GMA welding metal transfer mode study by high-speed imaging and electrical signal acquisition

Abstract

Weld metal transfer modes in gas metal arc welding process have an important role in electric arc stability, in the amount of absorbed gases by the melted metal in weld pool, allow out-of-position welding and influence in sparkles generation. The objective of the present work is to obtain images of the metal transfer to the weld pool, in order to better characterize the transfer mode boundaries. Besides, electric signals of welding current and voltage were acquired and compared with the generated images to confirm the results. High-speed imaging helps to identify the weld metal transfer mode. In this work, a high-speed camera and filter lenses were used to get images and movies of welding arcs generated by three different AWS ER70S-6 wire diameters (0.8, 1.0 and 1.2 mm). Also, different shielding gases and mixtures were tested (Ar, Ar + 2% O2, Ar + 10% CO2, Ar + 25% CO2 and CO2). Metal transfer modes could be observed at a frame rate of 5000 fps. Metal transfer mode maps were plotted to identify regions of each kind of metal transfer. Interchangeable globular/spray metal transfer occured in some cases of cyclic alternation between globular and spray transfer during the welding.