The fluidity of welding wires is an important but relatively unexplored area of research. In this study, we explore the concept of the fluidity of the wire that a welder feels during welding, rather than the fluidity of the weld itself. The existing definitions for the fluidity of metal through a spiral test done in casting cannot be used for wires. In this study, we propose a quantifiable metric of fluidity for aluminum welding wires and investigate the relationship between this metric and the fundamentals of the welding process. Developing a quantifiable metric of fluidity would help design alloys with better fluidity and help determine which parameters to improve in the filler material and the welding process.
Experiments to quantify fluidity in Al wires were performed with experienced welders. In this experiment, four alloys ER1100, ER4043, ER5356, and ER5356TM, of 1.2 mm diameter, were subjected through GMAW, and their WFS, Voltage was recorded in three modes AC Pulse, constant voltage, and pulsed. The welder's subjective impression of the fluidity experienced was recorded in each of these experiments. The welder determined wire feed speeds and voltage for each wire. Every experiment was randomized and single-blinded to the welder to obtain an unbiased perspective of the wire used. High-speed and high dynamic range videos were recorded for each weld using a phantom V210 and XIRIS XVC-1000e welding camera, respectively. Thermophysical properties, including their solidification behavior were obtained through Thermocalc for equilibrium and scheil solidification.
The results indicated that ER1100 was found to have the highest fluidity, and the lowest was ER4043. Both ER5356 and ER5356TM exhibited similar fluidity. The comments of the welder also assigned higher fluidity levels to welds on a hot plate. Analyzing the thermodynamics of the alloys, the dendrite freezing range through scheil solidification was found to be a more reliable metric when compared to equilibrium solidification. Although, the metric still needs modifications when accounting for wider beads. Based on the fast-moving heat source, a suitable criterion was the weld width minus the dendrite width. This criterion aligns with the welder's perspective that fluidity tends to increase with heat input and preheat, while it decreases with dendrite range and plate thickness.
The proposed criterion after certain modifications would be representative of the welder's perceptions, and this would provide direction for alloy modifications and process parameters and waveforms, not only in aluminum but in other alloys too.
Keywords: Fluidity, Aluminum, GMAW