| 摘要 |
PROBLEM TO BE SOLVED: To stably produce a thinly galvanized steel sheet, at the time of galva nizing a cold rolled steel sheet in a continuous galvanizing line, by regulating the concn. of Al in a galvanizing bath and the impregnating sheet temp. of the steel sheet into the plating bath. SOLUTION: A cold rolled sheet of a dead soft steel having a compsn. contg., by weight, 0.001 to 0.0035% C, <0.10% Si, 0.08 to 2.5% Mn, 0.005 to 0.15% P, 0.001 to 0.02% Si, 0.005 to 0.1% sol.Al, <0.035% N and 0.03 to 0.15% Ti and contg., at need, <0.0035% B is annealed at the Ac3 point or below in a continuous galvanizing line and is cooled to T deg.C (350 deg.C). Next, it is immersed into a galvanizing bath contg. Al. In this case, the content of Al and the immersing temp. T deg.C satisfy the inequalities (1), (2) and (3). An initial alloy layer composed of fineζphases is formed on the surface of the steel sheet, thereafter, it is pulled up from the zinc bath, and the coating weight of the hot-dip zinc is regulated to a small amt. of <=40g/m<2> by a gas wiping method or the like, by which the thinly galvanized steel sheet is produced with a high productivity.
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