Duplex 2205 buttweld fittings are made to ASTM A815 / ASME SA815 in grades WPS31803 and WPS32205. Their mixed austenite-ferrite structure gives roughly twice the yield strength of 316L, much better resistance to chloride stress corrosion cracking, and a pitting resistance in the mid-thirties (PREN), which is why 2205 is the standard choice for offshore, seawater, desalination and many chemical and refinery services.
Raaj Fittings manufactures duplex 2205 elbows, tees, reducers, caps, stub ends and bends in-house at our two plants in India, in seamless and welded construction from ½" up to 48", and exports them to projects across the Middle East, Europe and the Americas. Most current orders are for dual-certified UNS S31803/S32205 material.
| Material specification | ASTM A815 / ASME SA815 WPS31803, WPS32205; dual-certified S31803/S32205 |
|---|---|
| Class | WP-S (seamless), WP-W, WP-WX (welds radiographed), WP-WU (welds ultrasonically tested); CR for MSS SP-43 fittings |
| Dimensional standards | ASME B16.9, MSS SP-43; bevelled ends to ASME B16.25 |
| Size range | ½" to 48" NPS; larger sizes to order |
| Wall thickness | SCH 5S, 10S, 40S, 80S, SCH 10 to SCH 160, STD, XS, XXS |
| Heat treatment | Solution annealed at 1020–1100 °C and water quenched |
| Certification | EN 10204 3.1 mill test certificate as standard; EN 10204 3.2 on request |
| Element, % | WPS31803 | WPS32205 |
|---|---|---|
| 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 |
S32205 is the tighter, "upper-half" version of S31803: its higher minimum chromium, molybdenum and nitrogen guarantee a PREN of about 35. A fitting certified to both meets the S32205 chemistry.
| Property | WPS31803 | WPS32205 |
|---|---|---|
| Tensile strength, min. | 620 MPa (90 ksi) | 655 MPa (95 ksi) |
| Yield strength, min. | 450 MPa (65 ksi) | 450 MPa (65 ksi) |
| Elongation, min. | 20% | 20% |
| Hardness, max. | 290 HBW | 290 HBW |
| Grade | UNS | Werkstoff Nr. | EN designation | Forged equivalent |
|---|---|---|---|---|
| Duplex 2205 | S31803 / S32205 | 1.4462 | X2CrNiMoN22-5-3 | ASTM A182 F51 / F60 |
Duplex fittings depend on a correct austenite-ferrite balance, so heat treatment and verification matter more than for austenitic grades. Every heat is PMI-tested and checked for chemistry and mechanical properties against ASTM A815; fittings are solution annealed and water quenched, then pickled and passivated. Welded fittings are made in classes WP-WX or WP-WU when full radiographic or ultrasonic examination is required. Ferrite measurement, impact testing and testing for intermetallic phases to ASTM A923 can be added to the order, together with third-party inspection by the buyer's nominated agency and EN 10204 3.2 certification.
Both are duplex 2205. S32205 has tighter, higher minimums for chromium (22.0%), molybdenum (3.0%) and nitrogen (0.14%), which guarantees better pitting resistance. Dual-certified S31803/S32205 fittings meet the S32205 chemistry and are accepted wherever either grade is specified.
WP is the ASTM A815 class for fittings to ASME B16.9 dimensions, S31803 is the UNS grade, and WX means a welded fitting whose welds have been fully radiographed. Seamless fittings are marked WP-S, and WU means the welds were ultrasonically examined.
Duplex 2205 is normally used up to about 280 °C. Above that, long service can cause embrittlement of the ferrite phase. For colder service down to about −50 °C, impact testing is usually specified on the order.
Yes, dissimilar welds between duplex and austenitic stainless steel are common, normally using a duplex filler metal such as 2209. The welding procedure should be qualified for the combination, and the pipe material sets the corrosion resistance at the joint.
Every fitting is supplied with an EN 10204 3.1 mill test certificate showing heat chemistry and mechanical properties to ASTM A815. EN 10204 3.2 certification, ferrite reports and ASTM A923 test results are available when specified.