A method for applying a metallic protective coating to a surface of a steel product, where another surface is to remain free from the metallic protective coating, may involve applying the metallic protective coating by hot dip coating in a hot dip coating bath. A preliminary coating may be applied to the surface that is to remain free from the metallic protective coating prior to the hot dip coating. The preliminary coating may include SiO.sub.2 and may prevent the metallic protective coating from adhering to the intended surface during hot dip coating. Thus one surface of a steel product may be provided with a metallic protective coating, and another surface of the steel product may be kept free from the protective coating, all with a minimum of cost and complexity and with optimized resource economics. Further, the preliminary coating, deposited from a gas phase to that surface of the steel product that is to be kept free from the metallic protective coating, may be a layer that includes amorphous silicon dioxide and has a layer thickness of 0.5-500 nm.”

A method for applying a metallic protective coating to a surface of a steel product, where another surface is to remain free from the metallic protective coating, may involve applying the metallic protective coating by hot dip coating in a hot dip coating bath. A preliminary coating may be applied to the surface that is to remain free from the metallic protective coating prior to the hot dip coating. The preliminary coating may include SiO.sub.2 and may prevent the metallic protective coating from adhering to the intended surface during hot dip coating. Thus one surface of a steel product may be provided with a metallic protective coating, and another surface of the steel product may be kept free from the protective coating, all with a minimum of cost and complexity and with optimized resource economics. Further, the preliminary coating, deposited from a gas phase to that surface of the steel product that is to be kept free from the metallic protective coating, may be a layer that includes amorphous silicon dioxide and has a layer thickness of 0.5-500 nm.”

Disclosed herein is a high-strength plated steel sheet having a plated layer on the surface of a base steel sheet and containing predetermined steel components. The steel sheet includes, in the order from the interface of the base steel sheet and the plated layer towards the base steel sheet: a soft layer having a Vickers hardness that is 90% or less of the Vickers hardness at a portion t/4 of the base steel sheet, where t is a sheet thickness of the base steel sheet; and a hard layer consisting of a structure which is mainly composed of martensite and bainite and in which the average grain size of prior austenite is 20 μm or less. The average depth D of the soft layer is 20 μm or greater, and the average depth d of an internal oxide layer is 4 μm or greater and smaller than D.

Disclosed herein is a high-strength plated steel sheet having a plated layer on the surface of a base steel sheet and containing predetermined steel components. The steel sheet includes, in the order from the interface of the base steel sheet and the plated layer towards the base steel sheet: a soft layer having a Vickers hardness that is 90% or less of the Vickers hardness at a portion t/4 of the base steel sheet, where t is a sheet thickness of the base steel sheet; and a hard layer consisting of a structure which is mainly composed of martensite and bainite and in which the average grain size of prior austenite is 20 μm or less. The average depth D of the soft layer is 20 μm or greater, and the average depth d of an internal oxide layer is 4 μm or greater and smaller than D.

The high-strength plated steel sheet of the present invention has a plated layer on the surface of a base steel sheet and contains predetermined steel components. The steel sheet includes, in the order from the interface of the base steel sheet and the plated layer towards the base steel sheet: a soft layer having a Vickers hardness that is 90% or less of the Vickers hardness at a portion t/4 of the base steel sheet, where t is a sheet thickness of the base steel sheet: and a hard layer containing martensite, bainite, and ferrite in predetermined ranges. The average depth D of the soft layer is 20 μm or greater, and the average depth d of an internal oxide layer is 4 μm or greater and smaller than D.

The high-strength plated steel sheet of the present invention has a plated layer on the surface of a base steel sheet and contains predetermined steel components. The steel sheet includes, in the order from the interface of the base steel sheet and the plated layer towards the base steel sheet: a soft layer having a Vickers hardness that is 90% or less of the Vickers hardness at a portion t/4 of the base steel sheet, where t is a sheet thickness of the base steel sheet: and a hard layer containing martensite, bainite, and ferrite in predetermined ranges. The average depth D of the soft layer is 20 μm or greater, and the average depth d of an internal oxide layer is 4 μm or greater and smaller than D.

The present invention relates to an apparatus for removing top dross of a plating pot where a snout and an air knife are arranged, the snout being arranged between the front end region and the rear end region of a plating pot. The present invention provides an apparatus for removing top dross of a plating pot, the apparatus comprising: a first wiping means which is mounted on the plating pot and is arranged between the snout and the air knife so as to be movable in the width direction of the plating pot; a second wiping means which is mounted on the plating pot and is rotatably arranged between the air knife and the first wiping means so as to transfer, to the rear end region, the top dross transferred by the first wiping means; and a third wiping means which is mounted on the plating pot and is rotatably arranged between the air knife and the front end region so as to transfer the top dross to the front end region. Thereby, the present invention provides an advantageous effect of effectively removing dross.

The present invention relates to an apparatus for removing top dross of a plating pot where a snout and an air knife are arranged, the snout being arranged between the front end region and the rear end region of a plating pot. The present invention provides an apparatus for removing top dross of a plating pot, the apparatus comprising: a first wiping means which is mounted on the plating pot and is arranged between the snout and the air knife so as to be movable in the width direction of the plating pot; a second wiping means which is mounted on the plating pot and is rotatably arranged between the air knife and the first wiping means so as to transfer, to the rear end region, the top dross transferred by the first wiping means; and a third wiping means which is mounted on the plating pot and is rotatably arranged between the air knife and the front end region so as to transfer the top dross to the front end region. Thereby, the present invention provides an advantageous effect of effectively removing dross.

A hot-rolled strip steel product is described having a chemical composition consisting of, in terms of weight percentages (wt. %): 0.030%-0.10% C, 0%-1.10% Si, 0.50%-2.0% Mn, <0.020% P, <0.010% S,<0.010% N, 0%-0.60% Cr, 0%-0.20% Ni, 0%-0.25% Cu, 0%-0.30% Mo, 0%-0.15% Al, 0%-0.10% Nb, 0.10%-0.30% V, <0.020% Ti, 0%-0.0010% B, remainder being Fe and inevitable impurities, wherein the hot rolled strip steel product has a a microstructure comprising, in terms of volume percentages (vol. %), ferrite≥90, wherein the ferrite structure comprises bainite, at least 50% of polygonal ferrite and at most 10% quasi-polygonal ferrite, and wherein the steel strip product has an average hole expansion ratio≥50%, a yield strength (Rp0.2%) longitudinal to rolling direction of ≥660 MPa and a tensile strength≥760 MPa.

Method of hot press forming an article from zinc or zinc alloy coated steel, wherein the steel is a product obtained by: casting the molten steel into slabs; reheating the slabs; hot rolling the steel into a strip, preferably with an FRT above Ar3; coiling the hot rolled steel strip; pickling the hot rolled steel strip; continuous annealing the strip; hot dip coating the steel strip with the zinc or zinc alloy whilst: using a dipping time of 3 seconds or more; maintaining in the hot dip bath a bath temperature of 420° C. to 500° C.; wherein the zinc bath contains essentially zinc, at least 0.1% Al, and optionally up to 5% Al and optionally up to 4% Mg, the rest of the bath including further elements all individually less than 0.3%, and unavoidable impurities; hot press forming the article.