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 f umes produced during metal are welding can be influenced by changes in the welding wire composition, the flux or gas shielding used and by c hanges in the process parameters, including voltage, adopted. The pres ent paper describes modifications directed at reducing the concentrati on 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 th e Cr(VI) formation rate over the range of voltages used (18-24 V). Fum e from wires containing the addition of 1% zinc contained Cr(VI) conce ntrations 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 demonstrat e that at 18 V a significant reduction of Cr(VI) in welding fume can b e produced by the addition of 1% zinc to the welding wire. (C) 1996 BO HS. Published by Elsevier Science