| 摘要 |
PROBLEM TO BE SOLVED: To provide a steel sheet excellent in peeling resistance and sliding characteristic by regulating Fe content so that it is higher in the outermost surface of a plating layer than in the interface between the plating layer and the steel sheet. SOLUTION: Although the conventional galvannealed steel sheet has a phase structure in which Fe concentration is decreased with the approach to the surface of a plating layer, the galvannealed steel sheet of this invention has a phase structure (ζ-phase,δ-phase, andΓ-phase are successively formed) in which Fe concentration is increased with the approach to the surface of a plating layer. Fe content in the outermost surface of the plating layer is higher than Fe content in the interface between the plating layer and the steel sheet. A Zn phase free from diffusion of Fe is present between theζ-phase and/orδ1 -phase and the steel sheet. A hot dipping layer and an Fe or Fe-Zn alloy plating layer (<=50wt.% Zn content) are present in succession on an Al-Zn plating layer (0.07-0.25wt.% Al content). By this method, the steel sheet, free from surface defects and excellent in external appearance, can be obtained with high efficiency.
|
