With the increasing competition in the beverage packaging market, reducing the thickness of the plate, decreasing the wall thickness, lightening the weight of each can, improving material utilization, lowering production costs, and facilitating recycling and convenience in use are important goals for many can manufacturing companies.
One of the important ways to reduce costs in the production of aluminum cans is to reduce thickness, i.e., to require thinner aluminum strip material for can production. The thickness of can body material has decreased from 0.42mm in the 1970s to the current 0.254mm (most are still around 0.28mm), a 39.5% reduction in thickness over 30 years. Every 0.01mm reduction in can body material thickness can save $0.22 in material costs per thousand cans.
Over the decades, the manufacturing technology of aluminum cans has been continuously improved, and the weight of aluminum cans has been greatly reduced. In the early 1960s, the weight of a thousand aluminum cans (including the can body and lid) was 55lb (about 25kg). By the mid-1970s, it had dropped to 44.81b, and by the late 1990s, it had dropped to 331b. Now, it has dropped below 301b, which is nearly half of what it was 40 years ago. Since the 1980s, US can manufacturers have made breakthroughs in sealing machinery and other technologies, so the thickness of aluminum materials for US cans has decreased significantly, from 0.343mm to around 0.259mm.
There has also been significant progress in lightweighting the can lid. The thickness of the lid aluminum material has decreased from 0.39mm to 0.24mm. The diameter of the lid has also been reduced, and the weight of the lid has been continuously reduced. At the same time, the production speed has increased significantly. In the 1970s, only 650 to 1000 cans per minute could be produced, but now it has reached over 2000 cans per minute.
The leading US aluminum industry company in the production of aluminum strip for can making is targeting a thin wall of around 0.18mm. This development trend is also important for domestic aluminum strip production companies for can making, which must increase their R&D efforts and adjust their technology research directions to keep up with the global industry’s development and continuously enhance competitiveness.
(2) A single alloy is being developed to replace the original 3104, 5182, 5052 and other alloys used in the production of aluminum cans, in order to facilitate management, production, and recycling. As the three different alloys used for the can body (3004), can lid (5182), and pull tab (5042) make recycling and remelting difficult, a unified can-making alloy that integrates the can body, lid, and pull tab has become a new direction for the development of aluminum materials for cans. Known unified can-making alloys include the 5017 and 5349 alloys from Golden Aluminum in the United States, as well as a unified can-making aluminum alloy described in Japanese Patent Kokai No. 61-9180, consisting of 0.5%~2.0% Mn, 0.4%~2.0% Mg, 0.5% Si, 1.0% Fe, 0.5% Cu, 0.5% Zn, 0.2% Cr, 0.01% Be, 0.2% Ti, with the remainder being aluminum.
(3) The United States is developing a 0.3mm-thick can material and changing the cup-shaped discs into polygons, which is said to significantly reduce the scrap rate and save more raw materials than thinning. This new invention is worth paying attention to.
(4) Due to the fact that the lid of an aluminum can cannot be resealed once opened, it has gradually fallen out of favor. Therefore, several Japanese companies have begun to use screw caps on aluminum cans. This new type of aluminum can has better sealing performance, effectively preventing beverages from coming into contact with sunlight and oxygen, is lighter in weight, and is easier to recycle and recycle. Currently, as this new type of aluminum can gradually becomes popular throughout Japan, consumers are increasingly showing their preference for screw caps. Japanese can manufacturers hope to use this product to regain the market share lost to plastic bottles.
（5）In addition to developing new alloys and new varieties, the processing technology for can materials (such as hot rolling, cold rolling, and heat treatment) is also developing towards wider and thinner materials. One of the characteristics required for aluminum alloy strip used for can lids is low anisotropy. In order to minimize the fluctuations in mechanical properties or formability of the strip, in addition to controlling the alloy composition, strict control of the hot and cold rolling conditions and plate thickness deviation is also necessary.
(6) According to reports, developed countries have started using continuous casting and rolling technology to produce aluminum alloy materials for cans, further reducing processing costs. This still needs further confirmation.
(7) The “thin aluminum plate” produced by Southwest Aluminum (Group) Co., Ltd., the only domestic aluminum material production enterprise for cans, has achieved mass production, putting an end to the history of foreign monopoly on can materials in China. Since 1986, Southwest Aluminum has organized a group of experts and engineering technicians to work with relevant research institutes to develop technology for producing aluminum materials for cans. Two generations of technicians have participated in the development of this product over the past ten years. With the strong support and guidance of the national “Ninth Five-Year Plan” scientific and technological research program, the “863” research project, and the China Aluminum Corporation’s technology development funds, Southwest Aluminum has invested heavily in equipment necessary for can material production, as well as a large number of personnel and material resources to develop can material production technology. Utilizing the advanced “1+1” hot rolling production line equipment advantage and Southwest Aluminum’s technical advantages, on the basis of the early stage “1+1” can material production technology accumulation, and according to the technical characteristics of “1+4” hot continuous rolling, the can material production process and technology have been comprehensively optimized and innovated, forming a brand-new, full set of can material production technology suitable for advanced “1+4” equipment. This product was developed first in China, and the thickness of the product has developed from the initial 0.42mm to 0.285mm, and currently to 0.275mm, which is only one step away from the international advanced level of 0.265mm. The quality of the produced can materials has reached the international advanced level, becoming a new highlight in China’s aluminum processing industry.
(8)According to industry experts’ predictions, no later than 2008, the competition pattern in the world aluminum can material market will change, and China may become one of the six major can material producing countries in the world. At present, there are eight countries in the world that can produce aluminum alloy can materials: the United States, Brazil, Australia, Japan, South Korea, Germany, France, and Russia, as well as some countries and regions that can produce can lid and pull ring materials, such as Taiwan Province of China, Canada, Bahrain, Italy, etc. However, with the development of Southwest Aluminum Plate Strip Co., Ltd. in can material production, and the hot continuous rolling production line of Nanshan Group Aluminum Processing Co., Ltd. put into operation at the beginning of this year, as well as the hot continuous rolling production line of Asia Aluminum Industrial Park expected to be put into operation at the end of 2007, and the United States Bohai Aluminum Co., Ltd. expected to undergo joint testing in 2008, Chinese-produced can materials will participate in the global can material market competition, and China may become one of the six major can material producing countries in the world.
China Southwest Aluminum Co., Ltd. may achieve a can body production of 70,000 tons in 2008, while Nanshan Group and Asia Aluminum Group may produce about 30,000 tons. The national output could reach 100,000 tons, accounting for about 55% of domestic demand. Meizhou Bayi Aluminum Co., Ltd., with strong technical support from Alcoa, is expected to produce competitive can bodies in the Chinese and Southeast Asian markets within approximately eight months of normal equipment operation, which would be the shortest trial production time among the four major Chinese companies.
(9) A key factor that has not been solved in the localization of aluminum ingots is the neglect of effectively improving the metallurgical quality of aluminum materials. While strengthening purification and other melt treatments, it is also crucial to conduct in-depth and systematic research on the mechanism of melt treatment and the plastic deformation behavior of aluminum materials after melt treatment. Only in this way can reliable theoretical basis and practical guidance be provided for the reasonable formulation of cold and hot processing technology and effective control of product structure and performance, among other things.
As aluminum ingots must have excellent plastic deformation ability and certain strength, the study of the chemical composition, rolling process, annealing process, and other factors on their mechanical properties and plastic deformation behavior is essential but not sufficient to further explore the potential of their properties. For such high-tech products, especially for their low-grade and thin-walled can bodies, the impact of inherent metallurgical defects of the material is more prominent. Therefore, comprehensive treatment of aluminum melt must be strengthened to fundamentally eliminate the main factors that affect the plastic deformation ability of aluminum materials. Currently, researchers from Fuzhou University have conducted in-depth and systematic research and practice on improving the metallurgical quality and plastic deformation performance of aluminum ingots, especially on the purification principle of “exclusion as the main method and degassing as the auxiliary” and the melt treatment principle of “purification is the foundation of transformation and refinement,” and have obtained efficient technology for comprehensive treatment of aluminum melt. This has been successfully applied in the research of low-grade and thin-walled can bodies of aluminum ingots, achieving important progress and turning research results into productivity.