Numerical Analysis Of Fluid Flow And Velocity Field During Liquid Filler Droplet Spreading Behavior In Arc Brazing

Arc brazing is a newly developed joining technology which has obvious superiorities in joining of thin sheets and in the defects renovation. Now the research of such technology gets extensive recognitions by researchers at home and abroad. In the paper, the methods of spreading tests and the numerical simulation of fluid and velocity field are conducted to study the spreading process of filler metal droplet. And the studies are of great importance to accelerate the applications, development and innovation of the arc brazing technology. Firstly the dynamic spreading process tests of CuSi3 filler metal droplet under TIG arc heating are conducted. It can be seen that the spreading area and diameters increase and spreading heights and wetting angles decrease with the increase of arcing time and current when the arc length is 6mm. and when the arcing time is more than 4s, the change of spreading area, diameter, wetting angle and height becomes slower. The results showed that the optimize brazing parameters of CuSi3 filler on galvanized steel is I=70A, L=6mm, t=4s. For different filler metals, the wetting abilities of CuSn6 and CuSi3 are superior to AlMg5 and AlSi5 on galvanized steel sheet. Based on the experimental analysis, the governing equations and boundary conditions that are fit to the spreading process of filler metal under arc brazing are developed, and then they are transformed into finite volume equations. Using the SIMPLEST algorithm, the governing equations and boundary conditions are solved by the SEM and HOL methods implemented in PHOENICS code. The free surface evolution results of CuSi3 and AlSi5 filler are obtained. It can be seen that the simulation results are approached with experimental results. And the error is more with small parameters than with big parameters. From the analysis of simulation results, it can be seen that the spreading process of filler metal droplet is dominated by arc pressure, filler metal unit volume weight and surface tension. In addition, the flow and velocity field within CuSi3 filler droplet at different arcing time are also obtained by PHOENICS code. On the one hand the results showed that the flow direction under arc axes is downwards. And the flow direction is towards bilateral left or right. On the other hand the results showed that the maximum velocity under arc brazing is bigger than that of TIG fusion welding at the same welding parameters. Finally, the couple analysis of interfacial compound and micro flow, velocity field is conducted, the interfacial compound growth behavior under arc brazing are then enriched.