Influence of controlled and conventional short circuit waveforms on mechanical and microstructural effects in the gas metal arc welding processes

Abstract

Short Circuit Gas Metal Arc Welding (GMAW) is used extensively for high-productivity welding thin steel sheets and is also useful for positional welding of thicker section steels. The two main difficulties encountered when welding with short circuit transfer are burn-through and distortion in the case of sheet metal. To overcome this, several manufacturers have come forward with power sources using modern inverter techniques that control the arc current waveform, dynamic wire feed, or both. The research study has focussed on the arc voltage and current characteristics of the different Waveform-controlled GMAW variants developed for low heat input applications. The experiments were carried out on conventional short circuit transfer mode and modified short circuit transfer mode. It was concluded that the welding heat input greatly influences the weldment properties. Consequently, cold Metal Transfer uses both waveform control and dynamic wire feed control technologies, which makes it to reduces the droplet detachment power to 98 % of that of conventional short circuit mode. Moreover, the lap tensile strength of cold metal transfer mode was increased by 17.9 % compared with conventional short circuit transfer mode. The microhardness of the modified short circuit mode has significantly increased with conventional short circuit mode, which was evident by microscopic analysis.

Keywords

• Gas meal arc welding
• Cold metal transfer
• Short circuit
• Waveforms