JPH11170015A - Sliding device for continuous casting - Google Patents

Abstract

(57) [Summary] [Problem] To make the powder distribution in the vertical direction z uniform. The oscillation mark is suppressed or not generated. SOLUTION: A plurality of electric coils 5 to 10 each circling around a vertical axis z of a continuous casting mold MD and distributed in a vertical z direction; and a coil is provided for each of these electric coils. A continuous casting sliding device comprising current supply means 11 to 13 for supplying currents of different values whose current value distribution in the z direction is a predetermined pattern. Energizing means 1
1 to 13 change the current value distribution in the z direction in a time series. The energizing means 11 to 13 are provided in the z-direction
The electric coil is energized only during the suspension period of the vertical movement of the mold in synchronization with the operation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sliding device for facilitating the sliding of a continuous casting mold and a molten metal with respect to one another, and more particularly, to energizing an electric coil orbiting the mold to melt a pinch force toward the center thereof. It relates to a sliding device added to metal.

[0002]

2. Description of the Related Art Powder is poured onto a surface of a molten metal to smooth the drawing movement of the solidified shell of the molten metal with respect to a mold and to prevent seizure of the solidified shell. This powder enters the boundary between the inner surface of the mold and the molten metal, and facilitates sliding of the solidified shell. Since the solidified shell slides smoothly, seizure of the solidified shell to the mold is less likely to occur.

[0003] This effect is improved by uniformly distributing the powder over the entire inner surface of the mold. To achieve this, the mold is oscillated in the vertical direction z. It has also been practiced to apply a pinch force toward the center of the molten metal by periodically energizing an electric coil that circulates horizontally around the mold (Japanese Patent Laid-Open Nos. 8-155613 and 8-1688851). . Oscillation of mold
And the periodic application of a pinch force using an electric coil promotes the powder to enter the boundary between the inner surface of the mold and the molten metal, thereby facilitating the slab drawing operation.

[0004]

However, since the intrusion of the powder by the oscillate becomes periodic, the portions where the powder is large and the portions where the powder is small are distributed at a constant pitch in the slab longitudinal direction z on the slab surface. A so-called oscillation mark appears.
The oscillation mark has not only a slight amount of powder adhesion but also a microscopic variation in the slab surface structure. Even if the powder injection is promoted by applying the pinch force described above,
Oscillation marks occur.

A first object of the present invention is to perform powder injection more uniformly, and a second object is to suppress or prevent the occurrence of an oscillation mark.

[0006]

Means for Solving the Problems (1) The sliding device for continuous casting according to the present invention is characterized in that each of the continuous casting molds (MD) orbits around the vertical axis (z) thereof in the vertical z direction. A plurality of electric coils distributed (5 to 10); and energizing means for applying a current of a different value to each of these electric coils such that the current value distribution in the z direction in the coil unit has a predetermined pattern. (11-13);

[0007] In order to facilitate understanding, the reference numerals of the corresponding elements of the embodiment shown in the drawings and described later are added for reference in parentheses.

According to this, the distribution of the pinch force in the vertical z-direction corresponds to the current value (z-direction distribution) of the electric coils (5 to 10) distributed in the z-direction. Can be determined to be a pattern that constantly becomes uniform.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (2) The energizing means (11 to 13)
The current value distribution in the z direction is changed in a time series. According to this, the pinch force distribution in the z direction changes in a time series, and accordingly, powder movement in the z direction occurs, and the powder distribution in the z direction becomes uniform.

(3) The energizing means (11 to 13) is provided with the mold (MD)
The electric coil is energized in synchronization with the oscillation in the z direction.

(4) The energizing means (11 to 13) is provided with the mold (MD)
In synchronization with the z-direction oscillation, the electric coil is energized only during the pause of vertical movement of the mold. According to this,
A large amount of powder that has entered by the z-direction oscillation is dispersed in the z-direction due to the distribution of the pinch force in the vertical z-direction during the oscillation rest period, and the powder distribution in the z-direction is made uniform, so that the oscillation mark is formed. Weakens or disappears.

Other objects and features of the present invention will become apparent from the following description of embodiments with reference to the drawings.

[0013]

FIG. 1 shows a continuous casting mold MD equipped with one embodiment of the present invention.
1 shows a vertical cross section of FIG. Mold M composed of opposed two long sides 1F, 1L and opposed two short sides 4F, 4L sandwiched therebetween.
To D, molten steel is injected downward from above through an injection nozzle (not shown). The meniscus (upper surface) of the molten steel MM in the mold is covered with the powder PW. Mold MD
Is cooled by a cooling water flowing through a water box (not shown) and a water flow path in the mold, and the molten steel MM is gradually solidified from the surface in contact with the mold MD, and the slab SB is continuously drawn out. Is poured, there is always molten steel MM in the mold.

[0014] Six electric coils 5 to 10 distributed in the z-direction circulate around the vertical axis (z) of the mold MM around the mold MM. Each electric coil 5-1
When the current is applied to 0, a pinch force (cohesion force) corresponding to the coil current value acts on the molten metal at the level in the vertical direction z of each coil, and the x, y distribution of the molten metal MM changes to the center z of the mold.
The molten metal M contracts in the direction toward the axis, the meniscus rises by that amount, and the level (z direction) of the molten metal M at which the pinch force acts.
The gap between the solidified shell on the outer surface of M and the inner surface of the mold widens, and the powder enters into it.

In this embodiment, the three-phase power supply circuit 11 includes three-phase pulse voltages U, V, and Vs synchronized with the respective phase signals Us, Vs, and Ws provided by the three-phase signal generator 12 in the electric coils 5 to 10. Apply W. There is a phase delay of 120 degrees between the phase signals Us, Vs, Ws in this order.

The three-phase signal generator 12 has a ROM for generating a half-wave of a sine wave, which stores data representing the voltage level of each phase angle of a half cycle of an AC voltage (phase angle 0 to 179 degrees), and a phase angle. Counter, output latch (phase signals Us, Vs, W
D / A converters (3 pieces) for converting the data of the output latch into an analog voltage, and
A read control circuit for reading out each of the three-phase half-wave voltage data Us, Vs, Ws from the ROM based on the clock pulse count value of the phase angle counter and latching them in output latches (three) addressed to each phase. Including.

The phase angle counter is a circulation counter that counts up a clock pulse provided by the pinch controller 13 from 0, initializes the count value to 0 when the count value reaches 360, and then counts up again.

The read control circuit checks the count value of the phase angle counter when the clock pulse is generated and the phase angle counter completes one count-up in response to the clock pulse. If it is within the range, the voltage data corresponding to the count value (phase angle) is read out from the ROM and latched in the output latch (three addressed to Us, Vs, Ws) addressed to the first phase Us. When the count value is 180, the latch is cleared and 181-3
During 60, the clear (output value 0) is maintained. Next, a subtraction value obtained by subtracting 120 from the count value (3 when the value becomes a negative value)
(Addition of 60) is checked, and if it is within the range of 0 to 179, the voltage data corresponding to the subtraction value is read from the ROM and latched in the output latch addressed to the second phase Vs. , The latch is cleared when the subtraction value is 180, and the clear is maintained for 181 to 360. Next, a subtraction value obtained by subtracting 240 from the count value (36
Is checked, and if it is within the range of 0 to 179, the voltage data corresponding to the subtraction value is read out from the ROM and latched in the output latch addressed to the third phase Ws. , The latch is cleared when the subtraction value is 180, and the clear is maintained for 181 to 360.

These latch data are converted into analog voltages (analog signals Us, Vs, Ws: FIG. 3) by each D / A converter.
And is applied to the three-phase power supply circuit 11.

The analog signals Us, Vs, Ws are only the positive half-wave of each phase voltage of the three-phase AC signal. The frequency of this three-phase alternating current is 1/360 of the frequency of the aforementioned clock pulse.
And is determined by the frequency of the clock pulse. The clock pulse is generated by the pinch controller 13 in accordance with the drive frequency input from the operation panel 14 by the operator, and supplied to the three-phase signal generator 12. Clock pulse frequency = drive frequency designated by operator × 360.

FIG. 2 shows a configuration of the three-phase power supply circuit 11.
Thyristor bridge 22 for DC rectification is used for the three-phase AC power supply.
Is connected, and its output (pulsating flow) is
And the capacitor 26 smoothes it. The smoothed DC voltage is applied to a power transistor switching circuit 27 for outputting a three-phase pulse. The U-phase voltage (pulse) of the three-phase pulse output from the DC voltage is applied to the electric coils 5 and 8 shown in FIG. A voltage is applied to electric coils 6 and 9 and a W-phase voltage is applied to electric coils 7 and 10.

The coil voltage command value VdcA is given from the pinch controller 13 to the phase angle α calculator 24, and the phase angle α calculator 24 outputs the conduction phase angle α corresponding to the command value VdcA.
(Thyristor trigger-phase angle) is calculated, and a signal representing this is supplied to the gate driver 23. Gate driver 2
3 starts the phase count of the thyristor of each phase from the zero cross point of each phase and triggers the conduction at the phase angle α. As a result, the DC voltage indicated by the command value VdcA is applied to the switching circuit 27.

On the other hand, each phase voltage Us, Vs, Ws provided by the three-phase signal generator 12 is provided to the comparator 29. The comparator 29 also has a threshold voltage (analog voltage) of D / A
Provided by the converter 30. The pinch controller 13 supplies threshold data to the D / A converter 30, and the D / A converter 30 converts the threshold data into an analog voltage.

The comparator 29 sends a high-level signal H (transistor on) when the U-phase signal Us is higher than the threshold voltage, and a low-level signal L (transistor off) when the U-phase signal Us is lower than the threshold voltage. (To the U-phase output transistor). The same applies to the V-phase signal Vs and the W-phase signal Ws. In this embodiment, in order to avoid the simultaneous turning on of two or more of the three-phase switching transistors, the signals Us, Vs,
When the high level H of Ws overlaps, the sine wave signals Us, Vs,. W
s is shaped into pulse signals Su, Sv, and Sw, and supplied to the gate driver 28.

The gate driver 28 responds to the three-phase pulse signals Su, Sv, and Sw shaped in this way, and only while the signal is at H, the corresponding switching transistor (2).
7) is turned on. As a result, the U-phase pulse voltage of the three-phase pulse voltage is output to the power supply connection terminal U of the power supply circuit 11, the similar V-phase pulse voltage is output to the power supply connection terminal V, and the similar to the power supply connection terminal W. W-phase pulse voltages are output, and the levels of these pulse voltages are determined by the coil voltage command value VdcA.

The gate driver 23 responds to the power supply output on / off signal provided by the pinch controller 13 to output a voltage as described above when instructing to turn on, but instructs to turn off. Sometimes, the output is stopped.

Referring again to FIG. The pinch controller 13 is connected to an operation panel 14 for inputting data from the operator and for outputting data to the operator and for outputting data. The pinch controller 13 is a computer system centered on a CPU. The three-phase signal generator 12 has a driving frequency x 3 input to an operation panel 14 by an operator.
A clock pulse having a frequency of 60 is given to the three-phase power supply circuit 11 to turn on / off the power supply output signal and the coil voltage
dcA and threshold data.

The pinch controller 13 is connected to a casting control computer (host computer) (not shown) of the continuous casting facility via a communication line, and the pinch controller 13 is connected to the host computer. Upon receiving an oscillation synchronization pulse from the data processor, it outputs data to the host computer and the operation panel 14 indicating whether or not the pinch is being driven, and driving state data when the pinch is being driven.

An oscillating device (not shown) is mounted on the mold MD. The host computer instructs a mold oscillating device of the oscillating device, and an oscillating device from the oscillating device. The synchronization signal is provided to the pinch controller 13. The oscillation synchronization signal is a pulse signal which becomes high level H until the upper drive of the mold MD is started and returns to the lower position (original position).
The H of the pulse represents one reciprocating period of the mold MD in the z direction. L during H (pulse) indicates an oscillation rest period during which the mold does not move up and down.

When the power is turned on, the pinch controller 1
3 sets the internal register, counter, timer, and input / output port to a standby state, displays ready on the operation panel 14, and notifies the ready to the host computer. Then, it waits for a data input or a control instruction from the operation panel 14 or the host computer. When there is a data input, the data is stored in a register corresponding to the data type, and the start instruction is received. Wait for it to arrive. Operator or host computer
When a pinch drive start instruction is issued from the controller, the pinch controller 13 outputs the pinch drive condition data input from the operation panel 14 or the host computer to the three-phase signal generator 1.
The clock signal is supplied to the two-phase and three-phase power supply circuits 11 and the output of the above-described clock pulse is started to instruct the three-phase power supply circuit 11 to turn on the power supply output. In response to this instruction, the three-phase power supply circuit 1
1 applies each three-phase pulse voltage to the electric coils 5-10. As a result, the electric coils 5 to 10
Give M a pinch force. After starting the pinch drive, the pinch controller 13 turns on / off the gate driver 23, 28 of the power supply circuit 11 when it switches from L to H in synchronization with the oscillation synchronization pulse. The signal is switched to the OFF instruction level, and the oscillation synchronization pulse
Is switched to L, the on / off signal is switched to the on-instruction level.

FIG. 3 shows an input signal U of the three-phase power supply circuit 11.
s, Vs, Ws (output signals of the three-phase signal generator 12);
The time series change of the input signals Su, Sv, Sw of the gate driver 28 is shown. The voltage of the capacitor 26 (output voltage U) is applied to the electric coils 5 and 8 while the signal Su is H, and the voltage of the capacitor 26 (output voltage V) is applied to the electric coils 6 and 9 while the signal Sv is H. ) Is added to the electric coils 7 and 10 while the signal Sw is at the H level.
(Output voltage W). In this embodiment, U-, V-, and W-phase pulse voltages of three-phase pulse voltages are applied to the electric coils 5 to 7 (and 8 to 10) in this order.
The pinch force repeatedly moves in the depth direction -z of the molten metal MM. This pinch drive is an oscillation drive of the mold MM (one reciprocating motion in the vertical direction z; an oscillation synchronization signal:
During H), the operation is interrupted (dot-dot-filled area in FIG. 3).

Therefore, in this embodiment, the molten metal (and the solidified shell on the surface) of the mold MM is driven by the oscillation drive of the mold MM (one reciprocating motion in the vertical direction z).
Immediately after M moves up and down once and the joining between them is broken, a pinch force is applied to the molten metal MM and it moves in the −z direction. As a result, the molten metal MM peristally moves downward, and the mold / MM is moved by the oscillation of the tip of the mold MM.
The powder caught between the molten metals and the powder at the tangent (meniscus edge) between the meniscus and the inner surface of the mold are drawn into the boundary between the inner surface of the mold and the molten metal and driven downward. The peristaltic motion of the molten metal MM has an effect of leveling the distribution of powder at the boundary between the inner surface of the mold and the molten metal in the −z direction (uniformity).

Second Embodiment The outline of the configuration of the second embodiment is the same as that of the first embodiment shown in FIG. 1, but the configuration of the three-phase power supply circuit 11 is as shown in FIG. Is different from the first embodiment. In the second embodiment, in the three-phase power supply circuit 11 (FIG. 4),
The AND gates Au, Av, and Aw of the first embodiment are eliminated, and a sawtooth generator 31 is used in place of the D / A converter 30. The sawtooth generator 31 generates a sawtooth wave voltage of 3 KHz. This is given to the comparator 29. The comparator 29 has a high level H when the three-phase half-wave signals Us, Vs and Ws are equal to or higher than the sawtooth voltage, and a low level L when the three-phase half-wave signals are lower than the sawtooth voltage.
A PWM pulse for each of the U, V, and W phases is generated and applied to the gate driver 28. As in the first embodiment, the gate driver 28 turns on the U-phase transistor of the switching transistor circuit 27 while the PWM pulse directed to the U-phase is H while the on / off signal is at the on-instruction level. As a result, it is turned off while the PWM pulse is at L level. The same applies to the V and W phases.

However, the PWM duty H duty ratio (H
The time of the section / 3 cycle of 3 kHz) is the three-phase half-wave voltage U
Since the phase voltages are proportional to the levels of s, Vs, and Ws, the average values of the phase voltages U, V, and W applied to the electric coil substantially form a sine wave. That is, it is substantially a sine wave.

FIG. 5 shows a three-phase power supply circuit 11 of the second embodiment.
FIG. 4 shows time series changes of input signals Us, Vs, Ws (output signals of three-phase signal generator 12) and voltages U, V, W (average values) applied to electric coils 5 to 10 in FIG. .

In the second embodiment, since a three-phase AC half-wave voltage is applied to the electric coils 5 to 10, the movement of the pinch force in the -z direction is smoother than in the first embodiment. That is, the peristaltic motion of the molten metal is step-like in the first embodiment, but is continuous in the second embodiment.

In each of the first and second embodiments, the three-phase signal generator
By writing the ROM read data addressed to the phase to the latch addressed to the W phase and writing the ROM read data addressed to the W phase to the latch addressed to the V phase, the contents of Us and Ws of the signal output are interchanged. , The pinch force moves upward + z instead of downward -z. In this case, the effect of smoothing the powder bitten between the inner surface of the mold and the molten metal upward (return direction) by the oscillation of the mold is obtained.

In the case of the first and second embodiments, the downward pinch force movement not only equalizes the powder distribution, but also promotes the powder pull-in and the downward movement of the molten metal (and the slab). Suitable for increasing the speed or promoting powder injection. On the other hand, the mode of upward movement of the pinch force is that the upward movement of the pinch force not only makes the powder distribution uniform, but also suppresses powder injection and suppresses downward movement of the molten metal (and the slab). It is suitable for the case where the value is low or for suppressing powder injection.

Since the pinch force moves in the z direction in synchronization with the generation of the clock pulse, the pinch controller 13 sends the clock pulse to the three-phase signal generator 12 with a desired pinch force distribution (z direction). By stopping the output,
Alternatively, in the three-phase signal generator 12, a pinch control
By stopping the counting of the clock pulses at the phase designated by the controller 13 (the count value of the phase counter), the state of the desired pinch force distribution is maintained. This is for example
A pinch suitable for preventing seizure when a large amount of powder enters while maintaining this state for a certain period of time by setting the maximum pinch force on the meniscus portion, or when there is a possibility that the slab may stick to the mold. It can be used to set force distribution.

The above-described pinch down movement, up movement and maintenance of the desired pinch force distribution (z direction) can be selectively performed according to the operation state and with the change of the operation state.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a first embodiment of the present invention, in which a mold MD shows a full cross section.

FIG. 2 is a block diagram showing a configuration of a power supply circuit 11 shown in FIG.

FIG. 3 shows inputs Us, Vs, and Vs of the power supply circuit 11 shown in FIG.
This is a time chart showing a time series change of Ws and power supply output control signals Su, Sv, Sw.

FIG. 4 is a block diagram showing a configuration of a power supply circuit 11 used in a second embodiment of the present invention.

FIG. 5 shows inputs Us, Vs, and Vs of the power supply circuit 11 shown in FIG.
This is a time chart showing a time series change of Ws and output voltages U, V, W.

[Explanation of symbols]

 5-10: Electric coil

Claims (4)

[Claims] 1. A plurality of electric coils, each of which circulates around a vertical axis of a continuous casting mold and is distributed in a vertical z-direction; and each of these electric coils is provided in a z-direction of a coil unit. Means for supplying currents of different values such that the current value distribution is a predetermined pattern. 2. A sliding device for continuous casting according to claim 1, wherein said current supply means changes the current value distribution in the z direction in a time series. 3. The energizing means energizes the electric coil in synchronization with the oscillation of the mold in the z direction.
Or the sliding device for a continuous mold according to claim 2. 4. The electric coil according to claim 1, wherein said energizing means energizes said electric coil only during a pause of vertical movement of said mold in synchronization with said z-direction oscillation of said mold. Sliding device for continuous casting.