Introduction to the physical and chemical properties of magnesium bricks

 
The fire resistance of magnesium brick can reach above 2000 ℃, and its softening temperature under load varies greatly with the melting point of the cementitious phase and the amount of liquid phase produced at high temperature.
 
Generally, the load softening start temperature of magnesium brick is between 1520 ~ 1600 ℃, while high purity magnesium brick can reach 1800 ℃. The load softening onset temperature of magnesium bricks is not much different from the collapse temperature. The linear expansion rate of magnesium brick at 20 ~ 1000 ℃ is generally 1.2% ~ 1.4%, and it is approximately linear. When liquid phase appears in the brick at high temperature, it will suddenly shrink. Magnesium bricks have higher thermal conductivity, second only to carbon bricks and silicon carbide bricks in refractory products, and they decrease with increasing temperature. Magnesium bricks have poor thermal shock resistance. Increasing the purity of magnesium bricks can appropriately improve thermal shock resistance.
 
Magnesium bricks have a very poor resistance to acid slag. They cannot be directly contacted with silicon bricks during use. Generally, they are separated by neutral bricks. The conductivity of magnesia brick is very low at normal temperature, but it cannot be ignored at high temperature (such as 1500 ℃). If it is used in the bottom of electric furnace, it should be paid attention to.