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The nature and preparation method of tungsten

Added: Wednesday, March 3rd 2021 at 9:50pm by branthamil
 
 
 

In 1781 by the Swedish chemistdiscovered in scheelite, and extract the new elements acid ? tungsten acid, in1783 the Spanish discovered wolframite and extracted tungstate, the same year,with carbon reduce tungsten trioxide to first got tungsten powder, and named the element, tungsten content in the crust is 0.001%.Tungsten-containing minerals have been found 20 species. Tungsten deposits are generallyaccompanied by granitic magma activity to form. Through smelting tungsten is asilvery white lustrous metal, high melting point, great hardness.

Tungstenis silvery white, is a rare refractory metal, belonging to the sixth cycle ofthe periodic table (the second longest cycle) of the Group VIB. Tungsten is asilvery-white metal that looks like steel, high melting point, low vapor pressure,the evaporation rate is also smaller. Chemical properties of tungsten is verystable, at room temperature is not react with air and water, without heating,any concentration of hydrochloric acid, sulfuric acid, nitric acid,hydrofluoric acid and aqua regia can not work to tungsten, when the temperaturerose to 80%3-100, the above-mentioned acids, inaddition to hydrofluoric acid, the other acids are occurring weak effect withtungsten. At room temperature, the tungsten can be quickly dissolved in amixture of hydrofluoric acid and nitric acid, but it does not work in analkaline solution. With the presence of air, the molten base may be oxidizedtungsten to tungstate, rock drillbits in the case of oxidizing agent (NaNO3, NaNO2, KClO3,PbO2) exist, the reaction generated tungstate is more violent. Under hightemperature can be combined with chlorine, bromine, iodine, carbon, nitrogen,sulfur and so on, but not combined with a hydride.

Tungstenis a metal with the highest melting point, melting point is up to 3400%3,ranking first in all metals, boiling point is 5555%3,specific gravity (monocrystalline tungsten) is 19.3, and has a high hardness,good high temperature strength and conductivity, heat transfer properties,chemical properties is stable at room temperature, corrosion resistance, do notwork with hydrochloric acid or sulfuric acid. Concentrates are used for producingtungsten, tungsten carbide, tungsten alloys and compounds.

With areduce agent reducing pure tungsten compound to metal tungsten drill shank adapter powder is pyrometallurgicalprocess, a part of tungsten metallurgy process. According to metal powder supplier, the pure tungsten compounds for producing tungsten powder has tungstentrioxide, ammonium paratungstate and blue tungsten, etc., generally use hydrogen,carbon powder and so on as reducing agent. Since the application department hasstringent requirements on the chemical tungsten powder purity, particle sizeand particle size distribution, so it often to be based on the differentrequirements of tungsten powder to select production methods.

Themore widely used tungsten powder prepared method in modern industrialproduction is mainly the tungsten trioxide hydrogen reduction, ammoniumparatungstate hydrogen reduction and blue tungsten hydrogen reduction. Tungstenpowder for preparing tungsten carbide has also been used tungsten trioxidehydrogen reduction. Modern times is more commonly used hydrogen reduceparatungstate to prepare blue tungsten, then the blue tungsten by hydrogenreduction to prepare tungsten powder. In the 1960s developed fluorine(chlorine) tungsten hydrogen reduction method, using hydrogen reduce gaseousfluorine (chlorine) can be obtained ultrafine particles grade tungsten powderor can be directly made from tungsten tubes and other metal products. In orderto obtain with specific properties tungsten materials and tungsten alloys, itoften adding trace additives in blue tungsten raw materials. For example, whenpreparing with non-sag performance thermostability tungsten wire, addedsilicon, aluminum, potassiumcompounds and other trace additihttp://oscarspenc.blogtez.com/post1.php

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