Comparison of CMT with other arc modes for laser-arc hybrid welding of steel

In this study, three different arc modes in laser-arc hybrid welding with a gas metal arc were studied, i. e. the standard, pulsed and cold metal transfer (CMT) modes. The pulsed mode is more controlled than the standard mode and offers reduced heat input to the workpiece, which enables welding of thinner materials. The CMT mode utilizes surface tension drop transfer with controlled wire feeding, and therefore, involves less heat input than the other arcmodes, and it is also considered to generate less undercut and spatter than the other modes. This study compares hybrid welds made by the three arc modes with a close-to-production setup for low and medium wire deposition rates, within the limits of the CMT process. The welds were studied by scanning and high speed imaging. The study shows that the differences between the drop transfer modes are reduced due to the presence of a laser keyhole. The dominating influence on the solidification and melt flow is the arc and especially the gouge created ahead of the keyhole. The main pros and cons of the different arc modes are discussed.