A coated steel member includes: a steel sheet substrate containing, as a chemical composition, by mass %, C: 0.25% to 0.65%, Si: 0.10% to 1.00%, Mn: 0.30% 1.00%, P: 0.050% or less, S: 0.0100% or less, N: 0.010% or less, Ti: 0.010% to 0.100%, B: 0.0005% to 0.0100%, Nb: 0.02% to 0.10%, Mo: 0.10% to 1.00%, Cu: 0.15% to 1.00%, and Ni: 0.05% to 0.25%; and a coating formed on a surface of the steel sheet substrate and containing Al and Fe. The maximum Cu content in a range from the surface to a depth of 5.0 μm is 150% or more of the Cu content of the steel sheet substrate.

A coated steel member includes: a steel sheet substrate containing, as a chemical composition, by mass %, C: 0.25% to 0.65%, Si: 0.10% to 1.00%, Mn: 0.30% 1.00%, P: 0.050% or less, S: 0.0100% or less, N: 0.010% or less, Ti: 0.010% to 0.100%, B: 0.0005% to 0.0100%, Nb: 0.02% to 0.10%, Mo: 0.10% to 1.00%, Cu: 0.15% to 1.00%, and Ni: 0.05% to 0.25%; and a coating formed on a surface of the steel sheet substrate and containing Al and Fe. The maximum Cu content in a range from the surface to a depth of 5.0 μm is 150% or more of the Cu content of the steel sheet substrate.

A ferritic stainless steel sheet includes a base metal and a nitrided layer that is formed on a surface of the base metal, a chemical composition of the base metal contains, in mass %, C: 0.001 to 0.020%, Si: 0.01 to 1.50%, Mn: 0.01 to 1.50%, P: 0.010 to 0.050%, S: 0.0001 to 0.010%, Cr: 16.0 to 25.0%, N: 0.001 to 0.030%, Ti: 0.01 to 0.30%, and optional elements, with the balance: Fe and unavoidable impurities, a steel microstructure of the base metal includes, in volume ratio, 95% or more of a ferritic phase, the nitrided layer is a layer that is present in a region from a surface of a rolled surface to a 0.05 μm depth position in a sheet thickness direction, and an average nitrogen concentration in the nitrided layer is, in mass %, 0.80% or more.

A ferritic stainless steel sheet includes a base metal and a nitrided layer that is formed on a surface of the base metal, a chemical composition of the base metal contains, in mass %, C: 0.001 to 0.020%, Si: 0.01 to 1.50%, Mn: 0.01 to 1.50%, P: 0.010 to 0.050%, S: 0.0001 to 0.010%, Cr: 16.0 to 25.0%, N: 0.001 to 0.030%, Ti: 0.01 to 0.30%, and optional elements, with the balance: Fe and unavoidable impurities, a steel microstructure of the base metal includes, in volume ratio, 95% or more of a ferritic phase, the nitrided layer is a layer that is present in a region from a surface of a rolled surface to a 0.05 μm depth position in a sheet thickness direction, and an average nitrogen concentration in the nitrided layer is, in mass %, 0.80% or more.

A steel sheet includes: a predetermined chemical composition; and a steel structure represented by, in area %, first martensite in which two or more iron carbides each having a circle-equivalent diameter of 2 nm to 500 nm are contained in each lath: 20% to 95%, ferrite: 15% or less, retained austenite: 15% or less, and the balance: bainite, or second martensite in which less than two iron carbides each having a circle-equivalent diameter of 2 nm to 500 nm are contained in each lath, or the both of these, in which the total area fraction of ND//<111> orientation grains and ND//<100> orientation grains is 40% or less, and the content of solid-solution C is 0.44 ppm or more.

A steel sheet includes: a predetermined chemical composition; and a steel structure represented by, in area %, first martensite in which two or more iron carbides each having a circle-equivalent diameter of 2 nm to 500 nm are contained in each lath: 20% to 95%, ferrite: 15% or less, retained austenite: 15% or less, and the balance: bainite, or second martensite in which less than two iron carbides each having a circle-equivalent diameter of 2 nm to 500 nm are contained in each lath, or the both of these, in which the total area fraction of ND//<111> orientation grains and ND//<100> orientation grains is 40% or less, and the content of solid-solution C is 0.44 ppm or more.

This hot-rolled steel sheet has a predetermined chemical composition, in a microstructure at a 1/4 position of a sheet thickness in a sheet thickness direction from a surface, by area ratios, a primary phase is 95.00% to 98.00% of bainite, a secondary phase is 2.00% to 5.00% of tempered martensite, an average grain size of the secondary phase is 1.5 μm or less, a pole density in a (110)<112> orientation is 3.0 or less, an average grain size of an iron-based carbide is 0.100 μm or less, in a microstructure from the surface to a 1/16 position of the sheet thickness in the sheet thickness direction from the surface, a pole density in a (110)<1-11> orientation is 3.0 or less, and a tensile, strength TS is 980 MPa or more.

This hot-rolled steel sheet has a predetermined chemical composition, in a microstructure at a 1/4 position of a sheet thickness in a sheet thickness direction from a surface, by area ratios, a primary phase is 95.00% to 98.00% of bainite, a secondary phase is 2.00% to 5.00% of tempered martensite, an average grain size of the secondary phase is 1.5 μm or less, a pole density in a (110)<112> orientation is 3.0 or less, an average grain size of an iron-based carbide is 0.100 μm or less, in a microstructure from the surface to a 1/16 position of the sheet thickness in the sheet thickness direction from the surface, a pole density in a (110)<1-11> orientation is 3.0 or less, and a tensile, strength TS is 980 MPa or more.

The present invention relates to a steel material including, in mass %: 0.310≤C≤0.410; 0.001≤Si≤0.35; 0.45≤V≤0.70; Cr≤6.00; 6.25≤Mn+Cr; Mn/Cr≤0.155; Cu+Ni≤0.84; 0.002≤P≤0.030; 0.0003≤S≤0.0060; P+5S≤0.040; 2.03<Mo<2.40; 0.001≤Al≤0.050; and 0.003≤N≤0.050, with the balance being Fe and unavoidable impurities.

A case hardening steel includes a chemical composition containing C: 0.10 mass % to 0.35 mass %, Si: 0.01 mass % to 0.13 mass %, Mn: 0.30 mass % to 0.80 mass %, P: 0.02 mass % or less, S: 0.03 mass % or less, Al: 0.01 mass % to 0.045 mass %, Cr: 0.5 mass % to 3.0 mass %, B: 0.0005 mass % to 0.0040 mass %, Nb: 0.003 mass % to 0.080 mass %, N: 0.0080 mass % or less, Ti as an impurity: 0.005 mass % or less, and the balance being Fe and incidental impurities, and satisfying Formulae (1) and (2):
3.0[% Si]+9.2[% Cr]+10.3[% Mn]≥10.0  (1)
3.0[% Si]+1.0[% Mn]<1.0  (2) where [% M] represents the content of element M (mass %).