Monel Flanges
Monel 401 Flanges (UNS N04401) Monel Alloy Flanges
Monel 401 Flanges (UNS N04401) are nickel-copper alloy flanges engineered for high-performance applications requiring excellent strength, thermal conductivity, and corrosion resistance. Known for their low-temperature ductility and superior weldability, Monel 401 flanges are widely used in power generation, marine, chemical processing, and furnace components.
As a controlled expansion alloy, Monel 401 maintains mechanical stability over a wide temperature range and provides good resistance to corrosion in neutral and alkaline environments. These flanges deliver reliable performance in conditions where ordinary stainless steels may fail.
Key Features
High strength and toughness at both high and low temperatures
Excellent corrosion resistance in seawater, alkaline media, and mild acids
Good thermal conductivity suitable for heat transfer systems
Controlled thermal expansion properties
Excellent weldability and fabricability
Resistant to stress corrosion cracking
Maintains mechanical properties in cryogenic environments
Non-magnetic in annealed condition
Specification
| Specification | Details |
|---|---|
| Standard | ASTM B164 / ASME SB164 |
| UNS | N04401 |
| Werkstoff Nr. | – |
| Flange Types | WNRF, SORF, BLRF, SWRF, Threaded, Lap Joint, RTJ |
| Size Range | ½″ to 48″ |
| Pressure Rating | 150#, 300#, 600#, 900#, 1500#, 2500# |
| Dimension Standards | ASME B16.5, B16.47, B16.48 |
| Manufacturing Process | Forged / Machined / Plate-cut |
Equivalent Grades
| Standard | Grade |
|---|---|
| UNS | N04401 |
| AFNOR | – |
| BS | – |
| EN | – |
Available Sizes
Flange Size: ½” to 48″
Thickness: SCH 10 – SCH XXS
Custom dimensions available on request
Chemical Composition
| Element | % |
|---|---|
| Nickel (Ni) | 38 – 45 |
| Copper (Cu) | 55 – 63 |
| Iron (Fe) | ≤ 1.5 |
| Manganese (Mn) | ≤ 2.0 |
| Carbon (C) | ≤ 0.15 |
| Silicon (Si) | ≤ 0.5 |
| Sulfur (S) | ≤ 0.02 |
Mechanical Properties
| Property | Value |
|---|---|
| Tensile Strength | 485 MPa min |
| Yield Strength | 175 MPa min |
| Elongation | 30% min |
| Hardness | 95 HRB max |
| Density | 8.8 g/cm³ |
Physical Properties
| Property | Value |
|---|---|
| Melting Range | 1280 – 1350°C |
| Electrical Resistivity | 0.54 μΩ·m |
| Thermal Conductivity | 21 W/m·K |
| Specific Heat Capacity | 0.377 J/g·°C |
| Modulus of Elasticity | 179 GPa |
Weld Neck Flanges (WNRF)
Slip-On Flanges (SORF)
Blind Flanges (BLRF)
Socket Weld Flanges (SWRF)
Threaded Flanges
Lap Joint Flanges
Ring Type Joint (RTJ) Flanges
Orifice Flanges
Long Weld Neck Flanges
Custom Fabricated Flanges
Corrosion Resistance
Monel 401 exhibits good corrosion resistance in:
Neutral and alkaline salt solutions
Freshwater and seawater environments
Mild acids such as acetic and hydrofluoric acid
Alkaline caustic solutions
High-temperature steam
Stress-corrosion cracking environments
It is less resistant to strongly oxidizing acids.
Heat Resistance
Performs well up to 600°C in continuous service
Good strength retention at elevated temperatures
Resistant to thermal shock
Excellent oxidation resistance
Stable mechanical behavior across varying temperatures
Heat Treatment
Annealing: 850–1000°C followed by slow cooling
Stress Relieving: 500–700°C
Monel 401 is not age-hardenable, but properties improve through cold working
Welding
Excellent weldability using GTAW, GMAW, SMAW
No preheating required
Post-weld annealing recommended for critical applications
Filler metals commonly used: Monel 67 or compatible Ni-Cu fillers
Fabrication
Easily fabricated by machining, forming, forging, and cold working
Hot working temperature: 850–1200°C
Requires high-speed steel or carbide tools for machining
Work-hardening rate is moderate
Applications
Steam turbine components
Furnace parts
Marine and offshore equipment
Heat exchangers & condensers
Chemical processing units
High-temperature fasteners
Power generation equipment
Pump and valve components
Heat transfer piping
Aerospace and turbine exhaust systems