Duplex 2205
UNS S31803 / S32205 · Roughly double the yield strength of 304
Duplex 2205 has a roughly 50/50 austenite-ferrite microstructure, which gives it about twice the yield strength of standard austenitic grades together with markedly better resistance to chloride stress corrosion cracking. Its higher strength often allows a thinner wall for the same duty, which can offset the higher price per kilogram.
When to specify Duplex 2205
Choose 2205 where 316 is marginal on chlorides, where stress corrosion cracking is a risk, or where higher strength allows a lighter section. It is widely specified for offshore, seawater handling, chemical process and pressure vessels. Note the temperature limits below before specifying it for hot or cryogenic service.
Chemical Composition (%)
Composition and mechanical values are the limits set by the governing ASTM specification and are given for reference. The mill test certificate supplied with your consignment carries the actual heat analysis.
| Element | S31803 | S32205 |
|---|---|---|
| Carbon | 0.030 max | 0.030 max |
| Chromium | 21.0 – 23.0 | 22.0 – 23.0 |
| Nickel | 4.5 – 6.5 | 4.5 – 6.5 |
| Molybdenum | 2.5 – 3.5 | 3.0 – 3.5 |
| Nitrogen | 0.08 – 0.20 | 0.14 – 0.20 |
| Manganese | 2.00 max | 2.00 max |
| Phosphorus | 0.030 max | 0.030 max |
| Sulphur | 0.020 max | 0.020 max |
Mechanical & Physical Properties
| Property | Duplex 2205 | SS 316 for comparison |
|---|---|---|
| Tensile strength | 620 MPa min | 515 MPa min |
| Yield strength (0.2%) | 450 MPa min | 205 MPa min |
| Elongation in 50 mm | 25% min | 40% min |
| Hardness | 31 HRC max | 95 HRB max |
| Density | 7.80 g/cm³ | 8.00 g/cm³ |
| PREN (typical) | ≈ 35 | ≈ 25 |
Governing Standards
| Standard | Covers |
|---|---|
| ASTM A790 / A928 | Seamless and welded pipe |
| ASTM A789 | Tube |
| ASTM A240 UNS S31803 / S32205 | Plate, sheet and coil |
| ASTM A276 / A479 | Bar |
| ASTM A815 WP31803 / WPS32205 | Buttweld fittings |
| ASTM A182 F51 / F60 | Forged fittings and flanges |
Equivalent Designations
| Standard | Designation |
|---|---|
| EN | 1.4462 |
| JIS | SUS 329J3L |
| UNS | S31803 / S32205 |
| Common name | 2205, DSS 2205, Duplex 2205 |
Typical Applications
- Offshore and subsea piping
- Seawater cooling and desalination plant
- Chemical tankers and cargo handling
- Pressure vessels where strength allows a thinner wall
- Flue gas desulphurisation and pollution control
Industries Served
- Oil & Gas
- Marine
- Chemical
- Water Treatment
- Power
Duplex 2205 Products We Supply
Available in the forms below, minimum order quantity 5 kg, with a mill test certificate to EN 10204 3.1 traceable to the heat number.
Need Duplex 2205 in a form not listed above? We source to requirement — and we will confirm availability and lead time.
Duplex 2205 by product form
Governing standards, dimensions and stock availability for each form.
Duplex 2205 — Frequently Asked Questions
- What is the difference between S31803 and S32205?
- S32205 is a tightened version of S31803, with narrower ranges for chromium, molybdenum and especially nitrogen (0.14–0.20% against 0.08–0.20%). The higher guaranteed nitrogen improves pitting resistance and the stability of the weld. Most modern 2205 is dual-certified to both; if corrosion performance is critical, specify S32205.
- What temperature limits apply to Duplex 2205?
- Duplex grades are generally limited to about 300°C in continuous service. Above roughly 300°C the ferrite phase suffers embrittlement, and prolonged exposure between about 600°C and 950°C precipitates sigma phase, which severely reduces toughness and corrosion resistance. Duplex is also not used for cryogenic service, where austenitic grades retain toughness.
- Is Duplex 2205 harder to weld than 316?
- It requires more control. Heat input and interpass temperature must be managed to maintain the austenite-ferrite phase balance, and the correct filler — typically 2209 — must be used. It is routine work for a qualified fabricator but is not a drop-in substitute for 316 welding procedure.
Send your Duplex 2205 requirement
Tell us the form, size, quantity and standard and our technical team will confirm stock and send a firm price. Minimum order quantity 5 kg, mill test certificates supplied as standard.