| 摘要 |
PROBLEM TO BE SOLVED: To produce a galvannealed steel sheet excellent in powdering resis tance by specifying the content of nitrogen to a certain depth from the surface of a plating original sheet of an extra low carbon steel mixed with Ti and Nb. SOLUTION: A steel sheet having a compsn. contg., by weight, <=0.01% C, <=0.01% N and >=0.005% Ti and/or Nb contg., at need, 0.0002 to 0.005% B, and the balance Fe, and in which the average N content to a depth of 10μm from the surface satisfies N>11×(Ti/48-C/12-S/32) by weight ratio is galvanized and is thereafter subjected to alloying treatment. By prescribing the content of N to a depth of 10μm from the surface, the content of solid solution Ti in the vicinity of the surface is suppressed, by which the increase of the thickness of the alloy layer ofΓphases formed in the vicinity of ferrite is suppressed to improve its powdering resistance.
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