1. Measures to prevent wrinkling of zinc pot
When strip steel is galvanized in a zinc pot, the wave pattern of "zinc pot folds" often appears on the surface of the coating. This is mainly due to the air knife flow and the irregular flow of zinc solution in the coating, resulting in small strip vibration. By appropriately controlling the wiping pressure of the air knife wiping conditions, the distance from the nozzle to the steel, and the height of the nozzle to the zinc liquid surface, the "zinc wrinkle" pattern can be effectively prevented.
2. Measures to prevent zinc flower formation
In order to ensure the appearance of painted steel plates for automobiles, it is necessary to use galvanized steel plates with the smallest zinc flowers (very thin zinc flower patterns). The size of the zinc flower increases with the increase of the mass concentration of lead and antimony in the zinc solution, and decreases with the solidification rate of the zinc coating. After the surface of the conventional GI steel plate is corroded by the Cu2SO4 aqueous solution, the size of the zinc flower should be controlled, the lead content in the zinc liquid should be reduced to the lower limit, and the cooling rate above the zinc pot should be controlled to produce a small zinc flower steel plate. In addition, in large-scale continuous hot-dip galvanizing production line of steel strip, fine zinc flower can also be obtained by spraying water vapor or water-air mixture on the liquid zinc layer.
3. Measures to prevent the adhesion of zinc slag
1) Control the content of aluminum and iron in the zinc solution.
The effective aluminum content must be controlled to control the aluminum content in the zinc pot, and the iron content in the zinc solution must also be controlled so that the iron content in the zinc solution is less than 0.03% of the solubility of iron in the zinc solution.
2) Control of zinc liquid temperature.
When the zinc solution temperature is in the range of 480 ~ 530 ℃, the iron loss will increase sharply. In addition, excessively high temperature will also cause zinc and aluminum in zinc to oxidize themselves to produce zinc slag. The temperature of the zinc pot is generally controlled at 460±3℃.
3) Dredging slag.
In the production of galvanizing, the generation of zinc slag is inevitable. The main component of bottom slag is FeZn7, and the main component of scum is Fe2Al5. In general, the removal of bottom slag does not use the method of capturing slag, but uses chemical methods to convert it into scum. The dross is usually removed. It must be noted that the dross is removed at the steel strip outlet of the zinc pot, because the dross here is easy to adhere to the surface of the steel strip.
4) Double zinc pot is used.
In order to avoid the surface defects caused by the dross sticking to the surface of the strip steel, a zinc pot can be installed on the CGL unit, so that a special zinc pot can be used to produce gallium plates and germanium plates, and the amount of zinc slag generated after the zinc liquid is switched to At the lowest, the production of germanium can be carried out under the condition of stable zinc liquid, which can reduce the number of zinc slag spots attached to the surface of the germanium plate, and can produce a germanium plate with excellent appearance quality.
