JPS6240108B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and apparatus for safely and accurately controlling the drawing speed and mold level of a continuous casting machine.

In a continuous casting machine, it is extremely important to perform casting operations while maintaining a constant level of molten steel in the mold for safe operation and quality assurance. Also, if this is done automatically, the casting bed operator can be relieved from a dusty, hot environment and stressful work.

After the introduction of continuous casting machines, the automation of casting work leads to improvements in safety, economy, and working conditions.
More than 10 years have passed, and the reason why it is still slow to spread is that there are problems that cannot be easily solved even with today's advanced industrial technology (for example, problems such as sensors for the level of molten steel in the mold and control valves for the amount of molten steel injected). This is because the equipment is still under development and is not fully functional.

Typical conventional mold level control methods include a sliding valve (or stopper) operation method that adjusts the amount of molten steel injected as shown in Figure 1, and a method that adjusts the amount of slab withdrawal as shown in Figure 2. There are pinch roll operation methods, etc.

To explain the sliding valve operation method shown in Fig. 1, 1 in the figure is a tundish, 2
is the tandate molten steel level, 3 is the sliding valve (or stopper), 4 is the sliding valve operation motor, 5c is the sliding valve opening positioner, 6 is the mold level sensor, 7 is the sliding valve control amplifier, 8 is the level control amplifier, 9 is a level setting device, 10 is an injection nozzle, 11 is a water-cooled mold, 12 is a slab, 1
3 is a pinch roll for drawing slabs, 14 is a pinch roll motor, 15 is a pinch roll speed meter generator,
16 is a thyristor input power source, 17 is a thyristor power supply device, 18 is a speed control amplifier, 19 is a pinch roll speed setting device, and 20 is a molten steel level in the mold.

In a continuous casting machine with such a configuration, the speed of the pinch roll 13 is set constant by the pinch roll speed setting device 19, and the difference signal between the pinch roll speed meter generator 15 and the pinch roll speed setting device 19 is set. is given to the speed control amplifier 18, and the speed control amplifier 18
The firing angle of the thyristor power supply device 17 is controlled by the output signal of the pinch roll motor 14 to keep the speed of the pinch roll motor 14 constant regardless of the magnitude of the load torque. Hold at set value.

Further, under the condition that the drawing speed of the slab 12 is constant, a target level is set by the level setter 9 in order to keep the molten steel level 20 in the water-cooled mold 11 constant, and the mold level sensor 6 and the level setter 9 are set. The level deviation signal of the level control amplifier 8 is applied to the level control amplifier 8, and the deviation signal between the output signal of the level control amplifier 8 and the sliding valve opening positioner 5c is applied to the sliding valve control amplifier 7. Therefore, the sliding valve operation motor 4 is operated to open and close the sliding valve 3 until the target level is obtained, and the water is then poured from the tundish 1 through the injection nozzle 10 to the water-cooled mold 11.
By adjusting the flow rate of the molten steel to reach the mold level 20, the mold level 20 can be controlled by various external fluctuation factors (for example, changes in the tundish molten steel level 2, wear of the inner wall surface of the sliding valve 3, injection nozzle 10, etc., or the setting value of the casting speed). It is maintained constant even if the drawing speed of the slab 12 changes due to changes, etc.).

The above conventional method has the advantage of being able to maintain a constant drawing speed of the slab 12, but since all level fluctuation factors are dependent on the opening adjustment of the sliding valve 3, the sliding valve 3 is extremely reliable. However, a major drawback is that it is required to exhibit high-speed and fine flow rate adjustment performance for a long period of time.
However, the sliding valve 3 actually undergoes severe corrosion due to the high temperature and friction of the molten steel, the flow coefficient Cυ changes from moment to moment, and there is a loss time until the molten steel passes through the sliding valve 3 and reaches the mold molten steel level 20. Therefore, actual level control is extremely unstable and difficult.
It has not yet gone beyond the test run.

Next, the pinch roll operation method shown in FIG. 2 will be explained. In FIG. 2, 8a is a level control amplifier, 9a is a level setter, 21 is a signal adder, 2
2 is a sliding valve opening degree controller, 23 is a level control start switch, and the same symbols as those shown in FIG. 1 indicate the same components.

In a continuous casting machine having such a configuration, the opening of the sliding valve 3 is controlled using the opening controller 22, the sliding valve control amplifier 7, the sliding valve operating motor 4, and the sliding valve opening positioner 5c. Set it to a certain value,
On the other hand, by setting the drawing speed of the slab 12 to a value corresponding to the molten steel injection speed using the pinch roll speed setting device 19, the amount of molten steel supplied into the water-cooled mold 11 and the amount of molten steel pulled out from the lower part of the mold are controlled. The molten steel level 20 in the mold is set to a certain value by balancing. At this time, the level control start switch 23
When the molten steel level 20 in the mold detected by the mold level sensor 6 is higher or lower than the value preset in the level setting device 9a, the signal is sent to the level control amplifier 8a.
The output generated from the level control amplifier 8a is applied to the signal adder 21 via the level control start switch 23.

The deviation signal between the output signal of the signal adder 21 and the pinch roll speedometer generator 15 is sent to the thyristor power supply 17 to control the firing angle of the thyristor power supply 17, so that the output of the thyristor power supply 17 is controlled. increase or decrease, pinch roll 13
When the molten steel level 20 in the mold matches the setting value of the level setter 9a by increasing or decelerating the speed of the pinch roll 13, the speed of the pinch roll 13 is stabilized.

In the above conventional method, when the amount of molten steel injected from the tundish 1 to the water-cooled mold 11 changes, the change in the molten steel level 20 in the mold is detected and the level 20 is changed.
The level control system that changes the speed of the pinch roll 13 until the zero height is restored to its original position has the advantage of being extremely stable and achieving high level accuracy. 12
A major drawback is that the drawing speed varies. The first factors that can be cited as factors for fluctuations in the amount of injection into the water-cooled mold 11 are wear and tear on the inner walls of the sliding valve and injection nozzle due to high temperature and flow velocity friction of the molten steel, constriction due to adhesion of steel slag, etc., and changes in the molten steel level in the tundish. Can be mentioned. If the injection amount changes due to these factors, the drawing speed of the slab will change, which will change the residence time of the slab in the water-cooled mold 11 and other cooling zones, which will have an unfavorable effect on quality. receive.

The present invention has been made with the aim of eliminating the above-mentioned drawbacks of the conventional means.When the level of molten steel injected into the mold from the tundish reaches a predetermined level, pinch rolls are used to pull out the slab from the mold. The speed of the molten steel in the mold gradually increases as the molten steel level in the mold increases, and when the molten steel level in the mold reaches a preset molten steel setting level, the pinch roll speed at that time is set as the pinch roll setting speed, and the mold If the actual molten steel level changes with respect to the molten steel setting level, the amount of the variation is obtained as a molten steel level deviation, the molten steel level deviation is added to the pinch roll setting speed, and the rotation speed of the pinch roll is controlled by the addition signal. death,
A pinch roll speed deviation signal between the pinch roll set speed and the detected pinch roll speed is detected, and when the pinch roll speed deviation signal is smaller than a predetermined value, the pinch roll speed deviation signal is minimized. A means for adjusting the amount of molten steel injected into the mold is continuously controlled, and when the pinch roll speed deviation signal is larger than a predetermined value, the molten steel is injected into the mold so that the pinch roll speed deviation signal is minimized. This method is characterized in that the injection amount adjusting means is subjected to sampling control to control the level of molten steel in the mold to be constant.

Embodiments of the present invention will be described below with reference to FIG. 3 and subsequent drawings.

FIG. 3 shows an embodiment of the present invention, in which a sliding valve operating motor 4 is connected to a sliding valve 3 provided at the lower part of the tundish 1.
A sliding valve control amplifier 7 is connected to. Also, sliding valve operation motor 4
A sliding valve operating motor speed meter generator 5 is connected between the sliding valve control amplifier 7 and the sliding valve control amplifier 7.
is connected to the sliding valve control amplifier 7 so that the rotational speed of the sliding valve operating motor 4 can be supplied as a feedback signal to the sliding valve control amplifier 7.

The sliding valve control amplifier 7 is configured to rotate the sliding valve operating motor 4 in the forward and reverse directions to cause the sliding valve 3 to change the opening degree a shown in FIG.
In order to provide this, a dither generator 35 is connected which intermittently sends an output signal b at fixed time intervals as shown in FIG. 16 to the sliding valve control amplifier 7. The dither generator 35 provides a pulsating flow to the molten steel passing through the sliding valve 3 to effectively prevent steel slag and impurities from adhering to and growing inside the sliding valve 3.

A sliding valve opening controller 22 for arbitrarily setting the opening of the sliding valve 3 is connected to the sliding valve control amplifier 7, and level control is started before and after the sliding valve control amplifier 7. A sampling control timer 28 including a switch 23-2 and a sampling control timer contact 28a is provided to form a closed circuit.

The sampling control timer 28 is used to adjust the time lag between the change in the flow rate of the molten steel throttled by the sliding valve 3 and the time when the drawing speed of the slab 12 by the pinch rolls 13 (described later) reaches a steady state. The details are shown in FIG.

In Fig. 4, 28-1 is a reversible integrator for the timer, and the input side of the reversible integrator 28-1 for the timer is connected to a Zener diode 28-2 for setting a threshold value. On the output side of the reversible integrator 28-1, an output relay hysteresis imparting resistor 28-4, a negative output relay discrimination diode 28-
Negative output relay 28-8 in which 12 are connected, negative output relay normally open contact 28-9a, and positive output relay 28 in which positive output relay discrimination diode 28-11 are connected.
-5 are connected in parallel. The output relay hysteresis resistor 28-4 and the negative output relay normally open contact 28-9a are connected to form a closed circuit. -9a, a positive output relay normally open contact 28-6a is arranged in parallel.

The input side of the timer reversible integrator 28-1 is connected to a timer integrator reset resistor 28-3, and the positive output relay normally open contact 28-6b is connected to the timer integrator reset resistor 28-3. and negative output relay normally open contact 28-9b are connected in parallel.

The sampling control timer contact 28a consists of a positive output relay normally closed contact 28-7 and a negative output relay normally closed contact 28-10, and the normally closed contact 28-7 is connected to the normally open contact 2 via the positive output relay 28-5.
8-6b and normally closed contact 28-10 are respectively connected to normally open contact 28-9b via negative output relay 28-8. Also, in the middle of the wiring connecting the normally closed contact 28-7 and the normally open contact 28-6b, the normally open contact 28-6a is connected to the normally closed contact 28-10.
The normally open contacts 28-9a are connected to the intermediate portions of the wiring connecting the normally open contacts 28-9b and 28-9b, respectively.

A ratio setting amplifier 27 with a dead band and a low-pass filter 26 are connected in series to the sampling control timer contact 28a, and a signal subtracter 25, which will be described later, is connected to the low-pass filter 26.

Even if the output signals of the pinch roll speedometer generator 15 or the pinch roll speed setting device 19, which will be described later, change rapidly or noise signals are mixed in due to induction, the low-pass filter 26 blocks these input signals and temporarily It has the function of transmitting only input signals that change at a constant rate as output, and the ratio setting amplifier 27 with dead band does not produce an output unless the input exceeds a constant value, and does not generate an output when the input exceeds a constant value. It has the function of multiplying the value by a certain magnification (this magnification is set manually or by the received signal) and transmitting it as its output. The relationship between the output E ₀ and the input Ei of the ratio setting amplifier 27 with a dead band is not only set as E ₀ =K ₁ Ei as shown in the diagram in the ratio setting amplifier 27 with a dead band, but also when high efficiency operation is required. Alternatively, the convergence operation may be performed linearly with respect to the deviation by replacing it with a square root calculation function that satisfies E ₀ =K ₂ √i. Note that K ₁ ,
K ₂ indicates the proportionality constant.

The mold level sensor 6 provided in the water-cooled mold 11 is connected to a level control amplifier 8a connected to a level setter 9a, and the level control amplifier 8a is connected to a level deviation indicator 24 and a level control start switch 23-1. and is connected to a signal adder 21 to which the pinch roll speed setter 19 is connected.

The pinch roll 13 that pulls out the slab 12 can be rotated by a pinch roll motor 14, and a thyristor input power source 1 is connected between the speed control amplifier 18 and the pinch roll motor 14.
A thyristor power supply device 17 comprising 6 is provided.

A pinch roll speedometer generator 15 coupled to the pinch roll motor 14 is connected to a signal subtractor 25 and a speed control amplifier 18. Further, a signal subtracter 25 is connected between the pinch roll speed setter 19 and the signal adder 21.

In FIG. 3, the same reference numerals as those shown in FIG. 1 indicate the same components.

Next, the operation of the present invention will be explained.

When starting the first casting, the worker first manually operates the knob of the level setting device 9a to set the target value of the molten steel level in the water-cooled mold 11, that is, the target level, to the level control amplifier 8a, and then operates the sliding valve opening. A speed command is given to the sliding valve control amplifier 7 by manually operating the knob of the device 22. Then, the control amplifier 7 generates an output proportional to the rotation angle of the knob of the sliding valve opening operating device 22, and the sliding valve operating motor 4 operates at a high speed when the output signal from the control amplifier 7 is large. , when the output signal is small, the sliding valve 3 is driven at a low speed, and at a predetermined speed so that the relationship between the magnitude of the output signal and the driving speed is proportional, and the sliding valve 3 is moved.

The rotational speed of the sliding valve operating motor 4 is detected by a sliding valve operating motor speedometer generator 5 and sent as a feedback signal from the operating motor speedometer generator 5 to the sliding valve control amplifier 7, but The sliding valve operation motor 4 is operated at a speed corresponding to the signal from the sliding valve opening degree controller 22 as described above. Valve opening degree controller 22
Since it has a spring return type, when the operation is stopped, the speed immediately returns to zero, and the sliding valve operation motor 4 stops, and the sliding valve 3 is operated by the sliding valve opening degree controller 22 operated by the worker. The molten steel in the tundish 1 is fixed at a predetermined opening automatically determined by the rotation angle of the knob and the time the knob is held in an inclined state. 10 into a water-cooled mold 11. Note that, prior to the start of casting, a conventionally known dummy bar is inserted into the lower part of the water-cooled mold 11 by an appropriate means, and the opening degree of the sliding valve 3 is determined while visually observing the flow of molten steel from the injection nozzle 10. The worker will make adjustments as appropriate to what he or she deems to be the best condition.

Once the molten steel has accumulated in the water-cooled mold 11 to a certain extent (for example, about 1/3 of the depth of the mold 11), the worker manually operates the knob of the pinch roll speed setting device 19 to gradually move it. As a result, the output signal from the pinch roll speed setting device 19 is gradually increased, but since the molten steel level in the water-cooled mold 11 is initially lower than the predetermined position,
The pinch roll speed is set to such a speed that the level of molten steel supplied from the injection nozzle 10 into the water-cooled mold 11 gradually rises. The output signal from the pinch roll speed setter 19 increases the rotational speed of the pinch roll motor 14 through the signal adder 21, the speed control amplifier 18, and the thyristor power supply 17, thereby increasing the rotational speed of the pinch roll 13. The drawing speed of the slab 12 is increased.

When the molten steel level in the water-cooled mold 11 gradually rises and the molten steel level 20 in the mold reaches the target level, the worker stops operating the pinch roll speed setting device 19 and presses the operating lever of the pinch roll speed setting device 19 into the mold. It is fixed at the position where the internal molten steel level 20 reaches the target level. This fixing completes the setting of the pinch roll speed. By rotating the pinch rolls 13, the dummy bar is first pulled out, and then the slab is pulled out.

The degree of difference between the molten steel level 20 in the mold and the target level can be determined by visually observing the level deviation indicator 24 that indicates the difference between the level setter 9a and the mold level sensor 6 that measures the actual level. It can be easily confirmed. However, if the molten steel level 20 in the mold differs from the target level beyond the allowable range, the worker manually operates the pinch roll speed setting device 19 again to gradually increase the pinch roll speed from a slow state. Repeat the above operation at high speed. The operations up to this point are performed manually by the worker.

When the indicated value of the level deviation indicator 24 reaches approximately zero as described above, the level control start switch 23 is activated.
-1 and 23-2, the device enters the automatic control state. This automatic control state includes continuous control and sampling control. Continuous control is performed when the deviation between the set value of the pinch roll speed setting device 19 and the pinch roll speed, that is, the actual casting speed is, for example, 10% or less, and sampling control is performed. The deviation is 10%
Perform in the above cases.

First, continuous control will be explained.

Now, when the molten steel flowing through the injection nozzle 10 increases (decreases) due to some reason, for example, the tundish molten steel level 2 increases (or decreases), the molten steel level 20 in the mold increases (decreases). Therefore, the set level signal set by the level setter 9a and the actual level signal detected by the mold level sensor 6 are compared by the level control amplifier 8a to find a deviation, and the level control amplifier 8a
The output of the positive (negative) deviation signal output from is applied to the signal adder 21 via the level control start switch 23-1, and is applied to the speed standard of the pinch roll 13 given in advance by the pinch roll speed setting device 19. Acts to increase (decrease) the signal.

The deviation signal between the output signal of the signal adder 21 and the pinch roll speedometer generator 15 is sent to the thyristor power supply 17, which controls the firing angle of the power supply 17 to increase (decrease) the output of the thyristor power supply 17. )
let Therefore, the pinch roll motor 14 is accelerated (decelerated), and the pinch roll 13 is accelerated (decelerated).
The slab 12 is pulled out at a faster (slower) speed than before, and therefore the molten steel level in the mold is 2.
0 gradually decreases (rises), and when the molten steel level 20 in the mold matches the set value, the pinch roll 13
The operation continues at the speed at which the molten steel level 20 in the mold matches the set value.

When the flow rate of molten steel flowing through the injection nozzle 10 increases (decreases), the pinch roll motor 1
4 is increased (decelerated), but the pinch roll motor 14 has a pinch roll speedometer generator 1.
5 is connected, pinch roll motor 1
4 is continuously detected by the pinch roll speedometer generator 15 and applied to the signal subtractor 25 as the input signal c shown in FIG. The signal subtractor 25 as the input signal d shown in FIG.
The signal from the pinch roll speedometer generator 15 and the signal from the pinch roll speed setter 19 are subtracted in the signal subtracter 25.

The deviation between the signal of the pinch roll speedometer generator 15 and the signal of the pinch roll speed setter 19 subtracted by the signal subtractor 25 is positive (negative), and the output signal of the signal subtractor 25 is as shown in FIG. e to the low pass filter 26.

Among the signals sent to the low-pass filter 26, rapidly changing output signals of the pinch roll speedometer generator 15 and pinch roll speed setting device 19, or noise signals mixed in due to induction, are filtered out by the low-pass filter 26. Only the input signal that is blocked and changes at a constant rate over time as shown in FIG. 7 becomes the output signal f.
The signal is sent to the ratio setting amplifier 27 with a dead band.
Since the low-pass filter 26 is provided, a transient signal caused by, for example, an incorrect speed signal of the pinch roll motor 14 or an inadvertent sudden operation of the pinch roll speed setter 19 is suppressed for a certain period of time, and therefore the signal subtracter 25
The sliding valve operation motor 4 does not immediately respond to the output of the , and the sliding valve 3 is gradually and reliably operated over a sufficient period of time.

The signal sent to the ratio setting amplifier 27 with a dead band does not produce an output unless its input exceeds a certain value g, as shown in Figure 8, and is multiplied by a certain multiplier for inputs exceeding a certain value. value is its output signal h,
It is sent to the sliding valve control amplifier 7 as i. The output signal h has a positive output and double the gain, and the output signal i has a negative output and a double gain.

The signal sent to the sliding valve control amplifier 7 is output from the control amplifier 7 and sent to the sliding valve operating motor 4 and the sampling control timer 28, and as shown in FIG. 9, the output signal j of the control amplifier 7 is sampled. When the threshold k of the control timer 28 is less than a certain value, or when the time at which the value exceeds the certain value is less than a certain time (i.e., when the micro operation speed is such that there is no risk of overshooting the molten steel) )teeth,
The output signal j is sent to the sliding valve operating motor 4, which is actuated in accordance with the output signal j, so that the output of the signal subtractor 25 is zero, that is, it flows through the injection nozzle 10 and is supplied into the water-cooled mold 11. The molten steel level 20 in the mold by the molten steel maintains the level set by the level setter 9a, and the drawing speed of the slab 12 pulled out by the pinch rolls 13 substantially matches the set value set by the pinch roll speed setter 19. The sliding valve 3 is opened and closed until then, and continuous control is performed. In this case, the sampling control timer contact 28a is always closed as shown at time ta ₀ in FIG. When the deviation signal is no longer output from the ratio setter 27 with dead band, the adjustment operation is completed.

Next, to explain sampling control, sampling control is performed when the deviation between the set value of the pinch roll speed setting device 19 and the pinch roll speed, that is, the actual casting speed, is, for example, 10% or more, as described above. Due to reasons. That is, when the deviation of the pouring speed is large, the amount of opening and closing of the injection nozzle 10 also changes greatly, and the molten steel level in the mold is 2.
The change in 0 is also large. Therefore, when controlling the pinch roll motor 14 to correct the slab withdrawal speed so that the molten steel level 20 in the mold reaches the set level, the sliding valve 3 is activated after detecting a change in the molten steel level 20 in the mold. There is a time delay in one round of control until the molten steel level 20 in the mold reaches a predetermined state. Therefore, when continuous control is performed, the molten steel level 20 in the mold changes and does not easily reach the set level. For this reason, the molten steel level 20 in the mold is quickly stabilized by sampling control, which is not performed continuously but is performed in parts.

Specifically, this sampling control is performed as follows.

The output of the control amplifier 7, that is, the rotational speed of the sliding valve operating motor 4, changes over the time shown in FIG.
As shown in ta ₁ , ta ₂ , and ta ₃ , if the cell threshold k in FIG. The control timer contact 28a is set for a certain period of time ts ₁ , ts ₂ ,
ts ₃ ,... are in the open state and then automatically closed, and due to a certain time lag, the output signal from the ratio setting amplifier 27 with dead band is transferred from the sliding valve control amplifier 7 to the sliding valve operating motor. 4, and even if the timer contact 28a closes after a certain time lag, if there is a deviation in the pinch roll speed, that is, the actual casting speed, from the setting value of the pinch roll speed setting device 19, the signal is subtracted. The output of the device 25 is approximately zero, that is, as in the case of continuous control, the molten steel level 20 in the mold due to the molten steel flowing through the injection nozzle 10 and supplied into the water-cooled mold 11 maintains the level set by the level setting device 9a. The speed at which the slab 12 is pulled out by the pinch rolls 13 is determined by the pinch roll speed setting device 1.
Sampling control is performed by manipulating the opening degree of the sliding valve 3 until it substantially matches the set value set in step 9. When the deviation signal is no longer output from the dead band ratio setting amplifier 27, the adjustment operation is completed. By such sampling control, it is possible to adjust the time lag between the change in the molten steel level 20 in the mold and the change in the slab drawing speed by the pinch rolls 13.

The operation of the sampling control timer 28 during the sampling control described above is as follows.

The zener diode 28-2 shown in FIG. 4 has a zener diode 28-2 set therein in advance, and the positive (negative) of the control amplifier 7 during continuous control performed with the timer contact 28a closed.
If the output of The cumulative output is negative output relay 2 as shown in Figure 11.
When the excitation level m, m' of 8-8 (or positive output relay 28-5) is reached, the relay is energized and simultaneously opens the sampling control timer contact 28a and the normally open contact 28-9b of the negative output relay 28-8. (or normally open contact 28-6 of positive output relay 28-5
b) is closed, and a negative (or positive) constant level signal for resetting the integrator is applied to the integrator 28-1 via the reset resistor 28-8, and the reversible integrator for the timer is activated as shown in FIG. 28-1's output level n gradually decreases, and as a result, after a certain period of time, the output of the timer reversible integrator 28-1 becomes negative output relay 2.
8-8 (or the positive output relay 28-5) is reduced to the demagnetization level o, o' necessary for demagnetizing the relay 28-5 or 28-8.

That is, when the input time cumulative value reaches the timer operation value, the sampling control timer 28 times out and opens the sampling control timer contact 28a, and returns the contact 28a to the closed state after a certain period of time has elapsed since the contact 28a was opened. Thus, sampling control as described above is performed.

When the molten steel temperature decreases during operation, steel slag and the like tend to adhere to the sliding valve 3 and the inner wall of the injection nozzle 10, and especially in aluminum-killed steel types that contain aluminum, valves or nozzles are easily clogged, and once they adhere, When the steel slag separates and flows out to the water-cooled mold 11 side, the flow rate of molten steel inside the sliding valve 3 or the injection nozzle 10 suddenly increases, making it impossible to stably operate the control system shown in FIG. 3. It becomes difficult. In order to prevent this, the output signal b shown in FIG. 16 is transmitted from the dither generator 35 intermittently at regular time intervals. This transmitted output signal b is given to the sliding valve control amplifier 7, which instantaneously rotates the sliding valve operating motor 4 in the forward and reverse directions in the same state as the output signal b shown in FIG. The opening degree of the sliding valve 3 or the injection nozzle 10 is changed as shown in a.
gives a pulsating flow to the molten steel passing through. This allows the attached steel slag to flow out without growing, allowing stable continuous control and sampling control. Moreover, the flow rate change by the dither signal has a short cycle and is performed so that the temporal average of the molten steel flow rate is approximately zero, so the mold molten steel level 20 does not change to the extent that it disturbs the control system.

The output signal p of the dither generator 35 is also added to the output signal of the sliding valve control amplifier 7 as shown in FIG. 14, and this output signal q is alternately applied to the sampling control timer 28 as shown in FIG. However, since the algebraic sum of the time accumulation of the timer input becomes zero, the history of the dither signal does not remain inside the timer (reversible integrator for timer), and therefore may affect the sampling control timer 28, such as malfunction. No, dither generator 3
The sliding valve 3 is opened and closed in a vibratory manner according to the output signal from the valve 5, thereby preventing steel slag and the like from adhering to the inside of the valve 3 and the like.

FIG. 17 shows another embodiment of the present invention, in which an electromagnetic pump assembly 44 effective for regulating the flow rate of molten steel is provided instead of using a sliding valve as a means for regulating the flow rate of molten steel.
Control similar to the embodiment shown in FIG. 3 can be achieved by controlling the thyristor power control device for driving 4 through the output setting servo potentiometer 40. In the figure, 36 is an electromagnetic pump manual operator, 37 is a thyristor output control amplifier, and 3
8 is a thyristor power control device, 39 is a current transformer for output current feedback of the thyristor power control device, 41 is a servo motor for driving a servo potentiometer, 42 is a speedometer generator for servo motor speed feedback, and 43 is a flow rate control for an electromagnetic pump. The same reference numerals as those shown in FIG. 3 indicate the same components.

FIG. 18 shows still another embodiment of the present invention, in which a stopper 3a is disposed inside the tundish 1 instead of the sliding valve as a means for adjusting the flow rate of molten steel injected from the tundish 1 into the water-cooled mold 11. A stopper operating motor 4a is provided in place of the sliding valve operating motor,
A stopper operation motor speedometer generator 5a is installed in place of the sliding valve operation motor speedometer generator, a stopper control amplifier 7a is installed in place of the sliding valve control amplifier, and a stopper control amplifier 7a is installed in place of the sliding valve opening degree controller 22. The functions of each device and the operation of the overall control system are the same as those shown in FIG. 3, except that the stopper opening degree operating device 22a is used, so a description thereof will be omitted.

In the figure, 29 is a stopper arm attached to the upper end of the stopper 3a, 30 is a rod attached to one end of the stopper arm 29, and 31 and 32 are rods 3a.
A rod guide 33 that guides the rod 30 when the rod 30 moves up and down is pivotally connected to the middle part of a stopper handle 34 that is pivoted to the lower end of the rod 30, and serves as a fulcrum when the stopper handle 34 swings up and down. This is the link that will become.

It is also possible to use a sliding nozzle instead of the sliding bubble in the embodiment of the present invention, and instead of using a pinch roll speedometer generator as a means for detecting the drawing speed of the slab, It is also possible to dispose a measuring roll driven by the contact friction force of Of course, various changes can be made without departing from the spirit of the invention.

Since the method for controlling the drawing speed and mold level of a continuous casting machine according to the present invention has the above-described configuration, it exhibits various excellent effects as described below.

() When the molten steel level in the mold changes, in order to compensate for this change, the rotation speed of the pinch rolls is first controlled, and when the rotation speed of the pinch rolls is controlled, the ratio of slab withdrawal speed adjustment amount / amount of change in molten steel level changes. Since it is always constant and there is almost no time delay, it is possible to stably return the molten steel level to an appropriate level.

() After controlling the rotation speed of the pinch rolls, that is, after the molten steel level returns to a predetermined state, continuous control or sampling control is performed based on the control result of the pinch roll rotation speed, and the necessary and sufficient time is applied. Since the injection amount is corrected by gradually controlling the molten steel flow rate adjusting means, extremely stable adjustment of the molten steel injection amount is possible without causing hunting or excessive control.

() Since the change in the flow rate of molten steel injected into the tundish or water-cooled mold is obtained from the signal of the signal subtracter as a change in the speed of the pinch roll (that is, the speed correction amount of the pinch roll acting as a result of level control), Control can be performed with high precision.

() If the casting speed set by the pinch roll speed setting device is the target value of the molten steel injection flow rate, the output of the signal subtractor corresponds to the measured value of the flow rate deviation, so this signal can be used to detect the flow rate deviation. By forming a closed-loop flow control system that is used as a signal for the mold, the mold molten steel level can be adjusted using flow rate adjustment means such as sliding valves and stoppers whose flow coefficient Cυ changes moment by moment as wear progresses. It has become possible to maintain the pinch roll speed (casting speed) at a predetermined value in a stable state for a long period of time.

() Particularly in billet continuous casting machines with a small internal cross-sectional area of the mold, the level control that directly adjusts the flow rate using the signal from the mold level sensor is effective against slight characteristic flaws in the flow rate adjustment means (changes in flow coefficient and reproduction of flow rate adjustment). sexual defects, etc.)
However, as with this control method, transient level changes are compensated for by controlling the speed of the pinch rolls, and the remaining flow rate changes are then compensated for by controlling the flow rate. By operating the adjusting means, the flow rate change is restored to zero. As a result, safety, stability, level control accuracy, and casting speed accuracy are significantly improved compared to conventional level control methods, and the models range from small billet continuous casting machines to large-scale slab continuous casting machines. It is applicable up to

() Since it is equipped with a dither generator, there is no possibility of steel slag or impurities adhering to and growing on the inner walls of the sliding valve or nozzle stopper, or irregular flow rates caused by sudden outflow of these materials. , stable and highly accurate control becomes possible.

() A low-pass filter, a ratio setting amplifier 27 with a dead band to adjust the flow rate at a speed corresponding to the size of the pinch roll speed deviation (injection amount deviation), and automatic control from sampling control to continuous control depending on the size of the manipulated variable. Equipped with a sampling control timer 28 with a threshold value that selects the optimum conditions for the process, the pinch roll speed (casting speed) can be maintained with high accuracy and the flow rate of molten steel can be efficiently adjusted. It can be carried out.

[Brief explanation of the drawing]

FIGS. 1 and 2 are explanatory diagrams of mold molten steel level control in a conventional continuous casting machine, with FIG. 1 showing a sliding valve operating method and FIG. 2 showing a pinch roll operating method. 3 is an explanatory diagram of one embodiment of the present invention, and FIG. 4 is an explanatory diagram of an embodiment of the present invention.
A detailed explanatory diagram of the sampling control timer used in the embodiment shown in the figure, Figure 5 is a graph showing the relationship between the input signal of the signal subtracter and time, and Figure 6 is a graph showing the relationship between the output signal of the signal subtracter and time. Fig. 7 is a graph showing the relationship between the output signal of the low-pass filter and time, Fig. 8 is a graph showing the relationship between the output signal of the ratio setting amplifier with dead band and time, and Fig. 9 is the graph showing the relationship between the output signal of the low-pass filter and time. A graph showing the relationship between the output signal of the amplifier and time. Fig. 10 is a graph showing the operating state of the sampling control timer contact corresponding to the output of the sliding control amplifier. Fig. 11 shows the output of the reversible integrator for the timer and time. Figure 12 is a graph showing the relationship between the output of the sliding valve control amplifier and time, and Figure 13 is a graph showing the relationship between the output of the reversible integrator for the timer when the dither generator is activated and time. Fig. 14 is a graph showing the relationship between the output of the sliding valve control amplifier and time when the dither generator is activated, Fig. 15 is a graph for explaining changes in valve opening, and Fig. 16 is a graph showing the relationship between the output of the sliding valve control amplifier and time when the dither generator is activated. FIG. 17 is an explanatory diagram of another embodiment of the present invention, and FIG. 18 is an explanatory diagram of still another embodiment of the present invention. 1 is a tandate, 2 is a tandate molten steel level, 3 is a sliding valve, 3a is a stopper, 4 is a sliding valve operating motor,
4a is a stopper operating motor, 5 is a sliding valve operating motor speedometer generator, 5a is a stopper operating motor speedometer generator, 6 is a mold level sensor, 7 is a sliding valve control amplifier, 7a is a stopper control amplifier, 8a is a Level control amplifier, 9a is level setter, 10 is injection nozzle, 11 is water cooling mold, 12 is slab, 13 is pinch roll, 14 is pinch roll motor, 15 is pinch roll speedometer generator, 16 is thyristor input power supply , 17 is a thyristor power supply device, 18 is a speed control amplifier, 19 is a pinch roll speed setting device, 2
0 is the mold molten steel level, 21 is the signal adder, 2
3-1, 23-2 are level control start switches, 2
4 is a level deviation indicator, 25 is a signal subtracter, 26
27 is a low-pass filter, 27 is a ratio setting amplifier with a dead band, 28 is a sampling control timer, 28a is a sampling control timer contact, and 35 is a dither generator.

Claims (1)

[Claims] 1. When the level of molten steel injected into the mold from the tundish reaches a predetermined amount, the pinch rolls for pulling out the slab from the mold are rotated at such a speed that the level of molten steel in the mold gradually rises. When the molten steel level in the mold reaches a preset molten steel setting level, the pinch roll speed at that time is set as the pinch roll setting speed, and the actual molten steel level in the mold changes with respect to the molten steel setting level. Then, calculate the variation as the molten steel level deviation, add the molten steel level deviation to the pinch roll setting speed, control the rotation speed of the pinch roll by this addition signal, and calculate the difference between the pinch roll setting speed and the detected pinch roll speed. detecting a pinch roll speed deviation signal, and when the pinch roll speed deviation signal is smaller than a predetermined value, continuously adjusting the amount of molten steel injected into the mold so that the pinch roll speed deviation signal is minimized; control, and when the pinch roll speed deviation signal is larger than a predetermined value, the sampling control means for adjusting the amount of molten steel injected into the mold is controlled so that the pinch roll speed deviation signal is minimized; A method for controlling the drawing speed and mold level of a continuous casting machine, characterized by controlling the molten steel level to be constant. 2. A mold that receives molten steel from a tundish through an injection nozzle, a valve device or an electromagnetic pump assembly for adjusting the flow rate of molten steel supplied from the tundish to the mold, and detects the level of molten steel in the mold. A level sensor, a pinch roll for pulling out the slab from the mold, and a speed detection device for detecting the rotational speed of a drive device that drives the pinch roll, or a speed detection device that is rotationally driven by the slab to be pulled out and the speed at which the slab is pulled out. an operating device that issues a command to the driving device of the valve device to manipulate the valve opening degree or an operating device that gives a command to the power supply device of the electromagnetic pump assembly to manipulate the electromagnetic force; a molten steel level setting device in the mold, a setting device for setting the speed of the pinch roll, and a level for determining the deviation between the molten steel level in the mold detected by the level sensor and the molten steel level set by the molten steel level setting device. control amplifier,
a signal adder for adding the deviation signal from the level control amplifier and a setting value set by the pinch roll speed setting device; and a signal adder for adding the deviation signal from the level control amplifier to a setting value set by the pinch roll speed setting device; and a rotation speed of the pinch roll drive device based on the command signal from the signal adder. A power supply device to be controlled and a speed deviation signal obtained by subtracting the setting value set by the pinch roll speed setting device from the value detected by the speed detection device of the pinch roll or the measuring roll and the speed deviation signal of the valve device. A signal subtracter that outputs to a drive device that operates the valve opening degree or a power supply device that operates the electromagnetic force of the electromagnetic pump assembly, and a connection between the valve device or the electromagnetic pump assembly and the signal subtractor. 1. A control device for controlling the drawing speed and mold level of a continuous casting machine, characterized in that it is equipped with a sampling control device and a continuous control device. 3. A mold that receives molten steel from a tundish through an injection nozzle, a valve device or an electromagnetic pump assembly for adjusting the flow rate of molten steel supplied from the tundish to the mold, and a device that detects the level of molten steel in the mold. A level sensor, a pinch roll for pulling out the slab from the mold, and a speed detection device for detecting the rotational speed of a drive device that drives the pinch roll, or a speed detection device that is rotationally driven by the slab to be pulled out and the speed at which the slab is pulled out. an operating device that issues a command to the driving device of the valve device to manipulate the valve opening degree or an operating device that gives a command to the power supply device of the electromagnetic pump assembly to manipulate the electromagnetic force; a molten steel level setting device in the mold, a setting device for setting the speed of the pinch roll, and a level for determining the deviation between the molten steel level in the mold detected by the level sensor and the molten steel level set by the molten steel level setting device. control amplifier,
a signal adder for adding the deviation signal from the level control amplifier and a setting value set by the pinch roll speed setting device; and a signal adder for adding the deviation signal from the level control amplifier to a setting value set by the pinch roll speed setting device; and a rotation speed of the pinch roll drive device based on the command signal from the signal adder. A power supply device to be controlled and a speed deviation signal obtained by subtracting the setting value set by the pinch roll speed setting device from the value detected by the speed detection device of the pinch roll or the measuring roll and the speed deviation signal of the valve device. A signal subtracter that outputs to a drive device that operates the valve opening degree or a power supply device that operates the electromagnetic force of the electromagnetic pump assembly, and a connection between the valve device or the electromagnetic pump assembly and the signal subtractor. a sampling control device and a continuous control device, and a dither generator that applies vibrations to the drive device of the valve device or the power supply device of the electromagnetic pump assembly at regular time intervals. and mold level control device. 4. As the sampling control mechanism, a sampling control timer equipped with a reversible integrator with a self-hold that enables the sampling control time to be automatically selected depending on the magnitude of the speed deviation signal, and a sampling control timer connected to the sampling control timer in a loop. A drawing speed and mold level control device for a continuous casting machine according to claim 2 or 3, which is provided with a control timer contact.