JP5909873B2 - Weld defect detection system, method for manufacturing ERW steel pipe, and method for manufacturing welded product - Google Patents

Description

The present invention relates to a welding defect detection system, a method for manufacturing an ERW steel pipe, and a method for manufacturing a welded product.

As described in Patent Document 1, for example, in high-frequency heating welding or high-frequency resistance welding used for the manufacture of welded products such as ERW steel pipes, the heat generation and light emission of the welded portion are stable and stable in a normal state. doing. On the other hand, when abnormalities occur due to various welding conditions, fluctuations occur in the current and voltage of the heating coil and sparks are generated.
Spark is a phenomenon in which sparks violently scatter around the welded part, and it is known that the part where the spark is generated often results in poor welding. Accordingly, it is necessary to accurately detect whether or not a spark has occurred during welding, and when the spark is detected, it is necessary to excise (cut and remove) the part so as not to be shipped to the customer.

However, during welding, spatter, which is a light emission phenomenon due to sparks similar to sparks, also occurs. In general, spatter occurs more frequently than sparks, but there is a low probability that the sputtered portion will be welded poorly. Therefore, it is important to discriminate from the spatter when detecting the spark.
Therefore, in the invention described in Patent Document 1, by using a blue filter, the brightness of the spark is increased, the brightness at the time of sputtering and normal is decreased, and a threshold is set for the brightness level between them, thereby reducing the spark. Propose to detect.

  On the other hand, with regard to the defect detection technique, on-line flaw detection is generally performed on welds by ultrasonic oblique flaw detection. In this method, ultrasonic waves are incident obliquely on the inspection surface of the test material, and internal and external surface defects and internal defects of the test material are detected from reflected waves reflected by the defects. For example, a reflection method using an ultrasonic beam having a refraction angle of 45 ° at 5 MHz is usually applied to an electric resistance tube, and defects of the order of mm, for example, defects such as poor penetration, melt-down, and cracks due to inclusions are detected. ing. In the inspection by this ultrasonic flaw detection method, it is difficult to detect a minute welding defect of about several hundred μm or less. On the other hand, for example, according to the ultrasonic flaw detection method using an array probe as disclosed in Patent Document 2, it is possible to detect minute welding defects of about several tens of μm to several hundreds of μm. .

JP 2009-072788 A JP 2008-286640 A

  However, even with the best welding conditions within the scope of the prior art, very fine weld defects may still occur. This is a case where fine foreign matter is mixed in the electric-welded welded portion and a case where a paddle or the like is present at the end portion (edge portion) of the band material (tube material). In other words, iron oxide or iron on the surface of the tube material is peeled off during the electric seam forming welding process and exists as a small amount of dust in the atmosphere. In the electric seam welding process, the molten steel generated during welding is sputtered. Although present, when these dusts and spatter particles rarely jump into the weld, welding defects may occur. Furthermore, even when a portion where a slight wrinkle is generated at the end portion of the strip is electro-welded, the wrinkle may cause a welding defect. All of these weld defects are as small as several tens of μm to several hundreds of μm, and the occurrence positions may be distributed in a range from the inner surface to the outer surface of the tube along the weld line. there were.

In principle, the ultrasonic flaw detection method using the array probe has a low defect detection capability in the vicinity of the surface of the tube body. Therefore, when a minute defect of about 50 μm exists in the vicinity of the tube surface, the detection sensitivity is high. It may drop and be undetectable.
In addition, even if the spark generation site is excised using the spark detection technique, the mechanical properties of the weld may be locally degraded.

  In other words, the conventional defect detection technology has not yet been able to sufficiently detect defects in ERW welds, preventing the situation that ERW steel pipes containing local parts with deteriorated mechanical properties may be mixed into the product. There was a problem that it was difficult.

The inventors diligently studied to solve the above problems and obtained the following knowledge.
(I) When a sample is cut out from a pipe-forming length direction part where the mechanical properties of the welded part have deteriorated in the ERW steel pipe after excision of the spark generation site, and observed with a scanning electron microscope, extremely fine welding defects are found. Existing.
(ii) Extremely fine weld defects occur when fine foreign matter is mixed in the ERW weld and the width end of the strip that is a tube material (the circumferential edge of the tubular body after forming into a tubular shape) This is a case where there is a guess. In other words, iron oxide or iron on the surface of the tube material is peeled off during roll forming or electro-welding of the tube material, and is present as a small amount of dust in the atmosphere. Although molten steel exists as sputtered grains, welding defects may occur when these dusts or sputtered grains rarely jump into the weld.
(Iii) When the above-mentioned welding defect occurs, the luminance distribution state on the welding point extraction side (downstream side) instantaneously changes to the dark (dark) side.

In addition, a welding point refers to the boundary point of the already-welded part (this is also called a weld line) and the unwelded part in the welding advancing direction in the welding part at the time of welding. Further, the welding point output side refers to the already welded portion side (the weld line side) when viewed from the welding point.
(iv) Therefore, spark detection and brightness monitoring are performed in the vicinity of the welding point, and further, in addition to this, by performing an inspection with the ultrasonic flaw detector using the above array probe, only the defective weld portion is detected. In addition, it is possible to identify a portion where a fine welding defect is generated and to cut and remove those portions.

The present invention has been made by further study based on the above findings, and the gist thereof is as follows.
(1)
Targeting a welded part at the time of welding construction, imaging a light emission state of the object, a spark determination step of determining a spark from the captured image, and a luminance monitoring step of capturing and monitoring the luminance of the target as an image signal A welding defect detection system used for carrying out a welding defect detection method further comprising an inspection step of inspecting the welded portion after the monitoring step with an ultrasonic flaw detector using an array probe,
Using a spark sensor for imaging the light emission state of the target, a luminance sensor as a DS sensor that detects and monitors the brightness of the target as an image signal, and detects DS that is a dark spot, and the array probe Having an array UT which is a conventional ultrasonic flaw detector, and
Comprising a defect determination means for determining a weld defect based on the determination result of the spark determination step and the monitoring result of the luminance monitoring step; and
The defect determination means captures both image signals in the spark determination step and the luminance monitoring step in real time, performs image processing, and compares them with a predetermined threshold value. Based on the calculation results, instantaneous welding is performed. Determining weld defects by determining the suitability of the state; and
As a determination condition for the presence of a welding defect in the defect determination means, the amount of spark captured by the spark sensor indicates a peak height exceeding the upper limit of the natural light noise level, and the DS sensor detects DS within 5 seconds from the peak detection time point. A welding defect detection system characterized by adopting a condition of performing.
(2)
The spark determination step extracts the blue component intensity from the image signal of the captured image, and determines that a spark has occurred only when the blue component intensity is equal to or greater than a predetermined threshold. The welding defect detection system described.
(3)
The luminance sensor is characterized in that the luminance distribution of a linear region that is substantially orthogonal to the weld line, which is the width center line of the welded portion, is captured as an image signal by imaging at an imaging speed of 1 ms or less and an imaging frequency of 1000 times / s or more. The welding defect detection system according to (1) or (2).
(4)
The array UT includes a wave transmitting unit that inputs ultrasonic waves to the weld surface of the tube axis direction welded portion of the tube body, and a wave receiving unit that receives part or all of the reflected wave reflected by the welded portion. An ultrasonic flaw detector comprising: a transmitter and a receiver, wherein the transmitter and the receiver are composed of different transducer groups on one or more flaw detection array probes arranged in a circumferential direction of the tube The welding defect detection system according to any one of (1) to (3), wherein there is a welding defect detection system.
(5)
In the method for manufacturing an ERW steel pipe, wherein the edges of the V-shaped gap formed by forming a steel strip into a tubular shape are continuously electro-welded to each other, the above-mentioned (1) A method for manufacturing an ERW steel pipe, wherein the welding defect detection system according to any one of (4) is applied.
(6)
The method of manufacturing a welded product to facilities weld the metal material, characterized by applying a welding defect detection system as claimed in any one of the targeting weld by the welding (1) to (4) A method for manufacturing a welded product.

  According to the present invention, it is possible to accurately detect a minute welding defect caused by spark generation and / or dust or spatter particle jumping from the surface to the inside of the welded portion, and accordingly, a welded portion mechanical property lowered portion caused by the welded defect. Can be detected reliably and without excess and deficiency, and a welded product in which these portions are cut out can be obtained, so that the reliability of the welded product is remarkably improved.

It is a schematic diagram of the ERW steel pipe manufacturing line which shows an example of embodiment of this invention. It is a schematic perspective view which shows the A section detail of FIG. FIG. 3 is a partially cutaway plan view of FIG. 2. It is explanatory drawing which shows the determination method of a spark. It is a schematic diagram which shows transition of luminance distribution monitoring data. It is a diagram which shows an example of the transition curve of the sum total of the instantaneous luminance with respect to pipe making length. It is a diagram which shows one example of the transition curve of the half value width of the instantaneous luminance with respect to pipe making length. It is explanatory drawing which shows the principle of the array UT compared with the conventional UT.

  FIG. 1 is a schematic view of an ERW steel pipe production line showing an example of an embodiment of the present invention, FIG. 2 is a schematic perspective view showing the details of part A of FIG. 1, and FIG. 3 is a partially cutaway plane of FIG. FIG. 1 to 3, reference numeral 1 is a strip whose initial form is a coil shape, 1a is a welding point at which the welded portion is welded, and 1b and 1c are both ends of the strip in the width direction of the welded portion. 2 is an uncoiler, 3 is a roll forming machine, 4 is a high frequency heating device, 4a is a work coil, 4d is a high frequency oscillation device, 5 is a squeeze roll, 6 is a bead cutting machine, 7 is a cutting machine, 8 is a cutting machine Tube (in this example, ERW steel tube), 8W is a welded portion, 10 is a luminance sensor called a DS sensor, 11 is an array UT that is an ultrasonic flaw detector using an array probe, and 12 is an imaging device for detecting a spark. A certain spark sensor, 13 is an imaging region of the spark sensor 12, 14 is a weld line that is a center line in the width direction of the welded portion 8W, and 15 is a luminance monitoring region of the DS sensor 10.

  In the above line, the strip 1 is discharged by the uncoiler 2 and formed into a tubular shape by the roll forming machine 3, and the edges 1b and 1c of the formed V-shaped gap are moved from the high frequency oscillation device 4d to the work coil by the high frequency heating device 4. A high-frequency current is applied to 4a to generate an induced current at the edges 1b and 1c, and the convergence point of the V-shaped gap is pressed with the squeeze roll 5 while being heated to the melting point or higher by the Joule heat, and the resulting weld point By forming a welded portion 8W having the weld line 14 as the width center line on the downstream side of 1a, the welded portion 8W is welded to form the tube 8, and the bead cutting machine 6 cuts the outer surface bead of the welded portion 8W. Cutting to a predetermined length by the cutting machine 7. As the strip 1, a steel strip (hot rolled steel strip or cold rolled steel strip) or a material obtained by cutting the steel strip is used. In this example, an induction heating type device is shown as the high-frequency heating device 4, but this is not a limitation, and a direct current heating type device may be used. Incidentally, there may be a case where an electroimpedance welding is performed by inserting an impeller (not shown) on the inner side of the pipe material or the pipe within the passing direction range including the energized portion of the high-frequency current.

  In the line as described above, the present invention is directed to a welded part at the time of welding construction, images the light emission state of the object by the spark sensor 12, and determines the spark from the captured image, A luminance monitoring step of monitoring and monitoring the luminance of the target as an image signal by the DS sensor 10, and further, an inspection step of inspecting the welded portion after the monitoring step with an ultrasonic flaw detector using an array probe, that is, the array UT11 A welding defect detection system used for carrying out a welding defect detection method comprising: a spark sensor for imaging the light emission state of the object; and a luminance sensor for capturing and monitoring the luminance of the object as an image signal; And an array UT which is an ultrasonic flaw detector using the array probe.

Compared to the case where any one or two are provided, the possibility of being able to be detected in other processes even if there is an oversight of a weld defect in comparison with the case where any one or two are provided. Is greatly improved, and welding defects can be detected more reliably.
Therefore, for a certain length of welded product, only when it is determined that there are no welding defects in all of the spark judging process, the luminance monitoring process, and the inspection process, the welded product is assumed to be healthy over the entire length of the welded part. On the other hand, if any one or two of these three steps are determined to have no weld defects, but the remaining two or one is determined to have a weld defect, the welded product is a welded portion resulting from the weld defects. Since it has a length part that becomes a defective part of mechanical properties (unhealthy part), it is possible to prevent the unhealthy part from being mixed into the welded product with high accuracy by using the remainder after cutting the length part as a welded product. As a result, the quality and reliability of the welded product is significantly improved.

In the example of FIG. 1, a mode in which the inspection by the array UT11 is performed on the cut tube 8 (a mode in which inspection is performed off-line) is shown, but this is not limiting, and the inspection by the array UT11 is performed after bead cutting and before cutting. It is good also as a form (form to test | inspect on-line) with respect to this pipe | tube 8.
Hereinafter, each step will be described.
(Spark determination process)
Since the detailed description of the embodiment of the spark determination step is described in Patent Document 1, it will be described here briefly.

  The light emission state of the welded part at the time of welding is imaged using the spark sensor 12. As the spark sensor 12, a monochrome CCD camera, a CMOS camera, or the like is used. It is preferable that the imaging region 13 is about 300 mm square with the welding point 1a as the center, and is set at an angle of at least about 500 mm away from there. An image signal of the captured image is captured in a PC (personal computer) or the like and processed.

As imaging conditions, the number of imaging (the number of frames) = about 30 times / s and the imaging speed (exposure time) = (1/30) s = 33 ms are preferable, but are not limited thereto. However, in order not to overlook the spark, it is desirable that the number of imaging times × imaging time = 1 s is satisfied.
A blue filter having a maximum transmittance in a wavelength range of about 300 nm to about 500 nm may be attached to the front surface of the camera lens of the spark sensor. As a result, even a monochrome camera can extract and receive the blue component of the emitted light, and can detect sparks by distinguishing it from sputtering by changing the signal. In place of the monochrome camera, only a blue component signal may be extracted and processed using a color camera.

  The blue component intensity obtained from the image signal of the captured image is represented by the light amount (count number) as shown as data 21 and 22 in FIG. 4, for example, and changes with time. In FIG. 22, peaks 21a and 22a sometimes appear. Therefore, it is determined that a spark has occurred only when the height of these peaks exceeds a predetermined threshold 20 (threshold = 200 in the example of FIG. 4). That is, in FIG. 4A, it is determined that a spark has occurred (that is, spark detection), and in FIG. 4B, it has been determined that no spark has occurred. The threshold value 20 may be a value higher than the natural light noise region 30 and may be determined by a correspondence investigation experiment between the peak height at the peak detection site and the welded part mechanical characteristics.

Information related to the time at which the spark is detected (spark detection time information) is obtained by using a conventional tracking technique (for example, a technique for tracking the position in the running direction of the running material using a contact roll and a rotary encoder), and corresponding pipe forming length position information. In this way, the pipe forming length position corresponding to the spark detection time can be specified.
(Luminance monitoring process)
In the luminance monitoring step, the DS sensor 10 is used as means for capturing and monitoring the luminance of the welded portion at the time of welding as an image signal. The DS sensor 10 has a function of photographing the linear luminance monitoring region 15 and deriving the luminance distribution in the photographed screen, and for example, a commercially available line scan camera can be preferably applied.

  Luminance information (instantaneous luminance) for each shooting frame is captured and processed on a PC (personal computer) or the like, and as shown schematically in FIG. 5, the temporal change data of the image signal corresponding to the instantaneous luminance distribution curve is obtained. Can be monitored. The DS (dark spot) corresponding to the occurrence of welding defects due to rare jumps in dust or spatter or minute flaws at the end of the strip can be detected from the time-dependent data monitored. The information is converted into the corresponding tube forming position information by a conventional tracking technique, and the tube forming position corresponding to the DS detection time can be specified.

In order to reliably capture the change in instantaneous luminance, the luminance monitoring region 15 is substantially orthogonal to the welding line 14 (about 90 ° ± 10 °) around the welding line 14 at a position 20 to 500 mm downstream from the welding point 1a. ) Is desirable.
By the way, the speed of electric resistance welding (weld line generation speed or pipe forming speed) is classified as a high-speed welding method among various welding methods, and may be welded at a speed exceeding 100 m / min. At these welding speeds, in order to discriminate a welding defect of several mm or less, the photographing speed (exposure time of one photographing frame) must be 1 ms (= 1/1000 second) or less. When the imaging speed exceeds 1 ms, portions other than the luminance change portion of the weld defect portion enter the same imaging frame to a considerable extent, and DS detection becomes difficult. Furthermore, in order not to miss a minute welding defect, the number of times of photographing (number of photographing frames) must be 1000 times per second (1000 frames per second) or more. If the number of times of photographing is less than 1000 times per second, the weld defect part may be removed from the photographing frame, resulting in oversight.

Therefore, in the present invention, even when the speed of ERW welding exceeds 100 m / min, the luminance distribution monitored by the DS sensor is ensured so that the welding defect portion can be reliably identified and the welding defect portion is not overlooked. Is preferably captured as an image signal by shooting at a shooting speed of 1 ms or less and a shooting count of 1000 times / s or more.
Next, a more specific method for detecting DS from the monitoring result of the luminance monitoring process will be described.

In fact, the luminance distribution captured as an image signal obtained by photographing with the DS sensor does not necessarily indicate a simple and smooth mountain-shaped curve as schematically shown in FIG. In many cases, the curve shape is shown, and it is difficult to immediately detect the DS from the instantaneous luminance data of such a complicated distribution curve shape (that is, to determine whether the welding state is instantaneous or not). Therefore, the inventors examined a method for overcoming this difficulty, and as a result, processed the image signal and calculated the sum of instantaneous luminance and / or the half-value width (see FIGS. 6 and 7). It has been found that the DS detection is surely and easy to use. FIG. 6 shows an example of a transition curve (data 41) with respect to the tube forming length of the sum of instantaneous luminances obtained by processing and calculating the image signal. FIG. 7 shows the same image signal as FIG. An example of a transition curve (data 51) with respect to the pipe forming length of the half-value width of instantaneous luminance obtained by processing and calculating the above is shown. These transition curves in FIGS. 6 and 7 show a shape having a clear hollow portion in a substantially flat shape, and it can be seen that the tube-forming length portion where the DS is generated can be reliably and easily detected. The determination of the occurrence of DS uses a threshold value appropriately determined by experiments or the like (threshold 40 in FIG. 6 and threshold 50 in FIG. 7). And The threshold value 40 or 50 may be determined by a correspondence investigation experiment between the minimum luminance value and the welded portion mechanical characteristics at the luminance reduction detection site.
(Inspection process)
On the downstream side of the brightness monitoring region 15, the welded portion is inspected offline or online using the array UT11 as described above. As described above, according to the array UT, it is possible to detect a minute welding defect of about several tens of μm to several hundreds of μm. FIG. 8 is an explanatory view showing the principle of the array UT11 in comparison with the conventional UT, and by using such an array UT, it is much finer than the conventional UT of about φ0.5 mm to 1.0 mm. For example, a welding defect of φ250 μm or less can be detected.

  The array UT11 illustrated in FIG. 8 includes, as a preferred form, a wave transmitting unit that applies ultrasonic waves to the welding surface of the welded portion 8W extending in the tube axis direction of the tube (tube 8), and a welded portion. An array probe for flaw detection in which one or two or more flaw detection units are arranged in the circumferential direction of the tube. This is an ultrasonic flaw detector provided with a transmission / reception unit comprising different transducer groups on the child 11A.

  Note that the array UT having a more preferable form is configured to receive a ultrasonic wave incident on the welding surface of the welded portion in the tube axis direction of the tubular body and a part or all of the reflected wave reflected by the welded portion. A transmitting / receiving unit that includes a different transducer group on one or more array probes arranged in the circumferential direction of the tube, and a tube Thickness measurement probe for measuring the thickness distribution of the body, and based on the thickness distribution measured by the thickness measurement probe, using the array probe, A propagation path calculating means for calculating a propagation path of ultrasonic waves for scanning in the vertical direction, and transducers corresponding to the transmitting section and the receiving section on the array probe based on the calculated propagation path Control to scan the tube in the thickness direction by changing the group or changing the angle of the array probe Those in a form comprising a control unit, a (invention described in Patent Document 2).

  According to this further preferred embodiment of the array UT, a minute defect of about several hundreds μm or less located inside the thickness of a welded portion such as an electric resistance welded steel pipe having a thickened portion on the inner surface leaks from the inner surface to the outer surface. Because it becomes possible to detect without defects, it becomes possible to improve the welding process so that micro defects that affect the mechanical properties of the welded part of the welded steel pipe do not occur, or to select in the manufacturing process so that defects do not flow out, The quality of the welded steel pipe can be drastically improved, and it can be used under conditions that are severer than before (see the effect column of the invention described in Patent Document 2).

  Even more preferably, the number of transducers of the transducer group for transmission and the transducer group for reception is set to be smaller as it is closer to the welded portion and larger as it is farther from the welded portion. In this way, the opening width at the time of simultaneous excitation becomes narrower toward the side closer to the welded portion, so that the beam width does not become too narrow even if the focal length is short, and the side farther from the welded portion becomes closer to the time of simultaneous excitation. Since the aperture width is wide, the focusing coefficient can be increased even when the focal length is long, and the detection ability does not deteriorate. Accordingly, since the focusing characteristics from each transducer group can be made uniform, flaw detection can be performed with uniform detection sensitivity from the inner surface side to the outer surface side inside the welded portion.

In the present invention, it is necessary to use both of the brightness sensor (DS sensor) and the array UT, not both, as a means for detecting a weld defect that causes a welded part mechanical property defect exceeding the detection limit of the spark sensor. The reason is as follows.
In general, when a tube is used, stress tends to concentrate on the surface rather than the central portion in the thickness direction of the tube (strain is easily applied to the surface of the tube). Therefore, if there is a defect on the surface of the tube, the susceptibility to cracking is high, and even if it is a minute flaw, the mechanical characteristics are likely to deteriorate, which is likely to be a problem in use. That is, when there is a defect in the welded part, even if it is a defect of the same size compared to the central part in the thickness direction of the pipe, if the flaw is present in the central part in the thickness direction of the pipe, Although it does not become a problem, when a ridge exists in the vicinity of the surface of the pipe, problems such as cracking are likely to occur during use.

  The inventors have investigated in detail the influence of the presence form of defects, that is, the position and size of the defects, on the mechanical properties of the weld. As a result, if a defect having a size of 100 μm or more exists inside the welded portion of the pipe, the mechanical properties deteriorate, and even if a defect of less than 100 μm exists inside the welded portion of the tube, the mechanical properties are reduced. It has no effect, and when a defect of 50 μm or more exists near the surface of the welded part of the pipe, the mechanical properties deteriorate, and even if a defect of less than 50 μm exists near the surface of the welded part of the pipe It was discovered that it does not affect the mechanical properties.

By the way, the brightness sensor has a high defect detection capability in the vicinity of the surface of the welded part of the pipe, especially in principle for measuring the brightness of the surface of the object to be measured, and sufficiently detects a defect of about 30 μm near the surface of the welded part of the pipe. can do.
On the other hand, the array UT, in principle, has a low defect detection capability near the surface of the tube. Even if this is used, the detection sensitivity decreases when a minute defect of around 50 μm exists near the tube surface. Defects may not be detected.

For these reasons, in order to detect a minute defect of about 50 μm existing on the tube surface, monitoring with a luminance sensor is necessary.
By the way, in the array UT, flaw detection is possible with uniform detection sensitivity from the inner surface side to the outer surface side inside the tube. Therefore, it is possible to detect a minute defect of about 100 μm existing in the welded portion of the ERW steel pipe. For this purpose, it is preferable to set the number of transducers of the transmitting transducer group and the receiving transducer group to be smaller as it is closer to the welded portion and larger as it is farther from the welded portion. In this way, the closer to the welded portion, the narrower the opening width at the time of simultaneous excitation, so the beam width does not become too narrow even if the focal length is short. Since the aperture width is wide, the focusing coefficient can be increased even when the focal length is long, and the detection ability does not deteriorate. Accordingly, since the focusing characteristics from each transducer group can be made uniform, flaw detection can be performed with uniform detection sensitivity from the inner surface side to the outer surface side (see Patent Document 2 [0070] column).

On the other hand, the luminance sensor has a low defect detection capability inside the pipe in principle based on the principle of measuring the luminance of the surface of the object to be measured. Particularly, for a thick pipe having a thickness exceeding 6 mm, it is about 100 μm existing in the pipe weld. In some cases, a minute internal defect cannot be detected.
For these reasons, an array UT is required to detect minute defects of about 100 μm existing inside the pipe welded part without leaking from the inner surface side to the outer surface side.

Moreover, in this invention, it is preferable to provide the defect determination means which determines a welding defect based on the determination result of the said spark determination process, and the monitoring result of the said brightness | luminance monitoring process. Hereinafter, the defect determination means will be described.
(Defect determination means)
According to the study by the inventors, the welded portion mechanical characteristics are decreased at the portion where the spark is detected as described above, but the welded portion mechanical properties may be decreased even at the portion where the amount of spark light is lower than the threshold value. . On the other hand, at the DS occurrence portion detected as described above, the welded portion mechanical characteristics may or may not decrease.

Therefore, as a result of further studies, the mechanical properties of the welded part are surely lowered at the pipe length portion where the spark quantity shows a peak height exceeding the upper limit of the natural light noise level and the occurrence of DS is detected. I understood.
Therefore, in the present invention, as a determination condition for the presence of a weld defect in the defect determination means, the amount of spark captured by the spark sensor indicates a peak height that exceeds the upper limit of the natural light noise level, and almost simultaneously (about 5 seconds from the peak detection time). The condition that the DS sensor detects DS is preferably adopted.

Further, from the viewpoint of saving the capacity of the data storage means, the defect judgment means performs an operation for capturing both image signals in the spark judgment process and the luminance monitoring process in real time, and respectively comparing them with a predetermined threshold after image processing. It is preferable that the welding defect is determined by determining whether or not the instantaneous welding state is appropriate based on the calculation result.
In the above description of the embodiment, the case where the present invention is applied to the manufacturing process of an electric resistance welded steel pipe has been described. However, the welding defect detection method of the present invention is a welded product other than an electric resistance welded steel pipe (for example, a welded structure). Needless to say, the present invention can also be applied to applications such as welding monitoring in the welding manufacturing process.

  As an example, the present invention was implemented in the form shown in FIG. For the welded part at the time of welding construction, the light emission state was imaged with a spark sensor for a plurality of levels with a pipe forming length per level of 1000 m, and the light intensity exceeding the natural light noise level was shown from the captured images. The tube length part is specified, and the monitoring result (with or without brightness reduction) of the specified part is recorded, and the welded part is inspected over the entire length using the array UT in the downstream inspection process. .

  And about the specified site | part of each level, the 90 degree flatness test (For example, the flatness test prescribed | regulated to JIS G3445) of a welding part was done, and the flat characteristic (representing a welding part mechanical characteristic) of a welding part was investigated. The results are shown in Table 1. In the above flattening test, the tube is crushed in a direction orthogonal to the tube diameter direction passing through the welded portion of the tube, and the outer diameter in the tube crushing direction when a crack occurs in the welded portion is determined. The outer diameter ratio is a flat value.

  From Table 1, the flat value equivalent to the sound part is obtained only when it is determined that there is no welding defect (×) by any of the spark sensor, the DS sensor, and the array UT, and the portion having a high flat value, that is, welding is obtained. It can be seen that the part mechanical characteristic defect part (corresponding to the weld defect part) can be completely detected by the combined use of the spark sensor, the DS sensor and the array UT.

1 Band 1a Welding point (Point where welded part is welded)
1b, 1c Edge 2 Uncoiler 3 Roll forming machine 4 High-frequency heating device 4a Work coil 4d High-frequency oscillation device 5 Squeeze roll 6 Bead cutting machine 7 Cutting machine 8 Tube (Electric seam pipe)
8W weld 10 brightness sensor (DS sensor)
11 Ultrasonic flaw detector (array UT) using array probe
11A array probe 12 imaging device (spark sensor)
13 Spark sensor imaging area 14 Welding line 15 DS sensor brightness monitoring area 20, 40, 50 Threshold 21, 22, 41, 51 Data 21a, 22a Peak 30 Natural light noise area

Claims (6)

Targeting a welded part at the time of welding construction, imaging a light emission state of the object, a spark determination step of determining a spark from the captured image, and a luminance monitoring step of capturing and monitoring the luminance of the target as an image signal A welding defect detection system used for carrying out a welding defect detection method further comprising an inspection step of inspecting the welded portion after the monitoring step with an ultrasonic flaw detector using an array probe,
Using a spark sensor for imaging the light emission state of the target, a luminance sensor as a DS sensor that detects and monitors the brightness of the target as an image signal, and detects DS that is a dark spot, and the array probe Having an array UT which is a conventional ultrasonic flaw detector , and
Comprising a defect determination means for determining a weld defect based on the determination result of the spark determination step and the monitoring result of the luminance monitoring step; and
The defect determination means captures both image signals in the spark determination step and the luminance monitoring step in real time, performs image processing, and compares them with a predetermined threshold value. Based on the calculation results, instantaneous welding is performed. Determining weld defects by determining the suitability of the state; and
As a determination condition for the presence of a welding defect in the defect determination means, the amount of spark captured by the spark sensor indicates a peak height exceeding the upper limit of the natural light noise level, and the DS sensor detects DS within 5 seconds from the peak detection time point. A welding defect detection system characterized by adopting the condition of performing. The spark determining step, according to claim 1, wherein determining that extracts a blue component intensity from an image signal of an image of which an image is captured, is seen sparks when the blue component intensity is not smaller than a predetermined threshold value has occurred Welding defect detection system. The luminance sensor is characterized in that the luminance distribution of a linear region that is substantially orthogonal to the weld line, which is the width center line of the welded portion, is captured as an image signal by imaging at an imaging speed of 1 ms or less and an imaging frequency of 1000 times / s or more. The welding defect detection system according to claim 1 or 2 . The array UT includes a wave transmitting unit that inputs ultrasonic waves to the weld surface of the tube axis direction welded portion of the tube body, and a wave receiving unit that receives part or all of the reflected wave reflected by the welded portion. An ultrasonic flaw detector comprising: a transmitter and a receiver, wherein the transmitter and the receiver are composed of different transducer groups on one or more flaw detection array probes arranged in a circumferential direction of the tube The welding defect detection system according to any one of claims 1 to 3 , wherein the welding defect detection system is provided. In the manufacturing method of the ERW steel pipe which continuously welds the edges of the V-shaped gap formed by forming the steel strip into a tubular shape, the welded portion by the ERW welding is targeted. 4. A method for producing an electric resistance welded steel pipe, wherein the welding defect detection system according to any one of 4 is applied. The method of manufacturing a welded product to facilities weld the metal material, welding, characterized in that applying a welding defect detection system as claimed in any one of claims 1 to 4 as a target weld by the welding Product manufacturing method .

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