| 摘要 |
PROBLEM TO BE SOLVED: To provide a production method which stably yields a hot-dip galvanized steel sheet which is excellent in stretch-flange formability and is appropriate for an automobile component, etc. SOLUTION: Steel comprising, by mass, 0.04-0.13% C, 0.005-0.7% Si, 1.3-2.5% Mn,≤0.05% P,≤0.01% S, 0.01-0.2% sol. Al,≤0.005% N, 0.005-0.1% Nb, 0.02-0.2% V if required, and the balance substantially being Fe and unavoidable impurities, provided that Nb/(7.75×C) is 0.01-0.2, is melted, subsequently cast, hot-rolled, subsequently pickled, cold-rolled and subsequently annealed at a soaking temperature of≥Ac1 and <900°C. Here, the residence time t (sec) at 600-400°C when cooling to room temperature after soaking is 30≤t≤1,580×Nb/(7.75×C)+134. COPYRIGHT: (C)2005,JPO&NCIPI
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