Phase Transformation Rules of DP590 Steel during Continuous Cooling

The static CCT curve and the effect of heating temperature on continuous cooling transformation rule of DP590 steel were researched by thermal dilation experiment and microstructure observation. The results show that, the amount of austenite increased more and more with heating temperature increasing; the CCT curve of the steel could was divided into three regions, the F+P microstructure was obtained at cooling rate of 0.5-15 ℃·s-1, banite appeared at cooling rate over 15 ℃·s-1, and martensite emerged at cooling rate higher than 30 ℃·s-1. The pearlite region shifted to the right, incubation period of banite prolonged, martensite starting transformation temperature decreased, and the phase transformation region of martensite and banite seperated and martensite starting transformation temperature increased with the increase of the cooling rate. The ferrite and pearlite precipitation were depressed and martensite precipitation power increased with cooling rate increasing.The ferrite content increased and martensite panel become refine with heating temperature increasing.