Influence of Metal Transfer Stability and Shielding Gas Composition on CO and CO₂ Emissions during Short-circuiting MIG/MAG Welding

Influência da Estabilidade da Transferência Metálica e Composição do Gás de Proteção sobre Emissão de CO e CO₂ durante Soldagem MIG/MAG

Abstract:

Several studies have demonstrated the influence of parameters and shielding gas on metal transfer stability or on the generation of fumes in MIG/MAG welding, but little or nothing has been discussed regarding the emission of toxic and asphyxiating gases, particularly as it pertains to parameterization of the process. The purpose of this study was to analyze and evaluate the effect of manufacturing aspects of welding processes (short-circuit metal transfer stability and shielding gas composition) on the gas emission levels during MIG/MAG welding (occupational health and environmental aspects). Using mixtures of Argon with CO₂ and O₂ and maintaining the same average current and the same weld bead volume, short-circuit welding was performed with carbon steel welding wire in open (welder’s breathing zone) and confined environments. The welding voltage was adjusted to gradually vary the transfer stability. It was found that the richer the composition of the shielding gas is in CO₂, the more CO and CO₂ are generated by the arc. However, unlike fume emission, voltage and transfer stability had no effect on the generation of these gases. It was also found that despite the large quantity of CO and CO₂ emitted by the arc, especially when using pure CO₂ shielding gas, there was no high level residual concentration of CO and CO₂ in or near the worker’s breathing zone, even in confined work cells.

Key-words:
MIG/MAG welding; Metal Transfer Stability; Occupational health; Toxic and asphyxiating gases