Two-dimensional time-dependent modelling of fume formation in a pulsed gas metal arc welding process

Gas-metal arc welding (GMAW) is a process in which a non-constricted plasma arc is ignited between a workpiece that works as the cathode and a metal wire that works as the anode; the latter is melted by the heat from the arc and a metal transfer occurs from the wire to the workpiece. Following recent studies on health effects for welding workers exposed to fume inhalation, a huge effort is currently being devoted to the investigation of fume formation during the welding process and to the development of processes with lower fume production rate. In the welding process, fumes are generated by nucleation and growth of nanoparticles from the metal vapour coming from evaporating weld pool, droplets and metal wire.Even if experimental try and fail approaches have been adopted to develop operating conditions that induce a lower formation of fumes, modelling is a valuable tool that provides insight on those physical processes occurring during the formation phase that cannot be easily monitored by diagnostics. In this work, the simulation of fume formation in pulsed GMAW process is reported taking into account the metal transport and metal vapour formation in a self-consistent approach using the Volume-of-Fluid (VoF) method and modelling fume nanoparticles production using the method of moments (MoM) for the solution of the aerosol general dynamic equation. While this method has been widely used for the modelling of nanoparticle synthesis in thermal plasma reactors, this is the first attempt to implement the MoM approach in modelling fume formation in pulsed GMAW.