Tungsten,smelting,Tungsten,con business, insurance Tungsten smelting
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Tungsten concentrates decomposition method has fire method and wetmethod. Purification of tungsten compound Thesilicon, phosphorus and arsenic impurities in sodium tungstate solution arepresenting in sodium silicate, sodium hydrogen phosphate and sodium hydrogenarsenate state. Boiling solution and neutralized with dilute hydrochloric acid,when the solution pH is 8-9, the sodium silicate hydrolyze into silicatecondensation precipitation, add magnesium chloride and ammonium chloridesolution, make the phosphorus, arsenic generate a very small solubility ofmagnesium ammonium phosphate and arsenate ammonium magnesium precipitationremoved. Add sodium sulfide to the sodium tungstate solution, molybdenum firstform the thiosulfate molybdate with tungsten, neutralized with hydrochloricacid, make the solution pH from 2.5 to 3.0, molybdenum was formed of insolubleprecipitates molybdenum trisulfide removed. In the purified sodium tungstatesolution add calcium chloride solution to obtain calcium tungstate (CaWO)precipitation (ie synthetic scheelite), with hydrochloric acid decomposecalcium tungstate precipitation gets the industrial tungsten acid, at 700 ~ 800calcination, get industrial pure tungsten trioxide. If preparing chemicallypure tungsten trioxide, can be dissolved industrial tungstic acid in aqueousammonia, obtained ammonium tungstate solution, silicon and other impuritiesremain in the slag. The solution through evaporated and crystalline treatment,obtains a sheet-like ammonium paratungstate crystal. As the solubility ofammonium paramolybdate greater than ammonium paratungstate, aftercrystallization, ammonium paratungstate crystal was reduced molybdenum content.After the ammonium paratungstate dried, calcined at 500 ~ 800,can be obtained chemically pure tungsten trioxide. In 70s, use tertiary aminemethod to make sodium tungstate solution convert into ammonium tungstatesolution, simplifying the process and improve the recovery of tungsten. Preparation of tungsten powder Inindustry, use the method of hydrogen reducing tungsten trioxide or ammoniumparatungstate to prepare tungsten powder. Reduction process depends on theproduct tungsten powder particle size, particle size composition and oxygenrequirements. Hydrogen reduces tungsten trioxide preparing tungsten powder isgenerally taken two steps: first in the 550 ~ 800reduce tungsten trioxide into tungsten dioxide, and then at 750 ~ 900reduce tungsten dioxide into tungsten powder. Also be the first pass intohydrogen or not to reduce paratungstate into blue tungsten oxide (bluetungsten), and then use hydrogen to reduce into tungsten powder. Tungstenpowders particle size, particle size composition is tungsten powdersimportant indicator of quality. The reduction reaction was conducted in therotary tube furnace or electric furnace. Dense tungsten preparation Tungsten powder through forming, sintering, melting and other processing obtainsdense tungsten. The forming is taking tungsten powder into the steel die,pressed into the billet or a compact with hydraulic pressure. Large briquettesuse liquid and other static pressure method molding, can be obtained moreuniform density compact. Tungsten billet sintered divided into two steps: firstin the 1100 ~ 1200 temperature sintering, then the current directly through thebillet for vertical melting (ie, high temperature sintering). The density ofthrough vertical melting tungsten was not to17-19 g/cm. Small shaped, different shaped and large shaped tungstencompacts sintered usually use radiant heating or induction heating method toachieve the sintering required high temperature, at this time, do not have tocompletely separate operation low-temperature sintering and high-temperaturesintering. While preparing large tungsten ingots usually use a vacuum or inertgas protection arc melting method and an electron beam melting method. Preparehigh purity dense tungsten is usually use electron beam melting purified.Electron beam melting also can be obtained tungsten single crystals, the puritywas up to 99.99% or more. ArticleSource:http://www.mhcmp.com
Tungsten,smelting,Tungsten,con