JPH07190991A - Transformation rate-measuring method and device - Google Patents

Abstract

PURPOSE:To obtain a method and device for easily compensating the quality, thickness, and width of a steel plate and for measuring the transformation rate of the steel plate whose S/N ratio is improved by eliminating noise due to roll rotation by suppressing the fluctuation in the magnetic flux density output by a magnetic flux generation means generated due to the change in environmental temperature where a transformation rate measuring device is installed and the lapse of time. CONSTITUTION:The device including a magnetization equipment box 11 including a magnetization equipment for generating magnetic flux from the lower side of a steel plate 15, a detector box 17 including a magnetic sensor for detecting the magnetic flux at the upper side of the steel plate 15, and a signal processing circuit 24 for obtaining the transformation rate measured value from the output of the magnetic sensor is installed at a measuring point A and a reference point B immediately before a coiler 23 on a same manufacturing line. Then, with a measurement value V9 of the measurement point B as a reference value with a transformation rate of 100%, an operation circuit 25 for compensating and calculating a transformation rate measured value V8 of the measuring point A based on the reference value is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for electromagnetically measuring the transformation rate of a steel sheet after hot rolling by electromagnetic means.

[0002]

2. Description of the Related Art It is very important for maintaining high quality to maintain a constant final structure that greatly affects various mechanical properties and physical properties of steel sheets manufactured in a steel mill. It is a matter.

For example, magnetic permeability among magnetic properties has a high correlation with mechanical properties such as hardness and grain size. Therefore, if the correlation between the magnetic permeability and the mechanical properties is measured in advance, the mechanical properties of the steel sheet can be estimated to some extent by measuring the magnetic permeability.

Also in the production process control, during the heat treatment process of hot steel, the steel transforms from the austenite (γ) phase in the high temperature state to the ferrite (α) phase in the low temperature state. Monitoring is extremely important in controlling the material of the steel sheet, and development of a sensor for measuring the transformation rate online is desired.

In the measurement of this phase transformation, the fact that the γ → α phase transformation of steel is accompanied by a physical phenomenon of change from non-magnetic (γ phase) to ferromagnetic (α phase) is used, and a magnetic detector is used. There is a method of detecting the transformation behavior. In this method, the magnetic properties of the steel change greatly near the Curie point, and the Curie point of most commercial steels is around 750 ° C, so the transformation of the steel in the cooling process in this vicinity gradually progresses from the surface to the inside. The state of going can be detected with high sensitivity.

Further, in order to measure the magnetic properties of a steel sheet that is actually continuously flowing in the manufacturing process, it is necessary to perform these measurements in a non-contact and online state. Conventionally, when measuring the magnetic characteristics of such a steel sheet in a non-contact and online state, a transformation rate measuring device has been proposed that utilizes the property that the attenuation rate of the magnetic flux passing through the steel sheet changes depending on the magnetic characteristics of the steel sheet. Has been done,
For example, there is one disclosed in JP-A-56-82443.

FIG. 7 is a block diagram showing the configuration of the conventional transformation rate measuring device shown in the above document. In FIG. 7, a magnetizer 54 composed of a magnetized iron core 52 and an exciting coil 53 is provided on one side (lower side in the figure) of a steel plate 51 to be inspected at a predetermined distance d ₁ to form a pair of magnetic poles 54a. , 54b is steel plate 5
It is arranged so as to face 1. And magnetizer 54
An exciting current is supplied to the exciting coil 53 from the magnetizing power supply 55, and a magnetic flux is generated between the magnetic poles 54a and 54b. In addition to the magnetic flux passing through the inside of the steel plate 51, this magnetic flux also has a magnetic flux 59 leaking to the outside, and the magnetic flux 59 leaking to the outside.
Is detected by the magnetic detection element 56 arranged on the other side (upper side in the figure) of the steel plate 51 with a distance d ₂ therebetween. The leakage magnetic flux detection signal detected by the magnetic detection element 56 is transmitted to the arithmetic unit 58. The surface temperature of the steel plate 51 is measured by the thermometer 57, and this temperature measurement signal is also transmitted to the arithmetic unit 58.

According to the transformation rate measuring device having such a structure, if the steel plate 51 as a ferromagnetic material exists between the magnetizer 54 and the magnetic detecting element 56, the magnetic pole 54a of the magnetizer 54 outputs the magnetic field. Most of the generated magnetic flux passes through the steel plate 51 and is input to the other electrode 54b. And the steel plate 51
When the transformation rate of the steel sheet changes, the magnetic characteristics such as the magnetic permeability of the steel sheet 51 change, and the density Φ of the magnetic flux passing through the inside of the steel sheet 51.
Changes. Therefore, the transformation rate can be quantitatively obtained by previously obtaining the reference magnetic flux density in the test steel sheet having the known transformation rate and comparing the measured magnetic flux density Φ with the reference magnetic flux density. Further, while moving the steel plate 51 in a certain direction, the density Φ of the magnetic flux 59 leaked to the opposite side of the steel plate 51 is continuously measured by the magnetic detection element 56, and the point at which the magnetic flux density Φ largely changes is the conversion ratio of the steel plate. Can be regarded as the change point of.

[0009]

However, the conventional transformation rate measuring device as described above still has the following problems. That is, the shape of the hot-rolled steel sheet after being hot-rolled online moves at a considerable speed while vibrating, and in particular, it often rises at the front end and the rear end thereof. Therefore, if the magnetic flux detecting element is brought too close to the steel plate in order to improve the detection accuracy, a contact accident or the like may occur.

Therefore, in order to avoid a contact accident, the distance d ₂ between the steel plate and the magnetic flux detecting element must be at least 50 cm or more. But then, the magnetic flux density Φ
Is significantly reduced, and the winding resistance value of the exciting coil that constitutes the magnetizer, the magnetic permeability of the magnetized iron core, the detection sensitivity of the magnetic flux detection element, etc. change depending on the ambient temperature, and the magnet is used for a long time. The influence of the change in the magnetic flux density from the magnetizer due to the change in the magnetic permeability of the magnetized iron core cannot be ignored for the detection signal, and the measurement accuracy deteriorates.

Further, the leakage magnetic flux detection signal in the above-mentioned transformation rate measuring device is because the magnetic flux density Φ changes not only with the transformation rate of the steel sheet to be measured but also with the material, the sheet thickness and the sheet width. However, it is necessary to correct the width and material. However, these corrections are quite complicated, and it is extremely difficult to obtain the correction coefficient by using a steel plate having the same size as the sample flowing through the actual line in the off-line.

Further, since the conventional transformation rate measuring device is constructed so as to detect the transformation rate of the steel sheet by measuring the attenuation amount of the magnetic flux emitted from the exciting coil through the steel sheet by the magnetic flux detector in principle, If a disturbance magnetic field exists in addition to the magnetic field generated by the coil, this disturbance magnetic field mixes in as noise with respect to the detection signal and causes deterioration of S / N. As the source of the disturbance magnetic field, the roll located under the steel plate is a ferromagnetic material, so that there is residual magnetism in the roll, and therefore when the roll rotates, it becomes noise. Therefore, it is conceivable to replace the roll with a non-magnetic material such as SUS, but in consideration of seizure and wear resistance of the steel sheet, C
Since r type rolls are desirable, they cannot be replaced in practice.

The present invention has been made to solve the above problems, and suppresses a change in the environmental temperature in which the transformation rate measuring device is installed or a change in the magnetic flux density output by the magnetic flux generating means caused by the passage of time. Therefore, the material, thickness and width of the steel sheet can be easily corrected, and the noise due to the roll rotation during the transportation of the steel sheet is removed to improve the S / N ratio and the highly accurate transformation rate measurement of the steel sheet. The purpose is to obtain a method and a device.

[0014]

According to the transformation rate measuring method of the present invention, a magnetic flux generating means for generating a magnetic flux is provided on one side of a steel sheet to be inspected, and the other one is provided. A transformation rate measuring device for measuring a transformation rate of the steel sheet from a magnetic flux density detected by the magnetic flux detecting means is provided on a side of the magnetic flux detecting means for detecting a magnetic flux generated by the magnetic flux generating means and leaking through the steel sheet. In the transformation rate measuring method to be used, the two transformation rate measuring devices are respectively installed at the position for measuring the transformation rate and the reference position after the completion of transformation on the same production line of the steel sheet, and at the reference position. There is a correction calculation step for performing a correction calculation based on the reference value of the transformation rate measuring device installed at the position to be measured, using the value measured by the transformation rate measuring device installed as a reference value for the transformation rate of 100%. Than it is.

In the transformation rate measuring device according to the invention of claim 2, a steel sheet to be inspected is sandwiched, and magnetic flux generating means for generating magnetic flux is provided on one side of the steel sheet, and the magnetic flux generating means is provided on the other side. In the transformation rate measuring device for measuring the transformation rate of the steel sheet from the magnetic flux density detected by the magnetic flux detecting means provided by the magnetic flux detecting means, which detects the magnetic flux penetrating and leaking through the steel sheet, the traveling speed of the steel sheet. Is v, the plate thickness is t, the magnetic permeability is μ, the electric conductivity is σ, and the representative length determined by the measurement interval in the traveling direction is L, the magnetic flux generating means has v / L ≦ f ≦ 1 / ( It is provided with an AC magnetic flux generating means for generating an AC magnetic flux having a frequency f represented by πμσt ² ).

The transformation rate measuring device according to the invention of claim 3 is the transformation rate measuring device according to the invention of claim 2, wherein when a steel sheet is not present between the magnetic flux generating means and the magnetic flux detecting means, The magnetic flux detecting means is provided with an alternating magnetic flux density calibrating means for calibrating the alternating magnetic flux density generated by the alternating magnetic flux generating means such that the value of the magnetic flux density detected through the air becomes a predetermined calibration value.

In the transformation rate measuring apparatus according to the invention of claim 4, an E-shaped core is used as an electromagnet provided on one side of the steel sheet to be inspected, and the magnetic poles at both ends of the core have the same polarity. , A magnetic flux generating means for generating a magnetic flux whose direction is opposite to that of the center magnetic pole by exciting the central magnetic pole in the opposite polarity to the vertical extension line from the center of the core to the steel plate direction; Is provided at a right angle with respect to a vertical extension line from the center of the core on the other side sandwiching the core in the direction of the magnetic poles at both ends of the core, and is generated by the magnetic flux generating means. It is provided with a pair of magnetic flux detecting means for respectively detecting the horizontal components of the symmetrical magnetic flux penetrating and leaking, and a difference calculating means for calculating the difference between the magnetic flux density signals detected by each of the pair of magnetic flux detecting means. .

[0018]

In the invention according to claim 1, a magnetic flux generating means for generating a magnetic flux is provided on one side of the steel sheet to be inspected, and the other side is generated by the magnetic flux generating means. A magnetic flux detecting means for detecting a magnetic flux penetrating and leaking through the steel sheet is provided, and a transformation rate measuring device for measuring the transformation rate of the steel sheet from the magnetic flux density detected by the magnetic flux detecting means is provided on the same production line of the steel sheet. The position to measure the rate and the reference position after completion of the transformation are respectively set, and in the correction calculation step, the value measured by the transformation rate measuring device installed at the reference position is used as the reference value of the transformation rate of 100%, and the position to be measured. The measurement value by the transformation rate measuring device installed in 1 is corrected and calculated based on the reference value.

According to the second aspect of the present invention, an alternating magnetic flux generating means for generating an alternating magnetic flux is provided on one side of the steel sheet to be inspected, and the other side has the alternating magnetic flux generating means. Provided with a magnetic flux detection means for detecting the magnetic flux leaking through the steel sheet generated, in the transformation rate measuring device for measuring the transformation rate of the steel sheet from the magnetic flux density detected by the magnetic flux detection means, the AC magnetic flux generation means, The running speed of the steel plate is v, the plate thickness is t, the magnetic permeability is μ, the electrical conductivity is σ, and the representative length determined by the measurement interval in the running direction is L.
Then, an AC magnetic flux of frequency f represented by v / L ≦ f ≦ 1 / (πμσt ² ) is generated.

In the invention according to claim 3, in the AC magnetic flux density calibrating means added to the invention according to claim 2, a steel plate is provided between the magnetic flux generating means and the magnetic flux detecting means of the transformation rate measuring device. When it does not exist, the AC magnetic flux density generated by the AC magnetic flux generation means is calibrated so that the value of the magnetic flux density detected by the magnetic flux detection means through air becomes a predetermined calibration value.

In the invention according to claim 4, the magnetic flux generating means uses an E-shaped core as an electromagnet provided on one side of the steel sheet to be inspected, and the magnetic poles at both ends of the core have the same polarity. In addition, the central magnetic pole is excited to have a polarity opposite to that of the both ends, thereby generating a magnetic flux which is symmetrical with respect to the vertical extension line from the center of the core to the steel sheet direction and opposite in direction. The pair of magnetic flux detecting means are provided at right angles to the vertical extension lines from the center of the core on the other side sandwiching the steel plate and equidistant from each other in the magnetic pole direction at both ends of the core, The horizontal components of symmetrical magnetic fluxes generated by the magnetic flux generator and leaking through the steel sheet are detected. The difference calculation means calculates the difference between the magnetic flux density signals detected by each of the pair of magnetic flux detection means.

[0022]

EXAMPLE FIG. 4 is a diagram for explaining the operating principle of the transformation rate measuring device according to the present invention. In FIG. 4, reference numeral 10 denotes a magnetizer, which is composed of a magnetized iron core 10 a and an exciting coil 10 b and is arranged in a magnetizer box 11. The magnetizer box 11 is made of a material that is not affected by magnetism so that magnetic flux can freely pass therethrough, and the magnetizer 10 is water-cooled by constantly flowing in and out cooling water 12. Therefore, the magnetizer 10 has a waterproof structure, is electrically insulated from the cooling water 12, and its exciting coil 10b is connected to the constant current circuit 13. In this example, the magnetizer box 11 is installed below the steel plate 15 running online with a predetermined distance d ₁ therebetween.

A magnetic flux detecting element 16 is arranged in the detector box 17. Similar to the magnetizer box 11, the detector box 17 is made of a material through which magnetic flux can freely pass, and the cooling water 18 is always flown in and out to cool the magnetic flux detection element 16. Therefore, the magnetic flux detecting element 16 has a waterproof structure, is electrically insulated from the cooling water 18, and is connected to the magnetic detecting circuit 19. Detector box 17
Is installed at a position above the steel plate 15 facing the magnetizer box 11 and separated by a predetermined distance d ₂ .

The constant current circuit 13 is connected to a low frequency oscillator 14 which oscillates at a low frequency f, and excites the exciting coil 10b by an alternating current having the low frequency f. The method of setting the frequency f will be described later. The output signal of the magnetic detection circuit 19 is input to the lock-in amplifier 20, and the output signal of the low frequency oscillator 14 is also input to the lock-in amplifier 20 as a synchronization signal. The lock-in amplifier 20 incorporates a synchronous detector and an amplifier, synchronously detects the input signal from the magnetic detection circuit 19 by the output signal of the low-frequency oscillator 14, and outputs a voltage signal obtained by amplifying the detected signal. . Then, the voltage value of this output signal becomes a measurement signal corresponding to the transformation rate.

The transformation rate will be simply described here. The steel sheet immediately after hot rolling has both surface temperature and internal temperature at a high temperature equal to or higher than the Curie point, and is γ-phase nonmagnetic in the sheet thickness direction.
As this is cooled and controlled, the surface temperature decreases and becomes α-phase ferromagnetism, but the internal temperature is still high and there is a γ-phase nonmagnetic or weak magnetic state. In such a state, for example, 50% in the thickness direction if half is α phase and half is γ phase
The transformation rate is 100% when the transformation is completed in all the α-phases in the plate thickness direction.

The transformation rate measuring device configured as described above is
Even when the environmental temperature of the installation place changes, the temperature change in the magnetizer box 11 is suppressed, and the magnetic permeability of the iron core 10a of the magnetizer 10 and the resistance value of the exciting coil 10b become constant regardless of the environmental temperature. The constant current circuit 13 supplies a constant current to the exciting coil 10b, so that the magnetic flux density generated by the magnetizer 10 is kept constant. Similarly, since the temperature inside the detector box 17 is also kept constant, the temperature drift of the detection sensitivity of the magnetic flux detection element 16 can be suppressed. Therefore, there is no problem in relatively short-term use.

However, in spite of the above structure, when the apparatus is used for a long time, a change with time of the magnetic permeability of the iron core 10a of the magnetizer 10 becomes a problem. In addition, online, after a steel plate 15 having a certain length in the traveling direction has passed, the next steel plate 15 is usually conveyed after a certain time has elapsed. Therefore, in order to remove the influence of the change in magnetic permeability of the iron core 10a, each time the steel sheet 15 finishes passing (that is, the magnetizer box 11 and the detector box 17).
Every time the steel plate 15 is no longer present), the control circuit 21 adjusts the gain of the constant current circuit 13 so that the voltage value output from the lock-in amplifier 20 through the magnetic detection circuit 19 becomes a predetermined calibration value. However, calibration is performed so that a constant AC magnetic flux density is always supplied even when used for a long time.

Here, the constant current circuit 13 is the low frequency oscillator 14
The exciting coil 10b is excited by an alternating current having a frequency f on the basis of the output signal from the AC magnetic field generated by the magnetizer 10 because the influence of the earth magnetism is detected as an error when the applied magnetic field is DC. Is desirable.
However, as the excitation frequency of this alternating current is increased, the magnetic flux concentrates on the plate surface and becomes less permeable to the inside. Therefore, the upper limit of the excitation frequency is determined by how far the magnetic flux penetration depth is maintained.

Further, since at least one AC cycle is required to measure the transformation rate by this AC excitation, if the excitation frequency is lowered, the measurement interval (sampling interval) becomes large and the response to the change in the measured value becomes large. The sex becomes worse. Therefore, the lower limit of the excitation frequency is determined by the upper limit value that does not increase the measurement interval of the steel sheet 15 in the traveling direction to a certain value or more, and the lower limit value of the excitation frequency is obtained from the traveling speed of the steel sheet 15 based on this upper limit value.

Therefore, in the present invention, the excitation frequency f for generating the AC magnetic field is determined by the lower limit value in consideration of the response at the time of measurement and the upper limit determined by the relational expression between the excitation frequency and the penetration depth into the steel sheet. The values are set so as to satisfy the following expression (1). v / L ≦ f ≦ 1 / (πμσt ² ) (1) where v is the traveling speed of the steel sheet (unit is m / s), t is the thickness of the steel sheet (unit is m), and μ is the magnetic permeability of the steel sheet. (Unit is H /
m) and σ are electric conductivity of the steel sheet (unit is 1 / Ωm), L is a representative length (unit is m) determined by the measurement interval in the running direction of the steel sheet, and the lower limit of the excitation frequency f is determined by this value. Desired.

For example, when it is desired to set the measurement interval to 0.5 m or less and the traveling speed v is 20 m / s, f is 40.
It is necessary to set the frequency to Hz or higher, and in this case, L = 0.5 m. Further, when v is 10 m / s, f must be 20 Hz or higher, and in this case, L = 0.5 m. When the measurement interval is 1 m or less, the traveling speed v is 20 m.
When / s, f must be 20 Hz or higher, and in this case, L = 1 m. Further, when v is 10 m / s, f must be 10 Hz or higher, and in this case as well, L = 1 m. Thus, L has a value determined by the measurement interval in the traveling direction.

FIG. 2 is a block diagram showing the construction of an embodiment of the transformation rate measuring apparatus according to the present invention. In the figure, a magnetizer 10 including a magnetized iron core 10a and an exciting coil 10b, a magnetizer box 11, cooling waters 12 and 18, a constant current circuit 1
3, low frequency oscillator 14, steel plate 15, detector box 1
7, the lock-in amplifier 20 and the control circuit 21 are the same as those in FIG. Further, as in the case of FIG. 4, the magnetizer box 11 is installed below the steel plate 15 at a distance of d ₁ , and the detector box 17 is located above the steel plate 15 facing the magnetizer box 11 by a distance d _2. Are installed at intervals of. The magnetizer 10 installed in the magnetizer box 11 is
The exciting coil 10b is connected via a constant current circuit 13 to a low frequency oscillator 14 that oscillates at a frequency f.

In FIG. 2, 1 is a high frequency power source, 2 is a resistor, 3 is a magnetic sensor, which is composed of a sensor core 3a and an exciting coil 3b, and is arranged in a detector box 17. The magnetic sensor 3 in the detector box 17 has a waterproof structure because it is water-cooled by the cooling water 18, and is electrically insulated from the cooling water 18 and connected to the magnetic detection circuit 4. The magnetic detection circuit 4 outputs a voltage signal V ₃ proportional to the detected magnetic flux density based on the input signal from the magnetic sensor 3 and supplies the voltage signal V ₃ to the lock-in amplifier 20.

Here, the magnetic measuring device composed of the high frequency power source 1, the resistor 2, the magnetic sensor 3 and the magnetic detecting circuit 4 shown in FIG. 2 has been previously filed by the applicant of the present application, which is JP-A-1-30898.
The same device as the device described in "Magnetic measuring method and magnetic measuring device" of Japanese Patent No. 2 is used. That is, the magnetic sensor 3 is configured by winding a detection coil 3b around a sensor core 3a made of a ferromagnetic material, and a high frequency constant voltage signal output from the high frequency power supply 1 is passed through the resistor 2 to the detection coil 3b. The excitation current is constantly flowing as a result of being supplied. Then, the sensor core 3a is excited to the supersaturation region. Further, the magnetic detection circuit 4 includes a positive voltage detector and a negative voltage detector which individually detect a positive voltage and a negative voltage alternately generated at both ends of the detection coil 3b based on the high-frequency exciting current, and these two detectors. It is configured by an adder that adds the output voltages of the detectors to obtain a difference voltage.

When no magnetic flux exists in the installation region of the magnetic sensor 3 excited to the supersaturation region in this way, the peak values V _p of the positive voltage and the negative voltage alternately generated at both ends of the detection coil 3b and − It is equal to V _n . Therefore, the output obtained by adding the positive and negative DC voltages obtained by detecting the two peak values by the adder becomes zero. However, when an external magnetic flux is applied to the magnetic sensor 3, the sum of the peak values of the positive voltage and the negative voltage generated at both ends of the detection coil 3b does not change, but there is a difference between the positive and negative peak values V _p and -V _n. Occurs. Therefore, the difference voltage (V _p −V _n ) is obtained by adding positive and negative DC voltages obtained by detecting these two peak values with an adder. The difference voltage (V _p −V _n ) becomes a value corresponding to the external magnetic flux density given to the magnetic sensor 3. The magnetic detection circuit 4 sequentially outputs the detection signal V ₃ corresponding to the magnetic flux density applied to the magnetic sensor 3 by leaking from the steel plate 15 running in this way.

The response frequency of the detection signal V ₃ output from the magnetic detection circuit 4 based on the detection signal of the magnetic sensor 3 is sufficiently higher than the frequency f of the low frequency oscillator 14. By using this supersaturation type magnetic sensor 3 as a magnetic flux detector, a highly sensitive magnetic sensor is realized, and the distance d ₂ between the steel plate 15 and the detector box 17 housing the magnetic sensor 3 is measured at a distance of 1 m or more. Is possible,
Further, by separating them by 1 m or more, the influence of the variation of the pass line of the steel sheet 15 is removed, and the transformation rate of the steel sheet can be measured at a high S / N.

FIG. 3 is a waveform diagram for explaining the operation of the signal processing circuit of FIG. 2. The signal processing of FIG. 2 will be described with reference to FIG. The signal processing circuit of FIG. 2 includes a lock-in amplifier 20 and a low-pass filter (hereinafter referred to as LPF).
5, a zero adjustment circuit 6, an inverter 7 and a linearizer 8 are included. The output signal V ₃ of the magnetic detection circuit 4 is input to the lock-in amplifier 20, and the lock-in amplifier 20 receives the input signal from the magnetic detection circuit 4 based on the output signal of the low-frequency oscillator 14 as in the case of FIG. Synchronous detection is performed, and a voltage signal V ₄ obtained by amplifying this detection signal is output to output the control circuit 21.
And LPF5 (see (a) of FIG. 2).

As in the case of FIG. 4, the control circuit 21 eliminates the change with time of the magnetic permeability of the iron core 10a, so that the output of the lock-in amplifier 20 has a predetermined voltage value V after the steel plate 15 has passed through. The gain of the constant current circuit 13 is adjusted so as to obtain ₄ .

In the waveform diagram of FIG. 3, the vertical axis represents voltage and the horizontal axis represents cooling time. The high temperature side, which has a short cooling time, is the γ phase,
The low temperature side for a long time is the α phase. Since the output voltage V ₄ of the lock-in amplifier 20 contains a high-frequency noise component, low-pass filtering is performed by passing it through the LPF 5, and the output signal from which the noise component has been removed is supplied to the zero adjustment circuit 6. To do. The zero adjustment circuit 6 shifts the level of the input signal and supplies an output signal (see (b) in FIG. 2) to the inverter 7 so that the signal level in the γ phase becomes zero.

The inverter 7 inverts the polarity of the input signal,
The negative voltage V ₅ is output as the positive voltage V ₆ (see (c) of FIG. 2) and supplied to the linearizer 8. Since the slope of the γ-α transformation of the input signal is nonlinear in the linearizer 8,
A voltage signal V ₇ (see (d) of FIG. 2) obtained by linearly converting this is output as a measurement signal corresponding to the transformation rate. For example, when the output signal V _{7 of the} linearizer 8 changes in the range of 0 to 10V, the voltage value of V ₇ is 0V, 1V, 2V,
3V, ... 10V are 0%, 10%, 2 of the transformation rate, respectively.
Adjust to correspond to 0%, 30%, ... 100%.

FIG. 1 is a diagram for explaining a material, plate thickness and plate width correction method of the transformation rate measuring method according to the present invention. In the figure, the magnetizer box 11 in which the magnetizer 10 is arranged, the detector box 17 in which the magnetic sensor 3 is arranged, and the steel plate 15 as the test material are the same as those in FIG. Reference numeral 22 in FIG. 1 denotes a roll for conveying the steel plate 15, and 2
3 is a coiler that winds the steel plate 15 which has been transformed into the α phase after cooling (transformation rate is 100%), and 24 is a signal processing circuit, for example, the magnetic detection circuit 4 and the lock-in amplifier 20 in FIG. It is composed of an LPF 5, a zero adjustment circuit 6, an inverter 7 and a linearizer 8. Reference numeral 29 is an arithmetic circuit for correcting the transformation rate measurement value V ₈ based on the transformation rate reference value V ₉ ,
A recorder 26 records the output signal of the arithmetic circuit 25.

In FIG. 1, the coiler 2 and the position on the same production line where the transformation rate is to be measured (point A).
Immediately before step 3, the sample was cooled and the transformation to the α phase was completed (transformation rate 10
A transformation rate measuring device having the same structure (for example, a device having the structure shown in FIG. 2) is installed at each of two positions, which are 0%) and a reference position (referred to as point B). The transformation rate at point A is calculated. This means that even if the value of the transformation rate of 100% is measured at the point B immediately before the coiler 23, the measured value is different depending on the material of the steel plate 15, the plate thickness and the plate width. That is, since the parameter of the measured value includes the material, the plate thickness, and the plate width in addition to the transformation rate, the measured value at the point B is set as the reference value for the transformation rate of 100%, and A A correction calculation is performed on the measured value at the point to obtain the transformation rate at the point A in which the material, the plate thickness and the plate width are collectively corrected.

That is, in FIG. 1, the magnetic flux density generated by the magnetizer box 11 mounted between the pair of rolls 22 at the point A where the transformation rate is to be measured on the same production line is shown by the upper part of the steel plate 15. 2 is detected by the detector box 17 installed in the above, and the output voltage V ₈ is obtained through the signal processing circuit 24 including the detection circuit 4 and the linearizer 8 shown in FIG. Further, a device having exactly the same configuration as the point A is provided immediately before the coiler 23, that is, at the point B after the transformation is completed, and the output voltage V ₉ is similarly obtained. The two output signals V ₈ and V ₉ are input to the arithmetic circuit 25. Arithmetic circuit 2
The content of the correction calculation executed by 5 differs depending on whether the input signals V ₈ and V ₉ are linear signals or non-linear signals.

When the signal processing circuit 24 includes a linearizer and the input signals V ₈ and V ₉ are linear signals, the arithmetic circuit 25 sets the output value V ₉ at the point B after the transformation is completed to the transformation rate 1
The output value V ₈ at the measurement point A is divided by the reference value V ₉ and the quotient of the division result is V ₈ / V ₉ × 100.
% Is output as the transformation rate after the correction calculation at the measurement point A. Further, when the input signals V ₈ and V ₉ are non-linear signals, the arithmetic circuit 25 stores in advance an equation showing the non-linear characteristic between the standard voltage value and the transformation rate, or an approximate equation thereof, and stores the reference value. The transformation rate is calculated from the output value V ₈ at the measurement point A by a method such as, for example, a broken line approximation, where V ₉ is a value indicating the transformation rate of 100% in this nonlinear characteristic. Then, this calculated value is output as the transformation rate after the correction calculation at the measurement point A. The recorder 26 sequentially records and outputs the transformation rate after the correction calculation.

FIG. 5 is a constitutional block diagram showing another embodiment of the transformation rate measuring apparatus according to the present invention. In FIG.
An E-type electromagnet 33 is arranged between the lower table rolls 32a and 32b of the steel plate 31. In the E-type electromagnet 33, the coil 35 wound around the E-type core 34 is excited so that the magnetic poles 33a and 33c at both ends have the same polarity and the central magnetic pole 33b has the opposite polarity to both ends. As a result of the excitation of the E-type electromagnet 33 in this way, the direction is symmetrical with respect to the extension line V (hereinafter referred to as the center magnetic pole line) V extending perpendicularly to the steel plate direction from the center of the center magnetic pole 33b of the E-type electromagnet 33 Magnetic flux is generated. The rolls 32a and 32b generally rotate in synchronization.

On the upper side of the steel plate 15, the both end magnetic poles 33a, 33 are perpendicular (that is, horizontal) to the central magnetic pole line V extending from the central magnetic pole 33b of the E-type electromagnet 33.
Magnetic flux detectors 38a for respectively detecting horizontal components of the symmetrical magnetic flux generated from the E-type electromagnet 33 and leaking through the steel plate 31 at two positions separated by an equal distance d in the c direction,
38b are installed in the same direction.

The E-type electromagnet 33 including the magnetic flux detectors 38a and 38b, the E-type core 34 and the coil 35 shown in FIG.
Each of them has a waterproof structure, and as in FIG. 2, the magnetic flux is arranged in a pair of a detector box and a magnetizer box which are made of a material which penetrates freely and cooled by cooling water. Illustration is omitted.

The output signals of the magnetic flux detectors 38a and 38b are
The signals are amplified by the magnetic detection circuits 39a and 39b and then input to the subtraction circuit 40. The signal resulting from the subtraction by the subtraction circuit 40 is input to the signal processing circuit 41. The signal processing circuit 41 is composed of, for example, each device from the lock-in amplifier 40 to the linearizer 8 in FIG.

The operation of FIG. 5 will be described. The horizontal components of the signal magnetic fluxes 37a and 37b formed between the magnetic poles 33a and 33c and the central magnetic pole 33b at both ends of the E-type electromagnet 33 and detected by the magnetic flux detectors 38a and 38b are as shown by the solid line in the figure. In addition, since they are symmetrical (symmetric) with respect to the central magnetic pole line V, their absolute values are almost equal and their directions are opposite. The two detection signals having the opposite polarities and substantially the same absolute values are amplified by the magnetic detection circuits 39a and 39b and supplied to the subtraction circuit 40. The subtraction circuit 40 subtracts two input signals from the magnetic detection circuits 39a and 39b, which have opposite polarities and substantially equal amplitudes, so that substantially two amplitude values are added and a signal having a doubled amplitude value. The component will be output.

On the other hand, the disturbance magnetic flux 36 due to the roll remanence detected by the magnetic flux detectors 38a and 38b has substantially the same magnitude and the same direction, as indicated by the broken line in the figure. Therefore, the two detection signals based on the residual magnetism of the roll are subtracted as they are by the subtraction circuit 40 and cancelled. In this way, on the output side of the subtraction circuit 40, the signal component is added twice and the noise component is canceled out, so that the S / N is remarkably improved and a highly accurate transformation rate measurement becomes possible.

FIG. 6 is a diagram showing a comparison of the measurement results of the roll residual magnetic flux between the transformation rate measuring device of FIG. 5 and the conventional device. In FIG. 6 (a), the rolls 32a and 32b are rotated at a rotation speed (about 5 Hz) corresponding to a plate passing speed of 300 m / min in a state in which the excitation of the excitation coil is cut off using a conventional device. The residual magnetic field generated at this time is measured by one magnetic flux detector installed at a position 1 meter from the upper surface of the roll, and this measured value is frequency analyzed. From the figure, there is a peak value at about 4.8 Hz corresponding to the roll rotation frequency and its harmonic frequency part.

FIG. 6 (b) shows the result of frequency analysis of the difference value of the detection signals by arranging a pair of magnetic flux detectors using the transformation rate measuring apparatus of FIG. 5 under the same conditions. . Figure 6
It can be confirmed that the roll rotation noise is attenuated by about 30 dB at the roll rotation frequency of about 4.8 Hz as compared with (a).

[0053]

As described above, according to the present invention, two transformation rate measuring devices are installed at the transformation rate measuring position and the reference position after transformation on the same production line for steel sheets, respectively. Since the value measured by the transformation rate measuring device installed at the reference position is used as the reference value for the transformation rate of 100%, the value calculated by the transformation rate measuring device installed at the measuring position is corrected based on the reference value. It is possible to calculate the transformation rate by collectively correcting the effects of the material of the steel plate, the plate thickness and the plate width.

According to the present invention, the alternating magnetic flux generated from one side of the steel plate is generated by the alternating magnetic flux generating means,
Since the generation frequency of this AC magnetic flux is set to the optimum value between the lower limit value considering the response at the time of measurement and the upper limit value determined by the relational expression of the excitation frequency and the penetration depth into the steel plate, The transformation rate can be measured by removing the influence of the geomagnetism without impairing the responsiveness.

Further, according to the present invention, when there is no steel sheet between the AC magnetic flux generating means and the magnetic flux detecting means of the transformation rate measuring device, the value of the magnetic flux density detected by the magnetic flux detecting means through air is Since the AC magnetic flux density generated by the AC magnetic flux generating means is calibrated to be a predetermined calibration value, the magnetic permeability of the iron core included in the AC magnetic flux generating means generated when the device is used for a long time The transformation rate can be measured by removing the influence of aging.

According to the present invention, an E-type electromagnet is used as the magnetic flux generating means to generate a magnetic flux which is symmetrical with respect to the central magnetic pole line and whose direction is opposite to the central magnetic pole line. Since each horizontal component of the magnetic flux is detected and the difference between the pair of magnetic flux detection signals is calculated,
The signal component is doubled, the noise component due to the residual magnetism of the roll is canceled out, and it is possible to measure the transformation rate with high accuracy and improved S / N.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a method of correcting a material, a plate thickness and a plate width of a transformation rate measuring method according to the present invention.

FIG. 2 is a configuration block diagram showing an embodiment of a transformation rate measuring device according to the present invention.

3 is a waveform diagram for explaining the operation of the signal processing circuit of FIG.

FIG. 4 is a diagram for explaining the operating principle of the transformation rate measuring device according to the present invention.

FIG. 5 is a configuration block diagram showing another embodiment of the transformation rate measuring apparatus according to the present invention.

FIG. 6 is a diagram showing comparison of measurement results of roll residual magnetic flux between the transformation rate measuring device of FIG. 5 and a conventional device.

FIG. 7 is a configuration block diagram of a conventional transformation rate measuring device.

[Explanation of symbols]

 1 High-frequency power supply 2 Resistance 3 Magnetic sensor 3a Sensor core 3a Detection coil 4,19 Magnetic detection circuit 5 LPF 6 Zero adjustment circuit 7 Inverter 8 Linearizer 10 Magnetizer 10a Magnetized iron core 10b Magnetization coil 11 Magnetizer box 12, 18 Cooling water 13 Constant current circuit 14 Low frequency oscillator 15 Steel plate 17 Detector box 20 Lock-in amplifier 21 Control circuit 22 Roll 23 Coiler 24 Signal processing circuit 25 Arithmetic circuit 26 Recorder

Claims (4)

[Claims] 1. A magnetic flux generating means for generating a magnetic flux is provided on one side of a steel sheet to be inspected, and a magnetic flux generated by the magnetic flux generating means and leaking through the steel sheet is detected on the other side. In the transformation rate measuring method using two transformation rate measuring devices for measuring the transformation rate of the steel sheet from the magnetic flux density detected by the magnetic flux detecting means, the two transformation rate measuring devices are: On the same production line of the steel sheet, the transformation rate is measured and a reference position after the transformation is completed, and the measured value by the transformation rate measuring device installed at the reference position is used as the reference value of the transformation rate of 100%. A method for measuring a transformation rate, comprising a correction computation step of performing a correction computation on a measurement value by a transformation rate measurement device installed at the measurement position based on the reference value. 2. A steel sheet to be inspected is sandwiched, magnetic flux generating means for generating magnetic flux is provided on one side, and magnetic flux generated by the magnetic flux generating means and leaking through the steel sheet is detected on the other side. In the transformation rate measuring device for measuring the transformation rate of the steel sheet from the magnetic flux density detected by the magnetic flux detection means, the traveling speed of the steel sheet is v, the sheet thickness is t, and the magnetic permeability is μ. , Where the electrical conductivity is σ and the representative length determined by the measurement interval in the traveling direction is L, the magnetic flux generating means has v / L ≦ f ≦.
A transformation rate measuring device comprising an AC magnetic flux generating means for generating an AC magnetic flux having a frequency f represented by 1 / (πμσt ² ). 3. The value of the magnetic flux density detected by the magnetic flux detecting means through air when a steel plate is not present between the magnetic flux generating means and the magnetic flux detecting means of the transformation rate measuring device is a predetermined calibration value. The transformation rate measuring device according to claim 2, further comprising an AC magnetic flux density calibrating means for calibrating the AC magnetic flux density generated by the AC magnetic flux generating means. 4. An E-shaped core is used as an electromagnet provided on one side sandwiching a steel sheet to be inspected, and the magnetic poles at both ends of the core are excited to have the same polarity and the center magnetic pole is excited to have the opposite polarity to the both ends. By doing so, a magnetic flux generating means for generating a magnetic flux in a symmetrical direction with respect to a vertical extension line from the center of the core to the steel plate direction, and from the center of the core on the other side sandwiching the steel plate. The horizontal components of the symmetrical magnetic flux, which are provided at right angles to the vertical extension lines in the direction of the magnetic poles at both ends of the core and are equidistant from each other, are generated by the magnetic flux generating means and leak through the steel plate. A transformation rate measuring device comprising: a pair of magnetic flux detecting means for detecting; and a difference calculating means for calculating a difference between magnetic flux density signals detected by each of the pair of magnetic flux detecting means.