Abstract: Thermal-mechanical simulation tests of 316LN steel were carried out on Gleeble-1500D thermal-mechanical simulator with temperature in the range of 950 ~ 1200 ℃ and strain rates of 0.005, 0.05, 0.5 and 1 s^-1. The fractures were observed using a Scanning Electron Microscope (SEM). The plasticity and fracture mechanism of 316LN steel at elevated temperature were studied. The results show that the fracture of 316LN steel at elevated temperature is ductile fracture. The size and depth of dimples increase with the temperature and strain rate. The plasticity also increases with temperature and strain rate. Meanwhile, the relationship models between fracture strain and deformation conditions (temperature and strain rate) and between plastic indexes (elongation and area reduction) and deformation conditions were established using regression method, respectively. Employing these models, the fracture strain, elongation and area reduction of 316LN steel under certain conditions can be calculated. This study provides reference to the design of forging technology of 316LN steel.

Key words: metallic material, plasticity at high temperature, thermal-mechanical simulation, 316LN steel , fracture mechanism