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Difference between Monel 400 and Monel K-500 Tubes
How can you find nickel-based alloy pipes that are both corrosion resistant and mechanically strong in severe environments like maritime engineering and chemical equipment? As a global supplier of Monel alloy, we thoroughly examined the 8 significant differences between Monel 400 and K500 to save you 30% of the selecting time.
What are Monel Alloys?
Monel alloy is a Ni-Cu binary solid solution alloy with a nickel-based matrix composed of 65-70% nickel, 20-30% copper, and trace amounts of other alloying elements. The Ni-Cu ratio of Monel alloy corresponds to the "natural" composition found in its raw mineral form, which is why it is also known as a naturally corrosion-resistant alloy.
This alloy has a silvery-white metallic sheen and a strength greater than that of ordinary-grade steel. It has better corrosion resistance than bronze, particularly in brine and sulfuric acid conditions.
Because of its high nickel content, Monel alloy retains an austenitic single-phase structure throughout a wide temperature range, providing remarkable strength, toughness, and corrosion resistance. Monel alloy, which was originally employed in architecture and household applications, remains popular in high-risk, high-demand industries such as marine engineering, aerospace, and defense.
Features:
- Good low-temperature toughness, no ductile-brittle transition at liquid hydrogen temperature
- Excellent corrosion resistance
- Good electrical conductivity
- Good hot and cold processing properties
Common Monel alloy types are Monel 400 and Monel K-500.
1. Differences in chemical composition
|
|
Monel 400 |
Monel K-500 |
|
Nickel+Cobalt (Ni+Co) |
≥63.00 |
≥63.00 |
|
Carbon (C) |
≤0.30 |
≤0.25 |
|
Manganese (Mn) |
≤2.00 |
≤1.50 |
|
Silicon (Si) |
≤0.5 |
≤0.50 |
|
Sulfur (S) |
≤0.024 |
≤0.01 |
|
Iron (Fe) |
≤2.50 |
≤2.00 |
|
Copper (Cu) |
28.00-34.00 |
27.00-33.00 |
|
Aluminum (Al) |
- |
2.30-3.15 |
|
Titanium (Ti) |
- |
0.35-0.85 |
The addition of the microalloying elements Al and Ti to the Monel K-500 alloy is the main difference between the two, as can be seen from the comparison of the chemical composition tables of the two above. Other differences between the two are not very noticeable.
Microalloying components Al and T contribute to the Monel K-500 alloys aging strengthening, which significantly increases the materials strength and hardness. This is also the primary cause of K-500s noticeably greater tensile and yield strengths than Monel 400s.
2. Features of the metallurgical structure
- Monel 400: Structure of a single-phase solid solution
- Monel K-500: Mechanism of γ phase precipitation intensification
Copper and nickel are perfectly miscible at room temperature. With no notable second phases or precipitates, the Monel 400 alloys microstructure is primarily made up of a solid solution of copper and nickel.
After adding Al and Ti alloying components to Monel K-500s chemical composition, precipitation hardening is necessary to improve performance, which causes the alloy to form a γ (Ni3 (Al, Ti)) precipitation phase.
3. Mechanical properties
|
|
Condition |
Tensile Strength, MPa |
Yield Strength, MPa |
Elongation, % |
Hardness |
Shear Strength, MPa |
|
|
Monel 400 |
Annealed |
550-650 |
240-300 |
35-50 |
150–200 HV |
320-380 |
|
|
Monel K-500 |
Age- Hardened |
950-1200 |
650-900 |
15-25 |
250–350 HV |
530-720 |
We may observe from the data in the preceding table that:
- Comparison of tensile strength: At room temperature, the K500 is two to three times greater than the 400.
- Ductility: Monel K-500 is less ductile than Monel 400
- Hardness: Monel K-500 is more resistant to wear because of its higher hardness.
- Shear strength: Compared to Monel 400, Monel K-500 has a substantially higher shear strength, making it appropriate for certain applications requiring stronger connections
4. Physical properties
The mechanical characteristics and chemical makeup of Monel 400 and Monel K-500 alloys vary, which has an impact on their physical characteristics as well. The two alloys have differing physical characteristics, including density, electrical conductivity, thermal conductivity, and magnetism. In particular, Monel K-500s physical characteristics following precipitation hardening treatment differ from those of Monel 400.
|
|
Density |
Melting Point |
Modulus of Elasticity, 103 ksi |
Poisson’s Ratio |
||||
|
g/cm3 |
lb/in.3 |
°C |
°F |
Tension |
Compression |
Torsion |
||
|
Monel 400 |
8.80 |
0.318 |
1300-1350 |
2370-2460 |
26.0 |
26.0 |
9.5 |
0.32 |
|
Monel K-500 |
8.44 |
0.305 |
1315-1350 |
2400-2460 |
26.0 |
- |
9.5 |
0.32 |
Monel 400: Slightly magnetic
Monel K-500: Spark resistant and non-magnetic at -200 °F
5. Corrosion resistance
Common advantages: Resistant to seawater/hydrofluoric acid/alkaline solutions
Key difference: K-500 has a tendency to stress crack in high-temperature chloride environments
|
|
Monel 400 |
Monel K-500 |
|
Seawater and marine environment |
Excellent |
Excellent |
|
Chloride environment |
Excellent |
Good |
|
Weak acid environment |
Good |
Good |
|
Strong oxidizing environment (such as nitric acid) |
Bad |
Bad |
|
High-temperature environment |
Good |
General |
Monel 400 is especially well-suited for usage in corrosive and high-temperature situations due to its exceptional resistance to corrosion at elevated temperatures. At high temperatures, it exhibits robust resistance to oxidation and stress corrosion. Monel 400 works best at temperatures lower than 650°C, and in these conditions, its strength and resistance to corrosion are comparatively steady.
Monel K-500s resistance to oxidation at high temperatures is marginally less than that of Monel 400. Intergranular corrosion or embrittlement of its precipitation hardening phase may result from prolonged exposure, particularly in conditions above 450°C.
6. Applicable temperature
Monel 400: up to 650℃
Monel K-500: up to 450℃
7. Cost analysis
The production and processing costs of Monel K-500 are higher than those of Monel 400.
- The chemical composition contains more aluminum and titanium elements
- The production process is more complicated and requires precipitation hardening
- Higher hardness and strength, more difficult to process than alloy 400, and high machining costs
8. Equivalent grades
|
Grade |
UNS |
W.Nr. |
DIN |
BS |
GOST |
|
Monel 400 |
N04400 |
2.4360/2.4361 |
NiCu30Fe |
NA13 |
NMZhMts28-2,5-1,5 |
|
Monel K-500 |
N05500 |
2.4375 |
NiCu30Al |
NA18 |
N65D29JuT-ISh |
How to choose Monel alloy?
Monel 400:
- When you need very high corrosion resistance, particularly in situations that are acidic, alkaline, or saltwater
- When you want to preserve good machinability and weldability but need less mechanical strength
- It works well with heat exchangers, oil and gas pipelines, naval engineering, and the chemical industries.
Monel K-500：
- When you need more strength and hardness than alloy 400 but yet want to maintain strong corrosion resistance, use Monel K-500.
- K-500 is precipitation hardened and has poor weldability if you dont need it to be machinable and weldable.
- It works well for applications requiring great strength and the ability to support heavy mechanical stresses.
- It works well with springs, valve parts, pump shafts, maritime equipment, and aerospace components.
We provide premium Monel 400 and Monel K-500 nickel-based alloy tubes, with the option of customized processing to satisfy client needs. Whether you need standard specifications or have special demands, we can provide the perfect solution. Get in touch with us for further information.
Monel Alloy Tube
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