JPH0194201A - Method and apparatus for measuring thickness of molten slag - Google Patents

Abstract

PURPOSE:To enable highly accurate measurement of the thickness of a molten slag, by detecting impedance of a detection coil generating a high frequency magnetic field with a magnetic field generation coil arranged above the slag to separate and extract a resistance component thereof. CONSTITUTION:A slag 3 is dumped onto the surface of a molten iron 2 poured into a cast mold 1 to form a layer of a powder slag 3a and a molten slag 3b. A detection head 5 is arranged above the slag 3, a magnetic field generation coil 5a is connected to an oscillator 4 to generate a high frequency magnetic field and a pair of detection coils 5b is connected to an impedance measuring device 6 in opposite phase to measure impedance. A computing means 7 separates the impedance detected into an inductance and a resistance. In this manner, as the resistance component is caused by an eddy current loss induced onto the molten slag, there is a better correlationship between a resistance value and the thickness of the molten slag. Thus, the thickness D of the molten slag can be determined at a high accuracy from the resistance value.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a layer of molten slag that is formed on the molten metal by the melting of a part of the slag that is supplied together with the molten metal into the mold of a continuous metal casting machine. The present invention relates to a method and apparatus for measuring the thickness of.

[Prior art]

When continuously casting metal using a continuous casting machine, the surface of the molten metal in the mold is coated for the purpose of keeping the molten metal in the mold warm, absorbing non-metallic inclusions in the molten metal, and lubricating between the mold inner wall and the solidification seal. Slag is supplied.

A portion of the supplied slag is melted by the heat from the molten metal, forming a layer of molten slag on the surface of the molten metal.

By the way, the thickness of the layer of molten slag (hereinafter referred to as molten slag thickness) is the thickness of the layer of molten slag that flows between the inner wall of the mold and the solidified shell)
The viscosity of the molten slag has a dominant influence on the amount of inflow of molten slag, and excess or deficiency in the amount of inflow can lead to deterioration in the quality of slabs obtained by continuous casting or breakage, which can cause major operational problems. Therefore, it is necessary to measure the thickness of the molten slag and manage it to keep it constant.

Therefore, several methods have been proposed for measuring the thickness of molten slag. For example, as shown in FIG. 5, a rod-shaped material 10b having a melting point below the molten metal temperature and above the molten slag temperature] is coated around the periphery of the material 10b having a melting point below the molten slag temperature to create a coaxial shape. Needle wire 10 made into a wire member
is vertically inserted into the slag 3 and molten metal 2 of the mold 1 so as to cover both of them, and the molten slag thickness D is determined from the difference in the melting length of the image materials 10a and 10b that constitute the needle line 10. A method (needle line method) has been proposed. Note that instead of the needle line 10, the pixel +1'lOa,
In some cases, a pair of needle wires is used in which a pair of wire rods each made of 10b are arranged in parallel (Japanese Patent Laid-Open No. 61-2
No. 71401).

A method using a multi-frequency eddy current displacement meter has also been proposed (Japanese Patent Application Laid-Open No. 180402/1982). In this method, a magnetic field generating coil that generates a high-frequency magnetic field and a detection coil that measures impedance are arranged above the molten metal and slag in the mold, and the impedance changes as the distance between the detection coil and the molten slag and molten metal changes. Focusing on the fact that the change differs depending on the frequency of the high-frequency magnetic field, the magnetic field generation coil generates a low-frequency magnetic field with a frequency that is sensitive to the molten metal and a low-frequency magnetic field with a frequency that is sensitive to the molten slag, and This is a method to determine the molten slag thickness by comparing impedances.

[Problem that the invention seeks to solve]

However, in the case of the method using the needle wire 10 (or a pair of needle wires), it takes a certain amount of time from the time the needle wire 10 is inserted into the slag 3 and the molten metal 2 in the mold 1 until the needle wire 10 melts. There has been a problem in that large errors may occur due to changes in the molten steel scene (changes in the molten steel level) during that time. Furthermore, since intermittent measurements are usually performed manually, there is a problem in that the accuracy and reproducibility of this work are difficult, making it difficult to perform highly accurate measurements.

On the other hand, when using a method using a multi-frequency eddy current displacement meter, the amount of change is related to the molten slag thickness without fully analyzing the factors behind impedance change.
Errors due to various factors, such as fluctuations in the molten steel level and types of slag, tend to occur, making it difficult to obtain highly accurate measurement results.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method and apparatus for measuring the thickness of molten slag with high accuracy.

[Means for solving problems]

The method for measuring the thickness of molten slag according to the present invention includes disposing a magnetic field generating coil and a detection coil above the slag that is supplied together with the molten metal into the mold of a continuous casting machine and partially melting. The present invention is characterized in that the impedance of the detection coil is detected while generating a high-frequency magnetic field using a high-frequency magnetic field, and the thickness of the molten slag is determined from the resistance component separated and extracted from the detected impedance.

[Effect]

In the method of the present invention, the resistance component is separated and extracted from the impedance measured by the detection coil, but since the resistance is caused by eddy current loss induced on the molten slag, the resistance and the molten slag are There is a good correlation with slag thickness.

Therefore, the molten slag thickness can be determined with high accuracy from the resistance.

Note that when the resistance is separated and extracted from the impedance to measure the molten slag thickness, the inductance is also separated and extracted, but the inductance is at the molten steel level (specifically, it can be expressed by the distance between the detection coil and the molten metal surface). There is a good correlation between the impedance and the molten steel level, and the molten steel level can be determined with high accuracy from the impedance. And using the measured value of the molten steel level? The thickness of the molten slag can be adjusted by correcting errors based on fluctuations in the molten steel level when measuring the molten slag thickness, or by adding a mechanism that keeps the distance between the measured molten steel level and the detection coil constant. The measurement accuracy can be further improved.

Furthermore, when configuring the apparatus used to carry out the method of the present invention, if detecting coils are connected above and below the magnetic field generating coil in opposite phases, the temperature of the coil resistance will cause an error in measuring the thickness of the molten slag. This can be suppressed by offsetting the effects of fluctuations due to

〔Example〕

Hereinafter, the method of the present invention will be explained in detail based on the drawings showing examples thereof.

FIG. 1 is a vertical cross-sectional view schematically showing the implementation state of the method of the present invention, in which 1 is a mold, 2 is a molten metal, 3 is a slag,
Molten metal 2 is injected into the mold 1 for continuous casting, and slag 3 is applied to the surface of the molten metal 2 to keep the molten metal 2 warm, absorb nonmetallic inclusions in the molten metal 2, and solidify the molten metal 2. The solidified shell 2a produced by the process is supplied for the purpose of lubrication between the mold 1 and the solidified shell 2a. And the slag 3 is powder slag 3
It is supplied in the state of a, but a part of it melts and becomes molten metal 2.
A layer of molten slag 3b is formed on top.

Above the slug 3, there are a magnetic field generating coil 5a connected to the oscillation H4 to generate a high frequency magnetic field of an appropriate frequency, and a pair of detection coils 5b connected to the impedance measuring device 6 to detect impedance. A built-in detection head 5 whose cores are aligned with each other is arranged with its coil axis direction aligned with the injection direction of the molten metal 2.

The frequency of the high-frequency magnetic field generated by the magnetic field generating coil 5a is determined by a graph showing the correlation between the frequency and the rate of change in resistance when measuring the molten slag thickness D as in the method of the present invention (see FIG. 2). It is sufficient to adopt a frequency (specifically, a frequency around IMIlz) at which the resistance change rate is maximum from .

Also, a pair of detection coils 5 built into the detection coil 5
A coil with a small temperature coefficient is used as b, and the detection coil 5b is placed below the magnetic field generating coil 5a at an appropriate distance (
Specifically, they are connected in opposite phases with a separation distance of 10 mm. In this way, the pair of detection coils 5b having a small temperature coefficient are separated by an appropriate length above and below the magnetic field generating coil 5a and connected in opposite phases to reduce the coil resistance, which causes an error in measuring the molten slag thickness D. This is to suppress the influence of temperature fluctuations by offsetting them.

Furthermore, information regarding the impedance detected using the detection coil 5b (strictly speaking, using it and the impedance measuring device 6) is input to the calculation means 7, which separates it into inductance and resistance. The molten slag thickness D can be determined from the resistance. What about the inductance mentioned above? A strong Hell X is required.

Specifically, the impedance (Ro, ωLo) in the air core state including the influence of the surrounding mold 1, etc. is determined under the condition that the molten metal 2 and molten slag 3b are not present in the mold 1, and then Find the impedance (R, ωL) under several conditions where (
That is, the actual resistance and inductance caused by the presence of the molten metal 2 and the molten slag 3b are determined, and the relationship between the rate of change in resistance (substantive resistance) and the molten slag thickness D (see Fig. 3) and the The relationship between the impedance change rate (substantive inductance) and the molten steel level
Enter it in. Here, the resistance change rate and the molten slag thickness D
The relationship between the distance between the detection coil and the molten steel level is 1iillX
Therefore, it is necessary to keep the distance X constant or to calculate the distance X and correct the relationship shown in FIG. 3.

Note that the solid line in FIG. 3 indicates the case where the distance X is large, and the broken line indicates the case where the distance X is small. Then, the resistance and inductance were actually measured in a state where the molten metal 2 and slag 3 were supplied into the mold 1 and the molten slag layer 3h was formed, and based on the measurement results and the calibration results shown in FIG. 3 above, The molten slag thickness D is determined by the calculation means 7. Furthermore, from the inductance measured in the above state,
The molten steel level X can be determined based on the measurement results and the calibration results shown in FIG. 4 described above.

In this way, when measuring the molten slag thickness D, the molten slag thickness D is determined based on the result of separating impedance into inductance and resistance, so the factors that influence the measured value are clear, and as a result, their correction is also possible. It is easy to perform and enables highly accurate measurements.

Note that the difference in the brand of slag introduced affects the measurement result of the molten slag thickness D as a difference in specific resistance.
The influence can be suppressed as much as possible by performing the above-mentioned calibration according to the brand of slag.

Furthermore, the measurement sensitivity of the molten slag thickness D varies greatly depending on the distance between the molten metal 2 and the detection head 5, but in order to minimize the influence of this, the molten steel level It is also conceivable to control the position of the detection head 5 in order to keep the level X constant, and to measure the molten slag thickness D as described above under this control.

〔effect〕

As detailed above, according to the method of the present invention, the thickness of the molten slag can be measured with high accuracy, so that the thickness of the molten slag can be reliably controlled to be constant, and the inner wall of the mold can be The flow of molten slag flowing between the solidified shell and the solidified shell can be maintained appropriately. As a result, the present invention provides extremely useful means for continuous casting of metals, such as improving the quality of slabs obtained by continuous casting and preventing breakout orders during operation.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view schematically showing the implementation state of the method of the present invention, FIG. 2 is a graph showing the relationship between frequency and resistance change rate,
Fig. 3 is a graph showing the relationship between molten slag thickness and resistance change rate, Fig. 4 is a graph showing the relationship between molten steel level and inductance change rate, and Fig. 5 is a longitudinal section schematically showing the implementation state of the conventional method. It is a front view. 1... Mold 2... Molten metal 3... Slag 3b.
... Molten slag 5... Detection head 5a... Magnetic field generating coil 5b... Detection coil D... Molten slag thickness X... Molten steel level agent Patent attorney Noboru Kono −
i・h ward do ξ pasting

Claims (1)

[Claims] 1. A magnetic field generating coil and a detection coil are arranged above the slag, which is supplied with the molten metal into the mold of a continuous casting machine and partially melted, and the magnetic field generating coil is used to generate a high frequency magnetic field. detecting the impedance of the detection coil while generating
A method for measuring molten slag thickness, characterized in that the molten slag thickness is determined from the resistance separated and extracted from the detected impedance. 2. A magnetic field generating coil and a detection coil are placed above the slag, which is supplied together with the molten metal into the mold of a continuous casting machine and partially melted, and the magnetic field generating coil is used to generate a high frequency magnetic field while detecting the above. Detects the impedance of the coil,
A method for measuring molten slag thickness, characterized in that the detected impedance is separated into an inductance and a resistance, a molten steel level is measured from the inductance, and a molten slag thickness is determined from the measured molten steel level and the resistance. 3. A magnetic field generating coil and a detection coil are arranged above the slag which is supplied together with the molten metal into the mold of the continuous casting machine and a part of the slag melts, and the magnetic field generating coil is used to generate a high frequency magnetic field and detect the above. Detects the impedance of the coil,
Separate the detection impedance into an inductance and a resistance, measure the molten steel level from the inductance, and use the measured value to change the detection coil position so that the distance between the detection coil and the molten steel is constant, while changing the impedance. A method for measuring molten slag thickness, which is characterized by determining the molten slag thickness from the resistance of the molten slag. 4. A magnetic field generating coil that is placed above the slag that is supplied with the molten metal into the mold of a continuous casting machine and partially melts, and that generates a high frequency magnetic field, and a magnetic field generating coil that is placed above and below the magnetic field generating coil and that has an opposite phase. 1. A molten slag thickness measuring device comprising: a pair of detection coils connected to a molten slag; and means for separating the impedance of the detection coil into an inductance component and a resistance component.