The reaction process of magnesium oxide during high-temperature annealing of grain-oriented silicon steel can be divided into three stages:
Diffusion of Mg ions
When the annealing temperature reaches 800-900 degrees Celsius, Mg ions begin to diffuse from the magnesium oxide coating into the interior of the silica particles. The rate of Mg ion diffusion depends on the temperature, the grain size of MgO and the size of the silica particles.
Reaction of MgO with silica
After Mg ions diffuse into the interior of the silica particles, they react with the silica to form magnesium silicate. The crystal structure of magnesium silicate is orthorhombic and has good insulation properties.
Sintering of magnesium silicate
As the temperature continues to rise, the magnesium silicate particles will sinter to form a dense magnesium silicate layer. The magnesium silicate layer has good insulation and mechanical properties and can prevent oriented silicon steel from oxidizing and bonding at high temperatures.
The smooth progress of the magnesium oxide reaction process during high-temperature annealing of grain-oriented silicon steel is of great significance to ensuring the magnetic properties and service life of silicon steel.