White fused alumina powder

What is White Fused Alumina Powder?

White fused alumina is a synthetic, high-purity abrasive material produced by fusing high-quality alumina (Al₂O₃) in an electric arc furnace at temperatures over 2000°C. The “white” designation comes from its high purity (typically >99% Al₂O₃), resulting in a white or crystalline appearance, as opposed to the darker brown fused alumina which contains impurities.

Key Production Process

1. Raw Material:Industrial alumina powder .

2. Fusion: The alumina is melted in an electric arc furnace. The high heat allows it to crystallize into a dense, hard mass.

3. Cooling & Crushing: The fused mass is cooled, then crushed and precisely milled into grains.

4. Processing: The grains are washed, chemically treated (if needed), and sieved into specific grit sizes. Magnetic separation removes any iron contamination from the crushing process.

5. Classification: The powder is separated into standardized grit sizes, from coarse grits (e.g., P12) to very fine powders (microns and sub-microns).

Key Properties

• High Hardness: 9.0 on the Mohs scale, second only to diamond and silicon carbide. This makes it an excellent cutting and abrasive material.

• High Purity (>99% Al₂O₃): Low impurities mean it is chemically inert, does not react with the workpiece, and is suitable for applications where contamination is a concern.

• Sharp Angular Shape: When crushed, the grains form sharp, multifaceted edges, ideal for aggressive grinding and cutting.

• Excellent Toughness: More durable than silicon carbide, meaning it fractures less under pressure, making it suitable for heavy-duty grinding.

• High Heat & Chemical Resistance: Stable at high temperatures and resistant to most chemicals.

Common Grit Types & Forms

White fused alumina powder is classified by grit size (particle diameter):

• Macro Grits (Abrasives): Coarse to fine (e.g., F12 to F220). Used for grinding wheels, sandpaper, blasting media.

• Micro Grits (Micron Powders): Fine powders (e.g., P240 and finer, down to 1 micron or less). Used for precision polishing, lapping, and as a raw material for refractories and ceramics.

• Special Forms:

  • Standard Grain: For general abrasive tools.

  • Densified (Sintered) Alumina: Grains are sintered for higher toughness and durability.

  • Calcined Alumina: A heat-treated form for advanced ceramics, not typically used as an abrasive.

Applications

1. Abrasive Tools (Largest Market)

• Coated Abrasives: Sandpaper, sanding belts, discs, and rolls for metal, wood, and paint finishing.

• Bonded Abrasives: Grinding wheels, honing stones, and segments for precision grinding of steel, alloys, and hardened metals.

• Blasting & Surface Preparation: Used as a recyclable blasting media for cleaning, deburring, and creating surface profiles on metals (less dense than steel shot, so it’s less aggressive).

2. Refractories

• As a key aggregate in high-alumina bricks, castables, and mortars for furnaces, kilns, and incinerators due to its exceptional heat resistance.

3. Precision Polishing & Lapping

• Micro-grit powders are suspended in liquids for the final precision polishing of optical lenses, silicon wafers, and semiconductor components.

4. Anti-Skid & Traction

• Added to epoxy floor coatings, non-slip paints, and stair treads to provide grip.

5. Reinforcement & Composites

• Used as a filler to increase the hardness, wear resistance, and thermal conductivity of plastics, resins, and ceramic composites.

6. Other Specialized Uses

• Waterjet Cutting: Mixed with high-pressure water as an abrasive cutting medium.

• 3D Printing (SLA/DLP): As a filler in ceramic resin for producing high-strength technical ceramics.

Advantages vs. Other Abrasives

• vs. Brown Fused Alumina (BFA): WFA is harder, sharper, and more brittle. It generates less heat during grinding and is used for precision grinding of harder steels. BFA is tougher and better for rough grinding.

• vs. Silicon Carbide (SiC): SiC is slightly harder but more brittle and less tough. WFA is preferred for grinding high-tensile strength materials (like steel), while SiC is better for low-tensile materials (like cast iron, stone, glass) and non-ferrous metals.