Steel SUP11A QT-SP
Finish state
GB SUP11A
QT-SP = q&T + shot peened (and optionally stress-peened) spring
Standard finished-spring condition for fatigue-critical suspension parts — peening compressive layer roughly doubles usable fatigue life over as-tempered surface.
Values for the QT-SP condition
Other SUP11A tempers and conditions
SUP11A is listed in 7 conditions; see the grade overview at SUP11A.
Compare all 7 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Solution annealed | Softest condition — choose for cold forming, hole punching, eye rolling and machining before hardening. | 420 | 700 | 22 | 210 HB | 44 W/m·K |
Hot rolled | Mill supply condition for flats and bars that will be hot-formed and then quenched and tempered by the spring maker. | 550 | 900 | 14 | 27 HRC | 8.2 % IACS |
Normalized | Grain-refining step after hot forging or heavy hot forming, before final quench and temper. | 570 | 950 | 13 | 29 HRC | 8 % IACS |
oil quenched (~850 °C) and tempered ~450–500 °C | Tougher end of the spring hardness band — heavy leaf springs and torsion bars where impact and chipping resistance matter more than peak stress. | 1,180 | 1,330 | 11 | 42 HRC | — |
QT-SPRINGDefault Q&T spring temper 388–461 HBW (≈42–48 HRC) per JIS G 4801 | The standard delivered spring condition — oil quench from ~850 °C, temper ~420–480 °C to the JIS hardness band; used for essentially all finished SUP11A leaf and coil springs. | 1,300 | 1,450 | 9 | 45 HRC | — |
QT-SPThis page Q&T + shot peened (and optionally stress-peened) spring | Standard finished-spring condition for fatigue-critical suspension parts — peening compressive layer roughly doubles usable fatigue life over as-tempered surface. | 1,300 | 1,450 | 9 | 45 HRC | 7.8 % IACS |
quenched and tempered ~350–400 °C | Higher-strength variant for highly stressed parabolic springs and torsion bars; toughness and sag resistance margins shrink, so shot peening is essential. | 1,520 | 1,680 | 7 | 50 HRC | — |
What is SUP11A QT-SP?
SUP11A QT-SP is SUP11A supplied in the QT-SP condition — standard finished-spring condition for fatigue-critical suspension parts — peening compressive layer roughly doubles usable fatigue life over as-tempered surface. SUP11A QT-SP 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). SUP11A QT-SP 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). QT-SPRING is the default condition FabDigit quotes; QT-SP 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
- Difficult to machine — 18/100, worse than 97% of steel grades
- Limited formability — 8/100, worse than 97% of steel grades
- Limited ductility — 9%, worse than 93% of steel grades
- Limited service temperature — 230°C (446 °F), worse than 88% of steel grades
SUP11A QT-SP properties
Typical room-temperature values for SUP11A QT-SP; 22 are specific to this condition. Other listed values are SUP11A reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
SUP11A QT-SP 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).
Mechanical15
SUP11A QT-SP 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
SUP11A QT-SP is rated for continuous service to 230°C (446 °F). It conducts heat at 40 W/m·K (23.1 BTU/hr·ft·°F), worse than 64% of steel grades. Thermal expansion is 12.3 µm/m·K (6.83 µin/in·°F).
Electrical3
SUP11A QT-SP conducts electricity at 7.8 % IACS, worse than 57% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of SUP11A QT-SP takes about 27 MJ of energy and emits 2.1 kg of CO₂ — less than 59% of steel grades. Typical recycled content is 30%.
Manufacturability7
SUP11A QT-SP's machinability is poor (18/100, worse than 97% of steel grades); weldability not recommended (10/100); formability not recommended (8/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with SUP11A QT-SP
Is SUP11A easy to machine?
Machine, punch and drill in the spheroidize-annealed condition; after Q&T at 42–48 HRC only grinding or carbide/CBN finishing is practical.
Can SUP11A be welded?
Effectively unweldable in the hardened state — 0.6 %C plus B gives hard martensite and cracking; if unavoidable, preheat 300–350 °C, low-hydrogen filler and immediate post-weld temper, then re-heat-treat.
Can SUP11A be formed, bent or molded?
Hot form leaves/coils at 850–950 °C then oil quench and temper; cold bends only in annealed stock with generous radii (≥3–4 t).
What surface finishes work on SUP11A?
Shot peen after tempering, then phosphate + epoxy/powder paint or Zn-rich primer; avoid electroplating without 190–220 °C hydrogen bake-out.
SUP11A 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 | 0.56 – 0.64 | 0.6 |
| Si | 0.15 – 0.35 | 0.25 |
| Mn | 0.7 – 1 | 0.85 |
| P | ≤ 0.03 | — |
| S | ≤ 0.03 | — |
| Cr | 0.7 – 0.9 | 0.8 |
| Beffective boron; requires Ti/Al fixing of N to be effective | 5×10⁻⁴ – 0 | 0 |
| Curesidual, max | ≤ 0.3 | — |
| Fe | balance | — |
SUP11A QT-SP — frequently asked
What is SUP11A QT-SP used for?
SUP11A QT-SP is typically used for heavy vehicle leaf springs, suspension springs, trailer and axle spring leaves, off-highway equipment springs, spring plates and U-bolt saddles and torsion springs for heavy machinery. In short: boron-hardenability spring steel; low-chromium leaf spring grade; deep hardening in thick leaves.
What is the yield strength of SUP11A QT-SP?
SUP11A QT-SP 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 7 listed tempers.
Is SUP11A QT-SP easy to machine?
Not especially — machinability is rated poor (18/100, worse than 97% of steel grades). Machine, punch and drill in the spheroidize-annealed condition; after Q&T at 42–48 HRC only grinding or carbide/CBN finishing is practical.
Can SUP11A QT-SP be welded?
Not readily — weldability is rated not recommended (10/100). Effectively unweldable in the hardened state — 0.6 %C plus B gives hard martensite and cracking; if unavoidable, preheat 300–350 °C, low-hydrogen filler and immediate post-weld temper, then re-heat-treat.
What surface finishes work on SUP11A QT-SP?
Shot peen after tempering, then phosphate + epoxy/powder paint or Zn-rich primer; avoid electroplating without 190–220 °C hydrogen bake-out.
Can SUP11A QT-SP be formed, bent or molded?
Hot form leaves/coils at 850–950 °C then oil quench and temper; cold bends only in annealed stock with generous radii (≥3–4 t).
What is the maximum service temperature of SUP11A QT-SP?
SUP11A QT-SP 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.
What is the difference between SUP11A QT-SPRING and SUP11A-A?
QT-SPRING is the default condition — the standard delivered spring condition — oil quench from ~850 °C, temper ~420–480 °C to the JIS hardness band; used for essentially all finished SUP11A leaf and coil springs. A: softest condition — choose for cold forming, hole punching, eye rolling and machining before hardening. Yield strength is 1,300 MPa in QT-SPRING versus 420 MPa in A.
Sources
- JIS G 4801 — Spring steels — Japanese Standards Association (2021)
- GB/T 1222 — (60CrMnBA) — SAC (2016)
- ASM Handbook Vol.1: Properties and Selection — Irons, Steels, and High-Performance Alloys — ASM International (1990)
- ASM Handbook Vol.19: Fatigue and Fracture — ASM International (1996)
- SAE Spring Design Manual (HS-788) — SAE 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.