Super Duplex F52 is a nitrogen-bearing 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 27% chromium, 4.5% nickel, 1.7% molybdenum and a deliberate nitrogen addition (0.15-0.35%), F52 provides roughly twice the yield strength of standard austenitic grades, with strong resistance to chloride pitting, crevice corrosion and chloride stress-corrosion cracking. It is a nickel-economical duplex grade combining high strength with good general and localized corrosion resistance.
Typical applications include oil-and-gas equipment, offshore platforms, heat exchangers, subsea equipment, chemical-process piping and vessels, desalination and high-pressure reverse-osmosis plant, and high-strength corrosion-resistant mechanical parts.
| Property | Value | Unit |
|---|---|---|
| Density | 7.7 | g/cm³ |
| Melting range | 1390-1440 | °C |
| Young's modulus (20 °C) | 200 | GPa |
| Thermal conductivity (20 °C) | 16 | W/m·K |
| Coefficient of thermal expansion (20-100 °C) | 11 | 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 | 26.0 | 29.0 | Ferrite former; corrosion resistance |
| Nickel | Ni | 3.5 | 5.2 | Austenite former; phase balance |
| Molybdenum | Mo | 1.0 | 2.5 | Pitting + crevice resistance |
| Nitrogen | N | 0.15 | 0.35 | Austenite former; strength; pitting |
| Manganese | Mn | — | 2.0 | Deoxidiser |
| Silicon | Si | — | 0.60 | Deoxidiser |
| Carbon | C | — | 0.030 | Low (intergranular resistance) |
| Phosphorus | P | — | 0.035 | Residual impurity |
| Sulphur | S | — | 0.010 | Residual impurity |
Solution-annealed condition (1010-1150 °C, water quench), per ASTM A240 for UNS S32950.
| Property | Value | Unit |
|---|---|---|
| Tensile strength | >=690 | MPa |
| 0.2% yield strength | >=485 | MPa |
| Elongation at break | >=15 | % |
| Brinell hardness | <=293 | HB |
| Rockwell hardness | <=32 | HRC |
Confirm against the mill test report.
| Environment | Performance | Notes |
|---|---|---|
| Chloride SCC | Excellent | Key duplex advantage over austenitics |
| Chloride pitting | Good | Cr + Mo + N (PREN ~35) |
| Crevice corrosion | Good | Better than 316L |
| General (oxidizing) | Very good | High chromium |
| Sulphide / sour | Good | Listed in NACE MR0175 |
The duplex structure gives far better chloride-SCC resistance than austenitic 304/316.
Not hardenable by heat treatment; properties are set by solution annealing and phase balance.
Solution Anneal approximately 1010-1150 °C, followed by rapid water quench to retain the balanced ferrite-austenite structure and avoid embrittling intermetallic phases. Avoid prolonged exposure in the 300-900 °C range (sigma-phase / 475 °C embrittlement).
Weldable by common fusion and resistance methods; should not be joined by oxyacetylene welding. Use a matching or over-alloyed duplex/Ni-base filler and control heat input to maintain phase balance.
| Process | Applicability | Filler / Consumable |
|---|---|---|
| GTAW / TIG | Good | Duplex (e.g. ER2209) or Ni-base |
| GMAW / MIG | Good | Duplex (e.g. ER2209) |
| SMAW / stick | Good | Matching duplex electrode |
No preheat; control interpass temperature; a post-weld solution anneal + quench restores optimum phase balance on heavy sections.
Machining Guidelines
| Parameter | Recommendation |
|---|---|
| Machinability | Duplex; rigid setup, sharp tooling, moderate speeds |
| Work hardening | Significant; positive feeds, avoid dwelling |
| Coolant | Ample flood coolant |
Forming Processes
| Process | Notes |
|---|---|
| Hot forming | ~1200-950 °C; solution anneal + quench afterward |
| Cold forming | Higher forces than austenitics; lower ductility |
| Industry | Typical Components | Key Requirements |
|---|---|---|
| Oil & gas | Tubing, piping, subsea equipment | Sour-service + SCC resistance |
| Offshore | Platform components, firefighting systems | Chloride + SCC resistance |
| Chemical processing | Heat exchangers, vessels, piping | Pitting + SCC resistance |
| Desalination | RO plant, subsea pipelines | Hot chloride resistance |
| Mechanical | High-strength corrosion-resistant parts | Strength + corrosion resistance |
| Product Form | Standard | Notes |
|---|---|---|
| Plate, sheet and strip | ASTM A240 / ASME SA-240 · UNS S32950 | — |
| Forgings / fittings / flanges | ASTM A182 | — |
| Bar and shapes | ASTM A276 / A479 · UNS S32950 | — |
| Seamless / welded tube | ASTM A789 · UNS S32950 | — |
| Seamless / welded pipe | ASTM A790 · UNS S32950 | — |
| Sour service | NACE MR0175 / ISO 15156 | Acid-gas applications |
Nitrogen-bearing ferritic-austenitic (duplex) stainless steel. UNS S32950.
| UNS | Cr % | Ni % | Mo % | N % | Best Used For |
|---|---|---|---|---|---|
| F52 | 26-29 | 3.5-5.2 | 1.0-2.5 | 0.15-0.35 | N-bearing duplex; sour / chloride-SCC service |
| S31200 | 24-26 | 5.5-6.5 | 1.2-2.0 | 0.14-0.20 | N-bearing duplex |
| S32900 | 23-28 | 2.5-5.0 | 1.0-2.0 | — | Early duplex (no N spec) |
| S31803 | 22-23 | 4.5-6.5 | 3.0-3.5 | 0.14-0.20 | Standard duplex (higher PREN) |
| S32750 | 24-26 | 6.0-8.0 | 3.0-5.0 | 0.24-0.32 | Super duplex |




