JP3271242B2 - Continuous casting machine Mold level control device in mold - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for controlling the level of molten metal in a mold in a continuous casting machine, and in particular, it can efficiently and greatly reduce bulging level fluctuations during steady casting. The present invention relates to an apparatus for controlling a level of a molten metal in a continuous casting machine.

[0002]

2. Description of the Related Art Generally, controlling the level of molten metal (hereinafter referred to as molten steel) in a mold in a continuous casting machine is important not only for stable operation but also for ensuring the quality of cast slabs. That is.

[0003] Conventionally, PI control is often used as a level control in a mold of a continuous casting machine of this type. In this case, the control system is configured for the purpose of balancing the mass balance between the molten steel solidified and drawn out of the mold and the molten steel supplied to the mold depending on the opening of the sliding nozzle.

[0004] Fluctuations in the molten metal level in the mold occur when the disturbance of the mass balance cannot be sufficiently compensated, and it is considered that the main cause is fluctuation in the drawing flow rate. The largest variation in the drawing flow rate is referred to as strong periodic bulging-fluctuation of the molten metal level, and it is said that the variation occurs due to the vibration of the solidified shell of the slab between the drawing pinch rolls. It is known to have a frequency determined by a pinch roll pulling speed (casting speed) and a pinch roll interval.

On the other hand, from the viewpoint of disturbance compensation, it is generally desirable to employ PID control instead of PI control as a means for compensating for such flow disturbance. In particular, since the observed quantity is at the level of the molten metal and the flow rate fluctuation, which is a disturbance, cannot be reflected in the control in the correct phase unless the level of the molten metal of the observed quantity is differentiated. We understand the need. For this reason, there is known a technique of performing disturbance compensation by adding incomplete differential control using a low-pass filter as differential control that can be realized on site.

[0006]

However, since the differential characteristics have a high frequency and a high gain, the differential characteristics are incomplete from the viewpoint of reducing the effect of signal noise in the actual field and suppressing the generation of standing waves in the mold. The filter characteristics of the derivative must be enhanced.

For this reason, it is impossible to achieve a phase lead of 90 degrees which originally has a differential characteristic, and in practice, it is 20 to 3 phases.
At present, it is about 0 degrees, and the effect of the differentiation can hardly be expected.

It is an object of the present invention to provide a mold level control device in a mold of a continuous casting machine capable of efficiently and significantly reducing fluctuations in bulging property during steady casting.

[0009]

According to a first aspect of the present invention, there is provided a control device for controlling a molten metal level in a mold in a continuous casting machine. The level gauge for detecting the level of the molten metal and the opening level of the sliding nozzle provided in the tundish based on the deviation signal between the level and the level set continuously detected by the level gauge. A PI controller that outputs a degree command, a sliding nozzle controller that inputs an opening degree command output from the PI controller, adjusts the opening degree of the sliding nozzle to adjust the amount of molten metal flowing from the tundish, A large bulging-fluctuation level change of a specific cycle is extracted from a deviation signal between the level and the set level, and its phase characteristic is adjusted to a predetermined range (for example, 45 degrees). And a disturbance compensator having a characteristic of advancing and outputting at a range of 35 degrees, and a signal obtained by multiplying an output signal from the disturbance compensator by an adjustable gain to an opening degree command output from the PI controller. To the final opening command of the sliding nozzle.

Therefore, in the mold level control apparatus in the mold of the continuous casting machine according to the first aspect of the present invention, of the mold level fluctuations generated during the steady operation at a constant casting speed, the fluctuation width is large and the periodic bulging property level change is performed. During the steady casting by taking out the periodic component in the disturbance compensator and advancing the phase characteristic to convert it into a flow rate fluctuation, thereby correcting the sliding nozzle opening command output from the PI controller. The bulging characteristics of the molten metal level can be efficiently and significantly reduced, and there is no influence of standing waves or high-frequency noise, so that a cast slab of good quality without powder entrapment can be produced.

According to the second aspect of the present invention, in the first aspect,
In the mold level control device in the continuous casting machine mold according to the invention, a bulging frequency detecting means for detecting a bulging frequency which is a cycle of bulging property level fluctuation from a level signal continuously detected by the level gauge. In addition, the setting frequency of the disturbance compensator is continuously changed according to the bulging frequency detected by the bulging frequency detecting means.

Therefore, in the apparatus for controlling the level of the molten metal in the mold of the continuous casting machine according to the second aspect of the present invention, the set frequency of the disturbance compensator is continuously changed in accordance with the bulging frequency, so that the bulging is performed as in an unsteady state. Even if the cycle of the fluctuation of the molten metal level is changed by changing the casting speed (drawing speed), the same operation as in the case of the first aspect of the present invention is maintained, and a good quality cast piece without powder entrainment is manufactured. be able to.

According to a third aspect of the present invention, in the continuous level casting machine mold level control device according to the second aspect of the present invention, the bulging frequency detecting means continuously detects the level of the molten metal by a level gauge. A band-pass filter for extracting a signal only in a frequency band in which a bulging property level fluctuation exists from the signal of the above, and an FFT analyzer for detecting a bulging frequency by FFT-analyzing the signal extracted by the band-pass filter. ing.

Therefore, in the apparatus for controlling the mold level in the mold of the continuous casting machine according to the third aspect of the present invention, only the signal in the frequency band where the bulging level change exists is extracted from the signal of the mold level, and this signal is subjected to FFT analysis. By detecting the bulging frequency and continuously changing the set frequency of the disturbance compensator in accordance with the bulging frequency, the cycle of the bulging property level fluctuation as in the non-stationary state is determined by the casting speed (drawing speed). Even if it is changed by the change, the same operation as in the case of the invention of the second aspect is maintained, and a cast slab of good quality without powder entrainment can be manufactured.

According to a fourth aspect of the present invention, in the continuous casting machine mold level control apparatus of the second aspect of the present invention, as a bulging frequency detecting means, a speed of a pinch roll for extracting molten metal in the mold is used. A bulging cycle calculator that calculates a bulging frequency from the ratio between the (casting speed) and the interval between the pinch rolls is used.

Therefore, in the apparatus for controlling the level of molten metal in the continuous casting machine according to the fourth aspect of the present invention, the bulging frequency is calculated from the ratio between the speed of the pinch roll (casting speed) and the interval between the pinch rolls. By continuously changing the set frequency of the disturbance compensator in response, even if the cycle of the bulging level change due to the change of the casting speed (drawing speed) as in the unsteady state,
The same operation as in the inventions of the second and third aspects is maintained, and a cast slab of good quality without powder entrainment can be manufactured.

According to the fifth aspect of the present invention, the first aspect of the present invention is provided.
In the mold level control device in the mold of the continuous casting machine according to the invention, the output from the disturbance compensator is determined by the amplitude of the bulging property level fluctuation extracted from the level signal continuously detected by the level gauge. The magnitude of the adjustable gain multiplied by the signal is changed.

Therefore, in the apparatus for controlling the mold level in the mold of the continuous casting machine according to the fifth aspect of the present invention, the magnitude of the bulging level variation is determined from the level signal and the output of the disturbance compensator is determined based on the magnitude of the variation. The invention according to claim 1, wherein, even when the bulging property level fluctuation increases by changing the magnitude of the adjustable gain applied to the signal, the adjustable gain is increased to the limit of the flow rate adjustment. In this case, the same operation as in the above case is maintained, and a cast slab of good quality with less powder entrainment can be produced.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention utilizes the fact that one of the causes of a large level change of molten steel in a mold in a continuous casting machine is a bulging level change, which is a strong periodicity change. Then, the flow fluctuation, which is the main cause of the bulging level change, is estimated by creating a signal in which the phase of the level signal, which is the observation signal, is advanced more than the usual imperfect differentiation, and this signal is estimated. By using the signal as a disturbance compensation signal for adjusting the opening degree of the sliding nozzle, bulging-fluctuation level fluctuation is greatly reduced.

Hereinafter, embodiments of the present invention based on the above-described concept will be described in detail with reference to the drawings. (First Embodiment) FIG. 1 is a sectional view showing a configuration example of a peripheral portion of a mold of a continuous casting machine to which a mold level control device according to the present embodiment is applied.

In FIG. 1, molten steel 2 filled in a tundish 1 is injected into a mold 5 through an immersion nozzle 6 in accordance with an opening determined by a position of a sliding nozzle 3 installed at the bottom of the tundish 1. You.

The molten steel 2 injected into the mold 5
While being cooled from the side wall and solidifying from the surface, is pulled out by the pinch roll 9 in the drawing direction (downward) 7. At this time, the drawing speed (casting speed) is controlled to be substantially constant.

Further, the molten steel 2 injected into the mold 5
As described above, the amount is determined according to the opening degree of the sliding nozzle 3, and the sliding nozzle 3 is driven by an actuator 8 which is a sliding nozzle controller.

That is, the opening degree of the sliding nozzle 3 is adjusted by the actuator 8 according to the opening degree command of the sliding nozzle 3 output from the PI controller 10 described later, so that the inflow amount of the molten steel 2 from the tundish 1 is adjusted. You.

On the other hand, in the mold level control device in the mold, the PI controller 10 includes a mold level detection signal obtained from the mold level meter 4 for detecting the mold level of the molten steel 2 in the mold 5 and a mold level setting. The deviation signal from the value is continuously input, and the molten steel 2 in the mold 5 is
The opening command of the sliding nozzle 3 is given to the actuator 8 so that the molten metal level becomes constant.

Also, the disturbance compensator 11 receives a deviation signal between the above-mentioned molten metal level and the set molten metal level, and extracts a large bulging-fluctuation of the bulging characteristic at a specific cycle from the deviation signal.
In addition, the phase characteristic is set within a predetermined range (for example,
(In a range of 35 degrees).

Further, a signal obtained by multiplying the output signal from the disturbance compensator 11 by an appropriate adjustable gain 12 is added to the opening degree command of the sliding nozzle 3 output from the PI controller 10 so that the final signal is obtained. The opening degree command of the sliding nozzle 3 is obtained and becomes a command value to the actuator 8.

Next, the operation of the mold level control device in the mold of the continuous casting machine according to the present embodiment having the above-described configuration will be described with reference to FIGS. In FIG.
The level gauge 4 continuously detects the level of the molten steel 2 in the mold 5 and inputs the level to the PI controller 10.

The PI controller 10 controls the molten metal level of the molten steel 2 in the mold 5 to be constant based on a deviation signal between the molten metal level detection signal from the molten metal level meter 4 and the molten metal level set value. Then, the opening degree command of the sliding nozzle 3 is given to the actuator 8.

At this time, the disturbance compensator 11 extracts a large bulging level change of a specific cycle from the deviation signal between the level and the set level, and sets the phase characteristic to a predetermined range (for example, 45 degrees). (In the range from 135 degrees to 135 degrees).

The output signal from the disturbance compensator 11 is multiplied by an appropriate adjustable gain 12 and
Sliding nozzle 3 output from I controller 10
, The final opening command of the sliding nozzle 3 is obtained and given as a command value to the actuator 8.

As described above, of the level fluctuations occurring during the steady operation at a constant casting speed, the periodic bulging-type level fluctuation having a large fluctuation width is extracted from the disturbance compensator 11 by the periodic component, and the phase characteristic is obtained. Is converted to flow rate fluctuation,
Sliding nozzle 3 output from PI controller 10
Is corrected, the bulging property level fluctuation during steady casting can be efficiently and significantly reduced, and there is no influence of standing wave or high frequency noise, so there is no powder entanglement Good quality slabs can be produced.

Next, the above points will be described in more detail and concretely with reference to FIGS. FIG. 2 is a block diagram showing the above-described mold level control system in a mold linearized around an equilibrium point during a steady operation and represented as a model.

The molten steel 2 in the mold 5 in the continuous casting machine
The disturbance of the drawing flow rate which causes the fluctuation of the molten metal level is immediately before the mold 5 having the integral characteristic. Therefore, the observable fluctuation is accompanied by a phase delay of 90 degrees with respect to the flow fluctuation d entering the system, and even if the gain of the PI controller 10 is increased, the compensation amount with a delayed phase characteristic increases to the manipulated variable. The effect cannot be expected because it is only.

In such a case, theoretically, the phase is set to 90.
By adding a differential compensator for advancing the degree, the amount of operation with improved phase characteristics can be increased. However, as is well known, the differential compensator has an advantage of advancing the phase, but has a characteristic that the gain becomes higher as the frequency becomes higher, so that the measurement signal noise is increased and the differential compensator cannot be used substantially. Things.

On the other hand, as a pseudo-differential which can be mainly used in the field, a pseudo-differential with a low-pass filter called an incomplete differential is used. However, since a phase delay due to the filter is included, a great effect cannot be expected.

In this regard, in the present embodiment, the bulging property level fluctuation with a large level fluctuation level is reduced by adding a disturbance compensator 11 that is substantially close to the ideal differential to the original PI controller 10. The design method is described below.

The bulging property level fluctuation is caused by the fact that the slab swells in a direction perpendicular to the drawing direction 7 between the pinch rolls 9 for drawing the slab and the amount thereof fluctuates and becomes oscillating. It is said that the mass balance is lost. It is said that the characteristic of the fluctuation is that it has periodicity and has a period determined by the interval between the pinch rolls 9 and the drawing speed (the casting speed) which is the speed of the pinch rolls 9.

In the present embodiment, the periodic disturbance compensator 11 is used by utilizing the fact that the bulging
Is added to the PI controller 10 to reduce the bulging-fluidity level fluctuation.

For this reason, the disturbance compensator 11 has the following functions: (1) a function of extracting a bulging-fluid level change from a noisy level signal; and (2) a phase of the extracted bulging-fluctuation level component.
Two functions are required, that is, a function to advance the angle by about 0 degrees.

As one method for realizing this, a band-pass filter (hereinafter, referred to as a band-pass filter) C ₁ (s) for the above function (1) and a band-pass filter C ₁ (s) for the function (2) are used. There is a method which comprises a specific frequency phase lead compensator C ₂ (s). In this case, the configuration of the band-pass filter C ₁ (s) may be determined, for example, as follows.

[0042]

(Equation 1)

With such a determination, a signal passing through the band-pass filter C ₁ (s) becomes only a signal of the frequency ω _{0 and} a signal having no phase delay or advance can be obtained. Also,
The configuration method of the specific frequency phase lead compensator C ₂ (s) may be determined as follows, for example.

[0044]

(Equation 2)

This specific frequency phase lead compensator C ₂ (s)
Has a characteristic of advancing the phase characteristic of the signal component of the frequency ω ₀ by 90 degrees, and the high-frequency gain does not increase. For this reason, if the signal output from the band-pass filter C ₁ (s) is input to the specific frequency phase lead compensator C ₂ (s), the output signal is only the component of the specific frequency ω ₀ ,
Moreover, the phase is advanced by 90 degrees. That is, the bulging disturbance compensator C _d (s) is

[0046]

(Equation 3) It may be determined as follows.

At this time, the specific frequency ω ₀ = 0.2πrad
FIG. 3 shows the frequency characteristics of the bulging disturbance compensator C _d (s) with respect to gain and phase when the frequency is set to / sec, that is, 0.1 Hz.

As is apparent from FIG. 3, the gain characteristic is a characteristic that allows a signal component of 0.1 Hz to pass, and the phase characteristic is +90 degrees at 0.1 Hz.

Therefore, the bulging disturbance compensator C _d
If (s) is arranged in the disturbance compensator 11 shown in FIG. 1 and used together with the adjustable gain 12, differential compensation for bulging disturbance becomes possible, and the bulging molten metal surface fluctuation amount is greatly reduced as compared with the conventional case. Can be reduced.

FIG. 4 is a diagram showing an example of a simulation result showing the effect. FIG. 4 shows the effect of reducing the fluctuation level of the molten metal level when the disturbance compensator 11 is turned on during the PI control. The disturbance compensator 11 is turned on at a time of 48 seconds. As a result, the variation of ± 7 mm or more in the case of only the PI control is ± 5 mm after the disturbance compensation.
The results are as follows, and it can be seen that there is a fluctuation width reduction effect of about 30%.

As described above, in the mold level control apparatus in the mold of the continuous casting machine according to the present embodiment, of the mold level fluctuations that occur during the steady operation at a constant casting speed, the fluctuation range is large and the periodic bulging property is large. Disturbance compensator 1
In FIG. 1, the periodic component is extracted, and the phase characteristic is advanced to convert it into a flow rate fluctuation, thereby correcting the opening command of the sliding nozzle 3 output from the PI controller 10. The bulging-fluid surface level fluctuations can be efficiently and significantly reduced, and there is no effect of standing waves or high-frequency noise. Therefore, a cast slab of good quality without powder entrapment can be produced.

As a result, it is possible to realize mold level control in the mold in which bulging property level fluctuations during steady casting can be significantly reduced, thereby realizing stable operation, improving yield, and improving cast quality. Is obtained.

(Second Embodiment) FIG. 5 is a cross-sectional view showing an example of a configuration of a peripheral portion of a mold of a continuous casting machine to which a mold level control device according to the present embodiment is applied.
The same elements as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. Only different parts will be described here.

That is, in the present embodiment, as shown in FIG. 5, a bulging frequency detecting device 18 is added to FIG. The bulging frequency detecting device 18
A signal of the molten metal level continuously detected by the molten metal level meter 4 is input, and a bulging frequency which is a period of the bulging characteristic molten metal level fluctuation is detected from this signal.

Further, the set frequency of the disturbance compensator 11 is continuously changed according to the bulging frequency detected by the bulging frequency detector 18. Next, the operation of the mold level control device in the continuous casting machine mold of the present embodiment configured as described above will be described.

Here, only the operation of the parts different from the first embodiment will be described. In FIG. 5, the bulging frequency detector 18 detects the frequency of the bulging level fluctuation included in the level signal from the level meter 4, and the bulging frequency sequentially changes the set frequency of the disturbance compensator 11. Changed continuously online.

Actually, during steady casting, since the casting is performed at a constant casting speed, the frequency of the bulging-fluid level change is not changed. On the other hand, the speed is changed during unsteady work such as when increasing speed at the start of casting, at the time of deceleration at the end of casting, at the time of TD replacement, or at the time of primary deceleration at the time of changing the casting width. Also change.
In such a case, the first embodiment alone cannot provide a sufficient effect.

In this respect, in the present embodiment, the frequency of the bulging level change is detected from the level signal by some method, and the frequency is calculated, for example, by using ω _{0 in the} above equations (1) and (2). , The disturbance compensator 11 effectively works for any bulging-fluctuation level change at any frequency, and the same operation as in the first embodiment can be maintained.

As described above, since the set frequency of the disturbance compensator 11 is continuously changed in accordance with the bulging frequency, the cycle of the bulging property level fluctuation changes the pouring speed (drawing speed) as in an unsteady state. Even if it changes, the same operation as in the first embodiment can be maintained, and a cast slab of good quality without powder entrapment can be manufactured.

Therefore, even in the case where the pouring speed changes as in an unsteady state, the same effect as in the case of the first embodiment can be maintained. (Third Embodiment) FIG. 6 is a sectional view showing a configuration example of a peripheral portion of a mold of a continuous casting machine to which a mold level control device according to the present embodiment is applied. The same reference numerals are given and the description is omitted, and only different portions will be described here.

That is, in the present embodiment, as shown in FIG. 6, a band-pass filter 19 and an FFT analyzer 20 as bulging frequency detecting means are added to FIG.

The band-pass filter 19 receives a level signal continuously detected by the level gauge 4, and extracts a signal only in a frequency band in which a bulging level fluctuation exists from this signal.

The FFT analyzer 20 performs FFT analysis on the signal extracted by the band pass filter 19 to detect a bulging frequency. Further, the set frequency of the disturbance compensator 11 is continuously changed according to the bulging frequency detected by the FFT analyzer 20.

Next, the operation of the apparatus for controlling the level of the level in the mold of the continuous casting machine of the present embodiment having the above-described configuration will be described. Here, only the operation of the portion different from that of the first embodiment will be described.

In FIG. 6, the band-pass filter 19
Then, only the signal in the frequency band in which the bulging level change included in the level signal from the level gauge 4 is extracted. Thus, other fluctuation components included in the fluctuation of the molten metal level are removed in advance.

The signal from the band-pass filter 19 is subjected to FFT analysis by the FFT analyzer 20 to detect a bulging frequency, and the set frequency of the disturbance compensator 11 is sequentially and continuously changed on-line by the bulging frequency. You.

That is, the frequency band where the bulging property level fluctuation exists (generally in the range of about 0.02 to 0.4 Hz) is known. Therefore, by extracting a signal only in this range and detecting the frequency, it is possible to avoid detecting other fluctuation components included in the molten metal level fluctuation signal, and to reliably detect the bulging frequency.

As described above, a signal in only the frequency band in which the bulging property level fluctuation exists is extracted from the level signal, and this signal is subjected to FFT analysis to detect a bulging frequency, and disturbance compensation is performed in accordance with the bulging frequency. Vessel 1
When the set frequency of 1 is continuously changed, even if the cycle of the bulging level change is changed by changing the casting speed (drawing speed) as in an unsteady state, the second
The same operation as that of the embodiment can be maintained, and a good quality cast piece without powder entrapment can be manufactured.

Therefore, even when the pouring speed changes as in an unsteady state, the same effect as that of the second embodiment can be maintained. (Fourth Embodiment) FIG. 7 is a sectional view showing a configuration example of a peripheral portion of a mold of a continuous casting machine to which a mold level control device according to the present embodiment is applied. The same reference numerals are given and the description is omitted, and only different portions will be described here.

That is, in the present embodiment, as shown in FIG. 7, a pinch roll speed detector 21 and a bulging cycle calculator 22 which are bulging frequency detecting means are provided in FIG.
Is added.

The pinch roll speed detector 21 detects the speed (casting speed) of the pinch roll 9 for extracting the molten steel 2 in the mold 5. The bulging cycle calculator 22 calculates the bulging frequency from the ratio of the speed of the pinch roll 9 (casting speed) detected by the pinch roll speed detector 21 to the pinch roll interval 23.

Further, the set frequency of the disturbance compensator 11 is continuously changed in accordance with the bulging frequency detected by the bulging cycle calculator 22.
Next, the operation of the mold level control device in the continuous casting machine mold of the present embodiment configured as described above will be described.

Here, only the operation of the portions different from those in the first embodiment will be described. 7, the pinch roll speed detector 21 detects the pinch roll 9
Speed (casting speed) is detected.

Then, the bulging cycle calculator 22 calculates
From the ratio between the speed of the pinch roll 9 (the casting speed) from the pinch roll speed detector 21 and the pinch roll interval 23,
The bulging frequency is calculated, and the set frequency of the disturbance compensator 11 is sequentially and continuously changed on-line according to the bulging frequency.

That is, the fluctuation of the bulging water level is a mass balance fluctuation in the mold 5 caused by the lower pinch roll 9 pushing the solidified shell portion expanded at the pinch roll interval 23, and this fluctuation is a slab. Is periodically generated during the time of moving the pinch roll interval 23. Then, according to the actual data measurement result, the passage time of the place where the pinch roll interval 23 is constant and the cycle of the bulging-fluctuation level change substantially coincide.
Therefore, the bulging frequency Fb can be expressed as follows by the speed Vc of the pinch roll 9 and the pinch roll interval 23Bp.

[0076]

(Equation 4)

The bulging cycle calculator 22 can reliably detect the bulging frequency without adding any new equipment by realizing the calculation of the bulging frequency using the equation (4).

As described above, the bulging frequency is calculated from the ratio between the speed of the pinch roll 9 (casting speed) and the pinch roll interval 23, and the set frequency of the disturbance compensator 11 is continuously changed according to the bulging frequency. Thereby, even if the cycle of the bulging-fluid level changes due to a change in the casting speed (drawing speed) as in the unsteady state,
The same operation as that of each of the second and third embodiments can be maintained, and a slab of good quality without powder entrapment can be manufactured.

Therefore, even when the pouring speed changes as in an unsteady state, the same effect as that of each of the second and third embodiments can be maintained. (Fifth Embodiment) FIG. 8 is a sectional view showing a configuration example of a peripheral portion of a mold of a continuous casting machine to which a mold level control device according to the present embodiment is applied. The same reference numerals are given and the description is omitted, and only different portions will be described here.

That is, in the present embodiment, as shown in FIG. 8, an adjustable gain changing device 24 is added to FIG. The adjustable gain changing device 24 receives the control deviation signal (or the level signal), detects the amplitude of the bulging level change from the signal, and adjusts the adjustable gain 12 according to the amplitude. The size is changed.

On the other hand, the value set for the adjustable gain 12 has an upper limit and a lower limit. Here, the upper limit value is obtained from the stability limit of the control system by a root locus method or the like, and the lower limit value is determined by a disturbance suppression rate to be compensated at least as compared with PI control without a disturbance compensator. I do.

FIG. 9 is a block diagram showing a configuration example of the adjustable gain changing device 24. As shown in FIG. As shown in FIG. 9, a disturbance estimator for estimating a control deviation signal (or a level signal) from a disturbance estimation observer or an extraction disturbance such as an inverse characteristic filter of the disturbance to the control deviation (or the level). After input to the filter 25, the signal is input to a filter 26 for extracting a bulging-fluctuation level component.

The control system of the present embodiment is realized so that the control gain can be set by using the output signal of the filter 26 and the control gain table 27 in which the upper and lower limits of the control gain are determined.

As described above, the magnitude of the bulging-fluid level change is determined from the level signal and the magnitude of the adjustable gain applied to the output signal of the disturbance compensator is changed according to the level of the fluctuation. Even in the case where the bulging property level fluctuation increases, the adjustable gain is increased,
Until the flow rate can be adjusted, the same operation as in the first embodiment can be maintained, and a good quality cast piece with less powder entrainment can be manufactured. Therefore, even when the bulging property level fluctuation increases, the same effect as in the case of the first embodiment can be maintained.

[0085]

As described above, according to the apparatus for controlling the level of the molten metal in the continuous casting machine of the present invention, the level gauge for detecting the level of the molten metal in the mold in the continuous casting machine, A PI controller that outputs an opening degree command for a sliding nozzle provided in a tundish based on a deviation signal between a molten metal level and a set molten metal level continuously detected by a surface level meter; Input the opening command output and adjust the opening of the sliding nozzle to adjust the molten metal inflow from the tundish and the deviation signal between the level and the set level. A disturbance compensator having a characteristic of extracting a large bulging property level fluctuation of a cycle and outputting the phase characteristic by advancing the phase characteristic within a predetermined range; and The signal obtained by multiplying the force signal by the adjustable gain is added to the opening command output from the PI controller to obtain the final opening command of the sliding nozzle. Fluctuations in the molten metal level can be efficiently and significantly reduced.

Further, since the bulging frequency which is the cycle of the bulging level change is detected and the set frequency of the disturbance compensator is continuously changed in accordance with the bulging frequency, the bulging is performed as in an unsteady state. Even if the cycle of the change of the casting level changes due to the change of the casting speed (drawing speed), the variation of the bulging level during steady casting can be efficiently and significantly reduced.

Further, the amplitude of the bulging water level fluctuation is detected, and when the fluctuation level of the water level increases, the magnitude of the adjustable gain is increased to the limit of the control system. Even when the fluctuation increases, the bulging property level fluctuation suppressing effect can be maintained up to the limit at which the flow rate can be adjusted.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a configuration example of a peripheral portion of a mold of a continuous casting machine to which a mold level control device according to a first embodiment of the present invention is applied.

FIG. 2 is a block diagram showing a linear model of a mold level control system in a mold according to the present invention.

FIG. 3 is a diagram showing an example of a frequency characteristic of a disturbance compensator according to the present invention.

FIG. 4 is a diagram showing an example of a simulation for explaining the operation and effect of the present invention.

FIG. 5 is a sectional view showing a configuration example of a peripheral portion of a mold of a continuous casting machine to which a mold level control device according to a second embodiment of the present invention is applied.

FIG. 6 is a sectional view showing a configuration example of a peripheral portion of a mold of a continuous casting machine to which a mold level control device according to a third embodiment of the present invention is applied.

FIG. 7 is a cross-sectional view showing a configuration example of a mold peripheral part of a continuous casting machine to which a mold level control device according to a fourth embodiment of the present invention is applied.

FIG. 8 is a sectional view showing a configuration example of a peripheral portion of a mold of a continuous casting machine to which a mold level control device according to a fifth embodiment of the present invention is applied.

FIG. 9 is a block diagram showing a configuration example of an adjustable gain changing device in the mold level control device in the fifth embodiment;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Tundish, 2 ... Molten steel, 3 ... Sliding nozzle, 4 ... Level gauge, 5 ... Mold, 6 ... Immersion nozzle, 7 ... Pull-out direction, 8 ... Actuator, 9 ... Pinch roll, 10 ... PI controller, 11: disturbance compensator, 12: adjustable gain, 18: bulging frequency detector, 19: band-pass filter, 20: FFT analyzer, 21: pinch roll speed detector, 22: bulging cycle calculator, 23: pinch roll Interval, 24: Adjustable gain changing device, 25: Disturbance estimator, 26: Filter, 27: Control gain table.

Continuation of the front page (72) Inventor Hiroyuki Kondo 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nippon Kokan Co., Ltd. (72) Inventor Akira Miyamoto 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nippon Kokan Co., Ltd. (56) References JP-A-9-253818 (JP, A) JP-A-8-243703 (JP, A) JP-A-8-147044 (JP, A) JP-A-5-31560 (JP, A) JP-A-5-23811 (JP, A) JP-A-3-110051 (JP, A) JP-A-4-262845 (JP, A) WO 97/14521 (WO, A1) (58) Fields investigated (Int) .Cl. ⁷ , DB name) B22D 11/18 B22D 11/16 104 G05D 9/12

Claims (5)

(57) [Claims] 1. A controller for controlling the level of molten metal in a mold in a continuous casting machine, comprising: a level gauge for detecting a level of molten metal in the mold; A PI controller that outputs an opening degree command for a sliding nozzle provided in a tundish based on a deviation signal between a continuously detected level and a set level; and a PI output from the PI controller. A sliding nozzle controller that inputs an opening command and adjusts the opening of the sliding nozzle to adjust the amount of inflow of molten metal from the tundish.Specifically, based on a deviation signal between the molten metal level and a set molten metal level. A disturbance compensator having a characteristic of extracting a bulging-fluid level change having a large cycle and outputting the phase characteristic by advancing the phase characteristic within a predetermined range; A signal obtained by multiplying the output signal from the compensator by the adjustable gain is added to the opening command output from the PI controller to obtain a final opening command for the sliding nozzle. A feature of the continuous casting machine mold level control device in the mold. 2. The molten metal level control device in a mold of a continuous casting machine according to claim 1, wherein a signal of the molten metal level continuously detected by the molten metal level meter is used to determine a cycle of the bulging-fluid level. A bulging frequency detecting means for detecting a certain bulging frequency is added, and the set frequency of the disturbance compensator is continuously changed according to the bulging frequency detected by the bulging frequency detecting means. Continuous casting machine Mold level control device in mold. 3. The apparatus for controlling a level of a mold in a continuous casting machine mold according to claim 2, wherein the bulging frequency detecting means includes a signal of a level of the metal continuously detected by the level gauge. A band-pass filter for extracting a signal only in a frequency band in which a bulging property level fluctuation exists;
An FFT analyzer for detecting a bulging frequency by performing T analysis, and a mold level control device in a mold of a continuous casting machine, wherein: 4. The apparatus according to claim 2, wherein, as the bulging frequency detecting means, a speed (a casting speed) of a pinch roll for extracting molten metal in the mold is used as the bulging frequency detecting means. A mold level control device in a mold of a continuous casting machine, wherein a bulging cycle calculator for calculating a bulging frequency from a ratio to a pinch roll interval is used. 5. The level control apparatus according to claim 1, wherein the level of the bulging property is extracted from a level signal continuously detected by the level gauge. A mold level control device in a mold of a continuous casting machine, wherein a magnitude of an adjustable gain to be multiplied by an output signal from the disturbance compensator is changed according to the amplitude.