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

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 CO 2 and O 2 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 CO 2 , the more CO and CO 2 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 CO 2 emitted by the arc, especially when using pure CO 2 shielding gas, there was no high level residual concentration of CO and CO 2 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. Influência da Estabilidade da Transferência Metálica e Composição do Gás de Proteção sobre Emissão de CO e CO 2 durante Soldagem MIG/MAGResumo: Vários estudos têm demonstrado a influência dos parâmetros e proteção gasosa sobre a estabilidade de transferência metálica ou sobre a geração de fumos em soldagem MIG/MAG, mas pouco ou nada tem sido discutido sobre a emissão de gases tóxicos e asfixiantes, particularmente no que tange a parametrização do processo. O objetivo deste estudo foi analisar e avaliar o efeito de aspectos operacionais dos processos de soldagem (estabilidade da transferência metálica e composição do gás de proteção) sobre os níveis de emissão gasosa de durante a soldagem MIG/MAG (aspectos ambientais e de saúde ocupacional). Utilizando-se misturas de argônio com CO 2 e O 2 e mantendo-se a mesma corrente média e o mesmo volume de cordão de solda, soldagens com transferência por curto-circuito foram realizadas com arame de aço carbono em ambientes aberto (zona de respiração do soldador) e confinados. A tensão de soldagem foi ajustada gradualmente para modificar a estabilidade da transferência. Verificou-se que quanto mais rica a composição do gás em CO 2 , mais CO 2 e O 2 são emitidos pelo arco. No entanto, ao contrário de emissão de fumos, tensão e estabilidade da transferência metálica não têm efeito sobre a geração de gases. Verificou-se também que, apesar da grande quantidade de CO e CO 2 emitida pelo arco, especialmente quando se utiliza gás de proteção CO 2 puro, não se forma concentração res...

Determining the dynamics of carbon monoxide formation during gas welding processes

“…It is the umbrella gas concentrator that is the physical model of such a process of accumulation of welding gas. Carbon monoxide would accumulate in the area located near the respiratory system of the worker, which is dangerous and can cause occupational diseases and contribute to the occurrence of other concomitant diseases, the study of which is highlighted in [14][15][16][17].…”

“…The paper does not specify the means of protection of employees. In article [14], the purpose of the study was to analyze and assess the impact of production aspects of welding processes (the stability of short-circuit metal transfer and protective gas composition) on the level of gas emissions during MIG/MAG welding (the aspects of labor and the environment protection). It was found that the richer the composition of protective gas in СО 2 , the more CO and СО 2 is formed by the arc.…”

Assessment and prevention of the propagation of carbon monoxide over a working area at arc welding

“…Paper [10] provides an overview of welding fumes, their effect on health, and measures to protect welders against welding fumes. In the industrially developed countries, about 2 % of the workforce are employed in welding.…”

Evaluation of the Effect of Co and Co2 Gases Generation on Short-Circuit Metal Transfer in the Mig/Mag Welding Process

“…The use of mixtures with CO2 and pure CO2 as shielding gases emit significant amounts of CO2 and CO, capable of generating asphyxia and intoxication, respectively. The generation of these gases is not directly dependent on the arc stability and arc length, in the same proportion that the generation of fumes is sensitive to these factors, with the generation of CO2 and CO being greater according to the increase in the percentage of CO2 in the mixture used as shielding gas (MENESES; LEAL; SCOTTI, 2016).…”