Prediction of constitutive behaviour of 20CrMnTiH steel under hot deformation conditions

Isothermal compression tests are carried out on 20CrMnTiH steel using a Gleeble-1500 thermal simulator in the temperature range of 1223-1423 K and in the strain rate range of 0.01-10 s(-1). The flow behaviours of 20CrMnTiH steel are described, which are based on the analysis of true stress-true strain curves. The effects of hot deformation on the microstructure are investigated. The results show that there is a typical dynamic recrystallisation behaviour during deformation. A constitutive model coupling flow stress with strain, strain rate and temperature to 20CrMnTiH steel is proposed using a hyperbolic sinusoidal type equation. In the constitutive equation, the material constants alpha, n, ln A and Q are found to be functions of strain. The validity of the constitutive equation is assessed by the correlation coefficient (r), the average absolute relative error and the mean squared error.