Steel Sheet And Plated Steel Sheet

Abstract: Provided are a plated steel sheet and high-strength steel sheet having high plating properties, LME resistance, and hydrogen embrittlement resistance. Provided are a steel sheet and a plated steel sheet using the same. The steel sheet includes 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, and has, on the surface layer thereof, an internal oxide layer containing a fine granular oxide and coarse granular oxide. The number density in the internal oxide layer of the fine granular oxide is 4.0 pieces/µm2 or more. The number density in the internal oxide layer of the coarse granular oxide is 4.0 pieces/25 µm2 to 30.0 pieces/25 µm2. At a depth of 1/2 the average depth of the internal oxide layer as calculated from the cross-sectional SEM image of the steel plate, the oxide-free steel composition includes a surface depleted layer that satisfies Si = 0.6% and Al = 0.5% in mass%.

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