Chloride metallurgy is the recent development of the new technology , with the chlorination process tungsten mineral raw materials have a number of advantages , mainly in:

( 1 ) Chlorine is very active , and thus the decomposition rate is very high, high metal recovery , in addition to deal with the general tungsten , but also especially suitable for processing lean tungsten ore, tungsten fine mud , tungsten ore tailings and polymetallic composite ore.

( 2 ) low boiling point of many of the metal fluoride , there is a gap between each other , and thus the vapor pressure can be used for separation and purification of different , easily obtained pure tungsten chloride.

( 3 ) Hydrogen chloride reduction process for the gas-phase reaction , easily accessible from tungsten chloride to obtain fine tungsten powder or plating .

( 4 ) easy recovery of other valuable elements .

Therefore, the method is the decomposition of tungsten chloride mineral raw materials promising methods. At present chlorination is mainly used in the decomposition of tungsten alloy scrap tungsten and tungsten minerals and thus obtain fine tungsten powder, has small-scale production .

Fundamental

Professor Li Honggui materials under thermodynamic system draws 1100K when W-Cl-O system and Fe-W-Cl-O system thermodynamic equilibrium diagram . In the W-Cl-O system exists WO2Cl2, WOCl4, WCl2 other compounds , oxygen -bit systems is higher, the higher the content of mixed vapor WO2Cl2 , to get WCl4 or WCl2, must reduce the oxygen -bit system , to ensure adequate reducing atmosphere . Therefore, scheelite or wolframite chloride , often adding carbon as a reducing agent.

For scheelite such as the use of sulfur dioxide as a reducing agent , the reaction is : CaWO4 (s) + Cl2 (g) + SO2 (g) = CaSO4 (s) + WO2Cl2 (g)

Scheelite chloride decomposition using carbon as a reducing agent , such as , you must add a certain amount of calcium fluoride decomposition rate was high : CaWO4 (s) +3 C (s) +2 Cl2 (g) + CaF2 (s) = 2CaClF (s ) + WOCl2 (g) +3 CO (g)

Process Lndicators

Tungsten with carbon and mineral raw materials are first additive (CaF2) and binder mixed group ; system group for the purpose of the charge to ensure good air permeability , dehydration briquettes sufficiently dried , and then chlorination, chlorination process is usually vertical chlorination furnace , the temperature controlled at 600 ~ 800 ℃ ( different materials , chlorination temperature is not the same ) , the chlorination of a mixed oxide vapor is condensed , and then purified by means of separation , can be used to obtain pure tungsten chloride obtained by hydrogen reduction of tungsten powder or coating can also be hydrolyzed acid .

Wolframite use chlorine chloride , the temperature to 800 ~ 900 ℃ only when a full , but adding carbon as a reducing agent , the reaction starts 400 ℃ , 500 ℃ under faster , to 600 ℃ has chlorination more completely .

Scheelite plus carbon oxidation , if not additive CaF2, then at 600 ℃, tungsten chlorination rate of only 65% , if by adding the theoretical amount of calcium fluoride , ingredients of carbon and scheelite ratio of 0.075,600 ℃ chlorination of tungsten chloride rate up to 99% .


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The process is made ​​directly by the tungsten carbide, the former Soviet Union in this regard fruitful research. According to the Canadian Pacific International Industrial Co., Kirby said: used to produce tungsten carbide powder purity has reached 99.3% to 99.4%, while the cost of production of tungsten carbide with the traditional way of comparison can be reduced by half, so much attention.

Process and Principle

The process comprises three main technical steps: melt extraction, carbonation and the grinding gas into leaching purified.

(1) Melt Extraction

The tungsten and Na2SiO3, NaCl mixed and melted 1050 ~ 1100 ℃, the following reaction occurs:

2 (Fe, Mn) WO4 +3 Na2SiO3 +16 NaCl = 2 (Na2WO4 · 8NaCl) + Na2 (Fe, Mn) 2Si3O9

The resulting tungsten Na2WO4 · 8NaCl immiscible silicate phase, according to the density stratification, the upper silicate phases, the lower chloride - tungstate phase. The two phases were separated by decantation, the 98% to 99% of WO3 and a small amount of impurity in the titanium manganese tungstate phase.

In scheelite as raw material, Al2O3 and NaF should be added as a flux. But if the scheelite and wolframite 1:3 mix to join, you can add the free flux.

(2) Gas into Carbonized

The chloride - NaCl added tungstate scaling, and then in 1050 ~ 1070 ℃ when the pass into the natural gas, tungsten carbide reaction occurs as follows:

Na2WO4 +4 CH4 = Na2O + WC +3 CO +8 H2

(3) Purification Polishing Leaching

Tungsten periodically removed from the grinding and dispersion of salt furnace, first with 10% HCl and washed with 3% NaOH solution, extract, and then through the filter to remove impurities to get a more pure tungsten carbide powder.

Process Conditions and Indicators

Add the material ratio of: wolframite: NaCl: Na2SiO3 = 33:47:20; at 1050 ~ 1100 ℃ melted and incubated 2h, obtained chloride - tungstate phase substantially composed of: WO325% ~ 30% ; FeO about 0.24%; MnO about 0.3%; silicates containing approximately 0.5% WO3; WO3 recovery of this step to 98% to 99%.

The resulting molten chloride layered - tungstate phase and then in the 1050 ~ 1070 ℃ was passed through the gas, the main component of natural gas methane (CH4) in the utilization rate of approximately 2.2% carbon, 90% of WO3 are recovered into the WC, WC to ground and then acid leaching filtered to further remove impurities, the resulting WC WC carbide to achieve the general requirements.


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Most of the metal tungsten powder is used as a raw material for the production of tungsten carbide, so here describes a tungsten as a raw material, a direct method of producing tungsten carbide as the supplementary toner production methods are suitable.

In recent years, the development of the Russian Research Institute of Chemical Technology concentrates of the "furnace" aluminum thermal reduction method. Reliable naturally at high temperatures to restore directly from tungsten concentrate and make carbonation. Raw concentrates containing 55% ~ 60% WO3.

Aluminum thermal reduction of graphite, copper or steel crucible for, reduction and carburization process is very fast only 3 ~ 5min. The exothermic heat sufficient to melt all of the reaction product, and to a metal carbide-containing phase to obtain a good separation of the slag phase.

"Furnace" obtained by aluminothermic reduction of 55% tungsten metal phase containing 75% Fe 15% to 20%, the excess of the reducing agent from 1% to 4% of aluminum, the remaining metal impurities (Mn, Ni, Cu, etc. ) less than 2%, and a small amount of slag inclusions. CaO · 2Al2O3 slag phase and a mixture of CaO · Al2O3.
The metal phase crushed to 150μm, the obtained powder was acid leached to remove the acid-soluble substances, namely to obtain the final product tungsten carbide (WC).

X-ray diffraction analysis showed that the product contains only one phase WC. The chemical composition of tungsten carbide composite Russian technology standards TY48-19-265-91. WC product quality than traditional craftsmanship, carbonation completely free carbon content is reduced to 0.01% (typically less than 0.04%), the lattice defects are reduced, without W2C, Mo2C and Fe3W3C generation. Molybdenum scheelite lattice into the WC, do not generate separate Mo2C phase. It is very important to manufacture cemented carbide. WC impurity content of products (including Fe) meets the requirements, costs mean diameter of 9μm. Russia's experience has shown that the product can be used for drilling tools and carbide production.

High product quality, process simplicity and low cost of production is the production of tungsten carbide aluminum thermal reduction of the basic features. 


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Physical performance: Cemented carbide: HRA90—HRA92 Ma trix: RC30 'owing temperature:910-935 o C Standard Multi-edge particles can be used in the formation of the workpiece surface. For serious wear, with 1/3 of fine particles, need a broad particle size distribution to ncrease density and decrease in clearance of surfacing. Mesh size from 6.35MM-- 325 mesh.

Hardness 90.5 (8%) Shape Polygon in the workpiece surface alloy into distribution. This enables tighter particle inclusions and reduce the gap. Applied to extreme wear and tear. Three sizes: 8-10-16 16 14-20 5mm 8mm Particle shape is gravity cutting most important discovery. Those with sharp points and the sharp edge of particle coating is not good, so that there is a gap between the particles, reduced cutting edge and serious exposure. Gravity cutting alloy particles will have a very powerful cutting or grinding surface. Apply to play grinding, cutting, drilling, sawing, tools. The development of fine grades of coating alloy finds a solution to the problem of hard brittle, no wear-resistant due to softness.

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