Surface Treatments
Certifications
- ISO 9001:2015
- NORSOK M-650
- NACE MR0175
- ISO 15156-3
- PED 2014/68/EC
- EN 10204 type 3.2
- AD 2000 W2/W7/W10
Ferralium 255 (UNS S32550 / EN 1.4507), Cu-Bearing Super Duplex Stainless Steel
Ferralium 255 is a copper-bearing super duplex stainless steel (UNS S32550, EN 1.4507, X2CrNiMoCuN25-6-3) originally developed by Langley Alloys (UK). Nominal composition is 25 Cr – 5 Ni – 3 Mo – 2 Cu – 0.2 N; PREN ≥ 40; balanced austenite-ferrite microstructure (35–55% ferrite per NORSOK M-630); supplied solution-annealed (no precipitation hardening). Critical Pitting Temperature (CPT) ≥ 35 °C per ASTM G48 method A. The 2% copper distinguishes Ferralium 255 from other super duplex grades and gives improved resistance to reducing acids (HCl, H2SO4, brines). Used in seawater service, oil & gas downhole, subsea, desalination and chemical processing. Ferralium is a registered trademark of Langley Alloys.
Q: What is the chemical composition of Ferralium 255 (UNS S32550)?
Chemical Composition
| Element | Min % | Max % | Role |
|---|---|---|---|
| Carbon (C) | none | 0.04 | Cap to avoid carbide precipitation |
| Chromium (Cr) | 24.0 | 27.0 | Pitting resistance, ferrite stabiliser |
| Nickel (Ni) | 4.5 | 6.5 | Austenite stabiliser |
| Molybdenum (Mo) | 2.9 | 3.9 | Pitting / crevice corrosion (PREN x3.3) |
| Copper (Cu) | 1.5 | 2.5 | Reducing-acid resistance (Ferralium signature) |
| Nitrogen (N) | 0.10 | 0.25 | Austenite stabiliser, strength, PREN x16 |
| Manganese (Mn) | none | 1.5 | Deoxidiser |
| Silicon (Si) | none | 1.0 | Deoxidiser |
| Phosphorus (P) | none | 0.04 | Impurity |
| Sulphur (S) | none | 0.03 | Impurity (lowered for sour service) |
Q: What are the mechanical properties of Ferralium 255?
Mechanical Properties
| Property | Minimum | Test standard |
|---|---|---|
| 0.2% Yield strength (Rp0.2) | 550 MPa (80 ksi) | ASTM E8 |
| Ultimate tensile strength (Rm) | 760 MPa (110 ksi) | ASTM E8 |
| Elongation (A5) | 15% | ASTM E8 |
| Hardness | ≤ 32 HRC (NACE MR0175 limit) | ASTM E18 |
| Charpy V-notch at −46 °C | ≥ 45 J (NORSOK M-630) | ASTM E23 / ISO 148-1 |
| Density | 7.81 g/cm³ | none |
Q: How is Ferralium 255 heat-treated?
Heat Treatment, Solution Annealing Only
Ferralium 255 is supplied solution-annealed at 1100 °C followed by water quench, rapid cooling is essential to retain ferrite within the 35–55% range and to avoid sigma-phase, chi-phase, and Cr2N nitride precipitation in the 600–1000 °C range. Unlike precipitation-hardening alloys, super duplex grades do NOT undergo aging; cold work is also avoided as it can push hardness above the NACE MR0175 32 HRC limit and disturb the ferrite-austenite phase balance.
Q: Can Ferralium 255 be welded, and which filler metals are used?
Welding
Ferralium 255 can be welded by GTAW, GMAW, SMAW and SAW. Matching filler metal is typically 25.10.4.L (E/ER 2553 / 2594 type) which adds extra Ni for proper austenite reformation in the weld metal. Pre-heat is not required; interpass temperature limited to 150 °C; no post-weld heat treatment for thin sections. Heat input controlled to 0.5–2.5 kJ/mm to maintain the weld zone ferrite content within 35–65% per NORSOK M-630.
Q: Which ASTM, EN, NORSOK, and NACE standards cover Ferralium 255?
Spec Compliance, ASTM, EN, NORSOK, NACE
- ASTM A479, bar, billet, shapes (UNS S32550)
- ASTM A789, seamless / welded tube
- ASTM A790, seamless / welded pipe
- ASTM A815, wrought fittings
- ASTM A182, forged flanges, fittings, valves
- ASTM A276, bars and shapes (alternative)
- EN 10088-3 / EN 10222-5 / EN 10272 (1.4507)
- NORSOK M-650, manufacturer Qualification Test Records (QTR), MDS D55
- NACE MR0175 / ISO 15156-3, sour-service compliance
Q: How does Ferralium 255 compare to other super duplex and adjacent grades?
Compare to Other Super Duplex & Adjacent Grades
- Ferralium 255 vs Zeron 100, Cu-bearing vs W-bearing super duplex
- Ferralium 255 vs Super Duplex 2507, Cu vs no-Cu
- Ferralium 255 vs Duplex 2205, super duplex vs standard duplex upgrade
- Ferralium 255 vs Inconel 625, super duplex vs nickel alloy
Need Ferralium 255 (UNS S32550) super duplex stainless steel? Email info@torqbolt.com or WhatsApp +91-22-66157017 with form, dimensions, quantity, ASTM/EN spec, MTC level (3.1 / 3.2). NACE MR0175 sour-service stamp on every heat. NORSOK M-650 QTR on request. Per-heat EN 10204 type 3.2 MTC included with every consignment.
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