Steel SUP10 · heat-treated state
Steel SUP10 Q&T
Properties of the Q&T condition, compared with the other SUP10 tempers.
Standard spring condition: highest usable strength with adequate toughness for leaf, coil and torsion springs.
What is SUP10 Q&T?
SUP10 Q&T is SUP10 heat treated to Q&T — standard spring condition: highest usable strength with adequate toughness for leaf, coil and torsion springs. SUP10 Q&T has a yield strength of 1,300 MPa (189 ksi) and a tensile strength of 1,450 MPa (210 ksi) — stronger than 95% of steel grades. Elongation at break is 9% and the elastic modulus is 206 GPa (29.9 Msi). SUP10 Q&T has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,420°C (2,588 °F). Annealed is the default condition FabDigit quotes; Q&T is available on request or by drawing note.
Advantages
- High strength — 1,300 MPa (189 ksi), better than 95% of steel grades
Limitations
- Difficult to weld — 10/100, worse than 99% of steel grades
- Limited formability — 8/100, worse than 97% of steel grades
- Limited ductility — 9%, worse than 93% of steel grades
- Difficult to machine — 25/100, worse than 93% of steel grades
- Limited service temperature — 230°C (446 °F), worse than 88% of steel grades
SUP10 Q&T properties
Typical room-temperature values for SUP10 Q&T — 17 properties are specific to this condition; the rest are grade-level values shared by every SUP10 temper. Each bar shows where the value sits among the steel grades in FabDigit's library — further right is higher.
Physical3
SUP10 Q&T has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,420°C (2,588 °F).
Mechanical14
SUP10 Q&T has a yield strength of 1,300 MPa (189 ksi) and a tensile strength of 1,450 MPa (210 ksi) — stronger than 95% of steel grades. Elongation at break is 9% and the elastic modulus is 206 GPa (29.9 Msi).
Thermal6
SUP10 Q&T is rated for continuous service to 230°C (446 °F). It conducts heat at 44 W/m·K (25.4 BTU/hr·ft·°F), better than 57% of steel grades. Thermal expansion is 12.5 µm/m·K (6.94 µin/in·°F).
Electrical3
SUP10 Q&T conducts electricity at 7.5 % IACS, worse than 68% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of SUP10 Q&T takes about 30 MJ of energy and emits 2.2 kg of CO₂ — more than 55% of steel grades. Typical recycled content is 30%.
Manufacturability7
SUP10 Q&T's machinability is poor (25/100, worse than 93% of steel grades); weldability not recommended (10/100); formability not recommended (8/100).
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Other SUP10 tempers and conditions
SUP10 is also supplied in 7 other conditions. The full side-by-side table is on the SUP10 overview.
- AnnealedDefaultStock condition for machining, cold forming and pre-heat-treat blanks before quench and temper.480 MPa yield · 210 HB
- Hardened & TemperedPick when maximum strength/wear is needed (valve springs, hand tools, chisels) and toughness can be traded away.1,500 MPa yield · 48 HRC
- Q&TStandard spring condition: highest usable strength with adequate toughness for leaf, coil and torsion springs.1,300 MPa yield · 44 HRC
- Q&T 38-42 HRCUse where fatigue with impact loading matters more than peak stress (stabiliser bars, heavy leaf springs).1,120 MPa yield · 40 HRC
Working with SUP10 Q&T
Is SUP10 easy to machine?
Machine in the annealed condition (~55 % of 1212) with rigid setups and carbide at moderate speed; above 40 HRC switch to grinding, CBN or EDM.
Can SUP10 be welded?
Effectively not weldable in the hardened state — high carbon equivalent causes cracking; if unavoidable, preheat 300–350 °C, low-hydrogen consumables and re-quench/temper the whole part.
Can SUP10 be formed, bent or molded?
Cold form or coil only when annealed or as oil-tempered wire; hot forge 1050–1150 °C, finish above 900 °C, slow cool, then harden from 830–870 °C in oil and temper 400–500 °C.
What surface finishes work on SUP10?
No corrosion resistance of its own: shot-peen springs then phosphate + oil, powder coat or paint; avoid acid pickling and electroplating on hardened parts unless baked to relieve hydrogen.
SUP10 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 G4801 SUP10 | 0.47 – 0.55 | 0.51 |
| Si | 0.15 – 0.35 | 0.25 |
| Mn | 0.65 – 0.95 | 0.8 |
| P | ≤ 0.03 | — |
| S | ≤ 0.03 | — |
| Cr | 0.8 – 1.1 | 0.95 |
| Vgrain refinement, relaxation resistance | 0.15 – 0.25 | 0.2 |
| Cu | ≤ 0.3 | — |
| Fe | balance | — |
SUP10 Q&T — frequently asked
What is SUP10 Q&T used for?
SUP10 Q&T is typically used for coil springs, leaf springs and springs. In short: heavy-duty spring bar.
What is the yield strength of SUP10 Q&T?
SUP10 Q&T has a typical yield strength of 1,300 MPa (189 ksi) and a tensile strength of 1,450 MPa (210 ksi) — stronger than 95% of steel grades. Strength varies by condition: see the 8 listed tempers.
Is SUP10 Q&T easy to machine?
Not especially — machinability is rated poor (25/100, worse than 93% of steel grades). Machine in the annealed condition (~55 % of 1212) with rigid setups and carbide at moderate speed; above 40 HRC switch to grinding, CBN or EDM.
Can SUP10 Q&T be welded?
Not readily — weldability is rated not recommended (10/100). Effectively not weldable in the hardened state — high carbon equivalent causes cracking; if unavoidable, preheat 300–350 °C, low-hydrogen consumables and re-quench/temper the whole part.
What surface finishes work on SUP10 Q&T?
No corrosion resistance of its own: shot-peen springs then phosphate + oil, powder coat or paint; avoid acid pickling and electroplating on hardened parts unless baked to relieve hydrogen.
Can SUP10 Q&T be formed, bent or molded?
Cold form or coil only when annealed or as oil-tempered wire; hot forge 1050–1150 °C, finish above 900 °C, slow cool, then harden from 830–870 °C in oil and temper 400–500 °C.
What is the maximum service temperature of SUP10 Q&T?
SUP10 Q&T is rated for continuous use to about 230°C (446 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
Can FabDigit make parts in SUP10 Q&T?
Yes — SUP10 Q&T 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 4801 Spring steels — Japanese Standards Association (2021)
- GB/T 1222 (50CrVA) — SAC (2016)
- SAE J404 / ASTM A231 (6150 Cr-V spring steel) — SAE / ASTM (2020)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels — ASM International (1990)
- Machinery's Handbook (machinability ratings, spring design) — Industrial Press (2020)
- Mysteel / 1688 spring steel bar spot quotations (2026)
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.