STEEL SHEET AND HIGH STRENGTH PRESS HARDENED STEEL PART AND METHOD OF MANUFACTURING THE SAME

A steel sheet made of a steel having a composition comprising, C : 0.3 - 0.4 %, Mn : 0.5 - 1.0 %, Si : 0.4 - 0.8 %, Cr : 0.1 - 1.0 %, Mo : 0.1 - 0.5 %, Nb : 0.01 - 0.1 %, Al : 0.01 - 0.1 %, Ti: 0.008 - 0.03 %, B: 0.0005 - 0.003 %, P ≤ 0.020 %, Ca ≤ 0.001 %, S ≤ 0.004 %, N ≤ 0.005 % and comprising optionally Ni < 0.5%, having a microstructure comprising, in surface fraction, from 60% to 95% of ferrite, the rest being martensite-austenite islands, pearlite or bainite, and comprising a bulk and a skin layer occupying the outermost 10% of the thickness on either sides of the bulk, said skin layer having a skin layer inclusion population wherein the cumulated surface fraction of oxides, MnS and TiNbCN is equal to or below 75*10-6.