阅读说明：本技术 退火炉中的钢板的磁性转变率测定方法以及磁性转变率测定装置、连续退火工序、连续热浸镀锌工序 (Method and apparatus for measuring magnetic transformation ratio of steel sheet in annealing furnace, continuous annealing process, and continuous hot-dip galvanizing process ) 是由 日野善道 杉原广和 于 2018-05-23 设计创作，主要内容包括：本发明提供退火炉中的钢板的磁性转变率测定装置以及磁性转变率的测定方法、还有应用了该磁性转变率测定方法以及磁性转变率测定装置的连续退火工序、连续热浸镀锌工序。一种方法,在该方法中,使用配置于钢板的表面的一侧的驱动线圈、以及在与该驱动线圈相同面侧且在该驱动线圈的两侧相对于钢板的表面平行地配置的接收线圈,在由退火炉对钢板进行热处理之前测定钢板的磁性转变率,利用使用空心且具有板宽以上的大小的驱动线圈,对钢板的表面发送交流的驱动信号,利用使用空心且具有板宽以上的大小的接收线圈,对被钢板反射后的驱动信号进行测定,利用测定处理装置,使用由接收线圈测定出的驱动信号的测定值对钢板与驱动线圈的距离进行修改,并基于修改后的距离对钢板的磁性转变率进行测定。(The invention provides a device and a method for measuring magnetic transformation rate of a steel sheet in an annealing furnace, and a continuous annealing process and a continuous hot-dip galvanizing process using the device and the method for measuring magnetic transformation rate. A method for measuring the magnetic transition rate of a steel sheet before heat treatment of the steel sheet in an annealing furnace using a drive coil disposed on one side of the surface of the steel sheet and receiver coils disposed on the same surface side as the drive coil and in parallel to the surface of the steel sheet on both sides of the drive coil, wherein an alternating-current drive signal is transmitted to the surface of the steel sheet using a drive coil that is hollow and has a size equal to or larger than the sheet width, the drive signal reflected by the steel sheet is measured using a receiver coil that is hollow and has a size equal to or larger than the sheet width, the distance between the steel sheet and the drive coil is modified using the measurement value of the drive signal measured by the receiver coils by a measurement processing device, and the magnetic transition rate of the steel sheet is measured based on the modified distance.)

1. A method for measuring the magnetic transformation rate of a steel sheet in an annealing furnace, wherein the magnetic transformation rate of the steel sheet is measured before the steel sheet is heat-treated in the annealing furnace using a drive coil disposed on one side of the surface of the steel sheet and receiver coils disposed on the same surface side as the drive coil and in parallel to the surface of the steel sheet on both sides of the drive coil,

wherein the content of the first and second substances,

by using a hollow drive coil having a size equal to or larger than the plate width to transmit an alternating-current drive signal to the surface of the steel plate,

measuring the drive signal reflected by the steel plate by using a receiving coil having a hollow size and a plate width or larger,

the distance between the steel plate and the drive coil is modified by a measurement processing device using the measurement value of the drive signal measured by the receiver coil, and the magnetic transition rate of the steel plate is measured based on the modified distance.

2. The method of measuring magnetic transition rate of steel sheet in an annealing furnace according to claim 1, wherein,

the reception coils are paired with two reception coils, and the two reception coils are connected in reverse phase at positions symmetrical with respect to the drive coil, and the drive signal after reflection is measured.

3. The method of measuring magnetic transition rate of steel sheet in an annealing furnace according to claim 1 or 2, wherein,

two sets of two receiving coils connected in reverse phase are used as the receiving coils, and the two sets of receiving coils are arranged at different distances from the driving coil,

with the measurement processing device, the respective distances of the steel plate and the receiving coils are calculated based on the measured values of the drive signals in the two sets of receiving coils, and the magnetic transition rate is modified based on the calculated results.

4. A method for measuring the magnetic transformation rate of a steel sheet in an annealing furnace, wherein the magnetic transformation rate of the steel sheet is measured before the steel sheet is heat-treated in the annealing furnace using a drive coil disposed on one side of the surface of the steel sheet and receiver coils disposed on the same surface side as the drive coil and in parallel to the surface of the steel sheet on both sides of the drive coil,

wherein the content of the first and second substances,

by using a hollow drive coil having a size equal to or larger than the plate width to transmit an alternating-current drive signal to the surface of the steel plate,

measuring the drive signal reflected by the steel plate by using a receiving coil having a hollow size and a plate width or larger,

the measurement value of the drive signal measured by the receiver coil is divided into components having a phase of 90 ° with respect to the drive signal after transmission by a measurement processing device, and the magnetic transition rate of the steel sheet is measured based on the components having the phase of 90 °.

5. The method of measuring magnetic transition rate of steel sheet in an annealing furnace according to claim 4, wherein,

the measurement processing device divides the measurement value into a component having a phase of 0 ° and a component having a phase of 90 ° with respect to the drive signal after transmission, and measures the magnetic transition rate based on a ratio of the component having a phase of 90 ° with respect to the component having a phase of 0 °.

6. A magnetic transformation rate measuring device for a steel sheet in an annealing furnace measures the magnetic transformation rate of the steel sheet before heat treatment of the steel sheet in the annealing furnace using a drive coil disposed on one side of the surface of the steel sheet and receiving coils disposed on the same surface side as the drive coil and in parallel to the surface of the steel sheet on both sides of the drive coil,

wherein, have:

a drive coil that forms a closed circuit having a large area, which is hollow and has a size equal to or larger than a plate width, and that transmits an alternating-current drive signal to a surface of a steel plate;

a reception coil that constitutes a closed circuit having a large area, which is hollow and has a size equal to or larger than a plate width, and that receives the drive signal reflected by the steel plate and measures the drive signal; and

and a measurement processing device that modifies a distance between the steel plate and the drive coil using the measurement value of the drive signal measured by the receiver coil, and measures a magnetic transition rate of the steel plate based on the modified distance.

7. The apparatus for measuring magnetic transition rate of steel sheet in an annealing furnace according to claim 6, wherein,

the reception coils pair two reception coils and connect the two reception coils in reverse phase at positions symmetrical with respect to the driving coil.

8. The apparatus for measuring magnetic transition rate of steel sheet in an annealing furnace according to claim 6 or 7, wherein,

two sets of two reception coils connected in reverse phase are used as the reception coils, and the two sets of reception coils are arranged at different distances from the drive coil.

9. The apparatus for measuring magnetic transition rate of steel sheet in an annealing furnace according to any of claims 6 to 8, wherein,

the receiving coil is arranged such that the number of turns of the coil is changed for each receiving coil, and the distance from the driving coil is changed in accordance with the number of turns of the coil.

10. A magnetic transformation rate measuring device for a steel sheet in an annealing furnace measures the magnetic transformation rate of the steel sheet before heat treatment of the steel sheet in the annealing furnace using a drive coil disposed on one side of the surface of the steel sheet and receiving coils disposed on the same surface side as the drive coil and in parallel to the surface of the steel sheet on both sides of the drive coil,

wherein, have:

a drive coil that forms a closed circuit having a large area, which is hollow and has a size equal to or larger than a plate width, and that transmits an alternating-current drive signal to a surface of a steel plate;

a reception coil that constitutes a closed circuit having a large area, which is hollow and has a size equal to or larger than a plate width, and that receives the drive signal reflected by the steel plate and measures the drive signal; and

and a measurement processing device that extracts a component having a phase of 0 ° and/or a phase of 90 ° with respect to the drive signal after transmission using a measurement value of the drive signal measured by the receiving coil, and measures a magnetic transition rate of the steel sheet based on the phase component.

11. A continuous annealing process in which, in a continuous annealing step,

the method of measuring magnetic transformation rate of a steel sheet in an annealing furnace according to any one of claims 1 to 5, wherein the magnetic transformation rate of the steel sheet is measured before an induction heating device of the annealing furnace,

the measurement processing device performs feed-forward control of the induction heating device based on the measured magnetic transition rate.

12. A continuous hot dip galvanizing process in which,

the method of measuring magnetic transformation rate of a steel sheet in an annealing furnace according to any one of claims 1 to 5, wherein the magnetic transformation rate of the steel sheet is measured before an induction heating device of the annealing furnace,

the measurement processing device performs feed-forward control of the induction heating device based on the measured magnetic transition rate.

Technical Field

The present invention relates to a method and an apparatus for measuring magnetic transformation rate of a steel sheet in a continuous annealing furnace. The present invention also relates to a continuous annealing step and a continuous hot-dip galvanizing step to which the magnetic conversion measuring method and the magnetic conversion measuring apparatus of the present invention are applied.

Background

In order to obtain high strength and high workability of a steel sheet, the steel sheet is cooled in a state where the steel sheet is formed in a specific ratio of a γ phase (austenite phase) to α phase (ferrite phase).

Conventionally, as a method for grasping the ratio of each phase, a magnetic detector, that is, a device for measuring the magnetic transformation rate of a steel sheet has been used (see patent documents 1 and 2). Patent document 1 discloses a device for measuring a magnetic transition rate, which includes a drive coil for generating a magnetic field and a detection coil for measuring the magnetic field transmitted through a steel plate. Patent document 2 discloses a device for measuring a magnetic transition rate, which includes a drive coil for generating a magnetic field and a detection coil for measuring the magnetic field reflected by a steel plate.

Patent document 1: japanese laid-open patent publication No. 56-82443 (pages 1 and 2 and FIG. 1)

Patent document 2: japanese laid-open patent publication No. Sho 59-188508 (FIG. 2)

As described in the above-mentioned prior art, the determination of the ratio of the austenite phase to the ferrite phase of the steel, that is, the determination of the transformation ratio is advantageous in hot rolling and is also important in the annealing process of the high-strength cold-rolled steel sheet. In the annealing process of the high-strength cold-rolled steel sheet, the same measurement method as in the case of hot rolling can be applied as the measurement method of the conversion ratio.

However, in the measurement method using the measurement device described in patent document 1, as described in page 6 of patent document 2, there is a problem that the distance between the steel plate and the measurement device must be reduced in order to rationalize the penetration depth of the magnetic flux into the magnetic body. Therefore, when the measuring apparatus described in patent document 1 is applied to an annealing process of a high-strength cold-rolled steel sheet, the measuring apparatus must be installed close to the steel sheet in an annealing furnace that performs annealing at about 900 ℃.

On the other hand, in the measurement method using the measurement device (detection device) described in patent document 2, the excitation coil (drive coil) and the detection coil are disposed on the same side with respect to the steel material, so that the above-described problems relating to the installation are overcome. However, when the steel sheet is transferred in the vertical direction a plurality of times as in a vertical annealing furnace, the measuring device needs to be provided midway in the height direction of the furnace. In this case, a member having a large cross-sectional area is required to support the measuring apparatus having the heavy core in the annealing furnace at a high temperature. Therefore, there is a problem that the member having a large cross-sectional area for supporting the measuring device hinders heating and cooling of the annealing furnace.

In addition, there are also problems as follows: since each of the measuring apparatuses described in patent documents 1 and 2 is small, it is necessary to provide a large number of measuring apparatuses in the width direction in order to measure only the local transformation ratio of the steel sheet and the transformation ratio of the entire width of the steel sheet.

In recent years, high-strength steel sheets have a high austenite phase fraction. However, since the electromagnetic induction heating apparatus used for reheating in the continuous annealing furnace and reheating for alloying of zinc on the continuous hot dip galvanizing line has low heating efficiency, the output of the induction heating apparatus is in a high state, and undesirable fluctuation in the austenite phase fraction of the steel sheet occurs. This makes temperature control unstable. In particular, the following problems exist: when a variation in the austenite phase fraction occurs in the steel sheet, an electromotive force is generated in the electromagnetic induction heating device in accordance with the magnetic change of the steel sheet, and a rapid voltage variation occurs in the electric circuit and cannot be controlled any more. The voltage fluctuation is generated when a fluctuation portion of the austenite phase fraction enters the electromagnetic induction heating apparatus, and cannot be predicted in advance, and it is difficult to suppress the generated voltage fluctuation by control.

Disclosure of Invention

The present invention has been made in view of the above circumstances, and an object thereof is to provide a device and a method for measuring a magnetic transformation ratio of a steel sheet in a continuous annealing furnace, and a continuous annealing process and a continuous hot-dip galvanizing process to which the device and the method for measuring a magnetic transformation ratio are applied.

The present inventors have made intensive studies to solve the above problems, and as a result, the present inventors have recognized the following.

A method for measuring magnetic transition of a steel sheet, wherein a drive coil and a receiver coil, which are hollow and have a path extending across the width of the steel sheet, are arranged on the same surface side of the steel sheet in an annealing furnace, and a transition rate of the steel sheet is measured by transmitting an alternating-current drive signal from the drive coil and measuring a reflected wave from the steel sheet by the receiver coil.

In the present invention, when the reflected wave is used, two receiving coils are paired and arranged at symmetrical positions with the driving coil interposed therebetween and connected in a reverse phase, so that a signal change due to a magnetic change of the steel sheet can be easily recognized. In the case where two pairs of the above-described receiver coils are used, the distances between the receiver coils and the drive coil are made different in the two receiver coils, and the magnetic conversion rate signal is corrected by calculating the distance between the steel plate and the receiver coil from the drive signal received and measured by the two receiver coils.

In addition, the present invention extracts a component having a phase of 90 ° with respect to the transmitted drive signal from the drive signal measured by the receiving coil, and obtains the transition rate using the magnitude of the component having the phase of 90 °. The present invention divides the drive signal measured by the receiving coil into a 0 ° phase component and a 90 ° phase component with reference to the drive signal after transmission, and obtains the conversion rate by using the ratio of the phase components.

The present invention is a magnetic transition measuring apparatus for a steel sheet, wherein a driving coil and a receiving coil are disposed in an annealing furnace, respectively, and the driving coil and the receiving coil constitute a large-area closed circuit that traverses a sheet width direction of the steel sheet, and a core material is not used for each coil.

The present invention is a continuous annealing process and a hot dip galvanizing process, and the magnetic transformation measurement of the present invention is performed before induction heating, and feed forward control is performed in consideration of the influence of magnetization of a steel sheet.

The present invention has been completed based on the above findings, and the gist thereof is as follows.

[1] A method for measuring the magnetic transformation rate of a steel sheet in an annealing furnace, wherein the magnetic transformation rate of the steel sheet is measured before the steel sheet is heat-treated in the annealing furnace using a driving coil disposed on one side of the surface of the steel sheet and receiving coils disposed on the same surface side as the driving coil and in parallel to the surface of the steel sheet on both sides of the driving coil,

by using a hollow drive coil having a size equal to or larger than the plate width to transmit an alternating-current drive signal to the surface of the steel plate,

measuring the drive signal reflected by the steel plate by using a receiving coil having a hollow size and a plate width or larger,

the distance between the steel plate and the driving coil is modified by a measurement processing device using the measurement value of the driving signal measured by the receiving coil, and the magnetic transition rate of the steel plate is measured based on the modified distance.

[2] The method for measuring magnetic transformation rate of a steel sheet in an annealing furnace according to [1], wherein,

the receiver coils are formed by pairing two receiver coils, and the two receiver coils are connected in reverse phase at positions symmetrical to the drive coil, and the drive signal after reflection is measured.

[3] The method for measuring magnetic transformation ratio of a steel sheet in an annealing furnace according to item [1] or item [2], wherein,

two sets of two receiving coils connected in reverse phase are used as the receiving coils, and the two sets of receiving coils are arranged at different distances from the driving coil,

the measurement processing device calculates the respective distances between the steel plate and the receiving coils based on the measured values of the drive signals in the two sets of receiving coils, and modifies the magnetic conversion rate based on the calculation result.

[4] A method for measuring the magnetic transformation rate of a steel sheet in an annealing furnace, wherein the magnetic transformation rate of the steel sheet is measured before the steel sheet is heat-treated in the annealing furnace, using a drive coil disposed on one side of the surface of the steel sheet and receiving coils disposed on the same surface side as the drive coil and in parallel to the surface of the steel sheet on both sides of the drive coil,

by using a hollow drive coil having a size equal to or larger than the plate width to transmit an alternating-current drive signal to the surface of the steel plate,

measuring the drive signal reflected by the steel plate by using a receiving coil having a hollow size and a plate width or larger,

the measurement value of the drive signal measured by the receiver coil is divided into components having a phase of 90 ° with respect to the drive signal after transmission by a measurement processing device, and the magnetic transition rate of the steel sheet is measured based on the components having the phase of 90 °.

[5] The method for measuring magnetic transformation rate of a steel sheet in an annealing furnace according to [4], wherein,

the measurement processing device divides the measurement value into a component having a phase of 0 ° and a component having a phase of 90 ° with respect to the drive signal after transmission, and measures the magnetic transition rate based on a ratio of the component having a phase of 90 ° with respect to the component having a phase of 0 °.

[6] A magnetic conversion rate measuring device for a steel sheet in an annealing furnace, which measures the magnetic conversion rate of the steel sheet before heat treatment of the steel sheet in the annealing furnace, using a drive coil disposed on one side of the surface of the steel sheet and receiver coils disposed on the same surface side as the drive coil and in parallel with the surface of the steel sheet on both sides of the drive coil, the device comprising:

a drive coil that forms a closed circuit having a large area, which is hollow and has a size equal to or larger than a plate width, and that transmits an alternating-current drive signal to a surface of a steel plate;

a receiving coil that forms a closed circuit having a large area, which is hollow and has a size equal to or larger than a plate width, and that receives the drive signal reflected by the steel plate and measures the drive signal; and

and a measurement processing device that modifies a distance between the steel plate and the driving coil using the measurement value of the driving signal measured by the receiving coil, and measures a magnetic transition rate of the steel plate based on the modified distance.

[7] The apparatus for measuring magnetic conversion rate of steel sheet in an annealing furnace according to item [6], wherein,

the above-described reception coil pairs two reception coils, and connects the two reception coils in reverse phase at positions symmetrical with respect to the driving coil.

[8] The apparatus for measuring magnetic conversion rate of steel sheet in an annealing furnace according to [6] or [7], wherein,

two sets of two receiving coils connected in reverse phase are used as the receiving coils, and the two sets of receiving coils are arranged at different distances from the driving coil.

[9] The apparatus for measuring magnetic conversion rate of steel sheet in an annealing furnace according to any of [6] to [8], wherein,

the receiving coil is arranged such that the number of turns of the coil is changed for each receiving coil, and the distance from the driving coil is changed in accordance with the number of turns of the coil.

[10] A magnetic transformation rate measuring device for a steel sheet in an annealing furnace, which measures the magnetic transformation rate of the steel sheet before the steel sheet is heat-treated in the annealing furnace, using a drive coil disposed on one side of the surface of the steel sheet and receiver coils disposed on the same surface side as the drive coil and in parallel with the surface of the steel sheet on both sides of the drive coil, the device comprising:

a drive coil that forms a closed circuit having a large area, which is hollow and has a size equal to or larger than a plate width, and that transmits an alternating-current drive signal to a surface of a steel plate;

a receiving coil that forms a closed circuit having a large area, which is hollow and has a size equal to or larger than a plate width, and that receives the drive signal reflected by the steel plate and measures the drive signal; and

and a measurement processing device that extracts a component having a phase of 0 ° and/or a phase of 90 ° with respect to the drive signal after transmission, using a measurement value of the drive signal measured by the receiver coil, and measures a magnetic transformation rate of the steel sheet based on the phase component.

[11] A continuous annealing process in which, in a continuous annealing step,

the method for measuring magnetic transformation rate of a steel sheet in an annealing furnace according to any one of [1] to [5], wherein the magnetic transformation rate of the steel sheet is measured before an induction heating device of the annealing furnace,

the measurement processing device performs feed-forward control of the induction heating device based on the measured magnetic transition rate.

[12] A continuous hot dip galvanizing process in which,

the method for measuring magnetic transformation rate of a steel sheet in an annealing furnace according to any one of [1] to [5], wherein the magnetic transformation rate of the steel sheet is measured before an induction heating device of the annealing furnace,

the measurement processing device performs feed-forward control of the induction heating device based on the measured magnetic transition rate.

According to the present invention, since the air-core coil having a size not less than the sheet width and not using the iron core is used, it is possible to measure the average transformation ratio in the sheet width direction of the steel sheet while being lightweight and excellent in durability. Further, the distance between the measuring apparatus and the steel plate is modified using the signal of the receiving coil, and the magnetic transition rate is obtained based on the modified distance, so that the measurement accuracy of the magnetic transition rate is also improved. Further, by applying the present invention to the continuous annealing step and the hot dip galvanizing step, the feed forward control of the induction heating can be stably performed even if the magnetic transition rate changes.

Drawings

FIG. 1 is a perspective view illustrating a schematic configuration of a magnetic transformation rate measuring apparatus for a steel sheet in an annealing furnace according to the present invention.

Fig. 2 is a diagram illustrating the principle of a magnetic transition rate measurement method in the magnetic transition rate measurement device shown in fig. 1.

Fig. 3 is a perspective view illustrating an embodiment of the present invention.

Fig. 4 is a partially enlarged view illustrating another embodiment of the present invention.

FIG. 5 is a diagram illustrating the principle of a magnetic transition rate measuring method according to another embodiment of the present invention.

Fig. 6 is a graph illustrating a relationship between a distance (mm) between a steel sheet and a drive coil and a signal ratio (V' ÷ V) in another embodiment of the present invention.

Detailed Description

Hereinafter, embodiments of the present invention will be described. The present invention is not limited to the following embodiments.

First, the principle of the magnetic transformation rate measuring apparatus and the magnetic transformation rate measuring method for a steel sheet in an annealing furnace used in the present invention will be described with reference to fig. 1 and 2. FIG. 1 is a diagram illustrating a schematic configuration of a magnetic transition measuring apparatus 15 for a steel sheet in an annealing furnace 2 according to the present invention. Fig. 2 is a diagram illustrating the principle of the magnetic transition rate measurement method of the magnetic transition measuring apparatus 15 for a steel sheet shown in fig. 1.

As shown in fig. 1, the magnetic transition measuring apparatus 15 provided in the annealing furnace 2 includes a coil 5, a transmitter 9 (not shown), a voltmeter 10 (not shown), and a measurement processing apparatus 14.

The coil 5 is composed of one driving coil (exciting coil) and two or more receiving coils. The drive coil is a coil that transmits an alternating electromagnetic wave (drive signal) to the surface of the steel plate. The receiving coil is a coil that receives the drive signal reflected by the steel plate and performs measurement.

The coil 5 is formed in the hollow core 4 without using a core so as to pass through a wire. The receiving coil pairs two receiving coils and forms winding directions of respective wires to be opposite. The hollow 4 is, for example, a ceramic tube, an alumina tube or the like. The hollow portions 4 are provided so as to penetrate the furnace body of the annealing furnace 2 and are arranged in the direction of the pass plate at predetermined intervals. Here, a lead wire is passed between the two ceramic tubes, and a set of coils is formed so that the lead wire surrounds a surface parallel to the steel plate 1, and three sets of coils are arranged at predetermined intervals in parallel to the surface of the steel plate 1. The coil 5 disposed at the center is a driving coil (see reference numeral 6 in fig. 3 described later), and the pair of coils 5 disposed at both sides thereof are receiving coils (see reference numerals 7 and 8 in fig. 3 described later). For example, the distances between the two receiving coils and the driving coil are formed to be equally spaced.

The number of turns of the receiving coils may be different from one another, and when the number of turns of the receiving coils is different from one another, the two receiving coils may be arranged at different distances from the driving coil. Thus, even when the installation position in the annealing furnace 2 is narrow, the measurement device can be installed without being affected by the narrow installation position.

In the present invention, the receiving coils may be provided in a plurality of sets, with a pair of receiving coils being a set of receiving coils. By arranging a plurality of sets of receiving coils, the measurement accuracy is further improved. For example, when two sets of receiving coils are used, as shown in fig. 4, the two sets of receiving coils 7, 8, 12, and 13 are disposed to be opposed to the driving coil 6, and the distances between the two sets of receiving coils and the driving coil are different from each other.

The transmitter 9 is a power supply connected to a coil (driving coil) and configured to emit a sine wave having a predetermined frequency and a predetermined current value. Such as a sine wave transmitter, function generator.

The voltmeter 10 is connected to a coil (receiving coil), and measures a drive signal received by the receiving coil. Such as a lock-in amplifier.

The measurement processing device 14 is a computing device that: the distance between the steel plate and the drive coil is modified using the measured value of the drive signal measured by the receiver coil, and the magnetic transition rate of the steel plate is measured based on the modified distance. Alternatively, the measurement processing device 14 is a computing device that: a component having a phase of 0 DEG and 90 DEG with respect to the transmitted drive signal is extracted from the measured value of the drive signal measured by the receiving coil, and the magnetic transition rate is measured based on the phase component. That is, the measurement processing device 14 corrects the distance according to the difference in the installation positions of the plurality of receiving coils, the difference in the ratio (signal ratio) and the phase angle of the signals of the respective coils. Note that the method of measuring the magnetic transition rate in the measurement processing device 14 is explained below with reference to fig. 2, and thus is omitted here.

The magnetic transition measuring apparatus 15 may further include a thermometer 11. When the thermometer is provided, the actual measurement value of the steel sheet temperature can be used in the magnetic transformation ratio measurement method, and thus the measurement accuracy can be further improved. The thermometer 11 measures the surface temperature of the steel sheet 1, and is, for example, a radiation thermometer.

The magnetic transition measuring device 15 is provided with three sets of coils 5 (one driving coil and two receiving coils) parallel to the surface of the steel sheet 1, respectively, a transmitter (not shown) is connected to the driving coil, and a voltmeter (not shown) is connected to the receiving coil. The magnetic transition measurement device 15 controls transmission of electromagnetic waves (signals) to the drive coil based on input information via a controller by a magnetic transition measurement processing control device (not shown). When the steel sheet passes through the magnetic transition measuring device 15, a signal (drive signal) is sent to the steel sheet 1 by the drive coil, the signal reflected by the steel sheet 1 is measured by the receiver coil, the distance between the steel sheet and the drive coil is modified by the measurement processing device 14 using the measurement value of the drive signal measured by the receiver coil, and the magnetic transition rate of the steel sheet is obtained based on the modified distance. On the other hand, when the steel sheet does not pass through the magnetic transition measuring device 15, the signal from the driving coil is canceled by the receiving coil connected in the reverse phase, and thus the signal to be sent to the measurement processing device 14 does not appear.

Alternatively, when the steel sheet passes through the magnetic transition measuring device 15, the measurement processing device 14 extracts components having phases of 0 ° and 90 ° with respect to the drive signal transmitted based on the measurement value of the drive signal measured by the receiving coil, and obtains the magnetic transition rate based on the phase components. On the other hand, in the case before the steel sheet passes through the magnetic transition measuring device 15, the signal to the measurement processing device 14 does not appear as described above.

In the case of application to the continuous annealing step or the continuous hot dip galvanizing step, the magnetic transformation ratio of the steel sheet is measured before the steel sheet passes through the induction heating apparatus of the annealing furnace, and feedforward control is performed by the measurement processing apparatus 14 to transmit the measured magnetic transformation ratio to the subsequent induction heating apparatus.

The transmission of the driving coil in the magnetic transition measurement device 15 is based on a constant value, but when the reception signal at the reception coil (i.e., the measured value of the measured driving signal) is too large or too small, the magnitude of the transmission of the driving coil can be controlled by the magnetic transition measurement processing control device. For example, the signal of the drive coil is switched to one tenth or ten times in accordance with the over-range or under-range of the reception signal of the reception coil.

According to the present invention, the drive coil and the receiver coil for measuring the magnetic transformation rate of the steel sheet are formed as air coils without using an iron core, and are formed as rings that reciprocate in a path that traverses the annealing furnace, and therefore, the steel sheet is lightweight and excellent in durability. Further, since the drive coil and the receiver coil examine signals corresponding to the magnetic transition rate of the entire width of the steel sheet, there is an effect that the average transition rate in the width direction of the steel sheet (that is, the average magnetic transition rate in the width direction of the steel sheet) can be measured.

In addition, since the two receiver coils are paired and the two receiver coils are connected in reverse phase to perform measurement, the noise signals from the receiver coils cancel each other out. This makes it possible to clearly measure the magnetic signal of the steel sheet.

Next, the principle of the method for measuring the magnetic transformation ratio of a steel sheet according to the present invention will be described with reference to fig. 2.

The magnetic transformation ratio of a steel sheet is measured by utilizing the phenomenon that the paramagnetic property changes into ferromagnetic property as the steel is transformed from the austenite phase to the ferrite phase.

In the present invention, first, the drive coil is controlled by the magnetic transition measurement processing control device of the magnetic transition rate measurement device 15 via the controller. Further, the driving coil 6 transmits an electromagnetic wave (driving signal) toward the steel plate 1.

Reflected waves w from the steel plate 1 reflected from the surface side of the steel plate 1 under all influences in the plate thickness direction₁、w₂Incident on the two receiving coils 7, 8. At the receiving coils 7, 8, the reflected wave w is reflected₁、w₂Signals are generated so that the magnitude of each signal is measured by voltmeter 10.

Then, the measurement processing device 14 uses the reflected waves w received by the receiving coils 7 and 8₁、w₂The distances between the steel plate 1 and the receiving coils 7 and 8 are calculated according to the difference in size. Here, as shown in FIG. 2, the receiving coils 7, 8 are formedAre spaced from the steel plate 1 by different distances and are connected in a reverse phase. Therefore, the signals generated at the receiving coils 7 and 8 cancel each other. In addition, noise signals passing through the receiving coils 7 and 8 are also cancelled out, and thus noise can be prevented. However, since the radio wave is attenuated according to the distance, the signal generated by the driving coil 6 is not completely cancelled by the receiving coils 7 and 8, and only the signal from the steel plate can be obtained.

Therefore, in the present invention, the total signal of the receiver coils 7 and 8 is measured, and the amount of displacement of the steel plate 1 from the reference position is calculated using only the signal V incident from the steel plate. Then, based on the calculated displacement amount, the distance between the steel sheet 1 and the magnetic transition measuring device 15 is calculated. The "reference position of the steel plate" is the position of the steel plate 1 indicated by a broken line in fig. 2, and is the position of the steel plate in the case where the steel plate is stretched by the passing rolls without being loosened. Fig. 2 shows displacement by the amount of the double arrow shown in the figure.

Next, the measurement processing device 14 modifies the signal V incident on each of the receiving coils 7 and 8 to a signal corresponding to the case where the steel plate is located at the reference position using the calculated distance, and corrects the modified signal V₁And (6) performing calculation. For example, the calibration curve of the signal ratio to be recorded in advance in the storage unit of the magnetic transition rate measuring device 15 and the correction signal V₁And comparing, and calculating the magnetic transformation rate of the steel plate according to the relation graph of the temperature of the steel plate and the phase change based on the transformation rate. The calibration curve may be as follows: one or more signals are appropriately selected, and the distance between the steel plate and the coil amount can be obtained from the signal ratio. For example, when the magnitudes of the signals of the steel sheet in the 100% ferrite phase and the steel sheet in the 100% austenite phase, which are obtained from the standard steel sheet position (reference position of the steel sheet), are used, the correction signal V is calculated₁And comparing, and calculating the magnetic transformation rate of the steel plate according to the relation graph of the temperature of the steel plate and the phase change based on the transformation rate.

Here, as the steel sheet temperature, for example, estimation calculated by a control system of CAL and CGL processes is usedThe value is obtained. On the other hand, as described above, the thermometer 11 may be provided in the magnetic conversion rate measuring device 15. In this case, the temperature of the steel sheet is measured by the thermometer 11 provided before the steel sheet 1 passes through the three coils 5 of the magnetic transition measuring apparatus 15 of the present invention. Furthermore, the measured steel plate temperature and the phase change (correction signal V) calculated by the measurement processing device 14 can be used₁) The transformation ratio of the steel sheet is calculated from a graph of the relationship between the temperature of the steel sheet and the phase change based on the transformation ratio, which is measured and recorded in advance in a storage unit of the magnetic transformation ratio measuring apparatus 15 or the like.

In the present invention, a component (V90 °) having a phase of 90 ° with respect to the transmitted drive signal (excitation signal) is extracted from the above-described signal V (total signal) incident from the steel sheet, and the transition rate is calculated. This is because the signal of the phase component of 90 ° is based on the faraday's law of electromagnetic induction and reflects the magnitude of the magnetism of the steel sheet. By comparing the extracted component (V90 °) having the phase of 90 ° with a calibration curve measured in advance and recorded in a storage unit or the like of the magnetic conversion rate measuring apparatus 15, the magnetic conversion rate of the steel sheet can be calculated from a graph of the relationship between the temperature of the steel sheet and the phase change based on the conversion rate. The use of the phase component means that even the same steel sheet may have different measurement positions, and thus the signal V incident from the steel sheet may be different from the incident signal in a different magnetic state. Therefore, only the difference in magnetism is noted by extracting the phase component. In the present invention, the 90 ° phase component is used because it is most affected by the magnetism of the steel plate with respect to the signal received by the receiving coil.

In the present invention, the signal V incident from the steel plate is divided into a component (V0 °) having a phase of 0 ° with respect to the driving signal (excitation signal) after transmission and a component (V90 °) having a phase of 90 ° with respect to the driving signal after transmission, and extracted. Then, from the extracted component (V0 °) having the phase of 0 ° and the component (V90 °) having the phase of 90 °, the ratio (V90 °/V0 °) thereof is found, and the phase angle of the signal received by the receiving coil with respect to the drive signal (excitation signal) is calculated. Using the calculated phase angle, the magnetic transition rate of the steel sheet is calculated. In addition, the phase component of 0 ° is used because it is mainly affected by the electric resistance of the steel sheet. The 90 ° phase component is used because, as described above, the total signal V received by the receiver coils 7 and 8 is most affected by the magnetism of the steel sheet. The reason why the phase angle (arctan (V90 °/V0 °)) obtained from V90 °/V0 ° is used is that the magnitude of the signal based on the influence of the distance between the steel plate and the measurement position, that is, the magnitude of the signal of the drive coil is not affected when the magnetic conversion rate is calculated using a case where the phase angle differs depending on the state of the steel plate to be measured.

Here, the case where one pair of receiving coils is used has been described, but as described above, two or more pairs of receiving coils may be used in the present invention. In this case, the accuracy of the modification described above is improved as compared with the case of one set of receiving coils, and thus a more accurate magnetic transition rate can be measured. A specific measurement method in the case of using two sets of receiving coils is described in example 2 described later, and therefore, is omitted here.

According to the present invention, since the drive coil and the receiver coil are disposed on the same side with respect to the steel plate, the drive signal obtained by reflecting the electromagnetic wave (drive signal) emitted from the drive coil by the steel plate is received by the receiver coil. The size of which varies depending on the position of the receiving coil disposed apart from the steel plate. Therefore, by arranging two receiving coils so that the path lengths of the electromagnetic waves are different, the distance between the steel plate and the receiving coil is determined from the difference in the magnitudes of the drive signals received by the two receiving coils. Then, the signal of the receiving coil is modified according to the distance, and the magnetic transition rate can be obtained from the modified signal of the receiving coil. At this time, as the receiving coils, two sets of receiving coils forming two receiving coils as pairs of the inverted phases are used, so that the modification accuracy is improved and a clearer signal can be obtained. As a result, the accuracy of measuring the magnetic transition rate is also improved.

In addition, the signal of the reception coil is obtained by combining the influence of the magnetism of the steel plate and the influence of the induced current flowing through the steel plate. When the signal of the driving coil is formed into a sine wave, the magnitude and phase of the signal are different depending on the temperature and the transition rate of the steel plate. Therefore, according to the present invention, the phase component which is most affected by the magnetism of the steel sheet and is 90 ° with respect to the drive signal (excitation signal) is extracted from the total signal of the drive signals received by the receiving coil. The magnetic transition rate is obtained from the magnitude of the extracted 90 ° phase component or the magnitude of the correction of the steel plate reference position, and an accurate magnetic transition rate can be obtained.

Further, according to the present invention, the drive signal received by the receiving coil is divided into a signal having a 0 ° phase component and a signal having a 90 ° phase component with respect to the drive signal (excitation signal) and measured, and the ratio of these signals is obtained. Thus, the phase angle of the received drive signal with respect to the drive signal (excitation signal) is calculated, and the magnetic transition rate can be obtained regardless of the influence of the position of the steel plate and the drive coil, specifically, regardless of the magnitude of the signal based on the distance between the coil group (drive coil, receive coil) and the steel plate.

As described above, according to the present invention, since the driving coil and the receiving coil are formed to be hollow without using a core, a light coil made of only a conductive wire may be disposed so as to traverse the continuous annealing furnace. Thus, even in an atmosphere furnace heated to about 900 ℃, the coil is not damaged by its own weight, and the measurement can be stably performed.

In addition, the signal generated from the driving coil has a constant frequency and a constant intensity, for example, a sine wave, a rectangular wave, a pulse, or the like, depending on the responsiveness and the ease of signal processing. According to the present invention, when the drive coil and the receiver coil are disposed on either side of the front and back surfaces of the steel plate for measurement, two receiver coils are formed. The two reception coils are disposed at positions symmetrical with respect to the drive coil, and connected in reverse phase. This makes it possible to cancel (cancel) the signals generated at the two reception coils by the drive coil. In addition, the noise signals passing through the two receiving coils can also be cancelled (canceled), and thus noise can also be prevented. At this time, the signal emitted from the driving coil is reflected by the steel plate, and the reflected signal is incident on the two receiving coils and emitted. Since the distance from the steel plate is different between the two receiver coils and the magnitude of the generated signal is also different between the two receiver coils, it is possible to use only the signal incident from the steel plate by measuring the total signal of the two receiver coils connected in reverse phase.

In addition, according to the present invention, the reception coils connected in reverse phase can be arranged in two sets and at different distances from the drive coils. In this case, since the distances between the drive coil and each group of the receiver coils are different, the displacement of the steel plate from the reference position can be calculated using the difference in the ratio of the reflected signals from the steel plate (the signals incident on the receiver coils). The calculated displacement is used to modify the effect of the position of the steel plate on the magnitude of the signal of the receiver coil, thereby enabling a more accurate magnetic transition rate to be determined compared to a set of receiver coils.

The signal emitted from the driving coil and reflected from the steel plate is generated by eddy currents generated in the steel plate, but the reflected signal differs in magnitude and phase from the original signal due to the magnetic and electric resistances of the steel plate. In the case of steel, which is a ferromagnetic region, the magnetic influence of the steel plate occurs largely with a 90 ° phase component with respect to the drive signal of the receiver coil. Therefore, in the present invention, the magnetic field strength of the steel sheet can be clearly measured and the magnetic transition rate can be accurately measured by determining the transition rate of the steel sheet using the magnitude of the component having a phase of 90 ° with respect to the drive signal among the measured signals.

Further, according to the present invention, the measured signal is divided into components having a phase of 0 ° and a phase of 90 ° with respect to the drive signal, and the transition rate is determined according to the ratio of the components or the phase of the measured signal with respect to the drive signal. This makes it possible to measure the magnetic transformation rate accurately without affecting the change in the magnitude of the signal due to the change in the position of the steel sheet.

The magnetic conversion rate measuring apparatus and the magnetic conversion rate measuring method of the present invention described above can be applied to a continuous annealing process and a continuous hot dip galvanizing process. In this case, the magnetic transformation rate of the steel sheet can be grasped by performing the magnetic transformation rate measurement in the annealing furnace in the continuous annealing step, in the furnace in the continuous hot-dip galvanizing step, and before the electromagnetic induction heating device for reheating. Thus, the influence on the induction heating apparatus can be calculated in advance from the measurement result of the magnetic transition rate of the steel sheet, and the control can be performed so as to suppress the voltage fluctuation of the induction heating apparatus.

The temperature conditions of heating, soaking, cooling, plating, and the like in the continuous annealing step and the continuous hot dip galvanizing step of the present invention are not particularly limited, and known conditions can be used.

According to the present invention, the magnetic transformation ratio of the steel sheet in the annealing furnace can be known. Thus, in the continuous annealing step and the hot dip galvanizing step, the influence of the magnetic transformation rate on the induction heating apparatus can be known in advance before the electromagnetic induction heating is performed. Further, feed-forward control of the induction heating device can be performed, and induction heating can be stably performed even if there is a change in the magnetic transition rate.

Hereinafter, the present invention will be described in detail with reference to fig. 3 to 6 using examples. The present invention is not limited to the following examples. Fig. 3 is a diagram illustrating one embodiment of the present invention, and fig. 4 to 6 are diagrams illustrating other embodiments of the present invention.