Super Duplex Stainless Steel
Super Duplex 2507 Buttweld Pipe Fittings
High-alloy ferritic-austenitic stainless steel (UNS S32750, EN 1.4410) — elbows, tees, reducers and caps to ASME B16.9 / ASTM A815, 1/2" to 24" NB. PREN ~42 for seawater, subsea and aggressive chloride service. EN 10204 3.1 / 3.2 traceable.
Grade Overview
Super Duplex 2507 (UNS S32750, EN 1.4410) is a high-alloy ferritic-austenitic stainless steel developed for the most demanding chloride environments. With roughly 25% chromium, 7% nickel, 4% molybdenum and 0.28% nitrogen, it reaches a PREN of about 42 — enough to resist warm seawater and acid chlorides that defeat 2205 duplex and 6-Moly austenitic grades. It combines this with very high strength, allowing thinner walls and lighter piping.
Buttweld fittings in 2507 are covered by ASTM A815 (WP-S32750) to ASME B16.9 dimensions. After hot forming, fittings are solution annealed and water quenched to restore phase balance and dissolve intermetallics. Supplied with EN 10204 3.1 or 3.2 certification and PREN reporting on request.
Chemical Composition — S32750 / 1.4410
| Element | Requirement | Note |
|---|---|---|
| Chromium (Cr) | 24.0 – 26.0% | Pitting & oxidation resistance |
| Nickel (Ni) | 6.0 – 8.0% | Austenite stabiliser |
| Molybdenum (Mo) | 3.0 – 5.0% | Pitting resistance |
| Nitrogen (N) | 0.24 – 0.32% | Strength, austenite & pitting |
| Carbon (C) | ≤ 0.030% | Low-carbon, sensitization control |
| Manganese (Mn) | ≤ 1.20% | — |
PREN = %Cr + 3.3 × %Mo + 16 × %N ≈ 42, giving very high resistance to chloride pitting and crevice corrosion.
Mechanical Properties — Super Duplex 2507
| Property | Requirement |
|---|---|
| Tensile Strength (min) | 800 MPa (116 ksi) |
| Yield Strength (min) | 550 MPa (80 ksi) |
| Elongation (min) | ≥ 15% |
| Hardness (max) | ≤ 32 HRC / 310 HBW |
| Heat Treatment | Solution annealed ~1050–1100°C + water quench |
Equivalent Grades
| Product Form | Specification |
|---|---|
| Buttweld fittings | ASTM A815 WP-S32750 |
| EN designation | EN 1.4410 (X2CrNiMoN25-7-4) |
| Seamless pipe | ASTM A790 / A928 UNS S32750 |
| Forgings / flanges | ASTM A182 F53 |
Fitting Types Available in Super Duplex 2507
- Elbows — 45° / 90° / 180°, LR & SR (B16.9 / B16.28)
- Tees — equal & reducing (B16.9)
- Reducers — concentric & eccentric
- Caps — buttweld end closures
- Stub Ends — Type A & B for lap joints
- Laterals & Crosses — branch connections