Synchronous Observation of Topside Weld Pool, Keyhole Entrance and Keyhole Exit in Keyhole Plasma Arc Welding

A synchronous visual sensing system was established to observe the topside weld pool, keyhole entrance and keyhole exit in the same time during keyhole plasma arc welding. Complete topside weld pool was captured by a common CCD camera perpendicularly to the welding direction. Meanwhile two other cameras were employed to monitor the keyhole entrance from the rear view and to capture the keyhole exit from the substrate backside. The evolution process of the weld pool and keyhole behaviors and shapes along with the accumulated heat input were observed. The mechanism of their interactions were discussed and analyzed. The comprehensive investigation of the complicated physical process provided some fundamental and profound understandings. The potential application to predict or even control the penetration in real time will promote the automation and adaption of this welding technology.