A method of shaping an article from a zinc or zinc alloy coated steel blank, including the steps of: a) providing a blank of the zinc or zinc alloy coated steel; b) reheating of the blank obtained in step a) to a reheating temperature T.sub.RH in the range Ac3-200° C. of the steel; c) soaking the blank for a time up to 3 minutes at the reheating temperature T.sub.RH; d) shaping the article in a press; and e) cooling the article. The steel includes (in wt. %) C: 0.01-0.2; Mn: 3.1-9.0; Al: 0.5-3.0; and optionally further alloying elements selected from Si, Cr, V, Nb, Ti and Mo; inevitable impurities and the balance is Fe.

A method for producing a coated steel sheet having a tensile strength TS of at least 1450 MPa and a total elongation TE of at least 17% includes the successive steps of providing a cold rolled steel sheet made of a steel having a chemical composition comprising, in weight %: 0.34%≤C≤0.45%, 1.50%≤Mn≤2.30%, 1.50≤Si≤2.40%, 0%<Cr≤0.7%, 0%≤Mo≤0.3%, 0.10%≤Al≤0.7%, and optionally 0%≤Nb≤0.05%, the remainder being Fe and unavoidable impurities, annealing the cold-rolled steel sheet at an annealing temperature AT higher than the Ac3 transformation point of the steel, quenching the annealed steel sheet by cooling it down to a quenching temperature QT lower than the Ms transformation point of the steel and comprised between 150° C. and 250° C., and reheating the quenched steel sheet to a partitioning temperature PT between 350° C. and 450° C. and maintaining the steel sheet at the partitioning temperature PT for a partitioning time Pt of at least 80 s, and coating the steel sheet by galvannealing, with an alloying temperature GAT comprised between 470° C. and 520° C.

The invention relates to a method for producing a hot-rolled strip composed of a bainitic multi-phase steel and having a Zn—Mg—Al coating, comprising the following steps: melting a steel melt containing (in weight percent): C: 0.04-0.11, Si: <=0.7, Mn: 1.4-2.2, Mo: 0.05-0.5, Al: 0.015-0.1, P: up to 0.02, S: up to 0.01, B: up to 0.006, and at least one element from the group Nb, V, Ti in accordance with the following condition: 0.02<=Nb+V+Ti<=0.20, the remainder being iron including unavoidable steel-accompanying elements resulting from the melting process, casting the steel melt into a preliminary material, in particular a slab or a block or a thin slab, hot rolling the preliminary material into a hot-rolled strip having a final rolling temperature in the range of 800 to 950° C., cooling the hot-rolled strip to a winding temperature less than 650° C., winding the hot-rolled strip at a winding temperature less than 650° C., cooling the wound hot-rolled strip to room temperature in still air, wherein the microstructure of the wound hot-rolled strip then has a bainite fraction greater than 50% after the hot rolling, heating the hot-rolled strip to a temperature greater than 650° C. and less than Ac3, in particular less than Ac1+50° C., cooling the hot-rolled strip to zinc bath temperature, hot-dip coating the heated hot-rolled strip in a zinc alloy molten bath containing (in weight percent): Al: 1.0-2.0, Mg: 1.0-2.0, the remainder being zinc and unavoidable impurities. The invention further relates to the hot-rolled strip produced in accordance with the method above and to shaped, dynamically highly loadable components, in particular motor vehicle parts, that are produced from said hot-roiled strip and that are resistant to corrosive and abrasive influences.

The present invention provides a method for manufacturing more beautiful black coated steel sheets by uniformly blackening the coating layer. Specifically, the present invention provides a method for manufacturing black coated steel sheets, which brings Zn—Al—Mg alloy coated steel sheets (1) into contact with steam in a closed container (10), wherein said closed container (10) can maintain a predefined internal pressure through variable control of the amount of steam flowing into said closed container (10) and/or the amount of steam flowing out of said closed container (10), and in said closed container (10) that can maintain said predefined pressure, said Zn—Al—Mg alloy coated steel sheets (1) have contact with the steam introduced into said closed container (10).

According to one embodiment, a wet-area device includes a main part, a first layer, and a second layer. The first layer is provided on an outer surface of the main part. The second layer is provided on an outer surface of the first layer. A hardness of the second layer is greater than a hardness of the first layer. The first layer includes a first unevenness at a side of the outer surface of the first layer. The first unevenness includes a plurality of recesses and a plurality of protrusions. The second layer includes a second unevenness at a side of an outer surface of the second layer. The second unevenness includes a plurality of recesses and a plurality of protrusions. The second unevenness is arranged along the first unevenness. An average height of the first unevenness is less than an average length of the first unevenness.

The present invention relates to a surface treatment composition comprising, on the basis of 100 wt % of the solid part of the composition, 20-40 wt % of a water-soluble polyurethane resin, 40-60 wt % of a silane-based sol-gel resin in which three types of silane compounds are cross-linked, 5-15 wt % of a curing agent, 0.5-1.5 wt % of a corrosion inhibitor, 0.1-1.0 wt % of a molybdenum-based compound, 1.0-3.0 wt % of a silane coupling agent; 1.0-2.0 wt % of an organometallic complex, 1.0-2.0 wt % of an acid scavenger, 0.1-1.0 wt % of an aluminum-based compound, and 1.0-2.0 wt % of a lubricant. A ternary hot-dip galvannealed steel sheet treated with a chromium-free surface treatment coating agent, according to an exemplary embodiment in the present invention, has excellent resistance to blackening, alkali and corrosion, and provides excellent effects without concern for problems, in chromium treatment, of additional equipment installation, an increase in manufacturing costs and environmental pollution.

A coated steel material including: a base steel, and a coating layer containing a Zn—Al—Mg alloy layer disposed on a surface of the base steel, wherein the coating layer has a predetermined chemical composition, and, in a backscattered electron image of the Zn—Al—Mg alloy layer that is obtained at a time of observing the surface of the Zn—Al—Mg alloy layer after polishing to ½ of the layer thickness, under a scanning electron microscope at a magnification of 100×, Al crystals are present, and the average value of the cumulative circumferential length of the Al crystals is 88 to 195 mm/mm.sup.2.

A method for resistance spot welding comprising the following successive steps: —providing at least two steel sheets with thickness (th) comprised between 0.5 and 3 mm, at least one of the sheets being a zinc or zinc-alloy coated steel sheet (A) with a tensile strength (TS) higher than 800 MPa and a total elongation (TEL) such as (TS)×(TEL)>14000 MPa %, wherein the composition of the steel substrate of (A) contains, in weight: 0.05%≤C≤0.4%, 0.3%≤Mn≤8%, 0.010%≤Al≤3%, 0.010%≤Si≤2.09%, with 0.5%≤(Si+Al)≤3.5%, 0.001%≤Cr≤1.0%, 0.001%≤Mo≤0.5% and optionally: 0.005%≤Nb≤0.1%, 0.005%≤V≤0.2%, 0.005%≤Ti≤0.1%, 0.0003%≤B≤0.005%, 0.001%≤Ni≤1.0%, the remainder being Fe and unavoidable impurities, —performing resistance spot welding of the at least two steel sheets for producing a weld with an indentation depth (IDepth) on the surface of said steel sheet (A) such as: 100 μm≤(IDepth)≤18.68 (Zn.sub.sol)−55.1, wherein (IDepth) is in micrometers and wherein Zn.sub.sol is the solubility of Zn in the steel of sheet (A) at 750° C., in weight %.

The present invention relates to a method for the manufacture of a hot-dip coated steel sheet coated with a zinc or an aluminum based coating including the provision of a specific steel sheet, a recrystallization annealing with specific heating, soaking and cooling sub-steps using an inert gas and a hot-dip coating; the hot dip coated steel sheet and the use of the hot-dip coated steel sheet.

[Object] What is provided is a manufacturing method of a galvannealed steel sheet capable of further promoting alloying of zinc plating with the steel sheet. [Resolution Means] A manufacturing method of a galvannealed steel sheet, including: forming on a surface of a steel sheet after hot rolling and pickling which contains, by mass %, C: 0.001% to 0.350%, Si: 0.001% to 2.500% or P: 0.001% to 0.100%, or combination thereof, Mn: 0.10% to 3.00%, S: 0.001% to 0.010%, N: 0.0010% to 0.0065%, and sol. Al: 0.001% to 0.800% with a remainder being Fe and impurities, grooves having an opening surface width of 10 μm to 25 μm and a depth of 10 μm to 30 μm at intervals of 20 μm to 500 μm; cold rolling the steel sheet at a rolling reduction of 30% or more; reduction annealing the steel sheet after the cold rolling; immersing the steel sheet in a hot-dip galvanizing bath containing 0.10 mass % to 0.20 mass % of Al with a remainder consisting of Zn and optional components, and adhering a hot-dip galvanized layer to the surface of the steel sheet; and heating the steel sheet to which the hot-dip galvanized layer is adhered, and alloying the steel sheet with the hot-dip galvanized layer.