Visualization of fume formation process in arc welding with numerical simulation

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 considering Brownian force and Coulomb force as driving force of particle 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 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 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 mu m. (C) 2012 Elsevier B.V. All rights reserved.