Abstract
To improve the penetration depth and welding efficiency of TIG welding, we have proposed the “Electromagnetic Controlled
Molten Pool Welding Process” （hereinafter referred to as ECMP method）. Until now, by utilizing the electromagnetic force
generated when adding an external magnetic field to the current flowing in the arc and the molten pool, it has become possible to
increase the penetration depth, albeit under very limited conditions. However, the penetration depth varies greatly depending on the
distribution of the external magnetic field and the position of the magnetic poles, and the slight differences in these conditions could
result in a shallower penetration depth. In this study, in order to elucidate this mechanism, we observed in detail the effects of the
external magnetic fields on the arc, the surface flows of molten pool, and the bead shape. In addition, since it is clear that the flow
within the molten pool has a large effect on the penetration depth, we directly observed the flow within the molten pool by the X-ray
transmission observation. As a result, when a negative magnetic field was applied that inclined the arc backwards （at which time
electromagnetic force was generated in the arc in the opposite direction to the welding direction）, the penetration of TIG welding
increased and this mechanism was clarified from the observation results of the flows within the molten pool.
