Welding Penetration Control with Weld Pool Resonance in Traveling Pulse TIG Welding

There exists excellent corresponding relationship between weld pool oscillation frequency and weld pool size in TIG welding, which can be used to detect weld pool size and control the weld pool penetration. However, It is very difficult during fast travelling welding. In this paper, the weld pool is excited by pulsating welding current which is produced by superimposing a certain frequency sine wave current on the straight polarity DC current, and the oscillating signals of weld pool can be detected through arc voltage signals in travelling TIG welding. During the time when pulsating welding current works, along with the increase of weld pool size, weld pool resonance phenomenon happens when the nature oscillation frequency of the weld pool is equal to the frequency of sine wave current. The feature variant signal of weld pool resonance, detected from arc voltage signal, is better in strength, stability and repeatability than existing method with short pulse high welding current to detect the weld pool oscillation. Moreover, this method has been used for full penetration control in TIG welding and has acquired well effect.