For standard series and special designs, material and heat-treatment regime are determined by the construction, dimensions, load, speed, operating temperature, and ambient conditions. Critical parameters are verified against the batch process documentation.
Ring and rolling-element materials
Standard bearings use high-carbon chromium bearing steels. For large-size, corrosion-resistant, high-speed, and special designs, materials with appropriate hardenability, corrosion resistance, and contact-fatigue properties are used.
| Material per ISO | Chinese designation | Typical application |
|---|---|---|
| 100Cr6 | GCr15 | Standard rings and rolling elements |
| 100CrMnSi6-4 | GCr15SiMn | Rings with increased cross-section; enhanced hardenability |
| 100CrMo7-3 | GCr18MnMo | Large-size rings and rollers; designs with higher hardenability requirements |
| X65Cr14 | G65Cr14Mo* | Corrosion-resistant designs |
| X108CrMo17 | G102Cr18Mo | Stainless rings and rolling elements; grade 440C designs |
| Si₃N₄ | Si₃N₄ / 氮化硅 | Ceramic rolling elements for hybrid bearings |
Material as part of the design calculation
Load
Contact stresses, shock loads, and the required service life determine the hardness, structure, and material requirements of the working surfaces.
Size
As the ring cross-section increases, hardenability and structural uniformity become more significant. For large-size parts, the technology is selected separately.
Environment
Moisture, corrosive environments, vacuum, and special temperature conditions may require stainless or specialized materials.
Speed
For high-speed applications, the mass of the rolling elements, heat generation, cage material, and the compatibility of the contact-pair materials are taken into account.
Heat treatment
Required hardness is only part of the result.
Heat treatment must provide not only the hardness of the working surface but also the required microstructure, dimensional stability, and material properties through the cross-section.
OID's production system includes through-hardening and surface hardening, controlled heating and cooling cycles, and subsequent verification of heat-treatment parameters.
| Technology | Purpose |
|---|---|
| Through-hardening | Achieving the required mechanical properties through the working cross-section of the ring for standard designs |
| Induction hardening (HF) | Forming a hardened working layer while retaining the required core properties |
| Tempering and stabilization | Reducing internal stresses and ensuring dimensional stability before final processing |
| Controlled heating and cooling | Reproducibility of structure and hardness from batch to batch |
| Protective atmosphere | Limiting surface oxidation and decarburization during heat treatment |
Standard designs made of hardenable bearing steel typically fall in the range of approximately 58–63 HRC. The specific requirement for hardness, its distribution, and the depth of the hardened layer is established by the technical documentation of the specific product.
What is checked after heat treatment
| Checked parameter | What is confirmed |
|---|---|
| Chemical composition | Conformance of the material to specification |
| Hardness | Conformance to the required range |
| Microstructure | Material condition after heat treatment |
| Hardened-layer depth | Conformance of the hardening profile to the drawing |
| Ovality and taper | Dimensional stability after heat treatment |
| Runout | Geometric stability of the ring |
| Surface condition | Absence of unacceptable defects after processing |
The working surface is formed after heat treatment
After heat treatment, the ring undergoes precision machining of the working and fit surfaces. The final raceway geometry is formed by grinding and, for applicable designs, superfinishing.
The following are checked:
- raceway profile;
- ovality and taper;
- radial and axial runout;
- fit surfaces;
- surface roughness.
Cage material as part of the design
Steel
Standard and special designs where cage strength, stability, and compactness are required
Brass
Higher loads, special designs, and conditions requiring a solid, machined cage
PA66
Lightweight polymer cages for suitable temperature and speed ranges
PEEK / special polymers
Increased requirements for temperature, chemical resistance, and special operating conditions
Cage material is not selected in isolation. Bearing type, load, rotational speed, temperature, lubricant, accelerations, and design requirements are all taken into account.
Special designs
For non-standard conditions, material may be determined individually based on the customer's technical specification or drawing.
Corrosive environment
Stainless and special materials, coatings, and corresponding components.
High temperature and speed
Ring, rolling-element, and cage material and lubrication are considered as a single system.
Large-size designs
Hardenability, hardening profile, ring distortion, and geometric stability after heat treatment are evaluated separately.