Installation for producing powders of metals, alloys and chemical compounds by electric explosion of wire

FIELD: production of powders by electric explosion of wire.

SUBSTANCE: installation includes reactor for electric explosion of wire with high-voltage and low-voltage electrodes that are connected to pulse current sources; mechanism for feeding wire to reactor; gas and powder circulation system; unit for separating gas and accumulating powder. According to invention gas and powder circulation system is in the form of tubular gas discharging pipes communicated by their one ends with reactor in front of inter-electrode gap and by their other ends - with unit for separating gas and accumulating powder. Said unit is in the form of successively connected through branch pipes expanders. Each expander is provided with powder accumulator at providing relation Si/Si+1 ≥ 1.43 where i = 1, 2…, Si - total surface area of effective cross section of tubular gas discharging pipes; S2, S3 - surface area of connection branch pipes.

EFFECT: enhanced quality of product due to lowered agglomeration of powder.

2 dwg, 2 tbl

 

The invention relates to the field of powder metallurgy, namely, to obtain powders of metals, alloys and chemical compounds by the method of electrical explosion of wire for use in the manufacture of metal, cermet, ceramic, composite materials, sorbents, catalysts, etc.

A known device for producing fine powders of inorganic materials electric explosion (RF patent No. 2048278, IPC 7 B 22 F 9/14, publ. 20.11.1995,) that contains the charger, the drive, the reactor explosion piece of metal wire, comprising a metal body, two electrodes, mechanism for feeding the workpiece and the nozzle outlet of the powder and gas. The switch is connected to the drive and the reactor. The first electrode is isolated from the casing and connected with the switch, a second electrode connected to the housing, grounded and installed with clearance to the workpiece while the ratio of the magnitude of the gap to the workpiece diameter equal to 5-10. The mechanism by which the workpiece is electrically isolated from the housing and consists of a coil of wire, wire feed rollers and host strain wire. The latter is installed at a distance to the second grounded electrode, equal to 20-40 diameter of the workpiece. The reactor nozzle is connected to the collector of the powder, which has a pipeline to return gas to the reactor and the technology for powder.

A disadvantage of this device is the low output of the ultrafine fraction of the obtained powder.

Closest to the technical essence is the installation (patent RF №2093311, IPC 7 B 22 F 9/14, publ. 20.10.1997, containing the power source with power from the capacitive storage device, a switching system, the reactor explosion wire with high voltage and grounded electrodes, a wire feeder, a system for collecting powder and system of gas supply. The plant is equipped with a host of deformation of the wire, cyclone and electrostatic precipitator with bins to collect powder, a fan, a pneumatic classifier-vortex-type and truncated cone mounted in the chamber of the classifier with the formation of the gap at the lower base of the wall of the chamber, and the upper base of the cone is made in the form of cracks, aimed at the rotor classifier, and along the axis of the cone is installed pipe for gas supply of powder from the reactor, and a hopper for collecting the powder attached to the bottom chamber of the classifier through the pipeline with the shutter, and the host strain wire is made in the form of rings or freely rotating rollers with the guide groove, fortified in the cage, making a rotational movement around the axis of wire drawing, using rods to move the rings or rollers at a given distance from the axis of rotation of boymy.

A disadvantage of this device is the large output agglomerated powder, more than 30% wt. with the size of the agglomerates of ~30 μm, and therefore, the low quality of the powder.

The main technical result is to increase the quality of the product by reducing agglomeration of powders: the content of the agglomerates ≤ 6% wt. and diameter ≤ 2,3 µm. The use of this system allows to 19 times to reduce the characteristic size of the agglomerates and 10 times the content of the agglomerates in the powder compared to the prototype.

This technical result is achieved in that the device for producing powders of metals, alloys and chemical compounds by electrical explosion of wire containing reactor for electrical explosion of wire with high voltage and grounded electrodes connected to a source of pulsed current, the wire feeder into the reactor, the circulation system of gas and powder and the site of gas separation and collection of powder, according to the proposed solution circulation system of gas and powder is made in the form of a tubular flue connected one end to the reactor across the interelectrode gap, and by others to the site of gas separation and collection of powder, which is made in the form of serially connected through nozzle extenders, each of which is nebgen drive powder, ensuring ratio:

Si/Si+11,43,

where S1- the total area of the bore of the tubular flue,

S2, S3,... , Si- the cross-sectional area of the connecting pipes.

Figure 1 presents the scheme of the proposed installation to obtain powders of metals, alloys and chemical compounds, figure 2 - site of gas separation and collection of powder 11.

The apparatus comprises a reactor 1 for electrical explosion of wire 2 voltage 3 and grounded 4 electrodes, a source of voltage pulses 5, the wire feeder to a node in the warp 6, the gas supply system into the reactor 7, the fan 8, pipe 9 to return gas to the reactor 1. The circulation system of gas and powder and node separation of gas and powder collection is made in the form of a tubular flue 10 which is connected one end to the reactor across the interelectrode gap, and by others to the site of gas separation and collection of powder 11. In pilot plant 16 mounted tubular flue, the area of the bore of each of which is 7,0625 cm2and the total area of the orifice S1=113 cm2. Site of gas separation and collection of the powder 11 is made in the form of series-connected expanders 12, each of which is provided with a drive powder 13. The total flow section of the tubular is x flue in the pilot plant was S 1=113 cm2that section of the connecting pipe S2=68 cm2, S3=41 cm2. Relationship sections S1/S2=1,66, S2/S3=1,66, i.e. in the General form of Si/Si+1I1,43.

The plant is operated as follows.

Installation pre-akoumianakis, and then was filled with a working gas. To obtain aluminum powders used aluminum wire with a diameter of 0.35 mm and a length of 80 mm Charging voltage was 26 kV. The installation was re-injected neutral gas is argon. To obtain chemical compounds required pumping chemically active gas: nitrogen-containing gas to produce nitrides of metals, oxygen-containing gas to produce oxides, carbon-containing gas to produce carbides and other wire feeder 6 shall submit to the reactor 1 wire 2, which is rectified in the host strain of the feed mechanism 6. When the high-voltage wire electrode 3 is triggered, the switch of the source of voltage pulses 5. In the course of intense pulsed current, the wire 2 explodes with the formation of the powder. The powder in the gas stream is carried through the tubular vents 10 in the circulation system of gas and powder and the site of gas separation and collection of powder 11. As you progress through the series-connected extenders 12 b are separated the more coarse powder and deposited in storage powder 13. Cleared of powder gas after passing system dilator 12 is input to the fan 8, the output of which through pipe 9 is connected to the reactor 1 for electrical explosion of wire 2. By means of the fan 8 is ensured gas supply. The value entered in the wire 2 energy was determined by the waveform of the current through this wire. The size of the agglomerates in the powder was determined using a scanning electron microscope JSM-840.

Table 1 presents the test results of the proposed facility, with examples 3, 4 and 5 correspond to the claimed parameters. As can be seen from column 4 of table 1, when the values of Si/Si+11,43 reduced the size of the agglomerates to 2.3 μm and the content of powder to 6%.

The results of the comparison of the quality of powders produced prototype and the inventive installation, are given in table 2.

From table 2 it follows that the use of this system allows to 19 times to reduce the characteristic size of the agglomerates and 10 times the content of the agglomerates in the powder.

Device for producing powders of metals, alloys and chemical compounds by electrical explosion of wire containing reactor for electrical explosion of wire with high voltage and grounded electrodes, soy is inanime with pulsed current source, the wire feeder into the reactor, the circulation system of gas and powder and the site of gas separation and collection of powder, characterized in that the circulation system of gas and powder is made in the form of a tubular flue connected one end to the reactor across the interelectrode gap, and by others to the site of gas separation and collection of powder, which is made in the form of series-connected by means of pipe expanders, each of which is provided with a drive powder, ratio:

Si/Si+11,43, where i=1, 2... ,

S1- the total area of the bore of the tubular flue,

S2, S3...- the area of the cross sections of the connecting pipes.



 

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