PROCESS FOR MAKING COLD-ROLLED DUAL PHASE STEEL SHEET

摘要

A process for manufacturing a cold rolled high strength dual phase steel. The process includes soaking a steel slab within a temperature range of 1200-1300°C, hot rolling the soaked steel slab in a roughing treatment and producing a transfer bar, and hot rolling the transfer bar in a finishing treatment and producing hot rolled strip. The hot rolled strip is cold rolled with at least a 55% reduction in thickness. The cold rolled sheet is intercritically annealed at a temperature between 790-840 °C and rapidly cooled to a temperature between 450-500 °C. The rapidly cooled sheet has a ferrite plus martensite microstructure, a 0.2% yield strength of at least 550 MPa, a tensile strength of at least 980 MPa and a total elongation to failure of at least 10%