| 摘要 |
PROBLEM TO BE SOLVED: To obtain the above Al coated steel sheet without subjecting the steel sheet to coating or coating application of a resin by specifying surface roughness, the number of rugged parts formed on the surface and the variations in color tones. SOLUTION: Dull rolls formed with annular recessed parts having a prescribed diameter, pitch and depth by subjecting to a laser dulling are built into a rolling mill in order the form the annular rugged parts 13 having the prescribed diameter D, pitch S and height H on the Al coated steel sheet 10 by transfer working. The steel sheet consisting of base iron 11 is continuously subjected to surface cleaning and softening and is passed in a hot dip Al coated bath by which molten Al is adhered to its suffice. After the coating is adjusted to a prescribed coating surface density, the coating layer 12 is solidified by cooling. Next, the steel sheet is rolled by the dull rolls described above to transfer and form the rugged parts 13 in a tempering stage. The Al coated steel sheet which is 0.6 to 3μin the surface roughness Ra, >=600 pieces in the number of the many rugged parts 13 formed on the surface and <=3 in the variationΔL of the color tones in the state of non-coating and has the excellent uniformity of the surface color tones is obtd.
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