Corundum bricks are refractory products mainly composed of corundum as the primary crystalline phase in the aluminum-silicon system. These bricks possess excellent high-temperature mechanical properties, corrosion resistance, and good abrasion resistance.
Raw Materials: Natural hydrated aluminum oxides, including boehmite and diaspore, can be dehydrated through heating to obtain aluminum oxide (γ-Al2O3). This is then further heated to 1450°C, transforming it into corundum (α-Al2O3). However, due to the limited natural reserves of natural corundum and pure boehmite, industrial alumina is predominantly used as the raw material for corundum production. Industrial alumina consists primarily of α-Al2O3. The conversion from γ-Al2O3 to α-Al2O3 involves a volume contraction rate of 13%. To ensure well-developed α-Al2O3 crystals, the raw materials need to undergo treatment at higher temperatures. Following high-temperature firing, α-Al2O3 crystals can grow by 25 to 40 times their original size.
Production Processes: Corundum bricks can be categorized into three types: fused cast corundum bricks, electro-fused corundum re-bonded bricks, and sintered corundum bricks. Fused cast corundum bricks are produced by melting industrial alumina along with a small amount of pure alkali and quartz powder in an arc furnace. The resulting mixture is then mechanically processed, shaped into the desired forms and sizes through casting and annealing, and finally subjected to mechanical machining. Electro-fused corundum re-bonded bricks are created by mixing crushed electro-fused corundum particles and fine powder with a small amount of clay and binders. After thorough mixing, the mixture is molded using a brick press. The green bricks have a density ranging from 2.75 to 2.85 g/cm3 and are fired at temperatures between 1700 and 1800°C after drying.
The bulk density of corundum refractory brick is influenced by factors such as the particle size of the abrasive, particle composition, particle brand, particle size, and particle shape. In general, coarser particles exhibit lower density compared to finer particles, and the smaller the gaps between particles, the higher the density. The bulk density of a mixture of particles is higher than that of a single particle. The density of corundum bricks is directly affected by the density of the particles themselves. A higher particle density corresponds to a higher density of the corundum bricks. The true density of corundum bricks refers to the mass of abrasive contained per unit volume.
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