How to deal with zinc surface defects？

1. Measures to control zinc slag generation:

(1) Control the content of aluminum and iron in zinc liquid.

(2) Control the temperature of zinc liquid. When the temperature of zinc liquid is 480~530℃, the iron loss increases sharply. High temperature also easily oxidizes zinc and zinc aluminum to produce zinc slag. Part of the dissolved iron is taken away by the coating, and the rest is in the form of scum, bottom slag and free slag in the zinc pan. Zinc slag is easy to stick on the surface of strip steel, which affects the surface quality of strip steel. Generally, the temperature of the zinc pan is controlled at (460±3)℃, but when the temperature is too low, the fluidity and wettability of the zinc liquid also affect the surface quality of the strip.

(3) Dregs. In the production of zinc plating, due to the chemical properties of aluminum itself and the temperature of zinc liquid determine the production of zinc slag is inevitable, scum generally adopts the method of dredging slag, we must pay attention to the scum at the outlet of the strip steel in the zinc pot, because the scum here is easy to adhere to the surface of the strip steel.

2. thick edge defect solution:

Adjust the shape of the lip seam of the air knife and increase the injection pressure at the edge of the plate belt. In addition, it is more important that the height of the air knife be adjusted accordingly with the speed of the production line. When the speed of the production line is low, the time for the plate strip to reach the air knife after the zinc pan is longer, the edge of the plate strip is cooled faster in the zinc liquid cooling process, and the zinc liquid begins to solidify, so when it passes through the air knife, the zinc layer on the edge will be thicker. At this time, if the height of the air knife is reduced in time to shorten the zinc liquid cooling time, this problem can be solved. When the production line speed is high, due to the increase of the air knife injection pressure, the zinc liquid splash is also large, and it is easy to block the air knife, so the height of the air knife should be raised in time.

3. air knife streak defect solution:

The operator should not raise or lower the speed of the production line too much, and pay attention to the shape of the incoming plate. If the shape of the plate is poor, the spacing of the air knife should be adjusted in time, and the tension, calibration roll and stabilization roll should be adjusted to make the strip get a good flatness in the middle of the air knife nozzle to prevent the blockage of the strip scraper. If there are gas knife streaks, you can quickly open the gas knife when the weld passes and clean it with special tools.