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Monel 400 / Alloy 400

Monel 400 / Alloy 400

Alloy 400 (UNS designation N04400) is a nickel copper solid solution alloy with small additions of manganese, silicon and iron to enhance the grade’s strength and corrosion resistance. It exhibits high strength over a wide temperature range.

monel / alloy 400 round bars stacked

Alloy 400 has excellent resistance to a variety of corrosive environments from mildly oxidizing through neutral and in moderately reducing conditions. Alloy 400 also performs well in marine and other non-oxidising chloride solutions.

Alloy 400 is also particularly resistant to stress corrosion cracking and pitting corrosion in most fresh and industrial waters.

In the annealed condition, it is easy to form and fabricate and can be tempered or cold worked to enhance its mechanical properties. 

Columbia Metals is a leading supplier and distributor of Alloy 400 in the cold worked and stress relieved condition as standard. This condition ensures maximum mechanical strength, optimum machinability and best surface condition for the ultimate application.

Table of Contents

Alloy 400 (N04400) Standards & Specifications

Alloy 400 (Monel® 400) is released against the British standard BS3076 as NA13 and against the American standard ASTM B164 as UNS N04400. The use of the term Monel® relates to a trademarked alloy first developed in 1905, when Ambrose Monell was President of the International Nickel Company. The ASTM and BS specifications and the term Alloy 400 are equivalent alloys to Monel® 400.

Corrosion Resistance

Alloy 400 exhibits exceptional corrosion resistance to hydrofluoric acid and many reducing media and it performs better against oxidising media than high copper alloys. It is one of only a few alloys that can be used in contact with fluorine and hydrogen fluoride.  Alloy 400 is highly resistant to many forms of sulphuric and hydrochloric acids under reducing conditions, as well as alkalis. Alloy 400 is also resistant to stress corrosion cracking and pitting in most fresh and industrial waters, as well as having excellent corrosion resistance in flowing seawater, making it widely utilised in chemical and marine engineering applications.

Applications

Marine fixtures and fasteners, propellers, pump and propeller shafts, splash zone sheathing

Chemical processing equipment, components for the manufacture of chlorinated solvents, salt production, ethyl chloride purification, hydrochloric acid production, hydrofluoric acid and sulphuric acid process industry, brine heaters

Pumps, valves, process vessels and piping, crude petroleum stills, gasoline and fresh water tanks, boiler feedwater heaters

Heat exchangers, wire netting for insulation, oil well recovery pumps and crude oil distillation towers, electrical and electronic devices

Chemical Composition

Alloy 400 was one of the first nickel alloys mined from the original nickel-copper ore in Canada in the late 19th century. The composition of the original ore is roughly the same as the composition of Alloy 400 today.

Ni+Co Cu Fe Mn Si C S Al P
63.00 max
28.0-34.0
2.50 max
2.00 max
0.50 max
0.30 max
0.024 max
0.02 max
0.005 max

Mechanical Properties

Condition Yield Strength 0.2% offset Tensile Strength Elongation Elastic Modulus (E) Hardness
psi
MPa
psi
MPa
% in 2in
psi
GPa
HB
Annealed
35000
240
75000
520
45

26 x 106

180
110-150
Hot rolled
45000
310
85000
550
30

26 x 106

180
110-150

Alloy 400’s high strength and toughness is maintained over a wide range of temperatures up to 400°C (750°F). It can be used in temperatures up to 540°C (1000°F), and has a melting point between 1300-1350°C (2370-2460°F)

Alloy 400 has excellent mechanical properties at sub-zero temperatures, with an increase in strength and hardness and only a slight decrease in elongation.  With no ductile to brittle transition down even to cryogenic temperatures, Alloy 400 is suited to many applications where ferrous metals cannot be used.

Alloy 400 is low in strength in the annealed condition so a variety of tempers may be used to increase the strength.

Microstructure

Alloy 400 is a solid solution binary alloy with a face-centred cubic lattice structure. It is a single phase alloy as nickel and copper are mutually soluble.

Physical Properties

Property
Density
Density 8.8 g/cm3 (0.318 lb/in3)
Melting Range
1300-1350°C
Modulus of Elasticity
180 GPa
Curie Temperature
21-49°C
Specific Heat Capacity (room temp)
427 J/kg°K
Electrical Resistivity (room temp)
0.511 µΩm
Magnetic Permeability (20°C)
Alloy could show magnetism as Curie low
Mean Coefficient of Thermal Expansion (20-100°C)
1.41 x 10 -6 m/m/°C

Magnetic Properties

The Curie temperature of Alloy 400 lies within the ambient range, between values of 21°C and 49°C (70 -120°F). Monel 400 loses its magnetic properties at temperatures above this range.

The exact range boundary values are affected by the chemical composition of a given batch, so some will be slightly magnetic at room temperature and some will not. It is therefore not possible to accurately confirm this characteristic of the alloy at room temperature.

Monel 400 is not recommended if there is a strong requirement for non-magnetic characteristics.

Fabrication

Alloy 400 can be both hot worked and cold worked. With proper control of the amount of hot or cold work and by the selection of appropriate thermal treatments, finished fabrications can be produced to a wide range of mechanical properties.

Alloy 400 exhibits excellent cold forming characteristics normally associated with chromium nickel stainless steels. When cold worked the alloy exhibits work hardening somewhere in between that of a mild steel and 304 types of stainless steel. The alloy has a lower work hardening rate than T301 or T304 stainless steel and can be used in multiple draw forming operations where relatively large amounts of deformation occur between anneals.

Alloy 400 is softer than many steels in respect to its resistance to hot deformation. It can therefore be hot formed into almost any shape. The use of proper temperatures is critical when hot forming Alloy 400. The hot working temperature range is between 650°C and 1175°C (1200°F to 2150°F).

For heavy reductions the recommended metal temperature is 925°C to 1175°C (1700°F to 2150°F). For light reductions, the temperature may be taken down to 650°C (1200°F). Working at the lower temperatures produces higher mechanical properties and smaller grain size.        

In no case should the alloy be heated above 1175°C (2150°F) as permanent damage may result. Heavy forging should not be carried out so rapidly that the metal becomes overheated from working.

Alloy 400 is readily machinable and material in the cold worked and stress relieved condition offers the best machinability and surface finish.

A stress relief heat treatment is recommended to reduce distortion from machining and fabrication. A soak of one to two hours at a temperature between 760°C and 815°C is recommended for this operation.

Machining

The nature of Alloy 400 is such that it will work harden during machining and this can give a sense of “gumminess” when compared to machining of steels. Machinability can be improved by the use of sharp tools with a positive rake angle.

Procuring the alloy in the cold drawn stress relieved condition will give the best condition for the maintenance of dimensional stability and surface finish.

Monel 400 is a nickel-based heat resistant superalloy (HRSA) material with a machinability rating of 45%.

Recommended Cutting Speeds for Monel 400

Application VC (surface speed) (m/min) VC (surface speed) (ft/min)
Turning
155-205
510-670
Milling
115-155
380-510
Parting
95-130
310-430
Grooving
135-180
440-590
Drilling
135-180
440-590

Assuming:

Welding

Alloy 400 can be readily joined by most available commercial methods including welding, soldering and brazing. The most conventional welding processes for joining Alloy 400 to itself or other alloys are gas tungsten-arc, gas metal-arc and shielded metal-arc welding.

In each of these processes thorough cleaning of the joint area is necessary to avoid embrittlement from such sources as lubricants and paints. The material must be free of scale for optimal welding. The welding procedures for Alloy 400 are similar to those used for austenitic stainless steels. Neither preheating nor post-weld heat treatment is generally required.

During welding, the joint design is similar to that used for austenitic stainless steels with two exceptions.

The first is the need to accommodate the sluggish nature of the molten weld metal, necessitating a joint design sufficiently open to allow fuller filler wire access to fill the joint.

The second is the high thermal conductivity and purity of the material which makes weld penetration lower than in austenitic stainless steels.

Datasheet

Frequently Asked Questions

The Curie temperature of Alloy 400 lies within the ambient range, between values of 21°C and 49°C (70 -120°F). Monel 400 loses its magnetic properties at temperatures above this range.

The exact range boundary values are affected by the chemical composition of a given batch, so some will be slightly magnetic at room temperature and some will not. It is therefore not possible to accurately confirm this characteristic of the alloy at room temperature.

Monel 400 is not recommended if there is a strong requirement for non-magnetic characteristics.

The chemical composition of Alloy 400 is different to that of the Inconel alloys (such as Alloy 625 or Alloy 718).


The Monels are nickel-copper alloys while the Inconels are nickel-chromium-iron alloys. This composition difference produces differences in mechanical and corrosion performance.


The Monels have higher strength than the Inconels at room temperature while the Inconels show improved performance at higher temperatures (over 600°C). The corrosion performance of the Monels makes them more suitable for use in acidic environments.

An austenitic stainless steel such as 316 has similar thermal expansion and specific heat capacity but, due to its chemical composition, Alloy 400 can operate at higher temperatures and has a much better corrosion performance than the stainless steel.

When the mechanical properties are compared, Alloy 400 is  more ductile and therefore easier to work and shape.


Alloy 400 also has greater hardness and is more suitable for higher temperature use where greater strength is needed than C276. The nickel content of Alloy 400 also improves the weldability when compared to C276. The corrosion performances of the two alloys must be balanced.


Alloy 400 is more suitable than C276 in marine environments whilst C276 is the better performer in acidic or alkaline environments.

These two alloys are of similar chemical composition, differentiated by the strengthening mechanism, Alloy 400 being solid solution strengthened and K500 being precipitation strengthened.


Alloy K500 has a higher strength but Alloy 400 has a greater toughness. K500 would therefore be a better choice in higher strength or pressure environments. Alloy 400 has varying magnetic properties while K500 is consistently non-magnetic.

It is possible to specify a spring condition for Alloy 400 that will allow for the manufacture of springs that can be used in brackish water or sea water.

The Weight Calculator on the Columbia Metals website will allow for the calculation of approximate weights of Monel 400, or various other non-ferrous alloys, for a given material type, grade, form and size.

Monel 400 is also known as Alloy 400, so there is no difference, as it is one and the same material.

The chemical composition of Alloy 500 (Alloy K500) is very similar to that to Alloy 400, so that both alloys have similar corrosion resistance properties.


Alloy 400 (Monel® 400, UNS N04400, 2.4360) is a nickel-copper alloy resistant to seawater and steam at high temperatures and often used in the chemical, oil and marine industries. Alloy 400 exhibits good toughness, strength and corrosion resistance at temperatures up to 400°C. Alloy 400 shows good resistance to hydrofluoric and dilute non-oxidising acids, alkalis and salts, and it is not susceptible to stress corrosion cracking, similar to that of Alloy 500.


However Alloy 400 has much lower strength than Alloy K500 (Alloy 500, Monel® K500, UNS N05500, 2.4375), which has been developed to exhibit much superior mechanical properties, with the yield strength up to four times higher, and the tensile strength up to twice that of Alloy 400. This superior mechanical performance of Alloy 500 is due to the addition of titanium and aluminium (3-4% in total) and complex manufacturing process.


Columbia Metals offers a wide range stocks of Alloy K500 from ½” to 3.1/4” diameter and Alloy 400 from 4mm to 90mm diameter in solid round bar.

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