The Effect of Heating Process on Strength and the Original Austenite Grain Size of Hot Forming Parts

Abstract

Strength, microstructure and austenitic grain size of a hot formed steel WHT1300HF after simulative hot stamping were studied by using universal testing machine for materials and optical microscopy. The results show that the yield strength of the hot stamping parts presented the tendency of earlier decrease and later increase with the extension of holding time, tensile strength was first reduced and then hold above 1400 MPa. In addition, the microstructure of the hot stamping parts was lath martensite, and martensite lath length and packet width increases with the heating temperature increased from 850 °C to 1050 °C. Especially, the effect of heat temperature on the original austenite grain size was more obvious, such as the austenite grains grew up quickly with the increase of heating temperature, and the original austenite grain diameter was 37.8 μm when the temperature reached 1050 °C.