Stainless Steel 660 · precip hard
Stainless Steel 660 CW+Aged
Properties of the CW+Aged condition, compared with the other 660 tempers.
Highest strength form, used for high-temperature springs, retaining rings and fasteners where 1300–1500 MPa with 500–600 °C relaxation resistance is required.
What is 660 CW+Aged?
660 CW+Aged is 660 in the CW+Aged condition — highest strength form, used for high-temperature springs, retaining rings and fasteners where 1300–1500 MPa with 500–600 °C relaxation resistance is required. 660 CW+Aged has a yield strength of 1,250 MPa (181 ksi) and a tensile strength of 1,400 MPa (203 ksi) — stronger than 99% of stainless steel grades. Elongation at break is 6% and the elastic modulus is 201 GPa (29.2 Msi). 660 CW+Aged has a density of 7.94 g/cm³ (0.287 lb/in³), heavier than 78% of stainless steel grades. It melts at 1,370°C (2,498 °F). Solution Annealed is the default condition FabDigit quotes; CW+Aged is available on request or by drawing note.
Advantages
- High strength — 1,250 MPa (181 ksi), better than 99% of stainless steel grades
Limitations
- Difficult to machine — 12/100, worse than 100% of stainless steel grades
- Limited ductility — 6%, worse than 99% of stainless steel grades
- Limited formability — 8/100, worse than 97% of stainless steel grades
- High embodied carbon — 6.8 kg CO₂/kg, worse than 95% of stainless steel grades
- Low electrical conductivity — 1.9 % IACS, worse than 84% of stainless steel grades
660 CW+Aged properties
Typical room-temperature values for 660 CW+Aged — 9 properties are specific to this condition; the rest are grade-level values shared by every 660 temper. Each bar shows where the value sits among the stainless steel grades in FabDigit's library — further right is higher.
Physical3
660 CW+Aged has a density of 7.94 g/cm³ (0.287 lb/in³), heavier than 78% of stainless steel grades. It melts at 1,370°C (2,498 °F).
Mechanical13
660 CW+Aged has a yield strength of 1,250 MPa (181 ksi) and a tensile strength of 1,400 MPa (203 ksi) — stronger than 99% of stainless steel grades. Elongation at break is 6% and the elastic modulus is 201 GPa (29.2 Msi).
Thermal5
660 CW+Aged is rated for continuous service to 600°C (1,112 °F). It conducts heat at 13.4 W/m·K (7.74 BTU/hr·ft·°F), worse than 84% of stainless steel grades. Thermal expansion is 16.6 µm/m·K (9.22 µin/in·°F).
Electrical3
660 CW+Aged conducts electricity at 1.9 % IACS, worse than 84% of stainless steel grades.
Chemical & Environmental3
Corrosion resistance is good (62/100), worse than 53% of stainless steel grades.
Sustainability4
Producing a kilogram of 660 CW+Aged takes about 95 MJ of energy and emits 6.8 kg of CO₂ — more than 96% of stainless steel grades. Typical recycled content is 30%.
Manufacturability7
660 CW+Aged's machinability is not recommended (12/100, worse than 100% of stainless steel grades); weldability good (55/100); formability not recommended (8/100).
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Other 660 tempers and conditions
660 is also supplied in 7 other conditions. The full side-by-side table is on the 660 overview.
- Solution AnnealedDefaultStandard stock condition for bar, sheet and wire that will be machined or formed and then age hardened by the user.310 MPa yield · 160 HB
- CW+AgedHighest strength form, used for high-temperature springs, retaining rings and fasteners where 1300–1500 MPa with 500–600 °C relaxation resistance is required.1,250 MPa yield · 44 HRC
- STA-900Lower solution temperature keeps a finer grain size for higher room-temperature yield strength in bolting; slightly lower creep/rupture capability than the 980 °C treatment.760 MPa yield · 34 HRC
- Cold DrawnPick for close-tolerance bright bar and wire feedstock where strength above the solution-annealed level is wanted before final ageing.700 MPa yield · 23 HRC
- Age HardenedThe normal service condition: γ′ precipitation gives ~1000 MPa tensile with good 540–700 °C strength and stress-relaxation resistance for bolts and turbine hardware.690 MPa yield · 32 HRC
- AnnealedChoose for maximum cold formability of sheet/strip and for wire before drawing; must be aged afterwards to develop strength.280 MPa yield · 150 HB
Working with 660 CW+Aged
Is 660 easy to machine?
Gummy and highly work-hardening — machine in the solution-treated condition where possible with rigid setups, positive-rake carbide, heavy flood coolant, low speed (15–25 m/min) and constant feed to avoid glazing; aged material typically cut at ~15 % of AISI 1212 rates.
Can 660 be welded?
GTAW/EBW with matching A286 or Ni-base filler works, but the alloy is prone to hot cracking and strain-age cracking; weld in the solution-treated state, restrain minimally, and re-solution plus age the weldment for full properties.
Can 660 be formed, bent or molded?
Cold form and draw only in the annealed/solution-treated condition, allowing for high springback and ~2× the load of 304; hot work at 1100–950 °C then solution treat, and never form aged material.
What surface finishes work on 660?
Not anodizable — passivate per AMS 2700/ASTM A967, electropolish or mechanically polish; oxide films from ageing must be pickled or blasted off before plating, and silver or MoS2 coatings are common on fasteners to prevent galling.
660 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 | 1.3 |
| P | ≤ 0.04 | — |
| S | ≤ 0.03 | — |
| Cr | 13.5 – 16 | 14.8 |
| Ni | 24 – 27 | 25.5 |
| Mo | 1 – 1.5 | 1.25 |
| Tiγ′ (Ni3Ti) former | 1.9 – 2.35 | 2.1 |
| V | 0.1 – 0.5 | 0.3 |
| Al | ≤ 0.35 | 0.2 |
| Bgrain-boundary strengthener | 0 – 0.01 | 0.01 |
| Febalance, ~53 % | balance | — |
660 CW+Aged — frequently asked
What is 660 CW+Aged used for?
660 CW+Aged is typically used for aircraft engine fasteners and turbine bolting, gas-turbine discs and ring parts, exhaust valves, high-temperature springs, turbocharger components and jet engine casings and housings. In short: high-temp aerospace stainless.
What is the yield strength of 660 CW+Aged?
660 CW+Aged has a typical yield strength of 1,250 MPa (181 ksi) and a tensile strength of 1,400 MPa (203 ksi) — stronger than 99% of stainless steel grades. Strength varies by condition: see the 8 listed tempers.
Is 660 CW+Aged easy to machine?
Not especially — machinability is rated not recommended (12/100, worse than 100% of stainless steel grades). Gummy and highly work-hardening — machine in the solution-treated condition where possible with rigid setups, positive-rake carbide, heavy flood coolant, low speed (15–25 m/min) and constant feed to avoid glazing; aged material typically cut at ~15 % of AISI 1212 rates.
Can 660 CW+Aged be welded?
Yes — weldability is rated good (55/100). GTAW/EBW with matching A286 or Ni-base filler works, but the alloy is prone to hot cracking and strain-age cracking; weld in the solution-treated state, restrain minimally, and re-solution plus age the weldment for full properties.
What surface finishes work on 660 CW+Aged?
Not anodizable — passivate per AMS 2700/ASTM A967, electropolish or mechanically polish; oxide films from ageing must be pickled or blasted off before plating, and silver or MoS2 coatings are common on fasteners to prevent galling.
Can 660 CW+Aged be formed, bent or molded?
Cold form and draw only in the annealed/solution-treated condition, allowing for high springback and ~2× the load of 304; hot work at 1100–950 °C then solution treat, and never form aged material.
What is the maximum service temperature of 660 CW+Aged?
660 CW+Aged is rated for continuous use to about 600°C (1,112 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between 660 Solution Annealed and 660 STA-900?
Solution Annealed is the default condition — standard stock condition for bar, sheet and wire that will be machined or formed and then age hardened by the user. STA-900: lower solution temperature keeps a finer grain size for higher room-temperature yield strength in bolting; slightly lower creep/rupture capability than the 980 °C treatment. Yield strength is 310 MPa in Solution Annealed versus 760 MPa in STA-900.
Can FabDigit make parts in 660 CW+Aged?
Yes — 660 CW+Aged 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
- ASTM A453/A453M Grade 660 — Bolting with Expansion Coefficients Comparable to Austenitic Stainless Steels — ASTM International (2021)
- AMS 5731 / 5732 / 5734 / 5737 — Alloy Bars, Forgings and Rings, 15Cr-25.5Ni-1.2Mo-2.1Ti-0.3V-0.005B — SAE International (2018)
- JIS G 4311 SUH660 / GB/T 1221 (0Cr15Ni25Ti2MoAlVB, GH2132) — JISC / SAC (2016)
- ASM Specialty Handbook: Heat-Resistant Materials — ASM International (1997)
- MMPDS-17, Metallic Materials Properties Development and Standardization — Battelle/FAA (2022)
- A286 / Alloy 660 technical data sheet — Specialty steel producers (e.g. Carpenter, Aubert & Duval, VDM) (2023)
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.