Chromized and dos treated aluminium coil sheet can be seen as the best material for making closure pp caps with high performance. In addition to good deep drawing performance and low ear-making rate, aluminum pp cap materials made by chromized and dos treated aluminum also have certain strength advantages after being baked in the closure cap making process. The bottle caps made by aluminum closure sheet with chromized and dos treatment are very advantageous in terms of sealing and aesthetics, so the aluminum market for bottle caps will become better and better.
The chromized and dos treated aluminium coil sheet for caps have better performance than mill finish aluminum coil sheet for caps. Apply DOS oil under normal conditions is to prevent sticking or rusting. Aluminum bottle cap is made of special aluminum alloy materials, mainly used for packaging wine, beverages (with or without steam) and medical and health products, and can meet special requirements such as high-temperature cooking and sterilization. Applied to the pretreatment of aluminum parts before spraying, also known as chromization treatment, aluminum alloys will form a loose natural oxide film in the natural environment, and the thickness of the natural oxide film is 0.05μm. The effect of chromization is to improve the corrosion resistance of the surface oxide film and the bonding force between the aluminum closure sheet and the coating, so as to achieve the thickness, density and bonding force of the film layer to meet the spraying requirements.
The aluminum pp cap is mostly processed on a highly automated production line, so the requirements for the strength, elongation, and dimensional deviation of the chromized and dos treated aluminium coil sheet are very strict, otherwise cracks or creases will occur during the processing. In order to ensure the convenience of printing after the bottle cap is formed, it is required that the surface of the chromized and dos treated aluminium for cap material should be flat and free of rolling marks, scratches and stains. Generally used alloy states are 8011-H14, 3105-H14 and so on. The material specifications are generally 0.20 mm ~ 0.23 mm thick and 449 mm ~ 796 mm wide. Aluminum bottle cap materials can be produced by hot rolling, continuous casting and rolling, or cold rolling. At present, bottle cap manufacturers often use continuous casting and rolling billets, which are better than casting and rolling billets.