JP2022062933A - Method for detecting crack in weld zone, and device for detecting crack in weld zone - Google Patents

Abstract

To properly detect a crack occurring between a molten layer and a base metal layer.SOLUTION: A crack detection method is provided, for detecting a crack of a weld zone (30) of an object (10). The crack detection method includes: a step of detecting potential difference between: a measuring terminal (3a) arranged between the weld zone (30) on a first surface (10a) of the object (10) and an electrode terminal (2a); and a measuring terminal (3b) arranged between the weld zone (30) on the second surface (10b) of the object (10) and an electrode terminal (2b) while current is applied between a pair of the electrode terminals 2a, 2b which straddle the weld zone (30) and are arranged on a first surface (10a) and a second surface (10b) of the object (10), respectively; and detecting the crack of the weld zone (30) from a measurement result of the potential difference.SELECTED DRAWING: Figure 1

Description

The present disclosure relates to a technique for detecting a crack in a welded portion of a welded member.

Japanese Patent Application Laid-Open No. 62-231150 (Patent Document 1) discloses an inspection method for spot welding using a DC potential difference method. In this inspection method, current electrodes are placed across the weld on both sides of the spot-welded member to apply a direct current, and measurement terminals are placed at approximately the centers of both sides of the weld (molten layer). The potential difference between the measurement terminals is measured, and the quality of spot welding is judged from the measurement result.

Japanese Patent Application Laid-Open No. 62-231150

In the welded member, cracks may occur between the molten layer and the base metal layer around the molten layer. Since such interlayer cracks affect the quality of welding, it is desirable to detect them appropriately.

In the inspection method disclosed in Japanese Patent Application Laid-Open No. 62-231150, measurement terminals are arranged substantially at the centers of both sides of the welded portion (melted layer), and the result of measuring the potential difference between the measurement terminals indicates the quality of spot welding. Is determined. However, in this determination, the cracks generated between the molten layer and the base metal layer enter parallel to the straight line connecting the measurement terminals. In this case, it is difficult for the influence of the interlayer cracks to be reflected in the potential difference between the measurement terminals, and there is a concern that the interlayer cracks cannot be detected appropriately.

The present disclosure has been made to solve the above-mentioned problems, and an object thereof is to appropriately detect cracks generated between a molten layer and a base metal layer.

The method for detecting a crack in a welded portion according to the present disclosure is a plate-shaped object including a first surface, a second surface facing the first surface, and a welded portion extending between the first surface and the second surface. This is a method for detecting cracks in the welded part of an object. In this crack detection method, a current is applied between the first position offset from the welded portion on the first surface and the second position on the second surface facing the first position across the welded portion. In the state, the first measurement part placed in the area between the welded part and the first position on the first surface and the second measurement part placed in the area between the welded part and the second position on the second surface. It includes a step of measuring the potential difference or the electric resistance between the portions and a step of detecting a crack in the welded portion from the measurement result of the potential difference or the electric resistance.

The weld crack detection device according to the present disclosure is a plate-shaped object including a first surface, a second surface facing the first surface, and a weld extending between the first surface and the second surface. It is a device that detects cracks in the welded part of an object. This crack detection device is for applying a current between the first position offset from the welded portion on the first surface and the second position on the second surface facing the first position across the welded portion. From the power supply, the pinching mechanism having the first member and the second member for pinching the object in contact with the first surface and the second surface, respectively, and the virtual center line of the pinching mechanism in the first member. The first measurement terminal arranged at an offset position, the second measurement terminal arranged at a position facing the first measurement terminal across the virtual center line in the second member, the first measurement terminal, and the second measurement terminal. It includes a measuring instrument that measures the potential difference or electrical resistance between the measuring terminal and the detector, and a detector that detects cracks in the welded portion from the measurement results of the measuring instrument.

The crack detection device for a welded portion according to another aspect according to the present disclosure includes a first surface, a second surface facing the first surface, and a welded portion extending between the first surface and the second surface. It is a device that detects cracks in the welded part of a plate-shaped object. This crack detection device has a first electrode terminal arranged at a position offset from the welded portion on the first surface and a second electrode terminal arranged at a position on the second surface facing the first electrode terminal across the welded portion. A power source for applying a current between the two electrode terminals, the first electrode terminal and the second electrode terminal, and the first measurement arranged in the region between the welded portion and the first electrode terminal on the first surface. Measurement to measure the potential difference or electrical resistance between the terminal, the second measurement terminal arranged in the region between the welded portion and the second electrode terminal on the second surface, and the first measurement terminal and the second measurement terminal. It is equipped with a device and a detector that detects cracks in the weld from the measurement results of the measuring device.

According to the present disclosure, cracks generated between the molten layer and the base metal layer can be appropriately detected.

It is a figure which shows an example of the structure of the crack detection apparatus schematically. It is a figure which shows typically the object in the state which the pinching mechanism is installed. It is a figure which looked at the object in the state which the pinching mechanism was installed, from the normal direction of the 1st surface. It is a flowchart which shows an example of the process which a crack detection apparatus performs. It is a figure which shows the analysis model. It is a figure which shows the correspondence relationship between the length of the interlayer crack in the analysis model, and the potential difference between measurement terminals obtained by analysis.

Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. The same or corresponding parts in the drawings are designated by the same reference numerals and the description thereof will not be repeated.

FIG. 1 is a diagram schematically showing an example of the configuration of a crack detection device according to the present embodiment. This crack detection device detects cracks in the welded portion 30 of the object 10 to be detected. FIG. 1 shows a state in which the object 10 is installed in the crack detection device.

The object 10 includes two plate-shaped base materials 10A and 10B that are overlapped with each other in the thickness direction. The welded portion 30 is a molten layer formed by laser welding a portion where the base metal 10A and the base metal 10B are overlapped with each other. The welded portion 30 extends between the first surface 10a (upper surface of the base material 10A) and the second surface 10b (lower surface of the base material 10B) facing the first surface 10a.

The crack detection device includes a power supply 1, a pair of electrode terminals 2a and 2b, a pair of measurement terminals 3a and 3b, a measuring instrument 4, and a detector 5.

The pair of electrode terminals 2a and 2b straddle the welded portion 30 and are arranged on both sides of the object 10 (first surface 10a and second surface 10b), respectively. Specifically, the electrode terminal 2a is arranged at a position offset from the welded portion 30 on the first surface 10a. The electrode terminal 2b is arranged at a position on the second surface 10b facing the electrode terminal 2a with the welded portion 30 interposed therebetween.

The positive electrode of the power supply 1 is connected to the electrode terminal 2a, and the negative electrode of the power supply 1 is connected to the electrode terminal 2b. The power supply 1 applies a current between the pair of electrode terminals 2a and 2b.

The pair of measurement terminals 3a and 3b straddle the welded portion 30 in a region closer to the welded portion 30 than the pair of electrode terminals 2a and 2b, and are on both sides (first surface 10a and second surface 10b) of the object 10. Each is placed. Specifically, the measurement terminal 3a is arranged in the region between the welded portion 30 and the electrode terminal 2a on the first surface 10a. The measurement terminal 3b is arranged in a region on the second surface 10b between the welded portion 30 and the electrode terminal 2b.

The measuring instrument 4 is connected to a pair of measuring terminals 3a and 3b. The measuring instrument 4 measures the potential difference between the measuring terminals 3a and 3b in a state where a current is applied between the electrode terminals 2a and 2b, and outputs the measurement result to the detector 5.

The detector 5 detects a crack in the welded portion 30 from the measurement result of the measuring instrument 4. Specifically, the detector 5 determines that the welded portion 30 has a crack when the measured value of the potential difference by the measuring instrument 4 is larger than a predetermined threshold value, and when it is not, the welded portion 30 has a crack. Judge that there are no cracks. The detection result by the detector 5 is output to a notification device (display, lamp, speaker, etc.) (not shown), and is notified to the inspection worker via the notification device.

As described above, in a region where the pair of measurement terminals 3a and 3b are closer to the welded portion 30 than the pair of electrode terminals 2a and 2b, both sides of the object 10 (first surface 10a and second surface 10a and second) straddle the welded portion 30. Each is arranged on the surface 10b). In order to facilitate such arrangement of the measurement terminals 3a and 3b by the inspection worker, the crack detection device according to the present embodiment is in contact with the first surface 10a and the second surface 10b to be an object. A pinching mechanism for pinching the 10 is provided, and the electrode terminals 2a and 2b are arranged in the pinching mechanism in an offset state.

FIG. 2 is a diagram schematically showing an object 10 in a state where the holding mechanism 40 is installed. FIG. 3 is a view of the object 10 in the state where the pinching mechanism 40 is installed, as viewed from the normal direction of the first surface 10a. As shown in FIG. 3, the welded portion 30 is formed by laser welding and has an elongated rectangular shape when viewed from the normal direction of the first surface 10a.

The pinching mechanism 40 has a first member 41 and a second member 42 for sandwiching the object 10 in contact with the first surface 10a and the second surface 10b of the object 10, respectively. The measurement terminal 3a is arranged at a position offset with respect to the virtual center line CL of the pinching mechanism 40 in the first member 41. The measurement terminal 3b is arranged at a position on the second member 42 facing the measurement terminal 3a with the virtual center line CL interposed therebetween. By providing such a pinching mechanism 40, the inspection worker can simply pinch the object 10 with the pinching mechanism 40 so that the welded portion 30 is located near the virtual center line CL of the pinching mechanism 40. , The pair of measurement terminals 3a and 3b can be arranged on both sides (first surface 10a and second surface 10b) of the object 10 so as to straddle the welded portion 30.

Further, the surface of the welded portion 30 formed by laser welding may be raised more than the surface of the base metal around the welded portion 30. In the crack detection device according to the present embodiment, as described above, the measurement terminals 3a and 3b are arranged at positions offset from the welded portion 30 instead of the welded portion 30. As a result, the measurement terminals 3a and 3b can be appropriately installed on the object 10 even when the surface of the welded portion 30 is raised. As a result, the crack detection device according to the present embodiment can be easily applied to the laser welded portion.

<Detection of cracks in weld 30>
In the laser-welded object 10, an interlayer crack 31 may occur between the welded portion 30 and the base metal layer around the welded portion 30. Since such an interlayer crack 31 affects the quality of welding, it is desirable to detect it appropriately.

However, if the measurement terminals are arranged substantially at the centers of both sides (first surface 10a and second surface 10b) of the welded portion 30, the interlayer crack 31 will be parallel to the straight line connecting the measurement terminals. .. In this case, it becomes difficult for the influence of the interlayer crack 31 to be reflected in the potential difference between the measurement terminals, and as a result, there is a concern that the interlayer crack 31 cannot be detected properly.

In view of the above points, in the crack detection device according to the present embodiment, as described above, the pair of measurement terminals 3a and 3b are offset from the substantially centers of both sides of the welded portion 30 across the welded portion 30. It is placed in the same position. As a result, the interlayer crack 31 is likely to intersect the straight line connecting the measurement terminals 3a and 3b. As a result, the influence of the interlayer crack 31 is easily reflected in the potential difference between the measurement terminals 3a and 3b. As a result, the interlayer crack 31 can be appropriately detected.

FIG. 4 is a flowchart showing an example of a process executed when the crack detection device according to the present embodiment detects a crack in the welded portion 30. This flowchart starts with the object 10 installed in the crack detection device.

The measuring instrument 4 of the crack detecting device measures the potential difference between the measuring terminals 3a and 3b in a state where the current is applied between the electrode terminals 2a and 2b by the power supply 1 (step S12).

Next, the detector 5 of the crack detection device determines whether or not there is a crack in the welded portion 30 of the object 10 based on the measured value of the potential difference by the measuring device 4 (step S14). Specifically, the detector 5 determines that the welded portion 30 has a crack when the measured value of the potential difference by the measuring instrument 4 is larger than a predetermined threshold value, and when it is not, the welded portion 30 has a crack. Judge that there are no cracks. The "threshold value" used in step S14 can be determined in advance by analysis, measurement test, or the like. Further, in the present embodiment, the crack determination of the welded portion 30 is performed using the measured value of the potential difference between the measurement terminals 3a and 3b, but the parameter used for the crack determination of the welded portion 30 is between the measurement terminals 3a and 3b. The crack can be determined not only by the measured value of the potential difference of, but also by using, for example, the measured value of the electric resistance between the measuring terminals 3a and 3b.

<Analysis result>
The inventors of the present application have verified by analysis the difference between the crack detection device according to the present embodiment and the crack detection device of the comparative example (corresponding to the conventional case) in which the measurement terminals are arranged substantially at the centers of both sides of the welded portion 30. ..

FIG. 5 is a diagram showing an analysis model. This analysis model is formed by welding two aluminum plates with a gap of 0.1 mm. The size of each aluminum plate is 2 mm in thickness (dimension in the vertical direction in FIG. 5) and 10 mm in width (dimension in the depth direction in FIG. 5). The size of the welded portion is 1 mm in width (dimension in the left-right direction in FIG. 5) and 6 mm in length (dimension in the depth direction in FIG. 5).

In the analysis model shown in FIG. 5, an interlayer crack having a depth (vertical dimension in FIG. 5) of 10 mm and a length (depth dimension in FIG. 5) L is generated, and 1000 A is generated at both ends of the two aluminum plates. The potential difference between the measurement terminals when a current was applied was calculated.

As shown in FIG. 5, the positions V1 and V2 of the pair of measurement terminals of the crack detection device according to the present embodiment are set to X = 4.5 mm and 35, where X is the distance from the left end of the two aluminum plates. It was set to 5.5 mm. On the other hand, the pair of measurement terminals of the crack detection device of the comparative example (corresponding to the conventional case) are centered on both sides of the welded portion (X = 20 mm).

In such an analysis model, the potential difference between the measurement terminals was calculated while changing the length L of the interlayer crack.

FIG. 6 is a diagram showing the correspondence between the length L of the interlayer crack in the analysis model and the potential difference between the measurement terminals obtained by the analysis. Note that FIG. 6 shows the analysis result of the crack detection device according to the present embodiment and the analysis result of the crack detection device according to the comparative example.

From FIG. 6, the potential difference between the measurement terminals according to the comparative example is almost constant even if the length L of the interlayer crack changes, whereas the potential difference between the measurement terminals according to the present embodiment has the length L of the interlayer crack. It can be understood that the larger the size, the larger the size. This means that the arrangement of the measurement terminals according to the present embodiment makes it easier to detect interlayer cracks than in the comparative example. For example, in the analysis result shown in FIG. 5, by setting the potential difference of 49 mV as the threshold value, it is possible to detect an interlayer crack having a length L of 3 mm or more.

<Modification example>
In the above-described embodiment, the object 10 in which the welded portion 30 is provided at the portion where the two base materials 10A and 10B are overlapped in the thickness direction is shown, but the embodiment of the object 10 is not limited to this. For example, the present disclosure is also applicable to an object provided with a so-called butt welded portion in which a portion where the end faces of the two base materials 10A and 10B are butted is welded.

It should be considered that the embodiments disclosed this time are exemplary in all respects and not restrictive. The scope of the present disclosure is shown by the scope of claims rather than the above description, and is intended to include all modifications within the meaning and scope equivalent to the scope of claims.

1 power supply, 2a, 2b electrode terminal, 3a, 3b measurement terminal, 4 measuring instrument, 5 detector, 10 object, 10A, 10B base material, 10a first surface, 10b second surface, 30 weld, 31 crack, 40 Holding mechanism, 41 1st member, 42 2nd member, CL virtual center line.

Claims (9)

A crack in the welded portion of a plate-shaped object including a first surface, a second surface facing the first surface, and a welded portion extending between the first surface and the second surface. It ’s a way to detect
A state in which a current is applied between a first position offset from the welded portion on the first surface and a second position on the second surface that faces the first position with the welded portion interposed therebetween. In the first measuring portion arranged in the region between the welded portion and the first position on the first surface, and arranged in the region between the welded portion and the second position on the second surface. A step of measuring the potential difference or electrical resistance between the second measuring unit and the second measuring unit.
A method for detecting a crack in a welded portion, which comprises a step of detecting a crack in the welded portion from the measurement result of the potential difference or the electric resistance. The weld according to claim 1, wherein the step of detecting a crack in the weld portion includes a step of determining that the weld portion has a crack when the measured value of the potential difference or the electric resistance is larger than the threshold value. How to detect cracks in the part. The crack detection method for a welded portion according to claim 1, wherein the welded portion has a rectangular shape when viewed from the normal direction of the first surface. The object includes a first base material and a second base material, and includes the first base material and the second base material.
The method for detecting a crack in a welded portion according to any one of claims 1 to 3, wherein the welded portion is arranged in a portion where the first base material and the second base material are overlapped in the thickness direction. A crack in the welded portion of a plate-shaped object including a first surface, a second surface facing the first surface, and a welded portion extending between the first surface and the second surface. It is a device to detect
A power source for applying a current between a first position offset from the weld on the first surface and a second position on the second surface that faces the first position across the weld. When,
A sandwiching mechanism having a first member and a second member for sandwiching the object in contact with the first surface and the second surface of the object, respectively.
The first measurement terminal of the first member, which is arranged at a position offset from the virtual center line of the pinching mechanism,
The second measurement terminal in the second member, which is arranged at a position facing the first measurement terminal across the virtual center line, and the second measurement terminal.
A measuring instrument that measures the potential difference or electrical resistance between the first measuring terminal and the second measuring terminal,
A crack detection device for a welded portion, comprising a detector for detecting a crack in the welded portion from the measurement result of the measuring instrument. A crack in the welded portion of a plate-shaped object including a first surface, a second surface facing the first surface, and a welded portion extending between the first surface and the second surface. It is a device to detect
A first electrode terminal arranged at a position offset from the welded portion on the first surface,
A second electrode terminal arranged at a position facing the first electrode terminal on the second surface with the welded portion interposed therebetween.
A power supply for applying a current between the first electrode terminal and the second electrode terminal, and
A first measurement terminal arranged in a region between the welded portion and the first electrode terminal on the first surface,
A second measurement terminal arranged in a region between the welded portion and the second electrode terminal on the second surface, and a second measurement terminal.
A measuring instrument that measures the potential difference or electrical resistance between the first measuring terminal and the second measuring terminal,
A crack detection device for a welded portion, comprising a detector for detecting a crack in the welded portion from the measurement result of the measuring instrument. The crack detection device for a welded portion according to claim 5 or 6, wherein the detector determines that the welded portion has a crack when the measured value of the potential difference or the electric resistance is larger than the threshold value. The crack detection device for a welded portion according to any one of claims 5 to 7, wherein the welded portion has a rectangular shape when viewed from the normal direction of the first surface. The object includes a first base material and a second base material, and includes the first base material and the second base material.
The crack detection device for a welded portion according to any one of claims 5 to 8, wherein the welded portion is arranged in a portion where the first base material and the second base material are overlapped in the thickness direction.

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