Monel Fasteners – Monel 400 & K-500 Bolts, Nuts, Studs & Screws
What are Monel fasteners?
Monel fasteners are bolts, nuts, studs, screws and washers made from nickel-copper alloys – mainly Monel 400 (UNS N04400) and the age-hardened Monel K-500 (UNS N05500). They are the standard choice for seawater, brine and hydrofluoric acid, where stainless steel fasteners pit or crack. Bolts and studs are supplied to ASTM F468, nuts to ASTM F467, made from ASTM B164 / B865 bar.
Monel Fasteners – Quick Facts
- Grades: Monel 400, K-500, 405 (free-machining), R-405 and 401
- Specifications: ASTM F468 (bolts, screws, studs), ASTM F467 (nuts); bar to ASTM B164 (400 / 405), B865 (K-500)
- Strength: 400 – 80–130 ksi tensile; K-500 – 130–180 ksi tensile (F468 full-size, ¼”–¾”)
- Types: hex bolts, heavy hex bolts, studs, stud bolts, threaded rod, nuts, socket screws, washers
- Certificate: EN 10204 3.1 with mechanical and chemical results
ASC LLP, Mumbai, supplies Monel fasteners from stock and to drawing. See the full Monel product range and other nickel alloy fasteners.
Monel Fastener Grades
| Grade | UNS | Main feature | Fastener page |
| Monel 400 | N04400 | Ni-Cu, solid-solution; best general seawater and HF resistance | Monel 400 fasteners |
| Monel K-500 | N05500 | Ni-Cu + Al + Ti, age-hardened – about 2–3× the yield strength of 400 | Monel K-500 fasteners |
| Monel 405 | N04405 | 400 with added sulphur for free machining – screw-machine parts | Monel 405 fasteners |
| Monel R-405 | N04405 | Trade name for free-machining Monel 405 | Monel R-405 fasteners |
| Monel 401 | N04401 | Lower-nickel Ni-Cu alloy for electrical and electronic parts | Monel 401 fasteners |
Mechanical Properties – ASTM F468 Bolts, Screws & Studs
| Grade & size | F468 marking | Hardness | Full-size tensile | Yield (min) | Elongation (min) |
| Monel 400, ¼” – ¾” | F 468U | 75 HRB – 25 HRC | 80 – 130 ksi | 40 ksi | 20% |
| Monel 400, ⅞” – 1½” | F 468U | 60 HRB – 25 HRC | 70 – 130 ksi | 30 ksi | 20% |
| Monel K-500, ¼” – ⅞” | F 468W | 24 – 37 HRC | 130 – 180 ksi | 90 ksi | 20% |
Elongation is measured on machined specimens. Nuts to ASTM F467 are made in the matching grades (400, 405, K-500). Always specify the F468 / F467 grade on the order so the right heat treatment and marking are applied.
Monel Fastener Types & Sizes
| Fastener type | Size range (typical) | Standard dimensions |
| Hex & heavy hex bolts | ¼” – 2″ (M6 – M52) | ASME B18.2.1 / ISO 4014, 4017 |
| Studs & stud bolts | ¼” – 2½”, any length | ASME B16.5 flange bolting, B18.31.2 |
| Hex & heavy hex nuts | ¼” – 2½” | ASME B18.2.2 / ISO 4032 |
| Socket head cap screws | #4 – 1½” | ASME B18.3 / ISO 4762 |
| Threaded rod | ¼” – 2″, up to 3 m | UNC / UNF / metric |
| Washers | To match | ASME B18.21.1 / ISO 7089 |
Special profiles, metric threads and non-standard lengths are machined to drawing.
Monel Fastener Specifications
| Standard | Covers |
| ASTM F468 / ASME SF468 | Nonferrous bolts, hex cap screws, socket screws and studs (Ni-Cu alloys 400, 405, 500) |
| ASTM F467 / ASME SF467 | Nonferrous nuts in the same alloys |
| ASTM B164 / ASME SB164 | Monel 400 and 405 rod, bar and wire (raw material) |
| ASTM B865 / ASME SB865 | Monel K-500 rod, bar and wire (raw material) |
| DIN / W.Nr. | 2.4360 (Monel 400), 2.4375 (Monel K-500) |
Chemical Composition – Monel 400 vs K-500
| Element (wt %) | Monel 400 | Monel K-500 |
| Nickel (Ni) | 63.0 min | 63.0 – 70.0 |
| Copper (Cu) | 28.0 – 34.0 | Balance (≈ 27 – 33) |
| Aluminium (Al) | – | 2.30 – 3.15 |
| Titanium (Ti) | – | 0.35 – 0.85 |
| Iron (Fe) | 2.5 max | 2.0 max |
| Manganese (Mn) | 2.0 max | 1.5 max |
| Carbon (C) | 0.3 max | 0.25 max |
| Silicon (Si) | 0.5 max | 0.5 max |
| Sulphur (S) | 0.024 max | 0.01 max |
The aluminium and titanium in K-500 form fine Ni₃(Al,Ti) precipitates during age hardening, which give it much higher strength than Monel 400.
Physical Properties
| Property (approx.) | Monel 400 | Monel K-500 |
| Density | 8.80 g/cm³ | 8.44 g/cm³ |
| Melting range | 1,300 – 1,350 °C | 1,315 – 1,350 °C |
| Modulus of elasticity | ≈ 179 GPa (26 × 10⁶ psi) | ≈ 179 GPa (26 × 10⁶ psi) |
| Thermal conductivity | ≈ 22 W/m·K | ≈ 17 W/m·K |
| Magnetic behaviour | Slightly magnetic at room temperature | Non-magnetic down to about −100 °C |
Corrosion Resistance – Where Monel Fasteners Excel
- Seawater and brine: very low corrosion rates in flowing seawater; resistant to chloride stress-corrosion cracking that affects austenitic stainless steels.
- Hydrofluoric acid: one of the few alloys used in HF alkylation units and HF handling.
- Alkalis and neutral salts: excellent resistance to caustic soda and salt solutions.
- Limits: attacked by oxidising acids (nitric), oxidising salts (ferric and cupric chlorides) and aerated or hot mineral acids; sulphuric acid only when dilute and de-aerated.
- Galvanic contact: Monel is noble – avoid bolting it directly to aluminium or carbon steel in seawater without insulation.
Applications of Monel Fasteners
| Industry | Typical Monel fastener uses | Grade |
| Marine & shipbuilding | Hull fittings, propeller and rudder assemblies, deck hardware | 400, K-500 |
| Offshore oil & gas | Subsea bolting, valve and pump fasteners | K-500 |
| Chemical & refining | HF alkylation units, caustic and brine plants | 400 |
| Desalination & power | Seawater pumps, condensers, heat exchangers | 400 |
| Valves & pumps | Shafts, stems, bolting and impeller nuts | K-500, 405 |
Monel 400 or K-500 – Which Fastener?
- Monel 400: general seawater, brine and HF service at moderate loads; easier to obtain and lower cost.
- Monel K-500: high-strength bolting, subsea and pump/valve applications needing 90 ksi+ yield with the same corrosion resistance.
- Monel 405 / R-405: high-volume machined nuts and screws where free machining matters more than maximum corrosion resistance.
Matching Monel products: Monel flanges, Monel fittings, Monel pipes and Monel bars.
Why Buy Monel Fasteners from ASC LLP?
- Correct grade and marking: F468 / F467 grades with heat-treatment records and 3.1 certificates.
- Full range: Monel 400, K-500, 405, R-405 and 401 – bolts, studs, nuts, screws, washers and threaded rod.
- Custom fasteners: non-standard lengths, threads and profiles machined to drawing.
- Testing: PMI, hardness, tensile and proof-load tests; third-party inspection on request.
- Export packing and regular shipments to the Middle East, Europe, USA and Asia.
Send grade, fastener type, size, length and quantity to sales@amardeepsteel.com or call 022-67439130.
Frequently Asked Questions – Monel Fasteners
What are Monel fasteners used for?
Monel fasteners are used where seawater, brine, hydrofluoric acid or alkalis would corrode stainless steel – in marine and offshore hardware, desalination plants, HF alkylation units, and pump and valve assemblies.
What is the difference between Monel 400 and K-500 fasteners?
Monel 400 is a solid-solution nickel-copper alloy with 80–130 ksi tensile strength in F468 bolts. Monel K-500 adds aluminium and titanium and is age-hardened to 130–180 ksi tensile and 90 ksi minimum yield, with similar corrosion resistance.
Which ASTM standard covers Monel bolts and nuts?
Monel bolts, screws and studs are covered by ASTM F468, and Monel nuts by ASTM F467. The raw bar is ASTM B164 for Monel 400 and 405, and ASTM B865 for Monel K-500.
Are Monel fasteners magnetic?
Monel 400 is slightly magnetic at room temperature because its Curie point is close to ambient. Monel K-500 is non-magnetic down to about −100 °C.
Can Monel fasteners be used with stainless steel or aluminium?
Monel is more noble than aluminium and carbon steel, so in seawater it can cause galvanic corrosion of those metals. Use insulating washers and sleeves, or match fastener and part materials.
What is Monel 405 used for in fasteners?
Monel 405 is Monel 400 with added sulphur to improve machinability. It is used for high-volume machined nuts and screws where free machining is more important than maximum corrosion resistance.
Global Reach
ASC LLP supplies nickel-alloy fasteners, pipes, fittings and flanges to marine, offshore, chemical and power customers worldwide, with prompt delivery and full documentation. Buyers in the USA, Europe, the Middle East and Asia rely on our Monel fasteners for certified material and traceability.
Countries We Export To
UNITED STATES, EUROPE, UK, UAE, SAUDI ARABIA, OMAN, KUWAIT, JORDAN, QATAR, INDONESIA, MALAYSIA, BRAZIL, SPAIN, ITALY, FRANCE, GERMANY, BAHRAIN, SRI LANKA, AZERBAIJAN, AUSTRALIA, AUSTRIA, PHILIPPINES, TURKEY, RUSSIA, IRAN, IRAQ, CANADA, KOREA, JAPAN, YEMEN, FINLAND, ZIMBABWE, HUNGARY, PORTUGAL, VIETNAM, MOROCCO, THAILAND, SOUTH AFRICA, MEXICO, SINGAPORE, GREECE, KUWAIT, POLAND, NEW ZEALAND, SWEDEN, SWITZERLAND, BELGIUM, BHUTAN, BANGLADESH, TAIWAN, ROMANIA, CAMBODIA, KAZAKHSTAN, AFGHANISTAN.
