Steel Sheet And Manufacturing Method Therefor

Abstract: This steel sheet has a base steel sheet that has a prescribed chemical composition and a galvanization layer that is formed on the surface of the base steel sheet, wherein: where the sheet thickness of the base steel sheet is t, the metallographic structure of the base steel sheet at a t/4 location, which is a location at a depth of t/4 from the surface in a cross section in the sheet thickness direction, includes at least 85% of tempered martensite, at least 7% of retained austenite, and 0-8% of at least one substance selected from ferrite, pearlite, bainite, and fresh martensite by volume; the metallographic structure in a surface region, which is the range up to a location 50 µm from the surface in the cross section in the sheet thickness direction, includes at least 30% of bainite by volume, where the remainder is at least one substance selected from ferrite, pearlite, tempered martensite, fresh martensite, and retained austenite; and prior austenite grains in the surface region have a diameter in the sheet thickness direction of no more than 10.0 µm and a tensile strength of at least 1,470 MPa.

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