RU2616712C1 - Fine particles mixture production method - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: method is described of producing a mixture of particles of different particle size and/or chemical composition, in which particles of different particle size and/or chemical composition are obtained from separate sources by their dispersion in the working environment by pulses of electric current, for which each corresponding particle source is positioned above the vessel or a container with working fluid. In the process of particles obtaining, their packing is carried out which essentially represents particle mixing process, and the desired distribution of particles of different particle size and/or chemical composition, and the ratio between them are prepared by adding to each particle source of certain number of pulses per time unit and energy deposited into pulse.

EFFECT: obtaining increased uniformity of mixture that includes particles with a predetermined particle size or chemical composition and a predetermined concentration.

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Description

The invention relates to powder metallurgy, in particular to methods for preparing a mixture of powders for subsequent manufacture from a mixture of products, and can be used in mechanical engineering, nuclear and chemical industries.

The quality of products obtained by powder metallurgy methods largely depends on the homogeneity of the mixture prepared for subsequent operations. Preparation of a homogeneous mixture of powders with different particle size and chemical composition is a difficult task, not always solved by mechanical stirring. The need to prepare a mixture with particles uniformly or distributed according to a given law in its volume, the concentration (ratio) of which with respect to the concentration of particles prevailing in the prepared mixture is a fraction of a percent, requires the development of new ways to solve this problem.

A known method of preparing a mixture in a ball mill by mechanical grinding of source materials (particle sources), including the simultaneous production of particles with different particle size and chemical composition and their mixing (G. A. Libenson "Fundamentals of powder metallurgy", M .: "Metallurgy", 1975 , p. 11, 105-109).

The method has the following disadvantages:

1) the impossibility of preparing a mixture of particles of the same size, the materials of which differ significantly in density (hardness);

2) the impossibility of obtaining particles in a certain sequence and with the required concentration from different sources of particles when they are simultaneously loaded into the mill, while it is also impossible to simultaneously carry out the process of obtaining particles and stacking them in a container in a certain order and with a given concentration;

3) mechanical mixing of the obtained particles does not allow to prepare a homogeneous mixture with a uniform distribution of particles with sizes that differ by one or several orders of magnitude or with significantly different concentrations, which is uniform or distributed according to a given law, i.e. there is a high heterogeneity of the mixture being prepared;

4) lack of control over the production of particles - the impossibility of preparing the mixture only from the required particles due to the possibility of contamination of the mixture by the wear products of the mill elements.

A known method of preparing a mixture in a paddle mixer, including laying particles and their subsequent mechanical mixing (patent RU No. 2233197 "Method for preparing a mixture of bulk materials and installation for its implementation", IPC ⁷ B01F 7/04 and B01F 3/17, published July 27, 2004 )

The method has the following disadvantages:

1) the restriction of particles over a range of sizes and densities, since the loading of loaded particles is carried out along the length of the mixer in the order of decreasing particle sizes and / or increasing the density of the materials from which they are obtained;

2) the impossibility of obtaining a mixture with high uniformity, since the mixing of particles is carried out due to mechanical mixing - "piston" and shear movement, in which particle segregation is possible;

3) the impossibility of simultaneously combining the processes of obtaining particles, mixing and stacking them in a container in a certain order and with a given concentration.

A known method of preparing a mixture, including laying particles and mixing them (patent RU No. 2129911 "Method for mixing bulk components and a device for its implementation", IPC ⁶ B01F 3/18, published 05/10/1999).

The method has the following disadvantages:

1) the impossibility of obtaining a mixture with the distribution of particles in the tank with high accuracy according to any law, since the laying of the loaded particles is carried out by their dosing, carried out by mechanical separation of the supplied continuous flows of particles into microvolumes per unit time;

2) there is a violation of the ordered arrangement of particles (at the interfaces of the sectors), since the mixing of particles in the container for the mixture is carried out by the orderly laying of individual microvolumes in the form of angular sectors due to a change in the position of the container relative to particle flows and its own axis;

3) the impossibility of simultaneously combining the processes of obtaining particles, mixing and stacking them in a container in a certain order and with a given concentration.

A known method of preparing a mixture without mechanical stirring, including laying the particles and mixing them (patent RU No. 2271243 "Method for mixing bulk components and a device for its implementation", IPC B01F 3/18 (2006.01), published 03/10/2006).

The method has the following disadvantages:

1) the impossibility of obtaining a mixture with high uniformity, since the method is designed to prepare a mixture of particles obtained in advance (before performing the mixing operation), therefore, it can be used to prepare the mixture only from non-clumping particle sources, however, submicron particles are prone to rapid clumping, so how, even during short storage, they are combined into conglomerates comparable in size or significantly larger than other particles;

2) the impossibility of obtaining accurate microdoses of particles of a certain size or material as a result of mechanical separation of particle flows whose concentration in the mixture is fractions of a percent, grams or fractions of a gram for the volumes of the predominant particles in the resulting mixture, measured in kilograms. Laying the loaded particles, that is, controlling their ratio in the mixture being prepared, in this method, is carried out by dosing by mechanical separation of the particles fed in a continuous stream into microvolumes per unit time;

3) the limitation of the mixed particles by minimum sizes and minimum concentrations, since the ordered packing of particles is carried out first in order of increasing particle size, and then in order of decreasing;

4) the impossibility of achieving high homogeneity of the mixture, since the ordered packing of particles occurs due to the change in the capacities of their positions relative to the particle flows, which leads to the formation of sufficiently large microvolumes;

5) the impossibility of simultaneously combining the processes of obtaining particles, mixing and stacking them in a container in a certain order and with a given concentration.

The objective of the invention is to obtain a mixture with a given particle size and / or chemical composition of the particles, as well as with a given concentration, which in turn leads to an increase in the quality of the prepared mixture from particles significantly different in size and concentration, and therefore to an increase in the quality of such a mixture of products.

Due to the fact that none of the methods described in the known sources solves the problem, and these methods consist of time-divided operations (processes) - separately the operations of mixing and stacking particles or separately the operations of obtaining particles and mixing them, There are the above methods that do not allow to prepare the mixture while simultaneously combining in time all the processes - obtaining particles, mixing and stacking them in a specific order and with a given concentration, and also do not allow to prepare the mixture with a uniform or distributed according to a given law in its volume of particles, the concentration of which relative to the concentration of the particles predominant in the mixture being prepared is a fraction of a percent, and the present invention allows you to simultaneously combine the above processes in time, then none of the above methods can be taken as a prototype.

The technical result of the invention is to increase the uniformity of the prepared mixture of particles of different particle size and / or chemical composition with sizes and concentrations differing by more than an order of magnitude, the distribution of particles over the volume of the mixture with high accuracy according to any law; simultaneous combination in time of the processes of obtaining particles, their mixing and stacking.

The technical result is achieved by the fact that according to the invention, particles of different particle size and / or chemical composition are obtained from individual particle sources by dispersing such sources in a working medium by electric current pulses, for which each respective particle source is placed above a container or in a container with a working medium, in the process of obtaining particles, they are laid, which in essence is a process of mixing particles, and the required distribution of particles of different particle size distribution chemical and / or chemical composition and the ratio between them is obtained by applying to each particle source a certain number of pulses per unit time and the energy invested in the pulse (for particles that are predominant in the mixture and for any other (ith particles)). To determine the operating modes when implementing the proposed method, you can use the following dependencies:

where m ₀ , m _i - the required concentration of the predominant and i-th particles;

f ₀ , f _i - the number of pulses per unit time to obtain the prevailing and i-th

particles;

q ₀ , q _i - the power invested in the pulse to obtain the predominant and i-th particles;

P ₀ , P _i - tabular values of the erosion resistance of the materials of the sources of the predominant and i-th particles, which can be calculated by the thermophysical properties of the material (heat capacity, thermal conductivity, melting point) and density.

The choice of methods for producing particles is based on the possibility of obtaining narrow fractions of particles without the need for their subsequent sorting and separation. It is preferable to use known electroerosive methods for producing particles, for example, in pulsed electric discharges, which allow to obtain up to 80% of particles with a spread in sizes of no more than 10% (A. Goloveyko, “Dispersion of metals during a pulsed discharge in a liquid dielectric”, book “Physical fundamentals of electrospark processing of materials ”, Moscow:“ Nauka ”, 1966, p. 81).

An inert medium (with respect to one or all materials of the particles of the mixture being prepared) is used as the working medium in which particles can be obtained (in this case, the prepared mixture will consist of particles of the same chemical composition as the material of the particle source) or the corresponding medium allowing to obtain particles of metal oxides, carbides, nitrides (also with respect to one or all materials of the particles of the mixture being prepared) (in this case, the mixture to be prepared will consist of particles with chemical tavom different from the particle source material).

As an inert medium, it is proposed to use vacuum, a gas medium or a liquid; and as a suitable medium, allowing to obtain particles of oxides, carbides, nitrides of metals, according to the invention it is proposed to use a gas medium or liquid.

As a liquid in the preparation of the mixture, water is used, including distilled, hydrocarbons, alcohols. For example, spherical tungsten carbide particles are produced by exploding tungsten wires in kerosene. Using the electroerosion method (pulsed electric discharge, explosion of conductors, etc.), particles of an ideal spherical shape are obtained due to the high cooling rate of molten metal droplets in a liquid.

The use of various media in electroerosion methods for producing particles extends the range of use of sources of particles of the prepared mixture of high uniformity, namely: in an inert medium particles are obtained in the form of pure metals; in an environment that allows particles of metal oxides, carbides, nitrides to be obtained, particles of the mentioned materials are obtained (for example, in oxygen, water, ethanol particles are obtained in the form of oxides, in nitrogen in the form of nitrides, and in kerosene or transformer oil in the form of carbides )

It is proposed to lay particles in the process of their production in a vessel installed at the bottom of the tank, in which it is proposed to carry out subsequent technological operations with the mixture. Preparation of the mixture directly in the vessel, for example, in a graphite mold, allows the following operations, such as sintering, pressing, heat treatment, to be carried out without removing the mixture from the vessel.

It is proposed to move the container in the process of producing particles and their packing according to the invention with respect to the flows of the resulting particles, which allows the particles to be stacked on an area exceeding the size of the filling area of the mixture with a fixed tank and limited only by its size. Depending on the size and shape of the products that are supposed to be made from the mixture without pouring it before pressing, the container is moved in the horizontal plane by rotating it around the vertical axis, by translational motion or a combination of these movements.

The invention is illustrated by drawings, where in FIG. 1 shows a general view of a device for implementing a method for preparing a mixture with the most dense packing of particles from the same material, but with different particle size distribution, and FIG. 2 is a general view of a device for implementing a method of preparing a mixture of particles of different materials of the same particle size distribution, but significantly different in concentration.

The implementation of the method is considered on the example of the preparation by powder metallurgy of a mixture for the manufacture of a tungsten disk with a maximum material density (example 1), on the example of the preparation of a mixture for producing a tool alloy with a high uniformity of particle distribution — tungsten carbide, cobalt, molybdenum (example 2) and an example of the preparation of a mixture to obtain a dispersion-hardened alloys (example 3).

Example 1 - preparation of the mixture with the most dense packing of particles from the same material, but with different particle size distribution.

You can get a mixture with the most dense packing of particles only when using particles with certain ratios of sizes and concentrations. The theoretical value of the maximum density of the backfill of spherical particles of the same diameter (the fraction of the volume occupied by the solid material) is 0.64. With an increase in the ratio of the diameters of the mixed particles, the density of the mixture increases and, with an infinitely large ratio of a larger diameter to a smaller one, asymptotically approaches 0.87 (Khantadze D.V., Topuridze N.I. “The Mechanism of Compaction of Two-Component Bulk Media Modeled by Spherical Particles”, Engineering Physical Journal, 1977, v. 33, No. 1, pp. 120-125). A density of the mixture close to this limit value can be obtained with a ratio of the diameters of the mixed particles equal to 10.

A mixture consisting of two groups of particles for subsequent manufacture of an article from it (a tungsten disk with a diameter of 80 mm and a thickness of 10 mm) with the most dense packing of particles may consist of particles with a diameter of 40 μm (80%), which are predominant in the resulting mixture, and other particles with a diameter of 4 microns (20%). To obtain such particles, a well-known method of dispersing the material is chosen - electrical explosion of conductors, as the most preferred in this case.

As a working inert medium, vacuum is chosen.

Shown in FIG. 1 device for preparing the mixture consists of a container 1, current leads 2, sources of particles in the form of wires 3, fixed in devices 4 for feeding wires 3, a power source 5, sources of tungsten particles - exploding sections 6 of wire 3 located at the bottom of the mold 7 and the sealing capacity of the lid 1 (not shown in the figure).

Preparation of the mixture is as follows:

- on the bottom of the tank 1 with a depth of 200 mm, a mold 7 is installed (with a corresponding inner diameter of 80 mm to obtain the desired tungsten disk) for collecting and stacking the particles forming the mixture;

- in the tank 1 is placed two current leads 2 for tungsten wires 3 with a diameter of 0.35 and 0.2 mm;

- current leads 2 are connected to a power source 5;

- the container 1 is closed with a sealing cap (not shown in the figure) and vacuum up to 10 ^-4 mm Hg;

- include a power source 5 and a wire feed device 4. Moving wires 3 periodically close the electrical circuits of each of the particle sources. A large current flowing through section 6 of the wire 3 between the current leads 2 heats the section 6 until it evaporates, the steam condenses in an inert medium to powder, which settles in the mold 7.

Количество импульсов для получения каждой группы частиц определяется из соотношения -

С увеличением скорости подвода энергии в материал источника частиц, то есть с уменьшением продолжительности импульса при увеличении мощности, уменьшаются и размеры получаемых частиц. В данном примере преобладающие в смеси частицы вольфрама размером 40±2 мкм получают при подаче на «взрываемый» участок 6 проволоки 3 диаметром 0,35 мм одиночного импульса тока 150 А (при напряжении 600 В) продолжительностью 300 мксек, а частицы размером 4±1 мкм получают при подаче на «взрываемый» участок 6 проволоки 3 диаметром 0,2 мм одиночного импульса тока 300 А (при напряжении 1800 В) продолжительностью 50 мксек. Продолжительность импульсов для каждой проволоки 3 устанавливают настройкой электронного блока источника питания 5, а продолжительность интервалов между импульсами - скоростью подачи каждой проволоки 3. Необходимое соотношение между концентрациями частиц большего и меньшего размера (80% и 20%) получают при последовательной подаче четырех импульсов на проволоку 3 диаметром 0,35 мм и одного - на проволоку 3 диаметром 0,2 мм.The sizes of the obtained particles depend on the energy deposited in the current pulse, that is, on the magnitude of the current, voltage in the pulse and the duration of the pulse, as well as on the material and geometry of the wire 3. The particles of two groups of particles are obtained from the same material, the erosion resistance (P) of which is the same and which is determined by the Palatnik criterion according to the following formula: П = СρλT ² . The power (energy) (q) invested in unit pulses is also the same and is calculated by the formula -

The number of pulses to obtain each group of particles is determined from the ratio -

With an increase in the speed of energy supply to the particle source material, that is, with a decrease in the pulse duration with an increase in power, the sizes of the resulting particles also decrease. In this example, the tungsten particles prevailing in the mixture with a size of 40 ± 2 μm are obtained by applying a single current pulse of 150 A (at a voltage of 600 V) with a duration of 300 μs to a "blown" section 6 of wire 3 with a diameter of 0.35 mm and a particle size of 4 ± 1 μm is obtained by applying a single current pulse of 300 A (at a voltage of 1800 V) with a duration of 50 μs to a “blown” section 6 of wire 3 with a diameter of 0.2 mm. The duration of the pulses for each wire 3 is set by setting the electronic unit of the power source 5, and the duration of the intervals between pulses is the feed rate of each wire 3. The required ratio between the concentrations of particles of larger and smaller sizes (80% and 20%) is obtained by sequentially supplying four pulses to the wire 3 with a diameter of 0.35 mm and one on wire 3 with a diameter of 0.2 mm.

When explosive dispersion of 3 tungsten wires in a gaseous medium, for example, in helium, the time intervals between pulses is determined by the particle deposition rate calculated by the Stokes formula (“Chemistry Handbook”, Volume 5, 2nd ed. Reworked and add., M .-L.: “Chemistry”, 1996, p. 426). In this case, when placing the sources of particles in a container 1 with a depth of 200 mm, the first three intervals (between four pulses per wire 3 with a diameter of 0.35 mm and one pulse per wire 3 with a diameter of 0.2 mm) will be 0.2 sec., And the interval after the fourth impulse and before the start of the next group of impulses - 3 sec.

Thus, with the simultaneous action of the current source 5 on the wire 3, particles are obtained whose diameters differ by an order of magnitude and the concentration by four times;

- in the process of obtaining tungsten particles, the container 1 is rotated around its vertical axis to uniformly fill the mold 7 with the particles obtained. As a result of the ordered settling (stacking) of tungsten particles of different sizes, they are mixed and uniformly distributed over the mold 7, resulting in get a homogeneous mixture;

- to fill the mold 7 with particles, turn off the power source 5, remove the sealing cover (not shown in the figure), remove the mold 7 from the container 1 for subsequent disk manufacturing operations.

Example 2 - preparation of a mixture of particles of different materials of the same particle size distribution, but significantly different in concentration.

The quality of products made from carbide materials manufactured by powder metallurgy methods, in particular, cutting tools, depends on the uniformity of the prepared mixture. The complexity of the preparation of the press powder is a significant difference in the concentrations of the mixed particles, for example, the recommended composition of the instrumental alloy is as follows: 93 wt. % tungsten carbide, 5 wt. % cobalt and 2 wt. % molybdenum. As can be seen, the concentration of molybdenum in this alloy is almost 50 times lower than the concentration of tungsten carbide, which is predominant in this alloy, which, using conventional mechanical mixing, makes it impossible to obtain a mixture with a uniform distribution of molybdenum.

An inert medium in the form of a liquid (distilled water in relation to cobalt and molybdenum) and a medium allowing to obtain tungsten carbide particles (kerosene in relation to tungsten) was chosen as a working medium.

A method of preparing a mixture to obtain a tungsten-cobalt-molybdenum carbide tool alloy is carried out on the device shown in FIG. 2. The device contains a tank 1, three pairs of current leads 2, sources of particles in the form of flat electrodes 3. The tank is filled with distilled water (lower layer 8) and kerosene (upper layer 9). Each pair of electrodes 3 is connected to its power source 5, and a spark generator 10 is connected to the electrodes 3 of tungsten. A mold 7 is installed at the bottom of the tank 1.

Preparation of the mixture is as follows:

- on the bottom of the tank 1 install a graphite mold 7 with a suitable inner diameter;

- the tank 1 is filled with distilled water (lower layer 8) and kerosene (upper layer 9) in any sequence;

- after the separation of the liquids in the tank 1 in the upper layer 9 are placed electrodes 3 of tungsten with current leads 2 and in the lower layer 8 - electrodes 3 of cobalt and molybdenum (two rod electrodes 3 of these materials). The tungsten electrodes 3 are installed with a gap of 1-3 mm, the cobalt and molybdenum electrodes 3 are connected to a mechanism providing continuous closure and breaking of the electric circuit of each pair of electrodes 3 by their oscillatory movement relative to each other;

- electrodes 3 are installed in the tank 1 so that the resulting particles fall into the mold 7;

- tungsten electrodes 3 through current leads 2 are connected to a high-voltage switching power supply 5 and a high-frequency spark generator 10 initiating a discharge, cobalt and molybdenum electrodes 3 are connected to their low-voltage power supplies 5;

- include power sources 5 and a generator 10 and produce particles of all three materials while simultaneously continuously operating power sources 5 in predetermined modes by current, voltage and pulse duration. Tungsten carbide is formed due to the chemical interaction of dispersed tungsten with kerosene carbon. The resulting particles are deposited in the mold 7.

и

Соотношение энергий, вкладываемых в единичные импульсы, определяют с учетом эрозионной стойкости (П) материалов частиц и их необходимых концентраций по формуле - П=СρλT². Относительные вклады энергии в единичные импульсы для получения одинаковых весовых количеств частиц вольфрама (преобладающие частицы) и кобальта, вольфрама и молибдена в одном импульсе рассчитывают по формуле -

Энергия импульса при получении одинакового весового количества частиц вольфрама должна быть в 6,5 раза выше, чем для кобальта, и в 1,9 раз выше, чем для молибдена. Необходимое количество импульсов с такими энергиями для состава смеси карбид вольфрама (93%)-кобальт (5%)-молибден (2%) определяют из отношения концентраций частиц, преобладающих в смеси (вольфрама), и остальных. Из расчетов по формуле

следует, что на 1000 импульсов для вольфрама необходимо 57 импульсов для кобальта и 23 для молибдена. Уменьшением вкладываемой в импульс энергии для кобальта и молибдена в n раз по сравнению с энергией импульса для преобладающих в смеси частиц можно в n раз увеличить количество импульсов, что позволяет использовать существующие источники питания, например, генераторы импульсов тока, применяемые на станках электроэрозионной резки. Приготовление смеси ведут при следующих параметрах генератора:To prepare a mixture of "cobalt-molybdenum-tungsten carbide" with specified particle concentrations during continuous operation of all three sources of particles, the ratio of the number of pulses and the energy invested in them is determined by the formulas:

and

The ratio of the energies invested in unit pulses is determined taking into account the erosion resistance (P) of the particle materials and their required concentrations according to the formula - P = СρλT ² . The relative energy contributions to unit pulses to obtain the same weighted amounts of tungsten particles (predominant particles) and cobalt, tungsten and molybdenum in one pulse are calculated by the formula -

The pulse energy upon receipt of the same weighted amount of tungsten particles should be 6.5 times higher than for cobalt, and 1.9 times higher than for molybdenum. The required number of pulses with such energies for the composition of the mixture of tungsten carbide (93%) - cobalt (5%) - molybdenum (2%) is determined from the ratio of the concentration of particles prevailing in the mixture (tungsten) and the rest. From the calculations according to the formula

it follows that for 1000 pulses for tungsten, 57 pulses for cobalt and 23 for molybdenum are needed. By reducing the energy invested in the pulse for cobalt and molybdenum by n times compared to the pulse energy for particles prevailing in the mixture, the number of pulses can be increased n times, which allows the use of existing power sources, for example, current pulse generators used in EDM machines. The mixture is prepared with the following parameters of the generator:

a) for tungsten particles (fault current 10 A, frequency 10 kHz),

b) for cobalt (fault current 0.5 A, frequency 5.7 kHz),

c) for molybdenum (fault current 0.5 A, frequency 2.3 kHz);

- when preparing the mixture for large-sized products, the container 1 with the mold 7 is moved in a horizontal plane relative to the sources of particles so that the mold 7 is filled evenly to the required level throughout the volume. As a result of the ordered settling (stacking) of particles of tungsten carbide, cobalt and molybdenum, which have different densities, they are mixed and uniformly distributed throughout the mold 7, resulting in a uniform mixture;

- by filling the mold 7, turn off the power sources 5 and remove the mold 7 with the resulting mixture in order to conduct subsequent operations. Excess carbon, which may appear in the mixture during the production of particles in kerosene, is removed by liquid-phase sintering by backfilling of corax (aluminum oxide) over the pressed mixture.

Example 3 - preparation of the mixture to obtain dispersion-hardened alloys.

When materials with a melting temperature and strength greater than that of the predominant particles in the mixture are added, dispersion-hardened alloys are obtained whose quality primarily depends on the uniform distribution of the added hardening additive. The amount of hardening additives, for example, aluminum, yttrium or thorium oxides, in the alloy does not exceed 1-2%, and it is impossible to achieve its high uniformity of distribution by mechanical stirring. To increase uniformity, technologically sophisticated chemical and metallurgical methods are used, such as: mixing solutions of matrix and hardening metal salts, followed by evaporation, drying, and selective reduction of particles in hydrogen with preservation of oxides of hardening additives (Rakovsky BC et al. “Powder metallurgy of heat-resistant alloys and refractory metals ", M .:" Metallurgy ", 1974, pp. 176-179).

An inert medium in the form of a gas was chosen as the working medium (with respect to nickel, argon, and with respect to alumina, argon with oxygen additives).

In the proposed method, the sources of particles of the metal (nickel) prevailing in the alloy and the reinforcing additive (aluminum oxide) are conveniently placed above the container in which the particles are laid. Sources of particles are made in the form of electrodes. Particles are obtained by known methods: nickel — by dispersing the material of nickel electrodes by a pulsed electric discharge in an inert gas stream, and alumina — by dispersing aluminum electrodes in an inert gas stream containing controlled oxygen additives. The current source continuously affects the sources of nickel and alumina particles, but the performance of each source is determined by the energy invested in the pulses and the number of pulses per unit time. The ratio of the energies invested in the unit pulses, ensuring the formation of the same weighted amounts of particles during the dispersion of nickel and aluminum oxide, is P _i / P ₀ = q _i / q ₀ = 1.66. Thus, the energies invested in unit pulses during the dispersion of nickel and aluminum with a pulse duration of 300 μs are equal to 3.0 J (q ₀ ) and 5.0 J (q _i ), respectively. The ratio of the number of pulses per unit time in the preparation of a mixture containing 98% nickel (m ₀ ) and 2% aluminum oxide, which corresponds to 0.52% aluminum metal (m _i ) (Al ₂ O ₃ refers to Al as approximately 100 to 26) is: m _i / m ₀ = f _i / f ₀ . Taking the number of pulses to obtain 0.52% aluminum metal (f _i ) equal to 1, we obtain the necessary number of pulses to obtain 98% nickel (f ₀ ), f ₀ = 98⋅1 / 0.52 = 188. Thus, at 188 pulses per millisecond, when dispersing nickel, there should be one pulse when dispersing aluminum.

Thus, the preparation of mixed particles and the simultaneous control of their concentration during the preparation of the mixture without the use of mechanical stirring makes it possible to ensure high uniformity of the mixture and the distribution of particles in its volume with high accuracy by any law, increasing the quality of the mixture, which also improves the quality of products made from it . The proposed method allows to obtain a homogeneous mixture of particles, which differ in concentration and / or size by more than an order of magnitude. The movement of the container during the preparation of the mixture contributes to a more uniform distribution of particles (obtaining a high-quality mixture for the manufacture of large products from it by eliminating the violation of the uniformity of the mixture when pouring it into other containers).

Claims (15)

1. A method of preparing a mixture of particles of different particle size and / or chemical composition, characterized in that particles of different particle size and / or chemical composition are obtained from separate sources by dispersing electric current pulses in the working medium, for which each corresponding particle source is placed above the container or in a container with a working medium, while in the process of obtaining particles, they are laid, essentially representing the process of mixing particles, and the required distribution Particles of various particle size and / or chemical composition and the ratio between them are obtained by applying to each particle source a certain number of pulses per unit time and the energy invested in the pulse. 2. The method according to p. 1, characterized in that the number of pulses per unit time and the energy invested in the pulse to obtain particles that are predominant in the mixture and for any other i-th particles, is determined in accordance with the dependencies:

and

Where: m ₀ , m _i - the required concentration of the predominant and i-th particles; f ₀ , f _i - the number of pulses per unit time to obtain the prevailing and i-th particles; q ₀ , q _i - the power invested in the pulse to obtain the predominant and i-th particles; P ₀ , P _i - tabular values of the erosion resistance of the materials of the sources of the predominant and i-th particles. 3. The method according to p. 1, characterized in that when receiving particles of the same chemical composition as the materials of the sources of particles, an inert medium is used as the working medium. 4. The method according to p. 3, characterized in that as an inert medium using a vacuum, a gas medium or a liquid. 5. The method according to p. 1, characterized in that when receiving particles of oxides, carbides, nitrides of metals as the working medium using the appropriate medium, allowing to obtain particles of the mentioned materials. 6. The method according to p. 5, characterized in that as a medium that allows to obtain particles of oxides, carbides, metal nitrides, use a gas medium or liquid. 7. The method according to p. 1, characterized in that the packing of particles is carried out in a vessel mounted on the bottom of the tank. 8. The method according to p. 1, characterized in that the container in the process of obtaining particles is moved relative to the source of particles by rotating it around a vertical axis, translational movement or a combination of these movements.

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