Physics-Based Constitutive Model of Bi-metallic Ring Blank by Centrifugal Casting Under Hot Deformation

The hot deformation behavior of bi-metallic ring blanks has an important influence on the hot ring rolling. In this paper, the influences of strain rate and temperature on flow characteristic of centrifugal casting 40Cr/Q345B bi-metallic ring blank was investigated by hot compression tests, which were carried out on the Gleeble-3500 thermo-mechanical simulator over the strain rate range of 0.005–1 s−1 and temperature range of 950–1200 °C. The true stress-strain curves of 40Cr/Q345B bimetal all show typical dynamic recrystallization (DRX) behavior, and dynamic recovery (DRV) and DRX are the main softening mechanisms. The peak stress of 40Cr/Q345B bimetal is always higher than 40Cr and approached to Q345B. The constitutive model was established using the Estrin and Mecking (EM) method in the work hardening and dynamic recovery (WH-DRV) phase, coupled with the Avrami equation for describing the softening behavior of DRX phase. Characteristic stress and DRV rate as functions of lnZ were fitted by third-order polynomials to improve the accuracy of the constitutive equation. The correlation coefficients (R) and average absolute relative error (AARE) between the experimental and the stress predicted by established constitutive equation were 0.9976 and 3.088%, respectively. The constitutive model has high precision and can be used to simulate the hot rolling of 40Cr/Q345B bi-metallic ring blank.