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AssigneeNippon Steel Nisshin Co., Ltd.
InventorsHiroyasu Matsubayashi, Sadayuki Nakamura, Junichi Katsuki, Ryoji Hirota
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Provided is a martensitic stainless-steel sheet having a reduced anisotropy in workability and fatigue resistance which are attributable to oxide based inclusions. A martensitic stainless-steel sheet which has a steel composition that contains, in terms of mass %, 0.030 to 0.300% C, 0.20 to 2.50% Si, 0.15 to 4.00% Mn, 0.01 to 1.00% Ni, 11.00 to 15.00% Cr, 0.001 to 0.100% N, 0.0001 to 0.0350% Al, 0 to 0.50% V, 0 to 0.50% Nb, 0 to 0.50% Ti, 0 to 0.020% B, and a balance of Fe and unavoidable impurities, and that has a value of γmax, determined by the following equation (1), of 80.0 or greater, and in which oxide based inclusions are observed in the metallographic structure, the oxide based inclusions having a converted composition comprising up to 30 mass % or less Al2O3, 20 to 60 mass % SiO2, and 15 to 70 mass % MnO.
A martensitic stainless cold-rolled and annealed steel sheet having a sheet thickness of 0.05 mm to 0.5 mm and having a steel composition that comprises, in terms of mass %, 0.030 to 0.300% C, 0.20 to 2.50% Si, 0.15 to 4.00% Mn, 0.01 to 1.00% Ni, 11.00 to 15.00% Cr, 0.001 to 0.100% N, 0.0001 to 0.0350% Al, 0 to 0.50% V, 0 to 0.50% Nb, 0 to 0.50% Ti, 0 to 0.020% B, and a balance of Fe and inevitable impurities, and that has a value of γmax, which is determined by a following equation (1), of 80.0 or greater, and in which an average composition of oxide based inclusions observed in a metailographic structure has 30 mass % or less Al2O3, 20 to 60 mass % SiO2 and 15 to 70 mass % MnO in terms of mass ratio conversion of Al2O3, SiO2 and MnO, and maximum diameters of the oxide based inclusions in the sheet thickness direction are 1.0% or less of the sheet thickness:
A martensitic stainless cold-rolled and annealed steel sheet having a steel composition that comprises, in terms of mass %, 0.030 to 0.300% C, 0.20 to 2.50% Si, 0.15 to 4.00% Mn, 0.01 to 1.00% Ni, 11.00 to 15.00% Cr, 0.001 to 0.100% N, 0.0001 to 0.0350% Al, 0 to 0.50% V, 0 to 0.50% Nb, 0 to 0.50% Ti, 0 to 0.020% B, and a balance of Fe and inevitable impurities, and that has a value of γmax, which is determined by a following equation (1), of 80.0 or greater, and in which an average composition of oxide based inclusions observed in a metallographic structure has 30 mass % or less Al2O3, 20 to 60 mass % SiO2 and 15 to 70 mass % MnO in terms of mass ratio conversion of Al2O3, SiO2 and MnO and having a surface in which a number density of pits having an opening diameter of 1.0 μm or greater, which are formed as precipitated particles are detached in an acid pickling treatment after finish annealing, is 10 pits/0.01 mm2 or greater and a surface roughness Ra in a rolling-perpendicular direction is 0.500 μm or less:
Dependencies are inferred from the claim text.