Avaliação da influência do tamanho do bocal na eficiência térmica do processo de soldagem TIG

Abstract

Existing standards, such as the EN ISO 1101-01, stipulate a constant value for the thermal efficiency (k) for each welding process. On the other hand, values of k found in literature may vary over a wide range, going, for example, from 30% to 90% for the TIG process. One possible explanation is that researchers usually ignore the factors that may influence the k-value, such as the shielding gas flow, nozzle size, torch inclination angle, etc. The aim of the present work is to confirm that even a factor usually considered insignificant, such as the size of the torch nozzle, can influence the heat transfer from the arc to the object, changing the thermal efficiency of the TIG welding process. In order to demonstrate how the nozzle size influences the thermal efficiency of the TIG process, tests were performed using a continuous water flow calorimeter with three nozzle sizes (8, 10 and 12) while voltage and current were kept constant, and then the results were compared. It was found that the lower the torch nozzle (8), the higher the k value (57.85%), the geometric values of penetration and the melted areas of the weld bead, showing a greater heat transfer to the plate under these conditions. Some hypotheses to the results obtained were also discussed.