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.
Where Super Duplex 2507 Is Used
- ✓ Offshore seawater, firewater and injection systems
- ✓ Desalination brine and high-chloride process lines
- ✓ Service beyond the limits of duplex 2205
Super Duplex 2507 Compared With Related Grades
| Grade | PREN | Key difference |
|---|---|---|
| A403 WP316L | about 24 | Not suitable for warm seawater |
| A815 S32205 | about 35 | Lower cost; for moderate chloride service |
| A815 S32750 | about 42 | Highest pitting resistance and strength of the duplex family |
How to Specify Super Duplex 2507 Fittings on a Purchase Order
A complete order line avoids clarification rounds. Example:
Elbow 90° LR, 6" SCH 40S, ASTM A815 WPS32750, ASME B16.9, EN 10204 3.2
- ✓ Ask for ferrite content and an intermetallic phase test (ASTM A923)
- ✓ Ask for PMI on every piece
- ✓ State the inspection agency for 3.2 certificates
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 |
EN 10253 equivalent: see SUPER DUPLEX-2507 pipe fittings on arshyapipefittings.com, and the European grade EN 1.4410 (X2CrNiMoN25-7-4).
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
Related grades: Duplex 2205 · 316L · Laterals · IBR grades list
Testing & Inspection — Super Duplex 2507
- Chemical analysis of each heat, with PREN calculated from Cr, Mo and N (typically ≈ 42).
- Ferrite content measurement to confirm phase balance after solution annealing.
- ASTM A923 testing for harmful intermetallic phases available on request.
- Tensile and hardness tests (800 MPa min. tensile, 550 MPa min. yield, ≤310 HBW); Charpy impact tests on request.
- PMI, dimensional and visual inspection to ASME B16.9 / ASTM A815; NDE as specified.
Dimensions & Size Range — ASME B16.9
Super Duplex 2507 fittings are made to ASME B16.9 dimensions under ASTM A815, from 1/2" to 24" NB, in schedules SCH 10 to SCH 80 / XXS. Wall thickness matches the connecting pipe schedule. Centre-to-end dimensions for the most-ordered sizes:
| NPS | Outside diameter (mm) | 90° LR elbow “A” (mm) | 45° LR elbow “B” (mm) | Equal tee “C” (mm) |
|---|---|---|---|---|
| 1/2" | 21.3 | 38 | 16 | 25 |
| 1" | 33.4 | 38 | 22 | 38 |
| 2" | 60.3 | 76 | 35 | 64 |
| 3" | 88.9 | 114 | 51 | 86 |
| 4" | 114.3 | 152 | 64 | 105 |
| 6" | 168.3 | 229 | 95 | 143 |
| 8" | 219.1 | 305 | 127 | 178 |
| 10" | 273.1 | 381 | 159 | 216 |
| 12" | 323.9 | 457 | 190 | 254 |
| 16" | 406.4 | 610 | 254 | 305 |
| 20" | 508.0 | 762 | 318 | 381 |
| 24" | 610.0 | 914 | 381 | 432 |
Long-radius elbows have a centre-line radius of 1.5 × NPS; short-radius (ASME B16.28) 1.0 × NPS. Full tables to NPS 48, reducing tees, reducers and caps are available with every quotation. For EN 10253 dimensions see arshyapipefittings.com.
Export Documentation & Packing
We ship Super Duplex 2507 fittings to projects outside India with the documents EPC contractors and inspection agencies expect:
- Mill test certificate — EN 10204 3.1 as standard; 3.2 with third-party witness
- Third-party inspection — Bureau Veritas, TÜV, Lloyd’s Register, SGS, DNV or the client’s own inspector
- Traceability — every fitting marked with grade, size, schedule and heat number, matching the certificate
- Packing — seaworthy wooden cases or pallets, bevel ends protected with end caps
- Shipping documents — commercial invoice, packing list and certificate of origin; FOB, CFR or CIF terms
Send your BOQ through the RFQ form (Excel or PDF attachments accepted) or on WhatsApp — quotations are usually issued within 24 hours.
Super Duplex 2507 Fittings — Frequently Asked Questions
Super Duplex 2507 or Duplex 2205?
2507 has higher chromium, molybdenum and nitrogen (PREN ≈ 42 vs ≈ 35) and higher strength (550 vs 450 MPa yield). Choose it for seawater and high-chloride service where 2205 is marginal; 2205 is more economical elsewhere.
Is 2507 suitable for seawater systems?
Yes — it is widely used for offshore firewater, seawater cooling and injection lines. See 2507 for offshore seawater.
What matters when welding 2507 fittings?
Controlled heat input and suitable over-alloyed filler, to keep the ferrite balance right and avoid intermetallic phases. More: duplex welding and ferrite control.