Equipment for the continuous hot dip-coating of a metal strip 9 including an annealing furnace, a tank 2 containing a liquid metal bath 3, a snout connecting the annealing furnace and tank 2, through which the metal strip 9 runs in a protective atmosphere and the lower part of the snout, the sabot 5, is at least partly immersed in the liquid metal bath 3 in order to define with the surface of the bath, and inside this snout, a liquid seal 6, an overflow 7 not connected to the snout, the overflow 7 including at least one tray 8, placed in the vicinity of the strip 9 when entering the liquid metal bath 3 and encompassed by liquid seal 6.

Provided is a method for manufacturing a high-strength galvanized steel sheet. Heating in a first half of oxidizing treatment is performed at a temperature of 400° C. to 750° C. in an atmosphere having a particular O.sub.2 concentration and a particular H.sub.2O concentration, and heating in a second half of the oxidizing treatment is performed at a temperature of 600° C. to 850° C. in an atmosphere having a particular O.sub.2 concentration and a particular H.sub.2O concentration. Subsequently, heating in a heating zone for reduction annealing is performed to a temperature of 650° C. to 900° C. at a particular heating rate in an atmosphere having a particular H.sub.2 concentration and a particular H.sub.2O concentration with the balance being N.sub.2 and inevitable impurities, and soaking in a soaking zone for the reduction annealing is performed in an atmosphere having a particular H.sub.2 concentration and a particular H.sub.2O concentration with the balance being N.sub.2 and inevitable impurities.

An aluminum-based plated steel sheet according to an aspect of the present invention includes: a base material; an aluminum-based plating layer located above the base material; and an intermetallic compound layer that is located between the base material and the aluminum-based plating layer and contains an intermetallic compound of Al and Fe, in which the base material has a chemical component within a predetermined range, the aluminum-based plating layer contains, on average, 80 mass % or more and 97 mass % or less of Al, 3 mass % or more and 15 mass % or less of Si, 0 mass % or more and 5 mass % or less of Zn, 0 mass % or more and 5 mass % or less of Fe, 0 mass % or more and 3 mass % or less in total of one or more selected from the group consisting of Mg and Ca, and impurities so that a total amount thereof is 100 mass %, an average value of a thickness of the intermetallic compound layer is 2 μm or more and 10 μm or less, a maximum value of the thickness of the intermetallic compound layer is 10 μm or more and 25 μm or less, and a standard deviation of the thickness of the intermetallic compound layer is 2 μm or more and 10 μm or less.

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.

Embodiments of the present disclosure provides an aluminum alloy-plated steel sheet having high surface quality and weldability, a hot-formed member, and methods for manufacturing the aluminum alloy-plated steel sheet and the hot-formed member. The aluminum alloy-plated steel sheet includes: a base steel sheet; and an aluminum alloy plating layer formed on the base steel sheet, wherein the aluminum alloy plating layer includes, by weight %, Zn: 21% to 35%, Si: 1% to 6.9%, Fe: 2% to 12%, and the balance of Al and inevitable impurities.

[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.

A method for manufacturing a hot-dip galvanized steel sheet according to one aspect of the present invention includes an annealing step of reduction-annealing a steel sheet having a Si content of 1.0% by mass or more and 3.0% by mass or less at a temperature equal to or higher than an A3 point of the steel sheet in an atmosphere having a dew point of −20° C. or higher; and a hot-dip galvanizing step of making the annealed steel sheet enter into a galvanizing bath to form a galvanized layer on a surface of the steel sheet, wherein a temperature of the steel sheet entering into the galvanizing bath is set to 390° C. or lower.

A plated steel sheet having excellent post-coating corrosion resistance includes: a steel; and a plating layer that is provided on a surface of the steel, in which the plating layer includes, by mass %, Al: 5.00% to 35.00%, Mg: 2.50% to 13.00%, Fe: 5.00% to 35.00%, Si: 0% to 2.00%, Ca: 0% to 2.00%, and a remainder consisting of Zn and impurities, and in a cross section of the plating layer, the area fraction of a Fe.sub.2Al.sub.5 phase is 5.0% to 60.0%, the area fraction of an eutectic structure of Zn and MgZn.sub.2 is 10.0% to 80.0%, the area fraction of a massive MgZn.sub.2 phase is 5.0% to 40.0%, and the area fraction of a remainder is 10.0% or less.

A steel part includes a steel sheet substrate and a coating on at least one surface of the steel sheet substrate. The coating includes between 0.2 and 0.7% by weight of Al, with a remainder of the metal coating being Zn and inevitable impurities. The steel sheet substrate and the coating have at least one deformation. An outer surface of the coating has a waviness Wa.sub.0.8 of less than or equal to 0.43 μm.

A method of forming a coating of an Al—Zn—Si—Mg alloy on a steel strip to form an Al—Zn—Mg—Si coated steel strip is disclosed. The method includes the steps of dipping steel strip into a bath of molten Al—Zn—Si—Mg alloy and forming a coating of the alloy on exposed surfaces of the steel strip and cooling the coated strip with cooling water. The cooling step includes controlling the p H of cooling water to be in a range of pH 5-9. Particular embodiments focus on Al—Zn—Si—Mg alloys that contain the following elements in % by weight: Zn: 2 to 19, Si: 0.01 to 2, Mg: 1 to 10, and Balance Al and unavoidable impurities.