| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for stably producing a galvannealed steel sheet having excellent slidability upon press forming, and exhibiting satisfactory degreasing properties in alkaline degreasing treatment performed before chemical conversion treatment, and to provide the galvannealed steel sheet. SOLUTION: A steel sheet is galvanized, is galvannealed by a heating treatment, is subjected to skinpass rolling, and is made in contact with an acid solution. After the completion of the contact, the steel sheet is let to alone for 1 to 30 sec, and is washed with water, thus a Zn based oxide layer of≥10 nm is formed on the surface of the galvanized steel sheet. Thus, the galvannealed steel sheet in which the average thickness of the oxide layer in the surface layer of the flat part in the plated steel sheet is≥10 nm, and also, the oxide layer comprises Zn and P as essential components can be obtained. Further, the concentration of P in the acid solution is preferably 0.05 to 0.8 mol/l. COPYRIGHT: (C)2007,JPO&INPIT
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