Duplex 2205 is the most-specified standard duplex stainless steel grade globally, used in chemical processing, oil & gas, marine moderate-chloride service, pulp & paper, and food & beverage industries. Designated UNS S31803 / S32205 in the North American Unified Numbering System and EN 1.4462 / X2CrNiMoN22-5-3 under European Standards. Nominal composition: 22 Cr – 5 Ni – 3 Mo – 0.15 N; PREN ~35 (below the super duplex PREN ≥ 40 threshold). Above standard-duplex limits, super-duplex grades like Ferralium 255 are specified.
Duplex 2205 has a balanced two-phase austenite-ferrite microstructure (35–55% ferrite per NORSOK M-630), supplied solution-annealed at ~1050 °C with water quench. The grade combines the high strength of ferritic stainless steel (yield ≥ 450 MPa, tensile ≥ 620 MPa) with the corrosion resistance of austenitic stainless steel. It is approximately twice as strong as 304/316L austenitic stainless steel at room temperature, allowing thinner-section component design.
| Property | Minimum (Duplex 2205) | Test standard |
|---|---|---|
| 0.2% Yield strength (Rp0.2) | 450 MPa (65 ksi) | ASTM E8 |
| Ultimate tensile strength (Rm) | 620 MPa (90 ksi) | ASTM E8 |
| Elongation (A5) | 25% | ASTM E8 |
| Hardness, max | 293 HBW (~32 HRC NACE limit) | ASTM E18 |
| Charpy V-notch at −46 °C, min | 45 J (NORSOK M-630) | ASTM E23 |
| Density | 7.80 g/cm³ | none |
Full element-by-element composition table on Duplex 2205 chemical composition page. Summary: Cr 22–23%, Ni 4.5–6.5%, Mo 3.0–3.5%, N 0.14–0.20%, no Cu (vs Ferralium 255 with 1.5–2.5% Cu). PREN = %Cr + 3.3·%Mo + 16·%N ≈ 35 typical per heat.
Duplex 2205 service limits become binding when: chloride concentration exceeds typical seawater (3.5% NaCl); service temperature exceeds 30 °C in chloride environments; sour-gas (H2S) partial pressure exceeds NACE MR0175 thresholds for standard duplex; or when reducing acids (HCl, dilute H2SO4) are present. In these conditions, upgrade to a super duplex grade with PREN ≥ 40 such as Ferralium 255 (UNS S32550). See Ferralium 255 vs Duplex 2205 upgrade decision guide.
