Copper and aluminum tube welding technology problems successfully overcome

“We used 10 tons of copper and experimented numerous times before we discovered that the creative idea that is contrary to the world's leading welding methods is the real solution. This idea created a new type of air-conditioned copper-aluminum connecting pipe.” Ocean University of China Material Science Zhao Yue, a senior engineer at the Institute of Engineering, said.
Zhao Yue said that thin-walled copper-aluminum pipe welding technology, known as a world-class problem, suitable for industrial production, is the key technology for connecting aluminum-based copper to air-conditioner connecting pipes. It is not an exaggeration to say that it is a world problem. Many developed countries have studied it for many years. Industrially, only copper and aluminum pipes with a wall thickness of more than 1.0 mm can be welded. However, there has been no breakthrough in this thin copper-aluminum pipe welding technology. “And we have to solve the issue of butt welding for thin-walled copper and aluminum pipes that can be used in the production of air conditioners.”
Traditionally, refrigeration pipes for air-conditioning products use copper pipes. However, copper has always been a globally scarce resource, and the soaring price of copper has affected the development of the air-conditioning industry. China's aluminum resources are relatively abundant, and the aluminum industry is also more developed. Therefore, aluminum substitutes for copper for air-conditioning and refrigeration lines has become a general trend.
The key technology for using aluminum to replace copper is the problem of butt welding of copper and aluminum pipes. For this reason, Qingdao Haiqing Machinery General Factory, which is well-known in the domestic welding industry, joins up with China Ocean University to form a research team and actively undertake the task of this technology.
The reason why thin-walled copper-aluminum welding is called a world problem is that it has objective factors. The melting point of copper is 1083 degrees Celsius, and the melting point of aluminum is 660 degrees Celsius, which is a melting point of more than 400 degrees Celsius. The result is aluminized, and copper may still be soft. More difficult is that aluminum will naturally generate an oxide film on the surface. Because of the cleanliness of the refrigeration circuit, this oxide film cannot be removed by adding additives, and it is difficult to remove by physical means. This layer of oxide The melting point of the film reaches 2000 degrees Celsius. These three different melting points make the copper-aluminum welding extremely brittle and even impossible to weld. In the past, by using some special welding methods such as explosion welding, diffusion welding, energy storage welding, friction welding, etc., copper and aluminum welding can also be achieved through the application of welding auxiliaries, but these methods can only complete the copper and aluminum tubes above 1.0 mm. Welding, or because of high costs and complicated processes, is not suitable for industrial production. Some countries have attempted to use copper-aluminum eutectic structures to form welds and achieve thin-walled copper-aluminum welding. This has been studied extensively, but industrial applications have not been realized. The wall of the air conditioning and refrigeration pipeline is very thin. Only the invention of a new welding method for the industrial welding production of the thin-walled copper-aluminum pipe can achieve the goal of replacing aluminum with aluminum in the air conditioning and refrigeration pipeline.
“In the beginning, we followed the idea of ​​using a copper-aluminum eutectic structure to form the weld. We found that the eutectic structure was very fragile due to the thin wall of the tube. Therefore, the weld quality was very poor, even tearing with a tear. So we started looking for new ideas, Zhao recalls.
New ideas come from a large number of experiments and analysis.
The welding method adopted by the research group is the commonly used resistance welding method. They began to try to continuously increase the pressure parameters for experimentation. Some pipelines could be torn off after welding, and some couldn't be torn down. Through analysis, they found that everything could be done. The eutectic structure was formed when it was torn off, but no eutectic structure was found when it was torn off.
Why is there no copper-aluminum eutectic weld, but is it effective? After in-depth study, the research team found that in fact the copper-aluminum eutectic structure is the “culprit” for forming the Weld, and the key to the welding of thin-walled copper-aluminum pipes is to remove the Cu-Al eutectic from the weld, otherwise the weld The weak points of poor mechanical properties will be exposed, which is also the real reason why thin-walled copper and aluminum tubes are not easily welded.
After clarifying the reason, the research group began the research and development of the eutectic microstructure welding method. After one and a half years of research, after tens of thousands of repeated experiments, they had many deviations in pressure parameters, electrical parameters, size parameters, and material composition. All kinds of factors are clear to the heart, and finally invented a completely new welding method --- resistance pressure welding method. This welding method can realize the non-copper-aluminum eutectic structure and copper-aluminum atom combination in welding. The welding seam is very firm and there are no gaps in any mechanical tests such as stretching, bending, and flattening. As a result, the "copper-aluminum air-conditioning connecting pipe" project with this welding method as its core technology has obtained national invention patents and has been jointly identified by the Ministry of Science and Technology, the Ministry of Commerce, the General Administration of Quality Supervision, Inspection and Quarantine, and the four ministries and commissions of the State Environmental Protection Administration as national key new ones. product.
At present, this project is applying for international invention patents.
Qingdao Haiqing Machinery Plant adopts "copper-aluminum air-conditioning connecting pipe" produced by thin-wall copper-aluminum pipe welding technology, and its sales price is reduced by half compared with copper pipe, plus its performance, service life and installation convenience. All are better than pure brass, quickly won the favor of air-conditioning manufacturers, products in short supply. At present, most domestic air-conditioning companies have applied this technology product, and air-conditioning companies in South Korea and Japan have begun to use this technology product. At the same time, the quality of its products has withstood market inspections. Since it was put into production in 2004, it has put nearly 6 million sets of "copper-aluminum air-conditioning connecting pipes" on the market, with a pass rate of 100%.
“Accordingly, we have won a brand new market.” Zhao Yue said, “Only China’s air-conditioning market accounts for 50 million units of annual sales, which means that there will be nearly 2 billion yuan in copper-aluminum interconnecting pipe market capacity each year. At the same time there will be a reduction of 50,000 tons of copper." src=http