JPH06265525A - Apparatus for measuring particle size of crystal of steel plate - Google Patents

Abstract

PURPOSE:To obtain the particle size of crystals in a nondestructive and contactless manner not only for a hot rolled steel plate, but for a cold rolled steel plate having a different texture from that of the hot rolled steel plate. CONSTITUTION:For each of three or more kinds of steel plates, the actually- measured particle size of crystals, an average of values corresponding to the coercive force detected by a measuring part 40, the size of the magnetic anisotropy detected by a magnetic anisotropy measuring part 50, and the magnetic permeability measured by a permeability measuring device 60 are input to a computer 70. The computer 70, using the data, obtains a regression coefficient of each descriptive variable in a regression formula having an inverse umber of the particle size as a target variable, and the average value of values corresponding to the coercive force, the size of the magnetic anisotropy and the magnetic permeability as the descriptive variables. Moreover, the computer 70 obtains the particle size of crystals of a steel plate to be indirectly measured by substituting the average value of values corresponding to the coercive force, the size of the magnetic anisotropy and the magnetic permeability into the regression formula with the determined regression coefficient.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention measures the value of coercive force, the magnitude of magnetic anisotropy, and the magnetic permeability of a steel sheet such as a hot-rolled steel sheet or a cold-rolled steel sheet by a nondestructive noncontact method. The present invention also relates to an apparatus for measuring the crystal grain size of a steel sheet, which is used to determine the crystal grain size of the steel sheet based on these measurement data and indirectly measure the crystal grain size.

[0002]

2. Description of the Related Art In the steel plate production line of a steel mill, it is desired to be able to inspect online the mechanical properties of a steel plate continuously conveyed and run over the entire length of the steel plate. In this case, the crystal grain size of the steel sheet is one of the important parameters for estimating the mechanical properties of the steel sheet. It is known that the reciprocal of the crystal grain size of a steel sheet is proportional to the coercive force of the steel sheet (Kinakuka et al .: Handbook of Magnetic Materials, page 1070, Asakura Shobo, 1987).
Year).

Therefore, some of the inventors of the present invention measured the value corresponding to the coercive force of the steel sheet to be measured in a non-contact manner using a coercive force detecting sensor, and measured the coercive force equivalent value and the crystal. Utilizing the fact that the reciprocal of the grain size is in a linear proportional relationship as described above, the crystal grain size of the steel sheet is obtained using the measured coercive force equivalent value, and the indirect measurement of the crystal grain size is performed. This method was previously disclosed in the literature (Proceedings of the 31st SICE Conference Lecture, 655-656, 1992).
Year).

Furthermore, the present applicant has previously proposed a method for measuring the crystal grain size of a steel sheet, which is an improvement of the method disclosed in the above-mentioned document (Japanese Patent Application No. 5-5956). Hereinafter, this conventional crystal grain size measuring method will be described. FIG. 5 is a diagram showing an overall configuration of an example of a crystal grain size measuring device used for carrying out a conventional crystal grain size measuring method, FIG. 6 is a configuration explanatory diagram of the steel plate coercive force measuring device shown in FIG. 5, and FIG. FIG. 7 is a timing chart diagram for explaining the operation of the steel plate coercive force measuring device shown in FIG. 6.

First, a steel plate coercive force measuring device used for indirectly measuring the crystal grain size of a steel plate will be described below with reference to FIGS. 6 and 7. As shown in FIG. 6, the steel plate coercive force measuring device E1 in this example includes a coercive force detecting sensor (coercive force detecting head) 100 having a U-shaped core (ferrite core) 101, and a coercive force measuring device main body. 200
It consists of and. And the coercive force measuring device body 2
00 is the exciting coils 103a, 103 of the coercive force detecting sensor 100.
AC excitation current generator 300 that supplies AC excitation current to b
And the exciting current flowing through the exciting coils 103a and 103b is detected,
Excitation current detector 400 that uses a shunt resistor that outputs the voltage signal, and detection coil 10 of coercive force detection sensor 100.
The induced voltage generated in 2 and the exciting current detected by the detector 400 are used as input, and the signal processing described below is performed to detect the coercive force equivalent value of the steel plate (measured steel plate) S to be measured and to output the signal. And a signal processing device 500 for outputting.

As shown in FIG. 6, the coercive force detecting sensor 100 has coils formed on both legs of a U-shaped core 101, and alternating magnetic flux is supplied by supplying an alternating exciting current. Then, the two coils are connected in series so as to come out from one magnetic pole, pass through the steel plate S to be measured, and enter the other magnetic pole to form exciting coils 103a and 103b, and a detecting coil 102 is further provided at the center of the core. It will be. Further, the signal processing device 500 includes a gate circuit 501, a differentiator 502, and a zero point detector.
503, a first sample and hold circuit 504a, a second sample and hold circuit 504b, and an arithmetic circuit 505.

The gate circuit 501, the differentiator 502, and the zero-point detector 503, when the magnetic flux is passed through the steel plate S to be measured,
This is for detecting the time when the induced voltage generated in the detection coil 102 takes a peak value (peak value) every magnetization half cycle. The sample-and-hold circuits 504a and 504b have an exciting current value when the induced voltage generated in the detection coil 102 has a peak value in the previous magnetization half cycle and an excitation current value when the induced voltage has a peak value in the next magnetization half cycle. It is a circuit for detecting a current value. Further, the arithmetic circuit 505 is a circuit for obtaining an average value of the magnitudes of the two exciting current values, detecting the magnitude value as a coercive force equivalent value of the steel plate S to be measured, and outputting the value.

Next, the operation will be described. On the steel plate S to be measured, the coercive force detecting sensor 100 is arranged with a gap between the two magnetic poles of the core 101 and the steel plate S. Then, as shown in FIG. 7 (e), an alternating exciting current is passed through the exciting coils 103a and 103b of the coercive force detecting sensor 100 to pass a magnetic flux through the steel plate S to be measured.
In the detection coil 102 of 0, as shown in FIG.
Positive and negative pulsed induced voltages whose polarities alternately change every magnetization half cycle are output. Since the coercive force is the strength of the magnetic field when the magnetic flux density crosses zero, it indicates the time derivative of the magnetic flux density, and the time when the output of the detection coil 102 takes a peak value (peak value) is detected. The coercive force equivalent value can be obtained by detecting the exciting current value corresponding to the strength of the magnetic field.

The output of the detection coil 102 is a gate circuit.
As shown in FIG. 7C, the gate circuit 501 supplies a positive minute threshold value set to the zero volt point, which is the reference potential, to the detection coil 10 and the differentiator 502.
The output which becomes high level during the period when the output of 2 exceeds the positive polarity and the period when the output of the detection coil 102 exceeds the negative minute threshold in the negative polarity is the zero point detector 50.
Entered in 3. At the same time, the zero-point detector 503 receives the signal having the waveform shown in FIG. 7D from the differentiator 502.

The zero-point detector 503 detects when the output of the differentiator 502 crosses the zero volt point while the output of the gate circuit 501 is at a high level, that is, when the output of the detection coil 102 has a positive peak value. And when the negative peak value is taken, respectively. The zero-point detector 503 sends the first sample hold command signal to the first sample hold circuit 504a when the output of the detection coil 102 has a positive peak value.
Meanwhile, when the output of the detection coil 102 has a negative peak value while giving S1, the second sample hold command signal S2 is given to the second sample hold circuit 504b.

The first sample and hold circuit 504a includes the finger
Output of exciting current detector 400 when command signal S1 is given
Sampling and holding this detected signal,
Then, when the output of the detection coil 102 takes a positive peak value,
Indicates the value of the exciting current flowing through the exciting coils 103a and 103b in
Signal (I_H) Is output to the arithmetic circuit 505. In addition, the second service
The sample and hold circuit 504b receives the command signal S2.
Sampling the exciting current detector 400 output
Hold and detect this detected signal, ie the detection coil 102
The exciting current value at the time when the output of has a negative peak value
Signal (-I _H) Is output to the arithmetic circuit 505.

The arithmetic circuit 505 outputs the output (I _H ) of the first sample hold circuit 504a and the second sample hold circuit 504b.
Given the output (-I _H ) of [(I _H )-(-
I _H )] / 2, and the signal corresponding to the magnitude of the value is output as the coercive force equivalent value of the steel plate S to be measured.

Now, it will be explained that the coercive force equivalent value of the steel sheet measured as described above has direction dependency (angle dependency). FIG. 4 is a diagram showing the direction dependence of the coercive force equivalent value of the steel sheet. The figure shows that the coercive force detection sensor is positioned on the steel plate to be measured such that the distance between the two magnetic poles and the steel plate to be measured is about 1 mm. It is a plot of coercive force-equivalent values measured at every 6 ° with one rotation. In FIG. 4, coercive force equivalent values at an angle of 0 ° and an angle of 180 ° on the horizontal axis are
The coercive force detection sensor is positioned so that the magnetic flux passing through the steel sheet to be measured is in the rolling direction.

As described above, the coercive force equivalent value of the steel sheet has a direction dependence, and the degree of the direction dependence depends on the difference in the magnitude of the magnetic anisotropy energy of each steel sheet. It depends on the steel plate. Therefore, when the crystal grain size of the steel sheet is obtained by indirect measurement, it is necessary that the obtained crystal grain size does not cause an error due to the direction dependence of the coercive force equivalent value. .

Therefore, in the conventional method, as information for obtaining the crystal grain size of the steel sheet by indirect measurement, coercive force equivalent values in at least two directions orthogonal to each other in the plane of the steel sheet are measured and the arithmetic mean thereof is obtained. The average value of coercive force equivalent values is used. That is, as shown in FIG. 5, in this example, the crystal grain size measuring device is composed of two steel plate coercive force measuring devices E1 and E1 'and a computer 600 connected thereto. The coercive force detection sensor 100 of the steel plate coercive force measuring device E1 whose configuration has been described above has a support (not shown) on the steel plate S to be measured so that the direction between the magnetic poles thereof coincides with the rolling direction of the steel plate. The coercive force measuring device main body 200 '
The sensor 100 'for detecting the coercive force of the other steel plate coercive force measuring device E1' having the same configuration as the device E1 has
It is placed close to 0 and is positioned by a support tool (not shown) on the steel plate S to be measured in a non-contact manner so that the direction between the magnetic poles matches the plate width direction (direction orthogonal to the steel plate rolling direction). ing.

Next, the method of measuring the crystal grain size using the above apparatus will be described. First, a sample steel plate is prepared, the crystal grain size is measured by a known cutting method using a micrograph, and the crystal grain size is measured. The value d of is input to the computer 600 as data. Further, with respect to the sample steel plate, the coercive force equivalent value when one of the coercive force detecting sensors 100 is positioned along the steel plate rolling direction as described above is measured, and the coercive force equivalent value H _C1 is calculated. Is input to the computer 600, and the coercive force equivalent value is measured when the other sensor 100 'for detecting coercive force is positioned along the strip width direction (direction orthogonal to the rolling direction). The value H _C2 is input to the computer 600 as data. The computer 600 displays the average value H of coercive force equivalent values.
_CA is obtained by the calculation of H _CA = (H _C1 + H _C2 ) / 2, and the known crystal grain size d and the average value H _CA of coercive force equivalent values therein are stored as data.

Next, for the steel sheet S to be measured for which the crystal grain size is to be indirectly measured, the coercive force equivalent value when one coercive force detection sensor 100 is positioned along the steel sheet rolling direction is measured. An output indicating the magnetic force equivalent value H _C1 ′ is given to the computer 600, and the coercive force equivalent when the other coercive force detecting sensor 100 ′ is positioned along the strip width direction (direction orthogonal to the rolling direction). The value is measured, and the output indicating the coercive force equivalent value H _C2 'is provided to the computer 600.

Then, by the computer 600, H _CA ′
= (H _C1 ′ + H _C2 ′) / 2, the average value H _CA ′ of the coercive force equivalent values obtained by the calculation, the previously determined actual crystal grain size d by actual measurement, and the coercive force equivalent value thereof. Using the fact that the reciprocal of the crystal grain size and the coercive force equivalent value have a linear proportional relationship from the average value H _{CA of} d ′ = (d ·
The crystal grain size d ′ of the steel plate S to be measured is calculated by the calculation of H _CA ) / H _CA ′.

FIG. 8 relates to the prior art and is a diagram showing the relationship between the average value of coercive force equivalent values of hot-rolled steel sheet and the reciprocal of the actually measured grain size. In the graph shown in FIG. 8, the crystal grain size was changed by changing the carbon value in the steel and the heat treatment conditions.
This is obtained by producing 14 kinds of hot-rolled steel sheets for samples, and measuring the average value of the coercive force equivalent values in them using a coercive force detecting sensor equipped with a rotating mechanism. The horizontal axis of the figure shows the average value of the coercive force equivalent value which is the arithmetic mean of the coercive force equivalent values at every 6 ° angle when the coercive force detecting sensor is rotated once at an angle of 6 °. The axis shows the reciprocal of the crystal grain size measured by the cutting method.

As described above, according to the conventional method, as to the hot-rolled steel sheet, as shown in FIG. 8, the reciprocal of the measured crystal grain size and the average value of the coercive force equivalent values satisfy a substantially linear relationship. By obtaining the crystal grain size using the average value of the magnetic force equivalent values, it was possible to indirectly measure the crystal grain size without causing a large error.

[0021]

FIG. 9 relates to the prior art and shows the relationship between the average value of coercive force equivalent values of hot-rolled steel sheet and cold-rolled steel sheet and the reciprocal of the actually measured grain size. It is a figure. The graph of FIG. 9 shows an average value of coercive force equivalent values measured in the same manner as in the case of FIG. 8 for three types of cold-rolled steel sheets for samples that have been annealed after cold-rolling and their respective cold-rolled steel sheets. The reciprocal of the measured crystal grain size is plotted by being superimposed on FIG. As described above, according to the conventional method, as can be seen from FIG. 9, the relationship between the reciprocal of the actually measured grain size and the average value of the coercive force equivalent values is linear for the cold-rolled steel sheet having a different texture from the hot-rolled steel sheet. Something is out of relationship,
It was found that there is a problem that a large error may be included in the indirect measurement result of the crystal grain size.

The present invention is an apparatus for indirectly measuring the crystal grain size of a steel sheet by determining the magnetic characteristics of the steel sheet in a non-destructive and non-contact manner. It is another object of the present invention to provide a measuring apparatus for crystal grain size of a steel sheet, which can determine the crystal grain size of a cold-rolled steel sheet having a texture different from that of the above without causing a large error.

[0023]

In order to achieve the above object, the apparatus for measuring the grain size of a steel sheet according to the present invention comprises:
(A) One U-shaped core provided with an excitation coil and a detection coil through which an alternating excitation current for passing magnetic flux is passed through the steel plate to be measured, and the other U-shaped core provided with only the other detection coil A U-shaped core, and these two U-shaped cores are made to intersect with each other so as to be orthogonal to each other in the central part of the core, and the four magnetic poles are located at each vertex of a square on the same plane. A magnetic characteristic detecting sensor integrally fixed so as to be rotatable in parallel to the steel plate to be measured with a predetermined distance, and (b) an alternating excitation current flows through the magnetic characteristic detecting sensor. At this time, the exciting current value at the time when the induced voltage generated in the detection coil of the one U-shaped core provided with the exciting coil has a peak value corresponds to the coercive force of the steel plate to be measured. Is detected as the value of the An average value measuring means of the coercive force equivalent value for obtaining an average value of the coercive force equivalent value during at least half rotation of the gas characteristic detecting sensor; and (c) the magnetic characteristic detecting sensor to which an alternating exciting current is applied. Based on the output of the detection coil of the other U-shaped core of the magnetic characteristic detection sensor during at least half rotation of
Magnetic anisotropy measuring means for measuring the magnitude of magnetic anisotropy of the steel sheet to be measured, (d) Permeability measuring device for measuring the magnetic permeability of the steel sheet to be measured in a non-contact manner, (e) 3 or more types For each of the steel sheets, the measured crystal grain size, the average value of the coercive force equivalent value by the average value measuring means of the coercive force equivalent value, the magnitude of the magnetic anisotropy by the magnetic anisotropy measuring means, and the Given the magnetic permeability measured by a magnetic permeability measurement device, multivariate analysis using these data shows the reciprocal of the crystal grain size as the objective variable, the mean value of coercive force equivalent values, the magnitude of magnetic anisotropy, and the magnetic permeability. Data processing means for obtaining a regression coefficient of each explanatory variable in a regression equation having a magnetic susceptibility as an explanatory variable,
(F) For a steel sheet whose crystal grain size is to be indirectly measured, the average value of the coercive force equivalent values measured by the average value of the coercive force equivalent values, the magnitude of the magnetic anisotropy measured by the magnetic anisotropy measuring means, And a magnetic permeability measured by the magnetic permeability measuring device, by substituting into the regression equation in which the regression coefficient is determined by the data processing means, a calculation means for determining the crystal grain size thereof, To do.

[0024]

As shown in FIG. 9, the cause of the fact that the relationship between the average value of the coercive force equivalent values and the reciprocal of the actually measured grain size in the cold rolled steel sheet deviates from a linear relationship is as follows. The following can be considered. The texture of the cold rolled steel sheet is stronger than that of the hot rolled steel sheet. In the case of a cold rolled steel sheet with a strong texture, the magnetic anisotropy energy difference at the crystal grain boundaries is low because the adjacent crystals have the same orientation, and the crystal orientation is smaller than that of a steel sheet with random crystal orientation. The coercive force is small even if the diameter is the same. In a steel sheet having a high magnetic permeability, the exciting magnetic flux increases, the impedance of the exciting coil of the coercive force detecting sensor increases, the exciting current decreases, and the coercive force equivalent value is measured small.

Therefore, in the crystal grain size measuring apparatus according to the present invention, the crystal grain size of the steel sheet is measured by a non-destructive non-contact method, and the average value of the coercive force equivalent values of the steel sheet and the magnetic anisotropy By adopting the configuration obtained by using the size and the magnetic permeability, not only the hot-rolled steel sheet but also the cold-rolled steel sheet having a texture different from that of the hot-rolled steel sheet can be obtained without causing a large error.

[0026]

Embodiments of the present invention will be described below.
FIG. 1 is a diagram showing the overall configuration of an embodiment of the apparatus for measuring the grain size of a steel sheet according to the present invention.

In FIG. 1, reference numeral 10 is a magnetic characteristic detecting sensor for measuring the average value of the coercive force equivalent values and the magnitude of magnetic anisotropy of the steel sheet to be measured. As shown in the figure, the magnetic characteristic detecting sensor 10 is an exciting coil in which an alternating exciting current for passing a magnetic flux through a steel plate to be measured is passed.
It has one U-shaped core 11A provided with 13a and 13b and a detection coil 12A for detecting the magnetization state, and the other U-shaped core 11B provided only with the other detection coil 12B. The two U-shaped cores 11A and 11B are crossed so as to be three-dimensionally orthogonal to each other in the central part of the core, and the four magnetic poles are positioned on the respective vertices of a square on the same plane. On the other hand, a cylindrical resin mold that can rotate in parallel with a predetermined interval (for example, about 1 mm)
By applying 14, it is integrally fixed. AC excitation current generator 2 to pass magnetic flux through the steel plate to be measured
An exciting current detector 21 including 0 and a shunt resistor and exciting coils 13a and 13b are connected in series.

Reference numeral 30 is a sensor rotation pulse motor for rotating the magnetic characteristic detection sensor 10. In this embodiment, the magnetic characteristic detecting sensor 10 is rotated once at an angle of 6 ° and then rotated once in the opposite direction without performing the measurement, so that the electric wiring can be measured without being twisted and cut. It can be done. Also, the motor drive controller
The reference numeral 31 drives and controls the sensor rotation pulse motor 30, while 0, 6, ..., 354, 354, when rotating the sensor 10.
The sensor rotation angle of 360 ° gives a coercive force equivalent value detection command signal to an after-mentioned coercive force average value measuring section 40 as an average value measuring means of coercive force equivalent values at every 6 ° pitch. Further, the motor drive controller 31 sends a magnetic anisotropy detection command signal indicating a period during which the magnetic characteristic detecting sensor 10 is half a rotation (0 to 180 °, 180 to 360 °), to the magnetic anisotropy measuring means. To the magnetic anisotropy measuring unit 50 described later. The sensor rotation mechanism is configured by the sensor rotation pulse motor 30 and the motor drive controller 31.

The coercive force average value measuring unit 40 receives the coercive force equivalent value detection command signal from the motor drive controller 31 when the magnetic characteristic detecting sensor 10 to which the exciting current is supplied is rotated once. In the same manner as in the conventional art, the exciting current at each time when the induced voltage generated in the detection coil 12A of the one U-shaped core 11A has positive and negative peak values in one cycle ((e in FIG. 7) ) Represented by I _H and -I _H )
Is detected as the coercive force equivalent value, and the coercive force equivalent value detected during one rotation of the magnetic characteristic detecting sensor 10 in this embodiment is arithmetically averaged to obtain the coercive force equivalent value of the steel plate to be measured. The average value of is calculated. The average value of the obtained coercive force equivalent values is input to the computer 70 as data processing means and calculation means. The coercive force average value measuring unit 40 can be configured by, for example, adding a function of arithmetically averaging coercive force equivalent values to the arithmetic circuit 505 of the signal processing device 500 shown in FIG.

The magnetic anisotropy measuring section 50 receives the magnetic anisotropy detection command signal from the motor drive controller 31 when the magnetic characteristic detecting sensor 10 to which an exciting current is supplied is rotated once. , U-shaped core in the period when the sensor 10 is half rotated
The amplitude value (sum of peak value and valley value) of the output of the detection coil 12B wound around 11B is detected as the magnitude of magnetic anisotropy of the steel plate to be measured. FIG. 2 shows an example of how the output of the detection coil 12B changes indicating the degree of magnetic anisotropy when the magnetic characteristic detecting sensor 10 is rotated. In this example, the magnitude of the magnetic anisotropy of the steel sheet to be measured is the amplitude value during a half rotation corresponding to one cycle of the output change from 0 to 180 ° and the next half of the rotation from 180 to 360 °. Amplitude values during rotation are arithmetically averaged. The magnitude of the obtained magnetic anisotropy is calculated by the computer 70.
It is designed to be input to. For the detection coil 12B wound around the U-shaped core 11B of the magnetic characteristic detection sensor 10, there is a document "Non-contact stress measurement of rail steel by magnetic anisotropy sensor" (Kishimoto et al .: Journal of the Japan Society for Applied Magnetics). ， Vol.
13, No. 2, 1989, pp. 435-436), a voltage proportional to the magnitude of magnetic anisotropy of each steel sheet to be measured is induced.

Reference numeral 60 is a magnetic permeability measuring device for measuring the magnetic permeability of the steel sheet to be measured in a non-contact manner. This permeability measuring device 60
Is provided with a magnetic flux detecting coil and a magnetic field detecting coil, which are not shown, as described in, for example, Japanese Patent Laid-Open No. 19584/1992, and the measured magnetic permeability is input to the computer 70. The computer 70 performs an arithmetic process for creating a regression equation in which a regression coefficient for the crystal grain size, which will be described later, is obtained by a multivariate analysis using the input data, or indirectly using the regression equation. This is for performing arithmetic processing for obtaining the crystal grain size of the steel sheet to be measured.

The procedure of indirect measurement of the crystal grain size by the above apparatus will be described. First, at least three types of steel plates S
For each _i (i = 1 to n), the crystal grain size d _i (i =
1 to n), the average value H _i (i = 1 to n) of coercive force equivalent values, the magnitude K _{i of} magnetic anisotropy (i = 1 to n), and , Permeability μ _i (i = 1 to n)
Is measured and these data are input to the computer 70. Then, the computer 70 performs multivariate analysis using these data to determine the reciprocal of the crystal grain size d as an objective variable, an average value H of coercive force equivalent values, and a magnitude K of magnetic anisotropy.
And a constant α ₀ and regression coefficients α _{1 to} α ₃ in the regression equation represented by the following equation with the permeability μ as an explanatory variable. That is, from the above data, a constant α ₀ and regression coefficients α _{1 to} α ₃
Is estimated by the least squares method. (1 / d) = α ₀ + α ₁ H + α ₂ K + α ₃ μ ...

Next, the average value of the coercive force equivalent values, the magnitude of magnetic anisotropy, and the magnetic permeability measured on the steel sheet for which the crystal grain size is to be indirectly measured are computer data as measurement data.
Entered in 70. Then, the computer 70 substitutes the data into a regression equation in which the constant α ₀ and the regression coefficients α _{1 to} α ₃ are specifically determined, and the grain size of the steel sheet is calculated.

FIG. 3 relates to the present invention and is a diagram showing the relationship between the average value of coercive force equivalent values of hot-rolled steel sheets and cold-rolled steel sheets and the reciprocal of the actually measured grain size. The graph in FIG. 3 is for the same sample steel plates as in FIG. 9 (14 types of hot-rolled steel plates and 3 types of cold-rolled steel plates), and the average value of the coercive force equivalent values in the figure is the magnitude of magnetic anisotropy. And the magnetic permeability data are corrected by converting them into an average value of coercive force equivalent values. As can be seen from FIG. 3, according to the present invention, not only the hot-rolled steel sheet but also the cold-rolled steel sheet having a different texture from that of the cold-rolled steel sheet can be used in the non-destructive non-contact type without causing a large error. Can be obtained by indirect measurement of.

[0035]

As can be understood from the above description, according to the apparatus for measuring the grain size of a steel sheet according to the present invention, the crystal grain size of the steel sheet is measured by a non-destructive non-contact method. Since it is configured to be obtained by using the average value of the magnetic force equivalent value, the magnitude of magnetic anisotropy, and the magnetic permeability, crystals of not only the hot rolled steel sheet but also the cold rolled steel sheet having a different texture from this The particle size can also be determined by a non-destructive non-contact method without causing a large error.

[Brief description of drawings]

FIG. 1 is a diagram showing the overall configuration of an embodiment of an apparatus for measuring the grain size of a steel sheet according to the present invention.

FIG. 2 is a diagram showing an example of how the output of a detection coil indicates the degree of magnetic anisotropy when the magnetic characteristic detection sensor according to the present invention is rotated.

FIG. 3 is a diagram relating to the present invention and showing the relationship between the average value of coercive force equivalent values of hot-rolled steel sheets and cold-rolled steel sheets and the reciprocal of the actually measured grain size.

FIG. 4 is a diagram showing direction dependence of a coercive force equivalent value of a steel sheet.

FIG. 5 is a diagram showing an overall configuration of an example of a crystal grain size measuring apparatus used for carrying out a conventional crystal grain size measuring method.

FIG. 6 is a structural explanatory view of the steel plate coercive force measuring device shown in FIG.

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

FIG. 8 relates to a conventional technique and is a diagram showing a relationship between an average value of coercive force equivalent values of a hot-rolled steel sheet and a reciprocal of an actually measured crystal grain size.

FIG. 9 is a diagram relating to a conventional technique and showing a relationship between an average value of coercive force equivalent values of a hot-rolled steel sheet and a cold-rolled steel sheet and a reciprocal of an actually measured crystal grain size.

[Explanation of symbols]

10 ... Magnetic characteristic detection sensor 11A, 11B ... U-shaped core
12A, 12B ... Detection coil 13a, 13b ... Excitation coil 14
… Resin mold 20… AC excitation current generator 21… Excitation current detector 30… Sensor rotation pulse motor 31… Motor drive controller 40… Coercive force average value measurement unit 50… Magnetic anisotropy measurement unit 60… Permeability measurement Device 70 ... Computer E1,
E1 '... Steel plate coercive force measuring device 100, 100' ... Coercive force detecting sensor 101 ... Core 102 ... Detection coil 103a, 103b ... Excitation coil 200, 200 '... Coercive force measuring device main body 300 ... AC exciting current generator 400 ... Excitation current detector 500 ... Signal processing device 600 ... Computer S ... Steel to be measured

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Takeo Ogawa Inventor Takeo Ogawa 1-5-5 Takatsukadai, Nishi-ku, Kobe-shi, Hyogo Inside Kobe Research Institute of Kobe Steel, Ltd. (72) Masaru Akamatsu Takatsuka, Nishi-ku, Kobe-shi, Hyogo 1-5-5 Taiwan Kobe Works, Kobe Steel Co., Ltd. (72) Inventor Tsutomu Morimoto 1-5-5 Takatsukadai, Nishi-ku, Kobe City, Hyogo Prefecture Kobe Steel Works, Kobe Steel Co., Ltd.

Claims (1)

[Claims] (A) One U-shaped core provided with an excitation coil and a detection coil through which an alternating excitation current for passing a magnetic flux through a steel sheet to be measured is provided, and another detection coil is provided. And the other U-shaped core
The V-shaped cores are crossed so as to be orthogonal to each other in the central portion of the core, and the four magnetic poles are located at respective apexes of a square on the same plane and have a predetermined distance from the steel plate to be measured. A magnetic characteristic detecting sensor that is integrally fixed so that it can rotate in parallel with each other; and (b) the exciting coil is provided when an alternating exciting current is applied to the magnetic characteristic detecting sensor. The exciting current value at the time when the induced voltage generated in the detection coil of the one U-shaped core takes a peak value is detected as a value corresponding to the coercive force of the steel plate to be measured, and an alternating exciting current flows. An average value of coercive force equivalent values for obtaining an average value of the coercive force equivalent values during at least half rotation of the magnetic characteristic detecting sensor, and (c) the magnetic characteristic to which an alternating excitation current is applied. At least a detection sensor Magnetic anisotropy measuring means for measuring the magnitude of magnetic anisotropy of the steel sheet to be measured based on the output of the detection coil of the other U-shaped core of the magnetic characteristic detection sensor during half rotation. (D) A magnetic permeability measuring device for measuring the magnetic permeability of the steel sheet to be measured in a non-contact manner, and (e) an actual measurement of the crystal grain size and an average value of the coercive force equivalent values for each of three or more types of steel sheets. The average value of coercive force equivalent values by means, the magnitude of magnetic anisotropy by the magnetic anisotropy measuring means, and the magnetic permeability by the magnetic permeability measuring device are given, and by multivariate analysis using these data. , A data processing means for obtaining a regression coefficient of each explanatory variable in a regression equation in which the reciprocal of the crystal grain size is an objective variable, the average value of coercive force equivalent values, the magnitude of magnetic anisotropy, and magnetic permeability are explanatory variables. (F) Indirect measurement of crystal grain size For a steel plate, an average value of coercive force equivalent values by the average value measuring means of the coercive force equivalent value, a magnitude of magnetic anisotropy by the magnetic anisotropy measuring means, and a magnetic permeability by the magnetic permeability measuring device, A device for measuring a crystal grain size of a steel sheet, comprising: a calculation unit that obtains the crystal grain size by substituting the regression coefficient into the regression equation determined by the data processing unit.