AAAR 35th Annual Conference October 17 - October 21, 2016 Oregon Convention Center Portland, Oregon, USA
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Particulate Hexavalent Chromium, Aerosol Size Distribution, and Respiratory Deposition of Pulsed Metal Inert Gas Welding Fume
JUN WANG, Marcio Bezerra, Heng Wang, James Regens, University of Oklahoma
Abstract Number: 65 Working Group: Control and Mitigation Technology
Abstract Metal inert gas (MIG) welding fume contains high concentration of nano- to submicron-sized aerosols enriched with toxic metals such as hexavalent chromium. The fume forms in the extreme high-temperature welding arc zone through melting and evaporating the welding filament. Occupational inhalation exposure to welding fume can cause various carcinogenic, pulmonary, and neurological adverse effects. Pulsed MIG welding was created to reduce the heat input to the welding arc zone by high-frequency current fluctuation comparing to the steady current feed in non-pulsed MIG welding. Pulsed MIG welding was proved to improve the weld quality through cooler arc and less molten metal, while the benefits of fume reduction is still a hypothesis. The goal of this study was to investigate the pulse parameters (current, frequency, and time percentage) on formation and characteristics of welding fume aerosols. A pulsed MIG welder was placed in a conical metal fume chamber and welding with different combinations of pulse parameters as well as baseline (non-pulsed) were conducted through beading on 308L stainless steel plates. Particle size distribution was measured by a scanning mobility particle sizer and an aerodynamic particle sizer. Respiratory deposition fractions for head airways, tracheobronchial, and alveolar regions were estimated based on a simplified model. Hexavalent chromium content was determined by analyzing fume samples through an ion chromatography. The statistical results indicated the dominant parameter of particle emission characteristics was the pulse current. The pulsed welding did not drastically change the geometric distribution of the particle sizes comparing to the non-pulsed welding. However, pulsed welding reduced the total fume and hexavalent chromium emissions, without compromising the weld quality. Lower pulse current produced the least particle number concentrations (3.0E7 #/cm3 fine particles and 0.7E4 #/cm3 coarse particles) and for more upper respiratory tract deposition.