Welding inspection device and welding inspection method

Abstract

The present invention provides a welding inspection device for determining the presence or absence of an internal defect in a welded part with high precision. A welding inspection device is provided with: a transmission laser irradiation device that irradiates a transmission laser to a transmission point on a welded part; a detection device (a reception laser source and a reception laser detector) for detecting ultrasonic waves generated by the transmission laser light and reaching a reception point on the base material; and a control device for determining the presence or absence of an internal defect in the welded part. The control device extracts a detection result of a reflected wave reflected on the lower surface of the base material and reaching the reception point from among detection results obtained by the detection device, and calculates a reflected wave arrival time, which is the time for the reflected wave to reach the reception point from the transmission point, using the extracted detection result of the reflected wave. The presence or absence of an internal defect in the welded portion is determined on the basis of whether the calculated reflected wave arrival time has lagged with respect to the reference time.

Description

Technical Field

[0001] The present invention relates to a welding inspection device and a welding inspection method for inspecting a welded portion included in a base material. Background Art

[0002] Japanese Patent Publication No. 2023-20336 discloses a welding inspection device for inspecting a weld included in a base material. The welding inspection device comprises: a transmitting laser irradiation device for irradiating a transmitting laser for exciting ultrasonic waves onto the weld; a detection device for detecting ultrasonic waves excited by the transmitting laser and reaching a receiving point on the base material; and a control device for determining the presence or absence of internal defects in the weld. The control device calculates the attenuation of the intensity of the lower surface reflected wave based on the phenomenon that the path of the lower surface reflected wave reflected and received on the lower surface of the base material (the surface on the opposite side of the irradiation surface of the transmitting laser) is blocked due to the internal defects of the weld, and the intensity is reduced, and determines the presence or absence of internal defects in the weld based on the calculated attenuation of the intensity of the lower surface reflected wave. Summary of the invention

[0003] If the attenuation of the intensity of the lower surface reflected wave depends on the intensity of the ultrasonic signal detected by the detection device, it is considered that the intensity of the ultrasonic signal will be affected by various factors other than the internal defect (for example, the properties of the irradiation surface of the transmitting laser, the electrical noise when the ultrasonic signal is processed, etc.) and change. Therefore, when the presence or absence of an internal defect is determined based on the attenuation of the intensity of the lower surface reflected wave as in the welding inspection device disclosed in Japanese Patent Application Laid-Open No. 2023-20336, the presence or absence of an internal defect may be erroneously determined.

[0004] Therefore, an object of the present invention is to determine the presence or absence of internal defects in a weld with high accuracy.

[0005] (Item 1) The welding inspection device according to the present invention is a welding inspection device for inspecting a welded portion included in a base material, wherein the welding inspection device comprises: a first irradiation device for irradiating a transmission laser to a transmission point on the welded portion; a detection device for detecting ultrasonic waves generated by the transmission laser and reaching a receiving point on the base material; and a control device for determining whether there is an internal defect in the welded portion. The control device extracts the detection result of the reflected wave reflected from the lower surface of the base material and reaching the receiving point from the detection result obtained by the detection device, calculates the time until the reflected wave reaches the receiving point from the transmission point, i.e., the reflected wave arrival time, using the extracted detection result of the reflected wave, and determines whether there is an internal defect in the welded portion based on whether the calculated reflected wave arrival time lags behind the reference time.

[0006] (Item 2) In the welding inspection device according to Item 1, the reference time is a time equivalent to a reflected wave arrival time when there is no internal defect in the weld.

[0007] (Item 3) In the welding inspection device described in Item 1, the control device calculates an index value indicating the degree of delay of the calculated reflected wave arrival time relative to the reference time, and determines that an internal defect exists when the calculated index value is greater than a threshold value.

[0008] (Item 4) In the welding inspection device according to Item 3, the control device stores a reference time and a threshold value in advance.

[0009] (Item 5) In the welding inspection device according to Item 3, the control device acquires from the outside a reference time and a threshold value obtained through experiments or analysis.

[0010] (Item 6) In the welding inspection device described in any one of Items 1 to 5, the control device determines the presence or absence of an internal defect based on the attenuation of the extracted reflected wave in addition to whether the reflected wave arrival time is delayed relative to the reference time.

[0011] (Item 7) Based on the welding inspection device described in any one of Items 1 to 5, the detection device includes: a second irradiation device, which irradiates a receiving laser for detecting ultrasonic waves to a receiving point; and a laser interferometer, which performs interference measurement on the reflected light of the receiving laser.

[0012] (Item 8) The welding inspection method based on the present invention is a welding inspection method for inspecting a welding portion included in a base material, wherein the welding inspection method includes the following steps: irradiating a sending laser to a sending point on the welding portion; detecting an ultrasonic wave generated by the sending laser and arriving at a receiving point on the base material; extracting a detection result of a reflected wave reflected from the lower surface of the base material and arriving at the receiving point from the detection result obtained based on the step of detecting the ultrasonic wave; using the extracted detection result of the reflected wave to calculate the time it takes for the reflected wave to arrive at the receiving point from the sending point, i.e., the arrival time of the reflected wave; and determining the presence or absence of internal defects in the welding portion based on whether the calculated arrival time of the reflected wave lags behind a reference time.

[0013] The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a figure which shows the structure of a welding inspection apparatus.

[0015] Figure 2This is a diagram showing a state when there is no internal defect in the welded portion.

[0016] Figure 3 This is a diagram showing the relationship between the transmission position of ultrasonic waves and the arrival time of ultrasonic waves when there are no internal defects in the welded portion.

[0017] Figure 4 This is a diagram showing a state when an internal defect exists in a weld portion.

[0018] Figure 5 This is a diagram showing the relationship between the transmission position of ultrasonic waves and the arrival time of ultrasonic waves when there is an internal defect in the weld portion.

[0019] Figure 6 This is a flowchart (part 1) showing an example of a processing procedure of the control device.

[0020] Figure 7 This is a diagram showing the relationship between the transmission position of ultrasonic waves and the intensity of the bottom surface reflected waves.

[0021] Figure 8 This is a flowchart (part 2) showing an example of the processing procedure of the control device. DETAILED DESCRIPTION

[0022] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In addition, the same reference numerals are given to the same or corresponding parts in the drawings, and their description will not be repeated.

[0023] Figure 1 2 is a diagram showing the structure of a welding inspection device 1 according to the present embodiment. Figure 1 The welding inspection device 1 includes a transmitting laser source 10 , a transmitting laser irradiation device (first irradiation device) 12 , a receiving laser source 16 , a receiving laser detector (second irradiation device) 18 , a control device 22 and a display device 24 .

[0024] The welding inspection device 1 is used, for example, to inspect a weld (weld bead) 6 of a lap fillet weld of thin plate-shaped base materials 2 and 4. The base materials 2 and 4 are, for example, galvanized steel plates with a thickness of about 1 to 2 mm. It should be noted that, in the figure, the Y direction indicates the welding advancing direction (the extending direction of the weld bead), the Z direction indicates the normal direction of the base materials 2 and 4, and the X direction indicates the direction orthogonal to the Y direction and the Z direction.

[0025] The transmission laser source 10 generates excitation light for generating transmission laser light 14 in the transmission laser irradiation device 12, and outputs the excitation light to the transmission laser irradiation device 12. The transmission laser source 10 is constituted by, for example, an LD power supply.

[0026] The transmitting laser irradiation device 12 receives the excitation light from the transmitting laser source 10 to generate the transmitting laser 14 as a pulse laser, and irradiates the transmitting laser 14 to the welded portion 6 of the inspection object. The transmitting laser irradiation device 12 is configured to include, for example, a microchip laser that generates a YAG pulse laser, and a scanning mechanism that enables the irradiation position of the transmitting laser 14 to be scanned in the X direction. The scanning mechanism is configured to include, for example, a galvanometer mirror capable of adjusting an angle, and a driving mechanism that drives the galvanometer mirror.

[0027] The receiving laser source 16 is configured to include a laser interferometer. The receiving laser source 16 generates a receiving laser 20 (reference light) to be irradiated to the base material 4 of the lower plate, and outputs it to the receiving laser detector 18. In addition, the receiving laser source 16 receives the reflected light from the base material 4 of the receiving laser 20 irradiated to the base material 4 from the receiving laser detector 18, detects the interference light including the reference light and the reflected light, and outputs it to the control device 22.

[0028] The receiving laser detector 18 irradiates the receiving laser 20 to the preset receiving point 36 on the base material 4 of the lower plate. In addition, the receiving laser detector 18 receives the reflected light from the base material 4 of the receiving laser 20 irradiated to the base material 4, and outputs it to the receiving laser source 16 (laser interferometer).

[0029] In the welding inspection device 1, the laser ultrasonic method is used to detect the internal defects of the weld 6. That is, the transmitting laser 14 is irradiated to the transmission point 32 on the weld 6 to generate ultrasonic waves inside the inspection object, and the surface vibration corresponding to the intensity of the ultrasonic waves at the receiving point 36 on the base material 4 irradiated with the receiving laser 20 is detected by the interference light of the reference light and the reflected light of the receiving laser 20. Then, the presence or absence of the internal defects of the weld 6 is determined based on the detection difference between the case where the internal defects do not exist in the weld 6 and the case where the internal defects exist.

[0030] The control device 22 is configured to include a CPU (Central Processing Unit), a memory (RAM (Random Access Memory) and ROM (Read Only Memory)), and an input / output port (not shown) for inputting and outputting various signals. The CPU expands the program stored in the ROM to the RAM and executes it. The various processes executed by the control device 22 are described in the program stored in the ROM.

[0031] The control device 22 controls the transmission laser light source 10 so as to generate excitation light for generating the transmission laser light 14 in the transmission laser irradiation device 12. In addition, the control device 22 controls the transmission laser irradiation device 12 so as to scan the irradiation position of the transmission laser light 14 in the X direction. In addition, the control device 22 receives the oscillation timing (pulse irradiation timing) of the transmission laser light 14 in the transmission laser irradiation device 12 from the transmission laser irradiation device 12.

[0032] Furthermore, the control device 22 receives the interferometry measurement result of the receiving laser 20 obtained by the laser interferometer of the receiving laser source 16 from the receiving laser source 16, and determines the presence or absence of internal defects of the weld 6 based on the detection signal of the ultrasonic wave at the receiving point 36 on the base material 4. The method for determining the presence or absence of internal defects of the weld 6 will be described in detail later.

[0033] The display device 24 is a display for displaying various processing results of the control device 22. For example, a measurement screen called a B-scope showing the measurement results of the ultrasonic wave in the inspection object obtained by the welding inspection device 1 is displayed on the display device 24. The B-scope displays the distribution of the intensity of the ultrasonic wave arriving at the receiving point 36, with the position of the irradiation position of the transmission laser 14 on the weld 6, that is, the position in the X direction of the transmission point 32 as the horizontal axis and the time until the ultrasonic wave generated at the transmission point 32 due to the irradiation of the transmission laser 14 arrives at the receiving point 36 on the base material 4 (hereinafter also referred to as "ultrasonic wave arrival time") as the vertical axis. The control device 22 and the display device 24 are composed of, for example, a PC (Personal Computer).

[0034] <Method for determining the presence or absence of internal defects in welded parts>

[0035] Hereinafter, a method for determining the presence or absence of internal defects in the welded portion 6 using the welding inspection device 1 will be described in detail.

[0036] Figure 2 to Figure 5 This is a diagram for explaining the principle of detecting internal defects of the welded portion 6 by the welding inspection device 1 .

[0037] Figure 21 is a diagram showing a state when there is no internal defect in the weld 6. In the welding inspection device 1, the transmitting laser 14 (pulse laser) is irradiated from above (Z direction) to the area including the weld 6, so that ultrasonic waves are generated at the transmitting point 32. The ultrasonic waves generated at the transmitting point 32 pass through the weld 6, are reflected at the lower surface 5 of the base material 4 on the lower side, and then reach the receiving point 36 on the base material 4. The receiving laser 20 is used to measure the minute vibration generated at the receiving point 36 on the base material 4 due to the ultrasonic waves (hereinafter also referred to as "lower surface reflected waves") reflected at the lower surface 5 and reaching the receiving point 36, thereby detecting the lower surface reflected waves at the receiving point 36.

[0038] The transmission point 32 indicated by the × mark is obtained by using the transmission laser irradiation device 12 ( Figure 1 ) is used to scan in the X direction. After the measurement at a certain transmission point 32 is completed, the irradiation position of the transmission laser 14 is scanned to the next position, and the measurement at the next transmission point 32 is performed.

[0039] The receiving point 36 indicated by the circle is fixed in the X direction of the base material 4. The larger the distance in the X direction between the transmitting point 32 and the receiving point 36, the longer the propagation distance of the ultrasonic wave from the transmitting point 32 to the receiving point 36, and the intensity of the ultrasonic wave at the receiving point 36 (micro vibration of the surface) decreases due to diffusion attenuation.

[0040] Figure 3 This is a diagram showing the relationship between the ultrasonic transmission position (the position of the transmission point 32 in the X direction) and the ultrasonic arrival time (the time from the ultrasonic wave generated at the transmission point 32 to the ultrasonic wave reaching the receiving point 36) when there is no internal defect in the welded portion 6. Figure 3 In FIG. 1 , the horizontal axis represents the transmission position of the ultrasonic wave, and a larger value indicates that the transmission point 32 is farther from the receiving point 36. The vertical axis represents the arrival time of the ultrasonic wave.

[0041] The ultrasonic waves detected at the receiving point 36 include, in addition to the above-mentioned lower surface reflected waves, surface waves that reach the receiving point 36 from the transmitting point 32 through the surface layer of the welded portion 6 and the base material 4. Compared with the surface waves, the propagation path of the lower surface reflected waves to the receiving point 36 is longer, so the arrival time of the lower surface reflected waves is longer than the arrival time of the surface waves. By utilizing this phenomenon, it is possible to distinguish whether the ultrasonic waves detected at the receiving point 36 are surface waves or lower surface reflected waves.

[0042] It should be noted that B-scope Figure 3In the graph of , the lines L1 and L2 are displayed by changing the density according to the intensity of the ultrasonic wave at the receiving point 36 for each transmission position of the ultrasonic wave. In the B-scope, the ultrasonic wave arrival time and the ultrasonic wave intensity are displayed on one screen for each transmission position of the ultrasonic wave.

[0043] Figure 4 3 is a diagram showing a state when an internal defect 40 such as a pore exists in the weld 6. When an internal defect 40 such as a pore exists in the weld 6, the ultrasonic wave generated at the transmission point 32 is divided into a scattered wave component 41 and a diffracted wave component 43 according to the different transmission positions. The scattered wave component 41 is reflected because the path is blocked by the internal defect 40, and does not reach the receiving point 36 and is scattered. The diffracted wave component 43 is diffracted in the internal defect 40 and moves forward. In this case, the diffracted wave component 43 is reflected on the lower surface 5 of the base material 4 and reaches the receiving point 36, but the propagation distance of the diffracted wave component 43 is correspondingly longer due to diffraction compared to the case where the internal defect 40 does not exist. As a result, when the time equivalent to the arrival time of the lower surface reflected wave in the case where the internal defect 40 does not exist is used as the "reference time", the arrival time of the diffracted wave component 43 is delayed compared to the reference time.

[0044] Figure 5 : is a diagram showing the relationship between the ultrasonic transmission position and the ultrasonic arrival time when there are internal defects such as pores in the weld 6. When there are internal defects such as pores in the weld 6, the transmission position includes the area where the internal defects exist (the area where the diffraction wave component 43 mentioned above reaches the receiving point 36). In this area, the arrival time of the diffraction wave component 43 becomes the arrival time of the lower surface reflection wave, so the arrival time of the lower surface reflection wave becomes longer than the reference time. Regarding the lag time of the arrival time of the diffraction wave component 43 relative to the reference time, as shown in FIG. Figure 5 As shown, the following distribution was confirmed on the B-scope: only a part of the bottom surface reflected wave shifted to the time side longer than the reference time.

[0045] In view of such a phenomenon, the control device 22 based on the present embodiment extracts the detection result of the lower surface reflected wave from the detection result of the ultrasonic wave at the receiving point 36, calculates the arrival time of the lower surface reflected wave using the extracted detection result of the lower surface reflected wave, and determines the presence or absence of internal defects 40 in the weld 6 based on the result obtained by evaluating whether the calculated arrival time of the lower surface reflected wave lags behind the reference time.

[0046] Figure 6 This is a flowchart showing an example of a processing procedure of the control device 22 according to the present embodiment.

[0047] The control device 22 controls the scanning mechanism of the transmission laser irradiation device 12 so that the transmission laser 14 is irradiated to the above-mentioned transmission point 32 (step S10). The number of irradiation points (number of transmission points) and the irradiation position (transmission position) of the transmission laser 14 in the scanning of one line in the X direction are preset. When the transmission laser is irradiated for the first time, for example, the scanning mechanism is controlled to irradiate the transmission laser 14 to the position closest to the receiving point 36 among the plurality of transmission points 32.

[0048] Next, the control device 22 controls the receiving laser source 16 so as to irradiate the receiving laser 20 to the receiving point 36 (step S15). It should be noted that the position of the receiving point 36 in the X direction is fixed in advance. The irradiation of the receiving laser 20 can be started before the irradiation of the transmitting laser 14, or can be started at the same time as the irradiation of the transmitting laser 14.

[0049] Then, the control device 22 uses the laser interferometer of the receiving laser light source 16 to measure the interference between the reflected light of the receiving laser light 20 irradiated onto the base material 4 and the receiving laser light 20 (reference light) irradiated onto the base material 4 (step S20 ).

[0050] Next, the control device 22 determines whether or not scanning of one line of the transmission laser beam 14 has been completed (step S25 ). Specifically, it determines whether or not measurement of all the preset irradiation positions has been completed in scanning of one line in the X direction.

[0051] If scanning of one line is not completed (No in step S25), control device 22 updates the irradiation position of transmission laser 14 to the next position (step S30). Then, the process returns to step S10, and steps S10 to S30 are repeated until scanning of one line is completed.

[0052] When it is determined that the scanning of one line is completed (Yes in step S25), the control device 22 creates a B-scope and performs waveform processing (step S35). Specifically, the control device 22 creates a B-scope showing the relationship between the arrival time and intensity of the ultrasonic wave at each irradiation position (transmission position) of the transmission laser 14 in the X direction and the irradiation position (reception point) of the reception laser 20 for the measurement signal of the scanning of one line obtained in the processing of steps S10 to S30.

[0053] Next, the control device 22 extracts the signal of the lower surface reflected wave from the produced B-scope (step S40). As described above, in the B-scope, the lower surface reflected wave can be distinguished from the surface wave and the like and can be easily extracted. This extraction operation can be automatically performed in the control device 22.

[0054] Next, the control device 22 calculates the lag time of the arrival time of the lower surface reflected wave relative to the reference time (hereinafter, also simply referred to as "the lag time of the lower surface reflected wave") for the extracted signal of the lower surface reflected wave (step S45). As described above, the reference time is equivalent to the arrival time of the lower surface reflected wave when there is no internal defect 40 in the weld 6.

[0055] In the present embodiment, the reference time is obtained for each transmission position by a prior evaluation test or theoretical calculation, and is pre-stored in the internal memory of the control device 22. The control device 22 reads the reference time stored in the memory, calculates the difference between the arrival time of the lower surface reflected wave and the reference time for each transmission position, and calculates the maximum value of the difference between the arrival time of the lower surface reflected wave and the reference time as the lag time of the lower surface reflected wave.

[0056] It should be noted that the reference time is not necessarily limited to the reference time pre-stored in the internal memory of the control device 22. For example, the control device 22 may obtain the reference time pre-determined for each transmission position through a previous test or analysis from an external device.

[0057] Next, the control device 22 determines whether the lag time of the lower surface reflected wave calculated in step S40 is longer than the threshold time (step S50). The threshold time is appropriately set to a value that can distinguish the presence or absence of internal defects for each transmission position through a prior evaluation test or theoretical calculation. Like the reference time, the threshold time can be pre-stored in the internal memory of the control device 22 or obtained from an external device. In addition, when the control device 22 determines that the lag time of the lower surface reflected wave is longer than the threshold time (yes in step S50), the signal indicating that an internal defect is detected in the welding portion 6 is output to the display device 24 (step S55).

[0058] As described above, the control device 22 based on the present embodiment extracts the detection signal of the lower surface reflected wave from the detection results of the ultrasonic wave at the receiving point 36, calculates the arrival time of the lower surface reflected wave using the extracted detection signal of the lower surface reflected wave, and determines the presence or absence of the internal defect 40 of the weld 6 based on the result obtained by evaluating whether the calculated arrival time of the lower surface reflected wave lags behind the reference time.

[0059] That is, the control device 22 according to the present embodiment determines the presence or absence of the internal defect 40 based on the delay time of the lower surface reflected wave rather than the attenuation of the intensity of the lower surface reflected wave. Therefore, even if the intensity of the lower surface reflected wave is affected by factors other than the presence or absence of the internal defect 40 (electrical noise, etc.) and changes, the presence or absence of the internal defect 40 can be determined with high accuracy.

[0060] <Modification 1>

[0061] In the above-mentioned embodiment, the presence or absence of the internal defect 40 is determined based on the delay time of the lower surface reflected wave, but the physical quantity used in the determination of the presence or absence of the internal defect 40 can be any physical quantity indicating the delay degree of the arrival time of the lower surface reflected wave relative to the reference time, and need not be limited to the "delay time of the lower surface reflected wave". That is, the control device 22 may calculate an index value indicating the delay degree of the arrival time of the lower surface reflected wave relative to the reference time, and determine that the internal defect 40 exists when the calculated index value is greater than a threshold value.

[0062] <Modification 2>

[0063] In the above-mentioned embodiment, the presence or absence of the internal defect 40 is determined based on the delay time of the lower surface reflection wave. However, in order to determine the presence or absence of the internal defect 40 with higher accuracy, the presence or absence of the internal defect 40 may also be determined based on the attenuation degree of the intensity of the lower surface reflection wave in addition to the delay time of the lower surface reflection wave.

[0064] Figure 7 is a diagram showing the relationship between the transmission position of the ultrasonic wave and the intensity of the reflected wave from the lower surface. Figure 7 In FIG. 5 , the horizontal axis represents the transmission position of the ultrasonic wave (the position of the transmission point 32 in the X direction), and the vertical axis represents the intensity of the bottom surface reflected wave at the reception point 36 .

[0065] Line L3 represents the intensity of the bottom surface reflected wave when there is no internal defect in the weld 6. With respect to the intensity of the bottom surface reflected wave, the larger the value of the transmission position of the ultrasonic wave (the farther the position of the transmission point 32 in the X direction is from the receiving point 36), the more the signal intensity is attenuated due to diffusion attenuation.

[0066] Line L4 represents the intensity of the lower surface reflected wave when there is an internal defect (pores, etc.) in the weld 6. When the ultrasonic transmission position is greater than X1, an internal defect is generated in the weld 6. When an internal defect is generated, as described above, Figure 4 As described in FIG. 3 , in addition to diffusion attenuation, scattering attenuation occurs at the internal defect, so the intensity of the bottom surface reflected wave at the receiving point 36 becomes smaller than that in the case where there is no internal defect (line L3). In other words, the attenuation degree of the intensity of the bottom surface reflected wave when the internal defect occurs becomes larger than that in the case where there is no internal defect.

[0067] In view of such a phenomenon, the presence or absence of the internal defect 40 may be determined based on the attenuation degree of the intensity of the lower surface reflected wave in addition to the delay time of the lower surface reflected wave.

[0068] Figure 82 is a flowchart showing an example of the processing steps of the control device 22 according to the second modification. Figure 8 In the flowchart of Figure 6 Step S45 of the flowchart is replaced by step S45A, and step S52 is added. Figure 8 The other steps of the flowchart (labeled as above Figure 6 The steps with the same number as shown in the figure) have already been described and the detailed description will not be repeated here.

[0069] For the extracted signal of the lower surface reflected wave, the control device 22 calculates the attenuation of the intensity of the lower surface reflected wave in addition to calculating the lag time of the lower surface reflected wave (step S45A). Specifically, the control device 22 calculates the degree of reduction of the intensity of the ultrasonic wave corresponding to the transmission position. It should be noted that the control device 22 can also calculate the RMS (Root Mean Square) value of the signal intensity for the measurement signal obtained at each transmission position, and calculate the degree of reduction of the above RMS value corresponding to the transmission position.

[0070] Furthermore, when the control device 22 determines that the delay time of the lower surface reflected wave is longer than the threshold time (Yes in step S50), it determines whether the attenuation degree of the intensity of the lower surface reflected wave is greater than a threshold (step S52). The threshold is appropriately set to a value capable of distinguishing the presence or absence of internal defects through a prior evaluation test or the like.

[0071] Furthermore, when the control device 22 determines that the lag time of the lower surface reflected wave is longer than the threshold time (yes in step S50) and determines that the attenuation of the intensity of the lower surface reflected wave is greater than the threshold (yes in step S52), the control device 22 outputs a signal indicating that an internal defect has been detected in the welding portion 6 to the display device 24 (step S55).

[0072] As described above, by determining the presence or absence of the internal defect 40 using both the delay time of the bottom surface reflected wave and the attenuation degree of the intensity of the bottom surface reflected wave, the presence or absence of the internal defect 40 can be determined with higher accuracy.

[0073] The embodiments of the present invention have been described, but all points of the embodiments disclosed this time are illustrative and not restrictive. The scope of the present invention is indicated by the technical claims, and is intended to include all changes within the meaning and scope equivalent to the technical claims.

Claims

1. A welding inspection device for inspecting a welding portion included in a base material, wherein: The welding inspection device comprises: a first irradiation device for irradiating a transmission laser to a transmission point on the welding portion; a detection device for detecting ultrasonic waves generated by the transmitting laser and reaching a receiving point on the base material; and a control device for determining the presence or absence of internal defects in the welded portion, The control device performs the following operations: Extracting the detection result of the reflected wave reflected on the lower surface of the base material and reaching the receiving point from the detection results obtained by the detection device, The reflected wave arrival time, which is the time taken for the reflected wave to arrive at the receiving point from the transmission point, is calculated using the extracted detection result of the reflected wave. The presence or absence of the internal defect of the weld portion is determined based on whether the calculated arrival time of the reflected wave is delayed relative to a reference time.

2. The welding inspection device according to claim 1, wherein: The reference time is a time equivalent to the arrival time of the reflected wave when the internal defect does not exist in the weld portion.

3. The welding inspection device according to claim 1, wherein: The control device performs the following operations: calculating an index value indicating the degree of delay of the calculated arrival time of the reflected wave relative to the reference time, When the calculated index value is larger than a threshold value, it is determined that the internal defect exists.

4. The welding inspection device according to claim 3, wherein: The control device stores the reference time and the threshold value in advance.

5. The welding inspection device according to claim 3, wherein: The control device obtains the reference time and the threshold value obtained through experiments or analysis from the outside.

6. The welding inspection device according to any one of claims 1 to 5, wherein: The control device determines the presence or absence of the internal defect based on the extracted attenuation degree of the reflected wave in addition to whether the arrival time of the reflected wave lags behind the reference time.

7. The welding inspection device according to any one of claims 1 to 5, wherein: The detection device comprises: a second irradiation device that irradiates the receiving point with a receiving laser for detecting ultrasonic waves; and A laser interferometer performs interference measurement on the reflected light of the receiving laser beam.

8. A welding inspection method for inspecting a welded portion included in a base material, wherein: The welding inspection method comprises the following steps: irradiating a transmitting laser to a transmitting point on the welding portion; detecting ultrasonic waves generated by the transmitting laser and reaching a receiving point on the base material; extracting the detection result of the reflected wave reflected on the lower surface of the base material and reaching the receiving point from the detection results obtained based on the step of detecting the ultrasonic wave; Using the extracted detection result of the reflected wave, calculating the time until the reflected wave arrives at the receiving point from the transmission point, that is, the reflected wave arrival time; as well as The presence or absence of an internal defect of the weld portion is determined based on whether the calculated arrival time of the reflected wave is delayed relative to a reference time.

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