Welding inspection device, welding system, and welding inspection method

Abstract

To provide a weld inspection device, a welding system, and a weld inspection method that enable in-process detection during welding of internal defects in welded portions of lap fillet welding used for welding thin plates.SOLUTION: A transmission laser beam irradiation device 12 irradiates a welded portion 6 after welding with a transmission laser beam 14. A reception laser beam probe 18 irradiates, with a reception laser beam 20, an ultrasonic wave receiving point 36 where an ultrasonic wave that has passed through the welded portion 6 and has been reflected by a lower surface 5 of a base material 4 can be detected. A control device 22 determines whether there is an internal defect of the welded portion 6 based on a measurement result of a laser interferometer. The transmission laser beam irradiation device 12 includes a scanning mechanism configured to scan the irradiation position of the transmission laser beam 14 in a direction intersecting with a welding direction.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a welding inspection device, a welding system, and a welding inspection method. [Background technology]

[0002] Ultrasonic testing (UT) is known as a method for non-destructively detecting internal defects such as blowholes that occur in welds. However, because the target becomes very hot during welding, it is difficult to apply this method, which requires a probe to directly access the surface of the target, in-process during welding.

[0003] Therefore, a method of detecting internal defects using the so-called "laser ultrasonic method" is known, in which a laser light (transmitting laser light) is irradiated onto the surface of the object to generate ultrasonic waves inside the object, and then the ultrasonic waves are detected using a laser light (receiving laser light) that is separately irradiated onto the object to detect internal defects in a non-destructive manner.

[0004] For example, Japanese Patent No. 5651533 (Patent Document 1) discloses a welding inspection method for in-process detection of internal defects in a welded portion in groove welding of thick plates using a laser ultrasonic method. In this welding inspection method, a transmitting laser beam is irradiated onto the surface of the weld bead from above, and ultrasonic waves (scattered waves) reflected by the defects are detected using a receiving laser beam, thereby detecting internal defects in the welded portion. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 5651533 Summary of the Invention [Problem to be solved by the invention]

[0006] In welding (lap fillet welding) of thin plates such as steel plates for automobiles, the plate thickness is thin (for example, about 1 to 2 mm), making it difficult to detect ultrasonic waves (scattered waves) reflected by internal defects such as blowholes, and the welding inspection method described in the above-mentioned Patent No. 5651533 is also intended for groove welding of thick plates. Note that with regard to UT, the applicable plate thickness is set at 6 mm or more in JIS Z 3060 "Ultrasonic flaw detection test method for steel welds" and the Architectural Institute of Japan "Ultrasonic flaw detection inspection standard for welds of steel construction", and so forth, and welding (lap fillet welding) of thin plates such as steel plates for automobiles is not applicable.

[0007] Therefore, an object of the present disclosure is to provide a welding inspection device, a welding system, and a welding inspection method that are capable of detecting internal defects in a weld of a lap fillet weld used in welding thin plates in-process during welding. [Means for solving the problem]

[0008] The welding inspection device disclosed herein is a welding inspection device for inspecting a welded portion of a lap fillet weld, and includes first and second laser light irradiating devices, a laser interferometer, and a judgment device. The first laser light irradiating device irradiates a transmission laser light for exciting an ultrasonic wave inside the inspection object onto the welded portion of the inspection object after welding. The second laser light irradiating device irradiates a receiving laser light for detecting an ultrasonic wave at a predetermined position on the inspection object where the ultrasonic wave that passes through the welded portion and is reflected by the lower surface of the base metal of the inspection object can be detected. The laser interferometer performs interference measurement of the reflected light of the receiving laser light. The judgment device judges the presence or absence of an internal defect in the welded portion based on the measurement result of the laser interferometer. The first laser light irradiating device includes a scanning mechanism configured to scan the irradiation position of the transmission laser light in a direction intersecting with the welding direction.

[0009] In this welding inspection device, the scanning mechanism scans the irradiation position of the transmission laser light in a direction intersecting the welding direction. Then, internal defects are detected using ultrasonic waves that pass through the weld and are reflected by the bottom surface of the base material to be inspected, rather than ultrasonic waves (scattered waves) that are reflected by internal defects that occur in the weld. This makes it possible to detect internal defects in the welds of lap fillet welds used in welding thin plates in an in-process manner.

[0010] The determination device may determine that an internal defect has occurred in the welded portion when the attenuation of the intensity of the ultrasonic wave detected by using the receiving laser light and the laser interferometer exceeds a threshold value.

[0011] The welding system of the present disclosure includes an arc welding device including a welding torch, the above-mentioned welding inspection device that inspects a welded portion of a lap fillet weld formed by the arc welding device, and a welding robot. The welding torch and first and second laser light irradiation devices of the welding inspection device are mounted on an arm of the welding robot. The first and second laser light irradiation devices are disposed behind the welding torch in the welding advance direction.

[0012] According to the above welding system, by using the above welding inspection device mounted on the arm of a robot together with the arc welding device, internal defects in a welded portion of lap fillet welds made by the arc welding device can be detected in-process during welding.

[0013] The welding robot may include a controller that controls the arm, and the controller may control the arm so that the first and second laser light irradiation devices are positioned behind the welding torch in the welding advance direction during welding by the arc welding device.

[0014] The controller may stop welding by the arc welding device and operation of the arm when an internal defect in the weld is detected by the welding inspection device.

[0015] The controller may be configured to execute at least one of the following first and second processes when an internal defect in the weld is detected by the welding inspection device. The first process includes a process of changing the welding conditions of the arc welding device. The second process includes a process of controlling the arm to reduce the welding speed compared to when no internal defect is detected.

[0016] The welding system may further include an adjustment mechanism and a deformation measuring device. The adjustment mechanism is configured to adjust at least one of a position and an angle of the second laser light emitting device on the arm. The deformation measuring device is mounted on the arm and measures deformation at a predetermined position of the inspection target caused by welding. The adjustment mechanism may adjust at least one of the position and the angle based on a measurement result of the deformation measuring device so that a relative positional relationship between the predetermined position and the second laser light emitting device becomes a predetermined relationship.

[0017] The welding system may further include a surface treatment device configured to remove an oxide film formed on the surface of the inspection object by welding with the arc welding device, ahead of the predetermined position in the welding advance direction.

[0018] The first laser light irradiation device may be configured to include a plurality of pulsed laser light irradiation devices each irradiating a pulsed laser light for transmission onto the welded portion. The plurality of pulsed laser light irradiation devices may irradiate the pulsed laser light such that the laser light irradiation timings are shifted from each other.

[0019] In addition, the welding inspection method disclosed herein is a welding inspection method for inspecting a welded portion of a lap fillet weld, and includes the steps of irradiating a transmitting laser light for exciting ultrasonic waves inside the inspection object onto the welded portion of the inspection object after welding, irradiating a receiving laser light for detecting ultrasonic waves at a predetermined position on the inspection object where ultrasonic waves that have passed through the welded portion and been reflected by the underside of the base metal of the inspection object can be detected, interferometrically measuring the reflected light of the receiving laser light with a laser interferometer, and determining the presence or absence of an internal defect in the welded portion based on the measurement results of the laser interferometer, and the step of irradiating the transmitting laser light includes the step of scanning the irradiation position of the transmitting laser light in a direction intersecting the welding direction.

[0020] In this welding inspection method, the irradiation position of the transmission laser light is scanned in a direction intersecting the welding direction. Then, internal defects are detected using ultrasonic waves that pass through the weld and are reflected by the bottom surface of the base material to be inspected, rather than ultrasonic waves (scattered waves) reflected by internal defects that occur in the weld. This makes it possible to in-process detection of internal defects in the welds of lap fillet welds used in welding thin plates.

[0021] The determining step may include a step of determining that an internal defect has occurred in the welded portion when the attenuation of the intensity of the ultrasonic wave detected using the receiving laser light and the laser interferometer exceeds a threshold value. Effect of the Invention

[0022] According to the above-described welding inspection device, welding system, and welding inspection method, internal defects in a welded portion of a lap fillet weld used in welding thin plates can be detected in-process during welding. [Brief description of the drawings]

[0023] [Figure 1] 1 is a diagram showing a configuration of a welding inspection device according to a first embodiment. [Diagram 2] 1A to 1C are diagrams illustrating the principle of defect detection in a welded portion by a welding inspection device. [Diagram 3]1A to 1C are diagrams illustrating the principle of defect detection in a welded portion by a welding inspection device. [Figure 4] 11 is a diagram showing the relationship between the irradiation position of the transmission laser light and the arrival time of an ultrasonic wave at the irradiation position of the reception laser light. FIG. [Diagram 5] 11 is a diagram showing the relationship between the irradiation position of the transmission laser light and the signal intensity of the ultrasonic wave at the irradiation position of the reception laser light. FIG. [Figure 6] 1A to 1C are diagrams illustrating a method for determining the presence or absence of a defect in a welded portion. [Figure 7] 5 is a flowchart illustrating a series of process steps in the welding inspection device according to the first embodiment. [Figure 8] FIG. 11 is an overall configuration diagram of a welding system according to a second embodiment. [Figure 9] FIG. 9 is a diagram showing an image of in-process welding defect detection in the welding system shown in FIG. 8. [Figure 10] 10 is a flowchart illustrating a series of process steps in a welding system according to a second embodiment. [Figure 11] 10 is a flowchart showing an example of a process performed by the controller when the controller receives a defect detection signal from a control device. [Figure 12] 13 is a flowchart showing an example of a process performed by the controller when the controller receives a defect detection signal from the control device in the modified example. [Figure 13] 13 is a diagram showing the relationship between the amount of deviation in the height direction from the focal position and the receiving sensitivity of a receiving laser light probe. FIG. [Figure 14] 11 is a diagram showing the relationship between the angular deviation of a receiving laser light with respect to an object to be inspected and the receiving sensitivity of a receiving laser light probe. [Figure 15] FIG. 13 is a diagram showing a state in which the base material is deformed due to welding. [Figure 16] 10 is a diagram illustrating an example of the relationship between the surface state of an inspection object and the receiving sensitivity of a receiving laser light by a receiving laser light probe. [Figure 17] FIG. 11 is an overall configuration diagram of a welding system according to a third embodiment. [Figure 18] FIG. 4 is a plan view showing the irradiation position of the transmitted laser light during welding. [Figure 19] FIG. 11 is a diagram showing the relationship between the irradiation frequency of the transmission laser light and the spatial resolution in the welding proceeding direction. [Figure 20] FIG. 13 is a diagram illustrating a configuration example of a transmitting laser light irradiation device in the fourth embodiment. [Figure 21] 5 is a diagram showing the oscillation timing of pulsed laser light output from each of the transmitting laser light emitting devices. FIG. [Figure 22] FIG. 13 is a diagram illustrating a configuration example of a transmitting laser light irradiation device in a modified example of the fourth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] 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.

[0025] [Embodiment 1] Fig. 1 is a diagram showing a configuration of a welding inspection device according to a first embodiment of the present disclosure. With reference to Fig. 1, welding inspection device 1 includes a transmitting laser source 10, a transmitting laser light irradiation device 12, a receiving laser source 16, a receiving laser light probe 18, a control device 22, and a display device 24.

[0026] This welding inspection device 1 is used to inspect a weld 6 in lap fillet welding of thin plates (base materials 2, 4) such as steel plates for automobiles. The base materials 2, 4 are, for example, zinc-plated steel plates with a thickness of about 1 to 2 mm. In the figure, the Y direction indicates the welding progress direction, the X direction indicates a direction parallel to the base material and perpendicular to the welding direction (Y direction), and the Z direction indicates the normal direction of the base material.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] The receiving laser light probe 18 irradiates a predetermined position (ultrasound receiving point) of the base material 4 of the lower plate with a receiving laser light 20. 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).

[0031] In this welding inspection device 1, internal defects of the welded portion 6 are detected using a laser ultrasonic method. That is, a laser beam (transmitting laser beam 14) is irradiated onto the welded portion 6 to be inspected to generate ultrasonic waves inside the object, and surface vibrations corresponding to the intensity of the ultrasonic waves at a position (ultrasonic receiving point) on the base material 4 to which the receiving laser beam 20 is irradiated are detected by 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 welded portion 6 is determined based on the detection difference between when there is an internal defect in the welded portion 6 and when there is no internal defect. The principle of detection of internal defects in a welded portion by the welding inspection device 1 will be described in detail later with reference to Figs. 2 and 3.

[0032] 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.

[0033] 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.

[0034] The control device 22 receives from the receiving laser source 16 an interference measurement result of the receiving laser light 20 by the laser interferometer of the receiving laser source 16, and judges the presence or absence of an internal defect in the welded portion 6 based on the intensity of the ultrasonic wave (intensity of the surface vibration) at the irradiation position (ultrasonic wave reception point) of the receiving laser light 20. The method of judging the presence or absence of this internal defect will be described in detail later.

[0035] The display device 24 is a display for displaying various processing results of the control device 22. For example, a measurement screen called B-scope is displayed on the display device 24, which shows the measurement results of ultrasonic waves in an inspection object by the welding inspection device 1. The B-scope displays the arrival time and intensity of ultrasonic waves at the irradiation position (ultrasonic wave reception point) of the receiving laser light 20 according to the irradiation position (ultrasonic wave transmission point) of the transmitting laser light 14 scanned in the X direction. The control device 22 and the display device 24 are configured by, for example, a PC (Personal Computer). A method for detecting internal defects of a welded portion by the welding inspection device 1 will be described in detail below.

[0036] 2 and 3 are diagrams for explaining the principle of detection of internal defects in a welded portion by the welding inspection device 1. Fig. 2 shows a state where there is no defect in the welded portion 6, and Fig. 3 shows a state where an internal defect (such as a blowhole) occurs in the welded portion 6.

[0037] 2, in this welding inspection device 1, a transmitting laser beam 14 (pulse laser beam) is irradiated from above (Z direction) onto an area including a welded portion 6, and ultrasonic waves are excited at the position irradiated with the laser beam. The generated ultrasonic waves pass through the welded portion 6, are reflected off the lower surface 5 of the lower base material 4, and then reach the upper surface of the base material 4. The minute vibrations generated on the surface of the base material 4 by the reaching ultrasonic waves are measured using a receiving laser beam 20 (interferometry using a laser interferometer), and the intensity of the ultrasonic waves at the position irradiated with the receiving laser beam 20 (ultrasonic wave receiving point) is measured.

[0038] The irradiation position of the transmission laser light 14 is scanned in the X direction using a scanning mechanism of the transmission laser light irradiation device 12 (FIG. 1). A point 32 indicated by an x ​​mark indicates the irradiation position (ultrasound transmission point) of the transmission laser light 14, which is a pulsed laser light. After measurement at a certain irradiation position is completed, the irradiation position of the transmission laser light 14 is scanned to the next position, and measurement is performed at that irradiation position.

[0039] The irradiation position of the receiving laser light 20 is fixed in the X direction of the base material 4. A point 36 indicated by a circle indicates the irradiation position (ultrasound receiving point) of the receiving laser light 20. The greater the distance in the X direction between the receiving point 36 and the transmitting point 32, the longer the propagation time of the ultrasonic wave from the transmitting point 32 to the receiving point 36, and the intensity of the ultrasonic wave (micro-vibration of the surface) at the receiving point 36 also decreases due to diffusion attenuation.

[0040] 3, when a defect 40 such as a blowhole is present in the welded portion 6, scattering attenuation occurs at the defect 40 in addition to diffusion attenuation, so that the intensity of the ultrasonic wave 44 reaching the reception point 36 becomes smaller (attenuation becomes larger) than when the defect 40 is not present. Therefore, by capturing the degree of attenuation of the ultrasonic wave reaching the reception point 36, the presence or absence of the defect 40 in the welded portion 6 can be determined.

[0041] Fig. 4 is a diagram showing the relationship between the irradiation position of the transmitting laser light 14 and the arrival time of the ultrasonic wave at the irradiation position of the receiving laser light 20. In Fig. 4, the horizontal axis indicates the irradiation position in the X direction of the transmitting laser light 14 (ultrasound transmission position), and the larger the value, the farther it is from the irradiation position of the receiving laser light 20 (ultrasound reception point). The vertical axis indicates the time from the irradiation of the transmitting laser light 14 (from the generation of ultrasonic waves at the transmission position) to the arrival of the ultrasonic wave at the irradiation position of the receiving laser light 20 (ultrasound reception point).

[0042] 4, line L1 indicates the arrival time of ultrasonic waves (surface waves) that have propagated through the surfaces of the welded portion 6 and the base material 4. Line L2 indicates the arrival time of ultrasonic waves (reflected waves) that have passed from the transmission position of the ultrasonic waves through the welded portion 6 and have been reflected by the lower surface 5 of the base material 4.

[0043] Since the arrival time of the reflected wave is not affected by the presence or absence of a defect 40, it is possible to distinguish whether the ultrasonic wave detected at the irradiation position (ultrasonic reception point) of the receiving laser light 20 is a surface wave or an ultrasonic wave (reflected wave) reflected by the underside 5 of the base material 4 from the relationship between the ultrasonic transmission position and the arrival time.

[0044] Fig. 5 is a diagram showing the relationship between the irradiation position of the transmitting laser beam 14 and the intensity of the ultrasonic wave at the irradiation position of the receiving laser beam 20. In Fig. 5, the horizontal axis indicates the irradiation position in the X direction of the transmitting laser beam 14 (the transmitting position of the ultrasonic wave), as in Fig. 4. The vertical axis indicates the intensity of the reflected wave (line L2) in Fig. 4 at the irradiation position of the receiving laser beam 20 (the ultrasonic wave receiving point).

[0045] 5, line L3 indicates the intensity of the reflected wave (line L2) in FIG. 4 at the ultrasonic reception point when there is no internal defect in the weld 6. The larger the value of the ultrasonic transmission position is (the farther away from the ultrasonic reception point is), the more the signal intensity is attenuated due to diffusion attenuation.

[0046] Line L4 indicates the intensity of the reflected wave (line L2) in Fig. 4 at the ultrasonic reception point when an internal defect (such as a blowhole) exists in the welded portion 6. When the ultrasonic transmission position is greater than X1, the ultrasonic wave (reflected wave) that arrives at the ultrasonic reception point passes through the internal defect that has occurred in the welded portion 6. At that time, in addition to diffusion attenuation, scattering attenuation also occurs at the internal defect, so the intensity of the ultrasonic wave at the ultrasonic reception point is smaller than when there is no internal defect (line L3). In other words, the degree of attenuation of the ultrasonic wave when there is an internal defect at the ultrasonic reception point is greater than when there is no internal defect.

[0047] Note that the B-scope is a display in which the lines L1 and L2 in the graph of Fig. 4 are displayed with varying density according to the intensity of the ultrasonic waves at the ultrasonic reception point for each ultrasonic transmission position. In the B-scope, the arrival time and intensity of the ultrasonic waves at the ultrasonic reception point for each ultrasonic transmission position are displayed on one screen.

[0048] Fig. 6 is a diagram for explaining a method of determining whether or not there is an internal defect in the welded portion 6. Referring to Fig. 6, the presence or absence of an internal defect in the welded portion 6 is determined based on the magnitude of attenuation of the ultrasonic wave intensity (the intensity of the ultrasonic wave reflected by the lower surface 5 of the base material 4) at the irradiation position (ultrasonic wave receiving point) of the receiving laser light 20 according to the transmission position of the ultrasonic wave. That is, if the attenuation according to the transmission position of the ultrasonic wave is smaller than a predetermined threshold value, it is determined that there is no defect, and if the attenuation exceeds the threshold value, it is determined that an internal defect has occurred in the welded portion 6 to be inspected. The threshold value 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.

[0049] Fig. 7 is a flowchart illustrating a series of processing steps in the welding inspection device 1 according to the first embodiment. Referring to Fig. 7, first, the control device 22 controls the scanning mechanism of the transmission laser light irradiator 12 so as to irradiate the transmission laser light 14 to a predetermined position on the inspection target (step S10). Each irradiation position of the transmission laser light 14 in one scan is determined in advance in the X direction (e.g., 20 points in the area including the welded portion 6), and for example, the scanning mechanism is controlled so as to first irradiate the transmission laser light 14 to a predetermined position closest to the irradiation position of the reception laser light 20.

[0050] The control device 22 also controls the receiving laser source 16 so that the receiving laser light 20 is irradiated to a predetermined receiving point of the test object (step S20). The irradiation position (ultrasonic wave receiving point) of the receiving laser light 20 is determined to be a predetermined position in the X direction. 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.

[0051] Then, the receiving laser source 16 receives the reflected light of the receiving laser light 20 irradiated onto the base material 4 from the receiving laser light probe 18, and measures the interference between the reflected light and the receiving laser light 20 (reference light) irradiated onto the base material 4 using a laser interferometer (step S20).

[0052] Next, the control device 22 judges whether or not the scanning of the transmission laser light 14 is completed (step S25). Specifically, it is judged whether or not the measurement is completed at all of the predetermined irradiation positions in the X direction. If the scanning is not completed (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.

[0053] When it is determined in step S25 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 ultrasonic waves (ultrasonic waves that pass through the welded portion 6 from the transmission position and are reflected by the lower surface 5 of the base material 4) at the irradiation position (reception point) of the receiving laser light 20, for the measurement signal for one scan obtained in the processes of steps S10 to S30.

[0054] When creating the B-scope, the measurement signal obtained in step S20 may be subjected to frequency processing using an appropriate bandpass filter or the like in order to remove noise.

[0055] Next, the ultrasonic signal that has been reflected by the lower surface 5 of the lower plate (base material 4) and reached the ultrasonic reception point is extracted from the created B-scope (step S40). As described in Fig. 4, in the B-scope, ultrasonic waves (reflected waves) reflected by the lower surface 5 of the base material 4 can be easily extracted while being distinguished from surface waves, etc. This extraction operation may be performed manually or automatically by the control device 22.

[0056] In step S40, when the signal of the ultrasonic wave reflected by the lower surface 5 of the lower plate (base material 4) and reaching the ultrasonic wave receiving point is extracted, the control device 22 calculates the ultrasonic attenuation of the extracted signal according to the irradiation position (transmission position) of the transmission laser light 14 (step S45). Specifically, the control device 22 calculates the degree of decrease in ultrasonic intensity according to the transmission position. Note that 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.

[0057] Then, the control device 22 judges whether the attenuation calculated in step S45 is greater than a threshold value (step S50). This threshold value is appropriately set to a value that can distinguish the presence or absence of an internal defect by a preliminary evaluation test, as described above. Then, when it is judged that the attenuation is greater than the threshold value (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).

[0058] As described above, in this embodiment 1, internal defects are detected using ultrasonic waves that pass through the welded portion 6 and are reflected by the lower surface 5 of the base material 4 to be inspected, rather than ultrasonic waves (scattered waves) that are reflected by internal defects occurring in the welded portion 6. Specifically, the irradiation position of the transmission laser light 14 is scanned in the X direction, and if the attenuation of the ultrasonic waves at the ultrasonic reception point corresponding to the scanning of the irradiation position exceeds a threshold value, it is determined that an internal defect has occurred in the welded portion. According to this embodiment 1, with such a configuration, internal defects in the welded portion 6 of lap fillet welds used in welding thin plates can be detected in-process.

[0059] [Embodiment 2] In the second embodiment, a welding system in which the welding device and the above-mentioned welding inspection device are mounted on an automatic welding robot is shown.

[0060] 8 is an overall configuration diagram of a welding system according to the embodiment 2. With reference to FIG. 8, welding system 100 includes a robot arm 110, a welding torch 112, a wire 118, a welding power source 120, and a controller 122.

[0061] The robot arm 110 is a multi-joint arm, for example a six-axis multi-joint arm, and is controlled by a controller 122 so as to perform lap fillet welding of the base materials 102, 104 with a welding torch 112 at a set welding speed.

[0062] Welding torch 112 supplies a welding wire and a shielding gas (argon gas, carbon dioxide gas, etc.) (not shown) toward the joint between base materials 102, 104. Welding torch 112 receives a welding current from a welding power source 120 through wire 118, and generates an arc 114 between the tip of the welding wire and the joint between base materials 102, 104.

[0063] Instead of the welding wire, a non-consumable electrode (such as tungsten) may be used with the addition of a filler (filler material) to form the weld metal. That is, the arc welding by the welding torch 112 may be a consumable electrode type (such as MAG welding or MIG welding) that uses a welding wire, or a non-consumable electrode type (such as TIG welding) that involves the addition of a filler.

[0064] Welding power source 120 generates a welding voltage and a welding current for performing arc welding, and outputs the generated welding voltage and welding current to welding torch 112 .

[0065] Controller 122 controls the operation of robot arm 110 and the output of welding power source 120 so that lap fillet welding of base materials 102, 104 is performed by welding torch 112 at a set welding speed. At that time, controller 122 controls robot arm 110 so that a welding inspection head 130 (described later) constituting a welding inspection device is positioned behind welding torch 112 in the welding advance direction.

[0066] Furthermore, controller 122 cooperates with control device 164, which controls the welding inspection device, and exchanges various signals with control device 164. For example, controller 122 notifies control device 164 of the start, stop, and continuation of welding by welding torch 112. Furthermore, upon receiving a defect detection signal from control device 164 indicating that an internal defect has been detected in the welded portion, controller 122 stops welding by welding torch 112 or changes the welding conditions.

[0067] The controller 122 also includes a CPU, memory (RAM and ROM), 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. Various processes executed by the controller 122 are described in the program stored in the ROM.

[0068] Welding system 100 further includes a weld inspection head 130 , optical fibers 142 , 148 , a link 150 , a transmitting laser source 160 , a receiving laser source 162 , and a controller 164 .

[0069] The welding inspection head 130 includes a transmitting laser light irradiator 134 and a receiving laser light probe 144. The transmitting laser light irradiator 134 and the receiving laser light probe 144 are attached to a mounting member 132, and the mounting member 132 is connected to the robot arm 110 by a link 150.

[0070] The transmission laser light irradiation device 134 includes a microchip laser 136, a scanning mechanism 138, and a photodetector 140. The microchip laser 136 is a small solid-state laser using, for example, a YAG crystal, and receives excitation light from a transmission laser source 160 through an optical fiber 142 to generate a high-output pulsed laser light.

[0071] The scanning mechanism 138 includes a mechanism for scanning the irradiation position of the pulsed laser light generated by the microchip laser 136 in the X direction (welding width direction perpendicular to the welding direction (Y direction)). The scanning mechanism 138 includes, for example, a galvanometer mirror whose angle is adjustable, and a driving mechanism for driving the galvanometer mirror. The driving mechanism of the scanning mechanism 138 is controlled by the control device 164 so that the ultrasonic transmission point group 154 ​​irradiated with the transmission laser light 152 (pulsed laser light) includes the entire area of ​​the weld bead 106 in the X direction.

[0072] The photodetector 140 detects the oscillation of the transmission laser light 152 (pulse laser light), and outputs a trigger signal Tr to the control device 164 every time the pulse laser light is oscillated.

[0073] The receiving laser light probe 144 irradiates a receiving laser light 156 (reference light) received from a receiving laser source 162 through an optical fiber 148 onto an ultrasonic receiving point 158, which is a predetermined position in the X direction on the base material 104. The receiving laser light probe 144 also receives the reflected light from the base material 104 of the receiving laser light 156 irradiated onto the base material 104, and outputs the reflected light to the receiving laser source 162 through the optical fiber 148.

[0074] The receiving laser source 162 includes a laser interferometer, and outputs the receiving laser light 156 (reference light) to be irradiated onto the base material 104 to the receiving laser light probe 144 through the optical fiber 148. The receiving laser source 162 receives the reflected light of the receiving laser light 156 from the base material 104 received by the receiving laser light probe 144 from the receiving laser light probe 144, and outputs a detection signal IS of interference light including the reference light and reflected light of the receiving laser light 156 to the control device 164.

[0075] In addition, in consideration of in-process defect detection during welding, the irradiation positions of the transmitting laser light 152 and the receiving laser light 156 are desirably close to the welding position (molten pool 116), and can be, for example, 20 to 30 mm behind the molten pool 116 in the welding progression direction.

[0076] The control device 164 measures the detection signal IS of the interference light between the reference light and the reflected light of the receiving laser light 156 for a predetermined time (e.g., 10 μs) based on the trigger signal Tr from the photodetector 140, which indicates the timing at which the transmitting laser light 152 (pulse laser light) is oscillated. Then, the control device 164 measures the intensity of the ultrasonic wave at the ultrasonic receiving point 158 ​​corresponding to the trigger signal Tr from the measured detection signal IS of the interference light.

[0077] Control device 164 measures the intensity of the ultrasonic waves at ultrasonic receiving point 158 ​​as described above while scanning the irradiation position (ultrasonic transmission point) of transmission laser light 152. Then, when control device 164 completes the measurement for one scan, it determines whether or not an internal defect has occurred in the welded portion (weld bead 106) based on the attenuation of the ultrasonic waves (reflected waves) that have been reflected by the lower surface of the lower plate (base material 104) and reached reception point 158, using a method similar to that of embodiment 1.

[0078] In welding system 100 according to this embodiment 2, when control device 164 determines that an internal defect has occurred in the weld, a defect detection signal indicating that an internal defect has been detected in the weld is sent from control device 164 to controller 122 on the robot arm side, and welding by welding torch 112 is stopped or the welding conditions are changed (such as a change in welding speed or welding current).

[0079] Fig. 9 is a diagram showing an image of in-process welding defect detection in the welding system 100 shown in Fig. 8. Referring to Fig. 9, the upper diagram is a plan view of an inspection target including a welded portion. A weld bead 106 is formed behind a molten pool 116, and a defect 40 indicated by a dotted line is a blowhole or the like that has occurred inside the welded portion (weld bead 106).

[0080] At positions in the Y direction (welding progression direction) where no defect occurs in the welded portion, the degree of ultrasonic attenuation at ultrasonic receiving point 158 ​​in response to scanning of the irradiation position of transmission laser light 152 (pulse laser light) is smaller than the threshold value. On the other hand, at positions in the Y direction where a defect occurs in the welded portion, the degree of ultrasonic attenuation at ultrasonic receiving point 158 ​​in response to scanning of the irradiation position of transmission laser light 152 is larger than the threshold value. In this way, it is possible to determine in-process during welding where in the welding progression direction (Y direction) the defect 40 occurs in the welded portion (weld bead 106).

[0081] Fig. 10 is a flowchart illustrating a series of processing steps in the welding system according to the second embodiment. Referring to Fig. 8 together with Fig. 10, control device 164 controls scanning mechanism 138 to irradiate a predetermined position in the X direction of the welding target with transmission laser light 152 (step S110). Each irradiation position of transmission laser light 152 in one scan is determined in advance in the X direction, and in this example, 20 irradiation positions are determined in the area including weld bead 106.

[0082] Next, the photodetector 140 detects the oscillation (irradiation) of the transmission laser light 152 (pulse laser light), and a trigger signal Tr indicating the start of detection of the ultrasound corresponding to this pulse irradiation is transmitted from the photodetector 140 to the control device 164 (step S115).

[0083] The control device 164 measures the intensity of the ultrasonic wave at the ultrasonic reception point 158 ​​based on the interference light of the receiving laser light 156 obtained by the laser interferometer, for a predetermined time (eg, 10 μs) based on the trigger signal Tr (step S120).

[0084] Next, the control device 164 judges whether or not the measurement for one scan of the transmission laser light 152 has been completed (step S125). Specifically, it is judged whether or not the measurement has been completed at all of the predetermined irradiation positions (20 points in this example) in the X direction. If the measurement for one scan has not been completed (NO in step S125), the control device 164 updates the irradiation position of the transmission laser light 152 to the next position (step S130). Then, the process returns to step S110.

[0085] When it is determined in step S125 that the measurement for one scan of the transmission laser light 152 is completed (YES in step S125), the control device 164 creates a B-scope and executes waveform processing (step S135). Furthermore, from the created B-scope, a signal of the ultrasonic wave (reflected wave) that is reflected at the lower surface of the lower plate (base material 104) and reaches the receiving point 158 ​​is extracted (step S140). Furthermore, the control device 164 calculates the attenuation of the ultrasonic wave according to the irradiation position (transmission position) of the transmission laser light 152 for the extracted signal (step S145). Note that the processing of the above steps S135 to S145 is similar to the processing of steps S35 to S45 in FIG. 7 described in the first embodiment, and therefore detailed description will not be repeated.

[0086] Next, control device 164 determines whether the attenuation calculated in step S145 is greater than a threshold value (step S150). This threshold value is appropriately set to a value that can distinguish the presence or absence of an internal defect through a previous evaluation test. If it is determined that the attenuation is greater than the threshold value (YES in step S150), control device 164 outputs a defect detection signal indicating that a defect has been detected in the welded portion (weld bead 106) to controller 122 on the robot arm side (step S155). Note that if the attenuation is equal to or less than the threshold value (NO in step S150), control device 164 shifts the process to step S160 without executing the process of step S155.

[0087] Next, control device 164 determines whether or not welding is to be continued based on a signal from controller 122 indicating whether welding needs to be continued (step S160). If welding is to be continued (YES in step S160), control device 164 proceeds to measurement on the next measurement line (step S165) and returns the process to step S110.

[0088] On the other hand, in step S160, if it is determined based on the signal from controller 122 that welding is to be stopped (NO in step S160), control device 164 transitions the process to END and ends the series of processes.

[0089] Fig. 11 is a flowchart showing an example of processing by controller 122 when controller 122 receives a defect detection signal from control device 164. Referring to Fig. 11, controller 122 determines whether or not it has received a defect detection signal from control device 164 (step S210). If controller 122 has not received a defect detection signal (NO in step S210), controller 122 transitions to return without executing the following series of processes.

[0090] If it is determined in step S210 that a defect detection signal has been received from control device 164 (YES in step S210), controller 122 stops welding by welding torch 112 (step S220). Furthermore, controller 122 stops the operation of robot arm 110 (step S230).

[0091] Then, controller 122 notifies control device 164 (welding inspection device) that welding has been stopped (step S240). That is, in this example, inspection of the welded portion (weld bead 106) is performed in-process during welding, and if a defect in the welded portion is detected, welding is stopped in accordance with a defect detection signal output from control device 164 to controller 122 of the robot arm. Then, controller 122 notifies control device 164 on the welding inspection device side that welding has been stopped.

[0092] As described above, according to the second embodiment, by using a welding inspection device (welding inspection head 130) mounted on robot arm 110 together with welding torch 112, it is possible to detect internal defects in the welded portion (weld bead 106) by welding torch 112 in-process during welding. According to the second embodiment, the welding inspection device and the welding robot (robot arm 110 and welding torch 112) are linked together, and when an internal defect is detected in the welded portion by the welding inspection device, welding by the welding robot can be stopped.

[0093] [Variations] In the above second embodiment, welding is stopped when a welding defect is detected, but welding conditions may be changed and welding may be continued.

[0094] 12 is a flowchart showing an example of processing performed by the controller 122 in this modified example when the controller 122 receives a defect detection signal from the control device 164. This flowchart corresponds to the above-mentioned FIG.

[0095] 12, controller 122 determines whether or not a defect detection signal has been received from control device 164 (step S310). If controller 122 has not received a defect detection signal (NO in step S310), controller 122 transitions to RETURN without executing the following series of processes.

[0096] When it is determined in step S310 that a defect detection signal has been received from control device 164 (YES in step S310), controller 122 changes the conditions for welding by welding torch 112 (step S320). The change in the welding conditions is determined in advance, and for example, the welding current is changed.

[0097] Controller 122 also reduces the welding speed (step S330). The degree of reduction in the welding speed is also determined in advance, and the welding speed after reduction may be specified, or the reduction rate of the welding speed may be specified. Note that only the processing of steps S320 and S330 may be executed.

[0098] Then, when the processing of step S320 and / or step S330 has been executed, controller 122 notifies control device 164 (welding inspection device) that welding will continue (step S340). That is, in this example as well, inspection of the weld (weld bead 106) is performed in-process during welding, and if a defect in the weld is detected, the welding conditions and welding speed are changed in accordance with a defect detection signal output from control device 164 to controller 122 of the robot arm, and welding is continued. Then, controller 122 notifies control device 164 on the welding inspection device side that welding will continue.

[0099] As described above, according to this modified example, when an internal defect is detected in a weld by the welding inspection device, the welding conditions can be changed or the welding speed can be reduced so as to suppress the defect in subsequent welding.

[0100] [Embodiment 3] In defect detection using the laser ultrasonic method, non-contact vibration measurement is performed using the reflected light from the surface irradiated with the receiving laser light 156. In order to sufficiently capture the reflected light from the inspection object and increase the measurement sensitivity, the receiving laser light probe 144 needs to be placed directly opposite the surface irradiated with the receiving laser light 156 and at the focal position.

[0101] Fig. 13 is a diagram showing the relationship between the amount of deviation in the height direction from the focal position and the reception sensitivity of the receiving laser light probe 144. Fig. 13 shows the reception sensitivity when the receiving laser light probe 144 is directly opposed to the stainless steel mirror surface and the height of the receiving laser light probe 144 with respect to the stainless steel mirror surface is changed from the focal position.

[0102] As shown in the figure, when a deviation occurs in the height direction from the focal position, the reception sensitivity of the receiving laser light probe 144 decreases. That is, when the distance between the receiving laser light probe 144 and the irradiated surface of the receiving laser light 156 (the surface of the base material 104) changes, the reception sensitivity of the receiving laser light 156 by the receiving laser light probe 144 decreases.

[0103] Fig. 14 is a diagram showing the relationship between the angle deviation of the receiving laser light 156 with respect to the irradiation surface and the receiving sensitivity of the receiving laser light probe 144. Fig. 14 shows the receiving sensitivity when the receiving laser light probe 144 is directly opposed to the stainless steel mirror surface and the angle of the receiving laser light probe 144 with respect to the stainless steel mirror surface is changed.

[0104] As shown in the figure, when an angle deviation occurs in the receiving laser light 156, the receiving sensitivity of the receiving laser light probe 144 decreases. That is, when a deviation occurs between the irradiation direction of the receiving laser light 156 and the normal direction of the irradiation surface (surface of the base material 104) of the receiving laser light 156, the receiving sensitivity of the receiving laser light 156 by the receiving laser light probe 144 decreases.

[0105] In welding, the welding target may be deformed due to thermal strain caused by welding. In particular, in welding of thin plates, deformation of the base material due to welding is expected as shown in Fig. 15. As shown in the figure, when the lower base material 104 is deformed, if the arrangement of the receiving laser light probe 144 remains in the initial state, the reception sensitivity of the receiving laser light 156 by the receiving laser light probe 144 may decrease.

[0106] Therefore, in the third embodiment, the deformation of the irradiated surface of the receiving laser light 156 is measured during welding, and the information is used to adjust the position and angle of the receiving laser light probe 144. This prevents the decrease in the receiving sensitivity of the receiving laser light probe 144.

[0107] In addition, the receiving sensitivity of the receiving laser light probe 144 also changes depending on the state of the surface onto which the receiving laser light 156 is irradiated.

[0108] Fig. 16 is a diagram illustrating an example of the relationship between the surface state of the inspection target and the receiving sensitivity of the receiving laser light probe 144. Referring to Fig. 16, when smut (oxide film) after welding is attached to the irradiated surface of the receiving laser light 156, the receiving sensitivity of the receiving laser light probe 144 decreases. On the other hand, by polishing the irradiated surface of the receiving laser light 156, the receiving sensitivity of the receiving laser light probe 144 improves.

[0109] Therefore, in this embodiment 3, a tool is further provided for polishing the ultrasonic receiving point 158 ​​to which the receiving laser light 156 is irradiated. For example, a brush or laser light irradiation can be used as the tool. This further suppresses the decrease in the receiving sensitivity of the receiving laser light probe 144.

[0110] Fig. 17 is an overall configuration diagram of a welding system according to the embodiment 3. Referring to Fig. 17, this welding system 100A further includes a laser line scanner 170, a driving mechanism 146, and a surface treatment device 174 in addition to the components of welding system 100 shown in Fig. 8.

[0111] The laser line scanner 170 is attached to the mounting member 132 and measures the surface profile of the welded component after welding. More specifically, the laser line scanner 170 measures the surface profile of the base material 104 after welding at least in the XZ plane. A signal Pf indicating the measurement result of the laser line scanner 170 is output to the control device 164.

[0112] The drive mechanism 146 is controlled by the control device 164 and is configured to be able to change the position (Z direction) and angle (rotation angle on the XZ plane) of the receiving laser light probe 144 relative to the mounting member 132 .

[0113] Based on the signal Pf from the laser line scanner 170, the control device 164 controls the drive mechanism 146 so that the receiving laser light probe 144 faces the base material 104 directly and the position of the receiving laser light probe 144 relative to the base material 104 is the focal position.

[0114] The surface treatment device 174 is a tool for polishing the surface of the base material 104 in the welding direction ahead of the ultrasonic receiving point 158 ​​where the receiving laser light 156 is irradiated. For example, a brush can be used as the surface treatment device 174. Alternatively, the surface treatment device 174 may be configured by a laser light irradiator whose output is adjusted so as to remove smut after welding while leaving the plating layer on the surface of the base material 104.

[0115] In the above, the drive mechanism 146 is capable of changing the position and angle of the receiving laser light probe 144, but it may be capable of changing only one of the position and angle of the receiving laser light probe 144. Even if only one of the position and angle is changed, it is possible to suppress a decrease in the receiving sensitivity of the receiving laser light probe 144.

[0116] In the above description, the driving mechanism 146 corresponds to an "adjustment mechanism" that adjusts at least one of the position and angle of the receiving laser light probe 144. The laser line scanner 170 corresponds to a "deformation measuring device" that is mounted on the robot arm 110 and measures the deformation of the test target at the ultrasonic receiving point 158 ​​where the receiving laser light 156 is irradiated.

[0117] In the above, welding system 100A includes drive mechanism 146 and laser line scanner 170, but it may include only one of drive mechanism 146 and laser line scanner 170.

[0118] As described above, according to the third embodiment, by providing the driving mechanism 146 and / or the laser line scanner 170, it is possible to suppress a decrease in the reception sensitivity of the receiving laser light probe 144 caused by deformation of the welding object after welding and the formation of smut. As a result, it is possible to suppress a decrease in the detection accuracy of internal defects of the welded portion.

[0119] [Embodiment 4] Since welding inspection head 130 is mounted on robot arm 110 together with welding torch 112, welding inspection head 130 also moves in the welding proceeding direction together with welding torch 112 during welding. Therefore, the scanning direction of the irradiation position of transmission laser light 152 is inclined from the direction (X direction) perpendicular to the welding proceeding direction (Y direction).

[0120] Fig. 18 is a plan view showing the irradiation position of the transmission laser light 152 during welding. Referring to Fig. 18, the ultrasonic transmission point group 154 ​​irradiated with the transmission laser light 152 has a width Δy in the welding proceeding direction (Y direction) between the start point and the end point of the scan. This Δy can be said to represent the spatial resolution of the welding inspection in the welding proceeding direction.

[0121] This spatial resolution can be increased (Δy can be reduced) by (i) decreasing the moving speed of the welding inspection head 130, (ii) decreasing the number of irradiation points of the transmission laser light 152 (pulse laser light) in one scan, or (iii) increasing the irradiation frequency of the transmission laser light 152.

[0122] However, since the moving speed of the welding inspection head 130 is the welding speed, which is determined by the welding conditions, lowering the moving speed of the welding inspection head 130 is a change in the welding conditions, which is not easy. Furthermore, reducing the number of irradiation points of the transmission laser light 152 in one scan reduces the amount of information acquired, which may lead to a decrease in detection accuracy. Therefore, it is desirable to increase the irradiation frequency of the transmission laser light 152 (pulse laser light).

[0123] Fig. 19 is a diagram showing the relationship between the irradiation frequency of the transmission laser beam 152 and the spatial resolution in the welding proceeding direction. Referring to Fig. 19, the spatial resolution (Δy in Fig. 18) is shown when the irradiation frequency of the transmission laser beam 152 is changed in the case where the number of irradiation points of the transmission laser beam 152 in one scan is 20 and the welding speed is 1.0 m / min.

[0124] When the irradiation frequency (pulse frequency) of the transmission laser light 152 is 50 Hz, the spatial resolution is Δy=6.7 mm, and when the irradiation frequency is 100 Hz, the spatial resolution is half that. In this way, by increasing the irradiation frequency of the transmission laser light 152, the spatial resolution can be increased (Δy can be reduced).

[0125] It is not easy to increase the oscillation frequency of the microchip laser 136 in order to increase the irradiation frequency of the transmission laser light 152. Therefore, in the fourth embodiment, taking advantage of the small size of the microchip laser, a plurality of microchip lasers are used to increase the irradiation frequency of the transmission laser light 152.

[0126] Fig. 20 is a diagram showing a configuration example of a transmission laser light emitting device in the fourth embodiment. Referring to Fig. 20, in the illustrated example, transmission laser sources 160-1 and 160-2 and transmission laser light emitting devices 134-1 and 134-2 are provided as generating devices for the transmission laser light 152. The configuration of each of the transmission laser sources 160-1 and 160-2 is the same as that of the transmission laser source 160 described in Fig. 8, and the configuration of each of the transmission laser light emitting devices 134-1 and 134-2 is the same as that of the transmission laser light emitting device 134 described in Fig. 8.

[0127] The transmission laser light emitting devices 134-1 and 134-2 receive excitation light from the transmission laser sources 160-1 and 160-2 through optical fibers, respectively. Each of the transmission laser light emitting devices 134-1 and 134-2 generates a high-power pulsed laser light. The galvanometer mirrors of the pulsed laser light output from the transmission laser light emitting device 134-1 and the pulsed laser light output from the transmission laser light emitting device 134-2 are controlled so that the irradiation positions of the pulsed laser light are the same, while the oscillation timings of the pulsed laser light and the transmission laser light emitting devices are shifted from each other.

[0128] FIG. 21 is a diagram showing the oscillation timing of the pulsed laser light output from each of the transmission laser light irradiators 134-1 and 134-2. Referring to FIG. 21, the oscillation timing of the pulsed laser light is adjusted in each of the transmission laser light irradiators 134-1 and 134-2 so that the oscillation timings of the pulsed laser light output from each of the transmission laser light irradiators 134-1 and 134-2 are shifted by a half period from each other. This can substantially double the number of ultrasonic waves generated at the irradiation position of the transmission laser light 152. For example, when the frequency of the pulsed laser light output from each of the transmission laser light irradiators 134-1 and 134-2 is 100 Hz, the frequency of the transmission laser light 152 irradiated to the target can be set to 200 Hz.

[0129] Other configurations of the welding system in the fourth embodiment are the same as those of welding system 100 shown in FIG. 8 or welding system 100A shown in FIG.

[0130] As described above, according to the fourth embodiment, the spatial resolution of the welding inspection in the welding progression direction can be increased, thereby improving the detection accuracy of internal defects in the welded portion.

[0131] [Modification of the fourth embodiment] In the fourth embodiment, the number of ultrasonic waves generated at the irradiation position of the transmission laser light 152 is doubled by using the multiple transmission laser light irradiators 134-1 and 134-2, but the control of the scanning mechanism (galvanometer mirror) and the management of the trigger by the photodetector are required for multiple units, which may complicate the configuration of the entire device. Therefore, by configuring the multiple microchip lasers to share the optical system (scanning mechanism), the control of the scanning mechanism and the management of the trigger by the photodetector can be consolidated into one.

[0132] Fig. 22 is a diagram showing a configuration example of a transmission laser light emitting device in a modification of the fourth embodiment. Referring to Fig. 22, in this modification, a transmission laser light emitting device 180 is provided instead of the transmission laser light emitting devices 134-1 and 134-2 shown in Fig. 20. The transmission laser light emitting device 180 includes microchip lasers 136-1 and 136-2, a focusing mechanism 182, a scanning mechanism 138, and a photodetector 140. The configuration of each of the microchip lasers 136-1 and 136-2 is the same as that of the microchip laser 136 described in Fig. 8.

[0133] The microchip lasers 136-1 and 136-2 receive excitation light from the transmitting laser sources 160-1 and 160-2 through optical fibers, respectively. Then, each of the microchip lasers 136-1 and 136-2 generates a high-power pulsed laser light and outputs it to the light collecting mechanism 182. The pulsed laser light output from the microchip laser 136-1 and the pulsed laser light output from the microchip laser 136-2 are shifted in oscillation timing from each other. More specifically, as shown in FIG. 21, the oscillation timing of the pulsed laser light is adjusted in each of the microchip lasers 136-1 and 136-2 so that the oscillation timings of the pulsed laser light output from each of the microchip lasers 136-1 and 136-2 are shifted from each other by a half period.

[0134] The focusing mechanism 182 focuses the pulsed laser light output from the microchip laser 136-1 and the pulsed laser light output from the microchip laser 136-2, and outputs the focused light to the scanning mechanism 138. The focusing mechanism 182 is composed of a galvanometer mirror whose angle is adjusted so as to focus the pulsed laser light output from each of the microchip lasers 136-1 and 136-2 and output the focused light to the scanning mechanism 138.

[0135] The photodetector 140 detects the oscillation of the transmission laser light 152 (pulse laser light) output from the scanning mechanism 138, and outputs a trigger signal Tr to the control device 164 every time the pulse laser light is oscillated. The scanning mechanism 138 and the photodetector 140 have been described with reference to FIG. 8, and therefore description thereof will not be repeated.

[0136] In this modification, by providing a focusing mechanism 182, the scanning mechanism 138 and the photodetector 140 are shared by a plurality of microchip lasers 136-1 and 136-2, so that the overall configuration of the device can be simplified compared to the fourth embodiment.

[0137] 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]

[0138] 1 welding inspection device, 2,4,102,104 base material, 6 welded portion, 10,160 transmitting laser source, 12,134,134-1,134-2,180 transmitting laser light irradiation device, 16,162 receiving laser source, 18,144 receiving laser light probe, 22,164 control device, 24 display device, 100,100A welding system, 106 weld bead, 110 robot arm, 112 welding torch, 118 wire, 120 welding power source, 122 controller, 130 welding inspection head, 132 mounting member, 136,136-1,136-2 microchip laser, 138 scanning mechanism, 140 photodetector, 142,148 optical fiber, 146 driving mechanism, 150 link, 170 Laser line scanner, 174 Surface treatment device, 182 Light collecting mechanism.

Claims

1. A welding inspection device for inspecting a welded portion of a lap fillet weld, comprising: a first laser light irradiation device that irradiates a transmission laser light for exciting an ultrasonic wave inside an inspection object onto a welded portion of the inspection object after welding; a second laser light irradiation device that irradiates a receiving laser light for detecting the ultrasonic wave to a predetermined position on the inspection object at which the ultrasonic wave that has passed through the welded portion and been reflected by a lower surface of the base metal of the inspection object can be detected; a laser interferometer for interferometrically measuring reflected light of the receiving laser light; a determination device for determining the presence or absence of an internal defect of the welded portion based on a measurement result of the laser interferometer, the first laser light irradiation device includes a scanning mechanism configured to scan an irradiation position of the transmission laser light in a direction intersecting a welding direction, The judgment device is a welding inspection device that judges that an internal defect has occurred in the weld when the attenuation of the intensity of the ultrasonic waves detected using the receiving laser light and the laser interferometer exceeds a threshold value.

2. an arc welding apparatus including a welding torch; a welding inspection device according to claim 1, which inspects a welded portion of a lap fillet weld formed by the arc welding device; A welding robot is provided. the welding torch and the first and second laser light irradiation devices of the welding inspection device are mounted on an arm of the welding robot, A welding system, wherein the first and second laser light irradiation devices are disposed behind the welding torch in a welding advance direction.

3. The welding robot includes a controller that controls the arm. The welding system according to claim 2 , wherein the controller controls the arm during welding by the arc welding device so that the first and second laser light irradiation devices are positioned behind the welding torch in a welding advance direction.

4. The welding robot includes a controller that controls the arc welding device and the arm, The welding system according to claim 2 , wherein the controller stops welding by the arc welding device and operation of the arm when the welding inspection device detects an internal defect in the welded portion.

5. The welding robot includes a controller that controls the arc welding device and the arm, the controller is configured to execute at least one of a first process and a second process when an internal defect of the weld is detected by the welding inspection device; the first process includes a process of changing a welding condition of the arc welding apparatus, The welding system according to claim 2 , wherein the second process includes a process of controlling the arm to reduce a welding speed compared to a case in which the internal defect is not detected.

6. an adjustment mechanism configured to adjust at least one of a position and an angle of the second laser light irradiating device on the arm; a deformation measuring device mounted on the arm and configured to measure deformation of the inspection target at the predetermined position due to welding; 6. The welding system according to claim 2, wherein the adjustment mechanism adjusts at least one of the position and the angle based on a measurement result of the deformation measuring device so that a relative positional relationship between the predetermined position and the second laser light emitting device becomes a predetermined relationship.

7. 7. The welding system according to claim 2, further comprising a surface treatment device configured to remove an oxide film formed on a surface of the inspection object by welding by the arc welding device, ahead of the predetermined position in a welding advance direction.

8. the first laser light irradiation device includes a plurality of pulsed laser light irradiation devices each of which irradiates a pulsed laser light for transmission onto the welded portion; The welding system according to claim 2 , wherein the plurality of pulsed laser light irradiation devices irradiate the pulsed laser light such that the laser light irradiation timings are shifted from one another.

9. A welding inspection method for inspecting a welded portion of a lap fillet weld, comprising the steps of: A step of irradiating a transmission laser light for exciting an ultrasonic wave inside an inspection object onto a welded portion of the inspection object after welding; a step of irradiating a receiving laser light for detecting the ultrasonic wave at a predetermined position on the inspection target at which the ultrasonic wave that has passed through the welded portion and been reflected by a lower surface of the base metal of the inspection target can be detected; measuring the reflected light of the receiving laser light by a laser interferometer; and determining whether or not there is an internal defect in the welded portion based on a measurement result of the laser interferometer. the step of irradiating the transmission laser light includes a step of scanning an irradiation position of the transmission laser light in a direction intersecting a welding direction, The welding inspection method, wherein the determining step includes a step of determining that an internal defect has occurred in the weld when an attenuation of the intensity of the ultrasonic wave detected using the receiving laser light and the laser interferometer exceeds a threshold value.

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