Steel SUJ1-MQ (Martempered / austempered)
Heat-treated state
JIS SUJ1
Bainitic or martempered route chosen to cut quench distortion and raise toughness/compressive residual stress in thin rings.
Values for the MQ condition
Other SUJ1 tempers and conditions
SUJ1 is listed in 9 conditions; see the grade overview at SUJ1.
Compare all 9 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
AnnealedDefault spheroidize annealed (soft, as-supplied bar/tube) | Standard stock condition for machining, cold forming and turning of rings/rollers before hardening. | 400 | 660 | 22 | 190 HB | 46 W/m·K |
Hot rolled | Mill as-rolled condition, usually only an intermediate before spheroidizing; hard, low-ductility pearlite. | 550 | 950 | 12 | 29 HRC | — |
Normalized | Used to break up carbide networks in forgings before spheroidizing; not a delivery condition for machining. | 600 | 1,000 | 10 | 31 HRC | 6.2 % IACS |
Cold drawn | Choose for close-tolerance bright bar or seamless bearing tube going straight into automatic-lathe machining. | 620 | 780 | 12 | 235 HB | — |
Induction hardened | Use on larger sections where SUJ1's limited hardenability prevents through hardening: hard raceway surface, tougher core. | 950 | 1,100 | 6 | 60 HRC | 5.6 % IACS |
quenched and tempered ~250 °C (dimensionally stabilized) | Stabilized temper for parts running at 150–200 °C or needing tight long-term dimensional stability. | 1,650 | 1,950 | 2 | 57 HRC | — |
MQThis page Martempered / austempered | Bainitic or martempered route chosen to cut quench distortion and raise toughness/compressive residual stress in thin rings. | 1,700 | 2,050 | 2 | 58 HRC | 6 % IACS |
oil quenched from ~820–840 °C, tempered 150–180 °C | Standard service condition for balls, rollers and small rings in light/medium-duty bearings up to ~120 °C. | 1,800 | 2,200 | 1 | 60 HRC | 36 W/m·K |
oil quenched, tempered ~150 °C (maximum hardness) | Pick for maximum wear resistance and indentation strength on small sections; lowest toughness of the range. | 1,950 | 2,400 | 0.5 | 62 HRC | — |
What is SUJ1-MQ?
SUJ1-MQ is SUJ1 heat treated to MQ — bainitic or martempered route chosen to cut quench distortion and raise toughness/compressive residual stress in thin rings. SUJ1-MQ has a yield strength of 1,700 MPa (247 ksi) and a tensile strength of 2,050 MPa (297 ksi) — stronger than 99% of steel grades. Elongation at break is 2% and the elastic modulus is 208 GPa (30.2 Msi). SUJ1-MQ 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). Annealed is the default condition FabDigit quotes; MQ is available on request or by drawing note.
Advantages
- High strength — 1,700 MPa (247 ksi), better than 99% of steel grades
- Polishes to a fine finish — 80/100, better than 97% of steel grades
Limitations
- Difficult to weld — 5/100, worse than 100% of steel grades
- Limited ductility — 2%, worse than 99% of steel grades
- Limited service temperature — 150°C (302 °F), worse than 99% of steel grades
- Difficult to machine — 10/100, worse than 99% of steel grades
- Limited formability — 3/100, worse than 99% of steel grades
SUJ1-MQ properties
Typical room-temperature values for SUJ1-MQ; 22 are specific to this condition. Other listed values are SUJ1 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
SUJ1-MQ 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
SUJ1-MQ has a yield strength of 1,700 MPa (247 ksi) and a tensile strength of 2,050 MPa (297 ksi) — stronger than 99% of steel grades. Elongation at break is 2% and the elastic modulus is 208 GPa (30.2 Msi).
Thermal6
SUJ1-MQ is rated for continuous service to 150°C (302 °F). It conducts heat at 42 W/m·K (24.3 BTU/hr·ft·°F), worse than 56% of steel grades. Thermal expansion is 11.9 µm/m·K (6.61 µin/in·°F).
Electrical3
SUJ1-MQ conducts electricity at 6 % IACS, worse than 78% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of SUJ1-MQ takes about 29 MJ of energy and emits 2.1 kg of CO₂ — less than 53% of steel grades. Typical recycled content is 25%.
Manufacturability8
SUJ1-MQ's machinability is not recommended (10/100, worse than 99% of steel grades); weldability not recommended (5/100); formability not recommended (3/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with SUJ1-MQ
Is SUJ1 easy to machine?
Machine only in the spheroidize-annealed state (~190 HB) with coated carbide and rigid setups; after hardening use CBN hard turning or grinding.
Can SUJ1 be welded?
Effectively unweldable at ~1 %C — if unavoidable, preheat 300–400 °C, use low-hydrogen filler and re-anneal immediately; expect martensite cracking.
Can SUJ1 be formed, bent or molded?
Cold heading/ring rolling only from fully spheroidized stock; hot forging 1050–1100 °C with slow cool then spheroidize anneal (860 °C isothermal at ~720 °C).
What surface finishes work on SUJ1?
Grind, lap and superfinish for raceways; protect with oil, black oxide, manganese phosphate or hard chrome — no anodizing and negligible bare-metal corrosion resistance.
SUJ1 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 |
| Pimpurity limit | ≤ 0.03 | 0.01 |
| Simpurity limit | ≤ 0.03 | 0.01 |
| Crlower than SUJ2 (1.30–1.60), hence lower hardenability | 0.9 – 1.2 | 1.05 |
| Moresidual | ≤ 0.08 | 0.02 |
| Niresidual | ≤ 0.25 | 0.08 |
| Curesidual | ≤ 0.25 | 0.08 |
| Ooxygen limit for cleanliness (vacuum-degassed bearing steel practice) | ≤ 0 | 8×10⁻⁴ |
| Fe | balance | — |
SUJ1-MQ — frequently asked
What is SUJ1-MQ used for?
SUJ1-MQ is typically used for small ball and roller bearings, bearing balls and rollers, light-duty rollers and track wheels, needle roller pins, thin-section inner rings and cam follower rollers. In short: lightest-duty SUJ grade; easiest-forming bearing steel; 50100 equivalent.
What is the yield strength of SUJ1-MQ?
SUJ1-MQ has a typical yield strength of 1,700 MPa (247 ksi) and a tensile strength of 2,050 MPa (297 ksi) — stronger than 99% of steel grades. Strength varies by condition: see the 9 listed tempers.
Is SUJ1-MQ easy to machine?
Not especially — machinability is rated not recommended (10/100, worse than 99% of steel grades). Machine only in the spheroidize-annealed state (~190 HB) with coated carbide and rigid setups; after hardening use CBN hard turning or grinding.
Can SUJ1-MQ be welded?
Not readily — weldability is rated not recommended (5/100). Effectively unweldable at ~1 %C — if unavoidable, preheat 300–400 °C, use low-hydrogen filler and re-anneal immediately; expect martensite cracking.
What surface finishes work on SUJ1-MQ?
Grind, lap and superfinish for raceways; protect with oil, black oxide, manganese phosphate or hard chrome — no anodizing and negligible bare-metal corrosion resistance.
Can SUJ1-MQ be formed, bent or molded?
Cold heading/ring rolling only from fully spheroidized stock; hot forging 1050–1100 °C with slow cool then spheroidize anneal (860 °C isothermal at ~720 °C).
What is the maximum service temperature of SUJ1-MQ?
SUJ1-MQ is rated for continuous use to about 150°C (302 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between SUJ1 Annealed and SUJ1-MQ?
Annealed is the default condition — standard stock condition for machining, cold forming and turning of rings/rollers before hardening. MQ: bainitic or martempered route chosen to cut quench distortion and raise toughness/compressive residual stress in thin rings. Yield strength is 400 MPa in Annealed versus 1,700 MPa in MQ.
Sources
- JIS G 4805 High-carbon chromium bearing steels — JSA (2019)
- ASTM A295/A295M High-Carbon Anti-Friction Bearing Steel (incl. 50100) — ASTM (2014)
- GB/T 18254 (GCr9 / GCr15) — SAC (2016)
- ASM Handbook Vol.1: Properties and Selection — Irons, Steels, and High-Performance Alloys (bearing steels) — ASM International (1990)
- Machinery's Handbook (machinability ratings, heat treatment of bearing steels) — Industrial Press (2020)
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.