Electric arc welding is the most prevalent welding type in industry. It creates two main groups of health hazards for workers; fumes and gases, and radiant energy. Shielded Metal Arc (SMA) welding is the most widely used welding method in industrial plant welding shops. The main chemical health hazards associated with this type of welding are fumes. Fumes are particles formed when the electrode and base metal constituents are vaporized and condensed in the welding area. Potential health problems can be anticipated by measuring the concentration of fumes in the welding space and comparing these data to established exposure standards. If high concentrations of these fumes are present, control measures should be undertaken to reduce the potential toxic effect to workers. Most of the studies have been done on mild (carbon) steel welding where it is generally necessary to monitor only the total amount of fumes. Stainless steel welding differs from carbon steel welding in that it generates considerable fume concentrations of chromium and nickel, which are suspected human carcinogens. The first part of this study evaluated the health risks posed to workers exposed to chromium and nickel fumes from routine stainless steel welding procedures. All the welding was performed in an industrial plant welding shop by one experienced welder. The welded piece was a three-part stainless steel cylinder. The whole period of welding lasted almost three weeks, although the actual welding was done in eleven days during that period. All sampling was performed with filter cassettes connected to personal air pumps. Sampling was performed in welder's breathing zone, in the general area (background sample), and at conveniently located points outside the breathing zone for evaluation of ratios of chromium and nickel to total fumes. The results indicated that at this particular industrial plant, exposure levels did not exceed the Occupational Safety and Health Administration (OSHA) Permissible Exposure Limits (PELs) and the American Conference of Governmental Industrial Hygienists (ACGIH) Threshold Limit Values (TLVs). The results also indicated that it was not necessary to monitor the general area because of very low concentrations of chromium and nickel fumes. Rather, it is suggested that the monitoring focuses on the welder's breathing zone where it is important to sample hexavalent chromium (chromates) because of its proven carcinogenic effect and therefore very low TLV. Also, it was found that if TLV for chromates is not exceeded, then levels of total chromium and nickel are also likely to be below limits. The second part of the study sought to devise a simplified method of monitoring of welding operations. The results suggested that it is not always necessary to sample for all the components (total fumes, total chromium, chromates, and nickel) when estimating worker's exposure. Rather, it is possible to simplify the process by establishing the ratios of fume constituents during a period of heavy welding, thus enabling the industrial hygienist to make a reasonable estimate of exposure that occurs at other times. The estimate can be made by sampling either the main constituent (chromates) or total fumes, and predicting the exposure to remaining constituents of interest from these data. In addition, and in contrast to previous studies, it has been concluded that when fume concentrations are low, a welder's helmet does not provide any additional protection against fumes. Additional protection can be provided with the use of proper local ventilation, such as with a flexible hose, to reduce exposure well below suggested limits. / Graduation date: 1994

This project examined the feasibility of using flux modification to reduce the as-deposited hydrogen content of basic-type shielded metal arc welds. Additions of oxidizing ingredients (micaceous iron oxides) to the reference flux formulation lowered the diffusible weld hydrogen content by up to 70%. Increasing amounts of silica caused a slight reduction in hydrogen content, probably as a result of the reaction between SiO2 and CaF2, which produces SiF4 and CaO as reaction products. Flux formulations containing additions of fluorine-containing compounds and calcite displayed lower hydrogen levels, with the diffusible weld metal hydrogen content reaching a minimum with increasing additions. Higher levels caused an increase in the weld hydrogen content. Thermodynamic slag modelling attributes the existence of these minima to a decrease in slag water capacity with an increase in slag fluorine content (at constant basicity), brought about by higher concentrations of fluorine-containing compounds in the flux formulation. The effect of flux additions on the weld mechanical properties and the electrode operating characteristics was not evaluated during the course of this investigation. / Dissertation (MSc (Metallurgy))--University of Pretoria, 2007. / Materials Science and Metallurgical Engineering / unrestricted

Thesis (Ph. D.)--Ohio State University, 2009. / Title from first page of PDF file. Includes bibliographical references (p. 229-238).

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