Abstract: A steel sheet for hot stamping, including: C: 0.050 to 0.12 mass %; Si: 0.50 to 2.0 mass %; Mn: 2.1 to 3.0 mass %; P: 0.10 mass % or less (including 0 mass %); S: 0.010 mass % or less (including 0 mass %); Al: 0.01 to 0.10 mass %; Ti: 0.010 to 0.100 mass %; B: 0.0010 to 0.0100 mass %; and N: 0.010 mass % or less (including 0 mass %), and Fe, and satisfying the following formula: ?=[% C]/21?[% Si]/334+[% Mn]/81?[% Ti]/11+10×<% B>?0.03, where [% C], [% Si], [% Mn], and [% Ti] are the contents of C, Si, Mn, and Ti in mass %, respectively, and <% B> is the amount of solid solution B in mass %.

Abstract: A zinc-plated steel sheet for hot stamping according to an aspect of the present invention includes a base steel sheet satisfying a predetermined composition of chemical components, wherein an amount of solid-soluted B is 10 ppm or more and the base steel sheet has a hot-dip galvannealed layer or a hot dip galvanized layer on at least one face thereof.

Abstract: A steel plate for hot stamping contains, in % by mass, C: 0.25% or more and 0.4% or less, Si: 1.05% or more and 1.4% or less, Mn: 0% or more and 1.4% or less, Cr: 0.6% or more and 3.0% or less, P: 0% or more and 0.03% or less, S: 0% or more and 0.02% or less, Al: 0.01% or more and 1% or less, N: 0% or more and 0.01% or less, B: 0.0005% or more and 0.005% or less, Ti: 0.005% or more and 0.1% or less, and iron and inevitable impurities as remainder. This steel plate for hot stamping exhibits excellent hardness stability in addition to a balance between strength and toughness as a relational expression of [C]+2/9[Si]+7/9[Mn]+8/9[Cr]?7/4>0 is satisfied.

Abstract: A high-strength hot-dip galvannealed steel sheet may include a plating layer on a surface of a base steel sheet. The base steel sheet may satisfy a predetermined chemical composition, in a metallographic structure of the base steel sheet, wherein a volume ratio of martensite (including tempered martensite and self-tempered martensite) is 82 vol % or more, a volume ratio of ferrite, pearlite and bainite is 13 vol % or less in total, and volume ratio of retained austenite is 5 vol % or less, in an image obtained by observing the metallographic structure of the base steel sheet with a scanning electron microscope, the number of laths at a total length of 300 ?m, the number being measured by an intercept method is 200 or more, a yield strength is 970 MPa or more, and a tensile strength is 1,470 MPa or more.

Abstract: A zinc-plated steel sheet for hot stamping according to an aspect of the present invention includes a base steel sheet satisfying a predetermined composition of chemical components, wherein an amount of solid-soluted B is 10 ppm or more and the base steel sheet has a hot-dip galvannealed layer or a hot dip galvanized layer on at least one face thereof.

Abstract: A low-strength steel sheet for hot stamping according to an aspect of the present invention satisfies a predetermined chemical composition, the Ac3 point (° C.) represented by Equation (1) is 890° C. or more, and an area ratio of ferrite at a depth to be ¼ of a steel sheet thickness is 80% or more. Ac3 point (° C.)=910?203×[C]1/2+44.7×[Si]?30×[Mn]+700×[P]+400×[Al]+400×[Ti] . . . (1) In Equation (1), [C], [Si], [Mn], [P], [Al], and [Ti] are values denoting the percentage contents of C, Si, Mn, P, Al, and Ti in terms of % by mass, respectively.

Abstract: A steel plate for hot stamping contains, in % by mass, C: 0.25% or more and 0.4% or less, Si: 1.05% or more and 1.4% or less, Mn: 0% or more and 1.4% or less, Cr: 0.6% or more and 3.0% or less, P: 0% or more and 0.03% or less, S: 0% or more and 0.02% or less, Al: 0.01% or more and 1% or less, N: 0% or more and 0.01% or less, B: 0.0005% or more and 0.005% or less, Ti: 0.005% or more and 0.1% or less, and iron and inevitable impurities as remainder. This steel plate for hot stamping exhibits excellent hardness stability in addition to a balance between strength and toughness as a relational expression of [C]2/9[Si]+7/9[Mn]+8/9[Cr]?7/4>0 is satisfied.

Abstract: An aspect of the present invention is a steel sheet for quench hardening, satisfying a prescribed composition and having a Mn concentration satisfying the formula (1): S1+S2<?10×[Mn]+44 (1), where [Mn] is Mn concentration in a steel sheet analyzed by inductively coupled plasma emission spectrography (% by mass); S1 is an area % of the region where the Mn concentration analyzed by an electron beam microprobe analyzer in the structure at a position of ¼ of the steel sheet thickness is two times or more the [Mn]; and S2 is an area % of the region where the Mn concentration analyzed by an electron beam microprobe analyzer in the structure at a position of ¼ of the steel sheet thickness is 0.5 times or less the [Mn].

Abstract: A cold-rolled steel sheet has a chemical composition of C: 0.12% to 0.3%, Si: 0.5% or less, Mn: less than 1.5%, Al: 0.15% or less, N: 0.01% or less, P: 0.02% or less, and S: 0.01% or less, with the remainder including iron and inevitable impurities and has a martensite single-phase structure as its steel microstructure. In a surface region of the steel sheet from the surface to a depth one-tenth the gauge, the number density of n-ary groups of inclusions determined by specific n-th determinations is 120 or less per 100 cm2 of a rolling plane, where the distance in steel sheet rolling direction between outermost surfaces of two outermost particles of the group of inclusions is 100 ?m or more. The steel sheet is a high-strength cold-rolled steel sheet which has a sufficiently minimized rate of bending fracture starting from inclusions and thereby has excellent bending workability.

Abstract: A cold-rolled steel sheet has a chemical composition of C: 0.12% to 0.3%, Si: 0.5% or less, Mn: less than 1.5%, Al: 0.15% or less, N: 0.01% or less, P: 0.02% or less, and S: 0.01% or less, with the remainder including iron and inevitable impurities and has a martensite single-phase structure as its steel microstructure. In a surface region of the steel sheet from the surface to a depth one-tenth the gauge, the number density of n-ary groups of inclusions determined by specific n-th determinations is 120 or less per 100 cm2 of a rolling plane, where the distance in steel sheet rolling direction between outermost surfaces of two outermost particles of the group of inclusions is 100 ?m or more. The steel sheet is a high-strength cold-rolled steel sheet which has a sufficiently minimized rate of bending fracture starting from inclusions and thereby has excellent bending workability.