What is White Fused Alumina?

A Complete Guide to Properties, Applications, and Selection

1. Introduction to White Fused Alumina (WFA)

White Fused Alumina (WFA), chemically known as α-Al₂O₃, is a synthetic abrasive produced by melting high-purity alumina (Al₂O₃ ≥99.5%) in an electric arc furnace at temperatures exceeding 2200°C. Its exceptional hardness (Mohs 9.0), thermal stability, and low impurity content make it a cornerstone material for precision grinding, polishing, and refractory applications.

Key Features:

• High Purity: Al₂O₃ content ≥99.5%, minimal Fe₂O₃ (<0.05%), TiO₂ (<0.03%).

• Angular Crystals: Sharp-edged grains ensure aggressive cutting and consistent surface finishes.

• Thermal Resistance: Stable up to 1900°C, ideal for high-temperature environments.

2. Manufacturing Process of WFA

Step 1: Raw Material Selection

• Bauxite Refinement: Calcined alumina is derived from high-grade bauxite (Al₂O₃ ≥85%) through the Bayer process.

• Additives: Controlled amounts of borax (Na₂B₄O₇) or chromium oxide (Cr₂O₃) are added to optimize crystal structure.

Step 2: Electric Arc Furnace Melting

• Temperature: Sustained at 2200–2400°C for 18–24 hours.

• Cooling: Molten alumina is cooled slowly to form large, dense crystals.

Step 3: Crushing & Grading

• Primary Crushing: Jaw crushers reduce blocks to 0–50 mm.

• Milling & Sieving: Achieve precise grit sizes (F12–F2000) per FEPA/ANSI standards.

3. Technical Properties & Advantages

3.1 Mechanical Performance

• Hardness: Mohs 9.0 (superior to brown fused alumina, comparable to silicon carbide).

• Toughness: Higher than monocrystalline alumina due to interlocking crystal structure.

• Density: 3.95–4.0 g/cm³, ensuring durability in heavy-duty grinding.

3.2 Chemical Stability

• Acid/Alkali Resistance: Inert to most chemicals except hydrofluoric acid (HF).

• Oxidation Resistance: No phase changes below 1900°C, ideal for refractory linings.

4. Industrial Applications of WFA

4.1 Precision Grinding & Polishing

• Semiconductor Wafers: Ultra-fine WFA (F1200–F2000) achieves Ra ≤0.1μm surface finishes.

• Optical Lenses: Minimizes subsurface damage in glass polishing.

4.2 Refractory Materials

• Steel Ladle Linings: WFA aggregates (1–3 mm grit) enhance thermal shock resistance.

• Ceramic Fibers: WFA powder reinforces high-temperature insulation.

4.3 Advanced Manufacturing

• 3D Printing: WFA-coated nozzles resist abrasion in metal AM systems.

• Aerospace: Used in turbine blade grinding for tight tolerance control (±2μm).