100Cr6 is the steel the bearing industry was built on: 1% carbon, 1.5% chromium, through-hardened to 59–65 HRC, cheap, grindable and with the highest fatigue limit of any common bearing material.
| Designations | 100Cr6 (EN) · 52100 (AISI/SAE) · SUJ2 (JIS) · GCr15 (GB) · 1.3505 (DIN) |
|---|---|
| Chemistry | 0.95–1.10% C · 1.35–1.65% Cr · 0.25–0.45% Mn · ≤0.025% P · ≤0.015% S |
| Hardness | 59–65 HRC (typically 60–62 for rings, 62–65 for balls) |
| Density | 7.81 g/cm³ |
| Max service temperature | 120 °C standard · 200 °C (S1) · 250 °C (S2) with stabilising temper |
| Corrosion resistance | None — rusts in humid air without grease or coating |
| Magnetic | Ferromagnetic |
| Fatigue limit | Highest of any common bearing material at equal hardness |
| Relative cost | 1.0× — the baseline for every other material page |
| Availability | 6200/6300, 22200/22300, 30200/30300 series in stock across 11 brands |
The grade is a high-carbon chromium steel designed to harden all the way through a ring section, not just at the surface. Carbon gives the hardness; chromium gives hardenability — the ability to reach full hardness at the centre of a 20 mm wall, not only at the skin. After austenitising, quenching and tempering, the microstructure is tempered martensite with fine carbides, which is what resists rolling contact fatigue.
Chemistry alone does not make bearing steel. Cleanliness does the rest: oxygen content, inclusion size and distribution decide where fatigue cracks start. Bearing-grade 100Cr6 is specified to a cleanliness standard (ISO 4967 or the mill's internal rating) precisely because two heats with identical chemistry can differ by a factor in fatigue life.
Tempering temperature sets the ceiling. A standard temper leaves the ring stable to about 120 °C; above that the martensite continues to transform and the ring grows, which closes clearance and preloads the bearing. A stabilising temper — a second, hotter temper — trades a little hardness for dimensional stability at temperature. In catalogue terms that is S0 to S3:
| Class | Stable to | Hardness trade-off | When to specify |
|---|---|---|---|
| S0 (standard) | 150 °C | none | General purpose, standard grease |
| S1 | 200 °C | ≈1 HRC | Hot housings, motor end shields near a heat source |
| S2 | 250 °C | ≈2 HRC | Fans in ovens, kiln car wheels, hot conveyors |
| S3 | 300 °C | ≈3 HRC | Furnace duty — usually with a special lubricant or dry running |
Alternatives beat 100Cr6 on one axis each — 440C on corrosion, M50 on temperature, silicon nitride on speed — but none beats it on fatigue life per unit of cost in clean, lubricated, room-temperature duty. That is why the ISO 15 dimension plan, the ISO 281 life calculation and most bearing catalogues are implicitly written around this grade. When nothing in the application rules it out, it is the correct default.
| Property | 100Cr6 / 52100 | 440C stainless | Silicon nitride |
|---|---|---|---|
| Hardness | 59–65 HRC | 58–60 HRC | ≈1500 HV |
| Max service temp | 120 °C (250 stabilised) | 250 °C | 400 °C in a bearing |
| Corrosion | None | Good — pits in chlorides | None |
| Dynamic load | Baseline | ≈85–90% of baseline | Similar, but stiffer |
| Speed (dn) | Baseline | ≈90% of baseline | 1.5–2× baseline |
| Relative cost | 1.0× | 2.5–3.5× | 8–15× |
The highest-volume application of 100Cr6 — 6000, 6200 and 6300 series.
Read →Case-carburised variants for shock, through-hardened 100Cr6 for general duty.
Read →High radial load, often with a brass cage and C3 clearance.
Read →22200 and 22300 series in mining, steel and bulk handling.
Read →Functionally yes. 100Cr6 is the EN designation, 52100 the AISI/SAE designation, SUJ2 the JIS designation and GCr15 the Chinese designation. They are the same grade family with small allowed differences in chemistry; a certificate will show the exact heat analysis.
Not reliably. The standard temper is stable to about 120 °C, and above that the ring grows and the grease degrades. A stabilised variant (S1) is rated to 200 °C, but you must also change the grease, the cage and usually the clearance.
Yes, given humidity and temperature swings. Bearings are shipped with a preservative oil, not a permanent coating. Store them in the original packaging, below 25 °C and 60% RH, and do not remove the wrap until the bearing is going into the housing.
58–62 HRC is the usual drawing call-out for rings; balls are typically 60–65 HRC. Asking for the top of the range buys nothing and can reduce toughness — retained austenite and grinding burn matter more than the last point of hardness.
| Industry | Duty | Where it fits | |
|---|---|---|---|
| Electric Motors & Drives | continuous speed, long grease life and shaft voltages from PWM drives | Standard duty | Detail → |
| Fans, Blowers & HVAC | light load, condensation during shutdown and noise limits | Standard fan duty | Detail → |
| Pumps & Compressors | continuous running, thrust reversal and process fluid along the shaft | Standard process pumps | Detail → |
| Machine Tools & Spindles | speed, stiffness and thermal growth of the spindle | Spindle & screw support | Detail → |
| Automotive & Electric Vehicles | shock load, wide temperature swings and electrical erosion from the inverter | Wheel end & driveline | Detail → |
| Conveyors & Bulk Handling | slow speed, abrasive dust and frame misalignment | Head & tail pulleys | Detail → |
| Mining & Aggregate | shock, abrasion and water sprays with little maintenance access | Crushers & screens | Detail → |
| Steel & Metallurgy | very high load, heat and cooling water washing the grease out | Roll neck & mill drives | Detail → |
| Wind Turbines | very long life, oscillating pitch and yaw motion, moisture ingress | Gearbox & main shaft | Detail → |
| Robotics & Automation | high cycle count, oscillating motion and zero tolerance for play | Joints & reducers | Detail → |
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