Abstract: Thermal simulation tensile testing for a kind of medium-Mn hot stamping steel containing vanadium was carried out by the Gleeble-3500 thermal simulation testing machine. The high temperature tensile fracture morphology and microstructure near the fracture were observed, and the influence rules and mechanisms of tensile temperature and soaking temperature on mechanical properties of the steel at high temperature were studied. The results show that when the steel is tensile tested after soaking at 960 ℃ and 1200 ℃, the ductility trough appears at 830 ℃ and 850 ℃, and the percentage reduction of area are 79.8% and 58.4%, respectively. After soaking at 960 ℃ and then tensile testing at 830 ℃, more and larger inclusions and precipitates are observed, however, due to the smaller prior austenite grains, the steel has good ductility, and the tensile fracture shows ductile dimples. After soaking at 1200 ℃ and then tensile testing at 850 ℃, the inclusions and precipitates are relatively fewer and smaller, the prior austenite grains are larger, and the ductility is relatively poorer.

Key words: hot stamping steel containing V, tensile temperature, hot ductility, prior austenite grain