| 摘要 |
PROBLEM TO BE SOLVED: To clarify the structure of plated steel having the highest corrosion resistance in a Zn-Al-Mg plated layer and to provide the plated steel. SOLUTION: (1) As to this hot dip Zn-Al-Mg-Si plated steel excellent in the corrosion resistance of the uncoated part and coated edge face parts, in hot dip plating containing, by mass, 5 to 15% Al, 1 to 10% Mg and 0.01 to 1% Si and, if required, containing Pb, Ti, Mn, Sn and Ni by 0.01 to 2%, and the balance Zn with unavoidable impurities, an Al phase in which the length of the primary arms of dendrite structure of dendrite crystal precipitates is >=50μm and grown so as to form an angle of <=45 degrees in the direction of the surface layer of the plating is contained in the plated layer. (2) Further, the steel has a metallic structure in which the Al phase described in the (1) coexists in a ternary eutectic structure composed of Zn, Al and Zn2Mg and/or Mg2Si crystal precipitates with a crystal grain size of <=30μm are present in the plated layer.
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