Monel 400 (UNS N04400) is a nickel-copper alloy has exceptional corrosion resistance, high mechanical strength, and excellent performance in extreme environments. Originally developed by International Nickel Company (INCO), this alloy has become a standard material in marine, chemical, and oil & gas industries due to its unmatched resistance to seawater, acids, and high-temperature applications.
This blog explores the material properties, chemical composition, mechanical characteristics, and industrial applications of UNS N04400.
UNS N04400 Chemical Composition
Monel 400 is a solid-solution alloy with a unique balance of nickel and copper. Its typical composition includes:
Nickel (Ni) : 63–70% (providing inherent corrosion resistance and stability).
Copper (Cu) : 28–34% (enhancing resistance to reducing media and sulfuric acid).
Iron (Fe) : ≤2.5% (improving strength and oxidation resistance).
Manganese (Mn) : ≤2.0% and Silicon (Si) : ≤0.5% (aiding manufacturability).
Carbon (C) : ≤0.3% and Sulfur (S) : ≤0.024% (minimizing impurities).
This composition aligns closely with naturally occurring nickel-copper ores, contributing to the alloy's cost-effectiveness and performance in corrosive settings.
UNS N04400 Material Mechanical Properties
Monel 400 has robust mechanical performance across a wide temperature range. Key values in the annealed condition include:
|
Property |
Metric Value |
Imperial Value |
|
Ultimate Tensile Strength |
517–620 MPa |
75–90 ksi |
|
Yield Strength (0.2% Offset) |
172–345 MPa |
25–50 ksi |
|
Elongation at Break |
35–50% |
35–50% |
|
Modulus of Elasticity |
179 GPa |
26,000 ksi |
|
Hardness (Rockwell B) |
60–76 HRB |
60–76 HRB |
The alloy can be cold-worked to achieve higher strength, while hot-working allows for forming complex shapes.
UNS N04400 Material Physical and Thermal Properties
|
Property |
Metric Value |
Imperial Value |
|
Density |
8.8 g/cm³ |
0.318 lb/in³ |
|
Melting Point |
1300–1350°C |
2370–2460°F |
|
Thermal Conductivity |
21.8 W/m·K (at 21°C) |
151 BTU-in/hr-ft²-°F |
|
Electrical Resistivity |
5.47 × 10⁻⁵ ohm-cm |
5.47 × 10⁻⁵ ohm-cm |
|
Coefficient of Thermal Expansion |
13.9 µm/m-°C (20–100°C) |
7.7 µin/in-°F (70–212°F) |
These properties ensure stability in high-temperature applications and suitability for heat exchangers, boilers, and other thermal systems.
UNS N04400 Material Corrosion Resistance
Monel 400 excels in both reducing and oxidizing environments, with standout performance in:
Seawater and Brackish Water : Resistance to erosion, cavitation, and chloride-induced stress corrosion cracking.
Acids and Chemicals:
Withstands hydrofluoric acid (all concentrations, including deaerated forms) and sulfuric acid.
Resists alkalis, salts, and organic compounds but vulnerable to oxidizing acids.
Industrial Applications: Used in pumps, valves, heat exchangers, and marine components due to low corrosion rates in acidic and saline media.
UNS N04400 Material Fabrication and Machinability
Machining: Requires carbide tools and low cutting speeds to avoid work-hardening. Cold-drawn material is recommended for smoother finishes.
Welding: Compatible with gas-tungsten arc, gas-metal arc, and shielded metal arc processes. Post-weld heat treatment is unnecessary, but thorough cleaning is critical.
Heat Treatment:
Annealing: At 1300–1800°F in a sulfur-free atmosphere.
Stress Relieving: At 1000–1050°F for 1–2 hours.
Conclusion
Whether for seawater piping, acid-resistant equipment, or high-temperature applications, Monel 400 is a reliable and long-lasting material.
For procurement inquiries, ensure material certifications and proper fabrication practices to maximize performance.
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