Provided is a high-strength hot-rolled coated steel sheet having a TS of 980 MPa or more, excellent bulging formability and stretch flange formability, and excellent coatability. The high-strength hot-rolled coated steel sheet includes a steel sheet having a chemical composition containing, by mass %, C: 0.03% to 0.09%, Si: 0.01% to 1.60%, Mn: 2.20% to 3.60%, P: 0.100% or less, S: 0.0100% or less, Ti: 0.05% to 0.18%, B: 0.0005% to 0.0050%, Al: 0.005% to 0.40%, N: 0.010% or less, and a balance of Fe and inevitable impurities, in which a CSM value expressed by the equation 33.8[% C][% Mn]+12.4[% Si]/[% Mn] is 3.3 to 12.0, and a steel microstructure containing bainite in an amount of 85% or more in terms of area fraction and martensite in an amount of 2.0% or more and 15.0% or less in terms of area fraction and includes a coating layer or an alloyed coating layer on a surface of the steel sheet.

A method for producing a precoated steel sheet (1) includes providing a precoated steel strip comprising a steel substrate (3) having, on at least one of its main faces, a precoating comprising an intermetallic alloy layer and a metallic alloy layer. The metallic alloy layer is a layer of aluminum, a layer of aluminum alloy or a layer of aluminum-based alloy. The method also includes laser cutting said precoated steel strip so as to obtain at least one precoated steel sheet (1) comprising a cut edge surface (13) resulting from the cutting operation. The cut edge surface (13) includes a substrate region (14) and a precoating region (15) and the thickness of the precoated steel sheet (1) is comprised between 0.8 mm and 5 mm. The laser cutting is carried out such that it results directly in a corrosion-improved zone (19) of the cut edge surface (13). The surface fraction of aluminum on the substrate region (14) of the corrosion-improved zone (19) is greater than or equal to 9% and the surface fraction of aluminum on the bottom half of the substrate region (14) of the corrosion-improved zone (19) is greater than or equal to 0.5%.

Provided is a highly corrosion-resistant plated steel sheet having plating adhesion and resistance to liquid metal embrittlement. A highly corrosion-resistant plated steel sheet comprises a base steel sheet and a plated layer, which sequentially comprises an Fe—Al alloy layer and an MgZn.sub.2 layer from an interface with the base steel sheet.

A coated steel product including a base steel, and a coating layer containing a Zn—Al—Mg alloy layer disposed on a surface of the base steel, in which the coating layer has a predetermined chemical composition, the coated steel product including dendrite-shaped MgZn.sub.2 phase having a surface roughness Sa of 50 nm or less on a surface of the Zn—Al—Mg alloy layer, an area ratio of the dendrite-shaped MgZn.sub.2 phase having a surface roughness Sa of 50 nm or less being from 30% to 80% within a region of an observable field of view of 5 mm.sup.2, and among the dendrite-shaped MgZn.sub.2 phase having a surface roughness Sa of 50 nm or less, a number of dendrite-shaped MgZn.sub.2 phase having an area of 0.1 mm.sup.2 or more being from 5 to 100 within a region of an observable field of view of 25 mm.sup.2.

One aspect of the present invention relates to a plated steel sheet for hot press forming, having an excellent impact property.

Provided is a low-density clad steel sheet having excellent formability and fatigue properties, including a base material; and cladding materials provided on both side surfaces of the base material, wherein the base material is a lightweight steel sheet including, by weight, C: 0.3 to 1.0%, Mn: 4.0 to 16.0%, Al: 4.5 to 9.0%, and a remainder of Fe and inevitable impurities, and each of the cladding materials is martensitic carbon steel including, by weight, C: 0.1 to 0.45%, Mn: 1.0 to 3.0%, and a remainder of Fe and inevitable impurities.

The present invention relates to an automotive steel sheet and, more specifically, provides: an ultrahigh-strength and high-ductility steel sheet ensuring ultrahigh strength and high ductility and, simultaneously, having excellent cold formability due to a high yield strength ratio, and improved collision characteristics.

An aluminum-based coating of a flat steel product is applied in a hot-dipping method and comprises a mass percentage of silicon within a given range. The coating for a flat steel product, in particular for press mold hardening components, offers a shortened required minimum oven dwell time and a sufficiently large processing window when heating in an oven. This is achieved in that the surface of the coating has a degree of absorption for thermal radiation ranging between 0.35 and 0.95 prior to an annealing treatment, where the degree of absorption relates to an oven temperature ranging from 880 to 950° C. during the austenitizing annealing treatment. The invention additionally relates to an improved method for producing a flat steel product with an aluminum-based coating, to an inexpensive method for producing press-hardened components from such flat steel products, and to a press-hardened component made of such flat steel products.

A plated steel material comprising a steel base material and an Al—Zn—Mg-based plating layer formed on a surface of the steel base material, wherein the plating layer has a predetermined chemical composition, and in a surface structure of the plating layer, there is, by area ratio, 2.0% or more of an acicular Al—Zn—Si—Ca phase.

The present disclosure provides a composite coating and a method for fabricating the composite coating. The composite coating comprises a polymer layer, a metal interlayer and an amorphous metal coating. The polymer layer is formed on a substrate and acts as a diffusion barrier layer, which is thick and dense enough to prevent the corrosive substances from penetrating into the substrate. The metal interlayer is formed between the polymer layer and the amorphous metal coating for improving the adhesion of the amorphous metal coating to the substrate.