The main reasons are as follows:

1. The production equipment is not clean and the environment is not good

2. Low temperature of the ingot, inadequate intermediate annealing or homogenization annealing, and poor plasticity.

3. The lubricating oil of rolling aluminum plate process is not clean.

4. There are non-metallic foreign matters in the rolled aluminum slab.

5. During the production process, some non-metallic foreign matters fall on the aluminum plate.

6. In the rolling process, if the pass power is too large, or if the pass rolling times are reduced, and the metal composition inside is uneven, some problems may occur.

7. There are metal chips or dirt on the surface of roller or guide roller.

8. There are defects or foreign matters on the surface of straightening machine and other process equipment.

9. In the process of handling or storage, the aluminum plate collides with other objects due to improper operation and causes damage to the surface of the aluminum plate.