Monel Alloy 400 Fasteners

Nickel-Copper Alloy – Seawater, Hydrofluoric Acid & Marine Service

Buy Monel Alloy 400 (UNS N04400 / Werkstoff 2.4360 / ASTM B164) bolts, stud bolts, heavy hex nuts, socket cap screws, and custom CNC fasteners from Exotic Alloy. Monel 400 is a binary nickel-copper alloy containing approximately 67% Ni and 30% Cu, offering exceptional resistance to seawater, hydrofluoric acid, caustic alkalis, and a wide range of organic and reducing media from sub-zero to 480°C (900°F).

Exotic Alloy manufactures Monel 400 fasteners conforming to ASTM B164, ASME SB-164, and NACE MR0175 in metric M6–M100 and imperial ¼"–4" sizes with full EN 10204 3.1 material test certificates for marine engineering, desalination, chemical processing, and oil & gas industry applications.

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Technical Data

Alloy 400 Specifications

Chemical Composition — Monel Alloy 400 (wt. %)

Element	Ni	Cu	Fe	Mn	Si	C	S
Min %	63.00	28.00	–	–	–	–	–
Max %	Balance	34.00	2.50	2.00	0.50	0.30	0.024

Mechanical Properties — Monel Alloy 400

Condition	UTS (MPa)	YS 0.2% (MPa)	Elongation (%)	Hardness
Annealed (Hot-Finished Bar)	517–620	207–345	35–50	≤ 110 HB
Cold-Drawn (1/4 Hard)	620–793	414–621	15–30	≤ 180 HB
Cold-Drawn (1/2 Hard)	793–896	621–758	10–20	≤ 200 HB
Cold-Drawn (Full Hard)	896+	758+	2–10	≤ 225 HB

Physical Properties

Density	8.80 g/cm³
Melting Range	1300–1350°C (2372–2462°F)
Specific Heat Capacity	427 J/kg·K at 20°C
Thermal Conductivity	21.8 W/m·K at 100°C
Thermal Expansion	13.9 µm/m·°C (20–100°C)
Electrical Resistivity	0.547 µΩ·m

Equivalent Grades & Standards

UNS	Werkstoff / DIN	EN / BS	AFNOR
N04400	2.4360	NiCu30Fe	NU30

Key Specifications: ASTM B164 (Bar/Rod) / ASTM B127 (Plate/Sheet) / ASTM B163 (Tube) / ASTM B564 (Forgings)

Machinability: Monel 400 work-hardens less severely than Inconel grades, giving it better machinability ratings. Use sharp carbide tooling, moderate speeds (60–100 SFM), and continuous flood cooling with soluble cutting oil. Heavy feeds are preferred to keep the cutting edge continuously engaged and minimize rubbing and work-hardening ahead of the cut.

Welding: Monel 400 is readily welded by GTAW (TIG), GMAW (MIG), and SMAW using Monel 60 (ERNiCu-7) filler wire or Monel 190 electrode (ENiCu-7). Pre-heat is not required for sections under 13 mm. Keep inter-pass temperature below 100°C. Hot cracking is essentially absent in the weld zone.

Forging: Hot forge between 925–1175°C (1700–2150°F). The alloy has excellent hot workability. Below 900°C (1650°F) forging is not recommended as flow stress increases sharply. Cold forging is feasible with intermediate anneals at 760–870°C (1400–1600°F) to restore ductility.

Heat Treatment: Anneal at 760–870°C (1400–1600°F) for light sections, or 870–980°C (1600–1800°F) for heavier stock. Rapid cool (air or water quench) is preferred to avoid slow-cooling embrittlement. Monel 400 is not age-hardenable; strengthening is achieved only by cold work.

Monel 400 offers outstanding resistance to seawater (flowing) up to 29°C, hydrofluoric acid across all concentrations and temperatures (unique among alloys), sulfuric acid below 85% concentration at ambient temperatures, and strongly alkali solutions. High nickel provides immunity to chloride-induced stress corrosion cracking. Not recommended for strongly oxidizing acids, moist chlorine, or mercury-contaminated environments.

Key Characteristics

Outstanding resistance to seawater, brine, and hydrofluoric acid corrosion.
High nickel base provides immunity to chloride stress-corrosion cracking.
Good mechanical strength retainable from cryogenic temperatures to ~480°C.
Excellent resistance to alkalis, caustic soda, and reducing acids.
Superior biofouling resistance and marine corrosion resistance.

Typical Applications

Marine engineering: propeller shafts, pump shafts, and ship hardware.
Desalination plants: brine heater bolting and flash chamber hardware.
Offshore oil & gas: subsea Christmas tree fasteners and wellhead hardware.
Chemical processing: hydrofluoric acid plant bolting and valve components.
Naval engineering: submarine hull fittings and seawater system hardware.

Alloy 400