Abstract: The present invention provides a process of producing a family of hot rolled dual phase steel sheets having excellent formability and stretch flangeability, with yield strengths of from about 500 MPa to about 900 MPa from a single steel chemistry consisting of, by weight percent, 0.02-0.15% of C, 0.3-2.5% of Mn, 0.1-2.0% of Cr, 0.01-0.2% Al, 0.001-0.01% Ca, not more than 0.1% P, not more than 0.03% S, not more than 0.2% Ti, not more than 0.2% V, not more than 0.2% Nb, not more than 0.5% Mo, not more than 0.5% Cu, not more than 0.5% Ni, the balance being Fe and unavoidable impurities. A slab or ingot of this composition is reheated to a temperature of between 1050° C. and 1350° C. and held at this temperature for at least 10 minutes, then hot rolled, completing the hot rolling at between 800° C. and 1000° C. The sheet is cooled, immediately after completion of hot rolling, at a rate of not lower than 10 C/sec.

Abstract: A bake hardenable cold-rolled steel sheet and a method for producing the steel sheet are provided, wherein the steel sheet includes carbon in a range of about 0.003-0.1 wt. %, with the amount of carbon in solution being about 3-30 ppm, and the steel is substantially free of Ti, Nb, and V, which are otherwise commonly employed in producing low-carbon bake hardenable cold-rolled steel. The method includes a two stage batch or box anneal, a first stage of which is an intercritical batch anneal at a temperature between the A.sub.1 and A.sub.3 temperatures, and a second, subcritical batch anneal at a temperature below the A.sub.1 temperature and above 900.degree. F., with a slow controlled cooling from the intercritical temperature to the subcritical temperature, and from the subcritical temperature to ambient temperature.