| 摘要 |
To stably manufacture a high-quality molten metal plated steel strip while splashes caused in use of a gas wiping nozzle for controlling the plating amount is prevented. A gas wiping nozzle is used which includes a primary nozzle portion and at least one secondary nozzle portion provided either or both above and below the primary nozzle portion. The secondary nozzle portion jets a gas in a direction tilted from the direction in which the primary nozzle portion jets the gas, and the secondary nozzle portion jets the gas at a lower flow rate than the primary nozzle portion. The gas wiping nozzle has a tip whose lower surface forms an angle of 60° or more with the steel strip. By jetting a gas from the secondary nozzle portion at predetermined conditions, the gas jet can scrape molten metal effectively. By controlling the angle between the lower surface of the gas wiping nozzle and the steel strip, the plating can be scraped more effectively. Thus, the molten metal can be appropriately scraped without excessively increasing the gas pressure. Consequently, splashes can be reduced. Furthermore, the gas jetting port of the secondary nozzle portion is displaced in the direction opposite to the steel strip at least 5 mm apart from the gas jetting port of the primary nozzle portion, and the secondary nozzle portion jets the gas so that the flow rate of the secondary gas jet comes to 10 m/s or more at the confluence with the primary gas jet from the primary nozzle portion.
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