How are copper pipes and aluminum pipes welded in air conditioners?

Zhao Yue said that the welding technology of thin-walled copper-aluminum pipe, which is known as a world-class problem and suitable for industrial production, is the key technology to replace copper with aluminum for air-conditioning connecting pipes. It is no exaggeration to say that it is a world problem. Many developed countries have studied for many years and can only weld copper-aluminum pipes with wall thickness of 1.0 mm in industry, but the welding technology of copper-aluminum pipes thinner than this has not been broken. "What we want to solve is the butt welding problem of thin-walled copper-aluminum pipes that can be used to produce air conditioners." Traditionally, the refrigeration pipes of air-conditioning products are all copper pipes. However, copper has always been a scarce resource in the world, and the soaring copper price has affected the development of the air-conditioning industry. However, China is rich in aluminum resources and its aluminum industry is relatively developed. Therefore, it is the general trend to replace copper with aluminum for air conditioning and refrigeration pipelines. The key technology of replacing copper with aluminum is butt welding of copper-aluminum tubes. Therefore, Qingdao Christina Machinery General Factory and China Ocean University, which are well-known in the domestic welding industry, formed a research team and took the initiative to undertake the research task of this technology. Thin-walled copper-aluminum welding is called a world problem because of its objective factors. The melting point of copper is 1083 degrees Celsius, and the melting point of aluminum is 660 degrees Celsius, with a difference of more than 400 degrees Celsius. The result is aluminum plating, and copper may be just soft. What is more difficult is that aluminum will naturally form an oxide film on the surface. Due to the cleanliness requirement of refrigeration pipeline, this oxide film can not be removed by adding additives, and it is difficult to remove it by physical methods. The melting point of this oxide film reaches 2000 degrees Celsius. These three different melting points are easy to form virtual welding, and even copper and aluminum cannot be welded. In the past, some special welding methods, such as explosive welding, diffusion welding, energy storage welding, friction welding, etc. The welding of copper and aluminum can also be realized by applying welding AIDS, but these methods can only complete the welding of copper and aluminum pipes above 1.0mm, or are not suitable for industrial production because of high cost and complicated process. Some countries try to realize thin-walled copper-aluminum welding by using copper-aluminum crystal structure to form weld seams, and have done a lot of research on this, but it has not been industrialized. The wall of air conditioning refrigeration pipeline is very thin. Only by inventing a new welding method and forming the industrial welding production of thin-walled copper-aluminum pipes can we truly realize the goal of replacing copper with aluminum for air conditioning and refrigeration pipes. "At first, we followed the idea of using Cu-Al crystal structure to form welds. It was found that the weld quality was poor because the pipe wall was too thin and the crystal structure was very fragile, and even it was torn off by hand. So, we started looking for new ideas. " Zhao Yue recalled. This new idea comes from a lot of experiments and analysis. The welding method adopted by the research group is the commonly used resistance welding method. They began to try to increase the pressure parameters to carry out experiments. Some pipes can be torn off when welding, while others cannot. Through analysis, they found that all that could be torn off formed a * * * crystal structure, while none that could not be torn off found a * * * crystal structure. After finding the reason, the research group started the research and development of welding method for crystal structure without * * *. After a year and a half of research and tens of thousands of repeated experiments, they know all about many factors, such as pressure parameters, electrical parameters, dimensional parameters, material composition deviation, etc., and finally invented a brand-new welding method-resistance pressure welding method, which can realize the weld without copper and aluminum crystal structure and deviation. As a result, the project of "copper-aluminum air-conditioning connecting pipe" with this welding method as the technical core won the national invention patent, and was jointly recognized as a national key new product by the Ministry of Science and Technology, the Ministry of Commerce, the General Administration of Quality Supervision, Inspection and Quarantine and the State Environmental Protection Administration. At present, the project is applying for an international invention patent. After the "copper-aluminum air-conditioning connecting pipe" produced by Qingdao Christina Machinery General Factory with thin-walled copper-aluminum pipe welding technology was put on the market, its sales price was reduced by half compared with that of copper pipe, and its performance, service life and installation convenience were better than that of pure copper pipe, which quickly won the favor of air-conditioning manufacturers, and the products were in short supply. At present, most domestic air-conditioning enterprises have applied this technical product, and air-conditioning enterprises in Korea and Japan have also begun to use this technical product. At the same time, the quality of its products has withstood the test of the market. Since it was put into production in 2004, nearly 6 million sets of "copper-aluminum air conditioning connecting pipes" have been put into the market, and the qualified rate is 100%.