Stainless Steel S31266
UNS S31266 · ASTM A240/A312 · EN 1.4659
S31266 is a highly alloyed Cr-Ni-Mo-Cu-W-N superaustenitic stainless (ASTM A240/A312) developed for extreme chloride and acid environments, with pitting resistance rivaling some nickel-base alloys at lower cost.
Reference datasheet — S31266 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 SA condition
S31266 tempers and conditions
S31266 is supplied in 4 conditions, soft to hard. SA is the default FabDigit quotes; the values on this page are for it.
Compare all 4 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
As-welded deposit | Joint condition without post-weld solution anneal; weld metal strength governs and pitting resistance drops at the fusion line. | 450 | 750 | 35 | 210 HB | 1.7 % IACS |
SADefault Solution Annealed | Standard supply condition for all product forms — maximum corrosion resistance and ductility. | 480 | 810 | 46 | 17 HRC | 1.7 % IACS |
Forged and Solution Annealed (ASTM A182 flanges/fittings) | For forged flanges, valve bodies and fittings; requires re-solution anneal and quench after forging. | 480 | 800 | 42 | 18 HRC | 1.7 % IACS |
Cold drawn | Use when higher strength and close tolerance are needed; ductility and formability are reduced. | 720 | 950 | 25 | 29 HRC | 1.7 % IACS |
Supply forms, finishes and certifications
Ways S31266 is supplied — form, process route, surface or paperwork — without a datasheet of their own. The property values above apply.
| Option | What it is | Type |
|---|---|---|
SA-BAR | Solution Annealed Bar | Supply form |
SA-PIPE | Solution Annealed Pipe / Tube | Supply form |
SA-Plate | Solution Annealed Plate / Sheet | Supply form |
What is S31266?
S31266 is a highly alloyed Cr-Ni-Mo-Cu-W-N superaustenitic stainless (ASTM A240/A312) developed for extreme chloride and acid environments, with pitting resistance rivaling some nickel-base alloys at lower cost. Solution-annealed material gives 480 MPa yield, 810 MPa tensile, 46 % elongation and about 215 HB, and is used as plate, pipe, bar and forgings. It is difficult to cut (machinability score 22), forms stiffly (formability score 45) and must be welded with over-alloyed nickel-base filler; S31254 (6Mo) is the cheaper choice in less aggressive service. S31266 has a density of 8 g/cm³ (0.289 lb/in³), heavier than 92% of stainless steel grades. It melts at 1,320°C (2,408 °F). S31266 has a yield strength of 480 MPa (69.6 ksi) and a tensile strength of 810 MPa (117 ksi) — stronger than 75% of stainless steel grades. Elongation at break is 46% and the elastic modulus is 195 GPa (28.3 Msi).
What is S31266 used for?
- flue-gas desulfurization
- seawater and brine systems
- chemical process equipment
- oil & gas sour service piping
Advantages
- Good corrosion resistance — 92/100, better than 99% of stainless steel grades
- Tough — resists crack growth — 200 MPa·√m (182 ksi·√in), better than 86% of stainless steel grades
- Ductile — tolerates forming and impact — 46%, better than 83% of stainless steel grades
- High strength — 480 MPa (69.6 ksi), better than 75% of stainless steel grades
Limitations
- Poor heat conductor — 11 W/m·K (6.36 BTU/hr·ft·°F), worse than 99% of stainless steel grades
- Difficult to machine — 22/100, worse than 95% of stainless steel grades
- Low electrical conductivity — 1.7 % IACS, worse than 93% of stainless steel grades
- High embodied carbon — 6 kg CO₂/kg, worse than 88% of stainless steel grades
- Limited service temperature — 400°C (752 °F), worse than 78% of stainless steel grades
S31266 properties
Typical room-temperature values for S31266-SA; bars are the position among stainless steel grades.
Physical3
S31266 has a density of 8 g/cm³ (0.289 lb/in³), heavier than 92% of stainless steel grades. It melts at 1,320°C (2,408 °F).
Mechanical17
S31266 has a yield strength of 480 MPa (69.6 ksi) and a tensile strength of 810 MPa (117 ksi) — stronger than 75% of stainless steel grades. Elongation at break is 46% and the elastic modulus is 195 GPa (28.3 Msi).
Thermal6
S31266 is rated for continuous service to 400°C (752 °F). It conducts heat at 11 W/m·K (6.36 BTU/hr·ft·°F), worse than 99% of stainless steel grades. Thermal expansion is 14.5 µm/m·K (8.06 µin/in·°F).
Electrical3
S31266 conducts electricity at 1.7 % IACS, worse than 93% of stainless steel grades.
Chemical & Environmental3
Corrosion resistance is excellent (92/100), better than 99% of stainless steel grades.
Sustainability4
Producing a kilogram of S31266 takes about 85 MJ of energy and emits 6 kg of CO₂ — more than 92% of stainless steel grades. Typical recycled content is 40%.
Manufacturability7
S31266's machinability is poor (22/100, worse than 95% of stainless steel grades); weldability very good (70/100); formability fair (45/100).
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 stainless steel family
Yield strength against density for every stainless steel grade FabDigit runs. S31266 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with S31266
Is S31266 easy to machine?
Very tough and work-hardening: use rigid setups, positive-rake carbide, heavy feed with no dwell, ~50–70 % of the speed used for 316L and copious high-pressure coolant.
Can S31266 be welded?
GTAW/GMAW/SMAW with over-alloyed Ni-base filler (ERNiCrMo-3, -13 or -14), low heat input, interpass <100 °C, no preheat and no PWHT; back-purge with Ar or Ar+N₂.
Can S31266 be formed, bent or molded?
Cold forms well but needs roughly double the press force of 304 and generous bend radii; hot work at 1100–1200 °C and solution anneal + water quench afterwards.
S31266 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 | ≤ 0.03 | 0.02 |
| Si | ≤ 1 | 0.4 |
| Mn | 2 – 4 | 3 |
| P | ≤ 0.04 | 0.02 |
| S | ≤ 0.02 | 0 |
| Cr | 23 – 25 | 24 |
| Ni | 21 – 24 | 22 |
| Mo | 5 – 7 | 6 |
| Cu | 0.5 – 2 | 1.3 |
| W | 1 – 3 | 2 |
| Nhigh nitrogen for strength and pitting resistance | 0.35 – 0.6 | 0.45 |
| Fe | balance |
What surface finishes work on S31266?
Pickle/passivate with HNO₃-HF after hot work or welding to restore the passive film; electropolishing gives the best crevice and cleanability performance — do not anodise.
Surface treatments FabDigit runs on stainless 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).
Passivation
Organic Coating
Thermal Spray
Equivalent designations
Standards and trade names that resolve to Stainless Steel S31266 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- ASTM
- A240/A312
- EN / DIN / Werkstoff-Nr.
- 1.4659
How much does S31266 cost?
S31266 is a high-cost stainless steel ($$$$), pricier than about 78% 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.
S31266 — frequently asked
What is S31266 used for?
S31266 is typically used for flue-gas desulfurization, seawater and brine systems, chemical process equipment and oil & gas sour service piping. In short: nickel-alloy corrosion resistance; highest chloride resistance in family; sour service capable.
What is the yield strength of S31266?
S31266 has a typical yield strength of 480 MPa (69.6 ksi) and a tensile strength of 810 MPa (117 ksi) — stronger than 75% of stainless steel grades. Strength varies by condition: see the 4 listed tempers.
Is S31266 easy to machine?
Not especially — machinability is rated poor (22/100, worse than 95% of stainless steel grades). Very tough and work-hardening: use rigid setups, positive-rake carbide, heavy feed with no dwell, ~50–70 % of the speed used for 316L and copious high-pressure coolant.
Can S31266 be welded?
Yes — weldability is rated very good (70/100). GTAW/GMAW/SMAW with over-alloyed Ni-base filler (ERNiCrMo-3, -13 or -14), low heat input, interpass <100 °C, no preheat and no PWHT; back-purge with Ar or Ar+N₂.
What surface finishes work on S31266?
Pickle/passivate with HNO₃-HF after hot work or welding to restore the passive film; electropolishing gives the best crevice and cleanability performance — do not anodise.
Can S31266 be formed, bent or molded?
Cold forms well but needs roughly double the press force of 304 and generous bend radii; hot work at 1100–1200 °C and solution anneal + water quench afterwards.
What is the maximum service temperature of S31266?
S31266 is rated for continuous use to about 400°C (752 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between S31266-SA and S31266-CD?
SA is the default condition — standard supply condition for all product forms — maximum corrosion resistance and ductility. CD: use when higher strength and close tolerance are needed; ductility and formability are reduced. Yield strength is 480 MPa in SA versus 720 MPa in CD.
How much does S31266 cost?
S31266 is a high-cost stainless steel ($$$$), pricier than about 78% 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
- ASTM A240/A240M — Chromium and Chromium-Nickel Stainless Steel Plate, Sheet, and Strip — ASTM International (2023)
- ASTM A312/A312M — Seamless, Welded and Heavily Cold Worked Austenitic Stainless Steel Pipes — ASTM International (2022)
- ASTM A479/A479M — Stainless Steel Bars and Shapes for Pressure Vessels — ASTM International (2023)
- UR B66 / UNS S31266 superaustenitic stainless steel datasheet — Industeel (ArcelorMittal) (2020)
- ASM Handbook Vol. 1 — Properties and Selection: Irons, Steels, and High-Performance Alloys — ASM International (1990)
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.