Study On Brazing Of The Aluminum Liquid Storage Tank In Controlled Atmosphere Brazing Furnace

Automotive air conditioning system as one of the important device provides thecomfortable driving environment. The improvement of components structure,manufacturing process, performance of the air-conditioning unit and the rationality ofthe layout have been closely watched by car manufacturers. A new generation ofintegrated automotive air conditioning condenser is composed by the core body andliquid storage tank. Integrated automotive air conditioning condenser can reduce thespace which is occupied by refrigeration system, reduce the workload of installation,improve the efficiency of installation, and improve the heat exchange efficiency. Atpresent, the welding of liquid storage tank is MIG welding. This article adopted themethod of brazing after assemble core body and liquid storage tank instead of MIG. Inaddition to this, finite element analysis method was used to determine the better processparameters, and solve the problems of long cycle, low efficiency and high cost whichare caused by the scene debugging repeatedly.In this paper, the furnace brazing process was analyzed. According to the heattransfer of furnace brazing process and the feasibility of the numerical simulation,3Dtransient thermal analysis model of furnace brazing was built after making someassumptions. The brazing temperature field of aluminum liquid storage tank wassimulated. The temperature of liquid storage tank presented dramatic changes duringbrazing process. Brazing welding temperature distribution is uniform. Temperaturedifference between inside and outside surface is less than0.3℃. Brazing temperaturewas measured by using furnace temperature tester. The model accurately predicted thethermal cycle curve and the results coincided with experiment. Brazing processparameters was determined preliminarily by simulation method.Furnace brazing experiment was carried out the in a Chongqing automobile airconditioning production base. The brazing joints of liquid storage tank were analyzedby using metallographic microscope, scanning electron microscope and energyspectrum analyzer. In addition, hydrostatic test, helium mass spectrometer leak test andSWAAT sea salt spray corrosion test were made to test the brazing joints. Differentbrazing joints were tested to compare the appearance quality, air tightness andmicrostructure. The brazing joints with preset brazing foil and brazing paste can acquiregood appearance quality. But brazing joints with preset brazing wire has obvious groove, because preset brazing wire can’t fill the preset groove. The small dimension ofprefabricated groove makes brazing paste coating uneven, and causes insufficientbrazing filler metal of partial brazing seam, ultimately leads to gap defects. Comparedcomprehensively, the effect with preset filler metal in foil is the best, paste comessecond, wire is the worst. The effect of mesh belt speed (namely heat preservation time)on brazing joint microstructure and air tightness were investigated. Based on the testresults, the optimized processing parameters of storage tank were acquired. The storagetank is brazed with Al-Si alloy in foil. The brazing phase is divided into six partitions,that is,600℃-610℃-615℃-623℃-625℃-620℃. Mesh belt speed is750mm/min.Assembly gap is0-0.1mm. The results show that the process parameters can acquireeligible product, and finite element simulation is feasible on the process guidance.