Steel sheet and method for manufacturing steel sheet
AssigneeKabushiki Kaisha Kobe Seiko Sho (Kobe Steel, Ltd.)
InventorsShuya MAEKAWA, Ryosuke OTOMO, Hiroshi IRIE, Shoichi HIRAI, Kentaro KIGUCHI
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Abstract
A steel sheet in which a position in the sheet thickness direction where the carbon concentration (measured in mass %) is 50% of a bulk carbon concentration is in a region of 0.20% of the sheet thickness from a steel sheet surface, and a position in the sheet thickness direction where the carbon concentration (measured in mass %) is 90% of the bulk carbon concentration is in a region of no more than 8.0% of the sheet thickness from the surface of the steel sheet.
Claims8
A steel sheet, wherein, in a sheet thickness direction,
- a position where a carbon concentration measured in mass % is 50% of a bulk carbon concentration is in a region of 0.20% or more of a sheet thickness from a steel sheet surface, and
- a position where a carbon concentration measured in mass % is 90% of the bulk carbon concentration is in a region of 8.0% or less of the sheet thickness from the steel sheet surface.
A method for manufacturing a steel sheet, the method comprising
- annealing involving performing an oxidation treatment under conditions of an oxygen concentration of 0.1 to 2% and an attainment temperature of 650 to 750° C. and then performing a reduction treatment,
- wherein the reduction treatment includes a first reduction treatment having a dew point of −35 to −15° C., and a second reduction treatment having a dew point being −25 to 0° C. and being higher than the dew point of the first reduction treatment.
Dependencies are inferred from the claim text.