Investigation Of Welding Technology For Aluminum Alloy Plate-Fin Oil Cooler

Oil cooler is an important part of automotive engine cooling system,the main function of the oil cooler is to cool the engine oil. Nowadays, the most widely used automobile oil cooler is the multi-layer, dense zigzag arranged staggered fin connection with the floor made of aluminum alloy. The structure of oil cooler has the advantages of small size, light weight and high cooling efficiency, but the overall structure of the oil cooler is complex, on the other hand, there are very demanding requirements for sealing and corrosion resistance property of oil cooler. In order to realize the precision and high quality connection between the oil cooler fin and the core plate, the core plate and the front and back sealing plate, and the final objective is to achieve precision and reliable connection of the oil cooler and the cooling system, its connection method has become a very hot topic.This paper takes CA aluminum alloy plate-fin oil cooler as the research object,firstly, resistance spot welding(RSW) process of oil cooler roof section and Nocolok brazing of oil cooler core body were formulated, then, the effects of process parameters on macroscopic morphology, microstructure, microhardness and tensile properties of resistance spot welded were experimentally investigated, meanwhile, the effect of process parameters on microstructure of Nocolok brazing welded was investigated, and the comprehensive performance test of oil cooler was formulated. The aim is to provide a theoretical basis about welding process for the oil cooler.The main conclusions can be summarized as follows:1) The macroscopic morphology of resistance spot welding joint, consisted mainly of nugget, corona bond and base material. The microstructure of resistance spot welding nugget, consisted of equiaxed dendritic structure in the nugget center and a columnar structure at the nugget edge. The equiaxed dendritic structure coarsens gradually with increasing welding current and time. The number of columnar structure decreases with increasing the welding current, while, its number increases with increasing the electrode pressure.2) The influence of welding current, welding cycle and electrode pressure on microhardness and tensile properties of spot welding joints are different. The microhardness of the columnar crystal region is larger than the center of the weld. The minimum microhardness appears in the heat affected zone(HAZ).3) According to the experimental results, the spot welded joint with the process parameters of 22 kA, 8 cyc, 0.20 MPa, 25 cyc and 15 cyc performs the optimal properties of 40.64 Hv and 2.103 kN.4) The brazed zone consists of an ?(Al) solid solution layer and Al+Si eutectic structure. The optimal furnace brazed joint with the process parameters of six partitions is 600?-605?-610?-615?-620?-615? and brazing area's mesh belt speed is 320mm/min.Finally, the comprehensive performance test of the oil cooler shows that the qualified rate of the product is high. It can meet the requirement of production and use,and the optimal process parameters can be used to guide the actual welding production.