The present invention provides a high-strength steel sheet, which can be used in various applications including automobile parts and exhibits excellent collision safety and excellent moldability, and a method for manufacturing the high-strength steel sheet. The high-strength steel sheet according to an aspect of the present invention satisfies a predetermined chemical composition and has a metallographic microstructure having ferrite fraction: 0% to 10%, MA fraction: 0% to 30%, hard phase other than ferrite and MA: 70% to 100% in terms of area proportion and retained austenite fraction: 5% to 30% in terms of volume proportion, and in the high-strength steel sheet, the skewness of IQ as analyzed by the EBRD method is −1.2 to −0.3 when the skewness is expressed by a predetermined relational expression in a case where crystal grains having a bcc structure and a bct structure are regarded as an aggregation of regions having an area of 0.05 μm.sup.2.

Disclosed are a high strength thin specification high corrosion resistance steel and a manufacturing method therefor. The chemical ingredients of the steel in percentages by weight are as follows: 0.02-0.06% of C, 0.1-0.5% of Si, 0.4-1.7% of Mn, ≤0.02% of P, 4.0-6.0% of Cr, 1.0-3.0% of Ni, ≤0.007% of S, 0.004-0.010% of N, <0.001% of Als, 0.001-0.006% of B, 0.007-0.020% of total oxygen [O].sub.T, and the balance is Fe and inevitable impurities, and same simultaneously satisfy: comprising one or both elements of 0.01-0.08% of Nb or 0.01-0.08% of V; and Mn/S≥250. In the invention, micro-alloy elements such as Nb/V and a B element are selectively added to steel, the basicity of slag, the type and melting point of the inclusion in steel, the content of free oxygen in molten steel and the content of acid-soluble aluminum Als during the smelting process are controlled, and a strip is then cast by means of twin-roll thin strip continuous casting, and enters an online rolling mill for hot rolling in closed conditions, and after rolling, the strip steel is cooled by air atomization cooling.

A hot stamped body comprising a steel base material and an Al—Zn—Mg-based plating layer formed on a surface of the steel base material, wherein the plating layer has a predetermined chemical composition, the plating layer comprises an interfacial layer positioned at an interface with the steel base material and containing Fe and Al and a main layer positioned on the interfacial layer, the main layer comprises, by area ratio, 10.0 to 90.0% of an Mg—Zn containing phase, 5.0 to less than 30.0% of an Fe—Al containing phase, and 2.0 to 25.0% of an Al—Si containing oxide phase, the Mg—Zn containing phase comprises at least one selected from the group consisting of an MgZn phase, Mg.sub.2 Zn.sub.3 phase, and MgZn.sub.2 phase, and the Fe—Al containing phase comprises at least one of an FeAl phase and Fe—Al—Zn phase.

The present invention provides steel sheet having both bendability and hydrogen embrittlement resistance. The steel sheet of the present invention includes a central part of sheet thickness and a surface sort part formed at one side or both sides of the central part of sheet thickness. The microstructure of the central part of sheet thickness comprises, by volume ratio, 60% or more of tempered martensite, respectively less than 30% of ferrite, bainite, pearlite, and retained austenite, and less than 5% of as-quenched martensite. A thickness of the surface soft part is more than 10 μm per side and 15% or less of a thickness of the central part of sheet thickness, an average hardness of the surface soft part is 0.90 time or less of an average hardness of the central part of sheet thickness, the surface soft part includes carbides in a number density of 1×10.sup.4/mm.sup.2 or more, an average particle size of the carbides is 0.250 μm or less, and a standard deviation of a log of a particle size is 0.05 or less.

A hot-dip zinc-plated steel sheet includes a steel sheet, a boundary layer that is provided on a surface of the steel sheet, and a hot-dip zinc-plated layer that is provided on a surface of the boundary layer. In a surface layer region of the steel sheet, an average grain size is 4.0 μm or less and a standard deviation of grain sizes is 2.0 μm or less. In the boundary layer, a maximum Al concentration is 0.30 mass % or more.

This steel sheet for hot stamping includes a base material, an Al-Si alloy plating layer in which the Al content is 75 mass% or more, the Si content is 3 mass% or more and the total of the Al content and the Si content is 95 mass% or more and a Ni plating layer in which the Ni content is more than 90 mass% in this order, the chemical composition of the base material is, by mass%, C: 0.01% or more and less than 0.70%, Si: 0.005% to 1.000%, Mn: 0.40% to 3.00%, Nb: 0.010% to 0.200%, a solid solution of Nb: 0.010% to 0.150%, sol. A1: 0.00020% to 0.50000%, P: 0.100% or less, S: 0.1000% or less, N: 0.0100% or less, Cu: 0% to 1.00%, Ni: 0% to 1.00%, V: 0% to 1.00%, Ti: 0% to 0.150%, Mo: 0% to 1.000%, Cr: 0% to 1.000%, B: 0% to 0.0100%, Ca: 0% to 0.010%. REM: 0% to 0.300%, and a remainder: Fe and an impurity, the Al-Si alloy plating layer has a thickness of 7 to 148 .Math.m, and the Ni plating layer has a thickness of more than 200 nm and 2500 nm or less.

A composite material includes: an iron-based alloy layer; an intermediate layer provided on the iron-based alloy layer; and a tungsten-containing layer provided on the intermediate layer, wherein the intermediate layer is composed of pure nickel or is an alloy that contains at least one selected from a group consisting of copper, cobalt, and iron at more than 0 mass % and less than or equal to 71 mass % in total, and that contains nickel at more than or equal to 29 mass % and less than 100 mass %.

The present invention discloses a wire rod for an ultrahigh-strength steel cord and a manufacturing method thereof. The manufacturing method includes: smelting molten steel where inclusions in sizes ≥5 μm are at a number density ≤0.5/mm.sup.2 and sizes of inclusions are ≤30 μm; casting the molten steel into an ingot blank with a center carbon segregation value of 0.92-1.08; cogging the ingot blank into an intermediate blank with a center carbon segregation value of 0.95-1.05; rolling the intermediate blank into a wire rod; and performing temperature control cooling on the wire rod to obtain a wire rod with high purity, high homogeneity and tensile strength ≤1,150 MPa. The wire rod may be used for an ultrahigh-strength steel cord with single tensile strength ≥3,600 MPa.

A high-strength cold-rolled steel sheet having a high yield ratio and excellent stretch flangeability and a method for manufacturing the steel sheet. The high-strength cold-rolled steel sheet has a chemical composition including, by mass %, C: 0.10 to 0.30%, Si: 0.50 to 2.00%, Mn: 2.5 to 4.0%, P: 0.050% or less, S: 0.020% or less, Al: 0.10% or less, N: 0.01% or less, Ti: 0.100% or less, and B: 0.0003 to 0.0030%, with the balance being Fe and incidental impurities. N and Ti satisfy a specified formula, and the total area fraction of martensite and bainite is 95% or more. The number density of bainite grains having an area of 3 μm.sup.2 or more and a carbon concentration of less than 0.7C is 1200 grains/mm.sup.2 or less.

Provided are a plated steel sheet and a method for manufacturing same, the plated steel sheet comprising: a base steel sheet; a Zn—Mg—Al plating layer provided on at least one surface of the base steel sheet; and an Fe—Al inhibition layer provided between the base steel sheet and the Zn—Mg—Al plating layer. The plating layer comprises, by weight %, 4 to 10% of Mg and 5.1-25% of Al and the remainder being Zn and unavoidable impurities with respect to components not including iron (Fe) diffused from the base steel sheet. The plating layer comprises a 24-50% MgZn.sub.2 phase in phase fraction. In the MgZn.sub.2 phase, an Al single phase is present in the ratio of 1-30% relative to the cross-sectional area of the total MgZn.sub.2 phase.