded by fiber laser

Energy Technology Data Exchange (ETDEWEB)

Serizawa, Hisashi, E-mail: serizawa@jwri.osaka-u.ac.jp [Joining and Welding Research Institute, Osaka University, 11-1 Mihogaoka, Ibaraki, Osaka 567-0047 (Japan); Mori, Daiki; Ogiwara, Hiroyuki; Mori, Hiroaki [Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871 (Japan)

2014-10-15

Highlights: • The micro hardness of weld metal in F82H/SUS316L joint partially decreases after PWHT by shifting beam position to SUS316L. • Charpy impact energy of F82H/SUS316L joint obviously increases after PWHT due to the release of residual stress. • The tensile strength of weld metal in F82H/SUS316L joint is higher than that of SUS316L. • The fiber laser welding seems to be one of the most candidate methods to join between F82H and SUS316L pipes practically. - Abstract: A dissimilar butt-joint between reduced activation ferritic/martensitic steel F82H and SUS316L austenitic stainless steel was made by 4 kW fiber laser and the influence of laser beam position on its mechanical properties before and after post-weld heat treatment (PWHT) was examined at room temperature. From the nano-indentation measurements and the microstructural observations, it is found that the micro hardness of weld metal partially decreases after PWHT by shifting beam position to SUS316L because its phase seems to move from only the martensitic phase to the mixture of austenitic and martensitic phases. In addition, Charpy impact test suggests that the impact energy slightly increases by shifting beam position before PWHT and obviously increases after PWHT due to the release of residual stress. Moreover, the tensile test indicates that the tensile strength of weld metal is higher than that of SUS316L and the fracture occurs at the base metal of SUS316L regardless of laser beam position.

Mechanical properties and fatigue strength of high manganese non-magnetic steel/carbon steel welded joints

International Nuclear Information System (INIS)

Nakaji, Eiji; Ikeda, Soichi; Kim, You-Chul; Nakatsuji, Yoshihiro; Horikawa, Kosuke.

1997-01-01

The dissimilar materials welded joints of high manganese non-magnetic steel/carbon steel (hereafter referred to as DMW joints), in which weld defects such as hot crack or blowhole are not found, were the good quality. Tensile strength of DMW joints was 10% higher than that of the base metal of carbon steel. In the bend tests, the DMW joints showed the good ductility without crack. Charpy absorbed energy at 0(degC) of the DMW joints was over 120(J) in the bond where it seems to be the lowest. Large hardening or softening was not detected in the heat affected zone. Fatigue strength of the DMW joints is almost the same with that of the welded joints of carbon steel/carbon steel. As the fatigue strength of the DMW joints exceeds the fatigue design standard curve of JSSC for carbon steel welded joints, the DMW joints can be treated the same as the welded joints of carbon steel/carbon steel of which strength is lower than that of high manganese non-magnetic steel, from the viewpoint of the fatigue design. (author)

Experimental Investigation on Electric Current-Aided Laser Stake Welding of Aluminum Alloy T-Joints

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Xinge Zhang

2017-11-01

Full Text Available In the present study, aluminum alloy T-joints were welded using the laser stake-welding process. In order to improve the welding quality of the T-joints, an external electric current was used to aid the laser stake-welding process. The effects of the process parameters on the weld morphology, mechanical properties, and microstructure of the welded joints were analyzed and discussed in detail. The results indicate that the aided electric current should be no greater than a certain maximum value. Upon increasing the aided electric current, the weld width at the skin and stringer faying surface obviously increased, but there was an insignificant change in the penetration depth. Furthermore, the electric current and pressing force should be chosen to produce an expected weld width at the faying surface, whereas the laser power and welding speed should be primarily considered to obtain an optimal penetration depth. The tensile shear specimens failed across the faying surface or failed in the weld zone of the skin. The specimens that failed in the weld of the skin could resist a higher tensile shear load compared with specimens that failed across the faying surface. The microstructural observations and microhardness results demonstrated that the tensile shear load capacity of the aluminum alloy welded T-joint was mainly determined by the weld width at the faying surface.

Wear Resistance Analysis of A359/SiC/20p Advanced Composite Joints Welded by Friction Stir Welding

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O. Cuevas Mata

Full Text Available Abstract Advancement in automotive part development demands new cost-effective materials with higher mechanical properties and improved wear resistance as compared to existing materials. For instance, Aluminum Matrix Composites (AMC shows improved mechanical properties as wear and abrasion resistance, high strength, chemical and dimensional stability. Automotive industry has focused in AMC for a variety of applications in automotive parts in order to improve the fuel economy, minimize vehicle emissions, improve design options, and increase the performance. Wear resistance is one of the most important factors in useful life of the automotive components, overall in those components submitted to mechanical systems like automotive brakes and suspensions. Friction Stir Welding (FSW rises as the most capable process to joining AMC, principally for the capacity to weld without compromising their ceramic reinforcement. The aim of this study is focused on the analysis of wear characteristics of the friction-stir welded joint of aluminum matrix reinforced with 20 percent in weight silicon carbide composite (A359/SiC/20p. The experimental procedure consisted in cut samples into small plates and perform three welds on these with a FSW machine using a tool with 20 mm shoulder diameter and 8 mm pin diameter. The wear features of the three welded joints and parent metal were analyzed at constant load applying 5 N and a rotational speed of 100 rpm employing a Pin-on - Disk wear testing apparatus, using a sapphire steel ball with 6 mm diameter. The experimental results indicate that the three welded joints had low friction coefficient compared with the parent metal. The results determine that the FSW process parameters affect the wear resistance of the welded joints owing to different microstructural modifications during welding that causes a low wear resistance on the welded zone.

The numerical high cycle fatigue damage model of fillet weld joint under weld-induced residual stresses

Science.gov (United States)

Nguyen Van Do, Vuong

2018-04-01

In this study, a development of nonlinear continuum damage mechanics (CDM) model for multiaxial high cycle fatigue is proposed in which the cyclic plasticity constitutive model has been incorporated in the finite element (FE) framework. T-joint FE simulation of fillet welding is implemented to characterize sequentially coupled three-dimensional (3-D) of thermo-mechanical FE formulation and simulate the welding residual stresses. The high cycle fatigue damage model is then taken account into the fillet weld joints under the various cyclic fatigue load types to calculate the fatigue life considering the residual stresses. The fatigue crack initiation and the propagation in the present model estimated for the total fatigue is compared with the experimental results. The FE results illustrated that the proposed high cycle fatigue damage model in this study could become a powerful tool to effectively predict the fatigue life of the welds. Parametric studies in this work are also demonstrated that the welding residual stresses cannot be ignored in the computation of the fatigue life of welded structures.

Influence of Zn Interlayer on Interfacial Microstructure and Mechanical Properties of TIG Lap-Welded Mg/Al Joints

Science.gov (United States)

Gao, Qiong; Wang, Kehong

2016-03-01

This study explored 6061 Al alloy and AZ31B Mg alloy joined by TIG lap welding with Zn foils of varying thicknesses, with the additional Zn element being imported into the fusion zone to alloy the weld seam. The microstructures and chemical composition in the fusion zone near the Mg substrate were examined by SEM and EDS, and tensile shear strength tests were conducted to investigate the mechanical properties of the Al/Mg joints, as well as the fracture surfaces, and phase compositions. The results revealed that the introduction of an appropriate amount of Zn transition layer improves the microstructure of Mg/Al joints and effectively reduces the formation of Mg-Al intermetallic compounds (IMCs). The most common IMCs in the fusion zone near the Mg substrate were Mg-Zn and Mg-Al-Zn IMCs. The type and distribution of IMCs generated in the weld zone differed according to Zn additions; Zn interlayer thickness of 0.4 mm improved the sample's mechanical properties considerably compared to thicknesses of less than 0.4 mm; however, any further increase in Zn interlayer thickness of above 0.4 mm caused mechanical properties to deteriorate.

Elimination of the risk of brittle fracture in thick welded pressure vessels

International Nuclear Information System (INIS)

Leymonie, C.; Genevray, R.

1975-01-01

The builder of welded pressure vessels faces the risk of brittle fracture throughout fabrication. He is forced to observe many precautions, in selecting the following: materials possessing good impact strength in the service conditions of the vessels; filler materials preventing transverse cracking of the welds: welding parameters preventing cold cracking. Fracture mechanics establish the relationships between material characteristics and critical defect size for a given set of service conditions. These principles must be expanded to increase the safety of thick pressure vessels. However, in order to derive maximum benefit, a major effort must be applied to increasing the effectiveness of nondestructive testing [fr

Microstructural Characterization of Friction Stir Welded Aluminum-Steel Joints

Science.gov (United States)

2013-08-01

Sterling, R.J. Steel, C.-O. Pettersson. “Microstructure and mechanical properties of friction stir welded SAF 2507 super duplex stainless steel.” Mater...MICROSTRUCTURAL CHARACTERIZATION OF FRICTION STIR WELDED ALUMINUM-STEEL JOINTS By ERIN ELIZABETH PATTERSON A thesis submitted in...for his work producing the dissimilar weld samples used in this study. Without his work, this project would not have been possible. I would also

Fundamental studies on electron beam welding on heat resistant superalloys for nuclear plants, 6

International Nuclear Information System (INIS)

Susei, Syuzo; Shimizu, Sigeki; Nagai, Hiroyoshi; Aota, Toshikazu; Satoh, Keisuke

1980-01-01

In this report, base metal of superalloys for nuclear plants, its electron beam and TIG weld joints were compared with each other in the mechanical properties. Obtained conclusions are summarized as follows: 1) TIG weld joint is superior to electron beam weld joint and base metal in 0.2% proof stress irrespective of the material, and electron beam weld joint is also superior to base metal. There is an appreciable difference in tensile stress between base metal and weld joint regardless of the materials. Meanwhile, electron beam weld joint is superior to TIG weld joint in both elongation and reduction of area. 2) Electron beam weld joint has considerably higher low-cycle fatigue properties at elevated temperatures than TIG weld joint, and it is usually as high as base metal. 3) In the secondary creep rate, base metal of Hastelloy X (HAEM) has higher one than its weld joints. However, electron beam weld joint is nearly comparable to the base metal. 4) There is hardly any appreciable difference between base metal and weld joint in the creep rupture strength without distinction of the material. In the ductility, base metal is much superior and is followed by electron beam weld joint and TIG weld joint in the order of high ductility. However, electron beam weld joint is rather comparable to base metal. 5) In consideration of welded pipe with a circumferential joint, the weld joint should be evaluated in terms of secondary creep rate, elongation and rupture strength. As the weld joint of high creep rupture strength approaches the base metal in the secondary creep rate and the elongation, it seems to be more resistant against the fracture due to creep deformation. In this point of view, electron beam weld joint is far superior to TIG weld joint and nearly comparable to the base metal. (author)

Upgrading weld quality of a friction stir welded aluminum alloys AMG6

Science.gov (United States)

Chernykh, I. K.; Vasil'ev, E. V.; Matuzko, E. N.; Krivonos, E. V.

2018-01-01

In the course of introduction of FSW technology into the industry there is a keen interest in this process; there are issues such as how does joining take place, what is the structure of the joint, and where there are dangerous zones. The objective of this research is to obtain information about the structure of the joint, what are the temperatures that arise during the joining, what strength is apply to the tool when joining the material, what tensile strength of joint, and where fracture tended to occur. Specimens were produced at different modes of welding at a tool rotation speed of 315 to 625 rpm and tool travel speed of 40 to 125 mm/min. During the experiment, the strength applied to the tool was measured, which reached 800016000 N (Fz) and 400-1400 N (Fx) and the temperature on the surface of the tool, which is in the range 250-400°C. Before the welding process the tool was heated to a temperature in the range of 100-250 degrees, but the tensile strength is not had a tangible impact. The tensile strength is about 80 % of that of the aluminum alloy base metal tensile strength, and fracture tended is occur not at the line of joint but follow the shape of the tool. In the transverse cross section of a FSW material there is a microstructural regions such as weld nugget, thermomechanically affected zone and heat-affected zone with parent material.

Fatigue life evaluation based on welding residual stress relaxation and notch strain approach for cruciform welded joint

International Nuclear Information System (INIS)

Han, Jeong Woo; Han, Seung Ho; Shin, Byung Chun; Kim, Jae Hoon

2003-01-01

The fatigue strength of welded joint is influenced by the welding residual stress which is relaxed depending on local stress distributed in vicinity of stress raisers, eg. under cut, overlap and blow hole. To evaluate its fatigue life the geometry of the stress raisers and the welding residual stress should be taken into account. The several methods based on notch strain approach have been proposed in order to consider the two factors above mentioned. These methods, however, have shown considerable differences between analytical and experimental results. It is due to the fact that the amount of the relaxed welding residual stress evaluated by the cyclic stress-strain relationship do not correspond with that occurred in reality. In this paper the residual stress relaxation model based on experimental results was used in order to reduce the discrepancy of the estimated amount of the relaxed welding residual stress. Under an assumption of the superimposition of the relaxed welding residual stress and the local stress, a modified notch strain approach was proposed and verified to the cruciform welded joint

Dependence of fracture toughness of molybdenum laser welds on dendritic spacing and in situ titanium additions

International Nuclear Information System (INIS)

Jellison, J.L.

1979-01-01

The fracture toughness of molybdenum welds has been improved by in situ gettering of oxygen by means of physically deposited titanium. The addition of titanium suppressed brittle intergranular fracture. Pulsed laser welds (both Nd:YAG and CO 2 ) exhibited superior toughness to that of continuous wave CO 2 laser welds. Also, welds of vacuum arc remelted grades were tougher than those of sintered molybdenum. However, weld toughness could not be correlated with either oxygen or carbon content

Fusion welding of Fe-added lap joints between AZ31B magnesium alloy and 6061 aluminum alloy by hybrid laser-tungsten inert gas welding technique

International Nuclear Information System (INIS)

Qi, Xiao-dong; Liu, Li-ming

2012-01-01

Highlights: → Hybrid Laser-TIG fusion welding technique was used for joining Mg to Al alloys. → Laser defocusing amount determined penetration depth inside Al alloy of joints. → The addition of Fe interlayer suppressed Mg-Al intermetallics greatly in joints. → A maximum joint strength with optimum thickness of Fe interlayer was obtained. → Excessive addition of Fe interlayer was adverse for the strength improvement. -- Abstract: AZ31B magnesium alloy and 6061-T6 aluminum alloy were lap joined together with the addition of Fe interlayer by fusion welding of hybrid laser-tungsten inert gas (TIG) technique. The influence of location of laser focal spot (LFS) on joint penetration depth and that of the depth on joint strength were investigated. The results showed that when the LFS was just on the surface of Al plate, the deepest penetration could be obtained, which contributed to the improvement of shear strength of Fe-added joints, but not to the elevation of the strength of Mg/Al direct joints. The addition of Fe interlayer suppressed massive production of Mg-Al intermetallics but produced Fe-Al intermetallics in the fusion zone of the joints, whose micro-hardness was extremely high and was also adverse for the enhancement of joint shear strength. The effect of Fe-interlayer thickness on the joint shear strength was also examined, and the maximum shear strength of Fe-added joint could achieve 100 MPa with 0.13 mm thick Fe interlayer. The fracture modes of 0.07 and 0.13 mm Fe-interlayer-added joints were both quasi-cleavage, while those of direct and 0.22 mm interlayer-added joints were completely cleavage. The theoretical shear strength of the Fe-added joints was also discussed.

Microstructure and mechanical properties of electron beam welded dissimilar steel to Fe–Al alloy joints

Energy Technology Data Exchange (ETDEWEB)

Dinda, Soumitra Kumar; Basiruddin Sk, Md.; Roy, Gour Gopal [Department of Metallurgical and Materials Engineering, Indian Institute of Technology, Kharagpur (India); Srirangam, Prakash, E-mail: p.srirangam@warwick.ac.uk [Warwick Manufacturing Group (WMG), University of Warwick, Coventry CV4 7AL (United Kingdom)

2016-11-20

Electron beam welding (EBW) technique was used to perform dissimilar joining of plain carbon steel to Fe–7%Al alloy under three different weld conditions such as with beam oscillation, without beam oscillation and at higher welding speed. The effect of weld parameters on the microstructure and mechanical properties of dissimilar joints was studied using optical microscopy, SEM, EBSD, hardness, tensile and erichsen cup tests. Microstructure results show that the application of beam oscillation resulted in uniform and homogeneous microstructure compared to without beam oscillations and higher welding speed. Further, it was observed that weld microstructure changes from equiaxed to columnar grains depending on the weld speed. High weld speed results in columnar grain structure in the weld joint. Erichsen cup test results show that the application of beam oscillation results in excellent formability as compared to high weld speed. Tensile test results show no significant difference in strength properties in all three weld conditions, but the ductility was found to be highest for joints obtained with the application of weld beam oscillation as compared to without beam oscillation and high weld speed. This study shows that the application of beam oscillations plays an important role in improving the weld quality and performance of EBW dissimilar steel to Fe–Al joints.

Improving Mechanical Properties of PVPPA Welded Joints of 7075 Aluminum Alloy by PWHT

Directory of Open Access Journals (Sweden)

Guowei Li

2018-03-01

Full Text Available In this study, 7075 aluminum alloy with a thickness of 10 mm was successfully welded with no obvious defects by pulsed variable polarity plasma arc (PVPPA welding. The mechanical properties of PVPPA welded joints have been researched by post weld heat treatment (PWHT. The results indicate that the heat treatment strongly affects the mechanical properties of the welded joints. The tensile strength and the microhardness of the welded joints gradually improved with the increase of the solution temperature. With the increase of the solution time, the tensile strength, and microhardness first dramatically increased and then decreased slightly. The best tensile strength of 537.5 MPa and the microhardness of 143.7 HV were obtained after 490 °C × 80 min + 120 °C × 24 h, and the strength was nearly 91.2% of that of the parent metal, and increased about 35% compared with as-welded. The improvement of strength and microhardness was mainly due to the precipitation of η′ phase.

Laser-Arc Hybrid Welding of Dissimilar Titanium Alloy and Stainless Steel Using Copper Wire

Science.gov (United States)

Gao, Ming; Chen, Cong; Wang, Lei; Wang, Zemin; Zeng, Xiaoyan

2015-05-01

Laser-arc hybrid welding with Cu3Si filler wire was employed to join dissimilar Ti6Al4V titanium alloy and AISI316 stainless steel (316SS). The effects of welding parameters on bead shape, microstructure, mechanical properties, and fracture behavior were investigated in detail. The results show that cross-weld tensile strength of the joints is up to 212 MPa. In the joint, obvious nonuniformity of the microstructure is found in the fusion zone (FZ) and at the interfaces from the top to the bottom, which could be improved by increasing heat input. For the homogeneous joint, the FZ is characterized by Fe67- x Si x Ti33 dendrites spreading on α-Cu matrix, and the two interfaces of 316SS/FZ and FZ/Ti6Al4V are characterized by a bamboo-like 316SS layer and a CuTi2 layer, respectively. All the tensile samples fractured in the hardest CuTi2 layer at Ti6Al4V side of the joints. The fracture surface is characterized by river pattern revealing brittle cleavage fracture. The bead formation mechanisms were discussed according to the melt flow and the thermodynamic calculation.

Analysis of Welding Joint on Handling High Level Waste-Glass Canister

International Nuclear Information System (INIS)

Herlan Martono; Aisyah; Wati

2007-01-01

The analysis of welding joint of stainless steel austenitic AISI 304 for canister material has been studied. At the handling of waste-glass canister from melter below to interim storage, there is a step of welding of canister lid. Welding quality must be kept in a good condition, in order there is no gas out pass welding pores and canister be able to lift by crane. Two part of stainless steel plate in dimension (200 x 125 x 3) mm was jointed by welding. Welding was conducted by TIG machine with protection gas is argon. Electric current were conducted for welding were 70, 80, 90, 100, 110, 120, 130, and 140 A. Welded plates were cut with dimension according to JIS 3121 standard for tensile strength test. Hardness test in welding zone, HAZ, and plate were conducted by Vickers. Analysis of microstructure by optic microscope. The increasing of electric current at the welding, increasing of tensile strength of welding yields. The best quality welding yields using electric current was 110 A. At the welding with electric current more than 110 A, the electric current influence towards plate quality, so that decreasing of stainless steel plate quality and breaking at the plate. Tensile strength of stainless steel plate welding yields in requirement conditions according to application in canister transportation is 0.24 kg/mm 2 . (author)

Designing aluminium friction stir welded joints against multiaxial fatigue

Directory of Open Access Journals (Sweden)

L. Susmel

2016-07-01

Full Text Available The present paper investigates the accuracy of the Modified Wöhler Curve Method (MWCM in estimating multiaxial fatigue strength of aluminium friction stir (FS welded joints. Having developed a bespoke joining technology, circumferentially FS welded tubular specimens of Al 6082-T6 were tested under proportional and non-proportional tension and torsion, the effect of non-zero mean stresses being also investigated. The validation exercise carried out using the experimental results have demonstrated that the MWCM applied in terms of nominal stresses, notch stresses, and also the Point Method is accurate in predicting the fatigue lifetime of the tested FS welded joints, with its use resulting in life estimates that fall within the uniaxial and torsional calibration scatter bands.

Double Fillet Welding of Carbon Steel T-Joint by Double Channel Shielding Gas Metal Arc Welding Method Using Metal Cored Wire

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Mert T.

2017-06-01

Full Text Available Low carbon steel material and T-joints are frequently used in ship building and steel constructions. Advantages such as high deposition rates, high quality and smooth weld metals and easy automation make cored wires preferable in these industries. In this study, low carbon steel materials with web and flange thicknesses of 6 mm, 8 mm and 10 mm were welded with conventional GMAW and double channel shielding gas metal arc welding (DMAG method to form double fillet T-joints using metal cored wire. The difference between these two methods were characterized by measurements of mean welding parameters, Vickers hardness profiles, weld bead and HAZ geometry of the joints and thermal camera temperature measurements. When weld bead and HAZ geometries are focused, it was seen filler metal molten area increased and base metal molten area decreased in DMAG of low carbon steel. When compared with traditional GMAW, finer and acicular structures in weld metal and more homogenous and smaller grains in HAZ are obtained with double channel shielding gas metal arc welding.

A Study on Fatigue Design Automation of Plug- and Ring-type Gas-welded Joints of STS301L Taking Welded Residual Stress into Account

International Nuclear Information System (INIS)

Baek, Seung yeb; Yun, Ki Ho

2010-01-01

This paper presents a fatigue design method for plug- and ring-type gas-welded joints, which takes into account the effects of welding residual stress. To develop this method, we simulated the gas-welding process by performing nonlinear finite element analysis (FEA) To validate the FEA results, numerically calculated residual stresses in the gas welds were then compared with experimental results obtained by the hole-drilling method. To evaluate the fatigue strength of plug- and ring-type gas-welded joints influenced by welding residual stresses, the use of stress amplitude (σ a )R, which includes the welding residual stress in gas welds, is proposed (σ a )R on the basis of a modified Goodman equation that includes the residual stress effects. Using the stress amplitude (σ a )R at the hot spot point of gas weld, the relations obtained as the fatigue test results for plug and ring type gas welded joints having various dimensions and shapes were systematically rearranged to obtain the (σ a )R-N f relationship. It was found that more systematic and accurate evaluation of the fatigue strength of plug- and ring-type gas-welded joints can be achieved by using (σ a )R

Microstructural characterisation of friction stir welding joints of mild steel to Ni-based alloy 625

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Rodriguez, J. [Brazilian Nanotechnology National Laboratory (LNNano), P.O. Box 6192, Campinas, SP (Brazil); University of Campinas (UNICAMP), Campinas, SP (Brazil); Ramirez, A.J., E-mail: ramirezlondono.1@osu.edu [Brazilian Nanotechnology National Laboratory (LNNano), P.O. Box 6192, Campinas, SP (Brazil); University of Campinas (UNICAMP), Campinas, SP (Brazil); Department of Materials Science and Engineering, The Ohio State University — OSU, Columbus, OH 43221 (United States)

2015-12-15

In this study, 6-mm-thick mild steel and Ni-based alloy 625 plates were friction stir welded using a tool rotational speed of 300 rpm and a travel speed of 100 mm·min{sup −1}. A microstructural characterisation of the dissimilar butt joint was performed using optical microscopy, scanning and transmission electron microscopy, and energy dispersive X-ray spectroscopy (XEDS). Six different weld zones were found. In the steel, the heat-affected zone (HAZ) was divided into three zones and was composed of ferrite, pearlite colonies with different morphologies, degenerated regions of pearlite and allotriomorphic and Widmanstätten ferrite. The stir zone (SZ) of the steel showed a coarse microstructure consisting of allotriomorphic and Widmanstätten ferrite, degenerate pearlite and MA constituents. In the Ni-based alloy 625, the thermo-mechanically affected zone (TMAZ) showed deformed grains and redistribution of precipitates. In the SZ, the high deformation and temperature produced a recrystallised microstructure, as well as fracture and redistribution of MC precipitates. The M{sub 23}C{sub 6} precipitates, present in the base material, were also redistributed in the stir zone of the Ni-based alloy. TMAZ in the steel and HAZ in the Ni-based alloy could not be identified. The main restorative mechanisms were discontinuous dynamic recrystallisation in the steel, and discontinuous and continuous dynamic recrystallisation in the Ni-based alloy. The interface region between the steel and the Ni-based alloy showed a fcc microstructure with NbC carbides and an average length of 2.0 μm. - Highlights: • Comprehensive microstructural characterisation of dissimilar joints of mild steel to Ni-based alloy • Friction stir welding of joints of mild steel to Ni-based alloy 625 produces sound welds. • The interface region showed deformed and recrystallised fcc grains with NbC carbides and a length of 2.0 μm.

An Evaluation of Global and Local Tensile Properties of Friction-Stir Welded DP980 Dual-Phase Steel Joints Using a Digital Image Correlation Method.

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Lee, Hyoungwook; Kim, Cheolhee; Song, Jung Han

2015-12-04

The effect of the microstructure heterogeneity on the tensile plastic deformation characteristic of friction-stir-welded (FSW) dual-phase (DP) steel was investigated for the potential applications on the lightweight design of vehicles. Friction-stir-welded specimens with a butt joint configuration were prepared, and quasi-static tensile tests were conducted, to evaluate the tensile properties of DP980 dual-phase steels. The friction-stir welding led to the formation of martensite and a significant hardness rise in the stir zone (SZ), but the presence of a soft zone in the heat-affected zone (HAZ) was caused by tempering of the pre-existing martensite. Owing to the appearance of severe soft zone, DP980 FSW joint showed almost 93% joint efficiency with the view-point of ultimate tensile strength and relatively low ductility than the base metal (BM). The local tensile deformation characteristic of the FSW joints was also examined using the digital image correlation (DIC) methodology by mapping the global and local strain distribution, and was subsequently analyzed by mechanics calculation. It is found that the tensile deformation of the FSW joints is highly heterogeneous, leading to a significant decrease in global ductility. The HAZ of the joints is the weakest region where the strain localizes early, and this localization extends until fracture with a strain near 30%, while the strain in the SZ and BM is only 1% and 4%, respectively. Local constitutive properties in different heterogeneous regions through the friction-stir-welded joint was also briefly evaluated by assuming iso-stress conditions. The local stress-strain curves of individual weld zones provide a clear indication of the heterogeneity of the local mechanical properties.

Defect accumulation in welded joints of 12Kh1MF steel steam pipelines during creep

International Nuclear Information System (INIS)

Anokhov, A.E.; Alekhova, I.A.

1982-01-01

Technique for investigation of micropore accumulation in 12Kh1MF steel welded joints is proposed. The micropore density in different zones of welded joints in non-uniform. It is shown that failure localization in welded joint in the softening zone during the creep takes place due to the micropore priority accumulation in this zone. It is found out that accumulation of residual deformations in different zones of 12Kh1MF welded joints under creep runs more uniformly as the level of working stresses decreases and test duration increases

Friction stir welding of T joints of dissimilar aluminum alloy: A review

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Thakare, Shrikant B.; Kalyankar, Vivek D.

2018-04-01

Aluminum alloys are preferred in the mechanical design due to their advantages like high strength, good corrosion resistance, low density and good weldability. In various industrial applications T joints configuration of aluminum alloys are used. In different fields, T joints having skin (horizontal sheet) strengthen by stringers (vertical sheets) were used to increase the strength of structure without increasing the weight. T joints are usually carried out by fusion welding which has limitations in joining of aluminum alloy due to significant distortion and metallurgical defects. Some aluminum alloys are even non weldable by fusion welding. The friction stir welding (FSW) has an excellent replacement of conventional fusion welding for T joints. In this article, FSW of T joints is reviewed by considering aluminum alloy and various joint geometries for defect analysis. The previous experiments carried out on T joints shows the factors such as tool geometry, fixturing device and joint configurations plays significant role in defect free joints. It is essential to investigate the material flow during FSW to know joining mechanism and the formation of joint. In this study the defect occurred in the FSW are studied for various joint configurations and parameters. Also the effect of the parameters and defects occurs on the tensile strength are studied. It is concluded that the T-joints of different joint configurations can be pretended successfully. Comparing to base metal some loss in tensile strength was observed in the weldments as well as overall reduction of the hardness in the thermos mechanically affected zone also observed.

Possibility of designing television control system for welded joint formation on electron beam welding

International Nuclear Information System (INIS)

Lifshits, M.L.; Lobanova, N.G.

1987-01-01

Regression equations (models), connecting seam characteristics: width and depth with the welding bath leading front in joint gap and seam width respectively - are obtained at electron beam welding of circular articles with guaranteed clearance with application of television control system. Dispersion analysis showed the models adequancy to the process in the range, where they were identified

Numerical estimation of temperature field in a laser welded butt joint made of dissimilar materials

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Saternus Zbigniew

2018-01-01

Full Text Available The paper concerns numerical analysis of thermal phenomena occurring in the butt welding of two different materials by a laser beam welding. The temperature distribution for the welded butt-joint is obtained on the basis of numerical simulations performed in the ABAQUS program. Numerical analysis takes into account the thermophysical properties of welded plate made of two different materials. Temperature distribution in analysed joints is obtained on the basis of numerical simulation in Abaqus/Standard solver, which allowed the determination of the geometry of laser welded butt-joint.

Characteristics of Laser Beam and Friction Stir Welded AISI 409M Ferritic Stainless Steel Joints

Science.gov (United States)

Lakshminarayanan, A. K.; Balasubramanian, V.

2012-04-01

This article presents the comparative evaluation of microstructural features and mechanical properties of friction stir welded (solid-state) and laser beam welded (high energy density fusion welding) AISI 409M grade ferritic stainless steel joints. Optical microscopy, microhardness testing, transverse tensile, and impact tests were performed. The coarse ferrite grains in the base material were changed to fine grains consisting duplex structure of ferrite and martensite due to the rapid cooling rate and high strain induced by severe plastic deformation caused by frictional stirring. On the other hand, columnar dendritic grain structure was observed in fusion zone of laser beam welded joints. Tensile testing indicates overmatching of the weld metal relative to the base metal irrespective of the welding processes used. The LBW joint exhibited superior impact toughness compared to the FSW joint.

Mechanical properties of TIG and EB weld joints of F82H

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Hirose, Takanori, E-mail: hirose.takanori@jaea.go.jp; Sakasegawa, Hideo; Nakajima, Motoki; Tanigawa, Hiroyasu

2015-10-15

Highlights: • Narrow groove TIG minimized volume of F82H weld. • Mechanical properties of TIG and EB welds of F82H have been characterized. • Post weld heat treatment successfully moderate the toughness of weld metal without softening the base metal. - Abstract: This work investigates mechanical properties of weld joints of a reduced activation ferritic/martensitic steel, F82H and effects of post weld heat treatment on the welds. Vickers hardness, tensile and Charpy impact tests were conducted on F82H weld joints prepared using tungsten-inert-gas and electron beam after various heat treatments. Although narrow groove tungsten-inert-gas welding reduced volume of weld bead, significant embrittlement was observed in a heat affected zone transformed due to heat input. Post weld heat treatment above 993 K successfully moderated the brittle transformed region. The hardness of the brittle region strongly depends on the heat treatment temperature. Meanwhile, strength of base metal was slightly reduced by the treatment at temperature ranging from 993 to 1053 K. Moreover, softening due to double welding was observed only in the weld metal, but negligible in base metal.

Effect of Local Post Weld Heat Treatment on Tensile Properties in Friction Stir Welded 2219-O Al Alloy

Science.gov (United States)

Chu, Guannan; Sun, Lei; Lin, Caiyuan; Lin, Yanli

2017-11-01

To improve the formability of the aluminum alloy welds and overcome the size limitation of the bulk post weld heat treatment (BPWHT) on large size friction stir welded joints, a local post weld heat treatment method (LPWHT) was proposed. In this method, the resistance heating as the moving heat source is adopted to only heat the weld seam. The temperature field of LPWHT and its influence on the mechanical properties and formability of FSW 2219-O Al alloy joints was investigated. The evaluation of the tensile properties of FSW samples was also examined by mapping the global and local strain distribution using the digital image correlation methodology. The results indicated that the formability was improved greatly after LPWHT, while the hardness distribution of the FSW joint was homogenized. The maximum elongation can reach 1.4 times that of as-welded joints with increase the strength and the strain of the nugget zone increased from 3 to 8% when annealing at 300 °C. The heterogeneity on the tensile deformation of the as-welded joints was improved by the nugget zone showing large local strain value and the reason was given according to the dimple fracture characteristics at different annealing temperatures. The tensile strength and elongation of LPWHT can reach 93.3 and 96.1% of the BPWHT, respectively. Thus, the LPWHT can be advantageous compared to the BPWHT for large size welds.

Inhibition of the formation of intermetallic compounds in aluminum-steel welded joints by friction stir welding

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Torres López, Edwar A.

2015-12-01

Full Text Available Formation of deleterious phases during welding of aluminum and steel is a challenge of the welding processes, for decades. Friction Stir Welding (FSW has been used in an attempt to reduce formation of intermetallic compounds trough reducing the heat input. In this research, dissimilar joint of 6063-T5 aluminum alloy and AISI-SAE 1020 steel were welded using this technique. The temperature of welded joints was measured during the process. The interface of the welded joints was characterized using optical microscopy, scanning and transmission electron microscopy. Additionally, composition measurements were carried out by X-EDS and DRX. The experimental results revealed that the maximum temperature on the joint studied is less than 360 °C. The microstructural characterization in the aluminum-steel interface showed the absence of intermetallic compounds, which is a condition attributed to the use of welding with low thermal input parameters.La unión de juntas aluminio-acero, sin la formación de fases deletéreas del tipo FexAly, ha sido, por décadas, un desafío para los procesos de soldadura. La soldadura por fricción-agitación ha sido empleada para intentar reducir el aporte térmico y evitar la formación de compuestos intermetálicos. Usando esta técnica fueron soldadas juntas disimilares de aluminio 6063-T5 y acero AISI-SAE 1020. La soldadura fue acompañada de medidas de temperatura durante su ejecución. La interfase de las juntas soldadas fue caracterizada utilizando microscopía óptica, electrónica de barrido y electrónica de transmisión. Adicionalmente fueron realizadas medidas puntuales X-EDS y DRX. Los resultados experimentales revelan que la temperatura máxima en la junta es inferior a 360 °C. La caracterización microestructural en la interfase aluminio-acero demostró la ausencia de compuestos intermetálicos, condición atribuida al uso de parámetros de soldadura con bajo aporte térmico.

Extending ITER materials design to welded joints

Energy Technology Data Exchange (ETDEWEB)

Tavassoli, A.-A.F. [DMN/Dir, CEA/Saclay, Commissariat a l' Energie Atomique, 91191 Gif sur Yvette cedex (France)]. E-mail: tavassoli@cea.fr

2007-08-01

This paper extends the ITER materials properties documentation to weld metals and incorporates the needs of Test Blanket Modules for higher temperature materials properties. Since the main structural material selected for ITER is type 316L(N)-IG, the paper is focused on weld metals and joining techniques for this steel. Materials properties data are analysed according to the French design and construction rules for nuclear components (RCC-MR) and design allowables are equally derived using the same rules. Particular attention is paid to the type of weld metal, to the type and position of welding and their influence on the materials properties data and design allowables. The primary goal of this work, starting with 19-12-2 weld metal, is to produce comprehensive materials properties documentations that when combined with codification and inspection documents would satisfy ITER licensing needs. As a result, structural stability and capability of welded joints during manufacturing of ITER components and their subsequent service, including the effects of irradiation and eventual incidental or accidental situations, are also covered.

Double fillet lap of laser welding of thin sheet AZ31B Mg alloy

Science.gov (United States)

Ishak, Mahadzir; Salleh, M. N. M.

2018-05-01

In this paper, we describe the experimental laser welding of thin sheet AZ31B using double fillet lap joint method. Laser welding is capable of producing high quality weld seams especially for small weld bead on thin sheet product. In this experiment, both edges for upper and lower sheets were subjected to the laser beam from the pulse wave (PW) mode of fiber laser. Welded sample were tested their joint strength by tensile-shear strength method and the fracture loads were studied. Strength for all welded samples were investigated and the effect of laser parameters on the joint strength and appearances were studied. Pulsed energy (EP) from laser process give higher effect on joint strength compared to the welding speed (WS) and angle of irradiation (AOI). Highest joint strength was possessed by sample with high EP with the same value of WS and AOI. The strength was low due to the crack defect at the centre of weld region.

The investigation of typical welding defects for 5456 aluminum alloy friction stir welds

International Nuclear Information System (INIS)

Chen Huabin; Yan Keng; Lin Tao; Chen Shanben; Jiang Chengyu; Zhao Yong

2006-01-01

The external factors on the friction stir welding defects are so abundant that the experiments of friction stir welding were conducted for 5456 aluminum alloy. With the changes of the tool tilt angle and material condition, defects can be generated. These defects can be conventional ones (lack of penetration or voids), or lazy S, which are unique to friction stir welding. However, the origin of the defects remains an area of uncertainty. In this study, an attempt has been made to investigate the formation of these defects. The typical welding defects of friction stir welding joint for 5456 aluminum alloy were analyzed and discussed, respectively, by using optical microscopy (OM), energy-dispersive X-ray spectroscopy (EDS) and scanning electron microscope (SEM). The microscopic examination of the nugget zone and fracture location of the weld confirms that the tilt angle can change the plastic material flow patterns in the stir zone and accordingly control the weld properties. In addition, the oxide layer from the initial butt surface during FSW is dispersed at the grain boundary. These A1 2 O 3 particles are actually the major cause of failure of the joint

Friction Stir Welding-assisted Diffusion Bond of Al/Zn/Mg Lap Joint

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JIN Yu-hua

2018-03-01

Full Text Available Dissimilar materials welding between 2mm-thick AZ31B Mg alloy and 6061 Al alloy plates in overlap form was performed using the friction stir-induced diffusion bond with zinc foil as the interlayer. The microstructure and mechanical properties of the Al/Zn/Mg lap joints were analyzed by means of SEM, EPMA, XRD, tensile experiment and Vickers hardness test. The results show that diffusion layer consists of Al enrichment zone, Al5Mg11Zn4 layer and Mg-Zn eutectic zone at proper rotation speed; however, when rotation speed is low, the residual zinc interlayer remains in the diffusion layer; when rotation speed is high, the Al-Mg intermetallic compounds are present again. Due to the existence of intermetallic compounds in diffusion layer, its microhardness is significantly higher than that of base metal. The addition of zinc foil can improve the mechanical properties of Al/Mg lap joints. According to analysis on the fracture, joint failure occurs in the diffusion layer near to Al side.

A study on residual stress distribution of welded joints

International Nuclear Information System (INIS)

Huh, Sun Chul; Lee, Kwang Young; Park, Won Jo; Yang, Hae Sug; Junge, Hae Young

2005-01-01

Wings for defense industry such as fighters, missiles, and rockets should have no deformation or damage on the structure, strength, and hardness safety of constituted pared and the structures near to the bodies. The structures of existing wings had holes for light weight and plates and frames were fixed with rivets or screws, thus, there were difficulties and limits in light weight. In this study, an improvement was made in current joint methods through EB welding and laser welding for light weight of wings and welding strength was measured through strength test. In addition, finite element analysis was performed for welding process so as to induce optimum welding condition