A thin steel sheet has a steel structure which has a ferrite area fraction of 30% or less, a bainite area fraction of 5% or less, a martensite and tempered martensite area fraction of 70% or more, and a retained austenite area fraction of 2.0% or less and in which the ratio of the dislocation density in the range of 0 ?m to 20 ?m from a surface of the steel sheet to the dislocation density of a through-thickness central portion of the steel sheet is 90% to 110% and the average of the top 10% of the sizes of cementite grains located in a depth of up to 100 ?m from a surface of the steel sheet is 300 nm or less. The maximum camber of the steel sheet sheared to a length of 1 m in a longitudinal direction of the steel sheet is 15 mm or less.

High strength steel sheet and plated steel sheet having high plateability, LME resistance, and hydrogen embrittlement resistance, that is, steel sheet containing C: 0.05 to 0.40%, Si: 0.2 to 3.0%, Mn: 0.1 to 5.0%, and sol. Al: 0.4 to 1.50%, having an internal oxidation layer including fine granular oxides and coarse granular oxides in a surface layer of the steel sheet, a number density of fine granular oxides in the internal oxidation layer being 4.0/?m.sup.2 or more, a number density of coarse granular oxides in the internal oxidation layer being 4.0/25 ?m.sup.2 or more and 30.0/25 ?m.sup.2 or less, and including a surface depleted layer with a steel composition not including oxides which satisfies, by mass %, Si?0.6% and Al?0.05% at a depth of ? of the average depth of the internal oxidation layer calculated from the cross-sectional SEM image of the steel sheet, and a plated steel sheet using the same.

High strength steel sheet and plated steel sheet having high plateability, LME resistance, and hydrogen embrittlement resistance, that is, steel sheet containing C: 0.05 to 0.40%, Si: 0.2 to 3.0%, Mn: 0.1 to 5.0%, and sol. Al: 0.4 to 1.50%, having an internal oxidation layer including fine granular oxides in a surface layer of the steel sheet, a number density of fine granular oxides in the internal oxidation layer being 4.0/?m.sup.2 or more, and including a surface depleted layer with a steel composition not including oxides which satisfies, by mass %, Si?0.6% and Al?0.05% at a depth of ? of the average depth of the internal oxidation layer calculated from the cross-sectional SEM image of the steel sheet, and a plated steel sheet using the same.

High strength plated steel sheet having high hydrogen embrittlement resistance, that is, alloyed hot dip galvannealed steel sheet including steel sheet containing C: 0.05 to 0.40%, Si: 0.2 to 3.0%, Mn: 0.1 to 5.0%, and sol. Al: 0.4 to 1.50% and a alloyed hot dip galvannealed layer deposited on at least one surface of the steel sheet to 10 to 100 g/m.sup.2 and containing Fe: 5.0 to 15.0% and Al: 0.01 to 1.0%, having an internal oxidation layer including grain boundary oxides in a surface layer of the steel sheet, when examining a cross-section of a surface layer of the steel sheet, a Ratio A of the length of the grain boundary oxides projected an interface of the steel sheet and the alloyed hot dip galvannealed layer to the length of interface is 50% or more and 100% or less, and a surface depleted layer with a steel composition not including the grain boundary oxides which satisfies, by mass %, Si?0.6% and Al?0.05% is included at a depth of ? of the average depth of the internal oxidation layer.

Iron-based alloys and articles in strips, sheets, workpieces and the like are converted into high strength steel with a minimum of cost, time and effort, including producing dual phase materials. This is achievable by extremely rapid micro-treating of low, medium, and high carbon iron-based alloys and articles by rapid heating and rapid cooling at least a portion of the alloy/article. This heating step involves nearly immediately heating the iron-based alloy to a selected temperature above its austenite conversion temperature. Then, the alloy is immediately quenched, also at an extremely fast rate, on at least a portion of the iron-based alloy in a quenching unit adjacent the heating unit. This procedure forms high strength alloy in a desired area, depending upon where the treatment was performed.

A method for manufacturing a thin strip component, including a processing step of processing an amorphous thin strip member into a dimension shape larger than a target shape, and a heat treating step of heat treating and contracting the amorphous thin strip member processed in the processing step to form the amorphous thin strip member into a thin strip component of the target shape. A thin strip component which is a magnetic laminate in which a plurality of plate-shaped thin strip component members of the same shape are laminated, and has a recess over an entire side surface of the magnetic laminate is used. A motor including the thin strip component, a plurality of coils disposed on the thin strip component, and a rotor disposed between the plurality of coils is used.

A steel sheet comprising, by mass %, C: 0.05 to 0.40%, Si: 0.2 to 3.0%, and Mn: 0.1 to 5.0%, wherein a surface layer of the steel sheet contains grain boundary oxides, a Ratio A of a length of the grain boundary oxides projected on a surface of the steel sheet to a length of the surface of the steel sheet is 50% or more and 100% or less, a number density of granular oxides is less than 4.0/?m.sup.2, the steel sheet comprises an SiMn depleted layer having a thickness of 3.0 ?m or more from the surface of the steel sheet, and Si and Mn contents of the SiMn depleted layer at the ? position of the thickness and not containing oxides are respectively less than 10% of the Si and Mn contents at a sheet thickness center part of the steel sheet, and a plated steel sheet using the same are provided.

The present disclosure provides a hot-press formed part comprising a plated steel sheet and an aluminum alloy plated layer formed on the plated steel sheet, wherein the aluminum alloy plated layer comprises: an alloying layer (I) formed on the plated steel sheet and containing, by weight %, 5-30% of Al; an alloying layer (II) formed on the alloying layer (I) and containing, by weight %, 30 to 60% of Al; an alloying layer (III) formed on the alloying layer (II) and containing, by weight %, 20-50% of Al and 5-20% of Si; and an alloying layer (IV) formed continuously or discontinuously on at least a part of the surface of the alloying layer (III), and containing 30-60% of Al, wherein the rate of the alloying layer (III) exposed on the outermost surface of the aluminum alloy plated layer is 10% or more.

In a process for producing a cold- or hot-rolled steel strip from an ultrahigh-strength multiphase steel having a particular composition the required multiphase microstructure is generated during continuous heat treatment. The cold- or hot-rolled steel strip is heated in the continuous heat treatment furnace to a temperature in the range from 700 to 950 C. and the heat-treated steel strip is subsequently cooled from the heat treatment temperature at a cooling rate of from 15 to 100 C./s to a first intermediate temperature of from 300 to 500 C. followed by cooling at a cooling rate of from 15 to 100 C./s to a second intermediate temperature of from 200 to 250 C.; the steel strip is subsequently cooled at a cooling rate of from 2 to 30 C./s in air to room temperature or the cooling at a cooling rate of from 15 to 100 C./s is maintained from the first intermediate temperature to room temperature.

A metal mask material for OLED use reduced in amount warpage due to etching, a method for manufacturing the same, and a metal mask are provided. The metal mask material and metal mask of the present invention contain, by mass %, Ni: 35.0 to 37.0% and Co: 0.00 to 0.50%, have a balance of Fe and impurities, have thicknesses of 5.00 ?m or more and 50.00 ?m or less, and have amounts of warpage defined as maximum values in amounts of rise of four corners of a square shaped sample of the metal mask material of 100 mm sides when etching the sample from one surface until the thickness of the sample becomes ? and placing the etched sample on a surface plate of 5.0 mm or less.