Steel SUP12-HR (Hot rolled)
Supply condition
GB SUP12 · EN 60SiCr8
Mill delivery state of bar and rod for hot-coiled springs; hardened and tempered after forming.
Values for the HR condition
Other SUP12 tempers and conditions
SUP12 is listed in 7 conditions; see the grade overview at SUP12.
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 | — |
HRThis page 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-HR?
SUP12-HR is SUP12 supplied in the HR condition — mill delivery state of bar and rod for hot-coiled springs; hardened and tempered after forming. SUP12-HR has a yield strength of 650 MPa (94.3 ksi) and a tensile strength of 1,050 MPa (152 ksi) — stronger than 79% of steel grades. Elongation at break is 12% and the elastic modulus is 206 GPa (29.9 Msi). SUP12-HR 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). QT44-48 is the default condition FabDigit quotes; HR is available on request or by drawing note.
Advantages
- Low embodied carbon — 1.9 kg CO₂/kg, better than 92% of steel grades
- High strength — 650 MPa (94.3 ksi), better than 79% of steel grades
Limitations
- Difficult to weld — 12/100, worse than 96% of steel grades
- Low fracture toughness — 45 MPa·√m (41 ksi·√in), worse than 90% of steel grades
- Limited service temperature — 250°C (482 °F), worse than 85% of steel grades
- Limited ductility — 12%, worse than 84% of steel grades
- Difficult to machine — 35/100, worse than 84% of steel grades
SUP12-HR properties
Typical room-temperature values for SUP12-HR; 10 are specific to this condition. Other listed values are SUP12 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
SUP12-HR 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-HR has a yield strength of 650 MPa (94.3 ksi) and a tensile strength of 1,050 MPa (152 ksi) — stronger than 79% of steel grades. Elongation at break is 12% and the elastic modulus is 206 GPa (29.9 Msi).
Thermal6
SUP12-HR 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-HR 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-HR 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-HR's machinability is fair (35/100, worse than 84% of steel grades); weldability not recommended (12/100); formability poor (25/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with SUP12-HR
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.
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.
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 | — |
SUP12-HR — frequently asked
What is SUP12-HR used for?
SUP12-HR 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-HR?
SUP12-HR has a typical yield strength of 650 MPa (94.3 ksi) and a tensile strength of 1,050 MPa (152 ksi) — stronger than 79% of steel grades. Strength varies by condition: see the 7 listed tempers.
Is SUP12-HR easy to machine?
Not especially — machinability is rated fair (35/100, worse than 84% 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-HR 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-HR?
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-HR 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-HR?
SUP12-HR 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.
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. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.