Steel SUH660 · heat-treated state · default condition
Steel SUH660-STA
Properties of the STA condition, compared with the other SUH660 tempers.
Standard stocked condition: best balance of room-temperature strength, ductility and 650–700 °C creep/rupture life.
What is SUH660-STA?
SUH660-STA is SUH660 heat treated to STA — standard stocked condition: best balance of room-temperature strength, ductility and 650–700 °C creep/rupture life. SUH660-STA has a yield strength of 725 MPa (105 ksi) and a tensile strength of 1,010 MPa (146 ksi) — stronger than 82% of steel grades. Elongation at break is 22% and the elastic modulus is 201 GPa (29.2 Msi). SUH660-STA has a density of 7.94 g/cm³ (0.287 lb/in³), heavier than 93% of steel grades. It melts at 1,370°C (2,498 °F).
Advantages
- High service temperature — 700°C (1,292 °F), better than 100% of steel grades
- Good corrosion resistance — 58/100, better than 99% of steel grades
- Polishes to a fine finish — 75/100, better than 94% of steel grades
- Tough — resists crack growth — 130 MPa·√m (118.3 ksi·√in), better than 89% of steel grades
- High strength — 725 MPa (105 ksi), better than 82% of steel grades
Limitations
- Low electrical conductivity — 1.9 % IACS, worse than 100% of steel grades
- Poor heat conductor — 13 W/m·K (7.51 BTU/hr·ft·°F), worse than 99% of steel grades
- High embodied carbon — 6.5 kg CO₂/kg, worse than 98% of steel grades
- Difficult to machine — 20/100, worse than 97% of steel grades
SUH660-STA properties
Typical room-temperature values for SUH660-STA — 14 properties are specific to this condition; the rest are grade-level values shared by every SUH660 temper. Each bar shows where the value sits among the steel grades in FabDigit's library — further right is higher.
Physical3
SUH660-STA has a density of 7.94 g/cm³ (0.287 lb/in³), heavier than 93% of steel grades. It melts at 1,370°C (2,498 °F).
Mechanical16
SUH660-STA has a yield strength of 725 MPa (105 ksi) and a tensile strength of 1,010 MPa (146 ksi) — stronger than 82% of steel grades. Elongation at break is 22% and the elastic modulus is 201 GPa (29.2 Msi).
Thermal6
SUH660-STA is rated for continuous service to 700°C (1,292 °F). It conducts heat at 13 W/m·K (7.51 BTU/hr·ft·°F), worse than 99% of steel grades. Thermal expansion is 16.4 µm/m·K (9.11 µin/in·°F).
Electrical3
SUH660-STA conducts electricity at 1.9 % IACS, worse than 100% of steel grades.
Chemical & Environmental3
Corrosion resistance is good (58/100), better than 99% of steel grades.
Sustainability4
Producing a kilogram of SUH660-STA takes about 90 MJ of energy and emits 6.5 kg of CO₂ — more than 98% of steel grades. Typical recycled content is 30%.
Manufacturability6
SUH660-STA's machinability is poor (20/100, worse than 97% of steel grades); weldability good (55/100); formability poor (30/100).
Common Calculations5
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Other SUH660 tempers and conditions
SUH660 is also supplied in 4 other conditions. The full side-by-side table is on the SUH660 overview.
- STADefaultStandard stocked condition: best balance of room-temperature strength, ductility and 650–700 °C creep/rupture life.725 MPa yield · 30 HRC
- CD+AFastener wire/bar route: cold work before ageing lifts strength well above 1150 MPa at the cost of ductility and toughness.1,030 MPa yield · 38 HRC
- STA-900Choose for fasteners and highly stressed parts needing maximum room- and mid-temperature strength (finer grain, lower creep capability than 980 °C solution).790 MPa yield · 33 HRC
- STSoft supply condition for forming, deep machining or welding before final ageing.285 MPa yield · 190 HB
Working with SUH660-STA
Is SUH660 easy to machine?
Machine like a superalloy: rigid setups, sharp positive-rake carbide or ceramic, low speed / heavy positive feed, flood coolant — it work-hardens fast and glazes if the tool dwells; rough in ST condition and finish after ageing where possible.
Can SUH660 be welded?
GTAW/EBW with matching A286 or Ni-base filler works, but keep heat input low and weld in the solution-treated state, then re-solution and age to avoid strain-age (post-weld) cracking in the HAZ.
Can SUH660 be formed, bent or molded?
Cold form only in the solution-treated condition with generous radii and high press loads; hot work at 1010–1150 °C and always finish above ~950 °C to avoid Ti-rich phase and cracking.
What surface finishes work on SUH660?
Takes a good mechanical polish and can be passivated (nitric or citric) like a stainless; not anodizable — for high-temperature threads use silver, Cu-Ni or dry-film lubricant coatings to prevent galling.
SUH660 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 | ≤ 0.08 | 0.05 |
| Si | ≤ 1 | 0.5 |
| Mn | ≤ 2 | 1.2 |
| P | ≤ 0.04 | — |
| S | ≤ 0.03 | — |
| Ni | 24 – 27 | 25.5 |
| Cr | 13.5 – 16 | 15 |
| Mo | 1 – 1.5 | 1.25 |
| Tiγ′ Ni₃(Ti,Al) former | 1.9 – 2.35 | 2.1 |
| V | 0.1 – 0.5 | 0.3 |
| Al | ≤ 0.35 | 0.2 |
| Bgrain-boundary strengthening | 0 – 0.01 | 0.01 |
| Febalance ≈ 53 % | balance | — |
SUH660-STA — frequently asked
What is SUH660-STA used for?
SUH660-STA is typically used for aircraft engine fasteners, gas turbine bolts and studs, high-temperature springs, turbocharger wheel shafts, exhaust valves and aero-engine discs and rings. In short: high-temp aerospace bar.
What is the yield strength of SUH660-STA?
SUH660-STA has a typical yield strength of 725 MPa (105 ksi) and a tensile strength of 1,010 MPa (146 ksi) — stronger than 82% of steel grades. Strength varies by condition: see the 5 listed tempers.
Is SUH660-STA easy to machine?
Not especially — machinability is rated poor (20/100, worse than 97% of steel grades). Machine like a superalloy: rigid setups, sharp positive-rake carbide or ceramic, low speed / heavy positive feed, flood coolant — it work-hardens fast and glazes if the tool dwells; rough in ST condition and finish after ageing where possible.
Can SUH660-STA be welded?
Yes — weldability is rated good (55/100). GTAW/EBW with matching A286 or Ni-base filler works, but keep heat input low and weld in the solution-treated state, then re-solution and age to avoid strain-age (post-weld) cracking in the HAZ.
What surface finishes work on SUH660-STA?
Takes a good mechanical polish and can be passivated (nitric or citric) like a stainless; not anodizable — for high-temperature threads use silver, Cu-Ni or dry-film lubricant coatings to prevent galling.
Can SUH660-STA be formed, bent or molded?
Cold form only in the solution-treated condition with generous radii and high press loads; hot work at 1010–1150 °C and always finish above ~950 °C to avoid Ti-rich phase and cracking.
What is the maximum service temperature of SUH660-STA?
SUH660-STA is rated for continuous use to about 700°C (1,292 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between SUH660-STA and SUH660-ST?
STA is the default condition — standard stocked condition: best balance of room-temperature strength, ductility and 650–700 °C creep/rupture life. ST: soft supply condition for forming, deep machining or welding before final ageing. Yield strength is 725 MPa in STA versus 285 MPa in ST.
Can FabDigit make parts in SUH660-STA?
Yes — SUH660-STA 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 4311 — Heat-resisting steel bars — JSA (2019)
- AMS 5737 / AMS 5732 — Alloy Bars, Forgings (UNS S66286) — SAE International (2021)
- ASTM A453/A453M Grade 660 — ASTM International (2022)
- ASM Specialty Handbook: Heat-Resistant Materials — ASM International (1997)
- A286 (UNS S66286) alloy datasheet — specialty alloy producers (2023)
- GH2132/SUH660 (2025)
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.