| Heat exchanger is an important part in automotive air-conditioning system. With the continuous development of automotive air conditioning industry, more stringent requirements is proposed to the appearance and performance of heat exchangers. How to get aesthetic appearance and excellent heat transfer performance is one of the important research topics in the automotive industry. Brazing is the main processing methods of heat transfer, and also is a determining factor of affecting the heat transfer effect. This article, to proceed from the actual brazing quality of car air-conditioning condenser, combined with Brazing mechanism, studied on the "fin-erosion" phenomenon after brazed in detail.In the case of concentration in the flux of 5%, drying temperature of 230℃, the maximum brazing temperature 615℃, belt speed of 1080mm/min, nitrogen purity of 99.998% or more, some fins of automotive air-conditioning condenser disappeared after brazed, which called "fin-erosion" phenomenon and affects heat transfer effect severely. In order to solve the problem, first of all, the study from the chemical composition of various structures of the condenser to proceed. Collecting pipe and fin are composite layer material, and the solder coated the base metal. However, the composite layer material itself has a very complicated manufacturing process. As differences in manufacturers or production technology, solder thickness and uniformity will affect the heat transfer during brazing and solder flow, which create difficulties for the brazing process. Analysis shows that, when the composite layer is too thick or uneven thickness, it will cause excess solder flows from collecting pipe to the fin. With the inter-diffusion between the base metal and solder, "Si-erosion" appears as too much base metal dissolves in solder. Experimental analysis for brazing joint microstructure is proceeded in order to study the mechanism of this phenomenon. Experimental results show the existence of the "Si-erosion "phenomenon in brazed joints, because solder layer and the brazing process do not match. Too low belt speed or too high temperature will extend the solder's flow time, which increase the opportunities and volume of solder from collecting pipe to fin, then the probability and extent of "fin-erosion" increase. Moreover, minor scratches on the surface of the flat tube can intensify the "fin erosion" phenomenon.Based on above analysis and experiments, the surface quality of flat tube is improved, then,select the brigade-laboratory method to improve the brazing process. At first, just considering on the temperature factor, that is, keep the belt speeds constant and just change the temperature. Randomly choose 30 workpieces has been assembled to brazing and make quality inspection in groups, then,the two groups of the highest pass rate will continue to experiment for belt speed set. To remain the selecting set temperature unchanged, respectively set the belt speed to 1090mm / min, 1100 mm / min, 1110 mm / min to conduct experiment ditto. At last, select the optimum brazing parameters. Eventually ,when the temperature of the sixth and seventh temperature is set to 608℃and 610℃, and belt speed is set to 1100 mm/min, there isn't "fin- erosion" products, nearly 100% pass rate.The study has got satisfactory appearance of the condenser, and improved the passing rate of products, and the production costs is reduced. Ultimately, it is used to guide the production and provides a theoretical basis for the further study on the erosion during brazing.
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