ArcelorMittal S.A.
Double annealed steel sheet having high mechanical strength and ductility characteristics, method of manufacture and use of such sheets

Abstract:

A double-annealed steel sheet is provided. The composition of which includes, expressed in percent by weight, 0.20%.ltoreq.C.ltoreq.0.40%, 0.8%.ltoreq.Mn.ltoreq.1.4%, 1.60%.ltoreq.Si.ltoreq.3.00%, 0.015.ltoreq.Nb.ltoreq.0.150%, Al.ltoreq.0.1%, Cr.ltoreq.1.0%, S.ltoreq.0.006%, P.ltoreq.0.030%, Ti.ltoreq.0.05%, V.ltoreq.0.05%, B.ltoreq.0.003%, N.ltoreq.0.01%. A remainder of the composition includes iron and unavoidable impurities resulting from processing. The microstructure of the steel sheet includes, in area percentages, 10 to 30% residual austenite, 30 to 60% annealed martensite, 5 to 30% bainite, 10 to 30% fresh martensite and less than 10% ferrite A fabrication method and vehicle parts are also provided.