JPH07299551A - Method and device for controlling molten steel level in mold of continuous casting machine - Google Patents

Abstract

PURPOSE:To provide a method for controlling the molten steel level in a mold of a continuous casting machine capable of excellently keeping the control precision during the operation without the help of an operator and a device to be used in executing the method. CONSTITUTION:Times T1, T2 (T2<T1) are preset, and the first index H1 is calculated based on the fluctuation width of the molten steel level in the time zone from the present to the time T1, and the second index H2 is calculated based on the fluctuation width of the molten steel level in the respective time zones which are obtained by splitting the previous time zone by the time T2. The calculated first index H1 and second index H2 are compared with the corresponding thresholds THD1, THD2, and when the second index H2 is larger than the threshold THD2, the control gain is reduced. When the second index H2 is smaller than the threshold THD2 and the first index H1 is larger than the threshold THD1, the control gain is increased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling a molten metal level in a mold of a continuous casting machine and an apparatus used for implementing the method.

[0002]

2. Description of the Related Art In the continuous casting operation, molten metal (molten metal) is poured into a mold having upper and lower openings, and the molten metal is brought into contact with the water-cooled inner wall of the mold to cool the outer side with a solidified shell. Obtain a coated slab, further cooling while continuously pulling it from the lower opening of the mold, cut into a predetermined dimension after solidification progressed to the inside, in a post-process such as rolling. The procedure is to obtain a product slab as a raw material.

During this operation, various inconveniences such as overflow of molten metal from the mold and breakout which hinder stable operation are prevented in advance to improve the production capacity and to cool and solidify the inside of the mold. In order to stabilize the state and improve the quality of the product slab, the molten metal level control is performed to maintain the molten metal injected into the mold at a predetermined target level.

In the conventional molten metal level control, the molten metal level in the mold is detected, and a proportional-integral-derivative (PID) calculation based on the deviation between the detection result and the target level is used to inject the molten metal into the mold. The amount of opening adjustment of the pouring means (sliding nozzle or the like) is obtained, and feedback control is performed to operate the drive source (hydraulic cylinder or the like) of the pouring means in order to realize this.

However, in this method, for example, as disclosed in Japanese Unexamined Patent Publication No. 62-192246, when the PID calculation gain is increased to improve the control accuracy, the opening degree of the pouring means is adjusted. As a result of being excessively performed, the fluctuation of the molten metal level exceeds the target level, it takes time to settle it, and there is a problem that the control accuracy deteriorates on the contrary.

As one of the molten metal level control methods for solving this, there is an optimal control method proposed by the applicant of the present application in Japanese Patent Laid-Open No. 3-142469. This method uses the state quantity that affects the level of the molten metal, that is, the opening of the pouring means,
The optimum control gain for each of the molten metal level inside the mold and the pouring speed is obtained based on the response characteristic of the opening, the response characteristic of the molten metal level and the evaluation function, and the deviation between the current molten metal level and the target level ( Control deviation) and the detected value of each state quantity, and the opening change amount calculated based on the optimum control gain are controlled.

The optimum control method will be described in detail below. Assuming that the opening X of the pouring means is present, its response characteristic is expressed by the following equation including the opening command U. X _n = a ₁ X _n-1 + a ₂ X _n-2 + b ₁ U _n-1 + b ₂ U _n-2 (11) where a ₁ and a ₂ are constants b ₁ and b at the opening of the response characteristic. ₂ : Constant in response characteristic opening command n: Control timing

The response characteristic of the molten metal level Y inside the mold is expressed by the following equation including the opening X and the pouring speed V. Y _n = c ₁ Y _n-1 + c ₂ Y _n-2 + d ₁ X _n-2 + d ₂ X _n-3 + f ₁ V _n-1 + f ₂ V _n-2 (12) where c ₁ and c ₂ : Constant of response characteristic at molten metal level d ₁ , d ₂ : constant of opening of response characteristic f ₁ , f ₂ : constant of pouring speed of response characteristic

On the other hand, the opening change amount ΔU ^* is the control deviation E
And the amount of change ΔX, ΔY, ΔU, ΔV in the opening X, the molten metal level Y, the opening command U, and the pouring speed V, and the optimum control gains k _{1 to} k ₉ for them are represented by the following equation. It _{^{ΔU * = k 1 E n +}} k 2 ΔY n + k 3 ΔY n-1 + k 4 ΔX n + k 5 ΔX n-1 + k 6 ΔX n-2 + k 7 ΔU n-1 + k 8 ΔV n + k 9 ΔV n-1 ... (13)

[0010] Here, the value of each optimum control gains k ₁ to k ₉ in (13), obtains a state matrix on the basis of the (11) and (12), the control deviation E, the opening command U
And the weighting factor ω, the evaluation function J expressed by the following equation (14) is obtained by solving the Riccati equation so as to minimize it. Then, the opening X, the molten metal level Y, and the pouring speed V are measured, and the operation of the drive source of the pouring means is controlled so that the opening change amount ΔU ^* calculated based on the equation (13) is obtained.

[0011]

[Equation 1]

[0012]

However, in the continuous casting machine, there may be a short period fluctuation in the molten metal level temporarily, and in the conventional casting machine, the fluctuation in the molten metal level may occur. When the control method of No. 2 is applied, there is a problem that this fluctuation continues or increases and stable operation cannot be performed. Therefore, in order to prevent this, the operator increases the stability of the level control by adjusting the value of the control gain. However, if the operation is continued with the adjusted control gain, the response of the control is not sufficient, so good level control accuracy of the molten metal surface cannot be obtained, and the solidification state becomes unstable, and the quality of the product slab deteriorates. Therefore, the readjustment for increasing the control gain has to be performed, and there is a problem that the operation is complicated.

The present invention has been made in view of the above circumstances, and its purpose is to change to an optimum control gain according to the fluctuation state of the molten metal level so that the operator can operate without depending on the operator. It is an object of the present invention to provide a method for controlling a molten metal level in a continuous casting machine mold capable of maintaining good control accuracy and an apparatus used for implementing the method.

[0014]

A molten metal level control method in a continuous casting machine mold according to a first aspect of the invention detects a molten metal level in a mold and uses a control gain obtained based on the detected value. In the method of controlling the molten metal surface level in the continuous casting machine mold, the control gain is reduced when the fluctuation width of the cycle shorter than the predetermined time T ₂ is a predetermined value or more based on the detected fluctuation of the molten metal level. , The control gain is increased when the fluctuation range of the period from time T ₁ (T ₁ > T ₂ ) to time T ₂ is equal to or larger than a predetermined value.

A method for controlling a molten metal level in a continuous casting machine mold according to the second aspect of the invention detects a molten metal level in the mold and uses a control gain obtained based on the detected value to control the molten metal level in the continuous casting machine mold. In the method of controlling the molten metal level, the first index is calculated based on the fluctuation range of the molten metal level in the time domain from the present to the time T ₁ before, and the time domain is set to the time T
The second index is calculated based on the fluctuation range of the molten metal level in each time region divided into ₂ (T ₂ <T ₁ ), and the calculated first index and second index and the threshold values corresponding to each are calculated. In comparison, when the second index is larger than the corresponding threshold value, the control gain is decreased, when the second index is smaller than the corresponding threshold value, and when the first index is larger than the corresponding threshold value, the control gain is increased. It is characterized by doing.

According to a third aspect of the present invention, there is provided a method for controlling a molten metal level in a casting mold according to the first and second inventions, wherein the times T ₁ and T ₂ correspond to variations in the molten metal level in various cycles. It is characterized in that it is determined based on the control effect when different control gains are applied.

The molten metal level control device in the continuous casting machine mold according to the fourth aspect of the invention detects the molten metal level in the mold, and uses the control gain obtained based on the detected value to control the molten metal level in the continuous casting machine mold. an apparatus for controlling a molten metal surface level, based on the variation of the detected molten metal surface level, variation in a period shorter than the predetermined time T ₂ width and the time _{T 1 (T 1> T 2} ) from the period between time T ₂ A fluctuation range calculating means for calculating the fluctuation range, a comparing means for comparing each fluctuation range calculated by the fluctuation range calculating means with a corresponding predetermined value, and a time T based on the result of the comparing means. Control gain adjustment for decreasing the control gain when the fluctuation width of the cycle shorter than ₂ is a predetermined value or more, and for increasing the control gain when the fluctuation width of the cycle between time T ₁ and time T ₂ is the predetermined value or more And means.

The molten metal level control device in the continuous casting machine mold according to the fifth aspect of the invention detects the molten metal level in the mold, and uses the control gain obtained based on the detected value to control the molten metal level in the continuous casting machine mold. In a device for controlling the level of molten metal, a first index calculating means for calculating a first index based on the fluctuation range of the level of molten metal in the time region from the present to the time T ₁ before, and T ₂ ( Second index calculation means for calculating the second index based on the fluctuation range of the molten metal level in each time region divided into T ₂ <T ₁ ) and the first index and the second index calculated by both index calculation means Comparing means for comparing the index with the threshold value corresponding to each index, and if the second index is larger than the corresponding threshold value, the control gain is reduced to the second value.
When the index is smaller than the corresponding threshold value and the first index is larger than the corresponding threshold value, the control gain adjusting means for increasing the control gain is provided.

[0019]

FIG. 1 is a graph showing the results of simulating the control effect when different control gains are applied to the fluctuations in the molten metal level in various cycles. In FIG. 1, the horizontal axis represents the fluctuation period from the long cycle to the short cycle, and the vertical axis represents the control effect as (variation width during control / variation width during non-control). Therefore, the smaller the value of this ratio, the higher the control effect. The broken line shows the case where a small value control gain is applied, and the solid line shows the case where a large value control gain is applied. As is clear from FIG. 1, when the cycle of fluctuation of the molten metal level is longer than the time T _1, this can be almost completely eliminated regardless of the magnitude of the control gain.

The control effect gradually decreases as the cycle of fluctuations in the molten metal level becomes shorter than the time T _1. However, the decrease curve of the control effect is smaller when the control gain having a larger value is applied than when the smaller value is applied. It is loose. On the other hand, when the control gain with a small value is applied, the control effect decreases substantially linearly as the cycle of fluctuations in the molten metal level decreases, and on the longer cycle side than when a control gain with a large value is applied. Although its control effect is about 1.0, it maintains that state even when the fluctuation cycle becomes shorter. On the other hand, when a large value of the control gain is applied, the control effect is reduced to the same degree (approximately 1.0) as when a small value of the control gain is applied at time T ₂ on the short cycle side, and the cycle Is shorter than time T _{2, the} control effect is further deteriorated.

Therefore, based on the detected value of the molten metal level,
When the fluctuation width of the cycle shorter than the time T ₂ is equal to or larger than the predetermined value, the control gain is reduced. As a result, fluctuations in the molten metal level are eliminated while suppressing a decrease in control effect. And
When the fluctuation range of the period from time T ₁ to time T ₂ is equal to or larger than the predetermined value, the control gain is increased. This increases the control effect. If neither, the control gain is determined to be appropriate, and the above-described change is not performed.

On the other hand, the time region from the present time to the time T ₁ before is divided into second time periods T ₂ , and the second index is calculated based on the fluctuation range of the molten metal level in each time region. As a result, an index relating to the fluctuation range having a cycle shorter than the time T ₂ can be obtained. Then, the second index is compared with a threshold value set in advance, and when the second index is larger than the threshold value, it is determined that the fluctuation of the molten metal level is often in a cycle shorter than the time T ₂ , Reduce the control gain.

The time T from the present₁In the previous time domain
Calculate the first index based on the fluctuation range of the molten metal level
It By this, the time T₁The fluctuation range of the shorter cycle
The index to do is obtained. And the second index corresponds to it
If it is smaller than the threshold value,
Compared with the set threshold, the first index is larger than the threshold.
If it is not, the fluctuation of the level of the molten metal is time T₂Shorter period
There are few things, time T ₁It is determined that there are many shorter cycles
Turn off and increase the control gain.

When both the first index and the second index are smaller than the corresponding threshold values, the current control gain is considered to be appropriate and the same control gain as the current is set. This makes it possible to easily obtain the level information required for control without detailed analysis of changes in the level.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to the drawings showing the embodiments thereof. FIG. 2 is a schematic diagram of a continuous casting machine according to the present invention and a block diagram showing its control system.
Is a tundish in which the molten metal 3 is stored.
Below the tundish T, a mold M having upper and lower openings is arranged at a predetermined distance, and inside the mold M,
On the bottom surface of the tundish T, an immersion nozzle 4 having a base end opened is extended. Molten metal 3 in tundish T
Is injected into the mold M through the immersion nozzle 4, cooled by contact with the inner wall of the mold M, and becomes a slab 5 coated with the solidified shell 50 on the outer side. By the rotation, the mold M is continuously drawn out and further cooled, and further solidified to the inside, and then cut into an appropriate size to obtain a product slab.

In the middle of the dipping nozzle 4, there is a sliding nozzle 7 for opening and closing the dipping nozzle 4 by moving the gate plate 7a in a plane substantially orthogonal to the longitudinal direction of the dipping nozzle 4 to adjust the amount of molten metal poured into the mold M. It is fixed. The gate plate 7a is connected to the tip of the output rod of the hydraulic cylinder 8, and the opening degree of the sliding nozzle 7 is adjusted by moving the gate plate 7a by moving the hydraulic cylinder 8 forward and backward.

The opening of the sliding nozzle 7 adjusted as described above is detected by an opening detector attached to the hydraulic cylinder 8.
Detected by 70 through the retracted position of the output rod. In addition, injected through the sliding nozzle 7,
The level of the molten metal 3 staying inside the mold M is detected by a level detector 30 arranged facing the molten metal 3. Further, the pinch rolls 6 and 6 that apply a drawing force to the slab 5 are provided with a pouring speed detector 60 that detects the pouring speed of the molten metal 3 through the number of rotations thereof.

The molten metal level inside the mold M detected by the level detector 30, the pouring speed detected by the pouring speed detector 60, and the nozzle opening of the sliding nozzle 7 detected by the opening detector 70 are It is given to the opening degree control unit 1 together with a target level that is a control target. The opening control unit 1 calculates the opening of the sliding nozzle 7 for realizing the target level based on each detected value and the target level, and controls the cylinder with the calculation result as the opening command. Give to part 2.

The cylinder controller 2 also includes an opening detector 70.
The opening degree of the sliding nozzle 7 detected by the opening control section 1 is applied to the cylinder control section 2.
The deviation between the opening degree command given by the above and the nozzle opening degree of the sliding nozzle 7 is calculated, and an operation command is issued to the hydraulic cylinder 8 to eliminate the deviation. Then, the hydraulic cylinder 8 moves forward and backward in response to this operation command to open and close the gate plate 7a to adjust the opening of the sliding nozzle 7.

FIG. 3 is a block diagram showing the configuration of the opening control unit 1 shown in FIG. 2, and FIG. 4 is a flow chart showing the operation procedure of the opening control unit 1. The molten metal level Y is given to the frequency component calculating unit 12 of the opening control unit 1, and the fluctuation range of the molten metal level at each control timing is calculated as described later (step S1). Further, the frequency component calculation unit 12 is previously given a first time T ₁ and a second time T ₂ (T ₁ > T ₂ ) obtained by a simulation as described later, and the first time T ₁ before the present time Up to (first section) the fluctuation level H ₀ of the molten metal level Y, the first section to the second
A second level fluctuation index H ₂ that is the average value of the fluctuation range in a plurality of second sections divided for each time T ₂ , and a ratio between the fluctuation range H ₀ and the second level fluctuation index H ₂ . Level change index H
₁ is calculated (step S2), and this is given to the control gain selection unit 13. It should be noted that the first representing these fluctuating frequency components
The level variation index H ₁ and the second level variation index H ₂ are calculated every second time T ₂ .

The control gain selector 13 has a plurality of weighting factors ω.
And a table having optimum control gains k _{1 to} k ₉ for each weighting factor ω, and thresholds THD ₁ and THD ₂ corresponding to the _first molten metal level variation index H ₁ and the second molten metal level variation index H ₂ in advance. It is set, and the control gain selection unit 13 compares the _second molten metal level variation index H ₂ with the threshold value THD ₂ (step S
3) If H ₂ ≧ THD ₂ , as shown in Table ₁ below, select the optimum control gains k _{1 to} k ₉ calculated with the weighting factor ω being one point smaller (step S4), It is given to the opening change amount calculation unit 10.

On the other hand, when H ₂ <THD ₂ , the first molten metal level variation index H ₁ is further compared with the threshold value THD ₁ (step S 5), and when H ₁ ≧ THD ₁ , the weight is calculated. The optimum control gains k _{1 to} k ₉ calculated with the coefficient ω larger by one point are selected (step S6), and H ₁ <T
If it is HD ₁ , the current optimum control gains k _{1 to} k
₉ is selected (step S7), and the opening change amount calculation unit 1 is selected.
Give to 0. The threshold value THD ₁ is a value of 1.1 to 5.0, and is changed according to the fluctuation range H ₀ of the molten metal level Y from the present time to the first time T ₁ before, as described later. See also THD ₂
Is the maximum fluctuation range of the molten metal level when the control gain is appropriate in the section excluding the section in which short-cycle fluctuations occur temporarily.

[0033]

[Table 1]

The opening change amount calculation unit 10 includes a molten metal level Y,
The pouring speed V, the opening degree command U, and the nozzle opening degree X are given together with the target level, and the opening degree change amount calculation unit 10 uses the optimum control gains k _{1 to} k _{9 in the} following equation (1). Is updated to the value given by the control gain selection unit 13 (step S8) to calculate the nozzle opening change amount ΔU ^* (step S9), which is given to the opening command correction unit 11. The opening command correction unit 11 outputs a new opening command U obtained by adding the nozzle opening change amount ΔU ^* to the opening command U to the cylinder control unit 2 (see FIG. 2) (step S10). . ^{_{ΔU * = k 1 E n +}} k 2 ΔY n + k 3 ΔY n-1 + k 4 ΔX n + k 5 ΔX n-1 + k 6 ΔX n-2 + k 7 ΔU n-1 + k 8 ΔV n + k 9 ΔV n-1 ... (1) where E: Control deviation ΔX: Change amount of nozzle opening X ΔY: Change amount of molten metal level Y ΔU: Change amount of opening command U ΔV: Change amount of pouring speed V k _{1 to} k ₉ : Optimal control gain n: control timing

As a result, when a short period fluctuation occurs in the molten metal level, the optimum control gain k is increased in a direction in which the stability of control is increased in response to the fluctuation.
_{1 to} k ₉ are sequentially updated, and the fluctuation is eliminated while the control accuracy is maintained at a high level. Then, as the fluctuation is eliminated, the optimum control gains k ₁ to k ₉ are sequentially updated in the direction in which the control response is high, that is, in the direction in which the weighting factor ω is large, and the control accuracy is improved.

Next, a method for obtaining the first time and the second time will be described in detail. FIG. 5 is a block diagram showing the configuration of the simulation apparatus, and reference numeral 21 in the figure is an opening change amount calculation unit. The opening change amount calculation unit 21 includes a target level, an opening command U, a pouring speed V, a nozzle opening X, and a molten metal level Y _D.
Is entered. The opening change amount calculation unit
The above-mentioned expression (1) is set in 21. The opening change amount calculation unit 21 substitutes each input value into the expression (1) to calculate the nozzle opening change amount ΔU ^* , and adds it. Output to the container 22.

The output of the opening command U, which is the output of the adder 22, is fed back to the adder 22, and a new opening command obtained by adding the above-mentioned nozzle opening change amount ΔU ^* to the opening command U is added. U is the opening calculation unit 24 of the process simulation unit 23
And outputs it to the opening degree change amount calculation unit 21 described above. The opening degree calculation unit 24 calculates the nozzle opening degree X by the following equation (2) based on the opening degree command U, and uses it to calculate the molten metal level calculation unit.
It is output to 25 and is given to the opening degree change amount calculation unit 21. X _n = a ₁ X _n-1 + a ₂ X _n-2 + b ₁ U _n-1 + b ₂ U _n-2 (2) where a ₁ and a ₂ are constants b ₁ and b in the opening of the response characteristic ₂ : Constant in response command opening command

The pouring speed V is further supplied to the molten metal level calculation unit 25.
Is calculated, and the molten metal level Y is calculated by the following equation (3) and output to the adder 26. Y _n = c ₁ Y _n-1 + c ₂ Y _n-2 + d ₁ X _n-2 + d ₂ X _n-3 + f ₁ V _n-1 + f ₂ V _n-2 (3) where c ₁ and c ₂ : Constant of response characteristic at molten metal level d ₁ , d ₂ : constant of opening of response characteristic f ₁ , f ₂ : constant of pouring speed of response characteristic

Disturbances D of various frequencies are applied to the adder 26, and the molten metal level Y _D obtained by adding the molten metal level Y and the external disturbance D is output and the opening degree change calculation is performed. Give to part 21. Then, the graph of FIG. 1 described above is obtained by performing a simulation in the following procedure.

The disturbance D having a constant period is given to the adder 26 to obtain the fluctuation range of the molten metal level Y _D which is the output value of the process simulating unit 23. Next, the period of the disturbance D is variously changed to obtain the fluctuation range of the molten metal level Y _D. Furthermore, the above-mentioned equation (2),
Optimal control gains k _{1 to} k calculated based on the following expression (4), which is an evaluation function including the expression (3) and the weighting factor ω.
₉ by changing the value of the weighting factor ω to obtain a plurality of weighting factors ω and the optimum control gain k related to the weighting factors ω.
A table having _{1 to} k ₉ is prepared in advance, and the optimum control gains k _{1 to} k ₉ of the above-described formula (1) are sequentially changed to obtain the fluctuation range of the molten metal level Y _D as before. Meanwhile (1) obtaining a fluctuation range of the molten metal surface level Y _D in the non-control by an optimum control gain k ₁ to k ₉ zero in formula. When these are arranged, the graph of FIG. 1 is obtained.

[0041]

[Equation 2]

In FIG. 1, the weighting coefficient ω whose value is small
Two intersections of the curve (solid line) to which is applied and the curve (broken line) to which a large weighting factor ω is applied are obtained. And among the two intersections, the period of the intersection of the short cycle side and the second time T _2, the closest period to the first hour T ₁ to another intersection of the two curves at an integer multiple of the second hour T _2.

Next, the above-mentioned first level variation index H₁And the
2 Level change index H₂The method for obtaining is detailed. Present
First time T from now₁Each control timing (n, n
-1, ..., n-A + 1; A = T₁/ T, t is the control cycle)
Level Y at_n~ Y _{n-A + 1}As shown in Table 2 below
I mean, the maximum value F_maxAnd the minimum value F_minAsk for.

[0044]

[Table 2]

Levels Y _{n to} Y in Table 2
_{n-A + 1} is divided every second time T ₂ , and the molten metal surface levels Y _{n to} Y _{n-B + 1} , Y _{nB to} Y _{n-2B + 1} , ..., Y _n-A are divided. _{+ B}
~ Y _{n-A + 1} (B = T ₂ / t) maximum value G _max 1,
_{G max 2, ..., G max} m, the minimum value _{G mi n 1, G min 2} ,
, G _min m are respectively obtained (m = T ₁ / T ₂ ). Then, the first molten metal level variation index H ₁ and the second molten metal level variation index H ₂ are obtained by the following equations (5) and (6).

[0046]

[Equation 3]

Next, the result of the comparative test will be described. FIG. 6 is a graph showing the results of comparing the fluctuation level of the molten metal level between the method of the present invention and the conventional method under the same conditions. FIG. 6A shows the result of the method of the present invention, and FIG. 6B shows the result of the conventional method. In addition, in the continuous casting machine used for the comparative test,
The threshold value THD ₂ according to the method of the present invention is 4.0, and the threshold value TH
D ₁ is changed according to the value of the deviation H ₀ described above.

FIG. 7 is a graph showing the relationship between the value of the threshold value THD ₁ and the deviation H ₀ in the continuous casting machine used in this test. As shown in FIG. 7, the value of the threshold value THD ₁ is decreased as the deviation H ₀ increases.

As is apparent from FIGS. 6 (a) and 6 (b), the level fluctuation of ± 3.0 mm occurs in the conventional method, whereas the level fluctuation in the method of the present invention is approximately ½ of that, ± 1.5 mm. mm, and the control accuracy was improved about twice.

[0050]

As described in detail above, in the molten metal level control method for the continuous casting machine according to the first aspect of the invention, the fluctuation of the cycle shorter than the time T ₂ is predetermined based on the detected fluctuation of the molten metal level. If there is more than the above, the control gain is reduced and time T
_When the fluctuation of the cycle from ₁ (T ₁ > T ₂ ) to the time T ₂ is more than a predetermined value, the control gain is increased. Therefore, the control gain according to the cycle of fluctuation of the molten metal level is not required by the operator. Automatically, the control accuracy is kept good during operation.

Level control of the level of the continuous casting machine according to the second aspect of the invention.
According to the method, time T from now ₁Previous time domain
Calculates the first index based on the fluctuation range of the molten metal level
Then, the time domain is set to time T₂Each divided into
The second finger based on the fluctuation range of the molten metal level in the time domain
Since the target is calculated, the index corresponding to the present invention can be easily calculated.
Also, the calculation speed is fast.

In the molten metal level control method for the continuous casting machine according to the third aspect of the invention, the control gains having different values are applied to the times T ₁ and T ₂ with respect to the variation of the molten metal level in various cycles. Since it is determined based on the effect of control in case, both times can be appropriately determined corresponding to each mold of the continuous casting machine,
Control accuracy is improved.

Level control of the continuous casting machine according to the fourth aspect of the invention
The control device is based on the detected fluctuation of the molten metal level.
And a predetermined time T₂Fluctuation width of shorter cycle and time T₁
(T ₁> T₂) To time T₂Calculate the fluctuation range of the period between
Fluctuation range calculating means and the fluctuation range calculating means
Ratio that compares each fluctuation range with the corresponding predetermined value
The comparing means and the time T based on the result of the comparing means.₂Than
If the fluctuation width of a short cycle is more than a predetermined value, the control gain
The time T₁From time T₂Interval fluctuation range
Is greater than a predetermined value, the control gain is increased.
Since it has a gain adjustment means, it does not depend on the operator.
In addition, the control gain according to the cycle of fluctuations
It is dynamically changed, and good control accuracy is maintained during operation.

Level control of the continuous casting machine according to the fifth aspect of the invention
The device has a preset time T from now.₁Until before
Based on the fluctuation range of the molten metal level in the time domain of
A first index calculation means for calculating an index and the time domain
Time T₂(T₂<T ₁) Each of them
Based on the fluctuation range of the molten metal level in the time domain,
Since the second index calculation means for calculating the two indexes is provided,
The index corresponding to the invention is easily calculated, and the calculation speed is also
The degree is fast.

[Brief description of drawings]

FIG. 1 is a graph showing a result of simulating a control effect when control gains having different values are applied to fluctuations of a molten metal level in various cycles.

FIG. 2 is a schematic diagram of a continuous casting machine according to the present invention and a block diagram showing its control system.

FIG. 3 is a block diagram showing a configuration of an opening control section shown in FIG.

FIG. 4 is a flowchart showing an operation procedure of an opening degree control unit.

FIG. 5 is a block diagram showing a configuration of a simulation device.

[Fig. 6] The method of the present invention and the conventional method are carried out under the same conditions,
It is a graph which shows the result of having compared the fluctuation state of the molten metal level in both.

FIG. 7: Threshold TH in the continuous casting machine used in this test
Is a graph showing the relationship between the value and the deviation H ₀ of D _1.

[Explanation of symbols]

 1 Opening control unit 2 Cylinder control unit 3 Molten metal 4 Immersion nozzle 5 Cast slab 6 Pinch roll 7 Sliding nozzle 8 Hydraulic cylinder 30 Level detector 60 Casting speed detector 70 Opening detector M Mold T Tundish

Claims (5)

[Claims] 1. A method of controlling the level of molten metal in a continuous casting machine mold by detecting the level of molten metal in the mold and using a control gain obtained based on the detected value. Based on the predetermined time T ₂
When the fluctuation width of a shorter cycle is equal to or larger than the predetermined value, the control gain is reduced to change the time T ₁ (T ₁ > T ₂ ) to the time T.
_A method for controlling a molten metal level in a continuous casting machine mold, wherein the control gain is increased when the fluctuation width of the cycle between the _two is greater than or equal to a predetermined value. 2. A method for controlling the molten metal level in a continuous casting machine mold by detecting the molten metal level in the mold and using the control gain obtained based on the detected value, from the present to the time before T _1. The first index is calculated based on the fluctuation range of the molten metal level in the time domain, and the fluctuation range of the molten metal level in each time domain obtained by dividing the time domain into time T ₂ (T ₂ <T ₁ ). A second index is calculated based on the calculated first index and the second index, and the respective threshold values are compared. If the second index is larger than the corresponding threshold value, the control gain is decreased, A molten metal level control method in a continuous casting machine mold, wherein the control gain is increased when the index is smaller than the corresponding threshold value and the first index is larger than the corresponding threshold value. 3. The method according to claim ₁ , wherein the times T ₁ and T ₂ are determined on the basis of the effect of control when different control gains are applied to fluctuations in the molten metal level in various cycles. Continuous casting machine level control method in casting mold. 4. A device for controlling the molten metal level in the continuous casting machine mold by detecting the molten metal level in the mold and using the control gain obtained based on the detected value, the fluctuation of the detected molten metal level. Based on the predetermined time T ₂
A fluctuation range calculating means for calculating a fluctuation range of a shorter cycle and a fluctuation range of a cycle from time T ₁ (T ₁ > T ₂ ) to time T ₂ , and a fluctuation range calculated by the fluctuation range calculating means. Based on the result of the comparing means for comparing the respective predetermined values with each other, if the fluctuation width of the cycle shorter than the time T _{2 is} more than the predetermined value, the control gain is reduced to change from the time T _1. A molten metal level control device in a continuous casting machine mold, comprising: a control gain adjusting means for increasing the control gain when the fluctuation width of the cycle between times T ₂ is equal to or greater than a predetermined value. 5. An apparatus for controlling the level of molten metal in a continuous casting machine mold by detecting the level of molten metal in the mold and using the control gain obtained based on the detected value, from the present to the time before T _1. First index calculating means for calculating the first index on the basis of the fluctuation range of the level of the molten metal in the time domain, and the hot water in each time domain obtained by dividing the time domain by time T ₂ (T ₂ <T ₁ ). Second index calculation means for calculating the second index based on the fluctuation range of the surface level, comparison means for comparing the first index and the second index calculated by both index calculation means with respective threshold values, If the second index is larger than the corresponding threshold value, the control gain is reduced, and the second index is smaller than the corresponding threshold value.
A molten metal level control device in a continuous casting machine mold, comprising: a control gain adjusting means for increasing the control gain when the index is larger than a corresponding threshold value.