Study On Vacuum Brazing Process Of Aluminum Alloy Oil Cooler Used For Autocar

Oil cooler is an important part of vehicle body, as well as a key part to ensure the safe operation and life of automotive engines. Its structure is complex, now the mainstream of the oil cooler in the market is mostly used by the multi-layer dense zigzag arranged staggered fin connection with the floor made of welded aluminum complex structure as a whole. The structure of oil cooler has the advantage of small size, light weight, heat dissipation area, and high cooling efficiency. Ensure a high quality connection of the fin with the partitions, and partition with the base is a researchable complex scientific issues. Because good connection quality can not only play the role of good heat, but also improve the life of the oil cooler, lower vehicle maintenance costs, improve the competitiveness of car manufacturers and conserve resources.In view of the structural characteristics of the oil cooler, the vacuum brazing process was used to implement the connection for the complex structural parts. First of all, based on the actual vacuum brazing environment, using finite element analysis software ANSYS, founding a finite element model, and set the environment variable parameters, to simulate different vacuum brazing temperature, ensure the oil cooler fins and the temperature distribution between partitions. After analyzing the simulation results, the actual temperature range of the brazing process was determined.Then testing the method, multiple oil cooler parts were tested in a vacuum brazing furnace, and the test results was analysised to evaluate effect of brazing process on the brazing weld quality of oil cooler. By combining experiments and numerical simulation methods, the best vacuum brazing process for the"Yu-Ⅰ"typed oil cooler was explored: the set temperature of the furnace is 615 ~ 620℃, holding time of 4 minutes; and the actual brazing temperature is 600 ~ 612℃, brazing time of 4 minutes.Thirdly, the causes of defects and the controlling factors of the seam such as gap, porosity, slag, corrosion and metal oxides was discussed in this paper. The results showed that when the holding time is constant, the brazing temperature is the main factor to affect the brazing quality: when the soldering temperature is too low, defect of not welded in brazing welding is easily to occur; the other hand, if high temperature when brazing, brazed joint is in prone to corrosion defects.Finally, the existing form and diffusion behavior of the Si element in solder gap was analysed by SEM analysis, the results showed that the existing form and diffusion behavior of Si elements strongly influenced the quality of solder joint. The nature of corrosion was that Si elements existed in liquid diffused into the base material along the grain boundary during the brazing temperature phase, then when the process temperature reducing on, the liquid Si in the grain boundary solidified as the form of needle-like solid, so the corrosion occured.