1. Chemical composition
The alloy grades of aluminum foil for heat exchange fins mainly include 1100, 1200, 8011, etc. From the point of view of use, air conditioners have no strict requirements on the chemical composition of aluminum heat exchanger fins. Without surface treatment, 3A21 aluminum alloy has relatively good corrosion resistance, high mechanical properties such as strength and elongation, and high hardness. Which alloy to choose mainly depends on the final mechanical properties that the material can achieve and the difficulty of the ant process. For example, the rolling of 1100 aluminum alloy with higher purity is easier, while that of 8011 alloy is more difficult.
2. Mechanical properties
Mechanical properties mainly refer to the tensile strength, elongation and cupping value of aluminum foil. From the perspective of use, it is hoped that the higher the three indicators, the better, but as far as the material itself is concerned, these three indicators are contradictory, that is, when the tensile strength of the aluminum foil is relatively high, the elongation index will decrease; and When increasing the elongation of aluminum foil, it will cause a decrease in tensile strength. Therefore, in practical applications, the intermediate value of mechanical properties is generally taken, and the specific strength and plasticity values are related to the stamping die during heat exchange fin processing. Generally, the punching process of heat exchange fins is divided into stretching type and non-stretching type. Stretch-type dies require better plasticity of aluminum foil, that is, higher elongation, and the relative strength value can be slightly lower; while non-stretch dies also require higher strength of aluminum foil, and plasticity is a secondary indicator. There are many factors that affect the mechanical properties of aluminum foil, mainly the chemical composition and processing technology of aluminum foil. As far as the strength and plasticity of aluminum foil are concerned, by adjusting the chemical composition or changing the processing process and parameters, the plasticity or strength of the material can be changed within a certain range while keeping one side unchanged. That is to say, the matching value of aluminum foil strength and plasticity can be limitedly changed through the adjustment of chemical composition and processing technology.
According to the different mechanical performance requirements of heat exchange fins, there are three main use states of aluminum foil: H22, H24, and H26. Each state corresponds to a certain range of strength and plasticity. Judging from the current status of the domestic aluminum processing industry, there is no uniform standard for the range of mechanical properties in each state. At the same time, in practical applications, the range of mechanical properties of each state is too wide, and the mechanical properties of the product cannot be well controlled to satisfy users. Table 1 shows the state and mechanical properties of typical aluminum foil alloys for heat exchangers.