High Strength Steel Sheet

Abstract: Provided is a high-strength steel sheet including a plate thickness center section and a surface layer soft section formed on one or both sides of the plate thickness center section, wherein: the plate thickness center section has a prescribed chemical composition and a microstructure including 85% or more tempered martensite; the surface layer soft section has a thickness of more than 10 µm but not more than 5% of the plate thickness, has a microstructure including 80% or more ferrite, and includes an internally oxidized layer having a thickness of 3 µm or more from the surface; the average Vickers hardness (Hc) of the plate thickness center section and the average Vickers hardness (Hs) of the surface layer soft section satisfy Hs/Hc=0.50; and the void area percentage is 3.0% or less in the region from the surface up to the 10 µm depth position.

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