Research On Temperature Field Distribution Of Graphite Welding Pool In Cu/Ni Metal Wire Deep Penetration Brazing

The core of the heating cable is made of unequal diameter Cu wire(cold wire,?0.4-1.13mm)and Ni-based alloy heating wire(hot wire,?0.3-0.85mm)paired by deep-melt brazing.Deep-welding of heat-generating cable cores is a special welding method between the thermal conduction welding and the brazing.The main use of the contact resistance between the copper electrode and the holed graphite welding pool is to heat the Ag-based brazing filler metal.The brazing of the Cu/Ni base in the holed graphite welding pool is realized.Therefore,the heat transfer characteristics of the graphite weld pool is one of the key issues affecting the welding heat and welding quality.This subject is a subtopic of the National Natural Science Foundation of Guizhou University's Key Laboratory of Special Equipment and Manufacturing Technology of the National Natural Science Foundation of China under the project “The Effect and Mechanism of Ablation of Graphite Melts on the Flow of Brazing Materials”.The heat transfer performance,the distribution of the temperature field in the graphite weld pool under the action of ablation,and the experimental verification were studied.The specific research contents are as follows:1.On the basis of mastering the Cu/Ni wire deep penetration brazing process and establishing the mathematical model of the interface contact resistance between the copper electrode and the cylindrical graphite welding pool,the law of Fourier heat transfer and nonlinear transient heat conduction are utilized.Further clarify the elec tro-thermal coupling effect of Cu/Ni dissimilar metal wire deep penetration brazing,theoretically analyze the heat transfer mechanism of graphite weld pool and factors that affect the temperature field distribution of graphite weld pool.2.In the simulation calculation of heat transfer in the graphite weld pool,experimental testing techniques were used to obtain the temperature-dependent physical parameters of the four materials of ordinary graphite,fine graphite,molded graphite,and isostatic graphite,which improved the graphite welding pool of the four materials.Simulate calculation accuracy.3.Simulated and experimental tests were used to analyze the distribution and influencing factors of the temperature field of the graphite welding pool and the copper electrode during the heating process of deep-seated brazing.The heat transfer in the four welding pools of ordinary graphite,fine graphite,molded graphite and isostatic graphite was discussed.Characteristics,distribution of copper electrode-graphite welding pool temperature field.The thermal conductivity of ordinary graphite is lower than that of fine graphite,molded graphite,and isostatic graphite,resulting in a slow heat transfer rate to overcome the long temperature gradient of graphite,and the thermal resistance of the contact interface is large,which reduces the thermal conduction of the contact heat to the electrode,resulting in ordinary graphite welding.The temperature of the pool is high and the heat transfer effect is best.4.The temperature field of the graphite weld pool under ablation was calculated by simulation.The mechanism of the temperature field in the weld pool was discussed after the low temperature ablation of graphite,the ablation of the center of the inner hole,the wear of the orifice and other factors affecting the temperature field in the weld pool.The increase in ablation of holes in the graphite welding pool The temperature of the Ag-based solder and the welding wire decreases in the welding pool,which leads to a decrease in the flowability of the solder and affects the quality of the welded joint.