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
Super Duplex Stainless Steel Grades, S32750, S32760, S32550, S39274
The super duplex stainless steel grade family covers four UNS designations in routine commercial trade: S32750 (2507), S32760 (Zeron 100), S32550 (Ferralium 255), and S39274 (DP3W). All four sit at PREN 38 or higher and qualify as super duplex per NORSOK M-630. They are not interchangeable. The forging spec, the chemistry window, and the project specifications differ for each.
The most heavily traded grade worldwide is 2507 (UNS S32750 / EN 1.4410), which is the focus of TorqBolt's super duplex inventory. Zeron 100 and Ferralium 255 are project-specified alternatives in particular service environments. DP3W (UNS S39274) trades in lower volumes for specific subsea and chemical applications.
Grade Comparison
All four super duplex grades share the broad chromium, nickel, molybdenum and nitrogen window. Differences sit in copper, tungsten, and minor adjustments to other elements.
| UNS | Common Name | EN / Werkstoff | Cr | Mo | N | Cu | W | PREN | Forging Spec |
|---|---|---|---|---|---|---|---|---|---|
| S32750 | 2507 | 1.4410 | 24.0 to 26.0 | 3.0 to 5.0 | 0.24 to 0.32 | 0.50 max (residual) | (none) | 41 to 43 | ASTM A182 F53 |
| S32760 | Zeron 100 | 1.4501 | 24.0 to 26.0 | 3.0 to 4.0 | 0.20 to 0.30 | 0.50 to 1.00 | 0.50 to 1.00 | 41 to 44 | ASTM A182 F55 |
| S32550 | Ferralium 255 | 1.4507 | 24.0 to 27.0 | 2.9 to 3.9 | 0.10 to 0.25 | 1.50 to 2.50 | (none) | 38 to 42 | ASTM A182 F61 |
| S39274 | DP3W | (no EN) | 24.0 to 26.0 | 2.5 to 3.5 | 0.24 to 0.32 | 0.20 to 0.80 | 1.50 to 2.50 | 40 to 43 | ASTM A182 F54 |
UNS S32750 (2507)
UNS S32750 is the most heavily traded super duplex grade. Nominal composition is 25Cr-7Ni-3.5Mo-0.3N with no intentional copper and no intentional tungsten. PREN 41 to 43. The same chemistry is registered as EN 1.4410 / X2CrNiMoN25-7-4 in EN 10088-3. Mill trademarks include SAF 2507 (Sandvik), UR 52N+ (Industeel ArcelorMittal) and Avesta 2507 (Outokumpu). Forging spec is ASTM A182 F53. Full detail is on the UNS S32750 reference page.
UNS S32760 (Zeron 100)
UNS S32760 is the copper- and tungsten-bearing super duplex grade developed originally by Rolled Alloys under the Zeron 100 trademark. Composition adds 0.5 to 1.0 percent each of copper and tungsten to the base 25Cr-7Ni-3.5Mo-0.3N chemistry. PREN 41 to 44 (PREW slightly higher with the tungsten contribution). The EN designation is 1.4501. Forging spec is ASTM A182 F55. Zeron 100 is project-specified by name in many UK North Sea and oil major specifications, particularly for seawater pumps and subsea wellhead equipment. The grade is not a drop-in substitute for S32750, and S32750 is not a drop-in substitute for S32760.
UNS S32550 (Ferralium 255)
UNS S32550 is the high-copper super duplex grade developed originally by Langley Alloys under the Ferralium 255 trademark. Composition adds 1.5 to 2.5 percent copper to the base duplex chemistry, with no tungsten. PREN 38 to 42 places it just inside the super duplex window. The EN designation is 1.4507. Forging spec is ASTM A182 F61. The 1.5 to 2.5 percent copper improves resistance in dilute sulfuric acid and other reducing acid media, making it the preferred grade for seawater pumps and propeller shafts where dilute acid attack is a concern.
UNS S39274 (DP3W)
UNS S39274 is the tungsten-bearing super duplex grade originally developed by Sumitomo (now Nippon Steel) under the DP3W designation. Composition includes 1.5 to 2.5 percent tungsten with low to moderate copper. PREN 40 to 43. Forging spec is ASTM A182 F54. DP3W is project-specified for subsea control lines and chemical injection tubing, and is occasionally substituted for Zeron 100 in oil and gas tubing service.
Mechanical Properties Across the Grades
Required minimum properties per ASTM A479 in the solution-annealed condition. The four super duplex grades carry similar minimum yield strength but differ in elongation and detailed corrosion behaviour.
| Grade | Yield (MPa min) | Tensile (MPa min) | Elongation (%) | Hardness (HRC max) |
|---|---|---|---|---|
| 2507 (S32750) | 550 | 795 | 15 | 32 |
| Zeron 100 (S32760) | 550 | 750 | 25 | 32 |
| Ferralium 255 (S32550) | 550 | 760 | 15 | 32 |
| DP3W (S39274) | 550 | 800 | 15 | 32 |
Standards and Forging Specs
Each super duplex grade carries its own forging spec under ASTM A182. Project specifications and customer drawings cite the F-grade by number, and that determines which UNS chemistry must be supplied.
| Grade | ASTM A182 Forging Grade | EN Werkstoff | NORSOK MDS |
|---|---|---|---|
| 2507 (S32750) | F53 | 1.4410 | D55, D57 |
| Zeron 100 (S32760) | F55 | 1.4501 | D55, D57 |
| Ferralium 255 (S32550) | F61 | 1.4507 | (not standard) |
| DP3W (S39274) | F54 | (no EN) | (not standard) |
Product Forms
TorqBolt holds 2507 (UNS S32750) stock at the Mumbai warehouse across the form and fastener range. Zeron 100, Ferralium 255 and DP3W are stocked to project requirement. Type 3.1 mill test certificates per EN 10204 are standard; Type 3.2 third-party-witnessed certificates are available on request.
Super Duplex Grades Frequently Asked Questions
Which super duplex grade is most common?
UNS S32750 (2507) is the most heavily traded super duplex grade worldwide. The same chemistry is registered as EN 1.4410 / X2CrNiMoN25-7-4 in EN 10088-3. Mill trademarks include SAF 2507 (Sandvik), UR 52N+ (Industeel ArcelorMittal) and Avesta 2507 (Outokumpu).
What is the difference between S32750 and S32760?
Both are super duplex grades with PREN above 40. S32760 (Zeron 100) contains 0.5 to 1.0 percent each of copper and tungsten. S32750 (2507) contains neither. The forging spec for S32750 is ASTM A182 F53; for S32760 it is ASTM A182 F55. Project specifications that name one grade are not satisfied by the other.
What is the difference between S32750 and S32550?
S32750 (2507) has nominal 25Cr-7Ni-3.5Mo-0.3N with no intentional copper. S32550 (Ferralium 255) has nominal 25Cr-5Ni-3.3Mo-0.18N with 1.5 to 2.5 percent copper. Ferralium 255 is preferred for dilute sulfuric acid service; 2507 is preferred for seawater and chloride pitting service. Forging specs are ASTM A182 F53 (2507) and F61 (Ferralium 255).
What is DP3W?
DP3W (UNS S39274) is the tungsten-bearing super duplex grade originally developed by Sumitomo. Composition includes 1.5 to 2.5 percent tungsten with low to moderate copper. PREN 40 to 43. Forging spec is ASTM A182 F54. DP3W is used for subsea control lines and chemical injection tubing.
Which super duplex grade should I specify for seawater service?
For seawater piping, manifolds, pumps, valves and fasteners, 2507 (UNS S32750) is the default super duplex grade. Zeron 100 (UNS S32760) is preferred for seawater pumps and impellers in some UK North Sea and oil major specifications. Ferralium 255 (UNS S32550) is preferred where dilute sulfuric acid contamination is expected.
Which super duplex grades are covered by NORSOK M-630?
NORSOK M-630 material data sheets D55 and D57 cover both S32750 (2507) and S32760 (Zeron 100). Ferralium 255 and DP3W are not standard NORSOK MDS grades but may be specified by project addenda. Manufacturer qualification under NORSOK M-650 (QTR) is required for any super duplex grade supplied to Norwegian Continental Shelf projects.
Are all super duplex grades acceptable for sour service?
All four common super duplex grades qualify per NACE MR0175 / ISO 15156-3 in the solution-annealed condition 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.
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