ArcelorMittal S.A.
STEEL SHEET FOR MANUFACTURING PRESS HARDENED PARTS, PRESS HARDENED PART HAVING A COMBINATION OF HIGH STRENGTH AND CRASH DUCTILITY, AND MANUFACTURING METHODS THEREOF

Abstract:

A steel sheet for the manufacture of a press hardened part is provided, having a composition of: 0.15%.ltoreq.C%.ltoreq.0.22%, 3.5%.ltoreq.Mn<4.2%, 0.001%.ltoreq.Si%.ltoreq.1.5%, 0.020%.ltoreq.Al.ltoreq.0.9%, 0.001%.ltoreq.Cr.ltoreq.1%, 0.001%.ltoreq.Mo.ltoreq.0.3%, 0.001%.ltoreq.Ti.ltoreq.0.040%, 0.0003%.ltoreq.B.ltoreq.0.004%, 0.001%.ltoreq.Nb.ltoreq.0.060%, 0.001%.ltoreq.N.ltoreq.0.009%, 0.0005%.ltoreq.S.ltoreq.0.003%, 0.001%.ltoreq.P.ltoreq.0.020%. A microstructure has less than 50% ferrite, 1% to 20% retained austenite, cementite, such that the surface density of cementite particles larger than 60 nm is lower than 10 7/mm.sup.2, and a complement of bainite and/or martensite, the retained austenite having an average Mn content of at least 1.1*Mn %. Press-hardened steel part obtained by hot forming the steel sheet, and manufacturing methods thereof.