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A comprehensive introducion for Monel metal and its grades

By Thomas Huang December 8th, 2023 67 views

I, What is Monel metal?

Monel is an alloy made from nickel metal with the addition of copper, iron, manganese, and other elements.

II, Grades of Monel

Depending on the actual use of the alloy, it can be categorized into cast-mel Monel Alloys and deformed-mel Monel Alloys.

2.1 Monel 410, Monel 505, and Monel 506 are Casting Monel Alloys.

Monel 410 is a standard casting alloy; Monel 505 and Monel 506 are high-silicon high-strength and high-silicon medium-strength casting alloys, respectively.

2.2 Monel 4XX and Monel 5XX are Deformed Monel Alloys.

Monel 400 is a general-purpose alloy; Monel 404 is commonly used for waveguide materials and is a high copper monel alloy; Monel K500 is an age-hardening alloy; Monel 501 is an age-hardening alloy with easy-cutting characteristics; Monel 502 is an age-hardening low-carbon, low-titanium alloy; and Monel 406 is a low-carbon, high-nickel alloy.

III, Monel 400

3.1 Monel 400 Overview

Monel 400 is a nickel-copper alloy, also known as N04400, which consists of about 67% nickel and about 23% copper, with small amounts of other elements like iron, manganese, silicon, carbon, and so on.
Monel 400 is organized as a high-strength, single-phase solid solution. It is one of the largest used and versatile corrosion-resistant alloys with excellent all-around properties.

3.2 Monel400 similar grades

 Monel400  Ni68Cu28Fe  NW4400  N0.4400  MONEL400  2.4360  NiCu30Fe

3.3 Monel 400 Chemical Composition

 Ni  C  Si  Mn  Cu  Fe
 Monel 400  63~67  0.3  0.5  1.5  28~34  2.0

3.4 Monel400 Physical Properties:

 Density g/cm³   Thermal conductivity /w/(m.k) 100~900°C   Resistivity /(Ω.mm2/m 20~900°C  Specific heat capacity) /kg/(kg. k)°C 100~900°C   Coefficient of linear expansion/ (10-6/k)20~900°C
 8.83   24.048-48.24   0.51-0.477  0.51-0.477  0.51-0.67

3.5 Monel400 mechanical properties

Monel 400 alloy has a yield strength of 170 MPa, a tensile strength of 480 MPa, and an elongation of 35% at room temperature.

3.6 Corrosion resistance

Monel 400 alloy surface can generate a layer of Ni (OH) 2 passivation film in a variety of environments, so it has excellent corrosion resistance.
It is more resistant to corrosion of reducing media than pure nickel, and more resistant to corrosion of oxidizing media than pure copper.


Good corrosion resistance in freshwater, seawater, and fresh brine. So, it can be made into shafts, pump shafts, impellers, condensing heat exchangers, and structural components on the oil platform splash zone.


Very good corrosion resistance to H2SO4, carbon.


Good corrosion resistance to fluorine gas, H2SO4, Na2SO3, HF, and their derivatives, but it is not available in H3PO4, organic acids. It is one of the few important materials that can resist HF.


It is only suitable for HCl with a concentration of less than 15% under room temperature. Besides, it has more corrosion resistance to seawater corrosion and chemical corrosion resistance in seawater than copper-based alloys. Its resistance to chloride stress corrosion cracking is good.


Monel 400 has good corrosion resistance to the H2SO4 with a concentration of no more than 85%.


Good corrosion resistance to Aqueous Corrosion, pore corrosion, stress corrosion, etc. are rarely found, the corrosion rate is less than 0.025 mm/a. The highest temperatures of continuous work in the air are generally around 600 ℃. In the high-temperature steam, the corrosion rate is less than 0.026 mm/a.


Due to the high nickel content of the alloy, it can resist corrosion under anhydrous ammonia and ammoniated conditions under 585℃.


Good resistance to chloride salt, sulfide salt, nitrate, carbonates, aluminum sulfate, ammonium sulfate, NH4Cl, and zinc chloride.

3.7 Monel 400 Machining and Welding Properties


Monel 400 alloy does not produce stress corrosion cracks and has good cutting properties.

3.7.2 Monel400 hot working

It is easy to mold at thermal processing, the temperature within 927 ~ 1177℃, and has slight deformation under 649 ℃.
Heat treatment temperature is generally 871~982 ℃, but to perform and fine grain, the solid solution temperature shall not be too high.
Solution annealing is generally chosen between 871~982℃.

3.7.3 Good Welding Performance.

Monel400 can be welded by using various welding methods, such as SMAW (electrode arc welding), GTAW (tungsten gas shielded welding), GMAW (fusion electrode gas shielded welding), SAW (submerged arc welding), generally Monel60 and 190 welding wire.

3.8 Applications

Various types of heat transfer equipment, feedwater heaters of boilers, pipelines, vessels, pumps, valves, shafts, etc. in petroleum and chemical processes, desalination equipment, salt production equipment, propellers, shafts, as well as gasoline and water tanks.
Photo of Seawater desalination equipment

IV, Monel 500

4.1 Overview of Monel 500

The chemical composition of this alloy is generally the same as that of Monel 400, the most significant differences being the presence of 2.3-3.15% AL and 0.30-1.00% Ti.

4.2 Chemical Composition

 Ni  Cu  Fe  C  Mn  Si  S  Al  Ti
 Monel 500  63  27~33  2  0.18  1.5  0.5  0.01  2.3~3.15  0.35~0.85

4.3 Physical Properties

 Density  Melting point  Tensile strength  Yield strength  Elongation
 8.05  G/CM3  1288~1343°C  960 RM N/MM2  690 RP0.2N/mm2  20 A5%

4.4 Properties.

The Monel 500 alloy has the same corrosion resistance as Monel 400 in addition to excellent mechanical properties such as high strength, corrosion resistance, and non-magnetic properties.
The low corrosion rate of the alloy in flowing seawater and the high strength of the alloy makes it particularly suitable for the manufacture of centrifugal pump shafts which resist seawater corrosion.

4.5 Applications


It is suitable for all kinds of low-temperature equipment.


Monel 500 is mainly used for pump shafts, valve stems, conveyor scrapers, oil well drilling rings, elastic parts, and valve gaskets in petroleum, chemical, shipbuilding, pharmaceutical, and electronic sectors.

4.5.3 Application cases
Seamless transmission pipes and steam pipes in power plants.
Sea water exchanger and evaporator.
Components for sulfuric acid and hydrochloric acid circumstance.
Crude oil distillation.
Pump shafts and propellers of deep sea water equipment.
Production of uranium refining and isotope separation equipment in the nuclear industry.
Pumps and valves of hydrochloric acid-producing equipment.
Pumps and valves of hydrochloric acid-producing equipment.

V, Monel K500

5.1 Overview of Monel K500

Monel K500 is a typical precipitation-strengthened alloy consisting of a nickel-copper solid solution matrix with uniformly distributed spherical particles of Ni3(Al, X) precipitated phase and a small amount of TiC phase, where X can be Cu, Mn, Ti, or Si. 
There was an Al-Monel alloy made by adding an appropriate amount of aluminum to the Monel alloy matrix and then applying a series of heat treatments. 
Then it was renamed as K Monel alloys and evolved into Monel K-500 alloys.
Monel K500 is widely used in ship hulls and offshore equipment due to its excellent resistance to seawater corrosion and yield strengths over 690 MPa.

5.2 Properties:


Monel K500 has corrosion resistance in a wide range of media, resistance to chloride ion stress corrosion rupture, and high strength and hardness. 


Its mechanical properties are about 2 to 3 times stronger than Monel 400 in an aging state.


Monel K500 still has a high tensile strength, good fatigue corrosion resistance, and lower permeability at 650 ℃.


It still has no magnetism at a low temperature of -135 ℃.


The alloy has no plastic-brittle transition temperature.

5.3 Corrosion Resistance:


MONEL K500 alloy has the same corrosion resistance as 400.


The finest corrosion resistance is resisting a wide range of media, from pure water to inorganic acids, salts, and bases.


Monel K500 is remarkably resistant to chloride ion stress corrosion rupture.


The alloy is most susceptible to stress corrosion rupture in hydrofluoric acid vapors in the aging state when the stresses are close to yielding strength.


Monel K500 exhibits good corrosion resistance in high-velocity seawater and marine atmospheres, but pitting corrosion occurs in slow-moving or stationary seawater.


It also exhibits good corrosion resistance in acid gases.

5.4 Applications:

Monel K500 alloy has wide applications in the marine, chemical, petrochemical, and shipbuilding industries:


Valve seals, pump sleeves, and wear rings in marine environments (high strength and seawater corrosion resistance).


Fasteners such as bolts, used in marine atmospheres and tidal waters, are resistant to corrosion in chloride-containing environments.


Medical blades and scrapers;


Retractable metal housings - high strength, non-magnetic, and resistant to seawater corrosion;


Oil well drilling equipment such as non-magnetic drill bits, valve bodies, and instrument sleeves - resistant to corrosion in chloride-containing media and sour gas environments;


Springs - resistant to a variety of corrosive media;
photo of springs made from monel


Non-magnetic aviation instrument components.

VI, Monel R-405

6.1 Overview of Monel R-405

Monel R-405 is a nickel-copper alloy with a controlled amount of sulfur added to provide sulfide inclusions that act as chip breakers during machining.

6.2 Properties


Monel R-405 is resistant to high-temperature seawater and steam as well as salt and caustic solutions.


Monel R-405 has been developed for good machinability and is recommended for use in automatic screw machines.


It has special mechanical properties of forgings.

6.3 Applications:

Because of its special forging property, Monel R-405 can be used for:


Chemical pumps, piston pumps, pressure vessels, and air receivers. 


Shell and tube heat exchangers,  columns, towers, tanks.  heat exchangers


Silos, process modules. 


Evaporator and heaters' bodies for desalination plants of preheaters and brine.


The components such as piping, ball valves, check valves, filters, globe valves, gate valves, and plug valves for the following applications including subsea and deepwater offshore oil production systems, industrial air compressors, generators, nitrogen generators, and feedwater & steam generator of power plants.


Isotope separation for uranium refining and nuclear fuel production.
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