AISI 52100 Bearing Steel — High-Carbon Chromium Alloy for Bearings, Races & Rolling Elements
ASTM A295 (UNS G52986) · Published: 2026-06-14 · Updated: 2026-06-17
AISI 52100 is the standard bearing steel against which all other rolling-element bearing materials are measured. Its 1.0% carbon and 1.5% chromium composition creates a microstructure of hard martensite with uniformly dispersed fine chromium...
AISI 52100 is the standard bearing steel against which all other rolling-element bearing materials are measured. Its 1.0% carbon and 1.5% chromium composition creates a microstructure of hard martensite with uniformly dispersed fine chromium carbides — the ideal structure for resisting the Hertzian contact stresses that bearings experience with every revolution. A properly heat-treated 52100 bearing race can survive billions of stress cycles without spalling.
The critical metallurgical requirement for 52100 is microcleanliness. Non-metallic inclusions — particularly alumina (Al2O3) and titanium carbonitrides — act as stress concentrators that initiate fatigue spalling in bearing applications. Bearing-grade 52100 is produced to strict cleanliness specifications: ASTM A295 specifies maximum inclusion content, and premium bearing steel is often vacuum degassed (VIM-VAR) to achieve aircraft-quality cleanliness.
Beyond bearings, 52100 is used for high-wear applications: fuel injector plungers, ball screws, check valve balls, and precision gauges. The common thread: anywhere two surfaces roll or slide against each other under high contact stress, 52100 is in the conversation.
Quick Facts
| Category | Alloy Steel |
| Standard | ASTM A295 (UNS G52986) |
| Density | 7810 |
| Yield Strength | 1,400-2,000 MPa (through-hardened, dependent on temper) |
| Tensile Strength | 1,800-2,500 MPa |
Global Equivalents & Cross-Reference
| Alternative Standard / Grade | Action |
|---|---|
| EN 1.3505 | Compare |
| 100Cr6 | Compare |
| JIS SUJ2 | Compare |
| GB GCr15 | Compare |
Related Materials
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Frequently Asked Questions
52100 vs 440C for bearings — which to choose?
52100 for high-load, well-lubricated applications. 440C for corrosive environments or when lubrication may be intermittent. 52100 has higher fatigue life and load capacity than 440C; 440C has dramatically better corrosion resistance. If your bearing will see water, salt, chemicals, or intermittent lubrication — pay the premium for 440C. If it will run in clean oil at moderate temperatures — 52100 is the superior bearing material.
At what temperature does 52100 begin to lose hardness?
52100 is tempered at only 150-180°C, so it begins to lose hardness above approximately 120°C (250°F). For bearing applications above 150°C, spec M50 tool steel or a high-speed steel like M2 that retains hardness to 500°C+. Never use 52100 in applications exceeding 150°C without verifying that the reduced hardness is acceptable for the load.
References & International Standards
- ASTM International. Standard Specifications for Steel & Metal Alloys. astm.org
- International Organization for Standardization (ISO). Metallic Materials — Cross-Reference Database. iso.org
- American Iron and Steel Institute (AISI). Steel Grade Designations & Equivalents. steel.org
- European Committee for Standardization (CEN). EN Steel Standards & Numbering System. cencenelec.eu