Silica brick is an acidic refractory material with good resistance to acid slag erosion. Its softening temperature under load is as high as 1640～1670℃, and its volume is relatively stable under high temperature for long-term use. The silica content is above 94%. The true density is 2.35g/cm3. It has resistance to acid slag erosion. Higher high temperature strength. The load softening start temperature is 1620～1670℃. It will not deform after long-term use at high temperature. Low thermal shock stability (1~4 times of heat exchange in water) Natural silica is used as the raw material, and a proper amount of mineralizer is added to promote the conversion of quartz in the body to tridymite. Slowly fired at 1350～1430℃ under reducing atmosphere. When heated to 1450℃, there will be about 1.5~2.2% of the total volume expansion. This residual expansion will make the cut joints close and ensure that the masonry has good air tightness and structural strength.
The raw material for making silica bricks is silica. The higher the SiO2 content of the silica raw material, the higher the refractoriness. The most harmful impurities are Al2O3, K2O, Na2O, etc., which severely reduce the refractoriness of refractory products. Silica bricks use silica with SiO2 content not less than 96% as raw material, add mineralizers (such as iron scales, lime milk) and binders (such as molasses, sulfite pulp waste), and then mix, shape, dry, and burn Manufactured by other processes. When preparing silica brick mortar, a certain amount of waste silica brick is usually added to the ingredients, the purpose of which is to reduce the expansion and stress generated during the firing of the product, reduce the occurrence of cracks, and increase the yield. The amount added is related to the shape and weight of the brick. For special-shaped bricks weighing less than 25Kg: 20% can be added; for special-shaped bricks above 25Kg, 30% can be added; for special-shaped bricks, 30% can be added. Pay attention to this problem when adding waste silica bricks. Excessive addition will reduce the refractoriness and mechanical strength of the product and increase the porosity. Therefore, the amount of waste bricks should not be too much.
When preparing silica brick slurry, you should operate according to a certain feeding sequence. First, add various silica powder and waste silica brick powder into the wet mill in a certain proportion, dry mix for 2~3 minutes, and then add the sulfite pulp waste liquid and lime. The mixed liquid of milk and iron oxide powder, according to the requirements of the molding method, mix for another 8~17min. The length of the mud mixing time depends on the weight of the roller, the number of rotations of the roller, the amount of raw materials added, the hardness of the raw materials, the particle composition of the mud, and the molding method. Special-shaped bricks and mud used for manual molding require a longer mixing time than mud used for mechanical molding. The mixing time of different mud materials should be determined by experiment. The binders used in the manufacture of silica bricks are sulfite pulp waste liquid and lime milk. When lime milk is used as a binder, it acts as a plasticizer. The lime milk increases the strength of the brick during the drying process, and is called a mineralizer during firing, which promotes the conversion of quartz.
The water content of the mud used to make silica bricks is generally 5-9%, the water content of the hand-molded mud is 7-9%, and the water of the mechanical molding mud is 5 to 6%.
Nowadays, silica bricks are mainly used for the partition walls of the coking chamber and combustion chamber of coke ovens, the regenerator and slag chamber of steel open-hearth furnaces, soaking furnaces, refractory materials of glass melting furnaces, and firing kilns of ceramics. The vault and other load-bearing parts. It is also used for high temperature load-bearing parts of hot blast stoves and acid open hearth furnace tops
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