JP3029317B2 - Mold level control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a mold level control device used in, for example, a continuous casting facility.

[0002]

2. Description of the Related Art In general, in a continuous casting facility, it is very important to control a mold level to a constant value from the viewpoint of securing a product of a constant quality.

Conventionally, a mold level control device as shown in FIG. 3 has been developed from such a demand. That is,
In this control device, molten steel of a tundish 1 is injected into a mold 3 from a nozzle 2, and a steel piece 4 solidified by being indirectly cooled by cooling water of a mold wall is pulled out from a lower portion of the mold 3 by a pinch roll 5. It has a configuration.

On the other hand, the level controller 6 compares the molten steel level in the mold 3 measured by the gamma ray or eddy current level meter 7 with a predetermined set level, and makes the deviation thereof zero. Is performed to obtain an operation output value, and the stroke of the stopper 10 is adjusted by using the operation output value via the servo amplifier 8 and the hydraulic cylinder 9. In this way, by varying the amount of molten steel to flow out of the nozzle 2, the mold level is controlled to be at the set level. 11 is a hydraulic unit, and 12 is an opening meter.

[0005]

However, the following problems have been pointed out in the above mold level control device.

In general, since the nozzle flow rate characteristic when the stopper 10 is used is high in sensitivity to a change in the stopper stroke, the feedback control system of the conventional apparatus cannot provide a high feedback control gain and keeps the mold level constant. Very difficult to keep in value. In this type of control system, disturbances such as fluctuations in the casting speed, fluctuations in the amount of molten steel in the tundish 1, and adhesion of molten steel to the nozzle 2 and fluctuations in the nozzle flow rate due to chipping occur. Even if the control cycle of the level controller 6 is shortened, there is a limit in increasing the accuracy of the level control because the delay time itself and the response delay are relatively long.

The present invention has been made in view of the above circumstances. Even if the gain on the operation end side is high, the control gain of the feedback control system can be increased, and even if the level meter has a slow response time, An object is to provide a mold level control device capable of controlling a mold level with high accuracy.

[0008]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a mold level control apparatus for performing feedback control of a mold level to a constant value by adjusting a stopper stroke using a level controller. Nozzle basic flow rate according to the fluctuation of molten steel weight
An effective nozzle characteristic calculation unit for correcting characteristics and obtaining an effective nozzle flow characteristic, and the variation dL / dt of the mold level L is
dL / dt = (Q / A) -V (where Q: nozzle flow rate,
A: cross section of mold, V: measured casting speed)
The mold level is kept at a constant value based on the situation
In order to make the condition (dL / dt) = 0,
The speed measurement value V and a predetermined cross-sectional area A of the mold
Nozzle flow rate Q = A according to fluctuation of intake and casting speed
V calculating means for calculating V, and the flow rate calculating means
From the effective nozzle characteristic calculation unit based on the nozzle flow rate
Stopper stroke from output nozzle effective flow characteristics
A stroke calculation means for obtaining the this stroke
In this configuration, the mold level is controlled by superimposing the output of the arithmetic means on the feedback control signal that is the output of the level controller.

[0009]

According to the present invention, by taking the above-described means, a new effective nozzle characteristic calculating section , a flow rate calculating means and
A stroke calculation means is provided, and the effective nozzle characteristic calculation unit calculates the basic flow of the nozzle according to the fluctuation of the weight of molten steel in the tundish
After correcting the flow characteristics and extracting the nozzle effective flow characteristics,
It is sent to the trooke calculating means. On the other hand, the flow rate calculation means
Is the fluctuation dL / dt of the mold level L = (Q / A) −
V (where Q: nozzle flow rate, A: cross-sectional area of mold,
V: Pouring speed measurement value)
To maintain the mold level at a constant value (dL / d
In order to set t) = 0, the pouring speed measurement value V and the
Using the determined sectional area A of the mold and the casting speed,
Calculates the nozzle flow rate Q = AV according to the fluctuation of
To the computing means. This stroke calculation means is capable of
The effective nozzle based on the nozzle flow rate from the
Stopper straw is calculated from the nozzle effective flow rate characteristic of the characteristic calculation unit.
The feedback, which is the output of the level controller.
Thus , high-precision mold level control can be realized by superimposing the mold level control signal on the mold control signal .

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing one embodiment of the present invention. In this figure, the same parts as those in FIG. 3 are denoted by the same reference numerals, and detailed description thereof will be omitted. This apparatus is equipped with a mold 3 through a tundish 1 and a nozzle 2.
After injecting molten steel into the mold 3 and indirectly cooling the molten steel in the mold 3 with the cooling water of the mold wall, a steel piece 4 which gradually solidifies as it goes to the lower part of the mold 3 is obtained. After pulling out with the pinch roller 5 and amplifying the output of the level controller 6 with the servo amplifier 8,
Controlling the stroke of the stopper 10 by introducing it into the hydraulic cylinder 9 and adjusting the flow rate of the molten steel flowing out of the nozzle 2 are the same as in the conventional case. 11 is a hydraulic cylinder 9
A hydraulic unit for supplying hydraulic pressure to the valve 12 is an opening meter for indicating a stroke of the stopper 10. 13 is a pinch roll speed controller for controlling the casting speed of the billet 4, 14 is a motor for driving the pinch roll 5, and 15 is a tacho generator for measuring the casting speed of the billet 4.

The present apparatus is particularly different from the first embodiment in that an effective nozzle characteristic calculating unit 20 for correcting and calculating a nozzle flow characteristic based on the weight of molten steel in the tundish 1 and an effective flow characteristic obtained by the effective nozzle characteristic calculating unit 20 are provided. Stroke calculation unit 30 that calculates a stopper stroke from
And has been provided.

The effective nozzle characteristic calculating section 20 generates a nozzle characteristic generating means 21 for generating a nozzle basic flow rate characteristic of the nozzle 2 and a correction coefficient in consideration of a fluctuation of the molten steel flowing out of the nozzle due to a fluctuation of the molten steel weight measured by the weighing device 22. , And multiplication means 24 for multiplying the nozzle basic flow rate characteristic by the correction coefficient to obtain a nozzle effective flow rate characteristic.

The stopper stroke calculating section 30 calculates a flow rate of the nozzle corresponding to the casting speed, and a stopper based on the nozzle effective flow rate characteristic corrected by the effective nozzle characteristic calculating section 20 and the nozzle flow rate. A stroke calculating means for calculating the stroke of the stroke controller; and an adding means for adding the output of the stroke calculating means to the output of the level controller. The output of the adding means is sent to the hydraulic cylinder. Configuration.

Next, before describing the operation of the above-described apparatus, the flow rate characteristics of the stopper will be described with reference to FIG. FIG. 2 is a diagram showing the relationship between the stopper stroke and the nozzle flow rate. The horizontal axis represents the stopper stroke.
It shows that the opening degree of is increased. The vertical axis indicates the flow rate of the molten steel flowing out of the nozzle 2 (nozzle flow rate). The vertical axis indicates the flow rate of the molten steel flowing out of the nozzle 2 (nozzle flow rate).

As is apparent from FIG.
Is known to exhibit an S-shaped characteristic. This flow rate characteristic changes in a complicated manner due to the precipitation or lack of molten steel or the like on the nozzle surface, and the change is completely random and unpredictable. Therefore, the weight of the molten steel in the tundish 1 is measured, and the measured value is calculated. The purpose is to correct the feedback control system, which is the output of the level controller 6, based on this, and to correct the flow characteristics as a result. Note that the curve A is the basic flow rate characteristic of the nozzle output from the nozzle characteristic generating means 21, and is uniquely determined by the physical size and shape of the nozzle 2 and the stopper 10.

On the other hand, it is known that the amount of outflow from the nozzle 2 follows Bernoulli's law. That is, assuming that the basic flow rate characteristic for the molten steel weight W0 is f0 (x), the effective flow rate characteristic f (x) for the molten steel weight W is f (x) = f0 (x) (W / W0) ^{1 / 2} ...... (1)

## EQU1 ## From this equation, the effective flow characteristic f
It can be seen that (x) can be obtained by multiplying the basic flow characteristic by (W / W0) ^1/2 . Curve B shows the relationship between the stopper stroke and the nozzle flow rate for the molten steel weight W determined as described above.

Therefore, the present embodiment is to perform level control based on the flow characteristics as described above, and the operation thereof will be specifically described below. Now, when the weight W of the molten steel in the tundish 1 is measured by the weighing device 22 and is introduced into the square root calculating means 23, the weight W0 of the molten steel to be a predetermined constant is input here. The calculation (W / W0) ^{1/2 on} the right side of the above equation (1) is performed, and the obtained (W / W0) ^1/2 is supplied to the multiplication means 24. The multiplying means 24 adds the (W / W0) to the basic flow rate characteristic f0 (x) obtained from the nozzle characteristic generating means 21.
After obtaining the effective flow rate characteristic f (x) by multiplying by ^1/2 , it is sent to the stroke calculating means 32 of the stopper stroke calculating section 30.

Since the fluctuation of the mold level of the mold 3 occurs only due to the difference between the flow rate of the molten steel flowing out of the nozzle 2 and the amount of the molten steel to be drawn, the equation (2) is satisfied. dL / dt = Q / A−V (2) where L is a mold level, Q is a nozzle flow rate, A is a cross-sectional area of the mold 3, and V is a casting speed. Therefore, in order to keep the mold level at a constant value, dL / dt
From 0, the relationship of Q = AV (3) is established.

Therefore, since the drawing speed (= casting speed) V from the tachogenerator 15 is input to the flow rate calculating means 31 in the stopper stroke calculating section 30, the nozzle flow rate Q is calculated based on the above equation (3). After being obtained, it is supplied to the stroke calculation means 32. The stroke calculating means 32 calculates a second value based on the effective flow rate characteristic f (x) input from the multiplying means 24 and the nozzle flow rate Q.
After obtaining the stopper stroke X at the operating point C shown in the figure,
The stopper stroke X is sent to the adding means 23.
The adding means 23 adds the feedforward control signal of the stopper stroke X to the feedback control signal output from the level controller 6, amplifies the obtained operation output value by the servo amplifier 8, and then introduces it into the hydraulic cylinder 9. . The hydraulic cylinder 9 drives the stopper 10 to a stroke position as instructed based on the output of the servo amplifier 8.

Therefore, according to the configuration of the embodiment described above, the stopper stroke can be adjusted via the feedforward control so that the nozzle flow rate matches the pouring speed, so that the fluctuation of the mold level can be reduced. Can be. In addition, the feedback control gain can be increased, and the mold level can be controlled with high accuracy.

Incidentally, in the mold level control device of the present invention, as a result of applying to the continuous casting process of the billet using the γ-ray level meter 7 having a time constant of 1.5 seconds, the controllability is greatly improved as compared with the conventional example. Improved. Normally, the flow rate characteristic of the stopper 10 has a disadvantage that the slope is steeper than that of the slide nozzle, the on / off element is strong, and it is difficult to obtain a large gain of the level controller 6. Since the control output as an approximation is determined and the feedback system is used only for the correction, the deviation of the feedback system is small and the gain can be increased.

The above embodiment can be widely applied not only to the mold level control of the continuous casting equipment but also to various processes as long as the characteristics of the operating end can be theoretically predicted in advance. In particular, it is needless to say that the present invention is effective for a process that requires a high response speed and requires a long time to measure the process amount.

[0024]

As described above, according to the present invention, the feedforward control for calculating the stopper stroke from the nozzle flow rate characteristic curve is used together with the feedback control so that the nozzle flow rate matches the casting speed. The effect can be reduced, and the effect of feedback control can be enhanced even if a level meter having a slow response speed is used. Therefore, stable control of the mold level can be realized, which can greatly contribute to improvement of productivity and stabilization of quality.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing one embodiment of a mold level control device according to the present invention.

FIG. 2 is an explanatory diagram showing a relationship between a stopper stroke and a nozzle flow rate.

FIG. 3 is a block diagram showing a configuration of a conventional device.

[Explanation of symbols]

1 ... tundish, 2 ... nozzle, 3 ... mold, 4 ...
Steel billet, 5: pinch roll, 6: level controller, 7: level meter, 8: servo amplifier, 9: hydraulic cylinder, 10: stopper, 12: opening meter, 13: pinch roll speed controller, 14: motor , 15: Tacho generator, 20: Effective nozzle characteristic calculation unit, 21: Nozzle characteristic generating means, 22
... weigher, 23 ... square root calculation means, 24 ... multiplication means, 30
... Stopper stroke calculator, 31 ... Flow rate calculator, 3
2 ... Stroke calculating means, 33 ... Adding means.

──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Tetsuo Sumita 2-2-1 Otemachi, Chiyoda-ku, Tokyo Sumitomo Heavy Industries, Ltd. (72) Inventor Yasuto Ito 2-2-2 Otemachi, Chiyoda-ku, Tokyo 1 Sumitomo Heavy Industries, Ltd. (56) References JP-A-59-27762 (JP, A) JP-A-1-118343 (JP, A) JP-A-63-192545 (JP, A) JP-A-63 -180353 (JP, A) JP-A-62-192246 (JP, A) JP-A-62-168652 (JP, A) JP-A-64-53736 (JP, A) JP-B-52-41727 (JP, B1) (58) Fields surveyed (Int. Cl. ⁷ , DB name) B22D 11/18 G05D 9/12

Claims (1)

(57) [Claims] 1. A mold level control device for feedback-controlling a mold level to a constant value by adjusting a stopper stroke using a level controller, wherein a basic flow of a nozzle according to a change in weight of molten steel in a tundish.
The effective nozzle property calculating unit corrects the amount characteristics determine the nozzle effective flow characteristics, fluctuation dL / dt of the mold level L is dL / dt =
(Q / A) -V (However, Q: nozzle flow rate, A: mold
Cross section, V: measured casting speed)
Condition for maintaining the mold level at a constant value (d
L / dt) = 0, so that the measured casting speed V
And the predetermined cross-sectional area A of the mold
Calculates the nozzle flow rate Q = AV according to the fluctuation of the inflow speed
Flow rate calculating means, and the nozzle flow rate calculated by the flow rate calculating means.
Nozzle effective flow characteristics output from the effective nozzle characteristics calculation unit
And a stroke calculating means for obtaining a stopper stroke from the controller, wherein a mold level is controlled by superimposing an output of the stroke calculating means on a feedback control signal which is an output of the level controller.