| 摘要 |
PROBLEM TO BE SOLVED: To obtain a steel sheet excellent in blackening resistance without deteriorating the good corrosion resistance and workability of a regular spangle article by specifying the contents of Al, Pb, Sb and Sn in a galvanizing layer and specifying the orientation properties of the Zn crystals in the surface of the plating layer. SOLUTION: A steel sheet as a base material is heated at 600 to 900 deg.C in a reducing atmosphere having -30 deg.C dew point. Next, it is cooled to 480 to 450 deg.C in a reducing atmosphere having -30 to -60 deg.C dew point. Then, it is dipped into a hot dip galvanizing bath contg., by weight, 0.10 to 0.35% Al and one or more kinds among Pb, Sb and Sn by 0.05 to 0.20% in total, is cooled and is thereafter subjected to chromate treatment. The orientation properties in the (00.2) plane of the Zn crystals in the surface of the plating layer are controlled to >=3 as the index of orientation properties M. The index M of orientation properties is obtd. by M=IF(00.2)/IFR(00.2) (wherein, IF(00.2) is the X-ray diffraction integrated intensity ratio in the (00.2) plane; and IFR(00.2) is the X-ray diffraction integrated intensity ratio in the (00.2) plane of a Zn sample in the random orientation).
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