Monel 400: Properties, Temperature Limits & Marine Applications

← Back to Knowledge Center

Overview

Monel 400 (UNS N04400 / W.Nr. 2.4360) is a nickel-copper alloy with approximately 67% nickel and 30% copper content. It is one of the most widely used nickel alloys due to its excellent combination of corrosion resistance, strength, and fabricability. Monel 400 is particularly renowned for its outstanding resistance to seawater, hydrofluoric acid, and alkaline environments. The alloy maintains excellent mechanical properties from sub-zero temperatures up to approximately 480°C (900°F). Its solid-solution strengthened structure provides excellent ductility and toughness, making it readily formable and weldable.

Chemical Composition (ASTM B164 / ASTM B165)

The chemical composition of Monel 400 is closely controlled to achieve its characteristic corrosion resistance and mechanical properties. The nickel-copper ratio is optimized for resistance to seawater and reducing acid environments.

Element	Min %	Max %
Nickel (Ni)	63.0	Balance
Copper (Cu)	28.0	34.0
Iron (Fe)	—	2.5
Manganese (Mn)	—	2.0
Carbon (C)	—	0.30
Silicon (Si)	—	0.50
Sulfur (S)	—	0.024

Physical Properties

Monel 400 has a face-centered cubic (FCC) crystal structure, which provides excellent ductility and toughness at both room and cryogenic temperatures. The alloy's thermal and electrical conductivity are lower than copper but significantly higher than most stainless steels.

Property	Value	Unit
Density	8.83	g/cm3
Melting Point	1350	°C
Specific Heat (21°C)	427	J/kg·K
Thermal Conductivity (21°C)	21.8	W/m·K
Electrical Resistivity (21°C)	0.51	μΩ·m
Modulus of Elasticity (21°C)	179.5	GPa
Mean Coefficient of Thermal Expansion (21-93°C)	13.9	μm/m·°C
Curie Temperature	50	°C

Mechanical Properties at Room Temperature

The mechanical properties of Monel 400 depend on the degree of cold working and heat treatment. The data below represents typical values for hot-finished and annealed bar per ASTM B164.

Property	Hot-Finished	Cold-Drawn
Tensile Strength	550 MPa (80 ksi)	690 MPa (100 ksi)
Yield Strength (0.2% offset)	240 MPa (35 ksi)	550 MPa (80 ksi)
Elongation in 2 inches	35%	22%
Hardness (Rockwell B)	65-75 HRB	85-95 HRB

High-Temperature Mechanical Properties

Monel 400 maintains good strength at moderate temperatures but is not typically used for high-temperature applications above 480°C (900°F) due to oxidation and loss of strength. The alloy is ideal for applications requiring good mechanical properties at sub-zero and moderate temperatures.

Temperature (°C)	Tensile Strength (MPa)	Yield Strength (MPa)	Elongation (%)
21 (Room)	550	240	35
93	517	228	37
204	490	214	38
316	483	207	39
427	476	200	40
538	434	193	42

Corrosion Resistance

Monel 400 is renowned for its exceptional corrosion resistance in a wide variety of environments, particularly in seawater and reducing acid conditions. The alloy's high copper content provides excellent resistance to sulfuric acid and hydrofluoric acid, while the high nickel content provides resistance to alkaline environments.

Resistance to Specific Media:

• Seawater and Marine Environments: Exceptional resistance to pitting, crevice corrosion, and stress corrosion cracking in seawater at all temperatures. One of the best alloys for marine propeller shafts, pump shafts, and seawater valves. Biofouling resistance is also excellent.
• Hydrofluoric Acid: One of the few alloys that can withstand all concentrations of hydrofluoric acid up to the boiling point. Widely used in alkylation units and fluorine chemical production.
• Sulfuric Acid: Good resistance to sulfuric acid at concentrations up to 80% and temperatures up to 80°C. Widely used in pickling tanks and sulfuric acid handling equipment.
• Alkaline Environments: Excellent resistance to caustic soda (NaOH) and caustic potash (KOH) at all concentrations and temperatures. Used in caustic evaporators and alkaline piping systems.
• Chloride Stress Corrosion Cracking: Highly resistant to chloride-induced stress corrosion cracking, unlike 300-series stainless steels which are susceptible.
• Dilute Hydrochloric Acid: Good resistance to dilute hydrochloric acid at moderate temperatures. Superior to most stainless steels in this environment.

Applications

The exceptional corrosion resistance of Monel 400 in seawater and reducing acids makes it the material of choice for numerous critical applications:

• Marine Engineering: Propeller shafts, pump shafts, seawater valves, strainers, and piping systems. The alloy's resistance to seawater corrosion and biofouling is unmatched for these applications.
• Chemical Processing: Hydrofluoric acid handling equipment, sulfuric acid processing tanks, and alkaline chemical equipment. Used in alkylation units, fluorine production, and caustic soda plants.
• Oil and Gas: Downhole equipment, wellhead components, and production tubing in sour gas environments. The alloy resists sulfide stress cracking and chloride pitting.
• Power Generation: Feedwater heaters, condenser tubes, and boiler components. The alloy's resistance to fresh water and steam corrosion is excellent.
• Desalination: Evaporator tubes, heat exchanger tubes, and brine handling systems. Monel 400 is widely used in multi-stage flash (MSF) and multi-effect distillation (MED) plants.
• Electronics: Electrical and electronic components, transistor caps, and computer components. The alloy's good electrical conductivity and magnetic properties are utilized.

Available Product Forms

Hangbo Alloy Group manufactures and supplies Monel 400 in the following product forms, conforming to ASTM and ASME specifications:

• Round Bars: ASTM B164, diameters from 6 mm to 300 mm, hot-finished or cold-drawn, annealed or stress-relieved.
• Seamless Tubes & Pipes: ASTM B165, ASTM B163, sizes from 6 mm OD to 219 mm OD, various wall thicknesses.
• Plates & Sheets: ASTM B127, thicknesses from 0.5 mm to 50 mm, hot-rolled or cold-rolled.
• Forgings: ASTM B564, custom flanges, rings, and fittings per customer drawing.
• Welding Wire: AWS A5.14 ERNiCu-7, diameters 0.8 mm to 5.0 mm, precision-wound coils.

Related Standards

Standard	Description
ASTM B127	Plate, Sheet, and Strip
ASTM B164	Bar and Rod
ASTM B165	Seamless Pipe and Tube
ASTM B163	Condenser and Heat-Exchanger Tube
ASTM B564	Forgings
ASTM B366	Fittings
AWS A5.14	Welding Wire (ERNiCu-7)
ASME SB-127	Boiler and Pressure Vessel Code
ASME SB-165	Boiler and Pressure Vessel Code

Contact Us for Monel 400

Hangbo Alloy Group maintains extensive inventory of Monel 400 in all standard product forms. We provide mill test certificates, third-party inspection reports (SGS, TUV), and custom processing services including cutting, machining, and surface finishing.

For quotations, material certifications, or technical consultation, contact our sales team or call +86-136-1165-6360. We typically respond within 10 minutes.