Research On Temperature Of Cu/Al Tube Joint By Magnetic Hybrid Forming Assisted Fluxless Solidering Technology

Due to the social orientation of building a resource-saving society and the inherent demand of enterprises to improve product profits,the use of copper and aluminum heterogeneous metal tubes is an inevitable trend faced by the refrigeration industry.How to obtain copper-aluminum pipe joints efficiently and low cost is an important problem.In the brazing process of cu-al non-equal diameter pipe,it is difficult for the solder to spread effectively on the base metal surface and use brazing agent.In order to solve this kind of problem,the magnetic pulse semi-solid brazing process is put forward by studying and comparing the welding methods of different kinds of cu-al metals and taking advantage of magnetic pulse forming and semi-solid forming technology.Firstly,the gap between copper tube and solder and between solder and aluminum tube is reduced by magnetic pulse preforming to realize effective contact between solder and base metal.Then the magnetic pulse assisted semi-solid brazing is carried out for the preformed pipe to realize the metallurgical connection between the filler metal and the base metal.In order to understand the temperature distribution of solder in brazing process and develop a reasonable heating process.COMSOL was used to establish the induction heating temperature field model under the condition of the tooling,and the temperature field distribution of the solder was analyzed.The influence of coil parameters such as coil height and inner diameter on axial and radial temperature field distribution of solder was studied.The influence of current frequency and current size on heating rate was also studied.Based on the summary of the factors affecting the temperature field distribution of solder,a piecewise induction heating process was proposed,which reduced the temperature field non-uniformity of solder to some extent.The test results show that the Zn-15Al brazing temperature is 390?,semi-solid solder not enough liquidity,not remove Al parent metal surface oxide film.Zn-15Al brazing temperature is 410?,has realized the good metallurgical connection.Cooling time is shorter and cooling liquid composition is relatively uniform,making?phase in the brazing seam is relatively close to the ball.The Cu content of brazed joints increases with the increase of temperature,and the ternary phases of CuZn₅ and Al_4.2Cu_3.2Zn_0.7are generated.Zn-22Al brazing temperature is 430?,also can't remove the alumina membrane;But the spreading property of the filler metal is improved and the metallurgical connection with Cu base metal is realized.Zn-22Al brazing temperature is 460?,good metallurgical combination;Longer cooling time and the cooling process of liquid phase composition of non-uniformity increase,making?shape is irregular.Zn-22Al when brazing temperature to 490?,can often be found in the brazing seam CuAl2 phase.The spatter of solder affected by temperature condition results in different soldering rate.The temperature condition affects the solid phase ratio and spreading property of the filler metal and determines whether the metallurgical joint is formed or not.The microstructure of brazed joints is determined by the influence of temperature on Cu content and phase growth.