The main defect found in aluminum foil is known as pinholes, which can arise due to various factors both from the raw material and during the rolling process. Even dust particles in the air and rolling oil can contribute to the formation of pinholes, making it virtually impossible to eliminate them entirely. Instead, efforts are made to minimize the number and size of these defects through the improvement of rolling conditions and effective measures such as filtration and purification of the aluminum liquid. Pinholes are often linked to gas content, inclusions, compounds, and component segregation, and reducing these factors can significantly decrease the occurrence of pinholes. Aluminum foil rolled with high-quality hot-rolled materials can have less than 100 pinholes per square meter, while well purified casting and rolling materials can have less than 200. However, there are still instances where thousands of pinholes can appear per square meter. To reduce the occurrence of these defects, effective measures such as filtering of rolling oil, short-term roll replacement, dust protection measures, and using low tension rolling with a large rolling force are necessary.
Aluminum foil defects such as roller printing, roller eyes, and uneven gloss can be caused by roll-related issues. These defects can be categorized into three types - surface, line, and point. The presence of three cycles distinguishes these defects from others. Incorrect grinding of the roll, incoming material defects, and foreign objects can damage the roll, leading to these defects. Roll fatigue, impact, and slipping between rolls can also cause the same issues. Even slight uneven gloss can affect the surface state of the aluminum foil rolling roll due to the high surface finish. To avoid these defects, it is crucial to keep the rolling mill clean, regularly clean the roller cleaner, and change rollers at intervals. Regular and reasonable grinding is another important factor in ensuring the uniformity of the aluminum foil surface after rolling.
Due to the severe deformation of the plate, wrinkles form when the aluminum foil is rolled up or unrolled. This occurs because the tension applied is insufficient to flatten the surface of the foil. To maintain the desired shape of the foil surface, a device with a tension dimension of 20MPa must ensure that the shape does not exceed 30I. Any shape greater than 30I will inevitably result in wrinkling. It is important to note that the most significant tension is experienced during the rolling process compared to subsequent processing steps. Therefore, issues such as incorrect roll grinding, inappropriate roll shape, poor incoming material shape, and incorrect shape adjustments may cause the foil to exhibit poor shape only during rolling.
Bright marks, bright spots, and highlights can be seen on the surface of the double-joint due to inappropriate use of double-joint oil. This can be caused by insufficient strength of the oil film or an uneven rolling deformation caused by an uneven roll surface, which results in the appearance of a rough, textured look with impurities pressed into it. Fortunately, there are several effective solutions for this defect, including selecting a suitable duplex oil, keeping the incoming material clean and ensuring uniformity of the roll surface. Additionally, changing the reduction can also be helpful, as well as selecting a high-quality aluminum plate.