Brown fused alumina is produced from high-quality abrasive-grade bauxite, mixed with appropriate additives, and refined in an electric arc furnace at temperatures above 2250°C. Its refractoriness can exceed 1850°C.
This product possesses a range of excellent properties: it has high hardness and strength, as well as good self-sharpening ability. In addition, it offers outstanding impact resistance, high-temperature resistance, oxidation resistance, excellent corrosion resistance, and low creep, making it suitable for a wide variety of demanding working conditions.
Technical Specifications
Chemical composition:
The alumina (Al₂O₃) content is above 94%, with small amounts of impurities such as iron oxide (Fe₂O₃), silica (SiO₂), titanium, etc.
Mohs hardness:
9.0, second only to diamond and silicon carbide.
Density: 3.90–4.10 g/cm³.
Toughness:
Relatively high, with strong impact resistance and stable cutting performance.
High-temperature resistance:
Can withstand temperatures of approximately 1900°C and is not prone to decomposition or deformation.
Applications
Abrasive Tools: Grinding wheels, cutting discs, etc.
Brown fused alumina abrasive features high purity, strong self-sharpening properties, and excellent toughness, with an extremely low content of magnetic substances. Abrasives made from it cut sharply and efficiently, generate low heat during grinding, have a high grinding ratio, and do not easily adhere to workpieces. Sintered abrasives exhibit a uniform dark blue color after firing and are free of network cracks and rust spots. After washing, they produce very little dust.
This product is highly suitable for the production of vitrified-bond and high-density resin-bonded abrasives and is also widely used in various grinding and polishing applications.
Refractory Materials
Ladle and iron trough castables, ramming mixes, long nozzles, sliding plates, three key functional components for ladles, and various corundum bricks. During application, the product is characterized by no explosion, no pulverization, and no cracking.
Sandblasting Materials
Mainly used for decontamination, rust removal, corrosion protection, descaling, finishing, pattern making, and surface treatment of workpieces made from various materials.
Generally, three factors affect sandblasting performance:
1.Grinding force: Higher grinding force delivers a better sandblasting effect.
2.Bulk density: Higher bulk density delivers a better sandblasting effect.
3.Dust: Lower dust content delivers a better sandblasting effect.
Brown fused alumina with high bulk density (dry-washed grit) provides excellent sandblasting performance.
Smelting Process Principle
Brown fused alumina is produced using calcined high-alumina bauxite, carbon materials, and iron filings as raw materials. After being evenly mixed, the materials are fed into an electric arc furnace for high-temperature melting and impurity reduction, followed by cooling and crystallization to form large brownish fused blocks. Its main component is alumina, with a content generally ranging from 94.5% to 97%.
The smelting principle of brown fused alumina relies on the fact that aluminum has a greater affinity for oxygen than impurity elements such as iron, silicon, and titanium. By properly controlling the amount of reducing agent and using the reduction smelting process, the main impurities in the bauxite are reduced. The reduced impurities form a ferrosilicon alloy, which separates naturally from the corundum melt, thus producing high-quality brown fused alumina with compact crystals and an alumina content of more than 95%.
Raw Material Preparation
High-quality high-alumina bauxite is selected; coke and iron filings are added as reducing agents for certain products.
Electric Arc Furnace Smelting
Reduction smelting is carried out at temperatures above 2000°C to crystallize alumina into corundum.
Cooling and Crushing
Large brown fused alumina blocks are cooled and then crushed into particles.
Magnetic Separation
Free iron and magnetic impurities are removed.
Screening and Classification
The material is classified into different specifications according to particle size standards (such as F grade, P grade, micro-powder, etc.).
FAQ
01.What are brown fused alumina and white fused alumina?
Brown fused alumina is an abrasive made mainly from bauxite through high-temperature smelting. Its main component is alumina (Al₂O₃), with a content of more than 94%, and it contains small amounts of iron oxide and silicon dioxide.
White fused alumina is a high-purity abrasive whose main component is also alumina, but with much higher purity (about 99%) and almost no impurities.
02.What are the differences in hardness and toughness between brown fused alumina and white fused alumina?
Hardness: White fused alumina has higher hardness than brown fused alumina, making it suitable for processing high-hardness materials.
Toughness: Brown fused alumina has greater toughness than white fused alumina, making it suitable for heavy-duty and rough grinding, as well as other applications requiring high impact resistance.
03.What are the main applications of brown fused alumina?
Due to its high toughness and moderate hardness, brown fused alumina is mainly used for:
High-intensity grinding, such as rough grinding and heavy-duty grinding.
Processing moderately hard materials such as steel, castings, and wood.
Polishing and sandblasting, especially for surface roughening.
04.What are the typical applications of white fused alumina?
Due to its high hardness and high purity, white fused alumina is often used for:
Precision grinding and polishing, such as processing high-hardness metals and stainless steel.
Processing electronic components and ceramics with high surface quality requirements.
High-precision applications such as medical devices and optical instruments.
05. In which cases can brown fused alumina replace white fused alumina?
Brown fused alumina can replace white fused alumina in the following scenarios:
Processing materials with relatively low hardness, where extremely high abrasive hardness is not required.
Applications with low precision requirements, such as rough grinding or deburring.
Cost-sensitive applications, where brown fused alumina can significantly reduce expenses.
06.In which cases cannot white fused alumina be replaced by brown fused alumina?
White fused alumina cannot be replaced in the following cases:
Precision processing of high-hardness materials such as high-carbon steel and stainless steel.
Applications requiring extremely high surface quality, such as optical mirror polishing.
Applications sensitive to abrasive impurities, such as medical equipment or semiconductor processing.
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