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.

This steel sheet has a predetermined chemical composition, and has, at a t/4-position which is a position at a distance of t/4 from the surface in a sheet thickness direction cross section when the sheet thickness is defined as t, a metal structure including 20% or more of ferrite and a total of 40% or more of bainite and martensite in volume fraction, the remaining portion being at least one selected from retained austenite and perlite. In a square-shaped area in which the length of one side is t/4 and which is centered at the t/4-position in the sheet thickness direction cross section, when the Mn concentration is measured at multiple measurement points located apart at a 1 ?m-interval, the proportion of measurement points in which the Mn concentration is at least 1.1 times of the average value of the Mn concentration at all the measurement points is less than 10.0%. The steel sheet has a tensile strength of 980 MPa or more. The product between the tensile strength and the total elongation of the steel sheet is 10500 MPa.Math.% or more.

A multipurpose continuous processing line able for heat treating and hot dip coating a steel strip containing: an annealing section (1) for heating the steel strip to a predetermined annealing temperature and for maintaining the steel strip at said annealing temperature, a first transfer section (2), an overaging section (3) able to maintain the temperature of the steel strip between 300? C. and 700? C., a second transfer section (4) able to adjust the temperature of the steel strip to allow the hot dip coating of the strip and, a hot dip coating section (5), wherein the first transfer section (2) includes, in sequence, a cooling section (21) and a heating section (22).

A tailored rolled blank in which a plate thickness changes in a tapered shape in a rolling direction, comprises a thick-wall portion, and a thin-wall portion that is thinner than the thick-wall portion. In the tailored rolled blank, a ratio of an average hardness H.sub.tmax of a thickest wall portion at which the plate thickness is thickest to an average hardness H.sub.tmin of a thinnest wall portion at which the plate thickness is thinnest is in a range of more than 1.0 to 1.5. For the tailored rolled blank, an average dislocation density of the thinnest wall portion is 110.sup.14 m.sup.2 or less, and a number density of fine Ti carbo-nitrides having a particle diameter of 10 nm or less is more than 210.sup.17 per cm.sup.3.

A plated steel sheet includes: a steel sheet; and a plating layer that is formed on at least a part of a surface of the steel sheet, in which a chemical composition of the plating layer includes, b mass %, Al: 6.00% to 35.00 %, Mg: 3.00% to 15.00%, La+Ce: 0.0001% to 0.5000% in total, and Zn, and in a surface of the plating layer, the area ratio of a lamellar structure in which an (AlZn) phase and a MgZn.sub.2 phase are arranged in layers is 10% to 95%, the lamellar spacing of the lamellar structure is 2.5 ?m or less, and the area ratio of an (AlZn) dendrite is 10% or less.

A clad steel plate having tensile strength (TS) of 780 MPa or more, excellent ductility, bendability, collision resistance, and LME resistance. The clad steel plate having a base metal and a cladding metal on front and back surfaces of the base metal, and the chemical composition and microstructure of the base metal and the cladding metal being appropriately controlled so that the average Vickers hardness (HVL) of the cladding metal is 260 or less, the average Vickers hardness (HVL) of the cladding metal divided by the average Vickers hardness (HVB) of the base metal is 0.80 or less, the boundary roughness between the base metal and the cladding metal is 50 ?m or less at the maximum height Ry, and the number of voids at the boundary between the base metal and the cladding metal is controlled to 20 or fewer per 10 mm length of the boundary.

To provide a galvanized steel sheet having high strength, specifically, a tensile strength of 1,150 MPa or more, and excellent resistance spot weldability, a base steel sheet has a defined chemical composition, an amount of diffusible hydrogen in the base steel sheet is 0.20 mass ppm or less, and surface roughness Ra of the galvanized steel sheet is 0.6 ?m or less.

To provide a galvanized steel sheet having high strength; specifically, with a tensile strength of 1160 MPa or more and excellent resistance spot weldability. A chemical composition of a base steel sheet contains one or more of Ti, Nb, V, and Zr: 0.02% or more and 0.20% or less in total, and an amount of diffusible hydrogen in a zinc or zinc alloy coating layer is 0.40 mass ppm or less.

A high-strength galvanized steel sheet and method for producing the same. The high-strength galvanized steel sheet including a specified chemical composition and a microstructure comprising, in terms of area fraction, 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 15% or less, and other phases: 10% or less (including 0%), the other phases comprising a martensite phase: 3% or less (including 0%) and a bainitic ferrite phase: less than 5% (including 0%), the tempered martensite phase having an average grain size of 8 m or less, the ferrite phase having an average grain size of 5 m or less, and the retained austenite phase having a C content less than 0.7% by mass.

Disclosed is a steel composition for hot stamping that comprises carbon (C) in an amount of about 0.22 to about 0.25 wt %, silicon (Si) in an amount of about 0.2 to about 0.3 wt %, manganese (Mn) in an amount of about 1.2 to about 1.4 wt %, titanium (Ti) in an amount of about 0.02 to about 0.05 wt %, chromium (Cr) in an amount of about 0.11 to about 0.2 wt %, boron (B) in an amount of about 0.005 to about 0.01 wt %, zinc (Zr) in an amount of about 0.005 to about 0.02 wt %, niobium (Nb) in an amount of about 0.01 to about 0.05 wt %, tungsten (W) in an amount of about 0.1 to about 0.5 wt %, iron (Fe) constituting the remaining balance of the steel composition, all the wt % based on the total amount of the steel composition.