A Study of GTA Weld Pool Oscillation

This paper deals with the oscillation behavior of gas tungsten arc weld pools in mild steel Fe 360 and stainless steel AISI 304. The natural oscillation frequency of stationary weld pools of different sizes was determined by measuring the arc voltage variation after triggering the pool by means of an arc current pulse. It was found that for both partial penetration and full penetration, a relation exists between the natural oscillation frequency and the geometry of the weld pool. It appears that the natural oscillation frequency of a partial penetration pool is considerably higher than the natural oscillation frequency of a full penetration pool and that an abrupt transition occurs between both modes of oscillation. The results of this study show that weld pool geometry, in particular joint penetration, might be in-process controlled by monitoring the natural oscillation frequency of the weld pool.