Stainless Steel Discaloy-STA (Solution treated and aged)
Heat-treated state · default condition
UNS S66220
Standard supply and service condition for turbine discs, bolts and shafts needing strength to ~650 °C.
Values for the STA condition
Other Discaloy tempers and conditions
Discaloy is listed in 5 conditions; see the grade overview at Discaloy.
Compare all 5 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Solution annealed | Softest condition, used for forming, machining of complex shapes and welding before aging. | 300 | 700 | 40 | 190 HB | — |
Hot rolled | Mill product form supplied for re-forging or subsequent full heat treatment; properties not guaranteed. | 450 | 800 | 30 | 20 HRC | 1.9 % IACS |
ST + single age | Simplified single-step age; slightly lower strength but better ductility and notch toughness than double aging. | 660 | 940 | 23 | 28 HRC | 1.9 % IACS |
STADefaultThis page Solution treated and aged | Standard supply and service condition for turbine discs, bolts and shafts needing strength to ~650 °C. | 730 | 1,000 | 20 | 30 HRC | — |
Cold drawn | Choose for fasteners and springs where cold work plus subsequent aging gives the highest room-temperature strength. | 950 | 1,150 | 12 | 35 HRC | 1.9 % IACS |
What is Discaloy-STA?
Discaloy-STA is Discaloy heat treated to STA — standard supply and service condition for turbine discs, bolts and shafts needing strength to ~650 °C. Discaloy-STA has a yield strength of 730 MPa (106 ksi) and a tensile strength of 1,000 MPa (145 ksi) — stronger than 93% of stainless steel grades. Elongation at break is 20% and the elastic modulus is 196 GPa (28.4 Msi). Discaloy-STA has a density of 7.97 g/cm³ (0.288 lb/in³), heavier than 83% of stainless steel grades. It melts at 1,380°C (2,516 °F).
Advantages
- High strength — 730 MPa (106 ksi), better than 93% of stainless steel grades
Limitations
- Difficult to machine — 18/100, worse than 99% of stainless steel grades
- Difficult to weld — 35/100, worse than 86% of stainless steel grades
- Low electrical conductivity — 1.9 % IACS, worse than 84% of stainless steel grades
- Limited ductility — 20%, worse than 79% of stainless steel grades
- Limited formability — 25/100, worse than 78% of stainless steel grades
Discaloy-STA properties
Typical room-temperature values for Discaloy-STA; 13 are specific to this condition. Other listed values are Discaloy reference data and may not represent this condition. Bars are the position among stainless steel grades.
Physical3
Discaloy-STA has a density of 7.97 g/cm³ (0.288 lb/in³), heavier than 83% of stainless steel grades. It melts at 1,380°C (2,516 °F).
Mechanical14
Discaloy-STA has a yield strength of 730 MPa (106 ksi) and a tensile strength of 1,000 MPa (145 ksi) — stronger than 93% of stainless steel grades. Elongation at break is 20% and the elastic modulus is 196 GPa (28.4 Msi).
Thermal5
Discaloy-STA is rated for continuous service to 650°C (1,202 °F). It conducts heat at 14 W/m·K (8.09 BTU/hr·ft·°F), worse than 80% of stainless steel grades. Thermal expansion is 15.5 µm/m·K (8.61 µin/in·°F).
Electrical3
Discaloy-STA conducts electricity at 1.9 % IACS, worse than 84% of stainless steel grades.
Chemical & Environmental2
Corrosion resistance is good (62/100), worse than 52% of stainless steel grades.
Sustainability4
Producing a kilogram of Discaloy-STA takes about 80 MJ of energy and emits 5.5 kg of CO₂ — more than 89% of stainless steel grades. Typical recycled content is 35%.
Manufacturability8
Discaloy-STA's machinability is poor (18/100, worse than 99% of stainless steel grades); weldability fair (35/100); formability poor (25/100).
Common Calculations5
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with Discaloy-STA
Is Discaloy easy to machine?
Machine in the solution-treated state where possible: rigid setups, positive-rake carbide or ceramic tools, low speed/heavy feed, flood coolant — the alloy work-hardens rapidly and is abrasive when aged.
Can Discaloy be welded?
GTAW/EBW in the solution-treated condition with A-286-type or Ni-base filler, then full solution + age; avoid welding aged material because of strain-age (post-weld heat-treat) cracking.
Can Discaloy be formed, bent or molded?
Hot work at roughly 1050–1150 °C with finish above ~950 °C; cold forming only in the solution-treated condition with interstage anneals.
What surface finishes work on Discaloy?
Passivate or leave as ground/polished; for extended service above ~700 °C use aluminide or MCrAlY-type protective coatings. No anodizing.
Discaloy 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 |
|---|---|---|
| Clow carbon to avoid excessive carbide | ≤ 0.08 | 0.04 |
| Mn | 0.35 – 1.5 | 0.9 |
| Si | ≤ 1 | 0.6 |
| P | ≤ 0.04 | — |
| S | ≤ 0.03 | — |
| Croxidation resistance | 13 – 15 | 13.8 |
| Niaustenite stabiliser, γ′ former | 24 – 27 | 26 |
| Mosolid-solution strengthening | 2.5 – 3.5 | 2.75 |
| Tiγ′ Ni₃(Al,Ti) former | 1.5 – 2 | 1.75 |
| Al | ≤ 0.35 | 0.15 |
| Bgrain-boundary strengthening | 0 – 0.01 | 0.01 |
| Febalance, ≈54 % | balance | — |
Discaloy-STA — frequently asked
What is Discaloy-STA used for?
Discaloy-STA is typically used for gas turbine discs, turbine bolting and high-temperature fasteners. In short: A-286-class iron-base superalloy; 650 °C bolting strength; cheaper than nickel-base alloys.
What is the yield strength of Discaloy-STA?
Discaloy-STA has a typical yield strength of 730 MPa (106 ksi) and a tensile strength of 1,000 MPa (145 ksi) — stronger than 93% of stainless steel grades. Strength varies by condition: see the 5 listed tempers.
Is Discaloy-STA easy to machine?
Not especially — machinability is rated poor (18/100, worse than 99% of stainless steel grades). Machine in the solution-treated state where possible: rigid setups, positive-rake carbide or ceramic tools, low speed/heavy feed, flood coolant — the alloy work-hardens rapidly and is abrasive when aged.
Can Discaloy-STA be welded?
With care — weldability is rated fair (35/100). GTAW/EBW in the solution-treated condition with A-286-type or Ni-base filler, then full solution + age; avoid welding aged material because of strain-age (post-weld heat-treat) cracking.
What surface finishes work on Discaloy-STA?
Passivate or leave as ground/polished; for extended service above ~700 °C use aluminide or MCrAlY-type protective coatings. No anodizing.
Can Discaloy-STA be formed, bent or molded?
Hot work at roughly 1050–1150 °C with finish above ~950 °C; cold forming only in the solution-treated condition with interstage anneals.
What is the maximum service temperature of Discaloy-STA?
Discaloy-STA is rated for continuous use to about 650°C (1,202 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between Discaloy-STA and Discaloy-SA?
STA is the default condition — standard supply and service condition for turbine discs, bolts and shafts needing strength to ~650 °C. SA: softest condition, used for forming, machining of complex shapes and welding before aging. Yield strength is 730 MPa in STA versus 300 MPa in SA.
Sources
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels and High-Performance Alloys (heat-resistant Fe-Ni-Cr alloys) — ASM International (1990)
- Superalloys: A Technical Guide, 2nd ed. — ASM International (2002)
- SAE HS-1086 / Metals & Alloys in the Unified Numbering System (UNS S66220) — SAE International / ASTM (2017)
- Aerospace Structural Metals Handbook — iron-base heat-resistant alloys — CINDAS/Purdue (1998)
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.