Reduction of hexavalent chromium concentration in fumes from metal cored arc welding by addition of reactive metals

Previous work has demonstrated that both the mass and composition of fumes produced during metal are welding can be influenced by changes in the welding wire composition, the flux or gas shielding used and by changes in the process parameters, including voltage, adopted. The present paper describes modifications directed at reducing the concentration of hexavalent chromium [Cr(VI)] in welding fume by the addition of active metals-zinc, magnesium and aluminium to metal cored are welding wires containing 10% Cr. There were marked changes in both the Cr(VI) concentration in the fume and the fume formation rate and hence in the Cr(VI) formation rate over the range of voltages used (18-24 V). Fume from wires containing the addition of 1% zinc contained Cr(VI) concentrations in the fume below those in the control and in wires with 1% magnesium and wires with 1% aluminium additions. Also, at 18 V, the Cr(VI) formation rate was at a minimum compared to the other wires. This advantage was not sustained as the voltage was increased and above 21 V the Cr(VI) formation rate for all the three wires containing active metal additions was higher than the control. These results demonstrate that at 18 V a significant reduction of Cr(VI) in welding fume can be produced by the addition of 1% zinc to the welding wire. (C) 1996 BOHS. Published by Elsevier Science