Manufacturing process and material requirements for high-quality aluminum cans

The can making factory has very strict requirements for aluminum can materials, not only requiring good internal quality, optimized chemical composition, low gas and slag content, but also good deep drawing performance, low ear making rate (material anisotropy), small thickness tolerance, good plate shape, and good surface quality.

The production of aluminum cans goes through more than 40 processes, among which the main processes related to the performance of aluminum strips include material dropping, cup punching, thinning and deep drawing, trimming, rinsing, external printing, internal spraying, drying, necking, flanging, etc. Aluminum strip must have appropriate strength and good deep drawing formability to ensure smooth continuous punching, thinning and deep drawing, and appropriate yield strength after baking. In the production process of can bodies, the first step is to punch a strip with a thickness of 0.25-0.30mm into a round material with a diameter of about 138mm. Then, it is deep drawn twice to make a punching cup with a diameter reduction rate of more than 50%. After three thinning and deep drawing processes, the wall thickness is reduced to 0.08-0.10mm, and the stretching thinning rate exceeds 65%. Due to thinning and deep processing, the extensibility of the billet can be extremely low, so even small inclusions can become the cause of cracking and folding; Subsequently, it is necessary to ensure that there is no fracture during the trimming, necking, and flanging process, and that the material has good plasticity; After several baking cycles, it is necessary to ensure the axial pressure resistance and bottom pressure resistance of the tank body. The axial pressure resistance of the tank body is required to be 1.35kN, and the bottom pressure resistance strength is 630kPa to ensure smooth canning and storage transportation. Therefore, strict requirements have been put forward for the comprehensive performance of aluminum strip used for tank bodies: tensile strength of 270-310MPa, yield strength of 250-300MPa, elongation greater than 3%, and ear making rate less than 2%; The surface of the strip has no obvious ripples, uniform and consistent surface smoothness, no oxidation, and no visible defects such as inclusions, pressure marks, or blemishes; The thickness is uniform and consistent, with a thickness difference within 0.005mm.

The modern lid making line uses rolls, with 20 to 24 working positions for cup punching machines and a material width of 1500 to 1550mm; The width of the sheet used in the block production line is 850~970mm. The thickness of the cover material is 0.27mm. All the pre coated cover materials currently used in China are imported. The production of can lids involves first making base lids and pull rings separately on two production lines, and then combining them together to form a composite lid. The cover material not only has various width specifications, but also has more thickness specifications ranging from 0.22 to 0.315mm, such as 0.23mm, 0.25mm, 0.27mm, 0.28mm, and 0.30mm.