Abstract: Gleeble-3500 thermal simulation testing machine was used to conduct hot compression tests on a 1900 MPa heat-resistant bearing steel to study its hot deformation behavior and microstructure evolution at strain of 0.8 in the deformation temperature range of 900-1150 ℃ and strain rate range of 0.001-10 s^-1. The effect of deformation temperature and strain rate on the flow behavior of the tested steel was analyzed, the constitutive equations with strain ranges of 0.1-0.8 were constructed based on the Arrhenius model, and the hot processing maps with strain values of 0.2, 0.4, 0.6 and 0.8 were drawn based on the dynamic material model (DMM). The microstructure evolution of the tested steel was analyzed in different hot working zones to verify the optimal hot working zone obtained. The results show that under deformation conditions of 0.001-10 s^-1 and 1050-1150 ℃, the true stress-true strain curves exhibit a clear plateau after work hardening, which reflects the characteristics of dynamic recovery (DRV), while under deformation conditions of 0.001-10 s^-1 and 900-1100 ℃, the curves exhibit a clear peak, which reflects the characteristics of dynamic recrystallization (DRX). By establishing and verifying the constitutive equations, it is found that the correlation coefficient between the tested and calculated values of flow stress is R=0.973, which indicates that the established flow stress constitutive model can accurately predict the flow stress of the alloy. The hot processing maps show that the optimal process parameters within the test range are deformation temperature of 1070-1150 ℃, and strain rate of 0.01-0.1 s^-1.

Key words: 1900 MPa grade heat-resistant bearing steel, thermal deformation behavior, dynamic recrystallization, constitutive equation, hot processing map