Through-the-Arc Detection of Weld Defects in Pulsed GTAW
Timothy P. Quinn, D C. Oakley
A through-the-arc sensing system was used to detect defects in the welding of thin-walled stainless-steel tubing. It measures the process current and voltage and passes the resulting signals through a signal processing algorithm. The arc condition number, a measure of the (relatively) low frequency stability of the arc, was used to look for defects in the welds. Data were taken during welding on the factory floor both during production and while intentionally making defects. For the first series of tests, cardboard debris was placed on the seam of the rolled tube just before welding, causing 1-10mm defects (lack of fusion). The sensor detected all of the defects by monitoring when the arc condition number exceeded a tolerance. The tolerance was set so that no warning was given when no defect occurred. In a second series of tests the system was used in actural production and monitored the weld until unintentional defects were found. Two series of defects were flagged, and no nondefective weld was flagged.
International Conference on Computer Technology in Welding