Monel K500: properties, composition, uses and standards
Monel K500 is a age-hardenable nickel–copper alloy with aluminium and titanium, chosen for high-strength pump shafts, bolting and springs in seawater. UNS N05500, W.Nr 2.4375, density 8.44 g/cm³.
What is Monel K500?
Monel K500 is a age-hardenable nickel–copper alloy with aluminium and titanium. Engineers choose it for high-strength pump shafts, bolting and springs in seawater. It is also known as Alloy K-500, UNS N05500, W.Nr 2.4375, Age-hardened Monel.
- UNS
- N05500
- W.Nr
- 2.4375
- EN
- NiCu30Al
- Trade names
- Monel K-500 · Nicorros Al
- Density
- 8.44 g/cm³
- Melting range
- 1315 – 1350 °C
- Magnetic
- Non-magnetic to about −100 °C
Chemical composition and what each element does
| Element | Weight % |
|---|---|
| Nickel (+Co) | 63.0 min |
| Copper | 27.0 – 33.0 |
| Aluminium | 2.30 – 3.15 |
| Titanium | 0.35 – 0.85 |
| Iron | 2.0 max |
| Manganese | 1.5 max |
| Carbon | 0.25 max |
| Silicon | 0.5 max |
Per ASTM B865 for UNS N05500.
Aluminium and titanium let K500 be age-hardened to about three times the strength of Monel 400.
Keeps the seawater corrosion resistance of Monel 400.
Chosen where a part needs strength and seawater resistance together.
In sour service, check hardness limits in NACE MR0175 before specifying.
Mechanical properties
| Property | Value |
|---|---|
| Tensile strength | 965 MPa · 140 ksi |
| Yield strength 0.2% | 690 MPa · 100 ksi |
| Elongation | 20% |
Age-hardened bar, typical minimums — confirm the condition on order. Values for pipe, bar and forgings differ slightly — see the product standard.
Where Monel K500 is used
- Marine. Propeller and pump shafts. Industry →
- Oil & gas. Drill collars, valve trim and bolting. Industry →
- Fasteners. High-strength seawater bolting. Industry →
Welding K500
The matching filler is ERNiCu-7 (non-ageing). Weld in the annealed condition, then age.
Keep heat input moderate and interpass temperature low, clean joints thoroughly, and pickle or passivate after welding where the service is corrosive.
Monel K500 compared with similar grades
| Grade | PREN | Choose it for |
|---|---|---|
| Monel K500 | — | High-strength pump shafts, bolting and springs in seawater |
| Monel 400 | — | Seawater, hydrofluoric acid and marine service |
| Inconel 718 | — | Very high strength at temperatures up to about 650 °C |
| Super Duplex 2507 | ≈ 42 | Seawater and high-chloride service where strength also matters |
Monel K500 standards by product
| Product | Standard |
|---|---|
| Monel K500 fasteners | ASTM B865 |
| Monel K500 flanges | ASTM B865 |
Buying Monel K500: what to specify
- The product standard and the UNS or designation — for example ASTM B865 UNS N05500.
- Size, thickness or schedule, and quantity in pieces and kg or metres.
- Heat-treatment condition where the standard offers a choice.
- Certificate: EN 10204 3.1 as standard, 3.2 if a third party must witness.
- NACE MR0175 / ISO 15156 compliance if the service contains H₂S.