| Component | 99% Al₂O₃ | 99.5% Al₂O₃ |
|---|---|---|
| Al₂O₃ | ≥ 99.0% | ≥ 99.5% |
| SiO₂ | ≤ 0.20% | ≤ 0.10% |
| Fe₂O₃ | ≤ 0.10% | ≤ 0.05% |
| Na₂O | ≤ 0.20% | ≤ 0.10% |
| CaO + MgO | ≤ 0.50% | ≤ 0.25% |
| Property | 99% Al₂O₃ | 99.5% Al₂O₃ | ||||
|---|---|---|---|---|---|---|
| Al₂O₃ content | ≥ 99.0 % | ≥ 99.5 % | ||||
| Density | 3.85–3.90 g/cm³ | 3.90–3.95 g/cm³ | ||||
| Hardness (Rockwell A) | 88–90 | 88–90 | ||||
| Compressive strength | 2,200–2,500 MPa | 2,200–2,600 MPa | ||||
| Flexural strength | 310–350 MPa | 330–380 MPa | ||||
| Ball diameter variation | Spherical deviation | Surface roughness | Lot diameter variation | |
|---|---|---|---|---|
| Gade | Vdws | △Sph | Ra | DwL |
| μm | ||||
| 5 | 0.13 | 0.13 | 0.014 | 0.25 |
| 10 | 0.25 | 0.25 | 0.020 | 0.5 |
| 16 | 0.4 | 0.4 | 0.032 | 0.8 |
| 20 | 0.5 | 0.5 | 0.040 | 1.0 |
| 40 | 1.0 | 1.0 | 0.080 | 2.0 |
| 100 | 2.5 | 2.5 | 0.125 | 5.0 |
| Dia. (mm) | Inch | Weight / pc (g) | ||||
|---|---|---|---|---|---|---|
| 2.0 | — | 0.0163 | ||||
| 3.0 | — | 0.0551 | ||||
| 3.175 | 1/8" | 0.0654 | ||||
| 4.0 | — | 0.1307 | ||||
| 5.0 | — | 0.2553 | ||||
| 6.0 | — | 0.4411 | ||||
| 6.35 | 1/4" | 0.5229 | ||||
| 8.0 | — | 1.0455 | ||||
| 9.525 | 3/8" | 1.765 | ||||
| 10.0 | — | 2.042 | ||||
| 12.7 | 1/2" | 4.183 | ||||
| 15.875 | 5/8" | 8.169 | ||||
| 19.05 | 3/4" | 14.12 | ||||
| 25.4 | 1" | 33.46 | ||||
Half the weight of steel
At 3.90 g/cm³ an alumina ball weighs about 50% of a chrome steel ball the samesize. Less mass, less centrifugal force at speed — a hybrid ceramic bearing runs faster and cooler on the same cage.
Electrically insulating ceramic balls
Volume resistivity above 10¹⁴ Ω·cm. Insulating rolling elements break the shaft-current path in electric motors and generators, stopping the electrical discharge fluting that kills VFD-driven motor bearings.
Chemically inert, corrosion-proof without lubricant.
Inert alumina resists acids and alkalis except hydrofluoric acid, and needs no oil film to survive. These ceramic spheres run dry in water, chemicals and food-contact duty where chrome steel would rust within days.
Half the weight of steel
At 3.90 g/cm³ an alumina ball weighs about 50% of a chrome steel ball the samesize. Less mass, less centrifugal force at speed — a hybrid ceramic bearing runs faster and cooler on the same cage.
Electrically insulating ceramic balls
Volume resistivity above 10¹⁴ Ω·cm. Insulating rolling elements break the shaft-current path in electric motors and generators, stopping the electrical discharge fluting that kills VFD-driven motor bearings.
Non-magnetic
Zero magnetic signature and no attraction of ferrous debris — required in MRI equipment, magnetic separators, semiconductor handling and metal-detection lines where a non-magnetic ceramic ball is the only option.
Chemically inert, corrosion-proof without lubricant
Inert alumina resists acids and alkalis except hydrofluoric acid, and needs no oil film to survive. These ceramic spheres run dry in water, chemicals and food-contact duty where chrome steel would rust within days.
Hardness HRA 88–90, held at temperature
Harder than any bearing steel, and the hardness holds to 1,500 °C. Chrome steel begins to soften above 120 °C.
Dimensional stability across temperature
Thermal expansion of 8.0–8.4 ×10⁻⁶/K — roughly two-thirds that of steel — so running clearances shift less over a wide temperature swing.
Changzhou Risheng Steel Ball Co., Ltd. has manufactured precision balls in Wujin District, Changzhou since June 1995, building on the technical base of the Wujin Metal Ball Research Institute.
We produce around 5,000 tonnes of precision balls a year and export to 50+ countries. The range covers bearing steel (AISI 52100), stainless (201/304/316/420/440C), carbon steel, copper and alumina ceramic, in diameters from 0.8 to 25.4 mm — one supplier for a mixed bill of materials, quoted and shipped on a single order.
Alumina balls are [produced in-house / sourced from our long-term ceramic partner and 100% inspected in our own metrology lab before shipment].
Ceramic balls chip
Alumina is harder than steel but far less forgiving of impact, so we pack it differently from metal balls.
Individually separated
Balls above 6 mm go into moulded foam trays or partitioned boxes so they cannot strike each other in transit; smaller sizes ship in cushioned poly bags at limited fill weight.
No rust inhibitor needed
Alumina does not corrode — no anti-rust oil, no VCI film. The balls arrive clean and ready to install, with no degreasing step on your line.
Export-grade outer packing
Cartons on fumigation-free pallets, strapped,stretch-wrapped, fragile-marked on all faces.
Full labelling
Purity, precision grade, diameter, quantity and lot number on every carton; custom barcode labelling for OEM receiving systems supported.
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