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Sample records for cementite

  1. Cementite Solidification in Cast Iron

    Science.gov (United States)

    Coronado, J. J.; Sinatora, A.; Albertin, E.

    2014-06-01

    Two hypereutectic cast irons (5.01 pct Cr and 5.19 pct V) were cast and the polished surfaces of test pieces were deep-etched and analyzed via scanning electron microscopy. The results show that graphite lamellae intersect the cementite and a thin austenite film nucleates and grows on the cementite plates. For both compositions, graphite and cementite can coexist as equilibrium phases, with the former always nucleating and growing first. The eutectic carbides grow from the austenite dendrites in a direction perpendicular to the primary plates.

  2. Cementite Decomposition in Spherical Graphite Iron by Electropulsing

    Institute of Scientific and Technical Information of China (English)

    Oingchun Li; Guowei Chang; Oijie Zhai

    2009-01-01

    The influence of electropulsing on cementite decomposition in the spherical graphite iron has been studied.The results indicated that the cementite was decomposed in a short time by high current density electropulsing.With increasing electropulsing time, the in situ nucleation of graphite in cementite was accompanied with the quick decomposition of cementite. The dislocation accumulation adjacent to the cementite and the quick diffusion of carbon atom by electropulsing were main reasons for the quick decomposition of cementite. The in situ nucleation of graphite in the cementite resulted from the dislocation climbing crossing the cementite lamellae.

  3. Deformation of cementite in cold drawn pearlitic steel wire

    Energy Technology Data Exchange (ETDEWEB)

    Fang, Feng, E-mail: fangfeng@seu.edu.cn [School of Materials Science and Engineering, Southeast University, Nanjing 211189 (China); Zhao, Yufei; Liu, Peipei; Zhou, Lichu [School of Materials Science and Engineering, Southeast University, Nanjing 211189 (China); Hu, Xian-jun [Jiangsu Sha-Steel Group, Zhangjiagang 215625 (China); Zhou, Xuefeng [School of Materials Science and Engineering, Southeast University, Nanjing 211189 (China); Xie, Zong-han [School of Mechanical Engineering, University of Adelaide, SA 5005 (Australia)

    2014-07-01

    Nanostructural evolution of cementite lamellae in pearlitic steel wires subjected to cold drawing remains elusive, making it difficult to understand the origin of remarkable ductility in cementite. Using high-resolution transmission electron microscopy (HRTEM), the mechanisms underlying the inelastic deformation of cementite in pearlitic steel wires were examined and elucidated. Deformation of cementite in drawing should be included in two mechanisms: (1) Dislocation mechanism: deformation in low strain pearlite should rely on the movement of dislocation. Flat-crystal cementite was broken up into several different orientation cementite particles. (2) Grain rotation mechanism: the deformation mechanism should be by the rotation of cementite particles. Cementite still keeps lamellar shape, but it was divided into a multilayer structure: central nano-crystal and outermost amorphous cementite.

  4. Deformation of cementite in cold drawn pearlitic steel wire

    International Nuclear Information System (INIS)

    Nanostructural evolution of cementite lamellae in pearlitic steel wires subjected to cold drawing remains elusive, making it difficult to understand the origin of remarkable ductility in cementite. Using high-resolution transmission electron microscopy (HRTEM), the mechanisms underlying the inelastic deformation of cementite in pearlitic steel wires were examined and elucidated. Deformation of cementite in drawing should be included in two mechanisms: (1) Dislocation mechanism: deformation in low strain pearlite should rely on the movement of dislocation. Flat-crystal cementite was broken up into several different orientation cementite particles. (2) Grain rotation mechanism: the deformation mechanism should be by the rotation of cementite particles. Cementite still keeps lamellar shape, but it was divided into a multilayer structure: central nano-crystal and outermost amorphous cementite

  5. Specific saturation magnetization of cementite resulting from tempering of cobalt and nickel steels

    Energy Technology Data Exchange (ETDEWEB)

    Yatsura, M.M.; Kirichok, P.P.; Yatsura, O.R. (Ivano-Frankovskij Gosudarstvennyj Pedagogicheskij Inst. (Ukrainian SSR))

    1984-01-01

    Results of studying specific saturation magnetization of cementite formed in cobalt and nickel steels in the case of isothermal tempering, are presented. It is shown that tempering temperature increase or ageing duration increase bring about the increase of specific magnetization of cementite saturation of both cobalt and nickel steels. Co and Ni dissolving in cementite during steel tempering decreases its specific saturation magnetization.

  6. The effect of silicon on the nanoprecipitation of cementite

    OpenAIRE

    B. Kim; Celada, Carola de; San Martín, David; Sourmail, T.; Rivera-Díaz del Castillo, P.E.J

    2013-01-01

    The current work presents a comprehensive study that aims at understanding the role of silicon on θ precipitation, as well as on the ε → θ carbide transition in tempered martensite. Cementite nucleation was modelled under paraequilibrium conditions in order to ensure the presence of silicon in the carbide, where both thermodynamic and misfit strain energies were calculated to evaluate the overall free energy change. The growth stage was investigated using in situ synchrotron radiation; three ...

  7. Evolution of cementite morphology in pearlitic steel wire during wet wire drawing

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Xiaodan [Advanced Materials Laboratory, Department of Materials Science and Engineering, Tsinghua University, 100084 (China); Godfrey, Andrew, E-mail: awgodfrey@mail.tsinghua.edu.cn [Advanced Materials Laboratory, Department of Materials Science and Engineering, Tsinghua University, 100084 (China); Hansen, Niels; Huang Xiaoxu [Center for Fundamental Research: Metal Structures in Four Dimensions, Materials Research Division, Riso National Laboratory for Sustainable Energy, DTU, DK-4000 Roskilde (Denmark); Liu Wei [Advanced Materials Laboratory, Department of Materials Science and Engineering, Tsinghua University, 100084 (China); Liu Qing [School of Materials Science and Engineering, Chongqing University, Chongqing, 400030 (China)

    2010-01-15

    The evolution of the cementite phase during wet wire drawing of a pearlitic steel wire has been followed as a function of strain. Particular attention has been given to a quantitative characterization of changes in the alignment and in the dimensions of the cementite phase. Scanning electron microscope observations show that cementite plates become increasingly aligned with the wire axis as the drawing strain is increased. Measurements in the transmission electron microscope show that the cementite deforms plastically during wire drawing , with the average thickness of the cementite plates decreasing from 19 nm ({epsilon} = 0) to 2 nm ({epsilon} = 3.7) in correspondence with the reduction in wire diameter. The deformation of the cementite is strongly related to plastic deformation in the ferrite, with coarse slip steps, shear bands and cracks in the cementite plates/particles observed parallel to either {l_brace}110{r_brace}{sub {alpha}} or {l_brace}112{r_brace}{sub {alpha}} slip plane traces in the ferrite.

  8. Experimental measurement of Young’s modulus from a single crystalline cementite

    International Nuclear Information System (INIS)

    Pure Fe–C pearlite was heat-treated and selectively etched to extract [0 0 1]- and [1 0 0]-oriented single crystalline cementite sheets. The elastic properties of the shaped cementite were measured in a simple, in situ bending test system set up inside the scanning electron microscope using a micronewton-range force sensor. The Young’s modulus experimentally measured from a single crystal sheet was lower than the value obtained from theoretical calculation

  9. Effect of Experimental Conditions on Cementite Formation During Reduction of Iron Ore Pellets

    Science.gov (United States)

    Kazemi, Mania; Sichen, Du

    2016-08-01

    Experiments have been carried out to study the effect of temperature, gas composition, residence time, and type of iron ore pellets on formation of cementite during gaseous reduction of hematite. Industrial iron ore pellets have been reduced isothermally in a gas mixture with H2 and CO as main components. The presence of Fe3C in the partially reduced pellets shows that reduction and cementite formation take place at the same time. The maximum content of cementite is identified in the samples reduced by H2-CO at 1123 K (850 °C). The decrease in the carbide content due to addition of 1 pct CO2 to the initial gas mixture reveals the major influence of carbon potential in the gas atmosphere. Further increase of CO2 content increases the Fe3C. The variations of the amount of cementite with the CO2 content suggest that both the thermodynamics and kinetics of cementite formation are affected by the gas composition. Cementite decomposes to graphite and iron particles in reducing and inert atmospheres as the residence time of pellets at high temperature is increased above 60 minutes.

  10. Effects of deformation parameters on formation of pro-eutectoid cementite in hypereutectoid steels

    Institute of Scientific and Technical Information of China (English)

    管仁国; 赵占勇; 钞润泽; 刘相华

    2014-01-01

    Brittle pro-eutectoid cementite that forms along prior-austenite in hypereutectoid steels is deleterious to mechanical properties. The optimum process parameters which suppress the formation of pro-eutectoid cementite in hypereutectoid steels with carbon content in the range of 0.8%-1.3% in mass fraction, were investigated. Pro-eutectoid cementite formation is effectively hindered by increasing the deformation temperature and decreasing the amount of strain. Transformation at lower temperatures close to the nose of the cooling-transformation diagram also reduces the tendency of the formation of pro-eutectoid cementite. Control of prior-austenite grain size and grain boundary conditions is important. Due to larger number of nucleation sites, finer prior-austenite grain size results in the acceleration of transformation to pro-eutectoid cementite. However, large prior-austenite and straight boundaries lead to less nucleation sites of pro-eutectoid cementite. The cooling rate and carbon content should be reduced as much as possible. The transformation temperature below 660 °C and the strain of 0.5 at deformation temperature of 850 °C are suggested.

  11. Simulations of cementite: An analytical potential for the Fe-C system

    Science.gov (United States)

    Henriksson, K. O. E.; Nordlund, K.

    2009-04-01

    An analytical bond-order interatomic potential has been developed for the iron-carbon system for use in molecular-dynamics and Monte Carlo simulations. The potential has been successfully fitted to cementite and Hägg carbide, which are most important crystalline polytypes among the many known metastable iron carbide phases. Predicted properties of other carbides and the simplest point defects are in good to reasonable agreement with available data from experiments and density-functional theory calculations. The potential correctly describes melting and recrystallization of cementite, making it useful for simulation of steels. We show that they correctly describe the metastability of cementite and can be used to model carbide growth and dissolution.

  12. Effect of Microstructure of Cementite on Interphase Stress State in Carbon Steel

    Institute of Scientific and Technical Information of China (English)

    CHE Lei; GOTOH Masahide; HORIMOTO Yoshiaki; HIROSE Yukio

    2007-01-01

    The experiments related to stress states of ferrite and cementite in carbon steels were carried out including in situ four-point bending and tensile test by X-ray diffraction technique. Stresses in the cementite phase can be measured by conventional X-ray diffraction instrument after a specific treatment on the specimen surface. In order to estimate the stress states in two phases, the X-ray elastic constants of two phases in single-phase state (PXEC) are determined by the experimental X-ray elastic constants of them in composite state (CXEC). The effects of volume fraction and particle size of spheroidal cementite on the interphase stress state are estimated. The experimental results are in good agreement with the theoretical relationships reported in the previous studies.

  13. Calculation of the valence electron structures of alloying cementite and its biphase interface

    Institute of Scientific and Technical Information of China (English)

    刘志林; 李志林; 刘伟东

    2001-01-01

    The valence electron structures of alloying cementite θ-(Fe, M)3C and ε-(Fe, M)3C andthose of the biphase interfaces between them and α-Fe are calculated with Yu's empirical electrontheory of solid and molecules. The calculation results accord with the actual behavior of alloys.

  14. Orientation Relationships between Ferrite and Cementite by Edge-to-edge Matching Principle

    Institute of Scientific and Technical Information of China (English)

    Ning Zhong; Xiaodong Wang; Zhenghong Guo; Yonghua Rong

    2011-01-01

    The crystallographic features of pearlite were investigated by experiments and edge-to-edge matching principle. Two new orientation relationships between ferrite and cementite were determinated by selected area electron diffraction and then explained by our modified edge-to-edge matching method. The consistence of the experimental results with theoretical prediction confirms the practicability of the modified edge-to-edge matching model.

  15. Hypereutectoid cementite morphology and mechanical properties of Cr-Ni-Mo cast steel

    Directory of Open Access Journals (Sweden)

    E. Rożniata

    2006-04-01

    Full Text Available Purpose: The paper presents evaluation of the influence of grain normalization (refinement as a result of repeated austenitizing, cooling rate after repeated austenitizing on the morphology of hypereutectoid cementite and fracture toughness of G200CrMoNi4-6-3 cast steel. Moreover, the elimination of hypereutectoid cementite in structure of Widmannstätten type precipitates from the structure of investigated cast steel has been undertaken.Design/methodology/approach: Basic research of G200CrMoNi4-6-3 cast steel included metallographic analysis and fracture toughness research (impact strength, stress intensity factor KIc. The heat treatment has been planned on the basis of CCT diagram prepared for that cast steel.Findings: Heat treatment of investigated cast steel allows to refine the grain and eliminate from it’s structure the hypereutectoid cementite in structure of Widmannstätten type. At very low cooling rate the precipitates of hypereutectoid cementite become partially coagulated. The study of the influence of cooling rate on the mechanical properties of G200CrMoNi4-6-3 cast steel had proven that elimination of hypereutectoid cementite in structure of Widmannstätten type from the investigated cast steel structure to small degree increases it’s fracture toughness.Research limitations/implications: Research financed by the Ministry of Scientific Research and Information Technology, grant No. 3 T08B 057 29.Practical implications: G200CrMoNi4-6-3 cast steel of ledeburite class is used mainly for rolls production. Any data related to the structure and mechanical properties of that cast steel are precious for the manufacturers and users of the mill rolls.Originality/value: The new heat treatment of G200CrMoNi4-6-3 cast steel.

  16. Molecular dynamics simulation study of the effect of temperature and grain size on the deformation behavior of polycrystalline cementite

    International Nuclear Information System (INIS)

    Molecular dynamics simulations combined with quantitative atomic displacement analyses were performed to study the deformation behaviors of polycrystalline cementite (Fe3C). At low temperature and large grain size, dislocation glide acts as the preferred deformation mechanism. Due to the limited number of slip systems at low temperature, polycrystalline cementite breaks by forming voids at grain boundaries upon tensile loading. When the temperature rises or the grain size reduces, grain boundary sliding becomes the primary mechanism and plastic deformation is accommodated effectively

  17. Lattice strain measurements using synchrotron diffraction to calibrate a micromechanical modeling in a ferrite-cementite steel

    Energy Technology Data Exchange (ETDEWEB)

    Taupin, V.; Pesci, R. [Laboratoire d' Etude des Microstructures et de Mecanique des Materiaux, LEM3, CNRS, University of Lorraine/Arts et Metiers ParisTech, Metz Cedex 57045 (France); Berbenni, S., E-mail: stephane.berbenni@univ-lorraine.fr [Laboratoire d' Etude des Microstructures et de Mecanique des Materiaux, LEM3, CNRS, University of Lorraine/Arts et Metiers ParisTech, Metz Cedex 57045 (France); Berveiller, S.; Ouahab, R. [Laboratoire d' Etude des Microstructures et de Mecanique des Materiaux, LEM3, CNRS, University of Lorraine/Arts et Metiers ParisTech, Metz Cedex 57045 (France); Bouaziz, O. [Arcelor Research, Arcelor Mittal, Maizieres-les-Metz 57210 (France)

    2013-01-20

    In situ tensile tests were performed at room temperature on a ferrite-cementite steel specifically designed for this study. The evolution of the average stress in ferrite during loading was analyzed by X-ray diffraction. Lattice strain measurements were performed with synchrotron ring diffraction in both ferrite and cementite. These in situ tests were complemented by macroscopic tensile and reversible tensile-compression tests to study the Bauschinger effect. In order to reproduce stresses in ferrite and cementite particles, a recently developed micromechanical Internal Length Mean Field (ILMF) model based on a generalized self-consistent scheme is applied. In this designed ferrite-cementite steel, the third 'phase' of the model represents finite intermediate 'layers' in ferrite due to large geometrically necessary dislocation (GND) densities around cementite particles. The assumed constant thickness of the layers is calibrated thanks to the obtained experimental data. The ILMF model is validated by realistic estimates of the Bauschinger stress and the large difference between mean stresses in ferrite and in cementite phases. This difference cannot be reproduced by classic two-phase homogenization schemes without intermediate GND layers.

  18. Influence of bainite morphology on impact toughness of continuously cooled cementite free bainitic steels

    OpenAIRE

    García Caballero, Francisca; Roelofs, H; Hasler, St; Capdevila, Carlos; Chao, Jesús; Cornide, Juan

    2012-01-01

    The influence of bainite morphology on the impact toughness behaviour of continuously cooled cementite-free low carbon bainitic steels has been examined. In these steels, bainitic microstructures formed mainly by lath-like upper bainite, consisting of thin and long parallel ferrite laths, were shown to exhibit higher impact toughness values than those with a granular bainite, consisting of equiaxed ferrite structure and discrete island of marteniste/austenite (M/A) constituent....

  19. Microstructure evolution and mechanical properties of eutectoid steel with ultrafine or fine (ferrite+cementite) structure

    International Nuclear Information System (INIS)

    Eutectoid steel with the ultrafine or fine-grained ferrite (α)+cementite (θ) particles structure was formed by hot deformation of undercooled austenite at 0.1 s−1 or 5 s−1 at 650 °C using a Gleeble 1500 hot simulator and subsequent annealing. The microstructural evolution of fine (α+θ) structure was investigated by means of a scanning electronic microscope, electron backscattered diffraction and transmission electron microscope, and the mechanical properties of fine (α+θ) steel were analyzed in comparison with that of ultrafine (α+θ) steel. The results show that only dynamic transformation of undercooled austenite into proeutectoid ferrite occurs during hot deformation at 650 °C at 5 s−1. During water quenching, lamellar pearlite with small colony sizes is formed and the average size of pearlite colonies decreases with increasing the strain. By subsequent annealing at 650 °C for 30 min, the spheroidization of lamellar pearlite takes place, resulting in the formation of fine (α+θ) structure consisting of ferrite matrix with the average size of about 4.9 μm and fine cementite particles mainly within ferrite grains. In comparison with ultrafine (α+θ) steel consisting of ferrite matrix with the average size of about 1.8 μm and relatively large cementite particles mostly located at grain boundaries, the yield strength, tensile strength, uniform elongation, total elongation and work-hardening capability of fine (α+θ) steel improve markedly

  20. Mechanism of carbon influence on the transition from graphite to cementite eutectic in cast iron

    Directory of Open Access Journals (Sweden)

    E. Fraś

    2010-04-01

    Full Text Available In this work an analytical solution is used to explain mechanism of carbon influence on the transition from graphite to cementite eutectic in cast iron. It is found that this transition can be related to (1 the nucleation potential of graphite (characterized directly by the cell count, N and indirectly by nucleation coefficients Ns and b (2 the growth rate coefficient of graphite eutectic cell, (3 the temperature range, Tsc = Ts - Tc (where Ts and Tc is the equilibrium temperature of the graphite eutectic and formation temperature of the cementite eutectic respectively.and (4 the liquid volume fraction, fl after solidification of the pre-eutectic austenite. Method of estimation of Ns, b and values was presented. It has been shown that the main impact of carbon on the transition from graphite to cementite eutectic consist in increasing the eutectic cell count and growth rate of graphite eutectic cell. Analytical equations were derived to describe the absolute, CT relative chilling tendency, CTr and chill, w of cast iron.

  1. Controlled manufacturing of nanoparticles by the laser pyrolysis: Application to cementite iron carbide

    International Nuclear Information System (INIS)

    The laser pyrolysis is an attractive technique for the synthesis of different nanostructures from gas-phase precursors. The characteristics of this synthesized method are here exemplified by the production of almost pure cementite Fe3C nanomaterials, obtained by the pyrolysis of methyl methacrylate and iron pentacarbonyl (vapors). Those nanopowders exhibited core (Fe3C)-shell (MMA polymer-based) morphologies and mean particle diameters of about 8-9 nm. Preliminary magnetic measurements indicate rather high values for the saturation magnetization. By irradiating the same reactive mixture with a lower intensity radiation, the chemical content of nanopowders shifts towards mixtures of iron and maghemite/magnetite iron oxides.

  2. Mechanism of free sulfur influence on the eutectic cell count and transition from graphite to cementite eutectic in cast iron. Part II. Experimental verification

    Directory of Open Access Journals (Sweden)

    E Fraś

    2010-01-01

    Full Text Available In this work the mechanism of free sulfur influence on the transition from graphite to cementite eutectic in cast iron is experimentally verified. It has been shown that the main impact of free sulfur on the transition from graphite to cementite eutectic consist in reducing the growth rate of graphite eutectic cell.

  3. Fracture and Tensile Properties of Polyvinyl Alcohol Fiber Reinforced Cementitous Composites

    Institute of Scientific and Technical Information of China (English)

    XU Shilang; GAO Shuling

    2008-01-01

    Experiments were carried out to design polyvinyl alcohol(PVA)fiber reinforced cementitous composites(PVA-FRCCs)holding high ductility and energy consumption ability.Besides,the properties of each ingredients in composites,mixing method and technology for fresh mixture were described in detail.Then,the pseudo-strain-hardening(PSH)behavior was investigated in uniaxial tension test.As a result,them maximum ultimate tensile strain can reach 0.7 percent.On the other hand,the single edge notch(SEN)thin sheet specimens were employed to gain the normal tensile load via crack mouth opening displacement(CMOD)curves,which can show obvious PSH behavior.In addition,the curves can be divided into four zones whose fracture toughness calculation methods were discussed.The wedge splitting(WS)test method can be applied to discuss the fracture toughness.Moreover,fracture energy of SEN and WS specimens were both approximately evaluated.

  4. The crystal structure of the molybdenum cementite Mo12Fe22C10 (xi-phase)

    International Nuclear Information System (INIS)

    The crystal structure of molybdenum cementite Mo12Fe22C10 (xi-phase) has been determined by means of a single crystal x-ray diffraction study of crystal fragments. The lattice parameters were found to be: a=10.865(3), b=7.767(2), c=6.559(2) A and β=120.13(2)0, space group C2/m; Z=1. From the analysis of Patterson maps and difference Fourier analysis the atomic parameters were derived, yielding a residual of R=0.059. The crystal structure contains octahedral and triangular prismatic groups which accommodate the carbon atoms in their voids, as is usually found in interstitial compounds. The octahedral building group consists of four Mo- and two Fe-atoms, the triangular prism is built up by four Fe- and two Mo-atoms. The mode of filling of the metal polyhedra is discussed. (Author)

  5. Cementite Formation from Hematite-Graphite Mixture by Simultaneous Thermal-Mechanical Activation

    Science.gov (United States)

    Ashrafzadeh, Milad; Soleymani, Amir Peyman; Panjepour, Masoud; Shamanian, Morteza

    2015-04-01

    In this study, the effect of simultaneous thermal-mechanical activation (STMA) process on carbothermic reduction of hematite and also on iron carbide formation has been investigated. For this purpose, the STMA process was performed for 3 and 6 hours at 973 K (700 °C) and 1073 K (800 °C) on hematite-graphite powder mixtures (with 22 wt pct C) in argon atmosphere. The XRD patterns showed that by performing this process at 973 K (700 °C), the initial hematite reduction led to the formation of wüstite in the presence of graphite. Metallic iron phase was also formed along with wüstite phase at 1073 K (800 °C) for 3 hours, and by increasing the process time to 6 hours, in addition to the metallic iron, iron carbide was also formed. The SEM images and EDS analysis obtained at 1073 K (800 °C)were also indicative of the formation of pearlite structure along with proeutectoid cementite phase and free carbon in the form of graphite in the structure of the samples. According to the results of the image analysis, the percentage of the carbon content was more than 2.22 wt pct in this process lasting for 6 hours at 1073 K (800 °C). Also, DTA results showed that the sample hot milled for 6 hours at 1073 K (800 °C) contained more than 2.1 wt pct carbon. The mechanism of metallic iron and cementite formation from hematite was proposed. Therefore, the STMA process led to an increase in the rate of carbothermic reduction of hematite to metallic iron and reduced its starting temperature relative to the non-simultaneous application of each of the thermal and mechanical activation. Finally, this process can be brought up as a new method for the production of iron carbide from iron oxides.

  6. Electron-microscopic and chemical identification of an individual grain in the newly formed cementite in spheroidized pearlitic 12Kh1MF steel

    Science.gov (United States)

    Gerasimov, V. V.

    2015-12-01

    The microstructure of pearlitic 12Kh1MF steel having spent its service life is studied with a Neophot-32 optical microscope. A cementite grain is identified and its elemental composition is determined using a multipurpose EVO-50 scanning electron microscope equipped with an EDS/WDS X-ray spectrometer. A newly formed grain of alloyed cementite is detected at a triple junction. The diffusion processes that occur in loaded steel are refined.

  7. TEM Study of the Orientation Relationship Between Cementite and Ferrite in a Bainitic Low Carbon High Strength Low Alloy Steel

    OpenAIRE

    Illescas Fernandez, Silvia; Brown, A P; He, K.; Fernández, Javier; Guilemany Casadamon, Josep Maria

    2005-01-01

    Two different bainitic structures are observed in a steel depending on the sample heat treatment. The different types of bainitic structures exhibit different orientation relationships between cementite and the ferrite matrix. Upper bainite presents a Pitsch orientation relationship and lower bainite presents a Bagaryatski orientation relationship. Different heat treatments of low carbon HSLA steel samples have been studied using TEM in order to find the orientation relationshi...

  8. Comparative study and quantification of cementite decomposition in heavily drawn pearlitic steel wires

    Energy Technology Data Exchange (ETDEWEB)

    Lamontagne, A. [University of Lyon, INSA Lyon, MATEIS–UMR CNRS 5510, Bât. St Exupéry, 3ème étage, 25 Avenue Jean Capelle, Villeurbanne Cedex 69621 (France); Massardier, V., E-mail: veronique.massardier@insa-lyon.fr [University of Lyon, INSA Lyon, MATEIS–UMR CNRS 5510, Bât. St Exupéry, 3ème étage, 25 Avenue Jean Capelle, Villeurbanne Cedex 69621 (France); Kléber, X. [University of Lyon, INSA Lyon, MATEIS–UMR CNRS 5510, Bât. St Exupéry, 3ème étage, 25 Avenue Jean Capelle, Villeurbanne Cedex 69621 (France); Sauvage, X. [University of Rouen, GPM, UMR CNRS 6634, BP 12, Avenue de l’Université, 76801 Saint-Etienne du Rouvray (France); Mari, D. [Institute of Condensed Matter Physics, Ecole Polytechnique Fédérale de Lausanne, Station 3, Lausanne CH-1015 (Switzerland)

    2015-09-17

    Heavily cold-drawing was performed on a pearlitic steel wire and on an ultra-low carbon (ULC) steel wire in order to highlight and quantify the microstructural changes caused by this type of deformation. Both global techniques (thermoelectric power, electrical resistivity, internal fiction background) and local techniques (Atom Probe Tomography) were combined for this study. It was shown that two distinct stages have to be taken into account during the cold-drawing of pearlitic steels. The first stage (below a true strain of 1.5) was attributed mainly to the lamellar alignment, while the second stage (above a true strain of 1.5) was unambiguously interpreted as being due to a gradual enrichment of the carbon content of ferrite arising from the strain induced cementite decomposition. The carbon content in solid solution in ferrite was assessed as a function of the true strain. All the techniques showed that this carbon content exceeds the solubility limit of carbon in the ferrite above a true strain of 2.2. A correlation between the increase in the carbon content of ferrite and the increase in yield strength was also highlighted. Moreover, a scenario was proposed to explain the microstructural changes caused by drawing.

  9. Comparative study and quantification of cementite decomposition in heavily drawn pearlitic steel wires

    International Nuclear Information System (INIS)

    Heavily cold-drawing was performed on a pearlitic steel wire and on an ultra-low carbon (ULC) steel wire in order to highlight and quantify the microstructural changes caused by this type of deformation. Both global techniques (thermoelectric power, electrical resistivity, internal fiction background) and local techniques (Atom Probe Tomography) were combined for this study. It was shown that two distinct stages have to be taken into account during the cold-drawing of pearlitic steels. The first stage (below a true strain of 1.5) was attributed mainly to the lamellar alignment, while the second stage (above a true strain of 1.5) was unambiguously interpreted as being due to a gradual enrichment of the carbon content of ferrite arising from the strain induced cementite decomposition. The carbon content in solid solution in ferrite was assessed as a function of the true strain. All the techniques showed that this carbon content exceeds the solubility limit of carbon in the ferrite above a true strain of 2.2. A correlation between the increase in the carbon content of ferrite and the increase in yield strength was also highlighted. Moreover, a scenario was proposed to explain the microstructural changes caused by drawing

  10. Analysis of the variation in nanohardness of pearlitic steel: Influence of the interplay between ferrite crystal orientation and cementite morphology

    International Nuclear Information System (INIS)

    The influence of the relative orientation of the ferrite crystallite lattice and the cementite lamellae on the hardness of pearlitic steel has been investigated by a combination of nanoindentation and electron microscopy (electron back scatter diffraction (EBSD) and scanning electron microscopy (SEM)). Three pearlitic samples, each with a different interlamellar spacing, and one ferritic sample were nanoindented. Although the hardness of the ferritic sample is very similar at different spots on the sample, a large variation in hardness is obtained on each of the pearlitic samples. It has been found that this variation cannot be accounted for solely by the variation in interlamellar spacing and is related to differences in ferrite crystal orientation. As to explain the observed large variation in hardness, the ferrite crystal orientation was considered relative to the cementite lamellae orientation by calculation of the distance dislocations can glide between adjacent lamellae in the slip direction. However, no clear correlation was found for a scaling of this orientation factor with the hardness. Possible interpretations of this discrepancy are suggested

  11. Analysis of the variation in nanohardness of pearlitic steel: Influence of the interplay between ferrite crystal orientation and cementite morphology

    Energy Technology Data Exchange (ETDEWEB)

    Debehets, Jolien, E-mail: jolien.debehets@mtm.kuleuven.be [Department of Materials Engineering, KU Leuven, University of Leuven, Kasteelpark Arenberg 44 bus 2450, B-3001 Leuven (Belgium); Tacq, Jeroen [Department of Materials Engineering, KU Leuven, University of Leuven, Kasteelpark Arenberg 44 bus 2450, B-3001 Leuven (Belgium); Favache, Audrey; Jacques, Pascal [Institute of Mechanics, Materials and Civil Engineering, Université catholique de Louvain, Place Sainte Barbe 2 L5.02.02, 1348 Louvain-la-Neuve (Belgium); Seo, Jin Won; Verlinden, Bert; Seefeldt, Marc [Department of Materials Engineering, KU Leuven, University of Leuven, Kasteelpark Arenberg 44 bus 2450, B-3001 Leuven (Belgium)

    2014-10-20

    The influence of the relative orientation of the ferrite crystallite lattice and the cementite lamellae on the hardness of pearlitic steel has been investigated by a combination of nanoindentation and electron microscopy (electron back scatter diffraction (EBSD) and scanning electron microscopy (SEM)). Three pearlitic samples, each with a different interlamellar spacing, and one ferritic sample were nanoindented. Although the hardness of the ferritic sample is very similar at different spots on the sample, a large variation in hardness is obtained on each of the pearlitic samples. It has been found that this variation cannot be accounted for solely by the variation in interlamellar spacing and is related to differences in ferrite crystal orientation. As to explain the observed large variation in hardness, the ferrite crystal orientation was considered relative to the cementite lamellae orientation by calculation of the distance dislocations can glide between adjacent lamellae in the slip direction. However, no clear correlation was found for a scaling of this orientation factor with the hardness. Possible interpretations of this discrepancy are suggested.

  12. Simultaneous characterization of elemental segregation and cementite networks in high carbon steel products by spatially-resolved laser-induced breakdown spectroscopy

    International Nuclear Information System (INIS)

    The reliable characterization of the level of elemental segregation and of the extent of grain-boundary cementite networks in high carbon steel products is a prerequisite for checking product quality, for the purpose of product release to customers, and to investigate the presence of defects that may have led to mechanical property failure of the product. Current methods for the characterization of segregation and cementite networks rely on two different methods of sample etching followed by visual observation, where quality scores are given based on human perception and judgment. With the continuous demand on increasing quality, some of the conventional characterization methods and their associated scoring boards have lost relevance for the precision of characterization that is required today to distinguish between a product that will perform well and one that will not. In order to move away from a qualitative, human perception based situation for the scoring of the severity of segregation and cementite networks, a new method of data evaluation based on spatially-resolved LIBS measurements was developed to provide quantitative and simultaneous characterization of both types of defects. The quantitative assessment of segregation and cementite networks is based on the acquisition of carbon concentration maps. The ability to produce rapid scanning measurements of micro and macro-scale features with adequate spatial resolution makes LIBS the measurement method of preference for this purpose. The characterization of both different defects is extracted simultaneously and from the same carbon concentration map following a series of statistical treatment and data extraction rules. LIBS results were validated against recognized methods and were applied to a significant number of routine samples. The new LIBS method offers a step change improvement in reliability for the characterization of segregation and cementite networks in steel products over the conventional methods

  13. A low-cost cementite (Fe3C) nanocrystal@N-doped graphitic carbon electrocatalyst for efficient oxygen reduction.

    Science.gov (United States)

    Wu, Tianxing; Zhang, Haimin; Zhang, Xian; Zhang, Yunxia; Zhao, Huijun; Wang, Guozhong

    2015-11-01

    In this work, chitosan whiskers (CWs) were first extracted using low-cost and earth-abundant crab shells as materials by a series of chemical processes, and then assembled into chitosan whisker microspheres (CWMs) via a simple photochemical polymerization approach. Subsequently, a cementite (Fe3C) nanocrystal@N-doped graphitic carbon (Fe3C@NGC) nanocomposite was successfully fabricated by high temperature pyrolysis of CWMs adsorbed with ferric acetylacetonate (Fe(acac)3) at 900 °C. It was found that a suitable growth atmosphere generated inside CWMs during high temperature pyrolysis is critically important to form Fe3C nanocrystal cores, concurrently accompanying a structural transformation from chitosan whiskers to mesoporous graphitic carbon shells with natural nitrogen (N) doping properties, resulting in the formation of a core-shell structure Fe3C@NGC nanocomposite. The resulting samples were evaluated as electrocatalysts for oxygen reduction reaction (ORR). In comparison with sole N-doped graphitic carbon without Fe3C nanocrystals obtained by direct pyrolysis of chitosan whisker microspheres at 900 °C (CWMs-900), Fe3C@NGC showed significantly improved ORR catalytic activity. The tolerance to fuel cell molecules (e.g., methanol) and the durability of Fe3C@NGC are obviously superior to commercial Pt/C catalysts in alkaline media. The high ORR performance of Fe3C@NGC could be due to its large surface area (313.7 m(2) g(-1)), a synergistic role of Fe3C nanocrystals, N doping in graphitic carbon creating more catalytic active sites, and a porous structure of the nanocomposite facilitating mass transfer to efficiently improve the utilization of these catalytic active sites.

  14. A first-principles study of cementite (Fe{sub 3}C) and its alloyed counterparts: Elastic constants, elastic anisotropies, and isotropic elastic moduli

    Energy Technology Data Exchange (ETDEWEB)

    Ghosh, G., E-mail: g-ghosh@northwestern.edu [Department of Materials Science and Engineering, Robert R. McCormick School of Engineering and Applied Science, Northwestern University, 2220 Campus Drive, Evanston, IL 60208-3108 (United States)

    2015-08-15

    A comprehensive computational study of elastic properties of cementite (Fe{sub 3}C) and its alloyed counterparts (M{sub 3}C (M = Al, Co, Cr, Cu, Fe, Hf, Mn, Mo, Nb, Ni, Si, Ta, Ti, V, W, Zr, Cr{sub 2}FeC and CrFe{sub 2}C) having the crystal structure of Fe{sub 3}C is carried out employing electronic density-functional theory (DFT), all-electron PAW pseudopotentials and the generalized gradient approximation for the exchange-correlation energy (GGA). Specifically, as a part of our systematic study of cohesive properties of solids and in the spirit of materials genome, following properties are calculated: (i) single-crystal elastic constants, C{sub ij}, of above M{sub 3}Cs; (ii) anisotropies of bulk, Young’s and shear moduli, and Poisson’s ratio based on calculated C{sub ij}s, demonstrating their extreme anisotropies; (iii) isotropic (polycrystalline) elastic moduli (bulk, shear, Young’s moduli and Poisson’s ratio) of M{sub 3}Cs by homogenization of calculated C{sub ij}s; and (iv) acoustic Debye temperature, θ{sub D}, of M{sub 3}Cs based on calculated C{sub ij}s. We provide a critical appraisal of available data of polycrystalline elastic properties of alloyed cementite. Calculated single crystal properties may be incorporated in anisotropic constitutive models to develop and test microstructure-processing-property-performance links in multi-phase materials where cementite is a constituent phase.

  15. TEM study of bainitic low-carbon HSLA steel: the orientation relationships of cementite; TEM-Untersuchung eines kohlenstoffarmen bainitischen HSLA-Stahls: die Orientierungsbeziehungen von Zementit

    Energy Technology Data Exchange (ETDEWEB)

    Illescas, S.; Fernandez, J.; Guilemany, J.M. [Barcelona Univ. (Spain). Dept. de Ciencia dels Materials i Enginyeria Metallurgica; Asensio, J. [Oviedo Univ. (Spain). Dept. de Ciencia de los Materiales e Ingenieria Metalurgica

    2007-07-15

    Two different bainitic structures can be present in steel depending on the heat treatment to which the samples are subjected. The two different types of bainitic structures exhibit a different orientation relationship between the cementite and the ferrite matrix. The Pitsch orientation relationship is observed in upper bainite while the Bagaryatski orientation relationship is observed in lower bainite. Different heat treatment samples of low-carbon high strength low alloy (HSLA) steel were studied using TEM observations in order to ascertain the orientation relationship between ferrite and carbide in the different bainitic structures and to determine whether this relationship may indicate the type of bainitic structure. (orig.)

  16. Microstructural evolution of lamellar cementite in eutectoid steels by cold rolling%共析钢中片层状渗碳体冷轧后的形态变化

    Institute of Scientific and Technical Information of China (English)

    王莉; 郝士明

    2005-01-01

    The pearlitic transformation and the deformation behavior of lamellar cementite after cold rolling in eutectoid steels Fe-0.76%C-0. 137%Mn (mass fraction) were studied by means of Formastor-F (Full Automatic Transformation Testing Instrument) and field emission scanning electronic microscopy (FESEM) observation. Fine and coarse pearlite were obtained in the eutectoid steels austenitized at 900 ℃ for 15min, then hold at 620 ℃ for 90 s and 690 ℃ for 7 h, respectively. Thedeformation behavior of cold rolled lamellar cementite could be classified as: cleavage fracture, inhomogeneous slip, fragmentation, thinning or necking, and homogeneous bending. The cementite lamellae with the thickness of more than 100 nm could be deformed plastically.

  17. Cascades in model steels: The effect of cementite (Fe3C) and Cr23C6 particles on short-term crystal damage

    Science.gov (United States)

    Henriksson, K. O. E.

    2015-06-01

    Ferritic stainless steel can be modeled as an iron matrix containing precipitates of cementite (Fe3C) and Cr23C6. When used in nuclear power production the steels in the vicinity of the core start to accumulate damage due to neutrons. The role of the afore-mentioned carbides in this process is not well understood. In order to clarify the situation bulk cascades created by primary recoils in model steels have been carried out in the present work. Investigated configurations consisted of bulk ferrite containing spherical particles (diameter of 4 nm) of either (1) Fe3C or (2) Cr23C6. Primary recoils were initiated at different distances from the inclusions, with recoil energies varying between 100 eV and 1 keV. Results for the number of point defects such as vacancies and antisites are presented. These findings indicate that defects are also remaining when cascades are started outside the carbide inclusions. The work uses a recently developed Abell-Brenner-Tersoff potential for the Fe-Cr-C system.

  18. Cascades in model steels: The effect of cementite (Fe{sub 3}C) and Cr{sub 23}C{sub 6} particles on short-term crystal damage

    Energy Technology Data Exchange (ETDEWEB)

    Henriksson, K.O.E.

    2015-06-01

    Ferritic stainless steel can be modeled as an iron matrix containing precipitates of cementite (Fe{sub 3}C) and Cr{sub 23}C{sub 6}. When used in nuclear power production the steels in the vicinity of the core start to accumulate damage due to neutrons. The role of the afore-mentioned carbides in this process is not well understood. In order to clarify the situation bulk cascades created by primary recoils in model steels have been carried out in the present work. Investigated configurations consisted of bulk ferrite containing spherical particles (diameter of 4 nm) of either (1) Fe{sub 3}C or (2) Cr{sub 23}C{sub 6}. Primary recoils were initiated at different distances from the inclusions, with recoil energies varying between 100 eV and 1 keV. Results for the number of point defects such as vacancies and antisites are presented. These findings indicate that defects are also remaining when cascades are started outside the carbide inclusions. The work uses a recently developed Abell–Brenner–Tersoff potential for the Fe–Cr–C system.

  19. REFERENCE CASES FOR USE IN THE CEMENTITOUS PARTNERSHIP PROJECT

    Energy Technology Data Exchange (ETDEWEB)

    Langton, C.; Kosson, D.; Garrabrants, A.

    2010-08-31

    The Cementitious Barriers Partnership Project (CBP) is a multi-disciplinary, multi-institution cross cutting collaborative effort supported by the US Department of Energy (DOE) to develop a reasonable and credible set of tools to improve understanding and prediction of the structural, hydraulic and chemical performance of cementitious barriers used in nuclear applications. The period of performance is >100 years for operating facilities and > 1000 years for waste management. The CBP has defined a set of reference cases to provide the following functions: (i) a common set of system configurations to illustrate the methods and tools developed by the CBP, (ii) a common basis for evaluating methodology for uncertainty characterization, (iii) a common set of cases to develop a complete set of parameter and changes in parameters as a function of time and changing conditions, (iv) a basis for experiments and model validation, and (v) a basis for improving conceptual models and reducing model uncertainties. These reference cases include the following two reference disposal units and a reference storage unit: (i) a cementitious low activity waste form in a reinforced concrete disposal vault, (ii) a concrete vault containing a steel high-level waste tank filled with grout (closed high-level waste tank), and (iii) a spent nuclear fuel basin during operation. Each case provides a different set of desired performance characteristics and interfaces between materials and with the environment. Examples of concretes, grout fills and a cementitious waste form are identified for the relevant reference case configurations.

  20. Research of the Processes of High Temperature Influence on Cementitous Concrete

    OpenAIRE

    Bodnárová, L.; Válek, J. (Jan); Sitek, L. (Libor); Foldyna, J.

    2013-01-01

    The paper focuses on analysis of behaviour of cement composite materials (concrete) exposed to high temperatures. Experimental work was focused on designing and verification of mix-design with higher resistance to action of high temperature. Concrete specimens were exposed to thermal load at the temperatures 200 °C, 400 °C, 600 °C and 900 °C with isothermal dwell 60 minutes. After exposition to high temperature, physicalmechanical properties were tested and compared to reference specimens, wh...

  1. THE EXPERIMENTAL INVESTIGATION OF THE EFFECTS OF UNCOATED CEMENTIT CARBIDE INSERT AND CUTTING PARAMETERS ON SURFACE ROUGHNESS

    Directory of Open Access Journals (Sweden)

    Hasan GÖKKAYA

    2006-01-01

    Full Text Available In this work, AISI 1030 steel has been machined on a CNC lathe without cutting fluid, at various cutting speed and feed rate values with a constant depth of cut. Effect of cutting speed and feed rate on surface rougness were investigated by machining AISI 1030 steel by a carbide insert without coating. In the experiments five different feed rate values between 0.25 and 0.45 mm/dev and three different cutting speed settings 100, 200 and 300 m/dak were used. It is found that at lower feed rates, lower surface roughness is and at higher cutting speeds, higher surface roughness values are obtained. The lessening of cutting speed about 80 % improves the surface roughness 215 %, by increasing the cut-off rate about 200 % obtained an improvement of 13% respectively.

  2. Morphology of the cementite in archaeological steels that have suffered fire; Morfologia de la cementita en aceros arqueologicos que han sufrido incendio

    Energy Technology Data Exchange (ETDEWEB)

    Criado-Martin, A. J.; Garcia, L.; Carton, M.; Criado-Portal, A. J.; Dietz, C.; Martinez, J. A.

    2013-07-01

    We present a metallographic study of archaeological artefacts of steel, had been found in different archaeological sites, which characteristic microstructures reveal that have been affected by levels of fire. Study was performed using FEG (Field Emission Gun). In the laboratory, they are reproduced structures of steels archaeological. (Author)

  3. Influence of Carbide Precipitation and Dissolution on the Microstructure of Ultra-Fine-Grained Intercritically Annealed Medium Manganese Steel

    Science.gov (United States)

    Lee, Sangwon; De Cooman, Bruno C.

    2016-07-01

    The influence of cementite precipitation and dissolution on the formation of the carbide-free, ultra-fine-grained, ferrite + austenite microstructure of medium manganese steel was analyzed. During heating to the intercritical temperature, cementite nucleates at low-angle lath martensite boundaries, austenite subsequently nucleates at ferrite/cementite boundaries, and the cementite is gradually replaced by the growing austenite grains. The intercritical austenite carbon is therefore due to cementite dissolution, rather than carbon partitioning between ferrite and austenite.

  4. 用于直接拉拔的低渗碳体含量的珠光体盘条%Pearlitic Steel Wire Rods with Low Cementite Volume Fraction for Direct Drawing

    Institute of Scientific and Technical Information of China (English)

    Chul Min Bae; Young Jun Song; Seong Wook Yim; 窦光聚

    2004-01-01

    具有几乎全珠光体的中碳钢线材可以不经过铅浴淬火直接拉拔到Ф1.0mm钢丝,通过控制奥氏体晶粒尺寸和转变温度可得到这种组织,但在斯太尔摩(Stelmor)生产线上控制这种组织有些困难,因此,添加合金元素是用于斯太尔摩生产线上增加线材的珠光体体积分数的有效方法。Cr和Mn是减少

  5. Determination of the easy axes of small ferromagnetic precipitates in a bulk material by combined magnetic force microscopy and electron backscatter diffraction techniques

    Energy Technology Data Exchange (ETDEWEB)

    Batista, L., E-mail: leonardo.batista@izfp.fraunhofer.de [Fraunhofer Institute for Non-destructive Testing (IZFP), Campus E3 1, 66123 Saarbrücken (Germany); Rabe, U. [Fraunhofer Institute for Non-destructive Testing (IZFP), Campus E3 1, 66123 Saarbrücken (Germany); University of the Saarland, LZPQ, 66123 Saarbrücken (Germany); Hirsekorn, S. [Fraunhofer Institute for Non-destructive Testing (IZFP), Campus E3 1, 66123 Saarbrücken (Germany)

    2014-11-15

    A method to determine the magnetic easy axes of micro- and nanoscopic ferromagnetic precipitates embedded in a bulk material is proposed and applied to globular cementite (Fe{sub 3}C) embedded in a ferrite matrix. The method combines magnetic force microscopy (MFM) with electron backscattered diffraction (EBSD) measurements. Magnetic domain structures in globular and in lamellar cementite precipitates in unalloyed pearlitic steels were imaged using MFM. The domain structure of the precipitates was analyzed in dependency of their size, shape and crystallographic orientation. It was found that the magnetic moments of the cementite precipitates are highly geared to their crystalline axes. The combined MFM and EBSD studies allow the conclusion that the cementite easy direction of magnetization is the long [010] axis. For fine lamellae cementite the determination of their crystallographic orientations using electron diffraction techniques is very difficult. With the previous knowledge of the behavior of the domain structure in globular cementite, the crystalline orientations of the fine lamellae cementite can be estimated by simply observing the magnetic microstructures and the topographic profiles. - Highlights: • We develop a method to determine the easy axes of nanoscopic ferromagnetic precipitates in a matrix. • We combine the magnetic force microscopy and the electron backscatter diffraction techniques. • Globular and lamellar cementite (Fe{sub 3}C) precipitates are taken as examples. • MFM images revealed different orientations of the magnetic moments in cementite. • The cementite easy direction of magnetization is the long [010] axis.

  6. Determination of the easy axes of small ferromagnetic precipitates in a bulk material by combined magnetic force microscopy and electron backscatter diffraction techniques

    International Nuclear Information System (INIS)

    A method to determine the magnetic easy axes of micro- and nanoscopic ferromagnetic precipitates embedded in a bulk material is proposed and applied to globular cementite (Fe3C) embedded in a ferrite matrix. The method combines magnetic force microscopy (MFM) with electron backscattered diffraction (EBSD) measurements. Magnetic domain structures in globular and in lamellar cementite precipitates in unalloyed pearlitic steels were imaged using MFM. The domain structure of the precipitates was analyzed in dependency of their size, shape and crystallographic orientation. It was found that the magnetic moments of the cementite precipitates are highly geared to their crystalline axes. The combined MFM and EBSD studies allow the conclusion that the cementite easy direction of magnetization is the long [010] axis. For fine lamellae cementite the determination of their crystallographic orientations using electron diffraction techniques is very difficult. With the previous knowledge of the behavior of the domain structure in globular cementite, the crystalline orientations of the fine lamellae cementite can be estimated by simply observing the magnetic microstructures and the topographic profiles. - Highlights: • We develop a method to determine the easy axes of nanoscopic ferromagnetic precipitates in a matrix. • We combine the magnetic force microscopy and the electron backscatter diffraction techniques. • Globular and lamellar cementite (Fe3C) precipitates are taken as examples. • MFM images revealed different orientations of the magnetic moments in cementite. • The cementite easy direction of magnetization is the long [010] axis

  7. Molecular dynamics simulation of nanoindentation on nanocomposite pearlite

    OpenAIRE

    Ghaffarian, Hadi; Taheri, Ali Karimi; Ryu, Seunghwa; Kang, Keonwook

    2016-01-01

    We carry out molecular dynamics simulations of nanoindentation to investigate the effect of cementite size and temperature on the deformation behavior of nanocomposite pearlite composed of alternating ferrite and cementite layers. We find that, instead of the coherent transmission, dislocation propagates by forming a widespread plastic deformation in cementite layer. We also show that increasing temperature enhances the distribution of plastic strain in the ferrite layer, which reduces the st...

  8. Characteristic Features of Nanoscale Сarbide Inclusions Nucleation and Growth When Carburizing Steels

    Directory of Open Access Journals (Sweden)

    L.I. Roslyakova

    1990-01-01

    Full Text Available Thermodynamic calculations of the free energy of the formation of cementite type nanoscale carbides in supersaturated austenite alloyed with chromium and manganese are presented. It is shown that when carburizing steel, chromium stabilizing cementite facilitates its separation, in the form of dispersed inclusions. Manganese stabilizes cementite much weaker than chromium, though facilitates the growth of carbide inclusions due to the formation of the intermediate ε-phase at a reduced carbon content.

  9. Microstructure of Hot Rolled 1.0C-1.5Cr Bearing Steel and Subsequent Spheroidization Annealing

    Science.gov (United States)

    Li, Zhen-Xing; Li, Chang-Sheng; Zhang, Jian; Li, Bin-Zhou; Pang, Xue-Dong

    2016-07-01

    The effect of final rolling temperature and cooling process on the microstructure of 1.0C-1.5Cr bearing steel was studied, and the relationship between the microstructure parameters and subsequent spheroidization annealing was analyzed. The results indicate that the increase of water-cooling rate after hot rolling and the decrease of final cooling temperature are beneficial to reducing both the pearlite interlamellar spacing and pearlite colony size. Prior austenite grain size can be reduced by decreasing the final rolling temperature and increasing the water-cooling rate. When the final rolling temperature was controlled around 1103 K (830 °C), the subsequent cooling rate was set to 10 K/s and final cooling temperature was 953 K (680 °C), the precipitation of grain boundary cementite was suppressed effectively and lots of rod-like cementite particles were observed in the microstructure. Interrupted quenching was employed to study the dissolution behavior of cementite during the austenitizing at 1073 K (800 °C). The decrease of both pearlite interlamellar spacing and pearlite colony size could facilitate the initial dissolution and fragmentation of cementite lamellae, which could shorten the spheroidization time. The fragmentation of grain boundary cementite tends to form large-size undissolved cementite particles. With the increase of austenitizing time from 20 to 300 minutes, mean diameter of undissolved cementite particles increases, indicating the cementite particle coarsening and cementite dissolution occuring simultaneously. Mean diameter of cementite particles in the final spheroidized microstructure is proportional to the mean diameter of undissolved cementite particles formed during partial austenitizing.

  10. Magnetic carbon nanostructures: microwave energy-assisted pyrolysis vs. conventional pyrolysis.

    Science.gov (United States)

    Zhu, Jiahua; Pallavkar, Sameer; Chen, Minjiao; Yerra, Narendranath; Luo, Zhiping; Colorado, Henry A; Lin, Hongfei; Haldolaarachchige, Neel; Khasanov, Airat; Ho, Thomas C; Young, David P; Wei, Suying; Guo, Zhanhu

    2013-01-11

    Magnetic carbon nanostructures from microwave assisted- and conventional-pyrolysis processes are compared. Unlike graphitized carbon shells from conventional heating, different carbon shell morphologies including nanotubes, nanoflakes and amorphous carbon were observed. Crystalline iron and cementite were observed in the magnetic core, different from a single cementite phase from the conventional process.

  11. Atomic scale investigation of redistribution of alloying elements in pearlitic steel wires upon cold-drawing and annealing.

    Science.gov (United States)

    Li, Y J; Choi, P; Goto, S; Borchers, C; Raabe, D; Kirchheim, R

    2013-09-01

    A local electrode atom probe has been employed to analyze the redistribution of alloying elements including Si, Mn, and Cr in pearlitic steel wires upon cold-drawing and subsequent annealing. It has been found that the three elements undergo mechanical mixing upon cold-drawing at large strains, where Mn and Cr exhibit a nearly homogeneous distribution throughout both ferrite and cementite, whereas Si only dissolves slightly in cementite. Annealing at elevated temperatures leads to a reversion of the mechanical alloying. Si atoms mainly segregate at well-defined ferrite (sub)grain boundaries formed during annealing. Cr and Mn are strongly concentrated in cementite adjacent to the ferrite/cementite interface due to their lower diffusivities in cementite than in ferrite. PMID:23237772

  12. Atomic scale investigation of redistribution of alloying elements in pearlitic steel wires upon cold-drawing and annealing

    Energy Technology Data Exchange (ETDEWEB)

    Li, Y.J., E-mail: y.li@mpie.de [Institut für Materialphysik, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, D-37077 Göttingen (Germany); Max-Planck Institut für Eisenforschung, Max-Planck-Str. 1, D-40237 Düsseldorf (Germany); Choi, P. [Max-Planck Institut für Eisenforschung, Max-Planck-Str. 1, D-40237 Düsseldorf (Germany); Goto, S. [Department of Materials Science and Engineering, Faculty of Engineering and Resource Science, Akita University, Tegata Gakuencho, Akita 010-8502 (Japan); Borchers, C. [Institut für Materialphysik, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, D-37077 Göttingen (Germany); Raabe, D., E-mail: d.raabe@mpie.de [Max-Planck Institut für Eisenforschung, Max-Planck-Str. 1, D-40237 Düsseldorf (Germany); Kirchheim, R. [Institut für Materialphysik, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, D-37077 Göttingen (Germany); Max-Planck Institut für Eisenforschung, Max-Planck-Str. 1, D-40237 Düsseldorf (Germany)

    2013-09-15

    A local electrode atom probe has been employed to analyze the redistribution of alloying elements including Si, Mn, and Cr in pearlitic steel wires upon cold-drawing and subsequent annealing. It has been found that the three elements undergo mechanical mixing upon cold-drawing at large strains, where Mn and Cr exhibit a nearly homogeneous distribution throughout both ferrite and cementite, whereas Si only dissolves slightly in cementite. Annealing at elevated temperatures leads to a reversion of the mechanical alloying. Si atoms mainly segregate at well-defined ferrite (sub)grain boundaries formed during annealing. Cr and Mn are strongly concentrated in cementite adjacent to the ferrite/cementite interface due to their lower diffusivities in cementite than in ferrite. - Highlights: ► Mechanical alloying effect is studied on Mn, Si, and Cr in pearlite. ► Severe cold-drawing forces Mn and Cr into the ferrite. ► Si is only somewhat forced into the cementite. ► Following annealing, Si prefers to segregate at ferrite (sub)grain boundaries. ► Following annealing, Cr and Mn are strongly enriched in cementite.

  13. Mechanism of Austenite Formation from Spheroidized Microstructure in an Intermediate Fe-0.1C-3.5Mn Steel

    Science.gov (United States)

    Lai, Qingquan; Gouné, Mohamed; Perlade, Astrid; Pardoen, Thomas; Jacques, Pascal; Bouaziz, Olivier; Bréchet, Yves

    2016-07-01

    The austenitization from a spheroidized microstructure during intercritical annealing was studied in a Fe-0.1C-3.5Mn alloy. The austenite grains preferentially nucleate and grow from intergranular cementite. The nucleation at intragranular cementite is significantly retarded or even suppressed. The DICTRA software, assuming local equilibrium conditions, was used to simulate the austenite growth kinetics at various temperatures and for analyzing the austenite growth mechanism. The results indicate that both the mode and the kinetics of austenite growth strongly depend on cementite composition. With sufficiently high cementite Mn content, the austenite growth is essentially composed of two stages, involving the partitioning growth controlled by Mn diffusion inside ferrite, followed by a stage controlled by Mn diffusion within austenite for final equilibration. The partitioning growth results in a homogeneous distribution of carbon within austenite, which is supported by NanoSIMS carbon mapping.

  14. Characterization of Nanocrystallizatin Surface Layer of 0.4C-1Cr Low Alloy Steel Prepared by Ultrasonic Particulate Peening

    Institute of Scientific and Technical Information of China (English)

    ZHANGJun-bao; LIUYu-liang; ZHAOXin-qi; WUJie; SONGHong-wei; XIONGTian-ying

    2004-01-01

    A nanostructured surface layer was fabricated in a quenched and tempered 0.4C-ICr low alloy steel by ultrasonic particulate peening technique. The microstructure of the nanocrystalline surface layer was characterized by means of TEM and Moessbauer spectroscopy. Experimental results reveal that both cementite and ferrite nanocrystals with an average size of 5 nm were formed in the surface layer of the steel, phase transformation of austenite and dissolution of cementite maybe occur in the process of ultrasonic particulate peening.

  15. Characterization of Nanocrystallizatin Surface Layer of 0.4C-1Cr Low Alloy Steel Prepared by Ultrasonic Particulate Peening

    Institute of Scientific and Technical Information of China (English)

    ZHANG Jun-bao; LIU Yu-liang; ZHAO Xin-qi; WU Jie; SONG Hong-wei; XIONG Tian-ying

    2004-01-01

    A nanostructured surface layer was fabricated in a quenched and tempered 0.4C-1Cr low alloy steel by ultrasonic particulate peening technique. The microstructure of the nanocrystalline surface layer was characterized by means of TEM and Mossbauer spectroscopy. Experimental results reveal that both cementite and ferrite nanocrystals with an average size of 5 nm were formed in the surface layer of the steel, phase transformation of austenite and dissolution of cementite maybe occur in the process of ultrasonic particulate peening.

  16. CEL Working procedures for WRAP 2A formulation development test

    International Nuclear Information System (INIS)

    The WRAP 2A facility will encapsulate retrieved, stored, and newly generated contact-handled mixed low level waste (MLLW) into 55-500 gal cementitous forms. Standardized test procedures will be required to facilitate this process. Cementitous specimens will be prepared from simulated drum wastes and will be tested in the Chemical Engineering Laboratory using the laboratory operating/working procedures encorporated into this document

  17. Influence of Electropulsing Pretreatment on Solid-State Graphitization of Spherical Graphite Iron

    Institute of Scientific and Technical Information of China (English)

    LI Qing-chun; LI Ren-xing; LIN Da-shuai; CHANG Guo-wei; ZHAI Qi-jie

    2012-01-01

    The solid-state graphitization process of spherical graphite iron after electropulsing pretreatment was ob- served in-situ by using a high-temperature confocal scanning laser microscope (HTCSLM). The influence of electro- pulsing pretreatment on the decomposition of cementite and the formation of graphite during the solid-state graphiti- zation was studied. The result indicates that the electropulsing pretreatment can accelerate the decomposition of ce mentite, and make more neonatal graphite in small size be formed near the cementite. The neonatal graphite nucle ates and grows chiefly at the temperature range of 800 to 850 ℃, and the average growth rate of neonatal graphite is 0. 034 μm2/s during the heating process. For the spherical graphite iron after normal and electropulsing pretreat- ment, the decomposition rate of cementite during the heating process is 0.16 and 0.24 μm2/s, respectively. Analy- sis shows that the electropulsing pretreatment promotes the dislocation accumulation near the cementite, conse- quently, the decomposition of cementite and the formation of neonatal graphite is accelerated during the solid-state graphitization.

  18. Revealing microstructural and mechanical characteristics of cold-drawn pearlitic steel wires undergoing simulated galvanization treatment

    International Nuclear Information System (INIS)

    Highlights: ► Annealing time on microstructure and mechanical properties of cold-drawn steel wires were studied. ► Exothermic peak in cold-drawn wire was resulting from the spheroidization of lamellar cementite. ► Spheroidization of lamellar cementite is the main effect for torsion property of wires after annealing. - Abstract: Spheroidization of lamellar cementite often occurs in cold-drawn pearlitic steel wires during galvanizing treatment, leading to the degradation of mechanical properties. Therefore, it is important to understand effects of galvanization process on microstructure and mechanical properties of cold-drawn wires. In this paper, cold-drawn steel wires were fabricated by cold drawing pearlitic steel rods from 13 mm to 6.9 mm in diameter. Thermal annealing at 450 °C was used to simulate galvanizing treatment of steel wires. Tensile strength, elongation and torsion laps of steel rods and wires with, and without, annealing treatment were determined. Microstructure was observed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). In addition, differential scanning calorimetry (DSC) was used to probe the spheroidization temperature of cementite. Experimental results showed that tensile strength of wires increased from 1780 MPa to 1940 MPa for annealing 10 min. Elongation of wires decreased for annealing 5 min. Tensile strength and elongation of wires were both influenced by the strain age hardening and static recovery processes. Notably, torsion laps of wires hardly changed when annealing time was less than 2.5 min, and then decreased rapidly. Its value became constant when the hold time is greater than 10 min. Lamellar cementite began to spheroidize at annealing >2.5 min, starting at the boundary of pearlitic grains, and moving inward. A broad exothermic peak was found at temperatures between 380 °C and 480 °C, resulting primarily from the spheroidization of lamellar cementite, which is responsible for the

  19. Valence electron theory of graphite spheroidizing in primary crystallization

    Institute of Scientific and Technical Information of China (English)

    刘志林; 孙振国; 李志林

    1995-01-01

    Bond-length-difference (BLD) analysis results show that austenrte and cementite containing Mg, Zr. S have very different valence electron structures from Fe -C austenite and cementite. We find that this difference is the tie of absorption hypothesis, surface tension hypothesis, undercooling hypothesis in graphite spheroidizing theory. By using "the model of valence electron theory of drag-like effect" in our previous paper in crystallization theory, the spheroidizing effect of Mg and Zr and the anti-spheroidizing effect of S can be explained with the valence electron structure data of phases. Therefore, electron theory of graphite spheroidizing can be advanced.

  20. Chemical transformations in the zone of spall damageability

    Science.gov (United States)

    Buravova, S. N.; Petrov, E. V.; Alymov, M. I.

    2016-07-01

    The results of experiments on studying the perlite-ferrite structure in steels under short-term negative pressures are described. It is shown that in the localized deformation bands formed in the zone of interference of unloading waves, where the tension stress is lower than the dynamic strength of the material, the cementite bands in perlite are crushed, their fragments are in part dissolved and enriched with carbon, and the cementite can pass into a steady spherical form on the boundary with ferrite. At relatively high shock-wave amplitudes, the perlite in its entirety acquires a spheroidal shape.

  1. Magnetic-field-induced microstructural features in a high carbon steel during diffusional phase transformation

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Xiaoxue, E-mail: zhangxiaoxue1213@gmail.com [Key Laboratory for Anisotropy and Texture of Materials (MOE), Northeastern University, Shenyang 110004 (China); Laboratoire d' Etude des Microstructures et de Mecanique des Materiaux (LEM3), CNRS UMR 7239, Universite de Lorraine UL 57045 Metz (France); Laboratory of Excellence on Design of Alloy Metals for low-mAss Structures (DAMAS), Universite de Lorraine (France); Zhang, Yudong, E-mail: yudong.zhang@univ-metz.fr [Laboratoire d' Etude des Microstructures et de Mecanique des Materiaux (LEM3), CNRS UMR 7239, Universite de Lorraine UL 57045 Metz (France); Laboratory of Excellence on Design of Alloy Metals for low-mAss Structures (DAMAS), Universite de Lorraine (France); Gong, Minglong, E-mail: gml@mail.neuq.edu.cn [Key Laboratory for Anisotropy and Texture of Materials (MOE), Northeastern University, Shenyang 110004 (China); Esling, Claude, E-mail: claude.esling@univ-metz.fr [Laboratoire d' Etude des Microstructures et de Mecanique des Materiaux (LEM3), CNRS UMR 7239, Universite de Lorraine UL 57045 Metz (France); Laboratory of Excellence on Design of Alloy Metals for low-mAss Structures (DAMAS), Universite de Lorraine (France); Zhao, Xiang, E-mail: zhaox@mail.neu.edu.cn [Key Laboratory for Anisotropy and Texture of Materials (MOE), Northeastern University, Shenyang 110004 (China); Zuo, Liang, E-mail: lzuo@mail.neu.edu.cn [Key Laboratory for Anisotropy and Texture of Materials (MOE), Northeastern University, Shenyang 110004 (China)

    2012-12-15

    In this work, a high purity, high carbon steel was heat treated without and with a 12-T magnetic field. The microstructural features induced by magnetic field during its diffusion-controlled austenite decomposition were investigated by means of optical microscopy and SEM/EBSD. It is found that the magnetic field increases the amount of the abnormal structure, which is composed of proeutectoid cementite along the prior austenite boundaries and ferrite around it, because magnetic field increases the austenite grain size and promotes the transformation of carbon-depleted austenite to ferrite. No specific orientation relationship between abnormal ferrite and cementite has been found in the non-field- or the field-treated specimens. Magnetic field evidently promotes the spheroidization of pearlite, due to its effect of enhancing carbon diffusion through raising the transformation temperature and its effect of increasing the relative ferrite/cementite interface energy. As magnetic field favors the nucleation of the high magnetization phase-pearlitic ferrite, the occurrence of the P-P2 OR that corresponds to the situation that ferrite nucleates prior to cementite during pearlitic transformation is enhanced by the magnetic field. - Highlights: Black-Right-Pointing-Pointer The field-induced microstructural features in a high carbon steel during diffusional phase transformation has been investigated. Black-Right-Pointing-Pointer Magnetic field increases the amount of the abnormal structure and promotes the spheroidization of pearlite. Black-Right-Pointing-Pointer Magnetic field enhances the occurrence of the P-P2 OR.

  2. Structural, electronic, and magnetic properties of iron carbide Fe7C3 phases from first-principles theory

    NARCIS (Netherlands)

    Fang, C.M.; Van Huis, M.A.; Zandbergen, H.W.

    2009-01-01

    The iron carbide Fe7C3 exhibits two types of basic crystal structures, an orthorhombic (o-) form and a hexagonal (h-) one. First-principles calculations have been performed for the basic Fe7C3 forms and for the related θ-Fe3C cementite phase. Accurate total-energy calculations show that the stabilit

  3. Void nucleation in spheroidized steels during tensile deformation

    Energy Technology Data Exchange (ETDEWEB)

    Fisher, Jr, J R

    1980-04-01

    An investigation was conducted to determine the effects of various mechanical and material parameters on void formation at cementite particles in axisymmetric tensile specimens of spheroidized plain carbon steels. Desired microstructures for each of three steel types were obtained. Observations of void morphology with respect to various microstructural features were made using optical and scanning electron microscopy.

  4. Numerical modeling of coupled heat transfer and phase transformation for solidification of the gray cast iron

    DEFF Research Database (Denmark)

    Jabbari, Masoud; Hosseinzadeh, Azin

    2013-01-01

    In the present study the numerical model in 2D is used to study the solidification bahavior of the gray cast iron. The conventional heat transfer is coupled with the proposed micro-model to predict the amount of different phases, i.e. total austenite (c) phase, graphite (G) and cementite (C), in...

  5. Thermal Stability of Nanocrystalline Structure In X37CrMoV5-l Steel

    Directory of Open Access Journals (Sweden)

    Skołek E.

    2015-04-01

    Full Text Available The aim of the study was to investigate the thermal stability of the nanostructure produced in X37CrMoV5-1 tool steel by austempering heat treatment consisted of austenitization and isothermal quenching at the range of the bainitic transformation. The nanostructure was composed of bainitic ferrite plates of nanometric thickness separated by thin layers of retained austenite. It was revealed, that the annealing at the temperature higher than temperature of austempering led to formation of cementite precipitations. At the initial stage of annealing cementite precipitations occurred in the interfaces between ferritic bainite and austenite. With increasing temperature of annealing, the volume fraction and size of cementite precipitations also increased. Simultaneously fine spherical Fe7C3 carbides appeared. At the highest annealing temperature the large, spherical Fe7C3 carbides as well as cementite precipitates inside the ferrite grains were observed. Moreover the volume fraction of bainitic ferrite and of freshly formed martensite increased in steel as a result of retained austenite transformation during cooling down to room temperature.

  6. The microstructural evolution, crystallography, and thermal processing of ultrahigh carbon Fe-1.85 pct C melt-spun ribbon

    Science.gov (United States)

    Spanos, G.; Ayers, J. D.; Vold, C. L.; Locci, I. E.

    1993-01-01

    A study is presented to determine if fine microstructures could be achieved using rapid solidification to produce a fine-grained fully austenitic starting structure and then using thermal processing cycles to produce an even finer ferrite-cementite structure. The evolution, mechanisms of grain refinement, and crystallography of the resultant microstructures were examined by TEM. A thermal processing cycle consisted of quenching the ribbon in liquid nitrogen, tempering at 600 C for 10 sec, 'upquenching' to 750 C for 10 sec, and subsequently quenching again in liquid nitrogen. The heat-treatment resulted in martensite grains with sizes of about 1 micron or less in both length and thickness and cementite particles of 0.4 micron or less. It is concluded that these microstructures could be used for producing fine-grained ultrahigh carbon steels of very high strength without the brittleness associated with the formation of coarse carbide particles of the loss of strength due to graphite formation.

  7. Atomistic modelling of the Fe-Cr-C system

    Science.gov (United States)

    Wallenius, Janne; Sandberg, Nils; Henriksson, Krister

    2011-08-01

    For the purpose of modelling the impact of carbon on radiation damage phenomena in steels, we have performed an extensive set of first principle calculations on the Fe-Cr-C system. The calculated solution and diffusion enthalpies of carbon in iron and in chromium agree well with experimental data, as do the relative formation energies of mono-carbides, cementite, Hägg and M 23C 6 carbides. Our data further indicate that interstitial carbon is attracted to a solute iron atom in bcc chromium, while the reaction between carbon and a solute chromium atom in bcc iron is repulsive. An empirical potential fitted to data for iron carbides is capable of reproducing melting behaviour of cementite, while the predicted interaction with point defects agrees less well with DFT data than a potential recently published by Hepburn and Ackland.

  8. Effect of annealing cooling rate on microstructure and mechanical property of 100Cr6 steel ring manufactured by cold ring rolling process

    Institute of Scientific and Technical Information of China (English)

    魏文婷; 吴敏

    2014-01-01

    Pre-heat treatment is a vital step before cold ring rolling and it has significant effect on the microstructure and mechanical properties of rolled rings. The 100Cr6 steel rings were subjected to pre-heat treatment and subsequent cold rolling process. Scanning electron microscopy and tensile tests were applied to investigate microstructure characteristic and mechanical property variations of 100Cr6 steel rings undergoing different pre-heat treatings. The results indicate that the average diameter of carbide particles, the tensile strength and hardness increase, while the elongation decreases with the decrease of cooling rate. The cooling rate has minor effect on the yield strength of sample. After cold ring rolling, the ferrite matrix shows a clear direction along the rolling direction. The distribution of cementite is more homogeneous and the cementite particles are finer. Meanwhile, the hardness of the rolled ring is higher than that before rolling.

  9. Reheating Austenitizing Temperature of Spring Steel 60Si2MnA for Railway

    Institute of Scientific and Technical Information of China (English)

    CUI Juan; LIU Ya-zheng; PAN Hui; GAO Li-feng

    2008-01-01

    The microsturctural transformation of austenite grain,pearlite interlamellar spacing,and lamellar cementite thickness of spring steel 60Si2MnA for railway were studied in the hot-rolled and reheated states.Furthermore,the effect of microstructural characterization on its final mechanical properties was discussed.The results showed that as far as 60Si2MnA,the pearlite interlamellar spacing determined the hardness,whereas,the austenite grain determined the toughness.Compared with microstructure and mechanical properties in the hot-rolled state,after reheating treatment at 950℃,its average grain sizes are apparently fine and the pearlite interlamellar spacing and lamellar cementite thickness coarsen to some extent,but both hardness and impact toughness increase to HRC 48 and 8.5 J.respectively.In the course of making spring,the optimum reheating austenitizing temperature for the 60Si2MnA steel is 950℃.

  10. Study on deformation and microstructure characterizations of mild steel joints by continuous drive friction welding

    Institute of Scientific and Technical Information of China (English)

    Li Wenya; Yu Min; Li Jinglong; Gao Dalu

    2009-01-01

    Macro-deformation characteristics of continuous drive friction welded mild steel joints were examined by using one deformable workpiece (objective) and the other undeformable one (rigid). The microstructure evolution and hardness change across the joint were studied. The results show that the axial shortening and radial increment of joints increase with increasing the friction time at 1 200rpm. The cementite particles of pearlites in the weld center are uniformly distributed on the ferrite matrix, while the cementites of the pearlite in the thermal-mechanically affected zone are broken and discontinuously dispersed in the pearlite. The hardness decreases rapidly from the weld center to the parent metal under the coupled effects of heat and deformation during the rapid heating and cooling processes.

  11. Nanostructure and mechanical properties of heavily cold-drawn steel wires

    International Nuclear Information System (INIS)

    The effects of microstructure on the mechanical properties of the high-carbon steel wires were investigated. The wires were fabricated with carbon content of 0.82 and 1.02 wt.% and drawing strain from 4.12 to 4.32. The bending fatigue resistance and torsion ductility were measured by a Hunter fatigue tester and a torsion tester specially designed for fine wires. As the carbon content and drawing strain increased, the fatigue resistance and the torsional ductility of the steel wires decreased, and the tensile strength increased. To elucidate the causes of these behaviors, the microstructure in terms of lamellar spacing (λP), cementite thickness (tC) and morphology of cementite was observed using transmission electron microscopy (TEM) and 3-dimensional atom probe (3-DAP).

  12. Very high cycle fatigue behavior of SAE52100 bearing steel by ultrasonic nanocrystalline surface modification.

    Science.gov (United States)

    Cho, In Shik; He, Yinsheng; Li, Kejian; Oh, Joo Yeon; Shin, Keesam; Lee, Chang Soon; Park, In Gyu

    2014-11-01

    In this paper, the SAE52100 bearing steel contained large quantities of cementite dispersed in ferrite matrix was subjected to the ultrasonic nanocrystalline surface modification (UNSM) treatment that aims for the extension of fatigue life. The microstructure and fatigue life of the untreated and treated specimens were studied by using electron backscattered diffraction (EBSD) and transmission electron microscopy (TEM), and a developed ultra-high cycle fatigue test (UFT). After UNSM treatment, the coarse ferrite grains (- 10 μm) were refined to nanosize (- 200 nm), therefore, nanostructured surface layers were fabricated. Meanwhile, in the deformed layer, the number density and area fraction of cementite were increased up to - 400% and - 550%, respectively, which increased with the decrease in depth from the topmost treated surface. The improvement of hardness (from 200 Hv to 280 Hv) and high cycles fatigue strength by - 10% were considered the contribution of the developed nanostructure in the UNSM treated specimen. PMID:25958512

  13. Super-heater tube failure due to overheating when using bagasse as fuel

    OpenAIRE

    John Jairo Coronado Marín

    2010-01-01

    A super-heater’s boiler tubes presented external longitudinal cracks. The tubes’ external surfaces presented a reddish-white layer consisting of paraffin chains: CH, functional groups: CO, NH and sulphur compounds. This brittle layer prevented heat transfer, thereby causing increased tube temperature. Creep led to failure due to long-term overheating. The steel tubes’ microstructure presented grain growth, cementite globulisation and intergranular cracks on the external surface. The foregoing...

  14. MORPHOLOGY MODIFICATION OF CARBON CHROME MOLYBDENUM STEEL STRUCTURE INFLUENCED BY HEAT TREATMENT

    Directory of Open Access Journals (Sweden)

    V. A. Lutsenko

    2011-01-01

    Full Text Available The influence of temperature and time parameters of thermal treatment on structural change and properties of carbon chromium molybdenum steel has been studied. It has been shown that there are considerable areas with grainy morphology of cementite after high temperature tempering in the structure of steel. It assures reduction of steel microhardness by 25%, and there are no substantial structural changes after medium temperature tempering.

  15. CHANGE OF MORPHOLOGY OF THE CARBON CHROME-MOLYBDENUM STEEL STRUCTURE UNDER THE INFLUENCE OF THERMAL TREATMENT

    Directory of Open Access Journals (Sweden)

    V. A. Lutsenko

    2010-01-01

    Full Text Available Influence of temperature-temporal parameters of thermal treatment on changing of structure and characteristics of carbon chrome-molybdenum steel is studied. It is shown that there are considerable areas with granular morphology of cementite in metal structure after high-temperature tempering, what provides lowering of microhardness of steel by 25%, and after medium-temperature tempering there are no essential structural changes.

  16. MORPHOLOGY MODIFICATION OF CARBON CHROME MOLYBDENUM STEEL STRUCTURE INFLUENCEDBY HEAT TREATMENT

    OpenAIRE

    Lutsenko, V.; Anelkin, N.; Golubenko, T.; Scherbakov, V.; Lutsenko, O.

    2011-01-01

    The influence of temperature and time parameters of thermal treatment on structural change and properties of carbon chromium molybdenum steel has been studied. It has been shown that there are considerable areas with grainy morphology of cementite after high temperature tempering in the structure of steel. It assures reduction of steel microhardness by 25%, and there are no substantial structural changes after medium temperature tempering.

  17. CHANGE OF MORPHOLOGY OF THE CARBON CHROME-MOLYBDENUM STEEL STRUCTURE UNDER THE INFLUENCE OF THERMAL TREATMENT

    OpenAIRE

    V. A. Lutsenko; N. I. Anelkin; T. N. Golubenko; Shcherbakov, V. I.; O. V. Lutsenko; L. A. Drobyshevskij

    2016-01-01

    Influence of temperature-temporal parameters of thermal treatment on changing of structure and characteristics of carbon chrome-molybdenum steel is studied. It is shown that there are considerable areas with granular morphology of cementite in metal structure after high-temperature tempering, what provides lowering of microhardness of steel by 25%, and after medium-temperature tempering there are no essential structural changes.

  18. Morphology modification of carbon chrome molybdenum steel structure influenced by heat treatment

    OpenAIRE

    V. A. Lutsenko; N. L. Anelkin; T. N. Golubenko; Scherbakov, V. I.; O. V. Lutsenko

    2011-01-01

    The influence of temperature and time parameters of thermal treatment on structural change and properties of carbon chromium molybdenum steel has been studied. It has been shown that there are considerable areas with grainy morphology of cementite after high temperature tempering in the structure of steel. It assures reduction of steel microhardness by 25%, and there are no substantial structural changes after medium temperature tempering.

  19. Flexural reinforcement of concrete with textile reinforced mortar TRM

    OpenAIRE

    Gil Espert, Lluís; Escrig Pérez, Christian; Bernat Masó, Ernest

    2013-01-01

    This work presents a method of strengthening concrete structures based on textiles of high strength and mortars. The combination of textiles and mortars produces a new composite material of cementitic matrix. This material can be used for the reinforcement of concrete beams under bending loads. We tested several combinations of fibers: glass, PBO, steel and carbon fibers with mortar and we used them to reinforce precast concrete beams. All the specimens were tested with a four-point load test...

  20. Effects of MC-Type Carbide Forming and Graphitizing Elements on Thermal Fatigue Behavior of Indefinite Chilled Cast Iron Rolls

    Science.gov (United States)

    Ahiale, Godwin Kwame; Choi, Won-Doo; Suh, Yongchan; Lee, Young-Kook; Oh, Yong-Jun

    2015-11-01

    The thermal fatigue behavior of indefinite chilled cast iron rolls with various V+Nb contents and Si/Cr ratios was evaluated. Increasing the ratio of Si/Cr prolonged the life of the rolls by reducing brittle cementites. Higher V+Nb addition also increased the life through the formation of carbides that refined and toughened the martensite matrix and reduced the thermal expansion mismatch in the microstructure.

  1. Numerical modeling and experimental validation of microstructure in gray cast iron

    DEFF Research Database (Denmark)

    Jabbari, Masoud; Davami, Parviz; Varahram, Naser

    2012-01-01

    To predict the amount of different phases in gray cast iron by a finite difference model (FDM) on the basis of cooling rate (R), the volume fractions of total γ phase, graphite, and cementite were calculated. The results of phase composition were evaluated to find a proper correlation with cooling...... to correlate the phase volume fraction to hardness. The results are compared with experimental data and show reasonable agreement....

  2. Formation of internal stress fields in rails during long-term operation

    Science.gov (United States)

    Peregudov, O. A.; Morozov, K. V.; Gromov, V. E.; Glezer, A. M.; Ivanov, Yu. F.

    2016-04-01

    The structure and the internal stress fields in R65 rails withdrawn from operation because of side wear after long-term operation are studied and estimated. A high scalar dislocation density (higher by a factor of 1.5-2), the fragmentation of cementite lamellae, and the precipitation of carbide particles are detected in the layers adjacent to the roll surface. The stresses at the boundaries of the particles with the ferrite matrix can exceed the ultimate strength of the steel.

  3. Microstructure evolution during laser-aided direct metal deposition of alloy tool steel

    International Nuclear Information System (INIS)

    Laser-aided direct metal deposition has been used to form an alloy tool steel coating. The microstructure of the deposited material was analyzed by means of scanning electron microscopy and transmission electron microscopy. The formation relationships among martensite, ε-carbide, cementite and austenite in the coating are discussed. The effect of rapid solidification associated with direct metal deposition on lattice parameters is also reported.

  4. Effect of the concentrated heat flow treatment on the structure and the antiwear properties of cast iron

    Directory of Open Access Journals (Sweden)

    W. Orlowicz

    2009-04-01

    Full Text Available The influence of modes of surface fusion by electric arc plasma (GTAW method on the hardness and wear-resistance of plain cast ironwas studied. A possible mechanism of structural rearrangement in the processed material during the friction was analyzed. This mechanismis determined by specific behaviour of hardened martensitic structure under dynamic load. This martensitic structure forms a metalbasis of cementite eutectic under conditions of fast crystallisation.

  5. Influence of Ferrite Content on Fatigue Strength of Quenched and Tempered 42CrMoS4 Steel

    OpenAIRE

    Hanno, Mithaq Elias

    2012-01-01

    Specimens of steel 42CrMoS4 were quenched from the austenite (γ) and the ferrite (α) + austenite + cementite phase fields to produce fully martensitic matrices with 0 – 14 % ferrite dispersed in the matrix. After tempering at 300°C or 600°C mechanical and fatigue properties were determined. As expected yield strength, tensile strength and hardness decreased with increased tempering temperature and ferrite content. Quite unexpected, the fatigue properties were mildly affected. A small amount o...

  6. The microstructure of continuously cooled tough bainitic steel

    OpenAIRE

    García Caballero, Francisca; Capdevila, Carlos; Chao, Jesús; Cornide, J.; García Mateo, Carlos; Roelofs, H; Hasler, St; Mastrogiacomo, G.

    2010-01-01

    The influence of bainite morphology on the impact toughness behaviour of a continuously cooled cementite free low carbon C-Mn-B type of steel has been examined. Different bainite morphologies were obtained by cooling from the austenite regime to ambient temperature with different cooling rates. The resulting microstructures have been quantitatively analysed using light optical microscopy (LOM), scanning electron microscopy (SEM) and electron back scatter diffraction (EBSD) techniques. The rel...

  7. ATOM PROBE MICROANALYSIS OF WELD METAL IN A SUBMERGED ARC WELDED CHROMIUM-MOLYBDENUM STEEL

    OpenAIRE

    Josefsson, B.; Kvist, A.; Andrén, H.

    1987-01-01

    A submerged arc welded 2.25Cr - 1Mo steel has been investigated using electron microscopy and atom probe field ion microscopy. The bainitic microstructure of the as-welded steel consisted of ferrite and martensite. During heat treatment at 690°C the martensite transformed to ferrite and cementite and needle-shaped (Cr,Mo)2C carbides precipitated. Together with a substantial decrease in dislocation density, this resulted in an improvement of the toughness.

  8. Inoculation Effects of Cast Iron

    Directory of Open Access Journals (Sweden)

    E. Fraś

    2012-12-01

    Full Text Available The paper presents a solidification sequence of graphite eutectic cells of A and D types, as well as globular and cementite eutectics. The morphology of eutectic cells in cast iron, the equations for their growth and the distances between the graphite precipitations in A and D eutectic types were analyzed. It is observed a critical eutectic growth rate at which one type of eutectic transformed into another. A mathematical formula was derived that combined the maximum degree of undercooling, the cooling rate of cast iron, eutectic cell count and the eutectic growth rate. One type of eutectic structure turned smoothly into the other at a particular transition rate, transformation temperature and transformational eutectic cell count. Inoculation of cast iron increased the number of eutectic cells with flake graphite and the graphite nodule count in ductile iron, while reducing the undercooling. An increase in intensity of inoculation caused a smooth transition from a cementite eutectic structure to a mixture of cementite and D type eutectic structure, then to a mixture of D and A types of eutectics up to the presence of only the A type of eutectic structure. Moreover, the mechanism of inoculation of cast iron was studied.

  9. The Relationship Between Microstructural Evolution and Mechanical Properties of Heavy Plate of Low-Mn Steel During Ultra Fast Cooling

    Science.gov (United States)

    Wang, Bin; Wang, Zhao-dong; Wang, Bing-xing; Wang, Guo-dong; Misra, R. D. K.

    2015-07-01

    We describe here the electron microscopy and mechanical property studies that were conducted in an industrially processed 20- and 40-mm C-Mn thick plates that involved a new approach of ultrafast cooling (UFC) together with significant reduction in Mn-content of the steel by ~0.3 to 0.5 pct, in relation to the conventional C-Mn steels, with the aim of cost-effectiveness. The study demonstrated that nanoscale cementite precipitation occurred during austenite transformation in the matrix of heavy plate during UFC, providing significant precipitation strengthening. With decrease in UFC stop temperature and consequent increase in the degree of undercooling, there was a transition in the morphology of cementite from lamellar to irregular-shaped nanoscale particles in the 20 mm heavy plate. With the increase in plate thickness, nanoscale cementite precipitated in bainitic lath at the surface of 40 mm heavy plate, which significantly increased the strength and decreased the elongation. Simultaneously, microstructural evolution in hot-rolled sheets was studied via simulation experiments using laboratory rolling mill to define the limits of microstructural evolution that can obtained in the UFC process and develop an understanding of the evolved microstructure in terms of process parameters.

  10. cs of abrasive-reactive nanocomposite powder synthesis in the SiO2 − C/S system

    Directory of Open Access Journals (Sweden)

    Faryt Urakaev

    2015-03-01

    Full Text Available In this study, the syntheses of cementite (Fe3C and pyrite (FeS2 have been performed by mechanical activation of a mixture of graphite or sulfur with amorphous or crystalline silica in a planetary ball mill AGO-2 with steel fittings. XRD analysis was used to record products and changes of systems components after mechanical activation of the studied systems. The formation of nanocomposites based on cementite (or pyrite has been recorded and the quantitative characteristics of abrasive-reactive wear of steel milling tools have been evaluated. It has been demonstrated the possibility of steel material reaction of milling tools for direct mechanochemical preparation of composite based on cementite using abrasive properties of silica modifications. It has obtained nanocomposites based on pyrite and glass matrix during mechanical activation of quartz glass and sulfur in a time of 1-2 orders of magnitude lower than traditional mechanical alloying powders of iron and sulfur. It can be noted that any scrap metal and ceramic products can be used as milling tools. This significantly enhances the ability of the proposed method of abrasive-reactive nanowear of milling tools materials of mechanochemical reactors and processed materials.

  11. Effect of cyclic heat treatment on microstructure and mechanical properties of 50CrV4 steel

    Institute of Scientific and Technical Information of China (English)

    李红英; 韩茂盛; 李德望; 李俊; 徐德超

    2015-01-01

    An annealed 50CrV4 steel was subjected to cyclic heat treatment process that consists of repeated short-duration (200 s) held at 840 °C (aboveAc3 temperature of 790 °C) and short-duration (100 s) held at 700 °C (belowAc1 temperature of 710 °C). The spheroidization ratio of cementite and the average size of particles increase with increasing the cyclic number of heat treatment. After 5-cycle heat treatment, the spheroidization ratio of cementite is 100%, and the average size of the cementite particles is about 0.53μm. After cyclic heat treatment, the hardness, ultimate tensile strength and yield strength of the experimental steel gradually decrease with increasing cyclic number of heat treatment. The elongation of the as-received specimens is about 7.4%, the elongation of the 1-cycle specimen is 14.3%, and the elongation of 5-cycle specimen reaches a peak value of 22.5%, thereafter marginally decreases to 18.3% after 6-cycle heat treatment. Accordingly, the fractured surface initially exhibits the regions of wavy lamellar fracture. By increasing the cyclic number of heat treatment cycles, the regions of dimples consume the entire fractured surface gradually. Some large dimples can be found in the fracture surface of the specimen subjected to six heat treatment cycles.

  12. On-line spheroidization process of medium-carbon low-alloyed cold heading steel

    Institute of Scientific and Technical Information of China (English)

    Yu Fu; Hao Yu; Pan Tao

    2014-01-01

    Conventionally manufactured 35CrMo cold heading steel must undergo spheroidization annealing before the cold heading process. In this paper, different types of deformation processes with various controlled cooling periods were operated to achieve on-line spheroidal cementite using the Gleeble-3500 simulation technique. According to the measured dynamic ferrite transformation temperature (Ad3), the deformation could be divided into two types:low temperature deformation at 810 and 780°C;“deformation-induced ferrite transformation”(DIFT) deformation at 750 and 720°C. Compared with the low temperature deformation, the DIFT deformation followed by accelerated cooling to 680°C is beneficial for the formation of spheroidal cementite. Samples subjected to both the low-temperature deformation and DIFT deformation can obtain granular bainite by accelerated cooling to 640°C;the latter may contribute to the formation of a fine dispersion of secondary constituents. Granular bainite can transform into globular pearlite rapidly during subcritical annealing, and the more the dis-perse phase, the more homogeneously distributed globular cementite can be obtained.

  13. Atom Probe Tomography Examination of Carbon Redistribution in Quenched and Tempered 4340 Steel

    Energy Technology Data Exchange (ETDEWEB)

    Clarke, Amy J. [Los Alamos National Laboratory; Miller, Michael K. [ORNL; Alexander, David J. [Los Alamos National Laboratory; Field, Robert D. [Los Alamos National Laboratory; Clarke, Kester D. [Los Alamos National Laboratory

    2012-08-07

    Quenching and tempering produces a wide range of mechanical properties in medium carbon, low alloyed steels - Study fragmentation behavior as a function of heat-treatment. Subtle microstructural changes accompany the mechanical property changes that result from quenching and tempering - Characterize the location and distribution of carbon and alloying elements in the microstructure using atom probe tomography (APT). Perform complementary transmission electron microscopy (TEM). Tempering influences the mechanical properties and fragmentation of quenched 4340 (hemi-shaped samples). APT revealed carbon-enriched features that contain a maximum of {approx}12-14 at.% carbon after quenching to RT (the level of carbon is perhaps associated with the extent of autotempering). TEM confirmed the presence of twinned martensite and indicates {var_epsilon} ({eta}) transition carbides after oil quenching to RT. Tempering at 325 C resulted in carbon-enriched plates (> 25 at.% C) with no significant element partitioning (transition carbides?). Tempering at 450 C and 575 C resulted in cementite ({approx} 25 at.% C) during late stage tempering; Cr, Mn, Mo partitioned to cementite and Si partitioned to ferrite. Tempering at 575 C resulted in P segregation at cementite interfaces and the formation of Cottrell atmospheres.

  14. Residual stress analysis of cold-drawn pearlite steel wire using white synchrotron radiation

    International Nuclear Information System (INIS)

    Measurement of the residual stresses in cold-drawn pearlitic steel wire was conducted using an energy dispersive X-ray diffraction technique. The residual stresses of the ferrite and cementite phases were determined for different crystal orientations and large residual stresses were found to exist in the cold-drawn pearlitic steel wire. The residual stresses in the ferrite phase were compressive in the axial direction but nearly zero in the hoop and radial directions. In addition, the residual stresses of the reflection indices for the ferrite phase were similar to one another. For the cementite phase, while tensile residual stress existed in the axial direction, compressive residual stress existed in the hoop and radial directions. These stresses in the ferrite phase in the axial direction and cementite phase in all directions decreased along the radial positions. A residual stress state model was proposed on the basis of the aligned lamellar structure along the drawing direction; the model explains the effect of the lamellar direction on residual stress. Reanalysis of the wire sample using the proposed model provided residual strains and stresses in the lamellar direction that were different from the average values estimated using the simple stress analysis method. (author)

  15. Rationalisation of Austenite Transformation to Upper or Lower Bainite in Steels

    Directory of Open Access Journals (Sweden)

    Ławrynowicz Z.

    2014-06-01

    Full Text Available The paper presents an analytical evaluation of transition temperature from upper to lower bainite in Fe-C-Cr steel. The calculations was based on the model constructed by Matas and Hehemann which involves a comparison between the times needed to precipitate cementite within the bainitic ferrite plates (tθ, with the time required to decarburise supersaturated ferrite plates (td. The transition between upper and lower bainite is found to occur over a narrow range of temperatures (350-410°C and depends on the thickness of bainitic ferrite laths and the volume fraction of precipitated cementite. On comparing the td and tθ times it was found that the transition temperature from upper to lower bainite reaction (LS of about 350oC could be predicted if the thickness of bainitic ferrite laths is set as wo = 0.1 μm and volume fraction of cementite is set as ξ = 0.01

  16. CO2 corrosion resistance of carbon steel in relation with microstructure changes

    International Nuclear Information System (INIS)

    The microstructural effects on the corrosion resistance of an API 5L X42 carbon steel in 0.5 M NaCl solution saturated with CO2 was investigated. Four microstructures were considered: banded (B), normalized (N), quenched and tempered (Q&T), and annealed (A). Electrochemical measurements (polarization curves and electrochemical impedance spectroscopy) were coupled with surface analyses (scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS)) to characterize the formation of the corrosion product layers. Electrochemical results revealed that corrosion resistance increased in the following order: B < N < Q&T < A. From the polarization curves it was shown that specifically, cathodic current densities were affected by microstructural changes. SEM images indicated that ferrite dissolved earlier than cementite and a thin layer of corrosion products was deposited on the steel surface. XPS analyses revealed that this layer was composed of a mixture of iron carbonate and non-dissolved cementite. It was also found that the quantity of FeCO3 content on the steel surface was greater for Q&T and A microstructures. These results, in agreement with the electrochemical data, indicate that the deposition mechanism of iron carbonate is closely related to the morphology of the non-dissolved cementite, determining the protective properties of the corrosion product layers. - Highlights: • The effect of change in microstructure on CO2 corrosion resistance was evaluated. • An API 5LX 42 carbon steel was immersed in a 0.5 M NaCl solution saturated with CO2. • Banded, normalized, quenched-tempered and annealed microstructures were considered. • Electrochemical measurements were coupled with surface analysis. • Morphology and distribution of undissolved Fe3C control corrosion kinetics

  17. An Atom Probe Tomographic Investigation of High-Strength, High-Toughness Precipitation Strengthened Steels for Naval Applications

    Science.gov (United States)

    Hunter, Allen H.

    Novel high-strength high-toughness alloys strengthened by precipitation are investigated for use in naval applications. The mechanical properties of an experimental steel alloy, NUCu-140, are evaluated and are not suitable for the naval requirements due to poor impact toughness at -40°C. An investigation is conducted to determine optimum processing conditions to restore toughness. A detailed aging study is conducted at 450, 500, and 550°C to determine the evolution of the microstructure and mechanical properties. A combination of transmission electron microscopy (TEM), synchrotron X-ray Diffraction (XRD), and Local electrode atom probe (LEAP) tomography are used to measure the evolution of the Cu precipitates, austenite, NbC, and cementite phases during aging. The evolution of the Cu precipitates significantly affects the yield strength of the steel, but low temperature toughness is controlled by the cementite precipitates. Extended aging is effective at improving the impact toughness but the yield strength is also decreased due to coarsening of the Cu precipitates. To provide a foundation for successful welding of NUCu-140 steel, an investigation of the effects of gas metal arc welding (GMAW) are performed. The microstructures in the base metal (BM), heat affected zone (HAZ), and fusion zone (FZ) of a GMAW sample are analyzed to determine the effects of the welding thermal cycle. Weld simulation samples with known thermal histories are prepared and analyzed by XRD and LEAP tomography. A significant loss in microhardness is observed as a result of dissolution of the Cu precipitates after the weld thermal cycle. The cooling time is too rapid to allow significant precipitation of Cu. In addition to the NUCu-140 alloy, a production HSLA-115 steel alloy is investigated using TEM, XRD, and LEAP tomography. The strength of the HSLA-115 is found to be derived primarily from Cu precipitates. The volume fractions of cementite, austenite, and NbC are measured by XRD

  18. CO{sub 2} corrosion resistance of carbon steel in relation with microstructure changes

    Energy Technology Data Exchange (ETDEWEB)

    Ochoa, Nathalie, E-mail: nochoa@usb.ve [Departamento de Ciencia de los Materiales, Universidad Simón Bolívar, Aptdo., 89000, Caracas (Venezuela, Bolivarian Republic of); Vega, Carlos [Departamento de Ciencia de los Materiales, Universidad Simón Bolívar, Aptdo., 89000, Caracas (Venezuela, Bolivarian Republic of); Pébère, Nadine; Lacaze, Jacques [Université de Toulouse, CIRIMAT, UPS/INPT/CNRS, ENSIACET, 4 Allée Emile Monso, CS 44362, 31030 Toulouse Cedex 4 (France); Brito, Joaquín L. [Laboratorio de Físico-química de Superficies, Centro de Química, Instituto Venezolano de Investigaciones Cientificas (IVIC), Carretera Panamericana, Km 11, Altos de Pipe, Estado Miranda (Venezuela, Bolivarian Republic of)

    2015-04-15

    The microstructural effects on the corrosion resistance of an API 5L X42 carbon steel in 0.5 M NaCl solution saturated with CO{sub 2} was investigated. Four microstructures were considered: banded (B), normalized (N), quenched and tempered (Q&T), and annealed (A). Electrochemical measurements (polarization curves and electrochemical impedance spectroscopy) were coupled with surface analyses (scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS)) to characterize the formation of the corrosion product layers. Electrochemical results revealed that corrosion resistance increased in the following order: B < N < Q&T < A. From the polarization curves it was shown that specifically, cathodic current densities were affected by microstructural changes. SEM images indicated that ferrite dissolved earlier than cementite and a thin layer of corrosion products was deposited on the steel surface. XPS analyses revealed that this layer was composed of a mixture of iron carbonate and non-dissolved cementite. It was also found that the quantity of FeCO{sub 3} content on the steel surface was greater for Q&T and A microstructures. These results, in agreement with the electrochemical data, indicate that the deposition mechanism of iron carbonate is closely related to the morphology of the non-dissolved cementite, determining the protective properties of the corrosion product layers. - Highlights: • The effect of change in microstructure on CO{sub 2} corrosion resistance was evaluated. • An API 5LX 42 carbon steel was immersed in a 0.5 M NaCl solution saturated with CO{sub 2}. • Banded, normalized, quenched-tempered and annealed microstructures were considered. • Electrochemical measurements were coupled with surface analysis. • Morphology and distribution of undissolved Fe{sub 3}C control corrosion kinetics.

  19. Induction Tempering vs Conventional Tempering of a Heat-Treatable Steel

    Science.gov (United States)

    Sackl, Stephanie; Zuber, Michael; Clemens, Helmut; Primig, Sophie

    2016-07-01

    An induction heat treatment is favorable compared to a conventional one mainly due to significant time and cost savings. Therefore, in this study, the microstructure property relationships during induction and conventional heat treatment of a heat treatable steel 42CrMo4 is investigated. The yield strength and hardness is slightly higher for the conventionally heat-treated steel, whereas the induction heat-treated condition exhibits a roughly 30 J/cm2 higher impact energy. In a previous investigation of the authors, it has been proved that the difference in yield strength originates from the smaller block size of the conventionally heat-treated steel, which was already present after hardening. In the present work, it can be shown that during tempering the martensitic blocks become equi-axed ferrite grains due to recrystallization as revealed by electron back scatter diffraction. Nevertheless, a larger grain size usually is less favorable for the impact toughness of steels. Therefore, another mechanism is responsible for the higher impact energy of the induction hardened and tempered steel. With the aid of transmission electron microscopy a finer distribution of cementite was observed in the induction heat-treated samples. The delay of recovery is the reason for the presence of finer cementite in case of the induction heat-treated steel. Here, the higher heating rates and shorter process times reduce the annihilation of dislocation and as a consequence provide more nucleation sites for precipitation of cementite during tempering. From the obtained experimental results, it is believed that the finer distribution of carbides causes the observed higher impact toughness.

  20. Effect of phosphorous and boron addition on microstructural evolution and Charpy impact properties of high-phosphorous-containing plain carbon steels

    Energy Technology Data Exchange (ETDEWEB)

    Hong, Seokmin [Center for Advanced Aerospace Materials, Pohang University of Science and Technology, Pohang 790-784 (Korea, Republic of); Shin, Sang Yong [Microstructure Physics and Alloy Design, Max-Planck-Institut für Eisenforschung GmbH, Düsseldorf D-40237 (Germany); Lee, Junghoon [Center for Advanced Aerospace Materials, Pohang University of Science and Technology, Pohang 790-784 (Korea, Republic of); Lee, Chang-Hoon [Next Generation Products Research Group, Technical Research Laboratories, POSCO, Pohang 790-785 (Korea, Republic of); Lee, Sunghak, E-mail: shlee@postech.ac.kr [Center for Advanced Aerospace Materials, Pohang University of Science and Technology, Pohang 790-784 (Korea, Republic of)

    2013-03-01

    Four plain carbon steels were fabricated by controlling the addition of P and B, and then isothermal heat-treatments were conducted at 550 °C and 650 °C for 3 h on these steels to make ferrite–pearlite-based or ferrite–bainite-based microstructures, respectively. B was added for controlling the reduction in toughness due to grain boundary segregation of P because B was readily distributed on grain boundaries. In the 550 °C-treated steels, bainite grains were refined by the B addition, whereas the 650 °C-treated steels did not show the grain refinement due to the B addition. According to the critical time analysis for non-equilibrium grain boundary segregation of P and B, the present isothermal treatment time of 3 h was too short for the grain boundary segregation of P, and thus the fracture occurred mostly in a cleavage mode, instead of an intergranular mode. Since this 3 h-treatment time was too long for the grain boundary segregation of B, the grain boundary segregation of B was reduced, and the precipitation of cementites was promoted. In the 550 °C-treated steels, the area fraction of intergranular fracture increased with increasing volume fraction of grain boundary cementites, as they played an important role in initiating the intergranular fracture, although the area fraction of intergranular fracture was lower than 5%. In the 650 °C-treated steels having coarse grains, however, grain boundary cementites did not work for intergranular fracture because the crack readily propagated in a cleavage mode.

  1. Friction stir processing on high carbon steel U12

    Energy Technology Data Exchange (ETDEWEB)

    Tarasov, S. Yu., E-mail: tsy@ispms.ru; Rubtsov, V. E., E-mail: rvy@ispms.ru [Institute of Strength Physics and Materials Science SB RAS, Tomsk, 634055 (Russian Federation); National Research Tomsk Polytechnic University, Tomsk, 634050 (Russian Federation); Melnikov, A. G., E-mail: melnikov-ag@tpu.ru [National Research Tomsk Polytechnic University, Tomsk, 634050 (Russian Federation)

    2015-10-27

    Friction stir processing (FSP) of high carbon steel (U12) samples has been carried out using a milling machine and tools made of cemented tungsten carbide. The FSP tool has been made in the shape of 5×5×1.5 mm. The microstructural characterization of obtained stir zone and heat affected zone has been carried out. Microhardness at the level of 700 MPa has been obtained in the stir zone with microstructure consisting of large grains and cementitte network. This high-level of microhardness is explained by bainitic reaction developing from decarburization of austenitic grains during cementite network formation.

  2. Valence electron structure of cast iron and graphltization behaviour criterion of elements

    Institute of Scientific and Technical Information of China (English)

    刘志林; 李志林; 孙振国; 杨晓平; 陈敏

    1995-01-01

    The valence electron structure of common alloy elements in phases of cast iron is calculated- The relationship between the electron structure of alloy elements and equilibrium, non-equilibrium solidification and graphitization is revealed by defining the bond energy of the strongest bond in a phase as structure formation factor S. A criterion of graphitization behaviour of elements is advanced with the critical value of the structure formation factor of graphite and the n of the strongest covalent bond in cementite. It is found that this theory conforms to practice very well when the criterion is applied to the common alloy elements.

  3. Super-heater tube failure due to overheating when using bagasse as fuel

    Directory of Open Access Journals (Sweden)

    John Jairo Coronado Marín

    2010-04-01

    Full Text Available A super-heater’s boiler tubes presented external longitudinal cracks. The tubes’ external surfaces presented a reddish-white layer consisting of paraffin chains: CH, functional groups: CO, NH and sulphur compounds. This brittle layer prevented heat transfer, thereby causing increased tube temperature. Creep led to failure due to long-term overheating. The steel tubes’ microstructure presented grain growth, cementite globulisation and intergranular cracks on the external surface. The foregoing observations support microstructure deterioration facilitated by the presence of unsuitable super-heater tube material when just using bagasse as fuel.

  4. Enhanced thermal stability in nanostructured bainitic steel

    International Nuclear Information System (INIS)

    We report an attempt at increasing the thermal stability of nanocrystalline bainite to tempering heat treatments by enhancing the silicon concentration of the alloy. Validation experiments have been conducted using synchrotron X-irradiation during tempering heat treatment. It is found that the change in alloying successfully stabilizes the austenite at elevated temperatures by retarding cementite formation to temperatures as high as 500 °C. Other changes reflected in the lattice parameters of the major phases have revealed further information about the mechanisms involved

  5. Growth of lamellar pearlite in the weld zone between dissimilar steels

    Science.gov (United States)

    Nikulina, A. A.; Smirnov, A. I.; Bataev, I. A.; Bataev, A. A.; Popelyukh, A. I.

    2016-01-01

    Transmission electron microscopy is used to study the welds between high-carbon pearlitic and chromium-nickel austenitic steel workpieces performed by flash butt welding. It has been established that lamellar pearlite colonies alloyed with chromium and nickel are formed in the weld zones between dissimilar steels. Thin austenite interlayers have been detected in the center of ferrite plates. The structure formed presents the C-F-A-F-C-F-A-F (and so on) sequence of three plate-shaped phases. The ferrite-cementite structure in alloyed-pearlite colonies is finer than that in unalloyed pearlite.

  6. 回火

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    The influence of nitrogen on the structure and properties of Fe-10Cr-N and Fe-10Cr-IMo-N steels after tempering in the temperature range of 650-750℃.In-situ heat treatment system using YAG laser sourcetempering process after quenching.Modelling and characterization of Mo{sub}2C precipitation and cementite dissolution during tempering of Fe-C-Mo martensitic steel.Inductive heating for hardening and tempering of steel rails.Rapid tempering and stress relief via high-speed convection heating.

  7. Mathematical Model of the Processoof Pearlite Austenitization

    Directory of Open Access Journals (Sweden)

    Olejarczyk-Wożeńska I.

    2014-10-01

    Full Text Available The paper presents a mathematical model of the pearlite - austenite transformation. The description of this process uses the diffusion mechanism which takes place between the plates of ferrite and cementite (pearlite as well as austenite. The process of austenite growth was described by means of a system of differential equations solved with the use of the finite difference method. The developed model was implemented in the environment of Delphi 4. The proprietary program allows for the calculation of the rate and time of the transformation at an assumed temperature as well as to determine the TTT diagram for the assigned temperature range.

  8. Influence of supersaturated carbon on the diffusion of Ni in ferrite determined by atom probe tomography

    KAUST Repository

    Kresse, T.

    2013-09-01

    In patented and cold-drawn pearlitic steel wires dissociation of cementite occurs during mechanical deformation. In this study the influence of the carbon decomposition on the diffusion of nickel in ferrite is investigated by means of atom probe tomography. In the temperature range 423-523 K we observed a much smaller activation energy of Ni diffusion than for self-diffusion in body-centered cubic iron, indicating an increased vacancy density owing to enhanced formation of vacancy-carbon complexes. © 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  9. Microstructural Characterization and Mechanical Properties Analysis of Weld Metals with Two Ni Contents During Post-Weld Heat Treatments

    Science.gov (United States)

    Wu, Da-yong; Han, Xiu-lin; Tian, Hong-tao; Liao, Bo; Xiao, Fu-ren

    2015-05-01

    This study designed post-weld heat treatments, including reheating and tempering, associated with hot bending to investigate the microstructures, toughness, and hardness of two weld metals with different Ni contents (tempering. The large-angle grain boundary density from the AF improved the toughness despite the negative effect of cementite. The strengthening contributions were calculated, and the grain refinement was the greatest. The high Ni content decreased the effective grain size with a 2 deg tolerance angle, thus enhancing the grain refinement contribution.

  10. Interactions of hydrogen with the iron and iron carbide interfaces: a ReaxFF molecular dynamics study.

    Science.gov (United States)

    Islam, Md Mahbubul; Zou, Chenyu; van Duin, Adri C T; Raman, Sumathy

    2016-01-14

    Hydrogen embrittlement (HE) is a well-known material phenomenon that causes significant loss in the mechanical strength of structural iron and often leads to catastrophic failures. In order to provide a detailed atomistic description of HE we have used a reactive bond order potential to adequately describe the diffusion of hydrogen as well as its chemical interaction with other hydrogen atoms, defects, and the host metal. The currently published ReaxFF force field for Fe/C/H systems was originally developed to describe Fischer-Tropsch (FT) catalysis [C. Zou, A. C. T. van Duin and D. C. Sorescu, Top. Catal., 2012, 55, 391-401], and especially had been trained for surface formation energies, binding energies of small hydrocarbon radicals on different surfaces of iron and the barrier heights of surface reactions. We merged this force field with the latest ReaxFF carbon parameters [S. Goverapet Srinivasan, A. C. T. van Duin and P. Ganesh, J. Phys. Chem. A, 2015, 119, 1089-5639] and used the same training data set to refit the Fe/C interaction parameters. The present work is focused on evaluating the applicability of this reactive force field to describe material characteristics and study the role of defects and impurities in the bulk and at the precipitator interfaces. We study the interactions of hydrogen with pure and defective α-iron (ferrite), Fe3C (cementite), and ferrite-cementite interfaces with a vacancy cluster. We also investigate the growth of nanovoids in α-iron using a grand canonical Monte Carlo (GCMC) scheme. The calculated hydrogen diffusion coefficients for both ferrite and cementite phases predict a decrease in the work of separation with increasing hydrogen concentration at the ferrite-cementite interface, suggesting a hydrogen-induced decohesion behavior. Hydrogen accumulation at the interface was observed during molecular dynamics (MD) simulations, which is consistent with experimental findings. These results demonstrate the ability of the Reax

  11. Microstructure and Wear Behavior of TiC Coating Deposited on Spheroidized Graphite Cast Iron Using Laser Surfacing

    OpenAIRE

    E. R. I. Mahmoud; H. F. El-Labban

    2014-01-01

    Spheroidal graphite cast iron was laser cladded with TiC powder using a YAG fiber laser at powers of 700, 1000, 1500 and 2000 W. The powder was preplaced on the surface of the specimens with 0.5 mm thickness. Sound cladding and fusion zones were observed at 700, 1000 and 1500 W powers. However, at 2000 W, cracking was observed in the fusion zone.  At 700 W, a build-up zone consisted of fine TiC dendrites inside a matrix composed of martensite, cementite (Fe3C), and some blocks of retaine...

  12. Plasma Nitriding of Low Alloy Sintered Steels

    Institute of Scientific and Technical Information of China (English)

    Shiva Mansoorzadeh; Fakhreddin Ashrafizadeh; Xiao-Ying Li; Tom Bell

    2004-01-01

    Fe-3Cr-0.5Mo-0.3C and Fe-3Cr-1.4Mn-0.5Mo-0.367C sintered alloys were plasma nitrided at different temperatures. Characterization was performed by microhardness measurement, optical microscopy, SEM and XRD. Both materials had similar nitriding case properties. 1.4% manganese did not change the as-sintered microstructure considerably.It was observed that monophase compound layer, γ, formed with increasing temperature. Compound layer thickness increased with increasing temperature while nitriding depth increased up to a level and then decreased. Core softening was more pronounced at higher temperature owing to cementite coarsening.

  13. Friction stir processing on high carbon steel U12

    International Nuclear Information System (INIS)

    Friction stir processing (FSP) of high carbon steel (U12) samples has been carried out using a milling machine and tools made of cemented tungsten carbide. The FSP tool has been made in the shape of 5×5×1.5 mm. The microstructural characterization of obtained stir zone and heat affected zone has been carried out. Microhardness at the level of 700 MPa has been obtained in the stir zone with microstructure consisting of large grains and cementitte network. This high-level of microhardness is explained by bainitic reaction developing from decarburization of austenitic grains during cementite network formation

  14. Hybrid Friction Stir Welding of High-carbon Steel

    Institute of Scientific and Technical Information of China (English)

    Don-Hyun Choi; Seung-Boo Jung; Chang-Yong Lee; Byung-Wook Ahn; Jung-Hyun Choi; Yun-Mo Yeon; Keun Song; Seung-Gab Hong; Won-Bae Lee; Ki-Bong Kang

    2011-01-01

    A high-carbon steel joint, SK5 (0.84 wt% C), was successfully welded by friction stir welding (FSW), both without and with a gas torch, in order to control the cooling rate during welding. After welding, the weld zone comprised gray and black regions, corresponding to microstructural variation: a martensite structure and a duplex structure of ferrite and cementite, respectively. The volume fraction of the martensite structure and the Vickers hardness in the welds were decreased with the using of the gas torch, which was related with the lower cooling rate.

  15. Neutron strain scanning in straightened eutectoid steel rods

    Science.gov (United States)

    Martínez, M. L.; Borlado, C. R.; Mompeán, F. J.; Peng, R. L.; Daymond, M. R.; Ruiz, J.; García-Hernández, M.

    Neutron strain scanning has been performed on a neutectoid steel rod at a reactor-based source (REST diffractometer, at NFL) and at a pulsed source (ENGIN diffractometer, at ISIS). The rod is primarily obtained from a drawing process and has been subject to bending and straightening procedures, which induce residual stress. The material exhibits a pearlitic microstructure, with alternating ferrite (90 vol%) and cementite (10 vol%) layers. Strain profiles for the ferritic phase were measured on REST. Both phases were measured on ENGIN and analysed by single-peak (ferrite) and Rietveld refinement (ferrite and cementite) methods. The agreement between REST and ENGIN data is excellent for the three measured directions in the ferritic phase. Total stress profiles have been evaluated by combining phase stresses using the rule of mixtures. The experimental results compare well with analytical models for a two-phase material subject to bending and straightening operations under pure bending and unbending moments with perfect elastic behaviour up to the yield point and plastic Voce behaviour above.

  16. 82B盘条钢的组织性能及缺陷分析%Analysis on Microstructure and Properties and Defects of 82B Steel Wire Rod

    Institute of Scientific and Technical Information of China (English)

    孙莹; 于庆波

    2011-01-01

    通过对82B盘条钢的显微组织观察,研究了索氏体含量对82B盘条拉拔性能的影响,并对生产中常见的组织缺陷进行了分析.结果表明:生产中化学成分及工艺的不稳定是组织缺陷产生的主要原因;提高冷却速度可以增加索氏体含量、降低网状渗碳体含量;采用恒拉速可以减少块状渗碳体的形成.%By observing the microstructure of 82B steel wire rod, the effects of sorbite content on the drawing performance of 82B wire rod were investigated. The common defects in production were analyzed. The results indicate that the instability of chemical composition and technological process results in the defects. Increasing the cooling rate can increase the content of sorbite and decrease the content of network cementite; constant pulling speed can be used to decrease the formation of massive cementite.

  17. Optimization of chemical compositions in low-carbon Al-killed enamel steel produced by ultra-fast continuous annealing

    Energy Technology Data Exchange (ETDEWEB)

    Dong, Futao, E-mail: dongft@sina.com [The State Key Laboratory of Rolling and Automation, Northeastern University, Shenyang 110819 (China); Du, Linxiu; Liu, Xianghua [The State Key Laboratory of Rolling and Automation, Northeastern University, Shenyang 110819 (China); Xue, Fei [College of Electrical Engineering, Hebei United University, Tangshan 063000 (China)

    2013-10-15

    The influence of Mn,S and B contents on microstructural characteristics, mechanical properties and hydrogen trapping ability of low-carbon Al-killed enamel steel was investigated. The materials were produced and processed in a laboratory and the ultra-fast continuous annealing processing was performed using a continuous annealing simulator. It was found that increasing Mn,S contents in steel can improve its hydrogen trapping ability which is attributed by refined ferrite grains, more dispersed cementite and added MnS inclusions. Nevertheless, it deteriorates mechanical properties of steel sheet. Addition of trace boron results in both good mechanical properties and significantly improved hydrogen trapping ability. The boron combined with nitrogen segregating at grain boundaries, cementite and MnS inclusions, provides higher amount of attractive hydrogen trapping sites and raises the activation energy for hydrogen desorption from them. - Highlights: • We study microstructures and properties in low-carbon Al-killed enamel steel. • Hydrogen diffusion coefficients are measured to reflect fish-scale resistance. • Manganese improves hydrogen trapping ability but decrease deep-drawing ability. • Boron improves both hydrogen trapping ability and deep-drawing ability. • Both excellent mechanical properties and fish-scale resistance can be matched.

  18. Effect of initial microstructure on mechanical properties in warm caliber rolling of high carbon steel

    International Nuclear Information System (INIS)

    Highlights: → The effect of initial microstructure on change of micro-hardness, tension, and Charpy tests were investigated by warm caliber rolling (WCR). → Smaller ferrite grain and dispersed cementite particles with smaller interspacing increased the strength and toughness. → In WCR, elongation hardly decreased compared to the conventional hot rolling. → Depending on the microstructure change, WCR guaranteed higher impact energy and the mode of fracture varied as well. - Abstract: In this study, the effect of initial microstructure on change of mechanical properties was investigated by warm caliber rolling (WCR) of high carbon steel. Experiments were carried out with two different kinds of initial microstructures of pearlite and tempered martensite at the temperature of 500 deg. C. For comparison, the microstructure of austenite phase obtained from the conventional hot rolling at the temperature of 900 deg. C up to about 83% of the accumulative reduction in area was assumed to be a reference case. It was found that the WCR provided better mechanical properties in terms of strength and toughness compared to the conventional hot rolling based on experimental results of micro-hardness, tension, and Charpy impact tests. The improvement of strength and toughness was attributed to smaller ferrite grain and dispersed cementite particles with smaller interspacing aligned to the rolling direction after the WCR owing to field emission scanning electron microscopy. The investigated WCR might be useful in obtaining the high strength material with better toughness without adding new alloying elements for industrial applications according to the present investigation.

  19. Effect of Heat Treatment on Microstructures and Mechanical Properties of Severe Plastically Deformed Hypo- and Hyper-Eutectoid Steels by Caliber Rolling Process.

    Science.gov (United States)

    Yun, Shin-Cheon; Kim, Hyun-Jin; Bae, Chul-Min; Lee, Kee-Ahn

    2016-02-01

    This study investigated the effect of post-heat treatment on the microstructures and mechanical properties of severe plastically deformed hypo- and hyper-eutectoid steels that underwent a caliber rolling process. First, 28 passes of caliber rolling were performed on both the hypo-eutectoid steel with Fe-0.47% C (wt%) composition and the hyper-eutectoid steel with Fe-1.02%C (wt%) composition. Then, the caliber rolled materials underwent heat treatment at 500 degrees C for 1, 3, 5, 10, 30 and 60 minutes. The caliber rolled steel possessed a 300-400 nm-sized oval cementite structure created through elongating and segmentation regardless of the C composition. The observation of heat-treated microstructures showed that cementite structure became globular and ferrite size increased as heat treatment temperature increased. In the hardness measurement, the initial caliber rolled samples showed 372.8 Hv (hypoeutectoid) and 480.1 Hv (hyper-eutectoid). However, hardness dramatically decreased up to 10 min. heat treatments, and then showed a constant or small reduction with time. The yield strengths (compression) of caliber rolled hypo- and hypereutectoid steels obtained were 1097 MPa and 1426 MPa, respectively, and the yield strengths of the same steels after heat treatment (500 degrees C, 60 min.) were identified to be 868 MPa and 1316 MPa, respectively.

  20. Microstructural evolution of AISI 4340 steel during Direct Metal Deposition process

    International Nuclear Information System (INIS)

    Research highlights: → 4340 steel was successfully deposited using diode laser DMD system on mild steel. → Ferrite, martensite and cementite microstructural phases were identified in the clad. → Lattice parameters of identified phases are shorter than reported lattice parameters. → Microhardness of the clad decreases down the clad layers. → Decrease in microhardness corresponds to degree of tempering of martensite phase. - Abstract: In the current investigation AISI 4340 steel was laser deposited on a rolled mild steel substrate by Direct Metal Deposition (DMD) technology. The microstructural investigation of the clad was performed using optical and electron microscopes and X-ray diffraction techniques. The microstructure consisted of ferrite, martensite and cementite phases. Two types of martensite, lathe-type and plate-type, were observed in the microstructure. Decrease in microhardness values from the top layer to the alloy layer proves that the degree of tempering of the martensite phase increases in the same direction. The lattice parameters of the identified phases were found to be shorter than those reported in literature. The reported parameters in literature are from samples processed under equilibrium conditions.

  1. Microstructure of high strength niobium-containing pipeline steel

    Energy Technology Data Exchange (ETDEWEB)

    Shanmugam, S. [Center for Structural and Functional Materials, Department of Chemical Engineering, University of Louisiana at Lafayette, Lafayette, LA 70504-4130 (United States); Misra, R.D.K. [Center for Structural and Functional Materials, Department of Chemical Engineering, University of Louisiana at Lafayette, Lafayette, LA 70504-4130 (United States)]. E-mail: dmisra@louisiana.edu; Hartmann, J. [Mittal Steel, Indiana Harbor Works, 3001 Dickey Road, East Chicago, IN 46312 (United States); Jansto, S.G. [Reference Metals, 1000 Old Pond Road, Bridgeville, PA 15017 (United States)

    2006-12-15

    The paper describes the microstructural constituents in a industrially processed Nb-microalloyed pipeline steel having yield strength of {approx}620 MPa. The microstructure of base, heat affected zone (HAZ), and weld metal of the fabricated steel pipe was examined by optical and transmission electron microscopy. The microstructure of thermomechanically processed pipeline steel primarily consisted of non-equiaxed ferrite of mixed morphologies with small fraction of degenerated pearlite. The microstructure contained high dislocation density, sub-boundaries and dislocation substructures. The HAZ was characterized by a combination of fine and coarse grained polygonal ferrite structure with high density of dislocations and fine cementite particles. In the weld metal, the constituents of complex ferrite were low temperature transformation products formed during continuous cooling such as quasi-polygonal or massive ferrite, acicular ferrite, bainitic ferrite and dispersion of coarse and fine cementite particles in the ferrite matrix. The precipitates in the investigated pipeline steel were of duplex type containing either Nb and Ti or Ti and Mo, even though the steel contained low concentration of titanium. Precipitates of different morphology and size range were observed and include rectangular ({approx}100-130 nm), cuboidal/spherical ({approx}20-100 nm), fine ({approx}10-20 nm) and very fine (<10 nm). They were MC type of carbides.

  2. Microstructure of high strength niobium-containing pipeline steel

    International Nuclear Information System (INIS)

    The paper describes the microstructural constituents in a industrially processed Nb-microalloyed pipeline steel having yield strength of ∼620 MPa. The microstructure of base, heat affected zone (HAZ), and weld metal of the fabricated steel pipe was examined by optical and transmission electron microscopy. The microstructure of thermomechanically processed pipeline steel primarily consisted of non-equiaxed ferrite of mixed morphologies with small fraction of degenerated pearlite. The microstructure contained high dislocation density, sub-boundaries and dislocation substructures. The HAZ was characterized by a combination of fine and coarse grained polygonal ferrite structure with high density of dislocations and fine cementite particles. In the weld metal, the constituents of complex ferrite were low temperature transformation products formed during continuous cooling such as quasi-polygonal or massive ferrite, acicular ferrite, bainitic ferrite and dispersion of coarse and fine cementite particles in the ferrite matrix. The precipitates in the investigated pipeline steel were of duplex type containing either Nb and Ti or Ti and Mo, even though the steel contained low concentration of titanium. Precipitates of different morphology and size range were observed and include rectangular (∼100-130 nm), cuboidal/spherical (∼20-100 nm), fine (∼10-20 nm) and very fine (<10 nm). They were MC type of carbides

  3. Surface treatment of 0.20% C carbon steel by high-current pulsed electron beam

    Institute of Scientific and Technical Information of China (English)

    XU Guo-cheng; FU Shi-you; GUAN Qing-feng

    2006-01-01

    A high-current pulsed electron beam(HCPEB) generated on the system of Nadezhda-2 was applied to improve the microstructure and performance of 0.20% C low carbon steel. Surface layers of the samples bombarded by explosive electron beam at different pulses was observed by using electron microscopy. The physical model of the thermal-stress process and related modification mechanism as a result of HCPEB irradiation was also investigated. After HCPEB post treatments, obvious changes in microstructure and significant hardening occur in the depth of 200-250 μm from the surface after HCPEB irradiation. Rapid heating and subsequent rapid solidification induce heavy plastic deformation, which results in that the laminated structure of pearlite is substituted by dispersive rounded-like cementites in the near-surface. The effect of HCPEB treatment can reach more than 500 m depth from the surface. The original crystalline structure is changed to a different degree that grows with the numbers of bombardment, and in the surface layer amorphous states and nanocrystaline structures consisting of grains of γ-phase and cementite are found. The violent stress induced by HCPEB irradiation is the origin of the nanostructured and amorphous structure formation.

  4. Orientation Relationships between Precipitates and Their Parent Phases in Steels at Low Transformation Temperatures

    Science.gov (United States)

    Lee, Dong Nyung; Han, Heung Nam

    The directed growth of precipitates proceeds in their parent phases at low transformation temperatures. The growth needs the activation energy. The activation energy is usually supplied in the form of thermal energy. However, at low transformation temperatures, the thermal energy is not enough to surmount the activation barrier, and so the strain energy developed in the parent phase assists surmounting the barrier, resulting in the directed growth of precipitates. The strain energy can result from a difference in density between the nucleus and matrix and a lattice mismatch along the nucleus:matrix interface. The fundamental concept of the model is that the maximum growth rate of precipitate is along the direction that generates the maximum strain energy and minimizes the interface energy. In this paper, orientation relationships between ferrite precipitate and parent austenite, between orthorhombic cementite precipitate and parent austenite, between cementite precipitate and parent ferrite, and between hexagonal Mo2C precipitate and parent ferrite have been discussed based on the directed growth model.

  5. Influence of Post-Weld Heat Treatment on the Microstructure, Microhardness, and Toughness of a Weld Metal for Hot Bend

    Directory of Open Access Journals (Sweden)

    Xiu-Lin Han

    2016-03-01

    Full Text Available In this work, a weld metal in K65 pipeline steel pipe has been processed through self-designed post-weld heat treatments including reheating and tempering associated with hot bending. The microstructures and the corresponding toughness and microhardness of the weld metal subjected to the post-weld heat treatments have been investigated. Results show that with the increase in reheating temperature, austenite grain size increases and the main microstructures transition from fine polygonal ferrite (PF to granular bainitic ferrite (GB. The density of the high angle boundary decreases at higher reheating temperature, leading to a loss of impact toughness. Lots of martensite/austenite (M/A constituents are observed after reheating, and to a large extent transform into cementite after further tempering. At high reheating temperatures, the increased hardenability promotes the formation of large quantities of M/A constituents. After tempering, the cementite particles become denser and coarser, which considerably deteriorates the impact toughness. Additionally, microhardness has a good linear relation with the mean equivalent diameter of ferrite grain with a low boundary tolerance angle (2°−8°, which shows that the hardness is controlled by low misorientation grain boundaries for the weld metal.

  6. Distribution and anisotropy of dislocations in cold-drawn pearlitic steel wires analyzed using micro-beam X-ray diffraction

    International Nuclear Information System (INIS)

    To characterize the distribution and anisotropy of dislocations in cold-drawn pearlitic steel wires, X-ray diffraction line-profile analysis was performed using synchrotron radiation micro-beams. An analytical procedure for correcting the instrumental line broadening for highly directional micro-beams was developed using diffraction profiles of standard CeO2 powder. Although the CeO2 powder line profile includes line broadening due to its microstructural imperfections, the instrumental broadening can be obtained by estimating the effect of the microstructural imperfections on the line broadening. The plastic shear strain was generally more severe near the surface than the center of the wire, whereas the dislocation density distribution was almost constant from the center to the surface. On the other hand, the dislocation rearrangement, which evolves the dislocation cell structure, progressed closer to the surface. It was also revealed that a difference between the hardness in axial and transverse wire directions could be explained by anisotropic dislocation density. Line-profile analysis based on diffraction data at elevated temperatures was performed. Whereas the cementite recovery progressed at a constant rate, the ferrite phase recovery rate was temperature-dependent, suggesting that the ferrite phase recovery was less related to that of the cementite phase. (author)

  7. Structure–property relationship in a 960 MPa grade ultrahigh strength low carbon niobium–vanadium microalloyed steel: The significance of high frequency induction tempering

    Energy Technology Data Exchange (ETDEWEB)

    Xie, Z.J.; Fang, Y.P.; Han, G.; Guo, H. [School of Materials Science and Engineering, University of Science and Technology, 30 Xueyuan Road, Haidian Street, Beijing 100083 (China); Misra, R.D.K. [Department of Metallurgical and Materials Engineering, University of Texas at El Paso, El Paso, TX 79968 (United States); Shang, C.J., E-mail: cjshang@ustb.edu.cn [School of Materials Science and Engineering, University of Science and Technology, 30 Xueyuan Road, Haidian Street, Beijing 100083 (China)

    2014-11-17

    The present study describes the microstructure and precipitation behavior in an ultra-high strength low carbon niobium–vanadium microalloyed steel that was processed by quenching and high frequency induction tempering. Ultrahigh yield strength of ∼1000 MPa with high elongation of ∼15% and high low temperature toughness of 55 J (half thickness) at −40 °C was obtained after quenching from austenitization at 900 °C for 30 min, and tempering at 600 °C for 15 min by induction reheating with a reheating rate of ∼50 °C/s. While the yield strength increase on tempering was similar for both induction reheating and conventional reheating (electrical resistance reheating), there was ∼100% increase in low temperature toughness in induction reheated steel compared to the conventional reheating process. The underlying reason for the increase in toughness was attributed to the transformation of cementite film observed in conventional reheating and tempering to nanoscale cementite in induction reheating and tempering. The precipitation of nanoscale carbides is believed to significantly contribute to ultra-high strength, good ductility, and high toughness in the high frequency induction reheating and tempering process.

  8. Microstructure and mechanical properties of a low carbon carbide-free bainitic steel co-alloyed with Al and Si

    International Nuclear Information System (INIS)

    Highlight: ► A low carbon carbide-free bainitic steel was produced. ► Co-alloying with Al and Si suppresses the precipitation of cementite. ► Fine carbide-free bainite laths and thin film-like retained austenite obtained. ► Excellent combination of strength, ductility and toughness enabled. -- Abstract: A low carbon, low alloy steel has been investigated for producing low carbon carbide-free bainitic microstructure by co-addition of alloying elements of aluminum and silicon. The influence of heat treatment process on microstructure, impact toughness as well as tensile properties was investigated by light optical microscopy, transmission electron microscopy, X-ray diffraction and mechanical property tests. The results demonstrate that the co-addition of aluminum and silicon in the investigated steel plays an effective role in suppressing the precipitation of cementite. A desired microstructure consisting of mainly fine-scale carbide-free bainitic ferrite and thin film-like retained austenite located between the ferrite laths was obtained and accordingly an excellent combination of toughness, ductility and strength was achieved by optimized heat treatments, i.e. by isothermal treatment at 320 °C for ∼84 min or more. The microstructure-mechanical property relationships are discussed.

  9. Effect of initial microstructure on mechanical properties in warm caliber rolling of high carbon steel

    Energy Technology Data Exchange (ETDEWEB)

    Oh, Y.S. [National Research Laboratory for Computer Aided Materials Processing, Department of Mechanical Engineering, KAIST, 373-1, Guseong-dong, Yuseong-gu, Daejeon 305-701 (Korea, Republic of); Son, I.H. [Wire Rod Research Group, Technical Research Laboratories, POSCO, 1 Goedong-dong, Nam-gu, Pohang, Gyeongbuk 790-785 (Korea, Republic of); Jung, K.H.; Kim, D.K. [National Research Laboratory for Computer Aided Materials Processing, Department of Mechanical Engineering, KAIST, 373-1, Guseong-dong, Yuseong-gu, Daejeon 305-701 (Korea, Republic of); Lee, D.L. [Wire Rod Research Group, Technical Research Laboratories, POSCO, 1 Goedong-dong, Nam-gu, Pohang, Gyeongbuk 790-785 (Korea, Republic of); Im, Y.T., E-mail: ytim@kaist.ac.kr [National Research Laboratory for Computer Aided Materials Processing, Department of Mechanical Engineering, KAIST, 373-1, Guseong-dong, Yuseong-gu, Daejeon 305-701 (Korea, Republic of)

    2011-07-15

    Highlights: {yields} The effect of initial microstructure on change of micro-hardness, tension, and Charpy tests were investigated by warm caliber rolling (WCR). {yields} Smaller ferrite grain and dispersed cementite particles with smaller interspacing increased the strength and toughness. {yields} In WCR, elongation hardly decreased compared to the conventional hot rolling. {yields} Depending on the microstructure change, WCR guaranteed higher impact energy and the mode of fracture varied as well. - Abstract: In this study, the effect of initial microstructure on change of mechanical properties was investigated by warm caliber rolling (WCR) of high carbon steel. Experiments were carried out with two different kinds of initial microstructures of pearlite and tempered martensite at the temperature of 500 deg. C. For comparison, the microstructure of austenite phase obtained from the conventional hot rolling at the temperature of 900 deg. C up to about 83% of the accumulative reduction in area was assumed to be a reference case. It was found that the WCR provided better mechanical properties in terms of strength and toughness compared to the conventional hot rolling based on experimental results of micro-hardness, tension, and Charpy impact tests. The improvement of strength and toughness was attributed to smaller ferrite grain and dispersed cementite particles with smaller interspacing aligned to the rolling direction after the WCR owing to field emission scanning electron microscopy. The investigated WCR might be useful in obtaining the high strength material with better toughness without adding new alloying elements for industrial applications according to the present investigation.

  10. Application of headed studs in steel fiber reinforced cementitious composite slab of steel beam-column connection

    Science.gov (United States)

    Yao, Cui; Nakashima, Masayoshi

    2012-03-01

    Steel fiber reinforced cementitous composites (SFRCC) is a promising material with high strength in both compression and tension compared with normal concrete. The ductility is also greatly improved because of 6% volume portion of straight steel fibers. A steel beam-column connection with Steel fiber reinforced cementitous composites (SFRCC) slab diaphragms is proposed to overcome the damage caused by the weld. The push-out test results suggested that the application of SFRCC promises larger shear forces transferred through headed studs allocated in a small area in the slab. Finite element models were developed to simulate the behavior of headed studs. The failure mechanism of the grouped arrangement is further discussed based on a series of parametric analysis. In the proposed connection, the SFRCC slab is designed as an exterior diaphragm to transfer the beam flange load to the column face. The headed studs are densely arranged on the beam flange to connect the SFRCC slab diaphragms and steel beams. The seismic performance and failure mechanism of the SFRCC slab diaphragm beam-column connection were investigated based on the cyclic loading test. Beam hinge mechanism was achieved at the end of the SFRCC slab diaphragm by using sufficient studs and appropriate rebars in the SFRCC slab.

  11. Transient liquid phase bonding of carbon steel tubes using a Cu interlayer: Characterization and comparison with amorphous Fe–B–Si interlayer bonds

    Energy Technology Data Exchange (ETDEWEB)

    Di Luozzo, Nicolas, E-mail: nicolasdiluozzo@gmail.com [Laboratorio de Sólidos Amorfos, INTECIN, Facultad de Ingeniería, Universidad de Buenos Aires – CONICET, Paseo Colón 850, C1063ACV Buenos Aires (Argentina); Laboratoire des Matériaux et du Génie Physique (CNRS UMR 5628), Grenoble Institute of Technology, MINATEC, Grenoble Cedex 1 (France); Boudard, Michel; Doisneau, Béatrice [Laboratoire des Matériaux et du Génie Physique (CNRS UMR 5628), Grenoble Institute of Technology, MINATEC, Grenoble Cedex 1 (France); Fontana, Marcelo; Arcondo, Bibiana [Laboratorio de Sólidos Amorfos, INTECIN, Facultad de Ingeniería, Universidad de Buenos Aires – CONICET, Paseo Colón 850, C1063ACV Buenos Aires (Argentina)

    2014-12-05

    Highlights: • Cu and Fe–B–Si foils were used as interlayers to bond steel tubes by TLPB process. • The microstructure and mechanical properties were characterized. • In Cu bonded samples, the solidification process was not systematically completed. • When using Cu foils, evidences of epitaxial solidification were observed. • Tensile tests show that Cu and Fe–B–Si bonded samples failed away from the joint. - Abstract: In the present work the transient liquid phase bonding process was performed to join seamless carbon steel tubes using commercially pure Cu interlayers. The structural and mechanical characteristics of the resulting bonds are compared with those achieved using amorphous Fe–B–Si interlayers, under the same process parameters: a holding temperature of 1300 °C, a holding time of 7 min and an applied pressure of 5 MPa. The joined tubes microstructures were characterized by direct observations – scanning electron microscopy – and diffraction techniques – electron backscatter diffraction. Chemical analysis was performed using electron probe microanalysis. Whereas the amorphous Fe-B-Si interlayer leads to a completion of the bonding process over the whole bonding area, the bond performed using a Cu interlayer achieved the completion of the bonding process only partially. As the Cu is a cementite promoter, the amount of cementite coexisting with ferrite grains is higher in the joint region (JR) – corresponding to the higher concentration of Cu – as compared with the heat affected zone (HAZ) and the base metal (BM). An opposite effect is observed when using Fe-B-Si interlayers due to the fact that the cementite is unable to form in Si enriched zones – the microstructure at the JR presents only ferrite grains. Tensile tests show that the joined tubes using Cu or Fe–B–Si interlayers failed away from the bond, at the HAZ, attaining almost the same ultimate tensile strength of the BM, in the as-received condition. Hardness

  12. Transient liquid phase bonding of carbon steel tubes using a Cu interlayer: Characterization and comparison with amorphous Fe–B–Si interlayer bonds

    International Nuclear Information System (INIS)

    Highlights: • Cu and Fe–B–Si foils were used as interlayers to bond steel tubes by TLPB process. • The microstructure and mechanical properties were characterized. • In Cu bonded samples, the solidification process was not systematically completed. • When using Cu foils, evidences of epitaxial solidification were observed. • Tensile tests show that Cu and Fe–B–Si bonded samples failed away from the joint. - Abstract: In the present work the transient liquid phase bonding process was performed to join seamless carbon steel tubes using commercially pure Cu interlayers. The structural and mechanical characteristics of the resulting bonds are compared with those achieved using amorphous Fe–B–Si interlayers, under the same process parameters: a holding temperature of 1300 °C, a holding time of 7 min and an applied pressure of 5 MPa. The joined tubes microstructures were characterized by direct observations – scanning electron microscopy – and diffraction techniques – electron backscatter diffraction. Chemical analysis was performed using electron probe microanalysis. Whereas the amorphous Fe-B-Si interlayer leads to a completion of the bonding process over the whole bonding area, the bond performed using a Cu interlayer achieved the completion of the bonding process only partially. As the Cu is a cementite promoter, the amount of cementite coexisting with ferrite grains is higher in the joint region (JR) – corresponding to the higher concentration of Cu – as compared with the heat affected zone (HAZ) and the base metal (BM). An opposite effect is observed when using Fe-B-Si interlayers due to the fact that the cementite is unable to form in Si enriched zones – the microstructure at the JR presents only ferrite grains. Tensile tests show that the joined tubes using Cu or Fe–B–Si interlayers failed away from the bond, at the HAZ, attaining almost the same ultimate tensile strength of the BM, in the as-received condition. Hardness

  13. Measurement and modelling of residual stresses in straightened commercial eutectoid steel rods

    Energy Technology Data Exchange (ETDEWEB)

    Martinez-Perez, M.L. [ICMM, CSIC, Campus de Cantoblanco, E-28049 Madrid (Spain); Borlado, C.R. [ICMM, CSIC, Campus de Cantoblanco, E-28049 Madrid (Spain); Open University, Faculty of Technology, Milton Keynes, MK7 6AL (United Kingdom); Mompean, F.J. [ICMM, CSIC, Campus de Cantoblanco, E-28049 Madrid (Spain); Garcia-Hernandez, M. [ICMM, CSIC, Campus de Cantoblanco, E-28049 Madrid (Spain); Gil-Sevillano, J. [CEIT, Paseo de Manuel Lardizabal 15, E-20018 San Sebastian (Spain); Ruiz-Hervias, J. [Departamento de Ciencia de Materiales, UPM, E.T.S.I. Caminos, Canales y Puertos, c/ Profesor Aranguren s/n, E-28040 Madrid (Spain); Atienza, J.M. [Departamento de Ciencia de Materiales, UPM, E.T.S.I. Caminos, Canales y Puertos, c/ Profesor Aranguren s/n, E-28040 Madrid (Spain)]. E-mail: jmatienza@mater.upm.es; Elices, M. [Departamento de Ciencia de Materiales, UPM, E.T.S.I. Caminos, Canales y Puertos, c/ Profesor Aranguren s/n, E-28040 Madrid (Spain); Peng, Ru Lin [NFL Studsvik, Uppsala University, S-61182 Nykoeping (Sweden); Daymond, M.R. [Department of Mechanical and Materials Engineering, Queen' s University, Kingston, K7L 3N6 (Canada)

    2005-09-15

    Neutron strain scanning measurements on a eutectoid steel rod that has been subjected to standard industrial coiling and straightening operations are presented. Strains were determined non-destructively using two different diffractometers, one at a steady-state neutron source and the other at a pulsed spallation neutron source, with measurements made in both the ferrite and cementite components of the pearlitic microstructure. The residual stress state is explained in terms of a simplified analytical model for a two-phase material, which takes into account the successive loading operations contributing to residual stress. The results show that residual stresses generated by bending-straightening operations are significant and are likely to play an important role in the mechanical properties of the final wires.

  14. SWRH82B热轧盘条拉拔笔尖状断口分析%Analysis on Penpoint Fracture During Drawing of SWRH82B Wire Rod

    Institute of Scientific and Technical Information of China (English)

    李玉岗; 袁子成; 温国栋

    2011-01-01

    The penpoint fracture wire sample of SWRH82B steel was analyzed by SEM and microscope.The result showed that the main reason of wire broken in direct drawing was high network cementite in hot rolled rod.Furthermore,suggestions were put forward to improve%针对φ12.5 mm SWRH82B热轧盘条拉拔笔尖状断口缺陷,采用扫描电子显微镜和金相显微镜进行了专题研究。结果显示:盘条心部存在网状渗碳体是导致笔尖状断口的主要原因,并提出消除该缺陷的措施与办法。

  15. A microstructure based analysis of cyclic plasticity of pearlitic steels with Hill's self-consistent scheme incorporating general anisotropic Eshelby tensor

    Institute of Scientific and Technical Information of China (English)

    Xuesong Long; Xianghe Peng; Wenli Pi

    2008-01-01

    A pearlitic steel is composed of numerous pearlitic colonies with random orientations,and each colony consists of many parallel lamellas of ferrite and cementite.The constitutive behavior of this kind of materials may involve both inherent anisotropy and plastic deformation induced anisotropy.A description of the cyclic plasticity for this kind of dual-phase materials is proposed by use of a microstructure-based constitutive model for a pearlitic colony,and the Hill's self-consistent scheme incorporating anisotropic Eshelby tensor for ellipsoidal inclusions.The corresponding numerical algorithm is developed.The responses of pearlitic steel BS11 and single-phase hard-drawn copper subjected to asymmetrically cyclic loading are analyzed.The analytical results agree very well with experimental ones.Compared with the results using isotropic Eshelby tensor,it is shown that the isotropic approximation can provide acceptable overall responses in a much simpler way.

  16. Influence of long-term thermal aging on the microstructural evolution of nuclear reactor pressure vessel materials: An atom probe study

    Energy Technology Data Exchange (ETDEWEB)

    Pareige, P.; Russell, K.F.; Stoller, R.E.; Miller, M.K. [Oak Ridge National Lab., TN (United States)

    1998-03-01

    Atom probe field ion microscopy (APFIM) investigations of the microstructure of unaged (as-fabricated) and long-term thermally aged ({approximately} 100,000 h at 280 C) surveillance materials from commercial reactor pressure vessel steels were performed. This combination of materials and conditions permitted the investigation of potential thermal-aging effects. This microstructural study focused on the quantification of the compositions of the matrix and carbides. The APFIM results indicate that there was no significant microstructural evolution after a long-term thermal exposure in weld, plate, or forging materials. The matrix depletion of copper that was observed in weld materials was consistent with the copper concentration in the matrix after the stress-relief heat treatment. The compositions of cementite carbides aged for 100,000 h were compared with the Thermocalc{trademark} prediction. The APFIM comparisons of materials under these conditions are consistent with the measured change in mechanical properties such as the Charpy transition temperature.

  17. Microstructure and Mechanical Properties of Granular Pearlite Steel After Equal Channel Angular Pressing

    Science.gov (United States)

    Xiong, Yi; He, Tiantian; Li, Pengyan; Chen, Lufei; Ren, Fengzhang; Volinsky, Alex A.

    2015-07-01

    Equal channel angular pressing (ECAP) of granular pearlite high carbon steel was carried out at room temperature via the Bc route. The microstructure evolution was investigated by means of scanning and transmission electron microscopy, and the mechanical properties of granular pearlite steel were measured by tensile and microhardness testing. After four passes, the microstructure was obviously refined. An ultrafine microduplex structure with 400 nm equiaxed ferrite grains and 200 nm cementite particles were formed. The yield strength, ultimate tensile strength, microhardness, and the ratio of the yield to tensile strength increased with the number of ECAP passes, however, the elongation slightly reduced. The tensile fracture morphology changes gradually from ductile fracture to ductile and quasi-cleavage mixed fracture.

  18. Sulfate and acid resistant concrete and mortar

    Science.gov (United States)

    Liskowitz, John W.; Wecharatana, Methi; Jaturapitakkul, Chai; Cerkanowicz, deceased, Anthony E.

    1998-01-01

    The present invention relates to concrete, mortar and other hardenable mixtures comprising cement and fly ash for use in construction and other applications, which hardenable mixtures demonstrate significant levels of acid and sulfate resistance while maintaining acceptable compressive strength properties. The acid and sulfate hardenable mixtures of the invention containing fly ash comprise cementitious materials and a fine aggregate. The cementitous materials may comprise fly ash as well as cement. The fine aggregate may comprise fly ash as well as sand. The total amount of fly ash in the hardenable mixture ranges from about 60% to about 120% of the total amount of cement, by weight, whether the fly ash is included as a cementious material, fine aggregate, or an additive, or any combination of the foregoing. In specific examples, mortar containing 50% fly ash and 50% cement in cementitious materials demonstrated superior properties of corrosion resistance.

  19. Investigation of Transformation for Ultrahigh Strength Steel Aermet 100

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    @@The heat-stagnation curves of two quenched and cryogenically treated ultrahigh strength AF1410and Aermet 100 steels during heating and cooling in furnace have been measured. The results showed that the curve displayed an abnormal terrace in the course of heating, and within the temperature range corresponding to the terrace, the formation and growth of both cementite Fe3C and secondary hardening phase M2C in the steel make the carbon content in matrix obviously vary. It is in the region of terrace that the optimum combination of tensile strength and fracture toughness is obtained because of secondary hardening. Based on the measured heat-stagnation curve, several transformation points have been determined and the correctness was also verified by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Furthermore, the influence of heating rate and tempering temperature on the crystal structure and stability of austenite has been studied.

  20. Degradation of the pipe-steel structure upon long-term operation in contact with a hydrogen sulfide-containing medium

    Science.gov (United States)

    Schastlivtsev, V. M.; Tabatchnikova, T. I.; Tereshchenko, N. A.; Yakovleva, I. L.

    2011-03-01

    The phase composition and structure of defect portions of pipelines after long-term service in contact with a hydrogen sulfide-containing medium have been investigated. From structural changes, the process of the initiation of cracks and fracture of a low-carbon ferritic-pearlitic steel containing slag-induced laminations and precipitates of sulfides of the (Fe,Mn)S type has been reconstructed. The conditions under which a block cementite substructure is formed in the course of service and a transformation of the plate-type shape of the carbide phase occurs have been analyzed. It has been established that the dispersed carbides precipitating in this case limit the mobility of dislocations and thereby favor degradation of service properties of the pipe steel.

  1. Fading of inoculation effects in ductile iron

    Directory of Open Access Journals (Sweden)

    E. Fraś

    2008-03-01

    Full Text Available In work i t has bccn shown rcsults or invcsligations of influcncc of rime Iapsed form inoculation proccss on graphitc nucleation potentialrcprcscntcd by: numbcr of graphitc nodulcs N and N,, maximum undercooling AT,, during solidification of gmphile eutcct ic. abmlutcchilling tcndcncy CT and critical casting diametct dh. undcr which cementite euteclic occur (so-callcd chills. Morcovcr it has hccncstima~cd raic of changc of N and N, AT,,,. CT and dk,. Also, it has bccn provcd that altcr onc minutc sincc rhc momcnt of inocuIationproccss nhout 35% of prnphttc nucIeation potenrial is tost. by 40% chitking tendency, by 70% incrcascs maximum undcrcmling forgraphitc ci~tccrica nd by nearly 40% caging diameter has to bc incrcascd in ordcr to avoid chills.

  2. Structure-phase states evolution in rails during a long operation

    Energy Technology Data Exchange (ETDEWEB)

    Peregudov, Oleg, E-mail: gromov@physics.sibsiu.ru; Gromov, Victor, E-mail: gromov@physics.sibsiu.ru; Morozov, Konstantin, E-mail: gromov@physics.sibsiu.ru; Alsaraeva, Krestina, E-mail: gromov@physics.sibsiu.ru; Semina, Olga, E-mail: gromov@physics.sibsiu.ru [Siberian State Industrial University, Novokuznetsk, 654007 (Russian Federation); Ivanov, Yurii, E-mail: yufi55@mail.ru [Institute of High-Current Electronics SB RAS, Tomsk, 634055 (Russian Federation)

    2015-10-27

    By methods of scanning and transmission electron microscopy the transformation regularities of structure-phase states, defect substructure, fracture surface of rail surface layer up to 10 mm deep in process of long-term operation (passed tonnage of gross weight 1000 mln tons) were revealed. It has been shown that the surface layer ∼20 μm in thickness has a multiphase, submicro- and nanocrystalline structure and it contains micropores and microcracks. The increased density of bend extinction contours at 2 mm depth from the tread contact surface was noted. The analysis of structure morphological constituents and internal stress fields, created by intra- and interphase boundaries after long operation was carried out. It was shown that the maximum amplitude of stress fields was formed on the interphase boundary the globular cementite particle–matrix. The evaluation of stress fields was done.

  3. Low temperature superplasticity and thermal stability of a nanostructured low-carbon microalloyed steel

    Science.gov (United States)

    Hu, J.; Du, L.-X.; Sun, G.-S.; Xie, H.; Misra, R. D. K.

    2015-12-01

    We describe here for the first time the low temperature superplasticity of nanostructured low carbon steel (microalloyed with V, N, Mn, Al, Si, and Ni). Low carbon nanograined/ultrafine-grained (NG/UFG) bulk steel was processed using a combination of cold-rolling and annealing of martensite. The complex microstructure of NG/UFG ferrite and 50-80 nm cementite exhibited high thermal stability at 500 °C with low temperature elongation exceeding 100% (at less than 0.5 of the absolute melting point) as compared to the conventional fine-grained (FG) counterpart. The low temperature superplasticity is adequate to form complex components. Moreover, the low strength during hot processing is favorable for decreasing the spring back and minimize die loss.

  4. Design of a low-alloy high-strength and high-toughness martensitic steel

    Science.gov (United States)

    Zhao, Yan-jun; Ren, Xue-ping; Yang, Wen-chao; Zang, Yue

    2013-08-01

    To develop a high strength low alloy (HSLA) steel with high strength and high toughness, a series of martensitic steels were studied through alloying with various elements and thermodynamic simulation. The microstructure and mechanical properties of the designed steel were investigated by optical microscopy, scanning electron microscopy, tensile testing and Charpy impact test. The results show that cementite exists between 500°C and 700°C, M7C3 exits below 720°C, and they are much lower than the austenitizing temperature of the designed steel. Furthermore, the Ti(C,N) precipitate exists until 1280°C, which refines the microstructure and increases the strength and toughness. The optimal alloying components are 0.19% C, 1.19% Si, 2.83% Mn, 1.24% Ni, and 0.049% Ti; the tensile strength and the V notch impact toughness of the designed steel are more than 1500 MPa and 100 J, respectively.

  5. Tailoring the gradient ultrafine-grained structure in low-carbon steel during drawing with shear

    Directory of Open Access Journals (Sweden)

    G. I. Raab

    2016-04-01

    Full Text Available Conventional drawing and drawing with shear were conducted on the rods of low-carbon steel. Deformation by simple drawing forms basically a homogenous structure and leads to a uniform change in microhardness along the billet volume. A comparative analysis of the models of these processes showed that shear drawing of steel at room temperature reduces energy characteristics in half, normal forces on the die – by 1,8, and enhances the strain intensity from 0,5 to 1,6. During drawing with shear, strain-induced cementite dissolution occurs and a gradient structure is formed, which increases the microhardness of the surface layer up to values close to 7 000 MPa.

  6. The influence of drawing speed on structure changes in high carbon steel wires

    Directory of Open Access Journals (Sweden)

    M. Suliga

    2015-01-01

    Full Text Available In the paper the influence of the drawing speed on structure changes has been assessed. The Scanning Electron Microscope investigation confirmed that for wires drawn with high total draft, exceeding 80 %, makes it impossible to clearly assess the impact of drawing technology on structural changes in the drawn wires. Thus, to assess the structural changes necessary to apply quantitative methods. On the basis of examination of the wire structure by measuring of electrical resistance, the structure changes in drawn wires has been determined. It has been shown that the increase of drawing speed, especially above 15 m/s, causes an increase in structure defect, with a decline in platelet orientation of cementite in drawn wires.

  7. Effect of Cr and Mo on strain ageing behaviour of low carbon steel

    International Nuclear Information System (INIS)

    This work explores the effects of Cr (0.26-0.74 wt%) and Mo (0.09-0.3 wt%) additions on the kinetics of strain ageing process in low carbon steel. The strain ageing behaviour of the steels was investigated by using tensile tests and transmission electron microscopy. The results have shown that Mo-alloyed steels undergo the same four stages of ageing as unalloyed low carbon steel, whereas Cr-alloyed steels exhibit only three stages of ageing. At the same time, the addition of Mo accelerates the ageing response, while alloying with Cr reduces the rate of strain ageing by ∼3 times in comparison with non-alloyed low carbon steel. It especially delays the offset of Stage III. This is explained by the reduction of carbon content in ferrite due to the enrichment of cementite with Cr leading to the reduction of its equilibrium solubility in ferrite.

  8. Monitoring iron carbide production from iron ore by quantitative Moessbauer spectroscopy

    International Nuclear Information System (INIS)

    The process of converting iron ore (principally Fe2O3 or Fe3O4) into iron carbide (Fe3C) to be used as feedstock for steel-making yields complex mixtures of several iron containing compounds as a function of processing conditions. In addition to the above compounds (hematite, magnetite and cementite), the mixtures typically contain wustite (FeO) and metallic iron (Fe). Moessbauer spectroscopy has been developed into a quantitative analytical method for monitoring the degree of conversion to carbide from samples periodically extracted from a fluidized bed reactor type of pilot plant. Emphasis has been placed on standardizing and simplifying the analysis procedure for routine use in an industrial environment. (orig.)

  9. Anti-seismic behavior of HRB400 reinforced steel bars

    Institute of Scientific and Technical Information of China (English)

    QIN Bin; SHENG Guang-min; GONG Shi-hong

    2005-01-01

    The properties of anti-seismic HRB400 steel bars with 25 mm diameter were systematically investigated. The results showed that the properties of the HRB400 reinforced steel bars had been greatly enhanced comparing with HRB335 steel bars, i.e. coordination of strength and ductility, strain-aging sensibility, low temperature impact toughness, weld ability and high strain low cycle fatigue. The ductile-brittle transit temperatures of hot-rolled and strain-aged steel bars were evaluated as -17℃ and-8℃ respectively, and the low temperature impact toughness of HRB400 steel bars remains to be improved. Transmission electron microscopy (TEM) and electron diffraction showed little vanadium existed in ferrite as VN, most of which existed in pearlite as alloy cementite which resulted in the declination of impact toughness. Methods were suggested to improve the anti-seismic properties of steel bars.

  10. Investigation on tempering of granular bainite in an offshore platform steel

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Yanlei; Jia, Tao; Zhang, Xiangjun [The State Key Laboratory of Rolling and Automation, Northeastern University, P.O. Box 105, No. 11, Lane 3, Wenhua Road, HePing District, Shenyang 110819 (China); Liu, Zhenyu, E-mail: zyliu@mail.neu.edu.cn [The State Key Laboratory of Rolling and Automation, Northeastern University, P.O. Box 105, No. 11, Lane 3, Wenhua Road, HePing District, Shenyang 110819 (China); Misra, R.D.K. [Department of Metallurgical and Materials Engineering, University of Texas at El Paso, 500 W. University Avenue, El Paso, TX 79968-0521 (United States)

    2015-02-25

    Granular bainite, where M-A constituents dispersed in bainitic ferrite matrix usually presents at the half thickness region in thermo-mechanically processed heavy gauge offshore platform steel. In the present work, the decomposition of M-A constituents during tempering at 600 °C was firstly revealed by transmission electron microscopy (TEM) analysis, which primarily involves the precipitation of cementite, recovery and recrystallization of highly dislocated ferrite matrix. Then, the effect of tempering on mechanical properties was investigated by tempering at different temperature for 60 min. Results indicated that, at tempering temperature of 500–600 °C, large quantity of micro-alloying carbides precipitated and partially compensated the loss of strength mainly due to the decomposition of M-A constituents. Compared with the as-rolled state, the decomposition of M-A constituents and softening of bainitic ferrite matrix after tempering have resulted in higher density of microvoids and substantial plastic deformation before impact failure.

  11. Plastic Deformation and Softening of the Surface Layer of Railway Wheel

    Directory of Open Access Journals (Sweden)

    Ławrynowicz Z.

    2015-12-01

    Full Text Available In this study scanning electron microscope (SEM and optical micrograph observations were used to investigate the plastic deformation near the surface of the worn railway wheel following service. Microstructure, plastic deformation and micro-hardness of the material in the outermost tread layer of used passenger railway wheel were characterised. It was found that the material in the contact surface of wheel undergoes severe plastic deformation. Vickers micro-hardness measurements in the highly deformed layer could be correlated with softening of the outer wheel rim and the spheroidisation of the cementite phase. Examination of worn, railway wheel taken out of service, has indicated that cracks are predominantly initiated at the wheel surface down the edges of highly strained, pro-eutectoid ferrite zones (situated along prior austenite grain boundaries and that such pro-eutectoid ferrite zones also facilitate crack propagation.

  12. Study on microstructure and hardness uniformity of non-quenched prehardened steel for large section plastic mould

    International Nuclear Information System (INIS)

    Microstructures throughout a 460 mm x 800 mm cross-section of non-quenched prehardened (NQP) steel for plastic mould were characterized by optical microscopy, scanning electronic microscopy and transmission electronic microscopy. Strength and hardness of the NQP steel block was also tested. It is found that mechanical properties at core are close to that at surface and hardness distributes between 37 and 40 HRC through the whole section. Grains at core are coarser and deformation bands are observed at surface, while microstructures both at core and at surface are composed of bainitic ferrite laths with high dislocation density and interlath cementite and/or residual austensite. Considering continuous cooling transformation of the NQP steel, the small variation in hardness throughout the section is caused by the main microstructure bainite which possesses high hardenability. Moreover, the differences of the lath widths and dislocation density in baintic ferrite lath make hardness at surface a little higher than that at core

  13. Secondary Hardening, Austenite Grain Coarsening and Surface Decarburization Phenomenon in Nb-Bearing Spring Steel

    Institute of Scientific and Technical Information of China (English)

    2012-01-01

    The secondary hardening, the austenite grain coarsening and the surface decarburization phenomenon of Nb-bearing spring steel were investigated, and the effects of niobium on tempered microstructure was studied using scanning electron microscope. The results show that the micro-addition of niobium increases the tempering resistance and produces secondary hardening. The effect of niobium on the size and distribution of cementite particles is one of the primary reasons to increase the hardness after tempering. The grain-coarsening temperature of the spring steel is raised 150 ~C due to Nb-addition. Furthermore, both the secondary hardening and the austenite grain coarsening phenomenon congruously demonstrate niobium begins observably dissolving above 1 100 ℃ in the spring steel. Be- sides, niobium microalloying is an effective and economy means to decrease the decarburization sensitivity of the spring steels.

  14. Fracture Mechanisms in Steel Castings

    Directory of Open Access Journals (Sweden)

    Z. Stradomski

    2013-07-01

    Full Text Available The investigations were inspired with the problem of cracking of steel castings during the production process. A single mechanism of decohesion - the intergranular one - occurs in the case of hot cracking, while a variety of structural factors is decisive for hot cracking initiation, depending on chemical composition of the cast steel. The low-carbon and low-alloyed steel castings crack due to the presence of the type II sulphides, the cause of cracking of the high-carbon tool cast steels is the net of secondary cementite and/or ledeburite precipitated along the boundaries of solidified grains. Also the brittle phosphor and carbide eutectics precipitated in the final stage solidification are responsible for cracking of castings made of Hadfield steel. The examination of mechanical properties at 1050°C revealed low or very low strength of high-carbon cast steels.

  15. Microstructural features responsible for the combined high strength and ductility properties in CA processed HSLA steels

    Energy Technology Data Exchange (ETDEWEB)

    Michal, G.M. (Case Western Reserve Univ., Cleveland, OH (USA))

    Under a variety of CA processing conditions HSLA steels can develop superior combined strength and ductility properties compared to the same steels subject to BA processing. To determine the possible causes of the better properties of CA processed HSLA steels, a detailed optical and TEM evaluation of a series of Cb and Cb-V steels cold rolled 62% and annealed at 705 C to 871 C for 1 to 10 minutes was performed. Steels that developed yield strengths above 414 MPa (60 KSI) were often found to contain isolated regions of nonrecrystallized ferrite. These regions caused increases in yield strengths of as much as 75 MPa (11 KSI) with only a slight loss in ductility compared to fully recrystallized steels. Cementite inherited from the hot band spheroidized under certain annealing conditions. These and other results are presented and their ramifications for developing improved CA processing schemes are discussed.

  16. The application of metallographic techniques to the study of the tempering of HSLA-100 steel

    Energy Technology Data Exchange (ETDEWEB)

    Varughese, R.; Howell, P.R. (Pennsylvania State Univ., Univ. Park (United States))

    1993-06-01

    A study of a quenched, and a quenched and tempered low-carbon, copper-containing steel (HSLA 100) was conducted. The primary investigation technique employed was transmission electron microscopy. Quenching the steel from the austenitizing temperature yielded a microstructure that was predominantly lath martensite. However, a significant amount of retained austenite was also present.Niobium carbide particles were also documented in the as-quenched structures. Tempering at 605C for 1-3h yielded a heterogeneous distribution of [var epsilon]-Cu, much of which was associated with the lath boundaries. The austenite was highly resistant to decomposition during tempering at 605C and, as a consequence, little evidence of cementite precipitation was found.

  17. EFFECT OF COPPER ON PASSIVITY AND CORROSION BEHAVIOR OF FE-XC-5CU ALLOY

    Directory of Open Access Journals (Sweden)

    M. Ferhat

    2014-06-01

    Full Text Available The correlation between corrosion behavior rate of annealed Fe-xC-5Cu alloys and their microstructure and phase composition is presented. The metallurgical analyses, including, X-Ray diffraction (XRD, the scanning electron microscopy (SEM with energy dispersive analysis (EDX, and induction hardening characterization are conducted to study the Fe-C-Cu alloys. Corrosion parameters in H2SO4 1N solution have been established by carrying out electrochemical studies such as potentiodynamic (Tafel polarization and linear polarization, LP and electrochemical impedance spectroscopy (EIS. The coupled effect copper/microstructure is discussed. Alloying Cu showed a beneficial effect on hypoeutectoid steel and harmful effect on hypereutectoid steel. The improved corrosion resistance is related to cementite morphology and by a copper dissolution/re-deposition process.

  18. EFFECT OF COPPER ON PASSIVITY AND CORROSION BEHAVIOR OF FE-XC-5CU ALLOY

    Directory of Open Access Journals (Sweden)

    M. Ferhat

    2015-07-01

    Full Text Available The correlation between corrosion behavior rate of annealed Fe-xC-5Cu alloys and their microstructure and phase composition is presented. The metallurgical analyses, including, X-Ray diffraction (XRD, the scanning electron microscopy (SEM with energy dispersive analysis (EDX, and induction hardening characterization are conducted to study the Fe-C-Cu alloys. Corrosion parameters in H2SO4 1N solution have been established by carrying out electrochemical studies such as potentiodynamic (Tafel polarization and linear polarization, LP and electrochemical impedance spectroscopy (EIS. The coupled effect copper/microstructure is discussed. Alloying Cu showed a beneficial effect on hypoeutectoid steel and harmful effect on hypereutectoid steel. The improved corrosion resistance is related to cementite morphology and by a copper dissolution/re-deposition process.

  19. Influence of the Initial Microstructure on the Reverse Transformation Kinetics and Microstructural Evolution in Transformation-Induced Plasticity-Assisted Steel

    Science.gov (United States)

    Kim, Jeong In; Ryu, Joo Hyun; Lee, Sea Woong; Lee, Kyooyoung; Heo, Yoon-Uk; Suh, Dong-Woo

    2016-08-01

    The reverse transformation behavior upon heating to intercritical temperature was studied in Fe-0.21C-2.2Mn-1.5Si (wt pct) alloy with three initial microstructures. One is the cold-rolled (CR) structure and two others are martensite having different fractions of retained austenite. The CR structure exhibits slower reverse transformation kinetics than martensite due to the lesser population of potent nucleation sites and coarse cementite particles. The film type of retained austenite at the martensite lath boundary contributes to the earlier start of the reverse transformation, because it can proceed as the growth of pre-existing retained austenite, which makes the nucleation process less critical. Besides, the growth of interlath austenite plays an essential role in the evolution of fine lath-type reverse-transformed microstructure, which was difficult to obtain from similar initial microstructures of martensite having negligible fraction of interlath austenite.

  20. Influence of the Initial Microstructure on the Reverse Transformation Kinetics and Microstructural Evolution in Transformation-Induced Plasticity-Assisted Steel

    Science.gov (United States)

    Kim, Jeong In; Ryu, Joo Hyun; Lee, Sea Woong; Lee, Kyooyoung; Heo, Yoon-Uk; Suh, Dong-Woo

    2016-11-01

    The reverse transformation behavior upon heating to intercritical temperature was studied in Fe-0.21C-2.2Mn-1.5Si (wt pct) alloy with three initial microstructures. One is the cold-rolled (CR) structure and two others are martensite having different fractions of retained austenite. The CR structure exhibits slower reverse transformation kinetics than martensite due to the lesser population of potent nucleation sites and coarse cementite particles. The film type of retained austenite at the martensite lath boundary contributes to the earlier start of the reverse transformation, because it can proceed as the growth of pre-existing retained austenite, which makes the nucleation process less critical. Besides, the growth of interlath austenite plays an essential role in the evolution of fine lath-type reverse-transformed microstructure, which was difficult to obtain from similar initial microstructures of martensite having negligible fraction of interlath austenite.

  1. Microstructural and mechanical characterizations of steel tubes joined by transient liquid phase bonding using an amorphous Fe–B–Si interlayer

    Energy Technology Data Exchange (ETDEWEB)

    Di Luozzo, Nicolas, E-mail: nicolasdiluozzo@gmail.com [Laboratorio de Sólidos Amorfos, INTECIN, Facultad de Ingeniería, Universidad de Buenos Aires – CONICET, Paseo Colón 850, C1063ACV Buenos Aires (Argentina); Laboratoire des Matériaux et du Génie Physique (CNRS UMR 5628), Grenoble Institute of Technology, MINATEC, Grenoble Cedex 1 (France); Doisneau, Béatrice; Boudard, Michel [Laboratoire des Matériaux et du Génie Physique (CNRS UMR 5628), Grenoble Institute of Technology, MINATEC, Grenoble Cedex 1 (France); Fontana, Marcelo; Arcondo, Bibiana [Laboratorio de Sólidos Amorfos, INTECIN, Facultad de Ingeniería, Universidad de Buenos Aires – CONICET, Paseo Colón 850, C1063ACV Buenos Aires (Argentina)

    2014-12-05

    Highlights: • We joined steel tubes by means of TLPB process using a Fe–B–Si foil as interlayer. • We characterized both microstructure and mechanical properties of the joint. • The microstructure at the joint consists only of ferrite grains. • Evidences of non-epitaxial solidification were found. • Both tensile and hardness tests show the soundness of the joint. - Abstract: In this work the transient liquid phase bonding process was successfully used to join seamless carbon steel tubes using an amorphous Fe–B–Si foil as interlayer. The tubes were aligned with their butted surfaces in contact with the interlayer and the entire assembly was heated by means of an induction furnace under a reducing atmosphere. The temperature was raised to the process temperature (≈1300 °C) and then held for 7 min. The joining process was performed under a pressure of 5 MPa. The joined tubes microstructures were characterized by direct observations – scanning electron microscopy – and diffraction techniques – electron backscatter diffraction. Chemical analysis was performed by electron probe microanalysis. The joint region (JR) presents only ferrite grains - in contrast with the heat affected zone (HAZ) and the base metal (BM), whose microstructures consist of ferrite and cementite. Si content at the JR was precisely determined by chemical profiling, showing higher concentrations of Si compared with the HAZ and BM. These results are in accordance with the fact that the cementite is unable to form in Si enriched zones. Also, ferrite grains at the JR present high-angle grain boundaries with respect to the grains of the HAZ. Tensile tests show that the joined tubes failed away from the bond, at the HAZ, and reached 96% of the ultimate tensile strength of the BM, in the as-bonded condition. Microindentation hardness profiles across the bonding zone are in agreement with the observed microstructures at the different zones of the bond region.

  2. Reason Analysis on Fracture of Prestressed Steel Wires%预应力钢丝断裂原因分析

    Institute of Scientific and Technical Information of China (English)

    邹力扬

    2012-01-01

    通过化学成分分析、金相检验、低倍检验以及力学性能测试等方法,对82B盘条在拉拔成预应力钢丝过程中发生断裂的原因进行了分析。结果表明:造成82B盘条拉拔时发生脆断的主要原因是由于原料中存在严重的碳偏析,轧制时在富碳区出现过热,析出网状和块状渗碳体以及渗碳体魏氏组织;因而在相同的拉拔力作用下,盘条整个横截面上的塑性变形程度不同,容易产生微裂纹,在拉拔过程中发生断裂。%By means of chemical compositions analysis, metallographic examination, macroscopic examination and mechanical properties lest, the fracture reasons of prestressed steel wires during drawing from 82B steel wire rod were analyzed. The results show that the key reason of the brittle fracture was that the raw materials had defects of serious carbon segregation which resulted in overheating at the carbon-rich area and precipitation of mesh and massive cementite and cementite Widmanstatten structure when rolling. So in the same drawing force, the plastic deformation degree of the whole cross section of the wire rod was different, cracks produced and fracture happened during drawing.

  3. Microstructural and compositional evolution of iron carbonitride compound layers during salt bath nitrocarburizing

    Energy Technology Data Exchange (ETDEWEB)

    Somers, M.A.J.; Colijn, P.F.; Sloof, W.G.; Mittemeijer, E.J. (Technische Hogeschool Delft (Netherlands). Lab. of Metallurgy)

    1990-01-01

    An analysis was made of iron carbonitride compound layer development during nitrocarburizing of pure iron and two iron-carbon specimens, containing 0.3 wt.-% C and 0.6 wt.-% C, respectively, in an aerated cyanate-based salt bath at 853 K. The microstructural evolution was followed by means of light- and scanning electron microscopy and X-ray diffraction analysis. Composition-depth profiles were determined as a function of nitrocarburizing time applying electron-probe microanalysis and X-ray diffraction analysis. Compound layer formation on pure iron starts with the nucleation of cementite at the surface, which is immediately followed by nucleation of {epsilon} carbonitride containing a relatively high carbon content and a relatively low nitrogen content. Thereafter, {gamma}' (carbo)nitride and finally {epsilon} nitride develop at the outer surface. In general, on continued nitrocarburizing the nitrogen content at the outer surface increases and the carbon content decreases. Accordingly, the constitution of the compound layer is determined to a large extent by the (difference between the) absorption kinetics of carbon and of nitrogen rather than by equilibrium thermodynamics. In the surface-adjacent region, the layers are highly porous, predominantly as a consequence of corrosive attack by agents of the salt bath. As compared with nitrocarburizing of pure iron, the major effect of carbon present as cementite in pearlite regions in the iron-carbon specimens appears to be promotion of the formation of {epsilon} carbonitride in the compound layer at the cost of {gamma}' (carbo)nitride. (orig.).

  4. Microtwinning as a common mechanism for the martensitic and pearlitic transformations

    Energy Technology Data Exchange (ETDEWEB)

    Kraposhin, V., E-mail: kraposhin@gmail.com [Bauman Moscow State Technical University, 5, 2nd Baumanskaya Street, 105005 Moscow (Russian Federation); Jakovleva, I.; Karkina, L. [Institute of Metal Physics of Russian Academy of Science, Ekaterinburg (Russian Federation); Nuzhny, G. [Bauman Moscow State Technical University, 5, 2nd Baumanskaya Street, 105005 Moscow (Russian Federation); Zubkova, T. [Institute of Metal Physics of Russian Academy of Science, Ekaterinburg (Russian Federation); Talis, A. [A.N. Nesmeyanov Institute of Organoelement Compounds, Moscow (Russian Federation)

    2013-11-15

    Highlights: ► Diagonal flipping in the coordination polyhedra was proposed as the main mechanism of polymorph transformation. ► Microtwinning of crystal lattice can be effected by diagonal flipping in polyhedra. ► Martensite and perlite transformation can be fulfilled by the similar microtwinning. ► Twinning of austenite during perlite transformation has been observed by electron microscopy, thus confirming the proposed model. ► Orientation relationships predicted by model are in accordance with the experiment. -- Abstract: Common model for austenite transformations to pearlite and martensite has been proposed. The model uses a topological operation which is a local flipping of interatomic bonds resulting in formation of the structural unit of the coherent twin boundary. Main structural unit of a coherent twin boundary along {1 1 3} in the FCC lattice is a trigonal prism which is also the main building unit for the cementite structure. The atomic structure of such multiple {1 1 3} twins coincides with the structure of multiple twins along {1 1 2} of the BCC lattice, so the FCC–BCC transformation route is the FCC twinning along {1 1 3} and detwinning of {1 1 2} BCC twins into BCC structure. Carbon atoms serve as stabilizers to the prismatic iron configurations thus forming the cementite structure during pearlite transformation. High density of microtwins in the rest austenite after pearlite transformation in 1.2C–4Mn steel and new orientation relationships between pearlite constituents and austenite have been observed by transmission electron microscopy in full consistency with the proposed model. The twinning–detwinning mechanism prescribes also parallelism between {1 1 3} FCC and {1 1 2} BCC for martensite transformation in full accordance with published data.

  5. Metal Dusting-Mechanisms and Preventions

    Institute of Scientific and Technical Information of China (English)

    J.Q.ZHANG; D.J.YOUNG

    2009-01-01

    Metal dusting attacks iron, low and high alloy steels and nickel-or cobalt-base alloys by disintegrating bulk metals and alloys into metal particles in a coke deposit. It occurs in strongly carburising gas atmospheres (carbon activity aC>1) at elevated temperatures (400℃~1000℃). This phenomenon has been studied for decades, but the detailed mechanism is still not well understood. Current methods of protection against metal dusting are either directed to the process conditions-temperature and gas composition-or to the development of a dense adherent oxide layer on the surface of the alloy by selective oxidation. However, metal dusting still occurs by carbon dissolving in the base metal via defects in the oxide scale. The research work at UNSW is aimed at determining the detailed mechanism of metal dusting of both ferritic and austenitic alloys, in particular the microprocesses of graphite deposition, nanoparticle formation and underlying metal destruction. This work was carried out using surface observation, cross-section analysis by focused ion beam and electron microscopic examination of coke deposits at different stages of the reaction. It was found that surface orientation affected carbon deposition and metal dusting at the initial stage of the reaction. Metal dusting occurred only when graphite grew into the metal interior where the volume expansion is responsible for metal disintegration and dusting. It was also found that the metal dusting process could be significantly changed by alterations in alloy chemistry. Germanium was found to affect the iron dusting process by destabilising FeC but increasing the rate of carbon deposition and dusting, which questions the role of cementite in ferritic alloy dusting. Whilst adding copper to iron did not change the carburisation kinetics, cementite formation and coke morphology, copper alloying reduced nickel and nickel-base alloy dusting rates significantly. Application of these fundamental results to the dusting

  6. Colour Metallography of Cast Iron

    Institute of Scientific and Technical Information of China (English)

    By Zhou Jiyang; Professor

    2011-01-01

    5.5 Eutectic crystallisation of white iron When undercooled below the eutectic line ECF in the Fe-C phase diagram,liquid iron will start eutectic transformation (crystallization):eutectic liquid → cementite + austenite.Eutectic crystallisation is an important stage during the crystallization of white iron.At this stage,the nucleation and growth of eutectic cells (consisting of carbide or cementite + austenite) occur.The carbide in eutectic cells (or eutectic carbide) is the main hard and brittle phase structure which has an important effect on the properties of white iron.If there is no primary carbide in the structure,the effect of eutectic carbide is more prominent.5.5.1 Thermodynamics and kinetics of eutectic crystallisationWhether a eutectic melt follows the meta-stable system to crystallise as carbide + austenite,or follows the stable system to crystallise as graphite + austenite eutectic,is dependent on the nucleation and growth of the two high carbon phases (carbide and graphite),namely,on thermodynamic and kinetic conditions.Figure 5-23 shows the comparison of thermodynamic driving forces of the two eutectics.The two lines in the lower section of the figure represent the free energy of the two eutectics respectively and GL is the free energy of the undercooled iron melt.It is easy to see that the iron melt has the highest free energy and the graphiteaustenite has the lowest free energy;so,following a stable system,the thermodynamic condition favours the crystallisation of graphite-austenite eutectic from the iron melt.

  7. Effect of annealing on mechanical properties of ledeburitic cast steel

    Directory of Open Access Journals (Sweden)

    E. Rożniata

    2007-01-01

    Full Text Available Purpose: The paper presents evaluation of influence of grain normalization (refinement as a result of repeatedaustenitizing, and the inclination to precipitate the hypereutectoid cementite in Widmannstätten structure inG200CrMoNi4-6-3 cast steel. Four temperatures of heat refining have been applied.Design/methodology/approach: Basic research of G200CrMoNi4-6-3 cast steel included metallographicanalysis, and hardness and impact strength tests. The heat treatment has been planned on the basis of CCTdiagram prepared for that alloy cast steel.Findings: The test material has been G200CrMoNi4-6-3 hypereutectoid cast steel. The evaluation has beencarried out for four annealing temperatures, i.e. 850°C, 900°C, 950°C and 1050°C. At all annealing temperaturesin the structure of cast steel the precipitation of hypereutectoid cementite along grain boundaries of formeraustenite took place. At the temperature of 850°C one may observe the coagulated hypereutectoid cementiteprecipitates inside of primary grains of austenite. Whereas beginning from the temperature of 900°C thecementite in G200CrMoNi4-6-3 cast steel forms distinct „subgrains” inside of primary grains of austenite.Research limitations/implications: Research financed by the Ministry of Scientific Research and InformationTechnology, grant No. 3 T08B 057 29.Practical implications: G200CrMoNi4-6-3 cast steel of ledeburite class is used mainly for rolls production.Any data related to the structure and mechanical properties of that cast steel are precious for the manufacturersand users of the mill rolls.Originality/value: The new heat treatment of G200CrMoNi4-6-3 cast steel

  8. Study of the effect of nano-sized precipitates on the mechanical properties of boron-added low-carbon steels by neutron scattering techniques.

    Science.gov (United States)

    Seong, B S; Cho, Y R; Shin, E J; Kim, S I; Choi, S-H; Kim, H R; Kim, Y J

    2008-10-01

    Small-angle neutron scattering (SANS) and neutron powder diffraction (ND) techniques were used to study quantitatively the effect of nano-sized precipitates and boron addition on the mechanical properties of low-carbon steels. SANS was used to evaluate nano-sized precipitates, smaller than about 600 A in diameter, and ND was used to determine the weight fraction of the cementite precipitates. Fine core-shell structured spherical precipitates with an average radius of ~50 A, such as MnS and/or CuS, surrounded by BN layers were observed in the boron-added (BA) low-carbon steels; fine spherical precipitates with an average radius of ~48 A were mainly observed in the boron-free (BF) low-carbon steels. In the BA steels, the number of boron precipitates, such as BN, Fe(3)(C,B) and MnS, surrounded by BN layers increased drastically at higher hot-rolling temperatures. The volume fraction of the fine precipitates of the BA steels was higher than that of the BF steels; this difference is related to the rapid growth of the BN layers on the MnS and CuS precipitates. Boron addition to low-carbon steels resulted in a reduction in strength and an improvement in elongation; this behaviour is related to the reduction of the solute carbon and the nitrogen contents in the ferrite matrix caused by the precipitation of BN, as well by the increase in the volume fraction of the cementites. PMID:19461851

  9. Microstructural and mechanical characterizations of steel tubes joined by transient liquid phase bonding using an amorphous Fe–B–Si interlayer

    International Nuclear Information System (INIS)

    Highlights: • We joined steel tubes by means of TLPB process using a Fe–B–Si foil as interlayer. • We characterized both microstructure and mechanical properties of the joint. • The microstructure at the joint consists only of ferrite grains. • Evidences of non-epitaxial solidification were found. • Both tensile and hardness tests show the soundness of the joint. - Abstract: In this work the transient liquid phase bonding process was successfully used to join seamless carbon steel tubes using an amorphous Fe–B–Si foil as interlayer. The tubes were aligned with their butted surfaces in contact with the interlayer and the entire assembly was heated by means of an induction furnace under a reducing atmosphere. The temperature was raised to the process temperature (≈1300 °C) and then held for 7 min. The joining process was performed under a pressure of 5 MPa. The joined tubes microstructures were characterized by direct observations – scanning electron microscopy – and diffraction techniques – electron backscatter diffraction. Chemical analysis was performed by electron probe microanalysis. The joint region (JR) presents only ferrite grains - in contrast with the heat affected zone (HAZ) and the base metal (BM), whose microstructures consist of ferrite and cementite. Si content at the JR was precisely determined by chemical profiling, showing higher concentrations of Si compared with the HAZ and BM. These results are in accordance with the fact that the cementite is unable to form in Si enriched zones. Also, ferrite grains at the JR present high-angle grain boundaries with respect to the grains of the HAZ. Tensile tests show that the joined tubes failed away from the bond, at the HAZ, and reached 96% of the ultimate tensile strength of the BM, in the as-bonded condition. Microindentation hardness profiles across the bonding zone are in agreement with the observed microstructures at the different zones of the bond region

  10. Influence of activation modes on diametral tensile strength of dual-curing resin cements Influência dos métodos de ativação na resistência à tração diametral de cimentos resinosos duais

    Directory of Open Access Journals (Sweden)

    Renata Garcia Fonseca

    2005-12-01

    Full Text Available In metallic restorations, the polymerization of dual-curing resin cements depends exclusively on chemical activation. The effect of the lack of photoactivation on the strength of these cements has been rarely studied. This study evaluated the influence of activation modes on the diametral tensile strength (DTS of dual-curing resin cements. Base and catalyst pastes of Panavia F, Variolink II, Scotchbond Resin Cement, Rely X and Enforce were mixed and inserted into cylindrical metal moulds (4 x 2 mm. Cements were either: 1 not exposed to light (chemical activation = self-cured groups or 2 photoactivated through mylar strips (chemical and photo-activation = dual-cured groups (n = 10. After a 24 h storage in 37ºC distilled water, specimens were subjected to compressive load in a testing machine. A self-curing resin cement (Cement-It and a zinc phosphate cement served as controls. Comparative analyses were performed: 1 between the activation modes for each dual-curing resin cement, using Student’s t test; 2 among the self-cured groups of the dual-curing resin cements and the control groups, using one-way ANOVA and Tukey’s test (alpha = 0.05. The dual-cured groups of Scotchbond Resin Cement (53.3 MPa, Variolink II (48.4 MPa and Rely X (51.6 MPa showed higher DTS than that of self-cured groups (44.6, 40.4 and 44.5 MPa respectively (p 0.05. The self-cured groups of all the dual-curing resin cements presented statistically the same DTS as that of Cement-It (44.1 MPa (p > 0.05, and higher DTS than that of zinc phosphate (4.2 MPa. Scotchbond Resin Cement, Variolink II and Rely X depended on photoactivation to achieve maximum DTS. In the absence of light, all the dual-curing resin cements presented higher DTS than that of zinc phosphate and statistically the same as that of Cement-It (p > 0.05.Em restaurações metálicas, a polimerização dos cimentos resinosos duais depende exclusivamente da ativação química. Há poucas pesquisas sobre o efeito

  11. 形变-球化退火共析钢的组织和性能%Microstructure and properties of eutectoid steel processed by deformation and spheroidizing annealing

    Institute of Scientific and Technical Information of China (English)

    郑成思; 李龙飞

    2015-01-01

    Eutectoid steel with spheroidal pearlite was processed using subcritical annealing, and eutectoid steel with the microstructure consisting of fine-grained ferrite matrix (α) and cementite particles (θ) , i.e., fine (α+θ) structure, was formed by the warm deformation and divorced eutectoid transformation.The microstructure and the mechanical properties were analyzed by using scanning electron microscopy and room-temperature tensile test for eutectoid steel with spheroidal pearlite or fine (α+θ) structure.The results show that fine (α+θ) structure with high spheroidization rate can be obtained by the warm deformation and divorced eutectoid transformation in short time in comparison with subcritical annealing for eutectoid steel.Warm deformation of pearlite and proper temperature and time of austenitizing are critical to obtain a microstructure consisting of austenite and cementite particles suitable for divorced eutectoid transformation.The prolonged isothermal time in the temperature under the A1 causes the increase in the average size of ferrite grains and cementite particles but the decrease in the strength and the elongation for eutectoid steel with fine (α+θ) structure.%以共析钢为研究对象,通过亚温球化退火制备了一种球化珠光体,利用珠光体温变形和离异共析原理制备了3种高球化率的细晶铁素体(α)+渗碳体粒子(θ)复相组织,即细晶(α+θ)复相组织,并结合SEM和室温单轴拉伸试验等手段研究了其显微组织和力学性能。结果表明:与亚温球化退火相比,利用珠光体温变形和离异共析原理可以快速制备高球化率的细晶(α+θ)复相组织。珠光体温变形以及合适的奥氏体等温时间和温度是获取适于发生离异共析转变的粥状组织的关键。随着A1以下温度等温时间的延长,细晶(α+θ)复相组织中的铁素体晶粒和渗碳体粒子平均尺寸增大,强度和伸长率减小。

  12. 位错及掺杂对球铁冲击韧性影响的电子机理%Electronic Mechanism of Dislocation and Doping for Impact Toughness of Ductile Cast Iron

    Institute of Scientific and Technical Information of China (English)

    杨忠华; 刘贵立; 曲迎东; 李荣德

    2015-01-01

    Atom module of α⁃Fe [ 100 ] ( 010 ) edge dislocation is built in metallic matrix of ductile cast iron. Density functional theory CASTEP method is employed to calculate energy parameters of carbon doping edge dislocation system including atom embedded energy, affinity energy and Mulliken population. It shows that there exist C2v symmetry group in structure of α⁃Fe [100] (010) edge dislocation and localized effect of dislocation happens in limited range. Energy valley attracts light impurity carbon which forms atom clusters in dislocation corn. Interaction between C and Fe atoms is strengthened with charge transportation between C⁃4s and Fe⁃2p obtains which pins dislocation slipping. Mulliken population of Fe atom and C atom is high. Length is short. Iron carbide could be produced. Binding energy and PDOS of carbon doping cementite system show that silicon promotes cementite decomposing and nicalon becomes corn of graphite ball, which improve impact toughness of ductile cast iron.%在球墨铸铁金属基体中建立α⁃Fe[100](010)刃型位错原子模型,利用基于密度泛函理论的CASTEP方法计算C原子在位错芯区的埋置能、亲和能、电荷布居数等电子参数。结果表明:α⁃Fe[100](010)刃型位错芯区局域效应集中范围较小并具有C2v点群对称性。位错芯区的能量低谷吸引轻质杂质C原子偏聚,C原子的2p轨道与刃型位错尖端Fe原子的4s价轨道之间发生电荷转移,具有较强的相互作用,使位错运动受阻。 Fe⁃C原子间布居数较大、原子间距离较小表明,Fe⁃C原子间有生成渗碳体化合物的倾向。 Si原子掺杂渗碳体的结合能及各原子轨道分波态密度表明,Si原子能够促使渗碳体分解,析出碳硅化合物成为石墨球化的核心,从而改善球墨铸铁的冲击韧性。

  13. Influence of Different Heat Treatment Process on the Microstructure and Properties of 12Cr2Mo1R Steel%热处理工艺对12Cr2Mo1R钢的组织和性能影响

    Institute of Scientific and Technical Information of China (English)

    蒋善玉

    2013-01-01

    The influences of different heat treatment process on the microstructure and properties of 12Cr2Mo1R heat-resistant steel plate were discussed. The results showed that with normalizing temperature rise, the bainite content and the strength rise; after normalizing at 975℃, the microstructure is 100%bainite and (Fe,Cr)3C type cementite;with the increase of tempering temperature and the extension of tempering time, the strength decreases and the nanometer strengthening phase separated in tempering at 600℃grows into a needle, and at the same time, the (Fe,Cr)3C cementite spheroidizes continuously and gradually turns to (Fe,Cr)7C3; the tempering treatment at 650℃after normalizing makes negative creep phenomenon disappearing. In production, 12Cr2Mo1R ought to adopt normalizing+tempering treatment, the normalizing temperature is between 920 and 950℃, the holding time is 1.5-3.0 min/mm, the tempering temperature is 720-750℃and the holding time is 2.0-4.0 min/mm.%探讨了不同热处理工艺对12Cr2Mo1R耐热钢板性能和组织的影响,结果表明:随正火温度的升高贝氏体增加,强度提高,975℃正火后,显微组织为100%贝氏体和(Fe,Cr)3C型渗碳体;随回火温度的提高及回火时间的延长,强度降低,600℃回火时析出的纳米强化相不断长大成针状,同时,(Fe,Cr)3C型渗碳体不断球化,逐渐向(Fe,Cr)7C3型转化;正火处理后再经650℃回火处理,负蠕变现象消失。生产中12Cr2Mo1R钢宜采用正火+回火处理,正火温度920~950℃,保温时间1.5~3.0 min/mm;回火温度720~750℃,保温时间2.0~4.0 min/mm。

  14. Efeito do tratamento térmico na caracterização microestrutural e das propriedades mecânicas de um aço inoxidável martensítico do tipo 13Cr5Ni0,02C

    Directory of Open Access Journals (Sweden)

    Eloy Strobel Filho

    2007-03-01

    Full Text Available O controle dos ciclos térmicos, nos tratamentos térmicos de têmpera e revenido, nos aços inoxidáveis martensítico do tipo 13Cr5Ni0,02C, é essencial para se obter boa resistência mecânica associada à resistência à corrosão, principalmente em equipamentos para a extração de petróleo. Corpos-de-prova foram austenizados por três horas a 1025°C, com posterior têmpera ao ar e água e revenido a 680ºC por 10 horas e resfriados ao ar. Um segundo grupo de corpos-de-prova foi tratado, termicamente, nas mesmas condições, porém foi realizado alívio de tensão a 150ºC por 1 hora e resfriado ao ar. O revenimento aumenta, substancialmente, a tenacidade e a ductilidade e, em alguns casos, sem redução substancial da resistência mecânica. A elevada dureza e resistência da martensita revenida está relacionada à alta relação de área entre os contornos de cementita e da matriz, pois estas agem como barreiras à movimentação das discordâncias, durante a deformação plástica. Dessa maneira, a matriz que é dúctil, é reforçada pela cementita.The thermal cycle control of heat treatments for the quenching and tempering of martensitic stainless steels, type 13Cr5Ni0,02C, is essential for obtaining the good mechanical resistance which is associated to corrosion resistance, mainly in equipment used in petroleum extraction. Samples were austenized during three hours at 1025°C, with posterior air and water quenching and tempering at 680ºC during 10 hours and then, air-cooled. A second sample group was heat treated under the same conditions, but a stress relief was done at 150ºC for 1 hour and then, air-cooled. The tempering increases substantially its hardness and ductility and in some cases, without substantial reduction of the mechanical resistance. The great hardness and resistance of the tempered martensite is related to the large area relation between the cementite and matrix contours, because these act as barriers to the

  15. Common Quality Defects Analysis of SWRH82B Wire Rod%SWRH82B盘条常见质量缺陷分析

    Institute of Scientific and Technical Information of China (English)

    李文亚; 刘莉; 李智丽; 杨维宇

    2012-01-01

    The common surface defects of SWRH82B wire rod were summarized,including overlap,scab,microcrack,scratch and metallurgical defect.The causes were analyzed and prevention measures were proposed.The morphology of the inner defects including central netting cementite,central martensite,and central pipe was analyzed by SEM and OM,as well as the causes and harms;and corresponding solving programs and measures were put forward based on the actual production requirements.%综述了SWRH82B盘条常见的折叠、结疤、微裂纹、划痕等表面缺陷和冶金缺陷,分析了产生的原因并提出预防措施;采用SEM、OM分析了中心网状渗碳体、中心区域马氏体、中心缩孔等内部缺陷的组织形貌,分析产生的原因和危害,并根据生产实际要求提出相应的解决方案和措施。

  16. A micro-mechanical analysis and an experimental characterisation of the behavior and the damaging processes of a 16MND5 pressure vessel steel at low temperature; Etude micromecanique et caracterisation experimentale du comportement et de l'endommagement de l'acier de cuve 16MND5 a basses temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Pesci, R

    2004-06-15

    As part of an important experimental and numerical research program launched by Electricite De France on the 16MND5 pressure vessel steel, sequenced and in-situ tensile tests are realized at low temperatures [-196 C;-60 C]. They enable to associate the observation of specimens, the complete cartography of which has been made with a scanning electron microscope (damaging processes, initiation and propagation of microcracks), with the stress states determined by X-ray diffraction, in order to establish relevant criteria. All these measurements enable to supply a two-scale polycrystalline modeling of behavior and damage (Mori-Tanaka/self-consistent) which is developed concurrently with the experimental characterization. This model proves to be a very efficient one, since it correctly reproduces the influence of temperature experimentally defined: the stress state in ferrite remains less important than in bainite (the difference never exceeds 150 MPa), whereas it is much higher in cementite. The heterogeneity of strains and stresses for each crystallographic orientation is well rendered; so is cleavage fracture normal to the {l_brace}100{r_brace} planes in ferrite (planes identified by electron back scattered diffraction during an in-situ tensile test at -150 C), which occurs sooner when temperature decreases, for a constant stress of about 700 MPa in this phase. (author)

  17. Retained austenite thermal stability in a nanostructured bainitic steel

    International Nuclear Information System (INIS)

    The unique microstructure of nanostructured bainite consists of very slender bainitic ferrite plates and high carbon retained austenite films. As a consequence, the reported properties are opening a wide range of different commercial uses. However, bainitic transformation follows the T0 criteria, i.e. the incomplete reaction phenomena, which means that the microstructure is not thermodynamically stable because the bainitic transformation stops well before austenite reaches an equilibrium carbon level. This article aims to study the different microstructural changes taking place when nanostructured bainite is destabilized by austempering for times well in excess of that strictly necessary to end the transformation. Results indicate that while bainitic ferrite seems unaware of the extended heat treatment, retained austenite exhibits a more receptive behavior to it. - Highlights: • Nanostructured bainitic steel is not thermodynamically stable. • Extensive austempering in these microstructures has not been reported before. • Precipitation of cementite particles is unavoidable at longer austempering times. • TEM, FEG-SEM and XRD analysis were used for microstructural characterization

  18. Carbon partitioning during quenching and partitioning heat treatment accompanied by carbide precipitation

    International Nuclear Information System (INIS)

    Carbon partitioning from martensite into austenite in the quenching and partitioning (Q&P) process has been suggested to be controlled by the constrained carbon equilibrium (CCE) criterion. It defines an approach for predicting the carbon concentration in austenite under the condition that competing reactions such as carbide formation and bainite transformation are suppressed. Carbide precipitation in martensite is, however, often observed during the partitioning step, even in low-carbon steels as well as in high-carbon steels, even when containing a high amount of Si. Therefore, carbon partitioning from martensite into austenite is studied here, considering carbide precipitation in martensite. Carbon partitioning was investigated by means of a field-emission electron probe micro analysis (FE-EPMA) and atom probe tomography (APT), using 1.07 wt.% and 0.59 wt.% carbon steels with various martensite volume fractions. Carbon partitioning from martensite to austenite was clearly observed in all specimens, even though a considerable amount of carbide precipitated inside the martensite. The austenite carbon concentration after the partitioning step was not influenced by either the martensite volume fraction or the bulk carbon content. A modified model for predicting the austenite carbon concentration after the partitioning step was proposed to explain the experimental results by assuming carbon equilibria between austenite, ferrite and cementite under a constrained condition

  19. Microstructural and Phase Evolution of Compound Layers Growing on α-Iron During Gaseous Nitrocarburizing

    Science.gov (United States)

    Woehrle, T.; Leineweber, A.; Mittemeijer, E. J.

    2012-07-01

    The microstructural evolution of compound layers grown on 1-mm thick α-iron substrates after nitrocarburizing at 853 K (580 °C) in NH3/H2/N2/CO gas mixtures was investigated by light optical microscopy and X-ray diffraction. The evolution of the microstructure can be divided into several stages. Starting with the formation of the carbon-rich phase cementite, which practically does not contain nitrogen, the phase constitution of the compound layer develops through successive stages of microstructural change into the direction of the nitrogen-richer and carbon-poorer phases ɛ and γ'. These results are the consequences of (1) the kinetics of nitrogen and carbon uptake at the gas-solid interface and the considerably different solubilities of nitrogen and carbon in the α-iron substrate and (2) the occurrence of local equilibrium conditions prevailing at the solid-solid interphase boundaries in the compound layer. The change of the microstructure as a function of depth in the compound layer is shown to be compatible with so-called "diffusion paths" in the ternary Fe-N-C phase diagram.

  20. Effects of sphere size on the microstructure and mechanical properties of ductile iron-steel hollow sphere syntactic foams

    Institute of Scientific and Technical Information of China (English)

    Hamid Sazegaran; Ali-Reza Kiani-Rashid; Jalil Vahdati Khaki

    2016-01-01

    The effects of sphere size on the microstructural and mechanical properties of ductile iron–steel hollow sphere (DI–SHS) syntactic foamswere investigated in this study. The SHSs were manufactured by fluidized-bed coating via the Fe-based commercial powder–binder suspension onto expanded polystyrene spheres (EPSs). Afterwards, the DI–SHS syntactic foams were produced via a sand-mold casting process. The microstructures of specimens were investigated by optical microscopy, scanning electron microscopy (SEM), and en-ergy-dispersive X-ray spectroscopy (EDS). The microscopic evaluations of specimens reveal distinct regions composed of the DI matrix, SHS shells, and compatible interface. As a result, the microstructures and graphite morphologies of the DI matrix depend on sphere size. When the sphere size decreases, the area fractions of cementite and graphite phases are observed to increase and decrease, respectively. Compression tests were subsequently conducted at ambient temperature on the DI–SHS syntactic foams. The results reveal that the compres-sion behavior of the syntactic foams is enhanced with increasing sphere size. Furthermore, the compressed specimens demonstrate that mi-crocracks start and grow from the interface region.

  1. Effects of sphere size on the microstructure and mechanical properties of ductile iron-steel hollow sphere syntactic foams

    Science.gov (United States)

    Sazegaran, Hamid; Kiani-Rashid, Ali-Reza; Khaki, Jalil Vahdati

    2016-06-01

    The effects of sphere size on the microstructural and mechanical properties of ductile iron-steel hollow sphere (DI-SHS) syntactic foams were investigated in this study. The SHSs were manufactured by fluidized-bed coating via the Fe-based commercial powder-binder suspension onto expanded polystyrene spheres (EPSs). Afterwards, the DI-SHS syntactic foams were produced via a sand-mold casting process. The microstructures of specimens were investigated by optical microscopy, scanning electron microscopy (SEM), and energy- dispersive X-ray spectroscopy (EDS). The microscopic evaluations of specimens reveal distinct regions composed of the DI matrix, SHS shells, and compatible interface. As a result, the microstructures and graphite morphologies of the DI matrix depend on sphere size. When the sphere size decreases, the area fractions of cementite and graphite phases are observed to increase and decrease, respectively. Compression tests were subsequently conducted at ambient temperature on the DI-SHS syntactic foams. The results reveal that the compression behavior of the syntactic foams is enhanced with increasing sphere size. Furthermore, the compressed specimens demonstrate that microcracks start and grow from the interface region.

  2. Parameters Optimization of Low Carbon Low Alloy Steel Annealing Process

    Institute of Scientific and Technical Information of China (English)

    Maoyu ZHAO; Qianwang CHEN

    2013-01-01

    A suitable match of annealing process parameters is critical for obtaining the fine microstructure of material.Low carbon low alloy steel (20CrMnTi) was heated for various durations near Ac temperature to obtain fine pearlite and ferrite grains.Annealing temperature and time were used as independent variables,and material property data were acquired by orthogonal experiment design under intercritical process followed by subcritical annealing process (IPSAP).The weights of plasticity (hardness,yield strength,section shrinkage and elongation) of annealed material were calculated by analytic hierarchy process,and then the process parameters were optimized by the grey theory system.The results observed by SEM images show that microstructure of optimization annealing material are consisted of smaller lamellar pearlites (ferrite-cementite)and refining ferrites which distribute uniformly.Morphologies on tension fracture surface of optimized annealing material indicate that the numbers of dimple fracture show more finer toughness obviously comparing with other annealing materials.Moreover,the yield strength value of optimization annealing material decreases apparently by tensile test.Thus,the new optimized strategy is accurate and feasible.

  3. Multigrain indexing of unknown multiphase materials

    Science.gov (United States)

    Wejdemann, Christian; Poulsen, Henning Friis

    2016-01-01

    A multigrain indexing algorithm for use with samples comprising an arbitrary number of known or unknown phases is presented. No a priori crystallographic knowledge is required. The algorithm applies to data acquired with a monochromatic beam and a conventional two-dimensional detector for diffraction. Initially, candidate grains are found by searching for crystallographic planes, using a Dirac comb convoluted with a box function as a filter. Next, candidate grains are validated and the unit cell is optimized. The algorithm is validated by simulations. Simulations of 500 cementite grains and ∼100 reflections per grain resulted in 99.2% of all grains being indexed correctly and 99.5% of the reflections becoming associated with the right grain. Simulations with 200 grains associated with four mineral phases and 50–700 reflections per grain resulted in 99.9% of all grains being indexed correctly and 99.9% of the reflections becoming associated with the right grain. The main limitation is in terms of overlap of diffraction spots and computing time. Potential areas of use include three-dimensional grain mapping, structural solution and refinement studies of complex samples, and studies of dilute phases. PMID:27047308

  4. 磷高强石膏-粉煤灰-石灰的耐水性研究%Study on Water Resistance of Phosphogypsum Based on High Strength Gypsum-Fly Ash-Lime Materials

    Institute of Scientific and Technical Information of China (English)

    茹晓红; 汤琦; 马保国; 邹开波

    2015-01-01

    将粉煤灰及其激发剂石灰加入到磷石膏制备的高强石膏中制备出水硬性的磷石膏粉煤灰石灰( PGFL)复合胶凝材料。通过对比试验研究了石灰、粉煤灰、磷高强石膏(PGHH)掺量对产品软化系数、抗压强度性能的影响,结果表明:加入适量的粉煤灰、石灰可以显著提高PGFL的后期绝干抗压强度和软化系数,提高材料的耐水性,掺量过多则会带来不利影响。%Phosphogypsum-fly ash-lime cementitous materials ( PGFL) was prepared by phosphogypsum based high strength hemihydrate gypsum ( PGHH) mixed with fly ash and lime. Effects of lime, fly ash and PGHH additions to PGFL properties of compressive strength and softening coefficient were investigated through comparison testing. The results showed that water resistance of PGFL material was improved by long-term dry compressive strength and softening coefficient increased significantly with proper fly ash and lime contents. However, adverse impacts may caused by too much fly ash and lime additions.

  5. Road Performance of Fly Ash Slag Cement with Low Activity%水泥低活性粉煤灰钢渣路用性能试验研究

    Institute of Scientific and Technical Information of China (English)

    王志刚

    2011-01-01

    In order to study the road performance of fly ash slag cement with low activity,unconfined compressive strength,dry shrinkage property,flushing performance,anti-fatigue property are tested.The experimental data show that road performance of fly ash slag cement with activity is superior to steel slag and fly ash cement.It is suggested that fly ash slag cement with low activity should be adopted in road base construction in conditioned regions.%为研究水泥低活性粉煤灰钢渣路用性能,对其抗压强度、干缩性能、冲刷性能、抗疲劳性能进行了室内试验研究,数据分析表明水泥低活性粉煤灰钢渣路用性能优越于水泥钢渣和粉煤灰,因此,建议有条件的地区,道路基层施工可采用水泥低活性粉煤灰钢渣。

  6. A Conceptual Model for the Interaction between Carbon Content and Manganese Sulphide Inclusions in the Short-Term Seawater Corrosion of Low Carbon Steel

    Directory of Open Access Journals (Sweden)

    Robert E. Melchers

    2016-05-01

    Full Text Available The critical role of manganese sulphide (MnS inclusions for the initiation of the short-term growth of pitting or localized corrosion of low carbon steels has long been recognized. Classical results show that pitting probability and pitting severity increases with increased sulphide concentration for low carbon steels as a result of magnesium sulphides acting as local cathodes for initiating pitting corrosion. However, the iron carbides (cementite in steels can also act as local cathodes for initiation of pitting corrosion. Herein it is proposed that there is competition between pits for cathodic area and that this will determine the severity of pitting and general corrosion observed in extended exposures. Preliminary experimental data for immersion exposures of up to 56 days in natural seawater of three low carbon steels show, contrary to conventional wisdom, greater pit depths for the steels with lower S content. However, the pit depth results are consistent with lower C/S ratios. This is considered to support the concept of cathodic competition between C and S. It is proposed that this offers explanations for a number of other phenomena, including the thus far unexplained apparently higher reactivity of some MnS inclusions.

  7. The structure, properties and a resistance to abrasive wear of railway sections of steel with a different pearlite morphology

    International Nuclear Information System (INIS)

    The article presents the characteristics of pearlite rail steels used in the construction of railways. The article discusses the influence of isothermal annealing process parameters on the pearlite morphology and properties of the R260 steel. The pearlite structure with a diverse pearlite morphology was obtained in the physical modeling of the isothermal annealing on the 3800 Gleeble Simulator. After the heat treatment, the existence of the pearlite microstructure with pearlite colonies was identified. They were smaller in relation to colonies after the hot rolling process. It was shown that the reduction of isothermal holding temperature influences the decrease of the interlamellar distance in the pearlite steel. On the basis of the received results, the dependences between the resistance to the abrasive wear and the pearlite morphology for operational conditions occurring in the switches were estimated. The resistance to the abrasive wear tests were conducted for steel with a different morphology of pearlite on the Amsler stand in conditions of rolling- sliding frictions. The resistance to the abrasive wear of R260 steel with a different pearlite morphology increases, when the interlamellar distance in cementite decreases and decreases as the load and slip increase.

  8. Microstructure-properties correlation in fiber laser welding of dual-phase and HSLA steels

    International Nuclear Information System (INIS)

    Similar and dissimilar welds of dual-phase (DP) and high strength low alloy (HSLA) steels were made by fiber laser welding (FLW). The welds were characterized with respect to microstructure, micro- and nano-hardness, and tensile properties. The fusion zone (FZ) in the DP welds consisted of fully martensitic structure; whereas HSLA and dissimilar weld FZ microstructure were mixture of martensite and bainite. Analytical transmission electron microscopy (TEM) confirmed bainite structures containing bainitic ferrite laths with intralath and interlath cementite. Precipitation of single variant carbides inside the bainitic ferrite laths were confirmed by measuring the interplanar spacing. The cooling rate in the FZ, estimated using Rosenthal equation, and continuous-cooling-transformation diagrams corroborated the microstructure formed. Nanoindentation was used to verify the hardness of these individual microconstituents, since a much lower nano-hardness for bainite (4.11 GPa) was observed compared to martensite (6.57 GPa) phase. Tensile failure occurred in the tempered area of the heat affected zone (HAZ) in the DP steel welded, which was confirmed by typical cup-like dimple fracture; likewise failure in the HSLA base metal, which occurred in dissimilar and HSLA welds, indicated distinctive dimple and shear dimple ductile morphology

  9. Microstructure-properties correlation in fiber laser welding of dual-phase and HSLA steels

    Energy Technology Data Exchange (ETDEWEB)

    Saha, D.C., E-mail: dcsaha@uwaterloo.ca [Department of Mechanical and Mechatronics Engineering, University of Waterloo, 200 University Avenue West, Waterloo, ON, Canada N2L 3G1 (Canada); Westerbaan, D.; Nayak, S.S. [Department of Mechanical and Mechatronics Engineering, University of Waterloo, 200 University Avenue West, Waterloo, ON, Canada N2L 3G1 (Canada); Biro, E. [ArcelorMittal Global Research, 1390 Burlington Street East, Hamilton, ON, Canada L8N 3J5 (Canada); Gerlich, A.P.; Zhou, Y. [Department of Mechanical and Mechatronics Engineering, University of Waterloo, 200 University Avenue West, Waterloo, ON, Canada N2L 3G1 (Canada)

    2014-06-01

    Similar and dissimilar welds of dual-phase (DP) and high strength low alloy (HSLA) steels were made by fiber laser welding (FLW). The welds were characterized with respect to microstructure, micro- and nano-hardness, and tensile properties. The fusion zone (FZ) in the DP welds consisted of fully martensitic structure; whereas HSLA and dissimilar weld FZ microstructure were mixture of martensite and bainite. Analytical transmission electron microscopy (TEM) confirmed bainite structures containing bainitic ferrite laths with intralath and interlath cementite. Precipitation of single variant carbides inside the bainitic ferrite laths were confirmed by measuring the interplanar spacing. The cooling rate in the FZ, estimated using Rosenthal equation, and continuous-cooling-transformation diagrams corroborated the microstructure formed. Nanoindentation was used to verify the hardness of these individual microconstituents, since a much lower nano-hardness for bainite (4.11 GPa) was observed compared to martensite (6.57 GPa) phase. Tensile failure occurred in the tempered area of the heat affected zone (HAZ) in the DP steel welded, which was confirmed by typical cup-like dimple fracture; likewise failure in the HSLA base metal, which occurred in dissimilar and HSLA welds, indicated distinctive dimple and shear dimple ductile morphology.

  10. Segregation behavior of phosphorus in the heat-affected zone of an A533B/A182 dissimilar weld joint before and after simulated thermal aging

    International Nuclear Information System (INIS)

    Highlights: • Impacts of aging on P segregation in actual heat-affected zone were examined by 3D-APT. • Non-equilibrium segregation of P dominated in subsequent cooling after welding. • Equilibrium segregation of P prevailed in step-cooling heat treatment. • High enrichment of P at grain/packet boundaries occurred in CGHAZ and ICCGHAZ. • Level of P enrichment at precipitate/matrix interface seemed species-dependent. - Abstract: The segregation behavior of phosphorus (P) in the heat-affected zone (HAZ) of an A533B/A182 dissimilar weld joint before and after step cooling was investigated with atom probe tomography. At grain/packet boundaries, the final P segregation level consisted of non-equilibrium segregation that occurred during cooling after welding and post-weld heat treatment (PWHT) and equilibrium segregation that occurred during step cooling. In both processes, higher P coverage was observed in the coarse-grained and intercritically reheated coarse-grained HAZ than in the fine-grained HAZ and base material. The cooling after welding and PWHT seemed to have a pronounced impact on P segregation in the subsequent aging process. In addition, P segregation also occurred at the precipitate/matrix interfaces of cementite, Mo2C and Al–Si rich precipitates. The evolution of P coverage at these two types of sites suggested increasing risks of embrittlement with an increase in aging time

  11. Effect of Pearlite Interlamellar Spacing on Predominant Abrasive Wear Mechanism of Fully Pearlitic Steel

    Institute of Scientific and Technical Information of China (English)

    J. Ahmadi; M. Monirvaghefi; M. Salehi; B. Niroumand

    2004-01-01

    The aim of this investigation was the determination of the predominant wear mechanism on three-body abrasion of fully pearlitic low alloy steel. Furthermore, the effect of pearlite interlamellar spacing on wear behavior was investigated.For this purpose, the samples were subjected to the different heat treating to attaining different interlamellar spacing.Mechanical properties such as hardness, yield strength, tensile strength, elongation, and impact toughness were evaluated.Three body abrasion tests were conducted under ASTM standard condition using a rubber wheel abrasion test apparatus.Abraded surface and wear debris were investigated by light optical microscopy and scanning electron microscopy.The results showed that wear resistance of fully pearlitic steel depended to pearlite interlamellar spacing the and lower spacing has the greater wear resistance, so it may be due to subsurface work hardening and interlamellar spacing and cementite in fine and/or coarse pearlite, that influence on surface destruction during wear. Although during wear process the several mechanisms play roles, but study of surface and debris shows that with decreasing interlamellar spacing, the predominant mechanism wear changed from ploughing to cutting mode.

  12. CRYSTALLOGRAPHIC RELATIONS OF CEMENTITE–AUSTENITE–FERRITE IN THE DIFFUSIVE DECOMPOSITION OF AUSTENITE

    Directory of Open Access Journals (Sweden)

    BOLSHAKOV V. I.

    2016-05-01

    Full Text Available Summary. It was made a search for new and more accurate orientation relations between the crystal lattice in the pearlite and bainite austenite decomposition products. Methods. It were used the methods: transmission electron microscopy, the micro-, mathematical matrix and stereographic analysis. The purpose of the research is with theoretical, numerical and experimental methods to set up to a 0.2 degree angular orientation relations between the lattices of ferrite and cementite in the austenite decomposition products in the temperature range 400 ... 700С. Results. It was established a new, refined value for grids in the diffusion decay of γ → α + (α + θ. Practical significance. It was proposed a new oriented dependence and the corresponding double gnomonic projection with poles to planes α and θ phases, which can be used in patterns of crystallographic lattices relations studies at phase transitions, as well as the subsequent modeling of complex physical processes of structure formation in metals and binary systems.

  13. Influence of processing parameters on lattice parameters in laser deposited tool alloy steel

    International Nuclear Information System (INIS)

    Highlights: → Orientation relationships among phases in the DMD are given. → Martensite lattice parameters increased with laser specific energy. → Austenite lattice parameters decreased with laser specific energy. - Abstract: Laser aided direct metal deposition (DMD) has been used to form AISI 4340 steel coating on the AISI 4140 steel substrate. The microstructural property of the DMD coating was analyzed by means of scanning electron microscopy, transmission electron microscopy and X-ray diffractometry. Microhardness of the DMD was measured with a Vickers microhardness tester. Results indicate that DMD can be used to form dense AISI 4340 steel coatings on AISI 4140 steel substrate. The DMD coating is mainly composed of martensite and retained austenite. Consecutive thermal cycles have a remarkable effect on the microstructure of the plan view of the DMD coating and on the corresponding microhardness distribution. Orientation relationships among austenite, martensite and cementite in the DMD coating followed the ones in conventional heat treated steels. As the laser specific energy decreased, cooling rate increased, and martensite peaks broadened and shifted to a lower Bragg's angle. Also martensite lattice parameters increased and austenite lattice parameters decreased due to the above parameter change.

  14. Effect of microstructure on non-linear behavior of ultrasound during low cycle fatigue of pearlitic steels

    International Nuclear Information System (INIS)

    Research highlights: → Development of online NLU parameter determination system with proper calibration. → Correlation of microstructural changes with the variation of NLU parameter during low cycle fatigue in 0.3 wt.% carbon steel. → NLU parameter follows fatigue hardening and softening trends during low cycle fatigue in test material. → Before failure, fracture of cementite plates due to compressive stress causes a sharp increase in NLU parameter that could be the alarm for failure of components. Hence this technique may prevent catastrophic failure of components. - Abstract: Influence of microstructural changes on the second harmonics of sinusoidal ultrasonic wave during low cycle fatigue (LCF) deformation in pearlitic steel was studied. Fatigue tests were interrupted and at every interruption, non-linear ultrasonic (NLU) parameter (β) was determined. Microstructures of cyclically deformed specimens at various cycles were examined by transmission electron microscopy (TEM). The variation of β with fatigue cycles was correlated with the microstructural changes and the results were explained through the variation in dislocation morphology and carbon content of the steel.

  15. Effect of scanning speed during PTA remelting treatment on the microstructure and wear resistance of nodular cast iron

    Institute of Scientific and Technical Information of China (English)

    Hua-tang Cao; Xuan-pu Dong; Qi-wen Huang; Zhang Pan; Jian-jun Li; Zi-tian Fan

    2014-01-01

    The surface of nodular cast iron (NCI) with a ferrite substrate was rapidly remelted and solidified by plasma transferred arc (PTA) to induce a chilled structure with high hardness and favorable wear resistance. The effect of scanning speed on the microstructure, micro-hardness distribution, and wear properties of PTA-remelted specimens was systematically investigated. Microstructural characterization in-dicated that the PTA remelting treatment could dissolve most graphite nodules and that the crystallized primary austenite dendrites were transformed into cementite, martensite, an interdendritic network of ledeburite eutectic, and certain residual austenite during rapid solidifica-tion. The dimensions of the remelted zone and its dendrites increase with decreased scanning speed. The microhardness of the remelted zone varied in the range of 650 HV0.2 to 820 HV0.2, which is approximately 2.3-3.1 times higher than the hardness of the substrate. The wear re-sistance of NCI was also significantly improved after the PTA remelting treatment.

  16. Influence of processing parameters on lattice parameters in laser deposited tool alloy steel

    Energy Technology Data Exchange (ETDEWEB)

    Sun, G.F., E-mail: gfsun82@gmail.com [Center for Laser-Aided Intelligent Manufacturing, University of Michigan, Ann Arbor, MI, 48109 (United States); School of Mechanical Engineering, Jiangsu University, Zhenjiang, Jiangsu, 212013 (China); Bhattacharya, S. [Center for Laser-Aided Intelligent Manufacturing, University of Michigan, Ann Arbor, MI, 48109 (United States); Dinda, G.P.; Dasgupta, A. [Center for Advanced Technologies, Focus: Hope, Detroit, MI, 48238 (United States); Mazumder, J. [Center for Laser-Aided Intelligent Manufacturing, University of Michigan, Ann Arbor, MI, 48109 (United States)

    2011-06-15

    Highlights: {yields} Orientation relationships among phases in the DMD are given. {yields} Martensite lattice parameters increased with laser specific energy. {yields} Austenite lattice parameters decreased with laser specific energy. - Abstract: Laser aided direct metal deposition (DMD) has been used to form AISI 4340 steel coating on the AISI 4140 steel substrate. The microstructural property of the DMD coating was analyzed by means of scanning electron microscopy, transmission electron microscopy and X-ray diffractometry. Microhardness of the DMD was measured with a Vickers microhardness tester. Results indicate that DMD can be used to form dense AISI 4340 steel coatings on AISI 4140 steel substrate. The DMD coating is mainly composed of martensite and retained austenite. Consecutive thermal cycles have a remarkable effect on the microstructure of the plan view of the DMD coating and on the corresponding microhardness distribution. Orientation relationships among austenite, martensite and cementite in the DMD coating followed the ones in conventional heat treated steels. As the laser specific energy decreased, cooling rate increased, and martensite peaks broadened and shifted to a lower Bragg's angle. Also martensite lattice parameters increased and austenite lattice parameters decreased due to the above parameter change.

  17. The Determining Role of Finish Cooling Temperature on the Microstructural Evolution and Precipitation Behavior in an Nb-V-Ti Microalloyed Steel in the Context of Newly Developed Ultrafast Cooling

    Science.gov (United States)

    Li, Xiaolin; Wang, Zhaodong; Deng, Xiangtao; Wang, Guodong; Misra, R. D. K.

    2016-05-01

    We have studied here the impact of finish cooling temperature on the microstructural evolution and precipitation behavior in Nb-V-Ti microalloyed steel through thermo-mechanical simulation in the context of newly developed ultrafast cooling system. The microstructural evolution was studied in terms of morphology and crystallography of precipitates using high-resolution transmission electron microscopy. At finish cooling temperature of 933 K and 893 K (660 °C and 620 °C), the microstructure primarily consisted of polygonal ferrite, together with a small amount of wedge-shaped acicular ferrite and lamellar pearlite, while, at 853 K and 813 K (580 °C and 540 °C), the microstructure consisted of lath bainite with fine interlath cementite and granular bainite with martensite/austenite (M/A) constituent. In all the finish cooling temperatures studied, the near-spherical precipitates of size range ~2 to 15 nm were randomly dispersed in ferrite and bainite matrix. The carbide precipitates were identified as (Nb,V)C with NaCl-type crystal structure. With a decrease in the finish cooling temperature, the size of the precipitates was decreased, while the number density first increased with a peak at 893 K (620 °C) and then decreased. Using Ashby-Orowan model, the contribution of the precipitation strengthening to yield strength was ~149 MPa at the finish cooling temperature of 893 K (620 °C).

  18. Microstructures and Toughness of Weld Metal of Ultrafine Grained Ferritic Steel by Laser Welding

    Institute of Scientific and Technical Information of China (English)

    Xudong ZHANG; Wuzhu CHEN; Cheng WANG; Lin ZHAO; Yun PENG; Zhiling TIAN

    2004-01-01

    3 mm thick 400 MPa grade ultrafine grained ferritic steel plates were bead-on-plate welded by CO2 laser with heat input of 120~480 J/mm. The microstructures of the weld metal mainly consist of bainite, which form is lower bainite plates or polygonal ferrite containing quantities of dispersed cementite particles, mixed with a few of low carbon martensite laths or ferrite, depending on the heat input. The hardness and the tensile strength of the weld metal are higher than those of the base metal, and monotonously increase as the heat input decreases. No softened zone exists inheat affected zone (HAZ). Compared with the base metal, although the grains of laser weld are much larger, the toughness of the weld metal is higher within a large range of heat input. Furthermore, as the heat input increases, the toughness of the weld metal rises to a maximum value, at which point the percentage of lower bainite is the highest, and then drops.

  19. Nano-sized precipitation and properties of a low carbon niobium micro-alloyed bainitic steel

    International Nuclear Information System (INIS)

    The present work focuses on microstructure evolution and precipitation strengthening during tempering at region of 550–680 °C to elucidate the structure–property relationship in the steel. The effect of tempering on the development of a 700 MPa grade high strength hot rolled cost-effective bainitic steel was studied for infrastructure applications. Granular bainite with dispersed martenisit–austenite (M–A) constituents in the bainitic ferrite matrix was obtained after hot rolling and air cooling to room temperature. The decomposition of M–A constituents to cementite carbides and the precipitation of nano-sized NbC carbides in bainitic matrix on tempering were characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Nano-sized precipitates of NbC precipitated during tempering were in average diameter of ~4.1–6.1 nm. There were ~86–173 MPa increases in yield strength after tempering at region of 550–680 °C. It is noticeable that those nano-sized NbC precipitates provide an effective way to significantly increase the strength of the low carbon bainitic steel. High yield strength of 716 MPa with high ductility (uniform elongation of 9.3% and total elongation of 22.4%), low yield to tensile ratio of 0.9 and good low temperature toughness of 47 J (half thickness) at –40 °C was obtained after tempering at 680 °C for 30 min

  20. Effect of substrates on microstructure and mechanical properties of nano-eutectic 1080 steel produced by aluminothermic reaction

    Energy Technology Data Exchange (ETDEWEB)

    La, Peiqing, E-mail: pqla@lut.cn; Li, Zhengning; Li, Cuiling; Hu, Sulei; Lu, Xuefeng; Wei, Yupeng; Wei, Fuan

    2014-06-01

    Nano-eutectic bulk 1080 carbon steel was prepared on glass and copper substrates by an aluminothermic reaction casting. The microstructure of the steel was analyzed by an optical microscope, transmission electron microscopy, an electron probe micro-analyzer, a scanning electron microscope and X-ray diffraction. Results show that the microstructure of the steel consisted of a little cementite and lamellar eutectic pearlite. Average lamellar spacing of the pearlite prepared on copper and glass substrates was about 230 nm and 219 nm, respectively. Volume fraction of the pearlite of the two steels was about 95%. Hardness of the steel was about 229 and 270 HV. Tensile strength was about 610 and 641 MPa and tensile elongation was about 15% and 8%. Compressive strength was about 1043 and 1144 MPa. Compared with the steel prepared on copper substrate, the steel prepared on glass substrate had smaller lamellar spacing of the pearlite phase and higher strength, and low ductility due to the smaller spacing. - Highlights: • 1080-carbon steels were successfully prepared by an aluminothermic reaction casting. • Lamellar spacing of the nanoeutetic pearlite is less than 250 nm. • The compressive strength of the steel is about 1144 MPa. • The tensile ductility of the steel is about 15%.

  1. Segregation behavior of phosphorus in the heat-affected zone of an A533B/A182 dissimilar weld joint before and after simulated thermal aging

    Science.gov (United States)

    Zhai, Ziqing; Miyahara, Yuichi; Abe, Hiroshi; Watanabe, Yutaka

    2014-09-01

    The segregation behavior of phosphorus (P) in the heat-affected zone (HAZ) of an A533B/A182 dissimilar weld joint before and after step cooling was investigated with atom probe tomography. At grain/packet boundaries, the final P segregation level consisted of non-equilibrium segregation that occurred during cooling after welding and post-weld heat treatment (PWHT) and equilibrium segregation that occurred during step cooling. In both processes, higher P coverage was observed in the coarse-grained and intercritically reheated coarse-grained HAZ than in the fine-grained HAZ and base material. The cooling after welding and PWHT seemed to have a pronounced impact on P segregation in the subsequent aging process. In addition, P segregation also occurred at the precipitate/matrix interfaces of cementite, Mo2C and Al-Si rich precipitates. The evolution of P coverage at these two types of sites suggested increasing risks of embrittlement with an increase in aging time.

  2. Mechanism of Secondary Hardening in Rapid Tempering of Dual-Phase Steel

    Science.gov (United States)

    Saha, Dulal Chandra; Nayak, Sashank S.; Biro, Elliot; Gerlich, Adrian P.; Zhou, Y.

    2014-12-01

    Dual-phase steel with ferrite-martensite-bainite microstructure exhibited secondary hardening in the subcritical heat affected zone during fiber laser welding. Rapid isothermal tempering conducted in a Gleeble simulator also indicated occurrence of secondary hardening at 773 K (500 °C), as confirmed by plotting the tempered hardness against the Holloman-Jaffe parameter. Isothermally tempered specimens were characterized by analytic transmission electron microscopy and high-angle annular dark-field imaging. The cementite (Fe3C) and TiC located in the bainite phase of DP steel decomposed upon rapid tempering to form needle-shaped Mo2C (aspect ratio ranging from 10 to 25) and plate-shaped M4C3 carbides giving rise to secondary hardening. Precipitation of these thermodynamically stable and coherent carbides promoted the hardening phenomenon. However, complex carbides were only seen in the tempered bainite and were not detected in the tempered martensite. The martensite phase decomposed into ferrite and spherical Fe3C, and interlath-retained austenite decomposed into ferrite and elongated carbide.

  3. Influences of Short Discrete Fibers in High Strength Concrete with Very Coarse Sand

    Directory of Open Access Journals (Sweden)

    Mahyuddin Ramli

    2010-01-01

    Full Text Available Problem statement: High Strength Concrete (HSC normally content high cementitous amount and low water binder ratio. However, these would cause substantial volume changes to the concrete and therefore affected the strength development. In addition, the brittleness of HSC was increased when silica fume used as partial cement replacement to achieve high strength. Approach: This study discussed the effects of incorporated short discrete Coconut Fibers (CF, Barchip Fibers (BF and Glass Fibers (GF into HSC to enhance the performance of concrete while kept the binder content at moderate level. Additional specialty to this HSC was casted with very coarse sand with fineness modulus of 3.98. A total of thirteen mixes were casted and tested for slump, density, compressive strength, flexural strength and ultrasonic pulse velocity in accordance with British Standards. Results: The slump was slightly reduced by the short discrete fibers. All of the fibrous specimens had lower density than control. However, the compressive strength of the HSC had increased from 71.8-79.0 MPa using 1.8% of BF, while flexural strength had increased from 5.21-6.50 MPa. All specimens showed that ultrasonic velocity higher than 4.28 km sec-1. Conclusion/Recommendations: In short, combination of incorporated short discrete fibers and applied very coarse sand to produce HSC showed very satisfying results and improvements. Further assessment on durability and impact resistivity will be verified in the coming research.

  4. Integration of coal pyrolysis process with iron ore reduction:Reduction behaviors of iron ore with benzene-containing coal pyrolysis gas as a reducing agent☆

    Institute of Scientific and Technical Information of China (English)

    Xin Li; Helong Hui; Songgeng Li; Lu He; Lijie Cui

    2016-01-01

    An integrated coal pyrolysis process with iron ore reduction is proposed in this article. As the first step, iron oxide reduction is studied in a fixed bed reactor using simulated coal pyrolysis gas with benzene as a model tar com-pound. Variables such as reduction temperature, reduction time and benzene concentration are studied. The car-bon deposition of benzene results in the retarded iron reduction at low temperatures. At high temperatures over 800 °C, the presence of benzene in the gas can promote iron reduction. The metallization can reach up to 99%in 20 min at 900 °C in the presence of benzene. Significant increases of hydrogen and CO/CO2 ratio are observed in the gas. It is indicated that iron reduction is accompanied by the reforming and decomposition of benzene. The degree of metal ization and reduction increases with the increasing benzene concentration. Iron oxide can nearly completely be converted into cementite with benzene present in the gas under the experimental conditions. No sintering is found in the reduced sample with benzene in the gas.

  5. Design of TRIP Steel With High Welding and Galvanizing Performance in Light of Thermodynamics and Kinetics

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    A new type of transformation induced plasticity (TRIP) steel with not only high strength and high ductility but also superior welding and galvanizing properties was designed and developed recently. Low carbon and low silicon content were preliminarily selected with the aim of meeting the requirements of superior quality in both welding and galvanizing. Phosphorus was chosen as one of the alloying elements, because it could reduce carbon acttvity in cementite and increase the stability of austenite. In addition, the possibility of phosphorus segregating at grain boundary was also discussed by thermodynamics as well as kinetics. Phase diagram was estimated at high temperature and the composition of the steel was then selected in the hyperperitectic range to avoid problems, whichmight occur in sheet steel continuous casting. Phase diagram in the inter-critical temperature was estimated for the steel to obtain the starting temperature of fast cooling. For understanding the minimum rate of fast cooling, pearlite growth kinetics was calculated with self-developed diffusion coefficients of elements in grain boundary. Overaging temperature was determined through the calculation of T0 temperature by both equilibrium and para-equilibrium assumptions,which was different from the current determination, which is only based on an equilibrium estimation.

  6. Precipitates in Steels With Ti Additive Produced by CSP Process

    Institute of Scientific and Technical Information of China (English)

    LOU Yan-zhi; LIU De-lu; NI Xiao-qing

    2009-01-01

    Hot strips of low carbon steels with Ti additive [contain C 0.04%-0.07%, Si≤0. 6%, Mn≤0. 6%,Ti 0.06%-0.14% (mass percent)] produced by EAF-CSP (Electric Arc Furnaces-Compact Strip Production)process were examined by TEM, HREM and XRD. Carbonitrides with different N/C ratio were found in the samples. The varying composition of the Ti-carbonitrides resulted from the supersaturation of Ti and temperature at which the compound was formed. In the tested steel, total mass fraction of the precipitates including cementite, carbonitride and a small quantity of Fe3O4, Al2O3, Ti2 CS and AlN was about 0. 305%. XRD results showed that about a quarter of the powder extracted by electrolysis was titanium nitrides, carbonitrides and carbides. Particle arrays formed by interphase precipitation could be observed either in slabs or in hot strips. The dominant reaction mechanisms were discussed. Compared with the conventional cold charge process, small amount of Ti addition would be more effective for precipitation of fine precipitates in the steels produced by CSP process.

  7. Effects of alloying elements on fracture toughness in the transition temperature region of base metals and simulated heat-affected zones of Mn-Mo-Ni low-alloy steels

    Science.gov (United States)

    Kim, Sangho; Im, Young-Roc; Lee, Sunghak; Lee, Hu-Chul; Kim, Sung-Joon; Hong, Jun Hwa

    2004-07-01

    This study is concerned with the effects of alloying elements on fracture toughness in the transition temperature region of base metals and heat-affected zones (HAZs) of Mn-Mo-Ni low-alloy steels. Three kinds of steels whose compositions were varied from the composition specification of SA 508 steel (grade 3) were fabricated by vacuum-induction melting and heat treatment, and their fracture toughness was examined using an ASTM E1921 standard test method. In the steels that have decreased C and increased Mo and Ni content, the number of fine M2C carbides was greatly increased and the number of coarse M3C carbides was decreased, thereby leading to the simultaneous improvement of tensile properties and fracture toughness. Brittle martensite-austenite (M-A) constituents were also formed in these steels during cooling, but did not deteriorate fracture toughness because they were decomposed to ferrite and fine carbides after tempering. Their simulated HAZs also had sufficient impact toughness after postweld heat treatment. These findings indicated that the reduction in C content to inhibit the formation of coarse cementite and to improve toughness and the increase in Mo and Ni to prevent the reduction in hardenability and to precipitate fine M2C carbides were useful ways to improve simultaneously the tensile and fracture properties of the HAZs as well as the base metals.

  8. Carburisation of stainless steel caused by oil in sodium

    International Nuclear Information System (INIS)

    The primary objectives of this work were to investigate the kinetics of austenitic stainless steel carburisation in sodium caused by oil in sodium, and to measure the corresponding 'sodium carbon activity' (a quantitative measure of sodium steel carburisation potential). For comparative purposes, the steel carburising effects of chemically simpler carbon sources have also been studied. The specific experimental investigations have involved: (i) A study of the kinetics of stainless steel carburisation at 5500C caused by oil in sodium; (ii) A determination of the effective steel carburisation potential (carbon activity) arising from oil ingress, and its persistence with time, and (iii) A comparison of oil and chemically simpler carbon sources, namely graphite and cementite (as carburised iron, Fe-Fe3C), with regard to both kinetics of steel carburisation and sodium carbon activities produced. In all cases, the nature and extent of carburisation has been determined by optical metallography, X-ray and nuclear microprobe analysis. Preliminary studies on the mutual effect of steel surfaces in close proximity have also been conducted. Previous studies on steel carburisation in sodium are outlined, and the present results are discussed in the context of available thermodynamic and kinetic data pertaining to the carbon-steel and carbon-sodium systems. (author)

  9. Hydrogen Embrittlement of a 1500-MPa Tensile Strength Level Steel with an Ultrafine Elongated Grain Structure

    Science.gov (United States)

    Nie, Yihong; Kimura, Yuuji; Inoue, Tadanobu; Yin, Fuxing; Akiyama, Eiji; Tsuzaki, Kaneaki

    2012-05-01

    A deformation of a tempered martensitic structure ( i.e., tempforming) at 773 K (500 °C) was applied to a 0.6 pct C-2 pct Si-1 pct Cr steel. The hydrogen embrittlement (HE) property of the tempformed (TF) steel was investigated by a slow strain rate test (SSRT) and an accelerated atmospheric corrosion test (AACT). Hydrogen content within the samples after SSRT and AACT was measured by thermal desorption spectrometry (TDS). The tempforming at 773 K (500 °C) using multipass caliber rolling with an accumulative are reduction of 76 pct resulted in the evolution of an ultrafine elongated grain (UFEG) structure with a strong //rolling direction (RD) fiber deformation texture and a dispersion of spheroidized cementite particles. The SSRT of the pre-hydrogen-charged notched specimens and the AACT demonstrated that the TF sample had superior potential for HE resistance to the conventional quenched and tempered (QT) sample at a tensile strength of 1500 MPa. The TDS analysis also indicated that the hydrogen might be mainly trapped by reversible trapping sites such as grain boundaries and dislocations in the TF sample, and the hydrogen trapping states of the TF sample were similar to those of the QT sample. The QT sample exhibited hydrogen-induced intergranular fracture along the boundaries of coarse prior-austenite grains. In contrast, the hydrogen-induced cracking occurred in association with the UFEG structure in the TF sample, leading to the higher HE resistance of the TF sample.

  10. Precipitation behavior and martensite lath coarsening during tempering of T/P92 ferritic heat-resistant steel

    Science.gov (United States)

    Xu, Lin-qing; Zhang, Dan-tian; Liu, Yong-chang; Ning, Bao-qun; Qiao, Zhi-xia; Yan, Ze-sheng; Li, Hui-jun

    2014-05-01

    Tempering is an important process for T/P92 ferritic heat-resistant steel from the viewpoint of microstructure control, as it facilitates the formation of final tempered martensite under serving conditions. In this study, we have gained deeper insights on the mechanism underlying the microstructural evolution during tempering treatment, including the precipitation of carbides and the coarsening of martensite laths, as systematically analyzed by optical microscopy, transmission electron microscopy, and high-resolution transmission electron microscopy. The chemical composition of the precipitates was analyzed using energy dispersive X-ray spectroscopy. Results indicate the formation of M3C (cementite) precipitates under normalized conditions. However, they tend to dissolve within a short time of tempering, owing to their low thermal stability. This phenomenon was substantiated by X-ray diffraction analysis. Besides, we could observe the precipitation of fine carbonitrides (MX) along the dislocations. The mechanism of carbon diffusion controlled growth of M23C6 can be expressed by the Zener's equation. The movement of Y-junctions was determined to be the fundamental mechanism underlying the martensite lath coarsening process. Vickers hardness was estimated to determine their mechanical properties. Based on the comprehensive analysis of both the micro-structural evolution and hardness variation, the process of tempering can be separated into three steps.

  11. Effect of substrates on microstructure and mechanical properties of nano-eutectic 1080 steel produced by aluminothermic reaction

    International Nuclear Information System (INIS)

    Nano-eutectic bulk 1080 carbon steel was prepared on glass and copper substrates by an aluminothermic reaction casting. The microstructure of the steel was analyzed by an optical microscope, transmission electron microscopy, an electron probe micro-analyzer, a scanning electron microscope and X-ray diffraction. Results show that the microstructure of the steel consisted of a little cementite and lamellar eutectic pearlite. Average lamellar spacing of the pearlite prepared on copper and glass substrates was about 230 nm and 219 nm, respectively. Volume fraction of the pearlite of the two steels was about 95%. Hardness of the steel was about 229 and 270 HV. Tensile strength was about 610 and 641 MPa and tensile elongation was about 15% and 8%. Compressive strength was about 1043 and 1144 MPa. Compared with the steel prepared on copper substrate, the steel prepared on glass substrate had smaller lamellar spacing of the pearlite phase and higher strength, and low ductility due to the smaller spacing. - Highlights: • 1080-carbon steels were successfully prepared by an aluminothermic reaction casting. • Lamellar spacing of the nanoeutetic pearlite is less than 250 nm. • The compressive strength of the steel is about 1144 MPa. • The tensile ductility of the steel is about 15%

  12. Additional heat treatment of non-porous coatings obtained on medium carbon steel substrates by electron beam cladding of a Ti-Mo-C powder composition

    Science.gov (United States)

    Mul, D. O.; Drobyaz, E. A.; Zimoglyadova, T. A.; Bataev, V. A.; Lazurenko, D. V.; Shevtsova, L. I.

    2016-04-01

    The structure and microhardness of surface layers, obtained by non-vacuum electron beam cladding of Ti-Mo-C powder mixture on a steel substrate after different types of heat treatment, were investigated. After cladding samples were heat treated in a furnace at 200...500 °C, as well as quenched at 860 ° C and then underwent high-temperature tempering. Heat treatment of cladded coatings induced tempering of martensite and precipitation of cementite particles (Fe3C). Transmission electron microscopy of the samples after heating and holding at 300 ° C revealed precipitation of nanosized cubical TiC particles. The formation of hard nanosized particles led to the surface layer microhardness growth. The highest level of microhardness (which was 1.2...1.5-fold higher in comparison with coating microhardness after heat treatment) was achieved after heating of the claded material at 300 °C and 400 °C Additional quenching of samples at 860 °C did not increase the microhardness level.

  13. First-principles elasticity of monocarboaluminate hydrates

    KAUST Repository

    Moon, J.

    2014-07-01

    The elasticity of monocarboaluminate hydrates, 3CaO·Al2O3·CaCO3·xH2O (x = 11 or 8), has been investigated by first-principles calculations. Previous experimental study revealed that the fully hydrated monocarboaluminate (x = 11) exhibits exceptionally low compressibility compared to other reported calcium aluminate hydrates. This stiff hydration product can contribute to the strength of concrete made with Portland cements containing calcium carbonates. In this study, full elastic tensors and mechanical properties of the crystal structures with different water contents (x = 11 or 8) are computed by first-principles methods based on density functional theory. The results indicate that the compressibility of monocarboaluminate is highly dependent on the water content in the interlayer region. The structure also becomes more isotropic with the addition of water molecules in this region. Since the monocarboaluminate is a key hydration product of limestone added cement, elasticity of the crystal is important to understand its mechanical impact on concrete. Besides, it is put forth that this theoretical calculation will be useful in predicting the elastic properties of other complex cementitous materials and the influence of ion exchange on compressibility.

  14. Co-Ni超高强度钢的疲劳裂纹扩展行为与组织的关系%Relationship Between Fatigue Crack Growth Behaviour and Microstructures in Co-Ni Ultra-high Strength Steel

    Institute of Scientific and Technical Information of China (English)

    钟平; 凌斌; 王俊丽

    2001-01-01

    The relationship between fatigue crack growth behaviour and microstructures of 23NiCo steel was studied at the stress ratio R=0.1. 23NiCo steel showed slower fatigue crack growth rate than other steels with the same strength level,it is related to the characteristic of microstructures of 23NiCo steel.The absence of cementite and formation of reverted austenite at the plate boundaries tempered at 482℃ are the main factors.%研究了23NiCo钢应力比R=0.1的疲劳裂纹扩展行为与组织的关系。23NiCo钢比同一强度级钢具有较低的裂纹扩展速率的原因主要与钢的微观组织特征有关。23NiCo钢在482℃回火组织中板条边界形成薄膜状的逆转奥氏体和不存在渗碳体是主要的组织因素。

  15. Effect of Initial Microstructure on Impact Toughness of 1200 MPa-Class High Strength Steel with Ultrafine Elongated Grain Structure

    Science.gov (United States)

    Jafari, Meysam; Garrison, Warren M.; Tsuzaki, Kaneaki

    2014-02-01

    A medium-carbon low-alloy steel was prepared with initial structures of either martensite or bainite. For both initial structures, warm caliber-rolling was conducted at 773 K (500 °C) to obtain ultrafine elongated grain (UFEG) structures with strong //rolling direction (RD) fiber deformation textures. The UFEG structures consisted of spheroidal cementite particles distributed uniformly in a ferrite matrix of a transverse grain size of about 331 and 311 nm in samples with initial martensite and bainite structures, respectively. For both initial structures, the UFEG materials had similar tensile properties, upper shelf energy (145 J), and ductile-to-brittle transition temperatures 98 K (500 °C). Obtaining the martensitic structure requires more rapid cooling than is needed to obtain the bainitic structure and this more rapid cooling promote cracking. As the UFEG structures obtained from initial martensitic and bainitic structures have almost identical properties, but obtaining the bainitic structure does not require a rapid cooling which promotes cracking suggests the use of a bainitic structure in obtaining UFEG structures should be examined further.

  16. Effects of Nitrogen Content and Austenitization Temperature on Precipitation in Niobium Micro-alloyed Steels

    Institute of Scientific and Technical Information of China (English)

    Lei CAO; Zhong-min YANG; Ying CHEN; Hui-min WANG; Xiao-li ZHAO

    2015-01-01

    The influences of nitrogen content and austenitization temperature on Nb(C,N)precipitation in niobium micro-alloyed steels were studied by different methods:optical microscopy,tensile tests,scanning electron mi-croscopy,transmission electron microscopy,physicochemical phase analysis,and small-angle X-ray scattering. The results show that the strength of the steel with high nitrogen content is slightly higher than that of the steel with low nitrogen content.The increase in the nitrogen content does not result in the increase in the amount of Nb(C,N) precipitates,which mainly depends on the niobium content in the steel.The mass fraction of small-sized Nb(C,N) precipitates (1-10 nm)in the steel with high nitrogen content is less than that in the steel with low nitrogen con-tent.After austenitized at 1 150 ℃,a number of large cuboidal and needle-shaped particles are detected in the steel with high nitrogen content,whereas they dissolve after austenitized at 1 200 ℃ and the Nb(C,N)precipitates become finer in both steels.Furthermore,the results also show that part of the nitrogen in steel involves the formation of al-loyed cementite.

  17. Study on carbides at grain boundary in micro-alloyed fire resistant steel%微合金耐火钢晶界处碳化物的研究

    Institute of Scientific and Technical Information of China (English)

    曹双梅; 张伟荣; 刘文庆

    2012-01-01

    Field ion microscope ( FIM) and transmission electron microscope ( TEM) were applied to characterize the carbides at grain boundary in micro-alloyed fire resistant steel tempered at 500 t for 0. 5 ~ 4 h after solution treatment at 1200 ℃ for 0. 5 h. Cementites were observed at the grain boundary with huge difference in the size, fine Nb-V-C clusters were detected to distribute uniformly within the grain. It indicates that the quicker diffusing velocity of carbon enhance the growth of Fe3 C, and fine Nb-V-C clusters is attributed to the slower diffusing velocity of niobium and vanadium.%将Nb-Mo-V微合金耐火钢在1200℃保温0.5h后淬火,在500℃回火0.5~4h,用场离子显微镜(FIM)和透射电子显微镜(TEM)研究晶界处的碳化物.结果发现,晶界处存在尺寸差异很大的Fe3C,晶粒内均匀分布着细小的Nb-V-C团簇.这是因为晶界处碳元素扩散速度快,很容易形核长大形成Fe3C,晶粒内合金元素扩散速度慢,只能形成Nb-V-C的团簇.

  18. Nano-sized precipitation and properties of a low carbon niobium micro-alloyed bainitic steel

    Energy Technology Data Exchange (ETDEWEB)

    Xie, Z.J. [School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Department of Materials Science and Engineering, McMaster University, Hamilton L8S 4L8 (Canada); Ma, X.P. [Department of Materials Science and Engineering, McMaster University, Hamilton L8S 4L8 (Canada); Shang, C.J., E-mail: cjshang@ustb.edu.cn [School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Wang, X.M. [School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Subramanian, S.V. [Department of Materials Science and Engineering, McMaster University, Hamilton L8S 4L8 (Canada)

    2015-08-12

    The present work focuses on microstructure evolution and precipitation strengthening during tempering at region of 550–680 °C to elucidate the structure–property relationship in the steel. The effect of tempering on the development of a 700 MPa grade high strength hot rolled cost-effective bainitic steel was studied for infrastructure applications. Granular bainite with dispersed martenisit–austenite (M–A) constituents in the bainitic ferrite matrix was obtained after hot rolling and air cooling to room temperature. The decomposition of M–A constituents to cementite carbides and the precipitation of nano-sized NbC carbides in bainitic matrix on tempering were characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Nano-sized precipitates of NbC precipitated during tempering were in average diameter of ~4.1–6.1 nm. There were ~86–173 MPa increases in yield strength after tempering at region of 550–680 °C. It is noticeable that those nano-sized NbC precipitates provide an effective way to significantly increase the strength of the low carbon bainitic steel. High yield strength of 716 MPa with high ductility (uniform elongation of 9.3% and total elongation of 22.4%), low yield to tensile ratio of 0.9 and good low temperature toughness of 47 J (half thickness) at –40 °C was obtained after tempering at 680 °C for 30 min.

  19. Precipitation behavior and martensite lath coarsening during tempering of T/P92 ferritic heat-resistant steel

    Institute of Scientific and Technical Information of China (English)

    Lin-qing Xu; Dan-tian Zhang; Yong-chang Liu; Bao-qun Ning; Zhi-xia Qiao; Ze-sheng Yan; Hui-jun Li

    2014-01-01

    Tempering is an important process for T/P92 ferritic heat-resistant steel from the viewpoint of microstructure control, as it facili-tates the formation of final tempered martensite under serving conditions. In this study, we have gained deeper insights on the mechanism underlying the microstructural evolution during tempering treatment, including the precipitation of carbides and the coarsening of martensite laths, as systematically analyzed by optical microscopy, transmission electron microscopy, and high-resolution transmission electron mi-croscopy. The chemical composition of the precipitates was analyzed using energy dispersive X-ray spectroscopy. Results indicate the for-mation of M3C (cementite) precipitates under normalized conditions. However, they tend to dissolve within a short time of tempering, owing to their low thermal stability. This phenomenon was substantiated by X-ray diffraction analysis. Besides, we could observe the precipitation of fine carbonitrides (MX) along the dislocations. The mechanism of carbon diffusion controlled growth of M23C6 can be expressed by the Zener’s equation. The movement of Y-junctions was determined to be the fundamental mechanism underlying the martensite lath coarsening process. Vickers hardness was estimated to determine their mechanical properties. Based on the comprehensive analysis of both the micro-structural evolution and hardness variation, the process of tempering can be separated into three steps.

  20. Characterizations of Dynamic Strain-induced Transformation in Low Carbon Steel

    Institute of Scientific and Technical Information of China (English)

    Luhan Hao; Mingyue Sun; Namin Xiao; Dianzhong Li

    2012-01-01

    Dynamic strain-induced transformation of the low carbon steel Q(235) at 770℃ and 850℃ leads to fine ferrite grains. The microstructure characterization and mechanism of the fine ferrite grain were studied by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electron backscattered diffraction (EBSD) technique. The results show that strain-induced microstructure is the mixed microstructure of ferrite and pearlite, with cementite randomly distributed on ferrite grain boundaries and the grains interiors. EBSD images of grain boundaries demonstrate that high angle grain boundaries (HAGBs) are dominant in both of the deformation induced microstructures occurring below and above A(e3) , with only a few low angle grain boundaries (LAGBs) existing in the grain interiors. It implies that the dynamic strain-induced transformation (DSIT) happens above and below A(e3) temperature and has the same phase transition mechanisms. The refinement of ferrite is the cooperative effect of DSIT and continuous dynamic recrystallization (CDRX) of ferrite. Besides, DSIT is deemed as an incomplete carbon diffusion phase transition through the analysis of microstructure and the previous simulated results. The strengths of the Q(235) steel with refined ferrite and pearlite structure get doubled than the initial state without treated by DSIT and the residual stress in the refined structure is partly responsible for the ductility loss.

  1. Microstructure and Wear Behavior of TiC Coating Deposited on Spheroidized Graphite Cast Iron Using Laser Surfacing

    Directory of Open Access Journals (Sweden)

    E. R. I. Mahmoud

    2014-10-01

    Full Text Available Spheroidal graphite cast iron was laser cladded with TiC powder using a YAG fiber laser at powers of 700, 1000, 1500 and 2000 W. The powder was preplaced on the surface of the specimens with 0.5 mm thickness. Sound cladding and fusion zones were observed at 700, 1000 and 1500 W powers. However, at 2000 W, cracking was observed in the fusion zone. At 700 W, a build-up zone consisted of fine TiC dendrites inside a matrix composed of martensite, cementite (Fe3C, and some blocks of retained austenite was observed. In this zone, all graphite nodules were totally melted. In the fusion zone, some undissolved and partially dissolved graphite nodules appeared in a matrix containing bainite, ferrite, martensite and retained austenite. At 1500 W, the fusion zone had more iron carbides and ferrite, and the HAZ consisted of martensitic structure. At 2000 W, the build-up zone was consisted of TiC particles precipitated in a matrix of eutectic carbides, martensite plus an inter-lamellar retained austenite. The hardness of the cladded area was remarkably improved (1330 HV in case of 700 W: 5.5 times of the hardness of substrate

  2. Effect of deformation and cooling rate on the transformation behavior and microstructure of X70 steels

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The effects of the deformation in the non-recrystallization region of austenite and the cooling rate on the transformation behavior and microstructure of low-carbon low-alloy steel for pipeline application were studied on the thermal-mechanical simulator Gleeble-1500. It was shown that an increase in deformation amount can greatly increase the nucleation site of ferrite when deformed in the non-recrystallization region of austenite, and an increase in nucleation ratio can greatly refine grains. When the cooling rate is accelerated, the driving force of nucleation is increased and the nucleation rate also improves. Ultra-refine grains can be obtained by controlled rolling. The high density of ferrite nucleus, which forms along the austenite grain boundary, twin interface, and deformation band are introduced in the matrix of austenite by the control of hot rolling, after which the microstructure can be refined. It was found that the acicular ferrite has a very fine sub-structure, high dislocation density, and a thin slab with ultra-fine grains. Small M/A islands and cementite are precipitated on the matrix of the slabs by the analysis technique of TEM and SEM.

  3. Direct synthesis of carbon nanofibers from South African coal fly ash

    Science.gov (United States)

    Hintsho, Nomso; Shaikjee, Ahmed; Masenda, Hilary; Naidoo, Deena; Billing, Dave; Franklyn, Paul; Durbach, Shane

    2014-08-01

    Carbon nanofibers (CNFs), cylindrical nanostructures containing graphene, were synthesized directly from South African fly ash (a waste product formed during the combustion of coal). The CNFs (as well as other carbonaceous materials like carbon nanotubes (CNTs)) were produced by the catalytic chemical vapour deposition method (CCVD) in the presence of acetylene gas at temperatures ranging from 400°C to 700°C. The fly ash and its carbonaceous products were characterized by transmission electron microscopy (TEM), thermogravimetric analysis (TGA), laser Raman spectroscopy and Brunauer-Emmett-Teller (BET) surface area measurements. It was observed that as-received fly ash was capable of producing CNFs in high yield by CCVD, starting at a relatively low temperature of 400°C. Laser Raman spectra and TGA thermograms showed that the carbonaceous products which formed were mostly disordered. Small bundles of CNTs and CNFs observed by TEM and energy-dispersive spectroscopy (EDS) showed that the catalyst most likely responsible for CNF formation was iron in the form of cementite; X-ray diffraction (XRD) and Mössbauer spectroscopy confirmed these findings.

  4. A Study of the Influence of Thermomechanical Controlled Processing on the Microstructure of Bainite in High Strength Plate Steel

    Science.gov (United States)

    Liang, Xiaojun; DeArdo, Anthony J.

    2014-10-01

    Steels with compositions that are hot rolled and cooled to exhibit high strength and good toughness often require a bainitic microstructure. This is especially true for plate steels for linepipe applications where strengths in excess of 690 MPa (100 ksi) are needed in thicknesses between approximately 6 and 30 mm. To ensure adequate strength and toughness, the steels should have adequate hardenability (C. E. >0.50 and Pcm >0.20), and are thermomechanically controlled processed, i.e., controlled rolled, followed by interrupted direct quenching to below the Bs temperature of the pancaked austenite. Bainite formed in this way can be defined as a polyphase mixture comprised a matrix phase of bainitic ferrite plus a higher carbon second phase or micro-constituent which can be martensite, retained austenite, or cementite, depending on circumstances. This second feature is predominately martensite in IDQ steels. Unlike pearlite, where the ferrite and cementite form cooperatively at the same moving interface, the bainitic ferrite and MA form in sequence with falling temperature below the Bs temperature or with increasing isothermal holding time. Several studies have found that the mechanical properties may vary strongly for different types of bainite, i.e., different forms of bainitic ferrite and/or MA. Thermomechanical controlled processing (TMCP) has been shown to be an important way to control the microstructure and mechanical properties in low carbon, high strength steel. This is especially true in the case of bainite formation, where the complexity of the austenite-bainite transformation makes its control through disciplined processing especially important. In this study, a low carbon, high manganese steel containing niobium was investigated to better understand the effects of austenite conditioning and cooling rates on the bainitic phase transformation, i.e., the formation of bainitic ferrite plus MA. Specimens were compared after transformation from recrystallized

  5. Hole Expansion Properties of High Strength Automobile Steel Plates with Different Microstructures%汽车用不同显微组织高强钢板的扩孔性能

    Institute of Scientific and Technical Information of China (English)

    吴青松; 祝洪川; 王立新; 刘斌

    2016-01-01

    对热轧铁素体贝氏体双相钢 FB60、铁素体马氏体双相钢 DP600和铁素体珠光体钢SPFH590等三种汽车用高强钢板进行了扩孔试验,利用光学显微镜观察了扩孔裂纹的萌生和扩展,研究了不同钢的扩孔性能及开裂机理。结果表明:FB60钢的扩孔性能最优,DP600钢的最差;SPFH590钢与FB60钢具有相同的屈强比,但其扩孔性能却不及FB60钢的;组织对扩孔性能的影响与扩孔裂纹的萌生和扩展有关,FB60钢的裂纹萌生于铁素体内以及铁素体与贝氏体晶界,绕过贝氏体穿过铁素体扩展;SPFH590钢的裂纹萌生于铁素体与珠光体边界、珠光体内铁素体与渗碳体界面和铁素体内,极易沿铁素体与渗碳体片层扩展;DP600钢的裂纹萌生于铁素体与马氏体晶界,并沿晶界扩展。%Hole expansion tests were conducted for hot-rolled ferrite-bainite dual phase steel FB60,ferrite-martensite dual phase steel DP600 and ferrite-pearlite steel SPFH590.Optical microscope was used to observe formation and propagation of expansion cracks and analyze the hole expansion property and cracking mechanism of the steels.The results show that the FB60 steel exhibits the best hole expansion property,and DP600 steel exhibits the worst hole expansion property.However,the yield ratio of SPFH590 steel was equal to that of FB60 steel,but the hole expansion rate of SPFH590 steel less than that of FB60 steel.The effect of microstructure on hole expansion property was related to the formation and propagation of expansion cracks.The cracks formed not only at ferrite-bainite interfaces but also within ferrite grains in FB60 steel,and propagated along the phase interface between ferrite and bainite and by cutting off ferrite grains.The expansion cracks formed at ferrite-pearlite interfaces,ferrite-cementite interfaces within pearlite and within ferrite grains in SPFH590 steel,and propagated easily along the ferrite-cementite interface.The cracks formed

  6. Effect of tool microstructure on the white layer formation

    Directory of Open Access Journals (Sweden)

    J. Krawczyk

    2006-04-01

    Full Text Available Purpose: Purpose of this paper: This work supplements the knowledge concerning formation of the white layer on the surface of the tools being utilized in high temperature metal forming processes. Eight iron-based materials were tested: 3 ledeburitic cast steels, 2 hypereutectoid cast steels, normalized and stress relief annealed steel, hardened and tempered steel and nodular mottled cast iron.Design/methodology/approach: The exploitation tests were performed on the hot rolling mills for selected rolled sections, rolling stands and roll passes. The samples were cut out of the roll in such a way that they contained the roll working surface and were used for metallographic observations of the subsurface zone.Findings: It was found, that uniform distribution of dispersed precipitates of hypereutectoid cementite in the alloy matrix prevents the formation of the white layer on the surface of the rolls.Research limitations/implications: The white layer definition was given. An influence of the microstructure of iron base alloys on the susceptibility to form the white layer on their surface due to tribological contact was also determined.Practical implications: The procedure for obtaining rolled products of better quality as well as for restricting the probability of roll cracking was proposed. Obtained results should allow proper design of the microstructure of the materials for tools.Originality/value: This work contains several new aspects, which are: the unique tribological conditions for performing the tests, wide range of investigated materials, and combining the microstructure of the material with the susceptibility of the formation of the white layer on its surface. The results of this research may be used by the producers of tools for high temperature metal forming.

  7. Effect of double quenching and tempering heat treatment on the microstructure and mechanical properties of a novel 5Cr steel processed by electro-slag casting

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Jian, E-mail: healygo@163.com; Yu, Hao, E-mail: yuhao@ustb.edu.cn; Zhou, Tao, E-mail: zhoutao130984@163.com; Song, Chenghao, E-mail: songchenghao28@126.com; Zhang, Kai, E-mail: zhangkai8901@126.com

    2014-12-01

    The effect of double quenching and tempering (DQT) treatment as well as conventional high temperature quenching and tempering (CQT) treatment on the microstructures and mechanical properties of low carbon 5Cr martensitic as cast steel produced by electroslag casting was investigated. The microstructure changes were characterized by optical microscope (OM), scanning electron microscope (SEM), electron back scatter diffraction (EBSD) and transmission electron microscopy (TEM). The characteristics of carbides precipitated during tempering were analyzed on both carbon extraction replica and thin foil samples by TEM. The mechanical performance was evaluated by Vickers hardness test, tensile test, and Charpy V-notch impact test at ambient temperature. The results of microstructure study indicated that DQT treatment led to a finer microstructure than that of CQT. The carbides of the tempered samples were identified as M{sub 7}C{sub 3}. The carbides along the prior austenite grain boundaries nucleated directly while those within the laths should be transformed from cementite which formed at the early tempering stage. Compared with CQT condition, yield strength slightly increased after DQT treatment, and impact toughness improved a lot. The strengthening mechanisms were analyzed and it was found that grain refining and precipitation strengthening were mainly responsible for the increase of strength. The superior toughness of DQT condition was attributed to the finer microstructure resulting in more frequent deflections of the cleavage crack and the smaller size of carbides along the prior austenite boundaries. EBSD analysis showed that both martensitic block and packet of low carbon 5Cr tempered martensitic steel could hinder crack propagation, while the latter was more effective.

  8. Evolution of microstructure and mechanical properties during thermomechanical processing of a low-density multiphase steel for automotive application

    International Nuclear Information System (INIS)

    The evolution of the microstructure and mechanical properties in a low-density, low-alloy steel containing 6.57Al–3.34Mn–0.18C (wt.%) has been investigated as a function of processing. The steel was designed to have a duplex microstructure with ferrite as the major phase and austenite as the minor phase within the temperature range 800–1350 °C. The steel was processed to sheet form, which was thermomechanically treated and characterised by a variety of techniques such as optical metallography, scanning electron microscopy, electron backscatter diffraction, electron probe microanalysis, X-ray diffraction, transmission electron microscopy, tensile testing and density and elastic modulus measurements. The amount of austenite was found to decrease with an increase in the annealing temperature. While C and Mn partitioned into the austenite phase, Al partitioned into the ferrite. The tensile elongation increased with an increase in the amount of austenite in the microstructure. However, the austenite showed only a small transformation induced plasticity effect during tensile deformation due to its high stability. After annealing, mostly κ-carbide precipitates with a (Fe + Mn)/Al ratio of 3.6 appeared in the ferrite matrix, along with some cementite and complex carbides. These precipitates became coarser (330 nm) during a short time overageing treatment at 400 °C, causing a significant increase in elongation. The κ-carbides were found to have a close to Nishiyama–Wasserman type orientation relationship with the ferrite matrix. Although the Young’s modulus of the steel dropped due to the large amount of Al added, the reduced density was found to be beneficial for automotive applications, overriding the effect of a drop in Young’s modulus

  9. H82B钢盘条冬季控冷工艺%Controlled cooling process of H82B steel wire rod in winter

    Institute of Scientific and Technical Information of China (English)

    王雷; 麻晗; 峰公雄

    2011-01-01

    冬季低温脆断是高碳钢盘条的普遍问题,对盘条及下游客户拉丝生产造成了严重影响。使用传统斯太尔摩控冷工艺生产的H82B钢盘条常常因心部马氏体、网状渗碳体超标及塑性不达标造成判次,这种现象在冬季尤为明显。通过改进斯太尔摩线控冷工艺等措施,明显改善了盘条的金相组织和力学性能,缩短了冬季自然时效时间,减少了冬季脆断现象。最后阐述了优化控冷工艺的原理。%Winter brittleness is a common problem for high carbon wire rods,which always leads to breakage during the cold drawing process.For H82B steel wire rod,the brittleness is even worse due to center martensite,cementite network and deficient plasticity caused by faster cooling in winter.By improving the Stelmor cooling condition,the microstructure and mechanical properties were improved,the winter natural aging time was shortened,and the winter brittleness was overcome.Process route to minimize the brittleness was designed with discussion on the mechanism involved.

  10. Intergranular brittle fracture of a low alloy steel induced by grain boundary segregation of impurities: influence of the microstructure

    International Nuclear Information System (INIS)

    The study contributes to improve the comprehension of intergranular embrittlement induced by the phosphorus segregation along prior austenitic grain boundaries of low alloy steels used in pressurized power reactor vessel. A part of this study was performed using a A533 steel which contains chemical fluctuations (ghost lines) with two intensities. Axi-symmetrically notched specimens were tested and intergranular brittle de-cohesions were observed in the ghost lines. The fracture initiation sites observed on fracture surfaces were identified as MnS inclusions. A bimodal statistic obtained in a probabilistic model of the fracture is explained by the double population of ghost lines' intensities. A metallurgical study was performed on the same class of steel by studying the influence of the microstructure on the susceptibility to temper embrittlement. Brittle fracture properties of such microstructures obtained by dilatometric experiments were tested on sub-sized specimens to measure the V-notched fracture toughness. Fraction areas of brittle fracture modes were determined on surface fractures. A transition of the fracture mode with the microstructure is observed. It is shown that tempered microstructures of martensite and lower bainite are more susceptible to intergranular embrittlement than tempered upper bainitic microstructure. The intergranular fracture is the most brittle mode. The analysis of crystalline mis-orientations shows a grain boundary structure appreciably more coherent for tempered microstructures of martensite and lower bainite. The higher density of random grain boundaries is susceptible to drag the phosphorus in the upper bainitic matrix and to make the quantity of free phosphorus decreasing. Microstructure observations show a difference in the size and the spatial distribution of carbides, essentially cementite, between tempered martensite and upper bainite. It can explain the bigger susceptibility of this last microstructure to cleavage mode

  11. Effect of double quenching and tempering heat treatment on the microstructure and mechanical properties of a novel 5Cr steel processed by electro-slag casting

    International Nuclear Information System (INIS)

    The effect of double quenching and tempering (DQT) treatment as well as conventional high temperature quenching and tempering (CQT) treatment on the microstructures and mechanical properties of low carbon 5Cr martensitic as cast steel produced by electroslag casting was investigated. The microstructure changes were characterized by optical microscope (OM), scanning electron microscope (SEM), electron back scatter diffraction (EBSD) and transmission electron microscopy (TEM). The characteristics of carbides precipitated during tempering were analyzed on both carbon extraction replica and thin foil samples by TEM. The mechanical performance was evaluated by Vickers hardness test, tensile test, and Charpy V-notch impact test at ambient temperature. The results of microstructure study indicated that DQT treatment led to a finer microstructure than that of CQT. The carbides of the tempered samples were identified as M7C3. The carbides along the prior austenite grain boundaries nucleated directly while those within the laths should be transformed from cementite which formed at the early tempering stage. Compared with CQT condition, yield strength slightly increased after DQT treatment, and impact toughness improved a lot. The strengthening mechanisms were analyzed and it was found that grain refining and precipitation strengthening were mainly responsible for the increase of strength. The superior toughness of DQT condition was attributed to the finer microstructure resulting in more frequent deflections of the cleavage crack and the smaller size of carbides along the prior austenite boundaries. EBSD analysis showed that both martensitic block and packet of low carbon 5Cr tempered martensitic steel could hinder crack propagation, while the latter was more effective

  12. Coherent-Incoherent Transition of ɛ-Carbide in Steels Found with Mechanical Spectroscopy

    Science.gov (United States)

    Shimotomai, Michio

    2016-03-01

    Although a coherent-incoherent transition in the ɛ-carbide precipitated in steels is supposedly linked to hardening and microstructural changes, the existence of this transition has not yet been confirmed. In this paper, we investigate this subject using mechanical spectroscopy. By measuring mechanical loss spectra below room temperature of quench-aged Fe-C alloys, mild steel, and pearlitic steel, we reveal a new broad peak (NBP). This peak is related to thermal activation, and its line shape obeys the equation of the Debye peak with a distribution in relaxation time. The Arrhenius plot yielded a large activation energy and gigantic pre-exponential factor. Its intensity grew by aging at temperatures where precipitation of ɛ-carbide has been reported. However, it starts to decay at duration far too early for ɛ-carbide to transform to cementite. For isothermal aging at 393 K (120 °C), the intensity sharply decreased at durations over 3 hours. This decay was accompanied by appearance of another similar peak (NBP'), which had a peak frequency two orders higher than that of NBP. These peaks had comparable intensity. We attribute NBP and NBP' to coherent and incoherent ɛ-carbides, respectively. We produced a model that attributes the relaxation peaks to reorientations of extra carbon pairs in the ɛ-carbide. The extraordinary values of the Arrhenius parameters may be interpreted by using this model. Based on these results, we assert that mechanical spectroscopy can detect the coherent-incoherent transition in carbon steels. This method will be powerful in studying problems related to the coherency in carbon steels.

  13. Intergranular brittle fracture of a low alloy steel induced by grain boundary segregation of impurities: influence of the microstructure; Rupture intergranulaire fragile d'un acier faiblement allie induite par la segregation d'impuretes aux joints de grains: influence de la microstructure

    Energy Technology Data Exchange (ETDEWEB)

    Raoul, St

    1999-07-01

    The study contributes to improve the comprehension of intergranular embrittlement induced by the phosphorus segregation along prior austenitic grain boundaries of low alloy steels used in pressurized power reactor vessel. A part of this study was performed using a A533 steel which contains chemical fluctuations (ghost lines) with two intensities. Axi-symmetrically notched specimens were tested and intergranular brittle de-cohesions were observed in the ghost lines. The fracture initiation sites observed on fracture surfaces were identified as MnS inclusions. A bimodal statistic obtained in a probabilistic model of the fracture is explained by the double population of ghost lines' intensities. A metallurgical study was performed on the same class of steel by studying the influence of the microstructure on the susceptibility to temper embrittlement. Brittle fracture properties of such microstructures obtained by dilatometric experiments were tested on sub-sized specimens to measure the V-notched fracture toughness. Fraction areas of brittle fracture modes were determined on surface fractures. A transition of the fracture mode with the microstructure is observed. It is shown that tempered microstructures of martensite and lower bainite are more susceptible to intergranular embrittlement than tempered upper bainitic microstructure. The intergranular fracture is the most brittle mode. The analysis of crystalline mis-orientations shows a grain boundary structure appreciably more coherent for tempered microstructures of martensite and lower bainite. The higher density of randomgrain boundaries is susceptible to drag the phosphorus in the upper bainitic matrix and to make the quantity of free phosphorus decreasing. Microstructure observations show a difference in the size and the spatial distribution of carbides, essentially cementite, between tempered martensite and upper bainite. It can explain the bigger susceptibility of this last microstructure to cleavage mode

  14. Analysis on quenching crack of crankshaft for Toyota 3.8L car%丰田3.8L轿车曲轴淬火裂纹分析

    Institute of Scientific and Technical Information of China (English)

    邓军伟; 蔡婵婵; 高峰; 王磊

    2015-01-01

    对丰田3.8L曲轴裂纹进行了形貌及成分分析。结果表明,裂纹为淬火裂纹,主要原因是由于铸造时铁水均匀性差,元素沿晶界偏析,造成大量残留奥氏体和网状渗碳体。沿残留奥氏体晶界分布的网状渗碳体对基体起割裂作用;淬火冷却后期和回火时仍然有残留奥氏体转化为马氏体,曲轴体积发生膨胀,使表面承受过大的张应力,当张应力超过材料强度时,导致工件表面开裂。%Morphology and chemical composition of crankshaft crack for 3.8L car were analyzed.The results show that the crack is resulted from quenching.The main reason for the crack forming are poor uniformity of iron liquid and elements segregation along the grain boundary that results in a lot of retained austenite and cementite networks, which separates the matrix.The retained austenite transformed into martensite at the later stage of quenching and tempering, which causes crankshaft expansion, and the excessive tensile stress on the surface of the crankshaft, that induced the cracking.

  15. Influence of a matrix on properties of mottled cast iron applied for mill rolls

    Directory of Open Access Journals (Sweden)

    J. Krawczyk

    2010-07-01

    Full Text Available Mill rolls are ones of the most expensive tools applied in plastic working processes and have to satisfy several criteria, which allow them to be used. Cast iron mill rolls, due to their fracture toughness and tribological properties, are the most often applied at hot-rolling in the last rolling stands. This results from the smallest dynamic loads of such rolling stands and the decisive influence of the surface quality of these tools on the surface quality of the rolled product. An improper microstructure of rolls can lead to their premature wearing, e.g. broken flanges, pivots twisting off etc. By means of the heat treatment the matrix microstructure and morphology of carbide precipitationscan be modified and this in-turn can influence cast iron properties.Determination of the influence of microstructure changes, caused by the heat treatment, on the properties of EN-GJN-HV300 low-alloycast iron, after its modification and spheroidization – is the aim of the present paper. Those changes are based on the formation pearlitic or bainitic matrices at the similar morphology of graphite and ledeburitic cementite precipitations. The performed investigations should enable designing the heat treatment of cast iron metallurgical rolls in such a way as to obtain the optimal microstructures for functional parameters of these type of tools. The influence of changing the pearlitic matrix into the bainitic one on such properties as: hardness, impact strength, tensile strength, creep limit, bending strength and a stress intensity factor KIc was investigated in this study. Samples for testing, the listed above mechanical properties, were taken from an industrial casting with care to have pieces of very similar crystallization conditions.

  16. Tensile bond strength of indirect composites luted with three new self-adhesive resin cements to dentin

    Directory of Open Access Journals (Sweden)

    Cafer Türkmen

    2011-08-01

    Full Text Available OBJECTIVE: The aims of this study were to evaluate the tensile bond strengths between indirect composites and dentin of 3 recently developed self-adhesive resin cements and to determine mode of failure by SEM. MATERIAL AND METHODS: Exposed dentin surfaces of 70 mandibular third molars were used. Teeth were randomly divided into 7 groups: Group 1 (control group: direct composite resin restoration (Alert with etch-and-rinse adhesive system (Bond 1 primer/adhesive, Group 2: indirect composite restoration (Estenia luted with a resin cement (Cement-It combined with the same etch-and-rinse adhesive, Group 3: direct composite resin restoration with self-etch adhesive system (Nano-Bond, Group 4: indirect composite restoration luted with the resin cement combined with the same self-etch adhesive, Groups 5-7: indirect composite restoration luted with self-adhesive resin cements (RelyX Unicem, Maxcem, and Embrace WetBond, respectively onto the non-pretreated dentin surfaces. Tensile bond strengths of groups were tested with a universal testing machine at a constant speed of 1 mm/min using a 50 kgf load cell. Results were statistically analyzed by the Student's t-test. The failure modes of all groups were also evaluated. RESULTS: The indirect composite restorations luted with the self-adhesive resin cements (groups 5-7 showed better results compared to the other groups (p0.05. The surfaces of all debonded specimens showed evidence of both adhesive and cohesive failure. CONCLUSION: The new universal self-adhesive resins may be considered an alternative for luting indirect composite restorations onto non-pretreated dentin surfaces.

  17. Electrochemical Investigation of the Corrosion of Different Microstructural Phases of X65 Pipeline Steel under Saturated Carbon Dioxide Conditions

    Directory of Open Access Journals (Sweden)

    Yuanfeng Yang

    2015-05-01

    Full Text Available The aim of this research was to investigate the influence of metallurgy on the corrosion behaviour of separate weld zone (WZ and parent plate (PP regions of X65 pipeline steel in a solution of deionised water saturated with CO2, at two different temperatures (55 °C and 80 °C and at initial pH~4.0. In addition, a non-electrochemical immersion experiment was also performed at 80 °C in CO2, on a sample portion of X65 pipeline containing part of a weld section, together with adjacent heat affected zones (HAZ and parent material. Electrochemical impedance spectroscopy (EIS was used to evaluate the corrosion behaviour of the separate weld and parent plate samples. This study seeks to understand the significance of the different microstructures within the different zones of the welded X65 pipe in CO2 environments on corrosion performance; with particular attention given to the formation of surface scales; and their composition/significance. The results obtained from grazing incidence X-ray diffraction (GIXRD measurements suggest that, post immersion, the parent plate substrate is scale free, with only features arising from ferrite (α-Fe and cementite (Fe3C apparent. In contrast, at 80 °C, GIXRD from the weld zone substrate, and weld zone/heat affected zone of the non-electrochemical sample indicates the presence of siderite (FeCO3 and chukanovite (Fe2CO3(OH2 phases. Scanning Electron Microscopy (SEM on this surface confirmed the presence of characteristic discrete cube-shaped crystallites of siderite together with plate-like clusters of chukanovite.

  18. The effect of a non-circular drawing sequence on delamination characteristics of pearlitic steel wire

    International Nuclear Information System (INIS)

    Highlights: • A non-circular drawing (NCD) was applied to produce high-torsional ductility wire. • In the NCD, two processing routes were defined as the NCDA and NCDB, respectively. • The NCDB could impose relatively homogeneous plastic deformation on the wire. • A strength level of 2300 MPa wire was produced by the NCDB without delamination. - Abstract: In this study, a non-circular drawing (NCD) sequence was applied to investigate the effect of deformation behavior, microstructure and texture evolution on delamination characteristics of pearlitic steel wire under torsional deformation mode. The multi-pass NCD sequence was numerically and experimentally applied up to the 12th pass in comparison with conventional wire drawing (WD). For investigation of the deformation characteristics of the drawn wires, three-dimensional finite element and flownet analyses were carried out. These simulation results indicated that the NCD could impose relatively homogeneous plastic deformation on the wire compared to the WD. From the scanning electron microscopy and X-ray diffraction results, globular cementite and cylindrical texture component, which might increase likeliness of delamination fracture, were rarely observed in the NCD drawn wire. In the torsion test, the delamination fracture was observed in the WD drawn wire for the 10th pass while it did not occur for the 12th pass NCD. In addition, the ultimate tensile strength (UTS) of 2300 MPa grade wire was manufactured by the NCD and the UTS value was 257 MPa higher than the one of the WD. Therefore, it was demonstrated that the multi-pass NCD could impose relatively homogeneous plastic deformation on the wire, resulting in high-torsional ductility with better strength compared to the WD

  19. Micromechanical behavior of eutectoid steel quantified by an analytical model calibrated by in situ synchrotron-based X-ray diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Zheng, Chengsi [State Key Laboratory for Advanced Metals and Materials, University of Science & Technology Beijing, Beijing 100083 (China); Li, Longfei, E-mail: lilf@skl.ustb.edu.cn [State Key Laboratory for Advanced Metals and Materials, University of Science & Technology Beijing, Beijing 100083 (China); The Collaborative Innovation Center of Steel Technology (CICST), University of Science and Technology Beijing, Beijing 100083 (China); Wang, Yandong [State Key Laboratory for Advanced Metals and Materials, University of Science & Technology Beijing, Beijing 100083 (China); The Collaborative Innovation Center of Steel Technology (CICST), University of Science and Technology Beijing, Beijing 100083 (China); Yang, Wangyue [School of Materials Science and Engineering, University of Science & Technology Beijing, Beijing 100083 (China); Sun, Zuqing [State Key Laboratory for Advanced Metals and Materials, University of Science & Technology Beijing, Beijing 100083 (China)

    2015-04-17

    A eutectoid steel with three types of ferrite (α)+cementite particle (θ) microstructures, i.e., a coarse-grained α+θ structure, a fine-grained α+θ structure and an ultrafine-grained α+θ structure, was fabricated to explore the effects of the microstructural features on the micromechanical behavior of hard particle-strengthened two-phase alloys. An analytical model based on the Kocks–Mecking model was established to elucidate the evolution of the geometrically necessary dislocations (GNDs) and statistically stored dislocations (SSDs) in the hard particle-strengthened alloys and, hence, to predict the stress partitioning for each phase and the enhancement in the work hardening during uniform plastic deformation. In situ synchrotron-based X-ray diffraction was used to verify the stress partitioning and the important material parameters predicted by our analytical model. Our results showed that a decrease in the geometric slip distance leads to an appreciable increase in the GND density, whereas an increase in the grain size of the ferrite causes an increase in the SSD density under uniform plastic deformation for eutectoid steel with an α+θ structure. Both the stresses for the individual phase and the difference in stress between the two phases for eutectoid steel with various α+θ structures were closely related to the change in the GND density near the phase interfaces. The GND density also played an important role in determining the work-hardening rate for eutectoid steel with various α+θ structures.

  20. Tensile bond strength of indirect composites luted with three new self-adhesive resin cements to dentin

    Science.gov (United States)

    TÜRKMEN, Cafer; DURKAN, Meral; CİMİLLİ, Hale; ÖKSÜZ, Mustafa

    2011-01-01

    Objective The aims of this study were to evaluate the tensile bond strengths between indirect composites and dentin of 3 recently developed self-adhesive resin cements and to determine mode of failure by SEM. Material and Methods Exposed dentin surfaces of 70 mandibular third molars were used. Teeth were randomly divided into 7 groups: Group 1 (control group): direct composite resin restoration (Alert) with etch-and-rinse adhesive system (Bond 1 primer/adhesive), Group 2: indirect composite restoration (Estenia) luted with a resin cement (Cement-It) combined with the same etch-and-rinse adhesive, Group 3: direct composite resin restoration with self-etch adhesive system (Nano-Bond), Group 4: indirect composite restoration luted with the resin cement combined with the same self-etch adhesive, Groups 5-7: indirect composite restoration luted with self-adhesive resin cements (RelyX Unicem, Maxcem, and Embrace WetBond, respectively) onto the non-pretreated dentin surfaces. Tensile bond strengths of groups were tested with a universal testing machine at a constant speed of 1 mm/min using a 50 kgf load cell. Results were statistically analyzed by the Student's t-test. The failure modes of all groups were also evaluated. Results The indirect composite restorations luted with the self-adhesive resin cements (groups 5-7) showed better results compared to the other groups (p0.05). The surfaces of all debonded specimens showed evidence of both adhesive and cohesive failure. Conclusion The new universal self-adhesive resins may be considered an alternative for luting indirect composite restorations onto non-pretreated dentin surfaces. PMID:21710095

  1. Carbon-content dependent effect of magnetic field on austenitic decomposition of steels

    International Nuclear Information System (INIS)

    The transformed microstructures of the high-purity Fe–0.12C alloy and Fe–0.36C alloy heat treated without and with a 12 T magnetic field have been investigated to explore the carbon-content dependent field effect on austenitic decomposition in steels. Results show that, the field-induced transformed morphology characteristics in different alloys differ from each other. In the Fe–0.12C alloy, the pearlite colonies are elongated along the field direction, and shaped by the chained and elongated proeutectoid ferrite grains in the field direction. However, in the Fe–0.36C alloy, the field mainly reduces the amount of Widmänstatten ferrite and elongates the formed proeutectoid ferrite grains in the field direction. No clear field direction alignment is obtained. The magnetic field also demonstrates carbon-content dependent effect on the texture of the formed ferrite. It clearly enhances the 〈001〉 fiber of the ferrite in the transverse field direction in the Fe–0.36C alloy. This field effect is related to the crystal lattice distortion induced by carbon solution and this impact becomes stronger with the increase of the carbon content. For the Fe–0.12C alloy, this field effect is greatly reduced due to the reduced carbon oversaturation in ferrite and elevated formation temperature. The orientation relationships (ORs) between the pearlitic ferrite and the pearlitic cementite in both alloys are less affected by the magnetic field. No obvious changes in the either type of the appearing ORs and their number of occurrences are detected. - Highlights: ► The carbon-content dependent field effect on austenitic decomposition is studied. ► The field-induced morphology features vary with the carbon content. ► The field effect on ferrite texture is more pronounced in high carbon content alloy. ► Magnetic field hardly affects the orientation relationships between phases in pearlite.

  2. Variation of carbon concentration in proeutectoid ferrite during austenitization in hypoeutectoid steel

    Energy Technology Data Exchange (ETDEWEB)

    Jung, Minsu; Cho, Wontae; Park, Jihye; Jung, Jae-Gil; Lee, Young-Kook, E-mail: yklee@yonsei.ac.kr

    2014-08-15

    The variation of the C concentration in proeutectoid ferrite (α{sub PF}) during austenitization in hypoeutectoid steels was quantitatively investigated using the massive transformation start temperature (T{sub m}) of α{sub PF} to austenite (γ) measured by high-temperature confocal laser scanning microscopy and hardness of α{sub PF}. The C concentration in α{sub PF} at T{sub m} in hypoeutectoid steels increased with increasing total C concentration up to approximately 0.2 wt.% during heating. The hardness of α{sub PF} with isothermal holding time at 775 °C in S20C steel revealed C enrichment in α{sub PF} at the early stage of isothermal holding and its reduction with further holding. These results explain the redistribution of the C in α{sub PF} during austenitization as follows: free C atoms released from cementite during pearlite decomposition diffuse excessively into neighboring α{sub PF} as well as pearlitic ferrite. The supersaturated C concentration in α{sub PF} is reduced during the long-range diffusive transformation of α{sub PF} to γ. However, some of the excess C atoms still remain in α{sub PF} until α{sub PF} starts to massively transform to γ. - Highlights: • Massive transformation of αPF to γ in hypoeutectoid steels was observed using CLSM. • C content in αPF during austenitization was analyzed by measured Tm and hardness. • Tm decreases and C content in αPF at Tm increases with increasing total C. • C atoms released from θ during formation of P to γ diffuse excessively into αPF. • Supersaturated C content in αPF is reduced during transformation of αPF to γ.

  3. Variation of carbon concentration in proeutectoid ferrite during austenitization in hypoeutectoid steel

    International Nuclear Information System (INIS)

    The variation of the C concentration in proeutectoid ferrite (αPF) during austenitization in hypoeutectoid steels was quantitatively investigated using the massive transformation start temperature (Tm) of αPF to austenite (γ) measured by high-temperature confocal laser scanning microscopy and hardness of αPF. The C concentration in αPF at Tm in hypoeutectoid steels increased with increasing total C concentration up to approximately 0.2 wt.% during heating. The hardness of αPF with isothermal holding time at 775 °C in S20C steel revealed C enrichment in αPF at the early stage of isothermal holding and its reduction with further holding. These results explain the redistribution of the C in αPF during austenitization as follows: free C atoms released from cementite during pearlite decomposition diffuse excessively into neighboring αPF as well as pearlitic ferrite. The supersaturated C concentration in αPF is reduced during the long-range diffusive transformation of αPF to γ. However, some of the excess C atoms still remain in αPF until αPF starts to massively transform to γ. - Highlights: • Massive transformation of αPF to γ in hypoeutectoid steels was observed using CLSM. • C content in αPF during austenitization was analyzed by measured Tm and hardness. • Tm decreases and C content in αPF at Tm increases with increasing total C. • C atoms released from θ during formation of P to γ diffuse excessively into αPF. • Supersaturated C content in αPF is reduced during transformation of αPF to γ

  4. Ferrite morphology and residual phases in continuously cooled low carbon steels

    International Nuclear Information System (INIS)

    Although much research has been conducted on the isothermal transformation products of medium to high carbon hardenable steels, relatively little has been reported for transformation of low carbon structural steels under continuous cooling conditions. The trend towards reduced carbon levels (less than about 0.1 wt% C) has been driven by demands for formability and weldability, challenging steel designers to maintain strength by microalloying and/or thermomechanical controlled processing. Although control of the ferritic products formed in low carbon steels after hot rolling, normalising and welding is essential in order to ensure adequate strength and toughness, understanding of the microstructures formed on continuous cooling is still limited. In addition, transformation mechanisms remain controversial because of polarisation of researchers into groups championing diffusional and displacive theories for the transformation of austenite over a wide range of cooling rates. The present review compares and draws together the main ferrite classification schemes, and discusses some critical issues on kinetics and mechanisms, in an attempt to rationalise the effects of cooling rate, prior austenite structure and composition on the resulting ferrite structure and its mechanical properties. It is concluded that with increasing cooling rate the ferritic product becomes finer, more plate-like, more dislocated, more carbon supersaturated, more likely to be formed by a displacive mechanism, harder and stronger. Other conclusions are that: (i) 'bainitic ferrite', which is a pervasive form of ferrite in continuously cooled low carbon steels, is different from the conventional upper and lower bainites observed in higher carbon steels, insofar as the co-product 'phase' is typically martensite-austenite islands rather than cementite; and (ii) low carbon bainite rather than martensite is the dominant product at typical fast cooling rates (<500K/s) associated with commercial

  5. Molecular dynamics investigation of the interaction of dislocations with carbides in BCC Fe

    Energy Technology Data Exchange (ETDEWEB)

    Granberg, F., E-mail: fredric.granberg@helsinki.fi [Department of Physics, P.O. Box 43, FIN-00014 University of Helsinki (Finland); Terentyev, D. [Nuclear Materials Science Institute, SCK-CEN, Boeretang 200, B-2400 Mol (Belgium); Nordlund, K. [Department of Physics, P.O. Box 43, FIN-00014 University of Helsinki (Finland)

    2015-06-01

    Different types of carbides are present in many steels used as structural materials. To safely use steel in demanding environments, like nuclear power plants, it is important to know how defects will affect the mechanical properties of the material. In this study, the effect of carbide precipitates on the edge dislocation movement is investigated. Three different types of carbides were investigated by means of molecular dynamics, with a Tersoff-like bond order interatomic potential by Henriksson et al. The obstacles were 4 nm in diameter and were of Fe{sub 3}C- (cementite-), Fe{sub 23}C{sub 6}- and Cr{sub 23}C{sub 6}-type. The critical unpinning stress was calculated for each type at different temperatures, to get the temperature-dependent obstacle strength. The results showed a decreasing critical stress with increasing temperature, consistent with previous studies. The critical unpinning stress was seen to be dependent on the type of carbide, but the differences were small. A difference was also observed between the obstacles with the same structure, but with different composition. This study shows the relation between the existing Cr{sub 23}C{sub 6} carbide and the experimentally non-existing Fe{sub 23}C{sub 6} carbide, which needs to be used as a model system for investigations with interatomic potentials not able to describe the interaction of Cr in the Fe–C-system. We found the difference to be a between 7% and 10% higher critical unpinning stress for the chromium carbide, than for the iron carbide of the same type.

  6. Research on Wear-resisting Performance of 9SiCr Steel after Heat Treatment%热处理对9SiCr钢耐磨性能影响的研究

    Institute of Scientific and Technical Information of China (English)

    谢晓利

    2016-01-01

    对9SiCr钢试件进行了热处理,对比分析了试件热处理前后的金相组织、硬度及韧性等特征,以湿砂为磨料进行了磨料磨损试验,通过磨损失重、磨损表面形貌分析了9SiCr钢热处理前后的磨损性能.结果表明,9SiCr钢经热处理后,其组织形态由合金渗碳体为主变为以马氏体和下贝氏体为主,硬度及韧性显著加强,以磨损失重为指标的耐磨性提高了20.6%,磨损表面磨沟、凹坑、剥落等磨损特征减弱.%The heat treatment for 9SiCr steel has been deal,and the microstructure,hardness and ductile were compared and analyzed,the abrasive wear test was conducted by wet sand in order to research the change in wear behavior.The results show that,after heat treatment,the structure form of 9SiCr steel turns alloying cementite into martensite and lower bainite,the hardness and ductile improves significantly,the wear resistance characterized by wear weight loss is increased by 20.6%,the grinding groove,indentation,and peeling on wear surface is reduceed.

  7. Comparison of solidification behavior between in situ observation and simulation of Fe–C–Si system

    International Nuclear Information System (INIS)

    Highlights: • In situ time resolved X-ray imaging was obtained for solidification of Fe–C–Si alloy. • The techniques provided quantitative data of evolution and proportion of phases. • Thermo-Calc. and DICTRA was used to simulate the alloy solidification process. • Real-time observations were compared with the results of the simulation. • Further evaluation of DICTRA kinetic databases will be required. - Abstract: Over the last few years, important advances have been made in the understanding and modelling of phase transformations of metallic alloys including (a) the coupling of phase equilibria and kinetics for computerised simulation of multicomponent alloys and (b) in situ time resolved X-ray imaging of phase transformations in real time. Both techniques can be complementary. However the quality of the simulation relies to a large extent on the accuracy of phase equilibria and diffusion data obtained from existing experimental studies. In situ X-ray techniques provide quantitative information on the evolution and proportion of phases, and can validate the thermodynamic/kinetic packages. This validation in-turn improves the computational models and databases. In the present work, the phase transformation in the Fe–C–Si system from liquid to γ-Fe and the reaction liquid ↔ γ-Fe + Cementite was observed by using X-ray imaging at SPring-8 synchrotron. The relationship between fraction solid and temperature was obtained from the generated SPring-8 images. The results are compared with computer simulation using Thermo-Calc. and DICTRA. A critical analysis compares the results of the simulation with the real-time observations of the phase transformation

  8. Thermal sprayed iron base alloys coatings

    International Nuclear Information System (INIS)

    Particularities of thermal spraying of iron-based alloys coatings are associated with sufficiently great values of parameter of melting difficulty (for Fe D = 2.08 I-10/sup 10/ kJ.kg/sup -1/.m/sup -3/), and relatively low values of coefficients-of heat accumulation (for Fe b=C.raw.Lambda /sub 0.5/=108 W.m/sup -2/.K.sec/sup-0.5/). These materials are less inclined to form quality coating under the influence of the thermal activation and therefore it is reasonable to use in addition the mechanical activation of substrate surface. The powder of iron-base alloy FeSi/sub 7/AI/sub 3.5/C/sub 2/ was obtained by melt-atomization with water hardening of droplets. The main phase components of powder are alpha and gamma -solid solution on base of Fe (austenite), cementite (Fe/sub 3/C), metastable rhombic lattice x-phase, and possibly metastable carbide Fe/sub 2/C. When the powder particles shape is oval which axis dimensions about 80 and 300 micro meter, the main phase components of detonation sprayed coatings in case of oxy-acetylene gas mixture are alpha and gamma -phases, in case of oxy-propane-butane mixture the coating phase component the same as initial powder. When the powder particles size is 63-100 micro meter, the coatings phase components are alpha and gamma - solid solutions, Fe/sub 3/C, x-phase, Fe/sub 2/C, Fe/sub 3/0/sub 4/ and FeO. The main phase components of FeSi/sub 7/B/sub 12,6/ powder are alpha-solid solution, borides Fe/sub 2/B and FeB, X- phase. The sprayed coatings have the same phase composition. These types of Fe-base alloys powders have relatively low cost, easy available and can used for deposition of wear resistant coatings. (author)

  9. Influencia del revenido en la estructura y las propiedades de dureza, resistencia a la tracción y resiliencia del acero cubano al cromomanganeso- silicio-níquel. // Influence of tempering on structure and hardness, strength and resilience properties of ch

    Directory of Open Access Journals (Sweden)

    G. Tourón-Alonso

    2009-09-01

    Full Text Available La actual demanda de herramientas y accesorios para maquinarias agrícolas se presenta comofuente creciente de nuevas aplicaciones del acero al Cr-Mn-Si-Ni. Este criterio justifica la práctica detratamientos térmicos, para conseguir distintos valores de propiedades mecánicas, que orienten almaterial hacia las exigencias y circunstancias de aplicaciones concretas. El trabajo tiene comoobjetivo conocer la estructura del acero, heredadas de las transformaciones de fase en diferentesregímenes de tratamiento térmico de revenido, y la correlación entre dicha estructura y suspropiedades de dureza, resistencia a la tracción y resiliencia. Las observaciones al microscopioóptico de las muestras revenidas sugieren, en unos casos, una estructura compuesta por martensitarevenida, en otros, indican la presencia de partículas de ferrita y cementita. Los ensayos de dureza ytracción revelaron una disminución de la dureza y de la resistencia a la tracción con el aumento dela temperatura de revenido. El ensayo de impacto reveló un aumento de la resiliencia con elaumento de la temperatura de revenido, aunque aparecen dos intervalos de temperatura en que laresiliencia disminuye.Palabras claves: revenido, estructura, dureza, resistencia, resiliencia____________________________________________________________________________AbstractSpecimens were tempered after being hardened into oil. Tempered specimens for tension tests,were heated from 200 to 500ºC, in an interval of 100ºC; while, specimens for hardness andresilience tests, were heated from 200 to 550ºC, in an interval of 50ºC. Tempering time, for tensionand resilience tests, depends on specimens’ thickness, while, for hardness tests is 30, 60 and 90minutes. Tempered specimens microstructures at 200 and 300ºC indicate the presence of carbideparticles; it suggests a tempering martensite structure. Tempered specimens microstructures at500ºC indicate the presence of ferrite and cementite particles

  10. FLEXURAL AND TENSILE CHARACTERISTICS OF MICRO FIBER-REINFORCED VERY HIGH STRENGTH CONCRETE THIN PANELS

    Directory of Open Access Journals (Sweden)

    Taher M. Abu-Lebdeh

    2012-01-01

    Full Text Available The purpose of this research was to experimentally characterize the flexural and tensile characteristics of fiber-reinforced Very High-Strength Concrete (VHSC panels. The panels were made with a unique mix of cementitous materials achieving compressive strength of 26,000 psi (180 MPa or greater. VHSC panels were reinforced with polypropylene fibers of 1 inch (25.4 mm in length and Polyvinyl alcohol (PVA micro-fibers of ½ inch length, incorporated at 1.5% by volume. For the flexural behavior, 17×2×¾ inch flat panels were tested under third-point loading tests, while the direct tension experiments were tested on 10×3×½ inch tension panels under a direct tensile load. Flexural tests were conducted on three panels of plain VHSC, three panels of VHSC reinforced with polypropylene fibers and three panels of VHSC reinforced with ½ inch micro-fibers. Similar testing program was used to conduct the direct tension tests. Also, compression test conducted on 2×2×2 inch cubes and compressive test conducted on 4 inch by 8 inch cylinders test were used to establish compressive strength and modulus of elasticity respectively. Results show that the compressive strength, tensile strength and fracture toughness of the VHSC panels were much greater than those normally obtained by typical concrete material. The presence of fibers increases the toughness of VHSC specimens between 80 and 190% and increases the tensile strength by 23 to 47%. The modulus of elasticity and Poisson’s ratio recorded herein were determined according to ASTM C 469-02. Laboratory experiments on flexural and tensile properties of thin, very high-strength, fiber reinforced concrete panels, were used to study the material and characterize the panels’ reaction to load. Parameters such as compressive strength, tensile strength, toughness, elastic modulus, Poisson’s ratio and first-crack strength were determined and may be considered for potential use as

  11. Effect of cooling rate and austenitizing temperature on the spheroidizing annealing of 40 Cr steel%冷却速率和奥氏体化温度对40 Cr钢球化退火的影响

    Institute of Scientific and Technical Information of China (English)

    邱木生; 祭程; 朱苗勇; 徐东

    2015-01-01

    To study the impact of austenitizing temperature and cooling rate on the spheroidizing annealing process of 40Cr steel, the spheroidizing annealing behavior and the mechanical properties of 40Cr steel were investigated by conventional intercritical annea-ling. It is found that with the austenitizing temperature between 760℃ and 800℃, the hardness varies as a “V” shape but the ce-mentite spheroidization rate changes as an inverted“V” shape with increasing cooling rate from 10℃·h-1 to 30℃·h-1 . Higher sphe-roidization level and finer carbides, which are obtained at an austenitizing temperature of 760℃ and a cooling rate of 20℃·h-1 , make the steel having a better cold formability. A divorced eutectoid transformation ( DET) reaction mechanism of the spheroidizing annea-ling process was proposed, and the occurrence of the divorced eutectoid transformation reaction depends strongly on austenitizing tem-perature, cooling rate and holding time.%为探究奥氏体化温度和冷却速率对40Cr钢球化过程的影响,采用双相区球化退火研究了热轧态40Cr钢的球化退火行为和力学性能。奥氏体化温度从760℃提高到800℃,冷却速率从10℃·h-1上升到30℃·h-1,组织硬度随冷却速度呈V形变化,碳化物球化率随冷却速度变化正好与前者相反。奥氏体化温度为760℃,冷却速率为20℃·h-1所得到的球化组织球化率高,且碳化物细小,具有良好的冷成形性能,可大幅度缩短球化退火时间,显著提高生产效率。提出了球化退火过程中离异共析转变机制,控制好球化过程中奥氏体化温度、冷却速率及保温时间有利于离异共析转变的发生。

  12. A Brief History of Metallography: Ⅰ . The Beginning%金相学史话(1):金相学的兴起

    Institute of Scientific and Technical Information of China (English)

    郭可信

    2000-01-01

    Widmanstatten在19世纪初用硝酸水溶液腐刻铁陨石切片,观察到片状Fe-Ni奥氏体的规则分布(魏氏组织),予告金相学即将诞生。Sorby在1863年用反射式显微镜观察抛光腐刻的钢铁试样,不但看到珠光体中的渗碳体和铁素体的片状组织,还对钢的淬火和回火作了初步探讨,金相学已基本形成。到19-20世纪之交,Martens(马氏)和Osmond对金相学的发展和金相检验在厂矿中的推广做了重要贡献,同时Roberts-Austen(奥氏)和Roogzeboom初步绘制出Fe-C平衡图,为金相学奠定了理论基础。到了二十世纪中叶,金相学已逐步发展成金属学、物理冶金和材料科学。%In the beginning of the 19th century Widmanstatten used diluted water solution of nitric acid to etch a slice of iron meteorite and observed an oriented pattern of Fe-Ni austenite, anticipating the birth of metallography. In 1863 Sorby examined iron and steel specimens prepared by grinding, polishing,and etching by means of a reflection microscope and observed pearlite composed of fine cementite and ferrite lamellae. he has also discussed the possible transformations occurred in quenching and annealing of steels.This announced the birth of metallography. During the shift of the 19th century, Martens and Osmond made important contribution to the development of metallography and its application in the metal industry.In the meantime, Roberts-Austen and Roozeboom constructed the preliminary Fe-C phase diagram, which laid the foundation of metallography. Coming to the fifties of the 20th century, metallography developed successively into physical metallurgy and materials science

  13. 碳含量对纳米结构白口铸铁组织与力学性能的影响%Effect of carbon content on microstructure and mechanical properties of nanostructure white cast iron

    Institute of Scientific and Technical Information of China (English)

    喇培清; 甄小娟; 胡苏磊; 李翠玲; 魏玉鹏; 卢学峰; 王鸿鼎; 魏福安

    2014-01-01

    The nanostructure white cast irons without expensive elements were prepared by aluminothermic reaction, the effect of carbon content on its microstructures and mechanical properties was studied by XRD, OM, SEM, tension and compression test . The results show that, the white cast irons consist of pearlite with different shapes and cementite, the lamellar pearlite decreases and granular pearlite increases with increasing the carbon content. The average lamellar spacing of the pearlite phase is 165, 231 and 250 nm, respectively. With increasing carbon content, the vickers hardness of nanostructure white cast iron is 552, 577 and 575 HV, compressive strength is 2 224, 2 460 and 2 220 MPa, and tensile strength is 383, 416 and 245 MPa, respectively, which are all first increases and then decreases with increasing carbon content; the elongation rate is 3%, 2.5% and 1%. The mechanical properties of nanostructure white cast iron without expensive alloying elements are the same to Ni-Hard2 cast iron.%以铝热反应法制备无昂贵合金元素添加的纳米结构白口铸铁,采用XRD、OM、SEM和拉伸及压缩等分析、测试手段研究碳含量对纳米结构白口铸铁组织和力学性能的影响。结果表明:随碳含量增加,白口铸铁由不同形态的珠光体和渗碳体组成,其中层片状珠光体含量减少,粒状珠光体含量增加;层片状珠光体的片间距分别为165、231和250 nm。碳含量为3.5%,3.7%和4.3%的纳米结构白口铸铁的维氏硬度分别为552、577和575 HV,抗压强度为2224、2460和2220 MPa,抗拉强度为383、416和245 MP,均呈现先增大后减小的趋势;伸长率为3%、2.5%和1%,呈现逐渐下降的趋势。无昂贵合金元素添加的纳米结构白口铸铁的力学性能与Ni-Hard 2铸铁相当。

  14. THE PROCESS OF FORMATION OF RAILWAY WHEEL DAMAGES AND TIRES IN OPERATION

    Directory of Open Access Journals (Sweden)

    N. A. Grischenko

    2015-01-01

    Full Text Available Purpose. The dependence analysis of structural changes in the metal of railway wheels and tires from indicated influences in operation, for the further development of strategy of service reliability growth. Methodology. Test materials are the details selected from railway wheels which were taken out of operation beforehand because of various damages. Micro-structural researches were made with the use of light microscope Epiquant and electron microscope. The sizing of structural elements was done by using the methods of quantitative metallography. Findings. Over the past few decades the rapid development of industry was supported by the steady growth of intensity of using railway transport. In this case simultaneous increase of load at wheel set axle, with the increase of speed was accompanied by natural increase of the amount of cases of premature wheels and tires’ withdrawing out of operation. Railway wheel, except the formation of metal layer at rolling surface with the high defects concentration of crystal structure and first of all dislocations, falls under thermal influence from interaction with break blocks. The nature of joint influence (cold deformation and heating on the metal rim of a wheel is conditioned by the appearance of sufficiently high gradients of structural changes that can be considered as the influence on the level of internal residual stresses. In case of the rise of volume part of carbide phase at a constant ferrite grain size, it is achieved only by the increasing of dislocation nucleation sources without changing the number of annihilation positions. In this case the accumulation of dislocations at the initial stages of plastic deformation (in metal volume in front of delta arm crack will lead to the formation of cementite globes around certain interlocked dislocation density. In contrast the sharp increase of deformation hardening carbon steel parameters is observed. Originality. During the braking of locomotive the

  15. Carbon-content dependent effect of magnetic field on austenitic decomposition of steels

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Xiaoxue, E-mail: zhangxiaoxue1213@gmail.com [Key Laboratory for Anisotropy and Texture of Materials (MOE), Northeastern University, Shenyang 110004 (China); Laboratoire d' Etude des Microstructures et de Mecanique des Materiaux (LEM3), CNRS UMR 7239, University of Metz, 57045 Metz (France); Wang Shoujing, E-mail: wsj210725@yahoo.com.cn [Key Laboratory for Anisotropy and Texture of Materials (MOE), Northeastern University, Shenyang 110004 (China); Zhang Yudong, E-mail: yudong.zhang@univ-metz.fr [Laboratoire d' Etude des Microstructures et de Mecanique des Materiaux (LEM3), CNRS UMR 7239, University of Metz, 57045 Metz (France); Esling, Claude, E-mail: claude.esling@univ-metz.fr [Laboratoire d' Etude des Microstructures et de Mecanique des Materiaux (LEM3), CNRS UMR 7239, University of Metz, 57045 Metz (France); Zhao Xiang, E-mail: zhaox@mail.neu.edu.cn [Key Laboratory for Anisotropy and Texture of Materials (MOE), Northeastern University, Shenyang 110004 (China); Zuo Liang, E-mail: lzuo@mail.neu.edu.cn [Key Laboratory for Anisotropy and Texture of Materials (MOE), Northeastern University, Shenyang 110004 (China)

    2012-04-15

    The transformed microstructures of the high-purity Fe-0.12C alloy and Fe-0.36C alloy heat treated without and with a 12 T magnetic field have been investigated to explore the carbon-content dependent field effect on austenitic decomposition in steels. Results show that, the field-induced transformed morphology characteristics in different alloys differ from each other. In the Fe-0.12C alloy, the pearlite colonies are elongated along the field direction, and shaped by the chained and elongated proeutectoid ferrite grains in the field direction. However, in the Fe-0.36C alloy, the field mainly reduces the amount of Widmaenstatten ferrite and elongates the formed proeutectoid ferrite grains in the field direction. No clear field direction alignment is obtained. The magnetic field also demonstrates carbon-content dependent effect on the texture of the formed ferrite. It clearly enhances the Left-Pointing-Angle-Bracket 001 Right-Pointing-Angle-Bracket fiber of the ferrite in the transverse field direction in the Fe-0.36C alloy. This field effect is related to the crystal lattice distortion induced by carbon solution and this impact becomes stronger with the increase of the carbon content. For the Fe-0.12C alloy, this field effect is greatly reduced due to the reduced carbon oversaturation in ferrite and elevated formation temperature. The orientation relationships (ORs) between the pearlitic ferrite and the pearlitic cementite in both alloys are less affected by the magnetic field. No obvious changes in the either type of the appearing ORs and their number of occurrences are detected. - Highlights: Black-Right-Pointing-Pointer The carbon-content dependent field effect on austenitic decomposition is studied. Black-Right-Pointing-Pointer The field-induced morphology features vary with the carbon content. Black-Right-Pointing-Pointer The field effect on ferrite texture is more pronounced in high carbon content alloy. Black-Right-Pointing-Pointer Magnetic field hardly

  16. Microalloyed V-Nb-Ti and V steels Pt. 2 - precipitation behaviour during processing of structural beams

    Energy Technology Data Exchange (ETDEWEB)

    Tanniru, M.; Shanmugam, S.; Misra, R.D.K.; Panda, D.; Jansto, S.

    2005-02-15

    region was characterised by complete precipitation of cementite. In general, the microstructure had a low dislocation density. (author)

  17. Solidification microstructures and mechanical properties of high-vanadium Fe-C-V and Fe-C-V-Si alloys

    International Nuclear Information System (INIS)

    Fe-C-V and Fe-C-V-Si alloys of various C, V and Si compositions were investigated in this work. It was found that the phases present in both of these alloy systems were alloyed ferrite, alloyed cementite, and VCx carbides. Depending on the alloy composition the solidified microstructural constituents were granular pearlite-like, lamellar pearlite, or mixtures of alloyed ferrite + granular pearlite-like or granular pearlite-like + lamellar pearlite. In addition, it is shown that in Fe-C-V alloys the C/V ratio influences (a) the type of matrix, (b) the fraction of vanadium carbides, fv and (c) the eutectic cell count, NF. In Fe-C-V alloys, a relationship between the alloy content corresponding to the eutectic line was experimentally determined and can be described by Ce=7.91Ve-0.635 where Ce and Ve are the carbon and vanadium composition of the eutectic. Moreover, in the Fe-C-V alloys (depending on the alloy chemistry), the primary VCx carbides crystallize with non-faceted or non-faceted/faceted interfaces, while the eutectic morphology is non-faceted/non-faceted with regular fiber-like structures, or it possesses a dual morphology (non-faceted/non-faceted with regular fiber-like structures + non-faceted/faceted with complex regular structures). In the Fe-C-V-Si system, the primary VCx carbides solidify with a non-faceted/faceted interface, while the eutectic is non-faceted/faceted with complex regular structures. In particular, spiral eutectic growth is observed when Si is present in the Fe-C-V alloys. In general, it is found that as the matrix constituent shifts from predominantly ferrite to lamellar pearlite, the hardness, yield and tensile strengths exhibit substantial increases at expenses of ductility. Moreover, Si additions lead to alloy strengthening by solid solution hardening of the ferrite phase and/or through a reduction in the eutectic fiber spacings with a decrease in the alloy ductility.

  18. Solidification microstructures and mechanical properties of high-vanadium Fe-C-V and Fe-C-V-Si alloys

    Energy Technology Data Exchange (ETDEWEB)

    Fras, E.; Kawalec, M. [AGH - University of Science and Technology, Reymonta 23, 30-059 Krakow (Poland); Lopez, H.F., E-mail: hlopez@uwm.edu [Materials Department, University of Wisconsin-Milwaukee, 3200 N. Cramer Street, Milwaukee, WI 53211 (United States)

    2009-10-25

    Fe-C-V and Fe-C-V-Si alloys of various C, V and Si compositions were investigated in this work. It was found that the phases present in both of these alloy systems were alloyed ferrite, alloyed cementite, and VC{sub x} carbides. Depending on the alloy composition the solidified microstructural constituents were granular pearlite-like, lamellar pearlite, or mixtures of alloyed ferrite + granular pearlite-like or granular pearlite-like + lamellar pearlite. In addition, it is shown that in Fe-C-V alloys the C/V ratio influences (a) the type of matrix, (b) the fraction of vanadium carbides, f{sub v} and (c) the eutectic cell count, N{sub F}. In Fe-C-V alloys, a relationship between the alloy content corresponding to the eutectic line was experimentally determined and can be described by C{sub e}=7.91V{sub e}{sup -0.635} where C{sub e} and V{sub e} are the carbon and vanadium composition of the eutectic. Moreover, in the Fe-C-V alloys (depending on the alloy chemistry), the primary VC{sub x} carbides crystallize with non-faceted or non-faceted/faceted interfaces, while the eutectic morphology is non-faceted/non-faceted with regular fiber-like structures, or it possesses a dual morphology (non-faceted/non-faceted with regular fiber-like structures + non-faceted/faceted with complex regular structures). In the Fe-C-V-Si system, the primary VC{sub x} carbides solidify with a non-faceted/faceted interface, while the eutectic is non-faceted/faceted with complex regular structures. In particular, spiral eutectic growth is observed when Si is present in the Fe-C-V alloys. In general, it is found that as the matrix constituent shifts from predominantly ferrite to lamellar pearlite, the hardness, yield and tensile strengths exhibit substantial increases at expenses of ductility. Moreover, Si additions lead to alloy strengthening by solid solution hardening of the ferrite phase and/or through a reduction in the eutectic fiber spacings with a decrease in the alloy ductility.

  19. Influencia del revenido en la estructura y las propiedades de dureza, resistencia a la tracción y resiliencia del acero cubano al cromo-manganeso-silicio-níquel.

    Directory of Open Access Journals (Sweden)

    G. Tourón Alonso

    2009-09-01

    Full Text Available La actual demanda de herramientas y accesorios para maquinarias agrícolas se presenta como fuente creciente de nuevas aplicaciones del acero al Cr-Mn-Si-Ni. Este criterio justifica la práctica de tratamientos térmicos, para conseguir distintos valores de propiedades mecánicas, que orienten al material hacia las exigencias y circunstancias de aplicaciones concretas. El trabajo tiene como objetivo conocer la estructura del acero, heredadas de las transformaciones de fase en diferentes regímenes de tratamiento térmico de revenido, y la correlación entre dicha estructura y sus propiedades de dureza, resistencia a la tracción y resiliencia. Las observaciones al microscopio óptico de las muestras revenidas sugieren, en unos casos, una estructura compuesta por martensita revenida, en otros, indican la presencia de partículas de ferrita y cementita. Los ensayos de dureza y tracción revelaron una disminución de la dureza y de la resistencia a la tracción con el aumento de la temperatura de revenido. El ensayo de impacto reveló un aumento de la resiliencia con el aumento de la temperatura de revenido, aunque aparecen dos intervalos de temperatura en que la resiliencia disminuye.Specimens were tempered after being hardened into oil. Tempered specimens for tension tests, were heated from 200 to 500ºC, in an interval of 100ºC; while, specimens for hardness and resilience tests, were heated from 200 to 550ºC, in an interval of 50ºC. Tempering time, for tension and resilience tests, depends on specimens’ thickness, while, for hardness tests is 30, 60 and 90 minutes. Tempered specimens microstructures at 200 and 300ºC indicate the presence of carbide particles; it suggests a tempering martensite structure. Tempered specimens microstructures at 500ºC indicate the presence of ferrite and cementite particles. Both, hardness and strength decrease when the tempering temperature increases. The resilience increase with tempering temperature, but

  20. Development of a quantitative accelerated sulphate attack test for mine backfill

    Science.gov (United States)

    Shnorhokian, Shahe

    Mining operations produce large amounts of tailings that are either disposed of in surface impoundments or used in the production of backfill to be placed underground. Their mineralogy is determined by the local geology, and it is not uncommon to come across tailings with a relatively high sulphide mineral content, including pyrite and pyrrhotite. Sulphides oxidize in the presence of oxygen and water to produce sulphate and acidity. In the concrete industry, sulphate is known to produce detrimental effects by reacting with the cement paste to produce the minerals ettringite and gypsum. Because mine backfill uses tailings and binders---including cement---it is therefore prone to sulphate attack where the required conditions are met. Currently, laboratory tests on mine backfill mostly measure mechanical properties such as strength parameters, and the study of the chemical aspects is restricted to the impact of tailings on the environment. The potential of sulphate attack in mine backfill has not been studied at length, and no tests are conducted on binders used in backfill for their resistance to attack. Current ASTM guidelines for sulphate attack tests have been deemed inadequate by several authors due to their measurement of only expansion as an indicator of attack. Furthermore, the tests take too long to perform or are restricted to cement mortars only, and not to mixed binders that include pozzolans. Based on these, an accelerated test for sulphate attack was developed in this work through modifying and compiling procedures that had been suggested by different authors. Small cubes of two different binders were fully immersed in daily-monitored sodium sulphate and sulphuric acid solutions for a total of 28 days, after 7 days of accelerated curing at 50°C. In addition, four binders were partially immersed in the same solutions for 8 days for an accelerated attack process. The two procedures were conducted in tandem with leach tests using a mixed solution of

  1. 利用APT对RPV模拟钢中富Cu原子团簇析出的研究%STUDY ON THE PRECIPITATION OF Cu-RICH CLUSTERS IN THE RPV MODEL STEEL BY APT

    Institute of Scientific and Technical Information of China (English)

    徐刚; 蔡琳玲; 冯柳; 周邦新; 刘文庆; 王均安

    2012-01-01

    from 1.5 nm to 2.4 nm, and the average Cu content in the Cu-rich clusters vary from 45% to 55 % (atomic fraction). The number density of the Cu-rich clusters in both types of the specimens is at the order of 1022 m-3. The Cu concentration in the ferritic matrix is (0.15±0.02)% for the specimen aged at 370℃ for 13200 h, which is still higher than the limitation of Cu solubility in the ferritic matrix at 370℃ . It means that the precipitation process of Cu-rich clusters does not reach the equilibrium state. The analysis results also show that Ni, Si, P atoms, but not Cu atoms, segregate near the interface between the cementite and the ferritic matrix, and Mn, Mo, S atoms are enriched in the cementite.%提高了Cu含量的核反应堆压力容器(RPV)模拟钢经过880℃水淬和660℃调质处理,在370℃时效不同时间后,利用原子探针层析技术(APT)进行分析.结果表明:样品经过1150 h时效后,富Cu团簇正处于析出过程的形核阶段;经过3000和13200 h时效后析出了富Cu团簇,团簇的平均等效直径分别为1.5和2.4 nm,团簇中Cu的平均浓度分别为45%和55%(原子分数),团簇的数量密度约为4.2×1022 m-3;样品经过13200 h时效后,α-Fe基体中的Cu含量为(0.15±0.02)%,仍然高于Cu在α-Fe中平衡固溶度的理论计算值,说明这时富Cu团簇的析出过程还没有达到平衡.对渗碳体的分析结果表明,Ni,Si和P偏聚在渗碳体和α-Fe基体的相界面附近,Mn,Mo和S富集在渗碳体中;并没有观察到Cu在相界面上偏聚的现象.

  2. Effect of heat treatment on microstructure of high chrome steel by laser surface melting%热处理中高铬钢激光熔凝层的组织转变

    Institute of Scientific and Technical Information of China (English)

    李美艳; 王勇; 韩彬; 宋立新; 程义远

    2011-01-01

    Laser surface melting was carried on surface of high chrome steel, and then the samples were tempered in the range of 300-650 ℃. The effect of heat treatment on microstructure of the laser melted coating was investigated by means of SEM ,XRD and TEM.The results show that the austenite in the laser melted coating possesses a high tempering stability due to the increase of alloying elements in solid solution and refined grains. The hardness of the laser melted coating is elevated after tempering at 450 ℃ and reaches a peak of 672 HV0.2 at 560 ℃ and then decreases quickly at 650 ℃. After tempering at 450 ℃ the precipitation of fine M23C6 carbides and a small amount of martensite from the supersaturated austenite are contributed to the slight increase of hardness. At 560 ℃ the combined effect of the martensite phase transformation and the precipitation of carbides within the refined microstructure results in the maximum. At the same time,a small amount of M3C carbides precipitates from the martensite. Moreover, the decrease of hardness at 650 ℃ is caused by the formation of ferrite matrix and large quality of lamellar M3C cementite.%采用激光熔凝处理方法对高铬钢进行表面强化,然后在300~650℃区间回火处理,利用SEM、XRD和TEM等手段分析热处理对激光熔凝层组织的影响.结果表明,高铬钢激光熔凝处理后,得到的奥氏体组织中合金元素固溶度较高且晶粒细小,具有较高的回火稳定性.激光熔凝层450℃回火后硬度开始升高,560℃时达到最大值(672 HV0.2),回火温度高达650℃时硬度迅速降低.450℃回火后细小M23C6碳化物优先从过饱和奥氏体中析出,同时少量马氏体的生成使熔凝层硬度略有增加.560 ℃回火后由于M,C,和M23C6碳化物的析出、大量高硬度马氏体的生成以及位错强化的共同作用使硬度达到峰值,同时,马氏体组织中有少量的M,C渗碳体析出.650℃回火后基体完全转

  3. Teknologi Pembuatan Material Shot Blast untuk Mendukung Industri Pengecoran Logam Nasional

    Directory of Open Access Journals (Sweden)

    Fajar Nurjaman

    2009-01-01

    Full Text Available Shot blast material is a supporting material in foundry which is used at surface finishing process of metal casting. Recently, there is no one of national industry that produce shot blast material, in consequence, the purpose of this research is to lessen the dependence of using shot blast material import by making a shot blast material which improve its hardness exceed the shot blast material import. This research use the raw material from scrap iron with the following composition: C (3.2%, Si (1.18%, Mn (6.1%, Cu (0.35%, Fe (88.7%. The scrap is melted in induction furnace untill melt (hot metal, then the hot metal (1200 oC is tilted into a runner which is connected with pan crucible, which is consisted of 107 holes with diameter of each holes is 10 mm. Hot metal that is leave from the holes, is injected by pressurized water 1.1 atm with the velocity 0.8 m/s, untill obtained grains of shot blast material, then these grains goes into the water tank which it has temperature 40oC. From thermodynamic study, to avoid the happening of the explosion that is arising out because the effect of high temperature difference at injection process beetween water and hot metal, hence the comparison value beetween the mass of water and hot metal equal to 1:4.6. From this research is obtained shot blast material Ø0.8-3.2 mm with the metallography structure with martensite domination and dispersion of cementite and a little austenit. The hardness value of this material is 54.8 HRC, where this value is larger than shot blast material import (45-50 HRC. Abstract in Bahasa Indonesia: Material shot blast merupakan material pendukung pengecoran logam yang digunakan pada proses surface finishing benda cor logam. Saat ini belum ada satupun industri nasional yang memproduksi material shot blast, karena itu tujuan penelitian ini untuk mengurangi ketergantungan penggunaan material shot blast impor dengan membuat material shot blast yang nilai kekerasannya melebihi material

  4. Effects and characterization of an environmentally-friendly, inexpensive composite Iron-Sodium catalyst on coal gasification

    Science.gov (United States)

    Monterroso, Rodolfo

    were studied through characterization tests. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Mossbauer spectroscopy, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), gas chromatography (GC-MS) and nuclear magnetic resonance spectroscopy (NMR) were used to perform the analyses. The XRD results are consistent with interactive mechanisms or the formation of Na-Fe oxides as the catalytic pathway. Activity of the iron catalyst during late stages of the gasification process was confirmed through XPS. Mossbauer spectroscopy also indicated the presence of metallic iron and cementite in the char at different stages. The Fe catalysts were better at tar decomposition than the Na catalysts, as indicated by GC-MS analyses. NMR spectra confirmed that tar compositions vary with the catalytic mechanism. FTIR analysis confirmed the presence of high yields of aromatic components and long aliphatic chains in the tar. Composite Fe-Na catalysts provide a method to tailor the amounts and composition of product generated during gasification.

  5. Evaluation of thiosulfate as a substitute for hydrogen sulfide in sour corrosion fatigue studies

    Science.gov (United States)

    Kappes, Mariano Alberto

    This work evaluates the possibility of replacing hydrogen sulfide (H 2S) with thiosulfate anion (S2O32- ) in sour corrosion fatigue studies. H2S increases the corrosion fatigue crack growth rate (FCGR) and can be present in carbon steel risers and flowlines used in off-shore oil production. Corrosion tests with gaseous H2S require special facilities with safety features, because H2S is a toxic and flammable gas. The possibility of replacing H2S with S2O32-, a non-toxic anion, for studying stress corrosion cracking of stainless and carbon steels in H2S solutions was first proposed by Tsujikawa et al. ( Tsujikawa et al., Corrosion, 1993. 49(5): p. 409-419). In this dissertation, Tsujikawa work will be extended to sour corrosion fatigue of carbon steels. H2S testing is often conducted in deareated condition to avoid oxygen reaction with sulfide that yields sulfur and to mimic oil production conditions. Nitrogen deareation was also adopted in S2O3 2- testing, and gas exiting the cell was forced through a sodium hydroxide trap. Measurements of the sulfide content of this trap were used to estimate the partial pressure of H2S in nitrogen, and Henry's law was used to estimate the content of H2S in the solution in the cell. H2S was produced by a redox reaction of S2O 32-, which required electrons from carbon steel corrosion. This reaction is spontaneous at the open circuit potential of steel. Therefore, H2S concentration was expected to be maximum at the steel surface, and this concentration was estimated by a mass balance analysis. Carbon steel specimens exposed to S2O32- containing solutions developed a film on their surface, composed by iron sulfide and cementite. The film was not passivating and a good conductor of electrons. Hydrogen permeation experiments proved that this film controls the rate of hydrogen absorption of steels exposed to thiosulfate containing solutions. The absorption of hydrogen in S2O3 2- solutions was compared with the absorption of hydrogen in

  6. Effect of Si on Wear Resistance of Bainitic Cast Steel under High Stress Impact%硅对贝氏体铸钢高应力冲击磨损性能的影响

    Institute of Scientific and Technical Information of China (English)

    黄进峰; 方鸿生; 徐平光; 郑燕康

    2001-01-01

    The high stress-wear resistance and mechanism for bainitic cast steels with different Si content (0.7 %~2.4 %) have been studied systematically.The experiments have shown that the wear loss of high Si bainitic cast steels is only about 1/2 times as that of low Si baini tic cast steels, showing better wear resistance of the former under high stress impact.The reason is that the impact wear mechanism is different for low and hi gh Si bainitic cast steels.Low Si bainitic cast steel has poor wear resistance under high stress impact because of its low toughness, coarse dendrite and micro -segregation, etc.So the damage cracks are easily formed in the wear surface b efore formation of white layer, and propagate inside the deformation zone and ma trix, exhibiting mechanism of deformation zone and matrix delamination.The imp act toughness of high Si bainitic cast steels are improved apparently for the re ason that the brittle cementite is replaced by ductile retained austentite film, resulting in the brittle delamination of white layer.%研究了不同硅含量(0.7 %~2.4 %,质量分数,下 同)贝氏体铸钢的抗高应力磨损性能和失效机制。结果表明:高硅贝氏体铸钢的耐磨性能较 低硅钢显著提高,其磨损失重约是低硅贝氏体铸钢的1/2。这是因为硅使贝氏体铸钢在高应 力冲击磨损下表现出不同的失效机制。低硅(0.7 %)贝氏体铸钢由于韧性低、组织结构粗大 及树枝晶的微区成分偏析,故材料抵抗冲击的能力很低,常在表面还未形成强烈变形层(白 层)甚至变形层时,就在变形层和材料基体内产生裂纹并扩展,故低硅贝氏体铸钢的失效方 式为变形层和基体剥落机制。而硅含量为1.6 %~2.4 %的高硅贝氏体铸钢,因脆性的渗碳体 被韧性的残余奥氏体所代替,钢的韧性显著提高,失效方式表现为白层的剥落机制。

  7. Effect of Two Pig Irons on the Metallurgical Structure and Hardness of the Hardened Camshaft%两种生铁对可淬硬凸轮轴金相组织和硬度的影响

    Institute of Scientific and Technical Information of China (English)

    沈保罗; 李莉; 岳昌林; 白维均; 徐家富

    2011-01-01

    研究了四川钒钛生铁和河北球墨生铁对491Q可淬硬凸轮轴金相组织和硬度的影响.研究表明:四川钒钛生铁的金相组织由细小点状石墨+A型石墨+碳化物+珠光体组成;河北球墨生铁的金相组织由A型石墨+C型石墨+珠光体组成.由Ⅰ组配料(230kg四川钒钛生铁+100kg废钢+220kg回炉料+其它合金)铸造的凸轮轴的金相组织为4-6级A石墨+少量E型石墨+95%珠光体+5%渗碳体,基体硬度为252~255HB;由Ⅱ组配料(150kg河北球墨生铁+80kg四川钒钛生铁+100kg废钢+220kg回炉料+其它合金)铸造的凸轮轴的金相组织为4-6级A型+少量E型石墨+100%珠光体,基体硬度为210~229HB.作者初步分析了产生上述现象的原因.%Sichuan V-Ti pig iron and Hebei ductile iron have been used to manufacture 491Q type hardened camshaft and the effect of both iron on the microstructure and hardness of the camshaft been researched.Studies have shown that the microstructure of Sichuan vanadium-titanium pig iron consists of as tiny dot graphite+A type graphite+carbide+ pearlite while the microstructure of Hebei ductile iron consists of A-type graphite+C-type graphite+pearlite.The microstructure in the camshaft manufactured from the group- Ⅰ ingredient (230 kg Sichuan V-Ti pig iron + 100 kg scrap steel +220kg back charge+other alloys ) consists of the 4-6 grade A-type graphite +small amount E-type graphite +95% pearlite +about 5% cementite, and his matrix hardness is 252-255HB.The microstructure in the camshaft manufactured from the group- Ⅱ ingredient ( 150 kg Sichuan V-Ti pig iron+80 kg Hebei ductile iron+100 kg scrap steel+220 kg back charge+other alloys) consists of the 4-6 grade A-type graphite +small amount E-type graphite +100% pearlite,and its matrix hardness 210-229HB.The above-mentioned phenomenon has been given preliminary analysis.

  8. Effect of microalloying on pearlite transformation of high carbon wire steels

    Science.gov (United States)

    Miller, Stephanie L.

    Microalloying has been shown to improve strength in eutectoid steels for wire applications, and previous work on vanadium-microalloyed eutectoid steels showed delayed pearlite transformation with additions of niobium and accelerated pearlite transformation with additional nitrogen. This study investigates the origin of the CCT shifts with microalloying additions and whether trends in hardness and microstructural feature sizes observed in continuous cooling tests persist through industrial hot rolling simulations. An industrially hot rolled 1080 wire rod with vanadium additions and three laboratory-prepared alloys were studied. The base alloy, denoted the V steel, had a composition of 0.80C-0.50Mn-0.24Si-0.20Cr-0.079V-0.0059N (wt pct). The V+N steel contained 0.0088 wt pct N, and the V+Nb steel contained an additional 0.010 wt pct Nb. All alloys were subjected to a GleebleRTM 3500 torsion hot rolling simulation based on industrial wire rod hot rolling parameters. Microstructural constituents, Vickers hardness, pearlite colony size, and pearlite interlamellar spacing (ILS) were characterized for each alloy. All alloys exhibited pearlitic microstructures with some proeutectoid ferrite at prior austenite grain boundaries, with no evidence of shear transformation products. The V steel has the lowest overall hardness, while both nitrogen and niobium additions increase hardness by approximately 15 HV, correlating to a 43 MPa increase in yield strength. Niobium additions refined ILS, with an average ILS of 92 +/- 3 nm for the V+Nb steel compared to 113 +/- 5 nm for the V steel and 113 +/- 3 nm for the V+N alloy. Vanadium additions produced precipitation strengthening for all alloys and heat treatments, and additional precipitation strengthening with nitrogen and niobium additions was not apparent based on a Taleff regression analysis. Atom probe tomography of an industrially processed wire rod with vanadium additions revealed vanadium enrichment of cementite, and vanadium