Behavior of hot deformation and critical strain for dynamic recrystallization of a Q690 low carbon microalloyed steel

The hot deformation behavior of Q690 low carbon microalloyed steel was studied by compression testing on a Gleeble-3800 digital control heat/force simulation test machine at 850-1150 ℃ and true strain rate range from 0.01 s-1 to 30 s-1.The hot deformation activation energy of 356.05 kJ/mol is determined and constitutive equation for hot deformation of the steel is obtained by characterizing the flow stress using both the peak stress and steady-state stress.Based on the relationship between strain hardening rate and true stress,the critical strain is determined,and a equation characterizing the relationship between the critical strain and Zener-Hollomon factor is derived.