JP7477350B2 - Welding observation device and welding system - Google Patents

Description

The present invention relates to a welding observation device and a welding system.

Conventionally, arc welding has been widely used as a welding method. In this type of arc welding, if a welding defect occurs (for example, poor fusion due to unmelted base metal, blowholes due to entrapment of air or gas, etc.), it can cause destruction or a decrease in strength of the welded area, so it is desirable to observe the molten state of the welded area and prevent the occurrence of such welding defects.

Therefore, technologies have been devised to enable observation of the welded area during arc welding. For example, the following Patent Document 1 discloses a welding imaging device that uses an optical filter that transmits a desired wavelength band and a desired amount of light in order to clearly observe the state of the welded area, and receives the light that transmits the optical filter using a CMOS imaging element.

JP 2013-207439 A

In addition, a method for detecting abnormalities in the current and voltage waveforms during welding has been known as a conventional method for early detection of welding defects in arc welding. However, with this conventional technology, even if an abnormality in the current and voltage waveforms is detected, there are many cases where no welding defects have occurred in the arc welding, and it is not possible to detect welding defects in arc welding with a high degree of accuracy. For these reasons, the inventors of the present invention have recognized the need for a technology that can easily and accurately detect the occurrence of welding defects in arc welding.

One embodiment of the welding observation device is a welding observation device for observing a molten area in arc welding, and includes a first imaging means for capturing an image of a molten pool formed in the molten area, and a first detection unit for detecting bubbles generated in the molten pool from the image of the molten pool captured by the first imaging means.

According to one embodiment, the occurrence of welding defects in arc welding can be detected easily and with high accuracy.

FIG. 1 is a diagram showing a configuration of a welding system according to an embodiment; FIG. 1 is a schematic configuration diagram of a nozzle provided in a welding torch according to an embodiment; FIG. 2 is a diagram showing a functional configuration of a processing device according to an embodiment; FIG. 1 is a schematic diagram showing the configuration of each of two test specimens used in an example. FIG. 13 is a diagram showing a welding state of a welded portion (bead) of a first test piece as a result of an embodiment of the present invention; FIG. 13 is a diagram showing the welded state of the welded portion (bead) of a second test piece as a result of an embodiment of the present invention; FIG. 1 illustrates an example of an image of a molten pool captured by a first imaging device in an embodiment. FIG. 1 illustrates an example of an image of a molten pool captured by a first imaging device in an embodiment. FIG. 1 illustrates an example of an image of a molten pool captured by a first imaging device in an embodiment. FIG. 1 illustrates an example of an image of a molten pool captured by a first imaging device in an embodiment. FIG. 13 is a diagram showing the frequency of bubbles occurring in a molten pool as a result of implementing an embodiment. FIG. 1 shows an example of a bead having a weld defect formed in a fusion portion of a test specimen in one embodiment. FIG. 13 is a diagram showing an example of an image of a flow portion behind a molten pool captured by a second imaging device in an embodiment;

One embodiment will be described below with reference to the drawings.

[Configuration of Welding System 1]
1 is a diagram showing a configuration of a welding system 1 according to an embodiment. As shown in FIG. 1, the welding system 1 includes a welding device 10 and a welding observation device 20.

(Configuration of Welding Device 10)
The welding apparatus 10 is an apparatus for joining two base materials 30A, 30B by gas-shielded metal arc welding, and includes a welding torch 11, a welding wire 12, a power supply device 13, a shielding gas supply device 14, and a wire feeder 15.

The shielding gas supply device 14 is a device that supplies a shielding gas to the welding torch 11. The shielding gas is sprayed from the tip of a nozzle 11A provided on the welding torch 11 to the molten site, thereby covering the molten site and preventing the air from entering the molten site. The shielding gas used is argon gas, _CO2 gas, or a mixture of argon gas and _CO2 gas.

The wire feeder 15 is a device that automatically feeds the welding wire 12 to the welding torch 11. The welding wire 12 may be a solid wire, a flux-cored wire, or the like.

The power supply unit 13 is a device that supplies the welding wire 12 with a welding current to generate an arc between the welding wire 12 and the base materials 30A, 30B. One electrode of the power supply unit 13 is connected to one or both of the two base materials 30A, 30B. The other electrode of the power supply unit 13 is connected to a contact tip 11B (see Figure 2) provided on the welding torch 11.

The welding torch 11 has a nozzle 11A, and feeds the welding wire 12 supplied from the wire feeder 15 from the tip of the nozzle 11A to the melting site. The welding torch 11 also sprays the shielding gas supplied from the shielding gas supply device 14 from the tip of the nozzle 11A toward the melting site. The welding torch 11 also generates an arc 32 (see FIG. 2) between the welding wire 12 and the base materials 30A and 30B by supplying a welding current supplied from the power supply device 13 to the welding wire 12 fed from the tip of the nozzle 11A to the melting site. The welding torch 11 can weld the joint 30C in a straight line by moving over the joint 30C of the two base materials 30A and 30B with a moving means (not shown) such as a robot arm. The joint 30C is a portion where the end face of the base material 30A and the end face of the base material 30B are butted against each other. The specific configuration of the nozzle 11A will be described later with reference to FIG. 2.

(Configuration of Nozzle 11A)
Fig. 2 is a schematic diagram of a nozzle 11A included in a welding torch 11 according to an embodiment. As shown in Fig. 2, a contact tip 11B and a gas supply passage 11C are provided inside the cylinder of the nozzle 11A.

The contact tip 11B is a cylindrical metallic member. For example, copper material is used for the contact tip 11B. The welding wire 12 fed from the wire feeder 15 passes through the cylindrical interior of the contact tip 11B and is fed from the tip of the contact tip 11B to the melting site. The contact tip 11B is connected to the other electrode of the power supply unit 13, so that the welding current supplied from the power supply unit 13 can be supplied to the welding wire 12.

The gas supply passage 11C is provided around the contact tip 11B. The shielding gas supplied from the shielding gas supply device 14 passes through the gas supply passage 11C and is sprayed from the tip of the nozzle 11A to the melting site.

In the welding device 10 configured in this manner, the welding torch 11 moves over the joint 30C of the two base materials 30A, 30B along the joint 30C in the direction in which the joint 30C extends (the direction of the arrow A in the figure, the positive direction of the X-axis). At this time, a welding current is supplied from the power supply device 13 to the welding wire 12 via the contact tip 11B, generating an arc 32 between the welding wire 12 and the base materials 30A, 30B. Then, the high heat generated by the arc 32 melts the welding wire 12 and the base materials 30A, 30B, and the molten metal consisting of the molten welding wire 12 and the base materials 30A, 30B forms a molten pool 34 centered directly below the welding wire 12. Then, the molten metal is cooled and solidified along the joint 30C to form a bead 36. As a result, the two base materials 30A, 30B are welded.

(Configuration of welding observation device 20)
As shown in FIG. 1, the welding observation apparatus 20 includes a first imaging device 21 , a first communication cable 23 , a second imaging device 25 , a second communication cable 26 , and a processing device 27 .

The first imaging device 21 is an example of a "first imaging means." As shown in FIG. 1, the first imaging device 21 captures an image (video) of the molten pool 34 formed at the molten site from the front in the movement direction of the welding torch 11 (positive direction of the X-axis in the figure). Note that the "image of the molten pool 34" is an image that includes the entire molten pool 34 that is formed in a roughly circular shape centered directly below the welding wire 12. As shown in FIG. 1, the first imaging device 21 has a first optical filter 21A and a first imaging section 21B.

The first optical filter 21A is provided so as to cover the lens surface of the first imaging unit 21B. The first optical filter 21A transmits light of a specific wavelength band that is optimal for capturing an image of the molten pool 34. In this embodiment, a bandpass filter with a central transmission wavelength of 980 nm is used as an example of a suitable first optical filter 21A found by the inventors. This central transmission wavelength is a suitable one found by the inventors of the present invention. As a result, the first imaging device 21 can capture an image in which the state of the molten pool 34 can be easily determined simply by capturing an image of the molten pool 34 (i.e., without irradiating external light, providing multiple imaging devices, or performing special image processing). However, the first optical filter 21A is not limited to this, and may have other central transmission wavelengths as long as it can capture an image in which the state of the molten pool 34 can be easily determined.

The first imaging unit 21B captures an image of the molten pool 34 by receiving light of a specific wavelength band that has passed through the first optical filter 21A. For example, the first imaging unit 21B is configured with a lens, a sensor (e.g., a CCD sensor, a CMOS sensor, etc.), an image processor, etc. In this embodiment, a high-speed camera capable of capturing video at a high frame rate is used as the first imaging unit 21B.

The second imaging device 25 is an example of a "second imaging means." As shown in FIG. 1, the second imaging device 25 captures an image (video) of the rear flowing portion 34B of the molten pool 34 formed at the molten site from the rear in the movement direction of the welding torch 11 (negative direction of the X-axis in the figure). Note that the "image of the rear flowing portion 34B of the molten pool 34" is an image that includes the portion of the molten pool 34 that is formed in a roughly circular shape centered directly below the welding wire 12 and flows out rearward (i.e., the unsolidified bead 36) as the welding torch 11 moves forward. As shown in FIG. 1, the second imaging device 25 has a second optical filter 25A and a second imaging unit 25B.

The second optical filter 25A is provided so as to cover the lens surface of the second imaging unit 25B. The second optical filter 25A transmits light of a specific wavelength band that is optimal for capturing an image of the flow portion 34B behind the molten pool 34. In this embodiment, a bandpass filter with a central transmission wavelength of 980 nm is used as an example of a suitable second optical filter 25A found by the inventors. As a result, the second imaging device 25 can capture an image in which the state of the flow portion 34B behind the molten pool 34 can be easily determined simply by capturing an image of the flow portion 34B behind the molten pool 34 (i.e., without irradiating external light, providing multiple imaging devices, or performing special image processing). However, the second optical filter 25A is not limited to this, and may have other central transmission wavelengths as long as it can capture an image in which the state of the flow portion 34B behind the molten pool 34 can be easily determined.

The second imaging unit 25B captures an image of the molten pool 34 by receiving light of a specific wavelength band that has passed through the second optical filter 25A. For example, the second imaging unit 25B is configured with a lens, a sensor (e.g., a CCD sensor, a CMOS sensor, etc.), an image processor, etc. In this embodiment, a high-speed camera capable of capturing video at a high frame rate is used as the second imaging unit 25B.

In this embodiment, the preferred imaging angle θ1 of the first imaging device 21 from above the molten part is set to be within the range of 40° to 50°. In addition, in this embodiment, the preferred imaging angle θ2 of the second imaging unit 25B from above the molten part is set to be within the range of 30° to 40°. The imaging angles θ1 and θ2 are depression angles from above with respect to the plane when it is assumed that the welding torch 11 moves on the plane. These imaging angles θ1 and θ2 are also preferred angles found by the inventors of the present invention. For example, if the imaging angle θ1 exceeds 50°, there is a risk that the portion directly below the welding wire 12 will be blocked by the welding torch 11. Also, for example, if the imaging angle θ1 is less than 40°, there is a risk that the portion directly below the welding wire 12 will be blocked by the base material 30A, 30B, etc., and the portion directly below the welding wire 12 will not be able to be observed.

The first imaging device 21 and the second imaging device 25 may be configured to move together with the welding torch 11. In this case, the first imaging device 21 and the second imaging device 25 can maintain the imaging angles θ1 and θ2 relative to the molten area within a predetermined angle range without changing the imaging direction even when the welding torch 11 moves.

Alternatively, the first imaging device 21 and the second imaging device 25 may be configured not to move together with the welding torch 11. In this case, the first imaging device 21 may maintain a fixed imaging direction even when the welding torch 11 moves, provided that the imaging angles θ1 and θ2 relative to the molten site can be maintained within a predetermined angle range.

On the other hand, when the welding torch 11 moves and the imaging angles θ1, θ2 relative to the molten area cannot be maintained within the predetermined angle range, the first imaging device 21 is preferably configured so that the imaging direction is automatically changed by an arbitrary imaging direction changing means, thereby making it possible to maintain the imaging angles θ1, θ2 relative to the molten area within the predetermined angle range. In this case, the imaging direction changing means may calculate the imaging angles θ1, θ2 using a predetermined calculation formula, a predetermined conversion table, or the like, based on the positions of the first imaging device 21 and the second imaging device 25 and the position of the welding torch 11, for example.

The first communication cable 23 connects the first imaging unit 21B to the processing device 27. The image of the molten pool 34 captured by the first imaging unit 21B is transmitted to the processing device 27 via the first communication cable 23.

The second communication cable 26 connects the second imaging unit 25B to the processing device 27. The image of the flowing portion 34B behind the molten pool 34 captured by the second imaging unit 25B is transmitted to the processing device 27 via the second communication cable 26.

At least one of the first imaging unit 21B and the second imaging unit 25B may transmit images to the processing device 27 via wireless communication.

The processing device 27 can determine that a welding defect has occurred in the arc welding based on the image of the molten pool 34 captured by the first imaging unit 21B and the image of the flowing portion 34B captured by the second imaging unit 25B. As the processing device 27, for example, a PC (Personal Computer), a server device, etc. can be used.

(Functional configuration of the processing device 27)
Fig. 3 is a diagram showing a functional configuration of the processing device 27 according to an embodiment. As shown in Fig. 3, the processing device 27 includes a first image acquisition unit 301, a first detection unit 302, a first determination unit 303, a second image acquisition unit 304, a second detection unit 305, and a second determination unit 306.

The first image acquisition unit 301 acquires an image of the molten pool 34 captured by the first imaging device 21 from the front of the molten area. The image of the molten pool 34 captured by the first imaging device 21 is a video including multiple consecutive frames. Therefore, the first image acquisition unit 301 continuously acquires multiple frame images that make up the image of the molten pool 34.

The first detection unit 302 detects bubbles that have occurred in the molten pool 34 from the image of the molten pool 34 acquired by the first image acquisition unit 301. Specifically, the first detection unit 302 detects areas of a predetermined shape, a predetermined size, a predetermined color, a predetermined brightness, etc. as bubbles using a known image recognition process on the image of the molten pool 34. For example, in the image of the molten pool 34, the molten pool 34 is shown as an overall whitish high-brightness area, while the bubbles 34A are shown as shadows (black, low-brightness areas) that have occurred partially within the molten pool 34.

The first judgment unit 303 judges whether or not a welding defect has occurred in the arc welding based on the result of the bubble detection by the first detection unit 302. For example, the first judgment unit 303 judges that a welding defect has occurred in the arc welding when the frequency of the bubbles detected by the first detection unit 302 is equal to or greater than a predetermined threshold value. As described below, the inventor of the present invention has found that the more bubbles 34A are generated per unit time in the molten pool 34, the higher the possibility of a blowhole 36A occurring in the welded portion. Therefore, the first judgment unit 303 can easily and accurately detect the occurrence of a welding defect in the arc welding by determining that a welding defect has occurred in the arc welding when the frequency of the bubbles 34A is equal to or greater than a predetermined threshold value.

The first judgment unit 303 can judge whether or not a welding defect has occurred in the arc welding by using a threshold value according to the frame rate of the first imaging device 21. Bubbles 34A appear and disappear instantly in the molten pool 34. Therefore, the number of times bubbles 34A appear in the image of the molten pool 34 varies depending on the frame rate of the first imaging device 21. Specifically, the higher the frame rate of the first imaging device 21, the more times bubbles 34A appear in the image of the molten pool 34. Therefore, the higher the frame rate of the first imaging device 21, the higher the threshold value that the first judgment unit 303 can use to judge whether or not a welding defect has occurred in the arc welding.

The second image acquisition unit 304 acquires an image of the flowing portion 34B at the rear of the molten pool 34 captured by the second imaging device 25 from behind the molten area. The image of the flowing portion 34B captured by the second imaging device 25 is a video including multiple consecutive frames. Therefore, the second image acquisition unit 304 continuously acquires multiple frame images that make up the image of the flowing portion 34B.

The second detection unit 305 detects a cavity 34C that has occurred in the flow portion 34B behind the molten pool 34 from the image of the molten pool 34 acquired by the second image acquisition unit 304. Specifically, the second detection unit 305 detects an area having a predetermined shape, a predetermined size, a predetermined color, a predetermined brightness, etc. as the cavity 34C using a known image recognition process for the image of the flow portion 34B. For example, in the image of the flow portion 34B, the flow portion 34B is shown as an overall whitish high-brightness area, while the cavity 34C is shown as a shadow (a black, low-brightness area) that has occurred partially within the molten pool 34.

The second judgment unit 306 judges whether or not a welding defect has occurred in the arc welding based on the bubble detection result by the second detection unit 305.

For example, when the second detection unit 305 detects a cavity 34C that continues to remain in the flow portion 34B for a certain period of time or more, the second judgment unit 306 judges that a pinhole has occurred as a welding defect in the molten portion of the arc welding. This is because the inventor of the present invention found through testing that when a cavity 34C that has occurred in the flow portion 34B continues to remain for a certain period of time or more, the cavity 34C remains as a pinhole in the bead 36 after solidification. Therefore, the second judgment unit 306 judges that a pinhole has occurred when a cavity 34C continues to remain in the flow portion 34B for a certain period of time or more, and thereby it is possible to easily and accurately detect the occurrence of a welding defect (pinhole) in arc welding at a relatively early stage during welding.

For example, when the second detection unit 305 detects a cavity 34C that disappears immediately after it is generated in the flow portion 34B, the second judgment unit 306 judges that a blowhole 36A has occurred as a welding defect in the molten portion of the arc welding. This is because the inventor of the present invention found through testing that when a cavity 34C generated in the flow portion 34B disappears immediately, the cavity 34C is blocked by the flowing molten pool 34 and remains in the bead 36 after solidification as a blowhole 36A. For this reason, when a cavity 34C disappears immediately after it is generated in the flow portion 34B, the second judgment unit 306 judges that a blowhole 36A has occurred, and thus the occurrence of a welding defect (blowhole 36A) in arc welding can be easily and accurately detected at a relatively early stage during welding.

[One Example]
An example of the welding system 1 according to an embodiment will be described below. In this example, the welding system 1 described in the embodiment was used to perform seal welding on the joint between the lower metal plate 41 and the upper metal plate 42 of two test pieces T1 and T2 shown in Fig. 4 using the welding device 10. Then, for each of the two test pieces T1 and T2, the state of the welded portion (i.e., the bead 36) after welding and an image of the molten pool 34 captured by the first imaging device 21 during welding were confirmed.

(Configuration of test specimens T1 and T2)
4A and 4B are diagrams showing the configurations of two test specimens T1 and T2 used in an example. As shown in Fig. 4A and Fig. 4B, each of the test specimens T1 and T2 has a flat lower metal plate 41 (total length = 200 mm) in a horizontal state and an upper metal plate 42 (total length = 200 mm) standing vertically with respect to the surface of the lower metal plate 41.

However, in specimen T1, no scale is attached to the joint in the section from the welding start position to 50 mm, but scale is attached to the joint in the section from 50 mm to 150 mm. As a result, in specimen T1, blowholes 36A caused by scale are more likely to occur in the section from 50 mm to 150 mm.

Furthermore, specimen T2 has scale attached to the section from the welding start position to 50 mm, and a Zn-rich primer (Zinc Coat, manufactured by Ichino Chemicals) is applied to the section from 50 mm to 150 mm. As a result, specimen T2 is prone to blowholes 36A caused by scale in the section from the welding start position to 50 mm, and prone to blowholes 36A caused by the Zn-rich primer in the section from 50 mm to 150 mm.

(Implementation procedure)
In one embodiment, for each of the two test pieces T1 and T2 shown in FIG. 4, seal welding was performed by the welding device 10 on the section from the welding start position to 150 mm in the joint between the lower metal plate 41 and the upper metal plate 42. At that time, the first imaging device 21 captured an image of the molten pool 34 (high frame rate video), and the second imaging device 25 captured an image of the flowing portion 34B (high frame rate video). After the welding was completed, the inventor checked the state of the welded portion after welding, the image of the molten pool 34 captured during welding, and the image of the flowing portion 34B captured during welding. In one embodiment, in order to check reproducibility, the same test piece was used for each of the two test pieces T1 and T2, and the test was performed three times.

(Welding conditions)
The welding conditions used in one example (common to the two test pieces T1 and T2) are as follows:

Power supply mode: DC non-pulse mode Welding wire: YM-28S (φ1.2mm)
Extension length: 20 mm
Shielding gas: Ar + 20% _CO2 (20L/min)
Welding current: 300A
Welding voltage: 30V
Welding speed: 30 cm/min

(Imaging conditions of the first imaging device 21)
The imaging conditions of the first imaging device 21 used in one example (imaging conditions common to the two test specimens T1 and T2) are as follows.

Camera: Q1V (manufactured by NAC Image Technology)
Frame rate: 1000fps
External light source: None Filter: Bandpass filter (transmission wavelength: 980 nm)
Observation direction: forward Imaging angle θ1: 45°

(Imaging conditions of the second imaging device 25)
The imaging conditions of the second imaging device 25 used in one embodiment (imaging conditions common to the two test specimens T1 and T2) are as follows.

Camera: HX-7 (manufactured by NAC Image Technology)
Frame rate: 1000fps
External light source: None Filter: Bandpass filter (transmission wavelength: 980 nm)
Observation direction: rear Imaging angle θ2: 35°

(Implementation results)
Fig. 5 is a diagram showing the welded state of the welded portion (bead 36) of the first specimen T1 as an implementation result of the embodiment. Fig. 6 is a diagram showing the welded state of the welded portion (bead 36) of the second specimen T2 as an implementation result of the embodiment.

Figures 5 and 6 show images of the welded portion (bead 36) of test pieces T1 and T2 after welding, taken using radiation by RT (Radiographic Testing) inspection. In Figures 5 and 6, the area surrounded by a circle is the area where the occurrence of a blowhole 36A was confirmed by RT inspection.

As shown in Figure 5, in the welded portion (bead 36) of the first test piece T1, in the section from the welding start position to 50 mm, no scale was attached to the joint, and it was confirmed that a few blowholes 36A of about 1 mm were generated immediately after the start of welding. On the other hand, in the section from 50 mm to 150 mm, scale was attached to the joint, and it was confirmed that multiple blowholes 36A were generated continuously along the welding direction.

As shown in Figure 6, in the welded portion (bead 36) of the second test piece T2, in the section from the welding start position to 50 mm, scale was attached to the joint, and it was confirmed that multiple blowholes 36A of about 1 mm were generated consecutively along the welding direction immediately after welding started. On the other hand, in the section from 50 mm to 150 mm, Zn-rich primer was applied to the joint, and it was confirmed that multiple blowholes 36A were generated consecutively along the welding direction.

(An example of an image of the molten pool 34)
7 to 10 are diagrams showing examples of images of the molten pool 34 captured by the first imaging device 21 in one embodiment. That is, the images shown in Fig. 7 to 10 are images of the molten pool 34 captured from the front and above the welded portion at an imaging angle θ1 of 45°. In particular, Fig. 7 to 10 are images of the molten pool 34 corresponding to the area where the blowhole 36A was confirmed in the test specimens T1 and T2 (see Fig. 5 and Fig. 6).

As shown in Figures 7 to 10, a generally circular molten pool 34 is formed at the welded portion (the joint between the lower metal plate 41 and the upper metal plate 42) of the test pieces T1 and T2 by the arc 32 emitted from the tip of the welding wire 12, centered directly below the welding wire 12. Since the welding torch 11 advances forward (positive direction of the X-axis), as shown in Figures 7 to 10, the molten pool 34 has a shape that flows out backward (negative direction of the X-axis). The part of the molten pool 34 that flows out backward forms an unsolidified bead 36, and then changes state to a solidified bead 36 by cooling. In one embodiment, the transmission wavelength of the bandpass filter is 980 nm, which is suitable for capturing an image of the molten pool 34. Therefore, as shown in Figures 7 to 10, the shape and state of the molten pool 34 are clearly reflected in the image captured by the first imaging device 21.

The image shown in FIG. 7 visually depicts bubbles 34A that have been generated on the surface of the molten pool 34 that has been pushed down by the arc 32. The inventors confirmed that, in one embodiment, images depicting bubbles 34A as shown in FIG. 7 are frequently captured by the first imaging device 21 during welding of a section to which a Zn-rich primer has been applied.

The image shown in FIG. 8 visually depicts bubbles 34A that have formed on the side of the molten pool 34 that has been pushed down by the arc 32. The image shown in FIG. 9 visually depicts bubbles 34A that have formed on the wall of the molten pool 34 that has been pushed down by the arc 32. The inventors confirmed that, in one embodiment, images depicting bubbles 34A as shown in FIG. 8 and FIG. 9 are frequently captured by the first imaging device 21 during welding of a section with scale attached.

The image shown in FIG. 10 shows a visible bubble 34A behind the molten pool 34 pushed down by the arc 32. The inventors confirmed that in one embodiment, images showing bubbles 34A as shown in FIG. 10 were frequently captured by the first imaging device 21 during welding of a section with scale attached.

Figure 11 shows the frequency of bubbles 34A in the molten pool 34 as a result of one embodiment. Figure 11 shows the relationship between the number of bubbles 34A that occur in the molten pool 34 per unit time (1000 ms) and the location of blowholes 36A in the molten area when welding was performed on the second test piece T2, which has a section coated with a Zn-rich primer.

As shown in FIG. 11, from the start of welding until 10,000 ms, the number of bubbles 34A generated per unit time in the molten pool 34 is relatively low. Then, after 10,000 ms, the number of bubbles 34A generated per unit time in the molten pool 34 increases rapidly. Furthermore, after 10,000 ms, the number of bubbles 34A generated per unit time in the molten pool 34 increases, causing a large number of blowholes 36A with a diameter of 5 mm or more to appear.

Based on this, the inventor confirmed that, in one embodiment, gas emitted by impurities in the welded area generates bubbles 34A in the molten pool 34, and the more bubbles 34A are generated per unit time in the molten pool 34, the higher the possibility of blowholes 36A occurring in the welded area.

Therefore, the welding observation device 20 according to one embodiment detects bubbles 34A from an image of the molten pool 34, and if the frequency of occurrence of bubbles 34A is equal to or greater than a predetermined threshold, it determines that a welding defect has occurred in the welded area, thereby making it possible to easily and accurately detect the occurrence of a welding defect in arc welding.

(An example of a bead 36 having a welding defect)
Fig. 12 is a diagram showing an example of a bead 36 having a welding defect formed in a fusion portion of a test piece T2 in one embodiment. Fig. 12(a) shows the appearance of the bead 36. Fig. 12(b) shows an image of the bead 36 captured using radiation by RT inspection. The bead 36 shown in Fig. 12 has a blowhole 36A and a pinhole 36B as welding defects of arc welding.

As shown in FIG. 12(a), pinhole 36B formed in bead 36 is visible from the outside of bead 36, so it is easy to find after welding. On the other hand, as shown in FIG. 12(a) and FIG. 12(b), blowhole 36A formed in bead 36 is not visible from the outside of bead 36, so it is not easy to find after welding.

In addition, in the conventional technology, it was not possible to detect the occurrence of blowholes 36A and pinholes 36B during arc welding. For this reason, in the conventional technology, it was necessary to respond to the occurrence of blowholes 36A and pinholes 36B after welding.

(An example of an image of the flow portion 34B)
Fig. 13 is a diagram showing an example of an image of the flow portion 34B at the rear of the molten pool 34 captured by the second imaging device 25 in one embodiment. In the image shown in Fig. 13, a cavity 34C is generated in the flow portion 34B.

The inventors of the present invention have found through testing that if a cavity 34C that occurs in the flow portion 34B continues to remain for a certain period of time or more, the cavity 34C remains in the bead 36 after solidification as a pinhole. Therefore, as shown in FIG. 13, the welding observation device 20 of this embodiment observes the flow portion 34B using the second imaging device 25, and determines that a pinhole has occurred if a cavity 34C (see FIG. 13) continues to remain in the flow portion 34B for a certain period of time or more. As a result, the welding observation device 20 of this embodiment can easily and accurately detect the occurrence of welding defects (pinholes) in arc welding at a relatively early stage during welding.

The inventors of the present invention also found through testing that if a cavity 34C that occurs in the flowing portion 34B disappears immediately, the cavity 34C is blocked by the flowing molten pool 34 and remains in the solidified bead 36 as a blowhole 36A. As shown in FIG. 13, the welding observation device 20 of this embodiment observes the flowing portion 34B with the second imaging device 25, and determines that a blowhole 36A has occurred if a cavity 34C (see FIG. 13) disappears immediately after its occurrence in the flowing portion 34B. This makes it possible to easily and accurately detect the occurrence of a welding defect (blowhole 36A) in arc welding at a relatively early stage during welding.

As described above, the welding observation device 20 according to one embodiment is a welding observation device 20 for observing a molten area in arc welding, and includes a first imaging device 21 for capturing an image of the molten pool 34 formed in the molten area, and a first detection unit 302 for detecting bubbles 34A generated in the molten pool 34 from the image of the molten pool 34 captured by the first imaging device 21.

As a result, the welding observation device 20 according to one embodiment can detect bubbles 34A, which are a direct cause of poor welding in arc welding, during welding from the image captured by the first imaging device 21. Therefore, the welding observation device 20 according to one embodiment can easily and accurately detect the occurrence of poor welding in arc welding.

In addition, the welding observation device 20 according to one embodiment further includes a first judgment unit 303 that judges whether or not a welding defect has occurred in the molten area based on the detection result of the bubble 34A by the first detection unit 302.

Therefore, the welding observation device 20 according to one embodiment can determine the occurrence of a welding defect in arc welding during welding. Therefore, according to the welding observation device 20 according to one embodiment, it is possible to take measures against the occurrence of a welding defect in arc welding (e.g., stopping welding, notifying the occurrence of a welding defect, etc.) relatively early.

In addition, in the welding observation device 20 according to one embodiment, the first judgment unit 303 judges that a welding defect has occurred when the occurrence frequency of the bubbles 34A detected by the first detection unit 302 is equal to or greater than a predetermined threshold value.

As a result, the welding observation device 20 according to one embodiment can capture the direct events that lead to the occurrence of the blowhole 36A with high accuracy from the image of the molten pool 34. Therefore, the welding observation device 20 according to one embodiment can easily and accurately detect the blowhole 36A in arc welding.

In addition, in the welding observation device 20 according to one embodiment, the first judgment unit 303 judges whether or not a welding defect has occurred using a threshold value according to the frame rate of the first imaging device 21.

As a result, the welding observation device 20 according to one embodiment can use a variety of first imaging devices 21, and can determine with high accuracy whether or not a welding defect has occurred in arc welding by using a suitable threshold value according to the frame rate of the first imaging device 21.

In addition, in one embodiment of the welding observation device 20, the first imaging device 21 has a first optical filter 21A that transmits light in a specific wavelength band, and a first imaging unit 21B that captures an image of the molten pool 34 by receiving the light in the specific wavelength band that has transmitted through the first optical filter 21A.

As a result, the welding observation device 20 according to one embodiment can capture images that allow easy identification of the state of the molten pool 34 with a relatively simple configuration that simply requires providing the first optical filter 21A to the first imaging section 21B.

In addition, in one embodiment of the welding observation device 20, the first optical filter 21A is a bandpass filter with a transmission wavelength of 980 nm.

As a result, the welding observation device 20 according to one embodiment can capture images that make it even easier to determine the state of the molten pool 34.

In addition, in one embodiment of the welding observation device 20, the first imaging device 21 is disposed forward in the direction of movement of the welding torch 11 and has an imaging angle θ1 from above the molten area.

As a result, the welding observation device 20 according to one embodiment can capture images from an imaging direction that allows the state of the molten pool 34 to be clearly determined.

In addition, in one embodiment of the welding observation device 20, the imaging angle θ1 is in the range of 40° to 50°.

As a result, the welding observation device 20 according to one embodiment can capture images from an imaging direction that allows the state of the molten pool 34 to be clearly determined.

The welding observation device 20 according to one embodiment further includes a second imaging device 25 that captures an image of the flowing portion 34B behind the molten pool 34, and a second detection unit 305 that detects a cavity 34C that has occurred in the flowing portion 34B from the image of the flowing portion 34B captured by the second imaging device 25.

As a result, the welding observation device 20 according to one embodiment can detect the cavity 34C, which is a direct cause of poor welding in arc welding, during welding from the image captured by the second imaging device 25. Therefore, the welding observation device 20 according to one embodiment can easily and accurately detect the occurrence of poor welding in arc welding.

In addition, the welding observation device 20 according to one embodiment further includes a second judgment unit 306 that judges whether or not a welding defect has occurred in the molten area based on the detection result of the cavity 34C by the second detection unit 305.

Therefore, the welding observation device 20 according to one embodiment can determine the occurrence of a welding defect in arc welding during welding. Therefore, according to the welding observation device 20 according to one embodiment, it is possible to take measures against the occurrence of a welding defect in arc welding (e.g., stopping welding, etc.) relatively early.

In addition, in the welding observation device 20 according to one embodiment, when the second detection unit 305 detects a cavity 34C that continues to remain in the flow portion 34B for a certain period of time or more, the second judgment unit 306 judges that a pinhole has occurred as a welding defect in the molten portion.

Therefore, the welding observation apparatus 20 according to one embodiment can determine the occurrence of a pinhole during welding. Therefore, the welding observation apparatus 20 according to one embodiment can take measures against the occurrence of a pinhole (e.g., stopping welding, notifying the occurrence of a welding defect, etc.) relatively early.

In addition, in the welding observation device 20 according to one embodiment, when the second detection unit 305 detects a cavity 34C that disappears immediately after its occurrence in the flow portion 34B, the second judgment unit 306 judges that a blowhole has occurred as a welding defect in the molten portion.

Therefore, the welding observation device 20 according to one embodiment can determine the occurrence of a blowhole during welding. Therefore, the welding observation device 20 according to one embodiment can take measures against the occurrence of a blowhole (e.g., stopping welding, notifying the occurrence of a welding defect, etc.) relatively early.

In addition, in the welding observation device 20 according to one embodiment, the second imaging device 25 has a second optical filter 25A that transmits light in a specific wavelength band, and a second imaging section 25B that captures an image of the flowing portion 34B by receiving the light in the specific wavelength band that has transmitted through the second optical filter 25A.

As a result, the welding observation device 20 according to one embodiment can capture images that allow easy determination of the state of the flowing portion 34B with a relatively simple configuration that simply requires providing the second optical filter 25A to the second imaging section 25B.

In addition, in one embodiment of the welding observation device 20, the second optical filter 25A is a bandpass filter with a transmission wavelength of 980 nm.

As a result, the welding observation device 20 according to one embodiment can capture images that make it even easier to determine the state of the flow portion 34B.

In addition, in one embodiment of the welding observation device 20, the second imaging device 25 is disposed behind the welding torch 11 in the direction of movement and has an imaging angle θ2 from above the molten area.

As a result, the welding observation device 20 according to one embodiment can capture images from an imaging direction that allows the state of the flow portion 34B to be clearly determined.

In addition, in one embodiment of the welding observation device 20, the imaging angle θ2 is in the range of 30° to 40°.

As a result, the welding observation device 20 according to one embodiment can capture images from an imaging direction that allows the state of the flow portion 34B to be clearly determined.

The welding system 1 according to one embodiment includes a welding device 10 that arc welds the base material, and a welding observation device 20 that observes the molten area during arc welding.

As a result, the welding system 1 according to one embodiment can detect bubbles 34A, which are a direct cause of poor welding in arc welding, from the image captured by the first imaging device 21 in the welding observation device 20 during welding by the welding device 10. Therefore, the welding system 1 according to one embodiment can easily and accurately detect the occurrence of poor welding in arc welding.

Although one embodiment of the present invention has been described in detail above, the present invention is not limited to these embodiments, and various modifications and changes are possible within the scope of the gist of the present invention described in the claims.

For example, the first optical filter 21A and the second optical filter 25A are not limited to bandpass filters with a transmission wavelength of 980 nm. In other words, the first optical filter 21A and the second optical filter 25A may be any optical filter that can capture an image that allows the state of the molten pool 34 and the state of the flow portion 34B to be easily distinguished.

For example, in the above embodiment, the first optical filter 21A is provided separately from the first imaging unit 21B, but this is not limited thereto, and the first optical filter 21A may be provided integrally with the first imaging unit 21B. Also, instead of providing the first optical filter 21A, the first imaging unit 21B may have a configuration that can selectively receive light in a specific wavelength band (for example, an imaging element that can selectively receive light in a specific wavelength band).

For example, in the above embodiment, the second optical filter 25A is provided separately from the second imaging unit 25B, but this is not limited thereto, and the second optical filter 25A may be provided integrally with the second imaging unit 25B. Also, instead of providing the second optical filter 25A, the second imaging unit 25B may have a configuration that can selectively receive light in a specific wavelength band (for example, an imaging element that can selectively receive light in a specific wavelength band).

For example, in the above embodiment, the welding observation device 20 is equipped with both the first imaging device 21 and the second imaging device 25, but this is not limited to this. In other words, the welding observation device 20 may be equipped with either the first imaging device 21 or the second imaging device 25.

REFERENCE SIGNS LIST 1 Welding system 10 Welding device 11 Welding torch 11A Nozzle 11B Contact tip 11C Gas supply path 12 Welding wire 13 Power supply device 14 Shielding gas supply device 15 Wire feeder 20 Welding observation device 21 First imaging device 21A First optical filter 21B First imaging section 25 Second imaging device 25A Second optical filter 25B Second imaging section 27 Processing device 32 Arc 34 Molten pool 34
34A: Bubble 34B: Flowing portion 34C: Cavity 36: Bead 36A: Blow hole 36B: Pinhole 41: Lower metal plate 42: Upper metal plate 301: First image acquisition portion 302: First detection portion 303: First judgment portion 304: Second image acquisition portion 305: Second detection portion 306: Second judgment portion T1, T2: Test piece

Claims (14)

A welding observation device for observing a molten portion in arc welding, comprising:
a first imaging means for capturing an image of a molten pool formed in the molten portion;
a first detection unit that detects bubbles generated in the molten pool from an image of the molten pool captured by the first imaging means ;
a first determination unit that determines whether or not a welding defect has occurred based on the frequency of occurrence of the bubbles detected by the first detection unit;
A welding observation device comprising: The first determination unit is
The welding observation device according to claim 1 , wherein, when the frequency of occurrence of the bubbles detected by the first detection unit is equal to or greater than a predetermined threshold value, it is determined that the welding defect has occurred. The first determination unit is
The welding observation device according to claim 2 , wherein the presence or absence of the occurrence of the welding defect is determined using the predetermined threshold value corresponding to a frame rate of the first imaging means. The first imaging means includes:
a first optical filter that transmits light in a specific wavelength band;
and a first imaging unit that captures an image of the molten pool by receiving light of the specific wavelength band that has passed through the first optical filter. The first imaging means includes:
The welding observation device according to any one of claims 1 to 4 , characterized in that it is disposed forward in a moving direction of a welding torch, and has an imaging angle θ1 from above the molten site. The welding observation apparatus according to claim 5 , wherein the imaging angle θ1 is within a range of 40° to 50°. A second imaging means for capturing an image of a flow portion behind the molten pool;
and a second detection unit that detects cavities generated in the flow portion from an image of the flow portion captured by the second imaging means. The welding observation device according to claim 7 , further comprising a second determination unit that determines whether or not a welding defect has occurred in the molten portion, based on a detection result of the cavity by the second detection unit. The second determination unit is
The welding observation device according to claim 8, characterized in that, when the second detection unit detects the cavity remaining in the flow portion continuously for a certain period of time or more, it is determined that a pinhole has occurred as a welding defect in the molten portion . The second determination unit is
10. The welding observation device according to claim 8 , wherein when the second detection unit detects the cavity that disappeared immediately after its occurrence in the flow portion, it is determined that a blowhole has occurred as a welding defect in the molten portion. The second imaging means includes:
a second optical filter that transmits light of a specific wavelength band;
and a second imaging unit that captures an image of the flowing portion by receiving light of the specific wavelength band that has transmitted through the second optical filter. The second imaging means includes:
The welding observation device according to any one of claims 7 to 11 , characterized in that it is disposed rearward in a moving direction of a welding torch, and has an imaging angle θ2 from above the molten site. The welding observation apparatus according to claim 12 , wherein the imaging angle θ2 is within a range of 30° to 40°. A welding device for arc welding a base material;
A welding system comprising: the welding observation device according to claim 1 , which observes a molten site in the arc welding.

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