Static Softening Behavior of a High-Strength and High-Toughness Low-Alloy Martensite Steel

With the new developed high-strength and high-toughness 20SiMn3NiA low-alloy martensite steel as a research object, the double-pass compression tests were conducted on the steel by a thermal simulator at 900-1 000 ℃ and strain rate of 1.0 s^-1 for pass intervals between 1 s and 100 s. And the static softening behavior of the steel was studied. The results show that at the deformation temperature of 900 ℃, with the pass interval prolonging, the true stress-true strain curves during second pass deformation of the tested steel exhibited a change from dynamic recrystallization character (namely greater trend of softening than hardening) to static recrystallization character (namely greater trend of hardening than softening). The static recrystallization fraction increased from 6.48% with pass interval of 1 s to a nearly stable value of 85%. At the deformation temperature of 1 000 ℃, the true stress-true strain curves during second pass deformation had a static recrystallization character. The static recrystallization fraction increased from 84.48% with pass interval of 1 s to 96% with pass interval of 100 s. The static active energy of the tested steel was 448 kJ ·mol^-1.