Method of production of powders of refractory metals

 

(57) Abstract:

Usage: in the field of powder metallurgy for the production of powders of refractory metals, which can find application in the production of hard alloys, catalysts and bodies glow in the electronics industry. The inventive compounds of refractory metals in the form of acids or salts is subjected to thermal shock of cold. 2 C.p. f-crystals, 2 tab.

The invention relates to the production of powders of refractory metals and can be used in enterprises: non-ferrous metallurgy in the production of high-quality hard alloys; chemical industry for preparation of catalysts; the electronics industry in the manufacture of bodies glow and so on.

The end product of metallurgical and chemical processing of ores solid minerals and their concentrates are metal salts, for example, salts of tungstic acid, chlorides, fluorides, which play an essential role in the manufacture of oxides with a low content of impurities, respectively, and obtaining metals of high crystallographic perfection.

A method of obtaining powder of refractory metals, including extraction, is orgie. M. Metallurgy, 1969.)

The disadvantage of this method is the difficulty of obtaining powder of high purity due to the low degree of extraction of mineral raw materials (for number of elements, it is difficult to be extracted from the minerals include, for example, beryllium, zirconium, vanadium) and the difficulty of separating pure compounds from concentrates.

The known method of producing metal powder from a melt, comprising applying to the inside of the melt energy in the form of liquefied natural gas (ed. St. USSR N 117607, CL 5 B 22 F 9/08, publ.30.08.85, bull.N 32).

However, this method is applicable only to obtain an amorphous powder.

A method of obtaining powder by grinding solid material by mechanical impact on the material and coolant in the grinding zone. Moreover, for the intensification of the grinding process, first, for a certain period of time, perform only the mechanical stresses on the material, and then, simultaneously with the mechanical action, submit coolant (ed. St. USSR N 1551422, CL 5 B 02 19/18, publ.23.03.90, bull.N 11).

The disadvantage of this method are significant energy costs.

The closest proposed A acid (concentrated solutions of caustic soda or caustic potash), allocation in the form of crystals of parabolicamara ammonium, calcining it to obtain tungsten anhydride, followed by reduction to pure metal (Zelikman A. N. Nikitina L. S. Wolfram, M. Metallurgizdat, 1978).

The disadvantage of this method is that when extracting valuable components of the ore remains in them an increased amount of impurities, which represent 0.06% of the total volume, which leads to increased structural heterogeneity in pure metals. In addition, the known method cannot obtain powdered metal components with a particle size within a narrow range (for example, for tungsten 3 20 m) and its influence on physico-mechanical properties of finished products.

The purpose of the invention improve the quality of powders of refractory metals by increasing the depth of the decomposition of raw materials due to cracking of the crystals at the grain boundaries of the impurity atoms.

The aim is achieved in that in the method of production of powders of refractory metals, including grinding of the ore, removing the products of the compounds in the form of the acids or their salts, refining, calcining, and recovering the metal powder is injected operation thermal shock of cold. Pricol.

Under the action of low temperatures in the crystal lattice defects occur, which allow to deform it and to make the split at the temperature of liquid helium, which aligns the grain of the metal powder. The occurrence of defects always causes a loss of strength of ties in a solid, which is equivalent to increasing the propensity of it to the isothermal decomposition. thermal shock, sufficient to restore defects in the material structure and even split large conglomerates may increase if pre-raw components to heat up to temperatures that do not cause redox processes from 25 to 400oC.

Example 1. Obtained in a known manner from ore concentrates paraformat ammonium sprayed into liquid nitrogen and calcined in a furnace having three temperature zones (I 400oC, II 450oC, III 490oC), sieved and reduced to metallic tungsten. Cold treatment provides an excessive number of active centers, which allows to obtain the tungsten trioxide (WO3) high chemical activity and to improve the physicochemical and mechanical properties of metal powders.

Example 2. Heated to 70ooC paraformat ammonium sprayed into liquid nitrogen and calcined to obtain WO3.

Table 1 presents data on the change in purity WO3depending on the technology of production.

Table 2 presents changes in particle size distribution of powders of tungsten at different processing modes parabolicamara ammonium.

Cold treatment, as can be seen from the table.2, increases the depth of the decomposition of the original raw components and leads to a change in grain size fractions of metal powders.

In addition, the grain size of the powder, as it is known (T. Millner Actg. Techn, Hung, 17, 1957, c.67-112, 289-30h), is a criterion tendency to recrystallization produced from this powder products. The latter makes it clear that the fine powder of tungsten is a "guarantee high durability products to recrystallization".

Example 4. Paramolybdate ammonium extracted from ores known method, calcined at 450oC, is subjected to thermal shock of cold when the temperature of liquid nitrogen, the obtained molybdenum anhydride sift, restore in two stages (I 550oC, II 920oC) the metal powder is pressed and the experience a reduction of energy consumption on subsequent technological operations (welding, forging and wire drawing) due to the fineness of the structure of materials.

Example 5. The ammonium perrhenate is subjected to blow cold when the temperature of liquid helium and restore in two stages in the environment of hydrogen at a temperature of 360 and 970oC to obtain rhenium powder, which is pressed and bake.

The use of cryogenic cooling contributes to the refinement of the microstructure of the powder, the emancipation of impurity inclusions and improve the plasticity, which beneficially affects the process of rolling sheets to the size of the foil.

Thus, low-temperature processing allows to prevent abnormal growth of grains and to obtain uniform fine-grain structure of the metal needed to improve the quality of products made of refractory metals.

1. Method of production of powders of refractory metals, including grinding of the ore, removing the products of compounds of refractory metals in the form of the acids or their salts, refining, calcining, and recovering the metal powder, characterized in that the source components in the form of acids or salts of refractory metals subjected to thermal shock of the cold.

2. The method according to p. 1, characterized in that ishodny, not causing oxidative reactions.

3. The method according to PP. 1 and 2, characterized in that thermal shock of cold carried out at any stage of the selection acids or salts of refractory metals.

 

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