Brucite: specific use of magnesium oxide

After decarburization annealing of oriented silicon steel in continuous furnace, magnesium oxide coating solution needs to be evenly coated on the upper and lower surfaces of the strip steel. Magnesium oxide mainly acts as an isolating agent to prevent the adhesion of strip steel during high-temperature annealing. At the same time, it can remove nitrogen, sulfur and other impurities in steel. In addition, it also reacts with silicon dioxide on the surface of silicon steel to form an excellent magnesium silicate insulating bottom layer. Therefore, the coating quality of magnesium oxide coating solution on the surface of oriented silicon steel plays an important role in the quality of silicon steel products.


At present, magnesium oxide coating solution is coated by two roll coating machine. The two roll coating machine comprises an upper coating roll, a lower coating roll, a tray, a magnesium oxide coating liquid circulation device, and a nozzle for spraying the magnesium oxide coating liquid in the magnesium oxide coating liquid circulation device to the upper surface of the strip steel; The lower coating roller is immersed in the tray, and the magnesium oxide coating liquid sprayed on the upper surface of the strip steel by the nozzle overflows and enters the tray. The lower coating roller uses the magnesium oxide coating liquid in the tray to coat the lower surface of the strip steel.


However, due to the poor flow of magnesium oxide solution in the tray during the recycling of magnesium oxide coating solution, magnesium oxide reacts with water to form magnesium hydroxide precipitation, and magnesium hydroxide combines with carbon dioxide in the air to form magnesium carbonate which is easy to precipitate. Magnesium carbonate and magnesium hydroxide have poor fluidity and are prone to agglomeration and deposition. Therefore, the fluidity of the coating liquid in the tray is not high. With the passage of time, the coating liquid is easy to accumulate and scale, resulting in poor coating quality of the lower coating roll. There are double lines with different width and quantity in batches along the strip rolling to the plate surface, and wear the lower coating roll, directly resulting in product quality defect. In severe cases, it is also necessary to stop the machine to replace the coating roller, clean up the blockage of the circulating pipeline, and deal with the scaling of the tray. On the one hand, these adverse factors greatly increase the labor intensity of employees, on the other hand, interfere with the on-site continuous production and directly affect the production efficiency. At the same time, because the solidified magnesium oxide coating solution is bonded in the tray and can not be used, it is not only difficult to clean, but also causes magnesium oxide waste. In addition, due to the liquid rejection at the edge of the coating roller, the coating quality is affected, and the work of the coating machine is disturbed, resulting in scale accumulation at the edge of the coating roller, resulting in uneven coating at the edge of the strip steel.