Weld inspection device and weld inspection method

Abstract

To accurately determine presence / absence of an internal defect of a weld zone.SOLUTION: A weld inspection device comprises: a transmitting laser beam irradiation device for irradiating a transmission point on a weld zone with a transmitting laser beam; a detection device (a receiving laser source and a receiving laser beam probe) for detecting ultrasound that is generated by the transmitting laser beam and arrives at a receiving point on a parent material; and a control device which determines presence / absence of an internal defect of a weld zone. The control device extracts a detection result of a reflection wave which has been reflected on a lower surface of the parent material and arrived at the receiving point, from among the detection results by the detection device, and calculates a reflection wave arrival time that is a time required by the reflection wave to arrive at the receiving point from the transmitting point by using the extracted detection result of the reflection wave, in order to determine presence / absence of an internal defect of a weld zone on the basis of whether the calculated reflection wave arrival time is delayed relative to a reference time.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present disclosure relates to a welding inspection device and a welding inspection method for inspecting a welded portion included in a base metal. [Background technology]

[0002] JP 2023-20336 A discloses a welding inspection device for inspecting a welded portion included in a base material. This welding inspection device includes a transmission laser irradiation device that irradiates a transmission laser light for exciting ultrasonic waves onto the welded portion, a detection device that detects ultrasonic waves excited by the transmission laser light and reaching a receiving point on the base material, and a control device that determines the presence or absence of an internal defect in the welded portion. The control device uses the phenomenon that the bottom surface reflected wave, which is reflected and received by the bottom surface of the base material (the surface opposite to the irradiation surface of the transmission laser light) among the ultrasonic waves excited by the transmission laser light, is blocked by an internal defect in the welded portion and its intensity is reduced, to calculate the attenuation of the bottom surface reflected wave intensity, and determines the presence or absence of an internal defect in the welded portion based on the calculated attenuation of the bottom surface reflected wave intensity. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2023-20336 A Summary of the Invention [Problem to be solved by the invention]

[0004] The attenuation of the bottom surface reflected wave intensity depends on the intensity of the ultrasonic signal detected by the detection device, and it is considered that the intensity of the ultrasonic signal varies due to the influence of various factors other than the internal defect (for example, the properties of the irradiated surface of the transmission laser light, electrical noise during arithmetic processing of the ultrasonic signal, etc.). Therefore, when determining the presence or absence of an internal defect based on the attenuation of the bottom surface reflected wave intensity as in the welding inspection device disclosed in the above-mentioned JP 2023-20336 A, there is a risk of erroneously determining the presence or absence of an internal defect.

[0005] Therefore, an object of the present disclosure is to accurately determine the presence or absence of an internal defect in a weld. [Means for solving the problem]

[0006] (Item 1) A welding inspection device according to the present disclosure is a welding inspection device for inspecting a welded portion included in a base material, and includes a first irradiation device that irradiates a transmission laser light to a transmission point on the welded portion, a detection device that detects ultrasonic waves generated by the transmission laser light and reaching a reception point on the base material, and a control device that determines the presence or absence of an internal defect in the welded portion. The control device extracts a detection result of a reflected wave that is reflected on the underside of the base material and reaches the reception point from the detection results by the detection device, calculates a reflected wave arrival time, which is the time it takes for the reflected wave to reach the reception point from the transmission point, using the detection result of the extracted reflected wave, and determines the presence or absence of an internal defect in the welded portion based on whether the calculated reflected wave arrival time is delayed with respect to a reference time.

[0007] (Item 2) In the welding inspection device according to item 1, the reference time is a time corresponding to a reflected wave arrival time when there is no internal defect in the welded portion.

[0008] (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 a reference time, and determines that an internal defect is present when the calculated index value is greater than a threshold value.

[0009] (Item 4) In the welding inspection device according to item 3, the control device stores the reference time and the threshold value in advance.

[0010] (Item 5) In the welding inspection device according to item 3, the control device externally acquires the reference time and the threshold value determined by experiment or analysis.

[0011] (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 with respect to a reference time.

[0012] (Item 7) In the welding inspection device described in any one of Items 1 to 5, the detection device includes a second irradiation device that irradiates a receiving laser light to a receiving point to detect ultrasonic waves, and a laser interferometer that performs interference measurement of the reflected light of the receiving laser light.

[0013] (Item 8) A welding inspection method according to the present disclosure is a welding inspection method for inspecting a welded portion included in a base material, and includes the steps of irradiating a transmitting laser light to a transmission point on the welded portion, detecting ultrasonic waves generated by the transmitting laser light and reaching a receiving point on the base material, extracting a detection result of a reflected wave that is reflected off the underside of the base material and reaches the receiving point from the detection results of the ultrasonic wave detection step, calculating a reflected wave arrival time, which is the time it takes for the reflected wave to reach the receiving point from the transmission point, using the detection result of the extracted reflected wave, and determining the presence or absence of an internal defect in the welded portion based on whether the calculated reflected wave arrival time is delayed with respect to a reference time. Effect of the Invention

[0014] According to the present disclosure, the presence or absence of an internal defect in a welded portion can be determined with high accuracy. [Brief description of the drawings]

[0015] [Figure 1] FIG. 1 is a diagram showing a configuration of a welding inspection device. [Diagram 2] FIG. 2 is a diagram showing a state when there is no internal defect in a welded portion. [Diagram 3] 10 is a diagram showing the relationship between the ultrasonic transmission position and the ultrasonic wave arrival time when there is no internal defect in a welded portion. FIG. [Figure 4] FIG. 2 is a diagram showing a state when there is an internal defect in a welded portion. [Diagram 5]11 is a diagram showing the relationship between the ultrasonic transmission position and the ultrasonic arrival time when an internal defect is present in a welded portion. FIG. [Figure 6] 1 is a flowchart (part 1) illustrating an example of a processing procedure of a control device. [Figure 7] 11 is a diagram showing the relationship between the transmission position of ultrasonic waves and the intensity of the bottom surface reflected wave. FIG. [Figure 8] 13 is a flowchart (part 2) illustrating an example of a processing procedure of the control device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are designated by the same reference characters and their description will not be repeated.

[0017] Fig. 1 is a diagram showing the configuration of a welding inspection device 1 according to the present embodiment. With reference to Fig. 1, the welding inspection device 1 includes a transmitting laser source 10, a transmitting laser light irradiator (first irradiator) 12, a receiving laser source 16, a receiving laser light probe (second irradiator) 18, a control device 22, and a display device 24.

[0018] This welding inspection device 1 is used, for example, to inspect a welded portion (weld bead) 6 in lap fillet welding of thin base metals 2, 4. The base metals 2, 4 are, for example, zinc-plated steel sheets with a thickness of about 1 to 2 mm. In the figure, the Y direction indicates the welding progress direction (extension direction of the weld bead), the Z direction indicates the normal direction of the base metals 2, 4, and the X direction indicates the direction perpendicular to the Y direction and the Z direction.

[0019] The transmission laser source 10 generates excitation light for generating the transmission laser light 14 in the transmission laser light emitting device 12, and outputs the excitation light to the transmission laser light emitting device 12. The transmission laser source 10 is constituted by, for example, an LD power supply.

[0020] The transmission laser light irradiator 12 receives excitation light from the transmission laser source 10, generates a transmission laser light 14 which is a pulsed laser light, and irradiates the welded portion 6 to be inspected. The transmission laser light irradiator 12 includes, for example, a microchip laser that generates a YAG pulsed laser light, and a scanning mechanism that can scan the irradiation position of the transmission laser light 14 in the X direction. The scanning mechanism includes, for example, a galvanometer mirror whose angle is adjustable, and a driving mechanism that drives the galvanometer mirror.

[0021] The receiving laser source 16 includes a laser interferometer. The receiving laser source 16 generates a receiving laser beam 20 (reference beam) to be irradiated onto the base material 4 of the lower plate, and outputs the beam to a receiving laser beam probe 18. The receiving laser source 16 also receives, from the receiving laser beam probe 18, the reflected beam from the base material 4 of the receiving laser beam 20 irradiated onto the base material 4, and detects interference beams including the reference beam and the reflected beam to output the same to a control device 22.

[0022] The receiving laser light probe 18 irradiates a receiving laser light 20 to a predetermined receiving point 36 on the base material 4 of the lower plate. The receiving laser light probe 18 also receives the reflected light from the base material 4 of the receiving laser light 20 irradiated to the base material 4, and outputs the reflected light to a receiving laser source 16 (laser interferometer).

[0023] This welding inspection device 1 uses a laser ultrasonic method to detect internal defects in a weld 6. That is, a transmitting laser beam 14 is irradiated onto a transmitting point 32 on the weld 6 to generate ultrasonic waves inside the weld, and a surface vibration corresponding to the intensity of the ultrasonic waves at a receiving point 36 on the base material 4 to which a receiving laser beam 20 is irradiated is detected by an interference light between a reference beam and a reflected beam of the receiving laser beam 20. Then, the presence or absence of an internal defect in the weld 6 is determined based on a detection difference between when there is an internal defect in the weld 6 and when there is not.

[0024] The control device 22 includes a CPU (Central Processing Unit), memories (RAM (Random Access Memory) and ROM (Read Only Memory)), and input / output ports for inputting and outputting various signals (none of which are shown). The CPU loads a program stored in the ROM into the RAM and executes it. The program stored in the ROM describes various processes to be executed by the control device 22.

[0025] The control device 22 controls the transmission laser source 10 so as to generate excitation light for generating the transmission laser light 14 in the transmission laser light emitting device 12. The control device 22 also controls the transmission laser light emitting device 12 so as to scan the irradiation position of the transmission laser light 14 in the X direction. The control device 22 also receives the oscillation timing (timing of pulse irradiation) of the transmission laser light 14 in the transmission laser light emitting device 12 from the transmission laser light emitting device 12.

[0026] The control device 22 receives from the receiving laser source 16 the interference measurement result of the receiving laser light 20 by the laser interferometer of the receiving laser source 16, and determines the presence or absence of an internal defect in the welded portion 6 based on the detection signal of the ultrasonic wave at the receiving point 36 on the base material 4. The method of determining the presence or absence of an internal defect in the welded portion 6 will be described in detail later.

[0027] The display device 24 is a display for displaying various processing results of the control device 22. The display device 24 displays, for example, a measurement screen called a B-scope, which shows the measurement results of ultrasonic waves in an inspection target by the welding inspection device 1. The B-scope displays the distribution of the intensity of ultrasonic waves that have reached the reception point 36, with the horizontal axis representing the position in the X direction of the transmission point 32, which is the irradiation position of the transmission laser light 14 on the welded portion 6, and the vertical axis representing the time (hereinafter also referred to as "ultrasonic wave arrival time") until the ultrasonic waves generated at the transmission point 32 by irradiation of the transmission laser light 14 reach the reception point 36 on the base material 4. The control device 22 and the display device 24 are, for example, configured by a PC (Personal Computer).

[0028] <Method of determining whether or not there is an internal defect in a weld> A method for determining the presence or absence of an internal defect in the welded portion 6 using the welding inspection device 1 will be described in detail below.

[0029] 2 to 5 are diagrams for explaining the principle of detection of an internal defect in the welded portion 6 by the welding inspection device 1. FIG.

[0030] 2 is a diagram showing a state when there is no internal defect in the welded portion 6. In this welding inspection device 1, a transmitting laser beam 14 (pulsed laser beam) is irradiated from above (Z direction) onto an area including the welded portion 6, and ultrasonic waves are generated at a transmitting point 32. The ultrasonic waves generated at the transmitting point 32 pass through the welded portion 6, are reflected by the lower surface 5 of the base material 4 on the lower side, and then reach a receiving point 36 on the base material 4. The receiving laser beam 20 is used to measure micro-vibrations generated at the receiving point 36 on the base material 4 by the ultrasonic waves that are reflected by the lower surface 5 and reach the receiving point 36 (hereinafter also referred to as "lower surface reflected waves"), and the lower surface reflected waves at the receiving point 36 are detected.

[0031] The transmission points 32 indicated by cross marks are scanned in the X direction using the scanning mechanism of the transmission laser light emitting device 12 (FIG. 1). After measurement at a certain transmission point 32 is completed, the irradiation position of the transmission laser light 14 is scanned to the next position, and measurement at the next transmission point 32 is performed.

[0032] The receiving point 36 indicated by a circle is fixed in the X direction of the base material 4. As the distance in the X direction between the transmitting point 32 and the receiving point 36 increases, the propagation distance of the ultrasonic waves from the transmitting point 32 to the receiving point 36 increases, and the intensity of the ultrasonic waves (micro-vibrations on the surface) at the receiving point 36 also decreases due to diffusion attenuation.

[0033] Fig. 3 is a diagram showing the relationship between the ultrasonic transmission position (the position of transmission point 32 in the X direction) and the ultrasonic wave arrival time (the time it takes for the ultrasonic wave generated at transmission point 32 to reach reception point 36) when there is no internal defect in welded portion 6. In Fig. 3, the horizontal axis indicates the ultrasonic transmission position, and the larger the value, the farther the transmission point 32 is from reception point 36. The vertical axis indicates the ultrasonic wave arrival time.

[0034] The ultrasonic waves detected at the receiving point 36 include not only the bottom reflected waves described above, but also surface waves that pass from the transmitting point 32 through the surface layers of the weld 6 and the base material 4 and arrive at the receiving point 36. Because the bottom reflected waves have a longer propagation path to the receiving point 36 than the surface waves, the arrival time of the bottom reflected waves is longer than that 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 bottom reflected waves.

[0035] In addition, the B-scope is a display of lines L1 and L2 in the graph of Fig. 3, with the density changed according to the intensity of the ultrasound at the reception point 36 for each ultrasound transmission position. In the B-scope, the ultrasound arrival time and ultrasound intensity are displayed on one screen for each ultrasound transmission position.

[0036] FIG. 4 is a diagram showing a state when an internal defect 40 such as a blowhole is present in the welded portion 6. When an internal defect 40 such as a blowhole is present in the welded portion 6, depending on the transmission position, the ultrasonic wave generated at the transmission point 32 is divided into a scattered wave component 41 that is reflected by the internal defect 40 and scattered without reaching the reception point 36, and a diffracted wave component 43 that is diffracted by the internal defect 40 and travels. In this case, the diffracted wave component 43 is reflected by the lower surface 5 of the base material 4 and reaches the reception point 36, but the propagation distance of the diffracted wave component 43 is longer by the amount of diffraction compared to when the internal defect 40 does not exist. As a result, if the time corresponding to the arrival time of the lower surface reflected wave when the internal defect 40 does not exist is taken as the "reference time", the arrival time of the diffracted wave component 43 will be delayed compared to the reference time.

[0037] 5 is a diagram showing the relationship between the ultrasonic transmission position and ultrasonic arrival time when the welded portion 6 has an internal defect such as a blowhole. When the welded portion 6 has an internal defect such as a blowhole, the transmission position includes an area where the internal defect exists (the area where the above-mentioned diffracted wave component 43 reaches the receiving point 36), and in this area, the arrival time of the diffracted wave component 43 becomes the arrival time of the bottom reflected wave, so the arrival time of the bottom reflected wave becomes longer than the reference time. As shown in FIG. 5, the delay time of the arrival time of the diffracted wave component 43 with respect to the reference time is confirmed on the B-scope as a distribution in which only a portion of the bottom reflected wave has shifted to the longer time side than the reference time.

[0038] In consideration of this phenomenon, the control device 22 according to this embodiment extracts the detection result of the bottom reflected wave from the detection result of the ultrasonic wave at the receiving point 36, calculates the arrival time of the bottom reflected wave using the extracted detection result of the bottom reflected wave, and judges the presence or absence of an internal defect 40 in the weld 6 based on the result of evaluating whether the calculated arrival time of the bottom reflected wave is delayed with respect to a reference time.

[0039] FIG. 6 is a flowchart showing an example of a processing procedure of the control device 22 according to this embodiment.

[0040] The control device 22 controls the scanning mechanism of the transmission laser light emitting device 12 so as to irradiate the transmission laser light 14 to the above-mentioned transmission point 32 (step S10). The number of irradiation points (number of transmission points) and irradiation positions (transmission positions) of the transmission laser light 14 in scanning one line in the X direction are determined in advance. When irradiating the transmission laser light for the first time, for example, the scanning mechanism is controlled so as to irradiate the transmission laser light 14 to the position of the multiple transmission points 32 that is closest to the reception point 36.

[0041] Next, the control device 22 controls the receiving laser source 16 so that the receiving laser light 20 is irradiated to the receiving point 36 (step S15). The position of the receiving point 36 in the X direction is fixed in advance. The irradiation of the receiving laser light 20 may be started before the irradiation of the transmitting laser light 14, or may be started simultaneously with the start of irradiation of the transmitting laser light 14.

[0042] Then, the control device 22 uses the laser interferometer of the receiving laser 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).

[0043] Next, the control device 22 determines whether or not scanning of one line with the transmitting laser light 14 is completed (step S25). Specifically, it is determined whether or not measurement is completed at all of the predetermined irradiation positions in scanning of one line in the X direction.

[0044] If scanning of one line is not complete (NO in step S25), the control device 22 updates the irradiation position of the transmission laser light 14 to the next position (step S30). Then, the process returns to step S10, and the processes of steps S10 to S30 are repeated until scanning of one line is complete.

[0045] When it is determined that scanning of one line is completed (YES in step S25), the control device 22 creates a B-scope and executes waveform processing (step S35). Specifically, the control device 22 creates a B-scope that indicates the relationship between each irradiation position (transmission position) in the X direction of the transmitting laser light 14 and the arrival time and intensity of the ultrasonic wave at the irradiation position (reception point) of the receiving laser light 20 for the measurement signal for one line scanning obtained by the processing of steps S10 to S30.

[0046] Next, the control device 22 extracts the signal of the bottom reflected wave from the created B-scope (step S40). As described above, in the B-scope, the bottom reflected wave can be easily extracted while being distinguished from the surface wave, etc. This extraction operation can be performed automatically by the control device 22.

[0047] Next, the control device 22 calculates the delay time of the bottom reflected wave from the reference time for the extracted bottom reflected wave signal (hereinafter also simply referred to as the "bottom reflected wave delay time") (step S45). As described above, the reference time is a time corresponding to the arrival time of the bottom reflected wave when the internal defect 40 does not exist in the welded portion 6.

[0048] In this embodiment, the reference time is obtained for each transmission position by a prior evaluation test or theoretical calculation, etc., and is stored in advance in the internal memory of the control device 22. The control device 22 reads out the reference time stored in the memory, calculates the difference between the arrival time of the bottom-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 bottom-surface reflected wave and the reference time as the delay time of the bottom-surface reflected wave.

[0049] The reference time is not necessarily limited to being stored in advance in the internal memory of the control device 22. For example, the control device 22 may obtain a reference time, which is determined in advance for each transmission position by a prior test or analysis, from an external device.

[0050] Next, the control device 22 judges whether or not the delay time of the bottom surface reflected wave calculated in step S40 is longer than a threshold time (step S50). The threshold time is appropriately set to a value that allows distinguishing the presence or absence of an internal defect for each transmission position by a prior evaluation test or theoretical calculation, etc. The threshold time may be stored in advance in the internal memory of the control device 22, similar to the reference time, or may be acquired from an external device. Then, when it is judged that the delay time of the bottom surface reflected wave is longer than the threshold time (YES in step S50), the control device 22 outputs a signal indicating that an internal defect has been detected in the welded portion 6 to the display device 24 (step S55).

[0051] As described above, the control device 22 according to this embodiment extracts a detection signal of the bottom reflected wave from the detection results of the ultrasonic wave at the receiving point 36, calculates the arrival time of the bottom reflected wave using the extracted detection signal of the bottom reflected wave, and judges the presence or absence of an internal defect 40 in the weld 6 based on the result of evaluating whether the calculated arrival time of the bottom reflected wave is delayed with respect to a reference time.

[0052] That is, the control device 22 according to this embodiment determines the presence or absence of an internal defect 40 based on the delay time of the bottom reflected wave, rather than on the attenuation of the strength of the bottom reflected wave. Therefore, even if the strength of the bottom reflected wave fluctuates due to the influence of factors other than the presence or absence of the internal defect 40 (such as electrical noise), the presence or absence of the internal defect 40 can be determined with high accuracy.

[0053] <Variation 1> In the above embodiment, the presence or absence of an internal defect 40 is determined based on the delay time of the bottom reflected wave, but the physical quantity used to determine the presence or absence of an internal defect 40 may be any physical quantity indicating the degree of delay in the arrival time of the bottom reflected wave relative to a reference time, and is not necessarily limited to the "delay time of the bottom reflected wave." In other words, the control device 22 may calculate an index value indicating the degree of delay in the arrival time of the bottom reflected wave relative to a reference time, and determine that an internal defect 40 exists when the calculated index value is greater than a threshold value.

[0054] <Variation 2> In the above-described embodiment, the presence or absence of an internal defect 40 is determined based on the delay time of the bottom surface reflected wave. However, in order to more accurately determine the presence or absence of an internal defect 40, the presence or absence of an internal defect 40 may be determined based on the attenuation of the intensity of the bottom surface reflected wave in addition to the delay time of the bottom surface reflected wave.

[0055] 7 is a diagram showing the relationship between the ultrasonic transmission position and the intensity of the bottom reflected wave. In Fig. 7, the horizontal axis indicates the ultrasonic transmission position (the position of transmission point 32 in the X direction), and the vertical axis indicates the intensity of the bottom reflected wave at reception point 36.

[0056] Line L3 indicates the intensity of the bottom reflected wave when there is no internal defect in the weld 6. The intensity of the bottom reflected wave is such that the signal intensity attenuates due to diffusion attenuation as the value of the ultrasonic transmission position increases (as the position of the transmission point 32 in the X direction moves away from the reception point 36).

[0057] Line L4 indicates the intensity of the bottom reflected wave when an internal defect (such as a blowhole) is present in the weld 6. When the ultrasonic transmission position is greater than X1, an internal defect occurs in the weld 6. When an internal defect occurs, scattering attenuation at the internal defect occurs in addition to diffusion attenuation as explained in FIG. 4 above, so the intensity of the bottom reflected wave at the reception point 36 is smaller than when there is no internal defect (line L3). In other words, the degree of attenuation of the intensity of the bottom reflected wave when there is an internal defect is greater than when there is no internal defect.

[0058] In consideration of this phenomenon, the presence or absence of the internal defect 40 may be determined based on the degree of attenuation of the strength of the bottom reflected wave in addition to the delay time of the bottom reflected wave.

[0059] Fig. 8 is a flowchart showing an example of a processing procedure of the control device 22 according to the present modified example 2. The flowchart of Fig. 8 is obtained by replacing step S45 of the flowchart of Fig. 6 described above with step S45A, and further adding step S52. The other steps of the flowchart of Fig. 8 (the steps having the same numbers as the steps shown in Fig. 6 described above) have already been described, and therefore detailed description thereof will not be repeated here.

[0060] The control device 22 calculates the attenuation of the intensity of the bottom reflected wave in addition to the delay time of the bottom reflected wave for the extracted bottom reflected wave signal (step S45A). Specifically, the control device 22 calculates the degree of decrease in the intensity of the ultrasonic wave according to the transmission position. The control device 22 may 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 decrease in the RMS value according to the transmission position.

[0061] When it is determined that the delay time of the bottom reflected wave is longer than the threshold time (YES in step S50), the control device 22 determines whether the attenuation of the intensity of the bottom reflected wave is greater than a threshold (step S52). This threshold is appropriately set to a value that allows the presence or absence of an internal defect to be distinguished by a prior evaluation test or the like.

[0062] Then, if the control device 22 determines that the delay time of the bottom reflected wave is longer than the threshold time (YES in step S50) and that the attenuation of the intensity of the bottom reflected wave is greater than the threshold value (YES in step S52), the control device 22 outputs a signal indicating that an internal defect has been detected in the welded portion 6 to the display device 24 (step S55).

[0063] As described above, by determining the presence or absence of an internal defect 40 using both the delay time of the bottom reflected wave and the attenuation of the intensity of the bottom reflected wave, the presence or absence of an internal defect 40 can be determined with greater accuracy.

[0064] The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The technical scope of the present disclosure is defined by the claims, not by the description of the embodiments described above, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0065] 1 welding inspection device, 2, 4 base material, 5 underside, 6 welded portion, 10 transmitting laser source, 12 transmitting laser light irradiation device, 14 transmitting laser light, 16 receiving laser source, 18 receiving laser light probe, 20 receiving laser light, 22 control device, 24 display device, 32 transmitting point, 36 receiving point, 40 internal defect, 41 scattered wave component, 43 diffracted wave component.

Claims

1. A welding inspection device for inspecting a welded portion included in a base material, comprising: a first irradiation device that irradiates a transmission laser beam to a transmission point on the welded portion; a detection device for detecting ultrasonic waves generated by the transmitting laser light and reaching a receiving point on the base material; A control device for determining whether or not there is an internal defect in the welded portion, The control device includes: extracting a detection result of a reflected wave that is reflected from a lower surface of the base material and reaches the receiving point from among the detection results by the detection device; Calculating a reflected wave arrival time, which is a time taken for the reflected wave to arrive at the receiving point from the transmitting point, using the detection result of the extracted reflected wave; The welding inspection device determines whether or not the internal defect exists in the welded portion based on whether or not the calculated reflected wave arrival time is delayed with respect to a reference time.

2. The welding inspection device according to claim 1 , wherein the reference time is a time corresponding to the reflected wave arrival time in a case where the weld portion does not have the internal defect.

3. The control device includes: calculating an index value indicating a degree of delay of the calculated reflected wave arrival time with respect to the reference time; The welding inspection device according to claim 1 , wherein the presence of the internal defect is determined when the calculated index value is greater than a threshold value.

4. The welding inspection device according to claim 3 , wherein the control device prestores the reference time and the threshold value.

5. The welding inspection device according to claim 3 , wherein the control device externally acquires the reference time and the threshold value, the reference time and the threshold value being determined by an experiment or an analysis.

6. 6. The welding inspection device according to claim 1, wherein the control device determines the presence or absence of the internal defect based on an attenuation degree of the extracted reflected wave in addition to whether the reflected wave arrival time is delayed with respect to the reference time.

7. The detection device includes: a second irradiation device that irradiates the receiving point with a receiving laser light for detecting an ultrasonic wave; 6. The welding inspection device according to claim 1, further comprising a laser interferometer for interferometrically measuring the reflected light of the receiving laser light.

8. A welding inspection method for inspecting a welded portion included in a base metal, comprising the steps of: irradiating a transmission laser beam to a transmission point on the weld; detecting ultrasonic waves generated by the transmitting laser light and reaching a receiving point on the base material; extracting a detection result of a reflected wave that has been reflected on a lower surface of the base material and reached the receiving point from among the detection results of the ultrasonic wave detection step; calculating a reflected wave arrival time, which is a time taken for the reflected wave to arrive at the receiving point from the transmitting point, using the extracted detection result of the reflected wave; and determining whether or not there is an internal defect in the weld based on whether or not the calculated reflected wave arrival time is delayed with respect to a reference time.

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