Abstract：The chemical composition and phase transformation of 600MPa grade hot-rolled dual phase steels, which was made through two-stage cooling process in laboratory, was discussed. The microstructure and mechanical property of the dual-phase steel was investigated by using optical microscopy, scanning electron microscopy and the tensile tests. The results show that the temperatures of Acl and Ac3 are 785℃ and 940℃ respectively. After finally rolled at 830℃, the sheets are cooled to 750℃ within 10 seconds in the air, then quickly coiled to the temperature (≤200℃) in water, following the sheets are coiled. Typical ferrite and martensite（86.5%）structure of hot-rolled dual phase steels can be obtained, and its tensile strength and shear strength are respectively 651.6MPa and 3271MPa. In the meantime, the work hardening rate of the steel is up to 0.235 and the elongation rate reaches 25.7%.
2011, Vol. 46 
