Stable keyhole welding process with K-TIG

Keyhole welding process was successfully achieved by using a self-made K-TIG torch. High quality welds were produced in 8mm-thick stainless steel plates. To evaluate the keyhole stability in the novel manufacturing process, keyhole behavior was observed by using a vision system from backside of the workpiece. Efflux plasma interference was eliminated by using a filter glass. Keyhole exit behavior was imaged in real time during the welding process, keyhole size and position were extracted from the keyhole image sequence. Keyhole behavior parameters, including keyhole length, width, length/width, and deviation distance were measured. It was found that keyhole exit was deviated away from the torch axis even though the arc current was very high in K-TIG welding process, keyhole exit had an oval shape. Continuous open keyhole welding were easily achieved in K-TIG process, without unstable keyhole stage when the keyhole firstly opens. Keyhole size, shape and position were all related to welding current. The observation results lay solid foundation to understand the thermal-physical behavior in K-TIG, and for the further optimizing of the welding torch.