DEVELOPMENT AND VALIDATION OF A MODEL TO PREDICT THE METALLIC COMPOSITION OF FLUX CORED ARC-WELDING FUMES

Theoretical models have been developed to predict the concentration of metals in fumes from different systems used for the welding of metals. In the metal inert gas (MIG) system the model is based on two mechanisms of fume formation; direct (fractionated) vaporization of metals, primarily from the electrode tip, and unfractionated vaporization. These mechanisms each give rise to fume of different compositions. Methods have been derived previously for predicting the compositions of fractionated and unfractionated fume, as well as for determining the relative proportions of each in the total fume. This enables the total fume composition to be predicted for the major metals for processes involving MIG welding using mild steel and stainless steel alloys. The model has been extended to manual metal arc (MMA) and to flux cored systems; with both of these methods the situation is complicated by the presence of flux which is itself a source of fume. Fumes from a variety of welding systems have been generated using a mechanized system for fume generation and collection, and accurately analysed for the major metals. The results demonstrate the determination of the coefficients of transfer and the validation of the theoretical models. Such investigations are useful in the assessment of welding fume composition and form the basis for research into the modification of welding processes at source to effect control of fume.