JP2022103832A - Electromagnetic ultrasonic inspection device - Google Patents

Abstract

To provide an electromagnetic ultrasonic inspection device capable of performing flaw detection scanning of a test object in a direction perpendicular to the arrangement direction of magnets of an electromagnetic ultrasonic probe.SOLUTION: An electromagnetic ultrasonic inspection device of the invention includes: a magnet array 13 having a plurality of magnets 11 arranged in the axial direction of piping 1 and alternately arranged so that the outer side of the piping 1 in the radial direction becomes an N pole or an S pole; an electromagnetic ultrasonic probe 10 having coils (14A to 14D) wound around the magnet array 13 with the circumferential direction of the piping 1 as the central axis and separated from each other in the circumferential direction of the piping 1; a flaw detection device 20; and a calculation device 30. The flaw detection device 20 records a plurality of reception signals corresponding to the combination of the transmission coil and the reception coil by selecting and controlling the combination of the transmission coil and the reception coil among the coils 14A to 14D. The calculation device 30 extracts and sums the intensities of the plurality of received signals based on the propagation time of the ultrasonic waves for each position in the piping 1, and generates a flaw detection image showing the distribution of the summed intensities.SELECTED DRAWING: Figure 1

Description

The present invention relates to an electromagnetic ultrasonic inspection device including an electromagnetic ultrasonic probe.

As a method of performing a flaw detection inspection of a subject by ultrasonic waves, there are a method using an ultrasonic probe and a method using an electromagnetic ultrasonic probe (see, for example, Patent Document 1).

The ultrasonic probe includes a piezoelectric element that converts an electric signal and an ultrasonic wave, and contacts the surface of a subject via a contact medium. The ultrasonic probe transmits ultrasonic waves to the subject via the contact medium, and receives ultrasonic waves reflected by internal defects (specifically, cracks or the like) of the subject via the contact medium.

The electromagnetic ultrasonic probe of Patent Document 1 includes a magnet array having a plurality of magnets and one coil wound around the magnet array.

The plurality of magnets are arranged in one direction and in two rows along the surface of the subject. More specifically, the magnets in the first row are arranged so that one side in the direction perpendicular to the surface of the subject is the north pole and the other side is the south pole. The magnets in the second row are arranged so that one side in the direction perpendicular to the surface of the subject is the south pole and the other side is the north pole. The magnets in the first row and the magnets in the second row are arranged so as to alternate in the one direction. Therefore, the plurality of magnets are alternately arranged so that one side in the direction perpendicular to the surface of the subject becomes the north pole or the south pole. As a result, a static magnetic field (periodic magnetic field) is generated in which the direction of the magnetic field in the direction perpendicular to the surface of the subject changes alternately.

The coil is wound around the magnet array along the surface of the subject and with the other direction perpendicular to the one direction (that is, the direction of arrangement of the magnets) as a central axis.

The flaw detector applies a transmission signal (pulse signal) to the coil of the electromagnetic ultrasonic probe to generate an eddy current in the surface layer portion of the subject to which the coil faces. Then, ultrasonic waves are generated on the surface layer of the subject by the interaction between this eddy current and the static magnetic field of a plurality of magnets. This ultrasonic wave is propagated at a transmission angle (specifically, an angle oblique to the thickness direction of the subject) toward the arrangement direction of the magnet, is reflected by a defect inside the subject, and is reflected on the surface layer of the subject. Come back to the club. The flaw detector acquires a received signal (waveform signal) generated in the coil by the returned ultrasonic wave by an action opposite to the above-mentioned action. Thereby, the defect of the subject is detected.

Japanese Unexamined Patent Publication No. 2014-081235

The electromagnetic ultrasonic probe is expected to be fixed around the pipe, for example, to perform a flaw detection inspection of the pipe during operation (specifically, for example, when a high temperature fluid is flowing). When using an ultrasonic probe, for example, it is necessary to use an adhesive as a contact medium to maintain the contact state between the surface of the pipe and the probe, but when using an electromagnetic ultrasonic probe, the contact state is maintained. There is no need. Further, if a magnet having high heat resistance (specifically, for example, a samarium-cobalt magnet) is used as the magnet of the electromagnetic ultrasonic probe, the probe can be arranged even in a high temperature environment of 200 to 300 ° C. ..

In the electromagnetic ultrasonic probe of Patent Document 1, one direction of the probe (in other words, the arrangement direction of magnets) is obtained by changing the frequency of the transmission signal applied to the coil to change the transmission angle of the ultrasonic wave. It is possible to perform a flaw detection scan of the subject in. However, it is not possible to perform a flaw detection scan of the subject in the other direction of the probe (in other words, the direction perpendicular to the arrangement direction of the magnets). Therefore, if the position of the probe is fixed, the inspection range of the probe is limited.

An object of the present invention is to provide an electromagnetic ultrasonic inspection apparatus capable of performing flaw detection scanning of a subject in a direction perpendicular to the arrangement direction of magnets of the electromagnetic ultrasonic probe.

In order to achieve the above object, the present invention is arranged in one direction along the surface of the subject, and alternately arranged so that one side of the subject in the direction perpendicular to the surface becomes an N pole or an S pole. A magnet array having a plurality of magnets formed therein, and wound around the magnet array about the other direction along the surface of the subject and perpendicular to the one direction, and separated from each other in the other directions. A combination of an electromagnetic ultrasonic probe having a plurality of coils and a transmission coil and a reception coil among the plurality of coils is selected, and a transmission signal is applied to the transmission coil so that the transmission coils face each other. In addition to generating ultrasonic waves on the surface layer portion of the subject, the reception coil generated on the receiving coil by the ultrasonic waves reflected inside the subject and returned to the surface layer portion of the subject facing the receiving coil. It is assumed that the ultrasonic wave is reflected at the position of each position inside the subject and the flaw detector that records a plurality of received signals corresponding to the combination of the transmitting coil and the receiving coil by acquiring the signal. Based on the propagation time of ultrasonic waves according to the combination of the transmitting coil and the receiving coil in the case of It is equipped with a computing device that generates an image.

According to the present invention, it is possible to perform flaw detection scanning of a subject in a direction perpendicular to the arrangement direction of the magnets of the electromagnetic ultrasonic probe.

It is a block diagram which shows the structure of the electromagnetic ultrasonic inspection apparatus in one Embodiment of this invention. It is a figure which shows the structure of the electromagnetic ultrasonic probe in one Embodiment of this invention together with a part of a pipe. It is a vertical cross-sectional view by arrow view III-III of FIG. It is a vertical cross-sectional view by arrow view IV-IV of FIG. It is an inclined sectional view by the xz coordinate system of FIG. 2, and shows an example of the propagation path of ultrasonic waves in this embodiment. It is a figure which shows the data of the received signal corresponding to the combination of the transmitting coil and the receiving coil in one Embodiment of this invention.

An embodiment of the present invention will be described with reference to the drawings. In the present embodiment, a case where a flaw detection inspection is performed on a pipe (specifically, for example, a welded portion extending in the circumferential direction of the pipe) will be described as an example.

FIG. 1 is a block diagram showing a configuration of an electromagnetic ultrasonic inspection device according to the present embodiment. FIG. 2 is a diagram showing the structure of the electromagnetic ultrasonic probe in the present embodiment together with a part of the pipe. FIG. 3 is a vertical cross-sectional view taken along the line III-III of FIG. FIG. 4 is a vertical cross-sectional view taken along the line IV-IV of FIG. FIG. 5 is an inclined cross-sectional view based on the xz coordinate system of FIG. 2, and shows an example of the propagation path of ultrasonic waves in the present embodiment. FIG. 6 is a diagram showing a plurality of received signals corresponding to the combination of the transmitting coil and the receiving coil in the present embodiment. In FIGS. 2, 4, and 5, the surface of the pipe is actually a curved surface, but is shown as a flat surface for convenience.

The electromagnetic ultrasonic inspection device of the present embodiment controls the electromagnetic ultrasonic probe 10 fixed around the pipe 1 (subject) and the electromagnetic ultrasonic probe 10 to record a plurality of received signals. The flaw detection device 20, a calculation device 30 that generates a flaw detection image based on a plurality of received signals recorded by the flaw detection device 20, and a display device 40 that displays the flaw detection image generated by the calculation device 30 (specifically, for example, for example). A display) and an input device 50 (specifically, for example, a keyboard or a mouse) connected to the calculation device 30. The calculation device 30 has a ROM for storing a program, a CPU for executing processing according to the program, and a RAM for storing the processing result.

The electromagnetic ultrasonic probe 10 includes a magnet array 13 having a plurality of magnets 11 and a resin cover 12 covering most of the magnets 11 other than the portion facing the pipe 1, and a plurality of magnet arrays 13 wound around the magnet array 13. In this embodiment, four coils 14A to 14D and a casing 15 for accommodating the magnet array 13 and the coils 14A to 14D are provided.

The plurality of magnets 11 are arranged in the axial direction of the pipe 1 (in other words, in one direction along the surface of the pipe 1) and in a row, and in the radial direction of the pipe 1 (in other words, the direction perpendicular to the surface of the pipe 1). They are arranged alternately so that the outer side becomes the north pole or the south pole. As a result, a static magnetic field (periodic magnetic field) in which the direction of the magnetic field in the radial direction of the pipe 1 changes alternately is generated. The pitch W (interval) of the magnet 11 is the same as the width of the magnet 11.

The coils 14A to 14D are wound around the magnet array 13 about the circumferential direction of the pipe 1 (in other words, the other direction along the surface of the pipe 1 and perpendicular to the one direction) as the central axis, and are wound around the circumference of the pipe 1. They are separated from each other in the direction. The coil pitch p (interval) is larger than the coil width e.

The flaw detection device 20 and the calculation device 30 of the present embodiment are called Full Matrix Capture (FMC) / Total Focusing Method (TFM) or Synthetic Aperture Focusing Technique (SAFT). Using the method, the flaw detection scan of the pipe 1 in the circumferential direction of the pipe 1 (in other words, the direction perpendicular to the arrangement direction of the magnets 11 of the electromagnetic ultrasonic probe 10) is performed.

The flaw detector 20 selects and controls the combination of the transmitting coil and the receiving coil among the coils 14A to 14D of the electromagnetic ultrasonic probe 10, and thereby a plurality of receiving signals corresponding to the combination of the transmitting coil and the receiving coil. Is to be recorded. The details will be explained.

The flaw detector 20 includes a demultiplexer 21 that selects one of the coils 14A to 14D as a transmission coil, a pulser 22 that applies a transmission signal (pulse signal) to the transmission coil selected by the demultiplexer 21, and a coil 14A. The multiplexer 23 that selects any of 14D as the receiving coil, the receiver 24 that acquires the received signal (waveform signal) of the receiving coil selected by the multiplexer 23, and the information of the combination of the transmitting coil and the receiving coil are associated with each other. A data recording unit 25 for recording a plurality of received signals is provided. The data recording unit 25 is composed of, for example, a hard disk or a memory.

First, the demultiplexer 21 selects the coil 14A as the transmission coil. The pulsar 22 applies a transmission signal to the coil 14A via the demultiplexer 21 to generate an eddy current in the surface layer portion of the pipe 1 with which the coil 14A faces. Then, due to the interaction between this eddy current and the magnetic field generated by each magnet 11, a Lorentz force is generated on the surface layer portion of the pipe 1 on which each magnet 11 faces, and the original wave is generated by the displacement of the surface layer portion of the pipe 1 due to the Lorentz force. generate. In FIG. 3, the vibration direction of the prime wave is actually a direction perpendicular to the paper surface, but is shown in a direction parallel to the paper surface for convenience.

Since the directions of the magnetic fields due to the adjacent magnets 11 are inverted by 180 degrees, the phases of the adjacent prime waves are also shifted by 180 degrees. The plurality of elemental waves generated in the surface layer portion of the pipe 1 on which the coils 14A face each other (in other words, the plurality of magnets 11 face each other) have a phase in the direction of the transmission angle θ represented by the following equation (1). Since they match, a composite wave having a transmission angle θ (specifically, an SH wave, hereinafter simply referred to as an ultrasonic wave) is formed. In the equation, λ is the wavelength of the ultrasonic wave, V is the speed of sound, and f is the frequency of the ultrasonic wave. As is clear from the equation (1), the ultrasonic transmission angle θ can be set by the ultrasonic frequency f (that is, the frequency of the transmission signal applied to the coil 14A). For example, if the ultrasonic frequency f = V / W is set, the ultrasonic transmission angle θ = 30 °.

The multiplexer 23 sequentially selects the coils 14A to 14D as the receiving coil. The coil 14A as a receiving coil is propagated from the surface layer portion of the pipe 1 facing the coil 14A as a transmitting coil, reflected by a defect 2 inside the pipe 1, and the surface layer of the pipe 1 facing the coil 14A as a receiving coil. The received signal is generated by the ultrasonic waves returned to the unit. The coil 14B as a receiving coil is propagated from the surface layer portion of the pipe 1 facing the coil 14A as a transmitting coil, reflected by a defect 2 inside the pipe 1, and the surface layer of the pipe 1 facing the coil 14B as a receiving coil. The received signal is generated by the ultrasonic waves returned to the unit. The coil 14C as a receiving coil is propagated from the surface layer portion of the pipe 1 facing the coil 14A as a transmitting coil, reflected by a defect 2 inside the pipe 1, and the surface layer of the pipe 1 facing the coil 14C as a receiving coil. A received signal is generated by the ultrasonic waves returned to the unit (see FIG. 5). The coil 14D as a receiving coil is propagated from the surface layer portion of the pipe 1 facing the coil 14A as a transmitting coil, reflected by a defect 2 inside the pipe 1, and the surface layer of the pipe 1 facing the coil 14D as a receiving coil. The received signal is generated by the ultrasonic waves returned to the unit.

The receiver 24 combines the received signal W ₁₁ of the coil 14A, the received signal W ₁₂ of the coil 14B, the received signal W ₁₃ of the coil 14C, and the received signal W ₁₄ of the coil 14D when the coil 14A is selected as the transmitting coil. It is acquired via 23 and output to the data recording unit 25.

Next, the demultiplexer 21 selects the coil 14B as the transmission coil. The pulsar 22 applies a transmission signal to the coil 14B via the demultiplexer 21 to generate ultrasonic waves in the surface layer portion of the pipe 1 with which the coil 14B faces.

The multiplexer 23 sequentially selects the coils 14A to 14D as the receiving coil. The coil 14A as a receiving coil is propagated from the surface layer portion of the pipe 1 facing the coil 14B as a transmitting coil, reflected by a defect 2 inside the pipe 1, and the surface layer of the pipe 1 facing the coil 14A as a receiving coil. The received signal is generated by the ultrasonic waves returned to the unit. The coil 14B as a receiving coil is propagated from the surface layer portion of the pipe 1 facing the coil 14B as a transmitting coil, reflected by a defect 2 inside the pipe 1, and the surface layer of the pipe 1 facing the coil 14B as a receiving coil. The received signal is generated by the ultrasonic waves returned to the unit. The coil 14C as a receiving coil is propagated from the surface layer portion of the pipe 1 facing the coil 14B as a transmitting coil, reflected by a defect 2 inside the pipe 1, and the surface layer of the pipe 1 facing the coil 14C as a receiving coil. The received signal is generated by the ultrasonic waves returned to the unit. The coil 14D as a receiving coil is propagated from the surface layer portion of the pipe 1 facing the coil 14B as a transmitting coil, reflected by a defect 2 inside the pipe 1, and the surface layer of the pipe 1 facing the coil 14D as a receiving coil. The received signal is generated by the ultrasonic waves returned to the unit.

The receiver 24 combines the received signal W ₂₁ of the coil 14A, the received signal W ₂₂ of the coil 14B, the received signal W ₂₃ of the coil 14C, and the received signal W ₂₄ of the coil 14D when the coil 14B is selected as the transmitting coil. It is acquired via 23 and output to the data recording unit 25.

Next, the demultiplexer 21 selects the coil 14C as the transmission coil. The pulsar 22 applies a transmission signal to the coil 14C via the demultiplexer 21 to generate ultrasonic waves in the surface layer portion of the pipe 1 with which the coil 14C faces.

The multiplexer 23 sequentially selects the coils 14A to 14D as the receiving coil. The coil 14A as a receiving coil is propagated from the surface layer portion of the pipe 1 facing the coil 14C as a transmitting coil, reflected by a defect 2 inside the pipe 1, and the surface layer of the pipe 1 facing the coil 14A as a receiving coil. The received signal is generated by the ultrasonic waves returned to the unit. The coil 14B as a receiving coil is propagated from the surface layer portion of the pipe 1 facing the coil 14C as a transmitting coil, reflected by a defect 2 inside the pipe 1, and the surface layer of the pipe 1 facing the coil 14B as a receiving coil. The received signal is generated by the ultrasonic waves returned to the unit. The coil 14C as a receiving coil is propagated from the surface layer portion of the pipe 1 facing the coil 14C as a transmitting coil, reflected by a defect 2 inside the pipe 1, and the surface layer of the pipe 1 facing the coil 14C as a receiving coil. The received signal is generated by the ultrasonic waves returned to the unit. The coil 14D as a receiving coil is propagated from the surface layer portion of the pipe 1 facing the coil 14C as a transmitting coil, reflected by a defect 2 inside the pipe 1, and the surface layer of the pipe 1 facing the coil 14D as a receiving coil. The received signal is generated by the ultrasonic waves returned to the unit.

The receiver 24 combines the received signal W ₃₁ of the coil 14A, the received signal W ₃₂ of the coil 14B, the received signal W ₃₃ of the coil 14C, and the received signal W ₃₄ of the coil 14D when the coil 14C is selected as the transmitting coil. It is acquired via 23 and output to the data recording unit 25.

Next, the demultiplexer 21 selects the coil 14D as the transmission coil. The pulsar 22 applies a transmission signal to the coil 14D via the demultiplexer 21 to generate ultrasonic waves in the surface layer portion of the pipe 1 with which the coil 14D faces.

The multiplexer 23 sequentially selects the coils 14A to 14D as the receiving coil. The coil 14A as a receiving coil is propagated from the surface layer portion of the pipe 1 facing the coil 14D as a transmitting coil, reflected by a defect 2 inside the pipe 1, and the surface layer of the pipe 1 facing the coil 14A as a receiving coil. The received signal is generated by the ultrasonic waves returned to the unit. The coil 14B as a receiving coil is propagated from the surface layer portion of the pipe 1 facing the coil 14D as a transmitting coil, reflected by a defect 2 inside the pipe 1, and the surface layer of the pipe 1 facing the coil 14B as a receiving coil. The received signal is generated by the ultrasonic waves returned to the unit. The coil 14C as a receiving coil is propagated from the surface layer portion of the pipe 1 facing the coil 14D as a transmitting coil, reflected by a defect 2 inside the pipe 1, and the surface layer of the pipe 1 facing the coil 14C as a receiving coil. The received signal is generated by the ultrasonic waves returned to the unit. The coil 14D as a receiving coil is propagated from the surface layer portion of the pipe 1 facing the coil 14D as a transmitting coil, reflected by a defect 2 inside the pipe 1, and the surface layer of the pipe 1 facing the coil 14D as a receiving coil. The received signal is generated by the ultrasonic waves returned to the unit.

The receiver 24 combines the received signal W ₄₁ of the coil 14A, the received signal W ₄₂ of the coil 14B, the received signal W ₄₃ of the coil 14C, and the received signal W ₄₄ of the coil 14D when the coil 14D is selected as the transmitting coil. It is acquired via 23 and output to the data recording unit 25.

The data recording unit 25 records the above-mentioned received signal together with information on the combination of the corresponding transmitting coil and the receiving coil. However, the combination of the transmitting coil and the receiving coil may be changed as necessary, for example, when it is desired to limit the inspection area or when there is a defective coil.

The calculation device 30 corresponds to each position inside the pipe 1 based on the propagation time of the ultrasonic wave according to the combination of the transmission coil and the reception coil when it is assumed that the ultrasonic wave is reflected at that position. The intensities (amplitudes) of a plurality of received signals are extracted and added up to generate a flaw detection image showing the combined intensity distribution. The details will be explained.

For example, assuming that the defect 2 exists at the internal position (xi, zi) of the pipe 1 as shown in FIG. 5, the ultrasonic wave generated in the surface layer portion of the pipe 1 facing the transmission coil is along the propagation path F1. The ultrasonic wave propagating and reflected by the defect 2 propagates along the propagation path F2 and returns to the surface layer portion of the pipe 1 facing the receiving coil. Assuming that the position (xm, zm) of the surface layer portion of the pipe 1 facing the transmission coil, the propagation time τmi of the ultrasonic wave in the propagation path F1 is given by the following equation (2). Further, assuming that the position (xn, Zn) of the surface layer portion of the pipe 1 facing the receiving coil, the propagation time τni of the ultrasonic wave in the propagation path F2 is given by the following equation (3). Therefore, the propagation time of the ultrasonic wave in the propagation path (F1 + F2) is given by (τmi + τni).

A plurality of calculation devices 30 correspond to the positions (xi, zi) based on the ultrasonic wave propagation time (τmi + τni) according to the combination of the transmission coil and the reception coil for each position (xi, zi) inside the pipe 1. The strength W _nm (τmi + τni) of the received signal of is extracted and added up. That is, using the above equation (4) (however, in this embodiment, N = 4), the strength (total value) Si corresponding to the internal position (xi, zi) of the pipe 1 is calculated. Then, the intensity Si is converted into a pixel value to generate a flaw detection image showing the distribution of the intensity Si. The calculation device 30 outputs the generated flaw detection image to the display device 40 and displays it.

As described above, in the present embodiment, the flaw detection scan of the pipe 1 can be performed in the circumferential direction of the pipe 1 (in other words, the direction perpendicular to the arrangement direction of the magnets 11 of the electromagnetic ultrasonic probe 10). Therefore, even if the position of the electromagnetic ultrasonic probe 10 is fixed, a wide range of inspections can be performed. Further, when a plurality of electromagnetic ultrasonic probes 10 are arranged in the circumferential direction of the pipe 1, the distance between them can be increased.

It is preferable that the condition of the following equation (5) is satisfied with respect to the pitch p of the coil of the electromagnetic ultrasonic probe 10. Σ in the equation is a representative deflection angle of ultrasonic waves in the xz coordinate system (see FIG. 5). This makes it possible to suppress artifacts caused by so-called grating lobes.

Further, in the flaw detector 20 of the present embodiment, the demultiplexer 21 that selectively connects the coils 14A to 14D of the probe 10 to the pulser 22, and the receiver 24 that selectively connects the coils 14A to 14D of the probe 10 to the receiver 24. It includes a multiplexer 23 to be connected. Therefore, as compared with the case where the demultiplexer 21 is not provided and a plurality of pulsars connected to the coils 14A to 14D are provided, or the case where the multiplexer 23 is not provided and a plurality of receivers connected to the coils 14A to 14D are provided, the flaw detection device is provided. It is possible to reduce the size and cost of 20.

Although not particularly described in the above embodiment, the flaw detector 20 may change the frequency of the transmission signal applied to the transmission coil to change the transmission angle θ of the ultrasonic wave. That is, the flaw detection scan of the pipe 1 in the axial direction of the pipe 1 (in other words, the arrangement direction of the magnets 11) may be performed.

Further, in the above embodiment, the case where the calculation device 30 outputs and displays the flaw detection image on the display device 40 has been described as an example, but the present invention is not limited to this, and for example, the calculation device 30 may be output to a printing machine for printing. Alternatively, it may be output to a storage medium and stored.

Further, in the above embodiment, the case where the electromagnetic ultrasonic probe 10 includes four coils 14A to 14D has been described as an example, but the present invention is not limited to this. The electromagnetic ultrasonic probe 10 may include two, three, or five or more coils. Since it is possible to maintain the distance between the coil and the surface of the pipe 1 regardless of the number of coils, it is possible to maintain the sensitivity.

Further, in the above embodiment, the case where the plurality of magnets 11 are arranged in the axial direction and in a row of the pipe 1 has been described as an example, but the present invention is not limited to this, and the magnets 11 are arranged in a plurality of rows in the axial direction of the pipe 1. May be done. Further, in the above embodiment, the case where the subject is the pipe 1 has been described as an example, but the subject is not limited to this, and may be, for example, a flat plate.

1 Piping (subject)
10 Electromagnetic ultrasonic probe 11 Magnet 13 Magnet array 14A-14D Coil 20 flaw detector 30 Arithmetic logic unit

Claims (3)

A magnet array having a plurality of magnets arranged in one direction along the surface of the subject and alternately arranged so that one side of the subject in a direction perpendicular to the surface becomes an N pole or an S pole, and the said. An electromagnetic ultrasonic probe with a plurality of coils wound around the magnet array along the surface of the subject and around the other direction perpendicular to the one direction and separated from each other in the other direction. With a magnet,
A combination of a transmitting coil and a receiving coil among the plurality of coils is selected, and a transmitting signal is applied to the transmitting coil to generate ultrasonic waves on the surface layer portion of the subject to which the transmitting coil faces. A combination of the transmitting coil and the receiving coil by acquiring a received signal generated in the receiving coil by ultrasonic waves reflected inside the subject and returned to the surface layer portion of the subject facing the receiving coil. A flaw detector that records multiple received signals corresponding to
The plurality corresponding to the position based on the propagation time of the ultrasonic wave according to the combination of the transmission coil and the reception coil when it is assumed that the ultrasonic wave is reflected at the position for each position inside the subject. An electromagnetic ultrasonic inspection device provided with a calculation device that extracts and adds up the strengths of the received signals of the above and generates a flaw detection image showing the distribution of the total strengths. In the electromagnetic ultrasonic inspection apparatus according to claim 1,
The flaw detector is an electromagnetic ultrasonic inspection device characterized in that the frequency of a transmission signal applied to the transmission coil is variable. In the electromagnetic ultrasonic inspection apparatus according to claim 1,
The flaw detector includes a demultiplexer that selects one of the plurality of coils as the transmission coil, a pulser that applies a transmission signal to the transmission coil selected by the demultiplexer, and the plurality of coils. An electromagnetic ultrasonic inspection apparatus comprising: a multiplexer that selects any one of the above as the receiving coil, and a receiver that acquires a received signal of the receiving coil selected by the multiplexer.

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