| 摘要 |
PROBLEM TO BE SOLVED: To improve the plating adhesion of a plating layer and the uniformity of the appearance by forming a plating layer contg. Cu, Al and Fe, moreover contg., at need, Mg and Zn or Cu and Al and contg., at need, Mg and Zn, on a steel sheet by hot dip galvanizing. SOLUTION: The compsn. of a plating layer of a hot dip galvanized steel sheet is, by weight, 0.002 to 2.5% Cu, 0.05 to 0.2% Al and 5 to 13% Fe, furthermore contg., at need, 0.1 to 3% Mg, and the balance Zn, or the one contg. 0.002 to 2.5% Cu and 0.05 to 70% Al, further contg., at need, 0.1 to 10% Mg, and the balance Zn. This plating is executed in such a manner that the surface of a steel sheet is previously provided with Cu coating by substitution plating by a dipping method, which is subjected to reducing treatment, is thereafter applied with hot dip galvanizing at a prescribed temp. in a Zn-Al bath or in a Zn-Al-Mg bath and is, if required, subjected to alloying treatment of Fe as well. At this time, the coating weight of the plating is desirably controlled to about 10 to 150 g/m2.
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