Conclusions
This study confirms the emission of fine particles in the MAG
welding of carbon steel using mixtures of Ar+CO2, which
are clearly dependent on the distance to the welding front and
also on the main welding parameters, namely the current
intensity and the heat input in the welding process.
The emission of airborne fine particles increases with the
current intensity as fume formation rate does. A marked decay
of ultrafine particles with the distance to the weld area is
observed. When comparing the tested gas mixtures, higher
emissions are observed for more oxidant mixtures, that is,
mixtures with higher CO2 content, which result in higher
arc stability. The later mixtures originate higher concentrations
of fine particles (as measured by number of particles by cubic
centimeter) and higher values of alveolar-deposited surface
area of particles, thus indicating a severe worker’s exposure.
Size distribution of emitted particles does not seem to
differ significantly, and morphology analysis shows that fine
particles are lower than 10 nm, but form aggregates up to
diameters as high as 100 nm or more. Its composition is
mainly iron, resulting from projections of the molten material.
During the welding operations, resuspension and agglomeration
of fine particles were also noticed as reflected in the
evolution of alveolar-deposited surface area of emitted
particles and its size distribution