Surface Treatments
Certifications
- ISO 9001 - 2015 Certified
- PED 2014/68/EC
- NACE MR0175 / ISO 15156-2
- NORSOK M-650 Qualified
- API 6A Certified
- DFAR
- MERKBLATT AD 2000 W2/W7/W10
UNS S32750, Super Duplex Stainless Steel 2507
UNS S32750 is the Unified Numbering System designation for super duplex stainless steel widely known as 2507. The same chemistry is registered as EN 1.4410 (Werkstoff Nummer) and X2CrNiMoN25-7-4 in EN 10088-3. Mill trademarks for the identical UNS S32750 chemistry include SAF 2507 (Sandvik), UR 52N+ (Industeel ArcelorMittal), and Avesta 2507 (Outokumpu). Nominal composition is 25 Cr, 7 Ni, 3.5 to 4 Mo, 0.24 to 0.32 N with no intentional copper and no intentional tungsten. PREN, calculated as Cr + 3.3 times Mo + 16 times N, sits at 41 or higher.
The grade is covered by ASTM A479 (bar and shapes), ASTM A789 (tube), ASTM A790 (pipe), ASTM A815 (fittings, designation WP-S32750), ASTM A276 (shapes), and ASTM A182 grade F53 (forgings, flanges, forged fittings). International standards include EN 10088-3, NORSOK M-630, NORSOK M-650 (manufacturer qualification), NACE MR0175 / ISO 15156 for sour service, API 6A for wellhead equipment, and API 17D for subsea equipment.
UNS S32750 Chemical Composition (per ASTM A479)
The defining trait of UNS S32750 is the absence of intentional copper or tungsten. Adding either element changes the alloy entirely. Zeron 100 (UNS S32760) adds approximately 0.7 percent each of copper and tungsten. Ferralium 255 (UNS S32550) adds copper. The chemistry below is the canonical UNS S32750 window per ASTM A479, mirrored in EN 10088-3 (1.4410) and ASTM A182 grade F53 with negligible variation.
| Element | ASTM A479 Min % | ASTM A479 Max % | Typical Mill Heat |
|---|---|---|---|
| Carbon (C) | (no min) | 0.030 | 0.020 |
| Manganese (Mn) | (no min) | 1.20 | 0.80 |
| Phosphorus (P) | (no min) | 0.035 | 0.025 |
| Sulfur (S) | (no min) | 0.020 | 0.001 |
| Silicon (Si) | (no min) | 0.80 | 0.40 |
| Chromium (Cr) | 24.0 | 26.0 | 25.0 |
| Nickel (Ni) | 6.0 | 8.0 | 7.0 |
| Molybdenum (Mo) | 3.0 | 5.0 | 3.8 |
| Nitrogen (N) | 0.24 | 0.32 | 0.28 |
| Copper (Cu) | No intentional addition (key distinguisher from S32760 and S32550) | ||
| Tungsten (W) | No intentional addition (key distinguisher from S32760) | ||
| PREN | 41 to 43 (Cr + 3.3 times Mo + 16 times N) | ||
UNS S32750 International Equivalents
UNS S32750 is dual-listed against multiple international designations. All names below refer to the same chemistry window.
| Region or Standard | Designation |
|---|---|
| USA (UNS) | S32750 |
| Europe (EN 10088-3) | 1.4410 / X2CrNiMoN25-7-4 |
| USA (ASTM forgings) | ASTM A182 F53 |
| USA (ASTM bar) | ASTM A479 UNS S32750 |
| USA (ASTM pipe) | ASTM A790 UNS S32750 |
| USA (ASTM fittings) | ASTM A815 WP-S32750 |
| Norway (NORSOK MDS) | NORSOK M-630 MDS D55, D57 |
| Sandvik trademark | SAF 2507 |
| Industeel ArcelorMittal trademark | UR 52N+ |
| Outokumpu trademark | Avesta 2507 |
UNS S32750 Mechanical Properties
Required mechanical properties per ASTM A479 in the solution-annealed condition. There is no aging or precipitation hardening step in the heat-treatment cycle.
| Property | Minimum | Typical | Test Standard |
|---|---|---|---|
| Yield strength (0.2 percent offset) | 550 MPa (80 ksi) | 620 to 720 MPa | ASTM A370 |
| Tensile strength | 795 MPa (115 ksi) | 800 to 1000 MPa | ASTM A370 |
| Elongation in 50 mm | 15 percent | 25 to 35 percent | ASTM A370 |
| Hardness (sour-service limit) | 28 HRC max | 25 to 28 HRC | ASTM E18 / NACE MR0175 |
| Charpy V-notch at minus 46 degrees Celsius | 45 J min | 60 to 100 J | NORSOK M-630, ASTM E23 |
| Critical pitting temperature (CPT) | 50 degrees Celsius | 55 to 70 degrees Celsius | ASTM G48 Method E |
| Critical crevice temperature (CCT) | 35 degrees Celsius | 40 to 50 degrees Celsius | ASTM G48 Method F |
| Ferrite content (base metal) | 35 to 55 percent | 45 to 50 percent | NORSOK M-630, ASTM E562 |
Detailed property data including elevated-temperature tensile, modulus of elasticity, thermal expansion, and density is on the dedicated Super Duplex 2507 Mechanical Properties page.
UNS S32750 Heat Treatment
Solution annealing at 1040 to 1100 degrees Celsius followed by rapid water quench. There is no precipitation hardening, no aging, and no temper. The water quench must drive the material through the 600 to 1000 degrees Celsius band rapidly to prevent sigma-phase formation, which would compromise both Charpy toughness and pitting resistance. Slow cooling (air cooling, oil quench) is not acceptable for super duplex 2507. Full guidance is on the heat treatment page; the sigma-phase mechanism is detailed on the sigma-phase embrittlement reference.
UNS S32750 Covered Standards
UNS S32750 appears in the following international standards. The link in each row points to the dedicated reference page on this site.
| Standard | Scope |
|---|---|
| ASTM A479 | Stainless steel bars and shapes for boiler and pressure vessel use |
| ASTM A789 | Seamless and welded ferritic / austenitic stainless tube |
| ASTM A790 | Seamless and welded ferritic / austenitic stainless pipe |
| ASTM A815 | Wrought ferritic, ferritic / austenitic, and martensitic stainless piping fittings (WP-S32750) |
| ASTM A182 F53 | Forgings, flanges, and forged fittings (NOT F55, F55 is S32760) |
| ASTM A276 | Stainless bar and shapes |
| EN 10088-3 | Semi-finished products, bars, rods, wire, sections (1.4410) |
| NORSOK M-630 | Material data sheet (Norwegian Continental Shelf) |
| NORSOK M-650 | Manufacturer qualification (QTR) |
| NACE MR0175 | Sour service compliance, hardness 28 HRC max |
| ISO 15156-3 | Petroleum and natural gas, materials in H2S environments |
| API 6A | Wellhead and christmas tree equipment (PSL 3 / 3G) |
| API 17D | Subsea wellhead and tree equipment |
UNS S32750 vs S32760, S32550, S31803
UNS S32750 is one of four duplex stainless steels TorqBolt commonly stocks. They are not interchangeable; project specifications routinely call out the alloy by its UNS number.
| UNS | Common Name | Cu | W | PREN | Forging Spec |
|---|---|---|---|---|---|
| S32750 | Super Duplex 2507 | None | None | 41 to 43 | ASTM A182 F53 |
| S32760 | Zeron 100 | 0.5 to 1.0 | 0.5 to 1.0 | 41 to 44 | ASTM A182 F55 |
| S32550 | Ferralium 255 | 1.5 to 2.5 | None | 38 to 42 | ASTM A182 F61 |
| S31803 / S32205 | Duplex 2205 | None | None | 34 to 38 | ASTM A182 F51 |
Dedicated comparisons: S32750 vs S32760, S32750 vs S32550, S32750 vs S31803.
UNS S32750 Product Forms
TorqBolt holds UNS S32750 stock at the Mumbai warehouse across the form and fastener range. Type 3.1 mill test certificates per EN 10204 are standard; Type 3.2 third-party-witnessed certificates are available on request.
- Round bar, bar stock, hex bar, flat bar, square bar, forged bar, hollow bar, cold finished bar
- Sheet, plate, tube, pipe, welded pipe, wire and welding wire
- Buttweld fittings, flanges, forgings
- Fasteners: bolts, hex bolts, heavy hex bolts, stud bolts, eye bolts, U-bolts, nuts, hex nuts, heavy hex nuts, lock nuts, washers, flat washers, lock washers, socket head cap screws, screws, threaded rod
UNS S32750 Frequently Asked Questions
What is UNS S32750?
UNS S32750 is the Unified Numbering System designation for super duplex stainless steel commonly known as 2507. The grade has nominal composition 25Cr-7Ni-3.5Mo-0.3N with no intentional copper or tungsten. PREN of 41 or higher qualifies it as super duplex per NORSOK M-630. The same chemistry is registered as EN 1.4410 / X2CrNiMoN25-7-4 in EN 10088-3.
What is the difference between S32750 and S32760?
S32750 (2507) and S32760 (Zeron 100) are both super duplex stainless steels with PREN above 40. The difference is composition: S32760 contains nominal 0.7 percent each of copper and tungsten; S32750 contains neither. The forging spec for S32750 is ASTM A182 F53; for S32760 it is ASTM A182 F55. Project specifications that call out one grade are not satisfied by the other.
Is UNS S32750 the same as 1.4410?
Yes. UNS S32750 (American Unified Numbering System) and Werkstoff 1.4410 / X2CrNiMoN25-7-4 (European EN 10088-3) refer to the same super duplex stainless steel chemistry within negligible tolerance. Mill certificates routinely cite both designations.
Which mills produce UNS S32750?
The principal producers are Sandvik (under the trademark SAF 2507), Industeel ArcelorMittal (UR 52N+), and Outokumpu (Avesta 2507). All three meet the same UNS S32750 chemistry and mechanical-property requirements. Customer specifications often name a specific mill trademark; TorqBolt sources from authorised distributors of all three.
What is the heat treatment for UNS S32750?
Solution annealing at 1040 to 1100 degrees Celsius followed by rapid water quench. There is no precipitation hardening, no aging, no temper. The water quench must cool the material rapidly through 600 to 1000 degrees Celsius to avoid sigma-phase formation. Slow cooling causes embrittlement and corrosion-resistance loss.
Is UNS S32750 acceptable for sour service?
Yes, qualified per NACE MR0175 / ISO 15156-3 with hardness restricted to 28 HRC maximum and ferrite content within 35 to 65 percent. Specific H2S partial pressure and chloride limits depend on the application zone classification under ISO 15156. TorqBolt supplies UNS S32750 fasteners and forgings with NACE compliance certification on request.
What ASTM standards cover UNS S32750?
ASTM A479 (bar and shapes), A789 (tube), A790 (pipe), A815 (fittings, designation WP-S32750), A276 (shapes), and A182 grade F53 (forgings, flanges, forged fittings).
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