Matching 25.10.4.L super duplex consumables for GTAW, GMAW, SMAW, FCAW, and SAW joining of UNS S32550
Super duplex weld metal solidifies almost entirely as ferrite, then transforms partially to austenite during solid-state cooling. The fast cooling rate of a typical fusion weld leaves too much ferrite (and too little austenite) if the consumable matches the parent composition exactly. The standard fix is an over-alloyed filler: super duplex consumables carry roughly 2 to 3 percentage points more nickel than the parent metal to push the as-deposited microstructure back into the 35 to 65% ferrite acceptance band of NORSOK M-630. The 25.10.4.L family (25Cr, 10Ni, 4Mo, low C) covers Ferralium 255 and 2507 parent metal in matching service. AWS A5.4 (SMAW), A5.9 (bare wire for GTAW / GMAW / SAW), and A5.22 (flux-cored) classify the consumables.
| Process | AWS classification | Trade name examples | Use |
|---|---|---|---|
| GTAW (TIG) bare wire | AWS A5.9 ER2594 | Sandvik 25.10.4.L, Avesta 2507/P100, Metrode 25Cr-10Ni-4Mo | Root pass and thin-section all-position, gas Ar + 2% N2 |
| GMAW (MIG) solid wire | AWS A5.9 ER2594 | Same as GTAW wire | Fill and cap, spray transfer, gas Ar + 30% He + 2% N2 |
| SMAW (stick) electrode | AWS A5.4 E2594-15 or -16 | Sandvik 25.10.4.L, Avesta 2507/P100 | Field repair, position welding, basic-coated -15 for impact-critical |
| FCAW (flux-cored) wire | AWS A5.22 E2594-T1 | Sandvik 25.10.4.L FCW, Lincoln Cor-A-Rosta P10 | Production fill and cap, position-capable |
| SAW (submerged-arc) wire + flux | AWS A5.9 ER2594 + matched flux | Sandvik 25.10.4.L + 15W neutral basic flux | Heavy-section thick-wall fill, flat position only |
Per NORSOK M-630 the welded joint must satisfy: (a) chemistry per AWS classification with PREN ≥ 40, (b) ferrite content 35 to 65% per ASTM E562 on the weld metal cross-section, (c) hardness ≤ 32 HRC for NACE MR0175 sour service, (d) Charpy V-notch ≥ 45 J at -46 °C in the weld metal centreline (transverse) and ≥ 35 J in the HAZ, (e) corrosion test per ASTM G48 method A at 35 °C for 24 hours with mass loss ≤ 4 mg/cm² and no localised pitting. The weld procedure qualification (PQR) per ASME IX with NORSOK M-630 supplementary documents these on the qualifying coupon, and the production WPS controls heat input, interpass temperature, and shielding gas to stay within the qualified envelope.
