JP2013006206A - Method for measuring melt layer thickness of mold powder for continuous casting - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable continuous measuring of a melt layer thickness of a powder when continuous casting.SOLUTION: A method for measuring a melt layer thickness of a mold powder when continuous casting is performed when the reflection of microwaves at an interface between a powder part and a melt layer of a mold powder cannot clearly be obtained. The correlation for a melt layer thickness of the mold powder between a molten steel bath level measurement value L1 obtained according to the reflection of microwaves, which are affected by the average permittivity of the powder part and the melt layer of the mold powder, and the difference between the molten steel bath level measurement value L obtained according to an eddy current sensor, which is unaffected by the average permittivity, ΔL1 (=L1-L), is determined in advance, and the mold powder melt layer thickness is determined on the basis of the correlation that was determined in advance. The melt layer thickness of the powder used for continuous casting can be measured continuously and in favorable accuracy, thereby there is effectiveness for the development of a powder and the operation control/quality control.

Description

  In the present invention, the thickness of the molten layer of mold powder (hereinafter simply referred to as “powder”) to be poured on the molten steel surface poured into the mold during continuous casting can be accurately measured without affecting the product quality. The present invention relates to a method that enables continuous measurement.

  In continuous casting of steel, molten steel is poured into a mold and brought into contact with the mold to cool it to produce a solidified shell, and the produced solidified shell is drawn continuously below the mold to produce a slab. ing.

  In this continuous casting, the mold powder put on the molten steel surface in the mold is melted for the purpose of reducing the frictional force between the mold and the solidified shell and controlling the heat removal from the mold. It flows into the gap between them.

  That is, the powder charged on the molten steel surface in the mold is melted on the molten steel surface to form a molten layer having a thickness of several mm to several tens of mm. The molten powder flows between the mold and the solidified shell to form a powder film. The part on the mold side of the powder film is cooled and solidified, crystallizes or precipitates, moves to the lower part of the mold as the casting progresses, and is eventually discharged from the lower end. This amount of discharged powder film is called powder consumption.

  Therefore, in continuous casting, it is necessary to newly add powder corresponding to the powder consumption.

  By the way, in recent years, powders have been developed to cope with a wide variety of cast steel types. However, the physical properties of the molten powder may change depending on the floating oxide from the molten steel in the mold and the cast steel type components.

  This change in physical properties of the molten powder affects the thickness of the powder molten layer (hereinafter referred to as the powder molten layer thickness) and the amount of powder consumed. This leads to stable operation. Therefore, various methods for measuring the powder melt layer thickness have been proposed.

  As a method for measuring the powder melt layer thickness, batch measurement (non-continuous measurement) for measuring from the amount of erosion of the immersed measuring bar, or a method that enables continuous measurement with this measuring bar (for example, There exists patent document 1). In addition, a multi-frequency eddy current method (for example, Patent Documents 2 and 3) that measures the powder melt layer thickness using both the phase and the absolute value at each of a plurality of frequencies has been proposed.

  However, the measurement using a measuring bar is measured in the case of a low melting point powder because the melting difference between the iron bar or iron part that does not melt at the powder melting point and the melting point, for example, the aluminum bar or aluminum part, is the powder melt layer thickness. Is difficult. Further, when the measurement using the measuring bar is continuously performed, the molten aluminum is dissolved in the molten steel, so that there is a problem in practical use because impurities are added to the product.

  On the other hand, in the multi-frequency eddy current method, the measurement accuracy becomes worse when the measurement error becomes large or the thickness of the slab to be manufactured becomes narrow depending on the kind of the powder layer and the molten steel surface temperature. In addition, measurement data may vary depending on the vibration pattern of oscillation.

  Therefore, Patent Document 4 proposes a method for improving the problems of the multi-frequency eddy current method. The method proposed in Patent Document 4 includes the following four steps in order to calibrate the change in conductivity due to the temperature change of the powder melt layer and to increase the accuracy of the measured value of the powder melt layer thickness. Yes.

-Calibration data collection process for collecting calibration data before measurement-Measurement data collection process for obtaining phase information and absolute value information-Correction process for correcting measurement data collected in the measurement data collection process-Data corrected in the correction process Calculation process to calculate powder melt layer thickness based on

  However, the method proposed in Patent Document 4 still uses a multi-frequency eddy current sensor that is difficult to apply to a small-section mold due to its large size, and the multi-frequency eddy current sensor is expensive in its main body. There is a problem in practical use because of the facts. In addition, the multi-frequency eddy current method is a method of measuring (separating) the molten metal and the powder molten layer surface, and the thickness of the entire powder layer cannot be measured. is there.

Japanese Patent Laid-Open No. 9-79805 JP 2005-221282 A JP 2006-205227 A JP 2007-21529 A

  The problem to be solved by the present invention is that, at the time of continuous casting of steel, the method for continuously measuring the powder melt layer thickness accurately without affecting the product quality has not been established. It is.

The method for measuring the molten layer thickness of the continuous casting powder of the present invention is as follows.
To enable continuous measurement of powder melt layer thickness during continuous casting,
For example, a method for measuring the thickness of a molten powder layer during continuous casting when the reflection of microwaves at the interface between the powder portion and the molten layer cannot be clearly obtained,
Molten steel surface level measurement value L1 due to microwave reflection affected by the average dielectric constant of the powder part and molten layer of the powder, and the molten steel surface level by the eddy current sensor not affected by the average dielectric constant The correlation between the difference ΔL1 (= L1−L) in the level measurement value L and the molten layer thickness of the powder is obtained in advance,
Based on the correlation obtained in advance, the most important feature is to obtain the powder melt layer thickness.

  In the present invention described above, the correlation between the molten metal level measurement value L1 of the molten steel by microwave reflection, the difference ΔL1 of the molten steel level level L measured by the eddy current sensor, and the molten layer thickness of the powder obtained in advance. Based on the above, by obtaining the thickness of the powder melt layer, the thickness of the powder melt layer can be continuously and accurately measured.

  Since the present invention can continuously and accurately measure the thickness of the powder melt layer used for continuous casting, it is effective for powder development, operation management and quality control. It is a highly valuable invention.

It is a conceptual diagram of a powder thickness measurement test apparatus. It is the figure which showed an example of the result of having measured the powder thickness using the microwave whose center frequency is 20 GHz and whose modulation amplitude is 4 GHz. It is the figure which showed an example of the result of having measured the powder of thickness 40mm using the microwave whose center frequency is 32GHz and whose modulation amplitude is 8GHz. It is the figure which showed an example of the powder thickness measurement result using the microwave whose center frequency is 32 GHz and whose modulation amplitude is 8 GHz. It is a figure explaining the measurement principle of the powder fusion layer thickness of the invention which concerns on Claim 1. It is the figure which showed the calibration result of the powder layer thickness using a microwave. It is a figure explaining the measurement principle of the powder fusion layer thickness of the invention concerning Claim 2. It is the figure which showed the relationship between powder molten layer thickness and a microwave instruction | indication value. It is an example of measurement data using microwaves when the dielectric constant difference between the powder of powder and the powder melt layer is large.

  In the present invention, for the purpose of continuously enabling measurement of the thickness of the powder melt layer during continuous casting, for example, a molten steel surface level measurement value L1 obtained by microwave reflection obtained in advance and an eddy current sensor are obtained. This was realized by obtaining the powder melt layer thickness based on the correlation between the difference ΔL1 of the molten steel surface level measured value L and the melt layer thickness of the powder.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the accompanying drawings.
First, the process from the new idea of the present invention to the solution of the problem will be described.

  Management of the thickness of the molten powder layer during continuous casting of steel and the thickness of the entire charged powder (hereinafter referred to as “powder charged thickness”) has been an important factor in operation management. In particular, quantitative determination of the thickness of the powder melt layer has recently been an important management factor for powder development in dealing with a wide variety of cast steel types.

  However, conventionally, there is no method for measuring the thickness of the powder melt layer stably during continuous casting, and a method for measuring discontinuously using a measuring bar has been used. A method for measuring the thickness of the powder melt layer by a multi-frequency eddy current method has also been proposed, but it has not been put into practical use at present because of the problems described above.

  Therefore, the inventors have put microwaves in practical use as a method for measuring the interface between powders and solids, and are not affected by temperature changes in the air. Therefore, it was considered that the two interfaces could be separated by reflecting on the powder surface of the powder (hereinafter referred to as the powder input interface) and the molten steel surface (hereinafter referred to as the molten steel interface). In general, general-purpose microwaves that have been put to practical use for measuring the level of slag in converters and that have been used for the purpose of measuring the slag surface generally have a center frequency of around 10 GHz and a modulation amplitude of about 2 GHz. It is.

  Further, the thickness of the powder melt layer during continuous casting is usually a few tens of millimeters. Therefore, the inventors of the present invention, for the purpose of the present invention, required to measure the powder melt layer thickness and the powder input thickness, when the powder melt layer thickness is more than a dozen mm, between the powder input interface and the molten steel interface, A laboratory test was conducted to confirm whether the measurement (separation) of the two interfaces was possible.

  First, using a microwave with a center frequency of 20 GHz and a modulation amplitude of 4 GHz, the thickness after the powder (powder) is placed on the molten steel surface in the mold is changed, and the amount of powder input and the measurement indication value of the bottom of the input are determined. The change was investigated. As a result, it was found that there is a correlation between the amount of powder input and the indicated value at the bottom of the input, and there is a linear relationship with the total thickness of the input powder under the influence of the dielectric constant of the powder.

  Here, the input bottom surface instruction value refers to the distance from the measuring instrument to the molten steel interface (= molten steel surface). The modulation amplitude means a fluctuation frequency width from the center frequency of the microwave.

  The reason why the input bottom surface indication value changes depending on the amount of powder input is that the microwave is affected by the dielectric constant of the powder when it passes through the powder.

  Therefore, the inventors believe that if the change in the input bottom surface indication value due to the powder input thickness is measured in advance, the change in the powder melt layer thickness can be continuously measured by correcting using the calibration data. It was.

  However, since the microwave has a wavelength as long as several tens of millimeters and the distance measurement accuracy is poor, the measurement is performed in the case of measurement within a range of tens of centimeters such as the thickness of the powder melt layer and the powder injection interface intended in the present invention It was difficult to obtain accurate and stable reflected waves at the powder injection interface.

  In order to further improve the accuracy of measurement (separation) of the two interfaces of the powder injection interface and the molten steel interface, the inventors set the wavelength of the microwave to a few millimeters shorter than the microwave, and further modulated it. We thought that increasing the amplitude would be effective.

  The FMCW (Frequency Modulation Continuous Wave) method is generally effective for accurately measuring the distance using the microwave, and this microwave also adopts this method.

  The FMCW method is a method in which frequency modulation is continuously performed on a microwave, and modulation amplitude and center frequency are important. The advantage of increasing the center frequency is that it works in the direction of shortening the microwave wavelength, and increasing the modulation amplitude makes it easier to separate the delay in microwave reflection, leading to improved distance measurement accuracy. It has been.

  In order to further improve the distance measurement accuracy, the inventors use a 32 GHz microwave whose center frequency is increased from the 20 GHz microwave, and changes the modulation amplitude to change the microwave having the center frequency of 20 GHz. The same test as in the case of using was performed.

  As a result, by setting the modulation amplitude to 8 GHz, which is larger than the microwave of 4 GHz, it is possible to measure the separation between the target powder input interface and the molten steel interface from a powder input thickness of 15 mm. I found it.

The present invention has been made based on the above findings.
Hereinafter, the method for measuring the melt layer thickness of the powder for continuous casting according to the first aspect of the present invention will be described.
The inventors investigated the relationship between the powder input thickness and the change in microwave output value using the test apparatus shown in FIG. The microwave output value refers to the shape, intensity, and feedback time of the reflected wave reflected from the powder surface and the bottom surface of the box constituting the test apparatus of FIG.

  Reference numeral 1 in FIG. 1 denotes an irradiation / receiver that irradiates the microwave toward the powder 5 of the powder charged in the box 4 and receives the microwave transmitted through the powder 5 and reflected from the bottom surface of the box 4. The receiving antenna 1a is provided. The microwave received by the antenna 1a is sent from the irradiation / receiver 1 to the data collection PC 3 through the signal amplification amplifier 2.

  A part of the microwave irradiated from the irradiation / receiver 1 is reflected on the surface of the powder 5 (powder input interface).

  In the test using the test apparatus of FIG. 1, the interface between the powder 5 and the powder molten layer is close to the bottom surface of the box 4, but the reflected wave at the bottom surface of the box 4 corresponding to the molten steel interface in actual operation is generated. The biggest.

  Therefore, if the reflected wave at the bottom surface of the box 4 has a clear difference depending on the presence or absence of powder and changes linearly with respect to the change in the thickness of the powder, the change in the microwave output value in the powder melting state offline. By measuring and calibrating, the powder melt layer can be monitored continuously.

  Therefore, as a first stage test, the inventors changed only the thickness of the powder 5 charged in the box 4 in the test using the apparatus of FIG. We investigated how it changed under the influence of the rate. As a result, both obtained the knowledge which changes linearly.

  Next, as a second stage test, in order to simulate a molten powder having a higher density than the powder, the powder once melted and solidified is sandwiched between the powder and the powder melt layer. The same test was performed in a multilayer (powder + solid) state simulating

  As a result, the dielectric constant of the powder after melting and solidification is larger than the dielectric constant of the powder in the powder state. Therefore, it was confirmed that a large difference in the microwave output value was produced, and measurement was possible using this principle. There was found.

  However, in actual operation, the reflection of microwaves on the surface of the powder molten layer is close to the molten steel interface, and there is a concern that the reflection is reflected by the reflection of the molten steel interface, so that it is expected that it cannot be clearly distinguished.

  Therefore, as countermeasures against this, since the molten steel interface is a reflection on the metal surface, the inventors are able to obtain a stable reflection (microwave output) for the microwave passing through the powder powder and the molten powder layer. The following principle of the present invention has been conceived in which the powder melt layer thickness is converted by using.

  In other words, in the principle of the present invention, the microwave that has passed through the powder and the powder melt layer is not the microwave that has passed through the air, and therefore the microwave is affected by the average dielectric constant of the powder powder and the powder melt layer. Wave output value increases. That is, the output of the microwave is delayed and reflected to increase the apparent distance. Therefore, the powder melted layer thickness can be converted by holding the calibration value of the relationship between the microwave output value that has become this large distance and the actual powder melted layer thickness measured using, for example, a conventional measuring rod. It will be possible.

  The reflected wave from the molten steel interface in actual operation becomes a reflected wave affected by the dielectric constant of the powder, so if measurement (separation) between the molten steel interface and the powder injection interface is possible, the micro wave on the surface of the powder molten layer Even if there is no wave reflection, the powder melt layer thickness can be accurately estimated.

  In addition, since the reflection of a metal surface does not change with molten steel and solid, it confirmed as the meniscus (molten steel interface) in a casting_mold | template.

  Therefore, first, the powder is melted using a hot test, for example, a Tamman furnace (small test furnace), the actual powder powder thickness and the powder melt layer thickness are measured with a conventional measuring rod, and the molten steel interface, Calibration with the microwave output value when measuring multiple points such as the powder injection interface.

  And the powder input thickness obtained by subtracting the powder input interface from the molten steel interface measured using microwave (including the difference caused by the dielectric constant of the powder powder and the powder melt layer), For example, a calibration curve is obtained by calibrating with the actual powder melt layer thickness measured with a conventional measuring rod or the like.

  In actual continuous casting, the true value of the molten steel interface in the mold (also referred to as molten steel surface in the mold, also called meniscus) is constantly monitored by eddy current sensors used for flow control in normal operations. Therefore, the difference between the true value of the molten steel interface measured by the eddy current sensor and the measured value of the molten steel interface measured using microwaves is affected by the dielectric constant of the powder powder and the powder molten layer. Therefore, the powder melt layer thickness is estimated from the calibration curve examined in advance.

  In order to find out suitable conditions for the microwave used in the above method, the inventors first used a microwave having a center frequency of 20 GHz and a modulation amplitude of 4 GHz, and used the powders having the main component values shown in Table 1 below. The relationship between thickness and microwave output value was investigated. The result is shown in FIG.

  The measurement distance in FIG. 2 indicates the measurement distance from the base of the antenna 1a shown in FIG. 1 (the narrower side of the antenna waveguide) to the powder surface and the bottom of the box. The bottom surface of the box is output as if the apparent distance is increased due to the greater influence of the dielectric constant when the powder input thickness increases. On the other hand, the powder input interface which is the powder surface becomes closer to the antenna 1a as the powder input thickness increases, so the measurement distance becomes smaller.

  In addition, as a result of investigating whether it is possible to separate and measure the two interfaces of the bottom of the box, which is the powder input interface and the molten steel interface, the measurement distance to the measurement target surface changes almost linearly with the change of the powder input thickness. It was.

  As described above, in the measurement using the microwave having the center frequency of 20 GHz and the modulation amplitude of 4 GHz, it has been found that there is a correlation between the powder input thickness and the indicated value on the bottom surface of the box (marked with ▲ in FIG. 2).

  On the other hand, with respect to the powder surface (marked with ■ in FIG. 2), the reflected wave was unclear when the powder thrown thickness was 50 mm, there was no reflected wave when 100 mm, and a clear reflected wave was confirmed only when the thickness was 150 mm. .

  In order to measure (separate) the above-mentioned two interfaces of the powder by microwaves, which is a target in the present invention, it is necessary to have an accuracy when the powder input thickness is 100 mm or less.

  In order to perform measurements with higher accuracy, it is important to obtain two measured values for the molten steel interface (bottom of the box) in addition to the powder input interface (powder surface). A similar test was performed using a microwave of 32 GHz and a modulation amplitude of 8 GHz. The result is shown in FIG.

  FIG. 3 is an example of data showing the reflected waves from the two interfaces between the bottom surface of the box and the powder surface when the powder thickness is 40 mm, and the vertical axis shows the spectrum of the microwave reflected wave, It can be seen that the peak value is output in the distance conversion spectrum corresponding to the bottom surface.

  Further, in the test using the microwave having the center frequency of 20 GHz and the modulation amplitude of 4 GHz as described above, as shown in FIG. It was not possible to measure (separate) two interfaces.

  However, when a microwave having a center frequency of 32 GHz and a modulation amplitude of 8 GHz is used, as shown in FIG. 4, the powder input thickness changes from 15 mm to both the powder surface and the bottom of the box, and the powder input interface The separation measurement of the two interfaces of the molten steel interface was possible.

  Considering the actual operation, since the powder input thickness is hardly 15 mm or less, the scope of the present invention is considered to be a sufficiently applicable range in the continuous casting operation. Therefore, the inventors considered the application development to the powder melt layer thickness measurement.

  Since the change in the thickness of the powder melt layer appears as a change in the dielectric constant of the powder, it is possible to measure by measuring the change in the dielectric constant of the powder melt state and the separation output value of the two interfaces, the powder input interface and the molten steel interface, in advance. Based on the data, the powder melt layer thickness can be estimated continuously.

  By the way, the dielectric constant of the powder, the center frequency of the microwave, and the modulation amplitude affect the measurement accuracy of the two interfaces of the powder injection interface and the molten steel interface. In other words, the dielectric constant of the powder is somewhat affected by the powder properties, although it varies somewhat depending on the individual powder properties. In other words, the change in the dielectric constant of the powder can be replaced by the thickness of the molten layer, and the change in the measured value due to the influence of the dielectric constant of the powder reflects the change in the thickness of the powder molten layer. Is expressed as a change in powder dielectric constant.

  Therefore, it is possible to measure a large number of powder melt layer thicknesses by obtaining a calibration curve for the input thickness of the powder and the powder melt layer thickness, which are the basic patterns, for general powders in the range of components in practical use. It becomes possible. Of course, measuring the dielectric constant of each individual powder is not meaningless.

  That is, if the two interfaces of the powder input interface and the molten steel interface can be measured stably, the continuous measurement of the powder melt layer thickness intended in the present invention is sufficiently possible.

  In the continuous casting of steel, as shown in FIG. 5, the eddy current sensor 11 is generally installed for the purpose of measuring the surface level of the molten steel 13 in the mold. Molten steel 13 supplied from the immersion nozzle 12 is poured into the mold 14, forms a solidified shell 15 by cooling from the mold 14, and is drawn out below the mold. In the mold, powder 16 is introduced for the purpose of keeping and covering the injected molten steel 13 and lubricating the solidified shell 15 and the mold 14, and a powder molten layer 17 exists on the contact surface with the molten steel 13.

  The measurement principle of the thickness of the powder melt layer, which is the object of the present invention, is the measured level L (true value) of the molten steel 13 by the existing eddy current sensor 11 and the above-described powder input interface and molten steel interface using microwaves. By comparing and comparing the measured separation values of the two interfaces, the powder melt layer thickness is obtained.

  That is, the microwave irradiated from the irradiation / receiver 1 is received by the antenna 1a, and the measured value L2 of the powder injection interface and the measured value L1 of the molten steel level of the molten steel 13 are obtained. Of these, the measured value L2 at the powder input interface is a true value because it is measured in the air, but the measured value L1 at the hot water level is transmitted through the powder 16 and is therefore influenced by the powder dielectric constant. Have an error.

  Then, the difference between the measured value L (true value) of the molten steel level measured using the existing eddy current sensor 11 and the measured value L1 of the molten metal level measured by irradiating microwaves. From the measured value L2 of the powder input interface, the powder melt layer thickness change (dielectric constant change) is calibrated as described below, and the powder melt layer thickness is calculated.

(Conversion method of powder melt layer thickness)
The calculation principle of the powder melt layer thickness change will be described with reference to FIG.

  As shown in FIG. 2, there is a correlation between the distance to the powder surface and the bottom surface of the box measured using microwaves and the thickness of the powder, and the measurement distance of the bottom position of the box corresponding to the meniscus during continuous casting However, it tends to increase in proportion to the increase in the thickness of the charged powder due to the influence of the dielectric constant of the powder.

  An example of the relationship between the difference ΔL1 (= L1−L) between the distance L1 of the molten steel interface measured using the microwave and the distance L of the molten steel interface measured using the eddy current sensor 11 and the actual powder input thickness The figure shown is shown in FIG.

  As described with reference to FIG. 5, the true value of the molten metal surface (meniscus) of the molten steel 13 is continuously measured by the eddy current sensor 11.

  Therefore, if the measured value by the microwave is calibrated in advance based on the measured value by the eddy current sensor 11, the distance L1 to the molten steel interface measured by using the microwave and the eddy current sensor 11 are continuously measured. If the difference ΔL1 (= L1−L) of the true distance L to the molten steel interface is obtained, the powder input thickness can be estimated from FIG. For example, when the difference ΔL is 30 mm, it can be estimated from the calibration line for the powder powder single layer shown in FIG.

  Similarly, if the data is prepared by calibrating the relationship between the powder input thickness (powder powder + powder melt layer) and the powder melt layer thickness in advance, the powder melt layer thickness can be estimated continuously. .

  That is, the measured value L of the molten metal level of the molten steel 13 using the eddy current sensor 11 and the measured value L1 of the molten metal level of the molten steel 13 using microwaves are calibrated cold in advance and set to the same indicated value.

  When the powder 16 is put on the molten metal surface of the molten steel 13, the measured value L of the molten metal surface level by the eddy current sensor 11 does not change, but the measured value L1 of the molten metal surface level by the microwave is influenced by the average powder dielectric constant. Change in response.

  Since the difference ΔL1 (= L1−L) between these two measured values is proportional to the change in the powder input thickness (powder + powder melt layer), the previously obtained difference ΔL and the powder input thickness (powder) Body + powder melt layer), powder input thickness (powder + powder melt layer) and powder melt layer thickness calibration data, the powder melt layer thickness can be estimated. This is the invention according to claim 1.

  In other words, in the invention according to claim 1, the change in the powder input thickness is detected by the measured value L2 measured by the microwave reflected on the powder surface (powder input interface), and the amount of powder input (powder input thickness) and the calibration are detected. For the correction of the powder melt layer thickness using the data and the change in the molten metal level of the molten steel in the mold, the molten metal level measured value L by the eddy current sensor and the molten metal level measured value L1 by the microwave are monitored. Therefore, the measurement accuracy of the powder melt layer thickness is improved by correcting the change in the powder thickness and the change in the level of the molten metal in the mold.

  Next, the measurement principle and examples of the powder melt layer thickness of the invention according to claim 3 will be described.

  When the dielectric constant is greatly different between the powder portion of the powder and the powder melt layer, as shown in FIG. 7, the powder surface of the powder, the upper surface of the powder melt layer, and the molten steel surface (the lower surface of the powder melt layer) A distance-converted spectrum is detected.

  Therefore, the powder melt layer thickness can also be obtained by the difference ΔL2 (= L1−L3) between the molten steel level measurement value L1 of the molten steel and the upper surface level measurement value L3 of the powder melt layer.

FIG. 8 shows an example of the relationship between the powder melt layer thickness and the microwave instruction value.
During the measurement of the powder melt layer thickness by microwave, the actual powder melt layer thickness is measured using a measuring rod, and the correlation between the microwave indication value and the actual powder melt layer thickness as shown in FIG. 8 is obtained. Thus, it becomes possible to continuously estimate the powder melt layer thickness.

  The inventors measured when the dielectric constants of the powder portion and the powder melt layer differed greatly. An example of the data is shown in FIG. It can be seen that the microwave reflected wave corresponding to the molten steel surface level measured value L1, the powder molten layer upper surface level measured value L3, and the powder input interface measured value L2 as shown in FIG. 7 can be measured.

  That is, when the dielectric constants of the powder powder and the powder molten layer are greatly different, the measured value L1 of the molten steel surface level, the measured value L2 of the powder input interface, and the measured value L3 of the upper surface level of the powder molten layer are measured. Thus, the powder melt layer thickness can be estimated.

  Further, even when the difference in dielectric constant is small, as described above, it is possible to estimate the thickness of the molten powder layer by detecting the measured value L1 of the molten steel surface level and the measured value L2 of the powder input interface. The effectiveness of the present invention was confirmed.

  In the present invention, the measurement accuracy is improved in consideration of the change in the reflection phase of the microwave. That is, the amount of change in distance and the change in reflection phase of the microwave are in a proportional relationship, and the change in distance can be obtained by multiplying the change in phase by λ / (4π). Therefore, if the wavelength λ is as short as several millimeters to several centimeters, the distance variation can be accurately obtained from the change in the microwave reflection phase.

  The present invention is not limited to the above example, and it goes without saying that the embodiments may be changed as appropriate within the scope of the technical idea described in each claim.

  For example, when the reflection of the microwave at the interface between the powder portion of the powder and the molten layer is clearly obtained, the thickness of the molten layer of the powder may be measured as follows.

  The difference ΔL3 between the measured value L3 of the upper surface level by microwave reflection from the upper surface of the molten layer, which is the interface between the powder part of the powder and the molten layer, and the measured value L2 of the powder surface level by an arbitrary sensor such as laser or microwave reflection The thickness of the powder powder layer is determined by correcting (= L3−L2) with the powder dielectric constant in the powder state.

  The obtained thickness of the powder powder layer and the measured value L2 of the powder surface level are subtracted from the measured value L of the molten steel surface level obtained by the eddy current sensor. Thereby, the thickness of the mold powder melt layer can be obtained. This is the invention according to claim 2.

  In the above example, the true value of the molten steel interface in the mold is measured using an eddy current sensor. However, if the true value can be measured, it is measured by an arbitrary hot water level sensor. You may use the value that you did.

  Furthermore, in the above example, a microwave with a large center frequency of 32 GHz and a modulation amplitude of 8 GHz is provided to enable accurate measurement by increasing the center frequency and enabling separation measurement of the two interfaces of the powder injection interface and the molten steel interface. However, in order to enable measurement of the mold powder melt layer thickness of the present invention, it is sufficient that at least the center frequency is in the range of 20 GHz to 32 GHz and the modulation amplitude is within 8 GHz.

  The reason is that, even in the laboratory test that obtained the results shown in FIG. 2, it is difficult to measure the powder input surface, but it is possible to measure the input bottom surface.

  Incidentally, if the wavelength of the microwave is long (the center frequency is small), it is easy to transmit including the powder powder, but it is difficult to obtain the reflected wave on the powder surface. On the other hand, when the wavelength is shortened (center frequency is increased), reflection on the powder surface is facilitated, but it is difficult to transmit through the powder.

  Therefore, the inventors increased the center frequency of the microwave to a range of 20 GHz to 32 GHz and further widened the modulation amplitude to within 8 GHz, so that the reflected wave on the powder surface and the transmitted wave in the powder sufficient for measurement were obtained. It is possible to measure the separation of the two interfaces of the powder input interface and the molten steel interface.

1 Irradiation / Receiver 1a Antenna 2 Amplifier 3 Data collection PC
4 boxes 5 powder 11 eddy current sensor 12 immersion nozzle 13 molten steel 14 mold 15 solidified shell 16 powder 17 powder molten layer

Claims (5)

A method for measuring the thickness of a molten mold powder layer during continuous casting in the case where microwave reflection at the interface between the powder portion of the mold powder and the molten layer cannot be clearly obtained,
Molten steel level measurement L1 by the reflection of microwaves affected by the average dielectric constant of the powder part and molten layer of the mold powder, and the molten steel by the molten metal level sensor not affected by the average dielectric constant A correlation between the difference ΔL1 (= L1−L) in the measured level L of the molten metal and the molten layer thickness of the mold powder is obtained in advance.
A method for measuring a molten layer thickness of a mold powder for continuous casting, characterized in that a mold powder molten layer thickness is obtained based on the correlation obtained in advance. A method for measuring the thickness of a molten mold powder layer during continuous casting in the case where microwave reflection at the interface between the powder portion of the mold powder and the molten layer is clearly obtained,
Upper surface level measurement value L3 by microwave reflection from the upper surface of the molten layer, which is the interface between the mold powder powder portion and the molten layer affected by the average induction rate of only the powder portion of the mold powder, and powder by an arbitrary sensor The difference ΔL3 (= L3−L2) in the measured value L2 of the surface level is corrected by the powder dielectric constant in the powder state to obtain the thickness of the powder powder layer.
The thickness of the powder powder layer is obtained by subtracting the measured value L2 of the powder powder layer and the measured value L2 of the powder surface level from the measured value L of the molten steel level obtained by the molten metal level sensor. A method for measuring a molten layer thickness of a continuous casting mold powder. Mold powder melt layer thickness measurement method at the time of continuous casting, in the case where the reflection of the microwave on the interface between the powder part of the mold powder and the molten layer and the molten steel surface is obtained clearly,
Influenced by the average dielectric constant of only the powder part of the mold powder and the measured level L1 of the molten steel due to the reflection of the microwave affected by the average dielectric constant of the powder part and the molten layer of the mold powder. The correlation between the difference ΔL2 (= L1−L3) of the upper surface level measurement value L3 due to the microwave reflection from the upper surface of the molten layer, which is the interface between the powder portion of the mold powder and the molten layer, and the molten layer thickness of the mold powder is obtained in advance. Leave
A method for measuring a molten layer thickness of a mold powder for continuous casting, wherein the molten layer thickness of the mold powder measured by reflection of microwaves is calibrated based on the correlation obtained in advance.
In the molten layer thickness measuring method of the mold powder for continuous casting according to claim 1,
The difference ΔL1 (L1−L) between the measured level L1 of the molten steel by the microwave and the measured level L of the molten steel by the eddy current sensor is continuously measured, and based on the previously obtained correlation. A method for measuring a melt layer thickness of a mold powder for continuous casting, wherein the powder melt layer thickness is continuously obtained. In the melt layer thickness measuring method of the mold powder for continuous casting according to any one of claims 1 to 4,
A method for measuring a molten layer thickness of a mold powder for continuous casting, wherein the measurement value by microwave is measured using a change in reflection phase of microwave.

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