To produce a high quality hot-dip galvanized steel sheet by quickly precipitating and separating dross generated in molten zinc into the bottom part of a hot-dip galvanizing vessel, cleaning the plating bath and coating in the clean plating bath when the hot-dip galvanized steel sheet is produced.
When the hot-dip galvanized steel sheet is produced, the portion for holding the plating bath, is divided into a plating portion for plating on the steel sheet and a dross precipitating portion for precipitating the dross in the plating bath, and the plating liquid in the plating bath is circulated between the plating portion and the dross precipitating portion. Further, a staying time of the plating bath in the dross precipitating portion, is made to ≥1 hr. The dross, with which the surface quality of the steel sheet is deteriorated at the dross precipitating portion in the plating bath, is surely removed and the plating bath at the plating portion is made to clean.
MIYAGAWA YOICHI
SAKURAI MICHITAKA
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