Suppression of humping bead in high speed GMAW with external magnetic field

In high speed gas metal arc welding, the higher momentum of backward flowing molten jet in a weld pool contributes to the occurrence of humping bead. In this study, the external magnetic field is exerted to control the fluid flow and its velocity distribution inside the weld pool to suppress the humping bead. The effects of the external magnetic field on the weld pool flow dynamics, arc column and the metal transfer are experimentally investigated. The required excitation current levels to suppress humping bead under different welding conditions are obtained. It is found that the deflection of arc column and liquid metal stream at wire tip can be offset by a suitable backward inclination angle of torch. With appropriate combination of external magnetic flux density and backward inclination angle of torch, a good quality weld bead without humping and spatter can be obtained in high speed GMAW.