S31260 is a tungsten- and copper-bearing 25Cr ferritic-austenitic (duplex) stainless steel, with a microstructure of roughly equal ferrite and austenite. This datasheet presents the material within the American standard system.
With about 25% chromium, 6.5% nickel, 3% molybdenum, small tungsten and copper additions and nitrogen, S31260 offers roughly twice the yield strength of standard austenitic grades, together with strong resistance to chloride pitting, crevice corrosion and stress-corrosion cracking. The tungsten and copper additions enhance localized-corrosion and acid resistance, placing its performance between standard 2205 duplex and the higher-PREN super duplex grades.
Typical applications include oil-and-gas equipment, subsea components, seawater systems, heat exchangers and chemical-process equipment requiring high strength with chloride resistance.
| Property | Value | Unit |
|---|---|---|
| Density | 7.8 | g/cm³ |
| Melting range | 1350-1400 | °C |
| Young's modulus (20 °C) | 200 | GPa |
| Thermal conductivity (20 °C) | 16 | W/m·K |
| Coefficient of thermal expansion (20-100 °C) | 13 | µm/m·°C |
| Specific heat (20 °C) | 480 | J/kg·K |
| Magnetic response | Ferromagnetic (duplex) | — |
| Element | Symbol | Min % | Max % | Role in Alloy |
|---|---|---|---|---|
| Iron | Fe | Balance | — | Base element |
| Chromium | Cr | 24.0 | 26.0 | Ferrite former; corrosion resistance |
| Nickel | Ni | 5.5 | 7.5 | Austenite former; phase balance |
| Molybdenum | Mo | 2.5 | 3.5 | Pitting + crevice resistance |
| Copper | Cu | 0.20 | 0.80 | Acid resistance |
| Tungsten | W | 0.10 | 0.50 | Pitting resistance |
| Nitrogen | N | 0.10 | 0.30 | Austenite former; strength; pitting |
| Manganese | Mn | — | 1.00 | Deoxidiser |
| Silicon | Si | — | 0.75 | Deoxidiser |
| Carbon | C | — | 0.030 | Low (intergranular resistance) |
| Phosphorus | P | — | 0.030 | Residual impurity |
| Sulphur | S | — | 0.030 | Residual impurity |
Solution-annealed condition, per ASTM A240 for UNS S31260.
| Property | Value | Unit |
|---|---|---|
| Tensile strength | >=690 | MPa |
| 0.2% yield strength | >=485 | MPa |
| Elongation at break | >=25 | % |
| Brinell hardness | <=290 | HB |
| Rockwell hardness | <=31 | HRC |
Confirm against the mill test report.
| Environment | Performance | Notes |
|---|---|---|
| Chloride SCC | Excellent | Key duplex advantage over austenitics |
| Chloride pitting | Very good | Cr + Mo + W + N |
| Crevice corrosion | Very good | Better than 316L |
| Acids | Very good | Copper addition |
| General (oxidizing) | Very good | High chromium |
| Sulphide / sour | Good | Listed in NACE MR0175 |
Localized-corrosion resistance sits between standard 2205 duplex and the high-PREN super duplex grades.
Not hardenable by heat treatment; properties are set by solution annealing and phase balance.
Solution Anneal approximately 1040-1120 °C, followed by rapid water quench to retain the balanced ferrite-austenite structure and avoid embrittling intermetallic phases. Rapid cooling is critical owing to the high alloy content. Avoid prolonged exposure in the 300-1000 °C range (sigma-phase / 475 °C embrittlement).
Weldable by common fusion methods; use a matching or over-alloyed duplex/super-duplex filler and control heat input to maintain phase balance.
| Process | Applicability | Filler / Consumable |
|---|---|---|
| GTAW / TIG | Good | Duplex / super-duplex filler |
| GMAW / MIG | Good | Duplex filler |
| SMAW / stick | Good | Matching duplex electrode |
No preheat; control interpass temperature and heat input to maintain phase balance and avoid intermetallic phases.
Machining Guidelines
| Parameter | Recommendation |
|---|---|
| Machinability | Duplex; carbide tools, low-to-moderate speeds, rigid setup |
| Work hardening | Significant; positive feeds, avoid dwelling |
| Coolant | Ample flood coolant |
Forming Processes
| Process | Notes |
|---|---|
| Hot forming | ~1200-1000 °C; solution anneal + quench afterward |
| Cold forming | Higher forces than austenitics (high duplex strength) |
| Industry | Typical Components | Key Requirements |
|---|---|---|
| Oil & gas | Subsea components, tubing | Pitting + sour-service resistance |
| Marine / seawater | Seawater systems, heat exchangers | Chloride resistance |
| Chemical processing | Vessels, piping | Localized-corrosion resistance |
| Desalination | Heat exchangers | Chloride resistance |
| Product Form | Standard | Notes |
|---|---|---|
| Plate, sheet and strip | ASTM A240 / ASME SA-240 · UNS S31260 | — |
| Bar and shapes | ASTM A276 / A479 · UNS S31260 | — |
| Seamless / welded tube | ASTM A789 · UNS S31260 | — |
| Seamless / welded pipe | ASTM A790 / A928 · UNS S31260 | — |
| Forgings / fittings | ASTM A182 · UNS S31260 | — |
| Sour service | NACE MR0175 / ISO 15156 | Acid-gas applications |
Tungsten- and copper-bearing 25Cr ferritic-austenitic (duplex) stainless steel. UNS S31260.
| UNS | Cr % | Ni % | Mo % | W % | Cu % | Best Used For |
|---|---|---|---|---|---|---|
| S31260 | 24-26 | 5.5-7.5 | 2.5-3.5 | 0.1-0.5 | 0.2-0.8 | W+Cu 25Cr duplex; chloride service |
| S32205 | 22-23 | 4.5-6.5 | 3.0-3.5 | — | — | Standard duplex |
| S32750 | 24-26 | 6.0-8.0 | 3.0-5.0 | — | — | Super duplex |
| S32760 | 24-26 | 6.0-8.0 | 3.0-4.0 | 0.5-1.0 | 0.5-1.0 | W+Cu super duplex |
| S31803 | 21-23 | 4.5-6.5 | 2.5-3.5 | — | — | Standard duplex (original) |




