ArcelorMittal S.A.
METHOD FOR THE MANUFACTURE OF A GALVANNEALED STEEL SHEET

Abstract:

Method for the manufacture of a galvannealed steel sheet includes the following steps: A) the provision of a pre-coated steel sheet coated with a first coating comprising iron and nickel, such steel sheet having the following chemical composition in weight percent 0.10<C<0.40%, 1.5<Mn<3.0%, 0.7<Si<2.0%, 0.05<Al<1.0%, 0.75<(Si+Al)<3.0% and on a purely optional basis, one or more elements such as Nb.ltoreq.0.5%, B.ltoreq.0.005%, Cr.ltoreq.1.0%, Mo.ltoreq.0.50%, Ni.ltoreq.1.0%, Ti.ltoreq.0.5%, the remainder of the composition making up of iron and inevitable impurities resulting from the elaboration, B) the thermal treatment of such pre-coated steel sheet at a temperature between 600 to 1000.degree. C., C) the hot-dip coating of the steel sheet obtained in step B) with a second coating based on zinc and D) an alloying treatment to form a galvannealed steel sheet.