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The hot deformation behaviors of Cr5 steel were investigated. The hot compression tests were conducted in the temperature range of 900−1150 °C under strain rates of 0.01, 0.1 and 1 s−1. The constitutive equation and material constants (Q, n, α lnA) are obtained according to the hyperbolic sine function and Zener-Hollomon parameter. Besides, dynamic recrystallization (DRX) grain size model and critical strain model are acquired. The processing maps with the strain of 0.1, 0.3 and 0.5 are obtained on the basis of dynamic materials model. It has been observed that DRX occurs at high temperature and low strain rate. According to the processing map, the safety region exists in the temperature range of 920−1150 °C with strain rate of 0.01−0.20 s−1.

The dynamic recrystallization behavior of high strength steel during hot deformation was investigated. The hot compression test was conducted in the temperature range of 950-1150 °C under strain rates of 0.1, 1 and 5 s-1. It is observed that dynamic recrystallization (DRX) is the main flow softening mechanism and the flow stress increases with decreasing temperature and increasing strain rate. The relationship between material constants (Q, n, α and lnA) and strain is identified by the sixth order polynomial fit. The constitutive model is developed to predict the flow stress of the material incorporating the strain softening effect and verified. Moreover, the critical characteristics of DRX are extracted from the stress-strain curves under different deformation conditions by linear regression. The dynamic recrystallization volume fraction decreases with increasing strain rate at a constant temperature or decreasing deformation temperature under a constant strain rate. The kinetics of DRX increases with increasing deformation temperature or strain rate.