Provided are a steel sheet with excellent weldability, and a production method therefor. The steel sheet is characterized by having a specific composition and a metallographic structure containing, in terms of an area ratio, ferrite of 25% or more and 65% or less, martensite having iron-based carbides precipitated in the grains of 35% or more and 75% or less, and the balance structure other than the ferrite and the martensite of 20% or less (including 0%) in total, the average grain diameters of the ferrite and the martensite being respectively 5 m or lower, the total of concentration of Si and Mn at interface between the ferrite and the martensite being, in terms of an atomic concentration, 5% or more, and having a tensile strength of 900 MPa or higher.

A hot-rolled steel sheet has a chemical composition that contains, in mass %, C, Si, Mn, P, S, Al, N and Ti, and that satisfies Formula (1); and a microstructure containing bainite and ferrite. In the interior of the steel sheet an average value of pole densities of an orientation group {100}<011> to {223}<110> is 4 or less, and a pole density of a {332}<113> crystal orientation is 4.8 or less. In an outer layer of the steel sheet, a pole density of a {110}<001> crystal orientation is 2.5 or more. Furthermore, among Ti carbo-nitrides in the steel sheet, the number density of fine Ti carbo-nitrides having a particle diameter of 10 nm or less is 1.010.sup.17 per cm.sup.3 or less, and a bake hardening amount is 15 MPa or more.

[Ti]48/14[N]48/32[S]0(1)

An HPF molding member having a melted aluminum plating layer formed on the surface of a base steel sheet and excellent delamination resistance. The base steel sheet comprises: 0.18-0.25% by weight of C; 0.1-1.0% by weight of Si; 0.9-1.5% by weight of Mn; 0.03% by weight or less of P; 0.01% by weight or less of S; 0.01-0.05% by weight of Al; 0.05-0.5% by weight of Cr; 0.01-0.05% by weight of Ti; 0.001-0.005% by weight of B; 0.009% by weight or less of N; and the balance Fe and other impurities. The plating layer consists of a soft diffusion layer and a hard alloy layer, the hard alloy layer having a tau layer irregularly and non-continuously dispersed and distributed on the inside thereof at 10% or more of the entire area fraction. The difference in hardness between the alloy layer and the diffusion layer is 400 (Hv) or less.

A hot stamped component, includes: a base material; and a Zn-based plating layer provided in contact with the base material as an upper layer of the base material and containing Zn and Ni. A region of the Zn-based plating layer on a base material side is a FeZn solid solution containing Ni, and two or more twins exist in 10 crystal grains of the FeZn solid solution containing Ni adjacent to an interface between the base material and the Zn-based plating layer.

A steel sheet for a container includes: a steel sheet; a coated layer containing Ni provided as an upper layer of the steel sheet; and a chemical treatment layer as an upper layer of the coated layer, and containing a Zr compound in an amount of 3.0 to 30.0 mg/m.sup.2 in terms of Zr metal, and a Mg compound in an amount of 0.50 to 5.00 mg/m.sup.2 in terms of Mg metal, in which the coated layer is one of: a Ni coated layer which contains Ni in amount of 10 to 1000 mg/m.sup.2 in terms of Ni metal, and a composite coated layer which contains Ni in an amount of 5 to 150 mg/m.sup.2 in terms of Ni metal and Sn in an amount of 300 to 3000 mg/m.sup.2 in terms of Sn metal, and has an island-shaped Sn coated layer formed on an FeNiSn alloy layer.

A steel sheet for a container includes a steel sheet, a Sn coated layer which is provided as an upper layer of the steel sheet and contains Sn in an amount of 560 to 5600 mg/m.sup.2 in terms of Sn metal, and a chemical treatment layer which is provided as an upper layer of the Sn coated layer and contains a Zr compound in an amount of 3.0 to 30.0 mg/m.sup.2 in terms of Zr metal and a Mg compound in an amount of 0.50 to 5.00 mg/m.sup.2 in terms of Mg metal.

A Sn-plated steel sheet according to the present invention includes a steel sheet, a Sn-plated layer that is provided on at least one surface of the steel sheet, and a film that is provided on a surface of the Sn-plated layer and includes zirconium oxide and tin oxide, in which an amount of the zirconium oxide in the film is 0.2 mg/m.sup.2 to 50 mg/m.sup.2 in terms of metal Zr amount, in a depth direction analysis by X-ray photoelectron spectroscopy, a depth position A at which an element concentration of Zr present as the zirconium oxide is maximum is positioned closer to a surface of the film than a depth position B at which an element concentration of Sn present as the tin oxide is maximum, and a distance between the depth position A and the depth position B in a depth direction is 0.5 nm or more.

There is provided a hot-dip galvanized steel sheet and a hot-dip galvannealed steel sheet, which have excellent elongation properties, and methods for manufacturing the hot-dip galvanized steel sheet and the hot-dip galvannealed steel sheet. The present disclosure relates to a hot-dip galvanized steel sheet in which a hot-dip galvanized layer is formed on a surface of abase steel sheet, the hot-dip galvanized steel sheet having excellent elongation properties and being characterized by the composition and the microstructure thereof.

An objective of the present invention is to provide a steel sheet having a high strength which can provide excellent appearance quality. The steel sheet has a chemical composition including, in mass %, C: more than 0.030% to 0.145%, Si: 0% to 0.500%, Mn: 0.50% to 2.50%, P: 0% to 0.100%, S: 0% to 0.020%, Al: 0% to 1.000% or less, N: 0% to 0.0100%, and the like, wherein a metal micro-structures consisting of 70 to 95% of ferrite in volume fraction and 5 to 30% of hard phases in volume fraction, and a value X1 obtained by dividing a standard deviation of average Mn concentrations in a rolling direction at ? sheet-thickness positions in a sheet thickness direction by an average Mn concentration at the ? sheet-thickness positions is 0.025 or less.

A high-strength galvanized steel sheet that includes a chemical composition containing, by mass %, C: 0.15% or more and 0.25% or less, Si: 0.50% or more and 2.5% or less, Mn: 2.3% or more and 4.0% or less, P: 0.100% or less, S: 0.02% or less, Al: 0.01% or more and 2.5% or less, and Fe and inevitable impurities. The steel sheet having a microstructure containing, by an area percentage basis, a tempered martensite phase: 30% or more and 73% or less, a ferrite phase: 25% or more and 68% or less, a retained austenite phase: 2% or more and 20% or less, and other phases: 10% or less (including 0%), the other phases containing a martensite phase: 3% or less (including 0%) and a bainitic ferrite phase: less than 5% (including 0%).