The high temperature expansion of refractory fire brick refers to the high temperature performance of brick, and the coefficient of expansion refers to the relative change ratio of firebrick when the temperature rises.
Corundum brick and mullite brick belong to the high-grade materials in the field of refractory, also belong to the alumina series. In contrast, corundum brick has a lower expansion coefficient than mullite brick.
Corundum brick has high melting point, stable high temperature performance and good wear resistance.
Mullite brick is similar to high alumina firebrick. There are two types of mullite, one is mullite produced by high aluminum-containing clinker at high temperature, and the other is mullite brick made by molding and firing of extra mullite at high temperature. Especially with the addition of mullite refractory brick, sintering temperature above 1700℃, can form a layer of protective film at high temperature, and good flexibility.
After heating, firebrick will expand in volume, but also according to the composition of different minerals, the coefficient of thermal expansion is also different. The thermal expansion of clay brick, high alumina brick and magnesium brick is relatively large, but the expansion coefficient of silicon brick is larger due to polycrystalline transformation.
The larger the coefficient of thermal expansion, the more unmanageable the size of the corundum brick, and the thermal stability also has an effect. The greater the coefficient of thermal expansion is, the greater the internal stress will be after the brick is heated, and it is easy to damage when the temperature changes quickly.
The smaller the expansion coefficient is, the smaller the volume change caused by crystallization, crystal transformation and continuous sintering of firebrick under high temperature.
The expansion coefficient is one of the important indexes of firebrick. The volume of firebrick will change due to the influence of temperature during use. It will seriously affect the compact size of firebrick. Generally speaking, when firebrick is being laid, expansion joints should be set up according to bricks of different materials. If the expansion coefficient is too large and it is not handled in time, the furnace body will crack due to brick expansion and affect the use.
There are many types of refractory brick with different expansion coefficients. Compared with mullite and corundum brick, the expansion rate of corundum brick is lower than that of mullite.
