Alloy 400 - UNS N04400

Alloy 400, UNS N04400, is commonly associated with QQ-N-281 Class A - ASTM B127 - ASTM B164 - ASTM B165 - ASTM B564.
Alloy 400 is commonly known as Monel® 400. Alloy 400 is a Nickel-Copper alloy.
Mechanical properties here.


Ni C Mn S Si Cu Fe
Max % 0.3 2.00 0.024 0.5 34.0 2.50
Min % 63.0 28.0

Typical Inventory

Round Bar, Plate, Tubing, Pipe, Flange

Product Description

Alloy 400, also called Monel® 400, is a Nickel-Copper alloy that is highly resistant to sea water and steam at high temperatures as well as to salt and caustic solutions.

As a nickel-copper alloy, alloy 400 has excellent corrosion resistance in a wide variety of media. Alloy 400 is characterized by its general corrosion resistance, good weldability, and moderate to high strength in the tempered conditions. This alloy has excellent resistance to rapidly flowing and warm seawater, brackish water, and steam. It is particularly resistant to hydrochloric and hydrofluoric acids when they are de-aerated. This alloy is slightly magnetic at room temperature. Alloy 400 is widely used in the chemical, oil, and marine engineering industries.

General Data

  • Alloy 400 displays strong corrosion resistance in an extensive range of marine and chemical environments, including those containing pure water, nonoxidizing mineral acids, salts and alkalis.
  • This alloy is more resistant than pure nickel under reducing conditions and more resistant than pure copper under oxidizing conditions.
  • Alloy 400 displays good mechanical properties - even in environments with subzero temperatures up to about 480C.
  • Alloy 400 shows good resistance to sulfuric and hydrofluoric acids. Aeration however will result in increased corrosion rates. This alloy may be used to handle hydrochloric acid, but the presence of oxidizing salts will greatly accelerate corrosive attack.
  • Resistance to neutral alkaline and acid salts is shown in Alloy 400, but the alloy displays poor resistance with oxidizing acid salts ,such as ferric chloride.
  • Alloy 400 has excellent resistance to chloride ion stress corrosion cracking.


  • Feed water and steam generator tubing.
  • Brine heaters, sea water scrubbers in tanker inert gas systems.
  • Sulfuric acid and hydrofluoric acid alkylation plants.
  • Pickling bath heating coils.
  • Heat exchangers in a variety of industries.
  • Transfer piping from oil refinery crude columns.
  • Plant for the refining of uranium and isotope separation in the production of nuclear fuel.
  • Pumps and valves used in the manufacture of perchlorethylene, chlorinated plastics.
  • Monoethanolamine (MEA) reboiling tube.
  • Cladding for the upper areas of oil refinery crude columns.
  • Propeller and pump shafts.

Mechanical Properties

The typical properties listed can usually be provided in rounds, sheet, strip, plate, & custom forgings. We have the equipment to produce small quantities in special sizes to meet our customers’ specific needs.

Ultimate Tensile (ksi) Yield Strength (ksi) Elong. % in 2 in.
Min 185 150 12
Max 202.3 170.4 20.3

Common Specifications

Please, note that the specs listed are for reference and are not comprehensive nor indicative of the actual specifications listed on the Material Test Report (MTR). If you have a special spec requirement, then please reach out to our sales department at 1-800-472-5569.

Form Standard
Metal Type UNS N04400
Bar ASTM B164, QQ-N-281
Sheet ASTM B127, QQ-N-281, DIN 17750
Plate ASTM B127, QQ-N-281
Pipe ASTM B165
Tube ASTM B165
Forging ASTM B564
Weld Wire FM 60/ ERNiCu-7/ 17753
Weld Electrode FM 190 ENiCu-7
Din 2.4360


Nickel and cobalt based alloys can be difficult to machinine. However, it should be emphasized that these alloys can be machined using conventional production methods at satisfactory rates. These alloys harden rapidly, generate high heat during cutting, weld to the cutting tool surface and offer high resistance to metal removal because of their high shear strengths. The following are key points which should be considered during machining operations:

  • CAPACITY - Machine should be rigid and overpowered as much as possible.
  • RIGIDITY - Work piece and tool should be held rigid. Minimize tool overhang.
  • TOOL SHARPNESS - Make sure tools are sharp at all times. Change to sharpened tools at regular intervals rather than out of necessity. A 0.015 inch wear land is considered a dull tool.
  • TOOLS - Use positive rake angle tools for most machining operations. Negative rake angle tools can be considered for intermittent cuts and heavy stock removal. Carbide-tipped tools are suggested for most applications. High speed tools can be used, with lower production rates, and are often recommended for intermittent cuts.
  • POSITIVE CUTS - Use heavy, constant, feeds to maintain positive cutting action. If feed slows and the tool dwells in the cut, work hardening occurs, tool life deteriorates and close tolerances are impossible.
  • LUBRICATION - lubricants are desirable. Soluble oils are recommended especially when using carbide tooling.

Ulbrich's information on alloy 400

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