SU1243892A1 - Method and apparatus for controlling metal-casting process - Google Patents

Abstract

1. A method for controlling metal casting, which includes the formation of an ingot by the electromagnetic field of a high-frequency inductor current, ensuring the equilibrium hydrostatic pressure of the melt and the electrodynamic pressure of the field, by varying the voltage on the inductor, in order to eliminate the influence of input voltage oscillations induction of high-frequency power supply source of the inductor, the formation process, reduce energy consumption, increase ingot size accuracy and service safety and simplify management the process, casting of metals begins at a fixed voltage on the inductor, ensuring the equilibrium hydrostatic pressure of the melt and the electrodynamic pressure of the field, and change this voltage by an amount proportional to the change in the equivalent active resistance of the inductor with the metal when the pallet leaves its zone, maintaining the entire casting process is the resonant frequency of the inductor current. 2. A metal casting control device containing a thyristor variable-frequency converter consisting of thyristor rectifiers with a phase-impulse control system and a thyristor inverter with a control system and frequency control, the output of which is connected to an inductor, a shunt compensating balancer. capacitors, while in the output current circuit of the converter and the compensating capacitor bank, current sensors connected by the outputs to the automatic stabilization system are connected and the power factor of the thyristor inverter, and the latter is connected to the frequency control system of the inverter control system, which is to ensure that, in order to eliminate the influence of oscillations of 4

Description

voltage of the high-frequency inductor power supply to the process of shaping, reducing energy consumption, increasing ingot size accuracy and service safety, and simplifying process control, a device and a voltage sensor connected by an input to the inductor are inputted into the device, and control system rectifier.

3. The device according to claim 2, which is based on the fact that a three-phase bridge rectifier on Larionov's thyristors was used as a rectifier on thyristors with a phase-impulse control system. an inverter with a control and frequency control system used a three-bridge thyristor autonomous inverter with counter-parallel diodes, one diagonal of the bridge of which is formed by a switching choke and capacitor, and the other by a coupling capacitor, protective choke and load, The ice is connected through the input chokes of bridges to the output terminals. Straightening The invention relates to metallurgy and can find an application when casting aluminum alloys into an electromagnetic crystallizer, the inductor of which is powered by a thyristor frequency converter.

The aim of the invention is to eliminate the influence of fluctuations in the input voltage of a high-frequency inductor power supply on the formation process, reduction of energy consumption, increase in the accuracy of specified ingot sizes and service safety, and simplify process control.

Figure 1 is a diagram of the device that implements the proposed method; in FIG. 2oi8 - graphs of the function Q (iZd, o (., P) j calculated on a computer, in Fig. 3 - an ingot formation scheme in an electromagnetic mold on fi4) - an electric printer, the load consisting of a step-up transformer, the secondary winding of which shunted by a compensating capacitor bank and connected through a step-down transformer to an inductor of an electromagnetic crystallizer.

4. The device according to claim 2, which is based on the fact that a system containing current sensors included in the output current circuits of the inverter and the compensating capacitor bank, shunting the inductor, and current sensor outputs is used as the system for automatically stabilizing the power factor of the thyristor inverter. A pair of stabilizers are connected to the cathodes, the anodes of which are combined, and between the beginning of one current sensor and the end; the other is connected to a voltage divider whose output forms one diagonal of the diode bridge, which is different diagonal is connected via a resistor to the output capacitor and a resistor connected across the zener diode to the input of the control system and adjusting the frequency of the inverter.

a thyristor three-bridge autonomous inverter with counter-parallel diodes and a rectifier; Fig. 5 is an electrical diagram of a simplified device for automatically stabilizing the power factor of a thyristor inverter.

The essence of pouring into an electromagnetic mold is that the metal, when producing ingots, is kept from spreading by electromagnetic forces and at the same time cooled by water, so that

the ingot surface is smooth and does not require additional machining before rolling.

The alternating electromagnetic field of high frequency current generated

single coil inductor of an electromagnetic crystallizer encompassing

3

the ingot induces eddy currents in the metal, which, due to the appearance of the surface effect, are concentrated in the surface layer of the ingot. In this case, the perimeter of the ingot forms a closed coil with a current, the interaction of which with the inductor field contains a compressive pressure on the liquid metal. The receiving cross section of the ingot is similar to the shape of the inductor; therefore, the ingots can have any desired configuration.

To ensure the accuracy of the specified size of the ingot, it is necessary to ensure equality between the hydrost

melt pressure P and electrodynamic pressure P generated by the electromagnetic field

The hydrostatic pressure of the melt is determined by the height of the liquid zone of the melt.

Melt electrodynamic pressure is defined as

, (

) (,, Ь (1)

I - inductor current

 - the number of turns of the inductor; in - the height of the inductor; c - function of three variables, o criterion for frequency.

about

.

e

 - 6 ft with - I

R

DL magnetic permeability of vacuum;

the electrical conductivity of the metal, D 1 / R-, the active resistance of the metal;

circular current 4acToVa in the inductor, b current frequency of the high frequency inductor, coefficient, p g f / g „, the inductor radius, the calculated inductor radius;

coefficient, with (.. With constant constructive

the electromagnetic crystallizer capacitors Y and p are constant, and the criterion

the frequency is determined by

to

Where

.R

(2)

. f 2 IT G

IR

e.

t

electrical resistivity of metal} metal height, metal section.

On the other hand, the relative frequency criterion is

t15

4 K b "P o | 2 frJp., F / R,

(3)

Where

A,) U

o- IL

0

five

0

Thus, taking into account (2) and (3), it can be concluded that the relative frequency criterion depends on the frequency of the inductor current, the electrical resistivity and the active resistance of the metal.

The inductor of the electromagnetic crystallizer is connected in the general case in parallel to the compensating capacitor bank, forming a load circuit, the equivalent resistance of which is determined

L.,

R

5I

(four)

where l .. n

 - R.

inductance of the load circuit;

capacity of the compensating capacitor bank; is equivalent resistance of the inductor with o metal.

For given parameters of the inductor, ingot and frequency of current, the equivalent active resistance of the inductor with the metal R will be proportional to the change in the electrical resistivity of the metal. In turn, a change in the equivalent active resistance of the inductor with the metal also causes a change in the equivalent active resistance of the load circuit (4) Rj, which leads to a change in the voltage

On him

R,

and

electrodynamic pressure n,, violating the accuracy of the specified ingot dimensions, reducing the safety of the casting process, complicates the process of controlling the casting.

Represented in. (1) the value of the current, we obtain an expression for the determination of the electrodynamic pressure

R,. ((And, „,, р). (5)

H

Thus, a change in the electrical resistivity of the metal leads to a change in the equivalent active resistance of the Ren load circuit; for example, Yc on it and the functions of three fiepe- bounded 0 (ii o, o6,).

The essence of the proposed method of controlling the continuous and semi-continuous casting of metals by ingot formation by the electromagnetic field of a high-frequency current of the inductor is as follows.

When a sub-metal with the metal is in the inductor zone, the high-frequency power source tunes to the resonant frequency of the inductor current, at which it maximizes power and provides some fixed voltage on the inductor — providing an equilibrium hydrostatic pressure of the melt P and an electrodynamic pressure field of the RZ and preventing spreading and splashing out of metal.

As the pallet leaves the inductor zone, this area will have an increasing volume. The melt will occupy, and when the pallet leaves this zone, the inductor will contain only the melt with a crust, which is formed when the ingot is cooled.

Thus, at the beginning of the ingot formation, the metal inductor had equivalent resistance R, and the load circuit was R 5n. As the pan leaves the inductor's area, the equivalent resistance of the metal inductor increases, reducing the relative frequency criterion (3), and hence the function 0 (Mo, o (., Fi) 3J, as well as the equivalent resistance of the load circuit (4

. Reducing the equivalent active resistance of the load circuit leads to a decrease in the voltage on the inductor, which, together with a decrease in the function of the three variables E, leads to a decrease in the electrodynamic pressure P (5) and an imbalance between the hydrostatic pressure of the melt and the electrodynamic pressure field P P To eliminate this effect at

the output of the pallet from the zone of the inductor Change (increase) the voltage across it (for example, by changing the output voltage of the high-frequency inductor power supply) by

a value proportional to an increase in the equivalent active resistance of the inductor with the metal (a decrease in the equivalent active resistance of the load circuit),

establish the necessary balance between P and 7 g E7 while maintaining the resonant frequency of the inductor current.

When voltage fluctuations at the inductor caused by a change in the input voltage of the high-frequency inductor power supply, stabilize the voltage across it (at a level of a fixed voltage) by changing the voltage at the intermediate DC node of the high-frequency power source using, for example, a pulse phase voltage. control method.

Thus, controlling the voltage on the inductor by changing it by an amount proportional to the intensity of the equivalent resistance of the inductor with the metal,

it is possible: to increase the accuracy of the specified ingot sizes and service safety, since during the whole process the balance between the hydrostatic pressure of the melt and the electrodynamic pressure of the floor will be ensured, to reduce the energy consumption for the formation of the ingot, because during the voltage variation the high-frequency source will produce the maximum, power due to maintaining the resonant frequency of the inductor current (nominal mode of the source) i eliminate the effect of output voltage fluctuations astotic power source on

the formation process by adjusting the output voltage by changing the voltage of the intermediate DC link voltage.

A device for implementing the method (FIG. 1) is formed by a thyristor

variable frequency converter consisting of rectifier 1 on

thyristors with a phase-pulse control system 2 and a thyristor inverter. 3 with a control system 4 and an hour of regulation, the output of which is connected to the inductor 5, which is bridged by a compensating battery 6, capacitors, while in the output current circuit of the converter and compensating battery 6 the capacitors included current sensors 7 and 8, connected by outputs to the system 9 for automatic stabilization of the power factor of the thyristor inverter 3,

and the output of the latter is connected to the frequency control system 4 of the inverter 3 by the setting device 10 and the voltage sensor 11 connected by the input to the inductor 5, and the output through the setting data generator 10 to the phase-pulse system 2 of the control of the rectifier 1,

The ingot formation scheme in the electromagnetic mold (Fig. 3) is formed by an inductor 5, the shape of which corresponds to the configuration of the cast ingot, a water collector 12 located under the inductor 5, a screen 13 located above the inductor, the supply and distribution system liquid metal 14 and pallet 15, installed on the casting machine 16.

A device for implementing the method (FIG. 4), in which a three-phase bridge rectifier on Larionov's thyristors was used as rectifier 1 on thyristors with phase-impulse control system 2, and as a thyristor inverter. 3 with a system of 4 control and frequency regulation, a three-field 17, 18, 19 autonomous thyristor inverter (thyristors) 20, 21,22, 23 with counter-parallel diodes 24, 25, 26, 27, one diagonal of the bridge which is formed by commuting, are used.

The choke 28 and the capacitor 29, and the other, by the separation capacitor 30, the protective choke 31 and the load 32 and connected through the input chokes 33 of the bridges 17, 18 and 19 to the output terminals of the rectifier 1. In this case, the load 32 consists of a twisted transformer 34, the secondary winding of which is shunted by a compensating battery of 35 capacitors

and connected through step-down transform243892

a mattress 36 with an electromagnetic crystallizer inductor 5.

A device for implementing the method according to claim 2, wherein as the device is automatic stabilization. thyristor power factor

Inverter 1 used a device i containing sensors 7 and V current included in the output current circuits of the inverter 10 torus 1 (current sensor 7) and a compensating battery of 6 capacitors (current sensor 8) shunting the inductor 5, whose outputs are connected to the zener diodes 37 , 38 and 39, the anodes of which are combined, and between the beginning of one sensor and the end of another sensor 8 a voltage divider is connected to the resistances 40 and 41, the output of which forms one diagonal of the diode-20 bridge 42 (diodes 43, 44, 45 , 46), which is another diagonal across a resistor 47 connected to you one capacitor 48 and resistor 49, the zener communication zannomu 50 25 vho- home control system 2 and controlling the frequency of the inverter 1.

The device works as follows.

At the beginning of the control process of continuous and semi-continuous metal casting, the pallet 15 is in the zone of the inductor 5.

A thyristor frequency controlled transducer is turned on and molten metal is fed to the sub-25.

 The sensors 7 and B of the output current of the converter and the compensating battery 6 of capacitors (sensor B) give signals to the device 9 of the automatic Q power factor stabilization, which, acting on the control system 4 and frequency control of the inverter 3, adjusts the latter to the resonant frequency of the inductor current five.

Using the phase-pulse control system 2, the signal to which is supplied from the voltage sensor 11 of the voltage regulator 10, is installed at the output jj of the rectifier 1, and therefore on the inductor 5, a fixed voltage that ensures the equilibrium hydrostatic pressure of the melt Pp and the electrodynamic pressure of the field REV prevents spreading and splash-. Kivan e metal.

Thus, at the beginning of the control process, when the pallet

The BOM is in the zone of the inductor 5 and the inductor 5 with the melt has an equivalent

valence resistance R,

and the load circuit (inductor 5 with a melt, and a compensating battery 6 of capacitors) is a thyristor frequency-controlled converter Bv the maximum power and a fixed voltage on the inductor 5 for the state of the condition of the inductor 5 with metal, ensuring a balance of hydrostatic and electrodynamic pressures .

As the pallet leaves the zone of the inductor 5, the equivalent resistance of the inductor 5 with the metal increases as the electrical resistivity of the metal p increases, lowering, first, the relative frequency criterion, and the functions 6 (Co, oJ., | 5} . (see Fig. 2), secondly, the equivalent active resistance of the load circuit. A decrease in the equivalent active resistance of the load circuit leads to a decrease in the voltage on the inductor 5, 4to together with a decrease in the function of three variables will lead to a decrease the electrodynamic pressure P and the imbalance between the hydrostatic / melt pressure and the electrodynamic pressure of the inductor field 5,

To eliminate this effect, when the pallet leaves the inductor 5 zone, the voltage is increased (increased). by changing the output voltage of the rectifier 1 using the phase-pulse control system 2. The signal from the voltage sensor 11 becomes less than the set value of the sensor 10, which affects the phase-pulse control system 2 of the rectifier 1, increasing the output voltage of the latter and, therefore, the voltage on the inductor 5 by an amount proportional to the increase in the Equivalent resistance of the inductor 5 with the metal. As a result, the necessary equilibrium P – P is established, and the thyristor frequency regulator A converter with the help of the device 9 of automatic stabilization of the power factor supports the resonant frequency of the current in the inductor 5.

4389210

When voltage fluctuations on the inductor 5, caused by a change in the input (supply) voltage of the thyristor frequency controlled transducer, they change and maintain it at a predetermined level using the phase-pulse system 2 of the rectifier 1 control. the voltage fluctuations on the inductor 5, the signal from the voltage sensor 11 is supplied to the sensor 10 and is compared there with a fixed voltage. If the signal from the voltage sensor 11 becomes less than a predetermined fixed value, then from setpoint 10 a signal is sent to the phase-impulse control system 2, which, by operating, increases the output voltage of the rectifier 1, and hence the inductor 5 to a fixed value. The system works in a similar way when the voltage is exceeded.

Thus, controlling the voltage on the inductor by changing it 25 by an amount proportional to the change in the equivalent active resistance of the inductor with the metal is improved: the accuracy of the specified ingot dimensions and the safety of service are 30

the technological process will ensure an equilibrium between the hydrostatic pressure of the melt and the electrodynamic pressure of the field; reduce the energy consumption for ingot formation, since during a voltage change the thyristor frequency-controlled converter will produce the maximum power for a given state of the load circuit by maintaining the resonant frequency of the inductor current; excluding the effect of output voltage oscillations; variable frequency converter to the formation process by adjusting its output voltage by varying the output voltage of the rectifier.

Fig. 3 shows the process of forming an ingot.

The liquid4 metal (melt) comes from the supply system 14 and is distributed to the -15 pallet. Inductor 5, powered by a thyristor frequency-controlled transducer, creates an electromagnetic field. When interacting, the floor of the inductor 5 with the induced vortex currents 15

Kami create repulsive forces that hold the metal at some distance from the inductor, resulting in the size of the ingot g becoming

smaller than inductor g

and

and the liquid metal is not in contact with the formative (inductor). The ingot is cooled by supplying water from the collector 12 first to the base 15, then directly to the side surface of the ingot.

When the ingot is lowered with the help of the casting machine 16, the pallet 15 leaves the inductor zone and the solidified part of the ingot with the melt will be in the inductor until the end of the technological cycle. .

The crystallization front (the boundary between the liquid and solid zones of the ingot on its lateral surface) moves upwards, as a result of which along the cooling () is always below the front at a distance b, the height of the solidified part of the ingot (crust) b depends largely on the speed pour, to a lesser extent on the flow of water and practically does not depend on its temperature. The crystallization front should be at the level of the inductor axis, where the field strength is maximum.

The stability of the casting process is achieved when the height of the liquid zone Vi is 30-40 mm and in the presence of screen 13, Screen 13 is a closed ring of non-magnetic material, the thickness of which gradually increases towards the top. The screen 13 provides the required law of weakening the electrodynamic pressure in height, corresponding to the law of weakening hydrostatic pressure, and also reduces the pulsation and

melt circulation, which has a detrimental effect on the shaping and metal structure.

An electric circuit of a thyristor three-bridge autonomous inverter with counter-parallel diodes and a rectifier, (FIG. 4), works as follows.

The bridge capacitors 30 of the bridges .17, 18 and 19 are normally charged through the input chokes 33, the protective chokes 31 and the load 32 to the voltage of the rectifier 1 with the phase-pulse system 2 of the control.

24389212

Let the commutation capacitors 29 of the bridges 17, 18 and 19 have the voltage polarity indicated on. 4.

5 When the thyristors 20 and 22 of the bridges 17, 18 and 19 are turned on (by supplying control pulses from the control system 4 and frequency control), the commuting 10 capacitors 29 are charged through the commutating chokes 28, the protective chokes 31 and the load 32, which forms a direct half-wave load current 32.

The inverter parameters are calculated 15 so that the process is oscillatory. After the voltage on the commutation capacitors 29 becomes higher than the voltage of the isolating capacitors 30 (the output voltage of the rectifier 1) and the oscillating current flowing through the thyristors 20 and 22 passes through zero, they are turned off. Then through diodes 24, 26 and load 32 will begin to flow.

5, the current in the opposite direction forms the inverse half-wave of the load current 32, until the switching capacitors 29 discharge to a voltage lower than the output voltage of the rectifier 1, and the diodes 24.26 turn off, during a period of time while the diodes 24 and 26 are current, there is a slight reverse voltage across the thyristors 20 and 22

5 and they manage to regain their controllability. Further, thyristors 21, 23 bridges 17, 18, and 19 are turned on, and after they are turned off, diodes 25 and 27, Thus, for one

the cycle of operation of all thyristors and diodes in load 32 are formed by two full periods of sinusoidal voltage 5

0

five

Neither .. Due to the fact that the three bridges are parallel to one load 32, the power of such a source increases, which may allow it to be used for expanding metals into large ingots.

In order to increase the efficiency of using capacitors by a compensating battery of 5 capacitors for reactive power, the step-up transformer 34 is used, since the output voltage of the bridge autonomous inverters with counter-parallel diodes is small and is half the output voltage of the rectifier.

Due to the fact that the inductor 5 of the electromagnetic crystallizer is designed and operates at reduced voltages from 40 to 110 V, it is necessary to use an additional step-down transformer 36.

The output voltage of this converter is adjusted by adjusting the output voltage of the rectifier 1 using the phase-pulse control system 2, and the power control is controlled by the system and control and frequency control of the bridges 17, 18 and 19 of the autonomous inverter. The electrical circuit of the device (Fig. 5) of the automatic stabilization of the power factor of the thyristor inverter works as follows.

Voltage from current sensors 7 and 8, being shifted in phase by an angle equal to 90 electrical degrees. (Signals of load current and current of a compensating capacitor bank) arrive at a chain of Zener diodes 37, 38 and 39, where they are limited in amplitude and added. The resulting step curve is rectified by a diode bridge 42. The squabbleness of the received pulses is proportional to the power factor of the inverter 1 (inductor 5, condensing battery 6 condenser After integrating with a chain of re

2

14

Zistor 47 - capacitor 48 signal goes to the Zener diode 50 and to the master oscillator of the system 2 of the control and frequency control of the inverter 1, changing its frequency. The signal fed to the system 2 depends only on the phase angle between the inverter output current and the voltage on the load.

Thus, when the phase angle changes between the output current and the current of the compensating capacitor bank, the output signal, the control voltage, also changes,

leads to a decrease or increase in the frequency of the master oscillator of the control system and the frequency regulation, through automatic stabilization of the 1st power factor of the thyristor inverter.

As a thyristor frequency controlled converter, a converter with a rectifier according to the Larionov bridge circuit on TL2-200-10 thyristors will be used with two thyristors in the shoulder with a pulse-phase control system, and a three-bridge autonomous inverter with counter-parallel diodes (as a thyristor inverter) thyristors 1: 4-125-10, three in the arm and high-frequency diodes 200-10 in one diode in the arm) and a control and frequency control system.

:

BUT

one

with

FS / G.2

one

Gz

srig.5

Editor M. Bandura

Compiled by A. Abrosimrv

Tehred O. Sopko Proofreader L. Pilipenko

Order 3748/13 Circulation 757 Subscription

VNIIPI USSR State Committee

for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab., 4/5

Production and printing company, Uzhgorod, st. Project, 4

Claims (4)

1. The method of controlling the casting of a metal, including forming an ingot with an electromagnetic field of a high-frequency current of an inductor, ensuring the equilibrium of the hydrostatic pressure of the melt and the electrodynamic pressure of the field, by changing the voltage on the inductor, characterized in that, in order to eliminate the influence of fluctuations in the input voltage of the high-frequency power source of the inductor on-the-process of forming, reducing energy consumption, increasing the accuracy of the size of the ingot and the safety of service and simplifying the process control ohm metal casting is started at a fixed voltage on the inductor providing balance gidrosta melt and _ι electrodynamic field pressure cally pressure, and this voltage is changed by an amount proportional to the change in the equivalent resistance of the active inductor with metal at the outlet of its poddona- zone, maintaining throughout casting process resonant current frequency of the inductor. 2. A control device for casting a metal containing a thyristor frequency-controlled converter, consisting of a rectifier on thyristors with a phase-pulse control system and a thyristor inverter with a control and frequency regulation system, the output of which is connected to an inductor shunted by a compensating capacitor bank, while in the output current circuit transducer and compensating capacitor bank included current sensors connected by outputs to the system of automatic stabilization of the coefficient coagulant power thyristor inverter, and the latter is connected with the output of frequency control system of the inverter control system as claimed i e with the fact that in order to eliminate the influence of the input vibrations 1243892 А1 voltage of a high-frequency inductor power source to the process of forming, reducing energy consumption, increasing dimensional accuracy; ingot and safety of service and simplification of process control, a device and a voltage sensor connected to the inductor by the input and the output through the device to the phase-pulse rectifier control system are introduced into the device. 3. The device according to claim 2, wherein the rectifier on thyristors with a phase-pulse control system uses a three-phase bridge rectifier on Larionov thyristors, and a thyristor inverter with a control and frequency regulation system uses a three-bridge autonomous thyristor inverter with with parallel-parallel diodes, one diagonal of the bridge of which is formed by a commutating choke and capacitor, and the other by a dividing one. a capacitor, a protective choke and a load, the latter being connected through the input chokes of the bridges to the output terminals of the rectifiers of the body, while the load consists of a step-up transformer, the secondary winding of which is shunted by a compensating capacitor bank and connected through a step-down transformer to the electromagnetic mold inductor. 4. The device according to claim 2, characterized in that as a system for automatically stabilizing the power factor of the thyristor inverter, a system is used that contains current sensors included in the output current circuit of the inverter and the compensating capacitor bank shunting the inductor, the outputs of the current sensors are connected to the cathodes are pairs of stabilizers, the anodes of which are combined, and a voltage divider is connected between the beginning of one current sensor and the end of the other, the output of which forms one diagonal of the diode bridge, which is another diagonal alyu through a resistor connected to the output capacitor and resistor connected across the zener diode to the input of the control system and the frequency inverter regulation.