What is White Fused Alumina
White fused alumina is also called white fused alumina. It is an artificial abrasive material made by the fusing process. WFA is a high-grade refractory raw material and a commonly used wear-resistant material. The main crystal phase of fused white corundum is α-Al2O3 (Alpha Aluminum oxide), the color is white and flawless.
The production process of white fused alumina:
The production process of white fused alumina is a process of melting and recrystallizing high-purity industrial alumina powder at high temperatures up to 2250 °C. Unlike brown fused alumina, whose electrofusion is a process of oxidation and reduction to generate alumina. Industrial alumina powder is also made of bauxite. The content of Al2O3 is generally 98.5-99%. In addition, there are a small number of impurities such as Na2O, SiO2, and Fe2O3 in the alumina powder. The electro-fusing smelting can refine the powder to get white-fused alumina. However, the impurities cannot be completely removed. In the molten process, sodium oxide and aluminum oxide will generate β-Al2O3 (Na2O·11Al2O3). And it will increase as the content of Na2O increases. β-Al2O3 has a low melting point, low bulk density, and low hardness. When the white fused alumina blocks are cooled and crystallized, β-Al2O3 will precipitate in the upper part of white fused alumina lumps. That will seriously affect the refractory performance and hardness of the white-fused alumina material.
Thus, the production of fused white corundum must strictly control the content of sodium oxide. Selecting low-sodium alumina powder as the raw material can improve it. Furthermore, adding auxiliary materials that promote the volatilization of Na2O for smelting is also a general method to reduce Na2O.
The properties of white fused alumina:
High hardness: Mohs hardness is 9.0, Vickers hardness(HV) is 2000-2200.
Excellent toughness: Take F120 for example, the compressive strength of white fused alumina is 100KN/cm2.
High self-sharpening ability: the crystal shape of white fused alumina is Angular shape. The particle can get a new sharp edge after grinding. So WFA has a very aggressive grinding ability.
High-temperature resistance with low thermal conductivity and low coefficient of linear expansion. So it can resist thermal shock.
The indexes are as follows:
| Temperature(K) | 293 | 473 | 673 | 773 | 1073 | 1273 |
| Thermal conductivity(w/(k·m)) | 0.1 | 0.09 | 0.04 | 0.04 | 0.03 | 0.02 |
| Temperature(°C) | 573 | 673 | 773 | 8730 | 973 | 1073 | 1273 |
| Linear expansion coefficient (x10-6/ °C) | 3.34 | 4.46 | 5.10 | 5.75 | 6.02 | 6.28 | 6.63 |
PH value: White fused alumina is a neutral substance with PH Value of 7.0-8.0.
The good hydrophilicity and low oil absorption rate.
High resistance to chemical corrosion.
The white fused alumina powder with a suspension-treated process gets good flowability.
The application of white fused alumina:
1. Metal sandblasting surface treatment: remove the oxide layer of metals, stainless steel, aluminum alloy, tungsten molybdenum, titanium-containing metals, copper products, and other materials, and sandblasting to remove rust. White alumina has strong grinding power and high sandblasting efficiency. It can be recycled and will not leave residues on the surface of the workpiece. White fused alumina is iron-free without sulfur, chlorine, or other elements. It can be used in dentistry, food, medical equipment, aerospace, and other fields :
i-Surface treatment before spraying for spraying, painting, supersonic thermal spraying, etc., to increase the unevenness of the surface of the material and enhance the holding power of the sprayed material. Thus, it is suitable for preparing the surface treatment before painting the back panels of mobile phones and laptops.
ii.-Surface treatment before metal spray welding and titanium plating, such as sandblasting on the surface before brazing of super-hard grinding wheels and cemented carbide.
2. Manufacturing various abrasive products: cutting discs, ceramic grinding wheels, wire drawing wheels, polishing wheels, metallographic sandpaper, nail strips, sponge polishing wheels, sponge polishing blocks, rubber grinding heads, rubber grinding heads, silver polishing rods, etc. With products.
3. White fused alumina powder is the main raw material for the production of whetstone and honing whetstone. The particle size distribution of the powder is uniform, with fewer impurities, which reduces the rate of the unqualified whetstone.
4. Ceramic industry: FRP ceramic basin additive materials, flat ceramic membranes, tubular ceramic membranes. Moreover, WFA is a basic raw material for the production of alumina ceramic membranes and is also a raw material for alumina foam ceramics.
5. Surface treatment of glass and non-metallic materials: sandblasting, matting, polishing, and matte treatment of colored glass, glass products, ceramic products, bamboo chips, wood products, composite non-metallic materials, and other materials. For instance, rubber materials such as printing rubber rollers, rubber molds, PU materials, acrylic sheets, plastics, and other materials are surface-etched.
6. Semiconductor industry: White fused alumina grit can be used for surface treatment of aluminum alloy semiconductor components, sandblasting for surface treatment before vacuum sputtering, and removal of impurities on the back of wafers. White corundum grinding powder is used for grinding stainless steel components, mobile phone backplanes, grinding metal probes, and other components.
7. Hard alloy and super-hard abrasive tool industry. White fused alumina grain is used for grinding hard alloys such as tungsten alloys and molybdenum alloys. Furthermore, white fused alumina always works for surface treatment before brazing diamonds. White corundum powder is a commonly used auxiliary grinding material for diamond water abrasive pads.
8. Composite materials including printing rubber roller additive materials, thermally conductive glue, thermally conductive potting materials.
9. Dental industry: WFA can remove caries. On the other hand, it can make preparation for healthy tooth structure and of the cavity for bonding restoration with composite restoration materials.
10. Skincare industry: As a material for microdermabrasion in European and American markets, it can exfoliate, exfoliate, blackheads, improve uneven skin tone, reduce age spots, stretch marks, etc.
11. Handicraft industry such as blasting for button polishing, jewelry polishing, etc.
12. Mold processing industry: surface treatment of metal molds, forged steel molds, forged aluminum molds, mold steel, carbon steel.
At the same time, it works for mold processing industries such as matte surface treatment after mold biting. For example, wire cutting molds, glass molds, tire molds, conductive rubber molds, shoe molds, bakelite molds, electroplating molds, button molds, plastic product molds, and other molds all use alumina sand.
13. Addition of wear-resistant materials: White fused alumina grain and powder have high wear resistance, hardness, and a refractory temperature of 1850 degrees. It can be added to composite materials as a wear-resistant material to enhance the strength and heat resistance of the material. For instance, unsaturated polyester resin gel coat, glass fiber reinforced plastic FRP material with wear-resistant aggregate, locomotive brake disc with friction material, polyester glass fiber reinforced plastic grille surface sand, composite wood floor wear-resistant paper additive material, epoxy artesian floor coating wear-resistant Add wear-resistant materials to aggregates and ceramic glazes.
14. Moreover, white fused alumina works for refractory： manufacturing and production of white corundum crucibles, ceramic electronic components production container saggers, refractory bearing plates, and other products.
15. The casting surface sand of precision casting, the shell matrix material of investment casting, and the hanging sand material of shell casting. Meanwhile, white fused alumina can also be used as the raw material for casting coating.
