Effect of Ausforming Temperature on Bainite Transformation of High Carbon Low Alloy Steel

2015 ◽  
Vol 817 ◽  
pp. 454-459 ◽  
Author(s):  
Jian Guo He ◽  
Ai Min Zhao ◽  
Huang Yao ◽  
Chao Zhi ◽  
Fu Qing Zhao
Keyword(s):  
Low Temperature ◽  
Alloy Steel ◽  
Retained Austenite ◽  
Volume Fraction ◽  
Transformation Rate ◽  
Low Alloy Steel ◽  
High Carbon ◽  
Bainite Transformation ◽  
Electron Backscattered Diffraction ◽  
In Situ Experiments

The effect of ausforming temperature on bainite transformation of high carbon low alloy steel was studied by in situ experiments using a Gleeble 3500 thermal and mechanical testing system. Morphology and crystallography of ausforming bainite were examined by scanning electron microscopy (SEM) and electron backscattered diffraction (EBSD). It has been found that deformation at all temperatures range from 230°C to 600°C can accelerate low temperature bainite transformation, and transformation rate increased with deformation temperature reduced. Quantitative X-ray analysis shows that the volume fraction of retained austenite was about 35.84% after deformation and isothermal transformation for 20 hours, it was approximately the same amount with austempering bainite transformation process (no strain) which austenite volume fraction was about 32.01%. Low temperature bainite formation can be accelerated with a smaller increase amount of retained austenite by deformation at a low temperature range of 230~600 oC.

scholarly journals Thermal Stability of Retained Austenite and Properties of A Multi-Phase Low Alloy Steel

Metals ◽  
2018 ◽  
Vol 8 (10) ◽  
pp. 807 ◽  
Author(s):  
Zhenjia Xie ◽  
Lin Xiong ◽  
Gang Han ◽  
Xuelin Wang ◽  
Chengjia Shang
Keyword(s):  
Thermal Stability ◽  
High Temperature ◽  
Alloy Steel ◽  
Retained Austenite ◽  
Mechanical Stability ◽  
Volume Fraction ◽  
Low Carbon ◽  
Low Alloy Steel ◽  
Multi Phase ◽  
Thermal Stability Of

In this work, we elucidate the effects of tempering on the microstructure and properties in a low carbon low alloy steel, with particular emphasis on the thermal stability of retained austenite during high-temperature tempering at 500–700 °C for 1 h. Volume fraction of ~14% of retained austenite was obtained in the studied steel by two-step intercritical heat treatment. Results from transmission electron microscopy (TEM) and X-ray diffraction (XRD) indicated that retained austenite had high thermal stability when tempering at 500 and 600 °C for 1 h. The volume fraction was ~11–12%, the length and width remained ~0.77 and 0.21 μm, and concentration of Mn and Ni in retained austenite remained ~6.2–6.6 and ~1.6 wt %, respectively. However, when tempering at 700 °C for 1 h, the volume fraction of retained austenite was decreased largely to ~8%. The underlying reason could be attributed to the growth of austenite during high-temperature holding, leading to a depletion of alloy contents and a decrease in stability. Moreover, for samples tempered at 700 °C for 1 h, retained austenite rapidly transformed into martensite at a strain of 2–10%, and a dramatic increase in work hardening was observed. This indicated that the mechanical stability of retained austenite decreased.

Role of retained austenite in low alloy steel at low temperature monitored by neutron diffraction

2020 ◽  
Vol 177 ◽  
pp. 6-10 ◽  
Author(s):  
Takayuki Yamashita ◽  
Satoshi Morooka ◽  
Stefanus Harjo ◽  
Takuro Kawasaki ◽  
Norimitsu Koga ◽  
...  
Keyword(s):  
Low Temperature ◽  
Neutron Diffraction ◽  
Alloy Steel ◽  
Retained Austenite ◽  
Low Alloy Steel

Application of Quenching and Partitioning to Improve Ductility of Ultrahigh Strength Low Alloy Steel

2010 ◽  
Vol 654-656 ◽  
pp. 29-32 ◽  
Author(s):  
Wen Quan Cao ◽  
Cun Yu Wang ◽  
Jie Shi ◽  
Han Dong
Keyword(s):  
Alloy Steel ◽  
Retained Austenite ◽  
Volume Fraction ◽  
Tensile Elongation ◽  
High Strength ◽  
Total Elongation ◽  
Low Alloy Steel ◽  
Quenching And Partitioning ◽  
Multiphase Microstructure ◽  
Ultrahigh Strength

In this study Quenching and Partitioning (Q&P) as proposed by Speer was applied to improve the ductility of C-Mn high strength Low Alloy steel (HSLAs). Microstructural observations revealed a multiphase microstructure including first martensite, fresh martensite and retained austenite in the Q&P processed steel. During tensile process, the austenite volume fraction gradually decreased with strain increasing, suggesting the phase transformation induced plasticity for the Q&P processed steel. Ultrahigh strength about 1300-1800MPa and tensile elongation about 20% were obtained after Q&P processing at specific conditions, which is significant higher than that of ~10% of conventional martensitic steel. The the product of tensile strength to total elongation increased from 25 to 35GPa% with increasing carbon content in studied steel. This improved mechanical properties were related to the ductility contribution from TRIP effects of the retained austenite and strength contribution from the hard martensitic matrix. At last it was turned out that the Q&P process is a promising way to produce ultrahigh strength steel with relative high ductility under tailored heat treatment conditions for different micro-alloyed carbon steel.

scholarly journals Behavior of quenching crack in RRC test. Study on weld cold cracking in HAZ of medium, high carbon low alloy steel. Report I.

1987 ◽  
Vol 5 (1) ◽  
pp. 21-26 ◽  
Author(s):  
Fukuhisa Matsuda ◽  
Hiroji Nakagawa ◽  
Hwa Soon Park ◽  
Toshihiro Murakawa ◽  
Michio Yamaguchi
Keyword(s):  
Alloy Steel ◽  
Cold Cracking ◽  
Low Alloy Steel ◽  
High Carbon ◽  
Test Study

scholarly journals Martensitic Transformation of Retained Austenite in Ferrite Matrix for Low Alloy Steel

2018 ◽  
Vol 59 (5) ◽  
pp. 712-716
Author(s):  
Takayuki Yamashita ◽  
Norimitsu Koga ◽  
Osamu Umezawa
Keyword(s):  
Martensitic Transformation ◽  
Alloy Steel ◽  
Retained Austenite ◽  
Ferrite Matrix ◽  
Low Alloy Steel

scholarly journals Mechanism of the Microstructural Evolution of 18Cr2Ni4WA Steel during Vacuum Low-Pressure Carburizing Heat Treatment and Its Effect on Case Hardness

Materials ◽  
2020 ◽  
Vol 13 (10) ◽  
pp. 2352
Author(s):  
Bin Wang ◽  
Yanping He ◽  
Ye Liu ◽  
Yong Tian ◽  
Jinglin You ◽  
...  
Keyword(s):  
Low Temperature ◽  
Carbon Content ◽  
Retained Austenite ◽  
Mechanical Stability ◽  
Lath Martensite ◽  
Low Pressure ◽  
Low Carbon ◽  
High Carbon ◽  
Carburized Layer ◽  
Martensite Matrix

In this study, vacuum low-pressure carburizing heat treatments were carried out on 18Cr2Ni4WA case-carburized alloy steel. The evolution and phase transformation mechanism of the microstructure of the carburized layer during low-temperature tempering and its effect on the surface hardness were studied. The results showed that the carburized layer of the 18Cr2Ni4WA steel was composed of a large quantity of martensite and retained austenite. The type of martensite matrix changed from acicular martensite to lath martensite from the surface to the core. The hardness of the carburized layer gradually decreased as the carbon content decreased. A thermodynamic model was used to show that the low-carbon retained austenite was easier to transform into martensite at lower temperatures, since the high-carbon retained austenite was more thermally stable than the low-carbon retained austenite. The mechanical stability—not the thermal stability—of the retained austenite in the carburized layer dominated after carburizing and quenching, and cryogenic treatment had a limited effect on promoting the martensite formation. During low-temperature tempering, the solid-solution carbon content of the martensite decreased, the compressive stress on the retained austenite was reduced and the mechanical stability of the retained austenite decreased. Therefore, during cooling after low-temperature tempering, the low-carbon retained austenite transformed into martensite, whereas the high-carbon retained austenite still remained in the microstructure. The changes in the martensite matrix hardness had a far greater effect than the transformation of the retained austenite to martensite on the case hardness of the carburized layer.

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