The global standard for rolling-element bearings — GCr15 per GB/T 18254 and 100Cr6 per EN ISO 683-17, equivalent to SUJ2 and AISI 52100. High-carbon chromium steel with C ~1.0% and Cr 1.30–1.65%, quenched to 60–65 HRC with high contact fatigue strength for bearing rollers, steel balls and bearing rings.
440C is martensitic stainless bearing steel (C ~1.0%, Cr ~17%) for corrosive environments — food, marine, chemical. Reaches 56–60 HRC but lower contact fatigue than 100Cr6 due to larger carbides. GCr15/100Cr6 for standard industrial/automotive bearings where corrosion is handled by seals/plating.
GCr15/100Cr6 for standard bearings; 440C for corrosive environments.Case-carburized steels (20Cr2Ni4, 20MnCr5) have a soft, tough core and hard, carburized surface — for bearings under heavy impact (railway axleboxes, large gearboxes) where through-hardened 100Cr6 might crack. GCr15/100Cr6 is through-hardened uniformly — simpler to heat treat, more cost-effective for the vast majority of standard bearings under moderate impact.
GCr15/100Cr6 for standard bearings; carburized steel for heavy-impact bearings.GCr15SiMn (GB) adds Si (0.40–0.65%) and Mn (0.90–1.20%) for deeper hardening in larger bearing sections (rings above ~100 mm wall). GCr15 is sufficient for standard-size bearings (rings up to ~100 mm, balls up to ~50 mm) and is the more common grade. The choice follows bearing size and through-hardening requirement.
GCr15 for standard-size bearings; GCr15SiMn for large, heavy-section rings.| Element | GCr15 (GB/T 18254) % | 100Cr6 (EN ISO 683-17) % | SUJ2 (JIS G4805) % | Role |
|---|---|---|---|---|
| Carbon (C) | 0.95 – 1.05 | 0.93 – 1.05 | 0.95 – 1.10 | Through-hardening to 60+ HRC; forms hard carbides |
| Silicon (Si) | 0.15 – 0.35 | 0.15 – 0.35 | 0.15 – 0.35 | Deoxidizer |
| Manganese (Mn) | 0.25 – 0.45 | 0.25 – 0.45 | ≤ 0.50 | Hardenability; controlled to avoid carbide banding |
| Chromium (Cr) | 1.30 – 1.65 | 1.35 – 1.65 | 1.30 – 1.60 | Forms hard chromium carbides for wear resistance; deepens hardening |
| Phosphorus (P) | ≤ 0.025 | ≤ 0.025 | ≤ 0.025 | Residual; strictly controlled for fatigue life |
| Sulfur (S) | ≤ 0.025 | ≤ 0.015 | ≤ 0.025 | Residual; sulfides are fatigue initiation sites |
Reference: GB/T 18254; EN ISO 683-17; JIS G4805; ASTM A295 (AISI 52100). Values typical per standard, actual confirmed on MTC. Total oxygen typically ≤15 ppm (premium ≤8 ppm).
| Condition | Hardness (typ.) | Tensile (typ.) | Typical use |
|---|---|---|---|
| Spheroidized annealed (as-supplied) | 179 – 229 HB | ~700 – 850 MPa | Machining, turning, blanking, ring forming — part quenched afterwards |
| Quenched (830–860°C oil) + tempered (150–180°C) | 60 – 65 HRC | ~2,000 – 2,400 MPa | Finished bearing rings, rolling elements — service condition |
| Contact fatigue strength (Hertzian, Q&T) | ~1,500 – 2,000 MPa | — | Determines bearing L10 life under rolling contact |
Values typical per GB/T 18254 / EN ISO 683-17; actual confirmed on MTC. Rings: 60–64 HRC; rolling elements: 62–66 HRC. Contact fatigue depends on hardness, cleanliness and carbide size — premium quality extends L10 life by 2–5x.
| Standard | Grade | C (%) | Cr (%) | Notes |
|---|---|---|---|---|
| GB/T 18254 (China) | GCr15 | 0.95 – 1.05 | 1.30 – 1.65 | Base reference |
| EN ISO 683-17 (Europe) | 100Cr6 (1.3505) | 0.93 – 1.05 | 1.35 – 1.65 | European bearing steel; nearly identical |
| JIS G4805 (Japan) | SUJ2 | 0.95 – 1.10 | 1.30 – 1.60 | Japanese bearing steel; identical family |
| ASTM A295 (USA) | 52100 (AISI) | 0.98 – 1.10 | 1.30 – 1.60 | American bearing steel; slightly higher C min |
Equivalents approximate. For safety-critical bearings, confirm full chemistry, inclusion rating and oxygen content against your governing spec and the MTC.
0.8–3.0 mm strip, formed into inner/outer ring blanks by ring rolling or cold heading, spheroidized for turning, quenched (830–860°C oil) and tempered (150–180°C) to 60–64 HRC. High contact fatigue and uniform carbide distribution give rolling contact life for electric motor, appliance and automotive wheel bearings.
2.0–5.0 mm strip, formed into tapered cone/cup blanks, machined to raceway, quenched and tempered to 60–64 HRC, ground. Used in automotive wheel hubs, differentials and industrial gearboxes — through-hardened 100Cr6 provides subsurface fatigue strength for combined radial/axial loads.
0.30–2.0 mm strip, formed into thin-walled outer rings for needle roller and drawn-cup cylindrical bearings. Used in automotive transmissions, power tools and small motors where radial space is limited. Requires excellent flatness and consistent thickness to form true cylindrical rings; through-hardened 60–64 HRC resists line-contact pitting.
GCr15 / 100Cr6 wire (same billet as strip), cold-headed into ball blanks, deburred, hardened to 62–66 HRC, lapped to grade G10–G100 sphericity. High C and Cr give hardness and wear resistance for millions of revolutions. Ball hardness typically 2–3 HRC higher than ring hardness so wear occurs at the replaceable ring raceway.
Exact parameters confirmed for your section size and target hardness.
Before machining, spheroidize at 780–810°C then slow cool, producing globular cementite in ferrite. Gives soft, machinable 179–229 HB for turning, milling and blanking. Ensures uniform quench response.
After rough machining, austenitize at 830–860°C (typically 840°C), hold 15–30 min per 25 mm. Too low = incomplete hardening; too high = grain growth and retained austenite, reducing fatigue and stability. Controlled atmosphere prevents decarburization.
Oil quench at 60–80°C standard — high C and Cr give through-hardening in sections up to ~50 mm. Thin strip (≤2 mm) may air-harden fully. Martempering (hot oil/salt at 150–200°C) for large/thin-walled rings to minimize distortion. As-quenched: martensite + ~5–8% retained austenite + undissolved carbides.
Temper 150–180°C for 2–4 hours to relieve stresses and transform some retained austenite, reaching 60–65 HRC. For precision bearings, sub-zero treatment (−70 to −80°C) before tempering further reduces retained austenite for dimensional stability. Second low-temp temper sometimes applied after grinding for high-precision (machine tool, aerospace) bearings.
Include thickness × width, quantity, quality level and destination port. Reply within one working day.