Steel SUP9 · heat-treated state
Steel SUP9 Q&T
Properties of the Q&T condition, compared with the other SUP9 tempers.
Standard delivered condition for leaf springs, coil springs, torsion and stabiliser bars.
What is SUP9 Q&T?
SUP9 Q&T is SUP9 heat treated to Q&T — standard delivered condition for leaf springs, coil springs, torsion and stabiliser bars. SUP9 Q&T has a yield strength of 1,250 MPa (181 ksi) and a tensile strength of 1,420 MPa (206 ksi) — stronger than 95% of steel grades. Elongation at break is 9% and the elastic modulus is 206 GPa (29.9 Msi). SUP9 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 — 1,250 MPa (181 ksi), better than 95% of steel grades
Limitations
- Limited formability — 10/100, worse than 94% of steel grades
- Limited ductility — 9%, worse than 93% of steel grades
- Limited service temperature — 200°C (392 °F), worse than 93% of steel grades
- Difficult to machine — 28/100, worse than 91% of steel grades
- Difficult to weld — 15/100, worse than 91% of steel grades
SUP9 Q&T properties
Typical room-temperature values for SUP9 Q&T — 16 properties are specific to this condition; the rest are grade-level values shared by every SUP9 temper. Each bar shows where the value sits among the steel grades in FabDigit's library — further right is higher.
Physical3
SUP9 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
SUP9 Q&T has a yield strength of 1,250 MPa (181 ksi) and a tensile strength of 1,420 MPa (206 ksi) — stronger than 95% of steel grades. Elongation at break is 9% and the elastic modulus is 206 GPa (29.9 Msi).
Thermal6
SUP9 Q&T is rated for continuous service to 200°C (392 °F). It conducts heat at 46 W/m·K (26.6 BTU/hr·ft·°F), better than 71% of steel grades. Thermal expansion is 12.3 µm/m·K (6.83 µin/in·°F).
Electrical3
SUP9 Q&T conducts electricity at 7.8 % IACS, worse than 58% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (11/100), worse than 73% of steel grades.
Sustainability4
Producing a kilogram of SUP9 Q&T takes about 26 MJ of energy and emits 2 kg of CO₂ — less than 64% of steel grades. Typical recycled content is 30%.
Manufacturability7
SUP9 Q&T's machinability is poor (28/100, worse than 91% of steel grades); weldability poor (15/100); formability not recommended (10/100).
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Other SUP9 tempers and conditions
SUP9 is also supplied in 6 other conditions. The full side-by-side table is on the SUP9 overview.
- AnnealedDefaultDefault stock condition for machining, cold forming and subsequent heat treatment.440 MPa yield · 217 HB
- Hardened & TemperedPick for blades, agricultural tines, scrapers and wear parts where hardness matters more than toughness.1,500 MPa yield · 50 HRC
- Q&TStandard delivered condition for leaf springs, coil springs, torsion and stabiliser bars.1,250 MPa yield · 43 HRC
- Hot RolledMill as-supplied condition for spring makers who will form then quench and temper themselves.570 MPa yield · 28 HRC
- NormalizedUse to homogenise structure and refine grain before final quench and temper.530 MPa yield · 27 HRC
Working with SUP9 Q&T
Is SUP9 easy to machine?
Machine in the annealed/spheroidised state (≈60 % of 1212); above ~40 HRC use carbide or grind, and expect rapid tool wear.
Can SUP9 be welded?
Poor weldability due to high carbon equivalent — preheat 250–350 °C, low-hydrogen consumables, immediate post-weld temper, and re-heat-treat if the joint is load bearing.
Can SUP9 be formed, bent or molded?
Hot form 850–1050 °C or cold bend only when soft-annealed; harden by oil quench from 830–860 °C and temper 400–500 °C for spring temper.
What surface finishes work on SUP9?
No natural corrosion protection: shot peen for fatigue, then phosphate+oil, zinc/zinc-flake plating or epoxy paint; avoid hydrogen-embrittling plating without bake-out.
SUP9 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 |
|---|---|---|
| CSUP9A: 0.56–0.64 | 0.52 – 0.6 | 0.56 |
| Si | 0.15 – 0.35 | 0.25 |
| Mn | 0.65 – 0.95 | 0.8 |
| CrSUP9A: 0.70–1.00 | 0.65 – 0.95 | 0.8 |
| P | ≤ 0.03 | — |
| S | ≤ 0.03 | — |
| Curesidual, max | ≤ 0.3 | — |
| Niresidual, max | ≤ 0.25 | — |
| Fe | balance | — |
SUP9 Q&T — frequently asked
What is SUP9 Q&T used for?
SUP9 Q&T is typically used for coil springs, leaf springs and springs. In short: premium chromium spring bar.
What is the yield strength of SUP9 Q&T?
SUP9 Q&T has a typical yield strength of 1,250 MPa (181 ksi) and a tensile strength of 1,420 MPa (206 ksi) — stronger than 95% of steel grades. Strength varies by condition: see the 7 listed tempers.
Is SUP9 Q&T easy to machine?
Not especially — machinability is rated poor (28/100, worse than 91% of steel grades). Machine in the annealed/spheroidised state (≈60 % of 1212); above ~40 HRC use carbide or grind, and expect rapid tool wear.
Can SUP9 Q&T be welded?
Not readily — weldability is rated poor (15/100). Poor weldability due to high carbon equivalent — preheat 250–350 °C, low-hydrogen consumables, immediate post-weld temper, and re-heat-treat if the joint is load bearing.
What surface finishes work on SUP9 Q&T?
No natural corrosion protection: shot peen for fatigue, then phosphate+oil, zinc/zinc-flake plating or epoxy paint; avoid hydrogen-embrittling plating without bake-out.
Can SUP9 Q&T be formed, bent or molded?
Hot form 850–1050 °C or cold bend only when soft-annealed; harden by oil quench from 830–860 °C and temper 400–500 °C for spring temper.
What is the maximum service temperature of SUP9 Q&T?
SUP9 Q&T is rated for continuous use to about 200°C (392 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
Can FabDigit make parts in SUP9 Q&T?
Yes — SUP9 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 — JSA (2021)
- GB/T 1222 — (55CrMnA / 60CrMnA) — SAC (2016)
- ASTM A689 / SAE J404 (5160) — ASTM / SAE (2019)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels, and High-Performance Alloys — ASM International (1990)
- ASM Handbook Vol.16 — Machining; Vol.19 — Fatigue and Fracture — ASM International (1996)
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.