A cold-rolled sheet is provided. The cold-rolled sheet includes a steel substrate with a carbon content C.sub.0 between 0.07% and 0.5%, expressed by weight, and a metal pre-coating on at least the two principal faces of the steel substrate. The substrate has a decarburized area on the surface of each of the two principal faces. The depth p.sub.50% of the decarburized area is between 6 and 30 micrometers, and p.sub.50% is the depth at which the carbon content is equal to 50% of the content C.sub.0. The sheet does not contain a layer of iron oxide between the substrate and the metal pre-coating.

A flat steel product for hot forming may be produced from a steel substrate that includes a steel comprising 0.1-3% by weight Mn and up to 0.01% by weight B, along with a protective coating that is applied to the steel substrate. The protective coating may be based on Al and may contain up to 20% by weight of other alloy elements. Also disclosed are methods for producing such flat steel products, steel components, and methods for producing steel components. Absorption of hydrogen is minimized during heating necessary for hot forming. This is achieved at least in part through an alloy constituent of 0.1-0.5% by weight of at least one alkaline earth or transition metal in the protective coating, wherein an oxide of the alkaline earth or transition metal is formed on an outer surface of the protective coating during hot forming of the flat steel product.

A high strength steel sheet including, by mass, C: 0.03% or more and 0.25% or less, Si: 0.4% or more and 2.5% or less, Mn: 3.5% or more and 10.0% or less, P: 0.1% or less, S: 0.01% or less, Al: 0.01% or more and 2.5% or less, N: 0.008% or less, Si+Al: 1.0% or more, the balance being Fe and inevitable impurities. The area ratio of ferrite is 30% or more and 80% or less, the area ratio of martensite is 0% or more and 17% or less, the volume fraction of retained austenite is 8% or more, and the average grain size of retained austenite is 2 μm or less.

A press hardening method includes the following steps providing a carbon steel sheet coated with a barrier pre-coating including nickel and chromium wherein the weight ratio Ni/Cr is between 1.5 and 9, cutting the sheet to obtain a blank, thermal treatment of the blank in an atmosphere having an oxidizing power equal or higher than that of an atmosphere consisting of 1% by volume of oxygen and equal or smaller than that of an atmosphere consisting of 50% by volume of oxygen, such atmosphere having a dew point between −30 and +30° C., transfer of the blank into a press tool, hot-forming of the blank to obtain a part, cooling of the part to obtain a microstructure in steel being martensitic or martensito-bainitic or made of at least 75 wt. % of equiaxed ferrite, from 5 to 20 wt. % of martensite and bainite in amount less than or equal to 10 wt. %.

Disclosed is a hot-dip Al—Zn alloy coated steel sheet having excellent anti-corrosion property after coating, and a method for producing the same. In the disclosure, the hot-dip Al—Zn alloy coated steel sheet has a hot-dip coating layer containing by mass %, Al: 25% to 90%, and at least one of Sn: 0.01% to 2.0%, In: 0.01% to 10%, and Bi: 0.01% to 2.0%.

The present invention provides an iron-aluminum-based plated steel sheet, and a manufacturing method therefor, the iron-aluminum-based plated steel sheet comprising a base steel sheet and a plated layer formed on the surface of the base steel sheet, wherein the alloy plated layer comprises: a diffusion layer comprising an Fe—Al-based intermetallic compound having a cubic structure; and an alloyed layer formed on the diffusion layer and composed of an alloy phase differing from that of the cubic structure, the thickness of the diffusion layer is 3-20 μm, and the thickness of the diffusion layer is greater than 50% of the total thickness of the plated layer.

A steel for high-strength aluminum clad substrate, comprising the following chemical elements by mass percent: C: 0.008-0.02%, 0<Si≤0.005%, Mn: 0.25-0.5%, P: 0.018-0.03%, Al≤0.005%, N: 0.0040-0.010%, Ti: 0.02-0.04%, O: 0.02-0.050%, and the balance being Fe and other inevitable impurities. The manufacturing method therefor comprises the steps of: (1) smelting and casting; (2) reheating: reheating a casting blank to 1180° C.-1250° C.; (3) rough rolling; (4) finish rolling; (5) coiling; and (6) cooling to room temperature. The steel for high-strength aluminum clad substrate has good strength and good plasticity.

A method for manufacturing a sheet metal component including: annealing a flat steel product comprising 0.05-0.5% C, 0.5-3% Mn, 0.06-1.7% Si, ≤0.06% P, ≤0.01% S, ≤1.0% Al, ≤0.15% Ti, ≤0.6% Nb, ≤0.01% B, ≤1.0% Cr, ≤1.0% Mo, ≤1.0% Cr+Mo, ≤0.2% Ca, ≤0.1% V, remainder iron and impurities in a continuous furnace under an atmosphere consisting of 0.1-15% hydrogen and remainder nitrogen with a specific dew point and temperature profile; applying a coating consisting of ≤15% Si, ≤5% Fe, in total 0.1-5% of at least one alkaline earth or transition metal and a remainder Al and unavoidable impurities; heating the fat steel product to >Ac3 and ≤1000° C. for a time sufficient to introduce a heat energy quantity>100,000-800,000 kJs; hot-forming the flat steel product to form the component; and cooling at least one section of the component at a cooling rate sufficient to generate hardening structures.

Disclosed is a steel sheet for hot press forming, which includes: a base steel sheet; and a plating layer disposed on the base steel sheet and including a diffusion layer and a surface layer that are sequentially laminated, wherein the diffusion layer includes an Fe—Al alloy layer and an Fe—Al intermetallic compound layer that are sequentially disposed on the base steel sheet and each include silicon, and an area fraction of the Fe—Al intermetallic compound layer with respect to the diffusion layer is 84.5% to 98.0%.

A painted steel part includes a steel sheet precoated with a metallic coating and hot formed, the coating including: 2.0 to 24.0% by weight of zinc; 1.1 to 7.0% by weight of silicon; optionally from 0.5 to 3.0% by weight of magnesium when the amount of silicon is between 1.1 and 4.0%, and optionally additional elements chosen from Pb, Ni, Zr or Hf, a content by weight of each additional element being less than 0.3% by weight, a balance being aluminum, unavoidable impurities and residual elements resulting from feeding ingots or from a passage of the steel sheet in a molten bath; and a ratio Al/Zn by weight greater than 2.9; and a paint layer.