JPH0688113B2 - Molten metal level detector - Google Patents

Description

TECHNICAL FIELD The present invention relates to a device for automatically detecting a molten metal level in a mold over a wide range with high accuracy and high response.

[Conventional technology]

The level of molten metal level that is difficult to detect directly is one of the indirect detection methods that has been used in the past, for example, an electromagnetic coil mounted above the molten metal level so that it can be moved up and down using a drive device such as a servomotor. Is placed to detect the change in the inductance or eddy current corresponding to the change in the distance between the molten metal surface and the electromagnetic coil, and the electromagnetic coil is moved up and down so that the detected value is always a constant value. While keeping the gap between the coil and the molten metal surface constant,
An automatic tracking type detection device has been proposed which detects the position of the electromagnetic coil and sets it as the level of the molten metal surface. One of them is disclosed in Japanese Examined Patent Publication No. 54-42846, and the other one is Japanese Unexamined Patent Publication No. 57-2.
There is 04401 publication. The present invention relates to improvements in these automatic follow-up type molten metal level detection devices, and is intended to improve responsiveness.

[Problems to be Solved by the Invention]

It is said that these automatic follow-up molten metal level detectors have a wide measuring range and can obtain highly accurate level values, but the friction resistance of the moving parts of the lifting drive device, the weight of the electromagnetic coil, etc. The electromagnetic coil does not move until the level of the molten metal molten metal level changes enough to generate a driving force superior to the above.

For this reason, the detection device is delayed in tracking the change in the molten metal level, and the level signal always shows the value immediately before the current point and is not accurate. Even if the driving force is infinitely increased, the following delay can be made as close as possible to "0" for a small change in the molten metal level, but it cannot be made "0" in practical use. Further, it has been confirmed that the frictional resistance of the movable parts of the lifting drive device changes due to thermal changes of the device and deterioration over time.

This follow-up delay of the detection device is generally called a delay due to a dead zone, and this dead zone is expressed by the amount of change in the molten metal level, which is necessary to generate a force for driving the electromagnetic coil. The design value is ± 1 mm, ± 4 when used.
mm to ± 5 mm.

Due to this dead zone, the molten metal level detection device causes a delay time in level detection, and this delay time is found to have a bad influence on the control performance of the control device for keeping the molten metal molten metal surface level constant. did.

In particular, if there is a factor that causes a periodic change in the molten metal level (hereinafter referred to as disturbance), the control performance cannot be improved due to the effect of this delay time, so it is possible to suppress the level change sufficiently. However, if the performance is forcibly increased, the level change will be amplified.

In a continuous casting machine that handles molten metal, the support device for the slab in the solidification process (generally supported by multiple rolls after leaving the mold) is thermally and mechanically deformed to allow casting during solidification. Cyclically deforming the piece, causing a volume change of the unsolidified portion existing inside the slab, as a result of raising or lowering the level of the molten metal surface in the mold, it may become a disturbance of the level change Are known. This molten metal level level change cycle is often proportional to the speed at which the slab is drawn out, and a cycle of one rotation of the roll or a cycle depending on the time the slab advances along the roll pitch is known.

In the case of a continuous casting machine for steel, in the example of a casting speed of 1.2 m / min with a width of 1800 mm and a thickness of 250 mm, a change in the molten metal level at a period of 15 seconds to 30 seconds was observed. With respect to the disturbance of such a cycle, the delay time due to the dead zone of ± 4 mm reaches 3 seconds to 4 seconds, the control operation is delayed and the level change is amplified, and it is difficult to suppress the level change.

The present invention aims to remedy such conventional problems.

[Means for Solving the Problems]

According to the present invention, the electromagnetic coil 5 is suspended and supported above the molten metal surface in the mold 1 by the lifting / lowering drive devices 9, 10, 11, 12, and H, and an eddy current is generated in the molten metal in the mold 1 by the electromagnetic coil 5. The inductance detection device includes a device 6 for detecting the inductance of the coil when the coil is driven, and level transmitters 13 and 14 for measuring the height position of the coil and transmitting the melt level conversion value based on the measured value. In a molten metal level detecting device having comparison controllers 7 and 8 for comparing the detection signal from 6 with a reference value and controlling the height position of the electromagnetic coil 5 of the lifting drive device according to the deviation value; A distance conversion device 15 that introduces a signal from a detection device to convert a minute change amount into a height distance change amount, and a distance change amount from the same arithmetic unit and a level conversion value from the level transmitter 14 are introduced. The result of addition of And an adder 16 for transmitting the signal are provided.

[Action]

That is, in the dead zone area of the molten metal molten metal level detecting device of the automatic tracking method, the output change of the electromagnetic coil is recognized as the change of the molten metal molten metal level, and is added to the position signal of the electromagnetic coil to detect the dead zone area and The level detection delay time due to this is eliminated, and the control performance of the control device for keeping the molten metal surface level constant is improved.

According to this, the dead zone, which is the drawback of the automatic tracking type molten metal surface level detection device, can be eliminated in principle, and the change of the dead zone area due to the thermal change or deterioration of the frictional resistance of the moving part in use can be eliminated, and the control can be performed. It can greatly contribute to the improvement of the control function of the device.

Further, the region for converting the coil output change into the molten metal surface level change is sufficient if it corresponds to the dead zone region, the non-linear characteristic correction of the electromagnetic coil output can be stopped within a small range, and the detection accuracy is improved. be able to.

〔Example〕

 Hereinafter, the present invention will be described in detail with reference to the embodiments shown in the drawings.

FIG. 1 shows a concrete example of a molten metal surface level detecting device according to the present invention, which is an example of a continuous casting device.

Molten metal 2 is stored in the mold 1, cooled by the mold 1, and drawn out downward while forming a solidified shell (shell) 3, cooled by cooling water from immediately below the mold, and a support roll 4 is formed.
It solidifies while being supported by and forms a slab.

An electromagnetic coil 5 is arranged above the molten metal 2 in the mold 1 to detect the level of the molten metal surface 2a of the molten metal 2. The electromagnetic coil is driven by the servomotor 10 to drive the drum 11 and the pulley H. It is suspended and supported by a drive cable 12 which can be vertically moved from the horizontal direction to a substantially vertical direction, and moves up and down following a change in rising and falling of the molten metal surface 2a.

The detection signal 18 of the electromagnetic coil 5 is applied via a coil signal calculator 6 to a comparator 8 that controls the distance between the electromagnetic coil 5 and the molten metal surface 2a of the molten metal 2 to be kept constant. A reference signal corresponding to a preset distance between the molten metal surface 2a and the electromagnetic coil 5 is supplied to the comparator 8 as a reference signal setting device 7
The comparator 8 applies the difference signal between the electromagnetic coil detection signal 18 and the reference signal to the motor driver 9 as a drive signal, and the motor driver 9 follows the applied signal. To drive. The servo motor 10 rotates the drive cable winding drum 11 in response to the drive signal, winds or loosens the drive cable 12, raises and lowers the electromagnetic coil 5, and moves the electromagnetic coil 5
Are made to follow the molten metal surface 2a so as to maintain a constant interval with respect to the molten metal surface 2a.

The potentiometer 13 connected to the servomotor 10 detects the position of the electromagnetic coil 5, and the position signal calculator 14 converts the detection signal of the potentiometer 13 into an electromagnetic coil position signal 17. On the other hand, the distance conversion calculator 15 converts the electromagnetic coil detection signal 18 obtained by converting the output change of the electromagnetic coil 5 by the coil signal calculator 6 into the minute distance change signal 19 between the electromagnetic coil 5 and the molten metal surface 2a, and the adder 16 adds the minute distance change signal 19 to the electromagnetic coil position signal 17 and outputs it as the level signal 20 of the molten metal surface 2a of the molten metal 2.

The level signal 20 is displayed as a level signal on the molten metal level control device LCON that controls the opening of the sliding nozzle SN of the tundish TD so that the molten metal level is kept constant. Supplied.
In the figure, IN is an immersion nozzle.

Since the structure is as described above, when the level of the molten metal surface 2a of the molten metal 2 is lowered, a detection signal corresponding to the amount of decrease detected by the electromagnetic coil 5 is first transmitted from the electromagnetic coil 5, and the coil calculator is operated. Electromagnetic coil detection signal via 6
It is converted into 18 and applied to the comparator 8 and the distance conversion calculator 15. At this time, if the amount of decrease is in the dead zone, the servo motor 10 does not operate even if the output of the comparator 8 and the output of the motor driver 9 change, and only the minute distance change signal 19 output from the distance conversion calculator 15 is output. Changes and changes the level signal 20 via the adder 16. When the amount of decrease exceeds the dead zone, the servo motor 10 operates to rotate the drive cable winding drum 11 to loosen the drive cable and move the electromagnetic coil 5 downward by the amount of decrease of the molten metal surface 2a of the molten metal 2. Then
The distance from the molten metal surface 2a is kept constant. The potentiometer 13 detects the position of the electromagnetic coil 5 at this time, and lowers the level signal 20 via the position signal calculator 14 and the adder 16.

〔The invention's effect〕

As described above, the change in the distance from the molten metal surface is detected by the change in the output of the electromagnetic coil mounted so that it can be moved up and down with respect to the molten metal surface, and the electromagnetic coil is adjusted so that the detected value becomes a constant value. Since the distance between the electromagnetic coil and the molten metal surface is kept constant by raising and lowering it, it is possible to measure over a wide range regardless of the level change of the molten metal surface and complement the dead zone area when the electromagnetic coil moves up and down. By doing so, the dead zone and the response delay due to the dead zone are eliminated, and a highly accurate and highly responsive molten metal level signal is obtained.

Further, since the distance between the molten metal level and the electromagnetic coil is controlled to be constant, the sensitivity of the detector to the molten metal level change is maintained at a substantially constant value, and the level of the molten metal level is maintained. It is possible to stabilize the control performance of the molten metal surface level control device that performs control to keep the temperature constant.

Further, since the electromagnetic coil is controlled so as to be always kept at a constant distance from the molten metal surface, there is no danger of the electromagnetic coil being immersed in the molten metal, and the electromagnetic coil can be used semipermanently. Since the amount of radiant heat received from the molten metal is constant, the influence of temperature change can be reduced.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention. 1: Mold, 2: Molten metal 2a: Molten metal surface, 3: Solidified shell 4: Support roll, 5: Electromagnetic coil 6: Electromagnetic coil signal calculator, 7: Reference signal setter 8: Comparator, 9: Motor driver 10 : Servo motor, 11: Drum 12: Drive cable, 13: Potentiometer 14: Position signal calculator, 15: Distance conversion calculator 16: Adder, 17: Electromagnetic coil position signal 18: Electromagnetic coil detection signal 19: Minute distance change Signal, 20: Level signal

Claims (1)

[Claims] 1. A device for suspending and supporting an electromagnetic coil above a molten metal surface in a mold by a lifting drive device, and detecting an inductance of the coil when an eddy current is generated in the molten metal in the mold by the electromagnetic coil. , Having a level transmitter for measuring the height position of the coil and transmitting a melt level conversion value based on the measured value, comparing the detection signal from the inductance detecting device with a reference value, and depending on the deviation value, In a molten metal level detection device having a comparison controller for controlling the electromagnetic coil height position of a lifting drive device; a distance conversion calculation for introducing a signal from the inductance detection device and converting a minute change amount into a height distance change amount. And an adder for introducing the amount of change in distance from the calculator and the level conversion value from the level transmitter and transmitting the addition result as a molten metal level signal. And a molten metal level detecting device.