The hard component of welding aerosol is one of the main hazards, which are encountered by those working with welding and related technologies. The investigations on this subject have been carried out for more than half a century. The size and dispersity of the particles are of particular interest among the properties and peculiarities of structure of hard component of welding aerosol, as these parameters define the ways of penetrating into a living organism. The present study examines dispersity of particles of hard component of welding aerosol by means of several types of equipment, involving different analysis principles. It was shown that the technique of preparation of a sample for analysis and peculiarities of equipment greatly influence the results. The morphology of particles was also examined. 20 Ref., 5 Figures. K e y w o r d s : welding aerosol, hard component, dispersity, morphology, nanoparticle, agglomerate, laser granulometry, diffusion spectrometerFor more than half a century, welding aerosol has been one of the main objects of investigation of negative factors affecting human organism in the process of welding. Nowadays these investigations are of extreme importance in view of new data in medicine and toxicology.Welding aerosol is a by-product of welding process and consists of hard and gassy components, predetermined by its formation processes. Under high-temperature heating during welding, the components of coating undergo thermal destruction, and some part of base and electrode materials evaporates. As a result of blowing out of the formed gas-vapor mixture into relatively low-temperature environment, condensation of vapor phase occurs and the small hard particles are formed [1]. The primary object of investigation is the hard component of welding aerosol (HCWA), as it contains main hazardous constituents.The HCWA influence on a living organism (toxicity) is a complex characteristic and depends on many factors, namely size and morphology of single particles or their agglomerates, total quantitative distribution by sizes (dispersity), chemical composition, content of highlytoxic compounds, solubility. Each of these factors should be analyzed separately and in combination with others.
The paper presents a review of current state of the issue of studying the mechanism of welding aerosol (WA) formation, dispersity of welding aerosol solid component and its ability to penetrate into the human body, as an important toxicological factor. It is established that there exist two main mechanisms of WA formation -due to condensation of high-temperature evaporation products and due to formation of volatile oxides on molten metal surface. Here, the molten metal drop is the main evaporation source, but weld pool and metal spatter also participate in the evaporation process. It is known that penetrability depends, chiefly, on dimensions of particles and their agglomerates: the smaller their size, the higher the penetrability. In addition to the already known paths of WA particle penetration into the body through the respiratory tract and digestive organs, nanosized particles can penetrate directly into the brain through nerve endings in the sinuses, as well as penetrate into the blood-vascular and lymphatic systems. This results in their accumulation in the bone marrow, lymph nodes, spleen and heart. Issue of searching for the methods to lower the emissions in coated-electrode welding is still urgent, chiefly due to improvement of their coating composition, as well as the ability to control particle dispersity in WA. 25 Ref., 1 Figure. K e y w o r d s : particle, welding aerosol, solid component, toxicity, penetrability, sanitary-hygienic characteristics Coated electrodes for manual arc welding (MAW) have for a long time been the object of investigations, which were initially aimed at improvement of weldingtechnological characteristics, while the next stage was lowering their production cost. At present, electrode sanitary-hygienic characteristics and searching for ways of reducing the negative influence of welding process on workers in this sector, are one of priority directions of electrode research.As manganese is the main toxic component of welding aerosol (WA) in welding low-alloyed lowcarbon steels, it was and still is one of the main objects of research [1]. This is confirmed by the Bulletin published by IIW, which actualizes the issue of WA investigation and gives several recommendations [2]:• influence of WA and dust magnesium-containing compounds in welding and related technologies should be minimized, at least, within the respective national norms;• it is worthwhile to perform further investigations to improve the understanding of absorption of these compounds (welding products); their behaviour in the human body; dose-effect interaction and any possible neurological and neurobehavioural manifestations.On the other hand, American Conference of Governmental Industrial Hygienists (ACGIH) in 2013 revised their recommendations on manganese and proposed lowering the maximum allowable concentrations (MAC) of manganese: for WA solid component (WASC) with particle size below 2.5 µm -to 0.02 mg/m 3 , and for WASC with more than 2.5 µm particle size -to 0.1 mg/m 3 [3]. Over the next several years, the a...
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