Today, Topower Refractory will take you to understand that silica brick as China fire brick is mainly composed of scale, square and a small amount of residual time and glass.
The silicon content is above 94%. The true density is 2.35g/cm3. Acid slag corrosion resistance. High temperature strength. The starting temperature of load softening is 1620~1670℃. Long-term use under high temperature will not deform. Low thermal shock stability (1 to 4 times of heat exchange in water) Natural silica is used as raw material as China fire brick, and an appropriate amount of mineralizer is added to promote the transformation of the green body into flakes. Under reducing atmosphere, 1350~1430℃ is slowly fired. When heated to 1450°C, the total volume expansion is about 1.5~2.2%, and this residual expansion will make the incisions tightly combined to ensure that the masonry has good air tightness and structural strength.
The composition of the silica brick as China fire brick mineral phase is mainly tridymite and cristobalite, and a small amount of quartz and vitreous. Tridymite, cristobalite, and residual quartz change greatly in crystal shape at low temperature, while silica brick has poor thermal stability at low temperature. During use, it should be slowly heated and cooled below 800°C to avoid cracking. Therefore, it is not suitable for use in furnaces below 800°C.
The properties and processes of silica bricks as China fire brick are closely related to the crystal transformation of SiO2. Therefore, the real specific gravity is an important quality star index of silica bricks as China fire brick . The general requirement is lower than 2.38, and the high-quality silica brick as China fire brick should be lower than 2.35. The real specific gravity is small, which reflects the number of scales and squares in the brick and the amount of residual time, so the residual linear expansion is small, and the strength reduction in use is small.
Silica brick as China fire brick silica has seven crystalline variants and one amorphous variant. These two variants can be divided into two types. The former variants are Yingshi, scaly and Fang Yingshi. Their crystal structures are very different and are often slow to turn to each other. The latter variants are sub-αβ and y forms of the above variants, with similar structures and rapid mutual transformation.
The raw material for making silica bricks as China fire brick is silica. The higher the silica content of the silicon raw material, the higher the fire resistance. More harmful impurities are A203, K2O, Na20, etc. , which seriously reduces the fire resistance of refractory products. Silica bricks as China fire brick use silica with a silica content of more than 96% as raw material, add mineralizers (iron scale, lime milk, etc.) and binders (molasses, sulfite pulp waste liquid, etc.), through mixing, forming, Drying, firing and other technical production.
The silica brick as China fire brick market will gradually shrink. In the coking industry, a form of coke without coke oven production has been developed to replace some conventional cokes. In terms of ironmaking technology, new technologies of direct reduction and smelting reduction ironmaking are gradually being transformed into productivity. With the promotion of these new technologies, the demand for coke will gradually decrease. Recently, the number of complete sets of coke oven bricks in foreign countries has decreased, and the number of coke oven bricks used for repair has increased. There may be two main reasons: one is the increase in the amount of pulverized coal injection, and the demand for coke is reduced; The number of seats will be gradually reduced, the life of existing coke ovens will be extended as much as possible, and major repairs will be replaced by minor repairs. But it should be noted that even in industrially developed countries, it will take a long transition period for new technologies to replace old ones. During this period, the silica bricks as China fire brick required for major repairs of coke ovens will remain at a considerable level. At present, silica bricks and some breast wall bricks for glass kilns at home and abroad have been replaced by other bricks, and at the top of the furnace, silica bricks as China fire brick will still maintain their advantages.
