What is the reason why the annealed nickel strip is stained with copper?

Problems of wire drawing process and high annealing temperature.

1, drawing process problems. In the process of wire drawing, the equipment or process parameters of wire drawing machine are not fine enough, which may easily lead to uneven bumps or depressions on the surface of nickel strip, and copper is easily attached to these places.

2. The annealing temperature is too high. In the annealing process, if the temperature is too high or the time is too long, it is easy to change the surface of the nickel strip and form a layer of copper-containing compound, which will make copper easier to adhere to the surface. It is necessary to control the annealing temperature and time and select high quality materials.