Material Basics – Monel

Alloy 400 Alloy K-500 alloy R-405 basic material information basic material used in piping Basic Materials Basic materials in piping basic materials used in piping Design and Engineering Material Material and corrosion Material Engineering Materials Monel Monel 400 piping material Piping Material specification Piping Material Specifications piping materials selection of piping material UNS N04400 UNS N04405 UNS N05500

Material Basics – Monel

Introduction to Material Basics – Monel

This blog provides, basic information about Monel 400 (UNS N04400), MONEL alloy K-500 (UNS N05500) and Monel Alloy R-405 (UNS N04405) material basics like, its properties, applications etc.

Monel is a high tensile strength nickel-copper alloy that was discovered in 1905. It was found to be highly resistant to atmospheric corrosion, to seawater/ salt water, various acid and alkaline solutions and steam at high temperatures as well as to salt and caustic solutions.

MONEL® 400 (UNS N04400)

Alloy 400 is is the basic nickel-copper alloy (Ni 66.5 Cu 31.5) widely used where excellent corrosion resistance in a wide variety of media and moderate high or low temperature properties are needed.. Excellent corrosion resistance over wide range of temperatures and conditions, good weldability and moderate to high strength characterize the alloy. Alloy 400 can be magnetic depending upon composition and previous work history.

Notched-bar impact test shows Monel 400 is very tough. Monel 400 has structural strength, yet ductile, and excellent corrosion resistance in most environments. Conventional shop working practices can be used to fabricate Monel 400.

The alloy has been used in a variety of applications. It has excellent resistance to rapidly flowing brackish water or seawater. It is particularly resistant to hydrochloric and hydrofluoric acids when they are de-aerated. The alloy is slightly magnetic at room temperature. The alloy is widely used in the chemical, oil and marine industries.


Characterized by;

  1. Good/ high general corrosion resistance – Corrosion resistance in an extensive range of marine and chemical environments, from pure water to non-oxidizing mineral acids, salts and alkalis.
  2. Good weldability
  3. Good mechanical properties from subzero temperatures up to about 480C.
  4. Slightly magnetic at room temperature
  5. Impervious to the effects of steam, gas, salt water, ammonia, calcium chloride, and the acids associated with food products even at high temperatures.
  6. This alloy is more resistant to nickel under reducing conditions and more resistant than copper under oxidizing conditions, it does show however better resistance to reducing media than oxidizing.
  7. Good resistance to sulphuric and hydrofluoric acids. Aeration however will result in increased corrosion rates. May be used to handle hydrochloric acid, but the presence of oxidizing salts will greatly accelerate corrosive attack.
  8. Resistance to neutral, alkaline and acid salts is shown, but poor resistance is found with oxidizing acid salts such as ferric chloride.
  9. Excellent resistance to chloride ion stress corrosion cracking


  1. Feed water and steam generator tubing, feed water heaters and other heat exchangers.
  2. Brine heaters, seawater scrubbers in tanker inert gas systems.
  3. Sulphuric acid and hydrofluoric acid alkylation’s plants.
  4. Pickling bat-heating coils.
  5. Heat exchangers in a variety of industries
  6. Petroleum refining and production equipment
  7. Transfer piping from oil refinery crude columns.
  8. Plant for the refining of uranium and isotope separation in the production of nuclear fuel
  9. Pumps and valves used in the manufacture of perchlorethylene, chlorinated plastics
  10. Monoethanolamine (MEA) reboiling tube
  11. Cladding for the upper areas of oil refinery crude columns
  12. Propeller and pump shafts
  13. Marine engineering – fixtures, fasteners, electrical, and electronic components
  14. In the electrical and marine field as acid and alkali tanks
  15. Chemical and hydrocarbon processing equipment, valves, pumps, shafts, fittings and hardware, fasteners, diaphragms, and connectors


The commonly used welding methods work well with this alloy. Matching alloy filler metal should be used. Monel alloy 400 can be easily welded, in all positions, using Monel 190 electrodes. For submerged arc, MIG and TIG welding, use Monel 60 filler wire.

If matching alloy is not available then the nearest alloy richer in the essential chemistry (Ni, Co, Cr, Mo) should be used.


Conventional machining techniques used for iron based alloys may be used. This alloy does work-harden during machining and has higher strength and “gumminess” not typical of steels. Heavy duty machining equipment and tooling should be used to minimize c


This alloy has good ductility and may be readily formed by all conventional methods. Because the alloy is stronger than regular steel it requires more powerful equipment to accomplish forming. Heavy-duty lubricants should be used during cold forming.

Cold forming requires forces between those of mild steel and AISI T304. Hot forming is readily accomplished within the range of 1200-2150°F.

Corrosion Resistance

Resists corrosion from water, including seawater, and resistant to chloride stress-corrosion cracking. Good corrosion resistance to sulfuric acid, hydrochloric acid, hydrofluoric acid, and alkalis.

Heat Treatment

Not heat treatable, but may be annealed after cold working.


No data, however the alloy is readily forged.

Hot Working

No data, but the alloy may be hot worked.

Cold Working

Cold forming may be done using standard tooling although plain carbon tool steels are not recommended for forming as they tend to produce galling. Soft die materials (bronze, zinc alloys, etc.) minimize galling and produce good finishes, but die life is low.


Annealing may be done at 1700 F. A stress-relief anneal may be done at 1050 F for 1 to 2 hours, followed by slow cooling.


Hardens due to cold work only.

Related Metals

  • Nicorros ™
  • Silverin 400(tm)
  • Nickelvac 400(tm)
  • CM 400(tm)


ASTM B17, B127, B163, B164 CLASS A, B165, B366, B513, B564, F467, F468, F96, QQ-N-281, CLA, MIL-N-894, MIL-T-842, MIL-N-24106, MIL-T-23520, MIL-T-1368, AMS 4544, 4574, 4575, 4675, 4730, 4731, 7233, UNS N04400, DIN 2.4360, DIN 2.4366.

For ASME add “SB” prefix to ASTM specification numerals.

Reference Bar Sheet Plate Tube Pipe Fittings Forgings All Forms
AMS 4675 X           X  
ASTM B127   X X          
ASTM B163       X X      
ASTM B366         X    
ASTM B564             X  
QQ-N-281 X
UNS N04400               X
DIN 2.4360 X
17752 X
17750 X X
17754 X
17751 X X
NA 13 X
3076 X
3072 X X
3074 X X



Item Description Grades
Monel Wire .003” To .250” 400 K500

Wire is spooled to order and sold by the foot or meter.


Item Description Grades
Monel Sheet .010” to .250” 400 K500

Sheet is cut to order and sold by the square inch or square foot.

Powder, Shot, Pellets, & Ingot

Item Description Grades
Monel Pellets 0.125”L X 0.250”D 400 K500
Monel Pellets 0.250”L X 0.250”D 400 K500

Powder, shot, pellets, and ingots are packaged to order and sold by the gram or kilogram.

MONEL® alloy R-405 (UNS N04405)

Alloy R-405 is a nickel-copper-sulphur alloy (Ni 66.5 Cu 31.5 S 0.04) (Similar to MONEL alloy 400) Solid solution strengthened alloy with high strength and toughness over a wide range of temperatures. Corrosion resistant and oxidation resistant to 1000°F. Controlled sulphur added for improved machinability over alloy 400. Water meter parts, screw machine products, fasteners, valve parts.

MONEL® alloy K-500 (UNS N05500)

Alloy K-500 is a non-magnetic nickel-copper alloy with the addition of Aluminium and titanium (Ni 65.5 Cu 29.5 Al 2.7, Ti 0.6). It is a age-hardenable version of MONEL alloy 400 for increased strength and hardness. It combines the corrosion resistant properties of Monel alloy 400 with the added advantage of extra strength and hardness achievable by precipitation hardening.

Alloy K-500 has added aluminum and titanium for age hardening. It is totally nonmagnetic and spark resistant. Good strength and ductility from -423 to 1200°F. Pump shafts, doctor blades and scrapers, oil well drill collars and instruments, electronic components, springs, valve trim, fasteners.

The alloy is non-magnetic. The alloy should be annealed when performing welding or forming operations, and the weldment then stress relieved before aging. This is true with any precipitation hardenable material, for optimum corrosion resistance. When heat-treated, the hardness can reach as high as Rc 35, and sometimes harder by specification.

Uses: K-500 is used for gyroscope application and anchor cable aboard minesweepers. It is also used for propeller shafts on a wide variety of vessels and exhibits high fatigue strength in seawater. There is also application in chemical process applications for handling of organic acids, caustic and dry chlorine.

Monel alloy K-500 is supplied in the following conditions:

  • Cold Drawn, Spring Temper, Soap Coated
  • Cold Drawn, Spring Temper
  • Cold Drawn, Annealed

This alloy should be welded when annealed and the weldment then stress relieved before aging. Curie temperature °F (annealed)-210 – (age hardened)- 150. Monel alloy K-500 should be welded with Monel 190 electrode or Monel 60 filler metal


Typical Analysis – Impurities In Percent

Element Monel – Alloy 400 Monel – Alloy K – 500
Aluminium – Al 2.7 to 2.75
Al + Ti 3.5
Carbon – C 0.3 Max
Copper – Cu 31.0 30.0
Iron – Fe 2.50 Max 2.0
Manganese – Mn 2.0 Max 1.50
Nickel – Ni 66.5 66.5 (63.0 Min.)
Silicon – Si 0.50 Max 0.50
Sulphur – S 0.024 Max 0.10
Titanium – Ti 0.5 to 0.6
Werkstoff Nr. 2.4375
UNS Designation N 04400 N 05500

Physical Properties

Physical Properties Alloy 400 K – 500
Density 8.85 g/cm3 (0.318 Lbs./Cu. In) 8.44 g/cm³ (0.305 lbs/in³)
Specific Heat 430 J/kg K 0.100 Btu/Lb./°F at 700 F
Electrical Resisitivity 51.3 micro ohms cm
Curie Temperature 7 to 10 C (20 – 50o F)
Melting Point Range 1300 to 1350 C (2370-24600 F)
Maximum Use Temperature in Air 4500 C
Thermal Expansion (106K) 15.8 (20300 C)
Coefficient of expansion at 200 – 1000C 13.9 – 14.1 (x10-6 K-1)
Modulus of Elasticity 185 GPa
Modulus of Elasticity – Tension 26.0
Modulus of Elasticity – Compression 26.0
Modulus of Elasticity – Torsion 9.5
Young’s Modulus 179 kN/mm² (26.00 x 106 psi)
Rigidity Modulus 66 kN/mm² (9.50 x 106 psi
Electrical Conductivity 4 0/o IACS
Electrical Ressistivity 48 – 58 Micro Ohm/ cm (µOhmcm)
Poisson’s Ratio 0.32
Brinnell Hardness No 125 – 190
Izod Impact 110-140 J m-1
Rockwell Hardness No. B 68
Thermal Conductivity @RTP 21.7(Wm-1K-1 )

Average Physical Properties of Alloy 400

Physical Property Temp., °F British Units Temp., °C Metric Units
Density Room 0.319lb. cu. in Room 8.83g/cm
20.1 micro ohm-in
20.9 micro ohm-in
22.0 micro ohm-in
22.4 micro ohm-in
23.2 micro ohm-in
0.51 micro ohm-m
0.53 micro ohm-m
0.56 micro ohm-m
0.57 micro ohm-m
0.59micro ohm-m
Mean Coefficient
of Thermal
7.7micro inches/in-°F
8.6micro inches/in-°F
8.8micro inches/in-°F
8.9micro inches/in-°F
13.9X10-6 m/m*K
15.5X10-6 m/m*K
15.8X10-6 m/m*K
16.0X10-6 m/m*K
151 Btu-in/ft-hr-°F
167 Btu-in/ft-hr-°F
193 Btu-in/ft-hr-°F
215 Btu-in/ft-hr-°F
238 Btu-in/ft-hr-°F
21.8 W/m*K
24.1 W/m*K
27.8 W/m*K
31.0 W/m*K
34.3 W/m*K
of Elasticity
Room 26.0X10 psi Room 179 GPa

Mechanical Properties

Mechanical Properties Alloy 400 K – 500
Tensile strength 79/90 Kpsi (485N/mm sq.)
Tensile strength – Annealed 700-750 N/mm² (100-109 Ksi)
Tensile strength – Spring Temper & Aged 1100-1380 N/mm² (160-200 Ksi)
Tensile strength – Cold Drawn Rod 100,000 psi  
Tensile strength – (Hot Finished and Aged Bar) 160,000 psi
Yield strength 24/40 Kpsi 130,000 psi
Yield strength –     Cold Drawn Rod 75,000 psi
Yield strength –    (Hot Finished and Aged Bar)
20 C Temp 195 N/mm sq.
100 C 150 N/mm sq.
200 C 135 N/mm sq.
300 C 130 N/mm sq.
400 C 130 N/mm sq.
Elongation in two inches 60/ 35% (35% Min)
Elongation – Cold Drawn Rod 28 %
Elongation -(Hot Finished and Aged Bar) 24 %
Density (nominal) 0.319 lbs/cubic inch
Recommended Service Temperature Minimum: -100°C (-148°F) Maximum: 260°C 500°F)
Heat Treatment After cooling age at 530-550°C for 4-6 hours, furnace cool to 450°C at a rate of 8-15°C/hour, then air cool

Minimum Room Temperature Tensile Data of Alloy 400
Form Condition Ultimate Tensile Strength, Ksi (MPa) Yield Strength at 0.2% offset Ksi(MPa) Elongation in 2in. (50.8mm) or 4D, percent
Sheet, Plate, Strip Annealed 70.0 (480) 28.0 (185) 35
Bar Annealed 70.0 (480) 25.0 (170) 35

Comparison of Corrosion Resistance

Letter Means Letter Means
A Excellent D Poor
B Good F Not Suitable
C Fair
Chrome 440 SS 302 SS 316 SS Brass Monel
Industrial Environment C B B B C C
Domestic Water D B A A C A
Steam D B A A B C
Salt Air F C A A C A
Sea Water F F A A C B
Food Products F B A A D D
Dairy Products F C A A D C
Fruit & Vegetable Juices F B B A D D
Hot Sulphite F F A B C A
Dye F D D D D A
Nitric Acid F F F F F F
Phosphoric Acid F F F A C C
Ammonia B C A A F A

Comparison of Rockwell Hardness

Rockwell Hardness
 Chrome Steel 52100 Rc 60-67
Corrosion Resisting Hardened Steel



Rc 58-65

Rc 52 min

Corrosion Resisting Unhardened Steel




Rc 25-39

Rc 25-39

Rc 25-39

Carbon Steel Rc 60 min
Aluminium 2017 Rb 54-72
Aluminium Bronze Rb 94-98
Brass Rb 75-87
Bronze Rb 75-98
Monel 400 Rb 85-95
K-Monel Rc 27 min
Tungsten Carbide Ra 84-91.5