Modeling for collective growth of fume primary particles with charge effect in arc welding

A model is developed to calculate the collective growth of fume primary particles with charging due to collisions with ions and electrons from the plasma. The model also expresses a particle size distribution with any shape and calculates its transient behavior due to a collective growth of particles through homogeneous nucleation, heterogeneous condensation, and coagulation on the basis of aerosol dynamics. Using the model, numerical calculation is performed to reveal the mechanism of the particle formation and the charge effect on the growth process during MIG welding. In consequence, it is found that almost all particles generated in a typical condition of MIG welding are negatively charged. The effect of particle charge plays an important role on the collective growth process of primary particles of welding fume because the particle charge causes a repulsive Coulomb force which prevents the particles from growing by coagulation. It is recommended that charge effect should be taken into account for studying fume particle formation in MIG welding.