Updated by Reginald Davey 08/09/22
Topics Covered
Introduction
Chemical Composition
Physical Properties
Mechanical Properties
Other Designations
Fabrication and Heat Treatment
Annealing
Cold Working
Hot Working
Welding
Forging
Machinability
Applications
Introduction
Copper nickel alloys are comprised of 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. Their high oxidation resistance is seen in moist air and steam. These alloys are thermally stable and possess moderate strength even under elevated temperature conditions. 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 corrosion resistance and strength of these alloys are improved by the addition of manganese, iron, niobium, and or chromium.
Cupronickel indian coin. Image Credit: Jan Zwolinski/Shutterstock.com
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 which 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
- Sea water pipework
- Offshore fire water systems
- Tubes for power plants and ships
- Pumps, valves, sheathing and fittings for ship hulls
Properties, Chemical Composition, and Other Designations
There are several beneficial properties of copper nickel alloys that help them meet the tough rigors of applications they are used for. Copper nickel 70/30 alloy is a dense metal with a high melting point.
Chemical Composition
The chemical composition of UNS C71500 copper nickel alloys is 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.
| 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 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 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
UNS C71500 copper nickel alloys are annealed at temperatures between 649 and 816°C (1200 and 1500°F.) UNS C71500 copper nickel alloys have good cold working capacity and can be hot formed efficiently.
Copper nickel 70/30 alloys can be welded using spot welding, coated metal arc welding, butt welding, gas shielded arc welding, brazing, seam welding, soldering, and oxyacetylene welding processes. Temperatures between 927 and 1038°C (1700 and 1900°F) are suitable for the 70/30 copper nickel alloys. The machinability rating of copper nickel 70/30 alloys is 20%.
Annealing
UNS C71500 copper nickel alloys are annealed at temperatures between 649 and 816°C (1200 and 1500°F)
Cold Working
UNS C71500 copper nickel alloys have good cold working capacity.
Hot Working
Copper nickel 70/30 alloys are hot formed in an excellent manner.
Welding
Copper nickel 70/30 alloys 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 70/30 copper nickel alloys.
Machinability
The machinability rating of copper nickel 70/30 alloys is 20%.
Industrial Applications
UNS C75100 copper nickel alloys are used for applications that ordinary stainless steel is insufficient for, in environments where corrosion is a commonplace issue that affects the durability of parts and overall cost-effectiveness. The properties of copper nickel alloys make them highly beneficial for these industrial applications.
The main application for these alloys is in the underwater industry, where corrosion is a persistent problem that impacts the performance of metals used in parts. They are used in applications such as offshore piping, seawater cooling, and firewater systems.
Copper-nickel 70/30 alloys are commonly employed in desalination plants, both for multi-stage flash and multiple effect distillation plants. Alloy choice depends on both the corrosion conditions in the plant’s various parts and cost considerations. These alloys are used in heat recovery and brine heater components in multi-stage flash plants and for evaporator tubes and final heat recovery exchangers in multiple effect distillation plants.
Because of their resistance to seawater, these alloys are also used in the maritime industry as materials for components such as cooling systems, heat exchangers, and piping. In fact, naval seawater piping and condensers were the original applications of copper-nickel 70/30 alloys. A recent, novel, but limited use of these industrial materials in the maritime industry is in boat hull plates and sheathing.
These alloys are also increasingly being applied in the power generation sector. In fossil fuel and nuclear power plants, materials that can perform sufficiently in heat transfer processes are in high demand. Components that require suitable materials include coolers, condensers, heat exchangers, valves, and pipework.
Copper-nickel alloys can be used successfully in a range of water types including seawater, freshwater, brackish water, cooling tower water, and water with high proportions of dissolved solids.
Other uses for these alloys are as caging for aquaculture applications and as antimicrobial surfaces. The wide range of industrial applications makes copper-nickel 70/30 alloys key materials in multiple sectors.
More from AZoM: Properties and Classifications of Copper-Nickel Alloys (Cupronickel)
Further Reading and More Information
Nickel Institute (2022) Applications of copper-nickel alloys [online] nickelinstitute.org. Available at:
https://nickelinstitute.org/en/about-nickel-and-its-applications/copper-nickel-alloys/applications-of-copper-nickel-alloys/
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