Silica brick characteristics

(1) chemical composition and mineral composition

The chemical composition of silica brick varies with the raw materials of silica brick. The content of SiO2 is 93% -98%, and the content of Al2O3 + Fe2O3 + CaO is 2.0% ~ 0.7% .The mineral composition of ordinary silica brick is dominated by phosphosilicate, accounting for 30% ~ 70% Quartz-based, about 20% to 80%; residual quartz and amorphous quartz are a small amount.

(2) Refractoriness and load softening temperature

Refractory degree of silica brick mainly depends on the content and properties of SiO2 in the impurities. The higher the SiO2 content, the lower the impurity content, the closer the refractories are to the melting point of SiO2; conversely, the lower the refractoriness is. Refractory silicon brick is generally 1690 ~ 1730 ℃.

Silica brick load softening temperature is higher, about 1650 ℃. This is mainly due to the fact that the main crystal phase constituting the silica bricks is a tetragonal quartz crystal with a network structure and the matrix is ​​a glass phase having a relatively high viscosity. Silica brick load softening temperature and refractoriness close, which is a notable feature of silica bricks.

(3) thermal shock resistance

Silica brick thermal shock resistance is poor, at 850 ℃ water cooling is only 1 or 2 times. The reason is that in the high-temperature quenching process, the silicon crystal will undergo crystal transformation, which will cause a large volume change. This is a big weakness of silica bricks.

(4) slag resistance

Silica brick is acid refractory material, it has strong resistance to acid and weak acidic slag and corrosive gas.

(5) high temperature volume stability

In the heating process, in addition to the existence of a certain thermal expansion of silica bricks, but also with the occurrence of crystal transformation and volume expansion. If there is remaining unbound quartz in the brick, it will continue to become tridymite or cristobalite at high temperatures, which will result in large volumetric expansion.

According to the characteristics of silica brick, currently used for masonry furnace glass furnace and coke oven lining material. During the heating and baking process, the temperature should be slowly warmed to avoid damaging the masonry due to excessive expansion.