Tungsten concentrate

Eig. 2. Mean l ondon Metal bulletin price of tungsten concentrate by year. 

Table 5. World Tungsten Concentrate Production by Country ...

Tungsten concentrate Scheelite from iron oxides and other conductor minerals Roll 1,50 -0.6 1.0-1.5. 3... 

Samples were tested on in a melt of salts (75% Na SO, 25% NaCl) at 950°C in an air atmosphere for 24 hours. Micro X-rays spectrum by the analysis found that the chemical composition of carbides of an alloy of the ZMI-3C and test alloys differs noticeably. In the monocarbide of phase composition of an alloy of the ZMI-3C there increased concentration of titanium and tungsten is observed in comparison with test alloys containing chemical composition tantalum. The concentration of more than 2% of tantalum in test alloys has allowed mostly to deduce tungsten from a mono carbide phase (MC) into solid solution. Thus resistance of test alloys LCD has been increased essentially, as carbide phase is mostly sensitive aggressive environments influence. The critical value of total molybdenum and tungsten concentration in MC should not exceed 15%. 

Fig. 7.50 Magnetic hyperfine field //hf in Ni-W-alloys at the W-site as a function (a) of the tungsten concentration and (b) of the average magnetic moment (from [238])...

The largest producers of tungsten in the world are China (which produces the vast majority of the world s total), Russia, and Canada. A limited amount of tungsten concentrates were produced in the United States in 2008. Detailed information about the production and use of tungsten in the United States is not available. This information is withheld from the public to protect the companies interests that produce and use tungsten. 

Tungsten was discovered in 1781. The average tungsten concentration in the earth s crust is 0.006%. Tungsten occurs naturally as tungstate, mainly in compounds such as wolframaites and scheelites. 

The average tungsten concentration in ore deposits is generally low, which means mostly between 0.4 and 0.8% WO3 and only seldom between 1 and 2%. An exception is the Cantung Mine in the North West Territories of Canada with about 2.5%. 

Loss by recycling dilution includes residues containing low tungsten concentrations as a result of recycling, and are not uneconomical to recover. For example, tungsten as trace constituent in recycling of tool steel, carbides, etc. is lost into the steel melt. 

CaSO4—W53). Here energy migration does not occur in view of the low tungsten concentration. 

Until now, only small concentrations of tungsten have been evident in the atmosphere, and these are caused primarily by industrial emissions and nuclear fall-out. The ascertained air concentrations have been <1.5 tgm according to Cawse (1974). Rain water analyses performed in the UK by the same author showed that tungsten concentrations were mainly < 1 pgkg while seawater concentrations may be of the order of 0.1 pgkg (see also Bruland 1983). According to Sohrin etal. 

The industrial chemical treatment of tungsten concentrate uses scheelite, either concentrated scheelite or synthetic scheelite, manufactured from woframite concentrates. In this latter case wolframite is treated with sodium hydroxide or sodium carbonate to form sodium tungstate. Dissolution in water and filtering removes the hydroxides of iron and manganese. Addition of calcium chloride to the filtrate precipitates calcium tungstate - synthetic scheelite. 

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