Arc Welding Of Stainless Steel Research Articles

Surface and bulk chemical analysis on metal aerosols generated by manual metal arc welding of stainless steel

A scanning Auger electron spectroscope and an energy dispersive X-ray analyser were used to compare surface and bulk elemental concentrations of metal aerosols generated by manual metal arc welding of stainless steel. The good lateral resolution of both techniques was utilized by analysing not only the large area sample, but also two different particle populations. The argon ion sputtering in conjunction with Auger electron analysis facilitated the depth profiling of the elements in the particles. Light elements, such as K, Na, Si, F and O, predominated in the first surface atomic layers of the particles. The metals Cr, Ni and Fe were typically located below surface layers of a few nanometers and seemed to be concentrated in large slag-like particles. The sputtering of the samples also revealed that the growth mechanism of the particles depends roughly on the vapour pressures of the elements.

Welding fumes and chromium compounds in cell transformation assays

Fumes generated from mild steel and stainless steel welding were collected on paper filters and tested in the BHK and SHE cell transformation assays. Fumes from the manual metal arc welding of stainless steel (MMA/SS) had a toxic and transforming effect attributable to their Cr(VI) content. The fumes from metal inert gas stainless steel (MIG/SS) welding also had a toxic effect but this was 2-3 times greater than that expected from their soluble Cr(VI) content based on the activity of soluble Cr(VI) from pure chromium compounds. When collected in an impinger, the fumes from MIG/SS were found to contain approximately 10 times the soluble Cr(VI) content of samples collected on filters. This additional Cr(VI), when collected in a water impinger, also exhibited a greater toxicity compared with that found for the additional Cr(VI) collected in an impinger filled with growth medium. This comparison implies the presence of a short-lived biologically active Cr(VI) species usually lost in conventional sampling techniques. It also implies that there is a detoxification step associated with the formation of Cr(VI) organic complexes. Relatively insoluble Cr(VI) compounds showed a higher toxic and transforming effect in the BHK assay than could be ascribed to the soluble Cr(VI) content of the medium, indicating the importance of phagocytosis as a pathway for the uptake of Cr(VI) and other toxic substances from particulates.

Application of X-ray photoelectron spectroscopy to the analysis of stainless-steel welding aerosols

Aerosol particles (“fume”) from manual metal arc welding of stainless steel with E316L-16 electrodes were analysed by X-ray photoelectron spectroscopy. The inherent complexity of the particles required the use of a wide range of experimental techniques. These included IR spectrophotometry, TGA/DTA, XRF, XRD, AAS and electron microprobe analysis. The surface of the fume particles comprised ≈ 50 at% NaF and KF, ≈ 8 at.% soluble (probably K) chromate, ≈ 30 at% SiO 2 and several at.% transition-metal oxides, hydroxides or silicates. The fluorides and chromates were removed by washing to reveal a surface which was predominantly SiO 2 (≈ 60 at%) with the remainder comprising of transition-metal oxides, silicates and fluorides. Approximately 6 at% F remained on the surface of the water-washed particles, presumably as transition-metal fluoro-complexes. The water-soluble fraction of the fume contained K + , Na + , F − and CrO 2− 4 ions in the mole ratio 5:5:4:3. When aerosol particles are deposited in lung tissues, water-soluble constituents would be expected to dissolve rapidly. In view of the suspected carcinogenicity of stainless steel welding fume, a bio-medical study of the combined effects of F − and CrO 2− 4 ions on lung tissue is warranted.

Application of X-ray photoelectron spectroscopy to the analysis of stainless-steel welding aerosols

Aerosol particles (“fume”) from manual metal arc welding of stainless steel with E316L-16 electrodes were analysed by X-ray photoelectron spectroscopy. The inherent complexity of the particles required the use of a wide range of experimental techniques. These included IR spectrophotometry, TGA/DTA, XRF, XRD, AAS and electron microprobe analysis. The surface of the fume particles comprised ≈ 50 at% NaF and KF, ≈ 8 at.% soluble (probably K) chromate, ≈ 30 at% SiO 2 and several at.% transition-metal oxides, hydroxides or silicates. The fluorides and chromates were removed by washing to reveal a surface which was predominantly SiO 2 (≈ 60 at%) with the remainder comprising of transition-metal oxides, silicates and fluorides. Approximately 6 at% F remained on the surface of the water-washed particles, presumably as transition-metal fluoro-complexes. The water-soluble fraction of the fume contained K +, Na +, F − and CrO 2− 4 ions in the mole ratio 5:5:4:3. When aerosol particles are deposited in lung tissues, water-soluble constituents would be expected to dissolve rapidly. In view of the suspected carcinogenicity of stainless steel welding fume, a bio-medical study of the combined effects of F − and CrO 2− 4 ions on lung tissue is warranted.

Fibrogenic potential of welding fumes.

A search of 3600 indexed pathology cases has disclosed pulmonary fibrosis in 29 welders. Scanning electron microscopy of biopsy material revealed macrophages laden with inorganic particulates which have characteristics compatible with welding aerosols. In order to establish a possible relationship between fibrotic reaction and welding-fume exposure, the fibrogenic potential fo some 11 different welding fumes and metallic aerosols, considered to be reference standard surrogates for the commonly used welding technologies and applications responsible for 70% of welders exposure, were screened using the Rat Peritoneal Macrophage in vitro bioassay. Only one class of fumes, that from the manual metal arc welding of stainless steel, showed distinct fibrogenic potential. This fume is, however, not common to more than four or five of the heretofore 90 cases of pulmonary fibrosis reported among welders. Thus, although insoluble Cr(VI) is probably the active fibrogen in stainless steel fumes, an etiological factor common to all fibrogenic welding exposures must be sought. It is tentatively proposed to be NO2, a potential experimental in vivo fibrogen copiously produced by certain welding processes and ubiquitous at low concentrations in the welding environment.

RESEARCH ON INDUSTRIAL FERROUS METAL AEROSOLS

Ferrimagnetic metal aerosols originating from the processing of various steels and the resulting occupational exposure have been studied. A description of the phases of steel production is given and the respective dust emissions are characterized using chemical, physical and electronoptical analysis methods. Special attention has been paid to iron, chromium and nickel compounds. Recent developments of the magnetic measuring method for lung-retained ferrimagnetic dust are described, and the results compared with cumulative dust concentrations. The significance of urinary chromium and nickel concentrations as indicators of exposure has been evaluated. The results show that the solubility properties and the chemical composition of chromium and nickel compounds vary greatly between the different handling stages of stainless steel. Alveolar retention of fumes from manual metal arc welding of stainless steel seems to exceed that of the other dusts under study.

ステンレス鋼のプラズマアーク溶接におけるバックシールドガスの影響

In the plasma welding, the welding conditions, that is nozzle diameter, composition and flow rate of plasma gas and cover shield gas, welding current and travelling speed, must be selected according to material and thickness of the work. In the plasma arc welding of stainless steel, we discovered that the range of proper welding condition is remarkably affected by the quality of the back. shield gas.To study the effect of the composition of back shield gases on the forming of back beads, we examined plasma arc welding of 304 stainless steel (t=9 mm), with various back shield gases of Ar, N2, CO2, Ar mixed CO2, Ar mixed O2, N2 mixed CO2, and N2 mixed O2.A summary of the results is shown below.(1) When O2 or CO2 is mixed to inert gas as back shield gas, the length of back plasma flame is shorter than in the case of pure inert gas. There is a tendency of the flame be coming shorter according to the amount of O2 or CO2 mixed to inert gas.(2) When we used inert gas that is Ar or N2 as back shield gas, the range of proper welding condition is very narrow. Therefore welding work is very difficult. But the range of proper welding condition is remarkably expanded by mixing of oxidizing gas that is O2 or CO2 to inert gas.(3) By mixing of 10% O2 or 30% CO2 with Ar, the range of proper welding condition becomes maximum. With mixing of over 50% O2, the back bead is severely oxidized, spatter increase, undercut and concave occur at the back bead.(4) Indifferently to the composition of back shield gas, the cross section of welded metal appeared wine cup. And microstructure, hardness and corrosion resistibility of the welded metal were not affected by the composition of back shield gas.

Submerged Arc Welding of Stainless Steel in India

Leading Indian fabricators are using submergedarc welding process extensively for carbon and low alloy steels. Mostly, they depend upon imported wire and flux for welding of pressure vessels and boilers. However, they are hesitant to extend this process for austenitic steels also.

Studies on Plasma Arc Welding : Report 1, Plasma Arc Welding of Stainless Steel and Mild Steel

Studies on Plasma Arc Welding : Report 1, Plasma Arc Welding of Stainless Steel and Mild Steel