Classification, performance, physical and chemical indicators of high alumina bricks

High-alumina bricks are aluminosilicate refractories with a mass fraction of Al2O3 above 48%. Due to the high alumina content, it is called high alumina refractory material, which can be classified as follows according to the minerals contained in it.

Mullite-silica brick, in which the Al2O3 content is 40%~70%.

Mullite-corundum brick, which contains 79%~95% Al2O3.

Corundum raw material, Al2O3 content is 95%~100%.

It can also be classified according to the content of Al2O3, such as: Al2O3>75 for grade I; Al2O3 for grade II is 60%~75%, and Al2O3 for grade III is 48%~60%.

Properties of high alumina bricks

①High refractoriness

Due to the high content of Al2O3, the refractoriness is generally 1750~1790℃.

②High softening point under load

Due to the low content of impurities, the softening point under load is high; the high-temperature performance of high-alumina bricks is related to the microstructure of the material. The high temperature resistance of the matrix part is much lower than that of the particle part, and the slag first erodes the matrix part during use. 

③Good slag resistance

The content of Al2O3 in high alumina bricks is high, which is close to neutral materials. The slag resistance of high-alumina materials increases with the increase of Al2O3 content, but its corrosion resistance to basic slag is lower than that of basic refractory materials, and the reduction of impurity content is beneficial to improve slag resistance. At the same time, increasing the density of the material and reducing the porosity are also effective measures to improve its slag resistance.

④Good thermal stability

The expansion coefficient of brick is small. The thermal shock resistance of high alumina bricks is worse than that of clay bricks, which is closely related to the mineral composition of the material. 

Technical indicators of high alumina bricks

High alumina bricks are divided into five grades: LZ-80, LZ-75, LZ-65, LZ-55, LZ-48 according to physical and chemical indicators. In my country, LZ-48 high alumina bricks are used in the 6m coke oven.