Steel SUJ4 QT55-58HRC
Hardness band
JIS SUJ4
Choose for bearings and rolls running up to ~250 °C, where the Mo addition preserves hardness after high tempering.
Values for the QT55-58HRC condition
Other SUJ4 tempers and conditions
SUJ4 is listed in 7 conditions; see the grade overview at SUJ4.
- A
- HR
- CD
- QT55-58HRC
- BH
- QT58-62HRC
- QT60-64HRC
Compare all 7 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
ADefault Solution annealed | Standard supply condition for machining rings, rollers and blanks before hardening. | 420 | 700 | 22 | 190 HB | 45 W/m·K |
Hot rolled | Cheapest mill condition for forging or ring-rolling stock; must be spheroidize annealed before machining. | 550 | 950 | 12 | 27 HRC | 3.5 % IACS |
Cold drawn | Bright-drawn bar and cold-heading wire for small rollers, pins and turned parts with good size tolerance. | 620 | 800 | 12 | 21 HRC | 3.5 % IACS |
QT55-58HRCThis page high-temperature tempered (300–350 °C) for elevated-temperature service | Choose for bearings and rolls running up to ~250 °C, where the Mo addition preserves hardness after high tempering. | 1,650 | 1,950 | 1 | 57 HRC | 3 % IACS |
Bainite hardened | Lower-bainite treatment giving compressive surface stresses, higher toughness and better tolerance of contaminated lubrication or debris denting. | 1,750 | 2,100 | 2 | 60 HRC | 3.2 % IACS |
tempered 200–250 °C (dimensionally stabilized, S1/TS class) | Pick when the part sees 150–200 °C and dimensional stability matters more than peak hardness. | 1,800 | 2,150 | — | 60 HRC | 35 W/m·K |
oil/salt quenched, tempered 150–180 °C (standard martensitic hardening) | Standard finished-bearing condition: maximum contact fatigue life and wear resistance for service below ~120 °C. | 1,900 | 2,350 | 1 | 62 HRC | 34 W/m·K |
What is SUJ4 QT55-58HRC?
SUJ4 QT55-58HRC is SUJ4 heat treated to QT55-58HRC — choose for bearings and rolls running up to ~250 °C, where the Mo addition preserves hardness after high tempering. SUJ4 QT55-58HRC has a yield strength of 1,650 MPa (239 ksi) and a tensile strength of 1,950 MPa (283 ksi) — stronger than 99% of steel grades. Elongation at break is 1% and the elastic modulus is 210 GPa (30.5 Msi). SUJ4 QT55-58HRC has a density of 7.81 g/cm³ (0.282 lb/in³), lighter than 84% of steel grades. It melts at 1,400°C (2,552 °F). A is the default condition FabDigit quotes; QT55-58HRC is available on request or by drawing note.
Advantages
- High strength — 1,650 MPa (239 ksi), better than 99% of steel grades
- Polishes to a fine finish — 85/100, better than 99% of steel grades
Limitations
- Difficult to machine — 8/100, worse than 100% of steel grades
- Difficult to weld — 3/100, worse than 100% of steel grades
- Limited formability — 2/100, worse than 100% of steel grades
- Limited ductility — 1%, worse than 99% of steel grades
- Low electrical conductivity — 3 % IACS, worse than 91% of steel grades
SUJ4 QT55-58HRC properties
Typical room-temperature values for SUJ4 QT55-58HRC; 22 are specific to this condition. Other listed values are SUJ4 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
SUJ4 QT55-58HRC has a density of 7.81 g/cm³ (0.282 lb/in³), lighter than 84% of steel grades. It melts at 1,400°C (2,552 °F).
Mechanical15
SUJ4 QT55-58HRC has a yield strength of 1,650 MPa (239 ksi) and a tensile strength of 1,950 MPa (283 ksi) — stronger than 99% of steel grades. Elongation at break is 1% and the elastic modulus is 210 GPa (30.5 Msi).
Thermal6
SUJ4 QT55-58HRC is rated for continuous service to 250°C (482 °F). It conducts heat at 40 W/m·K (23.1 BTU/hr·ft·°F), worse than 64% of steel grades. Thermal expansion is 12 µm/m·K (6.67 µin/in·°F).
Electrical3
SUJ4 QT55-58HRC conducts electricity at 3 % IACS, worse than 91% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of SUJ4 QT55-58HRC takes about 33 MJ of energy and emits 2.4 kg of CO₂ — more than 76% of steel grades. Typical recycled content is 25%.
Manufacturability7
SUJ4 QT55-58HRC's machinability is not recommended (8/100, worse than 100% of steel grades); weldability not recommended (3/100); formability not recommended (2/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with SUJ4 QT55-58HRC
Is SUJ4 easy to machine?
Machine only in the spheroidize-annealed condition (≈40% of AISI 1212) with coated carbide and rigid setups; hardened 60+ HRC parts require grinding, honing or CBN hard turning.
Can SUJ4 be welded?
Essentially unweldable — ~1% C gives severe quench cracking; if repair is unavoidable use 300–400 °C preheat, low-hydrogen consumables and immediate post-weld temper.
Can SUJ4 be formed, bent or molded?
Hot forge/ring-roll at 1050–1100 °C (stop above ~900 °C) then spheroidize anneal at 780–800 °C with slow cooling; cold heading and cold ring rolling need fully spheroidized structure.
What surface finishes work on SUJ4?
Not anodizable; protect with rust-preventive oil, phosphate, black oxide or thin dense chrome, and superfinish/lap raceways to Ra ≤0.05 µm for bearing life.
SUJ4 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 |
|---|---|---|
| C | 0.95 – 1.1 | 1.02 |
| Si | 0.15 – 0.35 | 0.25 |
| Mn | ≤ 0.5 | 0.35 |
| Cr | 1.3 – 1.6 | 1.45 |
| Mothe distinguishing addition vs SUJ2; raises hardenability | 0.1 – 0.25 | 0.18 |
| Pimpurity limit | ≤ 0.03 | — |
| Simpurity limit | ≤ 0.03 | — |
| Niresidual | ≤ 0.25 | — |
| Curesidual | ≤ 0.25 | — |
| Ototal oxygen, vacuum-degassed bearing quality | ≤ 0 | 8×10⁻⁴ |
| Fe | balance | — |
SUJ4 QT55-58HRC — frequently asked
What is SUJ4 QT55-58HRC used for?
SUJ4 QT55-58HRC is typically used for large bearing rings and races, heavy-duty cylindrical rollers, thick-section tapered roller cups and cones, spherical roller bearing outer rings, gearbox and wind turbine bearing components and cam followers and track rollers. In short: deeper-hardening SUJ2 alternative; mo-alloyed bearing steel; for thick bearing sections.
What is the yield strength of SUJ4 QT55-58HRC?
SUJ4 QT55-58HRC has a typical yield strength of 1,650 MPa (239 ksi) and a tensile strength of 1,950 MPa (283 ksi) — stronger than 99% of steel grades. Strength varies by condition: see the 7 listed tempers.
Is SUJ4 QT55-58HRC easy to machine?
Not especially — machinability is rated not recommended (8/100, worse than 100% of steel grades). Machine only in the spheroidize-annealed condition (≈40% of AISI 1212) with coated carbide and rigid setups; hardened 60+ HRC parts require grinding, honing or CBN hard turning.
Can SUJ4 QT55-58HRC be welded?
Not readily — weldability is rated not recommended (3/100). Essentially unweldable — ~1% C gives severe quench cracking; if repair is unavoidable use 300–400 °C preheat, low-hydrogen consumables and immediate post-weld temper.
What surface finishes work on SUJ4 QT55-58HRC?
Not anodizable; protect with rust-preventive oil, phosphate, black oxide or thin dense chrome, and superfinish/lap raceways to Ra ≤0.05 µm for bearing life.
Can SUJ4 QT55-58HRC be formed, bent or molded?
Hot forge/ring-roll at 1050–1100 °C (stop above ~900 °C) then spheroidize anneal at 780–800 °C with slow cooling; cold heading and cold ring rolling need fully spheroidized structure.
What is the maximum service temperature of SUJ4 QT55-58HRC?
SUJ4 QT55-58HRC is rated for continuous use to about 250°C (482 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between SUJ4-A and SUJ4-BH?
A is the default condition — standard supply condition for machining rings, rollers and blanks before hardening. BH: lower-bainite treatment giving compressive surface stresses, higher toughness and better tolerance of contaminated lubrication or debris denting. Yield strength is 420 MPa in A versus 1,750 MPa in BH.
Sources
- JIS G 4805 High carbon chromium bearing steels — JSA (2019)
- ISO 683-17 Heat-treatable steels — Ball and roller bearing steels — ISO (2014)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels (bearing steels) — ASM International (1990)
- ASM Handbook Vol.19 — Fatigue and Fracture — ASM International (1996)
- Bearing steel grades 100Cr6 / 100CrMo7 data sheets — Sanyo Special Steel / Ovako (2022)
- GCr15/GCr15SiMo — Mysteel / 1688 (2025)
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.