Percorrer por autor "Quintino, M. L."
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- Evaluation of the amount of nanoparticles emitted in welding fume from stainless steel using different shielding gasesPublication . Pacheco, Rita; Gomes, João; Miranda, R.; Quintino, M. L.The primary objective of this study was to correlate the emission of macro and nanoparticles released during the process of metal inert gas/metal active gas (MIG/MAG) of stainless steel with different gas mixtures. Using different gas mixtures with different heat inputs, it was possible to determine fume formation rates and surface areas of nanoparticles with alveolar lung deposition capacity. It was found, how the various transfer modes and the type of gas protection, in particular, the percentage of active elements in the in the chemical composition of the gas, affect the amount of fumes generated and also the generation of nanoparticles with a high capacity of deposition. The spray transfer mode always shows higher values of nanoparticles surface area, unlike the fume formation rates. Among the tested mixtures 82%Ar+18%CO2 generates higher emissions of nanoparticles as well as fume formation rates.
- The effect of metal transfer modes and shielding gas composition on the emission of ultraafine particles in MAG steel weldingPublication . Gomes, João; Miranda, R. M.; Carvalho, P. A.; Quintino, M. L.The present study aims to characterize ultrafine particles emitted during gas metal arc welding of mild steel and stainless steel, using different shielding gas mixtures, and to evaluate the effect of metal transfer modes, controlled by both processing parameters and shielding gas composition, on the quantity and morphology of the ultrafine particles. It was found that the amount of emitted ultrafine particles (measured by particle number and alveolar deposited surface area) are clearly dependent from the main welding parameters, namely the current intensity and the heat input of the Welding process. The emission of airborne ultrafine particles increases with the current intensity as fume formation rate does. When comparing the shielding gas mixtures, higher emissions were observed for more oxidizing mixtures, that is, with higher CO2 content, which means that these mixtures originate higher concentrations of ultrafine particles (as measured by number of particles. by cubic centimeter of air) and higher values of alveolar deposited surface area of particles, thus resulting in a more hazardous condition regarding welders exposure.