The plated steel material is a plated steel material including a steel material and a plating layer provided on the surface of the steel material, wherein the plating layer has a predetermined average chemical composition, when the amount of Mg is % Mg and the amount of Al is % Al, % Mg/% Al is 0.80 or more, and a metal structure in a total field of view of 25,000 μm.sup.2 in a vertical cross section which is a cross section in a thickness direction of the plating layer includes 10 to 40 area % of a MgZn.sub.2 phase, 10 to 30 area % of an Al—Zn phase with a Zn content of 10% or more, 0 to 15 area % of an Al phase with a Zn content of less than 10%, and 25 area % or more of an Al/MgZn.sub.2/Zn ternary eutectic structure.

A method for forming a zinc-plated steel plate or steel belt having good corrosion resistance, comprising the following steps: 1) conveying the steel plate or steel belt into a heating furnace higher than Ac.sub.3, austenitizing the steel plate or steel belt, and keeping the temperature for 1-7 minutes; 2) before the steel plate or steel belt leaves the heating furnace and enters a forming mold, applying different cooling manners according to different plated thicknesses, wherein when the single-sided weight of the plating is less than or equal to 50 g/m.sup.2, only air cooling is required before transferring to the forming mold, when the single-sided weight of the plating is greater than 50 g/m.sup.2, aerial fog or water mist precooling is performed before transferring to the forming mold, and the steel plate is cooled to be below 700° C. at a cooling sped greater than 30° C./s; and 3) rapidly transferring the steel plate or steel belt to the mold for hot stamping forming, wherein a transferring duration does not exceed 1 minute, and the temperature of the hot stamping forming is controlled between 400-800° C. The tensile strength of the steel plate or steel belt after hot stamping is greater than 1,450 MPa, and substrate cracks caused by local press and LME in an element are avoided.

A galvannealed steel sheet according to one aspect of the present invention has a hot-dip galvannealed layer on at least one surface of the steel sheet, and the steel sheet has a predetermined chemical composition, in which the steel sheet contains 10% or more and 90% or less of ferrite, and 10% or more of tempered martensite and tempered bainite in terms of an area ratio, a sum of the ferrite, the tempered martensite, and the tempered bainite is 90% or more, carbides having a major axis of 50 nm or more and 300 nm or less are contained in grains of the ferrite in a number density of 20/μm.sup.2 or more, and a two-dimensional homogeneous dispersion ratio S of Mn is 0.75 or more and 1.30 or less.

A steel sheet having excellent fatigue resistance as a material for automobile parts and a TS of 590 MPa or more, and a method for producing the same. The steel sheet has a composition comprising, by mass %, C: 0.04% or more and 0.15% or less, Si: 0.3% or less, Mn: 1.0% or more and 2.6% or less, P: 0.1% or less, S: 0.01% or less, Al: 0.01% or more and 0.1% or less, N: 0.015% or less, one or two of Ti and Nb: 0.01% or more and 0.2% or less in a total, and the balance being Fe and unavoidable impurities. The steel sheet has 50% or more of ferrite and 10% or more and 50% or less of martensite in terms of an area ratio, and a microstructure in which a standard deviation of nano-hardness is 1.50 GPa or less and tensile strength of 590 MPa or more.

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 (Al—Zn) 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 μm or less, and the area ratio of an (Al—Zn) dendrite is 10% or less.

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 (Al—Zn) 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 μm or less, and the area ratio of an (Al—Zn) dendrite is 10% or less.

The present invention relates to steel used for members of chassis parts and wheel discs of commercial vehicles, or the like and, more specifically, to a high-strength steel with excellent durability and a method for manufacturing same.

The present invention relates to steel used for members of chassis parts and wheel discs of commercial vehicles, or the like and, more specifically, to a high-strength steel with excellent durability and a method for manufacturing same.

Provided is a galvanized steel sheet having excellent plating adhesion, having a plated layer with improved friction characteristics by means of a predetermined level of Fe elution, and having excellent corrosion resistance; and a manufacturing method therefor.

Provided is a galvanized steel sheet having excellent plating adhesion, having a plated layer with improved friction characteristics by means of a predetermined level of Fe elution, and having excellent corrosion resistance; and a manufacturing method therefor.