CONSTITUTIVE RELATIONSHIPS OF Nb MICROALLOYED STEEL DURING HIGH TEMPERATURE DEFORMATION

The flow stress curves of Nb microalloyed steel Q345B during hot compression deformation were obtained on Gleeble-3500 thermo-simulation machine. Based on the experimental results, the constitutive model of Nb microalloyed steel during high temperature deformation was established to describe the stress-strain relationship during dynamic softening (dynamic recovery and dynamic recrystallization) and in the steady flow state, in which the influences of the thermal deformation parameters (strain rate and deformation temperature) and dynamic softening mechanism (dynamic recovery and dynamic recrystallization) on the flow stress were considered. A method was provided to solve constitutive equation and establish the mathematic expressions of the correlation coefficients. It is shown that the predicted results by the model are in good agreement with the experimental ones.