Elemental composition of particles formed during welding with stick electrodes

Abstract

The elemental composition of welding fume (WF) respirable particles formed in carbon and low-alloy steels welding with stick electrodes with rutile (ANO-4) and the basic (UONI 13/45) type of coating was studied by X-ray-spectral electron-probe microanalysis. In the range from 0.25 to 16 µm aerodynamic diameter, all WF particles were divided into three groups according to their iron content: low (Fe≤20%), medium (20%<Fe<40%) and high (Fe≥40%). Each group contains various amounts of elements originating from the welding materials, which reflects their formation mechanism. Their relative abundance in WF depends on the particles aerodynamic diameter, type of electrode coating and the arc power. Particles with the medium iron content (agglomerates of nanosized primary particles) formed the largest group (over 70%) of respirable WF particles. For each electrode type, their average elemental composition does not depend on the size of the agglomerates. The low iron particles contain various combinations of electrode coating elements, and the variety of combinations increases with their aerodynamic diameter grows.These WF particles can be identified as aggregates of primary particles agglomerates and microspatters formed by disintegration of the electrode coating. WF particles with a high iron content are formed by aggregation of molten electrode metal microdroplets and nanosized primary particles agglomerates. They mainly contain iron (60–70%)and oxygen (15–35%). Their average elemental composition does not depend on the size of the aggregates, type of electrode coating and the arc power. The obtained results can be useful for the analysis and assessment of health risks for welders.