Hebei Messi Biology Co., Ltd. stated that silicon steel grade magnesium oxide is a kind of high-purity magnesium oxide, with a purity requirement of ≥98%, good suspension performance in water, and low hydration rate. In the process of producing oriented silicon steel sheets, silicon steel grade magnesium oxide is applied between silicon steel sheets in the form of a suspension, and forms a magnesium silicate insulation layer with silicates during high-temperature annealing, and plays a role in dephosphorization and desulfurization. my country has relatively rich magnesium resources, but there are few products with high added value. Therefore, the silicon steel grade magnesium oxide market needs to be further developed.
The name of silicon steel grade magnesium oxide actually indicates its use. It is suitable for making oriented silicon steel sheets. In order to meet the requirements of the electrical and physical properties of the iron core, the silicon steel sheets have a high-temperature annealing process of 1200-1250℃ during the production of oriented silicon steel sheets. In order to make the iron metal atoms complete regular orientation and arrangement during the annealing process, a good insulating film must be formed on the surface of the silicon steel sheet. This process must take 7 days to complete. In such a long high-temperature process, the silicon steel sheet will usually become iron. Scientific experiments have proved that the role of magnesium oxide is first as a high-temperature annealing barrier in the production of silicon steel sheets. In addition, it has the function of forming a magnesium silicate glass insulating coating with silicon, and it can remove impurities such as sulfur and phosphorus in silicon steel during high-temperature reactions. However, not every magnesium oxide can meet the needs of silicon steel production. This magnesium oxide should have its own special qualities.
This special quality mainly includes: high chemical purity, good suspension performance in water, low hydration rate, and magnesium oxide must have a certain activity. The slurry of magnesium oxide has strong bonding to the surface of silicon steel sheets. However, the current process of producing silicon steel grade magnesium oxide is relatively long, the purity is not high, and the product quality is unstable, which cannot meet the requirements of the rapid growth of domestic oriented silicon steel sheet production and development.
In order to solve the above technical problems, the prior art discloses a process for preparing high-purity silicon steel grade magnesium oxide from magnesium hydroxide. The process is to first calcine magnesium hydroxide at 500-750°C, add it to water, first heat it to 73-98°C for hydration, then adjust the temperature to 60-80°C, and slowly add ammonium bicarbonate solution to the water for carbonization to obtain a suspension; filter the suspension, wash and dry the filter residue, and then calcine it at 1050-1150°C to obtain high-purity silicon steel grade magnesium oxide. However, the above technical defects are that the process temperature and other parameters in the preparation can only obtain the corresponding effect based on the theoretical basis, and the intelligent control of the process parameters in actual production is poor, resulting in poor process stability.
Due to the van der Waals force, the magnesium oxide particles attract each other and form agglomerates. At the same time, magnesium oxide will produce a hydration reaction, thereby forming a certain amount of magnesium hydroxide on the surface of the magnesium oxide particles, which increases the surface roughness of the magnesium oxide particles and aggravates the agglomeration between the particles. When there are too many magnesium oxide agglomerates in the coating solution and the size of the agglomerates is too large, part of the magnesium oxide coated on the steel strip will still be in an agglomerated state (the size is generally between 10 and 100 microns). After such magnesium oxide agglomerates are coated on the strip, it is not easy to dry thoroughly, and there is residual moisture inside the agglomerates. During the high-temperature annealing stage, the water in the agglomerates will not be discharged smoothly, causing the surface of the micro-area steel strip to be overoxidized, thereby forming a point-like gold leakage defect. At the same time, when the water in the agglomerates expands under high temperature, it will cause plastic deformation of the micro-area of the steel strip, which will be inherited to the silicon steel finished product, forming a pitting or indentation defect, which seriously affects the surface quality of the product and affects the stacking coefficient. In short, the defect of the prior art is that it cannot effectively avoid the increase of impurities. The purity is not high, the product quality is unstable, and it cannot meet the requirements of the production and development of various oriented silicon steel sheets. In addition, the prior art has the disadvantages of high energy consumption and high production cost.