Abstract: Provided is a technique that can produce a hot dip Zn—Al—Mg-based alloy coated steel product with a good plating appearance, without the need for heating of a steel product prior to immersion in a hot dip plating bath. Flux (11) for hot dip Zn—Al—Mg-based alloy plating contains: ZnCl2; and a low-reactive chloride which has low reactivity with respect to Mg in a plating bath and contains at least two chlorides selected from the compound group consisting of alkali metal chlorides and alkaline-earth metal chlorides, and a composition of the ZnCl2 and the low-reactive chloride is adjusted so that a liquidus temperature of the flux is 450° C. or lower.

Abstract: Provided is a hot-dip aluminized steel sheet with fine-sized spangles produced in a different way from conventional methods, and a method of producing a hot-dip aluminized steel sheet with fine-sized spangles in a different way from conventional methods. The hot-dip aluminized steel sheet includes: a substrate steel sheet; and an aluminum-based coating which is formed by a hot-dip method on the surface of the substrate steel sheet and in which the average B concentration is not less than 0.005 mass % and the sum of the average Ti concentration and the average V concentration is not more than 0.03 mass %.

Abstract: A hot-dip coating equipment includes a cooling rate determining device that includes: a coefficient obtaining section configured to obtain coefficients ?, ?, ?, and ? associated with the hot-dip coating bath, in the following equation that expresses a degree of discoloration YI of the surface of a hot-dip coated steel sheet; and a rate determining section configured to determine an average cooling rate A so as to allow the YI of the following Expression (1) to be not more than a predetermined reference value, YI =(?×[SE]+?)×{(T?ST)/A}1/2+?×[SE]+? . . . (1), where: [SE] is a concentration (mass %) of a specific element contained in the hot-dip coating bath; T is a temperature (° C.) of the hot-dip coating bath; and ST is a solidification temperature (° C.) at which the hot-dip coating bath is solidified.

Abstract: Provided is a method for producing a hot-dip Al-based metal-plated steel sheet including a plated layer having a surface on which fine spangle are stably formed. A method for producing a hot-dip Al-based metal-plated steel sheet, includes a composition adjusting step of adding a B-containing master alloy so as to adjust a composition of an Al-based hot-dip plating bath (3) containing aluminum as a main component, the composition being adjusted so that the Al-based hot-dip plating bath has a B concentration of not less than 0.005 mass % and a K concentration of more than 0 mass % and less than 0.0005 mass %, the K concentration being reduced in the Al-based hot-dip plating bath by supplying gas into the Al-based hot-dip plating bath so as to remove a suspended matter on a surface of the Al-based hot-dip plating bath.

Abstract: Provided is a hot-dip aluminized steel sheet with fine-sized spangles produced in a different way from conventional methods, and a method of producing a hot-dip aluminized steel sheet with fine-sized spangles in a different way from conventional methods. The hot-dip aluminized steel sheet includes: a substrate steel sheet; and an aluminum-based coating which is formed by a hot-dip method on the surface of the substrate steel sheet and in which the average B concentration is not less than 0.005 mass % and the sum of the average Ti concentration and the average V concentration is not more than 0.03 mass %.

Abstract: Provided is (i) a hot-dip Al-based alloy-coated steel sheet which includes a coated layer having a surface on which fine spangles are stably and sufficiently formed and which has a beautiful surface appearance due to the fine spangles thus formed on the surface of the coated layer, and (ii) a method of producing such a hot-dip Al-based alloy-coated steel sheet. The hot-dip Al-based alloy-coated steel sheet includes: a substrate steel sheet; and a hot-dip aluminum-based alloy coated layer which is formed on a surface of the substrate steel sheet and which contains boron at an average concentration of not less than 0.005 mass % and contains potassium at an average concentration of not less than 0.0004 mass %.

Abstract: A problem to be solved by the present invention is to prevent discoloration of a surface of a hot-dip coated steel sheet after hot-dip coating. A cooling rate determining device includes: a coefficient obtaining section configured to obtain coefficients ?, ?, ?, and ? associated with the hot-dip coating bath, in the following Expression (1) which expresses a degree of discoloration YI of the surface of a hot-dip coated steel sheet; and a rate determining section configured to determine an average cooling rate A so as to allow the YI of the following Expression (1) to be not more than a predetermined reference value, YI=(?×[SE]+?)×{(T?ST)/A}1/2+?×[SE]+???(1), where: [SE] is a concentration (mass %) of a specific element contained in the hot-dip coating bath; T is a temperature (° C.) of the hot-dip coating bath; and ST is a solidification temperature (° C.) at which the hot-dip coating bath is solidified.

Abstract: Provided is (i) a hot-dip Al-based alloy-coated steel sheet which includes a coated layer having a surface on which fine spangles are stably and sufficiently formed and which has a beautiful surface appearance due to the fine spangles thus formed on the surface of the coated layer, and (ii) a method of producing such a hot-dip Al-based alloy-coated steel sheet. The hot-dip Al-based alloy-coated steel sheet includes: a substrate steel sheet; and a hot-dip aluminum-based alloy coated layer which is formed on a surface of the substrate steel sheet and which contains boron at an average concentration of not less than 0.005 mass % and contains potassium at an average concentration of not less than 0.0004 mass %.

Abstract: Provided is (i) a hot-dip Al-based alloy-coated steel sheet which includes a coated layer having a surface on which fine spangles are stably and sufficiently formed and which has a beautiful surface appearance due to the fine spangles thus formed on the surface of the coated layer, and (ii) a method of producing such a hot-dip Al-based alloy-coated steel sheet. The hot-dip Al-based alloy-coated steel sheet includes: a substrate steel sheet; and a hot-dip aluminum-based alloy coated layer which is formed on a surface of the substrate steel sheet and which contains boron at an average concentration of not less than 0.005 mass % and contains potassium at an average concentration of not less than 0.0004 mass %.