JPH0377757A - Apparatus for controlling molten metal surface level in mold in continuous casting machine - Google Patents

Abstract

PURPOSE:To correct valve opening degree and to keep molten metal surface level to the aimed level by detecting backlash value between a slide valve and piston rod based on outputs of the molten metal surface leveller and position detector for piston rod and adding the backlash value to output in a valve opening degree command part. CONSTITUTION:A molten metal surface level control unit in a mold provides a backlash detecting means 15 for automatically detecting the backlash value existing between the slide valve 5 and the piston rod 8a in a hydraulic cylinder 8 driving this in on-line based on the outputs of the leveller 12 and the position detector 11 and a backlash correcting control means 16 for operating the hydraulic cylinder 8 excessively by the backlash value obtd. with the backlash detecting means 15 at the time of changing the operating direction of hydraulic cylinder 8. Therefore, even at the time of exchanging the slide valve 5 or connecting part, etc., for connecting the slide valve with the piston rod 8a or in the case variation of the backlash value exists, the molten metal surface level at the time of casting can be accurately and quickly kept to the aimed molten metal surface level.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a mold level control device in a continuous casting machine.

[Prior Art] Conventionally, as a mold level control device for maintaining the level of molten metal in the mold at a target level in a continuous casting machine, the one shown in Fig. 7 has been known. There is.

That is, FIG. 7 is an explanatory diagram of the configuration of a continuous casting machine equipped with a mold level control device, and the reference numeral 51 shown in the figure is
is a molten ladle, and a bottom plate 5 is provided on the lower surface of a tundish 52 installed below this i* ladle 51, which has a through hole having the same diameter as the molten steel outlet hole of this tundish 52.
3 is fixed. A seal plate 54 having a through hole with the same diameter as the molten steel outflow hole is provided below this plate 53 at a predetermined distance, and a molten steel outflow hole of the tundish 52 is provided between both plates 53 and 54. A slide valve 55 is provided with a through hole having the same diameter as that of the slide valve 55. This slide valve 55 is for adjusting the amount of molten steel injected into the mold 56 from the tundish 52 to become the slab 57, and the molten metal level in the mold 56 is adjusted to a target level by a mold level control device, which will be described later. The opening degree of the through hole is corrected and adjusted so as to maintain the surface level.

To explain the structure of the mold level control device, as shown in the figure, a hydraulic cylinder 61 is attached to an upper bracket 52a fixed to the side surface of the tundish 52, and a piston of this hydraulic cylinder 61 is attached. The tip of the rod 61a is connected to the lower bracket 52 which is fixed to the tundish 52 below the upper bracket 52a.
The link 62 is connected by a pin to one end of a link 62 that is movably supported by the link 62 b. Furthermore, the other end side of this link 62 is connected to the above-mentioned slide valve 55 via a connecting rod 63. Further, 64 is a hydraulic cylinder 61
This is a differential transformer for detecting the position (displacement) of the piston rod 61a, and its main body is fixed to the hydraulic cylinder 61 etc. by a support member (not shown), and its rod-shaped core moves together with the piston rod 61a, A voltage signal is output according to the position of the londro 1a.

Further, 65 is a level meter such as an eddy current type or an electrode tracking type that detects the level of the hot water inside the mold 56, 65a is an amplifier of the level meter, and 66 is a target level for setting the target hot water level. The setting device 67 inputs the output of the level meter 65 via the amplifier 65a and the output of the target hot water level setting device 66, calculates the deviation of these using a PID calculation circuit, etc., and calculates a value corresponding to the difference between the two outputs. A valve opening command section 68 outputs an output, and 68 is a cylinder control section composed of a normal directional control valve, a servo amplifier, etc., which controls the output of the valve opening command section 67 and positioning. The hydraulic cylinder 61 receives the output of the differential transformer 64 used as an input, and controls the hydraulic cylinder 61 so as to maintain the hot water level in the mold 56 at the target hot water level according to the output of the valve opening command section 67.
This is to control the operation of the

Next, to explain the operation of the mold level control device configured as described above, an imbalance occurs between the amount of molten steel injected into the mold 56 via the slide valve 55 and the amount of slab 57 pulled out, and the level meter When a deviation occurs between the output of the valve 65 and the output of the target hot water level setting device 66, an output corresponding to the difference between the two outputs is given from the valve opening command section 67 to the cylinder control section 68. The cylinder control unit 68 operates the hydraulic cylinder 61 in response. For example, if the level of hot water in the mold 56 is higher than the target level, the piston rod 61a of the hydraulic cylinder 61 is extended and the link 6
The slide valve 55 is slid through the connecting rod 63 to reduce its opening degree, and the amount of molten steel injected into the mold 56 is adjusted to decrease.

[Problem to be solved by the invention]

However, although the above mold in-mold level control device is useful to some extent, it still has problems in the control accuracy of the level as described below.

In other words, since the hydraulic cylinder is operated and the slide valve is slid through a connecting part such as a link or a connecting rod to correct its opening, the hydraulic cylinder's opening is adjusted due to the play caused by the gap in this connecting part. There was a discrepancy between the amount of expansion and contraction of the piston rod and the amount of sliding of the slide valve, making it impossible to accurately control the hot water level.

In particular, when changing the sliding direction of the slide valve, which is important for controlling the hot water level, or in other words, when changing the operating direction of the hydraulic cylinder, play in this connection causes a delay in control and fluctuations in the hot water level. As a result, there was a problem in that the quality of the slab deteriorated.

Furthermore, the value of play in this connecting part changes due to the high temperature atmosphere during casting, and slide valves, links, connecting rods, etc. are replaced with the tundish. Since the value differs each time it is exchanged, it is difficult to know the value as a constant value in advance.

This invention was made to solve the above-mentioned problems, and detects the value of play that exists between the slide valve and the piston rod of the hydraulic cylinder during the hot water level control operation, To provide an in-mold molten metal level control device that can accurately control the molten metal level in a mold by operating a hydraulic cylinder an extra amount corresponding to this backlash when changing its operating direction.

[Means to solve the problem]

In order to achieve the above object, the mold level control device according to the present invention includes a hydraulic cylinder that extends and contracts a piston rod to adjust the opening degree of a slide valve that URvs the amount of molten steel injected into the mold from a tundish; A position detector detects the position of the piston rod, a level meter detects the level of molten metal in the mold, and the deviation between the output of the level meter and the output of the target level setting device is calculated, and the difference between both outputs is calculated. Equipped with a valve opening command section that outputs a value according to the difference,
In a mold level control device for a continuous casting machine, the level control device operates the hydraulic cylinder according to the output of the valve opening command unit to maintain the level of the level in the mold at a target level. Calculate the rate of change in the level of hot water in the mold based on the output of the meter, and calculate the movement of the piston rod of the hydraulic cylinder when the rate of change in the level of hot water is constant and the piston rod of the hydraulic cylinder is expanding and contracting. backlash detection means for detecting the amount of backlash existing between the slide valve and the piston rod based on the output of the position detector; and a backlash correction control means that makes a judgment based on the output and adds a backlash value obtained by the backlash detection means to the output of the valve opening command section when changing the operating direction. It is a feature.

[For production]

The backlash measurement principle according to the present invention will be explained based on the explanatory diagram of FIG. 6. As shown in FIG. The amount of molten steel injected changes due to the imbalance between In other words, when the opening degree of the slide valve is actually corrected by the operation of the hydraulic cylinder, the rate of change in the hot water level changes.Therefore, as shown in Figures 6(b) and (C), , the value of the play in the connection between the slide valve and the piston rod is the amount of movement of the piston rod when the rate of change in the hot water level is constant and the piston rod of the hydraulic cylinder is expanding and contracting. (ΔX1).

In the mold level control device according to the present invention,
Based on the outputs of the level meter and the position detector, the play detection means determines the play value based on the above play measurement principle. Then, the direction in which the hydraulic cylinder is operated is determined based on the output of the valve opening command section, and the above-mentioned backlash value is added to the output of the valve opening command section when changing the operating direction. Thereby, the opening degree of the slide valve can be reliably and precisely corrected by the expansion and contraction movement of the piston rod of the hydraulic cylinder.

(Example) An example of the present invention will be described below with reference to the drawings.

FIG. 1 is an explanatory diagram of the configuration of a continuous casting machine equipped with a mold level control device showing an embodiment of the present invention, in which the continuous casting machine has the same configuration as that explained in FIG. 7. 1 is a molten steel ladle, 2 is a kundishu, 3 is a bottom plate, 4 is a seal plate, 5 is a slide valve whose opening degree is adjusted by a mold level control device described later, 6 is a mold, 7 is a slab.

As shown in the figure, the structure of the mold level control device is that an extraction cylinder 8 is attached to an upper bracket 2a fixed to the side surface of the tundish 2, and the tip of the piston loft 8a of the extraction cylinder 8 is This part is connected by a pin to one end of a link 9 which is swingably supported by a lower bracket 2b fixed to the tundish 2 below the upper bracket 2a. Furthermore, the other end side of this link 9 is connected to the above slide valve 5 via a connecting rod IO. Further, 11 is a differential transformer for detecting the position (displacement) of the piston rod 8a of the hydraulic cylinder 8, and its main body is fixed to the hydraulic cylinder 8 etc. by a support member (not shown).
The rod-shaped core is moved together with the piston rod 8a, and a voltage signal is output depending on the position of the piston rod 8a.

Further, 12 is a level meter for detecting the level of hot water in the mold 6, 12a is an amplifier for the level meter, 13 is a target level setting device for setting the target level of hot water, and 14 is an amplifier 1.
The output of the level meter 12 via 2a and the output of the target hot water level setting device 13 are manually input, and the deviation between them is calculated as PIDi1g.
A valve opening command unit 15 calculates a value using an arithmetic circuit or the like and outputs a value according to the difference between the two outputs, and 15 receives the output of the level meter 12 and the output of the differential transformer 11, and connects the link 9, the connecting rod 10, etc. 16 is a signal of the play value from the output of the valve opening command section 14 and the play detection means 15. is input, and outputs a valve opening correction signal according to the procedure described later.Furthermore, 17 is a cylinder control section composed of a normal directional control valve, a servo amplifier, etc. The correction signal and the output of the differential transformer 11 are input, and the operation of the hydraulic cylinder 8 is controlled according to the valve opening correction signal.

The backlash detection means 15 and the backlash correction control means 16 are composed of a programmed microcomputer. That is, as shown in FIG. 2, the backlash detection means 15 includes a CPU, a memory in which programs and predetermined control data are stored, and an input/output interface circuit, and connects the output of the level meter 12 and a differential transformer. The outputs of 11 are respectively inputted via A/D converters, and the obtained backlash value signal is given to backlash correction control means 16. Furthermore, the backlash correction control means 16 includes a third
As shown in the figure, it is equipped with a CPU, a memory, and a human/output interface circuit, and the output of the valve opening command unit 14 is inputted via an A/D converter, and the valve opening correction signal is inputted via a D/A converter. The signal is supplied to the cylinder control unit 17 via a converter.

Next, the operation of the hot water level control device having the above configuration will be explained below with reference to the drawings.

First, an example of a method for detecting the play value by the play detection means 15 will be explained according to the flowchart shown in FIG.
(See Figure 6), and during the explanation of the flowchart, N1,
N2-- indicates the number of the processing procedure (step).

First, when the control is started, the hot water level obtained by the level meter 12 and the position of the piston rod 8a obtained by the differential transformer 11 are read at every predetermined sampling interval Δ. Then, it is determined whether the rate of change in the hot water level (-(L, -L□1)/Δt) calculated based on the current hot water level Regol L and the previous hot water level L□ is constant. (step Nl), tJ) If the rate of change in the surface level is not constant, repeat this step Nl. If the rate of change in the surface level is constant, move the piston from the same piston rod 8a position as before. It is determined whether the rod 8a is moving (step N2), and if the piston rod 8a is not moving, the process returns to step N1;
If the piston rod 8a is moving, the movement start position X of the piston rod 8a is stored (step N5)0
Next, based on the newly read hot water level obtained by the level meter 12, it is determined whether the rate of change in the hot water level is constant (step N4), and if the rate of change in the hot water level is constant, In other words, when the opening degree of the slide valve 5 is not corrected due to backlash even though the piston rod 8a has been moved, the newly read movement position 1fX of the piston rod 8a is stored (step N5), and this step N5 is repeated for each read hot water level and position of the piston rod 8a until the rate of change of the hot water level changes, thereby changing the movement position X of the piston rod 8a.

are updated sequentially.

If it is detected in step N4 that the rate of change in the hot water level has changed, that is, if it is confirmed that the backlash has been resolved and the opening degree of the slide valve 5 has been corrected, the above-mentioned piston From the difference between the movement position X of the rod 8a and its movement start position X, the same backlash value ΔX is calculated (
Step N6), return to step Nl. Then, the average (shi) of the predetermined number of backlashes fl obtained previously and the current backlash value ΔX7 is obtained, and this is given to the backlash correction control means 16 as the backlash average value (step N6). The play average value is provided to the play correction control means 16 every time it is updated.In addition, by performing the operation of obtaining this average value, thermal expansion of the slide valve 5, link 9, etc. , the backlash value ΔX due to the detection error of the point of change in the rate of change of the hot water level.

It is possible to improve the accuracy by rounding off the variations in

Next, an example of a correction control method by the backlash correction control means 16 will be explained according to the flowchart shown in FIG.

In the description of the flowchart, 5IS2... indicates the number of the processing procedure (step).

First, when control is started, the output MV (having positive and negative signs) from the valve opening command section 14 is read at predetermined sampling intervals. Then, from the sign of the product of the output MV read this time and the output MY read last time, the direction in which the hydraulic cylinder 8 is operated this time is determined (Step Sl), the hydraulic cylinder 8 is operated in the same direction as last time. If so, the current output MV is directly output as a valve opening correction signal to the cylinder control section 17 via the D/A converter, and the process returns to step S2) and step Sl.

On the other hand, if it is determined in step S1 to operate the hydraulic cylinder 8 in the opposite direction from the previous time, as shown in the figure, the output MV of the valve opening command section 14 this time has the above-mentioned play. The latest backlash average (iljK) given from the detection means 15 is added, and the backlash average (output MV corrected by direct K, . . . , that is, the current valve opening command unit 1
The output MV for operating the hydraulic cylinder 8 in the forward or reverse direction by the amount of play in excess of the output MV of 4 is sent to the cylinder control unit 17 via the D/A converter as a valve opening correction signal. Output (step S3). Note that in the first correction control, a predetermined initial value inputted in advance as the play average value may be used.

As a result of the above, the value of the backlash that exists between the slide valve and the piston rod of the hydraulic cylinder that drives it is automatically detected repeatedly and sequentially during hot water level control, and the operating direction of the hydraulic cylinder is changed. At times, the hydraulic cylinder is detected and operated extra to compensate for the backlash, so that the hot water level is controlled with extreme precision so as to maintain it at the target hot water level.

In the above embodiment, the differential transformer 1 is used to detect the position N (displacement) of the piston rod 8a of the hydraulic cylinder 8.
1 was used, but a potentimeter or the like may be used as the position detector.

Furthermore, the mold level control device according to the present invention has a configuration in which a hydraulic cylinder is disposed on the bottom side of the tundish, or the mold level level control device operates a hydraulic cylinder to adjust the level of the mold level by operating a stopper nozzle. Naturally, the present invention is also applicable to other configurations.

〔Effect of the invention〕

As explained above, the mold level control device for a continuous casting machine according to the present invention sequentially controls the level of the mold by adjusting the amount of backlash that exists between the slide valve and the piston rod of the hydraulic cylinder that drives the slide valve. There is a backlash detection means that automatically detects the backlash on-line based on the output of the level meter and position detector, and when changing the operating direction of the hydraulic cylinder, the backlash detected by the backlash detection means is installed in the hydraulic cylinder. It is equipped with a backlash correction control means that operates an extra amount by the value of .

Therefore, according to the hot water level control device according to the present invention, it is possible to prevent fluctuations in the backlash value due to replacement of the slide valve or the connecting part connecting it to the piston rond, or changes in ambient temperature, friction, etc. during control. Even if there is such a problem, the melt level during casting can be maintained at the target melt level very accurately and quickly, and this can contribute to improving the quality of the slab.

[Brief explanation of drawings]

The first factor is an explanatory diagram of the configuration of a continuous casting machine equipped with a mold level control device showing an embodiment of the present invention, Figure 2 shows the configuration of the microcomputer as a backlash detection means, and Figure 3 shows backlash correction. Components of the microcomputer as a control means, FIG. 4 is a flowchart showing an example of a procedure for detecting a play value by the play detection means, FIG. 5 is a flowchart showing an example of a control procedure by the play correction control means, and FIG. is an explanatory diagram of the backlash measurement principle according to the present invention, and FIG. 7 is an explanatory diagram of the backlash measurement principle according to the present invention. FIG. 2 is a configuration explanatory diagram of the machine. (Explanation of symbols) 1-molten steel ladle, 2-tandish, 2a...-upper bracket, 2b--lower bracket, 3
-Bottom plate, 4--Seal plate, 5--Slide valve, 6--Mold, 7--Slab, El-m
Pressure cylinder, 88- Piston rond, 9--Link, 10-- Connecting rod, 11- Differential transformer, 12-
・-Level meter, 12a...Level meter amplifier, 13・
-Target hot water level setting device, I4--Valve opening command unit, 15--Backlash detection means, 16--Backlash correction control means, 17--Cylinder control unit.

Claims (1)

[Claims] (1) A hydraulic cylinder that extends and retracts a piston rod to adjust the opening degree of a slide valve that adjusts the amount of molten steel injected into the mold from the tundish, a position detector that detects the position of the piston rod, and a It is equipped with a level meter that detects the hot water level, and a valve opening command unit that calculates the deviation between the output of the level meter and the output of the target hot water level setting device, and outputs a value according to the difference between the two outputs. , in the mold in-mold level control device for a continuous casting machine, wherein the hydraulic cylinder is operated in accordance with the output of the valve opening command section to maintain the in-mold level at a target level; The rate of change in the level of hot water in the mold is calculated based on the output of the level meter, and when the rate of change in the level of hot water is constant and the piston rod of the hydraulic cylinder is expanding and contracting. a play detecting means for detecting the amount of movement as a value of play existing between the slide valve and the piston rod based on the output of the position detector; and a valve opening command section for determining the direction in which the hydraulic cylinder is actuated. and a backlash correction control means for making a judgment based on the output of the valve opening command section and adding a backlash value obtained by the backlash detection means to the output of the valve opening command section when changing the operating direction. Features: A mold level control device in a continuous casting machine.