Hollow cathode centered negative pressure Arc

A novel welding arc named hollow cathode centered negative pressure arc (HCCNPA) is proposed in this paper. This is an arc discharge being ignited/maintained at a hollow cathode whose cavity is negatively pressurized. The authors designed an experimental system to stabilize the arc and monitored/studied the arc behavior using a highspeed image processing system. Arc behaviors were studied and correlated to the process pa-rameters. It was confirmed that the negative pressure constricted the arc and elevated the tungsten temperature. The dynamic change in the arc characteristics were reflected in the arc voltage waveform. In addition, the arc length, current, and inner pressure ail affected the characteristics of the resultant arc. To examine the distribution of this novel arc as a heat source, stagnation ablation experiments were designed and conducted on Grade D steel workpieces. Analyses on the bead appearance, cross section, and microstructure provided the evidence to support the claim that the resultant arc in the proposed HCCNPA process has a more evenly distributed energy density in the center and a higher energy gradient at the boundary in comparison with the conventional GTA, as have been expected.