Duplex 2205 – Chemical Composition, Equivalents & Products
Duplex 2205 is the most widely used duplex stainless steel – about 22% chromium, 5% nickel, 3% molybdenum and 0.15% nitrogen, with a microstructure of roughly equal austenite and ferrite. It has about twice the yield strength of 316L, much better resistance to chloride stress corrosion cracking, and a pitting resistance equivalent number (PREN) typically in the mid-30s. It is designated UNS S31803 and, with tighter limits, UNS S32205; material is usually dual certified.
Giriraj Impex supplies duplex 2205 in every product form – we manufacture flanges, fittings and bars, and stock and supply pipes, tubes and plates. This page gives the grade's composition, properties and equivalents.
Chemical composition
The composition limits for duplex and super duplex grades in ASTM A240 and A790 are shown together for comparison.
| UNS | Grade | C | Mn | P | S | Si | Cr | Ni | Mo | N | Other elements |
|---|---|---|---|---|---|---|---|---|---|---|---|
| S31803 | 2205 | 0.030 | 2.00 | 0.030 | 0.020 | 1.00 | 21.0–23.0 | 4.5–6.5 | 2.5–3.5 | 0.08–0.20 | – |
| S32205 | 2205 | 0.030 | 2.00 | 0.030 | 0.020 | 1.00 | 22.0–23.0 | 4.5–6.5 | 3.0–3.5 | 0.14–0.20 | – |
| S32750 | 2507 | 0.030 | 1.20 | 0.035 | 0.020 | 0.80 | 24.0–26.0 | 6.0–8.0 | 3.0–5.0 | 0.24–0.32 | Cu 0.50 |
| S32760 | Zeron 100 type | 0.030 | 1.00 | 0.030 | 0.010 | 1.00 | 24.0–26.0 | 6.0–8.0 | 3.0–4.0 | 0.20–0.30 | Cu 0.50–1.00, W 0.50–1.00 |
S32760 also requires a minimum PREN of 40. Footnotes as given in the standards.
S32205 has higher minimum chromium, molybdenum and nitrogen than S31803, which gives a more consistent PREN.
Mechanical properties
| UNS | Tensile strength, MPa (ksi) | Yield strength, MPa (ksi) | Elongation in 50 mm, % |
|---|---|---|---|
| S31803 | 620 (90) | 450 (65) | 25 |
| S32205 | 655 (95) | 450 (65) | 25 |
| S32750 | 795 (116) | 550 (80) | 15 |
| S32760 | 750 (108) | 550 (80) | 25 |
Hardness limits as given in the standard.
| UNS | Tensile strength, MPa (ksi) | Yield strength, MPa (ksi) | Elongation in 50 mm, % |
|---|---|---|---|
| S31803 | 620 (90) | 450 (65) | 25 |
| S32205 | 655 (95) | 485 (70) | 25 |
| S32750 | 800 (116) | 550 (80) | 15 |
| S32760 | 750 (109) | 550 (80) | 25 |
Hardness limits as given in the standard.
PREN of duplex 2205
PREN is calculated as %Cr + 3.3 × %Mo + 16 × %N. At the minimum limits of S32205 (22.0% Cr, 3.0% Mo, 0.14% N) the PREN works out at about 34, and typical production material is in the 34–36 range – which is why many specifications ask for a minimum PREN of 34 for 2205. By comparison 316L is around 24–26 and super duplex 2507 is 40 or more. The PREN of each heat can be calculated from the composition on the mill test certificate.
Equivalent grades and physical properties
| Grade | UNS | EN number | EN name | JIS |
|---|---|---|---|---|
| Duplex 2205 | S31803 / S32205 | 1.4462 | X2CrNiMoN22-5-3 | SUS329J3L |
| Super duplex 2507 | S32750 | 1.4410 | X2CrNiMoN25-7-4 | SUS327L1 |
Equivalent grades are similar but not identical; order to the standard you need.
| Property | Duplex 2205 | Super duplex 2507 |
|---|---|---|
| Density, g/cm³ | 7.8 | 7.8 |
| Thermal conductivity at 20 °C, W/m·K | approx. 15 | approx. 14 |
| Modulus of elasticity, GPa | approx. 200 | approx. 200 |
| Magnetic | Yes | Yes |
Typical values from recognised industry references, for guidance only; they are not specification limits.
More designations are in the grade equivalent chart.
Where duplex 2205 is used
2205 is used where 316L would suffer chloride stress corrosion cracking or pitting, and where its strength saves weight: offshore process and produced-water piping, desalination plants, seawater cooling in moderate conditions, chemical and fertiliser storage tanks, pulp and paper digesters and bleach plants, chemical tankers, heat exchangers with brackish or chloride-bearing cooling water, and bridges and structures. It is normally limited to service below about 250–300 °C because long exposure at higher temperature forms brittle phases.
Duplex 2205 products we supply
- Duplex pipes and tubes – ASTM A790, A789, A928.
- Duplex sheets and plates – ASTM A240.
- Duplex flanges – ASTM A182 F51, F60.
- Duplex pipe fittings – ASTM A815, A182.
- Duplex round bars – ASTM A276, A479.
See the duplex and super duplex steel page for the whole family.
Comparable grades
Compared with SS 316L, 2205 has a higher PREN, about twice the yield strength and far better resistance to chloride stress corrosion cracking, at a similar or modestly higher cost. Compared with super duplex 2507, it has a lower PREN and strength but is cheaper and easier to fabricate; 2507 is chosen for seawater and the most severe chloride service.
Testing duplex 2205
Project specifications for 2205 often add tests beyond the product standard. Ferrite content is measured to confirm the phase balance, typically within a stated range. Charpy impact tests at a low temperature confirm toughness. ASTM A923 detects detrimental intermetallic phases that can form if material is cooled too slowly. ASTM G48 Method A or similar pitting tests, at an agreed temperature, check corrosion resistance directly. These tests are normally applied to pipe, plate, fittings and forgings alike, so that every part of a duplex system meets the same standard.
Fabrication
2205 is welded with controlled heat input and interpass temperature, using 2209 filler metal (over-alloyed in nickel) to keep the weld's phase balance. Welding procedures are commonly qualified with ferrite measurement and impact tests. Hot forming must be followed by solution annealing and rapid cooling. Cold forming needs more force than 316L because of the higher strength.
Frequently Asked Questions
Duplex 2205 (UNS S32205) contains 22.0–23.0% chromium, 4.5–6.5% nickel, 3.0–3.5% molybdenum and 0.14–0.20% nitrogen, with 0.030% maximum carbon. S31803 has slightly wider limits.
At the minimum limits of S32205 the PREN is about 34, and typical material is in the 34–36 range. Many specifications require a minimum PREN of 34.
Duplex 2205 is EN 1.4462 (X2CrNiMoN22-5-3). Its UNS numbers are S31803 and S32205, and the Japanese equivalent is SUS329J3L.
Yes. Its minimum yield strength is about 450 MPa for plate under ASTM A240, compared with 170 MPa for 316L.
2209 filler metal is normally used. It contains more nickel than the base metal so that the weld has the correct balance of ferrite and austenite.
Duplex 2205 is normally limited to service below about 250–300 °C, as set by the design code, because prolonged exposure at higher temperature can form brittle phases.
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