Classification and rolling characteristics of aluminum foil
Aluminum foil is a kind of aluminum rolled material. Aluminum foil is mainly about thickness. In the industry, aluminum products with a thickness less than 0.2mm are usually called aluminum foil. The edges are usually cut vertically and delivered in rolls. Aluminum foil is a soft metal film. It not only has the advantages of moisture-proof, air-tight, light-shielding, abrasion resistance, fragrance retention, non-toxic and tasteless, but also because of its elegant silver-white luster, it is easy to process beautiful patterns and colors of various colors. pattern.
According to thickness, aluminum foil can be divided into double zero foil, single zero foil and thick foil. Double-zero foil refers to a foil that has two zeros after the decimal point when its thickness is measured in mm (i.e. thickness <0.01mm); similarly, single-zero foil refers to a foil that has one zero after the decimal point when its thickness is measured in mm. Foil (0.01mm≤thickness<0.1mm); thick foil refers to aluminum foil with a thickness between 0.1mm and 0.2mm.
Generally speaking, double zero foil is mainly used for food packaging, cigarette packaging, electronic optical foil, etc.; single zero foil is used for some food packaging, pharmaceutical packaging, electronic circuit signal shielding, air conditioning foil, etc.; thick foil is mainly used for air conditioning foil, Container foil, architectural decoration and industrial uses.
In the production of double foils, the rolling of aluminum foil is divided into three processes: rough rolling, intermediate rolling and finishing rolling. From a technological point of view, it can be roughly divided according to the thickness of the rolling exit. The general classification method is that the exit thickness is greater than Or equal to 0.05mm is rough rolling, the exit thickness between 0.013 and 0.05 is medium rolling, and the single finished product and double rolled finished product with exit thickness less than 0.013mm are finish rolling. The rolling characteristics of rough-rolled aluminum plates and strips are similar. The thickness control mainly depends on the rolling force and post-tensioning force. The thickness of rough-rolling processing rate is very small. Its rolling characteristics are completely different from the rolling of aluminum plates and strips. It has the characteristics of aluminum foil rolling. Its particularity mainly includes the following aspects:
(1) Aluminum plate and strip rolling. To make the aluminum strip thinner mainly depends on the rolling force, so the automatic control method of plate thickness is based on the constant roll gap as the main control method of AGC. Even if the rolling force changes, the thickness can be obtained by adjusting the roll gap at any time to keep the roll gap at a certain value. Consistent sheet and strip material. When aluminum foil is rolled to medium-finish rolling, due to the thin thickness of the aluminum foil, it is easier to increase the rolling force during rolling to cause elastic deformation of the roller than to produce plastic deformation of the rolled material. The elastic flattening of the roller cannot be ignored. Yes, the elastic rolling and flattening of the rollers determines that in aluminum foil rolling, the rolling force can no longer play the same role as rolling plates. Aluminum foil rolling is generally roll gap-free rolling under constant pressure conditions. The main purpose of adjusting the thickness of aluminum foil is Depends on adjusting the tension and rolling speed.
(2) Overlapping rolling. For aluminum foil with a thickness less than 0.012mm (the thickness is related to the diameter of the work roll), due to the elasticity of the roll, it is very difficult to roll it with a single sheet. Therefore, the double rolling method is used, that is, two sheets of aluminum foil are rolled. The aluminum foil is added with lubricating oil in the middle, and then rolled together (also called stack rolling). Laminated rolling can not only roll out aluminum foil that cannot be produced by single-sheet rolling, but also reduce the number of strip breaks and improve labor productivity. This process can be used to mass-produce single-sided aluminum foil of 0.006mm to 0.03mm.
(3) Speed effect. During the rolling process of aluminum foil, the phenomenon that the thickness of the foil becomes thinner with the increase of the rolling degree is called the speed effect. The explanation of the speed effect mechanism still needs in-depth research. The reasons for the speed effect are generally believed to have the following three aspects:
1) The friction state between the work roll and the rolling material changes. As the rolling speed increases, the amount of lubricating oil brought in increases, thus causing the lubrication state between the roll and the rolling material to change. The friction coefficient decreases, the oil film becomes thicker, and the thickness of the aluminum foil becomes thinner.
2) Changes in the rolling mill itself. In a rolling mill using cylindrical bearings, as the rolling speed increases, the roll neck will float in the bearing, so that the two interacting loaded rolls will move closer to each other.
3) Process softening when the material is deformed by rolling. The rolling speed of the high-speed aluminum foil rolling mill is very high. As the rolling speed increases, the temperature of the rolling deformation zone increases. According to calculations, the metal temperature in the deformation zone can rise to 200°C, which is equivalent to an intermediate recovery annealing, thus causing Process softening phenomenon of rolled materials.
