RU2002590C1 - Method of electroerosion dispersion and device for its implementation - Google Patents

Description

created by the gravity of the granule layer does not exceed Q (01 -pi) Y b. where p is the density of the metal of the granules; pi is the density of the working fluid; y is the fill factor of the bulk layer with metal; h is the height of the bulk layer of granules. Thus, if the height of the layer of iron granules in water is 50 cm, and the fill factor of the bulk layer is 0.5, then the pressure of the layer of granules reaches Q (7.8-1) 0, g / cm2. But this pressure is a layer of granules on the flat horizontal bottom of the vessel. On the vertical or inclined planes of the electrodes, the pressure of this layer of granules is much less than the calculated value, since the granule layer is not liquid, and in it the Pascal law does not work. Another disadvantage is that the granules at the bottom of the vessel, which are constantly compressed by the gravity of the granule layer, are compacted over time and stick together into lumps in which mobility between adjacent granules is lost, which is necessary to ensure sparking during electric discharges. In this case, the surface of the granules is oxidized and covered with a layer of highly dispersed erosion products, which sharply increases the electrical resistance of the discharge circuit and leads to loss of electrical energy for heating, as well as to malfunction of the device.

The aim of the invention is to reduce the consumption of electrode material and increase their service life.

This is achieved by that. that in the known method for producing electroerosion products by dispersing ferromagnetic material by electric discharges in a flow of a working fluid in a bulk layer of granules of ferromagnetic material between consumable electrodes to which adjacent granules are pressed, the granules are pressed to the electrodes by magnetizing the electrodes and / or granules .

This is also achieved by the fact that during operation, the magnetic field is periodically switched off while the ferromagnetic products of electroerosion are removed from the surface of the electrodes by the flow of the working fluid.

In addition, this is achieved by the fact that during magnetization the opposite electrodes face each other with the same magnetic poles.

In addition, this is achieved by the fact that during disabling the magnetic field, electrical discharges are stopped.

This is also achieved by the fact that the known device for producing products

electroerosion, which consists of a dielectric vessel with a working fluid and electrodes of ferromagnetic material immersed in it, between which a layer of ferromagnetic granules to be electro-erosively dispersed, as well as conductors from an electric current source to the electrodes, is deposited, contains an electromagnet whining

magnetization of the electrode and / or granules between the electrodes.

In addition, this is achieved by that. that the sections of the walls of the dielectric vessel located between the electrode and the pole

the electromagnet is made of metal, the electrodes are pressed to these areas by the force of attraction of the electromagnet, and the conductors leading to the source of electrical voltage are connected from the outside of the dielectric vessel to these metal sections of its walls, which serve as sections of the conductors.

In FIG. 1 shows a diagram of the proposed device with vertically mounted electrodes having one general view of both electrodes electromagnet; NC FIG. 2 is a diagram of the proposed device with obliquely mounted electrodes having two electromagnets (one each

each electrode).

The device consists of a dielectric vessel 1. having a hole in the bottom with a fitting 2 for supplying working fluid to the vessel, and there is an opening in the lid of the vessel

with a neck 3 for withdrawing the products of electroerosion together with the flow of the working fluid from the vessel 1, as well as for loading into the vessel 1 granules of the source material to be electroerosively processed. In the vessel 1 above the hole in the bottom there is an additional mesh or perforated dielectric bottom 4. Above it at the walls of the vessel 1 are placed flat metal electrodes 5 (best of

ferromagnetic material identical to the material of the granules subject to electroerosive dispersion) mounted either vertically parallel to each other (as shown in Fig. 1), or obliquely diverging upward from each other (as in Fig. 2). The conductors 6 from the source of pulses of electric current are connected to the electrodes 5 (not shown in Fig.). An electromagnet is placed outside the vessel 1 (or several electromagnets) 7. When the device is executed according to the circuit shown in FIG. 1. the opposite poles of the common electromagnet 7 are brought close to those sections of the walls of the vessel 1, beyond which

there are electrodes opposite to each other 5. When the device is executed according to the circuit shown in Fig. 2, each electrode 5 or only one of them has its own electromagnet 7, which is pressed by a pole to that part of the wall of the vessel 1, behind which there is an electrode 5. The sections of the walls 8 of the dielectric vessel 1, located between the pole of the electromagnet 7 and the electrode 5, are made of metal, and the electrodes 5 are pressed to these sections by the force of attraction of the electromagnets 7, These metal sections of the walls 8 of the vessel 1 serve as sections of the conductive s, and thereto from the outside of the vessel 1, bus conductors 6 are attached leading to an electric current source, which in FIG. not shown. In the manufacture of sections of the walls 8 of the vessel 1 from ferromagnetic material (for example, low-carbon steel), these sections of the walls of the vessel also serve as sections of the magnetic cores, and their thickness does not play a significant role. In the manufacture of them from non-ferromagnetic material (duralumin, stainless steel, etc.), these sections play the role of current conductors only, and it is recommended that their thickness be minimized to minimize the loss of magnetic flux passing through them.

The device shown in FIG. 1, works as follows.

In a vessel 1 with a working fluid (water, kerosene, etc.), a portion of granules of a ferromagnetic electrically conductive material to be electrically eroded is loaded through the neck 3. The loading is carried out to the level of the granule layer 1.5-3 times lower than the height of the vessel 1. Then, an electric current is supplied to the winding of the electromagnet 7. If the electrodes 5 are made of ferromagnetic material, then the electromagnet 7 magnetizes the electrodes 5. Moreover, the surfaces of the opposite electrodes 5 facing each other and to the granule layer between them play the role of magnetic poles. When magnetized by one common electromagnet, they acquire different polarity: one pole is north, the other is south. If the electrodes 5 are made of non-ferromagnetic material, then the electromagnet 7 magnetizes the entire space between the poles of the electromagnet 7, and the granules between them. In this case, the magnetic field lines penetrate the electrodes 5. In either case, a magnetic field appears in the space between the flat electrodes 5, the field lines of which extend from one electrode to another. The granules of the ferromagnetic material are attracted by the magnetic field to the electrodes 5 and to each other, interlocked by magnetic forces, closing the electric circuit between the electrodes 5. Since the magnetic field strength

the surface of the electrodes 5 is slightly higher than in the space between them (due to the presence of scattering fields), the granules are pressed; electrodes are stronger than to each other. This provides a better electrical contact between the pellets and the electrodes than with each other. After that, the flow of the working fluid from the pump is fed into the vessel 1 through the nozzle 2, and electrical impulses are supplied to the conductors 6 connected to the electrodes 5

5 voltage As a result, electrical discharges occur in the vessel 1 between the electrodes 5 in chains of granules in contact with each other and with the electrodes. At those points in these chains where the granules do not

They are very tightly in contact with each other or with the electrodes, spark discharges occur in the liquid, which carry out electroerosive dispersion of the material of the granules and electrodes and pyrolysis of the working fluid. Spark discharges occur more often between electrodes than at their surface. Electroerosion products (fine powder and gases)

0 liquid from the vessel 1 through the neck 3, Then they are separated from the working fluid, which is reused, returning it to the vessel 1 through the nozzle 2. Part of the powdered ferromagnetic products

5, electroerosion is attracted by the force of the magnetic field to the surface of the electrodes 5 and adheres to it. And although the force of attraction to the electrodes of these macroscopic particles is small (B millions times less than the force of attraction to the electrodes of the initial granules), and the viscosity of the working fluid prevents these particles from drifting to the electrodes, during prolonged operation, the surface of the electrodes is gradually covered with a layer of ferromagnetic products electroerosion. Filling the gaps between the granules and electrodes, these microscopic particles gradually worsen the electrical contact with the electrodes, which leads to an increase in the probability

0 spark discharges between the surface of electrodes and granules adjacent to them. As a result, an increase in unwanted electroerosive wear of the electrodes begins. To prevent this, it is proposed (according to claim 2) to periodically (for example, every 5 minutes) turn off the magnetic field during operation. To do this, it is enough to stop the supply of electric current to the winding of the electromagnet 7. In this case, the electrodes 5 and granules

between them the magnetization is lost (or its value decreases several times), and the flow of the working fluid in the vessel 1, going from the bottom up, begins to stir up or mix a layer of granules that are no longer pressed against each other and to the electrodes by the magnetic force. At the same time, the flow of the working fluid carries away from the surface of the electrodes a layer of the products of electroerosion accumulated on them, which are already unstable at the electrodes by the magnetic field. which is disconnected at this time. In the demagnetized state, it is recommended that the electrodes be kept for a while away from the surface of the electrodes of the ferromagnetic products of electroerosion by the flow of the working fluid. In practice, the duration of this time can be estimated as the time taken by this flow to travel the distance from the lower to the upper edge of the electrode 5. After that, an electric current is again applied to the winding of the electromagnet 7. And the work continues. With the erosion of the granules in the vessel 1, it is periodically replenished through the neck 3 with new portions of the granules of the ferromagnetic material.

Since during the mixing of the working fluid by the shelf, the granule layer between the electrodes with the magnetic field switched off, the granules are no longer pressed against the electrodes by the force of magnetic attraction. then at this time spark discharges also occur at the surface of the electrodes and are blown up to erosion treatment of their surface. But such a short-term erosion treatment may be useful in some cases. Thus, when the electrodes are filled with foam from a material that corrodes in a given working fluid, spark erosion during the mixing of the granules cleans the surface of the electrodes, which improves the conditions of their electrical contact with the granules after such cleaning. As a result, during subsequent magnetization of the electrodes, spark discharges between the surface of the electrodes and granules occur more rarely than between granules, which leads to a decrease in the total erosive wear of the electrodes. The negative role of erosive wear of the electrodes during mixing of the granules lies in the fact that it leads to a decrease in the service life of the electrodes. Therefore, in that case. when the electrodes are made of a material that is not subject to severe corrosion in a given working fluid and does not require thorough cleaning of its surface. 4 of the claims, it is proposed that during the demagnetization of the electrodes, the electrical discharges be stopped, thereby stopping the supply of electric voltage to the electrodes. In the device shown in FIG. 1, it is recommended that the granules of a material having a sufficiently high contact resistance to electric current (for example, spongy thermally passivated iron, cast iron, etc.) be subjected to electrical discharge machining, so that short circuits between the electrodes do not occur between conductive chains of granules tightly pressed against each other to a friend and to electrodes by magnetic field strength.

The device shown in FIG. 2 operates basically the same as in FIG. 1, with the difference that, with inclined electrodes in it, in the expanding quark the space between them creates better conditions for mixing the granules with an upward flow of the working fluid. In addition, in this device, each electrode (or one of the electrodes) has a separate electromagnet magnetizing this electrode, which allows the electrodes to be magnetized in any polarity. When the electrodes are magnetized in opposite polarities between, as in the device shown in Fig. 1, a continuous conductive bridge is created from tightly pressed to each other .1 to the pellet electrodes. In this case, the processes proceed as in the device 1 described above. When the electrodes are magnetized in the same polarity (as shown in Fig. 2 and 3 of the invention are recommended), an essentially inhomogeneous magnetic field is created between them, the intensity of which is minimal at surface of the electrodes and is equal to zero at the center line of symmetry between them (in this case, the electrodes are repelled from each other by the force of the magnetic field). The force of stretching of the ferromagnetic granules to the electrodes in this case increases sharply when approaching the electrodes and decreases when approaching the middle of the vessel 1. As a result, the granules of the ferromagnetic material located near the electrodes 5. are tightly pressed to their surface by the force of attraction of the magnetic field the granules located at the axis of the vessel 1 almost do not feel the magnetic field and are always agitated or stirred with an upward flow of the working fluid. This mode of operation is recommended for electroerosive processing of granules from metals having a low honkatt resistance to electric current and subject to soldering by electric discharges, for example, from nickel, low carbon steels. The presence in the middle of the discharge chain between the electrodes 5 in the vessel 1 of the section of granules weakly pressed against each other ensures the prevalence of spark discharges in the middle of the vessel and the almost complete absence of mx at the surface of the electrodes, where the granules are densely pressed against the electrodes by the magnetic field force.

When the sections of the walls 6 of the vessel 1 are made between the electrode 5 and the pole of the electromagnet 7 from metal and the electrodes 5 are pressed against these wall sections by the force of attraction of the electromagnet 5, there is no need to supply electric current to the electrodes through special conductors immersed in the working fluid. This allows the loss of electric current from these electrodes to leakage current through the working fluid. In addition, the implementation of these sections of the walls of the vessel 1 of ferromagnetic material can reduce the loss of magnetic flux and increase the intensity of the magnetic poly at the working surface of the electrodes 5, and thereby increase the attraction of granules to the electrodes.

The attraction of the granules to the electrodes by a magnetic field in the proposed method makes it easy and simple to press the granules to the electrodes using this field with a much greater force than the gravity pressing of the granules in the known method. The pressure developed by the magnetic field is defined by the formula, where B is the magnetic 1 induction (T) at the electrode surface: absolute magnetic permeability of the medium. And already at a relatively low magnetic field strength of 200 A / m, easily provided by a simple electromagnet, a magnetic induction of 0.5 T is created at the steel electrodes, which is sufficient to develop a pressure of granules on the electrodes of 1 kg / cm2. This is much greater than the above calculated pressure of the granule layer on the electrodes, or rather on the bottom of the vessel (170 g / cm), created by the gravity of the granule layer. The excess of the magnetic force of gravity over the gravity of steel products is widely used in technology for lifting these products with magnetic cranes. The proposed pressing of the granules to the electrodes with a magnetic field makes it possible, in contrast to the known method, to provide an equally large compressive force for any arrangement of the electrodes in space (horizontally, vertically, obliquely), which also gives an advantage compared to the known method in which the compressive force of granules to the surface the electrode by the force of gravity of the granules substantially depends on the angle of inclination of the electrode.

Example 1. In the device shown in Fig. 1, electrosionic dispersion of granules metallized by reduction in hydrogen and thermally passivated iron ore pellets (TU14-1-435-87) manufactured by the Starooskolsky electrometallurgical plant is carried out. The walls of the vessel 1 are made of organic glass, the electrodes 5 are made of sheet aluminum with a thickness of 10 mm and have dimensions of 150x150 mm. The interelectrode distance is -200 mm, Electromagnet 7 has a lined magnetic circuit (RMO) with a cross section of 100x100 mm made of electrical steel and a winding of 1000 turns of copper wire, which is connected to a direct current source - a rectifier

through a switching magnetic starter (not shown in FIG.). To the device shown in FIG. 1, serves the pump through the nozzle 2 distilled water, gradually increasing its flow rate until

until the flow of water begins to reverse the pellet pellet layer located between the electrodes 5 in the vessel. Then, a constant electric current is supplied to the winding of the electromagnet 7, the strength of which is indicated on

table. 8, as a result of the action of the magnetic field created between the electrodes 5, the pressure of the granules on the electrodes - up to 1 kg / cm - develops. After that, 800 V electrical voltage pulses are supplied to the electrodes 5 with a FREQUENCY of repetition of 2 kHz and a time average power of 50 kW. As a result, electrical discharges occur in the vessel 1 between the electrodes 5 in chains of contacting each other

and with pellet electrodes accompanied by spark discharges in water between the electrodes. The intensity of spark discharges observed through the transparent walls of vessel 1 in the middle of the vessel is much

more than at the surface of the electrodes 5. Spark discharges carry out electroerosive dispersion of the material of granules and electrodes. The products of electroerosion (finely dispersed powder and evolved gases) are carried out by the flow of water from the vessel 1 through its mouth 3. They are separated from the water by settling and filtration and used in the production of iron-aluminum catalysts.

Filtered water is reused, returning it to vessel 1 through pipe 2, At the inlet of the device as erosion is worn out and the material of granules in vessel 1 is consumed, it is periodically replenished with new portions of granules through the neck 3. Samples of the resulting electroerosion product are dried and weighed, determining the productivity dispersion. The electrodes 5 are also periodically removed from the vessel 1 and weighed, determining by the loss of their weight the rate of their erosive wear.

The parameters and results of the experiments, as well as comparative data of the parameters and the results of electroerosive dispersion of the same iron ore granules in water according to the known and proposed prototype method in the same device, but with the magnetic field turned off, are shown in the table.

Example 2. Electroerosive dispersion in water of granules of iron ore metallized pellets (TU 14-1-435-87) is carried out using the device shown in FIG. 2 and described in example 1. All operations are carried out in the same way as in example 1, with the difference that the electrodes 5 are made of steel St 3, and during operation the magnetic field is periodically turned off while the ferromagnetic products of electroerosion are removed from the surface of the electrodes by the flow working fluid. For this reason, the supply of electric current to the winding of the electromagnet 7 is interrupted periodically (every 5 min) for 10 s, without stopping the supply of water to the vessel 1 and the supply of voltage pulses to the electrodes 5. At this time, the electrodes 5 are demagnetized, the pressure of the granules to them stops magnetic field. The flow of water in the vessel 1 begins to stir up and mix the layer of granules between the electrodes 5, the entrainment of the ferromagnetic powder adhering to them from the surface of the electrodes is a product of electrorosion. At this time, spark discharges at the surface of the electrodes 5 occur with the same intensity as in the middle of the vessel 1 between the electrodes, and the electro-corrosion treatment of the surface of the electrodes takes place, which leads to their cleaning, but also to their wear. But in general, the repetition rate of discharges in the entire volume of the vessel 1 is reduced in comparison with the processing mode with a magnetic field. After resuming after 10 s the supply of electric current to the winding of the electromagnet 7, the magnetic field between the electrodes is restored, and as a result of the attraction of the granules to the electrodes and the adhesion of the granules to each other, mixing and agitating of the granule layer ceases. At the same time, the intensity of spark discharges at the surface of the electrodes again becomes lower than in the center of the vessel, where it increases. Options and

The experimental results are summarized in a table, which also shows comparative data on the parameters and results of electroerosive dispersion of the same granules in water according to the known prototype method in the same device, but with the magnetic field permanently switched off.

PRI me R 3. Electroerosive dispersion in water of iron ore granules

0 reconstituted pellets (TU 14-1-435-87) are carried out using the device of FIG. 2. At the vessel 1 of this device, the walls are made entirely of dielectric material (fiberglass 5 lithium and plexiglass) without metal sections and are inclined to the vertical at an angle of 15 °, Electrodes 5 are made of steel St 3 with a thickness of 10 mm with dimensions 150x150 mm. Conductors leading to the source of voltage and current impulses are welded to them. The interelectrode distance between the lower edges of the electrodes is 150 mm. Each electrode 5 is equipped with an electromagnet 7 having a winding of 500 turns

5 copper wires. The windings of the electromagnets 7 are interconnected in series so that when current is applied to these windings, the electrodes 5 are magnetized in the same polarity and are facing each other

0 to a friend of the same name by the magnetic poles, as shown in FIG. 2. The magnitude of the direct current supplied to the windings of the electromagnets is indicated in the table. All operations for electroerosive dispersion5 are carried out in the same way as in example 2. The processes proceed as in example 2, with the difference that spark discharges occur mainly in the center of the vessel in the middle of the intercellular gap, where the total magnetic The field is minimal and close to zero, and spark discharges are practically not observed at the electrode surface, where the magnetic field strength is maximum. The parameters and results of experiments, as well as comparative data on the parameters and results of electroerosive dispersion of the same granules in water according to the known and proposed methods, in the same device, but with the magnetic floor permanently turned off, are given in the table.

PRI me R 4. Electrosurgical dispersion in water of iron ore granules

5 metallized pellets (TU 14-1-435- 87) are carried out in the same way as in Example 3, using the same device, but with the difference that during the magnetic field is switched off, 5 voltage pulses to the electrodes are stopped. It leads to

the termination of electrical discharges during the time the magnetic field is turned off. The parameters and experimental results are shown in the table.

Example 5. Electroerosive dispersion of pellet pellets in water (TU 14-1-435-87) in water is carried out in the same way as in example 4 using the same device, but with the difference that only one electromagnet 7 mounted at the positive electrode 5 (anode). The intensity of the magnetic field created by him rapidly decreases with distance from this electrode, but, unlike in Example 4, at no point inside the vessel 1 is equal to zero. When the device is operating, the behavior of the granules in it when the magnetic field is on is intermediate between the case described in example 2. and the case described in example 4. Since the anode, when electrosparkly disperses iron in water without a magnetic field, is usually consumed faster than the cathode, the presence of an electromagnet is the anode provides a strong pressing of the granules to its surface, which reduces the consumption of anode metal to a value even less than the consumption of cathode metal. The parameters and experimental results are shown in the table.

Example Electroerosive dispersion in water of granules of gray cast iron. having dimensions of 5-15 mm, carried out in the same manner as in example 4, using the same device described in example 3. But in this device, shown in Fig. 2, sections of the walls 8 of the dielectric vessel 1, located between the pole of the electromagnet 7 and cast iron electrode 5, made of stainless steel sheets 1X18H10T with a thickness of 3 mm with dimensions of 170 x 170 mm. To these metal sections 8 of the walls of the vessel 1, conductors 6 are connected from its outer side, leading to a voltage pulse source. In this case, the cast iron electrodes 5 are pressed against the metal portions 8 of the vessel walls t by the magnetic field of the electromagnet 7 during the operation of the device. Holding the electrodes 5 in place with the magnetic field turned off is provided by dielectric guides in the vessel 1 (not shown in Fig. 2). The parameters and experimental results are shown in the table.

Example. Using the device. described in Example 5. Electroerosive dispersion in water of steel shavings, crushed into pieces with sizes up to 20 mm, is carried out. All operations are carried out as in example 4. with that

the difference is that the electrodes 5 are made of low carbon steel. The parameters and experimental results are shown in the table.

Example 8. Using the device

described in Example 5, electroerosive dispersion of nickel granules in water is carried out. All operations are carried out as in example 4, with

the difference is that the electrodes 5 are made of nickel. The parameters and experimental results are shown in the table.

Example 9. Using the device described in example 5, pyrolysis of petroleum products (a mixture of used transformer oils) is carried out in order to obtain gaseous pyrolysis products of unsaturated hydrocarbons (acetylene, etc.) by a method similar to that described in

4. Pyrolysis is carried out by spark discharges in a working fluid - a mixture of these petroleum products between cast iron granules loaded into the device shown in Figs. 2, in which the electrodes 5 are made of cast iron. All operations are carried out in the same way as in example 5, with the difference that the gaseous pyrolysis products carried out together with the working fluid from the vessel 1, are captured and collected in

gas holder. The parameters and results of the experiments are summarized in the table, which also shows comparative data of experiments carried out in the same device with the same parameters, but etc.

when the magnetic field is permanently turned off and when the conductors 6 are attached directly to the electrodes 5.

The proposed method and device have the following advantages:

the erosive wear of the electrode material is reduced as a result of a denser pressing of the granules to the electrodes by the force of a magnetic field compared to gravity;

the service life of the electrodes is increased; it is possible by turning off the magnetic field to prevent caking, tamping and clumping of granules; opportunities are being developed to design devices for producing electroerosion products with a very different arrangement of electrodes.

(56) Copyright certificate of the USSR isfe 663515, cl. B 23 P 1/02, 1979.

USSR copyright certificate No. 1217581, cl. B 22 F 9/14, 1986.

USSR copyright certificate N; 1077743.cl. B 22 F 9/14. 1984.

Table continuation

Table continuation

The claims

1. A method of electroerosive dispersion by applying electric discharges to granules of a ferromagnetic material placed between electrodes in a flow of a working fluid, characterized in that the electric discharges are effected while magnetizing the electrodes and / or granules.

2. The method according to claim 1. characterized in that magnetization is carried out periodically.

3. The method according to claim 1, characterized in that the magnetization of each electrode is carried out independently, while they are facing each other with the same magnetic poles.

4. A device for electroerosive dispersion comprising a dielectric vessel with electrodes, conductors and a power source, characterized in that it is provided with an electromagnet located outside the vessel.

5. The device according to claim 4, characterized in that the sections of the walls of the vessel located between the electrode and the pole of the electromagnet are made of metal, and the conductors leading to the source of electric current are connected from the outside of the vessel to the metal sections of the walls.

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