Special magnesium oxide is mainly used as high temperature annealing spacer in oriented silicon steel.When the high temperature annealing is heated to a certain temperature, magnesium oxide (MgO) will
Special magnesium oxide is mainly used as high temperature annealing spacer in oriented silicon steel.When the high temperature annealing is heated to a certain temperature, magnesium oxide (MgO) will react with silica (SiO2) oxide film on the surface of the steel belt to produce magnesium silicate bottom layer. A good magnesium silicate bottom layer is an important part of the insulating coating on the surface of the orientation steel.
In actual production process, due to improper coated magnesium oxide composition and process control, in the subsequent high temperature annealing process, unable to form a good magnesium silicate, bottom after follow-up of pickling and coating insulation coating adhesion, leads to the formation of a phosphate coating can't uniform surface and good insulation performance, even can cause surface to reveal the phenomenon of the silicon steel sheet substrate (also referred to as "Lou jing"), insulation resistance is zero, seriously affect the quality of the finished product.Therefore, oriented steel has special requirements for magnesium oxide, including the activity, purity, adhesion, particle size of magnesium oxide, as well as the coating hydration and coating amount have a great impact on the quality of the glass film.
Effect of magnesium oxide particle size on the properties of silicon steel
The activity and particle size of magnesium special oxide are closely related to the density of magnesium silicate bottom layer.Magnesium oxide of the same type, the better the activity, the smaller the particle size and the reaction degree of the steel plate surface is better, the resulting magnesium silicate crystal is small and dense, can effectively prevent the infiltration of the outside atmosphere, resulting in a thick bottom and bright spots, increase the loss of iron core.
(1) 900-950℃ is the reaction temperature of magnesium oxide and silicon dioxide on the surface of oriented silicon steel.The reaction performance of mgo-sio2 is influenced by the heating system and atmosphere conditions during high temperature annealing.
(2) special magnesium oxide has small particle size and high activity value. After high temperature annealing, the reaction layer of oriented silicon steel has more embedded matrix, uniform surface appearance, dense and fine particles.The particle size of special magnesium oxide increases and the activity value decreases. After high temperature annealing, the reaction layer of oriented silicon steel has less embedded matrix, and the bottom layer of magnesium silicate formed is also looser and more granular.