Specifications
Surface Treatments
Certifications
- ISO 9001 - 2015 Certified
- PED 2014/68/EC
- NACE MR0175/ISO 15156-2
- NORSOK M-650
- DFAR
- MERKBLATT AD 2000 W2/W7/W10
Monel 400 Welding - Filler Metals, Procedures and Dissimilar Joints
Monel 400 welding (also Monel 400 weldability, UNS N04400 welding, nickel-copper alloy welding, Alloy 400 welding) is well established. Monel 400 welds readily by GTAW, GMAW and SMAW with matching nickel-copper consumables ENiCu-7 (covered electrode, AWS A5.11) and ERNiCu-7 (bare wire, AWS A5.14). The alloy is single-phase FCC with no chromium and no precipitation-hardening additions; it does not form embrittling phases on cooling and does not require post-weld heat treatment up to 38 mm. Chemistry is constant per ASTM B127, B164, B165, B564 and F468. Monel® is a registered trademark of Special Metals Corporation; TorqBolt is not authorized by, affiliated with or endorsed by Special Metals.
Recommended Filler Metals
ENiCu-7 deposit chemistry is nominally 65 percent nickel, 30 percent copper, with titanium 1.5 to 3.0 percent for deoxidation. ERNiCu-7 bare wire holds the same nickel-copper window for GTAW and GMAW. For dissimilar joints to stainless or nickel-base alloys, switch to ERNiCrMo-3 (Inconel 625 filler).
| Joint | Process | Filler | AWS Spec |
|---|---|---|---|
| Monel 400 to Monel 400 | SMAW | ENiCu-7 | AWS A5.11 |
| Monel 400 to Monel 400 | GTAW, GMAW, SAW | ERNiCu-7 | AWS A5.14 |
| Monel 400 to carbon steel | GTAW, GMAW | ERNiCu-7 or ERNiCrMo-3 | AWS A5.14 |
| Monel 400 to SS 304 / 316 / 316L | GTAW, GMAW | ERNiCrMo-3 (Inconel 625) | AWS A5.14 |
| Monel 400 to Inconel 600 / 625 | GTAW, GMAW | ERNiCrMo-3 | AWS A5.14 |
| Monel 400 to Monel K-500 | GTAW | ERNiCu-7 | AWS A5.14 |
Welding Processes
GTAW (TIG) is the preferred process for thin sections, pipe root passes and high-quality work. GMAW (MIG) handles production fillets and plate above 6 mm. SMAW covers field repair and out-of-position work. Interpass temperature is held below 150 degrees Celsius in every process to limit hot cracking in the nickel-copper deposit.
| Process | Polarity | Shielding | Wire / Electrode | Heat Input |
|---|---|---|---|---|
| GTAW | DCEN | Argon, 12 to 15 L/min | ERNiCu-7, 1.6 or 2.4 mm | 0.8 to 1.5 kJ/mm |
| GMAW | DCEP | Argon + 25% He, or pulsed Ar | ERNiCu-7, 1.0 or 1.2 mm | 1.5 to 2.5 kJ/mm |
| SMAW | DCEP | Electrode coating | ENiCu-7, 2.5 to 4.0 mm | 1.0 to 2.0 kJ/mm |
| SAW | DCEP | Nickel-copper flux | ERNiCu-7, 2.4 or 3.2 mm | 2.0 to 3.5 kJ/mm |
GTAW uses 2 percent thoriated tungsten with stringer beads. SMAW electrodes are stored baked at 120 degrees Celsius to avoid porosity.
Joint Preparation and Cleaning
Surface cleanliness controls weld quality more than any other variable. Monel 400 is sensitive to sulphur, lead, phosphorus, zinc and chloride contamination in the HAZ, all of which cause hot cracking or stress corrosion cracking. Bevel by machining or grinding (not flame cutting) with carbide tooling, then degrease with acetone or isopropyl alcohol. Never use chlorinated solvents (trichloroethylene, perchloroethylene) within the HAZ; arc decomposition releases hydrogen chloride and induces stress corrosion cracking. Remove soapstone, sulphur-bearing crayons and paint markers within 50 mm of the joint. Joint geometry is a 60 to 75 degree V-groove with 1.5 mm root face for plate, or a J-bevel for thick sections, root gap 1.5 to 2.5 mm. Argon-purge inside pipe and tube until the third pass is complete. Pre-heat is not required below 25 mm.
Dissimilar Metal Joints
For Monel 400 to carbon steel, ERNiCu-7 is the conservative choice with ERNiCu-7 buttering on the carbon-steel side; PWHT on the carbon-steel side follows ASME IX. For Monel 400 to austenitic stainless (SS 304, 316, 316L), ERNiCrMo-3 (Inconel 625 filler) per AWS A5.14 is the standard consumable. For Monel 400 to Inconel 600 or 625, ERNiCrMo-3 deposits a matching nickel-chromium-molybdenum chemistry on both sides. For Monel 400 to copper-nickel (90/10, 70/30), ERNiCu-7 with preheat on the copper-nickel side. Welds on Monel K-500 with ERNiCu-7 must be followed by full age-hardening to restore strength in the HAZ.
Post-Weld Considerations
Monel 400 does not require PWHT up to 38 mm wall thickness. The as-welded joint develops the parent strength of annealed Monel 400. Stress relief at 540 to 595 degrees Celsius for one hour per 25 mm, air cool, is applied only to thick sections destined for service in dilute hydrofluoric acid, caustic above 50 percent at elevated temperature, or chloride environments where residual weld stress can drive stress corrosion cracking. Inspection follows ASME V: dye-penetrant on root and cap, radiography on butt welds, with acceptance to ASME VIII or the project code.
Frequently Asked Questions
Can Monel 400 be welded? Yes. By GTAW, GMAW and SMAW with matching ENiCu-7 (AWS A5.11) and ERNiCu-7 (AWS A5.14) consumables.
What filler is used? ENiCu-7 for SMAW, ERNiCu-7 for GTAW and GMAW. For dissimilar Monel 400 to stainless joints, ERNiCrMo-3 (Inconel 625 filler).
Does Monel 400 need PWHT? No up to 38 mm. Stress relief at 540 to 595 degrees Celsius is reserved for thick sections in chloride or HF service.
Can Monel 400 be welded to stainless steel? Yes with ERNiCrMo-3 per AWS A5.14, GTAW with argon shielding. The Monel side requires no PWHT.
Request a Quote
For Monel 400 welding consumables or UNS N04400 fasteners against a project WPS, send drawing, quantity, thickness and certification class (EN 10204 type 3.1 or 3.2) to info@torqbolt.com or WhatsApp +91-22-66157017. Ex-Mumbai price plus heat-numbered MTC inside one working day. References: chemistry, mechanical properties, bolts, seamless pipe; AWS A5.11, AWS A5.14, ASME IX, ASTM B127 / B164 / B564 / F468.
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