Copper nickel alloys comprise 2 to 30% nickel and have high oxidation resistance and stress corrosion cracking resistance. Their high oxidation resistance is seen in moist air and steam. These alloys are thermally stable and possess moderate strength even when the temperature is high. The corrosion resistance and strength of these alloys are improved by the addition of manganese, iron, niobium, and or chromium. Copper nickel alloys also have good fabricability and high inherent resistance to biofouling.
The soluble nature of nickel in copper provides the copper nickel alloys with single phase alpha structures. The alpha dendrites in the cast structures contain a large amount of nickel starting from the center up to the edge of the dendrite. A large quantity of nickel is also present in interdendritic regions. The dendrite structure is broken by mechanical treatments. The alloying elements do not get homogenized even by repeated thermal and mechanical treatments.
Copper nickel alloys are of two types that include 70/30 and 90/10. The 70/30 copper nickel alloys have great resistance to sea water-related corrosion due to the presence of significant amounts of manganese and iron.
Copper nickel alloys are used in the following areas:
- Desalination units
- Hydraulic lines
- Fish cages for aquaculture
- Heat exchangers and condensers
- Nickel Alloy Pipes for sea water pipework
- Offshore fire water systems
- Tubes for power plants and ships
- Pumps, valves, sheathing and fittings for ship hulls
Chemical Composition
The chemical composition of UNS C71500 copper nickel alloys Tubes are outlined in the following table.
| Element | Content (%) |
|---|---|
| Copper, Cu | 70.0 |
| Nickel, Ni | 30.0 |
Physical Properties
The following table shows the physical properties of UNS C71500 copper nickel alloys Tube.
| Properties | Metric | Imperial |
|---|---|---|
| Density | 8.94 g/cm3 | 0.323 lb/in3 |
| Melting point | 2140°F | 1171°C |
Mechanical Properties
The mechanical properties of UNS C71500 copper nickel alloys Tubes are displayed in the following table.
| Properties | Metric | Imperial |
|---|---|---|
| Tensile strength, ultimate | 372-517 MPa | 54000-75000 psi |
| Tensile strength, yield (depending on temper) | 88.0-483 MPa | 12800-70100 psi |
| Elongation at break (in 381 mm) | 45.0% | 45.0% |
| Charpy impact | 107 J | 78.9 ft-lb |
| Machinability (UNS C36000 (free-cutting brass) = 100%) | 20% | 20% |
| Shear modulus | 57.0 GPa | 8270 ksi |
| Poisson's ratio | 0.34 | 0.34 |
| Elastic modulus | 150 GPa | 21800 ksi |
Other Designations
Equivalent materials to UNS C71500 copper nickel alloys Tubes are:
| ASME SB111 | ASME SB171 | ASME SB359 | ASME SB395 | |
| ASME SB466 | ASME SB467 | ASME SB543 | ASTM B111 | |
| ASTM B122 | ASTM B151 | ASTM B171 | ASTM B359 | |
| ASTM B395 | ASTM B432 | ASTM B466 | ASTM B543 | |
| ASTM B552 | ASTM B552 | ASTM B608 | ASTM F467 | |
| ASTM F468 | DIN 2.0882 | MIL C-15726 | MIL T-15005 | |
| MIL T-16420 | MIL T-22214 | SAE J461 | SAE J463 |
Fabrication and Heat Treatment
Annealing
UNS C71500 copper nickel alloys Tubes are annealed at temperatures between 649 and 816°C (1200 and 1500°F)
Cold Working
UNS C71500 copper nickel alloys Tubes have good cold working capacity.
Hot Working
UNS C71500 Copper nickel 70/30 alloys Tubes are hot formed in an excellent manner.
Welding
UNS C71500 Copper nickel 70/30 alloys Tubes can be welded using gas shielded arc welding, spot welding, coated metal arc welding, butt welding, seam welding, brazing, soldering and oxyacetylene welding processes.
Forging
Temperatures between 927 and 1038°C (1700 and 1900°F) are suitable for the copper nickel 70/30 alloys Tubes.
Machinability
The machinability rating of copper nickel 70/30 alloys Tubes is 20%.
Applications
UNS C71500 copper nickel alloys Tubes are used in areas where stainless steel cannot be used due to chloride stress-corrosion cracking and in other parts requiring high corrosion resistance. These alloys are also used as machined and forged valve and pump parts that are utilized for seawater services.
