ASTM A295/A295M — Standard Specification for High-Carbon Anti-Friction Bearing Steel
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Scope
High-carbon chromium bearing steels for balls, rollers and races: 52100 (and 51100, 50100, 5195, K19526, 1070M) as bar, rod, wire and tube. Specifies chemistry including oxygen ≤ 15 ppm, inclusion cleanliness (E45 method A/D limits), decarburization, macroetch, annealed hardness and microstructure; heat-treated properties are by agreement. Carburizing bearing steels are in A534.
Grades covered by ASTM A295
| Grade | No. | Type | C % | Yield MPa | Tensile MPa | Nearest equivalents |
|---|---|---|---|---|---|---|
| 52100 | G52986 | High-carbon chromium bearing steel | 0.93 – 1.05 | ≈ 450 | ≈ 680 | 100Cr6, SUJ2, GCr15 |
Revision history and superseded standards
| Year | Change |
|---|---|
| 1946 | First issued |
| 2021 | A295/A295M-21 — current |
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Related standards
Bearing steel is judged on cleanliness
A295 covers high-carbon anti-friction bearing steel, dominated by 52100 (UNS G52986), and what distinguishes it from any other 1 % carbon chromium steel is not the analysis. It is the inclusion content.
A rolling-contact fatigue crack starts at a non-metallic inclusion under the raceway surface. Bearing steel is therefore specified with a maximum inclusion rating by type and size, vacuum degassing as a normal production route, and macroetch requirements for segregation and porosity. Two bars with identical chemistry can differ in bearing life by an order of magnitude on cleanliness alone.
Annealed on delivery, hardened in use
52100 is delivered spheroidise annealed, around 190–220 HB, which is the only condition in which it can be machined. The finished part is then austenitised near 840 °C, quenched in oil and tempered low — typically 150–180 °C — to reach 60–66 HRC.
That low tempering temperature is a service limit as well as a process step: above about 150 °C in use, the structure tempers further and the raceway loses hardness. Bearings for hot service are ordered in a stabilised condition, which is an explicit heat treatment variant rather than an operating assumption.