JP2008286639A - Coupling check method of ultrasonic oblique angle flaw detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily perform a coupling check even in an oblique angle flaw detection with tandem constitution. <P>SOLUTION: This device is provided with a transmitting part 6 which transmits ultrasonic 8 to an inspected object 1 (steel pipe 1) and a receiving part 7 receiving a part or whole of the reflected wave 9 from the inspected object. The transmitting part 6 and the receiving part 7 are equipped with a transmitting/receiving part composed of one or two or more different oscillator groups on an array probe 5, and an ultrasonic beam 8 having wider opening width is converged and transmitted to the inspected object 1. When coupling check is performed, the width of the opening part of the ultrasonic beam is reduced compared with the case of detecting flaw, and the ultrasonic beam having low directivity is hit against the surface of the inspected object 1 at right angle to detect surface echo. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a coupling check method for an ultrasonic oblique flaw detector, and more particularly, to an ultrasonic oblique flaw detector for accurately detecting minute defects generated in a welded portion of a welded steel pipe by ultrasonic flaw detection. The present invention relates to a coupling check method suitable for the above.

  In welded steel pipes, the quality of the welded part is very important, and in the manufacturing process, on-line flaw detection is generally performed 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. In general, for example, in an ERW pipe, a reflection method using an ultrasonic beam having a refraction angle of 45 ° at 5 MHz is applied. Detected.

  On the other hand, recently, quality requirements for welded steel pipes have become stricter, and detection of defects smaller than conventional ones has been required. For example, cold-welded defects and minute penetrators are used for electric-welded pipes, and blow holes are used for laser-welded pipes. These defects have a very small size of several tens to several hundreds of micrometers. In addition, the generation position may occur anywhere along the weld line from the inner surface to the outer surface, and the incident point and return point of the ultrasonic beam differ depending on the position of the defect. Because of these influences, there are many cases where detection cannot be performed by a conventional ultrasonic flaw detection method, and a technique capable of detecting with higher accuracy is required.

  As a method of detecting minute defects existing in welded parts such as welded steel pipes, a focus beam is formed by an array probe to improve the detection ability, and sector scanning scans from the inner surface side to the outer surface side of the welded portion. Thus, a technique that can detect a blowhole is known (for example, Patent Document 1).

  In such ultrasonic flaw detection, it is necessary to perform a coupling check to confirm whether or not the beam is properly incident on the inspection object from the probe before or during flaw detection.

  Therefore, in Patent Document 2, as shown in FIG. 6, ultrasonic transducers 62 of 1 to 64 CH, for example, are arranged circumferentially on the surface of a quarter cylindrical wedge 60, and are located above the apex of the wedge 60. It describes that a vertical flaw detection is performed using 16 ultrasonic transducers to detect a surface echo and perform a coupling check. In the figure, 1 is a steel pipe and 2 is a welded portion thereof.

Japanese Patent Laid-Open No. 11-183446 JP 2006-47328 A

  However, in the technique described in Patent Document 2, a wedge 60 having a curvature is required, and the position where the coupling check needs to be performed is one point (one point). There is a problem that it is limited to. In other words, there is a problem that it cannot be applied to the case of water immersion flaw detection without using a wedge, and it cannot be applied to a case where the area where the coupling check is performed is wide. Furthermore, even when a wedge is used, the wedge has a high sound speed and a large difference in attenuation due to the scanning line. Therefore, especially when the length of the scanning line is different as in a linear array probe, the fluctuation in sensitivity increases. There was also a risk that an accurate coupling check could not be performed.

  The present invention has been made in view of the above circumstances, and in ultrasonic flaw detection with a water immersion method and a wide area for performing a coupling check, an accurate coupling check can be easily performed without providing a separate check means. The challenge is to be able to do it.

  The invention according to claim 1 of the present invention includes a transmission unit that transmits ultrasonic waves to the inspection object, and a reception unit that receives part or all of the reflected waves from the inspection object, The transmission unit and the reception unit include a transmission / reception unit composed of different transducer groups on one or more array probes, and focuses and transmits an ultrasonic beam having a wide aperture width with respect to the inspection target. When performing a coupling check of an ultrasonic oblique angle flaw detector designed to perform the inspection, the aperture width of the ultrasonic beam is made narrower than that at the time of the flaw detection, and the ultrasonic beam with low directivity is applied to the surface to be inspected substantially perpendicularly, and surface echo is applied. It is a coupling check method of an ultrasonic oblique angle flaw detector characterized by detecting.

  In the invention according to claim 2 of the present invention, at the time of coupling check, the number of simultaneous excitations of the transducers on the array probe is made smaller than that at the time of flaw detection, thereby narrowing the aperture width of the ultrasonic beam. The coupling check method according to claim 1, wherein:

  The invention according to claim 3 of the present invention is the coupling check method for an ultrasonic oblique flaw detection apparatus according to claim 1 or 2, wherein the coupling check and the flaw detection are performed alternately.

  According to the present invention, even in the case of oblique flaw detection with a tandem configuration, an accurate coupling check can be easily performed without providing a separate check means. Also, when a wedge with a high sound speed is used, the incident angle becomes large, so the difference in attenuation due to the scanning line becomes large.In particular, in a linear array probe with a long length, sensitivity fluctuation due to position becomes a problem. According to the present invention, water with a low sound velocity can be used, so that it is possible to perform an accurate coupling check with less sensitivity fluctuations depending on the position than a wedge.

  An embodiment of the present invention is a tandem flaw detection in which an array probe is used to detect a difference between a transmitting transducer group and a receiving transducer group, and a welded portion of a welded steel pipe is detected by local water immersion. An example of such a case will be described below with reference to the drawings. FIG. 1 is a diagram illustrating a configuration example of the present invention. In the figure, 1 is a steel pipe as an object, 2 is a welded part, 3 is a defect in the thickness, 4 is water for transmitting ultrasonic waves, 5 is a linear array probe, and 6 is vibration for transmission. A child group, 7 is a receiving transducer group, 8 is a transmitted beam, and 9 is a portion (hereinafter also referred to as a received beam) that indicates an ultrasonic wave from a defect toward the receiving transducer group.

  Here, since it is a tandem flaw detection, as shown in FIG. 3, a part of the transducer group of the array probe is used as a transmission transducer group, and a predetermined focusing degree is set for each flaw detection position of the welded portion. The delay time is set for each transducer so that the light beams are converged by the above-mentioned distance and the predetermined deflection angle and the predetermined incident angle are obtained. Then, the ultrasonic transducer group using a transducer group different from the transducer group for transmitting after internal reflection so as to mainly receive the regular reflection component of the ultrasonic wave reflected by the welded portion Is controlled to be selected from among the array probes. Further, in order to improve detection ability, focusing is also performed in the tube axis direction using an acoustic lens or a curved vibrator. Although an example using one array probe will be described here, even if the flaw detection area is divided by two or more array probes, and each is used for transmission and reception, this The invention is applicable.

  Since the welded portion needs to be inspected over the range from the inner surface to the outer surface in the steel pipe thickness direction (tube diameter direction), as shown in FIG. 4, the receiving transducer group and the transmitting transducer group By controlling the position, the focal position of the ultrasonic wave changes in the thickness direction and is scanned. With respect to the pipe axis direction, all the welds of the pipe body can be inspected by mechanically moving the steel pipe or the probe. FIG. 1 and FIG. 3 show a timing state in which the focal point of the transmission beam and the reception beam coincides with the position of the defect 3 in the process of scanning in the thickness direction of the steel pipe. The ultrasonic beam propagates in the direction of. In addition, solid lines on both sides of the alternate long and short dash line indicate the widths of the transmitted beam 8 and the received beam 9, and alternate long and short dashed lines indicate the respective scanning lines.

  FIG. 5 shows a system configuration for performing flaw detection using the above-described array probe. In the object size input unit 30, values of the outer diameter and thickness of the steel pipe for flaw detection are input from an operator or a process computer. The array probe storage unit 31 stores the frequency, transducer pitch, and number of transducers of the array probe 5.

  In the transmission / reception control unit 32, the beam size, the position of the array probe for transmission, the number of transmission scanning lines, the transmission beam of each scanning line, according to the size of the steel pipe and the specification of the array probe. The path, the number of transducers of the transmission transducer group for each scanning line, the position of the transducer group for transmission, the focal length, and the deflection angle are calculated, and the delay time of each transducer is calculated for each scanning line. Each value determined in this way is referred to herein as an array transmission rule.

  The transmission / reception control unit 32 also determines the position of the array probe, the number of reception scanning lines, the path of the reception beam of each scanning line, and each scanning according to the size of the steel pipe and the specifications of the array probe. The number of transducers in the line receiving transducer group, the position of the receiving transducer group, the focal length, and the deflection angle are calculated, and the delay time of each transducer is calculated for each scanning line. Each of the above values determined in this way is referred to herein as an array reception rule. Furthermore, a defect detection gate position is determined based on the beam path calculated by the transmission / reception control unit 32 and stored in the gate position storage unit 33.

  Here, the array reception rule may be determined based on the previously obtained array transmission rule, or conversely, the array reception rule may be determined first and the array transmission rule may be determined based thereon. The array transmission rule and the array reception rule determined in this way are stored in the array transmission rule storage unit 34 and the array reception rule storage unit 35, respectively, and used for the following transmission / reception control.

  The array transmission unit 36 selects a transmission transducer group based on the array transmission rule stored in the array transmission rule storage unit 34, and generates a transmission pulse with a delay time added to each element. The array receiving unit 37 selects a transducer group for receiving waves based on the array receiving rule stored in the array receiving rule storage unit 35, adds a signal with a delay time to each element, and generates a flaw detection waveform. obtain. The gate unit 38 extracts a gate position signal stored in the gate storage unit 33.

  The defect determination unit 40 compares the defect determination threshold value input to the determination threshold value input unit 39 with the signal intensity in the gate, and determines that the defect is a defect if the signal intensity is equal to or greater than the threshold value. When the flaw detection for one scanning line is completed in this way, the next transducer group for transmission is selected based on the array transmission rule stored in the array transmission rule storage unit 34, and the flaw detection is performed in the same manner as described above. Repeat. In addition, regarding the determination of the defect, the defect may be determined when the signal intensity is equal to or more than a threshold value a plurality of times.

  The linear array probe 5 has a structure that is held by a local water immersion nozzle 50 as shown in FIG. The local water immersion nozzle 50 is provided with a water supply port 52 for the linear array probe 5 to form a water column. However, even with such a local submerged nozzle structure, there is a possibility that water flow may be disturbed or bubbles may be generated due to some abnormal operation. It is necessary to confirm. In general, it is only necessary to receive a reflected wave from the outer surface or the inner surface of the tubular body and determine whether the coupling is normal depending on whether the signal intensity is a predetermined intensity.

  First, it is examined whether a coupling check can be performed by forming a transmission beam and a reception beam in the same manner as in a normal tandem flaw detection as shown in FIG. In this case, oblique flaw detection is performed, and the beam setting uses many vibrators and widens the aperture width in order to focus the beam. For example, the opening width is 20.8 mm, the number of simultaneous excitation elements is 26 CH (pitch 0.8 mm), and the like. And since the incident angle of an ultrasonic wave is set, for example to 18.9 degrees, a surface echo can hardly be detected at such an incident angle, and a coupling cannot be checked. Therefore, in order to detect the surface echo, it is considered that a deflection angle of approximately −15 ° to −23 ° (depending on the location of the transducer) is added and the incident angle of the ultrasonic wave is set to 0 °. In practice, it is difficult to provide such a deflection angle due to the influence of an acoustic lens or a curved vibrator for converging the tube axis direction. This is because the focal length of the acoustic lens or the curved vibrator differs depending on the position of the array, so that if the aperture is large, the phase is disturbed, and it becomes difficult to set the deflection angle by delay time control.

  Therefore, in the present invention, an ultrasonic beam having a wide directivity angle is narrowed by using the transducers 1 to 4CH, as shown in FIG. Irradiate the surface. At this time, the delay time control is basically not performed. In this way, the opening width is 0.8 to 3.2 mm, the directivity angle is widened, and surface echoes incident on the surface approximately vertically can be detected.

  For example, when the aperture width is 0.8 mm, the component of 2 MHz has a directivity angle of ± 36 °, and when the aperture width is 1.6 mm, the component of 2 MHz has a directivity angle of ± 18 °. The frequency used for flaw detection is, for example, in the range of 5 to 15 MHz. However, since a component of about 2 MHz is actually included, surface echoes can be detected. Alternatively, if the aperture is about 4CH, the phase disturbance is small, so the deflection angle can be set by delay time control, and the surface echo can be detected.

  Then, based on the obtained signal intensity of the surface echo, it is determined whether or not the coupling is good.

  As a confirmation method, for example, as shown in FIGS. 2A to 2C, the horizontal axis indicates the position of the receiving transducer (corresponding to the circumferential direction of the tube), and the vertical axis indicates the propagation time. What is necessary is just to make the display which shows the signal intensity corresponding to time by light and dark, and to confirm the display state. For example, when the entire surface of the array probe is filled with water and surface echoes can be received by all transducers (that is, all regions in the circumferential direction of the local immersion nozzle), the coupling is good. If there is, a surface echo having a predetermined signal intensity over the entire surface can be obtained as shown in FIG. 2A (in the figure, a large signal intensity is displayed as a black dot, and a white display is displayed when the signal intensity is low. ). On the other hand, when there is not enough water and some vibrators are in contact with air instead of water, the ultrasonic wave does not propagate to the part that is not in contact with water, so the coupling is poor. As shown in FIG. 2 (b), the surface echo is not obtained with some transducers, and a part of the display disappears with respect to FIG. 2 (a) (black dots in the figure). Where is not displayed). Furthermore, as shown in FIG. 2 (c), when the region where water is insufficient widens, the number of transducers from which surface echo is obtained decreases, so that most of the surface echo disappears in the display (in the figure, black The area where dots are displayed has decreased.) FIG. 2 shows data at the opening 2ch.

  Even if the display screen as shown in FIG. 2 is not used, when the wave receiving transducer is changed, the waveform received by each wave receiving transducer has a predetermined propagation time range (gate range) in which surface echo is obtained. It may be determined whether there is a signal having a predetermined intensity or more, and the determination method is not particularly limited. Thus, if the intensity of the surface echo falls below a predetermined threshold, it can be determined that there is a coupling failure.

  In addition, the scan for oblique angle flaw detection (tandem flaw detection) and the scan for coupling check can be switched as appropriate using the transmission / reception control unit, so that, for example, the inspection can be performed alternately and always in a stable state. It becomes possible. Since coupling failures occur in a wide range, it is not necessary to move each element in the scanning of the coupling check, and the range of the length of the array probe is divided into, for example, about 3 to 5 locations. They may be moved in the same way.

  In this embodiment, at the time of coupling check, the number of simultaneous excitations of the transducers on the array probe is made smaller than that at the time of flaw detection, so that the aperture width of the ultrasonic beam is narrowed. It is simple.

  In addition, the position and shape of a water supply opening and a water supply exit are not limited to an Example. The inspection object is not limited to a steel pipe.

The figure explaining the Example of this invention The figure which shows the mode of the coupling check of the said Example The figure which shows the state of bevel flaw inspection similarly The figure which shows the example of the procedure of scanning similarly The figure which shows the function structural example of the ultrasonic flaw detector which concerns on this invention The perspective view which shows the prior art described in patent document 1

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Steel pipe 2 ... Welded part 3 ... Defect 4 ... Water 5 ... Array probe 6 ... Transmitter transducer group 7 ... Receiver transducer group 8 ... Transmitted beam 9 ... Received beam 30 ... Covered Specimen size input unit 31 ... Array probe storage unit 32 ... Transmission / reception control unit 33 ... Gate position storage unit 34 ... Array transmission rule storage unit 35 ... Array reception rule storage unit 36 ... Array transmission unit 37 ... Array reception unit 38 ... Gate 39: Determination threshold value input unit 40 ... Defect determination unit 50 ... Local water immersion nozzle 52 ... Water supply port 54 ... Water supply outlet

Claims (3)

A transmission unit for transmitting ultrasonic waves to the inspection object;
A receiving section that receives a part or all of the reflected wave from the inspection object;
The transmission unit and the reception unit are composed of different transducer groups on one or more array probes, and include a transmission / reception unit held in a local water immersion nozzle,
During the coupling check of an ultrasonic oblique flaw detector designed to focus and transmit an ultrasonic beam with a wide aperture width to the inspection object,
Coupling check of an ultrasonic oblique flaw detector characterized by narrowing the aperture width of the ultrasonic beam from the time of flaw detection, applying a low directivity ultrasonic beam substantially perpendicularly to the surface to be inspected, and detecting surface echo Method.   2. The coupling check according to claim 1, wherein at the time of the coupling check, the number of simultaneous excitations of the transducer group on the array probe is made smaller than that at the time of the flaw detection to narrow the aperture width of the ultrasonic beam. Method.   The coupling check method for an ultrasonic oblique angle flaw detector according to claim 1, wherein the coupling check and the flaw detection are performed alternately.

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