Micro-mechanism of static softening of high nitrogen austenitic stainless steel

Abstract

The stress softening behavior and microstructure evolution of Mn18Cr18N steel remelted by electroslag remelting during the holding process were studied through two-pass hot compression tests with different parameters. The static recrystallization kinetics model of the steel was established by calculating the softening rate in two-pass hot compression, and the activation energy of static recrystallization was calculated to be 279.81 KJ/mol. Investigation of microstructural showed that the occurrence of complete static recrystallization needed sufficiently pre-strain and temperature. The static recrystallization was basically completed when compressed to a pre-strain 0.26 after holding 120 s with 1 s−1 at 1273 K. While the pre-strain was lowered to 0.18 requires a longer holding time of 320 s or a higher temperature of 1373 K to obtain complete static recrystallization. The EBSD analysis of the static recrystallization grain structure shows that the static recrystallization nucleation mechanism of this steel is mainly dominated by dislocation driven grain boundary migration, and few annealing twins are generated during the grain boundary migration process, promoting the fine homogenisation of the grains.