Why does copper strip appear concave?

Believe there must be a lot of people come across the surface of the copper or copper strip with peeling or pits, copper belt due to these reasons cannot be used to do this is a very headache problem, but because the surface has a pit or pitting, peeling such phenomenon will cause the entire plate can't use, waste for many units will be very big, the cost also follow to improve a lot! But what causes it? Is there any way to avoid it?

Cold rolling of the surface of the copper plate will sometimes have peeling, pit, pitting phenomenon, one of the reasons is that the processing needs to go through a number of rolling process. In any process, the surface is not cleaned will have oxide attached to the surface of the copper plate, the next rolling, will be rolled in the copper plate, resulting in the back of the copper plate in the finished product processing, oxide off, then pits, pitting and other defects formed.

A simple example would be to sprinkle a few sesame seeds on the surface of the pie while rolling it with a rolling pin. The sesame seeds would be embedded in the pie, but if the sesame seeds fall off in the process of rolling the pie, it would become a pit!

Another kind of situation is also more common, that is, due to the transport process packaging tightness is not enough, resulting in the gap between copper plate and copper plate is too large, so in the transport process due to vehicle bumps and other conditions, causing surface collision friction! Copper, especially copper itself belongs to a relatively soft metal, hard to avoid after the collision and friction will leave ugly pit, this truth and hand to pinch the bread will leave ugly pit a nature.