Nippon Steel& Sumikin Engineering (hereinafter referred to as "NSENGI") has supplied forty-four Hot Dip Continuous Galvanizing Lines (hereinafter referred to as "CGL") all over the world and also NSENGI has been developing the Air knife for Coating machine, it's the key technology of CGL, and improving a product quality and productivity over forty years.This paper presents newly developed Air knife technology which is called "NS blade". In order to clarify the mechanism of zinc splash of strip edge and edge over coating(hereinafter referred to as "EOC") which harm the high speed and thin coating operation, for the first time, experiment with high speed operation has been carried out with the use of several types of Air knife for above harmful phenomenon. As a result, "NS blade" was the most effective as a countermeasure for zinc splash and EOC compared to the results of ordinary type of Air knife. Moreover, the effect is studied with the comparison of the results analysed by numerical simulation. "NS blade" has the position-variable blades inside the acute angle Air knife. The blade inside Air knife interrupts air jet so that air wiping width coincidences with strip width. The position of these blades is controlled suitable to the strip width by Edge Position Controller. As a result, "NS blade" allows air jet to scrape molten zinc off with air consumption reduction, to protect EOC and to reduce zinc splash even at high speed operation and thin coating operation. In addition, air jet noise level is reduced dramatically because there is no impinging jet except strip area. Therefore, "NS blade" enables noise environment-friendly operation for operators in CGL.
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