Steel Sheet And Plated Steel Sheet

Abstract: Provided are: a high-strength steel sheet having high plating properties, LME resistance, and hydrogen embrittlement resistance; and a plated steel sheet. Provided are: a steel sheet that contains 0.05-0.40% of C, 0.2-3.0% of Si, 0.1-5.0% of Mn, and 0.4-1.50% of sol. Al, that has, at a surface layer of the steel sheet, an inner oxide layer containing a fine granular oxide, a coarse granular oxide, and a grain boundary oxide, and in which the number density of the fine granular oxide in the inner oxide layer is at least 4.0 particles/µm2, the number density of the coarse granular oxide in the inner oxide layer is at least 4.0 particles/25 µm2, the ratio A of the length of the grain boundary oxide when being projected on the surface of the steel sheet with respect to the length of the surface of the steel sheet when a cross-section of the surface layer of the steel sheet is observed is 50-100%, and a surface layer depletion layer is included that has a steel composition satisfying Si = 0.6% and Al = 0.05%, in mass% but excluding oxides, at a depth of 1/2 of the average depth of the inner oxide layer as calculated from a cross-sectional SEM image of the steel sheet; and a plated steel sheet using the steel sheet.

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