Current status of production technology of aluminum foil for beer

With the rapid development of the packaging industry, most breweries are using beer bottle label aluminum foil (abbreviated as beer standard), and now the product used is 80112O, 0.0115mm foil. The following describes the technical process, product mechanical properties, pinholes, and user technical requirements for the production of aluminum foil for beer targets from cast-rolled billets. At the same time, the development trend of aluminum foil for beer targets is also predicted.

1, the main technical indicators of aluminum foil for beer

1.1 Chemical composition of aluminum foil for beer

In China, no matter whether it is a hot-rolled billet or a beer-marked aluminum foil produced by casting and rolling, the chemical composition is 8011 alloy. The main components of the alloy are shown in Table 1. However, in the production, the range of actual control components of different manufacturers is not the same. For example, North China Aluminum Corporation adopts alloys with low component control range to produce beer standard aluminum foil. The control range of its chemical composition mainly considers the tensile strength of products. Technical indicators such as elongation rate and pinhole degree of aluminum foil should meet the requirements of users.

1.2 Mechanical properties

The thickness of the aluminum foil used in beer is 0.0115mm, and tensile test specimens are generally used for testing the mechanical properties. These are tensile specimens with a parallel section width of 15mm, a length of 170mm, and a gauge length of 100mm. According to the user's effect, 80112O, 0.0115 The tensile strength of mm beer standard aluminum foil is generally between 80 and 90 N/mm2, and the elongation is between 2% and 2.5%. In addition, different users have additional requirements such as burst strength. These technical indicators are generally inspected by a liquor label printing factory, and the aluminum foil supplier does not independently perform inspections through process assurance.

1.3 Requirements of aluminum foil pinhole and surface quality

The thinner beer standard aluminum foil can only be used for sealing after being colored and printed. Therefore, the surface quality of the aluminum foil is required to be high. The surface of the aluminum foil is free from defects such as oil spots and obvious impressions. After the beer mark is printed, it is necessary to mark the surface of the aluminum foil evenly. This is a unique technical requirement of the beer mark. Therefore, the requirements for the pinhole degree of the aluminum foil are very strict, and almost no pinhole defects appear on the aluminum foil. If there are many original pinholes in the aluminum foil and the small holes marked by the finished beer mark itself, the surface of the aluminum foil will become a “sieve”, and other properties of the aluminum foil will also deteriorate, which will seriously affect the labeling speed of the brewery. However, at present, beer labels supplied with cast-roll stocks in China can achieve smaller aluminum foil pinholes, and in this respect, they can basically meet the requirements of users.

2, beer standard aluminum foil production process control points

The following is only a review of the process control points for the production of beer standard aluminum foil from casting and rolling stocks. The process flow is: cast smelting → composition adjustment → static furnace refining → online degassing → adding grain refiner → filtration → cast rolling → cold rolling → Intermediate thickness heat treatment → aluminum foil rolling → double rolling → finished product slitting → finished heat treatment → inspection packaging.

2.1 Process Control Points for Casting and Rolling Processes

In the production process of casting and rolling, the control of the melt quality of aluminum is relatively strict. In addition to the normal adjustment of the composition and the complete slag removal, the melt poured into the holding furnace (in standing furnace) must be refined. The refining time is determined by the weight of the charge. Generally, the refining medium should be N2 or N2 + CCl4 for more than 15 minutes. Before casting, on-line refining is carried out to minimize the amount of hydrogen in the aluminum melt entering the casting zone. In order to control the grain size of the cast-rolled slab, a grain refiner should be added before the melt enters the filter box. The commonly used Al2Ti2B wire with a diameter of 9.5 to 10 mm is slightly different depending on the width of the slab and the casting speed. If a 7.5 mm x 1200 mm cast slab is produced at a casting speed of 1.0 m/min, the addition speed of the Al2Ti2B filament is generally 200-250 mm/min.

2.2 Process Control Points for Cold Rolling and Foil Rolling Processes

2.2.1 Cold Rolling and Foil Rolling

Beer standard aluminum foil has high requirements for plate shape and surface quality. It is necessary to choose new grinding work rolls for aluminum foil rolling of the finished product pass. Work rolls and guide rolls must be in good condition, set in each pass or Select the appropriate plate curve to ensure the flatness of the aluminum foil.

2.2.2 Heat Treatment in Intermediate Thickness and Finished Thickness

In China, when using cast-rolled blanks to produce beer-marked aluminum foil, an annealing is usually performed in the middle of the cold-rolling. Since the annealing temperature is higher (generally above 500°C), it is called uniform annealing, and different manufacturers choose different The thickness is intermediately annealed, for example at 2.0 mm or 0.8 mm thick. Homogenizing annealing can improve the rolling properties of the blank and increase the elongation of the aluminum foil. The factors considered in the annealing of the finished aluminum foil are to eliminate the rolling oil on the surface of the aluminum foil and ensure the mechanical properties of the finished product. Generally, the oil is removed under low temperature for a long time, such as (180-230) °C (20-30) hours, degreasing. The effect can reach Class A water brushing performance as stipulated in GB3198 standard; considering the mechanical properties to meet the technical standards, it is generally kept at 300°C for 20 to 30 hours for annealing.

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