ArcelorMittal S.A.
Steel for press hardening and press hardened part manufactured from such steel

Abstract:

A process for manufacturing a press hardened steel part is provided. The steel of the part has a chemical composition including, in weight: 0.062%.ltoreq.C.ltoreq.0.095%, 1.4%.ltoreq.Mn.ltoreq.1.9%, 0.2%.ltoreq.Si.ltoreq.0.5%, 0.020%.ltoreq.Al.ltoreq.0.070%, 0.02%.ltoreq.Cr.ltoreq.0.1%, wherein: 1.5%.ltoreq.(C+Mn+Si+Cr).ltoreq.2.7%, 0.040%.ltoreq.Nb.ltoreq.0.060%, 3.4.times.N.ltoreq.Ti.ltoreq.8.times.N wherein: 0.044%.ltoreq.(Nb+Ti).ltoreq.0.090%, 0.0005.ltoreq.B.ltoreq.0.004%, 0.001%.ltoreq.N.ltoreq.0.009%, 0.0005%.ltoreq.S.ltoreq.0.003%, 0.001%.ltoreq.P.ltoreq.0.020%, optionally: 0.0001%.ltoreq.Ca.ltoreq.0.003%, and the remainder being Fe and unavoidable impurities. The process includes hot forming the heated blank in the forming press so as to obtain a formed part and cooling the formed part at a cooling rate CR1 between 40 and 360.degree.C/s in a temperature range from 750 to 450.degree.C. and at a cooling rate CR2 between 15 to 150.degree.C/s in a temperature range from 450.degree.C to 250.degree.C. wherein CR2<CR1.