| 摘要 |
PROBLEM TO BE SOLVED: To provide a galvannealed steel sheet having excellent slidability during the press-forming, excellent chemical conversion property, and excellent adaptability to a sub material. SOLUTION: An oxide layer having a Zn-OH bond and a Zn-SO<SB>4</SB>bond with the mean thickness of≥10 nm is deposited on a flat part surface layer of a plated steel sheet. Excellent slidability can be obtained consistently by uniformly depositing such an oxide layer. Further, even in the press-forming in which a contact area of a die with a work is increased with this thickness, the oxide layer on the surface layer is remained even when it is worn, and the slidability is not degraded. The oxide layer is readily soluble irrespective of the pH value of aqueous solution since the Zn-O<SB>4</SB>bond is present, and the dissolution rate is high. Thus, the etching effect of the outermost layer of the steel sheet by an alkali builder is sufficiently demonstrated, and degreasability is also enhanced. COPYRIGHT: (C)2007,JPO&INPIT
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