ABSTRACT: In this paper, the annealing process of ultra-thin high-conductivity Copper Strip with high precision is studied, and the annealing bonding problem of 0.05 mm ultra-thin high-conductivity Copper Strip is solved. Through a large number of experiments and analysis of the results, the optimum technological parameters are determined as follows: annealing temperature 380 °C, annealing time 30 minutes, annealing time 270 minutes.

Keywords: ultra-thin; Red Copper Strip; finished annealing; Bonding

The purpose of the introduction heat treatment is to change the internal structure of the Strip by means of certain heat effect, and to eliminate the metastable plasticity of the structure and properties caused by cold deformation. The Strip is annealed by recovery recrystallization, in order to obtain the required comprehensive performance. The final product annealing refers to the final product annealing, for the soft state product control performance. For this process, first of all, to meet the user requirements of the performance indicators, and requirements of uniform performance, surface scratch, no foreign pressing, smooth, no oxidation. The thickness of the ultra-thin copper strip is 0.05 mm. Because the Strip is too thin and the residual stress exists, it is easy to produce the bonding phenomenon in the bell-type annealing furnace.

Second, the reason analysis ultra-thin Copper Strip is easy to appear the bonding situation in the finished product annealing process, the cause of the bonding: The interlayer bonding is caused by the diffusion of copper atoms on the surface of two adjacent layers of copper strip during annealing. The greater the degree of atomic diffusion, the more serious the interlayer bonding. The degree of atomic diffusion is directly related to the following process parameters:

1. The greater the interlayer tension, the smaller the distance between the two adjacent copper bands and the larger the contact area, which leads to the increase of the number of atoms diffusing each other and the increase of the diffusion degree. The higher the annealing temperature and total annealing time, the faster the rate of atom diffusion, the longer the annealing time, the more the number of atom diffusion, and the more the diffusion degree. The greater the weight of the coil, the greater the interlaminar tension, the longer the total annealing time required, according to 1,2, the greater the degree of bonding; the less the weight of the coil, the reverse. 3. Solution 1. Air Cushion continuous annealing: The thickness of the minimum annealed strip is 0.1 mm, the annealing equipment of thin strip below 0.1 mm can not meet the requirements; Small Coil annealing has some disadvantages, such as poor stability of charging coil, high energy consumption and high cost. 2. In view of the above reasons, through many tests, the following technical schemes are determined to reduce the tension: under the premise that the side tower shape is not more than 1mm, the coiling tension is controlled below 12N/mm2; Reduce Coil Weight: In slitting machine will 5 tons above the finished material coil cut into no more than 500 kg small coil. The special annealing sleeve and furnace hoisting tool are designed and made, and the inner diameter of the steel reel is 300mm.

經多次討論及試驗，確定采用輥底式連續(xù)退火爐退火，  進行成品退火，制定退火工藝見表 1：

As can be seen from the metallographic structure of Fig. 2, when the annealing temperature is 360 °c, the grain grows slowly, but the grain growth is not sufficient. When the temperature reaches 380 °c, the grain size is more uniform, the smaller and more stable the grain size, the better the comprehensive performance, so many domestic and foreign manufacturers rely on controlling grain size to control the performance. When the temperature exceeds 400 °C or even reaches 420 °c, the grain size begins to be inhomogeneous. This is the stage where the grains swallow each other and grow inhomogeneously after recrystallization. Conclusion the important technical problems of annealing and bonding of strip are solved by studying the characteristics of roller hearth annealing furnace. After a lot of experiments and analysis of the results, the optimum technological parameters are determined as follows: annealing temperature 380 °C, annealing time 30 minutes, annealing time 270 minutes. After 0.05 mm ultra-thin Copper Strip was annealed in roller hearth annealing furnace, the comprehensive properties of three rolls of T2 and TU2 were analyzed. The results are as follows:

From Table 3, it can be seen that all the performance indexes of the finished strip meet the design requirements, and there is no adhesion between layers, and the resistivity is even. 

Source: Chinanews.com, by Liu Maoting

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