Lightweight corundum refractory bricks generally use polystyrene expanded beads as ember additives. The lightweight corundum bricks produced with polystyrene expanded beads are made by mixing polystyrene expanded beads into the corundum mud material in a certain proportion, and then fixed in the bricks by molding, and then fired in the bricks. Uniform spherical pores are left in the product, making the brick a porous structure and reducing the density. Because the pellets basically do not absorb water, the moisture content of the green body after molding is low, and the product is small in drying deformation, so the size of the finished product is more accurate, and the product can meet the size requirements without grinding bricks.
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If polystyrene expanded beads are used as the only incinerator additive, although it does not absorb water and shrinks when drying, it cannot help to transmit moisture. During the drying process, the surface of the brick is dried first, and the internal moisture cannot escape, which is very easy to crack. . In order to solve this contradiction, composite incinerator additives are generally used, that is, a substance that can both absorb water and incinerate is added to help transmit moisture and prevent bricks from cracking. Sawdust and polystyrene foam beads are commonly used. In use, fine wood chips should be used, which can also fill the gap between beads and reduce the density of refractory bricks.
Using single polystyrene expanded beads, the beads form larger pores after firing, but the surrounding are heavy and dense materials, the organization structure is unreasonable, and it is difficult to make bricks; The lightweight corundum brick has a more reasonable organizational structure.
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Corundum fine powder and alumina ball-milled fine powder calcined at 1450 ℃ are used, and appropriate amount of composite incinerator additives and binders are added.
It is formed by vibration or casting and fired at 1690°C. The product was fired in a tunnel kiln at a firing temperature of 1520°C and kept for 8 hours. The firing shrinkage of the product fluctuates between 10% and 13%. The fired products should also be cut and ground according to the required shape and size of refractory bricks, respectively, on a cutting machine and a polishing machine.
Lightweight corundum bricks made with the addition of ember sawdust and CaO, successfully used in annealing furnace linings with hydrogen as a medium for heat treatment of transformer steel and other furnaces with similar service conditions.
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