Analysis of the influence of shielding gas mixtures on the gas metal arc welding metal transfer modes and fume formation rate

The effect of metal transfer modes and shielding gas composition on the emission of ultrafine particles in MAG steel welding

“…Consequently, the arc power (I x U) decreases and the internal heat also decreases. This mode is seen to produce less spatter than globular transfer [1,17]. Additionally, the arc is short and the opening time, within a weld cycle is small.…”

“…Pires et al [1] concluded that the fume formation rate was low for short circuit transfer mode and increased for globular and spray transfer modes. This was intrinsically related to the acting forces on the arc, which are described by the static force balance theory [14] and the pinch instability theory [15].…”

“…The fume formation rate was seen to increase with the arc temperature and instability, the droplets size and the content of the active component on the shileding gas mixture, increasing for CO 2 or O 2 , more specifically with the thermal conductivity of the gas. Since CO 2 has a high thermal conductivity it leads to high fume formation rate [1]. In fact, Pires [16] observed that, as the thermal conductivity of the CO 2 rich gas mixtures increases, the arc stops enveloping the droplet, producing an anodic spot contraction, resulting in a shorter electric conduction zone.…”

“…The arc stability decreases with the increase of CO 2 content in the binary mixture of CO 2 +Ar when welding mild steel. This is due to the higher thermal conductivity of CO 2 which increases heat losses by conduction and thus arc instability for a constant current intensity [1]. In short circuit MAG, increasing the CO 2 content increases the weld heat and introduced heat increases the penetration.…”

“…It is well known that welders are exposed to significant amounts of welding fumes produced, which depend on process parameters and shielding gas composition [1]. Previous works [2] showed a correlation between processing parameters in metal active gas (MAG), that is, metal transfer modes, and the quantity of fumes formed expressed by the fume formation rate.…”