Effect of water quenching process on microstructure and tensile properties of low alloy cold rolled dual-phase steel

An investigation was made to determine the effect of water quenching process on microstructure and tensile properties of cold rolled dual-phase (DP) steel (0.06C–0.20Si–1.30Mn). Correlations of microstructure, tensile properties, and water quenching parameters were established. Analysis of optical and transmission electron microscopy shows that the microstructures are mainly composed of ferrite and martensite phases. The fraction of martensite covers from 20% to 68.36% in this study, which plays a key role on tensile properties. A small amount of retained austenite or bainite can also be found for different water quenching processes. It is observed that water quenching process can improve the DP steel grade of 450 MPa up to 600 MPa and still keep good ductility. Further, the ultimate tensile strength can even be improved above to 1000 MPa under some water quenching processes.