The true density of silica brick is the smaller, the lime change is the more complete, in the process of the oven, generated residual expansion is the smaller. In silica brick, the true density of tridymite crystal is smallest, the linear expansion rate is small, the thermal stability is better than quartz, thermal conductivity is good, refractoriness under load is high, slag corrosion resistance is strong, is the most stable volume form in quartz. In good firing silica brick, the content of tridymite is the highest, accounted for 50% ~ 80%. Cristobalite takes second place, only accounted for 10% ~ 10%. The content fluctuation of quartz and glass phase is in 5% ~ 5%.
When working temperature is below 600 ~ 700 ℃, silica brick volume change is bigger, the resistance to thermal shock performance is poor, thermal stability is not good. If the long-term work under the temperature of coke oven, masonry is easily broken.
The key to determine whether thermal stability of silica brick is true density, the size of true density is to determine one of the important marks of the quartz.
Silica brick is the ideal refractory products of coke oven, the important parts of the modern large and medium-sized coke oven (such as the combustion chamber, ramps and regenerator) all use silica brick to build. In the oven process, the biggest expansion of silica brick occurs between 100 ~ 300 ℃, 300 ℃ previous expansion of the volume is about 70% ~ 70% of total amount of expansion.