Study On The Spreading Behavior Of Brazing Material In Cu/Ni Metal Wire Deep Melting Brazin

Heating cable low-temperature radiant heating technology has the characteristics of energy conservation,environmental protection,safety and comfort.It has become an internationally recognized advanced heating mode.Its key technology is the manufacturing of heating cable core.The core of the heating cable is made of Cu wire with different diameters(cold wire,(?)0.4 ～ 1.13mm)and Ni based alloy wire(hot wire,(?)0.3 ～ 0.85mm)after deep penetration brazing.Deep penetration brazing is a special welding method between thermal conductivity welding and brazing.It mainly uses the contact resistance between copper electrode and graphite welding pool to generate heat source.After melting,Ag based solder flows and spreads to Cu/Ni wire in graphite welding pool,so as to realize the welding of Cu/Ni wire in graphite welding pool.Therefore,it is of great significance to study the flow and spread of Ag based solder in Cu/Ni wire to improve the quality of heating cable core welded joint.This subject is a sub subject of the national natural fund project "Research on the influence and mechanism of graphite molten pool ablation behavior on solder flow and spread" undertaken by Guizhou Key Laboratory of characteristic equipment and manufacturing technology.By establishing the mathematical model of deep penetration brazing welding heat source,this paper discusses and analyzes the distribution law of heat source temperature field of deep penetration brazing,and then studies the flow and spread behavior of Ag based solder in graphite welding pool.The specific research contents are as follows:1.By analyzing the heat source formation principle and influencing factors of Cu/Ni wire deep penetration brazing,combined with Hertz elastic contact theory and fractal rough contact theory,the fractal contact resistance model between copper electrode and graphite welding pool is established,and the mathematical model of Cu/Ni wire deep penetration brazing heat source is formed.2.The generation process of welding heat in Cu/Ni wire deep penetration brazing was simulated and analyzed by adding solid thin-layer element and setting resistivity with ANSYS software.The results show that the heat source is transferred from the outer surface of the graphite welding pool to the inner hole,and there is a difference of about 30℃ between the inside and outside.When Ag based solder and Cu/Ni wire enter the graphite welding pool,the temperature of the inner hole in the graphite welding pool decreases by about 15℃,indicating that Ag based solder and Cu/Ni wire have a significant effect on the heat source of the inner hole.3.Using ANSYS FLUENT software to establish a model in line with the welding conditions,it is obtained that the solder flow field rotates clockwise along the gap as a whole,and the surface tension is one of the main factors of solder flow.When the calculation time is 0.2s,due to the effect of surface tension,the maximum velocity of solder on the copper wire side increases from 0.14m/s to 0.16m/s,and the velocity of solder on the nickel wire side is less than that on the copper wire side;When the flow rate on the copper wire side increases to 18m/s,the calculated maximum flow rate on the nickel wire side increases to 6s;After the calculation time is 2s,the flow field tends to be stable.The larger the hole size in the graphite welding pool,the smaller the solder flow rate,and the poor spreadability in Cu/Ni wire;The effect of gravity is not obvious as that of surface tension.