99.8% WFA F100 for vitrified abrasive grinding wheel
99.8% WFA F100 White Fused Alumina grain is mostly adopted maetrial in vitrified bond grinding tools. High purity WFA F100 grain obtain excellent self-sharpening properties and grinding force, can significantly improve grinding efficiency, durability, and machining precision. Low-sodium 99.8% white corundum grain offers superior performance compared to ordinary white corundum abrasives. This is reflected in the following aspects:
1. Physical and Chemical Properties
The core characteristics of low-sodium WFA grit are its low Na₂O₃ content (typically ≤0.1%) and high Al₂O₃ purity ( ≥99.8%). This makes it more suitable for applications such as gear grinding and end face grinding.
a. Higher Hardness and Wear Resistance.
Low-sodium, high-purity white corundum has a Mohs hardness closer to its theoretical value of 9.0. After smelting, the α-Al₂O₃ conversion rate of low-sodium white corundum is increased from the normal 90% to over 95%, and the β-phase aluminum oxide content is lower—a substance that can reduce the abrasive’s crystal strength, hardness, and high-temperature resistance. As a result, low-sodium white corundum sand has higher individual grain compressive strength and improved self-sharpening properties, resisting chipping during grinding. It maintains a continuously sharp cutting edge and significantly extends the life of the abrasive tool.
b. Excellent High-Temperature Resistance.
Vitrified bonded abrasive tools are subjected to temperatures of 800-1200°C during sintering, and the grinding process is a typical hot process, generating high temperatures. Low-sodium white corundum has a higher melting point than standard sodium white corundum and is less susceptible to crystal transformation or softening at high temperatures. This prevents the abrasive from becoming “passive” at high temperatures or chemically reacting with the workpiece (such as stainless steel or carbide), ensuring consistent and stable grinding efficiency.
c. High Bulk Density.
Low-sodium white corundum sand has a high specific gravity. Specialized crushing and screening processes increase its bulk density, allowing more abrasive to be ground per unit area, extending the life of the grinding wheel and improving grinding efficiency.
2. High Compatibility with Vitrified Bonds: Improving Abrasive Tool Structural Stability
The core requirement of vitrified bonds (primarily composed of silicate materials such as feldspar, clay, and quartz) is to form a strong bond with the abrasive and a low differential expansion structure. Low-sodium white corundum offers significant advantages in this regard:
a. Reduces sintering defects and improves bond strength.
Impurities in ordinary white corundum react with the SiO₂ and Al₂O₃ in the vitrified bond to form a low-melting-point glass phase (such as albite). This causes excessive softening and uneven shrinkage of the bond during high-temperature sintering. Those will lead to problems such as “cracking” and “sand shedding” in the abrasive tool.
Low-sodium white corundum, with its extremely low content of impurities such as potassium, sodium, silicon, and iron, effectively inhibits this detrimental reaction, allowing the bond to form a tight and uniform interface with the abrasive particles, significantly improving the impact and flexural strength of the abrasive tool.
b. Low Thermal Expansion Coefficient, Reducing Deformation Risk.
Low-sodium white corundum has a very low silicon content, which prevents thermal expansion and volume change under heat. During the cooling process after sintering, it prevents internal stress concentration caused by the large thermal expansion difference between the abrasive and the binder, reduces deformation (such as warping and shrinkage) in the mold, and ensures dimensional accuracy.
3. Optimizing Processing Quality: Reducing Workpiece Damage and Improving Surface Accuracy
For high-precision grinding applications (such as finishing of bearing steel, optical glass, and semiconductor ceramics), low-sodium white corundum can improve workpiece quality by reducing contamination and controlling grinding forces:
1. Low Impurities, No Contamination, Ensuring Workpiece Cleanliness.
The total impurity content (Fe₂O₃, SiO₂, Na₂O) of low-sodium white corundum is ≤0.2%, significantly lower than that of ordinary white corundum. During the grinding process, abrasive impurities that fall off prevent contamination of the workpiece surface (such as “rust spots” on stainless steel workpieces or “scratches” on optical glass). This makes it particularly suitable for machining workpieces in the electronics and medical fields, where surface cleanliness is paramount.
2. More stable grinding force reduces workpiece burn and deformation.
Low-sodium white corundum sand has uniform particle strength, resulting in a more stable load per particle during grinding. This prevents excessive localized grinding forces that can cause workpiece burn such as oxidative discoloration on hardened steel surfaces. It can also avoid microscopic deformation such as warping in thin-walled ceramic parts. Furthermore, its sharp cutting edge reduces grinding heat generation, and combined with the excellent heat dissipation of the vitrified bond (which has a higher thermal conductivity than resin bonds), it improves machining accuracy.
