This steel sheet has a specific chemical composition, the tensile strength is 1300 MPa or more, the ratio (R/t) of the limit bend radius to the sheet thickness is less than 3.5, when a depth position of 30 μm from the surface in the sheet thickness direction is defined as a position A and a depth position of ¼ of the sheet thickness from the surface in the sheet thickness direction is defined as a position B, the number density of AIN at the position A is 3000 pieces/mm.sup.2 or more and 6000 pieces/mm.sup.2 or less, a metallographic structure at the position B includes 90% or more of martensite by volume percentage, and the hardness at the position A is 1.20 times or higher than the hardness at the position B.

The present disclosure relates to a high-strength hot-dip galvanized steel sheet having excellent surface quality and electrical resistance spot weldability, and a method for manufacturing the same. A galvanized steel sheet according to an aspect of the present disclosure is a galvanized steel sheet including a base steel sheet and a zinc-based plating layer formed on a surface of the base steel sheet, wherein a ratio (a/b) of a hardness of a surface layer portion (a) to a hardness of an internal portion (b) of the base steel sheet may be less than 0.95.

The present invention relates to a zinc plated steel sheet having excellent surface quality and spot weldability, and a manufacturing method therefore. A zinc plated steel sheet according to one aspect of the present invention comprises a base steel sheet and a zinc-based plating layer formed on the surface of the base steel sheet, wherein the GDOES profile of oxygen, which is measured in the depth direction from the surface of the base steel sheet, has a form in which a local minimum point and a local maximum point alternately appear in the depth direction from the surface, and the difference (a local maximum value—a local minimum value) between the oxygen concentration (a local minimum value) at the local minimum point and the oxygen concentration (a local maximum value) at the local maximum point can be 0.1 wt % or more.

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 method for manufacturing a hot-dip galvanized steel sheet according to one aspect of the present invention includes an annealing step of reduction-annealing a steel sheet having a Si content of 1.0% by mass or more and 3.0% by mass or less at a temperature equal to or higher than an A3 point of the steel sheet in an atmosphere having a dew point of −20° C. or higher; and a hot-dip galvanizing step of making the annealed steel sheet enter into a galvanizing bath to form a galvanized layer on a surface of the steel sheet, wherein a temperature of the steel sheet entering into the galvanizing bath is set to 390° C. or lower.

The disclosure provides a metal surface layer treating method, a metal assembly and an electronic device. The metal surface layer treating method includes: putting metal into a vacuum chamber, and vacuumizing the vacuum chamber to a first vacuum degree; adding a mixed gas of acetylene, nitrogen and hydrogen into the vacuum chamber; and heating the vacuum chamber to a temperature above an ambient temperature. In response to the temperature in the vacuum chamber reaching a first temperature value above the ambient temperature and a gas pressure of the vacuum chamber reaching a first pressure value, performing glow discharge so that a carbon-nitrogen gradient hardening layer is formed on a surface layer of the metal. The method includes removing part of a carbon layer of the surface layer of the carbon-nitrogen gradient hardening layer.

A grain-oriented electrical steel sheet according to an embodiment of the present invention may comprise: by weight %, 2.0-4.0% of Si, 0.04-0.2% of Mn, 0.010% or less (exclusive of 0%) of N, 0.01-0.05% of Sb, 0.005% or less (exclusive of 0%) of C, 0.03-0.08% of Sn, 0.01-0.2% of Cr, and the balance of Fe and inevitable impurities; and precipitates which have an average particle size of 5-50 nm and contain at least one of AIN, (Al, Si)N, (Al, Si, Mn)N, Mns, and CuS.

Provided are a high-carbon steel sheet having good surface quality and a manufacturing method therefor. The present invention provides a high-carbon pickled steel sheet having good surface quality, the steel sheet containing, in weight %, 0.4% or more and less than 1.2% of carbon (C), 0.5% or less (excluding 0%) of silicon (Si), 0.05% or less of phosphorus (P), 0.03% or less of sulfur (S), 0.1 to 2.5% of at least one of manganese (Mn) and chromium (Cr), and the balance of iron (Fe) and inevitable impurities, wherein the average thickness of an internal oxide layer and/or a decarburized layer formed in a surface layer portion of the steel sheet is 1 to 10 μm and the standard deviation of the thickness of the internal oxide layer and/or the decarburized layer in the length direction of the steel sheet is 2 μm or less.

This hot-stamping formed body has a predetermined chemical composition and has a metallographic structure consisting of, by area ratio, a total of 10% to 30% of ferrite and granular bainite and a remainder in microstructure consisting of one or more of martensite, bainite, and tempered martensite, and, in textures of a surface layer region and an inside region, ratios between a pole density of an orientation group consisting of {001}<1-10> to {001}<−1-10> and a pole density of an orientation group consisting of {111}<1-10> to {111}<−1-12> are controlled.