Steel SUJ2 · heat-treated state
Steel SUJ2 Bainite Hardened
Properties of the Bainite Hardened condition, compared with the other SUJ2 tempers.
Specified for large or shock-loaded bearing rings needing compressive surface stress, better toughness and lower distortion than martensitic hardening.
What is SUJ2 Bainite Hardened?
SUJ2 Bainite Hardened is SUJ2 heat treated to Bainite Hardened — specified for large or shock-loaded bearing rings needing compressive surface stress, better toughness and lower distortion than martensitic hardening. SUJ2 Bainite Hardened has a yield strength of 1,800 MPa (261 ksi) and a tensile strength of 2,100 MPa (305 ksi) — stronger than 99% of steel grades. Elongation at break is 3% and the elastic modulus is 210 GPa (30.5 Msi). SUJ2 Bainite Hardened has a density of 7.81 g/cm³ (0.282 lb/in³), lighter than 84% of steel grades. It melts at 1,425°C (2,597 °F). Annealed is the default condition FabDigit quotes; Bainite Hardened is available on request or by drawing note.
Advantages
- High strength — 1,800 MPa (261 ksi), better than 99% of steel grades
- Polishes to a fine finish — 85/100, better than 99% of steel grades
Limitations
- Difficult to machine — 9/100, worse than 100% of steel grades
- Limited ductility — 3%, worse than 99% of steel grades
- Limited service temperature — 180°C (356 °F), worse than 98% of steel grades
- Difficult to weld — 12/100, worse than 96% of steel grades
SUJ2 Bainite Hardened properties
Typical room-temperature values for SUJ2 Bainite Hardened — 10 properties are specific to this condition; the rest are grade-level values shared by every SUJ2 temper. Each bar shows where the value sits among the steel grades in FabDigit's library — further right is higher.
Physical3
SUJ2 Bainite Hardened has a density of 7.81 g/cm³ (0.282 lb/in³), lighter than 84% of steel grades. It melts at 1,425°C (2,597 °F).
Mechanical15
SUJ2 Bainite Hardened has a yield strength of 1,800 MPa (261 ksi) and a tensile strength of 2,100 MPa (305 ksi) — stronger than 99% of steel grades. Elongation at break is 3% and the elastic modulus is 210 GPa (30.5 Msi).
Thermal6
SUJ2 Bainite Hardened is rated for continuous service to 180°C (356 °F). It conducts heat at 46 W/m·K (26.6 BTU/hr·ft·°F), better than 71% of steel grades. Thermal expansion is 11.9 µm/m·K (6.61 µin/in·°F).
Electrical3
SUJ2 Bainite Hardened conducts electricity at 7 % IACS, worse than 74% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of SUJ2 Bainite Hardened takes about 30 MJ of energy and emits 2.3 kg of CO₂ — more than 55% of steel grades. Typical recycled content is 30%.
Manufacturability8
SUJ2 Bainite Hardened's machinability is not recommended (9/100, worse than 100% of steel grades); weldability not recommended (12/100); formability fair (35/100).
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Other SUJ2 tempers and conditions
SUJ2 is also supplied in 6 other conditions. The full side-by-side table is on the SUJ2 overview.
- AnnealedDefaultStandard stock condition for bars, tubes and rings that will be machined and then through-hardened.420 MPa yield · 192 HB
- Q&TThe functional bearing condition: maximum hardness, wear and rolling-contact fatigue resistance for races, balls and rollers.1,900 MPa yield · 62 HRC
- Bainite HardenedSpecified for large or shock-loaded bearing rings needing compressive surface stress, better toughness and lower distortion than martensitic hardening.1,800 MPa yield · 59 HRC
- Q&T 58-62 HRCPick when a little more toughness and dimensional stability is wanted at modest hardness loss (shafts, cams, gauge bodies).1,750 MPa yield · 60 HRC
- Stress RelievedUse for gauges, spindles and high-temperature bearings that must hold size up to ~200–250 °C, accepting 2–5 HRC lower hardness.1,650 MPa yield · 57 HRC
Working with SUJ2 Bainite Hardened
Is SUJ2 easy to machine?
Machine only in the spheroidize-annealed state (≈40 % of AISI 1212) with rigid setups and carbide tooling; hardened 60+ HRC parts require grinding, honing or CBN hard turning.
Can SUJ2 be welded?
Essentially not weldable — high carbon equivalent causes quench cracking; if unavoidable, preheat 300–400 °C and post-weld temper immediately.
Can SUJ2 be formed, bent or molded?
Cold heading and ring rolling are done from spheroidized stock; hot work 1050–850 °C followed by slow cooling and spheroidize annealing to avoid carbide network.
What surface finishes work on SUJ2?
No anodizing; protect with oil, phosphate, black oxide or thin hard chrome/nickel plating (bake to avoid hydrogen embrittlement), and superfinish raceways for low friction.
SUJ2 chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| CJIS G 4805 SUJ2 | 0.95 – 1.1 | 1 |
| Si | 0.15 – 0.35 | 0.25 |
| Mn | ≤ 0.5 | 0.35 |
| P | ≤ 0.03 | — |
| S | ≤ 0.03 | — |
| Cr | 1.3 – 1.6 | 1.45 |
| Ni | ≤ 0.25 | — |
| Cu | ≤ 0.25 | — |
| Mo | ≤ 0.08 | — |
| Otypical clean-steel oxygen limit for bearing quality | ≤ 0 | — |
| Fe | balance | — |
SUJ2 Bainite Hardened — frequently asked
What is SUJ2 Bainite Hardened used for?
SUJ2 Bainite Hardened is typically used for ball bearing rings and balls, roller bearings and rollers, precision shafts and spindles, linear guide rails, cam followers and gauges and measuring blocks. In short: premium bearing tool steel.
What is the yield strength of SUJ2 Bainite Hardened?
SUJ2 Bainite Hardened has a typical yield strength of 1,800 MPa (261 ksi) and a tensile strength of 2,100 MPa (305 ksi) — stronger than 99% of steel grades. Strength varies by condition: see the 7 listed tempers.
Is SUJ2 Bainite Hardened easy to machine?
Not especially — machinability is rated not recommended (9/100, worse than 100% of steel grades). Machine only in the spheroidize-annealed state (≈40 % of AISI 1212) with rigid setups and carbide tooling; hardened 60+ HRC parts require grinding, honing or CBN hard turning.
Can SUJ2 Bainite Hardened be welded?
Not readily — weldability is rated not recommended (12/100). Essentially not weldable — high carbon equivalent causes quench cracking; if unavoidable, preheat 300–400 °C and post-weld temper immediately.
What surface finishes work on SUJ2 Bainite Hardened?
No anodizing; protect with oil, phosphate, black oxide or thin hard chrome/nickel plating (bake to avoid hydrogen embrittlement), and superfinish raceways for low friction.
Can SUJ2 Bainite Hardened be formed, bent or molded?
Cold heading and ring rolling are done from spheroidized stock; hot work 1050–850 °C followed by slow cooling and spheroidize annealing to avoid carbide network.
What is the maximum service temperature of SUJ2 Bainite Hardened?
SUJ2 Bainite Hardened is rated for continuous use to about 180°C (356 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
Can FabDigit make parts in SUJ2 Bainite Hardened?
Yes — SUJ2 Bainite Hardened is available for CNC machining and sheet metal with instant online pricing. Upload a STEP file to get a price and a DFM check.
Sources
- JIS G 4805 High carbon chromium bearing steels — JISC (2019)
- GB/T 18254 High-carbon chromium bearing steel — SAC (2016)
- ASTM A295 Standard Specification for High-Carbon Anti-Friction Bearing Steel — ASTM (2020)
- EN ISO 683-17 (100Cr6) Heat-treatable steels — ball and roller bearing steels — ISO (2014)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels and High-Performance Alloys — ASM International (1990)
- ASM Handbook Vol.16 — Machining — ASM International (1989)
- 100Cr6 / SUJ2 bearing steel datasheet — Ovako / Böhler (2022)
Property data is compiled from published supplier and standards handbooks and normalised for comparison. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.