Dynamic Recrystallization Behavior and Microstructure Transformation of Cr8 Steel

Thermal compression deformation test of Cr8 roller steel was done by using Gleeble-3500 thermal/power simulation test machine under the condition of strain rate of 0.01~10 s-1 and deformation temperature of 950~1 200 ℃ to study its thermal deformation mechanical behavior and recrystallization law, and the change of microstructure and phase compositions after thermal deformation test was also analyzed. The results show that when strain rate was low of 0.01 s-1 and the deformation temperature was lower than 1 050 ℃, the thermal deformation microstructure of Cr8 steel was mainly dynamic recovery, and when the deformation temperature was higher than 1 100 ℃ it was dynamic recrystallization, and the dynamic recrystallization grain size gradually grew with the increase of deformation temperature. When the strain rate increased to 0.1 s-1, the thermal deformation microstructure was dynamic recovery when the temperature was below 1 050 ℃, it was dynamic recrystallization when the temperature was higher than 1 100 ℃. When the strain rate increased to 1 s-1 and the deformation temperature was higher than 1 050 ℃, thermal deformation microstructure underwent significant recrystallization, and most of the austenite grains had grown to equiaxial recrystallized grains. The phases of Cr8 steel after thermal deformation test were α-Fe and γ-Fe, and the microstructure was martensite and retained austenite.