Detailed explanation of Monel 400 (Monel400, N04400) material knowledge
Monel 400 material
Nickel alloy, also known as Monel alloy, Monel 400 alloy contains C-0.11%, Mn-0.99%, Si-0.16%, Cu-32.26%, Ni-65.02%, AI-0.04%, Iron-1.42%, S≤0.001%, P≤0.05%. Monel400 is a high-strength single-phase solid solution. It is a corrosion-resistant alloy with the largest dosage and the most widely used. It has excellent comprehensive properties. The alloy is in hydrofluoric acid and fluorine gas media. It has excellent corrosion resistance and also has excellent corrosion resistance to hot concentrated alkali liquid.
Selection of welding wire and electrode types
According to the comparison in Table 1, ERNiCu-7 welding wire, ENiCu-7 welding rod and Monel400 base metal are chemically formed components and are the best matching welding materials, while nickel FM61 (Nier-1) is the chemical composition of pure nickel welding wire. Typical values and guaranteed values are C (0.08%≤0.15%), manganese (0.43%≤1.0%), iron (0.5%≤1.0%), Si (0.3%≤0.75%), P(0.05). 002% ≤ 0.03%), S (0. 003% ≤ 0.015%), Ni (96. 0% ≥ 930%), copper (0. 11% ≤ 0.25%), aluminum (0. 9% ≤ 1.5%) , Ti(2.0%≤3.0%). Neil No. 1 is mainly used for welding nickel 200, 201 alloy, Monel alloy, copper-nickel alloy and carbon steel. Then compare it with the chemical composition of Monel400 alloy.
Choice of welding method
Monel 400 alloy can be welded through a variety of welding methods, such as SMAW (stick arc welding), GTAW (tungsten arc welding), GMAW (metal arc welding), SAW (submerged arc welding). The welding methods used are as follows: GTAW advantage:
1) Argon gas can effectively isolate the surrounding air; it itself is insoluble in metal and is disharmonious. Metal reaction, during the tungsten arc welding process, the arc also has the function of automatically cleaning the oxide film on the surface of the workpiece, because non-ferrous metals, stainless steel and various chemically active alloys can be successfully welded;
2) Tungsten argon arc welding under small power flow conditions is suitable for welding thin plates and ultra-thin plates;
3) The heat source and filler wire can be controlled independently, so the heat input is easy to adjust, and welding in various positions can be performed, and single-sided welding is also achieved. Ideal method for welding double-sided forming.
Disadvantages: 1) Deep melting, slow melting speed, and low productivity; 2) Tungsten electrode has poor current carrying capacity. Excessive current will cause the tungsten electrode to melt and evaporate, and its particles may enter the molten pool, causing pollution; 3) Inert gases (argon and helium) are expensive and different from other arc welding methods (manual arc welding, submerged arc welding, Compared with CO2 gas shielded welding, etc.), the production cost is higher.
Welding groove
The welding DC used for welding grooves is (a) first layer: 82A, second layer: 90A, arc voltage 10-12V, positive polarity. Mone400 is 3. Thickness 5mm, diameter 45mm, ASTM B163 standard material. The mixing ratio of shielding gas and tail shielding gas is 99%. The flow rate is 12 L/min gas, but the backside shielding gas flow rate is 10 L/min. Welding materials shall be ASME. Use SFA-5.14, φ 2.5mm, ERNiCu-7 brand, weld metal thickness is 3.5mm. The butt welding position is upward and downward, and the fillet welding position is horizontal butt welding. The single wire is welded into two layers at a time, the welding speed is 67-73 mm/min, and the interlayer temperature should be controlled at 100°C.
Because nickel alloy and high-alloy stainless steel have obvious physical property differences compared with carbon steel, they have low thermal conductivity and large thermal expansion coefficient. For this, clamping and large-area welding should be used. Welding feet (1-3mm) and other methods can be used to solve the problem. Because Monel 400 material has poor performance in welding molten metal flow, it is necessary to adopt a design with a large groove angle so that the welding wire can fill the weld seam.
In order to strictly control the influence of harmful impurities such as S and P, the bevel and welding wire should be cleaned with acetone before welding. The required purity of the protective argon gas used is 99.99%.
In order to ensure the stability of the arc during the welding process, attention should be paid to the centering of the tungsten electrode and the sharpness of its end. When welding, attention should be paid to controlling the fusion ratio below 50%. It is best to narrow the weld to 4.5. Monel400 alloy has a large shrinkage, and cracks are prone to occur in the weld and heat-affected zone, especially if this is a bottom weld. Therefore, the interpass temperature during welding is controlled. When the temperature of the base weld is lowered to 100 ~ 150°C, the second layer of weld is welded. If conditions permit, slow cooling measures should be taken for the cover weld.
