Physically-Based Constitutive Modelling of As-Cast CL70 Steel for Hot Deformation

Abstract

In order to conduct numerical simulation of plasticity forming and confirm the processing parameters of heat deformation for as-cast CL70 steel, the hot deformation behaviors of as-cast CL70 steel were studied by isothermal compression tests which used a Gleeble-1500D thermal mechanical simulation tester for the deformation temperatures ranging from 1173 to 1523 K and the strain rates ranging from 0.001 to 1 s−1. Flow stress curves of the steel were obtained under high temperature. The flow stress constitutive models of the work hardening-dynamical recovery period and dynamical recrystallization period were established for as-cast CL70 steel. In work hardening-dynamic recovery period, the flow stress was predicted by employing the evolution rule of dislocation density in the constitutive model. In dynamic recrystallization period, the flow stress after the critical strain was predicted by employing the dynamic recrystallization kinetics in the constitutive model. To improve the prediction accuracy of the model, the dynamic recovery coefficient is modified in the traditional physically-based constitutive model. The results indicate that the proposed physically-based constitutive model has high accuracy in predicting the flow stress under hot deformation for as-cast CL70 steel.