Bearing steel grades
1 bearing steel grades from 1 designation systems, each with a full data sheet. Sorted by system; the yield and tensile values are the first line of each grade's mechanical table.
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AISI / SAE
| Grade | No. | Type | C % | Yield MPa | Tensile MPa | Equivalents |
|---|---|---|---|---|---|---|
| 52100 | G52986 | High-carbon chromium bearing steel | 0.93 – 1.05 | ≈ 450 | ≈ 680 | 100Cr6, SUJ2, GCr15 |
One grade dominates, and cleanliness is why
Through-hardening bearing steel is essentially one material worldwide: 100Cr6 in EN, 52100 in AISI, SUJ2 in JIS, GCr15 in GB. About 1 % carbon and 1.5 % chromium, hardened to 60–64 HRC.
What separates a good bearing steel from a bad one is not the analysis but the inclusion content. A rolling-contact surface fails from subsurface fatigue that starts at a non-metallic inclusion, so oxygen content, inclusion rating to ASTM E45 or DIN 50602 and vacuum degassing are the real specification. Two bars of 100Cr6 with identical certificates of analysis can differ by an order of magnitude in bearing life.
Heat treatment defines the part
Bearing steel is supplied spheroidise-annealed for machining and then hardened. The cycle is unforgiving: austenitise around 840 °C, quench in oil, temper at 160–180 °C to relieve stress without losing hardness.
Retained austenite is the variable to watch. Too much and the part changes dimension in service as it transforms; too little and toughness suffers. Precision bearings are often sub-zero treated and stabilised at higher tempering temperatures for dimensional stability at operating heat.
faq.h
What is 100Cr6 steel used for?
Rolling-element bearings — balls, rollers, races — and by extension any through-hardened precision part needing 60 to 64 HRC and high rolling-contact fatigue resistance.
What is the AISI equivalent of 100Cr6?
AISI 52100. JIS SUJ2 and GB GCr15 are the Japanese and Chinese counterparts, all with about 1 % carbon and 1.5 % chromium.
Why does steel cleanliness matter so much in bearings?
Rolling-contact fatigue cracks initiate at non-metallic inclusions below the surface. Two bars with identical chemistry but different inclusion ratings can differ enormously in bearing life, which is why oxygen content and vacuum degassing are specified.
What hardness should a bearing be?
Typically 60 to 64 HRC after austenitising near 840 °C, oil quenching and tempering at 160 to 180 °C. Higher tempering temperatures are used where dimensional stability at operating temperature matters more than peak hardness.