Monel 400 / UNS N04400 / W.Nr. 2.4360 & 2.4361
Monel 400
Monel 400, also known as Alloy 400, is a nickel-copper alloy that boasts excellent resistance to sea water, steam, salt, and caustic solutions. This solid solution alloy is made up of 67% nickel and 23% copper, and can only be hardened through cold working. Its unique composition lends itself to good corrosion resistance, weldability, and high strength.
One of Monel 400’s standout features is its low corrosion rate in rapidly flowing brackish or seawater, making it a popular choice in marine applications. It also exhibits excellent resistance to stress-corrosion cracking in most freshwaters, and can withstand a variety of corrosive conditions.
This nickel alloy is particularly resistant to hydrochloric and hydrofluoric acids when they are de-aerated. However, it should be noted that alloy 400 is rapidly attacked by nitric acid and ammonia systems due to its high copper content.
Monel 400 is a versatile alloy that can perform well even in subzero temperatures, with a melting point of 2370-2460° F. It can be used in temperatures up to 1000° F, but its strength is low in the annealed condition. Fortunately, a variety of tempers may be used to increase the strength of this alloy.
Industries and Applications
Alloy 400 has found widespread use in various industrial applications. It comprises 67% nickel and 23% copper and boasts good corrosion resistance, weldability, and high strength. Here are some of the industries and applications where Monel 400 is commonly used:
Marine Industry: Monel 400’s exceptional resistance to sea water, steam, and saltwater corrosion makes it a go-to choice for the marine industry. It is widely used in the construction of offshore oil and gas rigs, seawater valves, pumps, and heat exchangers.
Chemical Processing Industry: The chemical processing industry relies on Monel 400 for its resistance to a wide range of corrosive chemicals. Monel 400’s resistance to hydrofluoric and hydrochloric acids, as well as caustic solutions, makes it ideal for chemical processing equipment, including heat exchangers, pumps, and valves.
Aerospace Industry: Monel 400’s high strength, good weldability, and resistance to corrosion and high temperatures make it a popular choice in the aerospace industry. It is used in the construction of aircraft components, such as fuel tanks and exhaust systems.
Oil and Gas Industry: Monel 400’s resistance to corrosion and high temperatures make it an excellent material for use in the oil and gas industry. It is commonly used in the construction of downhole equipment, valves, pumps, and piping.
Electrical and Electronics Industry: Monel 400’s electrical conductivity and resistance to corrosion and high temperatures make it an ideal material for electrical and electronic applications. It is used in the construction of electrical contacts, wire, and connectors.
Resistance to Corrosion
One of the key benefits of Monel 400 is its resistance to corrosion. This alloy is highly resistant to corrosion in a variety of environments, including seawater, acids, and alkalis. This makes it an ideal choice for applications in the marine industry, where it is used for everything from propeller shafts to seawater valves.
Another advantage of Monel 400 is its resistance to stress corrosion cracking. This is a type of corrosion that occurs when a material is exposed to a combination of tensile stress and a corrosive environment. Monel 400 is highly resistant to this type of corrosion, making it a popular choice for applications where high-stress levels are present.
In addition to its resistance to corrosion, Monel 400 also offers excellent resistance to a wide range of other forms of chemical attack. This includes resistance to hydrofluoric acid, sulfuric acid, and other highly corrosive substances. As a result, Monel 400 is often used in the chemical processing industry, where it is employed for everything from heat exchangers to process vessels.
Fabrication and Heat Treatment
Fabrication of Monel 400 typically involves a range of techniques, including welding, machining, and forming. Welding Monel 400 requires careful preparation of the joint, as well as the use of appropriate welding techniques to avoid the risk of cracking. Machining Monel 400 is generally best accomplished using low cutting speeds and plenty of lubrication to avoid work hardening and improve surface finish. Forming Monel 400 can be accomplished using a range of techniques, including cold working and hot working.
Heat treatment is also an important consideration when working with Monel 400. The alloy is known for its excellent ductility and toughness, which can be enhanced through annealing or stress relieving heat treatment. Annealing involves heating the material to a specific temperature and holding it at that temperature for a set period of time, followed by a controlled cooling process. This can help to improve ductility and toughness, as well as reduce the risk of cracking during subsequent processing steps.
Stress relieving is another heat treatment technique that can be used with Monel 400. This involves heating the material to a specific temperature to relieve any residual stresses that may have built up during processing or use. This can help to reduce the risk of stress corrosion cracking, improve dimensional stability, and enhance overall performance.
Monel 400 – Applicable Specifications
| Form | ASTM | ASME | Other Standard |
|---|---|---|---|
Monel 400 Sheet and Plate
|
B127 | SB127 | – |
Monel 400 Bar
|
B164 | SB164 | – |
Monel 400 Pipe and Tube
|
B165 | SB165 | – |
Monel 400 Fittings
|
B366 | SB366 | – |
Monel 400 Forgings |
B564 | SB564 | – |
Monel 400 Welding Wire |
B164 | SB164 | AWS A5.14 ERNiCu-7 |
Monel 400 Welded Pipe |
B725 | SB725 | – |
Monel 400 Seamless Pipe |
B165 | SB165 | – |
Common Trade Names
Monel 400 is known by several trade names, including Nicorros, Alkordur, and Monel K500. These names may be used interchangeably, but all refer to the same highly versatile and corrosion-resistant nickel-copper alloy.
Key Properties
(in annealed condition)
| Property | Alloy 400 |
|---|---|
| Tensile Strength | 480 MPa (70 ksi) |
| Yield Strength | 170 MPa (25 ksi) |
| Elongation | 35% |
| Hardness | Rockwell B 80-85 |
Chemical Composition (%)
| Element | Alloy 400 |
|---|---|
| Carbon | 0.030 max |
| Manganese | 1.20 max |
| Phosphorus | 0.035 max |
| Sulfur | 0.020 max |
| Silicon | 1.00 max |
| Chromium | 24.0-26.0 |
| Nickel | 6.00-8.00 |
| Molybdenum | 3.00-5.00 |
| Nitrogen | 0.24-0.32 |
| Iron | Balance |
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