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, by weight percent:

• 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≤0.0010%
• S≤0.004%
• N≤0.005%
• and comprising optionally:
• Ni<0.5%
• a remainder of the composition being iron and unavoidable impurities resulting from processing,
• the steel sheet having a microstructure comprising, in surface fraction, from 60% to 95% of ferrite, the rest being martensite-austenite islands, pearlite or bainite,
• the steel sheet comprising from the bulk to the surface of the coated steel sheet:
• the bulk, the bulk being topped by a skin layer occupying the outermost 10% of the thickness on either side of the bulk, the skin layer having a skin layer inclusion population wherein the cumulated surface fraction of oxides, MnS and TiNbCN is equal to or less than 75*10−6.