JPS61178616A - Device for measuring surface of liquid of liquefied metal invessel - Google Patents

Abstract

1. Apparatus for measuring the level of molten metal (M) in a vessel, especially a continous casting mould (K), by sensing the secondary electromagnetic fields emanating from the liquid metal, the apparatus comprising a primary coil (P, P2 , P4 ) creating a time varying electromagnetic field, two secondary measurement coils (S, S2 , S'2 ; S4 , S'4 ) extending along substantially the entire height of the primary coil and positioned on the opposed sides of the primary coil and means for delivering the difference of the signals sensed by the secondary measurement coils, characterized in that at least one of the coils (P; P2 ; P4 ; S, S'; S2 , S'2 ; S4 , S'4 ) is subdivided into at least two superimposed stages (40, 41, 42, 43, 44) having different magnetic properties and in that at least on stage of the secondary measurement coils (S, S2 , S4 ) includes at its ends connections for relaying the calibrating signals.

Description

[Detailed description of the invention] 11 ohms! The present invention is a device for measuring the level of liquid metal in a container, particularly in a continuous casting mold, and includes a primary coil for generating an electromagnetic field and two secondary coils for measurement. It is related to.

BACKGROUND OF THE INVENTION It is extremely important to know the level of liquid metal in a continuous casting mold at all times to control the rate at which liquid metal is injected into the mold and the rate at which the steel rod is released from the mold. It is. To achieve this objective, a number of measurement methods are already known, including measurement methods using television cameras and radioactive elements, as well as measurement methods that utilize the electromagnetic properties of the metal in the mold. Measurement methods based on electromagnetic phenomena, particularly methods for measuring Foucault current induced in liquid metal in a mold, have the following two problems.

- Copper molds absorb electromagnetic fields, making it difficult to separate signal from noise.

- Strong electromagnets are often attached to the molds to stir the liquid metal. These electromagnets generate magnetic fields hundreds of times larger than those inherent in liquid metals, which can disrupt measurements.

In European Patent No. 10.539, the applicant:
A method for measuring the level of liquid metal in a continuous casting mold is disclosed. According to this method, it is necessary to have two secondary coils identical to the primary coil, the secondary coils being connected oppositely and symmetrically with respect to the midplane of the primary coil, but also coaxially. It is provided. The primary coil and the secondary coil are provided around the mold so that they do not physically contact each other. It measures not only the voltage induced in the secondary coil but also the conductivity of the liquid metal. The measured and corrected voltage value and conductivity value are combined to determine the height of the liquid level. When the mold is empty, the total secondary voltage is zero. As the liquid level rises, a large voltage is induced in the lower coil. As a result, the overall voltage increases. The total secondary voltage is maximum when the liquid level is between the two secondary coils and the asymmetry is maximum. As the liquid level rises further, both the asymmetry and the total secondary voltage decrease again. From the above, a bell-shaped measurement curve with two substantially linear slopes at the 35% height position is obtained.

The coil is arranged perpendicular to the vector that induces the stirring electromagnetic field, and this electromagnetic field acts differently on the coil, so it is complicated to extract the desired signal from a combination of various signals. There is a problem. If the plates wear out or the temperature changes, the equipment must be adjusted, but just like recalibrating the measurement system, it is subtle and difficult.

Furthermore, as a result of having a bell-shaped measurement curve, it is not always possible to uniquely determine the metal liquid level within the measurement range. On the other hand, outside the measurement range, metal may be about to overflow.
Since a hole is drilled into a steel rod, it is not possible to identify the metal liquid level.

Problems to be Solved by the Invention As explained above, the conventional liquid level measurement method using electromagnetic phenomena includes a method of measuring Foucault current induced in liquid metal; There are two problems.

- Copper molds absorb electromagnetic fields, making it difficult to separate signal from noise.

-For the purpose of stirring the liquid metal, an electromagnet is often attached to the mold. These electromagnets generate magnetic fields hundreds of times larger than those inherent in liquid metals, which can disrupt measurements.

Furthermore, a liquid level measurement method using a combination of a primary coil and two secondary coils has been considered, but there are problems such as the inability to uniquely determine the liquid level position and the risk of metal overflowing.

Therefore, the present invention solves the above problems, is compact, easy to interpret the signal, has a wide measurement range, can automatically start casting, is easy to calibrate, and can accurately measure the liquid level. The purpose of this invention is to provide a liquid level measuring device.

Means for Solving the Problems The liquid level measuring device of the present invention, which solves the above problems, measures the liquid level of a liquid metal in a container, particularly an fP type for continuous casting, by using a secondary electromagnetic field emitted from the metal. A device for measuring by detecting AX Along both sides of the primary coil (substantially throughout its length).

At least one of the coils is divided into at least two superimposed stages having different magnetic properties.

Further, at least two stages of the divided coils have the same number of turns of the coil, which is different from the other stages.

Furthermore, in addition to the stage at the end of the coil, at least one stage of the secondary measurement coil is provided with an auxiliary connection member used for detecting the measurement signal.

Each of the coils has a substantially cylindrical shape and is entirely disposed beside and adjacent to the liquid metal so as to surround the container.

One of the secondary coils of the liquid level measuring device is used for measurement,
The other secondary coil is used for reference, and the reference secondary coil faces at least one of the measurement secondary coil located at a position lower than the liquid metal level and the divided measurement secondary coil. Connect.

The liquid level measuring device of the present invention is a device that measures the liquid level of a liquid metal in a container, particularly a continuous casting mold, by detecting a secondary electromagnetic field emitted from the metal, The device includes a primary coil for emitting varying electromagnetic waves, the device including a only secondary coil disposed between the liquid metal and the primary coil, the secondary coil substantially extending along the primary coil. The secondary coil can also be provided across its entire length, with the secondary coil connected face-to-face to a signal derived directly from the voltage applied to the primary coil or from a constant voltage source.

In this case as well, at least one of the secondary coils is divided into two stages, which have different magnetic properties and are superimposed on each other.

The liquid metal level measuring device of the present invention includes a primary coil that creates a time-varying electromagnetic field and two secondary coils for measurement.

A feature of the present invention is that at least one of these secondary coils is divided into several stages. The number of turns of the coil is changed in each stage. Adjustments are made through experiments so that the voltage change detected between the secondary coils corresponds one-to-one with the liquid level, and the excess signal is reduced.

By calibrating the relationship between the signal voltage value and the liquid level position, the liquid level position can be accurately known from the measured value of the signal voltage.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1 one can see the rectangular cross-section of a primary coil P surrounding a bath M of molten metal. The first secondary coil S for measurement is provided along and inside the primary coil P with the same length and at the same height. A second secondary coil S'' for compensation is provided outside the primary coil P. Considering the difference between the signals detected by the secondary coils S and S as a function of the bath height H, the ideal As shown in the right half of Figure 1, a monotonically increasing voltage 7 should be observed as the bath level rises. In fact, the measured ■ depends not only on the liquid level of the bath, but also on other physical quantities.It is impossible to make the exact position of the metal liquid level correspond to the measured voltage. In order to be able to do this, it is necessary to fill the bath almost completely with metal and measure the maximum voltage for each casting condition (iron condition, casting temperature, etc.). However, using such a calibration method not only risks overflowing the metal, but also risks overheating parts that are not expected to be used at such high temperatures. , the inventor proposes to divide the measuring secondary coil into at least two parts, for example into mutually equivalent parts S1 and 32 as shown in FIG.

It should be pointed out that it is desirable that the lower coil S1 of the secondary coil S is located slightly below the normal liquid level of the bath. In fact, when the difference between the signals detected by the lower coil S1 and the secondary coil S° is considered as a function of the bath height H, a maximum value appears (see curve 8 on the right hand side of Figure 1). When casting starts, curves ■6 and ■ appear. can be seen changing. Curve■. When Vex passes through its maximum value Vex, the difference in voltage appearing across the coils S and S' at that moment can be made to correspond to a certain level position in the bath, and the metal rises further to the level. The value ■ that would have been the maximum value of the curve ■7 if it had reached that height. .

can be extrapolated. Note that the maximum value V e m is mainly determined by the condition of the iron, the temperature, and the arrangement of the lower coil S1.

Similarly, it is also possible to calibrate continuously throughout the casting while lowering the liquid level below the upper end of the lower coil S1. It will be clear that a larger number of subdivisions of the secondary coil S (for example three or four) will make the calibration more accurate, if not more continuous.

FIG. 2 shows another embodiment of the measuring device of the present invention.

A cylindrical coil 20-30 cm long and 20-30 mm in diameter is placed in a suitable hole in a 40-50 mm thick copper plate of the mold. Since this measuring device must withstand considerable high temperatures, it consists only of coil wire that can withstand this high temperature and does not contain any active ingredients. The main part of this measuring device consists of a triple coil 20 with a length of 10 to 15 cn+ for liquid level measurement. In some cases, a triple coil 21 having a length of 2 to 5 cm is also provided for forming a liquid level detection and measurement system. The measurement triple coil 20 includes a primary coil P2, a measurement secondary coil S2, and a reference secondary coil S2''.

Further, the detection/calibration triple coil 21 similarly includes a primary coil P3, a measuring secondary coil S3, and a reference secondary coil S3°. The two secondary coils are located on either side of the primary coil, have the same length, and are located at the same height. If we carefully consider the arrangement of the secondary coils facing each other, as shown on the right side of each of the upper and lower coils in Fig. 2, the signal (V2n) is monotonous with respect to the distance (height H of the metal bath).

V3n) can be obtained. By using the lower triple coil 21, it is possible to easily detect the iron liquid level at the start of casting. As explained earlier using FIG. 1, the secondary coil S2 is
Furthermore, it can be divided into at least two parts. This measuring device, in the form of a bar with a circular cross section, is particularly compact and can be easily accommodated in the copper plate of the mold. In order to increase the surface area of the coil winding relative to the bath, the cross section of the measuring device is made rectangular.

FIG. 4 shows a particularly preferred embodiment of the primary and secondary coils according to the invention. This embodiment is similar to Fig. 1 and 2.
As shown in the figure, this was devised in consideration of the fact that the voltage difference between the secondary coil and the reference secondary coil with respect to the height of the liquid level does not exhibit the required linearity. Voltage■
. In order to make it change linearly, each coil is divided into several stages, and the number of turns of the coil is changed in each divided stage. Inside one tier, several compartments are stacked one on top of the other. Each section consists of a single layer of adjacent windings. For ease of manufacture, one section may span several levels. Given a single coil, the horizontal size is the same for each tier, so if there is a tier with fewer compartments, the empty space must be filled with cardboard or poured with plastic. Further, the diameter of the coil may be determined so as to exactly fill the empty space inside each stage. This latter method obviously cannot be used when the winding section spans several stages.

The number of sections that can be incorporated into one stage is the coil S
It is determined experimentally so that the difference between the signals detected at and S" changes as monotonically as possible with respect to the liquid level, and so that the extra signals are as small as possible. In general,
Reference secondary coil S.

contains no or only a few windings in the end stages. Further, the other stages include the same number of sections as the secondary coils S. On the other hand, the secondary coil S includes the largest number of sections (for example, 9 sections) at both ends, and the smallest number of sections (for example, 5 sections) at the center section. The step at the level of the bath has more compartments than the center (e.g. 7
). The number of sections included in each stage of the primary coil P is usually slightly smaller than the number of sections included in each stage of the secondary coil S. However, the diameter of the primary coil is generally larger than the diameter of the secondary coil. Some of the lower stages of the primary coil (with the exception of the lowest stage, which is the most important at the start of casting) may have no windings. Therefore, its role is only to connect two adjacent stages. For the purpose of calibrating the signals detected at both ends of the secondary coils S and S'' connected oppositely, at least one stage of the secondary coil S is provided with signal detection means. 5 stages 40.41.4 of 3 coils P4, S4, P' 4
The configuration of 2.43.44 is as follows.

- The number of winding sections per stage is proportional to the thickness of the coils in that stage (see Figure 4). Fill the empty space with insulating paper.

- The primary coil P4 has 7 compartments in its lowest stage 40 and the maximum number of compartments (10 compartments) in its top stage.

- The secondary coil S4 has the maximum number of sections (13 sections) in the stages 40 and 44 at both ends thereof.

- The reference secondary coil S'4 has stages 40 and 44 at both ends thereof.
has no winding.

- In the embodiment of FIG. 4, each winding section traverses the maximum number of stages each time. The reference secondary coil S' 4 has, for example, three stages 41.
42. It has 5 sections spanning 43, with 2 levels 41 and 4.
3 has two secondary compartments.

Of course, it is not necessary that the coil be divided into five stages. Depending on the application, the coil can be divided into more or fewer stages. Similarly, the gist of the present invention does not change even if the number of winding sections for each stage is changed or the number of secondary coils is changed.

In special cases, the reference secondary coil S' may be removed and the signal detected by the measuring secondary coil S may be directly derived from the voltage applied to the primary coil P, or even the constant voltage. The trick is to extract the signal from the source.

Although the explanation has been made above using the figures, the figures are merely one embodiment of the present invention.

Effects of the Invention One feature of the device of the present invention is that the volume of the coil can be reduced. This is particularly advantageous if the space of the coil to which the device for producing the agitation is attached is reduced. The stirring device exerts an effect on the measuring coil similar to that of the liquid metal being measured. If the coils are connected face-to-face, any signals generated by the stirring device will be largely canceled out. As a result of the symmetrical side-by-side arrangement of each coil and the limited overall volume, the effects of temperature changes are negligible.

This means that it can be calibrated at low temperatures for use. Therefore, the electronic circuit for signal processing can be made extremely simple.

Further, by using the device of the present invention, the liquid level can be accurately measured over a wide measurement range.

[Brief explanation of the drawing]

1 is a schematic cross-section of the coil of the invention and a graph of the measured voltage as a function of the height of the liquid metal in the mold; FIG. FIG. 3 is a schematic diagram of a cross-section of the detection device and a graph showing the measured voltage as a function of the height of the liquid metal in the mold; FIG. 3 shows the detection device shown in FIG. FIG. 4 is an enlarged view of the cut section taken at point (3). FIG. 4 is a schematic view of a portion of the cross section of the entire coil according to the present invention. (Main reference numbers) K...Mold, M...Metal bath, P, P2, P3, P4...Primary coil, SSS', 5L
S2, S2'', S3, S3'', S4, S4゜... Secondary coil, 40.41.42.43.44... Stage Patent Applicant Albed Nis, Ah.

Claims (10)

[Claims] (1) A device for measuring the level of a liquid metal in a container, particularly a continuous casting mold, by detecting a secondary electromagnetic field emanating from the metal; coil and two secondary coils for measurement, each of the two secondary coils being provided along both sides of the primary coil over substantially its entire length. Liquid level measuring device. (2) The liquid level measuring device according to claim 1, wherein at least one of the coils is divided into at least two overlapping stages having different magnetic properties. (3) The liquid level measuring device according to claim 2, wherein at least two stages of the divided coils have the same number of turns of the coil, which is different from that of the other stages. (4) In addition to the stage at the end of the coil, at least one stage of the secondary measuring coil is provided with an auxiliary connecting member used for detecting a measurement signal. liquid level measuring device. (5) The liquid level measuring device according to any one of claims 1 to 4, wherein each of the coils surrounds the container. (6) Each of the coils has a substantially cylindrical shape, and the entire coil is provided beside and near the liquid metal, according to any one of claims 1 to 4. liquid level measuring device. (7) There are two sets of the above cylindrical coils, each set of which is stacked on top of each other, the lower set has the same size in cross section as the upper set, and is slightly shorter in length, and is used at the beginning of casting. A liquid level measuring device according to claim 6, characterized in that: (8) comprising two secondary coils, one of which is divided into at least two parts, used for measurement;
The other secondary coil is used for reference, and the reference secondary coil faces at least one of the measurement secondary coil located at a position lower than the liquid metal level and the divided measurement secondary coil. The liquid level measuring device according to any one of claims 1 to 7, characterized in that the liquid level measuring device is connected to the device. (9) A device for measuring the liquid level of a liquid metal in a container, especially a continuous casting mold, by detecting a secondary electromagnetic field emitted from the metal, which device uses a primary a coil, the apparatus comprising a single secondary coil disposed between the liquid metal and the primary coil, the secondary coil disposed along substantially the entire length of the primary coil; , wherein the secondary coil is connected face-to-face to a signal obtained directly from the voltage applied to the primary coil or a signal from a constant voltage source. (10) At least one of the secondary coils is formed of at least two superimposed coils having different magnetic properties.
The liquid level measuring device according to claim 9, characterized in that it is divided into stages.