JPH0462828B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a technology for controlling the amount of molten steel supplied, and particularly to a technology for accurately and stably maintaining the liquid level of molten steel in a mold during continuous casting of molten steel.

(Prior Art) Casting of a steel billet by a continuous casting method is performed by continuously drawing a cast steel billet from a mold while pouring molten steel into the mold. At this time, it is extremely important to maintain the level of molten steel in the mold at a constant value in order to prevent inclusions from being caught in the molten steel and to improve the quality of the cast slab. In order to maintain a constant level of molten steel in the mold, it is necessary to establish a technique for accurately controlling the amount of molten steel supplied from a tundish containing molten steel to the mold.

FIG. 1 is a block diagram showing a conventional molten steel supply amount control system in continuous casting equipment that uses a sliding nozzle as a flow rate adjustment mechanism for regulating the amount of molten steel supplied from a tundish to a mold.

In the illustrated continuous casting equipment, molten steel 2 in a tundish 1 is supplied to a mold 4 via a sliding nozzle 3. As the cast billet 5 is continuously withdrawn from the mold 4, a corresponding amount of molten steel 2 is supplied through the sliding nozzle 3 to maintain a constant level of molten steel in the mold 4. . At this time, the opening degree of the nozzle 3 is adjusted by the hydraulic cylinder 6.

Now, the molten steel supply amount control system in the illustrated facility is configured as follows. Molten steel liquid level meter 7
Based on the molten steel level value measured via the detection head 7a and the cylinder position detected by the cylinder rod position detector 8, the calculator 9 calculates an output corresponding to the target opening value of the sliding nozzle 3. The cylinder position detected by the detector 8 corresponds to the opening degree of the nozzle 3. Arithmetic unit 9
The output and cylinder position are input to the servo amplifier 10. Based on these, the servo amplifier 10 drives the hydraulic cylinder 6 to control the opening of the nozzle 3 to the target opening value, thereby stabilizing the level of molten steel in the mold 4. The computing unit 9 is a PID computing unit that performs proportional-integral-differential operation (PID operation), and generally enables accurate control.

However, although the calculator 9 outputs a calculated value corresponding to the nozzle opening degree target value, the opening degree of the nozzle 3 does not accurately follow this. In other words, when the output of the calculator changes, the opening of the nozzle 3 does not respond quickly, and the relationship between the amount of change in the output of the calculator and the amount of change in the opening of the nozzle 3 has a considerable deviation from a perfectly proportional relationship. can be seen.

The graph in FIG. 2 shows this relationship. In the figure, the horizontal axis (x) indicates the computing unit output amplitude, that is, the amount of change in the computing unit output, while the vertical axis (y) indicates the sliding nozzle opening amplitude, that is, the change in nozzle opening that corresponds to the above variation. It shows the amount.
As shown in the figure, when the amount of change in the arithmetic unit output is within ±a%, the amount of change in the nozzle opening accompanying this remains within an extremely small range of ±b%. However, when the change in the arithmetic unit output exceeds ±a%, the nozzle opening rapidly changes accordingly.
That is, the relationship between the change in the output of the computing unit and the change in the nozzle opening is non-linear, and when the output of the computing unit changes, the nozzle opening follows it with a certain delay, that is, with a hysteresis characteristic.

Figure 3 shows the nonlinearity of the change in nozzle opening (Y) when the arithmetic unit output shown on the horizontal axis (X) increases from a constant value c to d and then decreases from this value d to c. , which schematically shows the hysteresis characteristic.

The following two factors are considered to be the main causes of the above-mentioned hysteresis characteristic, that is, nonlinear responsiveness, of the sliding nozzle 3. One is the play that occurs in the transmission mechanism 6a that transmits the movement of the hydraulic cylinder 6 to the sliding nozzle 3, that is, the play that occurs between the nozzle 3 and the cylinder.The other is the play that occurs between the nozzle 3 and the cylinder. Fixed plate 3 to decide
This is the operating resistance between a and the slide plate 3b. In other words, the play generated in the transmission mechanism 6a absorbs the movement of the cylinder 6, so that the opening degree of the nozzle 3 does not sufficiently follow the movement of the cylinder 6, and the operation of the nozzle 3 is delayed. Further, the opening degree of the nozzle 3 is determined by the size of the matching portion of the through holes formed in the slide plate 3a driven by the cylinder 6 via the transmission mechanism 6a and the upper and lower fixed plates 3a that sandwich this. However, if the operating resistance between the slide plate 3b and the fixed plate 3a is large, the operation of the cylinder 6 will no longer follow the control signal output from the calculator 9.

In the device shown in Fig. 1, the sliding nozzle 3
Conventionally, an excitation signal is superimposed on the output value of the calculator 9 in order to compensate for the above-mentioned hysteresis characteristic of the nozzle 3 and to match the time average of the opening degree of the nozzle 3 with the target value calculated by the calculator 9. It has been carried out since. That is, a square wave signal having a constant period and amplitude is generated by an oscillation circuit, and this is superimposed on the output of the arithmetic unit 9 as an excitation signal, thereby controlling the cylinder 6. Therefore, the opening degree of the nozzle 3 is controlled to oscillate around the target value calculated by the calculator 9.
The nonlinear characteristics of molten steel 2 are compensated for, and the supply amount of molten steel 2 is accurately controlled to a desired value.

FIG. 4 shows the calculated value A of the calculator 9 when the molten steel level is controlled by such a method.
1. Excitation signal B1 generated by the oscillation circuit, calculated value A
A graph showing temporal changes in the controller signal C1 obtained by superimposing the excitation signal B1 on the controller signal C1, the opening degree D1 of the sliding nozzle 3 driven by the hydraulic cylinder 6, and the molten steel level E1 in the mold 4. It is. ±3 to the calculated value A1 of the calculator 9
% vibration with a constant period and amplitude (A1+B1), and set this as the controller signal C1 to the servo amplifier 10.
By inputting, the opening degree D1 of the nozzle 3 is ±
It is vibrated around the target value with an amplitude of 3%, and as a result, the molten steel level E1 in the mold 4 is kept extremely stable with fluctuations within ±1.5 mm.

(Problems to be Solved by the Invention) However, even with such control using an excitation signal, the level of molten steel may not be constant.
FIG. 5 shows an investigation of changes in each quantity corresponding to the quantities shown in FIG. 4 in order to investigate the cause. In the case of FIG. 5, the calculated value A2 of the calculator 9 shows a considerable change over time, and as a result of superimposing the excitation signal B2 having the same characteristics as in FIG. The opening degree D2 of 3 is ±
It fluctuates irregularly at 5%. For this reason, the molten steel level within the mold 4 also varies within a range of ±4 mm and is unstable.

The reason why the supply amount of molten steel is not constant and the molten steel level in the mold 4 is unstable is considered to be as follows.

As already described in connection with FIGS. 2 and 3, the opening degree of the nozzle 3 has a nonlinear response characteristic to the control signal. That is, if the change in the value of the control signal corresponding to the output value of the arithmetic unit shown in FIG. 2 is within ±a%, the nozzle opening degree will not sufficiently follow this change. However, this numerical value a has a different value for each sliding nozzle cassette, which is composed of the sliding nozzle 3, the cylinder 6 that drives it, and the transmission mechanism that connects these two, and also varies depending on the usage time of the cassette. Change.

On the other hand, the excitation signal B2, which is superimposed to compensate for the nonlinear response of the nozzle 3, is always fixed at a constant period and amplitude. Therefore, when the above value a becomes larger than a certain level, the nonlinear characteristics of the nozzle 3 will not be sufficiently compensated for by the excitation signal B2 whose characteristics are fixed, and depending on the amplitude of the arithmetic unit A2 output from the arithmetic unit 9 This results in the nozzle opening oscillating irregularly. In such a case, the superimposition of the excitation signal B2 has the opposite effect, and the molten steel level E2 in the mold becomes unstable. The reason why the change range a of the control signal with a slow response of the nozzle 3 increases is due to the nonlinearity described in connection with FIGS. 2 and 3, that is, the transmission mechanism that connects the cylinder 6 and the nozzle 3. This is thought to be due to backlash that occurs in the nozzle 3 and changes over time in the operating resistance of the nozzle 3.

Therefore, the problems of the prior art that the present invention aims to solve can be summarized as follows.

In continuous casting equipment, the amount of molten steel supplied as a fluid is controlled by a sliding nozzle or the like that constitutes a flow control mechanism. At this time, in order to compensate for the nonlinear characteristics of the response of the sliding nozzle to the control signal for the opening degree, a method has traditionally been adopted in which an excitation signal is superimposed on the control signal to cause the opening degree to oscillate around the target value. . However, because the characteristics of this excitation signal, that is, the period and amplitude, are fixed, it is not possible to deal with the fact that the nonlinear characteristics of the flow rate adjustment mechanism differ from mechanism to mechanism and change over time.
Therefore, the amount of fluid supplied tends to become unstable. In continuous casting equipment, this means unstable fluctuations of the molten steel in the mold, posing extremely serious problems in terms of safety and quality control.

(Means and actions for solving the problem) The reason why the amount of molten steel supplied by the sliding nozzle in conventional continuous casting equipment is not constant and the molten steel level in the mold is unstable is due to sliding. Assuming that the nonlinear characteristics of the nozzle cassettes vary from one cassette to another and change over time for each cassette, the following method can be considered as a solution to the problems of the prior art. That is,
In order to compensate for the nonlinear characteristics of each cassette, the characteristics of the superimposed sliding nozzle excitation signal, that is, the period and amplitude, are changed as necessary to optimally compensate for the nonlinear characteristics of each cassette.

One of the various experiments conducted to confirm this
Examples are shown in FIGS. 6 and 7.

FIG. 6 shows the change in the fluctuation range of the molten steel level E when the amplitude of the excitation signal B superimposed on the calculated value of the calculator 9 is changed. In the figure, the amplitude of excitation signal B is the calculated value A to be superimposed.
It is expressed as a percentage of

On the other hand, FIG. 7 shows the results of an investigation conducted to confirm that when the nozzle opening degree D changes irregularly, the molten steel level E changes particularly severely. Focusing on the fact that the change in the opening degree D of the nozzle 3 is directly reflected in the displacement of the cylinder rod 6b coupled to the slide plate 3b of the nozzle 3, that is, the cylinder stroke, the amplitude of the excitation signal B is kept at a constant value of 4%. The relationship between the cylinder stroke amplitude and the fluctuation width of the molten steel level was investigated. As can be seen from the figure, the molten steel level E is unstable when the amplitude of the cylinder stroke is small with respect to the amplitude (4%) of the excitation signal B and shows irregular changes.

Therefore, specific means for solving the problems according to the present invention can be summarized as follows.

The control method of the present invention is a method of controlling the supply amount of molten steel by adjusting the opening degree of a sliding nozzle during continuous casting of molten steel, in which the opening degree is oscillated around a predetermined value when supplying molten steel, and
A method for controlling the amount of molten steel supplied, characterized by changing the amplitude and period of the vibration of the opening degree so as to maintain the liquid level at a predetermined value based on a measured value of the level of the supplied molten steel. It is.

That is, the method of the present invention is a fluid supply amount control method in which the opening degree of a flow rate regulating mechanism having a nonlinear response characteristic is controlled by excitation to compensate for the nonlinear characteristic. and an amount corresponding to the average supply of fluid by varying the amplitude to an optimal value depending on the nonlinear characteristics of the mechanism,
In other words, the molten steel liquid level is stably maintained at the target value.

More specifically, in controlling the amount of molten steel supplied by a sliding nozzle in continuous casting equipment for billets, the present invention adjusts the amplitude and period of the excitation signal of the nozzle opening to the point at which the molten steel liquid level is most stable. This automatically changes the value to the optimum value according to the characteristics of the nozzle.

Further, the control device according to the present invention includes a sliding nozzle that adjusts the amount of molten steel supplied by the opening degree, a molten steel liquid level meter that measures an amount corresponding to the average amount of molten steel supplied, and the molten steel liquid level. a calculation means for calculating a target opening degree of the sliding nozzle based on a measurement value of a level meter; an excitation means for superimposing an excitation signal on the opening degree calculated by the calculation means; and an excitation signal generated by the excitation means. and a sliding nozzle drive means for controlling the opening degree of the sliding nozzle according to the target opening calculated by the calculating means on which the molten steel is supplied. A control device for the amount of molten steel supplied, comprising an amplitude and period control means for changing the amplitude and period so as to maintain the liquid level at a predetermined value based on the measured value of the liquid level of the supplied molten steel. be.

(Example) Next, an example in which the present invention is applied to continuous casting equipment will be described with reference to FIG.

Molten steel 2 in a tundish 1 is supplied to a mold 4 via a sliding nozzle 3. As the cast steel pieces 5 are continuously pulled out from the mold 4, a corresponding amount of molten steel 2 is supplied, so that the liquid level of the molten steel in the mold 4 is maintained constant. The opening degree of the sliding nozzle 3 that adjusts the supply amount of molten steel is determined by the hydraulic unit 6.
It is controlled by the hydraulic cylinder 6 driven by c.

Next, an example of a method for controlling the supply amount of molten steel 2 by the nozzle 3 and the molten steel level in the mold 4 according to the present invention will be described with regard to this embodiment.

Molten steel liquid level meter 7 equipped with detection head 7a
measures the level of molten steel in the mold 4, which is an amount corresponding to the average supply amount of molten steel 2, and outputs the measured value. On the other hand, cylinder rod position detector 8
detects the position (cylinder stroke) of the rod 6b of the cylinder 6 corresponding to the opening degree of the sliding nozzle 3, and outputs this as a nozzle opening degree signal or rod position signal.

The controller 9 includes an arithmetic unit 9a and an oscillator 9
b, and an adder 9c. The computing unit 9a performs proportional-integral-differential operation (PID operation),
A value corresponding to the target opening value of the nozzle 3 is calculated based on the outputs of the level meter 7 and the position detector 8, and this is output as the calculated value. On the other hand, the oscillator 9b generates a square wave with a predetermined period and amplitude, and outputs this as an excitation signal. The period and amplitude of this excitation signal are fixed to a constant value while the molten steel liquid level in the mold 4 is stable, but when the liquid level becomes unstable, it is automatically controlled according to the command from the controller 11. It can be changed to the optimum value. This control device 11 determines the relationship between the amplitude and period of vibration of the nozzle 3 and the level of the supplied molten steel, and controls the period and amplitude of the excitation signal based on this relationship. This will be discussed later.
The calculated value outputted from the arithmetic unit 9a and this excitation signal are superimposed by the adder 9c, and outputted from the controller 9 as a controller signal. Please refer to FIG. 4 and its explanation for the waveforms and mutual relationships of these signals in the controller 9.

The servo amplifier 10 controls the hydraulic unit 6c based on the nozzle opening degree or rod position (cylinder stroke) detected by the position detector 8 and the controller signal output from the controller 9, and calculates the opening degree of the nozzle 3 by using the calculator 9a. The vibration is made around a target value corresponding to the calculated value of , thereby effectively compensating for the nonlinear response characteristics of the sliding nozzle 3, the transmission mechanism 6a, and the like.

However, if the fluctuation in the liquid level detected by the level meter 7 exceeds a predetermined value, or if the vibration of the rod position detected by the detector 8 becomes irregular, the oscillator controller 11 Based on these signals, the period and amplitude of the excitation signal output from the oscillator 9b are automatically changed to optimal values. This controller 11 is composed of, for example, a microcomputer.

FIG. 9 is a flowchart showing a preferred example of a procedure for controlling the amplitude A and period T of the excitation signal to optimal values by the controller 11.

When the conditions for entering automatic control are satisfied, the cylinder stroke of the hydraulic cylinder 6 (corresponding to the opening degree of the nozzle 3) is sampled at regular intervals based on the output of the position detector 8, and its amplitude (R1) is measured.
and detect irregularities (R2). Further, the fluctuation range of the molten steel liquid level, which is an amount corresponding to the average supply amount of molten steel 2 at that time, is detected based on the output of the level meter 7 (R3). In this case, as the amplitude of the cylinder stroke, the average value within the sampling period of the absolute value of the difference between adjacent maximum and minimum values of the cylinder stroke waveform (see nozzle opening D1 in FIG. 4) is used. Further, as an index of the irregularity, the average value within the period of the absolute value of the difference between adjacent maximum values of the stroke waveform can be used. That is, if the irregularity index exceeds a predetermined value, it is determined that the irregularity is irregular.

Here, the irregularity is a moving average value of the difference between adjacent peaks of the cylinder stroke signal, and is determined by the following equation.

△a=△1/2N ( _N 〓 ⁱ⁼¹ ｜a _i+1 −a _i ｜＋ _N 〓 ⁱ⁼¹ ｜b _i+1 −b _i ｜) where, a _i : Upper peak value of cylinder stroke signal b _i : Upper peak value of cylinder stroke signal N: Irregularity determination time width If it is determined that the liquid level fluctuation width does not exceed a predetermined value in the sampling period, nothing is done and the cylinder Repeat stroke and liquid level detection (R1, R2, R3) in the next cycle. On the other hand, if it is determined that the level fluctuation width exceeds the predetermined value, the following control routine is entered (R4).

In step R5, the irregularity of the cylinder stroke detected in step R2 is first determined, and if the irregularity is large, the excitation signal amplitude A and period T are increased (R7). On the other hand, if the irregularity is small, the process moves to the next judgment logic (R6). The irregularity index described above is used to determine this irregularity. The reason for the irregular cylinder stroke is thought to be that the cylinder 6 is difficult to move. Therefore, in R7, the amplitude A and period T of the excitation signal are increased by predetermined increments ΔA and ΔT, respectively, to deal with this problem. That's what I do.

If it is determined in R5 that the cylinder stroke is not irregular, the magnitude of the cylinder stroke amplitude detected in R1 is determined in three stages: large, medium (normal), and small (R6). If the amplitude is small, it is considered that the cylinder 6 is difficult to move, so the amplitude A and period T of the excitation signal are increased according to R7 above.
On the other hand, if the amplitude is large, it is considered that the cylinder 6 moves too much, so the amplitude A and the period T are decreased by ΔA and ΔT, respectively. (R8). Also, if the cylinder stroke amplitude is medium, that is, in good condition, it returns to the start, performs periodic cylinder stroke, and detects the liquid level (R1, R2,
R3).

With R7 and R8, the amplitude A and period T of the excitation signal are ΔA,
When increased or decreased by ΔT, the amplitude A′ and period T′ after the increase or decrease are respectively the predetermined upper and lower limit values Amax,
Check whether it is between Amin, Tmax, and Tmin (R9). That is, Amax≧A′≧Amin,
Determine whether Tmax≧T′≧Tmin is satisfied, and if these conditions are not met, return to the start after returning the relevant parameter (amplitude A or period T) to the value before increase/decrease. . If the above conditions are satisfied, the process returns to the start with the increased or decreased value and resumes periodic detection (R1, R2, R3) of cylinder stroke amplitude, etc.

As already noted, the cylinder stroke of the hydraulic cylinder 6 in the above description corresponds to the opening degree of the sliding nozzle 3, which is the flow rate adjustment mechanism. Therefore, the stroke amplitude corresponds to the nozzle opening amplitude, and the stroke irregularity corresponds to the nozzle opening irregularity.

FIG. 10 is a flowchart of another example of the operation method of the controller 11. Next, I will briefly explain this program.

Routine R1 shows a procedure for controlling the period T of the excitation signal to an optimum value. In this routine R1, a change in the rod position, that is, a cylinder stroke, detected by the detector 8 is detected (R11), and it is determined whether or not this is irregular (R12). In the case of irregularity, the period T of the excitation signal is increased by a predetermined increase width ΔT (R13), and this procedure is repeated until the period T exceeds the preset maximum value Tmax. Change to the optimal value.

If it is determined in routine R1 that the cylinder stroke is not irregular (R12) or if the period T exceeds the maximum value Tmax (R14), the amplitude A of the excitation signal is increased according to the procedure of routine R2 and the molten steel is Look at the change in the range of surface level fluctuation.

In other words, the amplitude A of the excitation signal is increased by a predetermined increment ΔA
(P22), and compared the range of molten steel level fluctuations detected before and after (R21, R23).
It is determined whether the fluctuation range has decreased due to the increase in amplitude A (R24). If the fluctuation width is decreasing, repeat this procedure until the amplitude A exceeds the preset maximum value Amax (R25), and when it exceeds the maximum value Amax (R25), reduce the amplitude A by ΔA. (R28) Set the optimum value to be less than or equal to the maximum value Amax.

On the other hand, if the liquid level changes and becomes larger due to the increase in amplitude A (R22) (R24), it is determined whether or not to proceed to the next routine R3 in which amplitude A is decreased (R27). In other words, when the flag is ON, fluctuations in the liquid level can be suppressed by increasing the excitation signal amplitude A; on the other hand, when this flag is OFF, the amplitude A must be decreased. Immediately enter routine R3.

Routine R3 is a procedure for reducing the amplitude A of the excitation signal and controlling it to an optimum value that stabilizes the molten steel level. After the amplitude A decreases by a predetermined width ΔA twice (R31, R33), the fluctuation range of the liquid level is detected (R32, R35),
These are compared to determine whether or not the liquid level has been stabilized due to the decrease in amplitude A (R32) (R35).
If the liquid level is stabilizing due to a decrease in the amplitude A, the amplitude A is set to a preset minimum value.
Repeat these steps until below Amin (R36). As a result, when the amplitude A falls below the minimum value Amin (R36), the amplitude A is increased by ΔA (R37).
The optimum value should be greater than or equal to the minimum value Amin. If the liquid level becomes unstable as a result of decreasing amplitude A (R35), increase amplitude A by ΔA (R37).
Finish the procedure.

In the operation method of the controller 11 described above, the oscillator 9b
The automatic adjustment of the excitation signal output by the controller is automatically started when the cylinder stroke amplitude becomes irregular, but it may also be started manually by the operator.

(Effects of the Invention) In order to confirm the effects of the present invention, fluctuations in the liquid level of molten steel in the mold 4 before and after the adjustment of the excitation signal was started by the controller 11 in the continuous casting equipment shown in FIG. investigated. This result is shown in FIGS. 11 and 12. FIG. 11 shows temporal changes in the excitation signal and liquid level before the start of adjustment. FIG. 12 shows the corresponding waveform after adjustment. The size of the cast steel billet 5 of the equipment used for this investigation was 268 mm x 1350 mm, and the drawing speed was 1.4 m/min.

As shown in FIG. 11, the amplitude of the excitation signal before the start of adjustment was ±3%, and the period was 2 seconds. Here, the maximum value and adjustment range mentioned above are each Tmax = 4
seconds, Amax=6%, Amin=2%, ΔA=0.1%,
As a result of adjusting the excitation signal by setting ΔT = 0.25 seconds and the adjustment period to 20 seconds, the period of the excitation signal was 2.5 seconds and the amplitude was ±, as shown in Figure 12.
It became 3.8%. The time required for this adjustment was approximately 4 minutes.

Comparing the fluctuations in the molten steel liquid level in Figs. 11 and 12, the period and amplitude of the excitation signal are adjusted according to the present invention to suit the nonlinearity of the sliding nozzle, etc., and the molten steel supply amount and liquid level are adjusted. It can be seen that the accuracy of surface level control is significantly improved.

[Brief explanation of drawings]

Figure 1 is a block diagram of continuous casting equipment using a conventional control method; Figures 2 and 3 are diagrams showing the response characteristics of a sliding nozzle used in continuous casting equipment; Figures 4 and 5 1 is a waveform diagram of signals, detected values, etc. in the apparatus of FIG. 1; FIGS. 6 and 7 are diagrams showing the results of control experiments conducted to establish the basic idea of the present invention; FIG. 8 teeth,
A block diagram showing an embodiment of the present invention applied to continuous casting equipment; FIG. 9 is a flowchart showing the procedure for adjusting the period and amplitude of the excitation signal in the device of FIG. 8; FIG. A flowchart showing another example of the procedure for adjusting the period and amplitude of the excitation signal in the device shown in FIG. 8; and FIGS. 11 and 12 show waveforms of the excitation signal and the control liquid level before and after adjustment of the excitation signal. It is a diagram. 1: tandate, 3: sliding nozzle, 4: mold, 5: cast billet, 6: hydraulic cylinder, 7: molten steel liquid level gauge, 9: controller, 9a: calculator, 9b: oscillator, 10: servo amplifier , 11: Oscillator controller.

Claims (1)

[Scope of Claims] 1. In a method of controlling the amount of molten steel supplied by adjusting the opening degree of a sliding nozzle during continuous casting of molten steel, the opening degree is oscillated around a predetermined value when molten steel is supplied, and A method for controlling the amount of molten steel supplied, comprising changing the amplitude and period of vibration of the opening degree so as to maintain the liquid level at a predetermined value based on a measured value of the liquid level of the supplied molten steel. 2. The change in amplitude and period is based on the amplitude and irregularity of the amount corresponding to the opening degree of the sliding nozzle and the measured value of the amount corresponding to the average supply amount of molten steel. A method for controlling the amount of molten steel supplied according to scope 1. 3. A sliding nozzle that adjusts the supply amount of molten steel by the opening degree, a molten steel liquid level meter that measures an amount corresponding to the average supply amount of the molten steel, and a molten steel liquid level meter that measures the amount corresponding to the average supply amount of the molten steel, and a a calculation means for calculating a target opening degree of the riding nozzle; an excitation means for superimposing an excitation signal on the opening degree calculated by the calculation means; and an operation of the calculation means on which the excitation signal is superimposed by the excitation means. and a sliding nozzle drive means for controlling the opening degree of the sliding nozzle in accordance with a target opening degree, which controls the amplitude and period of vibration of the sliding nozzle when supplying molten steel. A control device for the amount of molten steel supplied, comprising amplitude and periodic control means for changing the liquid level so as to maintain it at a predetermined value based on a liquid level measurement value. 4. The amplitude and period control means controls the changes in the amplitude and period by adjusting the amplitude and irregularity of the amount corresponding to the opening degree of the sliding nozzle and the amount of amplitude and irregularity corresponding to the average supply amount by the molten steel liquid level meter. 4. The molten steel supply amount control device according to claim 3, wherein the control device determines the amount based on the measured value.