Abstract: A steel sheet with a high concentration of contained Mn having an excellent uniform elongation characteristic and high strength is provided. A steel sheet characterized by containing, by mass %, C: greater than 0.10% and less than 0.55%, Si: 0.001% or more and less than 3.50%, Mn: greater than 4.00% and less than 9.00%, sol. Al: 0.001% or more and less than 3.00%, and a balance of iron and unavoidable impurities, wherein a metal structure at a position of ¼ thickness from a surface in an L-cross-section of the steel sheet comprises, by area %, 25% to 90% of tempered martensite, 3% or less of ferrite, 10% to 75% of residual austenite, and 5% or less of bainite.

Abstract: In a metal coated steel sheet, a chemical composition contains, in mass %, at least C: 0.03% to 0.70%, Si: 0.25% to 2.50%, Mn: 1.00% to 5.00%, P: 0.100% or less, S: 0.010% or less, sol. Al: 0.001% to 2.500, N: 0.020% or less, and a balance composed of iron and impurities, a metal structure contains greater than 5.0 vol % of retained austenite and greater than 5.0 vol % of tempered martensite, and satisfies a C content in the retained austenite being 0.85 mass % or more.

Abstract: A steel sheet according to an aspect of the present invention includes a predetermined chemical composition; in which a metallographic structure in a ¼ t portion contains residual austenite of 4 volume % to 70 volume %; [Mn]?/[Mn]ave>1.5 is satisfied in the ¼ t portion; f?s/f??0.30 and [C]×[Mn]?0.15 are satisfied in the ¼ t portion.

Abstract: A hot-pressed steel sheet member includes: a specific chemical composition; and a steel microstructure represented by, in area %, ferrite: 10% to 70%, martensite: 30% to 90%, and a total area ratio of ferrite and martensite: 90% to 100%. 90% or more of all Ti in steel precipitates, and a tensile strength of the hot-pressed steel sheet member is 980 MPa or more.

Abstract: A steel sheet for hot pressing includes: a specific chemical composition; and a steel structure comprising ferrite and cementite and represented, in area %: a total area ratio of bainite and martensite: 0% to 10%; and an area ratio of cementite: 1% or more; and a concentration of Mn in the cementite is 5% or more.

Abstract: A steel sheet for hot pressing includes a specific chemical composition and further includes a steel structure in which an area ratio of ferrite in a region ranging from a surface to 100 ?m in depth is 30% to 90% and an area ratio of pearlite including an average grain diameter of 5 ?m or more in a region excluding the region ranging from the surface to 100 ?m in depth is 10% to 70%.

Abstract: A steel sheet includes a predetermined chemical composition, and includes a steel microstructure represented by, in an area ratio, ferrite: 5% to 80%, a hard microstructure constituted of bainite, martensite or retained austenite or an arbitrary combination of the above: 20% to 95%, and a standard deviation of a line fraction of the hard microstructure on a line in a plane perpendicular to a thickness direction: 0.050 or less in a depth range where a depth from a surface when a thickness of a steel sheet is set as t is from 3t/8 to t/2.

Abstract: A hot-pressed steel sheet member includes a specific chemical composition and further includes a steel structure in which an area ratio of ferrite in a surface layer portion ranging from a surface to 15 ?m in depth is greater than 1.20 times an area ratio of ferrite in an inner layer portion being a portion excluding the surface layer portion, and the inner layer portion contains a steel structure represented, in area %, ferrite: 10% to 70%, martensite: 30% to 90%, and a total area ratio of ferrite and martensite: 90% to 100%. A tensile strength of the hot-pressed steel sheet member is 980 MPa or more.

Abstract: Provided is a hot-formed member according to the present invention, having a predetermined chemical composition and having a metallographic microstructure containing austenite at an area ratio of 10 area % to 40 area % and in which total number density of particles of the austenite and martensite is equal to or greater than 1.0 number/?m2, in which tensile strength is from 900 MPa to 1300 MPa.

Abstract: A hot-pressed steel sheet member includes a specific chemical composition and further includes a steel structure in which an area ratio of ferrite in a surface layer portion ranging from a surface to 15 ?m in depth is equal to or less than 1.20 times an area ratio of ferrite in an inner layer portion being a portion excluding the surface layer portion, and the inner layer portion contains a steel structure represented, in area %, ferrite: 10% to 70%; martensite: 30% to 90%; and a total area ratio of ferrite and martensite: 90% to 100%. A concentration of Mn in the martensite is equal to or more than 1.20 times a concentration of Mn in the ferrite in the inner layer portion, and a tensile strength of the hot-pressed steel sheet member is 980 MPa or more.

Abstract: A steel sheet for galvannealed steel contains, by mass %, C: 0.25 to 0.70%, Si: 0.25 to 2.50%, Mn: 1.00 to 5.00%, Al: 0.005 to 3.50%, P: 0.15% or less, S: 0.03% or less, N £ 0.02%, O £ 0.01%, and optionally one or more selected from Ti, Nb, V, Cr, Mo, Cu, Ni, B, Ca, REM, Mg, W, Zr, Sb, Sn, As, Te, Y, Hf and Co, a balance being Fe and impurities. The microstructure consists of, by vol. %, retained g: 10.0 to 60.0%, high-temperature tempered martensite3 5.0%, low-temperature tempered martensite3 5.0%, fresh martensite £ 10.0%, a: 0 to 15.0%, P: 0 to 10.0%, a balance being bainite. Total volume ratio of tempered martensite and bainite is 30.0% or more, tensile strength is 1470 MPa or more, tensile strength×uniform elongation is 13000 MPa % or more, and tensile strength×local elongation is 5000 MPa % or more.

Abstract: A base material (13) included in a plated steel sheet (1) includes a structure, at a ¼ sheet thickness position, represented by, in volume fraction: tempered martensite: 3.0% or more; ferrite: 4.0% or more; and retained austenite: 5.0% or more. An average hardness of the tempered martensite in the base material (13) is 5 GPa to 10 GPa, and a part or all of the tempered martensite and the retained austenite in the base material form an M-A. A volume fraction of ferrite in a decarburized ferrite layer (12) included in the plated steel sheet (1) is 120% or more of the volume fraction of the ferrite in the base material (13) at the ¼ sheet thickness position, an average grain diameter of the ferrite in the decarburized ferrite layer (12) is 20 ?m or less, a thickness of the decarburized ferrite layer (12) is 5 ?m to 200 ?m, a volume fraction of tempered martensite in the decarburized ferrite layer (12) is 1.

Abstract: A steel product has: a chemical composition represented by, in mass %, C: 0.050% to 0.35%, Si: 0.50% to 3.0%, Mn: exceeding 3.0% to 7.5% or less, P: 0.05% or less, S: 0.01% or less, sol. Al: 0.001% to 3.0%, N: 0.01% or less, V: 0% to 1.0%, Ti: 0% to 1.0%, Nb: 0% to 1.0%, Cr: 0% to 1.0%, Mo: 0% to 1.0%, Cu: 0% to 1.0%, Ni: 0% to 1.0%, Ca: 0% to 0.01%, Mg: 0% to 0.01%, REM: 0% to 0.01%, Zr: 0% to 0.01%, B: 0% to 0.01%, Bi: 0% to 0.01%, and the balance: Fe and impurities; and a metal structure in which a thickness of a decarburized ferrite layer is 5 ?m or less and a volume ratio of retained austenite is 10% to 40%, wherein tensile strength is 980 MPa or more.

Abstract: A hot formed steel sheet component including: a chemical composition including in terms of mass % C at from 0.100% to 0.340%, Si at from 0.50% to 2.00%, Mn at from 1.00% to 3.00%, P at 0.050% or less, S at 0.0100% or less, sol. Al at from 0.001% to 1.000%, and N at 0.0100% or less, with a remainder consisting of Fe and impurities; and a steel structure including ferrite, at least one of tempered martensite or tempered bainite, and martensite, wherein an area rate of ferrite is from 5% to 50%, a total area rate of tempered martensite and tempered bainite is from 20% to 70%, an area rate of martensite is from 25% to 75%, a total area rate of ferrite, tempered martensite, tempered bainite and martensite is 90% or more, and an area rate of retained austenite is from 0% to 5%.

Abstract: A hot-pressed steel sheet member includes a specific chemical composition and further includes a steel structure in which an area ratio of ferrite in a surface layer portion ranging from a surface to 15 ?m in depth is greater than 1.20 times an area ratio of ferrite in an inner layer portion being a portion excluding the surface layer portion, and the inner layer portion contains a steel structure represented, in area %, ferrite: 10% to 70%, martensite: 30% to 90%, and a total area ratio of ferrite and martensite: 90% to 100%. A tensile strength of the hot-pressed steel sheet member is 980 MPa or more.

Abstract: Steel has a chemical composition that contains 0.050% to 0.40% of C, 0.50% to 3.0% of Si, 3.0% to 8.0% of Mn, and 0.001% to 3.0% of sol. Al, by mass %, and has a metallographic structure that contains 10% to 40% of austenite in terms of % by volume. The average concentration of C in austenite is 0.30% by 0.60%, by mass %, structure uniformity, which is represented by a value obtained by subtracting the minimum value from the maximum value of Vickers hardness that is measured, in the metallographic structure is 30 Hv or less, and the tensile strength is 900 MPa to 1800 MPa.

Abstract: A hot-formed member according to the present invention has a predetermined chemical composition, a metallographic microstructure in which, in terms of area %, ferrite is 10% to 90%, unrecrystallized ferrite is 0% to 2.0%, martensite is 10% to 90%, the total area ratio of the ferrite and the martensite is 90% to 100%, and the average grain size of the ferrite is 0.5 ?m to 5.0 ?m, and the tensile strength of 900 MPa to 1800 MPa.

Abstract: Provided is a hot-formed member according to the present invention, having a predetermined chemical composition and having a metallographic microstructure containing austenite at an area ratio of 10 area % to 40 area % and in which total number density of particles of the austenite and martensite is equal to or greater than 1.0 number/?m2, in which tensile strength is from 900 MPa to 1300 MPa.

Abstract: A hot-pressed steel sheet member includes a specific chemical composition and further includes a steel structure in which an area ratio of ferrite in a surface layer portion ranging from a surface to 15 ?m in depth is equal to or less than 1.20 times an area ratio of ferrite in an inner layer portion being a portion excluding the surface layer portion, and the inner layer portion contains a steel structure represented, in area %, ferrite: 10% to 70%; martensite: 30% to 90%; and a total area ratio of ferrite and martensite: 90% to 100%. A concentration of Mn in the martensite is equal to or more than 1.20 times a concentration of Mn in the ferrite in the inner layer portion, and a tensile strength of the hot-pressed steel sheet member is 980 MPa or more.

Abstract: A hot-pressed steel sheet member includes: a specific chemical composition; and a steel microstructure represented by, in area %, ferrite: 10% to 70%, martensite: 30% to 90%, and a total area ratio of ferrite and martensite: 90% to 100%. 90% or more of all Ti in steel precipitates, and a tensile strength of the hot-pressed steel sheet member is 980 MPa or more.