| 摘要 |
PROBLEM TO BE SOLVED: To provide a galvannealed steel sheet having excellent slidability during the press-forming, and excellent chemical conversion property. SOLUTION: An oxide layer having a Zn-OH 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 the steel sheet is worn, and the slidability is not degraded. In addition, by removing simple oxides such as ZnO and FeO and hydroxide such as Fe(OH)<SB>2</SB>from the oxide layer as much as possible, non-uniform formation of chemical conversion crystals and a large number of scales can be prevented. COPYRIGHT: (C)2007,JPO&INPIT
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