The material of silica brick is quartzite as raw material, with the participation of a few mineralizers. Fired at high temperature, its mineral composition is composed of tridymite, cristobalite, and glassy composition at high temperature, and its AiO2 content is above 93%. In the well-fired silica brick, the content of tridymite accounts for 50%~80%; cristobalite is the second, only 10%~30%; and the content of quartz and glass phase fluctuates at 5%~15%.
Silica brick is an acidic refractory material and has strong corrosion resistance to acidic slag, but when it is severely corroded by alkaline slag, it is easily damaged by oxides such as Al2O3 and has excellent resistance to oxides such as ICAO, FeO, Fe2O3.
The disadvantage of the load is that the thermal shock stability is low and the refractoriness is not high, generally between 1690-1730 ℃, which limits its application scale.
Expansion
The thermal conductivity of the silica brick increases with the increase of the working temperature, and there is no remaining shortening. During the oven process, the volume of the silica brick increases with the increase of the temperature. In the oven process, the expansion of silica brick is between ℃, and the expansion before 300℃ is about 70%~75% of the total expansion. The reason is that SiO2 exhibits four crystal transformation points at 117°C, 163°C, 180~270°C, and 573°C during the oven process, and the volume expansion caused by cristobalite is between 180~270°C.
The high deformation temperature under load is the advantage of silica brick, which is close to the melting point of tridymite and cristobalite, about 1640~1680℃.
The defects of silica bricks are low thermal shock stability and low refractoriness, generally between 1690 and 1730 °C, which limits their application scale. The key to determining the thermal stability of silica brick is density, and the density is one of the important signs to confirming its quartz transformation. The smaller the density of the silica brick, the more complete the conversion of its lime, and the smaller the residual expansion that occurs during the oven process.
When the working temperature is lower than 600~700℃, the volume of the silica brick changes greatly, the anti-quick cooling and heating performance is poor, and the thermal stability is also poor. If the coke oven is operated at this temperature for a long time, the masonry will be easily broken and damaged.
Application of high-aluminum refractories in high-temperature industries
Classification of refractory properties and their application areas
High alumina bricks commonly used in industrial kilns
