JPH0234707A - Method for pulverizing a metal and apparatus for performing it - Google Patents

Abstract

PURPOSE: To stably produce grains of various size distributions at a high forming velocity by heating and melting a metallic material in a gas by means of an electric arc to perform evaporation and grain scattering and also properly performing arc irradiation and arc cessation alternately and periodically. CONSTITUTION: In a hermetically sealed vessel 1 containing a gas which is dissociated and activated by an electric arc, a metallic material 3 on a supporting tool 2 provided with a liquid cooling circuit 10 is at least partially melted by an electric arc 14. The resultant dissociated gas dissolves into the molten metal and reassociates. By this procedure, the metal is evaporated as fumes and metal particle are scattered. These are recovered as pulverized metal particles 12 by a receptor 11. In the above method for pulverizing a metal, the metallic material 3 is irradiated with the above arc 14 during the period when the above reaction reaches dynamic equilibrium and becomes insufficient reaction conditions to continue evaporation and scattering. Further, in the source of collection of the metallic vapor, after the metallic material 3 is cooled and a thermal nonequilibrium between a high temp. region and a low temp. region is reproduced, the above arc irradiation is started again and is periodically carried out.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention is directed to the application of an electric arc (plasma ), and relates to a method for simultaneously pulverizing and vaporizing a metal or alloy into particles having a size distribution in various ranges, and an apparatus for carrying out the method.

[Prior Art] In this type of method, the metal irradiated by an electric arc is at least partially melted (for example, the surface of the metal becomes liquid), and an activated gas is introduced into the molten metal, in particular the molten metal. When the metal melts into the hot region, the activated gas atoms recombine and the released energy causes the metal to boil and evaporate. When the arc is narrowed and concentrated over a relatively small area of the metal material of interest, the vapor produced becomes very dense and condenses into collectable submicron particles (fume or dust). . On the other hand, when heating is performed, the dissolved gas moves through the metal material along a somewhat lower temperature region (low temperature because it is not directly affected by the arc). In this low-temperature region, there is little or no evaporation, so the external pressure decreases, and the dissolved gas suddenly escapes as large bubbles, which burst, scattering the metal, and condensing the metal particles. Form particles larger than the resulting dust particles. The dimensions of the large particles thus formed are on the order of a few μm to several 100 μm.

Of course, depending on the operating conditions of the arc and other conditions such as the dimensions of the electrodes and metal materials, and the type of metal to be powdered, it is possible to reduce scattering and promote evaporation (formation of very fine particles of 1 μm or less), or vice versa. can promote the formation or scattering of air bubbles to continue forming large particles. Therefore, the energy density of the arc (ie, the resulting local temperature increase) is reflected in the distribution of fumes and large diameter particles. In the case of a narrow, high-density arc, metal evaporation primarily occurs, while in the case of a thick, low-density arc, large particles (albeit less stable) are primarily formed by scattering.

The above-mentioned general technique is disclosed in many publications, especially the following publications.

US-8-4,376,740 (NAT, RES, IN
5T, Liver TALS), a hydrogen stream is activated with an electric arc or plasma and directed toward a molten metal or alloy to pulverize the metal into particles with dimensions of 10 μm or less. As an activated hydrogen source,
Atomic hydrogen, N11. , CH,, C2H,, propane, and ethylene. The activated hydrogen can be diluted with a noble gas such as He, Ne, Ar, or the like. The metal powder is wiped away with a stream of hydrogen and ducted into a sedimentation vessel where it accumulates.

US-A-4, 4, 82, 134 (NAT, RES,
The method and apparatus disclosed in US Pat. Add appropriate means. In this method, the newly formed particles are rapidly cooled with an air stream, which then drives the particles into a holding tank where they are allowed to settle and settle.

No. 4,689,075 relates to a method for making ultrafine powders reliably smaller than 1 μm from metals or ceramics. In this method, at least two or more different types of materials are simultaneously pulverized by applying an electric arc under a gas pressure of hydrogen, nitrogen, oxygen, or a mixture thereof of 50 Torr to 3 atmospheres. Particles newly formed from two or more materials are introduced into the gas stream, and the turbulent movement of the gas ensures that the dissimilar particles are mixed as long as they are suspended in the gas. From the operating conditions disclosed in this publication, it appears that particle formation occurs by evaporation rather than by entrainment of air bubbles in the molten material.

As a technology similar to this, J^-59-190,30
2 (Daido Steel) describes the production of ultrafine particles by melting metals, semiconductor materials, or alloys under an electric arc in the presence of hydrogen, nitrogen, or hydrogen-generating gas. According to this publication, by arranging the molten metal coaxially with the arc generating electrode and installing a piston that acts on the molten metal to keep its level constant with respect to the electrode, the voltage and length of the electric arc can be increased. , and control the current constant.

Although the above known techniques are very interesting, they have the following drawbacks. That is, although means exist to cool the underlying support that supports the metal to be pulverized, the intense thermal effects to which the metal is exposed result in thermal and chemical damage occurring in very short periods of time, from one minute to several minutes. A state of equilibrium is reached and the milling process is hindered and slowed down or even stopped completely. The detailed reason why the pulverization process is disturbed in this way is as follows.
This is the temperature difference between the region where the gas enters and the region where the gas exits.That is, as the reaction progresses, this temperature difference decreases and the gas exchange between these regions decreases.

Thus, the larger the melting area of the metal, which is usually the case with unconfined arc irradiation, the less likely it is that dissolved gases will concentrate in the colder area surrounding the arc, and thus the less bubble formation will occur. Splashing also decreases over time.

On the other hand, metal vapor dissipated from the metal region directly below the arc acts as a screen and prevents contact between the activated gas and the molten metal. As a result, the degree of development also gradually decreases.

Moreover, as the reaction gradually slows down as mentioned above, the pulverization conditions change, which leads to a change in the production distribution of very fine particles (obtained by concentrating the hume) and large particles (due to the scattering phenomenon). The state gradually deviates from the state at the start of the reaction (for example, at the beginning of the reaction, almost only ultrafine particles are obtained by evaporation, but as the reaction progresses to a later stage, a mixture of fine dust and scattered large-diameter particles is obtained. In fact, as far as is known, no matter how many appropriate combinations of operating conditions are used in the prior art, it is not possible to select ultrafine particles due to evaporation, large particles due to fly 111!, or both. The present inventor has completed various studies to solve the above-mentioned drawbacks, and as a result, has completed the present invention.

[Problems to be Solved by the Invention] The present invention is directed to applying an electric arc (plasma) to a metal or an alloy in a powdering container in an atmosphere of a gas that is activated by dissociation or the like due to the action of plasma of an electric arc. The purpose of the present invention is to provide a method for producing particles having a size distribution in various ranges at a stable and high production rate by simultaneously pulverizing and vaporizing metals or alloys, and an apparatus for carrying out the method. .

[Means to solve the problem]

The above object, according to the present invention, is a method for pulverizing a metal material held in a holder in a closed container containing a gas which is dissociated and activated by the action of an electric arc, under an electric arc. The metal is at least partially melted under the action of the arc, the dissociated gas preferentially melts and reassociates into the hot regions of the molten metal, and the release of binding energy causes the molten metal to evaporate. At the same time, a part of the metal fume moves from the high-temperature region to the low-temperature region where the arc pressure is low and the gas solubility is insufficient, causing the gas to escape in the form of bubbles, which burst. In a method in which metal particles are dispersed and the rate of this process depends on the temperature difference between said hot and cold regions, the following steps: (1) during the activity fIJ1 during which said reaction reaches a dynamic equilibrium, i.e. The arc is directed over the metal during a period in which the release of the metal reduces the concentration of activated gas in contact with the molten metal, resulting in insufficient reaction conditions to continue splattering and evaporation. irradiating, and (2) removing the metal from the action of the arc during a period called rest or dormancy during which metal vapor is collected, cooling the metal material and separating the hot and cold regions. This is achieved by a method of pulverizing a metal, which is characterized by periodically carrying out the steps of reproducing the thermal imbalance and reproducing the initial reaction conditions of step (1) above.

As related technology, G8-Hei 2.176, 582
(Daido Steel) is explained. This publication discloses an apparatus for pulverizing molten metal by periodically applying a torch to plasma spray. This torch is in the form of a ring-shaped nozzle through which activatable gas is directed diagonally toward a metal ring housed in an annular pot placed coaxially with the nozzle. Inject a stream. This causes the gas to form a truncated conical curtain that hits the metal inside the pot. An electric arc is generated locally between the ring-shaped electric scraper in the nozzle and the metal to be pulverized by a magnetic field acting on a portion of the gas curtain and rotatable progressively along the ring by conventional means. The metal in the pot is heated and locally melted, and some of the gas activated by the arc melts into it. As the arc moves away, the part of the molten metal that is no longer under the arc cools slightly and becomes supersaturated with the injected gas, causing an eruption and creating flying particles, which are wiped away by an annular gas stream. Therefore, the method disclosed in this publication does not simultaneously control the evaporation of molten metal as in the present invention.

Furthermore, in the apparatus disclosed in the above-mentioned publication, a gas stream is continuously blown onto the peripheral edge of the metal to be pulverized, which is not economical in practical terms.

In contrast, in the present invention, no gas is sprayed onto the molten metal, and active periods (active periods) and dormant periods (dormant periods) are alternately repeated. a period in which the metal is irradiated with an electric arc to gradually reach a state of dynamic thermal and chemical equilibrium, and an initial period in which there is no generation of metal dust due to evaporation and which promotes effective comminution at the beginning of the next period. Continuously alternating with "cleaning" periods during which the metal cools sufficiently to restore chemical and thermal conditions. Furthermore, it is possible to carry out a step of removing metal dust or fumes produced by condensation of vapor from the area of action of the electric arc. This can be done, for example, by condensing the dust on surfaces that have particle-attracting properties, or by carrying the particles away and depositing them in a suitable container. Therefore, although the initial yield of pulverization becomes increasingly unstable due to the presence of metal vapor within the direct influence area of the electric arc,
The preferred operating conditions are renewed during the rest period and fully restored at the beginning of the next active period.

The length of the active and dormant periods is quite variable and depends on a number of factors, namely the type of metal being pulverized, the electric arc operating parameters, the dimensions of the metal particles, and particles of micron and larger dimensions (produced by entrainment). and the volume or weight distribution of submicron particles produced by condensation of metal vapors. In order to properly select the length of the active and dormant periods, one must also keep in mind the type of particles required. In other words, if only submicron particles (hueum) are required, before scattering starts,
In other words, the active period ends before the gas that has entered the melt is observed to erupt.

If it is necessary to suppress fume formation and promote scattering, adjust the arc parameters accordingly. In other words, the energy density, arc length, arc intensity, etc. are adjusted to suppress evaporation as much as possible, and the length of the activity period is adjusted according to the progress of the operation, such as the gradual suppression of the pulverization process. decide.

-C, the length of the active period and the rest period is on the order of several seconds to several minutes, for example, about 5 seconds to 5 minutes, and is set by experiment as necessary.

Of course, the lengths of the active period and the dormant period may be the same or different.

In order to temporarily remove the metal material to be pulverized from the action of the electric arc, the electric arc may be switched off or the metal material may be physically pulled out of the arc's reach. Each aspect will be described below with reference to the accompanying drawings.

The apparatus shown in FIG. 1 has a support structure (supporting tool) 2 for a metal material 3 to be pulverized in an airtight pulverization container 1. A cathode 4 made of zirconia/tungsten or l.lium tungsten (or other conductive refractory material) is placed opposite the metal material 3. This cathode 4
A liquid cooling circuit 5, a power line 6 connected to a power source (not shown), and a member 7 connected to a lever 8 at a position 9 for raising and lowering the cathode 4 are provided.

A receptacle lI is further provided in the container l, which surrounds the support 2 and is itself cooled by a liquid circuit 10. This receptor 11 is made of finely ground metal particles 1
2 is deposited at the bottom and collected.

Receptacle 11 is also cooled by liquid circuit 10a, and container 1 is also cooled by circuit 10b.

The container l is further provided with a gas inlet 13a and an outlet 13b connected to a decantation device (for example, a cyclone), not shown, for collecting the ultrafine dust generated by direct evaporation in a volume. There is. The flow rate of this gas is very slow (1-20 1/hr),
No mechanical or cooling effects are exerted on the metal being pulverized. This gas may be hydrogen gas or a H2/Ar mixture of hydrogen and a noble gas such as argon, for example in a ratio of 5 to 50% (v/v). Electrode 4 (cathode)
is connected to the negative terminal of the power supply, and the container 1 is connected to the positive terminal.

To start the device, the lever members 7, 8 lower the cathode towards the metal material 3, thereby creating an arc 14 between the electrode 4 and the metal material 3 (see FIG. 2). , the metal melts as the temperature rises, and begins to evaporate as shown by arrow 15 in the space directly affected by the arc. Under reduced pressure (e.g. 100-800 Torr)
The gas in the container at 200°C becomes activated by dissociation and begins to infiltrate into the molten metal. This phenomenon occurs particularly actively in the space 14 where the arc is striking the metal. The infiltrated gas is moved out of the hot region 14 by the thermal displacement of the molten metal, where it becomes supersaturated and begins to form bubbles 16. Bubbles near the metal surface burst and scatter as droplets or particles (often spherical). The size of these particles ranges from a fraction of a μm to several 1O or several hundred (
or more). These particles solidify during cooling and accumulate at the bottom of the receiver 11 (12);
The fume 15 formed when the metal vapor released into the space directly exposed to the arc irradiation condenses in the container is led to the outlet 13 and collected as submicron dust as already explained. . Alternatively, a screen (e.g., a removable barrier with electrostatic dust collection) is placed in the path of the fume;
Collect dust from this screen later. Therefore,
The above device is capable of sorting metal powders according to particle size. If the tip of the cathode is immersed in molten metal when the arc is cut, a metal coating (metal film) will form on the cathode.
It should be noted that . In this case, when restarting the arc, the direction of the current is temporarily reversed (
(by reversing the polarity), the metal film attached to the cathode can be easily pulverized.

Instead of periodically activating and deactivating the arc, the metal material may be temporarily physically removed from the action of the arc.

The electrically conductive refractory material support 22 shown in FIG.
Equipped with. This support has two depressions 24a, 24b.
Each recess contains the metal material to be pulverized. Each recess may alternately face the electric arc 14 (similar to metal material 3 in Figure 1) so that when one metal material is in an active period, the other metal material is in a dormant period. can. The transition from one position to the other may be gradual (slow continuous rotation) or with no or little transition time (fast 180° switch). .

Of course, the number of recesses that accommodate the metal material can be made larger than two, and the metal material can be placed in a continuous ring shape (G
B-A-2, 176, 582), and repeating the process of regularly rotating this ring to bring each part of the ring into the action area of the arc and then rotating it out of the action area. You can also.

According to the present invention, AI, Fe, Ni, Cu, Mn, Cr
, W, Ni, Ag, Au, Pd, PL.

Many metals, including common metals and precious metals such as Rh, and alloys of two or more of these metals, are
powder).

It should be noted that operating conditions can suppress evaporation and promote dispersion. For example, the outer surface layer of the metal is repeatedly melted and solidified to promote supersaturation of the injected gas. Such an operating method is advantageous if the active and rest periods need to be fairly short, ie 10 to 40 seconds.

In this case, the energy density should also be adjusted accordingly.

The actual pressure in the container also changes whether evaporation or scattering is more likely to occur, with lower pressures more likely to cause evaporation, and higher pressures (for example, 730 to 750 Torr) more likely to cause scattering.

The present invention will be explained in more detail below using Examples.

1 soup of membrane An apparatus similar to that schematically shown in FIG. 1 was used.

Container 1 is a 1 m 3 water-cooled Balzers airtight container.

A water-cooled copper crucible with a diameter of 6.3 cm was used. The crucible is connected to the vessel by a vertical post member.

The electrode is made of thorium tungsten, water-cooled, and has a diameter of 6
．． It is 4mm. The vessel is evacuated by two pumps: a roughing pump and a diffusion pump.

The gas used was a mixture of H2 and argon at a ratio of 20 to 50% (v/v). The generator is capable of generating an arc of approximately 50-200A.

As an experiment, a flaky metal sample (approximately 5-30 g) was placed in a crucible. After flushing the vessel with argon, the above gas mixture was introduced to bring the pressure to 740 Torr. Very slow flow rate (approximately 5 to 10
The gas was evacuated at a rate of 1/hr, and correspondingly introduced from the inlet 13a). Gas supply was carried out by a pressure cylinder equipped with a pressure reducer and a rotameter. After the electrode was brought close to the crucible (5 mm) to generate an arc, the electrode was pulled back slightly (gap 10 mm) and the current value was adjusted to a value smaller than that at the start of the arc. The arc was maintained during the active period. The current was then turned off and the whole was allowed to cool during a rest period. Thereafter, the arc was generated again and the process was repeated as above. Very fine (less than 1 μm) powder was collected in a cyclone device fitted with an exhaust port 13, while coarse (about lam to 100 μm) particles were deposited in vessel 11.

Silver, Palladium, and Silver/Palladium (70/20)
The results for the alloys are shown in Table 1. In the table, the total operating time is expressed as the number of operating cycles, ie the number of active periods expressed in minutes. A controlled experiment was conducted in which the activity period was set to be continuous for a time equal to the total time of the activity period during the test. The numerical values in parentheses in the two columns on the right represent the approximate improvement effect in terms of the pulverization speed according to the present invention.

Table 1 (Note) A: Active period, P: Inactive period.

Length Ai1 An iron/-Nokel alloy with a double star ratio of 50150 was converted into a metal under the following conditions.

Mixed gas: fiz/A r 25/ 75 (v/
v); 740 Torr, tungsten electrode (2% I/lium): diameter 6.3 mm, placed at a distance of 5 mm from the sample (active period), annealed 119 crucible (water-cooled), arc: 30
■, +5OA, active period/inactive period is 1 minute each.

Under these conditions, ultrafine particles (0.5~IIIm)
was obtained at a production rate of 200 g/hr. For comparison, when operated continuously without any rest period, the production rate is 94 g.
/hr.

Month lL example J A Cu-Ni alloy with a double star ratio of 50,150 was pulverized.

The operating conditions were as follows.

YiA gas: iIZ/Ar 30/70 (v/v)
750'rorr, the same electrode as in Example 3, set at a position 3 mm from the metal sample contained in a copper crucible cooled with circulating water'? -1: 25V, 1 BOA, active period and rest period similar to Example 3.

As a result, most of the ultrafine particles co, is ~1.7
μm), and the production rate was 200 g/hr. In the η control test (no rest period), it was only 9 tjg/hr.

Example 1-4 In the present invention, the gas used in the 8 vessel may be a type of gas that reacts with the molten metal to be pulverized. in this case,
A powder of a compound of a metal and a gas is prepared, for example, 90/10 (V/V) of nitrogen and hydrogen. '
; Titanium was pulverized in I gas (pressure cuff 40 Torr). Arc conditions: 40 V, 200 A, the same electrode as in the above example (however, the diameter was 3.5 mm), and the active period and body tl=ilJI period were each 1 minute. Under these conditions, titanium nitride (mostly about 0.1 μm) was obtained with a production rate of 20 g/hr. In a controlled experiment, the same was produced only at a production rate of 5 g/hr.

Real shoulder pierce 5- Copper was powdered in the following manner.

112/Ar 30/70 (v/v), 740To
rr; 20V, 150A; Tungsten/1%
Thorium electrode, 6.1 mm diameter, placed 6.4 mm from the sample; graphite crucible, activity 1 room 1
minutes; pause period t, S minutes.

Under these conditions, copper powders ranging mostly from 5 to 50 μm were obtained at a production rate of 46 g/hr. In the case of continuous operation carried out for comparison, the production rate was 2 g/hr.
It was less than

A similar steel sample was uncured at t5) under the following conditions.

H2/Ar 10/90 (v/v), 750 Tor
r 20V 180A; Tungsten/2%
Triu 1, electrode, diameter 3.5 mm, 3 mIn from the material
Place in position; graphite crucible.

Under these conditions, particles of O,111m or less are produced at a production rate of 30
Obtained in g/hr. In the case of comparative continuous operation it was 5 g/hr.

Powdering Al / Fe alloy with a ratio of 94/6,
Particles with an average size of about 2 μm or more were obtained at a production rate of more than 50 g/hr. The conditions were as follows.

H-/Ar 20/20 (V/v), 740 Tor
r; 17V, 120A; Tungsten/2% thorium electrode, diameter 6.3 mm, placed 8 mm from the sample; Copper crucible; 1 minute for both active and rest periods.

When operated continuously under these conditions, almost no powder was produced.

[Effects of the Invention] As explained above, according to the present invention, not only the production speed of fine pulverization is significantly improved due to the main factor of discontinuous operation, but also various factors affecting the pulverization process, such as It is clear that the uniform size of the powder particles can be changed by adjusting the gas pressure in the container, the material and dimensions of the electrode, the distance between the electrode and the metal material, the strength of the electric arc, etc. The larger the surface of the metal material that is affected by the electric arc, the greater the proportion of dust that can be obtained from one shot. In a very special case, for example, for a metal that melts easily, if a very strong arc is used and the duration of the action is long, in fact the entire surface of the metal material becomes 1. ) 1, the production of humes (ultrafine particles) becomes overwhelmingly large. Furthermore, as already explained, by controlling the dynamic parameters as necessary, most of the parts can be set to Hue 1,
Most of the particles can be generated as scattered particles, or both can be generated.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view schematically showing a device for pulverizing metal by the action of an electric arc in a hydrogen atmosphere diluted with an inert gas. Figure 2 is a highly enlarged view of the pulverization process. A schematic cross-sectional view and FIG. 3 are perspective views schematically showing a modification of the metal material support structure. 1: Airtight pulverization container, 2: Support structure (support tool), 3:
Metal material to be pulverized, 4; cathode, 5.1010a, 1
0b: Liquid cooling circuit, 6; Power line, 11: Receptor, I2
; Finely ground metal particles, 13a: Gas inlet, 13
b: gas outflow [], 14: electric arc, I5: fume, 16: bubble, 22: support, 23: shaft member, 24a,
24b: Hollow.

Claims (1)

[Claims] 1. A method of powdering under an electric arc a metal material held in a holder in a closed container containing a gas that dissociates and becomes activated by the action of an electric arc, the method comprising: Partially melted under the action of the arc, the dissociated gas preferentially melts and re-associates into the high temperature region of the molten metal, and the release of binding energy evaporates the molten metal, forming a metal As fumes begin to be generated, some of them move from the high-temperature region to the low-temperature region where the arc pressure is low and the gas solubility is insufficient, causing the gas to escape as bubbles, which burst and release metal particles. in a method in which the rate of this process depends on the temperature difference between the hot and cold regions, the following steps: (1) during the active period when the reaction reaches a dynamic equilibrium, i.e. the release of the metal; irradiating the metal with the arc during a period in which the gas reduces the concentration of activated gas in contact with the molten metal, resulting in insufficient reaction conditions to continue splattering and evaporation; and (2) removing the metal from the action of the arc during a period referred to as rest or dormancy during which metal vapor is collected, cooling the metal material and creating a thermal imbalance between the hot and cold regions. and reproducing the initial reaction conditions of step (1), which are periodically carried out. 2. A claim characterized in that when the metal vapor that escapes from the high-temperature region condenses into fine dust particles and spreads within the container, the dust is deposited or aggregated in a collectable form and removed. The method described in 1. 3. The method of claim 1, wherein the lengths of the active period and the rest period are equal or different and range from 5 seconds to 5 minutes. 4. The method of claim 1, further comprising removing the metallic material from the action of the arc by de-energizing the arc or physically withdrawing the metallic material from the reach of the arc. 5. Placing the metal material to be pulverized on the periphery of a horizontal rotary table, and rotating the rotary table by a predetermined angle in order to remove the metal material from under the action of the arc at the end of the activity period. 5. The method of claim 4, characterized in that: 6. Arrange two or more metal materials evenly on the rotating table,
Claim 4, characterized in that one material faces the arc and is in an active period, and the other materials are in a rest period.
Method described. 7. Arranging the metal material in a crown or ring shape around the periphery of the rotary table, and rotating the rotary table so that each element of the metal material is sequentially moved under the action of the electric arc and removed from the action; The method according to claim 4, characterized in that: 8. Depositing a film of solidified metal on the cathode tip by dipping it into the molten metal when turning off the electric arc, and turning on the electric arc at the beginning of the next active period; 5. The method of claim 4, wherein the direction of the current is temporarily reversed to effectively pulverize the metal of the film. 9. The method according to claim 1, wherein a diatomic gas is used alone or in combination with an inert gas as the gas in the container. 10. The method according to claim 9, characterized in that the gas is hydrogen mixed with argon at a ratio (v/v) of 5 to 50%. 11. The pressure of the gas in the container is 700-760T.
11. The method according to claim 10, characterized in that orr. 12. The size range of the above-mentioned scattered particles is about 1 to several 100 μm
A method according to claim 1, characterized in that m. 13. The method of claim 2, wherein the particle size of the dust generated by condensation of the metal vapor is in the submicron range. 14. A closed powdering container equipped with a conductive support for supporting the metal material to be pulverized; an electrode made of a conductive refractory material aligned with the metal support; movable means for moving away from or approaching the position, means for introducing a gas into said container and sweeping said container with said gas, means for collecting metal powder formed by evaporation and comminution, and said electrodes. For carrying out the method for pulverizing a metal according to any one of claims 1 to 13, characterized in that the method comprises means for generating an electric arc between the support and the metal material. equipment. 15. The apparatus according to claim 14, wherein the metal material collecting means is also capable of sizing according to particle size. 16. The apparatus of claim 15, wherein said means for collecting large diameter particles comprises a tank coaxial with said metal material support and in which particles are deposited by gravity. 17. In order to remove fine particles by the gas circulating in the container, the container is provided in the gas flow path as a screen on which particles accumulate or as a cyclone in which particles accumulate inside by sedimentation. 16. The apparatus of claim 15.