What is Monel 400
Monel 400 is an binary alloy of Copper (Cu) + Nickel (Ni) having UNS Number- N04400. It is also called 67Ni–30Cu alloy. Monel ASME Section IX P Number is 42 for welding & P No. 110 for Brazing. Monel being a primary Nickel base has austenitic microstructure and hence is a non-hardenable alloy by heat treatment. The properties such as hardness can only be enhanced by cold working. Monel 400 has high strength at room temperature as well as subzero temperature due to its solid solution structure & high toughness because of Nickel in many corrosion applicable where it offer very high corrosion resistance also. The application of Monel 400 are found in shipbuilding, oil & gas, crude oil refining & marine environment. Monel 400 loss its magnetization at 70-120°F (21-50°C) which is its curie temperature.
Monel 400 equivalent material
W. Nr 2.4360, AMS 4730, BS-3072NA13
Monel 400 chemical and mechanical properties
Density of Monel is 8.8 g/cm3. Monel 400 has a minimum tensile strength of 70 Ksi or 485 N/mm2 and Yield strength in the range of 25-50 ksi (172-345 N/mm2). The chemical properties of Monel 400 are given in below table.
welding Monel 400 to carbon steel
Stick or SMAW Welding of Monel 400 to Carbon steel or mild steel shall be carried out with ENiCu-7 (AWS SFA No. 5.11) or with ENi-1 (AWS SFA No. 5.11). The dissimilar welding of Monel 400 to carbon steel is readily weldable. No special baking or conditioning of welding electrodes are required. TIG or MIG welding of Monel 400 to carbon steel is welded using ERNiCu-7 or ERNi-1 (AWS SFA 5.15). ENi-1 is a nickel base electrode having 95% Ni and 2.5% Titanium and mainly used for welding pure nickel and welding of carbon steel to Nickel alloys.
The composition of ENiCu-7 are 66% Nickel, 30% Copper, 3% Mn, and 1% Iron (Fe) so basically a similar metallurgy to Monel 400 alloy.
welding Monel 400 to stainless steel
Stick or SMAW Welding of Monel 400 to stainless steel SS304 or any other 300 series stainless steel is welded using ENi-1 or ENiCrFe-2 or -3 (As per AWS SFA/A 5.11). Welding of Monel 400 to SS410, 430 or other 400 series stainless steel is carried out using ENiCu-7 electrode (AWS SFA/A 5.11). TIG or MIG Welding of Monel 400 to Monel to stainless steel SS304 or any other 300 series stainless steel is welded using ERNi-1 or ERNiCrFe-6 or ERNiCr-3 (As per AWS SFA/A 5.14). The TIG welding electrode equivalent of ENiCrFe-3 is ERNiCr-3 & equivalent of ENiCrFe-2 is ERNiCrFe-6.
Welding Monel 400 to 90-10 Cu-Ni & 70-30 Cu-Ni
Stick or SMAW Welding of Monel 400 to Cupronickel such as 90-10 Cu-Ni & 70-30 Cu-Ni is carried out using ENiCu-7 (AWS SFA No. 5.11).
Welding Monel 400 to Hastelloy
Welding of Monel 400 to Hastelloy is not advised as presence of copper in Hastelloy will increase chances of hot cracking. If still welding of Monel 400 to Hastelloy C22 or C276 is required, use ENi-1 or ERNi-1 welding electrode/ filler wire.
Welding Procedure for Monel 400
- Clean the parts to be joined.
- Weld using ENiCu-7 or ERNiCu-7 electrode/ Filler wire.
- Keep the heat input on lower side.
- Avoid the arc strikes on the base materials.
- Take precaution of using right welding condition and good quality shielding gases to avoid any porosity issues.
Stick/ SMAW Welding of Monel 400
Stick or SMAW Welding of Monel 400 to Monel 400 is carried out using ENiCu-7 (AWS SFA No. 5.11). ENiCu-7 is also known as Monel welding electrode 190 (Brand name of Special Metals). ENiCu-7 provides a weld deposit of similar metallurgy and give welding without any difficulties.
Tig & MIG Welding of Monel 400
Gas Tungsten arc welding (GTAW) cum TIG or Metal Inert Gas cum MIG Welding of Monel 400 to Monel 400 shall be carried out with ERNiCu-7 (AWS SFA No. 5.15). The composition of ENiCu-7 are 66% Nickel, 30% Copper, 3% Mn, and 1% Iron (Fe) so basically a similar metallurgy to Monel 400 alloy. Pure argon is used for shielding and gas backing/ purging work. The weld deposit are clean, and should be deposited with lower heat input to avoid any distortion issues.
Preheat, Interpass & PWHT of Monel 400
Being a Face Centered Cubic Microstructure having an austenitic phase, Monel 400 does not require any preheating. Interpass temperature for Monel 400 welding shall be kept maximum 300 °F (150 °C). throughout the welding operation. Post weld heat treatment (PWHT) is not required for Monel 400.
welding electrode for Monel 400
Stick welding or shielded metal arc welding (SMAW) of Monel 400 is carried out using ENiCu-7 rod. No special conditioning is required for the stick welding rods. Clean slag properly after each run to avoid any issue of slag entrapment which could otherwise reduce the material corrosion resistance. ENiCu-7 has good weldability.
Monel 400 vs Inconel 625
Monel 400 to Inconel 625 is also a combination not used in industries as both are alloy of different purposes. If you still need to join Monel 400 to Inconel 625, use ERNiCrFe-6 or ERNiCr-3 (As per AWS SFA/A 5.14). Use pure argon for shielding and purging.