What is the composition of Monel 400?
Overview
There are several variations of Monel alloy, starting with Monel 400, which contains at least 63% nickel, 29% to 34% copper, 2% to 2.5% iron, and 1.5% to 2% manganese. Monel 405 has no more than 0.5% silicon added, and Monel K-500 has between 2.3% and 3.15% aluminum and between 0.35% and 0.85% titanium. These and other variations are valued for their resistance to attack by acids and alkalis, high mechanical strength, and good ductility.
Monel 400 contains the same nickel and copper found in naturally occurring nickel ores in Ontario, Canada. It has high strength and can only be hardened by cold working. Due to its corrosion resistance, Monel 400 is most often used for components in marine and chemical environments.
While it is a very useful metal, it is cost-prohibitive for most applications. Monel 400 costs 5 to 10 times more than regular nickel or copper. As a result, it is rarely used-only when no other metal can do the same job. For example, Monel 400 is one of the few alloys that retains its strength in subzero temperatures, so it is used in such environments.
Fabrication
The processing techniques used for ferrous alloys can be used on Monel 400, although this is difficult because it hardens during processing. If the goal is to harden Monel 400, then cold working with soft tooling materials is the only option. With cold working, mechanical stress is used rather than heat to change the shape of the metal.
Gas arc welding, metal arc welding, gas electric metal arc welding, and submerged arc welding are performed on Monel 400. When hot working Monel 400, the temperature range should be 648-1,176 degrees Celsius (1,200-2,150 degrees Fahrenheit). It can be annealed at 926 degrees Celsius (1,700 degrees Fahrenheit).
Applications
Due to its resistance to acids, alkalis, and seawater, Monel 400 is often used in applications where corrosion may be a problem. This includes marine environments where fixtures, valves, pumps, and piping systems are required.
Other applications sometimes include chemical plants, including environments where sulfuric and hydrofluoric acids are used.
