Study On Quality Of Coating Layer Of Low Temperature Grain-Oriented Silicon Steel

Cold-rolled grain-oriented silicon steel is an important metal magnetic material, which mainly used for the mechanical and electrical industry and also the energy industry. It is the main material of electrical transformer. Because of the complex production equipment and the high technical requirements, the quality of grain-oriented silicon steel products of a country is often considered as an important measure of its special steel manufacturing level.As new generation grain-oriented silicon steel, low temperature grain-oriented silicon steel, in addition to having lower iron loss and higher magnetic properties, also has better production process and energy efficient. However due to its special production technics, its surface Mg2SiO4 glass membrane (also known as silicon steel’s coating layer) quality has been limited. So, to improve its coating layer quality has become the hardest and the most critical problem in the production of this kind product.Based on the study of Cu-containing low temperature grain-oriented silicon steel production process and condition of the coating layer’s formation, we put forward measures to improve coating layer quality from the MgO coating processes and high temperature annealing technics two aspects. High temperature annealing process including the first heating, low thermal insulation section, the second heating, high thermal insulation section and cooling section. The low thermal insulation section is critical for the formation of the coating layer. This paper put forward to improve the original low thermal insulation temperature from 650℃ to 700℃ to promote the formation of coating layer; In addition, in the MgO coating process, we put forward two improved schemes, adding a certain percentage of nanoscale MgO into the conventional MgO coating formulations and applying electrostatic spraying coating technics into the MgO coating process. Combined with the low temperature grain-oriented silicon steel production technics, we conduct comparative experiments to study the influence of these different measures on the coating layer quality and product properties.Experimental studies show that:Improving the low thermal insulation temperature to 700℃, beneficts the formation of SiO2 oxide layer, improves the quality of the Mg2SiO4 coating layer, but may damage the magnetic properties stability of the products.Adding nanoscale can improves the reactivity of MgO, has a significant quality improvement effect to the Mg2SiO4 layer, but adding excessive nanoscale MgO will increase moisture content and influence the magnetic properties of the product. Using the electrostatic spraying technics can avoid the negative factors of roller coating technics, the silicon steel products have a better coating layer quality, the surface is more smooth, the Mg2SiO4 layer is more uniform, besides the magnetic properties has no much difference compared to the traditional coating technics. In the electrostatic spraying MgO technics, sprying thin water before sprying MgO increases the action of crystal water in the formation of the coating layer, can prevent the surface of large area of exposed crystal. In the electrostatic spraying technics, spraying a layer of SiO2 solution on the steel surface instead water before sprying MgO powder can increase the amount of SiO2 directly, can get a more complete coating layer.In this paper, we put forward creative measures to improve the quality of the coating layer of low temperature grain-oriented silicon steel, and achieve good results. This has an important significance to improve the quality of the domestic high-grade grain-oriented silicon steel products.