| 摘要 |
PROBLEM TO BE SOLVED: To provide a production technique where, in continuous annealing for a thin, wide, soft, and delayed-aging surface-treated steel sheet for a vessel, stable annealing is made possible without causing a buckle in a furnace, and to provide a surface-treated steel sheet for a vessel. SOLUTION: A steel slab having a composition comprising, by mass, 0.015 to 0.08% C,≤0.05% Si, 0.05 to 0.6% Mn,≤0.04% P,≤0.02% S,≤0.04% sol.Al,≤0.006% N and 0.003 to 0.008% B, and the balance Fe with inevitable impurities is subjected to hot rolling, pickling and cold rolling, so as to be a cold rolled steel sheet. The cold rolled steel sheet is subjected to continuous annealing in such a manner that the sheet temperature is controlled to the range of from a recrystallization temperature to 660°C, also, the time to the start of primary cooling is controlled to≤0.9 s, also, the sheet temperature upon the start of the cooling is controlled to the range of a recrystallization temperature to 660°C, also, the primary cooling velocity is controlled to≥100°C/s, and, next, overaging treatment at 300 to 450°C for≥30 s and secondary cooling are performed in an overaging treatment furnace, and is subjected to skin pass rolling at a draft of 0.5 to 3%. COPYRIGHT: (C)2008,JPO&INPIT
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