A rolled steel sheet, for press hardening is provided, having a chemical composition where Ti/N>3.42, and the carbon, manganese, chromium and silicon contents satisfy:

[00001]$2.6.Math.C+\frac{\mathrm{Mn}}{5.3}+\frac{\mathrm{Cr}}{13}+\frac{\mathrm{Si}}{15}1.1.Math.\%.$

The sheet has a nickel content Ni.sub.surf at any point of the steel in the vicinity of the surface over a depth , such that: Ni.sub.surf >Ni.sub.nom, Ni.sub.nom denoting the nominal nickel content of the steel, and such that, Ni.sub.max denoting the maximum nickel content within :

[00002]$\frac{\left({\mathrm{Ni}}_{\max }+{\mathrm{Ni}}_{\mathrm{nom}}\right)}{2}\left(\right)0.6,$

and such that:

[00003]$\frac{\left({\mathrm{Ni}}_{\max }-{\mathrm{Ni}}_{\mathrm{nom}}\right)}{}0.01$

and the surface density of all of the particles D.sub.i and the surface density of the particles D.sub.(>2 m) larger than 2 micrometers satisfy, at least to a depth of 100 micrometers in the vicinity of the surface of said sheet:

D.sub.i+6.75 D.sub.(>2 m) <270

D.sub.i and D.sub.(>2 m) being expressed as number of particles per square millimeter, and said particles denoting all the oxides, sulfides, and nitrides, either pure or combined such as oxysulfides and carbonitrides, present in the steel matrix.

A high-strength cold-rolled steel sheet having a specified chemical composition and a microstructure including ferrite having an average crystal grain diameter of 2 m or less in an amount of 10% to 25% in terms of volume fraction, retained austenite in an amount of 5% to 20% in terms of volume fraction, martensite having an average crystal grain diameter of 2 m or less in an amount of 5% to 15% in terms of volume fraction, and the balance being a multi-phase structure including bainite and tempered martensite having an average crystal grain diameter of 5 m or less, in which a relational expression, 0.35V2/V10.75 (1), is satisfied, where V1 is a volume fraction of phases which are different from ferrite and V2 is a volume fraction of tempered martensite.

A method for producing steel sheets, in particular for body shell sheets of vehicles, in which a steel alloy of a desired composition is melted, poured, and then rolled into sheet form, the steel alloy being an interstitial free steel (IF steel) and after the rolling, the steel sheet being annealed and dressed and then provided with a metallic anti-corrosion coating by means of an electrolytic process or by means of vapor deposition, wherein in order to achieve a low Wsa value with the narrowest possible spread, a niobium content of >0.01% by weight, preferably >0.011% by weight, is added to the alloy of the steel.

A high-strength hot-dip galvanized steel sheet that is a steel sheet that includes major components and that contains at least 40 vol. % the sum of bainite and martensite, 8-60 vol. % retained austenite, and less than 40 vol. % ferrite, with the remainder comprising an incidental structure. The hot-dip galvanized steel sheet has, at the interface between the deposit layer formed by hot-dip galvanization and the base steel sheet, an intermetallic compound constituted of Fe, Al, Zn, and incidental impurities and having an average thickness of 0.1-2 m, the intermetallic compound having a crystal grain diameter of 0.01-1 m. After the deposit layer formed by hot-dip galvanization was removed, the surface of the base steel sheet has an arithmetic average roughness Ra of 0.1-2.0 m and gives a roughness curve in which the contour elements have an average length RSm of 5-300 m.

Provided are a high-strength galvanized hot-rolled steel sheet and a method for manufacturing the steel sheet. A steel sheet has a chemical composition, and a galvanized layer is disposed on the steel sheet. The chemical composition includes, in mass %, C: 0.02% or greater and 0.30% or less, Si: 0.01% or greater and 2.5% or less, Mn: 0.3% or greater and 3.0% or less, P: 0.08% or less, S: 0.02% or less, and Al: 0.001% or greater and 0.20% or less. The galvanized layer has a coating weight per side of 20 to 120 g/m.sup.2. A surface of the steel sheet has a specific surface area ratio, r, of 2.5 or less, and an amount of Si present in the galvanized layer and an amount of Mn present in the galvanized layer respectively satisfy: amount of Sir0.06, and amount of Mnr0.10.

A tin coated steel sheet is provided for manufacturing a drawn can having: a thickness inferior to 0.7 mm, a yield strength inferior to 400 MPa, an average grain aspect ratio below 1.5, a strain hardening coefficient below 1.5, a tin coating from 0.5 to 4.0 g.Math.m.sup.2 on a first face and from 2.8 to 11.2 g.Math.m.sup.2 on a second face, a chemical composition comprising in weight percent 0.002C0.09 and 0.0015B0.005 and a balance of Fe and unavoidable impurities, and the steel sheet having a ferritic microstructure with a mean grain size from 5 to 15 m.

A high strength steel sheet has a yield-point elongation of 1% or greater and a tensile strength of 980 MPa or greater. The high strength steel sheet has a specific chemical composition and microstructure. A ratio of retained austenite grains adjoining a retained austenite grain having a different crystal orientation to total retained austenite grains is 0.60 or greater, the ferrite has an average grain size of 5.0 m or less, and the retained austenite has an average grain size of 2.0 m or less. A value obtained by dividing a volume fraction Va by a volume fraction Vb is 0.40 or greater, where the volume fraction Va is a volume fraction of retained austenite in a fractured portion of a tensile test specimen after a warm tensile test at 150 C., and the volume fraction Vb is a volume fraction of retained austenite before the warm tensile test at 150 C.

To provide a steel sheet for hot stamping suitable for manufacturing, through hot-stamping working, a component having portions with different strengths, and a hot-stamped member having portions with different strengths. A steel sheet for hot stamping according to the present invention includes, on a surface of the steel sheet: a site having a surface-treated film whose emissivity at a wavelength of 8.0 m at 25 C. is 60% or more; and a site at which the surface-treated film is not provided, in which the surface-treated film contains carbon black, and one or more of oxides selected from a group consisting of a Zr oxide, a Zn oxide, and a Ti oxide, in which the carbon black and the oxides exist while being dispersed over the entire surface-treated film, the surface-treated film has a silica content of 0 to 0.3 g/m.sup.2, and when an adhesion amount of the carbon black and an adhesion amount of the oxides are set to X.sub.CB (g/m.sup.2) and X.sub.Oxide (g/m.sup.2), respectively, an equation (1) below is satisfied.

A hot stamped steel includes a base material, a plated layer that is formed on a surface of the base material, and an oxide film that is formed on a surface of the plated layer; chemical composition of the plated layer contains 20.00 to 45.00 mass % of Al, 10.00 to 45.00 mass % of Fe, 4.50 to 15.00 mass % of Mg, 0.10 to 3.00 mass % of Si, 0.05 to 3.00 mass % of Ca, 0 to 0.50 mass % of Sb, 0 to 0.50 mass % of Pb, 0 to 1.00 mass % of Cu, 0 to 1.00 mass % of Sn, 0 to 1.00 mass % of Ti, 0 to 0.50 mass % of Sr, 0 to 1.00 mass % of Cr, 0 to 1.00 mass % of Ni, and 0 to 1.00 mass % of Mn with a remainder of Zn and impurities; and chemical composition of the oxide film contains 20.0 to 55.0 at % of Mg, 0.5 to 15.0 at % of Ca, 0 to 15.0 at % of Zn, and 0 at % or more and less than 10.0 at % of Al with a remainder of O and a total of 5.0 at % or less of impurities, and the adhesion amount of the oxide film per one surface is in a range of 0.01 to 10 g/m.sup.2.

Provided is a high-strength hot-dip galvanized steel sheet having excellent plating adhesion, formability, and hole expandability with an ultimate tensile strength of 980 MPa or more, the hot-dip galvanized steel sheet comprising a hot-dip galvanized layer formed on a surface of a base steel sheet. The base steel sheet contains, by mass %, C: 0.05% to 0.4%; Si: 0.01% to 3.0%; Mn: 0.1% to 3.0%; Al: 0.01 to 2.0%; in which Si+Al>0.5%, P: limited to 0.04% or less; S: limited to 0.05% or less; N: limited to 0.01% or less; and a balance including Fe and inevitable impurities, a microstructure of the base steel sheet contains 40% or more by total volume fraction of martensite and bainite, 8% or more by volume fraction of residual austenite, and a balance of the microstructure being ferrite or ferrite and 10% or less by volume fraction of pearlite. The martensite contains 10% or more by total volume fraction of two or more kinds of three kinds of martensites (1), (2), and (3), and the hot-dip galvanized layer contains less than 7 mass % of Fe.