| 摘要 |
PROBLEM TO BE SOLVED: To improve the low temp. chipping resistance of a steel sheet and to furthermore improve its resistance to powdering and flaking by composing a plating film substantially of theδ1 , single phase and providing the surface with the specified number of cracks. SOLUTION: The plated film is substantially composed of theσ1 single phase through, partially, the other phase is contained on the base metal, and the amt. is preferably regulated to >=80 wt.%. For forming this plating film, at first, it is rapidly cooled to >=500 deg.C, preferably, at >=20 deg.C/sec. After that, it is rapidly cooled to 420 deg.C, preferably, at >=10 deg.C/sec. In this way, the plated film substantially composed of theδ1 phase is obtd., and into which, cracks are introduced by >=10 pieces per mm. For forming the cracks, the method of mechanically applying strains to the steel sheet is used. Concretely, the application of the strains by mechanical elongation is regulated to 0.4 to 2.0%, and as the applying means, skinpass rolling by, a tension leveller or the like are utilized.
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