Characteristics of welding and arc signal in narrow groove gas metal arc welding using electromagnetic arc oscillation

Narrow groove welding is an important technique for increasing productivity in the manufacture of thick-walled components. The nature of the process demands an automated approach and precise control to ensure consistently high weld quality. The most important objective of narrow groove welding is to maintain uniform and sufficient penetration at both groove faces. Several different approaches, such as wire bending technique and wire rotating method, have been adopted in an attempt to minimize the incomplete fusion in the narrow groove GMAW process. In this study, a welding system using electromagnetic arc oscillation was developed for narrow groove welding. The electromagnet for applying a magnetic field to the welding arc was designed from the electromagnetic analysis results. This paper shows the arc and bead characteristics in narrow groove GMAW using electromagnetic arc oscillation. Based on the results, the appropriate welding and oscillation conditions were selected to satisfy high weld quality. Consequently, magnetic arc oscillation resulted in uniform and sufficient penetration to both groove faces. Arc signal characteristics for automatic joint tracking were also investigated. The periodic change of welding current in electromagnetic arc oscillation was examined by experiments and numerical analysis. To establish the mathematical model of the arc sensor, some assumptions were needed to calculate the arc length. Analytical results using these assumptions showed good agreement with experimental ones. The periodic signal was adopted to develop an automatic joint tracking system in narrow groove GMAW.