JPH05264704A - Method and apparatus for measuring coercive force of steel plate - Google Patents

Abstract

PURPOSE:To measure the coercive force of a steel plate in a noncontact state without cutting off one part of the steel plate as a specimen in order to measure its coercive force. CONSTITUTION:A steel-plate excitation device 1 in which excitation coils 3a, 3b and a detection coil 4 have been executed to a U-shaped core 2 is arranged on a steel plate G under test in such a way that a gap is kepy between tip faces of both leg parts of the U-shaped core 2 and the steel plate S under test. An AC excitation current is made to flow to the excitation coils 3a, 3b which have been connected in series; the steel plate S under test is magnetized. A point of time when an induced voltage generated at the detection coil 4 takes a peak value at each magnetization half cycle is detected. Then, the following are detected: an excitation current value at a point of time when the induced voltage generated at the detection coil 4 takes a peak value at a previous magnetization half cycle; and an excitation current value at a point of time when the induced voltage generated at the detection coil takes a peak value at a next magnetization half cycle. Then, the mean value of absolute values of the excitation current values is found. The coercive force of the steel plate S under test is found on the basis of the excitation current value corresponding to the coercive force of the steel plate S under test.

Description

Detailed Description of the Invention

[0001]

This invention can measure the coercive force of a steel sheet in a non-contact state without cutting out a part of the steel sheet as a sample for measuring the coercive force. The present invention relates to a method and apparatus for measuring a coercive force of a steel sheet, which enables the coercive force of a traveling steel sheet in a production line to be measured in an online state for inspection.

[0002]

2. Description of the Related Art As a method for measuring the coercive force of a steel sheet,
An endless annular sample is cut out from the steel plate to be measured, an exciting current is passed through the exciting coil (primary coil) wound around this sample so that the magnetic flux passes through the sample annularly, and a detection coil (secondary coil) wrapped around the sample. As shown in FIG. 3, a BH curve (hysteresis curve) showing the relationship between the magnetic flux density B and the magnetic field strength H is obtained by investigating the magnetization state of the sample using, and H of oc = of A value, that is, the coercive force H _C is measured.

[0003]

By the way, there is a close correlation between the crystal grain size (grain size) of a steel sheet and the mechanical properties of the steel sheet. Further, there is a close correlation between the crystal grain size of the steel sheet and the coercive force of the steel sheet, and the larger the crystal grain size, the smaller the coercive force of the steel sheet. Therefore, it is required to be able to measure the coercive force of the running steel sheet in order to inspect the mechanical properties of the running steel sheet in a production line in an online state. However, in the above-mentioned conventional method, in order to measure the coercive force of the steel sheet, it is necessary to cut out a part of the steel sheet to be measured as a sample. There is a problem that the coercive force cannot be measured in the online state.

Therefore, according to the present invention, the coercive force of the steel sheet can be measured in a non-contact state without cutting out a part of the steel sheet as a sample for measuring the coercive force, thereby inspecting the mechanical properties of the steel sheet. Another object of the present invention is to provide a method and apparatus for measuring the coercive force of a steel sheet, which can measure the coercive force of a steel sheet during traveling on a production line in an online state.

[0005]

In order to achieve the above object, the method of measuring the coercive force of a steel sheet according to the present invention is applied to both legs of a U-shaped core so that magnetic flux is alternately applied to one core. A steel plate excitation device having an exciting coil connected in series so as to come out of the tip end surface of the leg and pass through the steel sheet to be measured to enter the other tip end surface of the core, and a detection coil provided at the center of the core. , The U-shaped core is provided with a gap between the tip surfaces of both leg portions and the steel plate to be measured, and an alternating exciting current is passed through an exciting coil of the steel plate exciting device to magnetize the steel plate to be measured, By detecting the time when the induced voltage generated in the detection coil of the steel plate exciter reached the peak value every magnetization half cycle, the induced voltage generated in the detection coil took the peak value in the previous magnetization half cycle. Exciting current value at the time and generated in the detection coil The exciting current value at the time when the induced voltage takes the peak value in the next magnetization half cycle is detected and the average value of the absolute values of these exciting current values is found, and the exciting current corresponding to the coercive force of this steel sheet to be measured. The coercive force of the steel sheet to be measured is obtained based on the value.

Further, the apparatus for measuring coercive force of steel sheet according to the present invention has a: U-shaped core arranged with a gap between the steel sheet to be measured and each leg portion of the U-shaped core. The magnetic flux is alternately applied to the core leg portion, and the magnetic flux has alternating excitation coils that are connected in series so as to pass through the steel plate to be measured and enter the tip end surface of the other core leg portion.
A steel plate excitation device having a detection coil in the center of the core,
b: an AC constant voltage power supply for supplying an AC exciting current to the exciting coil of the steel plate exciting device; and c: the steel plate when the measured steel plate is magnetized by passing an exciting current through the exciting coil by the AC constant voltage power supply. Peak timing detection means for detecting the time when the induced voltage generated in the detection coil of the exciter takes a peak value for each half-cycle of magnetization, and d: a detection coil based on the detection signal from the peak timing detection means. The exciting current value when the induced voltage generated had a peak value in the previous magnetization half cycle and the exciting current value when the induced voltage generated in the detection coil had a peak value in the next magnetization half cycle The coercive force-corresponding exciting current detecting means for detecting, e: An average value of absolute values of the two exciting current values detected by the coercive force-corresponding exciting current detecting means is obtained, and the coercive force of the steel sheet to be measured is obtained. Characterized by comprising calculating means for determining the coercive force of the measured steel sheet, a based on the excitation current value corresponding to.

[0007]

In the method and apparatus for measuring the coercive force of a steel sheet according to the present invention, the steel sheet exciting device is arranged with a gap between the tip surfaces of both legs of the U-shaped core and the steel sheet to be measured. When an alternating exciting current is passed through the exciting coil of this steel plate exciting device to magnetize the steel plate to be measured, the detection coil of the steel plate exciting device changes its polarity every half-cycle of magnetization and produces a pulse indicating a temporal change in magnetic flux density. Induced voltage is generated.
The point in time when the induced voltage generated in the detection coil takes a peak value every magnetization half cycle is detected. As a result, the exciting current value at the time when the induced voltage generated in the detection coil takes the peak value in the previous magnetization half cycle, that is, when the magnetic field strength in one direction is changed to zero the magnetic flux density The exciting current value corresponding to the strength of the magnetic field and the exciting current value at the time when the induced voltage generated in the detection coil takes the peak value in the next magnetization half cycle, that is, the strength of the magnetic field in the other direction, An exciting current value corresponding to the strength of the magnetic field when the magnetic flux density is changed to zero is detected. Then, the average value of the absolute values of these exciting current values is obtained, and the coercive force of the steel sheet to be measured is obtained based on the exciting current value corresponding to the coercive force of the steel sheet to be measured.

[0008]

EXAMPLES The present invention will be described below based on examples. FIG. 1 is a block diagram showing an example of the configuration of a coercive force measuring device for carrying out the coercive force measuring method according to the present invention. FIG. 2 is a timing chart for explaining the operation of the coercive force measuring device shown in FIG.

In FIG. 1, 1 is a steel plate excitation device.
In this steel plate excitation device 1, windings are wound around both legs of the U-shaped core 2 to apply excitation coils 3a and 3b, and
A detection coil 4 is provided by winding a winding around the center of the core, and the U-shaped core 2 is provided on the steel plate S to be measured.
The front end surfaces of both legs are arranged so as to have a gap with respect to the steel plate S to be measured. When an AC exciting current is applied by an AC constant voltage power source 5 described later, magnetic fluxes of the exciting coils 3a and 3b alternately come out from one tip end surface of the core leg and pass through the steel sheet S to be measured. They are connected in series so as to enter the tip end surface of the other core leg, and the number of turns of each is, for example, 30 turns. In addition, in this embodiment, one terminal of the detection coil 4 is set to the ground potential (reference potential).
As the induced voltage (voltage between both terminals of the coil with reference to the ground potential), a positive and negative pulsed voltage whose polarity alternates every half magnetization cycle is generated.
The number of turns of the detection coil 4 is, for example, 100 turns.

The AC constant voltage power source 5 is, for example, an exciting current detector 6 using a shunt resistor having a resistance value of 0.1 ohm.
Is a power supply for supplying an alternating exciting current to the exciting coils 3a and 3b connected in series via the. As this AC constant voltage power source 5, for example, one of 1V, 50 Hz is used. The exciting current detector 6 detects an alternating exciting current flowing through the exciting coils 3a and 3b, and outputs a voltage signal corresponding to this.

Reference numeral 7 denotes a gate circuit. This gate circuit 7
Is the period during which the induced voltage generated in the detection coil 4 exceeds the positive minute threshold value set for the zero volt point, which is the reference potential, in the positive polarity, and the negative minute threshold value set for the zero volt point. Is a high level output during a period in which the induced voltage generated in the detection coil 4 exceeds the negative polarity, and is a low level output during other periods. Reference numeral 8 is a differentiator that differentiates the induced voltage generated in the coil 4, that is, the output of the detection coil 4, and 9 is a zero-point detector.

The zero point detector 9 receives the outputs of the gate circuit 7 and the differentiator 8, and when the output of the differentiator 8 crosses the zero volt point while the output of the gate circuit 7 is at a high level, that is, the detection coil. The output of 4 (the induced voltage generated in the detection coil 4) takes a positive peak value and a negative peak value, respectively, and a pulse signal is output at that time. When the zero point detector 9 detects that the output of the detection coil 4 has a positive peak value, it gives the first sample hold command signal S1 to the first sample hold circuit 10a, and the output of the detection coil 4 changes. When it is detected that a negative peak value is taken, the second sample hold command signal S2 is given to the second sample hold circuit 10b. In this embodiment, the gate circuit 7, the differentiator 8 and the zero point detector 9 correspond to the peak timing detecting means.

The first sample and hold circuit 10a samples and holds the output of the exciting current detector 6 when the first sample and hold command signal S1 is given, and holds the detected signal, that is, the detection coil 4 A signal (I _H ) corresponding to the exciting current value of the exciting coils 3a and 3b at the time when the output takes a positive peak value is output to the arithmetic circuit 11. The second sample hold circuit 10b samples and holds the output of the exciting current detector 6 when the second sample hold command signal S2 is given, and holds the detected signal, that is, the output of the detection coil 4. There is for outputting excitation coil 3a at the time of taking the negative maximum value, a signal corresponding to the excitation current value of 3b and (-I _H) to the arithmetic circuit 11. In this embodiment, the exciting current detector 6 and the sample hold circuits 10a and 10b correspond to the exciting current detecting means corresponding to the coercive force.

In the present embodiment, the arithmetic circuit 11 serving as the above-mentioned arithmetic means includes the output (I _H ) of the first sample-hold circuit 10a and the second sample-hold circuit every magnetization cycle.
Using the output (-I _H ) of 10b, [(I _H )-(-I
_H )] / 2 is calculated to obtain the exciting current value corresponding to the coercive force of the steel sheet S to be measured, and based on the exciting current value corresponding to this coercive force, the previously determined exciting current and magnetic field strength are calculated. The coercive force H _C of the steel plate to be measured S is obtained from the relationship with A signal indicating the coercive force H _C of the steel plate S to be measured is sequentially output from the arithmetic circuit 11 every magnetization cycle.

Next, the method of measuring the coercive force of the steel sheet according to the present invention, which is carried out by using the above-mentioned coercive force measuring device, will be described with reference to FIGS. The steel plate excitation device 1 is arranged on the steel plate to be measured S with a gap between the tip surfaces of both legs of the U-shaped core 2 and the steel plate to be measured S. When an alternating exciting current is applied to the exciting coils 3a and 3b of the steel plate exciting device 1 by the AC constant voltage power source 5 as shown in FIG. 2 (e), and the steel plate to be measured S is magnetized by passing a magnetic flux through it. The detection coil 4 of FIG.
As shown in, a positive and negative pulsed induced voltage whose polarity alternates every half magnetization cycle is generated. This induced voltage shows a temporal change in the magnetic flux density (see FIG. 2A).

The output of the detection coil 4 (the induced voltage generated in the detection coil 4) is given to the gate circuit 7 and the differentiator 8, and the gate circuit 7 outputs the reference potential as shown in FIG. A period in which the output of the detection coil 4 exceeds the positive minute threshold value set for the zero volt point in the positive polarity and a period in which the output of the detection coil 4 exceeds the negative minute threshold value in the negative polarity. The output which becomes high level by and is input to the zero point detector 9. At the same time, the signal having the waveform shown in FIG. 2D is input from the differentiator 8 to the zero-point detector 9.

The zero point detector 9 detects the time when the output of the differentiator 8 crosses the zero volt point while the output of the gate circuit 7 is at a high level, that is, the time when the output of the detection coil 4 has a positive peak value. And the time when the negative peak value is obtained, and by detecting that the output of the detection coil 4 has the positive peak value, the first sample hold circuit 10
The first sample hold command signal S1 is given to a. on the other hand,
By detecting that the output of the detection coil 4 has a negative peak value, the second sample hold command signal S2 is given to the second sample hold circuit 10b.

The first sample and hold circuit 10a samples and holds the output of the exciting current detector 6 when the command signal S1 is given, and the detected signal, that is, the output of the detecting coil 4 is positive. A signal corresponding to the exciting current value of the exciting coils 3a and 3b at the time when the peak value is obtained (I
_H ) is output to the arithmetic circuit 11. The second sample and hold circuit 10b samples and holds the output of the exciting current detector 6 when the command signal S2 is given, and the detected signal, that is, the output of the detecting coil 4 has a negative peak. outputs exciting coil 3a at the time of taking the head value, a signal corresponding to the excitation current value of 3b and (-I _H) to the arithmetic circuit 11.

The arithmetic circuit 11 includes a first sample hold circuit 10
When a output (I _H) and the output of the second sample-and-hold circuit 10b (-I _H) and is inputted, the arithmetic circuit 11 uses these _{[(I H) - (- I} H) ] / 2 is calculated to obtain the exciting current value corresponding to the coercive force of the steel sheet S to be measured, and based on the exciting current value corresponding to this coercive force, from the previously obtained relation between the exciting current and the magnetic field strength. , determine the coercive force H _C of the measured steel sheet S, and outputs a signal indicating the coercive force H _C of the measured steel sheet S obtained.

The above-described operation is sequentially repeated for each magnetization cycle. In this way, the coercive force of the steel sheet can be measured in a non-contact state without cutting out a part of the steel sheet as a sample for coercive force measurement. As a result, the coercive force of a running steel plate in a production line can be measured online, so the mechanical properties of a running steel plate can be inspected online using the relationship between the coercive force of the steel plate and the grain size of the steel plate. Can be performed over the entire length of the steel sheet.

In the above embodiment, one terminal of the detection coil 4 is set to the ground potential (reference potential), and the induced voltage generated in the detection coil 4 with this as a reference is detected by the gate circuit 7, the differentiator 8 and the zero point. Although the example of inputting to the peak timing detecting means constituted by the device 9 has been shown, the induced voltage generated in the detecting coil 4 is input to the absolute value circuit (absolute value full wave rectification circuit) and the output of this absolute value circuit is You may make it input into a gate circuit and a differentiator. In this case, since the induced voltage generated in the detection coil 4 is output with a positive polarity from the absolute value circuit, the gate circuit may be configured to set only a positive minute threshold value.

In the above embodiment, the output (I _H ) of the first sample and hold circuit 10a in the previous magnetization half cycle and the output (I _H ) of the second sample and hold circuit 10b in the next magnetization half cycle are set for each magnetization cycle. -I _H ) is used to calculate [(I _H )-(-I _H )] / 2 to obtain an exciting current value corresponding to the coercive force of the steel sheet S to be measured, which corresponds to this coercive force. Although the example in which the coercive force H _C of the steel sheet to be measured S is obtained based on the exciting current value has been shown, the exciting current value corresponding to the coercive force is naturally magnetized in order to reduce the error. May be calculated as an average value for several cycles (for several cycles of the exciting current).

[0023]

As described above, the method and apparatus for measuring the coercive force of the steel sheet according to the present invention are applied to both legs of the U-shaped core, and the magnetic flux is alternately applied to the tip end surface of one core leg. A steel plate exciting device having an exciting coil connected in series so as to enter the other end of the core leg through the steel plate to be measured, and a detecting coil provided in the central part of the core,
The U-shaped core is arranged with a gap between the tip surfaces of both legs and the steel plate to be measured, and an alternating exciting current is applied to the exciting coil to magnetize the steel plate to be measured, and an induced voltage generated in the detection coil. By detecting the time when the peak value is taken every magnetization half cycle, the induced voltage value at the time when the induced voltage generated in the detection coil takes the peak value in the previous magnetization half cycle,
That is, the exciting current value corresponding to the magnetic field strength at the time when the magnetic field strength in one direction is changed to zero the magnetic flux density, and the induced voltage generated in the detection coil are peaked in the next magnetization half cycle. The exciting current value at the time when the value is taken, that is, the exciting current value corresponding to the magnetic field strength when changing the magnetic field strength in the other direction to make the magnetic flux density zero, is detected. The mean value of the absolute values is calculated, and the coercive force of the measured steel plate is calculated based on the exciting current value corresponding to the coercive force of the measured steel plate. Therefore, the coercive force of the steel sheet can be measured in a non-contact state without cutting out a part of the steel sheet as a sample for measuring the coercive force. As a result, the coercive force of a running steel plate in a production line can be measured online, so the mechanical properties of a running steel plate can be inspected online using the relationship between the coercive force of the steel plate and the grain size of the steel plate. Can be performed over the entire length of the steel sheet.

[Brief description of drawings]

FIG. 1 is a block diagram showing an example of the configuration of a coercive force measuring device for carrying out a coercive force measuring method according to the present invention.

FIG. 2 is a timing chart for explaining the operation of the coercive force measuring device shown in FIG.

FIG. 3 is a diagram showing a BH curve (hysteresis curve).

[Explanation of symbols]

1 ... Steel plate excitation device 2 ... U-shaped core 3a, 3b ... Excitation coil 4 ... Detection coil 5 ... AC constant voltage power source 6 ... Excitation current detector 7 ... Gate circuit 8 ... Differentiator 9 ... Zero point detector 10a, 10b … Sample-hold circuit 11… Arithmetic circuit S… Steel to be measured

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takeo Ogawa 1-4-1 Migatadai, Nishi-ku, Kobe (72) Inventor Masaru Akamatsu 1-4-1 Mikatadai, Nishi-ku, Kobe

Claims (2)

[Claims] 1. The U-shaped core is applied to both legs,
Magnetic flux was applied to the core part and the exciting coil connected in series so as to alternately flow out from one core leg tip surface, pass through the steel plate to be measured, and enter the other core leg tip surface. A steel plate excitation device having a detection coil is arranged with a gap between the tip surfaces of both leg portions of the U-shaped core and the steel plate to be measured, and an alternating excitation current is applied to the excitation coil of the steel plate excitation device. By magnetizing the steel sheet to be measured, and detecting the time when the induced voltage generated in the detection coil of the steel plate excitation device reaches the peak value every magnetization half cycle, the induced voltage generated in the detection coil is The exciting current value at the time when the peak value is obtained in the half cycle and the exciting current value at the time when the induced voltage generated in the detection coil takes the peak value in the next magnetization half cycle are detected and these exciting current values are Obtain the average of absolute values and measure Coercivity measurement method of the steel sheet, characterized in that to determine the coercive force of the measured steel sheet on the basis of the excitation current value corresponding to the coercive force of the plate. 2. A: A U-shaped core which is arranged with a gap between it and a steel plate to be measured. The U-shaped core is applied to both legs of the U-shaped core. Exciting steel plate that has an exciting coil connected in series so that it exits from the tip surface of the core leg, passes through the steel plate to be measured, and enters the tip surface of the other core leg, and a detection coil is applied to the center of the core. A device, b: an AC constant voltage power supply for supplying an AC excitation current to the excitation coil of the steel plate excitation device, and c: an excitation current is supplied to the excitation coil by the AC constant voltage power supply to magnetize the steel plate to be measured. A peak timing detection means for detecting a time point when an induced voltage generated in a detection coil of the steel plate excitation device takes a peak value for each magnetization half cycle; and d: based on a detection signal from the peak timing detection means, Occurs in the detection coil Detects the exciting current value when the induced voltage takes the peak value in the previous magnetization half cycle and the exciting current value when the induced voltage generated in the detection coil takes the peak value in the next magnetization half cycle Coercive force corresponding exciting current detecting means, e: An average value of absolute values of both exciting current values detected by the coercive force corresponding exciting current detecting means is obtained, and the exciting current value corresponding to the coercive force of the steel sheet to be measured. An apparatus for calculating a coercive force of a steel plate to be measured based on the above, and a coercive force measuring device for a steel plate.