Quench rate affects oxidation reactions in the formation of arc welding fumes

The formation process of fumes in gas metal arc welding (GMAW) has been modelled considering the iron oxidation reactions both in gaseous and condensed phases. The results show that fumes are composed of aggregates of primary particles that are nucleated from gas-phase FeO and further oxidized to Fe 3 O 4 or Fe 2 O 3 , depending on the quench rate. Increasing the latter results in two effects: on one side, it induces the formation of smaller primary particles, which are more easily oxidised, but at the same time it reduces the time for solid-state diffusion of oxygen, resulting in lower particle oxidation.