SU1623846A1 - Plasma welding plant - Google Patents

Abstract

The invention relates to welding, in particular, to installations for plasma welding with axial flow of a melting electrode, and can be used in various sectors of the industry for welding metals and surfacing layers with special properties on the surface of various products. The purpose of the invention is to improve the quality of the welded joint by expanding its technological capabilities. For this purpose, a plasma torch containing a plasma torch, two controllable rectifiers with their control units, a transformer, a pulse thyristor with its control unit, and a multivibrator with a toggle switch connected to its control input were inserted into it. Such a setup allows one to realize various modes of its operation - continuous, pulsed with coincidence in phase of the pulses of both arcs or antiphase pulses, with an additional position of short current pulses on the arc of the melting electrode at the moment of impulse or pause of this current, a combination of continuous burning of one of the arcs with a pulsed combustion mode are different. This expands the technological capabilities of the installation. The absence of a non-plasma electrode in the plasma torch significantly reduces the dimensions of the latter, and reduces energy losses in the plasma torch. 1 hp f-ly, 2 nl IS cl with to with

Description

The invention relates to a welding technique, in particular, to installations for plasma welding with axial feeding of a melting electrode, and can be used in various industries for welding metals, as well as for surfacing layers with special properties on the surface of various products.

The purpose of the invention is to improve the quality of the welded joint by expanding its technological capabilities.

Fig. 1 is a block diagram of an installation for plasma surfacing; Fig. 2 shows diagrams of the operation of the installation for plasma welding in various modes: possible modes of burning of a melting electrode (a - d) and possible modes of burning of a plasma arc (e, f).

The plasma welding machine consists of the mouthpiece I and the insulator 2 connected to it, the nozzle 3 for supplying protective gas is fixed on the housing 4 connected to the insulator 2,

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31623846

the nozzle 5 is screwed into the housing 4, melt

The connecting electrode 6 is fed through the mouthpiece 1 to the product 7, the power transformer 8 has taps from the secondary winding, the controlled rectifying unit 9 is connected to the secondary taps of the secondary winding, the input is connected to the taps of the secondary winding coil by means of the input rectifier unit 10 transformer 8, pulse thyristor 11 is connected to the secondary winding of transformer 8 with the ability to connect to various taps, the output of thyristor 11 is connected to the output of controlled rectifier unit 9 in such a way that the polarity of the output thyristor 11 coincides with the polarity of the output of the rectifier 9 to which it is connected, the control electrode of the thyristor 11 is connected to the output of the control circuit 12, the input of which is connected to the switch 13, the control input of the controlled rectifying unit 9 is connected to the output of the control circuit 14 , the input of the latter is connected via electronic keys 15 and 16 to the control points 17 and 18, the control input of the control rectifier unit 10 is connected to the output of the control circuit 19, the input of the control circuit 19 is connected to the electronic keys 20 and 21 s deadline 22 and 23, like poles of controlled rectifying blocks

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Installation for plasma welding works as follows

Power is supplied to the power transformer 8, a voltage appears at the outputs of the thyristor rectifying blocks 9 and 10, between the nozzle 5 and the melting electrode 6 an arc is excited by a high-frequency discharge. Since the internal channel com.l 5 has a cylindrical neck 27, the arc is excited in the gap between the melting electrode 6 and the neck 27 of the nozzle channel 5, since at this point the gap is the smallest, aroused arc is blown out of the neck 27 by a plasma-plasma wave gas into the conical part 28 of the nozzle channel, which is turned from the base to the product 7. Since this part of the nozzle channel is conical and expands as it moves away from the cylindrical neck 27, the arc moving from the cylindrical neck 27 to the shear of the nozzle 5 lengthens that leads to increased th voltage at its pole. The arc column is bathed in a plasma gas, thereby forming a plasma jet, which is indirect for article 7. Such a burning arc ensures its fixation relative to the cut of the nozzle 5 on the surface of the cone 28 of the channel. The plasma forming gas tends to blow an arc at the same time as the elongation of the arc

E and 10 are connected to mouthpiece 1, the power is increased on it and co0

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Installation for plasma welding works as follows

Power is supplied to the power transformer 8, a voltage appears at the outputs of the thyristor rectifying blocks 9 and 10, between the nozzle 5 and the melting electrode 6 an arc is excited by a high-frequency discharge. Since the internal channel com.l 5 has a cylindrical neck 27, the arc is excited in the gap between the melting electrode 6 and the neck 27 of the nozzle channel 5, since at this point the gap is the smallest, aroused arc is blown out of the neck 27 by a plasma-plasma wave gas to the conical part 28 of the nozzle channel, which is turned towards the product 7 by the base. Since this part of the nozzle channel is conical and expands as it moves away from the cylindrical neck 27, the arc, moving from the cylindrical neck 27 to the nozzle 5, elongates, which leads to increased th voltage at its pole. The arc column is bathed in a plasma gas, thereby forming a plasma jet, which is indirect for article 7. Such a burning arc ensures its fixation relative to the cut of the nozzle 5 on the surface of the cone 28 of the channel. The plasma forming gas tends to blow out an arc, while at the same time lengthening the arc

5 increases power on it and with

The block 9 pole is connected to the product 7, and the second pole of the block 10 is connected to the housing 4, the multivibrator 24 has a toggle switch 25 allowing it to be turned off in such a way that when the multivibrator 24 is off, its output voltage always has at the second output, there is no voltage, one output is multivibrate, if the arc for some reason

24 is connected to the control inputs of the electronic switches 16 and 20, and the other output of the multivibrator 24 to the control inputs of the electronic switches 15 and 21, the outputs of the multivibrator 24 are also connected to the switch 13 so that the input of the control circuit 12 can be connected to any of the outputs of the multivibrator 24 or not connected to any of them, the nozzle 5 is made with an internal channel in the form of two cones - internal 26 and external 28 with a cylindrical neck 27 between them.

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lights up inside the plasma torch, it moves along the internal nous 26 to the neck, both due to the plasma gas flow and according to the principle of the Steenbeck minimum. Thus, the proposed design of the nozzle 5 ensures the formation of a plasma jet and ensures stable arc burning at a given place. between the melting electrode 6 and the nozzle 5, the electrode spot of the arc is located on the melting electrode 6. As a result, an intense

chiefly the principle of the minimum of Steenbek, the arc tends to be positioned as close as possible to the neck 27 of the nozzle channel 5. According to the principle of the minimum of Steenbek, of all arc-burning modes that are implemented in any system, the voltage on the arc is minimal

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lights up inside the plasma torch, it moves along the internal nous 26 to the neck, both due to the flow of plasma gas and according to the principle of the minimum Steenbek. Thus, the proposed design of the nozzle 5 ensures the formation of a plasma jet and ensures stable arc burning at a given place. between the melting electrode 6 and the nozzle 5, the electrode spot of the arc is located on the melting electrode 6. As a result, intensive

 The heating of the electrode 6, in addition, this electrode is also heated by the plasma jet blown out of the nozzle 5 by a plasma-forming gas. Thus, in the proposed plasma welding installation, the heating of the melting electrode is more efficient than in the known installation, since the plasma arc for the melting electrode 6 is direct rather than indirect, while the heat input to the plasma is reduced. product 7, since the plasma arc for the product in the proposed installation is indirect, which allows welding of thin sheet metal, surfacing and welding with a small depth of the base metal melted, intense heating of the melting electrode 6 allows to reduce the plasma current arc that leads 20 is achieved by installing and deposit reduce thermal loads on the nozzle, it increases its durability and simplifying the cooling system q allows to reduce dimensions plazmotrona.Umen-

The size of the dimensions of the lashplate is 25 press.

The absence of a special switch is also possible. Pulse thyristor II can be

The connected electrode to it is connected to any of the taps. The high-power transformer 8 lowers the critical winding of the transformer 8, this voltage, the network to a value that is not necessary, allows you to change the welding width for wide spacing. Dumped strained 30 parameters pulses current melting

removed from the secondary windings of the transformer 8, having taps. The presence of taps allows you to adjust the voltage at the input of controlled rectifier blocks 9 and 10, which improves their mode of operation — operation with small cut-off angles becomes possible, this avoids fluctuations of the output voltage, stabilizes the arc Power-operated rectifier unit 9 applies voltage to the gchdeliya 7 and mouthpiece I, through which it is supplied to the melting electrode 6. Thus, this block carries out

The power supply of the melting electrode 6. 45 is connected to any of the outputs. 17 and 18. The electronic keys 15 and 16 are controlled by the multivibrator 24. Thus, the multivibrator 24 or be completely turned off. This makes it possible to give pulses ц the base-current pulse moment either at the moment of pause or not to give them at all. Thнn: 1 the elegiac possibilities of the plasma welding machine are greatly enhanced. Power controlled drive

The power supply unit 10 is powered from the taps; the torus turns on the keys 15 and 16 alternately, the secondary winding of the power transfer, therefore, the control circuit of the power supply 8, which also allows you to select the control devices 17 and select the optimum mode of operation. does not produce welding on the parameters of the welding mode and, surfacing in the pulsed mode of the burning, of the welding materials used

arc melting electrode. With the duration of the pulses and pauses, the multivibrator 24 is set, and the pulse current and the pause current are by the inclinations 17 and 18. When operating in the continuous mode, the sites 17 and 18 are set to the same position, except for TOio, the continuous mode

You can be achieved by turning off the multivibrator 24 using the toggle switch 25. Such a dual achievement of the continuous mode allows you to significantly expand the technological capabilities of the installation. So, if the continuous mode is reached by turning off the multivibrator 24 by the toggle switch 2, then the plasma arc is lit in the continuous mode, if the continuous mode

17 and 18 in the same position, then the multivibrator 24 continues to operate and the plasma arc can be burned in a pulsed mode.

electrode ,. Unlike the current pulses generated by the multivibrator 24, the current pulses flowing through the thyristor 1I are much shorter and are intended to control the transfer of the molten metal from the end of the melting electrode 6. The control circuit 12 controls the pulse thyristor 11, which is completely adjustable. the parameters of the current pulses flowing through thyristor II are the duration and frequency of their following. The control circuit 12 using the switch 13 may be a sub-switch 24 or be completely turned off. This makes it possible to supply pulses with a base-current pulse or at the moment of pause, or not to give them at all. Tac: 1 the ways of the plasma welding installation are greatly enhanced. Power controlled drive

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so that the thyristor drain angle is minimal - this stabilizes the plasma arc burning, since in this case the output voltage pulsations at the output of block 10 are minimal. The block 10 is controlled by control circuit 19, at its input via electronic switches 20 and 21 controllers 22 and 23 are connected. As well as for block 9, for block 10 there are two ways to obtain a continuous mode: setting the controllers 22 and 23 to the same position, while the melting arc can be powered by a pulsed current and switching off the multivibrator 24 t the current of the plasma arc and the base current of the arc of the melting electrode are continuous, however, the imposition of short pulses through the thyristor 11 on the base current of the Melga of the melting electrode 6 of short pulses through the thyristor 11 is also possible in this case. to the open output of the multivibrator 24 Otherwise, the operation of the circuit 19, the electronic switches 20 and 21, and the electronic sensors 22 and 23 is similar to the operation of the control circuit 14, the electronic switches 15 and 16, and the controllers 17 and 18.

To the mouthpiece 1 the like poles of the thyristor rectifying blocks 9 and 10 are connected, therefore, to the nozzle 5 the pole of the rectifying block 10 is connected (through the housing 4), which is the same as the pole of the block 9 connected to the product 7 Such switching on of the power controlled rectifying blocks 9 and 10 prevents the occurrence of an arc discharge between the nozzle 5 and the product 7, since the like poles are connected to them. This facilitates

When welding thin metal or chaplavka, the current of the melting electrode is reduced and for a controlled metal transfer, short 5 pulses are used (Fig. 2 $) generated by a pulsed thyristor

In cases when periodical crystallization of the weld pool is necessary, the current of the melting electrode can be pulsed (Figure 2d). At the same time, short emulses can also be superimposed on it, for example, when during the pauses there is a gray transition to undesirable large-drop transfer of the electrode metal, short pulses are applied to the welding current (Fig. 2). Short pulses can also be superimposed during a current pulse of a melting electrode.

The plasma arc current can be continuous () or pulsed (Figure 2e). The pulsed plasma arc burning mode increases the plasma jet temperature and improves the heating efficiency of the melting electrode. During the pause, the arc current is small, the arc is blown by the plasma-forming gas and the voltage drop gradient on its column increases, as the diameter of the column decreases. This leads to the arc going to a narrower part of the nozzle channel body, closer to the cylindrical neck, which is energetically more advantageous - less voltage drop across the arc. When a current pulse is applied in a small space, the arc is intensely compressed, as a result of which the plasma jet temperature rises. the degree of ionization of the plasma in it. The movement of the arc during the impulse of current to the expanding part of the cone is inertial in nature due to

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the operation of the installation reduces the heat input into the nozzle of the product 7. The insulation of the movement of active spots of the torus 2 prevents the closure of the plasma arc (especially the cathode

spot). During operation of a plasma installation, various combinations of laws for the variation of arc currents are possible. Thus, for example, a combination of the laws of changing arc currents by 2, b when synchronously applying current pulses (current pulses g flow in phase) allows the temperature of the drop of metal to drop at the end of the electrode to be reduced, which is especially favorable when surfacing composite alloys. During the current arc of the plasma arc, the degree of plasma ionization and melting

piece 1 to the housing 4, thereby causing the outlets of the rectifying units 9 and 10. The supply of protective gas to the welding zone takes place through a nozzle. The plasmatron is supplied with protective and plasma-forming gases, and cooling water is supplied and drained through fittings on the plasma torch body 4.

The melting electrode current may be continuous (Fig. 2a) in cases where its value is sufficient to provide a small drop or jet transfer of metal through an arc.

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When welding thin metal or chaplavka, the current of the melting electrode is reduced and for a controlled metal transfer, short 5 pulses are used (Fig. 2 $) generated by a pulsed thyristor

In cases when periodical crystallization of the weld pool is necessary, the current of the melting electrode can be pulsed (Figure 2d). In this case, short emulses can also be superimposed on it, for example, when during the pauses there is a gray transition to undesirable large-drop transfer of the electrode metal, short pulses are applied to the welding current (Fig. 2). Short pulses can also be superimposed during a current pulse of a melting electrode.

The plasma arc current can be continuous () or pulsed (Figure 2e). The pulsed plasma arc mode allows the plasma jet temperature to increase and the melting electrode to heat up. During the pause, the arc current is small, the arc is blown by the plasma gas flow and the voltage drop across its column increases, as the diameter of the column decreases. This leads to the arc going to a narrower part of the nozzle channel body, closer to the cylindrical neck, which is energetically more advantageous - less voltage drop across the arc. When a current pulse is applied in a small space, the arc is intensely compressed, as a result of which the plasma jet temperature rises. the degree of ionization of the plasma in it. The movement of the arc during a current pulse to the expanding part of the cone is inertial in nature due to the inertia

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the movement of active spots of the plasma arc (especially the cathode

of the activeness of the active spots of the plasma arc (especially the cathode

spot). During operation of a plasma installation, various combinations of laws for the variation of arc currents are possible. Thus, for example, a combination of the laws of changing arc currents by 2, b when synchronously applying current pulses (current pulses g flow in phase) allows the temperature of the drop of metal to drop at the end of the electrode to be reduced, which is especially favorable when surfacing composite alloys. During the current arc of the plasma arc, the degree of plasma ionization and melting

Since the electrode is immersed in a plasma jet with an excessive amount of charge carriers, the gradient of the drop on the springs in the electrode areas is reduced, and the active spots themselves increase in size (in fact, the arc melting from the electrode burns in forced ionization conditions), which reduces the concentration of heat input, decreases the heat flux density, as a result, a larger amount of electrode metal melts, but its temperature decreases.

The unit was tested when welding I2X18H9T steel with a thickness of 1.2 mm on a copper lining. Welding is carried out with a St I2X18H9T wire with a diameter of 1.2 mm with the direct polarity of both arcs in the following mode: Melting electrode arc current, A60

Short impulse current, A430 Short impulse frequency, Hz50 Short impulse duration, s 0.008 Base voltage of arc of melting electrode, V 19 Plasma arc voltage, V

in impulse21

in pause28

Plasma arc current, A

pulse110

in pause 30

Pulse duration, s0.4 Pause duration, s0.8 Argon consumption, l / min plasma-forming 3.6 protective 6 Welding speed, m / h 56 Welding is carried out in the mode corresponding to FIG. 25, b. Continuous low base current melting electrode is due to the small thickness of the metal being welded. Short pulses allow for fine-particle transfer of the electrode metal. The pulsed plasma arc mode provides an intermittent crystallization of the metal as separate points, which reduces its residence time in the liquid state and SOM is to reduce the consumption of protective argon

The surfacing of the landing wheels of the landing armored car is carried out by pressing wire consisting of,%: Magnesium

Carbide boron 18,4

Lithium fluoride 6 AluminumOther

Surfacing of the lead mode (figb, 2) with the following parameters:

Electrode diameter, mm 2.8 Arc current of a melting electrode, A

pulse400

in pause180

Arc voltage of melting electrode, V

in impulse .32

in pause 21

Arc current non-melting electrode, A

pulse220

in pause60

Arc voltage of non-flat electrode, V

in impulse30

in pause22

Pulse feed In phase Argon flow, l / min:

plasma-forming 3.9 protective11

The deposition rate, m / h 28 The deposited layer is a wear-resistant composite metal having a matrix of aluminum-magnesium alloy and the inclusion of a solid substance - boron carbide.

Claims (1)

1. An installation for plasma welding, comprising a plasma thermostat comprising a mouthpiece for feeding a melting electrode, a nozzle for supplying protective gas, a nozzle and a housing, while the mouthpiece for feeding a melting electrode is connected to the negative terminals of the first and second controlled rectifiers with their blocks control inputs of controlled rectifiers are connected to the secondary winding of the transformer, made with additional taps, the positive terminals of the first and second controlled rectifiers are connected respectively to the outputs of the anovki and plasma-body throne, characterized in that, in order to improve the quality of the welded joint and expand its technological capabilities, a pulse thyristor with its control unit, a switch, a vibrator and a toggle switch connected to the control input of the multivibrator, the first output of which is connected with the first inputs of the control units of the rectifiers and with the first contact of the switch, the second contact of which is connected to the second inputs of the control units of the rectifiers and the second output of the multivibrator, the third contact of the switch connected to the input control unit pulsed thyristor cathode pulsed thyristor connected with a mouthpiece for supplying melted electrode, and the anode of the thyristor is coupled to a pulsed secondary transformer winding 2 Installation according to claim 1, characterized in that a nozzle is installed in the plasma torch body, made with a channel in the form of two vertices of cones facing each other, between which there is a cylindrical neck, a protective gas supply nozzle and an insulator are also installed in the body In which the mouthpiece is inserted to supply the melting electrode. FIG. one JUUUUUUUL d Phage. 2