Ultrasonic flaw detection device and ultrasonic flaw detection method

Abstract

To provide a highly versatile ultrasonic wave flaw detection device and an ultrasonic wave flaw detection method using the same.SOLUTION: The ultrasonic wave flaw detection device performs ultrasonic wave flaw detection of a weld part by being moved toward the weld part on an outer surface of an inspection object having the weld part. The inspection object has an inflection point which changes its surface shape at a middle position. The ultrasonic wave flaw detection device includes: a probe which has a phased-array element which oscillates ultrasonic wave, scans ultrasonic wave so as to cover the weld part, and captures the ultrasonic wave reflected by singular points generated on the weld part; and a control part. The control part controls the phased-array element such that a position of a focal point juxtaposed line as a virtual line formed by juxtaposition of focal points of ultrasonic wave generated by scanning ultrasonic wave changes between on a front side and on a rear side of a moving direction of the probe.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to an ultrasonic flaw detection device and an ultrasonic flaw detection method. [Background technology]

[0002] For example, in nuclear power plants, it is necessary to periodically inspect various equipment and piping to see if there are any cracks, and if there are any, to determine their size. Ultrasonic flaw detection equipment has traditionally been used for such inspections. With this method, a probe that emits ultrasonic waves is moved along the outer surface of the piping, and cracks that have occurred inside the piping are captured and detected as reflected ultrasonic waves.

[0003] In some cases, two pipes with different diameters are connected by cutting the outer surface of one pipe into a tapered shape and then butt-welding the two pipes to match their outer diameters. In this case, the direction of extension of the pipe surface changes based on the tapered portion. In other words, an inflection point occurs on the outer surface of the pipe. At such an inflection point, the ultrasonic waves emitted from the probe are scattered, or the contact state between the probe and the pipe becomes unstable. This can result in the ultrasonic waves not reaching the target area, reducing the accuracy of crack detection.

[0004] To address this issue, the device described in Patent Document 1 below has been proposed. This device mainly comprises two arrays arranged in the extension direction of the pipe, with an inflection point between them, and a deformable connector that connects these arrays. The connector deforms while the two arrays are in close contact with the pipe across the inflection point. This is said to enable ultrasonic flaw detection to be performed without being affected by the inflection point. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2018-155582 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the distance from the weld to the inflection point is not uniform but varies widely depending on the location, which means that the versatility of the device disclosed in Patent Document 1 is limited.

[0007] The present disclosure has been made to solve the above-mentioned problems, and aims to provide a highly versatile ultrasonic flaw detection device and an ultrasonic flaw detection method using the same. [Means for solving the problem]

[0008] In order to solve the above problems, an ultrasonic flaw detection device according to the present disclosure is an ultrasonic flaw detection device that performs ultrasonic flaw detection on a welded portion of an inspection object by moving the ultrasonic flaw detection device on the outer surface of the inspection object toward the welded portion, the inspection object having an inflection point at a midpoint where a surface shape changes, the ultrasonic flaw detection device emitting ultrasonic waves and scanning the ultrasonic waves to cover the welded portion while comprising a probe having a phased array element that captures the ultrasonic waves reflected by a singularity generated in the welded portion, and a control unit that controls the behavior of the phased array element, and the control unit: By controlling the phased array elements, The position of the parallel focus line, which is a virtual line formed by aligning the ultrasonic focus points generated by scanning the ultrasonic wave, is changed. When the probe is located on the rear side of the movement direction, which is the side moving away from the welded portion with the inflection point as the reference, the control unit oscillates the ultrasonic waves with a relatively long focal length so that the parallel focal lines reach the welded portion, and when the probe is located on the front side of the movement direction, which is the side moving closer to the welded portion with the inflection point as the reference, the control unit oscillates the ultrasonic waves with a relatively short focal length so that the parallel focal lines reach the welded portion.

[0009] The ultrasonic flaw detection method according to the present disclosure is an ultrasonic flaw detection method using the ultrasonic flaw detection device described above, and includes the steps of moving the probe on the outer surface of the object to be inspected toward the weld, emitting ultrasonic waves from the phased array element, and capturing the ultrasonic waves reflected at the singular point by the phased array element. [Effects of the Invention]

[0010] According to the present disclosure, it is possible to provide a highly versatile ultrasonic flaw detection device and an ultrasonic flaw detection method using the same. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is an explanatory diagram showing the configuration and operation of an ultrasonic flaw detection device according to an embodiment of the present disclosure, illustrating a state in which the probe is positioned behind the inflection point. [Figure 2] 1 is an explanatory diagram showing the configuration and operation of an ultrasonic flaw detection device according to an embodiment of the present disclosure, illustrating a state in which the probe is positioned forward of the inflection point. FIG. [Figure 3] FIG. 2 is a functional block diagram showing a configuration of a control unit according to an embodiment of the present disclosure. [Figure 4] 10 is a flowchart illustrating an operation of a control unit according to an embodiment of the present disclosure. [Figure 5] 2 is a flowchart illustrating steps of an ultrasonic flaw detection method according to an embodiment of the present disclosure. [Figure 6] FIG. 2 is a hardware configuration diagram of a control unit according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0012] An ultrasonic flaw detection device 1 and an ultrasonic flaw detection method according to an embodiment of the present disclosure will be described below with reference to FIGS.

[0013] (Configuration of ultrasonic flaw detector 1) The ultrasonic flaw detector 1 is a device for detecting cracks inside a pipe 90 as an object to be inspected. It is particularly suitable for use in detecting and sizing cracks in a welded portion 91 of the pipe 90. The pipe 90 has a shape as shown in FIG. 1 as an example. To connect two pipe ends 92 of different diameters, one pipe end 92 is cut and butt-welded to the other pipe end 92 to align its outer diameter. The pipe ends 92 are joined together by the welded portion 91 formed by this butt welding. Therefore, a tapered portion is formed on the outer surface of one pipe end 92. At this portion, the extension direction (surface shape) of the outer surface of the pipe 90 changes midway. In the following description, the position where the extension direction (surface shape) changes in this way is referred to as an "inflection point 93."

[0014] The ultrasonic flaw detection device 1 includes a probe 10, a phased array element 11, and a control unit 20. The probe 10 is a member for moving the probe 10 toward the weld 91 along the extension direction of the pipe 90. In the following description, the direction in which the probe 10 moves is simply referred to as the "movement direction D," and the side of the movement direction D that is close to the weld 91 is referred to as the front side, and the side that is away from the weld 91 is referred to as the rear side. Although not shown in detail, the bottom surface of the probe 10 is arc-shaped when viewed from the movement direction D so as to fit the circumferential shape of the outer surface of the pipe 90.

[0015] A plurality of phased array elements 11 are provided inside the probe 10. The phased array elements 11 are arranged at intervals in the movement direction D, and the composite wave of ultrasonic waves emitted by each phased array element 11 scans the target area. If a singular point such as a crack is present when the ultrasonic waves are scanned, the ultrasonic waves are reflected. The reflected ultrasonic waves are captured by the phased array elements 11. The waveform captured by the phased array elements 11 is transmitted as image data to an external display device. The operator can recognize the position and size of the crack based on this image data.

[0016] More specifically, the phased array element 11 irradiates ultrasonic waves from the outer surface of the pipe 90 toward the inside of the pipe 90. At this time, the ultrasonic waves are configured to scan a predetermined angular range (range of refraction angle θ) based on the center line of the probe 10. This angular range is, for example, 30° to 70°. Note that the angular range may be wider or narrower than the above. In the area irradiated with the ultrasonic waves, the ultrasonic waves scan according to the above angular range, causing the position of the ultrasonic convergence point (focal point) to change continuously. Specifically, as shown in FIG. 1, the ultrasonic focal points are arranged in a linear fashion. In the following description, this imaginary line will be referred to as the focal point parallel line L. Ultrasonic flaw detection is performed along the focal point parallel line L, and if the above-mentioned singular point exists on this focal point parallel line L, a reflected wave is generated. This reflected wave is captured by the phased array element 11 as described above.

[0017] The ultrasonic flaw detection device 1 according to this embodiment is configured such that the position of the parallel focal line L changes between the front and rear sides of the movement direction D. As shown in FIGS. 1 and 2, the position of the parallel focal line L changes before and after an inflection point 93 in the movement direction D. As shown in FIG. 1, ultrasonic waves with a relatively long focal length are emitted behind the inflection point 93 and reach the weld 91. On the other hand, as shown in FIG. 2, ultrasonic waves with a short focal length are emitted ahead of the inflection point 93 and reach the weld 91. It is desirable that the angular range of the refraction angle θ described above be constant before and after the change in the position of the parallel focal line L. On the other hand, even within the same angular range, the region in which reflection due to a crack occurs changes between the front and rear sides of the inflection point 93.

[0018] A plurality of such positions of the parallel focal lines L (focal lengths of ultrasonic waves) are provided to the control unit 20 (described later) as individual setting information (setup files). The control unit 20 is configured to change the position of the parallel focal lines L by selecting an appropriate one of the plurality of setting information.

[0019] (Configuration of control unit 20) As shown in FIG. 3, the control unit 20 includes a setting information acquisition unit 81, a position determination unit 82, a probe position acquisition unit 83, a setting information selection unit 84, an inflection point position acquisition unit 85, and a storage unit 86.

[0020] The probe position acquisition unit 83 acquires the current position of the probe 10 in the movement direction D. The position of the probe 10 may be acquired by, for example, a position sensor, or may be acquired visually by an operator.

[0021] The inflection point position acquisition unit 85 acquires the position of the inflection point 93 of the pipe 90, which is given in advance as design information. That is, the inflection point position acquisition unit 85 acquires where the inflection point 93 exists on the path of the movement direction D.

[0022] The position determination unit 82 compares the position of the inflection point 93 with the position of the probe 10, and determines whether the probe 10 is located in front of or behind the inflection point 93, i.e., whether the probe 10 has passed through the inflection point 93.

[0023] Based on the determination result of the position determination unit 82, the setting information selection unit 84 selects an appropriate piece of setting information from the plurality of pieces of setting information and transmits it to the setting information acquisition unit 81. In other words, setting information including a focal length that can reach the welding zone 91 is selected and transmitted to the setting information acquisition unit 81.

[0024] The setting information acquisition unit 81 applies the specified one of the setting information to set the position of the target focal parallel line L. The storage unit 86 stores a plurality of pieces of setting information.

[0025] Next, the control flow of the control unit 20 will be described with reference to Fig. 4. First, the probe position acquisition unit 83 acquires the position of the probe 10 (step S101). Next, the inflection point position acquisition unit 85 acquires the position of the inflection point 93 (step S102). Note that steps S101 and S102 may be executed in reverse order, or may be executed in parallel.

[0026] Thereafter, the position determination unit 82 determines whether or not the probe 10 has passed the inflection point 93 (step S103). Based on the determination result in step S103, the setting information selection unit 84 selects appropriate setting information from among the plurality of setting information (step S104 or step S105). In the example of FIG. 4, two setting information items, "setting information 1" and "setting information 2," are selected. However, it is also possible to store even more types of setting information in the storage unit 86. Based on the setting information selected by the setting information selection unit 84, the phased array element 11 emits ultrasonic waves with an appropriate focal length. This completes the control flow of the control unit 20.

[0027] (About ultrasonic flaw detection methods) Next, an ultrasonic flaw detection method according to this embodiment will be described with reference to FIG. 5. In this ultrasonic flaw detection method, the ultrasonic flaw detection device 1 described above is used. First, the probe 10 is placed on the outer surface of the pipe 90 (step S1). Then, the probe 10 is moved in the moving direction D toward the weld 91 (step S2). Then, the position of the inflection point 93 is acquired (step S3). Based on whether the inflection point 93 has been passed or not, appropriate setting information is selected in the subsequent step S4. Based on the selected new setting information, the probe 10 is further moved (step S5). During this movement, singular points such as cracks are detected and evaluated (step S6). With the above, all steps of the ultrasonic flaw detection method according to this embodiment are completed.

[0028] (Action and effect) Now, consider the case where the probe 10 is positioned on the inflection point 93. In this case, the posture of the probe 10 becomes unstable, which causes the ultrasonic waves to be inappropriately emitted, resulting in the problem of being unable to fully detect flaws in the required range. Therefore, various methods have been proposed for performing flaw detection while avoiding the inflection point 93. However, the distance from the weld 91 to the inflection point 93 is not uniform for each pipe 90, but varies widely depending on the location. Therefore, there has been a growing demand for a highly versatile ultrasonic flaw detection device 1 that can accommodate any shape of pipe 90.

[0029] Therefore, this embodiment employs the ultrasonic flaw detection device 1 and ultrasonic flaw detection method described above. According to the above configuration, the position of the parallel focal line L changes between the front side and the rear side in the moving direction D. Therefore, by appropriately selecting the position of the parallel focal line L regardless of the surface shape of the pipe 90, ultrasonic flaw detection can be stably performed on the target area such as the weld 91.

[0030] Furthermore, in the above configuration, the control unit 20 oscillates ultrasonic waves with a relatively long focal length on the rear side of the movement direction D relative to the inflection point 93 so that the parallel focal line L reaches the welding portion 91. On the other hand, on the front side of the movement direction D, the control unit 20 oscillates ultrasonic waves with a relatively short focal length so that the parallel focal line L reaches the welding portion 91.

[0031] According to the above configuration, ultrasonic waves with different focal lengths can be directed toward the weld 91 while avoiding the inflection point 93. In particular, an appropriate focal length is selected and applied based on whether the location is in front of or behind the inflection point 93. This allows for more stable ultrasonic flaw detection without being affected by the inflection point 93. Furthermore, ultrasonic flaw detection can be performed flexibly in response to various types of pipes 90 with inflection points 93 at different locations. In other words, the versatility of the device can be further improved.

[0032] In the above configuration, the control unit 20 includes a setting information acquisition unit 81 that acquires a plurality of pieces of setting information in which the positions of a plurality of different types of focal parallel lines L are stored.

[0033] According to the above configuration, the setting information acquisition unit 81 acquires multiple types of preconfigured setting information, which makes it possible to change the position of the focal point parallel line L more easily and quickly than, for example, a configuration in which the position of the focal point parallel line L is manually input each time. This further improves the efficiency and speed of the work. In addition, since one probe 10 can oscillate ultrasonic waves with various types of focal lengths, the versatility of the device can be further improved.

[0034] In addition, in the above configuration, the control unit 20 has a probe position acquisition unit 83 that acquires position information of the probe 10 in the movement direction D, an inflection point position acquisition unit 85 that acquires the position of the inflection point 93 in the movement direction D, a position determination unit 82 that determines whether the probe 10 is located in front of or behind the inflection point 93 in the movement direction D, and a setting information selection unit 84 that selects appropriate setting information from multiple setting information with different positions of the focal parallel line L based on the determination result of the position determination unit 82.

[0035] According to the above configuration, the position of the probe 10 and the position of the inflection point 93 are collated, and the position of the focal point parallel line L can be appropriately changed before and after passing through the inflection point 93. This makes it possible to autonomously change the position of the focal point parallel line L before and after passing through the inflection point 93. In other words, the control unit 20 automatically selects appropriate setting information before and after passing through the inflection point 93, without the operator having to recognize the position of the inflection point 93 himself. This makes it possible to further improve the efficiency and speed of the work.

[0036] Furthermore, the phased array element 11 has a refraction angle θ, which is the angle formed by the direction of irradiation of the ultrasonic waves with respect to the direction of movement D with the center line of the probe 10 as a reference, of 30° to 70°, for example.

[0037] According to the above configuration, ultrasonic flaw detection can be performed over a wide range with high accuracy under a wide range of refraction angles θ. In particular, the wide range of refraction angles θ allows for flexible detection of relatively small cracks and the like, and enables them to be detected with high accuracy. This further improves the efficiency and accuracy of the work.

[0038] (Other embodiments) The above describes in detail the embodiments of the present disclosure with reference to the drawings, but the specific configuration is not limited to this embodiment, and design changes and the like are also included within the scope that does not deviate from the gist of the present disclosure.

[0039] For example, in the above embodiment, an example has been described in which the position of the focal point parallel line L is determined based on one piece of setting information selected from a plurality of pieces of setting information. However, the position of the focal point parallel line L may be configured to be continuously changeable. Specifically, a configuration is conceivable in which an operator rewrites the setting information at any timing and freely adjusts (continuously changes) the position of the focal point parallel line L.

[0040] According to the above configuration, the position of the parallel focal line L changes continuously, so that the influence of the surface shape of the pipe 90 can be avoided more effectively while ultrasonic flaw detection can be performed.

[0041] It is also possible to visually recognize the inflection point 93 and perform the flaw detection work while the operator manually selects the setting information without using the control unit 20. That is, in this case, the control unit 20 is configured to have only the setting information acquisition unit 81.

[0042] Furthermore, in the above embodiment, the inspection object is described as an example of the pipe 90. However, the inspection object is not limited to the pipe 90, and may be a wall surface, a duct, a container, or the like.

[0043] The order of the processes in the embodiments of the present disclosure may be changed as long as the processes are performed appropriately.

[0044] The storage unit 86 and other storage devices in the embodiments of the present disclosure may be provided anywhere within the range where appropriate information can be transmitted and received. Furthermore, there may be multiple storage units 86 and other storage devices within the range where appropriate information can be transmitted and received, and data may be stored in a distributed manner.

[0045] The above-described processing steps performed by the control unit 20 are stored in the form of a program on a recording medium that can be read by the computer 200, and the above processing is performed by reading and executing this program by the computer 200. A specific example of the computer 200 is shown below.

[0046] As shown in FIG. 6, the computer 200 includes a CPU 101, a main memory 102, a storage 103, and an interface 104. For example, the above-described control unit 20 is implemented in a computer 200. The operations of the above-described processing units are stored in the form of a program in storage 103. CPU 101 reads the program from storage 103, loads it into main memory 102, and executes the above-described processing in accordance with the program. Furthermore, CPU 101 allocates a storage area in main memory 102 corresponding to the above-described storage unit 86 in accordance with the program.

[0047] Examples of storage 103 include a hard disk drive (HDD), a solid state drive (SSD), a magnetic disk, a magneto-optical disk, a compact disc read only memory (CD-ROM), a digital versatile disc read only memory (DVD-ROM), and a semiconductor memory. Storage 103 may be an internal medium directly connected to the bus of computer 200, or an external medium connected to computer 200 via interface 104 or a communication line. Furthermore, when this program is distributed to computer 200 via a communication line, computer 200 that receives the program may load the program into main memory 102 and execute the above-mentioned processing. Storage 103 is a non-transitory tangible storage medium.

[0048] The program may also implement some of the functions described above. Furthermore, the program may be a file that can implement the functions described above in combination with a program already recorded in the computer 200 system, a so-called differential file (differential program).

[0049] In addition to or instead of the above configuration, a custom LSI (Large Scale Integrated Circuit) such as a PLD (Programmable Logic Device), an ASIC (Application Specific Integrated Circuit), a GPU (Graphics Processing Unit), or similar processing devices may be provided. Examples of PLDs include PAL (Programmable Array Logic), GAL (Generic Array Logic), CPLD (Complex Programmable Logic Device), and FPGA (Field Programmable Gate Array). In this case, some or all of the functions realized by the processor may be realized by the integrated circuit.

[0050] <Additional Notes> The ultrasonic flaw detection device 1 and the ultrasonic flaw detection method described in each embodiment can be understood, for example, as follows.

[0051] (1) The ultrasonic flaw detection device 1 according to the first aspect is an ultrasonic flaw detection device 1 that performs ultrasonic flaw detection on a weld 91 of an object to be inspected (piping 90) by moving the ultrasonic flaw detection device 1 on the outer surface of the object to be inspected toward the weld 91, the object to be inspected having an inflection point 93 at a midpoint where the surface shape changes, and the ultrasonic flaw detection device 1 comprises a probe 10 that emits ultrasonic waves and scans the ultrasonic waves to cover the weld 91 while capturing the ultrasonic waves reflected by a singularity that occurs in the weld 91, and a control unit 20 that controls the behavior of the phased array element 11, and the control unit 20 controls the phased array element 11 so that the position of a focal parallel line L, which is a virtual line formed by the parallel foci of the ultrasonic waves generated by the scanning of the ultrasonic waves, changes between the front side and the rear side of the movement direction D of the probe 10.

[0052] According to the above configuration, the position of the focal point parallel line L changes between the front side and the rear side in the movement direction D, so that ultrasonic flaw detection can be performed stably regardless of the surface shape of the pipe 90.

[0053] (2) The ultrasonic flaw detection device 1 according to the second aspect is the ultrasonic flaw detection device 1 of (1), wherein the control unit 20 oscillates the ultrasonic waves with a relatively long focal length on the rear side of the moving direction D relative to the inflection point 93 so that the parallel focal line L reaches the welding portion 91, and oscillates the ultrasonic waves with a relatively short focal length on the front side of the moving direction D so that the parallel focal line L reaches the welding portion 91.

[0054] According to the above configuration, ultrasonic waves with different focal lengths can be made to reach the welded portion 91 while avoiding the inflection point 93. This allows ultrasonic flaw detection to be performed without being affected by the inflection point 93.

[0055] (3) The ultrasonic flaw detection device 1 according to the third aspect is the ultrasonic flaw detection device 1 of (1) or (2), in which the control unit 20 is configured to be able to continuously change the position of the focal parallel line L in the movement direction D.

[0056] According to the above configuration, the position of the parallel focal line L changes continuously, so that the influence of the surface shape of the pipe 90 can be avoided more effectively while ultrasonic flaw detection can be performed.

[0057] (4) The ultrasonic flaw detection device 1 according to the fourth aspect is an ultrasonic flaw detection device 1 according to any one of aspects (1) to (3), and the control unit 20 has a setting information acquisition unit 81 that acquires multiple setting information items that store the positions of multiple different types of the focal parallel lines L.

[0058] According to the above configuration, the setting information acquisition unit 81 acquires a plurality of types of setting information configured in advance, so that the position of the focal point parallel line L can be changed easily and quickly.

[0059] (5) The ultrasonic flaw detection device 1 according to the fifth aspect is the ultrasonic flaw detection device 1 of (4), wherein the control unit 20 includes a probe position acquisition unit 83 that acquires position information of the probe 10 in the movement direction D, an inflection point position acquisition unit 85 that acquires the position of the inflection point 93 in the movement direction D, a position determination unit 82 that determines whether the probe 10 is located in front of or behind the inflection point 93 in the movement direction D, and a setting information selection unit 84 that selects appropriate setting information from multiple setting information having different positions of the focal parallel line L based on the determination result of the position determination unit 82.

[0060] According to the above configuration, the position of the probe 10 and the position of the inflection point 93 are collated, and the position of the focal point parallel line L can be appropriately changed before and after passing through the inflection point 93. This allows the position of the focal point parallel line L to be autonomously changed before and after passing through the inflection point 93.

[0061] (6) The ultrasonic flaw detection device 1 according to the sixth aspect is an ultrasonic flaw detection device 1 according to any one of the aspects (1) to (5), wherein the phased array element 11 has a refraction angle θ, which is the angle between the direction of irradiation of the ultrasonic waves and the direction of movement D, based on the center line of the probe 10, of 30° to 70°.

[0062] According to the above configuration, ultrasonic flaw detection can be performed over a wide range with high accuracy under a wide range of refraction angles θ.

[0063] (7) An ultrasonic flaw detection method according to a seventh aspect is an ultrasonic flaw detection method using an ultrasonic flaw detection device 1 according to any one of aspects (1) to (6), and includes the steps of moving the probe 10 on the outer surface of the object to be inspected toward the weld 91, emitting ultrasonic waves from the phased array element 11, and capturing the ultrasonic waves reflected at the singular point by the phased array element 11.

[0064] According to the above configuration, the influence of the inflection point 93 can be avoided and ultrasonic flaw detection can be performed with an appropriate focal length. [Explanation of symbols]

[0065] 1…Ultrasonic flaw detection equipment 10…Probe 11...Phased array element 20...Control unit 81...Setting information acquisition unit 82...Position determination section 83...Probe position acquisition section 84...Setting information selection section 85…Inflection point position acquisition unit 86…Storage section 90...Plumbing 91...Welded section 92...Pipe end 93...Inflection point 101...CPU 102...Main memory 103…Storage 104...Interface 200...Computer D…Movement direction L…focal parallel line θ: Refraction angle

Claims

1. An ultrasonic testing device that performs ultrasonic testing of a welded portion of an inspection object by moving the device toward the welded portion on an outer surface of the inspection object, the object to be inspected has an inflection point at a midpoint where the surface shape changes, The ultrasonic flaw detection device is a probe having a phased array element that emits ultrasonic waves, scans the ultrasonic waves so as to cover the welded portion, and captures the ultrasonic waves reflected by a singular point generated at the welded portion; a control unit that controls the behavior of the phased array element; Equipped with The control unit By controlling the phased array element, it is possible to change the position of a focal point parallel line, which is a virtual line formed by paralleling focal points of the ultrasonic waves generated by scanning the ultrasonic waves, The control unit When the probe is located on the rear side in the movement direction, which is a side away from the welded portion with respect to the inflection point, the ultrasonic waves having a relatively long focal length are oscillated so that the parallel focal lines reach the welded portion; When the probe is located forward in the direction of movement, closer to the weld, relative to the inflection point, the ultrasonic flaw detection device emits ultrasonic waves with a relatively short focal length so that the parallel focal lines reach the weld.

2. The ultrasonic flaw detection device according to claim 1 , wherein the control unit is configured to continuously change the position of the parallel focal lines in the movement direction.

3. The ultrasonic flaw detection device according to claim 1 or 2, wherein the control unit includes a setting information acquisition unit that acquires a plurality of pieces of setting information that store positions of a plurality of different types of parallel focal lines.

4. The control unit a probe position acquisition unit that acquires position information of the probe in the movement direction; an inflection point position acquisition unit that acquires the position of the inflection point in the movement direction; a position determination unit that determines whether the probe is located in front of or behind the inflection point in the movement direction; a setting information selection unit that selects appropriate setting information from a plurality of pieces of setting information that differ in the position of the focal parallel line based on a determination result of the position determination unit; The ultrasonic flaw detector according to claim 3, further comprising:

5. The ultrasonic flaw detection device according to any one of claims 1 to 4, wherein the phased array element has a refraction angle, which is the angle between the direction of irradiation of the ultrasonic waves and the direction of movement based on the center line of the probe, of 30° to 70°.

6. An ultrasonic flaw detection method using the ultrasonic flaw detection device according to any one of claims 1 to 5, moving the probe on the outer surface of the inspection object toward the weld; emitting the ultrasonic waves from the phased array elements; capturing the ultrasonic waves reflected at the singular point by the phased array elements; An ultrasonic flaw detection method comprising:

Images