JP4104486B2 - Recrystallization rate measuring apparatus and recrystallization rate measuring method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a recrystallization rate measuring device and a recrystallization rate measuring method for measuring, for example, a recrystallization rate of a steel material in a non-contact manner.
[0002]
[Prior art]
In the hot steel manufacturing process, various processing such as rolling is performed on the steel. Generally, a steel material having high strength and high toughness characteristics can be obtained by refining the crystal structure of the steel material. For example, as the steel material has a lower recrystallization rate, there are more lattice defects inside the crystal, and nuclei grow from the starting point, so that the crystal structure is more easily refined. Thus, the recrystallization rate is important information for knowing the state of the crystal structure of the steel material.
[0003]
Further, it is known that the recrystallization rate has a correlation with a sound velocity parameter representing the anisotropy of the shear wave sound velocity for the steel material. This correlation is disclosed in Non-Patent Document 1. Therefore, if such a sound speed parameter is obtained, the recrystallization rate of the steel material can be known.
[0004]
[Non-Patent Document 1]
NDT & E International, Vol.33, 2000, p.253-259, “Ultrasonic velocity measurements for characterizing the annealing behavior of cold worked austenitic stainless steel”
[0005]
[Problems to be solved by the invention]
However, conventionally, the recrystallization rate is not measured online in the hot steel manufacturing process. In the non-patent document 1 described above, the shear wave velocity is measured using a contact-type shear wave probe. Naturally, this method cannot be used for hot online measurement. If information about the recrystallization rate can be obtained online, for example, by feeding the information to the rolling conditions of the next process, it becomes possible to efficiently and stably produce steel with a fine structure. It can also contribute to the reduction of material variations due to high-precision steel manufacturing technology.
[0006]
This invention is made | formed based on the said situation, and it aims at providing the recrystallization rate measuring apparatus and the recrystallization rate measuring method which can measure the recrystallization rate of a measuring object hot on-line. Is.
[0007]
[Means for Solving the Problems]
  In order to achieve the above-mentioned object, the invention according to claim 1 provides a plate-like measurement object.On the surface, the first laser beam is focused and irradiated by the head unit to generate and propagate an ultrasonic wave inside the measurement object, and the second laser beam is irradiated from the surface to a predetermined position from the reflection, By a laser ultrasonic method for detecting the propagated ultrasonic wave using frequency change detection meansA recrystallization rate measuring device for measuring a recrystallization rate,The head portion isThe first laser beam is applied to the surface of the measurement objectLine focus beamBy irradiating, the inside of the measurement objectPolarized in a predetermined direction with respect to the line focus beam lineAn ultrasonic generator for generating a transverse ultrasonic wave, and the measurement objectThe second laser beam is placed at a predetermined position on the surface of the line focus beam on a straight line passing through the center point of the line focus beam and orthogonal to the bottom surface of the object to be measured and returned to the surface. Guiding and the predetermined positionBeam acquisition to acquire the second laser beam reflected byPartWhenConsists of,The frequency change detecting means includesThe beam acquisitionPartBased on the second laser beam acquired inSaidChanges in the frequency of the second laser beam caused by the vibration of transverse ultrasonic wavesAs transmitted light intensity changeDetectFurthermore, the ultrasonic wave generator has a rotation mechanism, and irradiates the first laser beam with the line focus beam line direction on the surface to be measured parallel to the width direction and the longitudinal direction of the measurement object. The first transverse wave ultrasonic wave polarized in the longitudinal direction in the direction of each line and the second transverse wave ultrasonic wave polarized in the width direction are generated,For each of the first transverse wave ultrasonic wave and the second transverse wave ultrasonic wave, it represents the frequency change of the second laser beam detected by the frequency change detection means.Of transmitted light intensity changeBased on the waveform data,eachObtain the propagation time of the transverse wave ultrasonic wave propagating through the object to be measured, and based on the obtained propagation time and the distance propagated by the transverse wave ultrasonic waveeachCalculate the speed of shear wave ultrasonic wavesAnd beforeUsing the sound velocity of the first transverse wave ultrasonic wave and the sound velocity of the second transverse wave ultrasonic wave, the measurement objectRepresents the anisotropy of shear wave velocityFind the sound speed parameterTheUsing the sound speed parameter,A sound velocity parameter representing the recrystallization rate and the anisotropy of the shear wave sound velocity for the same kind of material as the measurement object set in advance;And calculating means for obtaining a recrystallization rate for the measurement object based on data indicating the correlation between the measurement object and the measurement object.
[0008]
  The invention according to claim 2 is the recrystallization rate measuring apparatus according to claim 1,The ultrasonic wave generator includes a cylindrical lens that irradiates the surface of the measurement object as a line focus beam with the first laser beam incident from the first optical fiber that guides the first laser beam, and the beam acquisition unit includes: A first lens for condensing the second laser beam at the predetermined position, and a half mirror and a second lens for reflecting and condensing the second laser beam reflected at the predetermined position. The second optical fiber leads to the frequency change detecting means.
[0010]
  The invention according to claim 3 for achieving the above object is a plate-like object to be measured.The first laser beam is focused and irradiated on the surface of the object by generating and propagating ultrasonic waves inside the object to be measured, and the second laser beam is irradiated to the predetermined position from the surface to reflect the reflected light. And a laser ultrasonic method for detecting the propagated ultrasonic wave by using a frequency change detecting means.A recrystallization rate measuring method for measuring a recrystallization rate,Said1st laser beamBy the head partSurface of the measurement objectBy irradiating as a line focus beam, it is polarized in a predetermined direction with respect to the line of the line focus beam inside the measurement object.First to generate shear wave ultrasoundprocedureAnd the measurement objectOn the surface, the transverse ultrasonic waves are reflected on the bottom surface of the measurement object and reach the surface by the head unit on a straight line that passes through the center point of the line focus beam and is orthogonal.A second laser beam that guides the second laser beam to a predetermined position and acquires the second laser beam reflected at the predetermined position.procedureAnd the secondprocedureOn the basis of the second laser beam acquired in step (2), a change in the frequency of the second laser beam caused by the vibration of the transverse ultrasonic wave isAs a change in transmitted light intensity with frequency change detection meansDetect thirdprocedureWhen,Repeatedly irradiating the surface of the measurement object with the first laser beam so that the direction of the line is in the width direction and the longitudinal direction of the measurement object, respectively. A first transverse ultrasonic wave polarized in the longitudinal direction and a second transverse ultrasonic wave polarized in the width direction are generated, and the frequency of the reflected second laser beam caused by each transverse ultrasonic wave is generated. A first step of detecting waveform data of transmitted light intensity change representing a change;SaidoneDetected in step, Transmitted light intensity change for each of the first transverse wave ultrasonic wave and the second transverse wave ultrasonic waveBased on waveform data representing, First shear wave ultrasound and secondShear wave ultrasoundAbout eachThe inside of the measurement objectTo the predetermined positionDetermine the propagation timetwoStepWhen,The first transverse wave ultrasonic wave and the second transverse wave ultrasonic waveFor eachPropagation timeAnd the distance traveledOn the basis of theeachCalculate the sound velocity of shear wave ultrasonic wavethreeA sound velocity parameter that represents the anisotropy of the transverse sound velocity for the measurement object using the step, the sound velocity of the first transverse wave ultrasonic wave, and the sound velocity of the second transverse wave ultrasonic wave.FourSteps,Pre-set material of the same type as the measurement objectData showing the correlation between recrystallization rate and sound velocity parameterToOn the basis of,SaidA recrystallization rate for the object to be measured is obtained using a sound speed parameter.FiveSteps,Consists ofIt is characterized by that.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram of a recrystallization rate measuring apparatus according to an embodiment of the present invention, FIG. 2 is a schematic configuration diagram of a head portion in the recrystallization rate measuring apparatus, and FIG. 3 is a recrystallization rate and sound velocity of a steel type. It is a graph which shows the correlation with a parameter.
[0014]
The recrystallization rate measuring apparatus of this embodiment measures the recrystallization rate of a measurement object in a non-contact manner. Here, as an object to be measured, for example, a steel plate (thick plate) manufactured by a hot process is assumed in an ironworks. The surface temperature of such a thick plate is usually about 700 ° C. The thickness of the thick plate is about 10 mm to 100 mm. In the present embodiment, a case is considered where the crystal grain aspect ratio of the measurement object is substantially the same. For example, a measurement object having a crystal grain aspect ratio of 2 to 3 is used. Here, the crystal grain aspect ratio is the ratio of the crystal grain size in the longitudinal direction (rolling direction) of the steel material to the crystal grain size in the width direction of the steel material.
[0015]
In various steel materials, there is a close relationship between the recrystallization rate and a predetermined sound velocity parameter α obtained from the sound velocity of the transverse wave ultrasonic wave propagating through the steel material. An example of the correlation between the recrystallization rate and the sound speed parameter α for the steel types shown in FIG. 3 is shown. In FIG. 3, the horizontal axis represents the recrystallization rate of the steel material, and the vertical axis represents the sound velocity parameter α. Recrystallization is a phenomenon in which new crystal nuclei are generated at a grain boundary having a large strain, grow gradually, and the original crystal grains are replaced with the new crystal grains (recrystallized grains). The recrystallization rate is the ratio of recrystallized grains in a certain region. Further, the sound velocity parameter α represents the anisotropy of the sound velocity of the transverse wave ultrasonic wave propagating through the steel material, and (V_S1-V_S2) / {(V_S1+ V_S2) / 2}. Where V_S1Is the sound velocity of the transverse ultrasonic wave polarized in the longitudinal direction (rolling direction) of the steel material, and V_S2Is the speed of sound of transverse ultrasonic waves polarized in the width direction of the steel material.
[0016]
In the example of the graph of FIG. 3, it can be seen that the smaller the recrystallization rate of the steel material, the larger the absolute value of the sound velocity parameter α, and thus the greater the anisotropy of the shear wave sound velocity. It can also be seen that the larger the recrystallization rate of the steel material, the smaller the absolute value of the sound velocity parameter α, and therefore the smaller the anisotropy of the shear wave sound velocity. For example, immediately after rolling the steel material, recrystallized grains have not yet occurred, so the recrystallization rate is 0%. And the steel material just after this rolling has the same crystal orientation, and the anisotropy of a transverse wave sound speed is large. In the example of the graph of FIG. 3, the point plotted at the bottom left corresponds to the state immediately after rolling. In addition, since the recrystallized grains grow so that the crystal orientation becomes random, the anisotropy of the transverse wave speed decreases as the recrystallization rate approaches 100%. In the example of the graph of FIG. 3, the points plotted on the upper right correspond to the state where recrystallization has progressed.
[0017]
In the recrystallization rate measuring apparatus of the present embodiment, the sound velocity V of the transverse wave propagating in the steel material._S1, V_S2Then, the recrystallization rate of the steel material is obtained using the relationship between the recrystallization rate and the sound velocity parameter α as shown in FIG. At this time, the sound velocity of the transverse wave in the steel material is calculated using a laser ultrasonic method.
[0018]
As shown in FIG. 1, the recrystallization rate measuring apparatus of the present embodiment includes an ultrasonic generation laser 10, an ultrasonic detection laser 20, a head unit 30, an interferometer (frequency change detection means) 50, A photodetector 60 and a computer (calculation means) 70 are provided. In addition, this recrystallization rate measuring device is provided with optical fibers 91a, 91b, 91c, a condensing lens 92, and the like as optical components.
[0019]
The ultrasonic wave generation laser 10 is a laser for exciting ultrasonic waves in the measurement object 2. Examples of the ultrasonic generation laser 10 include a YAG laser and a CO.₂ A high energy pulsed laser such as a laser is used. The laser beam emitted from the ultrasonic wave generation laser 10 is guided to the head unit 30 via the optical fiber 91a.
[0020]
The ultrasonic detection laser 20 is a laser for detecting an ultrasonic wave generated in the measurement object 2 by being irradiated with the laser beam from the ultrasonic wave generation laser 10 and propagating through the measurement object 2. As the ultrasonic detection laser 20, a laser that emits a single-frequency laser beam is used. The laser beam emitted from the ultrasonic detection laser 20 is guided to the head unit 30 via the optical fiber 91b.
[0021]
As shown in FIG. 2, the head unit 30 includes an ultrasonic wave generation unit 31 and a beam acquisition unit 41. The ultrasonic generator 31 generates a first transverse ultrasonic wave polarized in the rolling direction of the measuring object 2 (rolling direction polarized transverse wave) inside the measuring object 2, and the inside of the measuring object 2. The second transverse wave ultrasonic wave (width direction polarization transverse wave) polarized in the width direction of the measurement object 2 is generated. The ultrasonic generator 31 includes a cylindrical lens 35 and a rotating mechanism (not shown) of the cylindrical lens 35.
[0022]
The laser beam guided to the ultrasonic wave generation unit 31 by the optical fiber 91 a is incident on the cylindrical lens 35. The cylindrical lens 35 condenses the laser beam from the ultrasonic wave generation laser 10 in a line shape and irradiates the surface of the measuring object 2 as a line focus beam (first laser beam) L1.
[0023]
In the present embodiment, for example, the diameter of the laser beam from the ultrasonic wave generation laser 10 is about 5 mm at the emission end of the optical fiber 91a. As the laser beam travels, its diameter increases. The distance between the emission end of the optical fiber 91a and the cylindrical lens 35 is adjusted so that the diameter of the laser beam is about 10 mm on the incident surface of the cylindrical lens 35. Further, the characteristics of the cylindrical lens 35, the cylindrical lens 35, the measurement object 2, and the like so that the line focus beam L 1 having a length of 10 mm and a width of 0.3 mm to 0.5 mm is irradiated on the surface of the measurement object 2. The distance etc. are designed.
[0024]
Further, the axis of the cylindrical lens 35 in the longitudinal direction can be directed in an arbitrary direction within a plane parallel to the surface of the measuring object 2 by the rotation mechanism of the cylindrical lens 35. This rotation mechanism is controlled by the computer 70, for example.
[0025]
When the surface of the measurement object 2 is irradiated with the line focus beam L1, it is possible to generate ultrasonic waves that travel obliquely at a predetermined angle φ with respect to the surface of the measurement object 2. At this time, the transverse wave ultrasonic wave and the longitudinal wave ultrasonic wave are generated simultaneously, and the traveling direction angle φ differs between the transverse wave ultrasonic wave and the longitudinal wave ultrasonic wave. In the present embodiment, only the transverse wave among the ultrasonic waves is mainly considered. This is because it is sufficient to obtain sound velocity information on the transverse wave to obtain the recrystallization rate from the relationship between the recrystallization rate and the sound velocity parameter α shown in FIG.
[0026]
Specifically, when the surface of the measurement object 2 is irradiated with the line focus beam L1 so that the direction of the line is parallel to the width direction of the measurement object 2, a polarization direction transverse wave in the rolling direction is generated, When the surface of the measurement object 2 is irradiated with the line focus beam L1 so that the direction of the line is parallel to the rolling direction of the measurement object 2, a transverse polarized wave is generated.
[0027]
When the surface of the measurement object 2 is irradiated with a point laser beam, ultrasonic waves that travel in various directions with respect to the surface of the measurement object 2 are generated. Naturally, these ultrasonic waves include rolling direction polarization transverse waves and width direction polarization transverse waves. However, since the intensity is small, it is necessary to accurately detect the rolling direction polarization transverse waves and the width direction polarization transverse waves. It is difficult. For this reason, in the present embodiment, by using the line focus beam L1 and changing the direction of the line, the rolling direction polarization transverse wave and the width direction polarization transverse wave are independently generated.
[0028]
The beam acquisition unit 41 detects the ultrasonic waves of the rolling direction polarization transverse wave and the width direction polarization transverse wave at a position (detection point position) where the ultrasonic wave is reflected on the bottom surface of the measurement object 2 and returned to the surface again. The second laser beam L2 emitted from the ultrasonic detection laser 20 is guided and the second laser beam L2 reflected by the surface of the measurement object 2 is acquired. The beam acquisition unit 41 includes condensing lenses 45 a and 45 b and a half mirror 46. Moreover, the beam acquisition part 41 is comprised integrally, and can move along a rolling direction and the width direction.
[0029]
The second laser beam L2 guided to the beam acquisition unit 41 by the optical fiber 91b is condensed by the condenser lens 45a, passes through the half mirror 46, and is irradiated to the detection point position on the measurement object 2. Here, since the traveling direction angle φ of the transverse wave ultrasonic wave propagating inside the measurement object 2 is known in advance, the position of the detection point of the transverse wave ultrasonic wave can be easily known. The beam acquisition unit 41 guides the second laser beam L2 condensed by the condenser lens 45a to the detection point position.
[0030]
Further, in the present embodiment, the beam acquisition unit 41 guides the second laser beam L2 on a straight line that passes through a substantially central point of the line focus beam L1 and intersects with the line and the surface of the measurement object 2. I have decided. That is, the predetermined position on the straight line becomes the detection point position. For example, at the end point of the line focus beam L1, the situation is the same as when a point laser beam is irradiated, and ultrasonic waves are generated in various directions. For this reason, ultrasonic waves generated in various directions return on a straight line where the plane perpendicular to the line passing through the end point of the line focus beam L1 and the surface of the measurement object 2 intersect, so that they are deviated in a predetermined direction. It is not possible to accurately detect the transverse wave that has been waved. On the other hand, since only a transverse wave polarized in a predetermined direction is generated at the approximate center point of the line focus beam L1, the plane perpendicular to the line passing through the approximate center point of the line focus beam L1 and the surface of the measurement object 2 By making the predetermined position on the straight line where the crosses with the detection point position, the transverse wave polarized in the predetermined direction can be accurately detected.
[0031]
Since the surface of the measuring object 2 is a rough surface, the second laser beam L2 is scattered almost isotropically on the surface of the measuring object 2. At this time, when the ultrasonic wave propagating through the measurement object 2 returns to the detection point position, the detection point position undergoes ultrasonic vibration. Thus, the frequency of the second laser beam L2 scattered on the surface of the measurement object 2 is changed by receiving a Doppler shift caused by ultrasonic vibration of the surface of the measurement object 2.
[0032]
A part of the second laser beam L2 scattered on the surface of the measurement object 2 is reflected by the half mirror 46, collected by the condenser lens 45b, and then enters the optical fiber 91c. The optical fiber 91c guides the second laser beam L2 to the interferometer 50. The second laser beam L2 emitted from the optical fiber 91c is collected by the condenser lens 92 and then enters the interferometer 50.
[0033]
As the interferometer 50, for example, a Fabry-Perot interferometer is used. The Fabry-Perot interferometer 50 detects a change in the frequency of the second laser beam L2 caused by ultrasonic vibration, and has two reflecting mirrors facing each other. The two reflecting mirrors constitute a resonator, and function as a band-pass filter by multiple reflection of the second laser beam L2 between the two reflecting mirrors. By adjusting the distance between the two reflecting mirrors, the frequency of light transmitted through the resonator can be adjusted.
[0034]
Here, a resonance curve in the Fabry-Perot interferometer 50 will be described. FIG. 4 shows an example of this resonance curve. In FIG. 4, the horizontal axis indicates the frequency f of the incident light, and the vertical axis indicates the output from the Fabry-Perot interferometer 50, that is, the intensity I of the light transmitted through the Fabry-Perot interferometer 50. As can be seen from FIG. 4, the transmitted light intensity I shows a sharp peak at a specific frequency, but rapidly decreases before and after the peak. The frequency showing this peak can be changed by adjusting the distance between the reflecting mirrors of the Fabry-Perot interferometer 50. Therefore, if the distance between the reflecting mirrors is adjusted so that the frequency at the point (resonance curve operating point) A at which the slope of the curve shown in FIG. 4 is maximum coincides with the oscillation frequency of the second laser beam L2. A slight change ± Δf in frequency can be converted into a relatively large change ± ΔI in transmitted light intensity. As a result, the Fabry-Perot interferometer 50 transmits the change in frequency when the second laser beam L2 whose frequency has been changed due to Doppler shift caused by ultrasonic vibration of the surface of the measurement object 2 is input. Output as change in light intensity.
[0035]
The transmitted light intensity output from the Fabry-Perot interferometer 50 is sent to the photodetector 60. The photodetector 60 converts transmitted light intensity into an electric signal. Thereby, the ultrasonic vibration is finally captured as an electrical signal. A signal from the photodetector 60 is sent to the computer 70 and recorded as waveform data.
[0036]
For each of the transverse ultrasonic waves in the rolling direction and in the width direction, the computer 70 applies the transverse ultrasonic waves to the inside of the measurement object 2 based on the waveform data representing the frequency change of the second laser beam L2. Propagation time is calculated until it propagates, reflects off its bottom surface, and returns to the surface. The timing at which the laser beam is emitted from the ultrasonic wave generation laser 10 and the timing at which the line focus beam L1 irradiates the measurement object 2 are known in advance. For this reason, the computer 70 can obtain the propagation time of the transverse ultrasonic wave by examining the timing at which the frequency change is detected based on the waveform data sent from the photodetector 60.
[0037]
Further, the computer 70 determines the sound velocity V of the rolling direction polarization transverse wave based on the propagation time of the rolling direction polarization transverse wave._S1And the sound velocity V of the transverse polarization transverse wave based on the propagation time of the transverse polarization transverse wave_S2Is calculated. And the calculated sound velocity V of the transverse wave in the rolling direction is calculated._S1And the speed of sound V of the transversely polarized transverse wave_S2Is used to determine the sound speed parameter α = (V_S1-V_S2) / {(V_S1+ V_S2) / 2}.
[0038]
The storage unit of the computer 70 stores data indicating the correlation between the recrystallization rate and the sound speed parameter α for each steel type as shown in FIG. The computer 70 obtains the recrystallization rate for the measurement object 2 based on the data indicating the correlation for the same steel type as the measurement object stored in the storage unit, using the obtained sound speed parameter α.
[0039]
The user needs to obtain in advance data indicating the correlation between the recrystallization rate and the sound speed parameter α for each steel type. In order to obtain data indicating such correlation, first, a plurality of samples (thick plates) are prepared for each steel type. Here, as the sample, a thick plate having a thickness of about 5 mm and a crystal grain aspect ratio of approximately the same, for example, 2 to 3, is used. Then, for each sample, the recrystallization rate and the sound speed parameter α are obtained individually. Specifically, the recrystallization rate is obtained by observing a cross section when the sample is cut along a plane perpendicular to the longitudinal direction with a microscope and measuring the proportion of recrystallized grains in a certain region. . On the other hand, the sound speed parameter α is obtained by using, for example, the apparatus of this embodiment. When the recrystallization rate and the sound speed parameter α thus obtained are represented by a graph, a graph as shown in FIG. 3 is obtained. In general, since the relationship between the recrystallization rate and the sound velocity parameter α differs for each steel type, this relationship is determined for each steel type.
[0040]
By the way, when obtaining the sound speed parameter α of the sample, it is desirable to use an apparatus as shown in FIG. 5 instead of the apparatus shown in FIG. FIG. 5 is a view for explaining a modification of the recrystallization rate measuring apparatus of the present embodiment. The recrystallization rate measuring apparatus shown in FIG. 5 includes an ultrasonic generation laser 10, an ultrasonic detection laser 20, an ultrasonic generation unit 31a, a beam acquisition unit 41a, an interferometer 50, and a photodetector 60. The computer 70 and the rotary stage 100 are provided. In the recrystallization rate measuring apparatus of FIG. 5, the same reference numerals are given to those having the same functions as those of the apparatus of FIG. 1, and detailed description thereof is omitted.
[0041]
The recrystallization rate measuring apparatus of FIG. 5 is mainly different from the apparatus shown in FIG. The first point is that the direction of the line focus beam L1 is changed by placing the measurement object 2 on the rotary stage 100 and rotating the rotary stage 100. That is, the ultrasonic wave generation unit 31 a does not have a rotating mechanism for the cylindrical lens 35. The second point is that the ultrasonic wave generation unit 31a and the beam acquisition unit 41a are configured separately, and the beam acquisition unit 41a is disposed on the opposite side of the ultrasonic wave generation unit 31a via the measurement object 2. That is, the beam acquisition unit 41a guides the second laser beam L2 to the position of the bottom surface of the measurement object 2 to which the transverse ultrasonic waves reach for each ultrasonic wave of the rolling direction polarization transverse wave and the width direction polarization transverse wave. The second laser beam L2 reflected from the bottom surface of the measurement object 2 is acquired. Other configurations are substantially the same as those of the recrystallization rate measuring apparatus of FIG.
[0042]
The recrystallization rate measuring apparatus shown in FIG. 5 has a simple configuration, and is particularly suitable for measuring a measurement object 2 that is not so large. Therefore, it is suitable for obtaining the sound speed parameter for the above-described sample. However, since this measurement object 2 is placed on the rotary stage 100, this apparatus cannot be used when performing hot online measurement.
[0043]
Next, a procedure for measuring the recrystallization rate of the measuring object 2 in the recrystallization rate measuring apparatus of the present embodiment will be described. FIG. 6 is a flowchart for explaining the procedure for measuring the recrystallization rate of the measuring object 2 in the recrystallization rate measuring apparatus.
[0044]
First, the computer 70 controls the rotation mechanism of the cylindrical lens 35 so that the longitudinal direction of the cylindrical lens 35 is the width direction (S1). Thereafter, a laser beam is emitted from the ultrasonic wave generation laser 10 and a second laser beam L2 is emitted from the ultrasonic wave detection laser 20. The laser beam from the ultrasonic wave generation laser 10 is condensed into a line shape by the cylindrical lens 35 and is irradiated onto the surface of the measurement object 2 as a line focus beam L1. At this time, since the direction of the line of the line focus beam L1 is parallel to the width direction of the measurement object 2, a rolling direction polarization transverse wave is generated inside the measurement object 2. When the second laser beam L2 scattered on the surface of the measurement object 2 is incident on the Fabry-Perot interferometer 50, the Fabry-Perot interferometer 50 is caused by vibration of ultrasonic waves in the rolling direction. The frequency change of the generated second laser beam L2 is detected. And the computer 70 calculates | requires the propagation time of a rolling direction displacement transverse wave based on the waveform data showing the frequency change (S2). This propagation time is stored in a predetermined memory of the computer 70.
[0045]
Next, the computer 70 controls the rotation mechanism of the cylindrical lens 35 so that the longitudinal direction of the cylindrical lens 35 is the rolling direction (S3). Thereafter, a laser beam is emitted from the ultrasonic wave generation laser 10 and a second laser beam L2 is emitted from the ultrasonic wave detection laser 20. At this time, since the direction of the line focus beam L1 collected by the cylindrical lens 35 is parallel to the rolling direction of the measuring object 2, a transversely polarized transverse wave is generated inside the measuring object 2. When the second laser beam L2 scattered on the surface of the measurement object 2 is incident on the Fabry-Perot interferometer 50, the Fabry-Perot interferometer 50 is caused by the vibration of the ultrasonic waves of the transversely polarized transverse waves. The frequency change of the generated second laser beam L2 is detected. Then, the computer 70 obtains the propagation time of the transversely polarized transverse wave based on the waveform data representing the frequency change (S4). This propagation time is stored in a predetermined memory of the computer 70.
[0046]
Once the propagation times for the rolling direction polarization transverse wave and the width direction polarization transverse wave are determined based on the waveform data thus detected, the computer 70 then calculates the rolling direction based on the propagation time of the rolling direction polarization transverse wave. Sound velocity of polarized shear wave V_S1And the sound velocity V of the transversely polarized transverse wave based on the propagation time of the transversely polarized transverse wave_S2Is calculated (S5). And the speed of sound V of the transverse wave in the rolling direction V_S1And the speed of sound V_S2Is used to obtain the sound speed parameter α (S6). Thereafter, the computer 70 uses the data indicating the relationship between the recrystallization rate and the sound velocity parameter α for the same kind of steel material as the measurement object 2 stored in the storage unit, and calculates the sound velocity parameter α of the measurement object 2. The recrystallization rate of the measurement object 2 is obtained (S7). The recrystallization rate of the measurement object 2 obtained in this way is displayed on the screen of the computer 70, for example.
[0047]
In the recrystallization rate measuring apparatus of this embodiment, by using a laser ultrasonic method, a transverse wave ultrasonic wave traveling obliquely with respect to the surface is generated inside a measurement object, and a transverse wave ultrasonic wave polarized in the rolling direction is generated. For each of the sound wave and the transverse wave polarized wave in the width direction, the propagation time of the transverse wave ultrasonic wave propagating through the object to be measured is obtained, and the sound velocity of the transverse wave ultrasonic wave is calculated based on the obtained propagation time. . Then, the sound velocity parameter for the measurement object is obtained using the sound velocity of the transverse polarization transverse wave and the sound velocity of the transverse polarization transverse wave, and the measurement object stored in the storage unit of the computer is obtained using the obtained sound velocity parameter. Based on the data showing the relationship between the recrystallization rate and the sound velocity parameter for the same steel type, the recrystallization rate for the measurement object is obtained. Therefore, if the recrystallization rate measuring apparatus of this embodiment is used, the recrystallization rate of a measuring object can be calculated | required hot online. For this reason, by feeding forward information on the recrystallization rate to, for example, the rolling conditions of the next process, it becomes possible to efficiently and stably manufacture a steel material with a fine structure, and to manufacture a highly accurate steel material. It can also contribute to the reduction of material variations due to technology.
[0048]
In addition, this invention is not limited to said embodiment, A various deformation | transformation is possible within the range of the summary.
[0049]
For example, in the above-described embodiment, by irradiating the surface of the measurement object with the line focus beam, a transverse wave is generated inside the measurement object, and the generated transverse wave is detected to obtain the sound velocity of the transverse wave. Although the longitudinal wave is generated at the same time as the transverse wave, the sound velocity of the transverse wave is obtained by detecting the mode-converted transverse wave, which is a component that converts the longitudinal wave into a transverse wave at the bottom surface of the measurement object. May be. However, in this case, it is necessary to detect a reflected longitudinal wave that has not undergone mode conversion on the bottom surface of the measurement object.
[0050]
In the above embodiment, the case where a thick plate manufactured by a hot process is used as a measurement object has been described. However, the recrystallization rate measuring apparatus of the present invention is not limited to any metal other than the thick plate. It can also be applied to.
[0051]
【The invention's effect】
As described above, in the recrystallization rate measuring apparatus of the present invention, by using the laser ultrasonic method, the transverse wave ultrasonic wave traveling obliquely with respect to the surface is generated inside the measurement object, and the recrystallization rate measuring apparatus is biased in the rolling direction. For each of the first transverse wave ultrasonic wave and the second transverse wave ultrasonic wave polarized in the width direction, the propagation time of the transverse wave ultrasonic wave propagating through the object to be measured is obtained, and based on the obtained propagation time. To calculate the speed of sound of the transverse ultrasonic waves. Then, the sound velocity parameter for the measurement object is obtained using the sound velocity of the first transverse wave ultrasonic wave and the sound velocity of the second transverse wave ultrasonic wave, and the measurement object stored in the storage means using the obtained sound velocity parameter. Based on the data showing the relationship between the recrystallization rate and the sound velocity parameter for the same steel type, the recrystallization rate for the measurement object is obtained. Therefore, when the recrystallization rate measuring apparatus of the present invention is used, the recrystallization rate of the measurement object can be obtained hot online.
[0052]
In addition, according to the recrystallization rate measuring method of the present invention, the recrystallization rate of the measurement object can be obtained hot online as described above.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a recrystallization rate measuring apparatus according to an embodiment of the present invention.
FIG. 2 is a schematic configuration diagram of a head portion in a recrystallization rate measuring apparatus.
FIG. 3 is a graph showing a correlation between a recrystallization rate and a sound velocity parameter for a certain steel type.
FIG. 4 is a diagram showing an example of a resonance curve of a Fabry-Perot interferometer in the recrystallization rate measuring apparatus of the present embodiment.
FIG. 5 is a diagram for explaining a modification of the recrystallization rate measuring apparatus of the present embodiment.
FIG. 6 is a flowchart for explaining a procedure for measuring a recrystallization rate of a measurement object in the recrystallization rate measuring apparatus of the present embodiment.
[Explanation of symbols]
2 ... Measurement object
10 ... Laser for ultrasonic generation
20 ... Laser for ultrasonic detection
30 ... Head
31, 31a ... ultrasonic wave generator
35 ... Cylindrical lens
41, 41a ... Beam acquisition unit
45a, 45b ... Condensing lens
46 ... Half Mirror
50 ... Interferometer
60. Photodetector
70: Computer
91a, 91b, 91c ... optical fiber
92 ... Condensing lens
100 ... Rotation stage

Claims (3)

The first laser beam is focused and irradiated onto the surface of the plate-shaped measurement object by the head unit to generate and propagate an ultrasonic wave inside the measurement object, and the second laser beam is moved from the surface to a predetermined position. A recrystallization rate measuring apparatus for measuring a recrystallization rate by a laser ultrasonic method for detecting the propagated ultrasonic wave using a frequency change detection means from irradiation and reflection thereof ,
The head unit irradiates the surface of the measurement target with the first laser beam as a line focus beam , whereby a transverse wave polarized in a predetermined direction with respect to the line of the line focus beam inside the measurement target. an ultrasonic generator for generating ultrasonic waves,
On the surface of the measurement object, the second ultrasonic wave is on a straight line passing through the center point of the line focus beam and orthogonal to the predetermined position where the transverse wave ultrasonic wave is reflected from the bottom surface of the measurement object and returns to the surface. with guiding the laser beam, is composed of a beam acquisition unit for acquiring said second laser beam reflected by the predetermined position,
It said frequency change detecting means, on the basis of the said second laser beam obtained by the beam acquiring unit, as the transmitted light intensity changes a change in frequency of the second laser beam caused by the vibration of the transverse ultrasonic waves Detect
Furthermore, the ultrasonic wave generator has a rotation mechanism, and irradiates the first laser beam with the line focus beam line direction on the surface to be measured parallel to the width direction and the longitudinal direction of the measurement object. The first transverse wave ultrasonic wave polarized in the longitudinal direction in the direction of each line and the second transverse wave ultrasonic wave polarized in the width direction are generated,
Wherein for each of the first transverse ultrasonic waves and said second transverse ultrasonic wave, on the basis of the waveform data of the transmitted light intensity variations representing a frequency change of said detected by the frequency deviation detection means second laser beam, each internally it obtains a propagation time obtained by propagation of transverse ultrasonic waves the measurement object, the determined and calculated respective transverse ultrasonic wave sound velocity on the basis of the propagation time and the transverse ultrasonic propagation distances of the previous SL first calculated sound velocity parameter representative of the anisotropy of the shear wave velocity of the measurement object by using the acoustic velocity of transverse ultrasonic waves of sound velocity and said second transverse ultrasonic waves, using the speed of sound parameters, preset the measuring Computation means for obtaining the recrystallization rate for the measurement object based on data indicating the correlation between the recrystallization rate for the same kind of material as the object and the sound velocity parameter representing the anisotropy of the transverse sound velocity. Characteristic Recrystallization rate measuring device that. The ultrasonic wave generator includes a cylindrical lens that irradiates the surface of the measurement object as a line focus beam with the first laser beam incident from a first optical fiber that guides the first laser beam, and the beam acquisition unit includes: A first lens for condensing the second laser beam at the predetermined position, and a half mirror and a second lens for reflecting and condensing the second laser beam reflected at the predetermined position. The recrystallization rate measuring device according to claim 1, wherein the frequency change detecting means is guided by a second optical fiber. The first laser beam is focused and irradiated onto the surface of the plate-shaped measurement object by the head unit to generate and propagate an ultrasonic wave inside the measurement object, and the second laser beam is moved from the surface to a predetermined position. A recrystallization rate measurement method for measuring a recrystallization rate by a laser ultrasonic method for detecting the propagated ultrasonic wave using a frequency change detection means from the reflected light, and comprising:
By irradiating with a line-focused beam to the surface of the object by the head portion of the first laser beam, transverse wave than that polarization in a predetermined direction relative to the internal line focus beam line of the measurement object A first step of generating sound waves;
On the surface of the measurement target, the head unit is on a straight line that passes through and is orthogonal to the center point of the line focus beam, and the transverse wave ultrasonic wave is reflected by the bottom surface of the measurement target and reaches a predetermined position. guides the second laser beam, and a second procedure for obtaining said second laser beam reflected by said predetermined position,
On the basis of the said second laser beam obtained by the second procedure, detecting a change in the frequency of the second laser beam caused by the vibration of the transverse ultrasonic wave as transmitted light intensity changes with the frequency change detecting means Repeat the third step ,
By irradiating the first laser beam on the surface of the transverse and longitudinal directions and such the measurement target in the so that the orientation of the line is the measurement object, the longitudinal direction in the interior of each of the measurement object The first transverse wave ultrasonic wave polarized in the direction and the second transverse wave ultrasonic wave polarized in the width direction are generated, and the change in the frequency of the reflected second laser beam caused by the respective transverse wave ultrasonic wave is expressed. A first step of detecting waveform data of transmitted light intensity change;
Based on the waveform data representing the transmitted light intensity change for each of the first transverse wave ultrasonic wave and the second transverse wave ultrasonic wave detected in the first step , the first transverse wave ultrasonic wave and the second transverse wave ultrasonic wave wherein a second step of obtaining the propagation time having propagated inside the measured object to the predetermined position, for each of the first transverse ultrasonic wave and the second transverse ultrasonic waves for each of the distance propagated to the propagation time A third step of calculating the speed of sound of each shear wave based on,
A fourth step of obtaining a sound speed parameter representing the anisotropy of shear wave velocity of the measurement object using the speed of sound in the first transverse ultrasonic wave sound velocity and said second transverse ultrasonic waves, is set in advance based on the data showing the correlation between the recrystallization ratio and the acoustic velocity parameters of the material of the object to be measured the same type, and a fifth step of obtaining a recrystallization ratio of the object to be measured using the acoustic velocity parameters , in configured recrystallization ratio measuring method comprising Rukoto.

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