RU2245767C1 - Apparatus for electric spark alloying - Google Patents

Abstract

FIELD: electro-physical treatment processes, particularly electric spark alloying of cutting tool, die fitting and machine parts.

SUBSTANCE: apparatus includes storage capacitor connected in parallel with tool-electrode; charging-discharging circuit with semistor having unit for controlling voltage supplied to semistor. The last includes capacitor, rectifier with transistor and potentiometer. Unit for driving electrode holders includes bridge type rectifier and diode rectifier with controlled thyristors connected through mode switches with vibration exciter. Unit for controlling vibration frequency and frequency of technological current pulses includes symmetrical multi-vibrator with potentiometer which is connected at one side with controlled thyristors of unit for driving electrode holders and at other side with controlled thyristors of charging-discharging circuit. Such circuit provides asynchronous operation of switching members in optimal order by signal of working electrode; change of pulse frequency repetition frequency from 1000 up to 1200 Hz.

EFFECT: enlarged manufacturing possibilities in variants of manual and automatic operation modes, possibility for controlling quality of created coating.

1 cl, 1 dwg

Description

The invention relates to electrophysical processing methods, in particular to electrospark alloying of a cutting tool, die tooling and machine parts.

Known devices for electrospark alloying containing a vibrator and a generator for generating pulses of the technological current, powering the vibrator winding, process control and management (see Av.St. USSR No. 837715).

Closest to the proposed technical solution is a device containing a power source, a vibrator and a generator, the electric circuit of which contains a storage capacitance, an electronic charging key made on the basis of two transistors and a transistor module, transistor key controls, a discharge thyristor with its controls, a unit synchronization of the vibrator and the pulse generator (see. Passport for installation ELITRON-22, AIIZ 299.157 PS, Chisinau, 1986, copy of the circuit diagram of the installation hesitating).

The main disadvantages of the known device are:

- low reliability and instability due to the presence in the circuit of electromagnetic relays and packet switches;

- high energy consumption for the alloying process;

- low efficiency;

- the installation is intended for only one type of use - work with a manual vibrator and does not provide work in a mechanized mode with special electric holders, single-electrode and multi-electrode heads;

- the installation generator does not allow changing the pulse repetition rate (pulse repetition rate is constant and is 100 Hz), which limits the possibility of controlling the quality of alloying and the quality of the coating formed.

The basis of the invention is the creation of a device for electrospark alloying with significantly expanded technological capabilities for working in both manual and mechanized modes, high reliability and stability in operation, lower specific energy consumption, higher productivity, efficiency.

The problem is solved in that in a device for electric spark alloying, including a power source, a charge-discharge circuit, a storage capacitor connected in parallel with the tool electrode, a control circuit and a vibrator (manual electrode holder), according to the invention, a triac with a voltage control unit is introduced into the charging circuit supplied to it, including a capacitor, a rectifier with a transistor and a potentiometer; In addition, an electrode holder drive assembly consisting of a bridge rectifier and a diode rectifier with controlled thyristors, which are connected to a vibrator by a mode switch, and also a vibration frequency and a pulse frequency control unit of a technological current, including a symmetric multivibrator with a potentiometer, and which is connected on the one hand with controlled thyristors of the electrode holder drive assembly; and on the other hand with controlled thyristors of the charge-discharge circuit.

The advantage of the proposed device is that the proposed circuit includes: a triac with a control unit, an electrode holder drive assembly, a control unit for the vibration frequency and pulse frequency of the process current, providing asynchronous operation of the switching elements in the optimal sequence according to the signal from the working electrode, changing the pulse repetition rate from 100 to 1200 Hz, expanding the technological capabilities of the installation with manual and mechanized work options and the ability to control quality by the formed coating; the efficiency of the installation is increased and the specific energy consumption for the process is reduced.

These advantages are achieved by reducing the number of electromechanical parts, such as electromagnetic relays in the control nodes and packet switches, which have low reliability characteristics, which allows to improve the stability and reliability of the device as a whole. The proposed technical solution will also allow to expand the range of possible processing modes by changing the frequency of rotation of the electrode holders and the vibration frequency of the manual electrode holder (vibrator).

The proposed device is illustrated in the drawing.

The device’s power source contains a power transformer 1 connected through a triac 2 to a rectifier 3 and a storage capacitor 4. A power source, through a charging circuit consisting of a switch 5 and charging thyristors 6 and 7, is connected to the working capacitors 8 and 9. The latter through diodes 10 and 11 and the common wire are connected to the electrode 12, and on the other hand through the discharge thyristors 13 and 14, diodes 15 and 16, the common wire, the vibrator 17 with the electrode-tool 18.

To the triac 2 is connected the control unit of the supplied voltage: through the rectifier 19, the capacitor 20, the transistor 21, the potentiometer 22.

The control unit of the vibration frequency and pulse frequency of the technological current, powered by the secondary winding of the transformer 1, is made according to the standard scheme in the form of a symmetric multivibrator 23 and potentiometer 24 with the possibility of periodically adjusting the pulse repetition rate from 100 to 1200 Hz and is connected to control thyristors 6, 7 , 25 (high voltage) and thyristors 13, 14, 26 (low voltage).

The drive assembly of the electric holders is also connected to the secondary winding of the transformer 1 and has a rectifier 27, a filtering capacitor 28, as well as a half-wave rectifier on a diode 30, a filtering capacitor 31, thyristors 25 and 26, to which a multivibrator 23 is connected, a delay capacitor 32. The switch 33 functionally provides connecting electrode holders for mechanized operation or a vibrator for using the unit in manual mode (shown by a dotted line).

The device operates as follows.

When the device is turned on in the network, the network indicator is an incandescent lamp 30, an emf is induced on the secondary windings of the transformer. At the output of rectifier 3, a constant voltage is set, which can be adjusted by potentiometer 22 from 0 to 96 V. The triac is the regulating element 2. The voltage is adjusted by changing the phase angle φ, at which the triac key is unlocked, when the voltage passes through "0". The storage capacitor 4 through the rectifier 3 is charged to a voltage determined by the position of the potentiometer 22. The voltage from the storage capacitor 4, depending on the position of the switch 5, is supplied to the charging thyristors 6 and 7. At the same time, the control unit for the vibration frequency and the pulse frequency of the technological current is launched, made in the form of a symmetrical multivibrator 23, at the first output of which, at points 3, 4, 9, 10, 13, 14, a high level voltage is set, which is supplied to the control electrodes of the thyristor at 25, 6 and 7, and at the second output of the multivibrator, at points 5, 6, 7, 8, 11, 12, a low voltage is set, which is supplied to the control electrodes of the thyristors 26, 13, and 14. After a certain time, switching occurs multivibrator, and the first output is set to low voltage, and the second output voltage is high. The multivibrator switching process is periodic and is regulated by potentiometer 24 with a switching frequency from 100 to 1200 Hz.

When the electrodes 12 and 18 are in contact, energy is transferred to the load, just as when charged by current along the circuit: charging thyristor 6 (7), working capacitances 8 (9), diode 15 (16) and the interelectrode gap; so when working capacitors are discharged along the circuit, working capacitances 8 (9), discharge thyristor 13 (14), interelectrode gap, and diode 10 (11). The process of passing electric pulses with a given frequency and voltage in the interelectrode gap between the electrodes 12 and 18, and hence the mass transfer process will be repeated until the electrodes 12 and 18 are diluted by an amount exceeding the breakdown.

The drive assembly of the electrode holders (vibrator) is included in the operation simultaneously with the inclusion of the device in the network and the position of the switch 33 provides power to either the drives of the electrode holders for mechanized operation or the vibrator of the installation in manual mode. In the first case, a voltage is established at the output of the rectifier 27, which is supplied to the drive of the electrode holders through a filter capacitor 28 and a regulating potentiometer 29; the speed control of the motor of the electric supports 17 is provided by a potentiometer 29. In the second case, the voltage from a half-wave rectifier on the diode 30, a filter capacitor 31, controlled from a multivibrator 23 of the thyristors 25 and 26 and a potentiometer 29 is supplied to the vibrator coil 17 with a adjustable frequency potentiometer 24. A capacitor 32 provides a delay in the operation of the vibrator after the passage of an electric pulse from the anode 18 to the cathode 12.

Tests of a prototype device of the proposed design were conducted. Spark hardening was applied to the working surfaces of a set of guillotine knives in the amount of 8 pieces of 8 surfaces with a total length of 420 mm on each part with a hardening width of 10 mm. The total area of hardening was 2888 cm ² , of which 2 knives were hardened using a vibrator in manual mode and 6 knives were hardened in a mechanized mode using a multi-electrode holder on a horizontal milling machine.

The hardening process was carried out in 1, 2, 3 modes with capacitances of discharge capacitors 150, 210, 240, 300 μF and frequencies of 100, 400, 600, 800, 1000 Hz. The working electrodes used in the process were made of materials of the VK-8 and T15K6 brand. Under optimal conditions in manual mode, 2 capacitors of 210 and a pulse repetition rate of 600 Hz, the plant achieved the highest productivity (1 cm ² in 0.4 min) with a thickness of the formed coating layer of 0.12 mm. Installation steadily provides the set mode. The microhardness of the coating was 16 GPa, which increased the wear resistance of the working surfaces (cutting edges) of the guillotine knives by 3.3 times. The value of the specific energy consumption per 1 cm ^{2 of the} hardened surface was reduced from 2.6 Wh · h to 1.8 Wh · h, the efficiency of the forming circuit increased from 38% to 48%. Under optimal conditions in mechanized mode 3, a capacitor capacitance of 300 μF and a pulse repetition rate of 800 Hz, the plant achieved the highest productivity (1 cm ² in 0.2 min) with a coating thickness of up to 0.08 mm. Installation steadily provides the set mode. The microhardness of the coating was 15.6 GPa, which increased the wear resistance of the working surfaces (cutting edges) of the guillotine knives by 3.3 times. The value of specific energy consumption per 1 cm ^{2 of the} hardened surface decreased from 2.6 Wh · h to 1.7 Wh; the efficiency of the forming circuit increased from 38% to 50%.

Claims (1)

A device for electric spark alloying, including a power source, a charge-discharge circuit, a storage capacitor connected in parallel with the electrode-tool, a control circuit and a vibrator (manual electrode holder), characterized in that a triac is introduced into the charging circuit with a voltage control unit supplied to it, including a capacitor, a rectifier with a transistor and a potentiometer, in addition, an electrode holder drive assembly consisting of a bridge rectifier and a diode rectifier with controlled thyristors, which are connected to the vibrator via the mode switch, as well as a control unit for the vibration frequency and pulse frequency of the technological current, including a symmetric multivibrator with a potentiometer and which is connected on the one hand to the thyristors controlled by the electrode holder drive unit and, on the other hand, to the charge-controlled thyristors discharge circuit.