Hot-dip Al-plated steel sheet and method for producing same
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 %.
1. A hot-dip aluminum-based alloy-coated steel sheet, comprising:
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 not more than 3.0 mass % and contains potassium at an average concentration of not less than 0.0004 mass % and not more than 0.02 mass %,
wherein not less than 100 spangle crystal nuclei are present on a surface of the hot-dip aluminum-based alloy coated layer per square centimeter surface area of the hot-dip aluminum-based alloy coated layer.
2. The hot-dip aluminum-based alloy-coated steel sheet as set forth in claim 1 , wherein the hot-dip aluminum-based alloy coated layer contains boron at an average concentration of not less than 0.02 mass % and not more than 3.0 mass % and contains potassium at an average concentration of not less than 0.0008 mass % and not more than 0.02 mass %.
3. A method of producing a hot-dip aluminum-based alloy-coated steel sheet according to claim 1 , comprising:
a coating step of dipping a substrate steel sheet in a hot-dip aluminum-based alloy-coating bath which contains aluminum as a main component,
the hot-dip aluminum-based alloy-coating bath containing boron at a concentration of not less than 0.005 mass % and not more than 3.0 mass % and containing potassium at a concentration of not less than 0.0004 mass % and not more than 0.02 mass %.
4. The method as set forth in claim 3 , wherein the hot-dip aluminum-based alloy-coating bath contains boron at a concentration of not less than 0.02 mass % and not more than 3.0 mass % and contains potassium at a concentration of not less than 0.0008 mass % and not more than 0.02 mass %.
5. The method as set forth in claim 4 , further comprising:
a composition adjusting step of adjusting a composition of the hot-dip aluminum-based alloy-coating bath,
the composition adjusting step including adding an aluminum master alloy containing boron and potassium.
6. The method as set forth in claim 3 , further comprising:
a composition adjusting step of adjusting a composition of the hot-dip aluminum-based alloy-coating bath,
the composition adjusting step including adding an aluminum master alloy containing boron and potassium.