What is Zirconia Fused Alumina?
Zirconia Fused Alumina (ZFA) is a synthetic, high-performance abrasive grain produced by fusing a mixture of alumina (Al₂O₃) and zirconia (ZrO₂) in an electric arc furnace at temperatures over 2000°C.
It is not a simple mixture but a unique eutectic composite structure. This means the molten alumina and zirconia cool and solidify together, forming a fine, interlocking microstructure where the two materials are intimately combined. This structure is the key to its superior properties.
The most common grade contains approximately 25% zirconia and 75% alumina, which is the optimal composition for the eutectic reaction and best mechanical properties.
| TYPICAL CHEMICAL ANALYSIS | TYPICAL PHISICAL PROPERTIES | ||
| SiC | ≥98% | Hardness: | Mohs:9.15 |
| SiO2 | ≤1% | Melting Point: | Sublimes at 2250 ℃ |
| H2O3 | ≤0.5% | Maximum service temperature: | 1900℃ |
| Fe2O3 | ≤0.3% | Specific Gravity: | 3.2-3.45 g/cm3 |
| F.C | ≤0.3% | Bulk density(LPD): | 1.2-1.6 g/cm3 |
| Magnetic content | ≤0.02% | Color: | Black |
| Particle shape: | Hexagonal | ||
How is it Made?
The manufacturing process is crucial:
Raw Materials: High-purity alumina (often from bauxite) and zirconium silicate (ZrSiO₄, zircon sand) are used as the primary raw materials.
Fusion: The materials are loaded into an electric arc furnace. A powerful electric current creates an arc with temperatures exceeding 2000°C, melting the batch completely.
Cooling & Solidification: The molten material is cooled under controlled conditions. It is during this cooling that the unique eutectic structure forms. In this structure, extremely fine platelets of zirconia are uniformly dispersed within an alumina matrix.
Crushing & Sizing: The resulting large, solidified ingot is then crushed, milled, and precisely screened into various grain sizes according to its intended application.
Key Properties
| Property | Description | Why It Matters |
|---|---|---|
| High Toughness | This is its standout feature. The fine zirconia platelets act as barriers, hindering the propagation of cracks through the alumina matrix. | The grain is much more resistant to fracturing under heavy pressure, leading to a longer-lasting abrasive. |
| Self-Sharpening | As the abrasive tool wears, the zirconia platelets help the grain fracture in a micro-level way, constantly exposing new, sharp cutting edges. | It maintains a consistent cutting rate and does not become dull or “glaze over” as quickly as other abrasives. |
| High Strength | The interlocking eutectic structure provides excellent mechanical strength. | It can withstand the high forces encountered in heavy-duty grinding and cutting-off operations. |
| Good Hardness | While not as hard as pure alumina or silicon carbide, its combination of hardness and extreme toughness is what makes it so effective. | It can efficiently cut through hard metals. |
Applications
Zirconia Fused Alumina is a premium abrasive chosen for the most demanding applications, primarily in metalworking.
Abrasive Tools:
Reinforced Cutting-Off Wheels: This is a major application. Its toughness allows for fast, durable cutting of steel bars, rods, and other high-tensile strength materials.
Grinding Wheels: Used for heavy-duty grinding, snagging (removing imperfections from castings), and conditioning steel billets and slabs.
Coated Abrasives: Used in high-performance sanding belts and discs for metal and wood, where long life and aggressive cutting are needed.
Blasting & Surface Preparation:
Used as a recyclable blasting media for heavy-duty cleaning, deburring, and creating a surface profile on steel (e.g., in shipbuilding, structural steel work).
Refractories:
Its high temperature resistance and toughness make it an excellent aggregate for high-performance refractory castables and bricks used in furnaces and kilns.
