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
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
Monel 400 has robust mechanical performance across a wide temperature range. Key values in the annealed condition include:
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517–620 MPa |
75–90 ksi |
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Yield Strength (0.2% Offset) |
172–345 MPa |
25–50 ksi |
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35–50% |
35–50% |
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179 GPa |
26,000 ksi |
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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
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8.8 g/cm³ |
0.318 lb/in³ |
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1300–1350℃ |
2370–2460℃F |
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21.8 W/m·K (at 21℃) |
151 BTU-in/hr-ft²-℃F |
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5.47 × 10⁻⁵ ohm-cm |
5.47 × 10⁻⁵ ohm-cm |
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13.9 µm/m-℃ (20–100℃) |
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
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.
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
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.
Annealing: At 1300–1800℃F in a sulfur-free atmosphere.
Stress Relieving: At 1000–1050℃F for 1–2 hours.
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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