| 主权项 |
1. A process for producing a cold-rolled dual-phase steel, the process comprising:
providing a steel slab with a chemical composition within the range, in weight percent, of 0.085-0.11 C, 1.4-2.0 Mn, 0.09-0.21 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; soaking the steel slab at temperatures between 1160-1280° C.; hot rolling the steel slab into a transfer bar using a roughing treatment; hot rolling the transfer bar into the hot-rolled strip using a finishing treatment, the finishing treatment having an entry temperature between 1050-1120° C. and an exit temperature between 860-910° C.; and 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 760-800° C.; and rapidly cooling the intercritically annealed cold-rolled sheet to a temperature less than 450° C. using “Ultra Rapid Cooling” using an air plus hydrogen gas mixture and adjustable plenum positions to move cooling fans closer to the intercritically annealed cold-rolled sheet during the Ultra Rapid Cooling; the ultra rapidly cooled sheet having a ferrite-martensite microstructure with less than 6 vol% bainite, a 0.2% yield strength of at least 330 MPa, a tensile strength of at least 590 MPa, a total elongation to failure of at least 18% and a uniform elongation of at least 10%. |
