Dust tungsten

Toxicology. Cobalt causes skin irritation, allergic contact dermatitis, and occupational asthma interstitial pulmonary fibrosis is associated with exposure to hard metal dust (tungsten and cobalt). 

Ha2ards encountered with tungsten may be caused by substances associated with the production and use of tungsten, eg. As, Sb, Pb, and other impurities in tungsten ores, Co aerosols and dust in the carbide industry, and thoria used in welding electrodes. Lanthanum is being promoted as a substitute for thoria in this appHcation. 

Tungsten dust, powder, and fine particles will explode, sometimes spontaneously, in air. The dust of many of tungstens compounds is toxic if inhaled or ingested. 

More recently, mngsten oxide fibers have been detected in a hard metal production plant. Subsequent in vitro experiments showed that the tungsten oxide fibers were cytotoxic to human lung cells. The role of tungsten in the development of hard metal dust pulmonary fibrosis remains unclear. 

The Pico abrader is specified in D222857. This device uses a pair of tungsten carbide knives which rub the test piece whilst it rotates on a turntable. The direction of rotation is reversed at intervals throughout a test and a dusting powder is fed to the test piece surface, which doubtless helps to avoid stickiness. The apparatus is calibrated by the use of no less than five standard rubbers and the result also expressed as an abrasion index. Force on the test piece and speed of rotation can be varied and, presumably, different abradant geometries could be used, although the distinctive feature of the Pico is the use of blunt metal knives in the presence of a powder. 

Indium occurs in very. small amounts in z.ine blende, tungsten, tin and iron ores of certain localities. The recovery or indium from zinc Due dust (sometimes. I part per thousand) is effected by treating with a slight deficiency of HCI and allowing to stand The residue is subjected to a series of treatments until finally pure indium sulfttlc is obtained, a solution of which when electrolyzed yields compact indium metal. A thin surface layer of indium is used on some bearings. 

One further condition is necessary that has not been discussed. In the foregoing discussion it was tacitly assumed that the deformation and flow of the container were small compared to those of the sample. If the material in the pressure cavity is harder or stronger than the apparatus, the flow will occur in the apparatus and not in the sample. However, when we attempted to pressure-sinter diamond dust, it was the apparatus that flowed and not the diamond particles. Besides the high pressure, it is essential that the sample be softer than the material of the apparatus. This last limitation precludes very few materials from study, since the parts of the apparatus in contact with the sample are compacted tungsten carbides, such as G. E. Carboloy 999, which is extremely hard. 

ITER. This will remain a major difficulty unless experimentally validated in tokamaks with impurities and relevant wall materials to provide a realistic test-bed which would closely mirror options proposed for the next-step device (e.g., beryllium walls and carbon and/or tungsten divertor proposed for ITER). Such experiments would indeed help answer questions including the magnitudes of erosion and tritium co-deposition, dust formation in the vessel, the ease of tritium removal from mixed-materials, as well as operational aspects (e.g., of using beryllium on the first wall). 

Electric Furnace Baghouse Dust, BOF Dust, OH Dust, Coke Fines, Raw Materials, Iron Ore Pelletizing Baghouse Dust, Mold Sand Fines Silicon, Ferrosilicon, Ferromanganese, Ferrochrome Concentrates, Smelter Dust, Precipitates Concentrates, Sinter Mix, Flue Dust, Drosses Tungsten, Molybdenum, Antimony, Brass, Tin,... 

Tungsten has no essential role in the health of plants, humans, or animals. In moderate amounts, it also presents virmally no health danger. Exposure to tungsten dust or fumes may cause mild irritation of the skin, eyes, and respiratory system. 

Sand, angular Sand, average -Sand, rounded x Tungsten powder ---Flue dust, fused, spherical... 

Thorium is a radioactive element and a natural a-emitter (specific activity 4250 Bq/g and half-life 1.4 x lO a). Health and environmental considerations (evaporation and inhalation of thorium during welding disposal of grinding dust) have therefore in the past led to a partial replacement of thoriated tungsten for welding operations and in the lighting industry by thoria-free ODS tungsten alloys [6.24]. 

All these findings very clearly demonstrate that only the combination of cobalt with tungsten carbide is a necessary condition to induce severe alveolitis leading to fibrosis. The pulmonary response produced by hardmetal dust is much more pronounced than that caused by pure cobalt or cobalt compounds, while WC alone shows almost no effect. Hardmetal disease is not a consequence of one of the hardmetal components but is a result of interaction between Co and WC particles, producing toxic activated oxygen species, presumably hydroxyl radicals. 

There do not exist any special values for permissible concentrations of hardmetal dust on the work place. Therefore, the MAK values for insoluble W and Co are valid (5mgWC/m and 0.5mgCo/m ). The ITIA (see Section 13.6) is encouraging inducing enhanced activity in regard to acute toxicity tests to be conducted on tungsten compounds including hardmetals (ITIA Newsletter, Jime 1997). 

The thiocyanate method has been used for determining rhenium in dusts and in molybdenite [51], eopper ores and eoncentrates [28,71,72], molybdenum, tungsten, and vanadium [73], and coal [16]. 

TUNGSTEN (7440-33-.7) W The finely divided dust or powder is highly flammable. May ignite spontaneously in air. The powdered metal may ignite on contact with air or oxidants (e.g., bromine pentafluoride, bromine, chlorine trifluoride, potassium perchlorate, potassium dichromate, nitryl fluoride, fluorine, oxygen difluoride, iodine pentafluoride, hydrogen sulfide, sodium peroxide, lead(IV) oxide). 

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