Isothermal microstructure and strength and toughness of 20Si2Mn2CrNi steel below Ms

doi:10.13251/j.issn.0254-6051.2023.07.003

Abstract

Abstract: Phase transformation kinetics of a low carbon low alloy B/M dual-phase high-strength 20Si2Mn2CrNi steel during isothermal quenching around 386 ℃ was studied using thermal expansion method. The volume fraction of martensite below the Ms point during isothermal quenching was qualitatively calculated using the K-M model, and the influence of microstructural transformation under different isothermal quenching processes on the mechanical properties was investigated. The results show that the experiment steel transforms to upper bainite when it is isothermally quenched above 386 ℃, while forming not only martensite but also low-temperature bainite with the same kinematics as bainite transformation from austenite above 386 ℃ when it is isothermally quenched below 386 ℃. When the experimental steel is isothermally quenched at 300 ℃, the volume fraction of martensite is 91.74%, the hardness is 41.7 HRC, and the impact absorbed energy is 91.7 J, showing good comprehensive mechanical properties of strength and plasticity due to the well-coordinated deformation between bainite and martensite microstructure.

Key words: 20Si2Mn2CrNi steel, bainite, martensite, austempering, mechanical properties

CLC Number:

TG142.1

Wu Zhongchao, Zhou Yongjun, Duan Baoyu, Hou Yuan, Hu Yunfei, Gao Zhanyong. Isothermal microstructure and strength and toughness of 20Si2Mn2CrNi steel below Ms[J]. Heat Treatment of Metals, 2023, 48(7): 15-21.

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