Specifications
Surface Treatments
Certifications
- ISO 9001 - 2015 Certified
- PED 2014/68/EC
- NACE MR0175/ISO 15156-2
- NORSOK M-650
- DFAR
- MERKBLATT AD 2000 W2/W7/W10
What is Monel 400? Nickel-Copper Alloy (UNS N04400) - Composition, Uses, Properties
Monel 400 (also Alloy 400, Nickel 400, UNS N04400, Werkstoff 2.4360) is a nickel-copper alloy at 63 to 70 percent nickel and 28 to 34 percent copper, with iron up to 2.5 percent, manganese up to 2.0 percent and carbon up to 0.30 percent. It is a single-phase FCC solid solution with no chromium, aluminium or titanium. Covered by ASTM B164, ASTM B127, ASTM B165, ASTM B564, ASTM F468, DIN 17743 and NACE MR0175 for sour service. Monel® is a registered trademark of Special Metals Corporation.
What is Monel 400 made of?
Monel 400 is roughly two-thirds nickel and one-third copper. The two metals dissolve fully into one FCC crystal lattice, so the alloy stays single-phase across the working temperature range. Iron, manganese, carbon, silicon and sulphur sit in solid solution. The absence of chromium is the key fact for HF service; the absence of aluminium and titanium separates Monel 400 from precipitation-hardened Monel K-500 (UNS N05500). Detail on chemical composition.
What is Monel 400 used for?
Monel 400 is specified where the joint sees hydrofluoric acid, flowing seawater, sour gas at NACE MR0175 limits, naval non-magnetic hardware or hot caustic soda. The canonical service environments:
| Service environment | Reason Monel 400 is specified | Reference |
|---|---|---|
| HF alkylation, HF storage | Default bolting per API RP 751; resists 70 to 95 percent HF | HF alkylation |
| Flowing seawater, brackish water | Resists chloride attack under flow; shipboard piping, condenser tubes | marine applications |
| Sour gas service (H2S) | ASTM F468 caps hardness at 25 HRC, tighter than NACE MR0175 35 HRC | sour service NACE |
| Naval non-magnetic hardware | Permeability close to 1.0 annealed; minesweeper fittings, bulkhead studs | magnetic permeability |
| Caustic soda (NaOH) up to 80 percent | Resists hot caustic; evaporator tubes, reboiler internals | corrosion resistance |
Common Monel metal uses across industries
Monel 400 use clusters into five groups. Oil and gas refining takes the largest volume on HF alkylation valves, flanges and bolting. Marine engineering uses it for pump shafts, propeller-shaft sleeves and raw-water piping. Chemical processing specifies it for HF and caustic vessels with the related fittings and flanges. Naval and defence use the non-magnetic and seawater behaviour for minesweeper hardware. Instrumentation uses thermowells and tubing where stainless cannot survive the process side.
Why Monel 400 is specified over stainless steel in these services
Austenitic stainless steel (304, 316L) survives by holding a chromium oxide film. That film fails in three places where Monel 400 holds: HF acid (chromium oxide dissolves in HF), hot caustic above 70 degrees Celsius (caustic SCC on stainless), and chloride-rich seawater above 60 degrees Celsius (pitting on stainless). Monel 400 does not depend on chromium; it depends on the nickel-copper matrix. Full comparison on Monel vs stainless steel.
What forms does Monel 400 come in?
The form is set by the governing ASTM spec: round bar and wire (B164), plate and sheet (B127), seamless pipe and tubing (B165), forging and flanges (B564), plus threaded rod, fasteners, bolts, nuts and washers (F467 and F468). All forms ship against EN 10204 type 3.1 MTC; type 3.2 is available for sour service and pressure equipment.
Frequently Asked Questions
What is Monel 400? A nickel-copper solid-solution alloy at 63 to 70 percent Ni and 28 to 34 percent Cu, registered as UNS N04400 and Werkstoff 2.4360.
What is Monel 400 used for? HF alkylation, seawater and brackish heat exchangers, sour gas to NACE MR0175, naval non-magnetic hardware and caustic soda vessels. Default bolting on HF alky units per API RP 751.
Is Monel 400 the same as Inconel? No. Monel 400 (UNS N04400) is nickel-copper with no chromium. Inconel 600 (UNS N06600) and Inconel 625 (UNS N06625) are nickel-chromium alloys for high-temperature oxidising service. Both names are trademarks of Special Metals Corporation; the chemistry differs.
Is Monel 400 magnetic? Annealed Monel 400 is nominally non-magnetic at room temperature, with relative permeability close to 1.0. Cold-worked or high-iron heats can show measurable permeability. Detail on magnetic permeability.
Does Monel 400 rust? No. It forms a nickel-copper oxide film that resists seawater, HF acid, dilute sulphuric acid and caustic soda. In stagnant seawater above 200 ppm chloride with oxygen depletion, pitting and crevice attack are possible.
Related Pages
Properties: chemical composition, mechanical properties, density, corrosion resistance, magnetic permeability, welding, machinability.
Standards and service: ASTM B164, ASTM B127, ASTM B564, ASTM F468, UNS N04400, NACE MR0175, HF alkylation, marine applications, sour service NACE.
Product forms: round bar, plate, sheet, seamless pipe, tubing, wire, forging, fasteners, bolts, nuts, flanges.
Request a Quote
For Monel 400 in any form against a specific ASTM B127, B164, B165, B564 or F468 brief, send drawing, quantity and certification class (EN 10204 type 3.1 or 3.2) to info@torqbolt.com or WhatsApp +91-22-66157017. Ex-Mumbai price plus heat-numbered MTC inside one working day; export through JNPT.
References
- ASTM B127 Nickel-Copper Alloy (UNS N04400) Plate, Sheet, Strip
- ASTM B164 Nickel-Copper Alloy Rod, Bar, Wire
- ASTM B564 Nickel Alloy Forgings, UNS N04400
- ASTM F468 / F468M Nonferrous Bolts and Studs
- DIN 17743 NiCu30Fe, Werkstoff 2.4360
- NACE MR0175 / ISO 15156-3 H2S-containing environments
- API RP 751 HF Alkylation Units
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