Introduction to the composition and production of silicon brick

 

The mineral phase composition of silica brick is mainly scaly quartz and cristobalite, and a small amount of quartz and glassy. Squam quartz, cristobalite, and residual quartz have large changes in volume at low temperatures due to crystalline changes, so the thermal stability of silica bricks at low temperatures is poor. During use, slowly heat and cool below 800 ℃ to avoid cracks. Therefore, it should not be used in furnaces with sudden temperature changes below 800 ℃.

The properties and process of silicon brick are closely related to the crystal form conversion of SiO2. Therefore, the true specific gravity is an important quality index of silicon brick. The general requirements are below 2.38, and high-quality silicon bricks should be below 2.35. The true specific gravity is small, reflecting the large number of scale quartz and cristobalite in the brick, and the small amount of residual quartz, so the residual linear expansion is small, and the strength decreases during use.

 

There are seven crystalline variants and one amorphous variant of silica. These variants can be divided into two categories: the first variant is quartz, scaly quartz and cristobalite, which have very different crystal structures and are slow to transform each other; the second variant is a subspecies of the above ──αβ and γ types, their structures are similar, and they transform each other faster. 

 

The raw material for making silica bricks is silica. The higher the SiO2 content of the silica raw material, the higher the fire resistance. The most harmful impurities are Al2O3, K2O, Na2O, etc., which severely reduce the fire resistance of refractory products. Silica bricks use silica with SiO2 content of not less than 96% as raw materials, adding mineralizers (such as iron scales, lime milk) and binders (such as molasses, sulfurous acid pulp waste liquid), which are kneaded, shaped, dried, and fired. And other processes.