Corundum mullite bricks are high-alumina refractory bricks composed of corundum and mullite main crystal phases. Corundum mullite bricks refer to refractory bricks made of high-purity or relatively pure raw materials. Among them, the presence of low melting point oxide impurities will reduce its high temperature performance. The price of corundum mullite bricks is much higher than that of ordinary high alumina bricks.
Performance
Performance: It has good high temperature strength, high temperature creep resistance, thermal shock resistance and corrosion resistance. The physical and chemical properties of a typical corundum mullite brick are: Al2O3≥85%, Fe2O3 0.45%, apparent porosity 19%, normal temperature compressive strength greater than 55MPa, load softening temperature greater than 1700°C, heating wire change (1600°C, 3h )-0.1%, thermal shock resistance (1100℃ water cooling) greater than 30 times.
Process
Manufacturing process: Synthetic mullite is usually used to make corundum mullite bricks. Mullite particles can be used as aggregates, α-Al2O3 powder can be used as powder, and fused or sintered corundum particles can also be used as aggregates and synthetic materials. Mullite powder is a powder material. Aggregate and powder are blended according to a certain ratio and particle size gradation, and the sulfite pulp waste liquid is used as a binding agent, and the materials are added in a certain order. Mix thoroughly and evenly, and use friction brick press or hydraulic brick press to form. After the bricks are dried, they are fired at 1650 ~ 1750°C.
Some use fused or sintered corundum sand as aggregate, and use α-Al2O3 high bauxite or clay mixed fine powder with mullite or corundum mullite composition ratio as powder to make bricks. The corundum mullite brick made by the process has a slightly poorer density, so this process is not widely used.
Process points: Use pure mullite raw materials synthesized with industrial alumina powder and pure clay, bauxite or silica as raw materials, especially the content of alkali metal oxides should be as low as possible, and made with mullite particles as aggregates The product has good thermal shock resistance, but its corrosion resistance is slightly worse. The product with corundum sand as the aggregate has good corrosion resistance, but the thermal shock resistance is slightly worse.
application
Scope of application: Mainly used in high-temperature hot-blast furnaces, and also used in glass melting furnaces and as ceramic firing kiln furniture.
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