Steel SUP12
GB SUP12 · EN 60SiCr8
SUP12 is a JIS chromium-vanadium spring steel used for high-performance automotive and machinery springs, available hot rolled, annealed, cold drawn, oil tempered and quenched and tempered to 44–48 HRC or 48–52 HRC.
Reference datasheet — SUP12 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 QT44-48 condition
SUP12 tempers and conditions
SUP12 is supplied in 7 conditions, soft to hard. QT44-48 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 for machining, cold drawing or cold coiling before final hardening. | 470 | 780 | 18 | 235 HB | — |
Hot rolled | Mill delivery state of bar and rod for hot-coiled springs; hardened and tempered after forming. | 650 | 1,050 | 12 | 31 HRC | — |
Cold drawn | Close-tolerance bright bar or pre-drawn wire feedstock for cold-coiled springs that are hardened afterwards. | 750 | 900 | 10 | 27 HRC | 8 % IACS |
QT44-48Default Q&T 44–48 HRC | Standard service condition for hot- and cold-coiled SUP12 springs: best balance of elastic limit, toughness and sag resistance. | 1,620 | 1,800 | 9 | 47 HRC | — |
Q&T + shot peened | Choose when fatigue life dominates: compressive surface stress raises endurance limit typically 20–30 %. | 1,620 | 1,800 | 9 | 47 HRC | 7 % IACS |
Oil-tempered spring wire | Ready-to-coil hardened-and-tempered wire for cold-coiled valve and suspension springs; only stress relief after coiling. | 1,750 | 1,950 | 8 | 51 HRC | 6.8 % IACS |
Q&T 48–52 HRC | Higher-strength temper for valve springs and small-section high-stress springs where toughness demand is lower. | 1,780 | 1,980 | 6 | 50 HRC | — |
What is SUP12?
SUP12 is a JIS chromium-vanadium spring steel used for high-performance automotive and machinery springs, available hot rolled, annealed, cold drawn, oil tempered and quenched and tempered to 44–48 HRC or 48–52 HRC. It is the strongest of the JIS spring grades listed here, with 1620 MPa yield, 1800 MPa tensile, 9 % elongation and about 455 HB (47 HRC) in the default condition. Trade-offs are a 250 °C service limit, very low machinability (score 15) and formability (10), and a weldability score of 12 that rules out welding on spring-active sections. SUP13 is the alternative when larger section sizes must through-harden. SUP12 has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,400°C (2,552 °F). SUP12 has a yield strength of 1,620 MPa (235 ksi) and a tensile strength of 1,800 MPa (261 ksi) — stronger than 98% of steel grades. Elongation at break is 9% and the elastic modulus is 206 GPa (29.9 Msi).
What is SUP12 used for?
- Valve and clutch coil springs
- Torsion bars
- Suspension coil springs
- Stabilizer bars
- Machinery compression springs
- Oil-tempered spring wire components
Advantages
- High strength — 1,620 MPa (235 ksi), better than 98% of steel grades
- Low embodied carbon — 1.9 kg CO₂/kg, better than 92% of steel grades
Limitations
- Difficult to machine — 15/100, worse than 98% of steel grades
- Difficult to weld — 12/100, worse than 96% of steel grades
- Limited formability — 10/100, worse than 95% of steel grades
- Limited ductility — 9%, worse than 93% of steel grades
- Low fracture toughness — 45 MPa·√m (41 ksi·√in), worse than 90% of steel grades
SUP12 properties
Typical room-temperature values for SUP12-QT44-48; bars are the position among steel grades.
Physical3
SUP12 has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,400°C (2,552 °F).
Mechanical16
SUP12 has a yield strength of 1,620 MPa (235 ksi) and a tensile strength of 1,800 MPa (261 ksi) — stronger than 98% of steel grades. Elongation at break is 9% and the elastic modulus is 206 GPa (29.9 Msi).
Thermal6
SUP12 is rated for continuous service to 250°C (482 °F). It conducts heat at 40 W/m·K (23.1 BTU/hr·ft·°F), worse than 64% of steel grades. Thermal expansion is 11.5 µm/m·K (6.39 µin/in·°F).
Electrical3
SUP12 conducts electricity at 7 % IACS, worse than 74% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of SUP12 takes about 25 MJ of energy and emits 1.9 kg of CO₂ — less than 82% of steel grades. Typical recycled content is 25%.
Manufacturability7
SUP12's machinability is poor (15/100, worse than 98% of steel grades); weldability not recommended (12/100); formability not recommended (10/100).
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. SUP12 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with SUP12
Is SUP12 easy to machine?
Machine in the annealed/spheroidized state (~230 HB) with carbide tooling; after Q&T at 45+ HRC only grinding, EDM or CBN turning are practical.
Can SUP12 be welded?
Not recommended for spring service — high carbon equivalent gives hard martensitic HAZ; if unavoidable, preheat 300–350 °C, low-hydrogen consumables and immediate post-weld temper.
Can SUP12 be formed, bent or molded?
Hot coil at 850–950 °C or cold coil from annealed/oil-tempered wire, then oil quench from 850–870 °C and temper 440–490 °C to the target hardness; protect against decarburisation during austenitising.
SUP12 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 | 0.51 – 0.59 | 0.55 |
| Sihigh Si gives sag/relaxation resistance | 1.2 – 1.6 | 1.4 |
| Mn | 0.6 – 0.9 | 0.75 |
| Cr | 0.6 – 0.9 | 0.75 |
| P | ≤ 0.03 | |
| S | ≤ 0.03 | |
| Curesidual, max | ≤ 0.3 | |
| Niresidual, max | ≤ 0.25 | |
| Fe | balance |
What surface finishes work on SUP12?
Shot peen after tempering for fatigue life, then phosphate + epoxy/powder paint or zinc-rich/Zn-Ni coating; bake 200 °C for ≥4 h after any electroplating to avoid hydrogen embrittlement.
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
Equivalent designations
Standards and trade names that resolve to Steel SUP12 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- EN / DIN / Werkstoff-Nr.
- 60SiCr8
How much does SUP12 cost?
SUP12 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.
SUP12 — frequently asked
What is SUP12 used for?
SUP12 is typically used for valve and clutch coil springs, torsion bars, suspension coil springs, stabilizer bars, machinery compression springs and oil-tempered spring wire components. In short: 1800 MPa spring steel; cr-V high-fatigue grade; for highly stressed coils.
What is the yield strength of SUP12?
SUP12 has a typical yield strength of 1,620 MPa (235 ksi) and a tensile strength of 1,800 MPa (261 ksi) — stronger than 98% of steel grades. Strength varies by condition: see the 7 listed tempers.
Is SUP12 easy to machine?
Not especially — machinability is rated poor (15/100, worse than 98% of steel grades). Machine in the annealed/spheroidized state (~230 HB) with carbide tooling; after Q&T at 45+ HRC only grinding, EDM or CBN turning are practical.
Can SUP12 be welded?
Not readily — weldability is rated not recommended (12/100). Not recommended for spring service — high carbon equivalent gives hard martensitic HAZ; if unavoidable, preheat 300–350 °C, low-hydrogen consumables and immediate post-weld temper.
What surface finishes work on SUP12?
Shot peen after tempering for fatigue life, then phosphate + epoxy/powder paint or zinc-rich/Zn-Ni coating; bake 200 °C for ≥4 h after any electroplating to avoid hydrogen embrittlement.
Can SUP12 be formed, bent or molded?
Hot coil at 850–950 °C or cold coil from annealed/oil-tempered wire, then oil quench from 850–870 °C and temper 440–490 °C to the target hardness; protect against decarburisation during austenitising.
What is the maximum service temperature of SUP12?
SUP12 is rated for continuous use to about 250°C (482 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between SUP12 QT44-48 and SUP12-A?
QT44-48 is the default condition — standard service condition for hot- and cold-coiled SUP12 springs: best balance of elastic limit, toughness and sag resistance. A: softest condition for machining, cold drawing or cold coiling before final hardening. Yield strength is 1,620 MPa in QT44-48 versus 470 MPa in A.
How much does SUP12 cost?
SUP12 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)
- JIS G 3561 — Oil tempered wire for valve springs (SWOSC-V) — Japanese Standards Association (2009)
- SAE J404 / J1993 — Chemical compositions of SAE alloy steels (9254) — SAE International (2009)
- GB/T 1222 — (55SiCr, 60Si2CrA) — SAC (2016)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels, and High-Performance Alloys — ASM International (1990)
- ASM Specialty Handbook / Spring design and materials data — ASM 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.