Importance

Loading Importance Indicators...

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.degree. C. and 1350.degree. C. and held at this temperature for at least 10 minutes, then hot rolled, completing the hot rolling at between 800.degree. C. and 1000.degree. C. The sheet is cooled, immediately after completion of hot rolling, at a rate of not lower than 10 C/sec., without requiring specific cooling patterns, and coiled at a temperature of not less than 450 C. The cooling temperature is controlled to produce the desired yield strength within the range of from about 500 MPa to about 900 MPa.

Loading the Abstract Image...

First Claim