ArcelorMittal S.A.
Process for manufacturing steel sheet

Abstract:

The invention relates to a hot-rolled steel sheet having a tensile strength of greater than 1200 MPa, an R.sub.e/R.sub.m ratio of less than 0.75 and an elongation at break of greater than 10%, the composition of which contains, the contents being expressed by weight: 0.10%.ltoreq.C.ltoreq.0.25%; 1%.ltoreq.Mn.ltoreq.3%; Al.gtoreq.0.015%; Si.ltoreq.1.985%; Mo.ltoreq.0.30%; Cr.ltoreq.1.5%; S.ltoreq.0.015%; P.ltoreq.0.1%; Co.ltoreq.1.5%; B.ltoreq.0.005%; it being understood that 1%.ltoreq.Si+Al.ltoreq.2%; Cr+(3.times.Mo).gtoreq.0.3%, the balance of the composition consisting of iron and inevitable impurities resulting from the smelting, the microstructure of the steel consisting of at least 75% bainite, residual austenite in an amount equal to or greater than 5% and martensite in an amount equal to or greater than 2%.