Process for making coated cold-rolled dual phase steel sheet

A process for producing a coated dual-phase steel, the process comprising:

• soaking a steel slab at temperatures between 1160-1280° C., the steel slab having a chemical composition within the range, in weight percent, of 0.085-0.11 C, 1.4-2.0 Mn, 0.19-0.21 Mo, 0.02-0.05 Al, 0.16-0.5 Si, 0.13-0.5 Cr, 0.016 max Ti, 0.06 max Ni, 0.003 max S, 0.015 max P, 0.006 max N, balance Fe and incidental melting impurities;
• hot rolling the steel slab into hot-rolled strip, the hot rolling including a finishing treatment with an entry temperature between 1050-1120° C. and an exit temperature between 860-910° C.;
• cooling the hot rolled strip at a cooling rate between 15-35° C./sec;
• coiling the hot rolled strip at temperatures between 600-680° C., the coiled hot rolled strip having a ferrite-pearlite microstructure;
• cold-rolling the coiled hot-rolled strip into cold-rolled sheet, the cold-rolled sheet having at least a 60% reduction in thickness compared to a thickness of the coiled hot-rolled strip;
• intercritical annealing the cold-rolled sheet at temperatures between 780-820° C.;
• rapidly cooling the intercritically annealed cold-rolled sheet in a first cooling step using a first cooling rate to a stop temperature between 505-515° C. without a hold treatment, the stop temperature between 505-515° C. being between 25-65° C. above a molten metal or alloy bath temperature which is between 450-480° C.;
• cooling the rapidly cooled sheet in a second cooling step using a second cooling rate from the stop temperature between 505-515° C. to a temperature close to the molten metal or alloy bath temperature which is between 450-480° C., wherein the second cooling rate is less than the first cooling rate;
• and
• passing the rapidly cooled sheet through a molten metal or alloy bath at temperatures between 450-480° C. and producing a coated steel sheet;
• the coated steel sheet having a dual-phase ferrite-martensite microstructure with less than 4 volume percent bainite, a yield strength of at least 310 MPa, a tensile strength of at least 580 MPa, a total elongation to failure of at least 18%, a uniform elongation of at least 10% and a Lankford coefficient r-value between 0.8-1.1.