Brown Fused Alumina
Brown Fused Alumina
Brown fused alumina is the most commonly used material in abrasives and refractory materials, where it offers an extremely high strength, toughness, and durability.brown fused alumina It has excellent acid and alkali corrosion resistance, oxidation resistance, and chemical stability at very high temperatures. Typical applications include grinding wheels, sandpaper, refractories, and blasting media.
It is derived from bauxite and is produced by heating calcined bauxite in an electric arc furnace until the desired crystallization temperature is reached. It is then fused and refined to form a dense, high-strength material that resists oxidation, corrosion, and thermal stress. It is a hard, highly durable mineral with a mohs hardness of 9 or more and a low iron content.
The production of brown fused alumina is primarily carried out in the Asia Pacific region, and is also largely consumed in North America. In the United States, it is a common ingredient in the manufacture of metal abrasives, and is mainly used in the construction and industrial flooring industries.
Fused alumina is available in many different particle sizes and grit densities for use in a variety of abrasive applications. The most popular grit and powder sizes are 7102 and 8202. The latter is suited for fine grit grinding wheels and brake lining filler applications.
Washington Mills produces and delivers brown fused alumina in standard grit and powder sizes, as well as custom abrasive grain sizes for specific requirements. It is ideal for use in refractories, ceramics shapes, and abrasive grains in grinding wheels, sandpaper, and blasting media.
It offers the best combination of purity, crystalline liquidity, and hydrophilia. It is also the strongest abrasive grain with a high Mohs hardness, good self-sharpening ability, and a low coefficient of linear expansion. It is suitable for refractory applications, and is widely used in the production of sandpaper, refractories, glass beads, lapping compounds, and metal abrasives.
Brown fused alumina is a highly crystalline material, consisting of oxygen hexagonal close packed planes with Al3+ ions occupying tetrahedral or octahedral interstitial sites (Figure 2). A-Alumina has the highest thermal conductivity, crush strength, and wear resistance of all alumina phases.
This alumina has a high degree of chemical purity with controlled particle size and shape (Figure 2(a)). It is produced by heating 2 cm diameter pellets of calcined alumina at temperatures near melting point until conversion to large elongated alumina crystals occurs. The closed porosity in the resulting alumina grain (Figure 2(b)) contributes to the high crushing strength and abrasion-resistance of the grain.
The high purity of alumina is also believed to improve its refractoriness and strength. For this reason, it is often used as a binder in refractories to be fired at low temperatures. Alumina is also the most abundant phase in aluminosilicate refractories to be used at high temperatures such as firebricks.
GCMC utilizes the spent catalyst residues from spent hydroprocessing catalysts as the raw material for alumina smelting to produce a wide range of fused alumina grades and other useful products. The alumina residues are typically mixed with a reductant to produce a mixed alloy containing Ni, Co, Mo, and V during smelting. The resulting alumina is then smelted in an electric arc furnace to produce refractory grade fused alumina for ceramic and refractory applications.
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