Arc interruption phenomena and internal causes in narrow gap P-GMAW

Among the factors that influence welding defects, arc interruption is an important and unavoidable problem. When the welding torch swings during narrow gap pulsed gas metal arc welding (P-GMAW), arc interruption phenomenon always occurs at the same position along the torch trajectory and is therefore governed by some concrete conditions. Prior to arc interruption, the arc exhibits a distinct shape and the voltage signals fluctuate significantly. Internal causes of the distinct arc shape were investigated, and it was found that narrowness of the gap played an important role. As the metal vapor is easily ionized, the arc rises along with the rising vapor plume, expanding beyond the end of the wire and forming an approximately parabolic shape. The effect of narrow grooves on the droplets and weld beads, especially when the torch deviates from the groove center, will be beneficial for the generation and collection of metal vapor. Since the arc will always be prolonged prior to interruption and the voltage will fluctuate, the arc interruption of this kind can be predicted and eliminated, thus improving the welding quality of narrow gap.