Abstract
CO2 blended with Ar is the most common shielding gas used for short-circuit gas metal arc welding (GMAW). There has been some technical knowledge devised from the process application over the years (personal opinion and results from practice) on the selection of the gas blend composition. However, there is still a lack of more scientific data to explain the performance of the mixtures. This paper presents a systematic study of the influence that CO2 content in mixture with Argon has on the operational performance of the short-circuit GMAW. The objectives of this study were to describe, to quantify and to explain the alterations in the metal transfer behavior, spatter generation, weld bead geometry and bead finish due to the different CO2 contents in the shielding gas. Carbon steel plates were welded in adequate parametric conditions for each CO2 + Ar shielding gas composition (CO2 ranging from 2 to 100 %). These parametric conditions were found by applying a metal transfer regularity index over welds carried out at different voltage settings for each gas blend. A target of 130 A was applied as base for comparison. Laser shadowgraphy with high-speed filming and current and voltage oscillograms were used as analysis tools. The results showed (and confirmed) that the increase of the CO2 content deteriorates metal transfer regularity, leading to excessive spatter generation and uneven bead appearance, but increases the penetration and the fusion area of the weld beads and improves bead convexity. In general, the CO2 content should neither be lower than 10 % (unless for thin plates) nor higher than 30 %.
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Acknowledgments
The authors wish to thank all team members of the welding group Laprosolda (Center for Research and Development of Welding Processes) of the Federal University of Uberlandia, Brazil, for infrastructure, support and advice. They also give thanks to the Brazilian organizations for Research and Development, Fapemig (through project TEC 604/2005), CNPq (for the scholarships) and Capes (through the program PROEX)
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Doc. IIW-2508, recommended for publication by Commission XII “Arc Welding Processes and Production Systems.”
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Liskevych, O., Scotti, A. Influence of the CO2 content on operational performance of short-circuit GMAW. Weld World 59, 217–224 (2015). https://doi.org/10.1007/s40194-014-0196-x
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DOI: https://doi.org/10.1007/s40194-014-0196-x