Duplex 2205 flanges are forged to ASTM A182 / ASME SA182 grade F51 (UNS S31803) and F60 (UNS S32205). The roughly equal mix of austenite and ferrite gives them about twice the yield strength of 316L, a pitting resistance (PREN) of about 35 and strong resistance to chloride stress corrosion cracking, which makes 2205 the workhorse flange material for offshore topsides, seawater systems, desalination and chloride-bearing process streams.
Raaj Fittings forges, heat treats and machines duplex 2205 flanges in-house at our two plants in India, from ½" to 60" and Class 150 to Class 2500, in every flange type we make, for EPC contractors and fabricators across the Middle East, Europe and the Americas. Dual-certified F51/F60 material is available.
| Material specification | ASTM A182 / ASME SA182 F51 (UNS S31803), F60 (UNS S32205); dual-certified F51/F60 |
|---|---|
| Dimensional standards | ASME B16.5 (½" to 24"), ASME B16.47 Series A and B (26" to 60"), EN 1092-1, DIN, BS 4504, JIS B2220 |
| Pressure class | ASME Class 150, 300, 600, 900, 1500 and 2500; PN 6 to PN 400 |
| Facing | Raised Face (RF), Flat Face (FF), Ring Type Joint (RTJ), Male & Female, Tongue & Groove |
| Heat treatment | Solution annealed and water quenched |
| Certification | EN 10204 3.1 mill test certificate as standard; EN 10204 3.2 on request |
| Element, % | F51 (S31803) | F60 (S32205) |
|---|---|---|
| Carbon (C) | 0.030 max | 0.030 max |
| Manganese (Mn) | 2.00 max | 2.00 max |
| Phosphorus (P) | 0.030 max | 0.030 max |
| Sulphur (S) | 0.020 max | 0.020 max |
| Silicon (Si) | 1.00 max | 1.00 max |
| Chromium (Cr) | 21.0 – 23.0 | 22.0 – 23.0 |
| Nickel (Ni) | 4.5 – 6.5 | 4.5 – 6.5 |
| Molybdenum (Mo) | 2.5 – 3.5 | 3.0 – 3.5 |
| Nitrogen (N) | 0.08 – 0.20 | 0.14 – 0.20 |
| Property (min.) | F51 (S31803) | F60 (S32205) |
|---|---|---|
| Tensile strength | 620 MPa (90 ksi) | 655 MPa (95 ksi) |
| Yield strength (0.2% offset) | 450 MPa (65 ksi) | 450 MPa (65 ksi) |
| Elongation | 25% | 25% |
| Grade | UNS | Werkstoff Nr. | EN designation | Forging grade |
|---|---|---|---|---|
| Duplex 2205 | S31803 / S32205 | 1.4462 | X2CrNiMoN22-5-3 | ASTM A182 F51 / F60 |
A duplex flange is only as good as its microstructure. Forging temperature, solution annealing and a fast water quench must leave a balanced ferrite-austenite structure free of intermetallic phases such as sigma, which would destroy toughness and corrosion resistance. That is why duplex orders often add:
Tell us which of these your project specification requires and they are built into the production and test plan.
Every heat is PMI-verified and its chemistry and mechanical properties are confirmed against the material specification before the flanges are released. Each piece is marked with grade, size, rating and heat number for traceability to its EN 10204 3.1 mill test certificate. EN 10204 3.2 certification and inspection by the buyer's nominated third-party agency are available on request, as are PED 2014/68/EU compliance for European projects and IBR certification for Indian boiler applications.
Both are duplex 2205. F51 is UNS S31803 and F60 is UNS S32205, which has higher minimum chromium, molybdenum and nitrogen for better pitting resistance and a higher minimum tensile strength. Dual-certified F51/F60 flanges meet both.
Duplex steel relies on a balance of ferrite and austenite. Wrong forging or heat treatment can unbalance it or form brittle intermetallic phases, so specifications usually require ferrite measurement and often ASTM A923 testing.
Yes, 2205 is widely used in seawater and firewater systems at ambient temperature. For warm seawater or very long crevices, super duplex 2507 or Zeron 100 flanges are often specified for extra margin.
Duplex 2205 is normally used from about −50 °C to 280 °C. Below that, impact testing is needed; above it, prolonged service can embrittle the ferrite.
Yes, duplex 2205 flanges can be supplied to NACE MR0175 / ISO 15156 for sour service when it is specified on the order, with the hardness and documentation the standard requires.