Alloy 32750
Also known as SAF 2507®, Alloy 2507, UNS S32750, EN 1.4410
Alloy 32750 (2507) is a super duplex stainless steel with PREN over 40, listed in NACE MR0175 for sour service.
Alloy 32750 (UNS S32750), widely known as SAF 2507, is a super duplex stainless steel with 25% chromium, high nitrogen and molybdenum content, achieving a Pitting Resistance Equivalent Number (PREN) exceeding 40. Listed in NACE MR0175 / ISO 15156 for sour service and suitable for working temperatures up to 300°C.
With 550 N/mm² minimum proof stress and excellent toughness to sub-zero temperatures, it offers approximately twice the yield strength of standard austenitic grades while maintaining full corrosion resistance. Critical Pitting Temperature exceeds 50°C. ASME Pressure Vessel approval is carried.
We stock bar in the UK and USA, and plate in the USA. Tube and fittings are available on enquiry; forgings and castings to order.
- PREN exceeding 40 - outstanding resistance to pitting and crevice corrosion in seawater and chloride environments
- Critical Pitting Temperature exceeding 50°C
- Higher strength than austenitic and 22%Cr duplex stainless steels
- Excellent ductility and impact strength at both ambient and sub-zero temperatures
- High resistance to abrasion, erosion and cavitation erosion
- Excellent resistance to stress corrosion cracking in chloride environments
- Listed in NACE MR0175 / ISO 15156 for sour service
- ASME Approval for Pressure Vessel application
| Element | Min | Max |
|---|---|---|
| Chromium (Cr) | 24.50 | 26.00 |
| Nickel (Ni) | 6.00 | 8.00 |
| Molybdenum (Mo) | 3.00 | 5.00 |
| Copper (Cu) | - | 0.50 |
| Iron (Fe) | Bal | |
| Manganese (Mn) | - | 1.20 |
| Nitrogen (N) | 0.24 | 0.32 |
| Silicon (Si) | - | 0.80 |
| Carbon (C) | - | 0.03 |
| Phosphorus (P) | - | 0.035 |
| Sulphur (S) | - | 0.020 |
Work out the PREN for this composition with our PREN calculator.
| Property | Imperial | Metric |
|---|---|---|
| 0.2% Proof stress (min) | 79.8 ksi | 550 N/mm² |
| Tensile strength (min) | 116 ksi | 800 N/mm² |
| Elongation (5.65√S0) | 25% | 25% |
| Reduction of area | 45% | 45% |
| Hardness (Brinell) | ≤ 271 HB | ≤ 271 HB |
| Impact strength (Room Temp) | 80 J | |
| Impact strength (-46°C) | 45 J av (35 J min long, 33 J min trans) |
| Property | Imperial | Metric |
|---|---|---|
| 0.2% Proof stress (min) | 79.8 ksi | 550 N/mm² |
| Tensile strength (min) | 115 ksi | 795 N/mm² |
| Elongation (5.65√S0) | 25% | 25% |
| Reduction of area | 45% | 45% |
| Hardness (Brinell) | 220-270 HB | 220-270 HB |
| Impact strength (Room Temp) | 80 J | |
| Impact strength (-46°C) | 45 J (min 35 J) |
| Property | Value |
|---|---|
| Density (kg/m³) | 7810 |
| Magnetic permeability (20°C) | 33 |
| Young's modulus (kN/mm²) | 199 |
| Specific electrical resistance, 20°C (µΩ.m) | 0.80 |
| Mean coefficient of thermal expansion, 20-300°C (m/m/°C) | 11.1 x 10⁻⁶ |
| Specific heat, 20°C (J/kg.K) | 475 |
| Thermal conductivity, 20°C (W/m.K) | 14.2 |
Equivalents & cross-references
Standard designations
- UNS
- S32750Unified Numbering System; also designated Alloy 2507
- EN
- 1.4410European harmonised standard; X2CrNiMoN25.7.4
- ASTM
- A182 F53Forgings and fittings A479Bar and shapes
- NACE
- MR0175 / ISO 15156Sour service
- API
- 6AWellhead and tree equipment
- NORSOK
- M-650Qualification of manufacturers for subsea equipment
Alloy 32750 is also designated UNS S32750, EN 1.4410, ASTM A182 F53, ASTM A479, NACE MR0175 / ISO 15156, API 6A and NORSOK M-650.
Trade name equivalents
-
SAF 2507
Alleima
SAF 2507 is a trade name of Alleima for Alloy 32750.
-
Alloy 2507
Alloy 2507 is an alternate designation for Alloy 32750.
Common questions
What is Alloy 32750 equivalent to?
Alloy 32750 is a super duplex stainless steel covered by UNS S32750, also known as Alloy 2507, with equivalents ASTM A479, ASTM A182 F53 and EN 1.4410 (X2CrNiMoN25.7.4). It is supplied in the solution annealed condition and is listed in NACE MR0175/ISO 15156, API 6A and Norsok M-650, with a Pitting Resistance Equivalent Number (PREN) of 41. Langley Alloys stocks it as bar; tube and fittings are available on enquiry, and forgings and castings are to order.
What is Alloy 32750 used for?
Alloy 32750 is used for oil and gas pumps, valves, pipe, vessels, wellhead and subsea equipment; marine propellers, shafts, rudders, shaft seals, pumps, fasteners and valves; and oil and chemical tankers. It is also used in process components for nitric acid, polypropylene and PVC production, pollution control and flue gas desulphurisation, pulp and paper equipment, and sewage treatment, seawater cooling and desalination plant.
Is Alloy 32750 suitable for sour service and higher temperatures?
Yes. Alloy 32750 is listed in NACE MR0175/ISO 15156 for sour service, with hardness controlled to a maximum of 28 HRC, and holds ASME approval for pressure vessel applications. In the annealed condition it achieves a yield strength of 80 ksi (550 MPa), greater than most austenitic and duplex grades, and it offers a Critical Pitting Temperature above 50°C. It has a low coefficient of thermal expansion and higher heat conductivity than austenitic steels, and is suitable for working temperatures up to 300°C. It cannot be hardened by heat treatment but can be strengthened by cold working.
What is SAF 2507?
SAF 2507 is a trade designation used by Alleima for UNS S32750, a super duplex stainless steel also designated EN 1.4410 (X2CrNiMoN25.7.4) and Alloy 2507. Langley Alloys stocks this grade as Alloy 32750 to ASTM A479, ASTM A182 F53, NACE MR0175/ISO 15156, API 6A, and Norsok M-650.
Is SAF 2507 the same as Alloy 32750?
Yes. SAF 2507 is Alleima's trade designation for UNS S32750, which Langley Alloys stocks as Alloy 32750. Both refer to the same super duplex stainless steel with a PREN of 41, meeting ASTM A479, A182 F53, and Norsok M-650.
What is the UNS number for SAF 2507?
The UNS number for SAF 2507 is S32750. The grade is also known as Alloy 2507 and carries the EN designation 1.4410 (X2CrNiMoN25.7.4). Langley Alloys stocks it as Alloy 32750.
What is EN 1.4410 stainless steel?
EN 1.4410 (X2CrNiMoN25.7.4) is the European designation for UNS S32750, a super duplex stainless steel stocked by Langley Alloys as Alloy 32750 and commonly known as SAF 2507 or Alloy 2507.
What is the density of Alloy 32750?
Alloy 32750 has a density of approximately 7.81 g/cm³ (7810 kg/m³).
Is Alloy 32750 magnetic?
Yes. Alloy 32750 is a super duplex stainless steel with a part-ferritic structure, so it is ferromagnetic (magnetic).
25% chromium super duplex (2507)
Alloy 32750 is a 25% chromium super duplex stainless steel, also known as UNS S32750 and 2507.
Its high chromium, molybdenum and nitrogen give it a pitting resistance well above standard stainless, combining the strength of a ferritic grade with the toughness of an austenitic one. It's a mainstay for the most demanding oil and gas, marine and chemical-processing service, and we stock it heavily in bar.
Visit our YouTube channelSolution annealed and water quenched; bar supplied peeled and polished to 125CLA or better, ultrasonically tested and visually inspected.
Processing capability
Cutting
Automated band sawing to 650mm section. CNC sawing at all sites.
Cutting servicesFirst-stage processing
Water jet cutting, turning, boring and grinding undertaken in-house.
Processing servicesInspection & testing
Each bar ultrasonically tested and visually inspected. ASTM G48A pitting corrosion test and ferrite content certification available.
Inspection & testing
Tools for this grade
Pitting & crevice resistance
Pitting & Crevice Resistance
Rank alloys by PREN and get an indicative pitting temperature for a chloride service. Pick a grade and a service temperature to see whether it has margin against pitting, or compare the range in the table below. A first-pass screen for chloride and seawater service.
| Grade | UNS | PREN | Indicative CPT | Relative pitting resistance |
|---|
Indicative screen, not a certified result. PREN ranks pitting resistance; the pitting temperature here is estimated from PREN (CPT ≈ 2.5 × PREN - 50), consistent with Langley's "PREN >40, CPT exceeding 50°C" for super duplex. Real critical pitting/crevice temperature depends on test method, product form, surface finish and service chemistry. Crevice corrosion starts well below the pitting temperature - allow a margin at gaskets, deposits and flange faces. Use certified data for design.
Sour-service screen (NACE MR0175)
Sour-Service Screen
Work out whether a service is sour from the H2S partial pressure, and see each alloy's NACE MR0175 / ISO 15156 status and hardness limit. A first-pass screen for oil & gas material selection - the full environmental envelope for a grade is set in ISO 15156-3 Annex A.
Candidate grade
| Grade | Family | NACE status | Hardness limit |
|---|
First-pass screen only. This shows whether the service is sour (from H2S partial pressure) and each material group's NACE MR0175 hardness limit and general suitability. It does not reproduce the full environmental windows (maximum H2S partial pressure, temperature, chloride, in-situ pH per grade) - those are in ISO 15156-3 Annex A and must be checked there for the specific grade, product form and condition. Qualification also depends on heat treatment, cold work and welding.
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