Monel 400 (UNS N04400 / ASTM B127): A Nickel-Copper Alloy with High Corrosion Resistance
Alloy Definition and Chemical Composition
Monel 400 is an alloy consisting essentially of nickel and copper, with a nickel content in the range of approximately 63–70%. This alloy is known for its excellent corrosion resistance to sea water and chemical environments, its high strength and its ductility. Monel 400 shows excellent resistance especially to hydrofluoric acid, sea water, acids, alkalis and neutral salt solutions.
Chemical composition (typical):
- Nickel (Ni): 63.0% min
- Copper (Cu): 28.0–34.0%
- Iron (Fe): 2.5% max
- Manganese (Mn): 2.0% max
- Carbon (C): 0.3% max
- Silicon (Si): 0.5% max
- Sulphur (S): 0.024% max
This simple, solid solution alloy cannot be hardened by precipitation hardening; instead its mechanical strength is increased by cold forming.
Monel 400 Standards and Specifications
Monel 400 appears in many international standards. These standards set out both the chemical and the mechanical properties of the material:
- ASTM B127 – For Monel 400 plate, sheet and strip
- ASTM B164 – For Monel 400 bar and wire products
- ASTM B165 – Seamless pipes
- UNS N04400 – Unified Numbering System code
- AMS 4675, AMS 4574
- ISO 6208
- DIN 2.4360 / 2.4361
Monel 400 products manufactured within the framework of these standards show suitability for high performance applications in the chemical, energy and marine sectors.
Monel 400 Trade Names and Equivalent Materials
Monel 400 is marketed under various trade names by specialist producers:
- Monel® 400 – Registered brand of Special Metals Corporation (SMC)
- Alloy 400 – Common synonymous name
- Nicrofer 3826 – Thyssenkrupp VDM equivalent
- Nicorros® 400 – Haynes International
- 2.4360 (bar, pipe), 2.4361 (sheet, plate) – DIN/Werkstoff numbers
These trade names may appear as different variants in the product catalogues encountered during the purchasing process. All of them, however, share the same technical properties as UNS N04400.
Mechanical and Physical Properties
Monel 400 stands out with both its mechanical strength and its excellent ductility. It offers high tensile strength at room temperature and is suitable for cold forming.
- Tensile Strength: 480–620 MPa
- Yield Strength (0.2% offset): 170–275 MPa
- Elongation (%): 30–40%
- Brinell Hardness (HB): 110–180
- Density: 8.80 g/cm³
- Melting range: 1300–1350 °C
- Thermal conductivity: ~22 W/m·K
- Electrical conductivity: ~34% IACS
Monel 400 preserves its mechanical and chemical strength in the temperature range from -200 °C to 550 °C. That it shows no embrittlement at low temperatures provides an advantage for cryogenic applications.
Application Areas
The principal reason Monel 400 is preferred is the durability it shows in chemically aggressive environments. Its application areas are summarised below:
1.Chemical and Petrochemical Industry
*Hydrofluoric acid transport and storage tanks
*Reactors and exchangers working with alkaline solutions
*Chemical pump and valve components
2.Marine and Shipbuilding
*Sea water pipelines, condensers
*Pump shafts, propeller shafts
*Desalination systems
3.Energy and Nuclear Industry
*Nuclear reactor water systems
*Heat exchanger tubes
*Fuel processing equipment
4.Aerospace
*Fuel tanks and connection equipment
*Exhaust and heat transfer systems
5.Food and Beverage Industry
*Process lines using caustic soda in sugar production
*Agitators and tanks in contact with acidic media
Monel 400 differs from its alternatives especially through its durability against sea water and alkaline solutions.
Advantages
- High Corrosion Resistance: It shows top level durability in sea water, saline solutions, acids and alkaline environments.
- Remaining Ductile at Low Temperature: It preserves its ductility without embrittlement even in cryogenic conditions.
- High Strength-Ductility Balance: Thanks to its high tensile strength and elongation value above 30% it can be formed under difficult conditions.
- Weldability: It can be welded with nickel-based welding electrodes. It has a low tendency to cracking.
- Good Mechanical Machinability: With attention to tool life, it can be machined with high surface quality under suitable conditions.
Disadvantages
- High Cost: Because of its nickel-based structure it is expensive compared with carbon steels and stainless steels.
- Sensitivity to Acid Oxidation: It has low resistance in the face of oxidising acids such as nitric acid.
- Not Suitable for Precipitation Hardening: Strength cannot be increased by heat treatment. It gains strength only by cold forming.
- High Density: Its density of 8.8 g/cm³ may be limiting in systems where the weight criterion is critical in the design.
Conclusion and Engineering Evaluation
Monel 400 offers a critical engineering solution in the chemical process, marine, energy and aerospace sectors thanks to its high corrosion durability and ductility. Its unrivalled durability in non-oxidising chemical environments and in sea water makes it longer-lived and more reliable than stainless steel and bronze alloys.
However costly an alloy it may be, the advantage of the low maintenance and high performance Monel 400 offers throughout its service life reduces the total cost of ownership and thereby makes it the preferred choice. Especially for designers seeking a nickel-based high performance solution, Monel 400 is technically an optimum choice.
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| Chemical Composition (Monel 400) | | Room Temperature Mechanical Properties | |
|---|---|---|---|
| Grade | Monel 400 (2.4360 – 2.4361) | Properties | Values |
| Ni | min 63.0% | Density (Specific Gravity) | 8800 kg/m³ |
| Fe | max 2.50% | Melting Point | 1300-1350°C |
| C | max 0.30% | | |
| Mn | max 2.00% | | |
| Si | max 0.50% | | |
| S | max 0.024% | | |
| Cu | 28.0-34.0% | |
We supply this material
We supply Monel 400 (2.4360) — to AMS 4675, AMS 4544 standards, in the dimensions and forms required. For stock availability and pricing:
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