JP2011169872A - Device, method, and program for measuring crystal particle size - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To precisely measure a crystal particle size of a plate to be measured even at a high temperature as well as a room temperature. <P>SOLUTION: A waveform of an ultrasonic wave at each frequency of a prescribed frequency region including a resonance frequency propagated in a thickness direction of the plate 2 to be measured is measured by a waveform detection means 30, and an energy value of an ultrasonic wave at each frequency of a prescribed frequency region is calculated by an energy value calculation means 40, based on the detected waveform of the ultrasonic wave. Then, the maximum energy value, namely an energy value of an ultrasonic wave at the resonance frequency, is detected, and the maximum energy value and other energy values other than the maximum energy value are converted at a room temperature by a correction means 60 to get the ratio of the energy values calculated by a ratio calculation means 80, so that a crystal particle size in the plate 2 to be measured is calculated, based on the ratio of the energy values calculated by the ratio calculation means 80, by a particle size calculation means 100. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a crystal grain size measuring apparatus, method, and program for measuring the crystal grain size of a plate to be measured using ultrasonic waves.

  As a method for measuring the crystal grain size of a material such as a steel plate by a non-destructive test, a measurement using a resonance method by an electromagnetic ultrasonic transducer (EMAT: Electro Magnetic Acoustic Transducer) has been proposed. An example of a conventional method for measuring the crystal grain size using the resonance method using electromagnetic ultrasonic waves will be described below. FIG. 15 is a schematic diagram for explaining a resonance method using electromagnetic ultrasonic waves (EMAT). In FIG. 15, reference numeral 111 denotes an electromagnetic ultrasonic transducer, which is used for both transmission and reception of electromagnetic ultrasonic waves. Reference numeral 112 denotes a plate to be measured having a plate thickness d made of a plate-like material. When an alternating voltage is applied to the electromagnetic ultrasonic transducer 111 and the frequency of the alternating voltage is continuously changed, ultrasonic resonance occurs inside the measurement target plate 112 when the following formula 1 is satisfied.

  In Formula 1, d is the plate thickness of the measurement target plate 112, λ is the wavelength of the ultrasonic wave, and n is a positive integer. That is, ultrasonic resonance occurs when the thickness d of the measurement target plate 112 is an integral multiple of half the wavelength λ of the ultrasonic wave. Here, the resonances when n is 1, 2, 3,... Are called primary, secondary, tertiary,. FIG. 15 shows a standing wave formed in the secondary resonance state as an example. On the other hand, it is generally well known that the following formula 2 holds between the ultrasonic velocity V, wavelength λ, and frequency f.

  Further, from the formulas 1 and 2, the following formula 3 can be derived.

Since f in Formula 3 is the frequency at the n-th resonance, rewriting as f _n to clearly show this, Formula 4 is obtained.

  Regarding the measurement of the resonance frequency, for example, in the electromagnetic ultrasonic transducer 111, an ultrasonic wave whose frequency is continuously changed oscillates with respect to the measurement target plate 112 and propagates in the thickness direction of the measurement target plate 112. This is done by measuring the resonance spectrum of the ultrasonic wave. FIG. 16 is a characteristic diagram showing an example of the measurement result of the resonance spectrum.

  Here, FIG. 16 shows a value obtained by taking the frequency (MHz) of the ultrasonic wave oscillated on the horizontal axis and the energy value of the detected ultrasonic waveform (attenuation waveform) on the vertical axis. In FIG. 16, the measurement target plate 112 has a plate thickness of 0.35 mm and an average crystal grain size of 40.4 μm, and a plate thickness of 0.35 mm and an average crystal grain size of 87.5 μm. Different types of resonance spectra are shown, and the frequencies at the maximum energy values P1 and P2 respectively correspond to the resonance frequencies.

  In the conventional crystal grain size measuring apparatus, the crystal grain size of the measurement target plate 112 is calculated from the attenuation coefficient at the resonance frequency and the received signal amplitude at the resonance frequency (see, for example, Patent Documents 1 and 2). .

  By the way, as can be seen from the measurement result of the resonance spectrum shown in FIG. 16, the crystal grains having a large crystal grain size (in the example of FIG. 16, the average crystal grain diameter is 87.5 μm) are those having a small crystal grain diameter ( In the example of FIG. 16, the energy value of the ultrasonic waveform (attenuation waveform) at the resonance frequency is smaller than that of the average crystal grain size of 40.4 μm, and the ultrasonic waveform (attenuation) at other frequencies that do not resonate. The ratio of the energy value of (waveform) is large. This is presumably because the larger the crystal grain size, the greater the scattering at the crystal grain interface in the oscillated ultrasonic wave.

  In the example of FIG. 16, since the plate thickness d of the plate to be measured 112 is both 0.35 mm (350 μm), about 8 to 9 in the plate thickness direction of the plate to be measured 112 when the average crystal grain size is 40.4 μm. If the average crystal grain size is 87.5 μm, only about four crystal grains exist in the thickness direction of the measurement target plate 112. That is, when the ratio of the crystal grain size to the plate thickness d of the plate to be measured 112 becomes higher, in other words, the plate thickness of the plate to be measured 112 with respect to the crystal particle size of the plate to be measured 112. As d decreases, the energy value of the ultrasonic waveform (attenuation waveform) at the resonance frequency decreases as described above, and the ratio of the energy value of the ultrasonic waveform (attenuation waveform) at other frequencies that do not resonate. Is getting bigger.

  In the conventional crystal grain size measuring apparatus, since the crystal grain size of the plate to be measured 112 is calculated based on the resonance frequency range, the smaller the plate thickness d of the plate to be measured 112 is, the smaller the crystal grain size is. The measurement error of the crystal grain size due to the scattering of the ultrasonic wave due to the size becomes large, and there is a problem that it is difficult to measure the crystal grain size with high accuracy.

  In view of the above-mentioned problems, the present applicant can accurately measure the crystal grain size of the plate to be measured in Patent Document 3 even when the plate thickness of the plate to be measured is very thin. In order to achieve this, it is proposed to calculate the average grain size by calculating the ratio of the maximum energy value, which is the ultrasonic energy value at the resonance frequency, to other energy values other than the maximum energy value is doing.

JP 2001-343366 A JP-A-6-347449 JP 2007-101360 A

  By the way, when the steel plate in the process of a manufacturing process is made into a to-be-measured board in a steelworks, the temperature and atmospheric temperature of a steel plate are not always room temperature. For example, it may be required to measure the crystal grain size of a heated steel sheet.

  However, when the temperature of the steel sheet and the atmospheric temperature are high, the temperature-dependent physical property value of the steel sheet changes or the sensitivity characteristics of the transmission / reception probe including the electromagnetic ultrasonic transducer change compared to the room temperature. For this reason, there is a risk that the measurement accuracy may deteriorate. In any of the above-described patent documents, it is assumed that the temperature is room temperature, and it is not assumed that the temperature of the measurement target plate or the ambient temperature is high.

  The present invention has been made in view of the above points, and an object of the present invention is to make it possible to measure the crystal grain size of a plate to be measured with high accuracy not only at room temperature but also at a high temperature.

The crystal grain size measuring apparatus of the present invention oscillates ultrasonic waves in a predetermined frequency region including a resonance frequency in the plate thickness direction of the measurement target plate via a transmission / reception probe arranged at a predetermined position on the surface of the measurement target plate. Ultrasonic wave detecting means, waveform detecting means for detecting, via the transmitting / receiving probe, an ultrasonic waveform at each frequency in the predetermined frequency region propagated in the thickness direction of the measurement target plate, and the waveform detecting means Energy value calculating means for calculating the energy value of the ultrasonic wave at each frequency in the predetermined frequency region based on the waveform of the ultrasonic wave detected in step, and the resonance value among the energy values calculated by the energy value calculating means. A maximum energy value detecting means for detecting a maximum energy value which is an energy value of an ultrasonic wave at a frequency, and a maximum detected by the maximum energy value detecting means; An energy value and an energy value other than the maximum energy value among the energy values calculated by the energy value calculation means, at least one of temperature information of the transmitting / receiving probe and temperature information of the measurement target plate A correction means for correcting each using one of them, a ratio calculation means for calculating a ratio between the maximum energy value corrected by the correction means and another energy value corrected by the correction means, and a calculation by the ratio calculation means And a crystal grain size calculating means for calculating a crystal grain size in the plate to be measured based on the ratio of the measured energy values.
Another feature of the crystal grain size measuring apparatus of the present invention is that, among the energy values calculated by the energy value calculating means, an average value of each energy value excluding the maximum energy value is used as the other energy. It is in the point to be a value.
Another feature of the crystal grain size measuring apparatus of the present invention is that the correction means includes a maximum energy value detected by the maximum energy value detection means and an energy value calculated by the energy value calculation means. The other energy values other than the maximum energy value are converted at room temperature.
The crystal grain size measuring method of the present invention oscillates ultrasonic waves in a predetermined frequency region including a resonance frequency in the plate thickness direction of the measurement target plate via a transmission / reception probe arranged at a predetermined position on the surface of the measurement target plate. An ultrasonic oscillation step, a waveform detection step for detecting, via the transmission / reception probe, an ultrasonic waveform at each frequency in the predetermined frequency region propagated in the thickness direction of the measurement target plate, and the waveform detection step An energy value calculating step for calculating an energy value of the ultrasonic wave at each frequency in the predetermined frequency region based on the waveform of the ultrasonic wave detected in the step, and the energy value calculated in the energy value calculating step from the resonance value A maximum energy value detecting step for detecting a maximum energy value which is an energy value of an ultrasonic wave at a frequency, and the maximum energy The maximum energy value detected in the detection step and the energy value calculated in the energy value calculation step other than the maximum energy value are used as temperature information of the transmission / reception probe and the measurement target plate. A correction step for correcting each using at least one of the temperature information, a ratio calculation step for calculating a ratio between the maximum energy value corrected in the correction step and another energy value corrected in the correction step; And a crystal grain size calculating step for calculating a crystal grain size in the plate to be measured based on the ratio of energy values calculated in the ratio calculating step.
The program of the present invention is an ultrasonic oscillator that oscillates an ultrasonic wave in a predetermined frequency region including a resonance frequency in a plate thickness direction of the measurement target plate via a transmission / reception probe arranged at a predetermined position on the surface of the measurement target plate. Processing, a waveform detection process for detecting an ultrasonic waveform at each frequency in the predetermined frequency region propagated in the thickness direction of the measurement target plate via the transmission / reception probe, and an ultrasonic wave detected by the waveform detection process. Based on the waveform of the sound wave, the energy value calculation process for calculating the energy value of the ultrasonic wave at each frequency in the predetermined frequency region, and the ultrasonic wave at the resonance frequency from the energy value calculated by the energy value calculation process A maximum energy value detection process for detecting a maximum energy value that is an energy value of the maximum energy value detected by the maximum energy value detection process. Energy value other than the maximum energy value among energy values calculated by the energy value calculation process, at least one of temperature information of the transmitting / receiving probe and temperature information of the measurement target plate Correction processing for correcting each using one, ratio calculation processing for calculating a ratio between the maximum energy value corrected by the correction processing and another energy value corrected by the correction processing, and calculation by the ratio calculation processing Based on the ratio of the measured energy values, the computer is caused to execute a crystal grain size calculation process for calculating a crystal grain size in the measurement target plate.

  According to the present invention, the crystal grain size of the plate to be measured can be measured with high accuracy not only at room temperature but also at a high temperature.

It is a block diagram showing a schematic structure of a crystal grain size measuring device concerning an embodiment of the present invention. It is a flowchart which shows an example of the crystal grain size measuring method performed with the crystal grain size measuring device which concerns on embodiment of this invention. It is a figure which shows an example of the ultrasonic waveform oscillated from an ultrasonic oscillation means. It is a figure which shows an example of the waveform of the ultrasonic wave in the certain frequency detected with the waveform detection means. It is a figure which shows the calculation image of the energy value with respect to the detection waveform of the ultrasonic wave of FIG. It is a characteristic view of the energy value of the ultrasonic wave in each frequency of a predetermined frequency region (frequency 3 MHz to 5 MHz) calculated by the energy value calculation means. It is a characteristic view showing the relationship between the ratio of the maximum energy value and other energy values and the average crystal grain size. It is a figure which shows the result of the crystal orientation, sound speed, and resonance frequency in each to-be-measured board. It is a figure which shows the apparatus outline | summary for the test which considers about the precision of the crystal grain size measurement by temperature. It is a figure which shows the result of a test. It is a figure which shows the result of a test. It is a characteristic view which shows the temperature dependence of magnetic permeability (micro | micron | mu) and electrical resistivity R. It is a characteristic view which shows the result converted at room temperature. It is a characteristic view which shows the result converted at room temperature. It is the schematic for demonstrating the resonance method by an electromagnetic ultrasonic wave (EMAT). It is a characteristic view which shows an example of the measurement result of a resonance spectrum.

Preferred embodiments of the present invention will be described below with reference to the accompanying drawings.
FIG. 1 is a block diagram showing a schematic configuration of a crystal grain size measuring apparatus according to an embodiment of the present invention. In FIG. 1, reference numeral 2 denotes a plate to be measured having a thickness d made of a steel plate or the like, and 3 denotes a support that supports the plate 2 to be measured. Reference numeral 1 denotes a crystal grain size measuring device for measuring the crystal grain size of the measurement target plate 2 on the support 3. A temperature sensor (not shown) (for example, a radiation thermometer) that measures the surface temperature of the measurement target plate 2 is installed, and the temperature information T ₁ is input to the crystal grain size measuring apparatus 1.

In the crystal grain size measuring apparatus 1, reference numeral 10 denotes a transmission / reception probe, which is disposed at a predetermined position on the surface of the measurement target plate 2, transmits ultrasonic waves to the measurement target plate 2 and extends in the thickness direction of the measurement target plate 2. The propagated ultrasonic wave is received. The transmission / reception probe 10 is composed of, for example, an electromagnetic ultrasonic transducer. The example aspects of the transmission and reception probe 10, the temperature sensor (not shown) (e.g., thermocouples) are installed, the temperature information T ₂ is obtained.

  Reference numeral 20 denotes an ultrasonic wave oscillating means for oscillating an ultrasonic wave, and a predetermined frequency including a resonance frequency in the plate thickness direction of the measurement target plate 2 via a transmission / reception probe 10 arranged at a predetermined position on the surface of the measurement target plate 2. Oscillates the ultrasonic waves in the area.

  Reference numeral 30 denotes a waveform detection means, which oscillates from the ultrasonic oscillation means 20 and propagates in the thickness direction of the plate 2 to be measured, and the waveform (attenuation waveform) of the ultrasonic wave at each frequency in a predetermined frequency region. It detects via the transmission / reception probe 10 arrange | positioned in the predetermined position of the surface of this.

  Reference numeral 40 denotes energy value calculation means, which calculates the ultrasonic energy value at each frequency in a predetermined frequency region based on the ultrasonic waveform (attenuation waveform) detected by the waveform detection means 30.

  Reference numeral 50 denotes a maximum energy value detection unit that detects the maximum energy value that is the energy value of the ultrasonic wave at the resonance frequency from the energy values calculated by the energy value calculation unit 40.

Reference numeral 60 denotes a correction unit that corrects the maximum energy value detected by the maximum energy value detection unit 50 using the temperature information T ₁ of the measurement target plate 2, and out of the energy values calculated by the energy value calculation unit 40. Then, other energy values other than the maximum energy value are corrected using the temperature information T ₂ of the transmission / reception probe 10.

  A physical property value storage unit 70 stores physical property values used for correction by the correcting means 60. In this embodiment, as will be described later, for each target material for crystal grain size measurement (the type of the plate 2 to be measured), the magnetic permeability μ depending on the temperature and the electric resistivity R depending on the temperature are stored.

  A ratio calculating unit 80 calculates a ratio between the maximum energy value corrected by the correcting unit 60 and another energy value corrected by the correcting unit 60.

  Reference numeral 90 denotes a correlation value storage unit, which stores a correlation value of an average crystal grain size with respect to a ratio between the maximum energy value and other energy values calculated in advance through experiments or the like.

  Reference numeral 100 denotes a crystal grain size calculation unit, which refers to the correlation value stored in the correlation value storage unit 90 on the basis of the ratio of energy values calculated by the ratio calculation unit 80, whereby the average crystal in the measured plate 2 is measured. Calculate the particle size.

  Next, a crystal grain size measuring method by the crystal grain size measuring apparatus 1 will be described. FIG. 2 is a flowchart showing an example of a crystal grain size measuring method performed by the crystal grain size measuring apparatus 1 according to the embodiment of the present invention.

  First, after the transmission / reception probe 10 is arranged at a predetermined position on the surface of the plate 2 to be measured, in step S101, the ultrasonic oscillating means 20 passes the transmission / reception probe 10 and the resonance frequency in the thickness direction of the plate 2 to be measured. Are oscillated independently for each frequency.

  In this step S101, for example, a so-called burst wave as shown in FIG. 3 is oscillated for each frequency. FIG. 3 shows an example of oscillating five burst waves having a frequency of 3 MHz. In the present embodiment, the following description will be given by taking a frequency of 3 MHz to 5 MHz as an example as the predetermined frequency region of the oscillating ultrasonic wave.

  Subsequently, in step S102, the waveform detection means 30 oscillates the ultrasonic wave at each frequency in a predetermined frequency region (frequency 3 MHz to 5 MHz) oscillated from the ultrasonic oscillation means 20 and propagated in the thickness direction of the measurement target plate 2. A waveform (attenuated waveform) is detected via the transmission / reception probe 10.

  FIG. 4 is a diagram showing an example of an ultrasonic waveform at a certain frequency detected by the waveform detecting means 30. The ultrasonic waveform shown in FIG. 4 shows the amplitude of the ultrasonic wave in voltage (V) on the vertical axis and the elapsed time (t) on the horizontal axis. In the present embodiment, the waveform detection means 30 detects the waveform of the ultrasonic wave that has reached the predetermined time T after detecting the first wave of ultrasonic waves.

  Subsequently, in step S103, the energy value calculation means 40, based on the ultrasonic waveform (attenuation waveform) detected by the waveform detection means 30, the ultrasonic wave at each frequency in a predetermined frequency region (frequency 3 MHz to 5 MHz). Calculate the energy value. FIG. 5 is a diagram showing a calculation image of energy values for the ultrasonic detection waveform of FIG. The sum of the integral values of the portion indicated by the oblique lines in FIG. 5 is the calculated energy value.

  Subsequently, in step S104, the maximum energy value detection means 50 determines the resonance frequency at the resonance frequency from the energy values at each frequency in the predetermined frequency region (frequency 3 MHz to 5 MHz) calculated by the energy value calculation means 40 in step S103. The maximum energy value, which is the ultrasonic energy value, is detected.

  FIG. 6 is a characteristic diagram of ultrasonic energy values at each frequency in a predetermined frequency region (frequency 3 MHz to 5 MHz) calculated by the energy value calculation means 40. In FIG. 6, the vertical axis represents the ultrasonic energy value, and the horizontal axis represents the frequency. FIG. 6 shows ultrasonic waves at each frequency in a predetermined frequency region (frequency 3 MHz to 5 MHz) of each measurement target plate 2 having an average crystal grain size of 12.0 μm, 20.5 μm, 35.7 μm, and 53.6 μm. The characteristic figure of energy value of is shown. In the example of FIG. 6, the maximum energy value detection means 50 detects the maximum energy value P3 in the case of the measurement target plate 2 having an average crystal grain size of 12.0 μm, and the average crystal grain size is 20. In the case of the measurement target plate 2 having a thickness of 5 μm, the maximum energy value P4 is detected, and in the case of the measurement target plate 2 having an average crystal grain size of 35.7 μm, the maximum energy value P5 is detected. In the case of the measurement target plate 2 having a diameter of 53.6 μm, the maximum energy value P6 is detected. Here, these maximum energy values P <b> 3 to P <b> 6 correspond to ultrasonic energy values of the resonance frequency in the plate thickness direction of each measurement target plate 2.

Subsequently, in step S105, the correction means 60, the maximum energy values detected by the maximum energy value detecting means 50 in step S104, converted at room temperature using the temperature information T ₁ of the object to be measured plate 2. The correction means 60, among the energy values calculated by the energy calculator 40 in step S103, the other energy values other than the maximum energy value, room temperature when translated using the temperature information T ₂ of the transmitting and receiving probes 10 To do.

Here, as another specific calculation method of the energy value, among the energy values calculated by the energy value calculation means 40, each energy value excluding the maximum energy value that is the ultrasonic energy value at the resonance frequency is used. A method in which the average value is used as the other energy value can be considered. As a specific method for removing the maximum energy value, it is conceivable to use the feature that the energy value near the resonance frequency is pulsed as follows. First, frequency and energy data are recorded as digital data such as (f _i, P _i ), and (f _imax, P _imax ) is the resonance energy value and the energy value at which the maximum energy value is obtained. To do. However, i is an integer of 1, 2, 3,..., N, f _N is a maximum frequency value measured and recorded, and imax is an integer of 1 to N. Here, i is incremented by one from imax as i = imax + 1 and i = imax + 2, and i that first satisfies P _i <P _imax × (1/100) is searched as iupper, and similarly i = imax−1, i = imax-2 is decreased by 1 from imax one by one. First, _{i that} satisfies P _i <P _imax × (1/100) is searched for, and ilow is excluded from ilow to iupper. to calculate the average value of P _i. By such a method, it is possible to calculate an average value of other energy values corresponding to a frequency sufficiently separated from the resonance frequency that is the maximum energy value. In the present invention, other energy value calculation methods are not limited to these specific calculation methods.

In this case, there are multiple orders (n = 1, 2, 3,...) Of resonance frequencies f _n as shown in Equation 4, and each resonance is shown in FIGS. Waveform peaks appear at frequency. When calculating other energy values, the energy values of ultrasonic waves at these resonance frequencies are not included. For this purpose, a predetermined frequency region (frequency 3 MHz to 5 MHz in this embodiment) is appropriately set so as not to include a plurality of resonance frequencies (waveform peaks). Alternatively, when a plurality of resonance frequencies (peaks of waveforms) are included in a predetermined frequency region (frequency 3 MHz to 5 MHz in the present embodiment), other than the energy value of ultrasonic waves at these plurality of resonance frequencies. The energy value of is calculated.

In this step S105, the maximum energy value S _T1 (maximum energy value at the surface temperature T ₁ of the plate 2 to be measured) detected by the maximum energy value detecting means 50 in step S104 is converted to room temperature by the following formula 9. The magnetic permeability μ _T1 and electrical resistivity R _T1 used in Equation 9 correspond to the temperature information T ₁ of the plate 2 to be measured according to the target material for crystal grain size measurement (the type of the plate 2 to be measured). Extracted from the physical property value storage unit 70.
S _room = (R _T1 / R _room ) * (μ _room / μ _T1 ) ² * S _T1 (Equation 9)
However, R _room represents the electrical resistivity at _room temperature, and μ _room represents the magnetic permeability at _room temperature.

Further, in step S105, among the energy values calculated by the energy calculator 40 in step S103, the other energy values N _T2 other than said maximum energy value, is converted at room temperature by the following equation 10. The other energy value N _T2 is considered as thermal noise generated at the transmission / reception probe 10 (thermal noise at the temperature T ₂ of the transmission / reception probe 10), and the thermal noise is based on being proportional to √T.
N _room = (√room temperature / √T ₂ ) * N _T2 (Equation 10)

  Subsequently, in step S106, the ratio calculation means 80 calculates a ratio between the maximum energy value converted at room temperature by the correction means 60 in step S105 and another energy value converted in room temperature by the correction means 60 in step S105. calculate.

  Subsequently, in step S107, the crystal grain size calculating unit 100 calculates the average crystal grain size in the measurement target plate 2 based on the ratio of the energy values calculated by the ratio calculating unit 80 in step S106.

  Here, the calculation method of the average crystal grain size of the plate 2 to be measured will be specifically described. First, the relationship between the ratio of the maximum energy value and other energy values and the average crystal grain size is obtained in advance by experiments or the like for the sample plate formed in the same process as the plate 2 to be measured. FIG. 7 is a characteristic diagram showing the relationship between the ratio of the maximum energy value and other energy values and the average crystal grain size. Then, as shown in FIG. 7, the obtained characteristic value is approximated to calculate the correlation value of the average crystal grain size with respect to the ratio between the maximum energy value and other energy values, and each calculated correlation The value is stored in the correlation value storage unit 90 in advance. The crystal grain size calculation means 100 extracts the correlation value of the corresponding average crystal grain size stored in the correlation value storage unit 90 based on the ratio of the energy values calculated by the ratio calculation means 80, and the measured plate The average crystal grain size in 2 is calculated.

  By performing the processing from step S101 to step S107, the average crystal of the plate 2 to be measured based on the ratio between the maximum energy value of the ultrasonic wave in the resonance spectrum and other energy values other than the maximum energy value. The particle size is calculated.

  In Patent Document 3, a measurement target plate (average in the example of FIG. 16) having a large average crystal grain size is compared with a measurement target plate having a small average crystal grain size (in the example of FIG. 16, the average crystal grain size is 40.4 μm). The energy value of the ultrasonic waveform (attenuation waveform) at the resonance frequency (with a crystal grain size of 87.5 μm) is small, and the ratio of the energy value of the ultrasonic waveform (attenuation waveform) at other frequencies that do not resonate is large. The phenomenon of becoming is considered.

  First, paying attention to the crystal orientation of the crystal grains as a cause of the above-mentioned phenomenon, it is a sample different from the plate to be measured in FIG. 16, but compared with the plate to be measured having a small average crystal grain size and the plate to be measured. For each of the plates to be measured having a large average crystal grain size, the main crystal orientation in the plate thickness direction was measured. Under the present circumstances, it measured using the steel plate as a to-be-measured board. FIG. 8 shows the result.

  As shown in FIG. 8, the main crystal orientation in the plate thickness direction is the crystal orientation <111> for the measurement target plate having a small average crystal grain size, and the crystal orientation <111> for the measurement target plate having a large average crystal grain size. And <110> were obtained. And it tried to calculate the resonance frequency in the plate | board thickness direction of each to-be-measured board from this crystal orientation. The calculation method is shown below.

  When a steel plate is used as the plate to be measured, the crystal is cubic, and it is known that the elastic modulus tensor T when the x, y, and z axes are taken as the crystal axes can be expressed by the following Equation 5. .

  In addition, when the propagation direction of the transverse wave ultrasonic wave is the crystal orientation <111>, it is known that the sound velocity Vs of the transverse wave ultrasonic wave can be expressed by the following Equation 6.

  Further, when the propagation direction of the transverse ultrasonic waves is the crystal orientation <110>, there are two kinds of sound velocities of the transverse ultrasonic waves, and the respective sound velocities Vs1 and Vs2 can be expressed by the following equations 7 and 8. I know.

Here, in Equations 6 to 8, in the case of an iron single crystal, the elastic constant C ₁₁ is 2.331 × 10 ¹¹ (N / m ² ), and the elastic constant C ₄₄ is 1.178 × 10 ¹¹ (N / M ² ), the elastic constant C ₁₂ is 1.354 × 10 ¹¹ (N / m ² ), and the density ρ is 7.86 × 10 ³ (kg / m ³ ).

  In the plate to be measured having a small average crystal grain size, the main crystal orientation is <111>. Therefore, when the sound speed of the transverse ultrasonic wave is calculated based on Equation 6, 3023 (m / s) is obtained as shown in FIG. The result was obtained. On the other hand, since the main crystal orientations are <111> and <110> in the plate to be measured having a large average crystal grain size, the sound speed of the transverse ultrasonic wave is calculated based on Equations 6 to 8, and is shown in FIG. Thus, the result of mixing three kinds of sound speeds of 3023 (m / s), 2492 (m / s) and 3871 (m / s) was obtained.

  Then, when the resonance frequency is calculated based on Equation 4 from the sound velocity of the transverse wave ultrasonic waves at each measurement plate (in this case, n = 1), as shown in FIG. 8, the average crystal grain size is small. In the measurement plate, only one type of resonance frequency is 4.318 (MHz), whereas in the measurement target plate having a large average crystal grain size, the resonance frequencies are 4.318 (MHz) and 3.56 (MHz). ) And 5.53 (MHz).

  As a result, in the measurement target plate having a small average crystal grain size, since only one kind of resonance frequency exists, it has been found that the maximum energy value increases and the ratio of energy values at other non-resonant frequencies decreases. . On the other hand, since there are three types of resonance frequencies in the plate to be measured having a large average crystal grain size, the maximum energy value decreases and the ratio of energy values at other frequencies other than the maximum energy value increases. It has been found. That is, it was proved that the energy value of the ultrasonic wave propagating through the measurement target plate is caused by the crystal orientation of the measurement target plate.

  Here, the inventor considered the accuracy of crystal grain size measurement based on the temperature of the transmission / reception probe 10 and the temperature of the measurement target plate 2. As shown in FIG. 9, the sample plate 52 is placed in the high-temperature test chamber 51, and the transmission / reception probe 53 is arranged at a predetermined position on the surface of the sample plate 52. The transmission / reception probe 53 uses an EMAT sensor using a 200 ° C. heat-resistant epoxy resin. Thermocouples are installed on the surface of the sample plate 52 and the side surface of the EMAT sensor 53, respectively, and the surface temperature of the sample plate 52 (referred to as sample temperature) and the side surface temperature of the EMAT sensor 53 (referred to as sensor temperature) are measured. .

  First, about the sample plate 52 of the general structural rolled steel material (SS400) of thickness 2.3mm, the test was implemented by the case where the inside of the high temperature test tank 51 was made into room temperature, and the case where it was made 200 degreeC. FIG. 10A is a characteristic diagram of the ultrasonic energy value at each frequency in the frequency range of 1 MHz to 5 MHz. The vertical axis indicates the ultrasonic energy value, and the horizontal axis indicates the frequency. The broken line in the figure represents the characteristic at room temperature, and the solid line represents the characteristic at 200 ° C. As shown in FIG. 10 (a), there are five types of resonance frequencies, and it can be seen that there is a shift between room temperature and 200 ° C. in any case.

  FIG. 10B shows the sample temperature and sensor temperature measured at intervals of about 3 minutes while increasing the temperature from room temperature to 200 ° C. In the figure, ◆ represents the sample temperature, and ■ represents the sensor temperature. In this test, since the transmission / reception probe 53 is arranged at a predetermined position on the surface of the fixed sample plate 52, there is almost no difference between the two temperatures.

  FIG. 10C shows a ratio (hereinafter referred to as “resonance peak SN value”) between the maximum energy value and other energy values calculated in each measurement time of FIG. 10B. In FIG. 10A, the frequency range of 1 MHz to 5 MHz is shown. However, in the calculation of the resonance peak SN value here, in the frequency range of 1.5 MHz to 2.8 MHz, corresponding to the actual measurement. Evaluating. As shown in FIG. 10 (c), although the sample plate 52, that is, the same crystal grain size, the resonance peak SN value decreased as the temperature increased.

  Moreover, about the sample board 52 of the austenitic stainless steel (SUS304) of thickness 2mm, the test was implemented by the case where the inside of the high temperature test tank 51 was made into room temperature, and 200 degreeC. FIG. 11A is a characteristic diagram of the ultrasonic energy value at each frequency in the frequency range of 1 MHz to 5 MHz, where the vertical axis indicates the ultrasonic energy value and the horizontal axis indicates the frequency. The broken line in the figure represents the characteristic at room temperature, and the solid line represents the characteristic at 200 ° C. As shown in FIG. 11 (a), there are three types of resonance frequencies, and it can be seen that there is a difference between room temperature and 200 ° C. in any case.

  FIG. 11B shows the sample temperature and sensor temperature measured at intervals of about 3 minutes while increasing the temperature from room temperature to 200 ° C. In the figure, ◆ represents the sample temperature, and ■ represents the sensor temperature. In this test, since the transmission / reception probe 53 is arranged at a predetermined position on the surface of the fixed sample plate 52, there is almost no difference between the two temperatures.

  FIG. 11C shows the resonance peak SN value calculated in each measurement time of FIG. In FIG. 11A, the frequency region of 1 MHz to 5 MHz is shown. However, in the calculation of the resonance peak SN value here, in the frequency region of 1.5 MHz to 2.8 MHz, corresponding to the actual measurement. Evaluating. As shown in FIG. 11C, although the same sample plate 52, that is, the same crystal grain size, the resonance peak SN value decreased as the temperature increased.

  From the results of these tests, it can be seen that when crystal grain size measurement is performed, accuracy is degraded unless temperature correction is performed.

The present inventor considered that there is a possibility that the energy value of the ultrasonic wave at the resonance frequency can be converted at room temperature from temperature-dependent physical properties such as magnetic permeability and electrical resistivity. The received voltage V _R which is a detection signal of the EMAT sensor 53, by using magnetic flux density B, the shape factor by the sending and receiving coils and the inspection of the EMAT the sensor G, constant with frequency and density, etc. Z, an eddy current I _E, the following This is expressed by Equation 11. The magnetic flux density B depends on the magnetic permeability μ, and the eddy current _IE depends on the electric resistivity R. Regarding SS400 and SUS304, when the temperature dependence of the magnetic permeability μ and the electrical resistivity R is investigated from a data book or the like, those shown in FIGS. 12A and 12B are obtained.

According to Equation 11, the reception voltage V _R that is a detection signal of the EMAT sensor 53 is proportional to B ² and proportional to the eddy current _IE . However, since a constant voltage is applied to the eddy current coil, it is inversely proportional to the electrical resistivity R of the target material. Therefore, the maximum energy value when the surface temperature of the target material is T ₁ is expressed by Equation 9.

  FIG. 13 and FIG. 14 show resonance peak SN values obtained by converting to room temperature using Equations 9 and 10. FIG. FIG. 13 shows the result corresponding to FIG. 10 in which SS400 is the target material. FIG. 14 shows a result corresponding to FIG. 11 in which SUS304 is the target material. The information shown in FIG. 12 was used for the magnetic permeability μ and the electrical resistivity R.

  In FIGS. 13 and 14, ● represents the raw data results (the same results as in FIGS. 10C and 11C), and ○ represents the results converted at room temperature. By converting at room temperature, the phenomenon that the resonance peak SN value decreases as the temperature rises disappears, and it can be seen that even when the temperature rises, the resonance peak SN value substantially matches the room temperature. This correction is valid.

  As described above, according to the crystal grain size measurement to which the present invention is applied, even if the plate thickness of the plate to be measured 2 is very thin, the crystal grain size of the plate to be measured 2 is measured with high accuracy. be able to.

  Moreover, the crystal grain size of the plate to be measured can be measured with high accuracy not only at room temperature but also at high temperatures. This makes it possible to measure the crystal grain size of various target materials online. For example, in the case of a certain kind of steel material, since the hardness increases as the crystal grain size increases, there may be a problem that the steel sheet breaks in the rolling stage of the manufacturing process. In such a case, it is possible to prevent breakage by measuring the crystal grain size before the rolling stage and controlling the rolling speed accordingly.

As mentioned above, although this invention was demonstrated with various embodiment, this invention is not limited only to these embodiment, A change etc. are possible within the scope of the present invention. For example, in the above embodiment it has been adapted to measure the temperature information T ₂ of the temperature information T ₁ and transmission and reception probe 10 of the measurement plate 2 respectively, FIG. 10, as described in the test example in FIG. 11, the measured When the plate 2 is fixed, there is almost no difference between the two temperatures. Therefore, only one of the temperatures may be measured. However, in a state in which the measurement plate 2 is being conveyed, since there may be a difference in both temperatures occurs, preferred to measure the temperature information T ₂ of the temperature information T ₁ and transmission and reception probe 10 of the measurement plate 2, respectively It is.

  In the above-described embodiment, room temperature conversion is performed using Equations 9 and 10. However, for example, data as shown in FIG. 10C and FIG. It is also possible to use it and convert it to room temperature. However, in that case, it is necessary to collect data for each target material for crystal grain size measurement. Therefore, when various types of steel plates are used as the target material, conversion at room temperature using Equations 9 and 10, which do not require data collection in advance, is advantageous.

(Other embodiments)
The present invention can also be realized by executing the following processing. That is, software (program) that realizes the functions of the above-described embodiments is supplied to a system or apparatus via a network or various storage media, and a computer (or CPU, MPU, etc.) of the system or apparatus reads the program. It is a process to be executed.

1: Crystal grain size measuring device 2: Plate to be measured 3: Support 10: Transmission / reception probe 20: Ultrasonic oscillation means 30: Waveform detection means 40: Energy value calculation means 50: Maximum energy value detection means 60: Correction means 70: Physical property value storage unit 80: Ratio calculation unit 90: Correlation value storage unit 100: Crystal grain size calculation unit

Claims (5)

An ultrasonic oscillating means for oscillating ultrasonic waves in a predetermined frequency region including a resonance frequency in the plate thickness direction of the measurement target plate via a transmission / reception probe disposed at a predetermined position on the surface of the measurement target plate;
Waveform detection means for detecting the waveform of the ultrasonic wave at each frequency in the predetermined frequency region propagated in the thickness direction of the measurement target plate via the transmission / reception probe;
Energy value calculating means for calculating the energy value of the ultrasonic wave at each frequency in the predetermined frequency region based on the waveform of the ultrasonic wave detected by the waveform detecting means;
Among the energy values calculated by the energy value calculating means, a maximum energy value detecting means for detecting a maximum energy value that is an ultrasonic energy value at the resonance frequency;
The maximum energy value detected by the maximum energy value detection means and the energy value calculated by the energy value calculation means other than the maximum energy value, the temperature information of the transmission / reception probe and the energy value Correction means for correcting each of the temperature information of the measurement target plate using at least one of the temperature information;
A ratio calculating means for calculating a ratio between the maximum energy value corrected by the correcting means and another energy value corrected by the correcting means;
A crystal grain size measuring device comprising crystal grain size calculating means for calculating a crystal grain size in the plate to be measured based on a ratio of energy values calculated by the ratio calculating means.   2. The crystal grain size according to claim 1, wherein an average value of the energy values excluding the maximum energy value among the energy values calculated by the energy value calculating unit is set as the other energy value. Measuring device.   The correction means converts the maximum energy value detected by the maximum energy value detection means and the energy values calculated by the energy value calculation means from other energy values other than the maximum energy value, respectively, at room temperature. The crystal grain size measuring device according to claim 1 or 2, wherein An ultrasonic oscillation step of oscillating ultrasonic waves in a predetermined frequency region including a resonance frequency in the plate thickness direction of the measurement target plate via a transmission / reception probe arranged at a predetermined position on the surface of the measurement target plate;
A waveform detection step of detecting, via the transmission / reception probe, a waveform of an ultrasonic wave at each frequency in the predetermined frequency region propagated in the thickness direction of the measurement target plate;
Based on the waveform of the ultrasonic wave detected in the waveform detecting step, an energy value calculating step for calculating an energy value of the ultrasonic wave at each frequency in the predetermined frequency region;
A maximum energy value detecting step for detecting a maximum energy value that is an energy value of an ultrasonic wave at the resonance frequency from the energy values calculated in the energy value calculating step;
The maximum energy value detected in the maximum energy value detection step, and the energy value calculated in the energy value calculation step other than the maximum energy value, the temperature information of the transmission / reception probe and the energy value A correction step of correcting each of the temperature information of the measurement target plate using at least one of the temperature information;
A ratio calculating step for calculating a ratio between the maximum energy value corrected in the correcting step and another energy value corrected in the correcting step;
A crystal grain size measuring method, comprising: a crystal grain size calculating step for calculating a crystal grain size in the plate to be measured based on a ratio of energy values calculated in the ratio calculating step. An ultrasonic oscillation process for oscillating ultrasonic waves in a predetermined frequency region including a resonance frequency in the plate thickness direction of the measurement target plate via a transmission / reception probe arranged at a predetermined position on the surface of the measurement target plate;
Waveform detection processing for detecting an ultrasonic waveform at each frequency in the predetermined frequency region propagated in the thickness direction of the measurement target plate via the transmission / reception probe;
Based on the ultrasonic waveform detected by the waveform detection process, an energy value calculation process for calculating an ultrasonic energy value at each frequency in the predetermined frequency region;
Among the energy values calculated in the energy value calculation process, a maximum energy value detection process for detecting a maximum energy value that is an ultrasonic energy value at the resonance frequency;
The maximum energy value detected by the maximum energy value detection process, and the energy value calculated by the energy value calculation process other than the maximum energy value, the temperature information of the transmission / reception probe and the energy value Correction processing for correcting each of the temperature information of the measurement target plate using at least one of the temperature information;
A ratio calculation process for calculating a ratio between the maximum energy value corrected by the correction process and another energy value corrected by the correction process;
A program for causing a computer to execute a crystal grain size calculation process for calculating a crystal grain size in the measurement target plate based on a ratio of energy values calculated in the ratio calculation process.

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