Introduce Nickel silver CuNi18Zn20
Nickel silver CuNi18Zn20 provides good resistance to atmospheric corrosion, organic compounds as well and neutral and alkaline saline solutions.
It is poorly resistant to oxidizing acids.
The sensitivity to stress corrosion cracking of this alloy is much lower than that of brass.
Nickel silver uNi18Zn20 has an alpha single-phase structure.
The alloy has excellent cold-forming properties, on the other hand, its hot-formability is limited.
The color is silvery, sharply greyer than that of CuNi12Zn24. Nickel silver is mainly used for the fabrication of connectors, and relay springs, and in the optical and watch-making industry, for example. Its machinability is rather
poor.
It is better to use a leaded nickel silver, e.g. CuNi12Zn25Pb1 (B420) if good machinability is necessary.
Nickel silver CuNi18Zn20 can be easily polished or plated and can be brazed or welded.
Its weldability by laser however is not good. Its annealing temperature is situated typically between 620 and 700°C.
To decrease the presence of internal stress, a stress-relieving heat treatment between 300-350°C is possible.
Chemical composition % of grade C7521, CuNi18Zn20, CuNi12Zn24, NS105, CW409j, CuNi5Zn21, CuNi15Zn22, C75400, BZn15-20
| Fe | Mn | Ni | Cu | Pb | Sn | Others | - |
| max 0.3 | max 0.5 | 17 - 19 | 60 - 63 | max 0.03 | max 0.03 | total 0.2 | Zn - remainder |
Mechanical properties of grade C7521, CuNi18Zn20, CuNi12Zn24, NS105, CW409j, CuNi5Zn21, CuNi15Zn22, C75400, BZn15-20
| Rm - Tensile strength (MPa) (R380) | 380-450 |
| Rm - Tensile strength (MPa) (R450) | 380-450 |
| Rp0.2 0.2% proof strength (MPa) (R380) | 250 |
| Rp0.2 0.2% proof strength (MPa) (R450) | 250 |
| A - Min. elongation at fracture (%) (R380) | 37 |
| A - Min. elongation at fracture (%) (R450) | 18 |
| A - Min. elongation Lo = 50mm (%) (R380) | 27 |
| A - Min. elongation Lo = 50mm (%) (R450) | 9 |
| Vickers hardness ( HV): (H085) | 85 - 115 |
| Vickers hardness ( HV): (H115) | 115 - 160 |
