Ultrasonography device, ultrasonography method, and program

Abstract

To appropriately and easily evaluate a bonding state on a boundary surface between a base material and an overlay weld.SOLUTION: An ultrasonography device 30, which is an ultrasonography device applied to the evaluation of a bonding state of a boundary surface between a base material and an overlay weld performed on the base material, comprises: a signal acquisition unit 41 for acquiring a reflected echo signal as a test echo signal when an ultrasonic wave is emitted to a test object having the overlay weld performed on the base material; a correction value acquisition unit 44 for acquiring a correction value corresponding to the surface shape of the test object using correction information where parameters related to a curvature are associated with the correction value; and a correction unit 45 for correcting a threshold level for evaluating the signal value of the test echo signal or the bonding state using the acquired correction value.SELECTED DRAWING: Figure 7

Description

Technical Field

[0001] The present disclosure relates to an ultrasonic inspection apparatus, an ultrasonic inspection method, and a program.

Background Art

[0002] Conventionally, it has been known to perform build-up welding of a cobalt-based hard alloy having a higher hardness than the valve base material on the valve seat and valve body of a main valve such as a steam control valve used in a steam turbine. By performing such build-up welding, it becomes possible to make the valve less susceptible to damage due to thermal shock caused by the inflow and outflow of high-temperature and high-pressure superheated steam, and wear such as erosion-corrosion.

[0003] However, if there is a welding defect during build-up welding, the build-up welded portion may peel off during the operation of the steam turbine, which may damage the valve. In addition, over the course of operation of the steam turbine, the build-up welded portion may be damaged and peeling may occur, so it is necessary to periodically inspect the build-up welded portion.

[0004] Conventionally, ultrasonic flaw detection testing (UT: Ultrasonic Testing) has been used to inspect build-up welded portions. It is known that UT causes a decrease in sensitivity when a gap occurs between the probe and the test object. Valve seats and valve bodies used in steam turbines, particularly those for small and medium-sized (industrial) steam turbines, have large curvatures in both the steam flow direction and the circumferential direction, and there is a risk that the probe will float, creating a gap between the test specimens. Therefore, when applying conventional UT to such a test object, a decrease in sensitivity may occur, and appropriate inspection may not be possible.

[0005] As an inspection method for solving such problems, for example, the method disclosed in Patent Document 1 is known. In Patent Document 1, a defect of a size serving as an evaluation criterion for the quality of bonding is provided in a test piece simulating the object to be inspected, and a threshold value (reference echo intensity) used for the pass / fail determination is set based on the reflected echo signal when ultrasonic inspection is performed on this test piece. By comparing this threshold value with the inspection echo signal of the actual object to be inspected, a method for evaluating the bonding state at the interface between the base material and the build-up welded part is disclosed.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] Since the method disclosed in Patent Document 1 sets the threshold value for the quality of bonding using a test piece simulating the object to be inspected, it can solve the problem of sensitivity reduction as described above and perform appropriate inspection. However, it is necessary to prepare a test piece having the same shape as the object to be inspected every time a test is performed, which requires labor and time.

[0008] The present disclosure has been made in view of such circumstances, and an object thereof is to provide an ultrasonic inspection apparatus, an ultrasonic inspection method, and a program capable of appropriately and easily evaluating the bonding state at the interface between the base material and the build-up welded part.

Means for Solving the Problems

[0009] One aspect of the present disclosure is an ultrasonic inspection apparatus applied to the determination of the bonding state at the interface between a build-up welded portion applied to a base material and the base material, the apparatus including: a signal acquisition unit that acquires a reflected echo signal when ultrasonic waves are transmitted to a test object having a build-up welded portion applied to the base material as an inspection echo signal; a correction value acquisition unit that acquires a correction value corresponding to the surface shape of the test object using correction information in which a parameter related to curvature and a correction value are associated; and a correction unit that corrects a signal value of the inspection echo signal or a threshold value for evaluating the bonding state using the acquired correction value.

[0010] One aspect of the present disclosure is an ultrasonic inspection method applied to the determination of the bonding state at the interface between a build-up welded portion applied to a base material and the base material, the method including: an inspection signal acquisition step of acquiring a reflected echo signal when ultrasonic waves are transmitted to a test object having a build-up welded portion applied to the base material as an inspection echo signal; a correction value acquisition step of acquiring a correction value corresponding to the surface shape of the test object using correction information in which a parameter related to curvature and a correction value are associated; and a correction step of correcting a signal value of the inspection echo signal or a threshold value for evaluating the bonding state using the acquired correction value, the steps being executed by a computer.

[0011] One aspect of the present disclosure is a program for causing a computer to function as the above ultrasonic inspection apparatus.

Advantages of the Invention

[0012] According to the present disclosure, there is an effect that the bonding state at the interface between the base material and the build-up welded portion can be appropriately and easily evaluated.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Figure 15

Figure 16

Figure 17

Figure 18

Figure 19

Figure 20

Figure 21

Figure 22

Embodiments for Carrying Out the Invention

[0014] Hereinafter, an embodiment of an ultrasonic inspection apparatus, an ultrasonic inspection method, and a program according to the present disclosure will be described with reference to the drawings. In the following description, the case of inspecting the joint state (for example, welding defects, peeling, etc.) of the build-up welding part in the steam valve used in the steam turbine will be exemplified and described, but it is not limited thereto. For example, the ultrasonic inspection apparatus, the ultrasonic inspection method, and the program according to the present disclosure can be widely applied to the evaluation of the joint state of the build-up welding part constructed on the base material.

[0015] FIGS. 1 to 4 are diagrams for explaining an example of an object to be inspected according to an embodiment of the present disclosure. FIG. 1 is a longitudinal sectional view showing an example of the internal structure of a steam valve used in a steam turbine. In FIG. 1, by fastening a valve cover 2 to a valve body 1 of the steam valve with bolts 3, a casing 4 of a throttle valve as a pressure vessel is formed. Inside this casing 4, a valve body 7 that is brought into contact with and separated from a valve seat 6 via a valve rod 5 is disposed, and a strainer 8 for retaining foreign matter in the steam is provided on the outer peripheral portion of the valve body 7. The valve rod 5 is held by a guide member 9, and a driving device (not shown) for operating the valve body 7 in the vertical direction is provided at its end.

[0016] The steam in the steam valve flows into the casing 4 from, for example, a steam pipe (not shown) as indicated by the arrow IN, passes through the flow path between the valve body 7 and the valve seat 6 formed by the upward movement of the valve body 7 shown in FIG. 1, and flows out to the arrow OUT. A valve seat sheet portion 10 (see FIGS. 2 to 4) is formed at the contact portion between the valve body 7 and the valve seat 6.

[0017] FIG. 2 is a perspective view of the valve seat sheet portion 10 shown in FIG. 1, FIG. 3 is a schematic longitudinal sectional view of the valve seat sheet portion 10, and FIG. 4 is a longitudinal sectional view showing an enlarged portion A of the valve seat sheet portion 10 shown in FIG. 3. As shown in FIGS. 2 to 4, the valve seat sheet portion 10 has a build-up welded portion 11 formed by performing build-up welding over the entire circumference in the circumferential direction of the base material. As an example, a Stellite material, which is a cobalt-based corrosion and heat-resistant alloy, is build-up welded. Examples of such a method for build-up welding a Stellite material include an oxyacetylene method using a cobalt-based hard alloy welding wire, a TIG (Tungsten Inert Gas) method, a PTA (Plasma Transferred Arc) method, a method of spraying a cobalt-based matrix alloy powder, and the like. The base material is not particularly limited, but as an example, a forged material can be mentioned.

[0018] In the present embodiment, a case of evaluating the bonding state (such as welding defects and peeling) between the build-up welded portion 11 formed on the valve seat sheet portion 10 of the valve seat 6 and the base material will be exemplified and described.

[0019] FIG. 5 is a diagram showing the overall configuration of an ultrasonic inspection system 50 according to an embodiment of the present disclosure. In FIG. 5, the ultrasonic inspection system 50 includes an ultrasonic probe (hereinafter simply referred to as a "probe") 20 and an ultrasonic inspection device 30.

[0020] The probe 20 irradiates ultrasonic waves into the interior of the object to be inspected, receives the reflected echoes returning from the object to be inspected, and outputs an output signal regarding the received reflected echoes (hereinafter referred to as "reflected echo signal") to the ultrasonic inspection apparatus 30. In the present embodiment, as the probe 20, a single-element vertical probe that transmits an ultrasonic beam perpendicularly incident on the surface (inspection surface) of the object to be inspected is used. The vertical probe may be configured by, for example, a single sensor, or may be a phased array probe configured by a plurality of sensors. Also, it is possible to use a wheel type (tire type) probe or the like. In the present embodiment, the case of being configured by a single sensor will be exemplified and described. The size of the probe 20 is preferably selected to be appropriate according to the size of the defect serving as the evaluation criterion for joint defect determination and the curved surface shape of the surface of the build-up welded portion 11. Also, an appropriate contact medium may be used according to the inspection. As an example, clean machine oil, castor oil, glycerin paste (sonicate), grease, etc. may be mentioned. In the present embodiment, as an example, the case of using glycerin paste will be exemplified.

[0021] Further, the probe 20 according to the present embodiment is provided with a probe movement distance measuring device (not shown) for creating an internal scope image (for example, a B-scope, a C-scope, etc. described later). This probe movement distance measuring device is composed of an encoder attached to the probe 20. By outputting a pulse corresponding to the movement amount of the probe 20 from the encoder, the ultrasonic inspection apparatus 30 can associate the inspection position in the object to be inspected with the reflected echo signal.

[0022] The ultrasonic inspection apparatus 30 inspects the interior of the object to be inspected based on the reflected echo signal received from the probe 20, and notifies the inspector by displaying the inspection result on a display or the like.

[0023] FIG. 6 is a schematic configuration diagram showing an example of the hardware configuration of an ultrasonic inspection apparatus 30 according to an embodiment of the present disclosure. The ultrasonic inspection apparatus 30 is a computer system and includes, for example, a processing circuit 40 and a communication interface 35 as shown in FIG. 6. The ultrasonic inspection apparatus 30 may also include an input device 36, an output device 37, an external interface (not shown) for connecting to an external device, and the like. These components are directly or indirectly connected to each other via a bus and cooperate with each other to execute various processes.

[0024] The processing circuit 40 includes, for example, a CPU (Central Processing Unit) 31, a main memory 32, and a secondary storage 33.

[0025] The CPU 31 controls the ultrasonic inspection apparatus 30 by an OS (Operating System) stored in the secondary storage 33 connected via a bus, and executes various processes by executing various programs stored in the secondary storage 33. One or more CPUs 31 may be provided and may cooperate with each other to realize processing.

[0026] The main memory 32 is composed of, for example, a writable memory such as a cache memory and a RAM (Random Access Memory), and is used as a work area for reading the execution program of the CPU 31, writing processing data by the execution program, and the like.

[0027] The secondary storage device 33 is a non-transitory computer readable storage medium. The secondary storage device 33 is, for example, a magnetic disk, a magneto-optical disk, a CD-ROM, a DVD-ROM, a semiconductor memory, etc. Examples of the secondary storage device 33 include a ROM (Read Only Memory), an HDD (Hard Disk Drive), an SSD (Solid State Drive) flash memory, etc. The secondary storage device 33 stores, for example, an OS for controlling the entire ultrasonic inspection device 30 such as Windows (registered trademark), iOS (registered trademark), Android (registered trademark), a BIOS (Basic Input / Output System), various device drivers for hardware operation of peripheral devices, various application software, and various data and files. Also, the secondary storage device 33 stores a program for realizing various processes and various data required for realizing various processes. A plurality of secondary storage devices 33 may be provided, and the programs and data as described above may be divided and stored in each secondary storage device 33.

[0028] The communication interface 35 functions as an interface for connecting to a network and communicating with other devices to transmit and receive information. For example, the communication interface 35 communicates with other devices by wire or wirelessly. Examples of wireless communication include communication through lines such as Bluetooth (registered trademark), Wi-Fi, mobile communication systems (3G, 4G, 5G, 6G, LTE, etc.), and wireless LAN. An example of wired communication includes communication through a line such as a wired LAN (Local Area Network).

[0029] Examples of the input device 36 include a keyboard, a touch pad, a pointing device, etc. Examples of the pointing device include a mouse, a touch panel, a pen tablet, a track pad, a track ball, etc. Examples of the output device 37 include a display, a projector, a printer, and the like.

[0030] Next, an example of the functions of the ultrasonic inspection apparatus 30 according to the present embodiment will be described with reference to the drawings. FIG. 7 is a functional block diagram showing an example of the functions of the ultrasonic inspection apparatus 30 according to the present embodiment. A series of processes for realizing various functions described later are stored in the secondary storage device 33 in the form of a program as an example. The CPU (processor) 11 reads this program into the main storage device 32 and executes information processing and arithmetic processing, thereby realizing various functions. Note that the program may be applied in a form pre-installed in the secondary storage device 33, a form provided in a state stored in a non-transitory computer-readable storage medium, a form distributed via wired or wireless communication means, or the like. Examples of the non-transitory computer-readable storage medium include a magnetic disk, a magneto-optical disk, a CD-ROM, a DVD-ROM, and a semiconductor memory.

[0031] As shown in FIG. 7, the ultrasonic inspection apparatus 30 includes, for example, a signal acquisition unit 41, a storage unit 42, a correction necessity determination unit 43, a correction value acquisition unit 44, and a correction unit 45. The ultrasonic inspection apparatus 30 may also include an evaluation unit 46 and a display control unit 47.

[0032] The signal acquisition unit 41 receives a reflected echo signal (inspection echo signal) output from the probe 20. For example, the signal acquisition unit 41 acquires, as an inspection echo signal, a reflected echo signal when ultrasonic waves are transmitted to a test object having a build-up welded joint 11 formed on a base material during inspection of the test object.

[0033] The storage unit 42 stores correction information in which parameters related to the curvature (the curvature of the surface shape of the object under inspection) and correction values are associated. Further, the correction information may be associated with parameters related to the curvature, correction values, and contact media. Fig. 8 shows a correction table as an example of the correction information. In Fig. 8, the radius of curvature [mm] is adopted as the parameter related to the curvature, but it is not limited thereto. For example, the curvature may be used instead of the radius of curvature. Further, as the contact media, glycerin paste and machine oil are exemplified, but it is not limited thereto. Instead of or in addition to these, other contact media may be associated. Further, the correction information may be, for example, a function for deriving a correction value from parameters related to the curvature (for example, the radius of curvature, the curvature, etc.). In this case, functions corresponding to each contact medium may be stored in the storage unit 42. The method for creating the correction information will be described later.

[0034] Further, the storage unit 42 stores a threshold value R1_ref related to the curvature for determining whether correction is necessary. In the present embodiment, a threshold value of the radius of curvature is adopted as the threshold value related to the curvature. This threshold value R1_ref is used by a correction necessity determination unit 43 described later. The method for setting this threshold value will be described later.

[0035] Further, the storage unit 42 stores various data required for evaluating the bonding state at the interface between the base material, which is the object under inspection, and the build-up welded portion 11. For example, the storage unit 42 stores information on a threshold value (reference echo intensity) used when evaluating the bonding state. Further, the storage unit 42 may store a reflected echo signal (hereinafter referred to as "inspection echo signal") acquired by a signal acquisition unit 41 described later.

[0036] The correction necessity determination unit 43 determines the necessity of correction using the threshold value R1_ref stored in the storage unit 42. Specifically, it compares the radius of curvature in the vapor flow direction A (see FIG. 9) of the inspection object with the threshold value R1_ref. If the radius of curvature is less than the threshold value R1_ref, it is determined that correction is necessary. If the radius of curvature is greater than or equal to the threshold value R1_ref, it is determined that correction is not necessary.

[0037] The correction value acquisition unit 44 acquires a correction value corresponding to the radius of curvature of the surface shape of the inspection object using the correction information stored in the storage unit 42. Here, regarding the radius of curvature of the inspection object, for example, it can be acquired from the drawing data of the inspection object. Also, by scanning the inspection object in advance using a 3D scanner or the like to acquire shape data and analyzing the shape data, the radius of curvature of the surface shape of the inspection object may be obtained.

[0038] The correction unit 45 corrects the inspection echo signal using the correction value acquired by the correction value acquisition unit 44. For example, the inspection echo signal is corrected by adding the correction value to the signal value of the inspection echo signal. Note that the correction method varies depending on what value the correction value registered in the correction information has. Therefore, for the correction method, an appropriate method corresponding to the correction value may be applied.

[0039] The evaluation unit 46 evaluates the bonding state of the inspection object using the corrected inspection echo signal. For example, the evaluation unit 46 evaluates the bonding state at the interface between the base material and the build-up welded part 11 based on the comparison between the peak value (maximum signal intensity) of the corrected inspection echo signal and the threshold value (reference echo intensity). Specifically, the evaluation unit 46 determines that it is defective when the peak value of the inspection echo signal is greater than or equal to the threshold value. Note that regarding the evaluation method by the evaluation unit, since numerous known techniques have been proposed, those techniques can be appropriately adopted.

[0040] The display control unit 47 creates, for example, a display screen for notifying an inspector of the inspection results and displays it on an output device 37 such as a display. For example, the display control unit 47 causes the display to display a reflected echo image (A-scan) of the object under inspection created based on the corrected inspection echo signal, a cross-sectional scan image (B-scan) created based on the corrected inspection echo signal, a planar image (C-scan) created based on the corrected inspection echo signal, and the like. Note that since numerous known techniques have been proposed for the method of displaying the results of ultrasonic inspection, appropriate images may be created by adopting them, and the display may be performed based on various input instructions input from the input device 36.

[0041] Further, the ultrasonic inspection apparatus 30 may include a signal processing unit for performing preprocessing necessary for evaluating the joint state with respect to the inspection echo signal. The signal processing unit performs, for example, time axis adjustment processing, evaluation gate setting processing, and the like.

[0042] Next, a method for creating the correction information described above will be described. First, a plurality of test pieces are created (test piece creation step). For example, the shape of the valve seat seat portion 10, which is the object under inspection in the present embodiment, is various. That is, although the valve seat seat portion 10 has a standard design specification, minor changes and the like have been made, and irregular shapes also exist. Therefore, a test piece according to the standard design specification is created, and a plurality of test pieces having irregular shapes corresponding to minor changes are created. Here, in the case of the valve seat seat portion 10, as shown in FIG. 9, there are a curvature in the steam flow direction A and a curvature in the circumferential direction B, and it is necessary to grasp the influence of these two curvatures on the sensitivity reduction. Therefore, a plurality of test pieces are created with different combinations of the curvature (radius of curvature) in the steam flow direction and the curvature (radius of curvature) in the circumferential direction.

[0043] Fig. 10 shows an example of the shape of the test piece 60. In Fig. 10, (a) is a front view of the test piece 60, and (b) is a bottom view. As shown in Fig. 10, the test piece 60 has curvatures in the steam flow direction A (the first direction) and the circumferential direction B (the second direction), respectively. The test piece is preferably manufactured using the same material (for example, a stellite material) as the build-up welded portion 11 of the object to be inspected. However, if the influence of the material and shape is small or can be corrected, even if the material and shape are different from those of the object to be inspected, it may be applied as a test piece.

[0044] Each test piece 60 is provided with a flat-bottomed hole ho having a bottom Sa at a position of a surface depth d [mm] corresponding to the interface S (see Fig. 4) between the base material and the build-up welded portion 11 in the object to be inspected. This flat-bottomed hole ho simulates, for example, the space (the gap generated by peeling) between the base material and the build-up welded portion 11. The diameter of the flat-bottomed hole ho is set to the defect size of the evaluation criterion for determining the quality of the joint. For example, when it is determined as defective when a defect of α [mm] or more is detected, a flat-bottomed hole ho of size α [mm] is provided. In Fig. 10, the flat-bottomed hole ho is provided at the center of the test piece 60, but it is not limited to this example, and any position where a reflection echo signal in the defect can be surely obtained is acceptable.

[0045] Fig. 11 is a diagram showing an example of the combination of the radius of curvature R1 in the steam flow direction and the radius of curvature R2 in the circumferential direction of each test piece 60. Here, the radius of curvature is the reciprocal of the curvature. The larger the radius of curvature, the smaller the curvature, and it becomes a gentle curve. Each point shown in Fig. 11 corresponds to each test piece 60 and shows the combination of the radius of curvature R1 and the radius of curvature R2 of that test piece 60. The number of test pieces 60 and the combination of the radii of curvature R1 and R2 may be appropriately adjusted according to the characteristics of the object to be inspected, etc.

[0046] Subsequently, for each of the plurality of test pieces 60, reflection echo signals when ultrasonic waves are transmitted under the same conditions are respectively acquired (signal acquisition step).

[0047] First, before inspecting each test piece 60, calibration of the flaw detection sensitivity is performed. In calibration, a test piece 70 for sensitivity adjustment is used. FIG. 12 is a longitudinal sectional view of the test piece 70 as an example. As shown in FIG. 12, the test piece 70 for sensitivity adjustment is a flat plate test piece, and a flat bottom hole ho' having a bottom Sb is provided at a position of a surface depth d [mm] corresponding to the interface S (see FIG. 4) between the base material and the build-up welded part 11. The size and shape of this flat bottom hole ho' are the same as those of the test piece 60 (see FIG. 10) described above. Further, the material of the test piece 70 for sensitivity adjustment is the same as that of the test piece 60 described above.

[0048] In calibration, while moving the probe 20 along the surface of the test piece 70, ultrasonic waves are transmitted, and the reflected waves at each inspection position are received as reflected echo signals. Then, the maximum signal value (peak value) is specified from the obtained reflected echo signals, and the gain of the ultrasonic inspection device 30 is adjusted so that the output becomes 100% with this peak value as the reference echo intensity. Calibration may be performed by an inspector or automatically.

[0049] When the calibration is completed, each test piece 60 is tested, and the reflected echo signals of each test piece 60 are acquired. Specifically, in each test piece 60, ultrasonic waves are transmitted into the test piece by moving the probe 20 along the surface shape, and the reflected echo signals at that time are received. Then, among these, the reflected echo signal from the bottom Sa is acquired as a specific echo signal.

[0050] Subsequently, the relationship between the radius of curvature R1 in the vapor flow direction, the radius of curvature R2 in the circumferential direction, and the sensitivity reduction is analyzed from the specific echo signals of each test piece 60 (analysis step).

[0051] As shown in FIG. 10, since each test piece 60 is provided with a flat bottom hole ho under the same conditions as the test piece 70 for sensitivity adjustment, when no sensitivity reduction occurs, the signal value of the specific echo signal should be 100%, which is the reference echo intensity. On the other hand, when the signal value of the specific echo signal is 100% or less, it means that sensitivity reduction has occurred.

[0052] Therefore, in order to understand the relationship between the radius of curvature R1 in the steam flow direction and the radius of curvature R2 in the circumferential direction and the sensitivity degradation, the signal values of the specific echo signals obtained from each test piece 60 are aggregated, and a graph showing each radius of curvature R1, R2 and the signal value of the specific echo signal is created. Specifically, first information showing the relationship between the radius of curvature R1 in the steam flow direction and the signal value of the specific echo signal (parameter related to sensitivity degradation) and second information showing the relationship between the radius of curvature R2 in the circumferential direction and the signal value of the specific echo signal are created.

[0053] FIG. 13 is a diagram showing an example of the first information indicating the relationship between the signal value of the specific echo signal for each radius of curvature R1 in the steam flow direction, and FIG. 14 is a diagram showing an example of the second information indicating the relationship between the signal value of the specific echo signal for each radius of curvature R2 in the circumferential direction. Further, FIG. 15 is a diagram showing the relationship between the signal value of the specific echo signal for each radius of curvature R1 in the steam flow direction and showing the variation in the signal value of the specific echo signal due to the radius of curvature R2 in the circumferential direction by the width.

[0054] The first information shown in FIG. 13 is, for example, as shown in FIG. 16, a graph in which test pieces having substantially the same radius of curvature R1 in the steam flow direction are grouped, the average value of the signal values of the specific echo signals in each group is calculated, and an approximate curve based on the calculated average value is shown. Similarly, FIG. 14 is a graph in which test pieces having substantially the same radius of curvature R2 in the circumferential direction are grouped, the average value of the signal values of the specific echo signals in each group is calculated, and an approximate curve based on the calculated average value is shown. Note that the first information and the second information only need to be information that can show the relationship (tendency) between the signal value of the specific echo signal for each curvature (radius of curvature), and are not limited to the above example. For example, the first information and the second information may be obtained by statistically processing the signal values of the specific echo signals obtained from each test piece using a known statistical method.

[0055] When comparing the first piece of information (Figure 13) with the second piece of information (Figure 14), regarding the steam flow direction shown in Figure 13, for the region where the radius of curvature R1 is small (the region with a large curvature), the smaller the radius of curvature (the larger the curvature), the smaller the signal value of the specific echo signal. From this, it can be seen that there is a strong correlation between the sensitivity reduction and the radius of curvature R1. In contrast, regarding the circumferential direction shown in Figure 14, even when the radius of curvature R2 changes, the signal value of the specific echo signal does not change much, indicating that there is no correlation between the two. This is also clear from the graph shown in Figure 15, and the variation in the signal value of the specific echo signal due to the radius of curvature R2 in the circumferential direction is not very large, indicating that the sensitivity reduction is dominated by the radius of curvature R1 in the steam flow direction.

[0056] Next, correction information is created based on the above analysis results (correction information creation step). That is, from the above analysis, it was found that the influence of the radius of curvature R1 (curvature) in the steam flow direction is dominant for the sensitivity reduction related to the ultrasonic flaw detection of the valve seat portion 10. Therefore, correction information associating the radius of curvature in the steam flow direction with the correction value is created. The correction value is a value that compensates for the sensitivity reduction.

[0057] Specifically, as shown in Figure 17, in the first piece of information, the amount of decrease in the signal value of the specific echo signal for each radius of curvature R1 in the steam flow direction is used as the correction value, and correction information associating the radius of curvature R1 with the correction value is created. Thereby, for example, correction information as shown in Figure 8 is created. Also, based on the first piece of information shown in Figure 17, a function for deriving the correction value from the radius of curvature R1 can be created, and this function can also be used as correction information.

[0058] Also, the sensitivity reduction is affected by the contact medium. Therefore, by implementing the above correction information creation method while changing the contact medium respectively, correction information for each contact medium can be obtained. For example, Figure 18 shows a comparison of the relationship between the radius of curvature R1 and the peak value when glycerin paste is used as the contact medium and the relationship between the radius of curvature R1 and the peak value when machine oil is used as the contact medium. In FIG. 18, the variation in the signal value of the specific echo signal due to the radius of curvature R2 in the circumferential direction is shown as the width. As shown in FIG. 18, it can be seen that the sensitivity of machine oil decreases more significantly compared to glycerin paste.

[0059] Also, from FIG. 17, the value R1_ref of the radius of curvature R1 that does not require correction can be determined. That is, in the region where the radius of curvature R1 is greater than or equal to the threshold value R1_ref, since there is no decrease in sensitivity, correction is not required. From this, when the radius of curvature R1 in the vapor flow direction of the object to be inspected is less than the threshold value R1_ref, correction using the correction information may be performed.

[0060] The correction information and the threshold value R1_ref created in this way are stored in the storage unit 42 (see FIG. 7) and used in the inspection of the object to be inspected.

[0061] Next, an ultrasonic inspection method using the ultrasonic inspection system 50 according to the present embodiment will be described with reference to FIGS. 19 and 20. FIGS. 19 and 20 are flowcharts showing an example of the procedure of the ultrasonic inspection method according to the present embodiment.

[0062] First, using a test piece 70 for sensitivity adjustment, calibration of the flaw detection sensitivity is performed (SA1). Since the calibration is the same as the calibration performed before inspecting each test piece 60, detailed description is omitted.

[0063] Subsequently, the probe 20 is moved along the surface of the object to be inspected (SA2). In the present embodiment, for example, the probe 20 is scanned along the circumferential direction or the vapor flow direction of the valve seat sheet portion 10 shown in FIG. 2. Note that the scanning of the probe 20 may be manually performed by an inspector, or the probe 20 may be automatically moved according to a preset scanning route.

[0064] As a result, ultrasonic waves are irradiated into the subject at each inspection position of the subject, and the reflected echoes are sequentially received. The reflected echoes of the subject thus obtained are subjected to predetermined processing and associated with position information, and then sequentially output as inspection echo signals to the ultrasonic inspection apparatus 30. An example of an inspection echo signal (A-scope) is shown in FIG. 21.

[0065] In the ultrasonic inspection apparatus 30, when the inspection echo signals at each inspection position are acquired (SA3), an evaluation gate G is set in the A-scope at each inspection position based on the distance from the surface of the build-up weld to the boundary surface S (SA4).

[0066] Subsequently, for each inspection echo signal acquired at each inspection position, the peak value of the inspection echo signal is acquired within the time range of the evaluation gate G (SA5). Subsequently, it is determined whether or not the radius of curvature R1 in the vapor flow direction of the subject is greater than or equal to a threshold value R1_ref (SA6). As a result, when the radius of curvature R1 is less than the threshold value R1_ref (SA6: NO), a correction value corresponding to the radius of curvature R1 is acquired from the correction information (SA7), and the peak value is corrected using the acquired correction value (SA8). On the other hand, when the radius of curvature R1 is greater than or equal to the threshold value R1_ref (SA6: YES), the process proceeds to step SA9 without correcting the peak value (see FIG. 20).

[0067] In step SA9, the peak value (when correction is performed, the corrected peak value) at each inspection position is compared with a threshold value (reference echo intensity set to 100% by gain adjustment), and it is determined whether or not the peak value is greater than or equal to the threshold value (SA9). As a result, when the peak value is less than the threshold value (SA9: NO), it is determined as qualified (SA10), while when the peak value is greater than or equal to the threshold value (SA9: YES), it is determined as defective (SA11), and the process proceeds to step SA12.

[0068] In step SA12, the inspection result is displayed on the display (SA12), and the process ends. In the display of the inspection result, an A-scope, B-scope, C-scope, etc. based on the inspection echo signal acquired during the inspection (the corrected inspection echo signal if corrected) may also be displayed on the display together with the inspection result. Thereby, when a defect determination is made, it becomes possible to notify the inspector of the position where peeling has occurred, the size of the peeling, and the like.

[0069] As described above, according to the ultrasonic inspection apparatus, ultrasonic inspection method, and program according to the present embodiment, a correction value corresponding to the object to be inspected is obtained from correction information in which a parameter related to curvature and a correction value are associated, and the signal value of the inspection echo signal is corrected using the obtained correction value. Here, since the correction information associates the parameter related to each curvature with the correction value, it is possible to compensate for the sensitivity reduction due to the shape of the object to be inspected by an easy process of obtaining an appropriate correction value according to the object to be inspected. As a result, it is no longer necessary to create a test piece simulating the object to be inspected every time an inspection is performed as in the prior art, and it becomes possible to reduce the labor and time required for the inspection.

[0070] As described above, the present disclosure has been described using embodiments. However, the technical scope of the present disclosure is not limited to the scope described in the above embodiments. Various changes or improvements can be made to the above embodiments without departing from the gist of the disclosure, and the forms with such changes or improvements are also included in the technical scope of the present disclosure. Also, the above embodiments may be combined as appropriate. In addition, the preprocessing procedure and the ultrasonic inspection method procedure described in the above embodiments are also examples, and unnecessary steps may be deleted, new steps may be added, or the processing order may be changed within the scope not departing from the gist of the present disclosure.

[0071] For example, in the above ultrasonic inspection method, although the case where the acquisition of the inspection echo signal and the evaluation of defects are performed simultaneously during the inspection has been exemplified and described, it is not limited to this example. For example, the acquisition of the inspection echo signal (for example, SA1 to SA3 in FIG. 19) and the evaluation process of the joint state based on the inspection echo signal (for example, SA4 in FIG. 19 to SA12 in FIG. 20) may be performed individually. For example, the inspection echo signal obtained by the inspector moving the probe 20 along the surface of the object to be inspected is stored in the storage unit 42 (see FIG. 7) in association with the inspection position, and afterwards, the inspection echo signals at each inspection position stored in the storage unit 42 are read out, and the above-described evaluation process and the like may be performed using the read inspection echo signal.

[0072] Also, in the above embodiment, the inspection echo signal has been corrected using the correction value, but it is not limited to this. For example, instead of the inspection echo signal, the threshold value (reference echo intensity, the threshold value used in step SA9 in FIG. 20) used when evaluating the joint state at the interface between the base material and the build-up welded part 11 may be corrected. That is, without correcting the inspection echo signal, the threshold value is corrected by subtracting the correction value from the reference echo intensity set to 100% by gain adjustment. By correcting the threshold value used for the pass / fail determination in this way, it is possible to simplify the correction process compared to the case of correcting each inspection signal.

[0073] Also, in the above embodiment, the ultrasonic inspection device 30 includes the correction necessity determination unit 43, but the correction necessity determination unit 43 can be omitted. In this case, for example, in the correction information, a correction value of "0" may be set for the radius of curvature (curvature) for which correction is unnecessary. Also, for the radius of curvature (curvature) for which correction is unnecessary, the correction value may not be set, and it may be determined that correction is unnecessary when the correction value is not set.

[0074] In the above-described embodiment, the ultrasonic inspection apparatus 30 is provided with the storage unit 42. However, the storage unit 42 is not limited to this example. For example, the storage unit 42 may be provided so that the ultrasonic inspection apparatus 30 can access it. For example, it may be configured to be accessed via a network, such as a cloud server or the like.

[0075] Also, in the above-described embodiment, the case where a vertical probe is used as the probe has been illustrated, but the present invention is not limited to this example. For example, it is also possible to use other probes such as an angled probe.

[0076] Also, in the above-described embodiment, the case where the valve seat sheet portion 10 is the object to be inspected has been illustrated and described. However, the ultrasonic inspection apparatus, the ultrasonic inspection method, and the program according to the present embodiment can also be applied when other structures are the object to be inspected.

[0077] For example, it is also possible to use the valve body 7 as the object to be inspected. In the case of the valve body 7, it is generally spherical, and the relationship between the radius of curvature R1 in the steam flow direction and the radius of curvature R2 in the circumferential direction is constant. Therefore, in the case of the valve body 7, as shown in FIG. 22, a similar test may be performed using a test piece 80 having a spherical surface, and correction information may be created.

[0078] The ultrasonic inspection method, the ultrasonic inspection apparatus, and the program described in the above-described embodiment are understood as follows, for example.

[0079] The ultrasonic inspection device according to the first aspect of the present disclosure is an ultrasonic inspection device (30) applied to the determination of the bonding state at the interface (S) between the build-up welded portion (11) constructed on the base material and the base material, and includes a signal acquisition unit (41) that acquires a reflected echo signal when transmitting ultrasonic waves to a test object having a build-up welded portion (11) constructed on the base material as an inspection echo signal, a correction value acquisition unit (44) that acquires a correction value corresponding to the surface shape of the test object using correction information in which a parameter related to curvature and a correction value are associated, and a correction unit (45) that corrects the signal value of the inspection echo signal or a threshold value for evaluating the bonding state using the acquired correction value.

[0080] According to the above aspect, a correction value corresponding to the test object is acquired from correction information in which a parameter related to curvature and a correction value are associated, and the signal value of the inspection echo signal or the threshold value for evaluating the bonding state is corrected using the acquired correction value. Here, since the correction information associates the parameter related to each curvature with the correction value, it is possible to compensate for the sensitivity decrease due to the shape of the test object by an easy process of acquiring an appropriate correction value according to the test object. As a result, it is not necessary to create a test piece simulating the test object every time an inspection is performed, and it is possible to reduce the labor and time required for the inspection.

[0081] The ultrasonic inspection device according to the second aspect of the present disclosure is, in the first aspect, wherein the correction information associates curvature, a correction value, and a contact medium, and the correction value acquisition unit acquires a correction value corresponding to the surface shape of the test object and the contact medium used in the ultrasonic inspection from the correction information.

[0082] According to the above aspect, since the contact medium is associated with the correction information, it is possible to compensate for the sensitivity decrease due to the contact medium used when inspecting the test object. As a result, it is possible to improve the inspection accuracy.

[0083] The ultrasonic inspection apparatus according to the third aspect of the present disclosure includes, in the first aspect or the second aspect, a correction necessity determination unit (43) that determines that correction is unnecessary when a parameter related to the curvature of the surface shape of the object to be inspected satisfies a predetermined condition.

[0084] According to the above aspect, when a parameter related to the curvature of the surface shape of the object to be inspected satisfies a predetermined condition, it is determined that correction is unnecessary, so it is possible to easily determine whether correction is necessary according to the surface shape of the object to be inspected.

[0085] The ultrasonic inspection apparatus according to the fourth aspect of the present disclosure is, in any one of the first aspect to the third aspect, the object to be inspected is a valve body (7) or a valve seat (6) of a steam valve in a steam turbine, and the parameter related to the curvature is the curvature or the radius of curvature in the steam flow direction of the valve body (7) or the valve seat (6).

[0086] For example, regarding the valve body or the valve seat (valve seat seat portion) of the steam valve in the steam turbine, it has been found that there is a strong correlation between the radius of curvature of the steam flow and the sensitivity reduction, while there is almost no correlation between the radius of curvature in the circumferential direction and the sensitivity reduction. Therefore, by using correction information that associates the curvature or the radius of curvature in the steam flow direction of the valve body (7) or the valve seat (6) with the correction value, it is not necessary to consider the radius of curvature in the circumferential direction, so correction can be easily performed.

[0087] The ultrasonic inspection apparatus according to the fifth aspect of the present disclosure is, in any one of the first aspect to the fourth aspect, an evaluation unit (46) that evaluates the joining state at the interface between the base material and the build-up welded portion based on a comparison between the signal value of the inspected echo signal after correction and a predetermined threshold value, or a comparison between the inspected echo signal and the threshold value after correction.

[0088] According to the above aspect, since the joining state at the interface between the base material and the build-up welded portion is evaluated using the signal value or the threshold value of the inspected echo signal after the sensitivity reduction is compensated, the evaluation accuracy can be improved, and the reliability of the inspection can be improved.

[0089] The ultrasonic inspection method according to the sixth aspect of the present disclosure is an ultrasonic inspection method applied to the determination of the bonding state at the interface between the build-up welded portion applied to the base material and the base material, and includes an inspection signal acquisition step (SA3) of acquiring a reflected echo signal when ultrasonic waves are transmitted to a test object having a build-up welded portion applied to the base material as an inspection echo signal, a correction value acquisition step (SA7) of acquiring a correction value corresponding to the surface shape of the test object using correction information in which a parameter related to curvature and a correction value are associated, and a correction step (SA8) of correcting the signal value of the inspection echo signal or a threshold value for evaluating the bonding state using the acquired correction value, which are executed by a computer.

[0090] The program according to the seventh aspect of the present disclosure is a program for causing a computer to function as the ultrasonic inspection apparatus according to any one of the first aspect to the fifth aspect.

Explanation of Signs

[0091] 1: Valve body 6: Valve seat 7: Valve element 10: Valve seat seat portion 11: Build-up welded portion 20: Probe 30: Ultrasonic inspection apparatus 31: CPU 32: Main storage device 33: Secondary storage device 35: Communication interface 36: Input device 37: Output device 40: Processing circuit 41: Signal acquisition unit 42: Storage unit 43: Correction necessity determination unit 44: Correction value acquisition unit 45: Correction unit 46: Evaluation unit 47: Display control unit 50: Ultrasonic inspection system 60: Test piece 70: Test piece 80: Test piece

Claims

1. An ultrasonic inspection apparatus applied to the determination of the bonding state at the interface between a build-up welded portion applied to a base material and the base material, comprising: a signal acquisition unit that acquires a reflected echo signal when ultrasonic waves are transmitted to a test object having a build-up welded portion applied to a base material as an inspection echo signal; a correction value acquisition unit that acquires a correction value corresponding to the surface shape of the test object using correction information in which a parameter related to curvature and a correction value are associated; a correction unit that corrects a signal value of the inspection echo signal or a threshold value for evaluating the bonding state using the acquired correction value; An ultrasonic inspection apparatus comprising the above.

2. The correction information associates curvature, a correction value, and a contact medium, The ultrasonic inspection apparatus according to claim 1, wherein the correction value acquisition unit acquires a correction value corresponding to the surface shape of the test object and the contact medium used in ultrasonic inspection from the correction information.

3. The ultrasonic inspection apparatus according to claim 1, further comprising a correction necessity determination unit that determines that correction is unnecessary when a parameter related to the curvature of the surface shape of the test object satisfies a predetermined condition.

4. The test object is a valve body or a valve seat of a steam valve in a steam turbine, The ultrasonic inspection apparatus according to claim 1, wherein the parameter related to the curvature is the curvature or the radius of curvature in the steam flow direction of the valve body or the valve seat.

5. An evaluation unit that evaluates the bonding state at the interface between the base material and the build-up welded portion based on a comparison between the signal value of the inspection echo signal after correction and a predetermined threshold value, or a comparison between the inspection echo signal and the threshold value after correction. The ultrasonic inspection apparatus according to claim 1.

6. An ultrasonic inspection method applied to the determination of the bonding state at the interface between a build-up welded portion applied to a base material and the base material, comprising: an inspection signal acquisition step of acquiring a reflected echo signal when ultrasonic waves are transmitted to a test object having a build-up welded portion applied to a base material as an inspection echo signal; a correction value acquisition step of acquiring a correction value corresponding to the surface shape of the test object using correction information in which a parameter related to curvature and a correction value are associated; a correction step of correcting a signal value of the inspection echo signal or a threshold value for evaluating the bonding state using the acquired correction value; An ultrasonic inspection method executed by a computer.

7. A program for causing a computer to function as the ultrasonic inspection apparatus according to any one of claims 1 to 5.

Images