Softened tissue detection method, remaining life estimation method, and inspection object selection method

Abstract

A softened structure detection method for detecting a softened structure in an inspection object of welded metal by ultrasonic flaw detection, the method comprising: a first flaw detection step for performing ultrasonic flaw detection on the inspection object, the ultrasonic flaw detection unit causes a first ultrasonic beam to be incident from at least one oblique angle probe in an oblique direction and acquires a reflected wave of the first ultrasonic beam returned to the oblique angle probe. A second flaw detection step in which a second ultrasonic beam is incident in an inclined direction from a transmission-side probe, and a reflected wave of the second ultrasonic beam received by a reception-side probe disposed between the reception-side probe and the transmission-side probe with a welding metal interposed therebetween is performed on the inspection object; and a determination step for determining the presence or absence of a softened structure in the inspection object on the basis of the ultrasonic flaw detection results in the first flaw detection step and the ultrasonic flaw detection results in the second flaw detection step.

Description

Technical Field

[0001] This disclosure relates to a method for detecting the softened structure of weld metal, a method for estimating the remaining life of weld metal, and a method for selecting the weld metal to be inspected.

[0002] This application claims priority based on Japanese Patent Application No. 2023-128934, filed with the Japan Patent Office on August 8, 2023, the contents of which are incorporated herein by reference. Background Technology

[0003] In recent years, it has been known that softening structures develop in welded sections or heat-affected zones of the base material in high-temperature steam piping (high-chromium steel piping) used in thermal power generation equipment (see, for example, Patent Document 1). The softening structures generated in metal components used under high temperature and high pressure conditions exhibit significantly reduced hardness and coarser grains compared to normal areas (base material and weld metal). Therefore, the presence of this softening structure may lead to a reduction in the strength of the metal components, and the demand for non-destructive testing of softening structures is expected to increase in the future.

[0004] Ultrasonic testing (UT) is a known method for non-destructive inspection of metal parts (see Patent Document 1). In ultrasonic testing, short pulse signals of ultrasonic waves are transmitted (wave transmission) from a flaw detector to the object being inspected, such as a welded section of a high-temperature steam pipe, and the reflected waves (echo signals) are received and analyzed. This allows the presence and location of defects within the inspected object to be determined.

[0005] Existing technical documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2021-169935 Summary of the Invention

[0007] The problem that the invention aims to solve

[0008] Ultrasonic testing can distinguish between softened structures and welding defects in weld metal using known methods. However, ultrasonic testing has the problem of difficulty in differentiating between softened structures and columnar crystals (dendritic grains) in weld metal. Furthermore, Patent Document 1 made the following attempt: Ultrasonic testing of the object under inspection was performed using ultrasound waves with a set frequency corresponding to the assumed grain size of the grains forming the softened structure, thereby determining whether softened structures were present in the object.

[0009] In view of the above, the object of at least one embodiment of this disclosure is to provide a method for detecting softened structures that can determine whether there are softened structures in weld metal.

[0010] Methods for solving problems

[0011] The softened structure detection method of at least one embodiment of this disclosure is used to detect softened structures within an inspection object of weld metal by ultrasonic testing. The softened structure detection method includes the following steps: The first flaw detection step involves performing ultrasonic flaw detection on the object to be inspected, wherein a first ultrasonic beam is incident from at least one angled probe along an inclined direction, and the reflected wave of the first ultrasonic beam returning to the angled probe is obtained. The second flaw detection step involves performing ultrasonic flaw detection on the aforementioned object, wherein a second ultrasonic beam is incident from a transmitting probe along an inclined direction, and the reflected wave of the second ultrasonic beam is received by a receiving probe, wherein the receiving probe is configured with a welded metal ground spaced between it and the transmitting probe; and The determination step, based on the ultrasonic flaw detection results of the first flaw detection step and the ultrasonic flaw detection results of the second flaw detection step, determines whether the softened tissue exists in the object being inspected.

[0012] The remaining life estimation method of at least one embodiment of this disclosure is used to estimate the remaining life of weld metal. The above-described method for estimating remaining life includes a remaining life estimation step. In this step, the remaining life of the weld metal is estimated by using the correlation between the determination result of the determination step obtained by the softened tissue detection method and the rate of reduction of the remaining life of the weld metal.

[0013] The inspection target selection method of at least one embodiment of this disclosure is used to select the weld metal of the inspection target object that is present or absent in the softened structure detection method described above. The inspection target selection method includes the following steps: The step of obtaining the weld bead distance involves obtaining the weld bead distances of multiple candidate weld metals that are the objects to be inspected; and In the weld metal selection step, the weld metal that will be the object of inspection is selected by considering the weld bead distances of the plurality of weld metals obtained in the weld bead distance acquisition step.

[0014] Invention Effects

[0015] According to at least one embodiment of the present disclosure, a method for detecting softened structure is provided, which can determine whether there is softened structure in weld metal. Attached Figure Description

[0016] Figure 1 This is a flowchart illustrating an example of a softened tissue evaluation method that includes a softened tissue detection method according to an embodiment of the present invention.

[0017] Figure 2 This is a flowchart illustrating an example of a softened tissue detection method according to one embodiment of the present disclosure.

[0018] Figure 3 This is a diagram that schematically illustrates the structure of an ultrasonic flaw detection system according to one embodiment of the present disclosure.

[0019] Figure 4 This is a diagram illustrating ultrasonic testing in the first flaw detection step of a softened tissue detection method according to an embodiment of this disclosure.

[0020] Figure 5 This is a diagram illustrating ultrasonic testing in the first flaw detection step of a softened tissue detection method according to an embodiment of this disclosure.

[0021] Figure 6 This is a diagram illustrating the ultrasonic testing step in the second flaw detection step of a softened tissue detection method according to one embodiment of this disclosure.

[0022] Figure 7 This is a diagram illustrating the ultrasonic testing results of the first and second flaw detection steps in a softened tissue detection method according to an embodiment of this disclosure.

[0023] Figure 8 This is a diagram illustrating the determination step in a softened tissue detection method according to one embodiment of this disclosure.

[0024] Figure 9 This is a diagram illustrating the probe movement step in a softened tissue detection method according to one embodiment of the present disclosure.

[0025] Figure 10 This is a diagram illustrating a method for estimating remaining lifetime according to one embodiment of this disclosure.

[0026] Figure 11 This is a flowchart illustrating an example of a method for estimating the remaining lifetime according to one embodiment of the present disclosure.

[0027] Figure 12 This is a diagram illustrating a method for selecting an inspection object according to one embodiment of this disclosure. Detailed Implementation

[0028] Hereinafter, several embodiments of the present disclosure will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of the constituent components described as embodiments or shown in the drawings are not intended to limit the scope of the present disclosure, but are merely illustrative examples.

[0029] (Evaluation method for softened tissue)

[0030] Figure 1 This is a flowchart illustrating an example of a softened structure evaluation method M, which includes a softened structure detection method M2 comprising one embodiment of the present disclosure. Several embodiments of the softened structure evaluation method M are methods for non-destructively evaluating abnormal metallic structures, i.e., softened structures 21, that sometimes precipitate in a portion of the weld metal 2. For example... Figure 1 As shown, it can be broadly divided into three types: inspection object selection method M1, softened tissue detection method M2, and remaining life estimation method M3. That is, the softened tissue evaluation method M includes: inspection object selection method M1, softened tissue detection method M2, and remaining life estimation method M3. In addition, the inspection object selection method M1, softened tissue detection method M2, and remaining life estimation method M3 of this disclosure can be implemented independently of the other methods of the softened tissue evaluation method M.

[0031] Inspection object selection method M1 is a method for selecting weld metal 2 as the inspection object to be inspected for the presence or absence of softened structure 21. Softened structure detection method M2 is a method for detecting softened structure 21 within the inspection object 3 of the weld metal 2, which is the inspection object, using ultrasonic testing (UT). Remaining life estimation method M3 is a method for estimating the remaining life of the weld metal 2 by taking into account the softened structure 21 within the inspection object 3 of the weld metal 2 detected in softened structure detection method M2. Inspection object selection method M1 is sometimes performed before softened structure detection method M2, and in softened structure detection method M2, the weld metal 2 selected in inspection object selection method M1 may also be used as the inspection object. Remaining life estimation method M3 is performed after softened structure detection method M2.

[0032] (Methods for detecting softened tissue)

[0033] Figure 2 This is a flowchart illustrating an example of a softened tissue detection method M2 according to one embodiment of the present disclosure. Figure 3 This is a diagram that schematically illustrates the structure of an ultrasonic flaw detection system 1 according to one embodiment of the present disclosure. Figure 1 and Figure 2 As shown, the softened tissue detection method M2 in several embodiments includes: a first flaw detection step S21, a second flaw detection step S22, and a judgment step S23.

[0034] (First flaw detection step)

[0035] Figure 4 and Figure 5 This is a diagram illustrating the ultrasonic testing in the first flaw detection step S21 of the softened tissue detection method M2 according to one embodiment of the present disclosure. In the first flaw detection step S21, as... Figure 4and Figure 5 As shown, the inspection object 3 of the welded metal 2 is subjected to ultrasonic testing (first ultrasonic testing) as follows: a first ultrasonic beam is incident from at least one angled probe 41 along an inclined direction, and the reflected wave of the first ultrasonic beam returning to the angled probe 41 is obtained. In the first ultrasonic testing, ultrasonic testing based on the pulse-echo method can also be performed.

[0036] Weld metal 2 is the metal that melts and solidifies during welding. For example... Figure 3 As shown, the welding part 20 includes welding metal 2 and a heat-affected zone (HAZ) 202 of the base material 201, which is the metal material to be welded. The welding metal 2 does not include the heat-affected zone 202 of the base material 201.

[0037] The inspection object 3 includes at least one weld section 31 along a direction orthogonal to the depth direction (welding direction) DD of the weld metal 2. Hereinafter, as... Figure 3 As shown, the direction away from the outer surface 203 of the weld metal 2 (lower direction in the figure) is defined as the height direction (wall thickness direction) HD of the weld metal 2, and the direction orthogonal to the height direction HD in the weld section 31 (left and right direction in the figure) is defined as the width direction WD of the weld metal 2. The side closer to the center (center position CP in the width direction) in the width direction WD of the weld metal 2 is defined as the first side FS, and the side closer to the center (center position CP in the width direction) in the width direction WD of the weld metal 2 is defined as the second side SS.

[0038] In the illustrated embodiment, the at least one angled probe 41 described above includes a plurality of angled probes 41 (41A, 41B). The plurality of angled probes 41 includes a first angled probe 41A and a second angled probe 41B disposed with a weld metal 2 spaced apart from the first angled probe 41A. In the first flaw detection step S21, ultrasonic flaw detection is performed to obtain reflected waves from the first ultrasonic beams returned to the first angled probe 41A and the second angled probe 41B, respectively. Alternatively, in other embodiments, ultrasonic flaw detection may be performed using a single angled probe 41 in the first flaw detection step S21.

[0039] exist Figure 4 and Figure 5In the illustrated embodiment, a first bevel probe 41A is mounted on the outer surface 204 of the base material 201 adjacent to the first side FS of the weld metal 2. A second bevel probe 41B is mounted on the outer surface 205 of the base material 201 adjacent to the second side SS of the weld metal 2. The first bevel probe 41A directs the first ultrasonic beam along an inclined direction relative to the height direction HD toward the other side (right side in the figure) in the width direction WD. Additionally, the first bevel probe 41A receives the reflected wave of the first ultrasonic beam that bounces back along the inclined direction relative to the height direction HD toward the other side (right side in the figure) in the width direction WD. The second bevel probe directs the first ultrasonic beam along an inclined direction relative to the height direction HD toward the other side (left side in the figure) in the width direction WD. Additionally, the second bevel probe receives the reflected wave of the first ultrasonic beam that bounces back along the inclined direction relative to the height direction HD toward the other side (left side in the figure) in the width direction WD.

[0040] Multiple angled probes 41 (41A, 41B) each have a transmitter 411 for transmitting a first ultrasonic beam (the incident wave IW1 of the first ultrasonic wave) and a receiver 412 for receiving the reflected wave (echo signal) RW1 of the first ultrasonic beam transmitted by the transmitter 411. A transmitting-side vibrator for generating the first ultrasonic beam is assembled in the transmitter 411, and a receiving-side vibrator for receiving the first ultrasonic beam is assembled in the receiver 412.

[0041] (Second flaw detection step)

[0042] Figure 6 This diagram illustrates the ultrasonic testing in the second flaw detection step S22 of the softened tissue detection method M2 according to one embodiment of this disclosure. In the second flaw detection step S22, as... Figure 6 As shown, for the inspection object 3 of the weld metal 2, a second ultrasonic beam is incident from the transmitting probe 42 along an inclined direction, and ultrasonic testing (second ultrasonic testing) is performed to obtain the reflected wave of the second ultrasonic beam received by the receiving probe 43, which is arranged with the weld metal 2 spaced apart from the transmitting probe 42. In the second ultrasonic testing, ultrasonic testing based on the capture method can also be performed. The inspection object 3 described above includes at least one weld section 31 along a direction orthogonal to the depth direction of the weld metal 2. The inspection object 3, i.e., the weld section 31, in the second testing step S22 is preferably the same as the inspection object 3, i.e., the weld section 31, in the first testing step S21.

[0043] exist Figure 6In the illustrated embodiment, the transmitting probe 42 is mounted on the outer surface 204 of the base material 201 adjacent to the first side FS of the weld metal 2. The receiving probe 43 is mounted on the outer surface 205 of the base material 201 adjacent to the second side SS of the weld metal 2. The transmitting probe 42 directs the second ultrasonic beam along an inclined direction relative to the aforementioned height direction HD toward the other side (right side in the figure) in the width direction WD. The receiving probe 43 receives the reflected wave of the second ultrasonic beam that bounces back along the inclined direction relative to the aforementioned height direction HD toward the aforementioned side (left side in the figure) in the width direction WD.

[0044] The transmitting-side probe 42 has a transmitter 421 for transmitting a second ultrasonic beam (the incident wave IW2 of the second ultrasonic wave). The receiving-side probe 43 has a receiver 431 for receiving the reflected wave (echo signal) RW2 of the second ultrasonic beam transmitted by the transmitter 421. A transmitting-side vibrator for generating the second ultrasonic beam is assembled in the transmitter 421, and a receiving-side vibrator for receiving the second ultrasonic beam is assembled in the receiver 431.

[0045] like Figure 3 As shown, in the first flaw detection step S21 and the second flaw detection step S22, ultrasonic flaw detection can also be performed using a first ultrasonic probe 4A (4) that functions as a first angled probe 41A and a transmitting probe 42, and a second ultrasonic probe 4B (4) that functions as a second angled probe 41B and a receiving probe 43. In the illustrated embodiment, the first ultrasonic probe 4A has the aforementioned transmitter 411, receiver 412, and transmitter 421. The second ultrasonic probe 4B has the aforementioned transmitter 411, receiver 412, and receiver 431. Alternatively, the first ultrasonic probe 4A may also have a receiver 431, and the second ultrasonic probe 4B may also have a transmitter 421. That is, the first ultrasonic probe 4A may also function as a receiving probe 43, and the second ultrasonic probe 4B may also function as a transmitting probe 42. The first ultrasonic probe 4A and the second ultrasonic probe 4B are array probes assembled with at least one of a plurality of transmitting and receiving transducers. By using ultrasonic testing with the first ultrasonic probe 4A and the second ultrasonic probe 4B, the first flaw detection step S21 and the second flaw detection step S22 can be performed simultaneously.

[0046] (Ultrasonic flaw detection system)

[0047] In the illustrated embodiment, the softened tissue detection method M2 described above comprises an ultrasonic flaw detection system 1 (refer to...). Figure 3The ultrasonic flaw detection system 1 includes: multiple ultrasonic probes 4 (4A, 4B); a measuring device 11, which, after transmitting ultrasonic beams from the transmitters 411, 421 of each of the multiple ultrasonic probes 4, uses receivers 412, 431 to measure (observe) the intensity of the reflected wave (signal level of the echo signal) of the ultrasonic beam, thereby generating signal data of the reflected wave; and a judgment device 12, which, based on the signal data of the reflected wave generated in the measuring device 11, determines whether there is softened tissue 21 in the object under inspection 3.

[0048] After transmitting an ultrasonic beam from transmitters 411 and 421, measuring device 11 uses receivers 412 and 431 to measure the intensity of the reflected wave of the ultrasonic beam (signal level of the echo signal), thereby generating intensity data (time series data), which is the time progression of the intensity of the reflected wave of the ultrasonic beam observed during a predetermined period from when the ultrasonic beam is transmitted from transmitters 411 and 421.

[0049] like Figures 4-6 As shown, through the ultrasonic testing in the first flaw detection step S21 and the second flaw detection step S22 described above, the location and size of the ultrasonic beam reflection source within the inspected object 3 can be estimated. Examples of ultrasonic beam reflection sources detected in the first flaw detection step S21 and the second flaw detection step S22 include softened tissue 21, columnar crystals (dendritic grains) 22 of weld metal 2, and welding defects (defects) 23. The ultrasonic beams transmitted from transmitters 411 and 421 are reflected by these reflection sources, and the reflected ultrasonic beams (reflected waves) are received by receivers 412 and 431. Therefore, there are locations where the intensity of the reflected ultrasonic beam (the signal level of the echo signal) varies greatly (reflection source echo).

[0050] (Judgment Steps)

[0051] Figure 7 This is a diagram illustrating the ultrasonic testing results of the first flaw detection step S21 and the second flaw detection step S22 in a softened tissue detection method according to an embodiment of the present disclosure. Figure 8 This is a diagram illustrating the determination step S23 in a softened tissue detection method M2 according to one embodiment of this disclosure. (See diagram for reference.) Figure 7 As shown, ultrasonic testing in the first flaw detection step S21 yields reflected echoes from the softened structure 21, columnar crystals 22, and welding defects 23, with a particularly high reflected echo from the columnar crystals 22. Ultrasonic testing in the second flaw detection step S22 also yields reflected echoes from the softened structure 21, columnar crystals 22, and welding defects 23, but the reflected echo from the columnar crystals 22 is relatively low.

[0052] In the ultrasonic testing of the first flaw detection step S21, the ultrasonic waves in the direction orthogonal to the tilt of the columnar crystal 22 are strongly reflected. Therefore, different ultrasonic testing conditions can be used on the surface and deep sides of the weld metal 2. Here, the surface side of the weld metal 2 is the area within a predetermined distance from the outer surface 203 of the weld metal 2, and the deep side of the weld metal 2 is the area beyond the predetermined distance from the outer surface 203 of the weld metal 2. Compared with the surface side, the distance in the width direction WD of the pair of angled probes 41 (41A, 41B) can be increased on the deep side of the weld metal 2, and the central refraction angle θ of each of the pair of ultrasonic probes angled probes 41 (41A, 41B) can be decreased. The central refraction angle θ is the angle at the center of the range of angles of refraction of the ultrasonic beam incident from the incident point of the ultrasonic probe 4 in a cross section along a direction orthogonal to the welding direction of the weld metal 2, and is the angle relative to an imaginary line VL extending from the incident point of the ultrasonic probe 4 along the height direction HD of the weld metal 2.

[0053] In the ultrasonic testing of the second flaw detection step S22, when a pair of ultrasonic probes 4A and 4B are used, which function as the transmitting probe 42 and the receiving probe 43 respectively, flaw detection can be performed centered on the intersection axis of the ultrasonic beam (central beam) extending along the central refraction angle θ of the pair of ultrasonic probes 4A and 4B. Therefore, different ultrasonic testing conditions can be used on the surface and deep sides of the weld metal 2. Compared with the surface side, the distance in the width direction WD of the pair of ultrasonic probes 4A and 4B can be increased on the deep side of the weld metal 2, and the central refraction angle θ of each pair of ultrasonic probes 4A and 4B can be decreased.

[0054] The inventors have discovered that the reflected waves of the first ultrasonic beam and the reflected waves of the second ultrasonic beam behave differently (e.g., in intensity) in the softened tissue 21 and the columnar crystal 22, and based on these differences in behavior, it is possible to determine which one of the softened tissue 21 and the columnar crystal 22 is present.

[0055] In determination step S23, the presence or absence of softened tissue 21 within the inspection object 3 is determined based on the ultrasonic testing results of the first flaw detection step S21 and the second flaw detection step S22. In the illustrated embodiment, determination step S23 is performed by determination device 12. Each step included in determination step S23, described later, is also performed by determination device 12. In the ultrasonic testing results of the first flaw detection step S21, a relatively high reflection source echo from columnar crystal 22 is obtained; conversely, in the ultrasonic testing results of the second flaw detection step S22, a relatively low reflection source echo from columnar crystal 22 is obtained. Therefore, the position and size of columnar crystal 22 can be estimated based on the ultrasonic testing results of the first flaw detection step S21 and the second flaw detection step S22. Furthermore, the welding defect 23 is a void reflection, different from the softened tissue 21 which becomes a tissue reflection; therefore, the softened tissue 21 and the welding defect 23 can be identified by known methods, such as waveform analysis described in Patent Document 1. Therefore, it is possible to identify the softened tissue 21, columnar crystals 22, and welding defects 23, which are the reflection sources of the ultrasonic beam, and thus it is possible to infer whether there is softened tissue 21 in the object under inspection 3.

[0056] According to the above method, in the first flaw detection step S21 and the second flaw detection step S22, the reflected wave of the first ultrasonic beam and the reflected wave of the second ultrasonic beam are obtained. In the determination step S23, it is possible to determine whether it is the softened structure 21 or the columnar crystal 22 based on the behavior of these reflected waves. Therefore, it is possible to determine whether there is a softened structure 21 in the weld metal 2.

[0057] In the softened tissue detection method M2 of several implementations, such as Figure 5 As shown, the at least one angled probe 41 includes the first angled probe 41A and the second angled probe 41B. In the first flaw detection step S21, ultrasonic flaw detection is performed to obtain the reflected wave of the first ultrasonic beam incident from the first angled probe 41A and the reflected wave of the first ultrasonic beam incident from the second angled probe 41B.

[0058] The columnar crystal 22A formed in the welding section 31 on the first angled probe 41A side, i.e., the first side FS, extends in a manner that is inclined toward the first side FS (the aforementioned side) as it moves away from the outer surface 203 of the welding metal 2. The columnar crystal 22B formed in the welding section 31 on the second angled probe 41B side, i.e., the second side SS, extends in a manner that is inclined toward the second side SS (the aforementioned other side) as it moves away from the outer surface 203 of the welding metal 2.

[0059] According to the above method, the first ultrasonic beam from the first angled probe 41A can be incident relative to the columnar crystal 22A formed on the side of the first angled probe 41A in the welding section 31, in a direction orthogonal to the extension direction of the columnar crystal 22A. Therefore, the position and size of the columnar crystal 22A, which serves as a reflection source, can be estimated with high accuracy. Similarly, the first ultrasonic beam from the second angled probe 41B can be incident relative to the columnar crystal 22B formed on the side of the second angled probe 41B in the welding section 31, in a direction orthogonal to the extension direction of the columnar crystal 22B. Therefore, the position and size of the columnar crystal 22B, which serves as a reflection source, can be estimated with high accuracy.

[0060] In the softened tissue detection method M2 of several embodiments, the inspection object 3 described above includes at least one weld section 31 along a direction orthogonal to the welding direction of the weld metal 2. For example... Figure 2 As shown, the above-mentioned determination step S23 includes a first flaw detection image generation step S232 and a second flaw detection image generation step S233.

[0061] In the first flaw detection image generation step S232, based on the ultrasonic flaw detection results of the first flaw detection step S21 (e.g., intensity data of the reflected wave of the first ultrasonic beam), a flaw detection image based on the first ultrasonic beam of at least one weld section 31 is generated, namely, the first flaw detection image DI1 (refer to...). Figure 7 In the second flaw detection image generation step S233, based on the ultrasonic flaw detection results of the second flaw detection step S22 (e.g., intensity data of the reflected wave of the second ultrasonic beam), a flaw detection image based on the second ultrasonic beam of at least one weld section 31, namely the second flaw detection image DI2 (refer to...), is generated. Figure 7 ).

[0062] The first flaw detection image DI1 and the second flaw detection image DI2 are generated using known flaw detection image generation techniques, such as TFM (Total Focusing Method). The determination device 12 displays the generated flaw detection images (first flaw detection image DI1, second flaw detection image DI2, etc.) to the display (reference). Figure 3 The image is output from a visual display device 13, such as a printer, to display the aforementioned flaw detection image. The position and size of the ultrasonic beam reflection source within the weld section 31 are depicted in the first flaw detection image DI1 and the second flaw detection image DI2. The first flaw detection image DI1 can also be generated from a flaw detection image based on the first ultrasonic flaw detection result of the first angled probe 41A. Figure 5 The image on the left side of the middle section is compared with the flaw detection image generated based on the first ultrasonic flaw detection result based on the second angle probe 41B. Figure 5 The image on the right side of the middle section is generated by merging elements such as overlapping.

[0063] According to the method described above, the display states in the first flaw detection image DI1 and the second flaw detection image DI2 are different in the softened structure 21 and the columnar crystals 22. Therefore, it is easy to determine whether it is the softened structure 21 or the columnar crystals 22 based on the first flaw detection image DI1 and the second flaw detection image DI2. Thus, it is easy to determine whether there is softened structure 21 in the weld metal 2 using image analysis techniques. The determination of whether it is the softened structure 21 or the columnar crystals 22 based on the first flaw detection image DI1 and the second flaw detection image DI2, as well as the image analysis techniques, are performed, for example, by the determination device 12 described above.

[0064] In the softened tissue detection method M2 of several embodiments, the inspection object 3 described above includes at least one weld section 31 along a direction orthogonal to the welding direction of the weld metal 2. For example... Figure 2 As shown, the determination step S23 above includes the first flaw detection image generation step S232, the second flaw detection image generation step S233, and the image estimation step S234.

[0065] In the image estimation step S234, for each of the multiple segmented regions 32 divided in the weld section 31, the first characteristic value corresponding to the intensity of the reflected wave of the first ultrasonic beam in the first flaw detection image DI1 and the second characteristic value corresponding to the intensity of the reflected wave of the second ultrasonic beam in the second flaw detection image DI2 are compared, thereby estimating the position and size of the softened tissue 21 within the weld section 31 (length W in the width direction WD and length H in the height direction HD, referencing...). Figure 9 ).

[0066] The multiple segmented regions 32 are regions formed by dividing the weld section 31 represented by the first flaw detection image DI1 and the second flaw detection image DI2 into multiple regions along the height direction HD and width direction WD of the weld metal 2, respectively, and constituting a part of the weld section 31. The first feature value can simply be the value representing the intensity of the reflected wave of the first ultrasonic beam of the first flaw detection image DI1, for example, it can also be the brightness (echo height) of each segmented region 32 of the first flaw detection image DI1. The second feature value can simply be the value representing the intensity of the reflected wave of the second ultrasonic beam of the second flaw detection image DI2, for example, it can also be the brightness (echo height) of each segmented region 32 of the second flaw detection image DI2.

[0067] Alternatively, before comparing the first feature value and the second feature value, adjustments can be made by multiplying the first feature value or the second feature value by a predetermined correction value, taking into account the conditions of the first and second ultrasonic flaw detection.

[0068] According to the above method, the segmented region 32 in the weld section 31 where the first characteristic value is higher than the second characteristic value can be identified as columnar crystal 22, and the segmented region 32 in the weld section 31 where the first characteristic value is lower than the second characteristic value can be identified as softened structure 21. Based on the segmented region 32 in the weld section 31 identified as softened structure 21, the position and size of the softened structure 21 in the weld section 31 can be estimated. In addition, by setting the characteristic values ​​(brightness, echo height) of the segmented region 32 in the weld section 31 where the first characteristic value is higher than the second characteristic value to zero and setting the characteristic values ​​(brightness, echo height) of the segmented region 32 in the weld section 31 where the second characteristic value is higher than the first characteristic value to the second characteristic value, it is possible to generate Figure 8 As shown, the flaw detection image DI3 of the softened tissue 21 was extracted.

[0069] In the above-described embodiments, a first flaw detection image DI1 and a second flaw detection image DI2 are generated. However, the location and size of the softened tissue 21 within the weld section 31 (inspection object 3) can be estimated without generating the first flaw detection image DI1 and the second flaw detection image DI2. In the softened tissue detection method M2 of several embodiments, the aforementioned inspection object 3 includes at least one weld section 31 along a direction orthogonal to the welding direction of the weld metal 2. Figure 1 As shown, the determination step S23 above includes the estimation step S231.

[0070] In the estimation step S231, for each of the multiple segmented regions 32 divided in the weld section 31 (inspection object 3), the information related to the intensity of the reflected wave of the first ultrasonic beam obtained from the ultrasonic testing results of the first flaw detection step S21 is compared with the information related to the intensity of the reflected wave of the second ultrasonic beam obtained from the ultrasonic testing results of the second flaw detection step S22, thereby estimating the location and size of the softened tissue 21 in the inspection object 3.

[0071] The information related to the intensity of the reflected wave of the first ultrasonic beam and the intensity of the reflected wave of the second ultrasonic beam, which are the comparison objects in the estimation step S231, can be the intensity of the reflected wave of each segmented region 32 (signal level of the echo signal), or the difference in intensity of the reflected wave of each segmented region 32 relative to the incident wave, or the ratio of the intensity of the reflected wave of each segmented region 32 to the intensity of the incident wave (attenuation rate). Alternatively, before comparing the information related to the intensity of the reflected wave of the first ultrasonic beam and the information related to the intensity of the reflected wave of the second ultrasonic beam, adjustments can be made by multiplying this information by predetermined correction values, considering the conditions of the first and second ultrasonic flaw detection.

[0072] According to the above method, the intensity of the reflected wave from the first ultrasonic beam from the columnar crystal 22 is relatively high, while the intensity of the reflected wave from the second ultrasonic beam from the columnar crystal 22 is relatively low. Therefore, the segmented region 32 in the inspection object 3 where the intensity of the reflected wave from the first ultrasonic beam is higher than that from the second ultrasonic beam can be identified as the columnar crystal 22, and the segmented region 32 in the inspection object 3 where the intensity of the reflected wave from the first ultrasonic beam is lower than that from the second ultrasonic beam can be identified as softened tissue 21. Based on the segmented region 32 in the inspection object 3 identified as softened tissue 21, the position and size of the softened tissue 21 in the inspection object 3 (length W in the width direction WD and length H in the height direction HD, refer to...) can be estimated. Figure 9 ).

[0073] (Probe movement steps)

[0074] Figure 9 This is a diagram illustrating the probe movement step S24 in a softened tissue detection method M2 according to one embodiment of this disclosure. (See diagram for example.) Figure 2 As shown, the softened tissue detection method M2 in several embodiments further includes a probe moving step S24, which moves at least one angled probe 41 (41A, 41B), the transmitting probe 42, and the receiving probe 43 along the welding direction of the weld metal 2. Figure 3 As shown, the inspection object 3 mentioned above includes multiple weld sections 31 that are separated from each other along the welding direction of the weld metal 2 and are perpendicular to the welding direction. That is, the weld sections 31 at multiple locations within the probe movement range in the probe movement step S24 are subjected to the first flaw detection step S21, the second flaw detection step S22, and the judgment step S23, respectively.

[0075] exist Figure 2 In the embodiment shown, the determination step S23 is performed after the probe movement step S24 is completed, but it can also be performed quickly on the weld section 31 that has undergone the first flaw detection step S21 and the second flaw detection step S22 during the execution of the probe movement step S24.

[0076] The measuring device 11 uses receivers 412 and 431 to measure (observe) the intensity of the reflected wave (signal level of the echo signal) of the ultrasonic beam at multiple locations within the range of motion of the probe, thereby generating signal data and intensity data (time series data) of the reflected wave at each of the multiple locations.

[0077] According to the above method, by moving the angled probe 41, the transmitting probe 42, and the receiving probe 43 along the welding direction of the weld metal 2, the presence or absence of softened structure 21 can be determined at multiple welding sections 31. By determining the presence or absence of softened structure 21 at multiple welding sections 31, the position and size of the softened structure 21 in the welding direction of the weld metal 2 (length L in the welding direction, refer to...) can be estimated. Figure 9 ).

[0078] (Method for estimating remaining useful life)

[0079] Figure 10 This is a diagram illustrating a remaining life estimation method M3 of one embodiment of this disclosure. Figure 11 This is a flowchart illustrating an example of a remaining life estimation method M3 according to one embodiment of the present disclosure. The remaining life estimation method M3 of several embodiments is a method for estimating the remaining life of weld metal 2. The weld metal 2 to which the remaining life is estimated is preferably weld metal 2 that has actually undergone the softening structure detection method M2 described above. In the remaining life estimation method M3, the remaining life of weld metal 2 is estimated based on the determination result of determination step S23 obtained in the softening structure detection method M2, utilizing the correspondence between the determination result of determination step S23 in the softening structure detection method M2 and the rate of reduction of the remaining life of weld metal 2. The remaining life estimation method M3 can be performed by the determination device 12 described above, or by other devices different from the determination device 12 (remaining life evaluation device).

[0080] In one embodiment, the life reduction of the weld metal 2 is calculated based on the first association information that establishes an association between the information obtained by the determination result of the determination step S23 and the information related to the position and size (length W, H, L, etc.) of the softened tissue 21 in the weld metal 2, namely the size information of the softened tissue 21, and the life reduction of the weld metal 2.

[0081] The first correlation information represents the correspondence between the dimensional information of the softened structure 21 and the reduction in the lifespan of the weld metal 2. When the dimensional information of the softened structure 21 is used as input information, the output information only needs to be the reduction in the lifespan of the weld metal 2 corresponding to the input information. The first correlation information includes lists, tables, mappings, functions, machine learning models, strength analysis models, etc., that indicate the correspondence between input and output information. The first correlation information can be generated based on stable test data, or it can be generated based on past actual or experimental values, numerical analysis results, etc., which are not based on stable test data.

[0082] exist Figure 10 The figure shows the S (stress)-N (life) curve of weld metal 2. Figure 10 Curve C1 shown is the life evaluation curve without considering the softened structure 21 in the weld metal 2. Figure 10 Curve C2 shown is a corrected life evaluation curve that takes into account the softened structure 21 within the weld metal 2. It is a curve that corrects curve C1 by calculating the life reduction of the weld metal 2 based on the dimensional information of the softened structure 21. Curve C2 can be used to estimate the remaining life of the weld metal 2 under evaluation temperature and stress conditions.

[0083] According to the above method, the remaining life of the weld metal 2 can be estimated based on the position and size of the softened tissue 21 within the judgment object 3 obtained from the judgment result of the judgment step S23 of the softened tissue detection method M2.

[0084] In the remaining lifetime estimation method M3 of several implementations, such as Figure 11 As shown, the remaining lifetime estimation step S31 includes an area ratio calculation step S311 and a remaining lifetime reduction rate calculation step S312. In the area ratio calculation step S311, the area ratio of the softened structure 21 is calculated based on the determination result of the determination step S23. In the area ratio calculation step S311, the determination result of the determination step S23 can be obtained from the size information of the softened structure 21 obtained from multiple weld sections 31 of the weld metal 2, or it can be obtained from any representative weld section 31 of the weld metal 2. The area ratio of the weld metal 2 can be calculated based on the size information of the softened structure 21.

[0085] In the remaining life reduction rate calculation step S312, the remaining life reduction rate of the weld metal 2 is calculated based on the area ratio of the softened structure 21 calculated in the area ratio calculation step S311, using the correspondence between the area ratio of the softened structure 21 and the remaining life reduction rate of the weld metal 2.

[0086] In the illustrated embodiment, in the remaining life reduction rate calculation step S312, the remaining life reduction rate F of the weld metal 2 is calculated based on the area ratio R of the softened tissue 21 calculated in the area ratio calculation step S311, according to the second association information that establishes a relationship between the area ratio R of the softened tissue 21 and the remaining life reduction rate F of the weld metal 2.

[0087] The second set of correlation information represents the correspondence between the area ratio R of the softened structure 21 and the reduction rate F of the remaining life of the weld metal 2. When the area ratio R of the softened structure 21 is used as input information, the output information only needs to be the reduction rate F of the remaining life of the weld metal 2 corresponding to the input information. The second correlation information includes lists, tables, mappings, functions, machine learning models, etc., indicating the correspondence between input and output information. The second correlation information can be created based on stable test data, or it can be created based on past actual or experimental values, numerical analysis results, etc., which are not based on stable test data.

[0088] In the illustrated embodiment, the remaining life estimation step S31 further includes: a remaining life acquisition step S313, which uses the life evaluation curve (curve C1) of the weld metal 2 without considering the softened structure 21 to obtain the remaining life t without considering the softened structure 21. r0 ; and the remaining lifetime calculation step S314, which calculates the remaining lifetime t obtained in the remaining lifetime acquisition step S313. r0 Multiply by the remaining lifetime reduction rate F calculated in the remaining lifetime reduction rate calculation step S312 to calculate the remaining lifetime t considering the softened tissue 21. r .

[0089] According to the method described above, there is a tendency that the higher the area ratio of the softened structure 21, the higher the rate of reduction in the remaining life of the weld metal 2. Based on the area ratio of the softened structure 21 calculated in the area ratio calculation step S311, the rate of reduction in the remaining life of the weld metal 2 can be calculated using the correlation between the area ratio of the softened structure 21 and the rate of reduction in the remaining life of the weld metal 2.

[0090] (Method for selecting the inspection object)

[0091] Figure 12 This diagram illustrates an inspection target selection method M1 according to one embodiment of this disclosure. The inspection target selection method M1 of several embodiments is a method for selecting weld metal 2 that is an inspection target for the presence or absence of softened structure 21 in the aforementioned softened structure detection method M2. For example, in a power plant boiler, there are thousands or more candidate weld metals 2 that could be inspection targets; therefore, performing the softened structure detection method M2 on all weld metals 2 is impractical.

[0092] like Figure 1As shown, the inspection object selection method M1 includes a weld bead distance acquisition step S11 and a weld metal selection step S12. In the weld bead distance acquisition step S11, the weld bead distances DWP of multiple candidate weld metals 2 that are to be inspected are acquired. In the weld metal selection step S12, the weld metal 2 that will be the inspection object is selected by considering the weld bead distances of the multiple weld metals 2 acquired in the weld bead distance acquisition step S11.

[0093] Since the weld bead distance DWP is difficult to determine from the attached drawings, it is preferable to perform ultrasonic testing on multiple candidate weld metals 2 that are the objects to be inspected to obtain the weld bead distance DWP. In the step S11 of obtaining the weld bead distance, as follows... Figure 12 As shown, for any weld section (representing the weld section) 31 of the weld metal 2, ultrasonic testing is performed by incident an ultrasonic beam from an angled probe 44 along an inclined direction and obtaining the reflected wave of the ultrasonic beam returning to the angled probe 44. The angled probe 44 has the same transmitter 411 and receiver 412 as the angled probe 41. Ultrasonic testing based on the angled probe 44 can also be performed on a portion representing the weld section 31. For example, the target area for ultrasonic testing based on the angled probe 44 can be either the first side FS or the second side SS, or either the surface side or the deep side mentioned above.

[0094] The aforementioned measuring device 11 generates signal data (intensity data) of the reflected wave, and the aforementioned judging device 12 generates an ultrasonic flaw detection image DI4 based on the angled probe 44. The flaw detection image DI4 depicts multiple weld beads 24 separated from each other in the height direction HD within the representative weld section 31. The distance between a pair of adjacent weld beads 24 in the height direction HD in the flaw detection image DI4 (distance in the height direction HD) can be obtained as the weld bead distance DWP.

[0095] According to the method described above, the shorter the weld bead distance DWP of the weld metal 2, the greater the local heat input during welding, and therefore the higher the risk of the formation of softened structure 21 within the weld metal 2. The weld bead distance DWP of the weld metal 2 is closely related to the risk of the formation of softened structure 21. Therefore, by using the weld bead distance DWP of the weld metal 2 as a parameter, weld metal 2 with a high risk of forming softened structure 21 can be selected as the object of inspection.

[0096] In this specification, expressions such as "in a certain direction", "along a certain direction", "parallel", "orthogonal", "center", "concentric" or "coaxial" that indicate relative or absolute configurations not only strictly indicate such configurations, but also indicate a state of relative displacement by angle or distance with tolerances or to the extent that the same function can be obtained.

[0097] For example, expressions such as "same," "equal," and "homogeneous" that indicate the state of equality of things not only indicate a state of strict equality, but also indicate a state of difference where there is a tolerance or a degree of difference in the ability to obtain the same function.

[0098] Furthermore, in this specification, the description of shape, such as quadrilateral shape or cylindrical shape, not only refers to quadrilateral shape or cylindrical shape in a strict geometric sense, but also to shapes that include concave or convex parts or chamfered parts within the range that can achieve the same effect.

[0099] Furthermore, in this specification, expressions such as "having," "comprising," or "possessing" a constituent element are not exclusive expressions that exclude the existence of other constituent elements.

[0100] This disclosure is not limited to the above-described embodiments, but also includes modifications to the above-described embodiments and appropriate combinations thereof.

[0101] The contents described in the above-described embodiments are as follows.

[0102] 1) The softened structure detection method (M2) of at least one embodiment of the present disclosure is used to detect softened structure (21) in the inspection object (3) of weld metal (2) by ultrasonic testing. The softened structure detection method (M2) includes the following steps: In the first flaw detection step (S21), ultrasonic flaw detection is performed on the above-mentioned inspection object (3) in the following manner: the ultrasonic flaw detection is performed by a first ultrasonic beam incident from at least one angled probe (41) along the inclined direction, and the reflected wave of the first ultrasonic beam returning to the angled probe (41) is obtained. The second flaw detection step (S22) involves performing ultrasonic flaw detection on the object to be inspected (3) as follows: the ultrasonic flaw detection involves a second ultrasonic beam incident from a transmitting probe (42) along an inclined direction, and obtaining the reflected wave of the second ultrasonic beam received by a receiving probe (43), wherein the receiving probe (43) is disposed with the weld metal (2) spaced between it and the transmitting probe (42); and In the determination step (S23), based on the ultrasonic testing results of the first flaw detection step (S21) and the ultrasonic testing results of the second flaw detection step (S22), it is determined whether the softened tissue (21) exists in the above-mentioned inspection object (3).

[0103] The inventors have discovered that the reflected waves of the first and second ultrasonic beams behave differently (e.g., in intensity) in the softened structure (21) and columnar crystals (22), and based on these differences in behavior, it is possible to determine whether it is the softened structure (21) or the columnar crystals (22). By obtaining the reflected waves of the first and second ultrasonic beams according to the method described in 1), it is possible to determine whether it is the softened structure (21) or the columnar crystals (22) based on the behavior of these reflected waves, and thus it is possible to determine whether there is a softened structure (21) in the weld metal (2).

[0104] 2) In several embodiments, according to the softened tissue detection method (M2) described in 1) above, wherein, The above-mentioned determination step (S23) includes an estimation step (S231). In the above estimation step (S231), for each of the multiple segmented regions (32) that are divided in the above-mentioned inspection object (3), the information related to the intensity of the reflected wave of the first ultrasonic beam obtained from the ultrasonic flaw detection result of the first flaw detection step (S21) and the information related to the intensity of the reflected wave of the second ultrasonic beam obtained from the ultrasonic flaw detection result of the second flaw detection step (S22) are compared, thereby estimating the location and size of the softened tissue (21) in the above-mentioned inspection object (3).

[0105] According to the method described in 2), the intensity of the reflected wave from the first ultrasonic beam from the columnar crystal (22) is relatively high, while the intensity of the reflected wave from the second ultrasonic beam from the columnar crystal (22) is relatively low. Therefore, the segmented region (32) in the object under inspection (3) where the intensity of the reflected wave from the first ultrasonic beam is higher than that from the second ultrasonic beam can be identified as the columnar crystal (22), and the segmented region (32) in the object under inspection (3) where the intensity of the reflected wave from the first ultrasonic beam is lower than that from the second ultrasonic beam can be identified as the softened tissue (21). The location and size of the softened tissue (21) in the object under inspection (3) can be estimated based on the segmented region (32) identified as the softened tissue (21) in the object under inspection (3).

[0106] 3) In several embodiments, according to the softened tissue detection method (M2) described in 2) above, wherein...

[0107] The aforementioned inspection object (3) includes at least one weld section (31) along a direction orthogonal to the welding direction of the aforementioned weld metal (2). The above determination step (S23) includes: The first flaw detection image generation step (S232) generates a flaw detection image of the at least one welded section (31) based on the ultrasonic flaw detection result of the first flaw detection step (S21), namely, the first flaw detection image; and The second flaw detection image generation step (S233) generates a flaw detection image of the at least one welded section (31) based on the ultrasonic flaw detection result of the second flaw detection step (S22), namely, the second flaw detection image.

[0108] According to the method described in 3), the display states in the first flaw detection image and the second flaw detection image are different in the softened structure (21) and columnar crystal (22). Therefore, it is easy to determine which one is the softened structure (21) and columnar crystal (22) based on the first flaw detection image and the second flaw detection image. Therefore, it is easy to determine whether there is a softened structure (21) in the weld metal (2) using image analysis technology.

[0109] 4) In several embodiments, according to the softened tissue detection method (M2) described in 3) above, wherein, The above-mentioned determination step (S23) also includes an image estimation step (S234). In the above image estimation step (S234), for each of the multiple segmented regions (32) that are respectively divided in the above weld section (31), the first feature value of the first flaw detection image corresponding to the intensity of the reflected wave of the first ultrasonic beam and the second feature value of the second flaw detection image corresponding to the intensity of the reflected wave of the second ultrasonic beam are compared, thereby estimating the position and size of the softened tissue (21) in the above weld section (31).

[0110] According to the method described in 4) above, the segmented region (32) in the weld section (31) where the first characteristic value is higher than the second characteristic value can be identified as columnar crystals (22), and the segmented region (32) in the weld section (31) where the first characteristic value is lower than the second characteristic value can be identified as softened structure (21). The location and size of the softened structure (21) in the weld section (31) can be estimated based on the segmented region (32) identified as softened structure (21) in the weld section (31).

[0111] 5) In several embodiments, the softened tissue detection method (M2) according to any one of 1) to 4) above, wherein, The softened tissue detection method (M2) further includes a probe moving step (S24), in which at least one angled probe (41), the transmitting probe (42), and the receiving probe (43) are moved along the welding direction of the weld metal (2). The inspection object (3) includes multiple weld sections that are separated from each other along the welding direction of the weld metal (2) and along a direction orthogonal to the welding direction.

[0112] According to the method described in 5), by moving the angled probe (41), the transmitting probe (42), and the receiving probe (43) along the welding direction of the weld metal (2), it is possible to determine whether there is a softened structure (21) at multiple welding sections (31). By determining whether there is a softened structure (21) at multiple welding sections (31), the position and size of the softened structure (21) in the welding direction of the weld metal (2) can be estimated.

[0113] 6) In several embodiments, the softened tissue detection method (M2) according to any one of 1) to 5) above, wherein, The aforementioned at least one angled probe (41) includes: a first angled probe (41A); and The second angled probe (41B) is disposed with the first angled probe (41A) separated by the aforementioned welding metal (2). In the first flaw detection step (S21) described above, ultrasonic flaw detection is performed to obtain the reflected waves of the first ultrasonic beam that return to the first angle probe (41A) and the second angle probe (41B) respectively.

[0114] According to the method described in 6) above, the first ultrasonic beam from the first angled probe (41A) can be incident relative to the columnar crystal (22A) formed on the side of the first angled probe (41A) in the welding section (31) in a direction orthogonal to the extension direction of the columnar crystal (22A), thus the position and size of the columnar crystal (22A) as a reflection source can be estimated with high accuracy. Similarly, the first ultrasonic beam from the second angled probe (41B) can be incident relative to the columnar crystal (22B) formed on the side of the second angled probe (41B) in the welding section (31) in a direction orthogonal to the extension direction of the columnar crystal (22B), thus the position and size of the columnar crystal (22B) as a reflection source can be estimated with high accuracy.

[0115] 7) The remaining life estimation method (M3) of at least one embodiment of this disclosure is a remaining life estimation method (M3) for estimating the remaining life of weld metal (2). The remaining life estimation method (M3) described above includes a remaining life estimation step (S31). In the remaining life estimation step (S31), based on the determination result of the determination step (S23) obtained in the softened tissue detection method (M2) described above (2) or (4), the remaining life of the weld metal (2) is estimated by using the correspondence between the determination result of the determination step (S23) of the softened tissue detection method (M2) and the rate of reduction of the remaining life of the weld metal (2).

[0116] According to the method described in 7), the remaining life of the weld metal (2) can be estimated based on the location and size of the softened tissue (21) within the judgment object (3) obtained from the judgment result of the judgment step (S23) of the softened tissue detection method (M2).

[0117] 8) In several embodiments, the remaining lifetime estimation method (M3) described in 7) above is used. The above-mentioned remaining useful life estimation step (S31) includes: The area ratio calculation step (S311) calculates the area ratio of the softened tissue (21) based on the determination result of the determination step (S23) above; and The remaining life reduction rate calculation step (S312) calculates the remaining life reduction rate of the weld metal (2) based on the area ratio of the softened tissue (21) calculated in the area ratio calculation step (S311) and the correspondence between the area ratio of the softened tissue (21) and the remaining life reduction rate of the weld metal (2).

[0118] According to the method described in 8) above, there is a tendency that the higher the area ratio of the softened structure (21), the higher the rate of reduction in the remaining life of the weld metal (2). Based on the area ratio of the softened structure (21) calculated in the area ratio calculation step (S311), the rate of reduction in the remaining life of the weld metal (2) can be calculated using the correspondence between the area ratio of the softened structure (21) and the rate of reduction in the remaining life of the weld metal (2).

[0119] 9) An inspection object selection method (M1) of at least one embodiment of the present disclosure is used to select the weld metal (2) of the inspection object that is a material with or without softened tissue (21) in any of the softened tissue detection methods (M2) described in any of the above 1) to 6), and the inspection object selection method (M1) includes the following steps: In the weld bead distance acquisition step (S11), the weld bead distances of the candidate weld metals (2) that are the objects to be inspected are acquired; and In the welding metal selection step (S12), the welding metal (2) that becomes the inspection object is selected by taking into account the weld bead distance obtained in the weld bead distance acquisition step (S11).

[0120] According to the method described in 9), the shorter the distance between weld beads of weld metal 2, the greater the local heat input during welding, and therefore the higher the risk of generating softened structure (21) in weld metal 2. The distance between weld beads of weld metal (2) is closely related to the risk of generating softened structure (21). Therefore, by using the distance between weld beads of weld metal (2) as a parameter, weld metal (2) with a high risk of generating softened structure (21) can be selected as the object of inspection.

[0121] Explanation of reference numerals in the attached figures

[0122] 1. Ultrasonic Flaw Detection System

[0123] 2 Welding metal

[0124] 3. Inspection Object

[0125] 4A and 4B ultrasonic probes

[0126] 11 Measuring Apparatus

[0127] 12. Judgment Device

[0128] 13 Display devices

[0129] 20 Welding Section

[0130] 21. Softening tissue

[0131] Columnar crystals 22, 22A, 22B

[0132] 23 Welding defects

[0133] 24 weld beads

[0134] 31 Welded Section

[0135] 32. Segmentation Region

[0136] 41, 41A, 41B, 44 Angled probes

[0137] 42 Send side probe

[0138] 43. Receiver-side probe

[0139] M Softened tissue evaluation method

[0140] M1 Check Object Selection Method

[0141] M2 Softened Tissue Detection Method

[0142] M3 Remaining Life Estimation Method

[0143] Steps for obtaining the distance between weld beads (S11)

[0144] S12 Welding Metal Selection Steps

[0145] S21 First Flaw Detection Step

[0146] S22 Second Flaw Detection Procedure

[0147] S23 Judgment Steps

[0148] S31 Remaining life estimation procedure.

Claims

1. A method for detecting softened structures, used to detect softened structures within an inspection object of welded metal by ultrasonic testing, the method comprising the following steps: The first flaw detection step involves performing ultrasonic flaw detection on the object to be inspected, wherein a first ultrasonic beam is incident from at least one angled probe along an inclined direction, and the reflected wave of the first ultrasonic beam returning to the angled probe is obtained. The second flaw detection step involves performing ultrasonic flaw detection on the object under inspection, wherein a second ultrasonic beam is incident from a transmitting probe along an inclined direction, and the reflected wave of the second ultrasonic beam received by a receiving probe is obtained. The receiving probe is configured with a welded metal ground spaced between it and the transmitting probe. The determination step, based on the ultrasonic flaw detection results of the first flaw detection step and the ultrasonic flaw detection results of the second flaw detection step, determines whether the softened tissue exists in the object under inspection.

2. The method for detecting softened tissue according to claim 1, wherein, The determination step includes an estimation step. In the estimation step, for each of the multiple segmented regions divided in the inspected object, information related to the intensity of the reflected wave of the first ultrasonic beam obtained from the ultrasonic testing results of the first flaw detection step is compared with information related to the intensity of the reflected wave of the second ultrasonic beam obtained from the ultrasonic testing results of the second flaw detection step, thereby estimating the location and size of the softened tissue within the inspected object.

3. The method for detecting softened tissue according to claim 1, wherein, The object to be inspected includes at least one weld cross-section along a direction orthogonal to the welding direction of the weld metal. The determination step includes: The first flaw detection image generation step generates a flaw detection image of the at least one welded section based on the ultrasonic flaw detection result of the first flaw detection step, namely the first flaw detection image. and The second flaw detection image generation step generates a flaw detection image, i.e., a second flaw detection image, of the at least one welded cross section based on the ultrasonic flaw detection result of the second flaw detection step.

4. The method for detecting softened tissue according to claim 3, wherein, The determination step also includes an image estimation step. In the image estimation step, for each of the multiple segmented regions divided in the weld section, a first feature value corresponding to the intensity of the reflected wave of the first ultrasonic beam in the first flaw detection image and a second feature value corresponding to the intensity of the reflected wave of the second ultrasonic beam in the second flaw detection image are compared, thereby estimating the location and size of the softened tissue within the weld section.

5. The method for detecting softened tissue according to any one of claims 1 to 4, wherein, The softened tissue detection method further includes a probe moving step, in which the at least one angled probe, the transmitting probe, and the receiving probe are moved along the welding direction of the weld metal. The inspection object comprises multiple weld sections that are separated from each other along the welding direction of the weld metal and along a direction orthogonal to the welding direction.

6. The method for detecting softened tissue according to any one of claims 1 to 4, wherein, The at least one angled probe includes: First angled probe; and The second angled probe is positioned apart from the first angled probe by the weld metal ground. In the first flaw detection step, ultrasonic flaw detection is performed to obtain the reflected waves of the first ultrasonic beam that return to the first angled probe and the second angled probe, respectively.

7. A method for estimating the remaining life of weld metal. The remaining life estimation method includes a remaining life estimation step, in which the remaining life estimation step is used to estimate the remaining life of the weld metal based on the determination result of the determination step obtained by the softened tissue detection method according to claim 2 or 4, and by utilizing the correspondence between the determination result of the determination step and the rate of reduction of the remaining life of the weld metal.

8. The method for estimating remaining useful life according to claim 7, wherein, The remaining lifetime estimation step includes: The area ratio calculation step, based on the determination result of the determination step, calculates the area ratio of the softened tissue; and The remaining life reduction rate calculation step involves calculating the remaining life reduction rate of the weld metal based on the area ratio of the softened structure calculated in the area ratio calculation step, and utilizing the correspondence between the area ratio of the softened structure and the remaining life reduction rate of the weld metal.

9. A method for selecting an inspection object, used to select weld metal as an inspection object for the presence or absence of softened structure in any of the softened structure detection methods of claims 1 to 4, the method comprising the following steps: The step of obtaining the weld bead distance involves obtaining the weld bead distances of multiple candidate weld metals that are the object to be inspected; and In the weld metal selection step, the weld metal that will be the object of inspection is selected by taking into account the inter-weld distance of the plurality of weld metals obtained in the inter-weld distance acquisition step.

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