ArcelorMittal S.A.
HOT-ROLLED AND COATED STEEL SHEET FOR HOT-STAMPING, HOT-STAMPED COATED STEEL PART AND METHODS FOR MANUFACTURING THE SAME

Abstract:

A method for manufacturing a hot-rolled and coated steel sheet having a thickness between 1.8 mm and 5 mm. The method contains the steps of: providing a semi-product having a composition containing: 0.04%.ltoreq.C.ltoreq.0.38%, 0.40%.ltoreq.Mn.ltoreq.3%, 0.005%.ltoreq.Si.ltoreq.0.70%, 0.005%.ltoreq.Al.ltoreq.0.1%, 0.001%.ltoreq.Cr.ltoreq.2%, 0.001%.ltoreq.Ni.ltoreq.2%, 0.001%.ltoreq.Ti.ltoreq.0.2%, Nb.ltoreq.0.1%, B.ltoreq.0.010%, 0.0005%.ltoreq.N.ltoreq.0.010%, 0.0001%.ltoreq.S.ltoreq.0.05%, 0.0001%.ltoreq.P.ltoreq.0.1%, Mo.ltoreq.0.65%, W.ltoreq.0.30%, Ca.ltoreq.0.006%, hot-rolling with a final rolling temperature FRT, to obtain a hot-rolled steel product having a thickness between 1.8 mm and 5 mm, then cooling down to a coiling temperature T.sub.coil satisfying: 450.degree. C..ltoreq.T.sub.coil.ltoreq.T.sub.coilmax with T.sub.coilmax=650-140.times.f.gamma., T.sub.coilmax being expressed in degrees Celsius and f.gamma. designating the austenite fraction just before the coiling, and coiling to obtain a hot-rolled steel substrate, pickling and coating the hot-rolled steel substrate with Al or an Al alloy by continuous hot-dipping in a bath, to obtain a hot-rolled and coated steel sheet containing a hot-rolled steel sheet and an Al or an Al alloy coating, having a thickness between 10 and 33 .mu.m, on each side of the hot-rolled steel sheet.