Visualization of Fume Formation Process in GMA Welding

In order to clarify fume formation mechanism in arc welding, quantitative investigation based on understanding of

interaction among the electrode, arc and weld pool is indispensable. A fume formation model consisting of heterogeneous

condensation model, homogeneous nucleation model and coagulation model has been developed and coupled with a GMA welding

model. A series of processes from evaporation of metal vapor to fume formation from the metal vapor was totally investigated

by employing this simulation model. This study aims to visualize the fume formation process and clarify the fume formation

mechanism theoretically through numerical analysis. Furthermore, the reliability of the simulation model was also evaluated

through comparison of the simulation result with experimental result. As a result, it was also clarified that that most part

of the fume was produced in downstream region of the arc originating from the metal vapor evaporated mainly from the

droplet. This kind of the fume was constituted of particles with size of several nm. On the other hand, if the metal

transfer becomes unstable and the metal vapor near the droplet diffuses directly toward the surroundings of the arc not

getting on the plasma flow, the sizes of particles reach 1 micro m.