Study On Droplet Behaviors Of GMAW Based On Rotating Arc Sensor

The rotating GMAW (Gas Metal Arc Welding) not only has the advantages ofgeneral GMAW, but also is easy to realize the seam tracking and the weldingautomation, it is getting more and more attention in industrial production. The droplettransfer behaviors of rotating GMAW welding is an important factor affecting thestability of welding process and welding quality. By using the numerical method tosimulate droplet behaviors, we not only can obtain the quantitative relationshipbetween the droplet shape, size, transition frequency and the welding parameters, butalso in-depth study of current density distribution in the droplet, droplet force modeland arc temperature field, it also can provide date foundation for the numericalsimulation of molten pool and provide the basis for the establishment of weldingprocess.Based on MHD theory, this paper uses the commercial CFD software FLUENTto establish the three-dimensional mathematical models of rotating GMAW weldingand general GMAW welding at first. With the help of the secondary development ofFLUENT with UDF functions, the arc temperature field, velocity field and the staticpressure field of the different models is simulated. Then by using of Tecplot which isa post-processing software to analyze the data of result, the results show that whenthe rotation frequency is not big, the centrifugal force has little influence on the arcplasma, the main reason of the inclination of rotating GMAW welding arc shape is theinclination of wire head which is caused by the centrifugal force effect of droplet.To simulate the droplet transfer behaviors of rotating GMAW welding, the VOFmodel and moving mesh technology are used to establish the three-dimensionaltransient mathematical model of droplet transfer in rotating GMAW welding, and atwo-dimensional axisymmetric mathematical model of general GMAW welding isalso buid for comparison and analysis. With the same welding parameters, the dropletshape, droplet size and transition frequency at different moments in the two kinds ofmodel can be obtained in FLUENT, and the inside velocity field of droplet isanalyzed. The droplet transfer behaviors of different rotation frequencies are simulated for analyze the law between rotating frequency and droplet behavior.Finally, a high speed camera platform, which has the synchronous signalacquisition function, is used to verify the accuracy of the simulation results with thesame welding parameters. The droplet diameter and transition frequency ofexperiment results are in good agreement with the simulation ones, and also thereasons of error are analyzed. Combined with simulation and experiment results, itshows that the effect of centrifugal force of the droplet will increase significantly withthe decrease of the current in rotating GMAW welding, the metal transfer cycle andthe droplet diameter will decrease with the increase of the rotation frequency, whichfollows the law of centrifugal force is proportional to the rotation frequency.