A model for prediction of fume formation rate in gas metal are welding (GMAW), globular and spray modes, DC electrode positive

Prediction of fume formation rate during metal are welding and the composit ion of the fume are of interest to occupational hygienists concerned with r isk assessment and to manufacturers of welding consumables. A model for GMA W (DC electrode positive) is described based on the welder determined proce ss parameters (current, wire feed rate and wire composition), on the surfac e area of molten metal in the are and on the partial vapour pressures of th e component metals of the alloy wire, The model is applicable to globular a nd spray welding transfer modes but not to dip mode. Metal evaporation from a droplet is evaluated for short time increments and total evaporation obt ained by summation over the life of the droplet. The contribution of fume d erived from the weld pool and spatter (particles of metal ejected from the are) is discussed, as are limitations of the model. Calculated droplet temp eratures are similar to values determined by other workers. A degree of rel ationship between predicted and measured fume formation rates is demonstrat ed but the model does not at this stage provide a reliable predictive tool. (C) 2001 British Occupational Hygiene Society. Published by Elsevier Scien ce Ltd. All rights reserved.