Steel SUP11A
GB SUP11A
SUP11A is a JIS boron-alloyed spring steel that uses boron to raise hardenability for heavy leaf springs while economizing on chromium content.
Reference datasheet — SUP11A is not in the instant-quote catalog. Upload your part and an engineer will quote it in this grade or suggest the closest stocked equivalent.
Values for the QT-SPRING condition
SUP11A tempers and conditions
SUP11A is supplied in 7 conditions, soft to hard. QT-SPRING is the default FabDigit quotes; the values on this page are for it.
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 | — |
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?
SUP11A is a JIS boron-alloyed spring steel that uses boron to raise hardenability for heavy leaf springs while economizing on chromium content. It is supplied hot rolled, annealed, normalized or quenched and tempered to 40–45 HRC, 48–52 HRC and shot-peened spring conditions; the default QT state gives 1300 MPa yield, 1450 MPa tensile, 9 % elongation and about 425 HB (45 HRC). Limits are a 230 °C service ceiling, very poor machinability (score 20), formability (12) and weldability (15) after hardening, and no corrosion resistance. SUP9A is the usual chromium-bearing alternative for the same duty. SUP11A 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). SUP11A 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).
What is SUP11A used for?
- Heavy vehicle leaf springs
- Suspension springs
- Trailer and axle spring leaves
- Off-highway equipment springs
- Spring plates and U-bolt saddles
- Torsion springs for heavy machinery
Advantages
- High strength — 1,300 MPa (189 ksi), better than 95% of steel grades
Limitations
- Difficult to machine — 20/100, worse than 97% of steel grades
- Limited ductility — 9%, worse than 93% of steel grades
- Limited formability — 12/100, worse than 92% of steel grades
- Difficult to weld — 15/100, worse than 91% of steel grades
- Limited service temperature — 230°C (446 °F), worse than 88% of steel grades
SUP11A properties
Typical room-temperature values for SUP11A-QT-SPRING; bars are the position among steel grades.
Physical3
SUP11A 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 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 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 conducts electricity at 7.8 % IACS, worse than 57% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (10/100), worse than 86% of steel grades.
Sustainability4
Producing a kilogram of SUP11A 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's machinability is poor (20/100, worse than 97% of steel grades); weldability poor (15/100); formability not recommended (12/100).
Common Calculations5
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Strength versus weight in the steel family
Yield strength against density for every steel grade FabDigit runs. SUP11A is highlighted; hover a dot for its name, or open the interactive family chart.
Working with SUP11A
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).
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 |
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.
Surface treatments FabDigit runs on steel parts — pick them in the quote configurator or call them out on the drawing. Each links to its datasheet in the surface-finish library (thickness, specs, call-out, material verdicts).
Organic Coating
Black / Phosphate
Thermal Spray
How much does SUP11A cost?
SUP11A is a budget-cost steel ($), cheaper than about 90% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
SUP11A — frequently asked
What is SUP11A used for?
SUP11A 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?
SUP11A 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 easy to machine?
Not especially — machinability is rated poor (20/100, 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 be welded?
Not readily — weldability is rated poor (15/100). 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?
Shot peen after tempering, then phosphate + epoxy/powder paint or Zn-rich primer; avoid electroplating without 190–220 °C hydrogen bake-out.
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 is the maximum service temperature of SUP11A?
SUP11A 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.
How much does SUP11A cost?
SUP11A is a budget-cost steel ($), cheaper than about 90% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
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; hardness values on non-Brinell scales are converted approximately for charting only. Manufacturability limits are FabDigit quote-engine defaults and may be relaxed by engineering review. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.