CONTACT TUBE WEAR DETECTION IN GAS METAL ARC-WELDING

A real-time algorithm has been developed to detect contact tube wear d uring gas metal are welding. The integral from 0.3 to 4 Hz of the powe r spectral density of voltage (constant current and pulsed current pow er sources) or current (constant voltage power sources) is called the wear parameter and is used to measure wear. The contact tube is predic ted to be worn when the parameter grows nonlinearly or exceeds a thres hold. For 11 contact tubes worn by welding on a rotating pipe, the wea r parameter predicted the observed increase in the area of the contact tube's exit bore of 140% of the original area within a standard devia tion of 20%. Welds were made with a constant voltage power source and with a pulsed current power source at two different voltages. The puls ed current welds were made with and without automatic voltage control by wire feed speed and with and without weaving in a V-groove. No sign ificant differences were detected between the wear parameters for all test welds, indicating that the algorithm can be used under these weld ing conditions.