Brown Fused Alumina (BFA) is one of the most fundamental and widely used raw materials in the manufacture of abrasive tools. Its properties make it exceptionally well-suited for a broad range of applications.
| Chemical Properties (% wt) | Item | Typical | Min | Max |
| Al2O3 | 95.50 | 95.50 | 96.00 | |
| Fe2O3 | 0.15 | – | 0.30 | |
| SiO2 | 0.88 | – | 1.20 | |
| TiO2 | 2.70 | 2.50 | 3.20 | |
| Physical Properties(% wt) | Magnetics | 0.03 | – | 0.05 |
| Moisture | 0.05 | – | 0.20 | |
| Hardness | 2090 Knoop | 9 Mohs | – | |
| Grain form | Angular-cubic | |||
| Bulk density g/cm3 | 3.94 | 3.90 | – | |
| Grit sizes | A full range of size from # 10 to # 320 TO ANSI,ISO and FEPA specifications | |||
| Packing | In 1,000-1,500 kilos super sacks,or 25 kilos paper bags Special quantity packaging and labeling available. | |||
1. Key Properties of BFA for Abrasive Tools
High Hardness (Mohs scale ~9.0): it can effectively grind hard materials like carbon steel, alloy steel, malleable iron, and hard wood.
High Toughness and Strength: BFA grains are less brittle than white fused alumina. They can withstand high grinding pressures without fracturing prematurely, making them ideal for heavy-duty operations.
Sharp Angular Shape: The crushing and milling process produces grains with sharp, multifaceted edges. This results in excellent “cutting” or “stock removal” capabilities.
Good Chemical Stability: It is inert and does not react with the materials being ground in most common applications, ensuring a consistent grinding process.
2. Common Types of Abrasive Tools Made with BFA
BFA is used as the primary abrasive grain in both Bonded and Coated abrasive tools.
A. Bonded Abrasives (Rigid Tools)
In these tools, BFA grains are held together by a bonding material (the “matrix”).
- Grinding Wheels: This is the most classic application.
- Uses: For off-hand grinding, precision grinding, cutting-off, and snagging on workshop floors and in steel mills.
- Why BFA? Its toughness allows it to handle the high forces and intermittent cuts involved in grinding steel, especially when removing weld seams or heavy stock.
- Mounted Points and Cones: Small, specialized wheels for die grinders and toolroom applications for deburring and shaping metal in intricate areas.
- Honing Stones: Used for finishing the internal surfaces of engine cylinders and other bores to a precise size and fine surface finish.
- Segmented Blades: Large-diameter blades for cutting concrete, stone, and asphalt. BFA provides the necessary abrasion resistance.
B. Coated Abrasives (Flexible Tools)
Here, BFA grains are glued onto a flexible backing material like cloth, paper, or fiber.
Sandpaper (Abrasive Paper): Specifically, what is commonly called “sandpaper” for metalworking is very often made with BFA.
Grinding Discs (Depressed Center Wheels): The discs used on angle grinders for metal fabrication, weld cleaning, and stock removal.
Flap Discs: A combination of coated abrasive flaps that provide a conformable and fast-cutting action, excellent for blending and finishing welds.
Belts for Abrasive Belt Grinding: Used on large, powerful belt grinders for leveling surfaces, deburring, and finishing large metal sheets or components.