Dynamic behaviour of CO2 laser GMA hybrid welding

Abstract

Laser GMA welding has demonstrated its fitness for industrial application in the past few years and is now widely regarded as an appropriate welding process for various applications e.g. in thick-section welding. However, as it is a combination of two welding processes, a wide variety of parameters has to be optimized. Moreover, due to the fact that the specific advantages of hybrid welding arise from the interaction of these two processes and, consequently, of their parameters, the challenge during process optimization is even greater. To contribute to an improvement in this situation, basic investigations into factors influencing arc behaviour and, as a consequence, weld quality in CO2 laser GMA hybrid welding of various mild and stainless steel grades were conducted at BIAS. Among the factors studied were shielding gas composition, welding direction (leading laser / leading arc), laser power, focal position and welding speed as well as several arc parameters. By the help of high-speed videography and recordings of arc current and voltage, interaction effects were identified and demonstrated. Within this paper, some results of these investigations will be presented and discussed. Moreover, some practical applications of these basic findings for welding of mild and stainless steels in shipbuilding will be demonstrated.