RU2449859C2 - Plant for producing nanodisperse powders from current conducting materials - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention relates to powder metallurgy, particularly, to production of nanodisperse powders from whatever current conducting materials by electric erosion. Proposed plant comprises electric erosion dispersion reactor to receive current conducting materials, voltage regulator and pulse generator. Pulse generator is connected in one-link circuit with resonance charging of operating capacitive accumulator by constant voltage source and comprises power unit and control unit. Note here that power unit consists of single-phase rectifier with it output connected with reference bank of capacitors with their output connected with operating accumulator connected with discharge thyristor switch and load made up of spark gap. Control unit consists of PC used as master oscillator with its outputs connected with generators of control signal for charge and discharge thyristor switches.

EFFECT: reduced powder dispersity.

5 dwg

Description

The present invention relates to the field of powder metallurgy, and in particular to devices for producing nanodispersed powders from any conductive materials, including their wastes, by the method of electroerosive dispersion (EED) for their subsequent use in technological processes of manufacturing, restoration and hardening of machine parts, tools etc. EED is the destruction of conductive material as a result of local exposure to short-term electrical discharges between the electrodes [1]. For practical implementation of the EED process, current pulses with a certain amplitude and frequency, separated by intervals during which there is no current between the electrodes, must pass through the interelectrode gap (MEP). The formation of pulses of electrical energy supplied to the MEP occurs using special pulse generators (GI).

GI-based installations are known in which current pulses are generated by interrupting the current of a primary power source. When pulses are generated in such GIs from a power source through a switching device and a current-limiting circuit, electric energy enters the MEP at the moments when the switching device is in a conducting state. The duration and duty cycle of the received pulses are set by the switching device, and the current amplitude is determined by the voltage of the power source and the resistance of the current-limiting circuit.

The main disadvantages of installations based on such GIs are the implementation of pulsed capacities in the load that do not exceed the power of the supply network, and the direct connection of the load to the supply network [2].

The closest technical solution, selected as a prototype, is a GI-based installation, in which preliminary accumulation of electric energy and its pulse transfer to the load are carried out. As the drive used electrochemical, electromechanical, inductive and capacitive energy storage [3]. Capacitive energy storage devices (electric capacitors) have the best performance in terms of pulse power and permissible short circuit current, referred to volume, mass and cost.

The disadvantage of installations based on GI of this type is:

1. The inability to control the parameters of the current pulses, except for their repetition rate.

2. The relatively high dispersion of the obtained powders (1 μm or more).

The objective of the invention is the ability to more accurately control the parameters of the current pulses and, as a consequence, reduce the dispersion of the powders.

The problem is solved in that the installation for producing nanodispersed powders from conductive materials contains an electroerosive dispersion reactor for loaded conductive materials, a voltage regulator and a pulse generator assembled according to a single-link scheme with a resonant charge of a working capacitive storage from a constant voltage source and containing a power unit and a control unit, and the power unit consists of a single-phase rectifier, the output of which is connected to the backup battery condensate a ditch, the output of which is connected to a charging thyristor switch, the output of which is connected to a working drive, connected to a discharge thyristor switch and then with a load in the form of an interelectrode gap, and the control unit consists of a personal computer used as a master oscillator, the outputs of which are connected to output drivers of control signals for charging and discharge thyristor switches.

List of figures

Figure 1 - Structural diagram of the installation of EED;

figure 2 - External view of the GI installation EED: a) assembled; b) without a top cover;

figure 3 - Structural diagram of the GI installation EED;

figure 4 - Schematic diagram of a) power unit; b) control unit;

figure 5 - Schematic diagram of the electrical circuit: a) a frequency meter; b) power supply.

Example

The EED installation, the structural diagram of which is shown in Figure 1, consists of a voltage regulator, a pulse generator, and an electroerosive dispersion reactor for the conductive materials loaded into it.

The voltage regulator serves to regulate and set the required alternating voltage at the input of the pulse generator in the range from 0 to 250 V. A single-phase voltage regulator RNO-250-10 TU 16-517.298-70 is used as a voltage regulator.

GI, the appearance and structural diagram of which are presented in figures 2 and 3, consists of two main functional units: a power unit and a control unit (figure 4).

The power unit includes (Figure 4a): a single-phase rectifier that converts an alternating voltage of 0-250 V into a constant; reference battery of capacitors filtering rectified voltage; charging thyristor switch, which provides a resonant charge of the working drive and its disconnection from the capacitor reference battery for the duration of the discharge current pulse formation; working drive, accumulating electrical energy and giving it to the load; a thyristor discharge switch that connects a charged working drive to the load and eliminates the influence of discharge modes on the modes of consumption of electric energy from the mains.

To control the operating modes of the power unit, the following are provided: a constant voltage voltmeter (U reference), indicating the voltage value on the reference capacitor bank, and an amplitude values voltmeter (U working), indicating the maximum voltage on the working drive.

The control unit (figure 4b) is designed to issue control signals for the charging and discharge switches, to determine and display the operating frequency of the pulse generator, to quickly change modes during operation and tuning. The control unit includes a master oscillator, which is used as an external generator - a personal computer that generates signals of various shapes, frequencies and amplitudes using a special generator program and an installed sound card; output drivers of control signals for charging thyristor and discharge thyristor switches and a power supply unit (Figure 5b), which ensures the operation of the control unit.

GI works as follows. The master oscillator generates clock pulses, the frequency of which can be regulated and displayed by the operating frequency indicator. From these pulses, control pulses of the thyristor and discharge thyristor switches are generated, which are fed to the output drivers, which generate control signals of the thyristor and discharge thyristor switches of the corresponding frequency and amplitude, and also provide galvanic isolation (based on the optocoupler) between the power unit and the control unit and noise immunity of the control unit.

Under the influence of control signals of the charging thyristor and discharge thyristor switches, they are periodically turned on and off at a frequency determined by the master oscillator, as a result of which the working drive is periodically charged from the mains and discharged to the load (interelectrode gap).

In this GI, it is proposed to use an external generator as a master oscillator - a personal computer (Figure 2) that generates signals of various shapes, frequencies and amplitudes using a special generator program and an installed sound card.

The reactor serves as a container into which the waste of sintered hard alloys is loaded and in which the EED process takes place directly. The reactor volume is closed, and the dispersion zone is cooled by convection of the working fluid. This makes it possible to capture all particles and work with the entire volume of loaded solid alloy waste. The temperature of the working fluid is set constant on average due to the constant heat exchange between the reactor and the environment.

The proposed device for producing nanodispersed powders allows them to be obtained by electroerosive dispersion from virtually any conductive material, including their waste. The powders obtained in this installation have a particle size of from 0.001 to 100 microns. Moreover, by changing the electrical parameters of the dispersion process (voltage at the electrodes, capacitance of the capacitors and pulse repetition rate), it is possible to control the width and offset of the particle size interval, as well as the performance of the process. A centrifuge is used to separate nanoparticles from large ones. These powders are suitable for their subsequent use in technological processes of manufacturing, restoration and hardening of machine parts and tools, etc.

Information sources

1. Nemilov E.F. Electroerosive processing of materials [Text] / L.: Mechanical engineering, Leningrad. Otdel, 1983. - 160 p.

2. Livshits A.L. Pulse electrical engineering [Text] / A.L. Livshits, M.Sh. Otto. - M .: Energoatomizdat, 1983 .-- 352 p.

3. Artamonov B.A. Pulse generators for electric discharge machining [Text] / B.A. Artamonov, A.I. Kruglov, L.I. Stebaev. - M.: Mechanical Engineering, 1976. - 124 p.

Claims (1)

Installation for producing nanodispersed powders from conductive materials, containing an electroerosive dispersion reactor for loaded conductive materials, a voltage regulator and a pulse generator assembled according to a single-link circuit with a resonant charge of a working capacitive storage from a constant voltage source and containing a power unit and a control unit, and a power unit the unit consists of a single-phase rectifier, the output of which is connected to a reference battery of capacitors, the output of which is connected to the charge one thyristor switch, the output of which is connected to a working drive connected to the discharge thyristor switch and then to the load in the form of an interelectrode gap, and the control unit consists of a personal computer used as a master oscillator, the outputs of which are connected to the output drivers of control signals for charging and discharge thyristor switches.

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