JP2000111328A - Method for inspecting welding part of welding pipe - Google Patents

Abstract

PROBLEM TO BE SOLVED: To successively and reliably the reduction of the thickness of a welding part by measuring the thickness of a part where fused metal is finally coagulated by an ultrasonic wave. SOLUTION: A welding pipe 3 is being moved in a direction market by an arrow A at specific speed. A joint-line detection sensor 1 is arranged while the sensor opposes a welding part. In the case of measurement, the welding pipe 3 passes through a water tank for traveling, and an ultrasonic probe 2 is also arranged under water. The ultrasonic probe 2 is arranged closest to the joint-line detection sensor 1. When the joint-line detection sensor 1 is provided on a water surface, a polarization filter is provided to eliminate the influence of reflection due to the wave of the water surface. Furthermore, when merely an objective-lens system such as an endoscope is provided under water, an image can be picked up at a position closer to the ultrasonic probe 2. When a tire-type probe or the like is used, the thickness of an ultrasonic wave can be measured without allowing the welding pipe 3 to pass under water, thus simplifying the configuration of a device.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to inspection of a welded portion of a welded pipe.

[0002]

2. Description of the Related Art Japanese Patent Application Laid-Open No. 56-35057 discloses a method for inspecting a welded portion of a welded pipe. This is because, in an ERW pipe, after grinding the inner and outer peripheral surfaces of the welded part, the ultrasonic thickness gauge is periodically reciprocated in the circumferential direction of the pipe around the welded part, and the thickness output by the ultrasonic thickness gauge is measured. The purpose is to detect the inner surface grinding shape of the welded portion of the electric resistance welded pipe based on the locus.

[0003]

A welded pipe having a perforated portion at the welded portion is not only weak in strength but also fatally defective particularly for a welded pipe for piping. It has been strictly inspected. But,
At the time of eddy current inspection, even if there is no drilling defect, a hole may be generated when stress is applied by the subsequent manufacturing process, especially when the wall thickness is small because the welding strength is originally low. Easy to come. However, there is no welding strength inspection method that can foresee the part where there is a possibility of drilling in advance, so it is dealt with by welding so that the thickness of the molten metal part is greater than the base material thickness. . In pressure welding performed by pressing the butted portion, the molten metal portion rises and the wall thickness becomes larger than that of the base metal, but arc welding, TIG
In a welded tube formed by fusion welding such as welding and electron beam welding, the thickness of a molten metal portion may be smaller than the thickness of a base material (hereinafter, referred to as wall thinning). 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.

[0004] As a method of judging wall thinning, there is a method of measuring the thickness of a molten metal portion on a cross section of a welded pipe using a micrometer or a projector, but it is a destructive inspection and cannot be applied inline. On the other hand, in the above-mentioned known example, it is possible to detect whether or not the wall thickness is reduced, but the ultrasonic probe must be periodically swung over the welded area to detect the thickness of both the molten metal part and the base material. In addition, a high-speed pipe-forming line has a welded portion that cannot be measured, and there is a problem in reliability of the inspection. An object of the present invention is to provide a method for inspecting a welded portion, which can reliably determine thinning in the manufacture of a continuously manufactured welded pipe.

[0005]

SUMMARY OF THE INVENTION The present invention relates to a method for inspecting a welded portion of a welded pipe formed by forming a hoop material into a tube and welding an abutting portion. It is characterized in that the thickness is measured with an ultrasonic wave, and whether the thickness is reduced is determined by comparing the dimension value with the thickness of the base material. Further, the portion where the molten metal solidifies last may be detected optically. As an optical detection method, the molten metal portion may be two-dimensionally imaged by a TV camera using a two-dimensional image sensor to detect luminance in a predetermined area, or a one-dimensional image sensor may be used. The line sensor camera may be arranged so that the imaging direction is orthogonal to the welding pipe, and the luminance detection in the linear area may be sequentially performed in accordance with the movement of the welding pipe. The present invention also relates to a method for inspecting a welded portion of a welded pipe formed by forming a hoop material into a tubular shape and fusing the butted portion. The thickness of the portion is detected by ultrasonic measurement of the thickness of the portion, and whether the thickness is reduced is determined by comparing the dimension value with the thickness of the base material. The fusion welding is preferably performed by TIG welding without adding a filler material. This is because the brightness of the molten metal portion solidified last is different from that of the peripheral portion, and the identification becomes easy.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a diagram schematically showing a device configuration for explaining the present invention. The welding pipe 3 is manufactured by continuously forming a thin (about 0.1 mm to 2 mm) hoop material into a cylindrical shape and TIG-welding abutting portions facing each other in the longitudinal direction. (The manufacturing apparatus is not shown) and is moving at a predetermined speed in the direction of arrow A shown in the figure. In addition, a molten metal part is hereafter called a bead. The joining line detection sensor 1 is a sensor that is arranged so as to face a welded portion which is a region including a bead of the welded pipe 3 and a surrounding base material, and obtains imaging information of the welded portion, and is a two-dimensional imaging device such as a TV camera. Means may be used, but it is also possible to use a one-dimensional imaging means such as a line sensor camera and arrange and use the imaging device so as to be substantially perpendicular to the longitudinal direction of the welded pipe. A probe (hereinafter, abbreviated as an ultrasonic probe) 2 of an ultrasonic thickness gauge is provided downstream of the joining line detection sensor 1. The ultrasonic thickness gauge mentioned here refers to a device that can measure the thickness by ultrasonic waves, including an ultrasonic flaw detector. Ultrasonic probe 2
Are arranged movably in the circumferential direction B of the welded pipe in accordance with information from the joining line detection sensor 1.

FIG. 2 shows a photograph of a halftone image displayed on a display by imaging the surface of the welded portion with a TV camera. The welds can be identified on the image in three ways: the bead, the base material on both sides thereof, and the joining line on the bead. The joining line 4 is a band-like portion connecting the last solidified portions in the bead, and is located substantially at the center of the bead. The joining line 4 is a black-and-white image and is usually observed as a bright image. This is because the solidification phenomenon in the bead progresses sequentially from the base metal part side, but in the final solidification part in the center part, solidification structures from both directions are crowded,
This is probably because the reflection intensity on the surface is increased and the luminance is increased. The joining line 4 is displaced from the absolute coordinates of the traveling line due to a change in the position of the welding electrode due to the lateral displacement of the welding pipe. The joining line detection sensor 1 images this joining line,
The information is output to a control device (not shown). The control device extracts a bright portion by a known image processing method to detect the joint line 4, calculates a center line of the joint line 4, calculates a displacement, and connects the downstream ultrasonic probe 2 to the joint line. A control command is output based on the amount of displacement so as to be at the center of the joining line 4.

In order to automatically perform ultrasonic thickness measurement, a liquid, for example, water is used as a medium. Therefore, the welding pipe 3 is made to run through a water tank, and the ultrasonic probe 2 is also arranged in water. I do. In addition, even if the position of the joint line 4 fluctuates, the ultrasonic probe 2 and the joint line detection sensor 1 are brought as close as possible so that the ultrasonic probe 2 can accurately measure the part imaged by the joint line detection sensor 1. It is desirable to arrange. Therefore, the joining line detection sensor 1 may be arranged so as to image the welding pipe 3 before entering the water tank, but may be provided on the water surface of the water tank near the ultrasonic probe 2. In this case, it is preferable to provide a polarizing filter so as to remove the influence of the reflection caused by the wave on the water surface and image the joining line 4. Further, the joint line detection sensor 1 can be provided in water as a waterproof type. Furthermore, if only an objective lens system such as an endoscope or a fiberscope is provided in water, an image can be taken at a position closer to the ultrasonic probe 2. In addition, if a known tire type probe or a water immersion type probe is used, the ultrasonic thickness measurement can be performed without passing the welding pipe 3 through water, and the apparatus configuration is simplified. Ultrasonic probe 2
It is good to use a point focus type probe,
The thickness in a certain length range may be averagely measured using a line focus type probe along the longitudinal direction of the joining line.

FIG. 4 schematically shows the cross-sectional shape of the bead at the welded portion. In the bead shape, the portion that solidifies last is often a depression, and the thickness of the bead in the depression is referred to as the joining line thickness. FIG. 4A shows a normal welded portion having a small depression and a joining wire thickness larger than the thickness of the base material portion. FIG. 4B shows an example in which the depression becomes conspicuous, the joining line thickness becomes smaller than the thickness of the base material portion, and the thickness is reduced. The thinning occurs due to the fact that the melting amount of the base material portion is insufficient due to a change in welding conditions or the like.

FIG. 3 shows a comparison between the distribution of the thickness of the bead in the direction orthogonal to the joining line 4 measured by an ultrasonic thickness gauge and the distribution obtained by cutting the relevant portion and obtaining the cross-sectional shape. .
The width of the bead was about 1 mm, and the thickness was about 0.2 mm, which indicates that they were in good agreement. The concave portion at the approximate center of the bead is the joint line portion. From this, the joining line is detected from the image of the welded portion, the thickness at that portion is measured with an ultrasonic thickness gauge, and the thickness is reduced by comparing the thickness with the thickness of the base material portion. It can be seen that the judgment can be made. In addition, when the thickness around the joining line is measured by using the electronic scanning probe, more thickness information can be obtained, and the thinning can be determined more accurately.

[0011]

As described above, according to the present invention, it is possible to determine whether the thickness is reduced by determining the position of the joint line and measuring the weld at that position with an ultrasonic thickness gauge.
The inspection can be performed in-line without using the destructive inspection. Since the thickness measurement with the ultrasonic thickness gauge can be performed at high speed,
It is possible to continuously collect real-time information on the quality of a weld during manufacturing, and control welding conditions and hoop material forming conditions. As a result, a welded pipe having a stable quality can be manufactured with high productivity. As described above, the description has been given of the welding pipe by TIG welding. However, the welding method is not limited to this and can be applied to other welding methods.
In particular, it is suitable for welding pipes by fusion.

[Brief description of the drawings]

FIG. 1 is a diagram showing an outline of a device arrangement for explaining the present invention;

FIG. 2 is a photograph of a halftone image obtained by imaging a surface of a welded portion and displaying the image on a display.

FIG. 3 is a diagram showing a thickness distribution measured by an ultrasonic thickness gauge and a thickness distribution measured from a cross-sectional shape;

FIG. 4 is a schematic view of a cross-sectional shape of a bead at a weld portion.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Joining line detection sensor 2 Ultrasonic probe 3 Welded pipe 4 Joining line

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2F068 AA28 BB03 BB09 BB23 CC00 CC16 DD07 FF03 FF14 FF18 JJ22 KK04 KK12 LL02 LL04 LL23 NN02 PP01 PP06 TT07 2G047 AA07 AB01 AB07 BC18 EA11 GE02

Claims (3)

[Claims] 1. A method for inspecting a welded portion of a welded pipe formed by forming a hoop material into a tube and welding an abutting portion, wherein a thickness of a portion where a molten metal solidifies last is measured by ultrasonic measurement. ,
A method for inspecting a welded portion of a welded pipe, comprising determining whether or not the thickness is reduced by comparing the dimension value and the thickness of the base material. 2. The method according to claim 1, wherein a portion where the molten metal solidifies last is optically detected. 3. A method for inspecting a welded portion of a welded pipe by forming a hoop material into a tubular shape and fusing the abutting portion, wherein an image of the welded portion is obtained, and the brightness of the molten metal is substantially different from that of the periphery at a substantially central portion on the molten metal. A welded pipe characterized in that the thickness of the portion is detected by ultrasonic measurement of the thickness of the portion, and the thickness is compared with the thickness of the base material to determine whether the thickness is reduced. Welding inspection method.