Super Duplex 2507 – Chemical Composition, Equivalents & Products
Super duplex 2507 (UNS S32750, EN 1.4410) is a high-alloy duplex stainless steel with about 25% chromium, 7% nickel, 4% molybdenum and 0.27% nitrogen. Its PREN is typically 41 or more, giving excellent resistance to pitting and crevice corrosion in seawater, and its minimum yield strength of 550 MPa is more than three times that of 316L. It is the standard material for seawater and high-chloride systems in offshore oil and gas, desalination and chemical plants.
Giriraj Impex supplies super duplex 2507 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
| 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.
UNS S32760 (known as Zeron 100) is a related super duplex grade with copper and tungsten additions.
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 super duplex 2507
Using PREN = %Cr + 3.3 × %Mo + 16 × %N, typical 2507 compositions give a PREN of 41–43. Because the composition limits alone allow lower values, oil and gas and desalination specifications usually add a minimum PREN – commonly 40 or 41 – which is checked against the actual analysis on the mill test certificate. This is the main reason 2507 is accepted for seawater where 2205 (PREN about 34–36) is not.
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.
See the grade equivalent chart for more designations.
Where super duplex 2507 is used
2507 is used for seawater lift, injection, cooling and firewater piping offshore; subsea manifolds, flowlines and umbilical tubing; desalination high-pressure piping and pump parts; seawater-cooled heat exchangers; pulp bleaching; and chemical plants handling hot chloride solutions. Its high strength also suits pressure vessels, pumps and valves where weight matters. Like other duplex grades it is limited to moderate temperatures – normally below about 250–300 °C – and its upper limit in seawater is set by the project materials specification.
Super duplex 2507 products we supply
- Super duplex pipes and tubes – ASTM A790, A789, A928.
- Super duplex sheets and plates – ASTM A240.
- Super duplex flanges – ASTM A182 F53.
- Super duplex pipe fittings – ASTM A815 WPS32750, A182 F53.
- Super duplex round bars – ASTM A276, A479.
See the duplex and super duplex steel page for the whole family.
Comparable grades
Duplex 2205 is cheaper and easier to fabricate, with a PREN of about 34–36 and lower strength; it suits brackish water and many chloride process streams but not warm seawater. Zeron 100 (S32760) is a super duplex grade with similar strength and pitting resistance; projects specify one or the other. 6% molybdenum austenitic grades such as 254 SMO offer similar pitting resistance with easier fabrication but lower strength.
Testing super duplex 2507
Because super duplex is more prone than 2205 to intermetallic phases, especially in thick sections, project specifications nearly always add ASTM A923 testing, Charpy impact tests at low temperature and ferrite measurement, and often an ASTM G48 pitting test at a set temperature. For forgings and heavy fittings, test pieces may be taken from the thickest section or from a sacrificial part of the same heat and heat-treatment batch. Positive material identification is also common, as super duplex looks the same as other stainless steels.
Fabrication
2507 is less forgiving than 2205: welding requires tightly controlled heat input and interpass temperature, 2594-type over-alloyed filler metal and suitable shielding and backing gas, with procedures qualified by ferrite, impact and corrosion tests. Thick sections must be solution annealed and quenched quickly to avoid intermetallic phases, and hot forming must be followed by re-annealing. Material is commonly tested to ASTM A923 and ASTM G48 when supplied.
Frequently Asked Questions
UNS S32750 contains 24.0–26.0% chromium, 6.0–8.0% nickel, 3.0–5.0% molybdenum and 0.24–0.32% nitrogen, with 0.030% maximum carbon and 0.50% maximum copper.
Typical 2507 has a PREN of 41–43. Specifications usually require a minimum PREN of 40 or 41, checked against the actual composition on the mill test certificate.
Super duplex 2507 is EN 1.4410 (X2CrNiMoN25-7-4). Its UNS number is S32750.
The minimum yield strength of UNS S32750 is 550 MPa (80 ksi) for both plate (ASTM A240) and pipe (ASTM A790).
2507 is UNS S32750. Zeron 100 is the trade name for UNS S32760, which adds copper and tungsten. Both are super duplex grades with similar strength and pitting resistance.
A 2594-type super duplex filler metal, over-alloyed in nickel, is normally used so the weld keeps the correct phase balance and corrosion resistance.
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Zeron® 100 are trademarks of Rolled Alloys; 254 SMO® of Outokumpu.