Effect of Quenching Heating Rate on Microstructure and Mechanical Properties of the Cold Rolled 980 MPa Dual Phase Steel

The effect of heating rate before quenching on microstructure and mechanical properties of the 980 MPa dual phase steel was investigated by means of scanning electron microscopy, transmission electron microscopy, tensile testing machine. The results show the ferrite grains refined and the martensite size got more uniformly with increasing the heating rate from 5 ℃·s-1 to 150 ℃·s-1. Tensile strength of the steel increased to 1 300 MPa, and then almost kept no changes. The yield strength and elongation increased firstly and decreased afterward. When heating rate was 100 ℃·s-1, the combination properties was best and the tensile strength was 1 328 MPa, the elongation was about 13% and the yield ratio was 0.32.