JP2000271743A - Weld zone inspecting method, its inspecting device and welded pipe for piping - Google Patents

Abstract

PROBLEM TO BE SOLVED: To inspect the thining of weld beads in line without executing a destructive inspection by judging the thining of the weld beads in butt welding for the base stock of a thin sheet based on surface properties of a weld zone. SOLUTION: A slit light flood lamp 50 is set up so that a light cutting line 52 orthogonal to the longitudinal direction of a welded pipe traverses a weld zone 1. A slit light flooding stroboscopic light source is connected to the slit light flood lamp 50, a stroboscopic light source 58 for lighting the weld zone surface is connected to an illuminator 55 for the weld zone surface, light emission timing is controlled by a central controller 56, and a light cutting line image and a weld zone surface image are image picked up by the same image pickup unit 53 witch a time lag. The information of the light cutting line image and the weld zone surface image which are image picked up are sent to a surface shape characteristic calculating part, the boundary point between the base stock part and beads is decided on the cutting line image based on the information of both images, a prescribed substitute characteristic value is obtained and is sent to the central controller 56. The substitute characteristic value is compared with the threshold to which the substitute characteristic value is set by the central controller 56 to judge whether the thining is executed or not.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inspection of a welded portion for judging whether or not a thinning of a weld bead having a portion thinner than a base material thickness has occurred when thin plates are joined by butt fusion welding. More particularly, the present invention relates to a welding portion inspection method and an inspection device suitable for in-line inspection of a pipe welding pipe manufactured by forming a hoop material into a tubular shape and welding the same.

[0002]

2. Description of the Related Art A method for inspecting a welded portion of a welded pipe in-line is disclosed in Japanese Patent Publication No. 60-7568 (known example 1). This is based on the finding that, in ERW pipes, the metal flow angle of the weld is an indicator of the strength of the weld, and that there is a correlation between the metal flow angle and the width and height of the weld bead, Slit light is applied to the welded part of the moving tube immediately after welding, the width and height of the bead at the welded part are measured by a light cutting method, and the metal flow angle is calculated in real time. In addition, Japanese Patent Publication No. 60-7
No. 587 describes a method for controlling welding heat input to obtain good welding quality in the production of ERW pipes, in which a light-cutting method is used to reduce the amount of dent, the curvature of the tip, and the amount of overhang of the tip of a weld bead. And controlling the voltage of the high-frequency oscillator for electric resistance welding so that the bead tip keeps a predetermined curvature or a predetermined overhang amount is disclosed. (Known example 2).

[0003]

A welded pipe having a perforated portion at the welded portion is not only weak in strength but also fatally defective especially for a welded pipe for piping. It has been strictly inspected. But,
At the time of eddy current inspection, even if there is no perforation defect, holes may be generated when stress is applied by the subsequent manufacturing process. Particularly, flexible pipes that are formed in bellows in the subsequent process However, it is easy to cause a problem because of its low welding strength. However, there is no welding strength inspection method that can foresee a portion where there is a possibility of drilling in advance, so welding is performed so that the thickness of the weld bead (hereinafter abbreviated as “bead”) is equal to or greater than the thickness of the base material. Have been addressed by that. In pressure welding that is performed by pressing the butt,
The bead rises and the wall thickness becomes larger than the base metal, but it is difficult to apply pressure welding to a thin plate with a base metal thickness of about 1 mm, and fusion welding by arc welding, TIG welding, electron beam welding, etc. is used. Is often done. However, welding tubes by fusion welding, especially welding tubes by fusion welding in non-consumable electrode type,
Since only the butted portion is melted and solidified and joined, the bead thickness may be smaller than the base material thickness (hereinafter, referred to as thickness reduction). For this reason, welding conditions are set so as not to cause wall thinning and welding is performed under strict control, but it is also important to actually measure and confirm the presence or absence of wall thinning.

[0004] The thickness of the bead may be measured to confirm the thickness reduction. For this purpose, a welded pipe is usually cut and its cross section is measured using a micrometer or a projector. However, this method is a destructive inspection and cannot be applied inline. Further, non-destructive thickness measurement can be performed by using ultrasonic waves, but there is a limitation on the measurement speed because the probe is scanned. Inspection of the welded portion in the above-mentioned known example 1 can be performed in-line by measuring the bead portion size of the surface of the welded portion using a light cutting method, but the purpose is to determine the metal flow angle as a bead shape. It is to calculate. In the second known example, the bead size of the surface of the welded portion is similarly obtained by using the light cutting method. However, the heat input of the weld is controlled based on the detection results. These are all related to the manufacture of ERW pipes by pressure welding, in which abutting portions formed by shaping a hoop material into a substantially circular shape are heated and pressed while being pressed, and the beads are raised from the base material as described above. Formed,
Its thickness is thicker than the base material. Therefore, the purpose and action of the inspection based on the difference in the welding method are different from the fusion welding of the base material of a thin plate as in the present invention, and cannot be applied to the thinning inspection. SUMMARY OF THE INVENTION An object of the present invention is to provide a method and an apparatus for inspecting a welded portion, which can be inspected without destructive inspection, preferably in-line, without reducing the thickness of a welded portion obtained by butt-welding thin plates. An object of the present invention is to provide a welded pipe for piping which is manufactured and has a stable wall thickness.

[0005]

SUMMARY OF THE INVENTION According to the present invention, there is provided a method for reducing the thickness of a weld bead when the base material of a thin plate is butt-welded and has a thinner portion than the thickness of the base material. The determination is made based on the surface properties of the welded portion 1 shown in FIG. In addition, the surface referred to here is the side on which the welding operation is performed, and refers to the outer peripheral side if it is a welded pipe, and the surface texture refers to the shape, surface roughness, reflectance at the time of light irradiation, pattern, and the like. . The welded portion 1 includes a base material manufactured by rolling, a weld bead solidified after the base material is melted, and a boundary portion that is a transition region between the base material and the weld bead. And the difference in internal organization resulting therefrom, and the present invention utilizes the difference in the characteristics.

According to an embodiment of the present invention, a substitute characteristic in which the feature of the surface shape of a weld is expressed by a mathematical expression is used to determine whether or not the substitute specific value is within an allowable range with a predetermined threshold value to judge wall thinning. I do. As substitute properties, the amount of depression indicating the unevenness of the weld bead, the fourth-order approximation formula indicating the shape of the weld bead, the butting angle indicating the butting state of the base material, the bead width or bead width indicating the degree of welding, and the welding There is a ratio of the pipe outer diameter, etc., but in any calculation, the boundary point where the boundary between the base metal and the weld bead appears on the surface when the welded section is taken in a direction substantially orthogonal to the welding progress direction Is used. The boundary point is a point where a surface property different from the surface property of the base material appears, and is detected as a boundary point among the surface properties represented by the above-described shape, surface roughness, reflectance at the time of light irradiation, and pattern. It can be selected according to the characteristics that are easy to use and the measurement accuracy of the measuring equipment used.

Hereinafter, a method for judging thinning of the present invention using some substitute characteristics will be described with reference to FIG. First, the case where the amount of depression is used as a substitute characteristic will be described. The depression amount is represented by the distance from the boundary point between the base material and the weld bead to the uneven point of the weld bead. For example, a straight line connecting the boundary point between the base material and the weld bead is defined as the reference line 10, and the reference line 10 The lower depression amount 25 which is a vertical distance to the depression point 20 which is a depression point of the welding bead, and the vertical distance from the right apex 23 which is the most apex of the projection points of the welding bead to the depression point 20 to the reference line 10. Is obtained. An allowable range is set for each depression amount, and when at least one of the depression amounts is out of the allowable range, it is determined that the thickness is reduced.

Next, the case where the abutment angle is used will be described. The butting angle is an angle representing the abutting state of the base material, a reference line 10 which is a straight line connecting a boundary point between the base material and the weld bead, a tangent line 11 drawn in the tangential direction of the base material at the boundary point, and 12 based on the intersection angle with the welding bead 12, the left butting angle 13 with respect to the left boundary point of the welding bead, the right butting angle 14 with respect to the right boundary point, and the intersection angle between the two tangents. The three types of base material butting angle 15 that can be obtained even when the butting angles are added can be used as appropriate. An allowable range is set for each butting angle, and if the hitting angle deviates from the allowable range, the thickness is reduced. Is determined. The determination of thinning may be performed by using the above-described substitute characteristics alone, or may be determined by appropriately combining a plurality of alternatives. Note that the substitute characteristics shown here are merely examples, and as described above, the substitute characteristics may be obtained by quantifying features such as the degree of unevenness of the welded portion, the shape balance, and the angle of each portion.

Further, the present invention provides an apparatus for inspecting a welded portion in a case where a weld bead when a thin plate base material is butt-butted and fusion-bonded has a thick portion thinner than the base material thickness. Means for measuring the surface shape of a cross section in a direction substantially orthogonal to the welding progress direction of the welded part consisting of the base material and the weld bead adjacent to the weld bead, and means for detecting a boundary point between the base material and the weld bead Control means for determining a predetermined point of the weld bead based on the data from each of the means, calculating a predetermined substitute characteristic, and comparing the substitute characteristic value with a threshold value to determine wall thinning. And The welding portion inspection method or the welding portion inspection device of the present invention is effective when applied to a case where a thin plate hoop material is formed into a substantially tubular shape and a welded portion for a pipe formed by fusing a butt portion is inspected for thinning. In particular, in a continuous pipe-making line, it is more effective when inspecting in-line wall thinning. In addition, the welding pipe to be used is preferably a pipe having a thickness of about 1 mm and formed by fusion welding without adding a filler material by TIG welding.
It is more effective when applied to a thinner one such as mm.

A pipe welding pipe according to the present invention is a pipe welding pipe manufactured in a continuous pipe manufacturing line having a process of forming a hoop material into a substantially tubular shape and fusing the butted portions together. In the case where the weld bead has a thicker portion than the base material thickness, the thinning is inspected based on the surface properties of the welded portion composed of the base material and the weld bead adjacent to the weld bead, and the inspection data is obtained. The molding or fusion welding process is fed back to the molding and fusion welding process to control the molding or fusion welding conditions, so that the thickness reduction range is within a predetermined value.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The present inventors reduced the thickness of a thin hoop material having a thickness of about 1 mm by using a welded pipe in which only a base material was melted without adding a filler material by a TIG method and joined. And the relationship between bead surface shapes. FIG. 3 is a schematic view showing a cross section of the welded portion 1 for explaining the present invention.
The welded portion 1 is a portion surrounded by a substantially circular mark, and is a portion composed of a bead and a base material (also referred to as a base material portion) adjacent to the bead.
When the hoop material is formed into a tubular shape, the bead 4 has a left base material portion 2 shown on the left side in the drawing on one side and a right base material portion shown on the right side in the drawing on the other side. No. 3 is solidified after melting by the heat of the electrode. The bead 4 is divided into a left solidified region 5 solidified from the left base material portion 2 and a right solidified region 6 solidified from the right base material portion 3, and a joint between the two solidified regions is referred to as a joint. Further, a portion where the boundary between the left base material portion 2 and the left solidification region 5 appears on the surface is a left boundary point 7, and a portion where the boundary between the right base material portion 3 and the right solidification region 6 appears on the surface is a right boundary point. Called 8.

FIG. 4 schematically shows the state of formation of the bead 4 in the welded portion 1. FIG. 4A shows a normal weld where the thickness of the bead 4 is larger than the thickness of the base materials 2 and 3. The thickness of the bead 4 is referred to as the minimum dimension value. However, in welding in which thin plates are butt-welded without pressing the base material and without adding a filler material, the bead is slightly recessed at the joint. In many cases, the thickness of the hollow portion is targeted. FIG. 4B shows an example in which the depression at the joining portion becomes conspicuous and the wall thickness is reduced. This occurs because the amount of melting of the base material is insufficient due to fluctuations in welding conditions and the like. FIG. 4C shows an example in which the thickness of the bead 4 is uniformly reduced and the thickness of the bead 4 is reduced. When the hoop material is formed into a tubular shape, it occurs when the base materials 2 and 3 on both sides are slightly opened.

With respect to the above-mentioned wall thinning phenomenon, several types of substitute characteristics obtained by formulating the surface shape state were obtained, and the relationship between the substitute characteristic values and the wall thinning was examined in detail. It has been found that evaluation can be made particularly well. 1) Depression amount of bead As a result of examining a thinned product as shown in FIG. 4 (b), the depressed amount and reduced thickness of the bead surface appearing on the outer surface without looking at the bead surface on the inner diameter side which cannot be seen from the outer surface. Was found to be related by experiments. The correlation between the method of calculating the depression amount and the wall thickness reduction will be described later. 2) Abutment angle of base material As a result of examining a thinned product as shown in FIG. 4 (c), the molding state of the base material immediately before welding, which can be represented as an abutment angle, that is, opening of the base material It was found through experiments that thinning occurs depending on the condition. The relationship between the butting angle calculation method and the wall thickness reduction will be described later.

Hereinafter, the present invention will be described based on the above findings. FIG. 1 shows an example of the configuration of a weld inspection apparatus according to the present invention. Although not shown, the welded pipe is manufactured continuously by forming a hoop material into a continuous cylindrical shape, and TIG welding abutting portions facing each other along the longitudinal direction. It is moving at a constant speed in the direction of the arrow. The slit light projector 50 is installed such that the slit light 51 is irradiated obliquely from above, and the light cutting line 52 crosses the welded portion 1 substantially orthogonally to the longitudinal direction of the welded pipe. The imaging device 53 is arranged in a direction different from that of the slit light projector 50, and an image of the welding portion including the light cutting line 52 is taken and the image
4

The imaging information relating to the light-section line captured by the image processing device 54 is sent to a surface shape calculation unit 541, and a light-section image 100 as shown in FIG. 2A is obtained. Since the light-section line 52 has a higher brightness than the other parts, the light-section line image 521 is clearly displayed, and represents the contour of the outer surface of the welded portion 1 (hereinafter simply referred to as the surface). Therefore, based on the shape change of the light-section line image 521, the surface shape can be obtained by a known method, and the uneven point of the bead and the boundary point between the base material and the bead can be detected. However, depending on how the beads are generated, the base material portion and the bead surface are smoothly continuous, and as schematically shown in FIG.
In some cases, it is difficult to catch the shape change at the boundary between the base material portion and the bead on the base material 21.

As a means for coping with this, a welding surface illumination device 55 is provided. The welding portion surface illumination device 55 is provided above a position where the light cutting line 52 is generated, and illuminates the welding portion 1 with scattered light. The reflected light from the surface of the weld is picked up by the same image pickup device 53 as described above and sent to the image processing device 54. The imaging information relating to the captured surface reflected light is transmitted to a bead boundary detection unit 5.
42, and a weld surface image 110 as shown in FIG. 2B is obtained. The base metal part and the bead are different in the surface roughness due to the difference in the production process between the rolled surface and the free solidified surface of the molten metal, the difference in the amount of light reflected from the surface due to the light reflectance, etc. Due to the difference in curvature and inclination, for example, when a monochrome CCD element is used, the base metal part 2,
3 and bead 4 have different shades. Therefore, by the known edge extraction processing, the boundary images 71 and 8 connecting the edges are obtained.
1 can be clearly detected. In the present measuring device, the boundary points 7 and 8 are obtained as points on the boundary line images 71 and 81.

The slit light projector 50 has a strobe light source 57 for projecting a slit light, and a welding surface illumination device 55.
Is connected to a strobe light source 58 for illuminating the surface of the welding portion, and the light emission timing of each strobe light source is controlled by a central control unit 56. Therefore, the light cutting line image 100 and the welded portion surface image 110 are imaged by the same imaging device 53 with a time lag due to the light emission timing. By determining the light emission timing based on the moving speed of the welding pipe and the imaging field of view, it is possible to image the welded portion where the light cutting line image 521 has been captured so as to be present in the welded portion surface image 110.

The obtained information of the light-section line image 100 and the welded portion surface image 110 is sent to the surface shape feature calculation unit 543. The surface shape feature calculation unit 543 calculates the boundary points 711 and 8 between the base material and the bead on the light section line image 521 based on both images.
11 and a predetermined substitute characteristic value is determined.
To send to. The central control unit 56 compares the substitute characteristic value with a preset threshold value and determines whether or not the thickness is reduced.

Although it is difficult to strictly specify the boundary point of the welded portion where the light section line image 521 is obtained from the boundary line images 71 and 81 appearing in the welded portion surface image 110, it is usually within one screen area. The variation of the boundary line image is very small, and the average luminance change is obtained by averaging the luminance of the boundary line image in the longitudinal direction of the weld, for example, using a known image processing technique, and the average luminance change is obtained from this luminance change point. There is no particular problem even if the position that is set as the boundary point.
As described above, the light section line image 100 and the weld portion surface image 110 can be captured instantaneously, and the image processing and the comparison determination process can be performed at high speed. At the same time, the thinning determination processing can be performed in a non-destructive manner and inline in a continuous pipe-making line.

Although the present invention has been described above with respect to the case where the light-section line image and the weld surface image are separately obtained by changing the timing with the same image pickup device, the light-section line image and the weld surface image are simultaneously captured. You can also. in this case,
For example, using a light source of a different wavelength for the slit light and the welding part illumination, the image pickup device performs spectroscopy or selective extraction of only a specific wavelength to separate the light cutting line image and the boundary line image, or the slit light is used as the welding part illumination light. By dividing the light section line image and the boundary line image by increasing the intensity to a greater extent and superimposing and displaying them on one screen, a boundary point can be easily obtained in the light section line image. In addition, even if the light section image and the weld surface image are not necessarily captured by the same imaging device, if the imaging device corresponding to each illumination is prepared, each imaging position can be separated, and the speed of the welding pipe and the imaging position can be separated. If the image is taken at a time shifted by the time determined by the distance, images at almost the same location can be obtained. When the base material and the bead are not smoothly continuous and the boundary points 711 and 811 can be identified on the light-section line image 521, the welding portion lighting device 55 is not necessarily used.

Next, a description will be given of a method of calculating the substitute characteristics and the relationship with the thickness reduction. First, the amount of depression will be described.
In FIG. 3, a left boundary point 7 on the surface portion forming a boundary between the left base material portion 2 and the left solidification region 5 and a right boundary point 8 on the right base material portion 3 side are similarly obtained. A reference line 10 passing through the point 8 is drawn. The depression point 20 is the lowest part of the concave portion on the surface of the bead 4 and mainly occurs at the joint. The depression amount can be represented by a lower depression amount 25 and an upper depression amount 24 with the depression point 20 as a boundary. The lower depression amount 25 is a vertical distance between the straight line 21 passing through the depression point 20 parallel to the reference line 10, and the upper depression amount 24
Draws a straight line parallel to the straight line 21 and passing through the left vertex 22 of the left coagulation region 5 and the right vertex 23 of the right coagulation region 6, and sets the distance as the larger distance.

Next, the butting angle will be described. At the left boundary point 7 and the right boundary point 8, a left tangent line 11 and a right tangent line 12 that are in contact with the surface of each base metal part are drawn, and the angle formed by the reference line 10 and the left tangent line 11 is defined as a left butting angle 13;
The angle between 0 and the right tangent 12 is referred to as a right abutment angle 14. Further, an angle formed by the left tangent 11 and the right tangent 12 is defined as a base material abutment angle 15. The base material abutment angle 15 is
It is also an angle obtained by adding the left butting angle 13 and the right butting angle 14. When forming a hoop material to manufacture a welded pipe, it is important to maintain these three types of butting angles within a predetermined value range.
Is important.

FIGS. 5 and 6 show an example of measurement results showing the relationship between the amount of depression and the reduction in thickness when an experiment was performed on a welded pipe having a base material thickness of 0.2 mm and an outer diameter of 18 mm. . The vertical axis in FIG. 5 is the lower depression amount 25 in which the distance from the reference line 10 to the depression point 20 is described with the outer diameter direction being the positive direction. The vertical axis in FIG. 6 is an upper dent amount 24 in which the distance from the dent portion 20 to the predetermined vertex is also described with the outer diameter direction being the positive direction. The abscissa indicates the number of the sample product. In FIGS. 5 and 6, the same number indicates the same sample. 1 to 20 are thinned products. As shown in FIG. 5, the lower dent amount 25 is a predetermined value stably for a non-thinned product, in this example, 4
While the thickness is 0 μm or more, the thickness of the thinned product is less than the predetermined value, and some of them have a negative value.
Is inside the reference line 10, and it can be presumed that it is almost a thinned product. That is, it can be said that the thinned product has a small amount of bead rising from the base material. From this, a predetermined threshold is determined and an allowable range is set,
Those deviating therefrom can be determined to be thin.

As shown in FIG. 6, the upper dent amount 24 is stably a predetermined value for a non-thinned product, that is, 6 μm or less in this example, while the thinned product is not less than the predetermined value. Has a very large value. If the value is large, the unevenness of the surface is large, and it can be estimated that welding is not performed stably, and it is assumed that such a thing has a high possibility of thinning, and a predetermined threshold value is used as described above. Is determined and an allowable range is set, and a product deviating therefrom can be determined as a thinned product. As described above, the thinning determination using the upper dent amount 24 and the lower dent amount 25 has been described. However, any one or both of them may be appropriately combined to determine the thinning, or the two dent amounts may be determined. The sum may be added to the criterion as a new factor.

FIG. 7 shows an example of measurement results showing the relationship between the base material abutment angle 15 and the wall thickness reduction. This sample is different from the one used in the above-mentioned experiment, and is made with different molding conditions of the hoop material. 1 to 20 are thinned products. As is apparent from the figure, the base material abutment angle 15
It can be seen that if the value is within a predetermined value, in this example, within 22 degrees, no thinning occurs. From this, it is possible to determine a predetermined threshold value and set an allowable range also in terms of the abutting angle, and determine that a value outside the allowable range is a thinning. In addition,
Although the data for the left butting angle 13 and the right butting angle 14 are not shown, the basic concept is the same in this case as well. The butting angle may be the angle shown in FIG. 3 or its supplementary angle, and an allowable range may be set according to the supplementary angle. In addition, the dimensions, material,
It is desirable that the abutment angles are appropriately combined from the above-mentioned substitute characteristics or used in combination with the above-described determination based on the amount of depression according to manufacturing conditions, inspection specifications, and the like.

As described above, the surface of the welded portion is measured in a non-contact manner, the amount of depression and the abutment angle are calculated, compared with the respective allowable ranges, and reduced if at least one of the allowable ranges is not satisfied. It can be quickly judged that it is meat. Therefore, in a continuous pipe production line such as welding pipe production from hoop material, thinning information can be collected in-line in real time, and by controlling welding conditions and hoop material forming conditions, stable quality can be obtained. Welded pipes can be manufactured with high productivity. The target is TI
The present invention is not limited to the welding pipe by G welding, and can be applied to other welding products and welding methods, but is particularly suitable for a welding method by fusion.

For measuring the surface shape of the welded portion, in addition to the light cutting method used in this case, a method using moire fringes or light interference, a multi-view three-dimensional measurement method, an ultrasonic wave or a method using light from the surface. A similar effect can be obtained by using a length measurement method using reflection or the like. In addition, the welding part inspection method of the present invention can be applied not only in-line but also off-line. In this case, the surface contour shape may be obtained by a contact type length measuring device or a surface roughness meter.

As a method for detecting the boundary between the base material portion and the bead portion, in addition to the method of illuminating the welded portion and obtaining the reflected or scattered light as an image, it is not always necessary to capture the light as an image. Without using the fact that the bead part and base material part have different surface properties due to the generation process, such as surface roughness, scan the spot beam and detect the reflected or scattered light with a photodetector. You can also use the method. Also, by utilizing the fact that the structures of the bead and the base material are different, it is also possible to irradiate the welded part with radiation such as X-rays and gamma rays and to grasp the intensity distribution of the radiation transmitted through the welded part.

[0029]

As described above, according to the present invention, it is possible to determine whether or not the thickness is reduced by merely measuring the surface properties of the welded portion, so that the inspection can be performed nondestructively. Furthermore, it is possible to accurately determine a boundary point even for a bead having little swelling which is seen when a thin plate is butt-welded and welded, and the accuracy of the substitute characteristic is improved, so that a highly reliable thinning inspection is performed. be able to. In addition, since it is manufactured through a highly reliable inspection process for wall thinning, it is possible to provide a welded pipe for piping with less variation in quality related to wall thinning.

[Brief description of the drawings]

FIG. 1 is a view showing a configuration of a weld inspection apparatus according to the present invention.

FIG. 2 is a diagram showing a light section line image and a surface image of a weld obtained by a weld inspection apparatus.

FIG. 3 is a view showing a cross section of a welded portion for explaining wall thinning.

FIG. 4 is a diagram showing the relationship between the formation of a weld bead and the reduction in thickness.

FIG. 5 is a diagram showing an example of a measurement result showing a relationship between a lower depression amount and a wall thickness reduction.

FIG. 6 is a diagram illustrating an example of a measurement result indicating a relationship between an upper depression amount and a wall thickness reduction.

FIG. 7 is a diagram showing an example of a measurement result showing a relationship between a base material abutment angle and wall thickness reduction.

[Explanation of symbols]

1 ... welded part 2 ... left base material part 3 ... right base material part 4 ...
Bead: 5: Left coagulation zone, 6: Right coagulation zone, 7: Left boundary point, 8: Right boundary point, 10: Reference line, 11: Left tangent line,
12 right tangent, 13 left contact angle, 14 right contact angle, 15 base material contact angle, 20 depression, 24 upper depression amount, 25 lower depression amount, 51 slit light, 52 ... Light cutting line, 53 ... Imaging device, 54 ...
Image processing device, 55: Welding surface illumination device, 56: Central control unit, 57: Strobe light source for slit light projection, 58 ...
Strobe light source for welding surface lighting,

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Yoshihiro Usami 2nd Daifuku, Kuwana-shi, Mie Inside Kuwana Plant of Hitachi Metals, Ltd.

Claims (8)

[Claims] 1. A method for reducing the thickness of a weld bead when a thin base material is butt-butted and fusion-bonded to a base material adjacent to the weld bead, wherein the thickness of the weld bead is smaller than the thickness of the base material. A method for inspecting a welded portion, wherein the determination is made based on the surface properties of the welded portion. 2. A predetermined substitute characteristic is calculated by using a boundary point where a boundary between a base metal and a weld bead on the surface of a welded section in a direction substantially orthogonal to the welding progress direction appears on the surface;
The welding part inspection method according to claim 1, wherein the thinning is determined by comparing the substitute characteristic value with a predetermined threshold value. 3. The welding part inspection method according to claim 2, wherein the substitute characteristic is a depression amount representing a state of the weld bead unevenness based on the boundary point and the unevenness point of the weld bead. 4. The substitute characteristic is a striking angle representing a striking state of the base material based on a straight line connecting two boundary points and a tangent drawn in the tangential direction of the base material at the boundary points. The method for inspecting a weld portion according to claim 2. 5. The method according to claim 1, wherein the hoop material is formed into a substantially tubular shape, and the thickness of the welded pipe for pipe formed by fusing the butted portions is inspected.
5. The weld inspection method according to any one of claims 1 to 4. 6. An apparatus for inspecting a thinning of a weld bead when a thin base material is butt-butted and fusion-bonded has a thinner portion than a thickness of the base material, wherein the weld bead is adjacent to the weld bead. Means for measuring the surface shape of the cross section in a direction substantially perpendicular to the welding progress direction of the welded portion consisting of the base material and the weld bead, means for detecting the boundary between the base material and the weld bead, and data from the respective means. A welding part inspection apparatus comprising: a control unit for calculating a predetermined substitute characteristic based on a predetermined point of a weld bead based on the calculated characteristic value, and comparing the substitute characteristic value with a threshold value to determine thinning. 7. A pipe-shaped welded pipe formed by fusing a hoop material into a substantially tubular shape and welding the butted portions to each other.
4. The weld inspection device according to claim 1. 8. A welded pipe for piping manufactured in a continuous pipe-forming line having a process of forming a hoop material into a substantially tubular shape and fusing the butt portions, wherein after the pipe-forming, the weld bead is formed from the thickness of the base material. The thinning, which is a case having a thin wall, is inspected based on the surface properties of the welded portion consisting of the base metal and the weld bead adjacent to the weld bead, and the inspection data is fed back to the forming and fusion welding processes. And a welding pipe for a pipe manufactured by controlling a forming or fusion welding condition so that a thickness reduction range is within a predetermined value.