Abstract: Hot forming process of T1500HS and CR1300/2000HS steels was simulated by using Gleeble-3500 thermal testing machine, and the influence of different heating temperature(890-950 ℃), holding time (240-1000 s), chemical compositions, and surface condition (oiled or oil-free) on the decarburization of the cold-rolled hot forming steels was studied. The results show that under normal heating temperature (910-950 ℃), holding time (240-480 s) and with good protective atmosphere in the furnace, there is little decarburization after hot forming for the cold-rolled steel. With the increase of heating temperature, holding time, the C content and the surface oiling, the depth of the decarburized layer is increased after forming for the cold rolled hot forming steel. When the depth of the decarburized layer is not more than 20 μm, the decarburization layer has little effect on the tensile properties of tested steel after hot forming. While the decarburized layer has great impact on the hardness of the hot forming steel, as the depth of the decarburized layer increases, the hardness decreases.

Key words: hot forming steel, T1500HS steel, CR1300/2000HS steel, decarburization, hardness