| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for stably producing an undercoated hot-dip galvanized IF steel sheet good in surface appearance, free from linear marks, having high strength, excellent in plating uniformity and moreover excellent in adhesion and an IF undercoated galvannealed IF steel sheet furthermore free from unevenness in alloying and excellent in powdering resistance. SOLUTION: At the time of galvanizing IF steel having a compsn. contg., by weight, &h100 ppm C, and in which at least C and N are precipitately fixed by Ti or Nb, one or >= two kinds selected from a carbon compd., a nitrogen compd. and a boron compd. are adhered to the surface of the steel sheet by 0.1 to 1000 mg/m<2> as the contents of C, B and N, after that, it is annealed in a nonoxidizing atmosphere, is thereafter immersed in a hot-dip zinc bath contg. at least 0.05 to 0.30% Al and is applied with plating.
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