| 摘要 |
PROBLEM TO BE SOLVED: To obtain an aluminum-zinc plated steel sheet having spangles of uniform size and free from unevenness and excellent in external surface appearance by regulating the spangle pattern on a plating surface by means of the center line height of surface roughness of a steel sheet before plating. SOLUTION: In a method of plating a steel sheet with an alloy having a composition consisting of, by weight, 25-70% aluminum, silicon in an amount not smaller than 0.5% of aluminum content, and the balance zinc, the spangle pattern of a plating surface is regulated by the surface roughness of the steel sheet before plating and a plating layer of >=1.8mm average grain size of spangle is formed on the steel sheet having a surface roughness of >=0.5μm center line average height Ra. As a method for regulating the surface roughness of the starting sheet for plating, a method where the surface characteristic of a rolling roll, treated by grinding, shot blasting, electric-discharge machining, laser-beam machining, etc., is transferred to the steel sheet, a method where surface roughness is applied to the steel sheet itself by similar treatment, etc., are preferred.
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