Constitutive equations of a high-strength carburizing steel during high temperature thermal deformation

Hot compression test of a high-strength carburizing steel 9310 was carried out on a Gleeble-3800 thermo-mechanical simulator at deformation temperatures of 1173 to 1473 K and strain rates of 0.01 to 10 s-1. Based on the tested true stress-strain curves, two models of dislocation model and Sellars model were employed to develop the hot deformation constitutive equations of the steel. According to the occurrence of dynamic recrystallization during hot deformation, the constitutive equations of 9310 steel at different deformation stages were established. The results show that the error of the dislocation model based on the dislocation density and dynamic softening mechanism is less than 15% at the dynamic softening and steady-state phases with the stain Ε >0.1, however, this equation has more parameters with a large amount of calculation. The accuracy of Sellars model is higher under the deformation condition of low temperatures (T0.5), furthermore the model is relatively simple and easy of application. Sellars model is recommended as the prediction equation of flow stress under the deformation condition of large strain during industrial production of the high-strength carburizing steel 9310, and the error can be less than 10%. Moreover, to improve the accuracy of the constitutive equation based on Sellars model, the values of related parameters in the stress decrement Δσ which is caused by dynamic recrystallization may be further amended.