JPH05277687A - Device for controlling molten metal surface level in mold in continuous caster - Google Patents

Abstract

PURPOSE:To secure the safety in the operation by restraining the variation of molten metal surface level accompanied with the abnormality of a level meter caused by noise signal, disconnection, etc., in a device for holding and controlling the molten metal level in a mold for continuous caster to the aimed molten metal surface level with high accuracy. CONSTITUTION:In this device, a noise deciding part 1, by which the variation of the molten metal surface level detected with the level meter 65 is observed and in a case this variation is abnormal, it is decided that the noise signal is overlapped to the output of the level meter 65, is provided. In the case of deciding the existence of the noise signal by this noise deciding part 1, the aimed molten metal surface level SV as the detected result of the level meter 65 inputted to a control means 67, is inputted and held to the condition which a hydraulic cylinder 61 is not driven in plactical.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for maintaining and controlling a molten metal level in a mold in a continuous casting machine at a target molten metal level with high accuracy.

[0002]

2. Description of the Related Art Conventionally, as a molten metal level controller in a mold for keeping the molten metal level in a mold at a target molten metal level in a continuous casting machine, for example, one shown in FIG. 7 is known. ing.

FIG. 7 is a block diagram showing a conventional casting machine equipped with a conventional level controller for molten metal in a mold. In FIG. 7, reference numeral 51 denotes a molten steel ladle, which is a tundish installed below the molten steel ladle 51. A bottom plate 53 having a through hole 53a having the same diameter as the molten steel outflow hole 52c of the tundish 52 is fixed to the lower surface of the 52. A seal plate 54 having a through hole 54a having the same diameter as the molten steel outflow hole 52c is arranged at a position below the plate 53 at a predetermined interval, and the tundish 52 is provided between the plates 53, 54. A slide valve 55 provided with a through hole 55a having the same diameter as the molten steel outflow hole 52c is interposed.

The slide valve 55 is a tundish 5
It is for adjusting the amount of molten steel that is poured into the mold 56 from 2 to form the cast slab 57, and the molten metal level inside the mold 56 is kept at the target molten metal level by the in-mold molten metal level control device described later. By sliding the position of the through hole 55a with respect to the through holes 53a and 54a of the other plates 53 and 54, the opening degree of the through hole 55a is corrected and adjusted.

The structure of the conventional level controller for the molten metal in the mold will be described. An upper bracket 52a is fixedly attached to the side surface of the tundish 52.
A hydraulic cylinder (actuator) 61 is swingably attached to the. A lower bracket 52b is fixed to the side surface of the tundish 52 below the upper bracket 52a, and a link 62 is swingably attached to the lower bracket 52b. The tip of the piston rod 61a is pin-connected. Further, the other end of the link 62 is connected to the slide valve 55 via a connecting rod 63.

Reference numeral 64 is a differential transformer for detecting the position (displacement) of the piston rod 61a of the hydraulic cylinder 61. The main body of the differential transformer is fixed to the hydraulic cylinder 61 and the like by a support member (not shown), and its rod-shaped core is provided. Is moved together with the piston rod 61a,
A voltage signal is output according to the position of a.

Further, 65 is a level meter of eddy current type for detecting the level of molten metal in the mold 56, electrode following type, etc., 65a is an amplifier of the level meter 65, and 66 is for setting a target molten metal level. , And the output of the level meter 65 and the output of the target molten metal level setting device 66 via the amplifier 65a are input, and the deviation between them is determined by PID.
A valve opening command section (control means) 68 which calculates by a calculation circuit or the like and outputs a value corresponding to the difference between both outputs, 68 is a cylinder control section which is composed of a normal directional control valve, a servo amplifier, and the like. The cylinder control unit 68 receives the output of the valve opening command unit 67 and the output of the differential transformer 64 used for positioning control as input, and according to the output of the valve opening command unit 67, the molten metal level in the mold 56. This is for controlling the operation of the hydraulic cylinder 61 so that the level is maintained at the target molten metal level.

Next, the operation of the conventional molten metal level controller in the mold constructed as described above will be explained. An imbalance between the molten steel amount injected into the mold 56 through the slide valve 55 and the withdrawal amount of the cast piece 57 is unbalanced. Occurs, level meter 6
When a deviation occurs between the output of No. 5 and the output of the target molten metal level setter 66, the valve opening command unit 67 gives an output corresponding to the difference between the two outputs to the cylinder control unit 68.

The cylinder control unit 68 operates the hydraulic cylinder 61 accordingly. For example, when the molten metal level in the mold 56 is higher than the target molten metal level, the piston rod 61a of the hydraulic cylinder 61 is extended and the slide valve 55 is slid through the link 62 and the connecting rod 63 to open the opening. Is adjusted so as to reduce the amount of molten steel injected into the mold 56.

[0010]

Although not shown in FIG. 7, an induction heating device or the like for heating the molten steel in the tundish 52 is installed near the tundish 52 and the mold 56. However, when the above-mentioned conventional level control device for the molten metal in the mold is used in combination with these devices, the indication of the level meter 65 is momentarily zero due to a sudden noise signal from the induction heating device or the like. %
Or, it may change to 100%, and the actuator (hydraulic cylinder 61) may operate, making normal control impossible.

Also, when an abnormality such as disconnection occurs in the level meter 65, the level meter 65 indicates 0% or 100%.
% Until the operator recognizes the abnormality, there is a possibility that the actuator operates and the fluctuation of the molten metal level in the mold 56 becomes large.

The present invention is intended to solve such a problem, and secures operational safety by suppressing fluctuations in the level of the molten metal due to an abnormality in the level meter due to noise signals or disconnection. An object of the present invention is to provide a molten metal level control device in a mold in a continuous casting machine.

[0013]

In order to achieve the above-mentioned object, a molten metal level control device in a mold in a continuous casting machine of the present invention (claim 1) adjusts the amount of molten steel injected from a tundish into the mold. An actuator, a level meter for detecting the level of the molten metal in the mold, and a control for controlling the actuator by calculating a deviation between the detection result of the level meter and the target molten metal level and outputting a value according to the deviation. Means for holding and controlling the molten metal level in the mold at the target molten metal level by operating the actuator according to the output of the control means, the molten metal level detected by the level meter. A noise determination unit is provided for monitoring the level variation and determining that the noise signal is superimposed on the output of the level meter when the variation is abnormal. Noise when the signal perforated to have been determined, enter the target melt-surface level as a detection result of the level meter is input to the control means, the actuator is characterized by retaining the state of not operated by.

The apparatus of claim 2 is the same as that of claim 1, wherein the level of the molten metal in the mold is estimated and calculated based on the output of the control means, and the level is detected. A noise determination unit that determines that the noise signal is superposed on the output of the level meter when the variation of the molten metal level is abnormal and the variation is abnormal,
When it is determined by the noise determination unit that there is a noise signal, the estimated molten metal level from the estimation unit is input as the detection result of the level meter input to the control unit.

[0015]

In the above-mentioned level control device for the molten metal level in the mold in the continuous casting machine of the present invention (claim 1),
When an abnormality occurs due to a noise signal or disconnection, and a sudden change occurs, the noise determination unit determines that there is an abnormality, that is, a noise signal based on the variation, and as a result, the target is detected as the detection result of the level meter to the control means. The bath level will be entered. Therefore, the level deviation calculated by the control means becomes 0, the actuator is maintained in a substantially non-operating state, and fluctuations in the molten metal level due to an abnormal indication on the level meter are suppressed.

Further, in the apparatus according to the second aspect, when the noise determining section determines that the noise signal is present as in the apparatus according to the first aspect, the detection result of the level meter to the control means is as follows.
By inputting the estimated molten metal level from the estimating means,
It is possible to reduce the influence of disturbances such as changes in the dynamic characteristics of the process and changes in the casting speed while suppressing the fluctuation of the molten metal level caused by the abnormal indication of the level meter, and to continue the molten metal level control with a certain degree of accuracy.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIGS. 1 to 3 show a molten metal level control device in a mold in a continuous casting machine as a first embodiment of the present invention (claim 1
1 is a control block diagram thereof, FIG. 2 is a flow chart for explaining the operation thereof, and FIG. 3 is a timing chart for explaining the operation thereof. The continuous casting machine to which the molten metal level control device in the mold of the present embodiment is applied is exactly the same as that shown in FIG. 7, and in the following description of the present embodiment, the reference numerals described above with reference to FIG. 7 are used together. To do.

In FIG. 1, 56 is a tundish 52.
(See FIG. 7) A mold into which molten steel is injected, 61 is a slide valve 5 provided at the bottom of the tundish 52 for adjusting the amount of molten steel injected from the tundish 52 into the mold.
5 is a hydraulic cylinder (actuator) for driving 5 (see FIG. 7), 65 is a level meter such as an eddy current type for detecting the molten metal level in the mold 56, an electrode following type, and 67 is an output PV of the level meter 65 Of the deviation Er from the target molten metal surface level set value SV is calculated by the subtractor 67a, a value corresponding to the deviation Er is calculated by the PID calculator 67b, and the valve opening command value MV is output. Means). The above configuration is exactly the same as that of the conventional one shown in FIG. 7, and the hydraulic cylinder 61 is operated in accordance with the valve opening command value MV which is the output of the valve opening command section 67, so that the inside of the mold 56 is changed. The molten metal level is maintained / controlled at the target molten metal level SV.

By the way, in the present embodiment, as shown in FIG. 1, a portion for feeding back the detection result PV by the level meter 65 to the valve opening command section 67, that is, the level meter 6
The noise determination unit 1 is provided between the valve 5 and the valve opening command unit 67. This noise determination unit 1 has a level meter 6
The fluctuation of the molten metal level PV detected by
It is calculated and monitored as the slope (difference) of the V value, and when the slope is within a predetermined range (for example, less than -k in this embodiment), it is determined that a noise signal is superimposed on the output of the level meter 65. Is.

Further, when it is determined that there is a noise signal, the noise determination unit 1 outputs the target molten metal level SV as the output PV 'to the valve opening command unit 67 by the timer for the predetermined period T ₀ . It is a thing. If the noise determination unit 1 determines that there is no noise signal, the level meter 6
The detection result PV from 5 is output as it is to the valve opening command unit 67 as the output PV '.

The operation of the molten metal level controller in the mold of the first embodiment constructed as described above will be described with reference to FIGS. In the noise determination unit 1 of this embodiment, 10 msec
In this cycle, the inclination (difference) of the detected molten metal level PV from the level meter 65 is calculated, and it is determined whether or not the inclination is less than the predetermined value −k (step A1). If the slope is less than -k, it is determined that a noise signal has been superimposed on the output of the level meter 65, that is, a noise signal is present, and a flag with noise is set (step A2).

On the other hand, when the inclination is -k or more, it is determined whether or not the timer has counted for a predetermined period T ₀ or more, or a deviation | PV between the detection result PV from the level meter 65 and the target molten metal level SV. It is determined whether -SV | has become equal to or less than a predetermined value E (that is, it means that the noise signal has disappeared) (step A3). If it is determined that any of the conditions is satisfied, no noise is detected. The flag is set (step A4), and if it is determined that none of the conditions is satisfied, the process proceeds to step A5.

In step A5, it is determined whether or not the flag with noise is set, and if it is set, the timer is counted up and the output PV 'of the noise determination unit 1 is set to the target molten metal surface. Match level SV
(Step A6). On the other hand, when it is determined in step A5 that the flag with noise is not set, the timer is reset (count value is 0) and the output PV 'of the noise determination unit 1 is output from the level meter 65. Is detected as PV (step A7).

As described above, for example, as shown in the upper part of FIG. 3, when the output of the level meter 65 becomes abnormal due to a noise signal, disconnection, or the like and a sudden change occurs, the noise determination unit 1 responds to the change. Is determined to be abnormal, that is, a noise signal is present, and until the noise signal disappears or until the timer counts up the predetermined period T ₀ , as shown in the lower part of FIG. The target molten metal level SV is input as the surface level.

As a result, the level deviation calculated by the subtractor 67a of the valve opening commanding unit 67 is always 0 during that time, and the hydraulic cylinder 61 is maintained in a substantially non-operating state, causing an abnormal indication by the level meter 65. Fluctuations in the molten metal level are suppressed, and operational safety can be secured.

Next, FIGS. 4 to 6 show a molten metal level control device (corresponding to claim 2) in a continuous casting machine as a second embodiment of the present invention. FIG. 4 shows the control. FIG. 5 is a block diagram, FIG. 5 is a flow chart for explaining the operation, and FIG. 6 is a timing chart for explaining the operation. The continuous casting machine to which the molten metal level control device in the mold of the present embodiment is applied is exactly the same as that shown in FIG. 7, and the same reference numerals as those used above indicate the same parts, The description is omitted.

As shown in FIG. 4, in the second embodiment, using the flow coefficient Kn, the mold cross-sectional area A, and the casting speed Vc, the fluctuation of the molten metal level in the mold 56 due to the output MV of the valve opening command unit 67. A molten metal level estimating circuit (estimating means) 2 for estimating and calculating the amount ΔPV is provided. In order to improve the accuracy of the estimated value ΔPV by the molten metal level estimation circuit 2 (to reduce the influence of the change in the dynamic characteristics of the process), the molten metal level actually detected by the level meter 65 before noise is generated. The time constant T and the flow coefficient Kn of the hydraulic cylinder (actuator) are identified in comparison with the level PV.

Further, the noise judgment unit 1A of the present embodiment, like the noise judgment unit 1 of the first embodiment, changes the fluctuation of the molten metal level PV detected by the level meter 65 with respect to the slope (difference) of the PV value. ) Is calculated and monitored, and the inclination is within a predetermined range
When it is (for example, less than −k), it is determined that a noise signal is superimposed on the output of the level meter 65,
In the second embodiment, when it is determined that there is a noise signal, the detection result PV ₀ of the level meter 65 immediately before the noise occurrence is held and continuously output, and the switch 3 is closed (ON).
As a state, the level variation ΔPV from the level estimation circuit 2 and PV ₀ are added by the adder 3, and PV ₀ + ΔPV is output as PV ′ to the valve opening command unit 67.
Is output for a predetermined period T ₀ by a timer. When the noise determination unit 1A determines that there is no noise signal, the switch 3 is opened (OFF), and the detection result PV from the level meter 65 is output as it is to the valve opening command unit 67 as PV '. To do.

The operation of the molten metal level controller in the mold of the second embodiment having the above-mentioned structure will be described with reference to FIGS. The operation of the noise determination unit 1A of the present embodiment is exactly the same as the above-described steps A1 to A5 of FIG. 2 of the first embodiment, as shown in steps A1 to A5 of FIG. Then, steps A8 and A9 of FIG. 5 are executed in place of steps A6 and A7 of the first embodiment.

That is, in step A5, it is determined whether or not the flag with noise is set, and if it is set, the timer is counted up (incremented) and output to the valve opening command section 67. Let PV ′ be the sum of the melt level PV ₀ immediately before the noise occurrence and the estimated melt level variation ΔPV from the melt level estimation circuit 2 and continue the melt level control by the valve opening command section 67. (Step A8). On the other hand, when it is determined in step A5 that the flag with noise is not set, the timer is reset (count value is 0) and the output PV 'to the valve opening command unit 67 is changed to The detection result PV from the level meter 65 is set (step A7).

In this way, for example, as shown in the upper part of FIG. 6, when the output of the level meter 65 becomes abnormal due to a noise signal, disconnection, or the like and a sudden change occurs, the noise determination unit 1 responds to the change. Is determined to be abnormal, that is, a noise signal is present, and until the noise signal disappears or the timer counts up (increments) the predetermined period T ₀ , as shown in the lower part of FIG. Estimated molten metal level PV ₀ + as the detected molten metal level
ΔPV will be input. As a result, fluctuations in the level of the molten metal caused by abnormal indications on the level meter 65 are suppressed and operational safety is ensured, while the effects of changes in the process dynamic characteristics and casting speed are reduced, and the molten metal level is maintained with a certain degree of accuracy. Level control can continue.

Incidentally, in any of the above-mentioned first and second embodiments, when the noise determining section 1 or 1A determines that a noise signal is present, it may be configured to issue an alarm to the outside.

[0033]

As described above in detail, according to the molten metal level control device in the casting mold of the continuous casting machine of the present invention (Claim 1), it is determined that a noise signal is superimposed on the output of the level meter to cause an abnormality. In this case, the level deviation calculated by the control means is set to 0 by giving the target molten metal level to the control means as the detection result of the level meter, and the actuator is kept in a substantially non-operated state. This has the effect of suppressing fluctuations in the level of the molten metal due to abnormal indications and ensuring operational safety.

According to the apparatus of claim 2, when it is determined that the noise signal is superposed on the output of the level meter to cause an abnormality, the estimated molten metal level from the estimating means is given to the control means. While controlling the level fluctuations caused by abnormal level meter indications and ensuring operational safety, the effects of process dynamic characteristics and casting speed changes are reduced, and level control continues with a certain degree of accuracy. There is an effect that can be done.

[Brief description of drawings]

FIG. 1 is a control block diagram showing a molten metal level control device in a mold in a continuous casting machine as a first embodiment of the present invention.

FIG. 2 is a flow chart for explaining the operation of the device of the first embodiment.

FIG. 3 is a timing chart for explaining the operation of the device of the first embodiment.

FIG. 4 is a control block diagram showing a molten metal level control device in a mold in a continuous casting machine as a second embodiment of the present invention.

FIG. 5 is a flow chart for explaining the operation of the device of the second embodiment.

FIG. 6 is a timing chart for explaining the operation of the device of the second embodiment.

FIG. 7 is a configuration diagram showing a continuous casting machine provided with a conventional molten metal level control device in a mold.

[Explanation of symbols]

 1, 1A Noise determination unit 2 Liquid level estimation circuit (estimation means) 3 Switch 4 Adder 56 Mold 61 Hydraulic cylinder (actuator) 65 Level meter 67 Valve opening command unit (control means) 67a Subtractor 67b PID calculator

Claims (2)

[Claims] 1. An actuator for adjusting the amount of molten steel injected from a tundish into a mold, a level meter for detecting a molten metal level in the mold, and a deviation between a detection result of the level meter and a target molten metal level. And a control means for controlling the actuator by outputting a value according to the deviation and operating the actuator according to the output of the control means to change the level of the molten metal in the mold to the target molten metal level. In the mold level control device in the continuous casting machine that holds and controls the level, the fluctuation of the molten metal level detected by the level meter is monitored, and if the fluctuation is abnormal, the output of the level meter is displayed. A noise determination unit that determines that a noise signal is superimposed is provided, and if the noise determination unit determines that a noise signal is present, the control unit is input. The target molten metal surface level type, said actuator mold molten steel level control device in the continuous casting machine, characterized in that to hold the state of not operating as the detection result of the level meter is. 2. An actuator for adjusting the amount of molten steel injected from a tundish into a mold, a level meter for detecting a molten metal level in the mold, and a deviation between the detection result of the level meter and a target molten metal level. And a control means for controlling the actuator by outputting a value according to the deviation and operating the actuator according to the output of the control means to change the level of the molten metal in the mold to the target molten metal level. In a mold level control device in a continuous casting machine for holding and controlling the level, an estimation unit for estimating and calculating the level of the molten metal in the mold based on the output of the control unit, and the level detected by the level meter. A noise determination unit that monitors a variation in the surface level and, if the variation is abnormal, determines that a noise signal is superimposed on the output of the level meter. When it is determined that the noise signal is present by the noise determination unit, the estimated molten metal level from the estimation unit is input as the detection result of the level meter input to the control unit. Level control device for the molten metal level in the continuous casting machine.