JP5590249B2 - Defect detection apparatus, defect detection method, program, and storage medium - Google Patents

Description

  The present invention relates to a defect detection device and a defect detection method for detecting a defect present on a weld surface formed along a pipe axis direction of a welded steel pipe, a program for causing a computer to execute the defect detection method, and the program to be stored. The present invention relates to a computer-readable storage medium. In this specification, a case where defect detection is performed on a small diameter electric resistance steel pipe having a pipe diameter of 5 inches or less and a pipe thickness of 7.5 mm or less will be described as an example. However, the present invention is not limited to this. For example, another welded steel pipe such as an arc welded steel pipe may be the target of defect detection.

  First, the general manufacturing method of an electric resistance steel pipe is demonstrated. FIG. 18A and FIG. 18B are schematic views showing an example of a general method for manufacturing an electric resistance welded steel pipe. As shown in FIG. 18A, in a general method for manufacturing an electric resistance welded steel pipe, a number of roll groups (not shown) are conveyed while continuously transporting a strip-shaped steel plate (strip steel) 201 in a direction 202. The butt end surface 203 is melted by induction heating by a high frequency coil 204 or direct current heating by a contact tip (not shown) and pressed by a squeeze roll 205 to weld the butt end surface 203. To form the welded portion 210. In this way, as shown in FIG. 18B, the electric resistance welded steel pipe 200 in which the welded portion 210 (welded surface) is formed along the pipe axis direction 220 is manufactured. In this specification, the welded surface is the end surface of the hot-rolled steel sheet formed into an open tubular shape, heated and melted, and the molten surface is discharged by applying pressure to complete the bonding. Say. The welding surface may be referred to as a welding contact surface.

  In the electric resistance welded pipe 200, the quality of the welded portion 210 is very important, and in the manufacturing process of the electric resistance welded pipe 200, on-line flaw detection is generally performed to determine whether or not there is a defect in the welded portion 210 by ultrasonic oblique angle flaw detection. It has been broken.

  FIG. 19 is a schematic diagram showing an example of a conventional oblique flaw detection method. FIG. 19 shows a cross section of the electric resistance welded steel pipe 200 shown in FIG. 18B (more specifically, the vicinity of the welded portion 210 in the cross section of the electric resistance welded steel pipe 200). And the array probe 250 which transmits / receives an ultrasonic beam is installed in the outer side of the outer surface 200G of the ERW steel pipe 200. FIG. In such a state, in the conventional oblique flaw detection method shown in FIG. 19, an ultrasonic beam is output from the array probe 250 to the outer surface 200G of the electric resistance welded steel pipe 200, and the ultrasonic beam is subjected to the electric resistance sewing. The inner surface 200N of the steel pipe 200 is reflected once and irradiated to the welded portion 210 (welded surface), the reflected ultrasonic beam is received by the array probe 250, the received ultrasonic beam is analyzed, and the welded portion 210 ( It is detected whether or not there is a defect on the welding surface.

  Japanese Patent No. 4544240 discloses a so-called tandem flaw detection technique in which separate array probes are provided for transmission and reception of ultrasonic beams.

  However, in the conventional oblique flaw detection method shown in FIG. 19 described above, since the ultrasonic beam is once reflected by the inner surface 200N of the electric resistance welded steel pipe 200 and irradiated to the welded portion 210 (welded surface), the welded portion 210 is irradiated. When the ultrasonic beam cannot be irradiated substantially perpendicularly to the (welded surface) and, as a result, a defect exists in the welded portion 210 (welded surface), the normality from the defect reaching the array probe 250 can be reduced. The reflected ultrasonic beam is weakened. Therefore, for example, there is a problem that it is difficult to detect a minute defect (about 0.2 mm) such as a penetrator.

  In the technique of the above-mentioned Japanese Patent No. 4544240, when flaw detection is performed on a relatively thin (less than about 7.5 mm) pipe diameter electric resistance steel pipe having a diameter of 5 inches or less, the welded portion 210 is used. There was a problem that the SN ratio related to the reflected ultrasonic beam from the defect existing on the (welded surface) decreased.

  The present invention has been made in view of such problems, and can detect minute defects, and improve the detection accuracy of defects even in a small-diameter welded steel pipe with a relatively small thickness. The purpose is to provide a mechanism to do this.

  As a result of intensive studies, the present inventor has conceived various aspects of the invention described below.

According to a first aspect of the present invention, there is provided a defect detection device for detecting a defect existing on a weld surface formed along a pipe axis direction of a welded steel pipe, which is installed outside the outer surface of the welded steel pipe. From a phased array probe in which a plurality of ultrasonic transducers are arranged, and a group of ultrasonic transducers for flaws including a part or all of the plurality of ultrasonic transducers, from the outer surface of the welded steel pipe The ultrasonic inspection beam incident on the welded steel pipe is directly incident on the welded surface substantially perpendicularly to the welded surface without being reflected by the inner surface of the welded steel pipe and converges on the welded surface. An ultrasonic beam, and an effective beam diameter determined on the basis of the pipe thickness of the welded steel pipe and the displacement distribution of the ultrasonic beam for flaw detection on the weld surface in the pipe thickness direction of the welded steel pipe ; Based on the welding surface Dividing into a plurality of regions along the direction of the tube thickness, and transmitting the ultrasonic beam for flaw detection a plurality of times so that the ultrasonic beam for flaw detection is sequentially incident on each divided region of the welding surface Transmitting means, receiving means for receiving the reflected ultrasonic beam for flaw detection via the ultrasonic transducer group for flaw detection, and the welding surface based on the ultrasonic beam for flaw detection received by the receiving means And a defect determination means for determining whether or not a defect exists.

  According to a second aspect of the present invention, there is provided the defect detection apparatus according to the first aspect, wherein the welded steel pipe is a small diameter electric resistance steel pipe having a pipe diameter of 5 inches or less and a pipe thickness of 7.5 mm or less. .

  According to a third aspect of the present invention, water is present as a medium through which the ultrasonic beam for flaw detection propagates between the phased array probe and the outer surface of the welded steel pipe, and the transmission The means further transmits a water determination ultrasonic beam substantially perpendicular to the outer surface of the welded steel pipe from a water determination ultrasonic transducer group including a part or all of the plurality of ultrasonic transducers. The receiving means further receives the reflected ultrasonic beam for water determination via the ultrasonic transducer group for water determination, and based on the ultrasonic beam for water determination received by the receiving means, There is provided a defect detection apparatus according to the first or second aspect, further comprising water determining means for determining whether or not a space between the phased array probe and the outer surface of the welded steel pipe is filled with water.

  According to a fourth aspect of the present invention, when the transmission means determines that the water determination means is filled with water between the phased array probe and the outer surface of the welded steel pipe. A defect detection apparatus according to a third aspect of transmitting the flaw detection ultrasonic beam from the flaw detection ultrasonic transducer group is provided.

  According to a fifth aspect of the present invention, the ultrasonic beam for flaw detection is provided between the phased array probe and the outer surface of the welded steel pipe so as to correspond to the phased array probe. A defect detection apparatus according to any one of the first to fourth aspects further including a focusing lens for focusing in the axial direction is provided.

According to a sixth aspect of the present invention, the transmission means includes a plurality of ultrasonic vibrations included in the flaw detection ultrasonic transducer group according to the number N of sections of the weld surface in the tube thickness direction. dividing the child into N groups, first to sequentially flaw ultrasonic beams to divided each regions of the weld surface transmits sequentially flaw ultrasonic beam from each group is divided so as to enter A defect detection apparatus according to any one of the fourth aspects is provided.

  According to a seventh aspect of the present invention, the ultrasonic beam for flaw detection is provided between the phased array probe and the outer surface of the welded steel pipe so as to correspond to the phased array probe. A focusing lens for focusing in the axial direction, wherein the focusing lens has a curvature radius of a curved surface along the tube axis direction that varies along an arrangement direction of the plurality of ultrasonic transducers; A defect detection apparatus is provided according to a sixth aspect in which the radius of curvature is increased in a direction in which a propagation distance of the flaw detection ultrasonic beam from a phased array probe to the weld surface increases. .

According to an eighth aspect of the present invention, before Symbol transmitting means such that said the flaw ultrasonic beams to divided each regions of the weld surface is sequentially incident, the plurality of portion of the ultrasonic vibrator There is provided a defect detection apparatus according to any one of the first to fifth aspects, in which a transmission direction is sequentially switched from a single flaw detection ultrasonic transducer group including the flaw detection ultrasonic beam.

According to a ninth aspect of the present invention, before Symbol transmitting means such that said the flaw ultrasonic beams to divided each regions of the weld surface is sequentially incident, all of the plurality of ultrasonic transducers The transmission ultrasonic beam for flaw detection is transmitted by sequentially switching the transmission direction from the ultrasonic transducer group for flaw detection, and the welding is performed from the ultrasonic transducer group for water determination including a part of the plurality of ultrasonic transducers. A defect detection apparatus according to the third or fourth aspect is provided for transmitting the water determination ultrasonic beam to the outer surface of a steel pipe.

  According to a tenth aspect of the present invention, the ultrasonic beam for flaw detection is provided between the phased array probe and the outer surface of the welded steel pipe so as to correspond to the phased array probe. A defect detection apparatus according to a ninth aspect, further comprising a focusing lens for focusing in the axial direction is provided.

According to an eleventh aspect of the present invention, the transmitting means rounds up the value obtained by dividing the pipe thickness of the welded steel pipe by the effective beam diameter of the flaw detection ultrasonic beam on the weld surface to the first decimal place. A defect detection apparatus according to any one of the first to tenth aspects is provided in which a value is set as the number of sections in the direction of the tube thickness of the weld surface .

  According to a twelfth aspect of the present invention, the effective beam diameter is 0.5 or more when the maximum value of the displacement inside the welded steel pipe due to vibration of the flaw detection ultrasonic beam is 1. A defect detection apparatus according to any one of the sixth to eleventh aspects corresponding to the range is provided.

According to a thirteenth aspect of the present invention, using a phased array probe installed outside the outer surface of a welded steel pipe and arranged with a plurality of ultrasonic transducers, along the pipe axis direction of the welded steel pipe. A defect detection method by a defect detection device for detecting defects present on the weld surface formed by
Based on the pipe thickness of the welded steel pipe and the effective beam diameter determined based on the internal displacement distribution of the ultrasonic beam for flaw detection on the welded surface in the pipe thickness direction of the welded steel pipe, A region dividing step of dividing into a plurality of regions along the thickness direction, and a group of ultrasonic transducers for flaws including a part or all of the plurality of ultrasonic transducers, from the outer surface of the welded steel pipe The flaw detection ultrasonic beam incident on the welded steel pipe is directly incident on the welded surface substantially perpendicularly without being reflected by the inner surface of the welded steel pipe, and is focused on the welded surface and is divided into the welded surfaces. A first transmission step of transmitting the flaw detection ultrasonic beam a plurality of times so that the flaw detection ultrasonic beam is incident on each region; and the reflected flaw detection ultrasonic beam is transmitted to the flaw detection ultrasonic vibration. Child group And a defect determination step for determining whether or not there is a defect on the weld surface based on the ultrasonic beam for flaw detection received in the first reception step. Including defect detection methods are provided.

  According to a fourteenth aspect of the present invention, there is provided the defect detection method according to the thirteenth aspect, wherein the welded steel pipe is a small diameter electric resistance steel pipe having a pipe diameter of 5 inches or less and a pipe thickness of 7.5 mm or less. .

  According to a fifteenth aspect of the present invention, water is present as a medium through which the flaw detection ultrasonic beam propagates between the phased array probe and the outer surface of the welded steel pipe. A second transmission step of transmitting a water determination ultrasonic beam substantially perpendicularly to the outer surface of the welded steel pipe from a water determination ultrasonic transducer group including a part or all of the ultrasonic transducers of A second reception step of receiving the reflected water determination ultrasonic beam via the water determination ultrasonic transducer group, and the water determination ultrasonic beam received in the second reception step. A defect determination method according to the thirteenth or fourteenth aspect, further comprising: a water determination step of determining whether or not a space between the phased array probe and the outer surface of the welded steel pipe is filled with water. Provided.

According to a sixteenth aspect of the present invention, using a phased array probe that is installed outside the outer surface of a welded steel pipe and in which a plurality of ultrasonic transducers are arranged, along the pipe axis direction of the welded steel pipe. A program for causing a computer to execute a defect detection method by a defect detection device for detecting defects existing on a weld surface formed by the method, comprising: pipe thickness of the welded steel pipe and ultrasonic beam for flaw detection on the weld surface ; A region dividing step of dividing the welding surface into a plurality of regions along the tube thickness direction based on an effective beam diameter determined based on an internal displacement distribution of the welded steel tube in the tube thickness direction ; A flaw detection ultrasonic beam incident from the outer surface of the welded steel pipe into the welded steel pipe from the group of ultrasonic flaw detectors for flaws including a part or all of the plurality of ultrasonic vibrators is an inner surface of the welded steel pipe. A plurality of times so that the ultrasonic beam for flaw detection is directly incident on the welding surface substantially without being reflected, is focused on the welding surface, and is incident on each divided region of the welding surface. A first transmission step of transmitting the flaw detection ultrasonic beam; a first reception step of receiving the reflected flaw detection ultrasonic beam via the flaw detection ultrasonic transducer group; and the first reception. There is provided a program for causing a computer to execute a defect determination step of determining whether or not a defect exists on the weld surface based on the ultrasonic beam for flaw detection received in the step.

  According to a seventeenth aspect of the present invention, water is present as a medium through which the flaw detection ultrasonic beam propagates between the phased array probe and the outer surface of the welded steel pipe. A second transmission step of transmitting a water determination ultrasonic beam substantially perpendicularly to the outer surface of the welded steel pipe from a water determination ultrasonic transducer group including a part or all of the ultrasonic transducers of A second reception step of receiving the reflected water determination ultrasonic beam via the water determination ultrasonic transducer group, and the water determination ultrasonic beam received in the second reception step. A program according to a sixteenth aspect of causing the computer to further execute a water determination step of determining whether or not a space between the phased array probe and the outer surface of the welded steel pipe is filled with water. The

  According to an eighteenth aspect of the present invention, there is provided a computer-readable storage medium storing a program according to the sixteenth or seventeenth aspect.

  According to the present invention, it is possible to detect a minute defect, and it is possible to realize an improvement in defect detection accuracy even with a small-diameter welded steel pipe having a relatively small thickness.

It is a figure which shows an example of schematic structure of the defect detection apparatus which concerns on the 1st Embodiment of this invention. It is a figure which shows the 1st Embodiment of this invention and shows an example of transmission / reception of the ultrasonic beam for flaw detection shown in FIG. It is a figure which shows the 1st Embodiment of this invention and shows an example of the acoustic lens shown in FIG. FIG. 2 is a schematic diagram of the phased array probe shown in FIG. 1 according to the first embodiment of the present invention. FIG. 5 is a diagram illustrating an example of the correlation between the aperture diameter of the phased array probe illustrated in FIG. 4 and the SN ratio related to defect detection according to the first embodiment of the present invention. It is sectional drawing of the ERW steel pipe which showed the 1st Embodiment of this invention and was used for simulation. It is a schematic diagram of the simulation model in the flaw detection method of the comparative example 1. It is a schematic diagram of a simulation model in the flaw detection method of the present invention. It is a schematic diagram of a simulation model in the flaw detection method of Comparative Example 2. It is a schematic diagram of the simulation model in the flaw detection method of the comparative example 3. It is a figure which shows the analysis result by the simulation model in each flaw detection technique of the flaw detection technique of this invention shown to FIG. 7A-FIG. 7D, and the flaw detection technique of a comparative example. It is a figure which shows the 1st Embodiment of this invention and shows the analysis model of the effective beam diameter in the focus of the ultrasonic beam for flaw detection. It is a figure which shows the 1st Embodiment of this invention and shows the analysis result of the effective beam system in the focus of the ultrasonic beam for flaw detection. It is a figure which shows an example of schematic structure of the phased array probe in the 1st Embodiment of this invention. It is a figure for showing a 1st embodiment of the present invention and explaining a coupling check. It is a figure which shows the 1st Embodiment of this invention and shows an example of the received waveform of the reflected ultrasonic beam for a coupling check. It is a figure for demonstrating the 1st Embodiment of this invention and explaining the acoustic lens shown in FIG.1 and FIG.3. FIG. 4 is a diagram illustrating a relationship between a radius of curvature of the acoustic lens illustrated in FIGS. 1 and 3 and an array length (array position) of a phased array probe according to the first embodiment of the present invention. It is a flowchart which shows an example of the process sequence of the defect detection method by the defect detection apparatus which concerns on the 1st Embodiment of this invention. It is a figure which shows the 1st Embodiment of this invention and shows an example of the received waveform of the reflected ultrasonic beam for flaw detection. It is a figure which shows the 1st Embodiment of this invention and shows an example of the received waveform of the reflected ultrasonic beam for flaw detection. It is a figure which shows the 1st Embodiment of this invention and shows an example of a two-dimensional map. It is a schematic diagram which shows an example of the manufacturing method of a general ERW steel pipe. It is a schematic diagram which shows an example of the manufacturing method of a general ERW steel pipe. It is a schematic diagram which shows an example of the conventional oblique flaw detection method.

Hereinafter, embodiments (embodiments) for carrying out the present invention will be described with reference to the drawings.
(First embodiment)
FIG. 1 is a diagram illustrating an example of a schematic configuration of a defect detection apparatus 100 according to the first embodiment of the present invention. This defect detection apparatus 100 is an apparatus for detecting defects included in a welded portion 210 (welded surface) formed along the pipe axis direction (220 in FIG. 18B) of an electric resistance welded steel pipe 200 which is a kind of welded steel pipe. It is. Further, FIG. 1 shows a cross section of the electric resistance welded pipe 200 shown in FIG. 18B (more specifically, the vicinity of the welded portion 210 in the cross section of the electric resistance welded pipe 200).

  As shown in FIG. 1, the defect detection apparatus 100 according to the present embodiment includes an acoustic lens 110, a phased array probe 120, and a control processing device 140. The control processing device 140 also includes an object condition input unit 141, a transmission / reception condition setting unit 142, a transmission / reception control unit 143, a transmission unit 144, a reception unit 145, a reception signal processing unit 146, and a defect determination unit 147. And a water determination unit 148 and a recording / display unit 149.

  The acoustic lens 110 is provided corresponding to the phased array probe 120 between the phased array probe 120 and the outer surface 200G of the ERW steel pipe 200. The acoustic lens 110 is a focusing lens for focusing the flaw detection ultrasonic beam 131 output from the phased array probe 120 in the tube axis direction. Here, the flaw detection ultrasonic beam 131 is transmitted in order to detect a defect when a defect exists in the welded portion 210 of the ERW steel pipe 200.

  The phased array probe 120 is installed outside the outer surface 200G of the electric resistance welded steel pipe 200, and is formed by arranging a plurality of ultrasonic transducers 121. The phased array probe 120 according to the present embodiment outputs a flaw detection ultrasonic transducer group that outputs a flaw detection ultrasonic beam 131 and a coupling check ultrasonic beam (water determination ultrasonic beam) 132. The coupling check ultrasonic transducer group (water determination ultrasonic transducer group) is composed of mutually different ultrasonic transducers. That is, in the case of the present embodiment, the flaw detection ultrasonic transducer group is configured by a part of a plurality of ultrasonic transducers among the plurality of ultrasonic transducers 121 arranged in the phased array probe 120, The ultrasonic transducer group for coupling check is a part of a plurality of ultrasonic transducers 121 of the plurality of ultrasonic transducers 121 arranged on the phased array probe 120, and the ultrasonic transducer group for flaw detection. It is comprised from the ultrasonic transducer | vibrator different from the some ultrasonic transducer | vibrator which comprises.

  Between the phased array probe 120 (strictly speaking, the acoustic lens 110) and the outer surface 200G of the ERW steel pipe 200, water exists as a medium for efficiently propagating the flaw detection ultrasonic beam 131. ing. In the coupling check, the space between the phased array probe 120 (acoustic lens 110) and the outer surface 200G of the ERW steel pipe 200 is filled with water without air or the like, so that the ultrasonic wave 131 for flaw detection is normally transmitted and received. This is a process for confirming whether the environment can be used.

  The subject condition input unit 141 performs a process of inputting a condition (subject condition) of the electric resistance welded steel pipe 200 that is the subject. For example, the subject condition input unit 141 performs a process of inputting the subject condition input by the user into the control processing device 140. Here, examples of the subject condition include the outer diameter and thickness of the electric resistance welded steel pipe 200, the length in the pipe axis direction 220, and the pipe making speed.

  The transmission / reception condition setting unit 142 performs processing for setting transmission / reception conditions based on the subject condition input by the subject condition input unit 141. Here, as the transmission / reception conditions, for example, the transmission / reception timing of the flaw detection ultrasonic beam 131 and the coupling check ultrasonic beam 132, the transmission frequency of these ultrasonic beams, and the ultrasonic wave used for transmission / reception of these ultrasonic beams are used. Each channel of the ultrasonic transducer group for flaw detection so that the ultrasonic transducer 121 (hereinafter referred to as “channel (ch)” as necessary) and the flaw detection ultrasonic beam 131 are focused at the welded portion 210 (welded surface). The delay time of the transmission timing.

  The transmission / reception control unit 143 controls the transmission unit 144 and the reception unit 145 based on the transmission / reception conditions set by the transmission / reception condition setting unit 142.

  Based on the control by the transmission / reception control unit 143, the transmission unit 144 transmits the flaw detection ultrasonic beam 131 from the flaw detection ultrasonic transducer group of the phased array probe 120, and performs a coupling check of the phased array probe 120. A process for transmitting the coupling check ultrasonic beam 132 from the ultrasonic transducer group is performed. Specifically, the transmitter 144 outputs the ultrasonic testing beam 131 at an oblique angle from the ultrasonic transducer group for testing of the phased array probe 120 toward the outer surface 200G of the electric resistance welded steel pipe 200. The flaw detection ultrasonic beam 131 incident from the outer surface 200G of the steel pipe 200 is directly incident on the welded portion 210 (welded surface) directly without being reflected by the inner surface 200N of the ERW steel pipe 200 and is incident on the welded surface. The flaw detection ultrasonic beam 131 is transmitted so as to be focused (to form a focal point on the weld surface). Further, the transmission unit 144 transmits the coupling check ultrasonic beam 132 from the coupling check ultrasonic transducer group of the phased array probe 120 substantially perpendicularly to the outer surface 200G of the ERW steel pipe 200.

  The receiving unit 145 receives the reflected ultrasonic beam 131 for flaw detection through the flaw detection ultrasonic transducer group based on the control by the transmission / reception control unit 143, and receives the reflected ultrasonic beam 132 for coupling check. A process of receiving via the coupling check ultrasonic transducer group is performed.

  The reception signal processing unit 146 processes the ultrasonic beam (reception signal) received by the reception unit 145.

  The defect determination unit 147 performs processing for determining whether or not there is a defect in the welded portion 210 of the electric resistance welded steel pipe 200 based on the flaw detection ultrasonic beam 131 received by the reception unit 145. Furthermore, the defect determination part 147 also performs the process which determines the position and magnitude | size, when the defect exists in the welding part 210. FIG.

  Based on the coupling check ultrasonic beam 132 received by the receiving unit 145, the water determination unit 148 determines whether the phased array probe 120 (strictly speaking, the acoustic lens 110) and the outer surface 200 </ b> G of the ERW steel pipe 200. A process for determining whether the space is filled with water without air or the like is performed.

  The recording / display unit 149 performs processing for recording and displaying the result of processing by the reception signal processing unit 146 and the determination result by the defect determination unit 147 and the water determination unit 148. Further, the recording / display unit 149 performs processing for recording and displaying various data and various information as necessary.

  When there is no coupling problem as a result of the coupling check (that is, the water determination unit 148 causes the phased array probe 120 (strictly speaking, the acoustic lens 110) and the ERW steel pipe 200 to When it is determined that the space between the outer surface 200 </ b> G and the outer surface 200 </ b> G is filled with water, processing for transmitting the flaw detection ultrasonic beam 131 from the flaw detection ultrasonic transducer group of the phased array probe 120 is performed.

  Next, transmission / reception of the flaw detection ultrasonic beam 131 will be described. FIG. 2 is a diagram showing an example of transmission / reception of the flaw detection ultrasonic beam 131 shown in FIG. 1 according to the first embodiment of the present invention. Here, in FIG. 2, only the ERW steel pipe 200 and the phased array probe 120 shown in FIG. 1 are illustrated.

  In the present embodiment, the flaw detection ultrasonic transducer group of the phased array probe 120 that outputs the flaw detection ultrasonic beam 131 includes a plurality of ultrasonic transducers 121. In the present embodiment, the flaw detection ultrasonic beam 131 is transmitted from the flaw detection ultrasonic transducer group, and the flaw detection ultrasonic beam 131 is about 70 with respect to the incident direction on the outer surface 200G of the ERW steel pipe 200. It is refracted and directly irradiated to the welded portion 210 (welded surface) substantially perpendicularly without being reflected by the inner surface 200N of the ERW steel pipe 200. Hereinafter, such a flaw detection method using the flaw detection ultrasonic beam 131 will be referred to as a “70 ° flaw detection method”.

  In the present embodiment, a focused beam is incident on the welded portion 210 (welded surface) substantially perpendicularly for the purpose of improving the detection sensitivity of the defect 211 existing in the welded portion 210 (welded surface). . This is because the focused beam is incident substantially perpendicularly to the welded portion 210 (welded surface), so that the reflected ultrasonic beam directly from the defect 211 is directly reflected in the regular reflection direction without causing loss of ultrasonic energy due to multiple reflection. This is because it can be received. Although it is possible to form a focused beam to some extent by using an ordinary single focusing probe, the beam is favorably placed at a target position in the ERW steel tube 200 due to the influence of the curvature of the ERW steel tube 200. It is difficult to focus on. Therefore, in the present embodiment, the phased array probe 120 is employed to favorably focus the beam on the targeted position in the ERW steel pipe 200 without being affected by the curvature of the ERW steel pipe 200. If the phased array probe 120 is adopted, a focused beam can be formed in consideration of the curvature of the ERW steel pipe 200 by selecting the ultrasonic transducer group for flaw detection and controlling the delay time of ultrasonic transmission by each ultrasonic transducer. Therefore, it is possible to realize higher defect detection performance than a single focusing probe.

  FIG. 3 is a diagram showing an example of the acoustic lens 110 shown in FIG. 1 according to the first embodiment of the present invention. As described above, the acoustic lens 110 is provided corresponding to the phased array probe 120 between the phased array probe 120 and the outer surface 200G of the ERW steel pipe 200. The acoustic lens 110 focuses the flaw detection ultrasonic beam 131 output from the phased array probe 120 in the tube axis direction 220 of the ERW steel tube 200. Thus, by providing the acoustic lens 110, the flaw detection ultrasonic beam 131 can be focused in the tube thickness direction of the ERW steel pipe 200 by the phased array probe 120. It is also possible to focus in the tube axis direction 220.

<Evaluation by two-dimensional simulation>
Next, the evaluation result by two-dimensional simulation (finite element method) will be described. Table 1 below shows the simulation conditions.

  First, the optimal phased array probe 120 was analyzed. At this time, the thickness of the ERW steel pipe 200 was 3.4 mm, the outer diameter was 101.6 mm, and the defect size set at the center in the depth direction of the weld was 0.2 mm in height and 0.1 mm in width. .

  FIG. 4 is a schematic diagram of the phased array probe 120 shown in FIG. 1 according to the first embodiment of the present invention. FIG. 5 shows the first embodiment of the present invention and is a diagram showing an example of the correlation between the aperture diameter of the phased array probe 120 shown in FIG. 4 and the SN ratio related to defect detection.

  In this analysis, the frequencies of ultrasonic waves to be transmitted are 5 MHz and 10 MHz, the width of each ultrasonic transducer 121 (element width e in FIG. 4), and the interval between adjacent ultrasonic transducers 121 (pitch p in FIG. 4). The ratio of signal to noise (SN ratio) in a 0.2 mm micro defect in the tube thickness direction was compared. The result is shown in FIG. At this time, the signal-to-noise ratio was defined as the ratio of the maximum amplitude of the ultrasonic wave from the defect and the noise as the amplitude of the ultrasonic wave immediately before the ultrasonic wave from the defect.

  As a result of the analysis, as shown in FIG. 5, when the frequency of ultrasonic waves to be transmitted is 5 MHz, the pitch p of the ultrasonic transducers 121 is 0.5 mm, and the aperture diameter is 8 mm, the S / N ratio is 200 and the maximum. It became. The number of elements (number of channels) of the ultrasonic transducer 121 when the SN ratio is maximized is 16 elements (16 ch) since it can be expressed as opening diameter≈pitch × number of elements as shown in FIG. In the present embodiment, the specification that maximizes the S / N ratio is adopted for the phased array probe 120.

  Next, the flaw detection method of the present invention was compared with other flaw detection methods by simulation analysis.

  FIG. 6 is a cross-sectional view of the ERW steel pipe 200 used for the simulation, showing the first embodiment of the present invention. In the electric resistance welded steel pipe 200 shown in FIG. 6, the pipe thickness is set to 3.4 mm, and three defects 211G, 211C, and 211N are provided in the welded portion 210. Specifically, the outer surface vicinity defect 211G having a thickness of 0.2 mm to 0.4 mm from the outer surface 200G of the ERW steel pipe 200 and a thickness of about 0. A 2 mm center vicinity defect 211C and an inner surface vicinity defect 211N having a thickness ranging from 0.2 mm to 0.4 mm from the inner surface 200N of the ERW steel pipe 200 were provided.

  7A to 7D are schematic diagrams of simulation models in each flaw detection technique of the flaw detection technique of the present invention and the flaw detection technique of the comparative example. FIG. 7A shows a schematic diagram of a model of Comparative Example 1 using a single focus probe and a 70 ° flaw detection method, and FIG. 7B shows a 70 ° flaw detection using an array probe as an ultrasonic probe. FIG. 7C shows a model schematic diagram of Comparative Example 2 according to the conventional oblique flaw detection method shown in FIG. 19, and FIG. 7D shows the model schematic diagram of the present invention according to the method. The model outline figure of the comparative example 3 by the tandem flaw detection method which the ultrasonic probe is an array probe and is shown in patent 4544240 gazette is shown.

  Specifically, the specifications of each ultrasonic probe shown in FIGS. 7A to 7D were as follows. The single focusing probe shown in FIG. 7A has a frequency of 5 MHz, a transducer diameter of 13 mm, and a focal length of 51 mm. The array probe shown in FIGS. 7B and 7C was used with a frequency of 5 MHz, a pitch p of 0.5 mm, an element width e of 0.4 mm, and 16 elements (16 channels). That is, the correlation diagram shown in FIG. 5 was used under conditions where the SN ratio was maximum (200). The array probe shown in FIG. 7D was used having a frequency of 5 MHz, a pitch p of 0.5 mm, an element width e of 0.4 mm, and 64 elements (64 channels). At this time, as shown in FIG. 7D, the number of transmitting elements was 20 (20 ch), and the number of receiving elements was 24 (24 ch).

  Moreover, each flaw detection method shown to FIG. 7A-FIG. 7D was as follows. In the 70 ° flaw detection method shown in FIGS. 7A and 7B, the water distance, the incident point of the ultrasonic wave, and the position of the welded portion 210 are fixed, and three defects (211G, 211C, 211N), the ultrasonic beam hits vertically. Precisely, although the ultrasonic beam does not hit the outer surface vicinity defect 211G and the inner surface vicinity defect 211N perpendicularly, since the pipe thickness of the ERW steel pipe 200 is as thin as 3.4 mm, it was approximated as substantially vertical. Further, the focal point of the ultrasonic beam was set so as to be focused on the welded portion 210 in the calculation. In the conventional oblique flaw detection method shown in FIG. 7C, the water distance, the ultrasonic incident point, and the position of the welded portion 210 are fixed to the same settings as in the 70 ° flaw detection method, and the defect near the outer surface 211G and the vicinity of the central portion are fixed. A single reflection method is adopted in which an ultrasonic beam is reflected once by the inner surface 200N and incident on the defect 211C. Further, the inner surface vicinity defect 211N is omitted because it has the same aim as the 70 ° flaw detection method. In the tandem flaw detection method shown in FIG. 7D, a model was created following the method described in Japanese Patent No. 4544240. Specifically, as shown in FIG. 7D, the refraction angle of the ultrasonic beam is 45 °, the water distance is 22.6 mm (array probe central axis), the number of transmitting elements is 20 ch, and the number of receiving elements is 24 ch. Only analysis for defect 211C was performed.

  FIG. 8 is a diagram showing an analysis result by a simulation model in each flaw detection method of the flaw detection method of the present invention shown in FIGS. 7A to 7D and the flaw detection method of the comparative example. FIG. 8 shows, from the left, the analysis result of the model of Comparative Example 1 shown in FIG. 7A, the analysis result of the model of the present invention shown in FIG. 7B, the analysis result of the model of Comparative Example 2 shown in FIG. The analysis result of the model of the comparative example 3 shown to is shown. Further, in FIG. 8, the reception waveform of the ultrasonic beam targeting the defect 211G near the outer surface is shown in the column “near the outer surface”, and the reception waveform of the ultrasonic beam targeting the defect 211C near the center is expressed as “near the center”. ", And the received waveform of the ultrasonic beam targeting the inner surface vicinity defect 211N is shown in the" inner surface vicinity "column.

In the receiving waveform shown in FIG. 8, S ₁ represents the reflected ultrasonic waves from the outer surface 200G of the electric resistance welded steel pipe 200, F ₁ represents the reflected ultrasound from respective defect. That is, if there is no defect in the welded portion 210 (welded surface), F ₁ is not detected. Further, as described above, the S / N (S / N ratio) is the magnitude of the maximum amplitude of the ultrasonic wave (F ₁ ) from the defect and the noise is the magnitude of the ultrasonic amplitude immediately before the ultrasonic wave from the defect. As defined by these ratios.

  Comparing with the S / N (S / N ratio) shown in FIG. 8, it was confirmed that the flaw detection method based on the model of the present invention (70 ° flaw detection method using an array probe) was good overall.

  Next, an effective beam diameter at the focal point of the ultrasonic beam was analyzed in order to determine the number of ultrasonic scans in the thickness direction of the electric resistance steel tube 200.

  FIG. 9A and FIG. 9B are diagrams showing an analysis model of an effective beam diameter at the focus of the flaw detection ultrasonic beam 131 and an analysis result thereof according to the first embodiment of the present invention. In this analysis, no defect 211 is provided in the welded part 210 (welded surface) having a thickness of 3.4 mm, and a waveform acquisition point is set in the thickness direction of the welded part 210 (welded surface) as shown in FIG. The displacement distribution inside the ERW steel pipe 200 due to the vibration of the ultrasonic beam 131 was read, and the -6 dB width was obtained. At this time, as shown in FIG. 9A, the ultrasonic beam 131 for flaw detection is aimed at the center in the thickness direction of the welded portion 210 (welded surface), and the specification of the phased array probe 120 has a frequency of 5 MHz and a pitch. p was 0.5 mm, and the number of elements was 16 elements (16 ch). The analysis result in this case is shown in FIG. 9B.

  As shown in FIG. 9B, the maximum value of the displacement inside the ERW steel pipe 200 due to the vibration of the flaw detection ultrasonic beam 131 is 1, and the displacement is -6 dB width (that is, the displacement is 0.5). As a result, an effective beam diameter defined as a range of 1.6 mm was obtained. From this result, for example, when the thickness of the ERW steel pipe 200 is 3.4 mm, it is necessary to scan the ultrasonic beam at least three times in the pipe thickness direction in order to perform accurate ultrasonic flaw detection. I understood. Here, in this embodiment, in the transmission / reception condition setting unit 142, the pipe thickness of the welded steel pipe 200 (the thickness of the welded part 210) and the effective beam diameter of the ultrasonic beam 131 for flaw detection in the welded part 210 (welded surface) Based on the above, the number N of divisions for dividing the region in the pipe thickness direction in the welded portion 210 (welded surface) into N pieces (N is an integer of 1 or more) is set. This division number N corresponds to the number of scans described above. In the case of this example, the transmission / reception condition setting unit 142 rounds up the first and second decimal places for 2.125, which is a value obtained by dividing the pipe thickness of the welded steel pipe 200 by 3.4 mm by the effective beam diameter of 1.6 mm. , “3” is set as the division number N. And in this embodiment, with respect to the area | region of the pipe thickness direction in the welding part 210 (welding surface), it is the 1st-Nth area | region (this example 1st-3rd in an ascending order from the outer peripheral surface 200G side). Area). At this time, in this embodiment, the region in the pipe thickness direction in the welded portion 210 (welded surface) is equally divided into N, and the first to Nth regions (in this example, the first to third regions) are divided. Set.

  Based on the results of the above simulation analysis, the phased array probe 120 in the present embodiment was set. FIG. 10 is a diagram illustrating an example of a schematic configuration of the phased array probe 120 according to the first embodiment of the present invention.

  The phased array probe 120 in the first embodiment includes a coupling check ultrasonic transducer group 122 for transmitting a coupling check ultrasonic beam 132, and a welded portion 210 (welded surface) of the ERW steel pipe 200. ) Near the inner surface 200N (that is, the third surface (Nth region)) near the inner surface flaw detection ultrasonic beam (third flaw detection ultrasonic beam (Nth flaw detection ultrasonic beam)) 131N Near the inner surface for transmitting the ultrasonic transducer group (third ultrasonic transducer group for flaw detection (Nth ultrasonic transducer group for flaw detection)) 123 and the welded portion 210 of the ERW steel pipe 200 Near the central portion for transmitting the ultrasonic beam for near-center flaw detection (second ultrasonic wave for flaw detection) 131C near the central portion (that is, the second region) of the pipe thickness of the (welded surface). Acoustic transducer group (second flaw detection sound An ultrasonic beam for flaw detection near the outer surface (first ultrasonic wave for flaw detection) near the outer surface 200G of the welded portion 210 (welded surface) of the ERW steel pipe 200 and the outer surface 200G (ie, the first region). ) The ultrasonic transducer group near the outer surface for transmitting 131G (first ultrasonic transducer group for flaw detection) 125 is constituted by different ultrasonic transducers. That is, in the phased array probe 120 according to the first embodiment, the ultrasonic transducer group for flaw detection is classified according to the number of N (three in this example) of the welded portion 210 (welded surface). By the (divided) flaw detection ultrasonic transducer group (inner surface vicinity flaw detection ultrasonic transducer group 123, central portion flaw detection ultrasonic transducer group 124 and outer surface flaw detection ultrasonic transducer group 125). Composed. In the present embodiment, for example, the number of the ultrasonic transducers 121 of the coupling check ultrasonic transducer group 122 is four (4ch), and the ultrasonic transducers 121 of the flaw detection ultrasonic transducer groups 123 to 125 are used. The number of elements is 16 elements (16 ch), and the phased array probe 120 is composed of at least 52 elements (52 ch).

  In the example shown in FIG. 10, the scanning order of the ultrasonic beam is as follows: coupling check ultrasonic beam 132, inner surface near-surface flaw detection ultrasonic beam 131N, central portion near-surface flaw detection ultrasonic beam 131C, and outer surface near-surface flaw detection. Although the order of the ultrasonic beam 131G for use is in this order, the present invention is not limited to this. For example, the scanning order of the ultrasonic beam is the order of the ultrasonic beam 132 for coupling check, the ultrasonic beam 131G near the outer surface, the ultrasonic beam 131C near the center, and the ultrasonic beam 131N near the inner surface. It may be.

  In the present embodiment, each of the ultrasonic transducer groups for flaw detection divided (divided) into N (three in this example) groups in the phased array probe 120 is selected one by one and each ultrasonic wave is selected. By transmitting and receiving the beam, the ultrasonic beam is scanned in the tube thickness direction of the welded portion 210 (welded surface), and the welded portion 210 (welded surface) is flawlessly detected. Further, in the present embodiment, by using several elements at the end of the phased array probe 120 (the right end in the example of FIG. 10), the coupling check superstructure is substantially perpendicular to the outer surface 200G of the electric resistance welded steel pipe 200. The coupling check is performed by transmitting the acoustic beam 132 and detecting the reflected ultrasonic beam.

  Next, details of the coupling check will be described. FIG. 11 is a diagram for explaining the coupling check according to the first embodiment of this invention. As described above, the medium for efficiently propagating the flaw detection ultrasonic beam 131 between the phased array probe 120 (strictly speaking, the acoustic lens 110) and the outer surface 200G of the ERW steel pipe 200. As water is present. In the coupling check, the space between the phased array probe 120 (acoustic lens 110) and the outer surface 200G of the ERW steel pipe 200 is filled with water without air or the like, so that the ultrasonic wave 131 for flaw detection is normally transmitted and received. This is a process for confirming whether the environment can be used. In the coupling check, an ultrasonic beam 132 for coupling check is transmitted / received via the ultrasonic transducer group 122 for coupling check. In the example shown in FIG. 11, the four elements (4ch) at the right end of the phased array probe 120 are used as the coupling check ultrasonic transducer group 122.

FIG. 12 is a diagram illustrating an example of a reception waveform of the reflected coupling check ultrasonic beam 132 according to the first embodiment of this invention. In the example shown in FIG. 12, the outer surface echo (S ₁ ) reflected by the outer surface 200G of the ERW steel pipe 200, the inner surface echo (B ₁ ) reflected by the inner surface 200N of the ERW steel pipe 200, the inner surface echo ( Multiple echoes (B ₂ , B ₃ ,...) Between the outer surface 200G and the inner surface 200N are detected after B ₁ ). For example, in the coupling check, if a reflected echo is detected before the outer surface echo (S ₁ ), the phased array probe 120 (strictly speaking, the acoustic lens 110) and the outer surface 200G of the ERW steel pipe 200 Therefore, it is determined that the environment is not capable of normally transmitting / receiving the ultrasonic beam 131 for flaw detection. On the other hand, if no reflected echo is detected before the outer surface echo (S ₁ ), there is water between the phased array probe 120 (strictly speaking, the acoustic lens 110) and the outer surface 200G of the ERW steel pipe 200. Therefore, it is determined that the environment is such that the ultrasonic wave 131 for flaw detection can be normally transmitted and received. In the coupling check, since multiple echoes (B ₂ , B ₃ ,...) Are detected after the inner surface echo (B ₁ ), the ultrasonic beam for flaw detection in 70 ° flaw detection performed after the coupling check is performed. The transmission of 131 requires a certain amount of time after the transmission of the coupling check ultrasonic beam 132.

<Design of acoustic lens 110>
Next, the design of the acoustic lens 110 will be described.

  The phased array probe 120 focuses the ultrasonic beam only in the thickness direction of the ERW steel pipe 200. In the present embodiment, the acoustic lens 110 is further attached to the phased array probe 120 in order to focus the ultrasonic beam also in the tube axis direction 220 of the electric resistance welded steel tube 200.

  FIG. 13 is a view for explaining the acoustic lens 110 shown in FIGS. 1 and 3 according to the first embodiment of the present invention.

  The relational expression of the acoustic lens 110 is as shown in the following expressions (1) to (2).

R = (1−C ₂ / C ₁ ) f (1)
f = f _W + (C ₃ / C ₂ ) f _S (2)
Here, R represents the radius of curvature of the acoustic lens 110, f is focal length in water, C ₁ is a longitudinal wave sonic speed of the acoustic lens 110, C ₂ underwater longitudinal wave acoustic velocity, C ₃ steel pipe in shear wave velocity, f _w is the water path length , F _S is the path in the steel pipe. Specific numerical values of each parameter are as shown in FIG.

  As shown in Table 1, since only a longitudinal wave propagates in water, a longitudinal wave ultrasonic beam is transmitted from the phased array probe 120. The longitudinal ultrasonic beam transmitted from the phased array probe 120 is refracted by about 70 ° with respect to the incident direction on the outer surface 200G of the ERW steel pipe 200 and propagates through the ERW steel pipe 200. In the electric resistance welded steel pipe 200, a substantially transverse ultrasonic beam propagates.

  FIG. 14 shows the first embodiment of the present invention, and shows the relationship between the radius of curvature of the acoustic lens 110 shown in FIGS. 1 and 3 and the array length (array position) of the phased array probe 120. is there. FIG. 14 shows the conversion of the radius of curvature of the acoustic lens 110 at the point where the ultrasonic beam central axis corresponding to each depth of the welded portion 210 (welded surface) and the phased array probe 120 intersect with each ultrasonic beam path length. It is what I asked for. However, the pitch p of the phased array probe 120 is set to 0.5 mm so that the ultrasonic beam incident on the center of the welded portion 210 (welded surface) becomes the array center of the phased array probe 120.

  Here, as shown in FIG. 10, the phased array probe 120 of the present embodiment includes a coupling check ultrasonic transducer group 122 and an inner surface vicinity ultrasonic transducer group (third flaw detection ultrasonic transducer group). Ultrasonic transducer group (Nth ultrasonic transducer group for flaw detection)) 123, ultrasonic transducer group for flaw detection near the center (second ultrasonic transducer group for flaw detection) 124, and flaw detection near the outer surface An ultrasonic transducer group (first flaw detection ultrasonic transducer group) 125 is employed. Here, in FIG. 14, for example, an array length (array position) of 18.5 mm to 10.0 mm is an outer surface vicinity ultrasonic transducer group (first ultrasonic ultrasonic transducer group shown in FIG. 10). ) 125 and an array length (array position) of 10.0 mm to 1.5 mm corresponds to the ultrasonic transducer group for flaw detection near the center (second ultrasonic transducer group for flaw detection) 124 shown in FIG. Correspondingly, an array length (array position) of 1.5 mm to -7.0 mm is near the inner surface of the ultrasonic transducer group for flaw detection (third ultrasonic transducer group for flaw detection (Nth flaw detection) shown in FIG. This corresponds to the ultrasonic transducer group for use)) 123. That is, the acoustic lens 110 has a radius of curvature from an area corresponding to the outer surface flaw detection ultrasonic transducer group (first flaw detection ultrasonic transducer group) 125 to the inner surface flaw detection ultrasonic transducer group. (Third flaw detection ultrasonic transducer group (Nth flaw detection ultrasonic transducer group)) 123 increases in size. In other words, in the acoustic lens 110, the curvature radius of the curved surface along the tube axis direction 220 changes along the arrangement direction of the plurality of ultrasonic transducers, and the welded portion 210 ( The radius of curvature increases in the direction in which the propagation distance of the flaw detection ultrasonic beam up to the weld surface increases. In the present embodiment, the acoustic lens 110 is designed in this way, so that a suitable ultrasonic beam 131 for flaw detection can be transmitted and received through each flaw detection ultrasonic transducer group.

<Consideration of flaw detection repetition frequency>
Next, in the defect detection apparatus 100 according to the present embodiment, it is considered whether or not the defect inspection of the welded portion 210 (welded surface) can be performed without leakage in the tube axis direction 220 of the electric resistance welded steel pipe 200.

  It is assumed that the beam focusing diameter in the tube axis direction is generally 1 mm due to the focusing of the ultrasonic beam in the tube axis direction 220 by the acoustic lens 110. Further, assuming that the flaw detection is performed by switching the flaw detection depth of the welded portion 210 (welded surface), as shown in FIG. 10, the ultrasonic wave 131 for the flaw detection is transmitted three times and the ultrasonic beam for the coupling check is used. It is assumed that the ultrasonic beam is transmitted and received a total of four times, that is, the number of times of transmission / reception 132 is one.

  Further, if the pipe making speed of the electric resistance welded steel pipe 200 is about 40 m / min, which is the moving speed of the electric resistance welded steel pipe 200 in a typical actual operation line, this is 667 mm / second, and therefore leaks in the pipe axis direction 220. In order to detect flaws without fail, it is necessary to transmit and receive an ultrasonic beam 2668 times (4 × 677) per second. Therefore, the flaw detection repetition frequency of the defect detection apparatus 100 needs to be at least 2668 Hz (about 2.7 kHz).

  On the other hand, since a defect inspection apparatus using the phased array probe 120 in recent years has a maximum repetition frequency of several tens of kHz, the above-described inspection repetition frequency (about 2.7 kHz) can be sufficiently realized. Is employed in the defect detection apparatus 100 in the present embodiment, it is possible to perform defect inspection without leakage in the tube axis direction 220 of the electric resistance welded steel pipe 200.

<Processing procedure by defect detection device>
Next, a processing procedure of the defect detection method by the defect detection apparatus 100 according to the present embodiment will be described.

  FIG. 15 is a flowchart illustrating an example of a processing procedure of the defect detection method performed by the defect detection apparatus 100 according to the first embodiment of the present invention. The description of the flowchart shown in FIG. 15 will be made using the configuration of the defect detection apparatus 100 shown in FIG.

  First, in step S1, the subject condition input unit 141 performs a process of inputting a condition (subject condition) of the electric resistance welded steel pipe 200 that is the subject. For example, the subject condition input unit 141 controls a subject condition (for example, the outer diameter and thickness of the electric resistance welded pipe 200, the length in the pipe axis direction 220, the pipe making speed, etc.) input by the user. The process of inputting into 140 is performed. Here, the outer diameter of the ERW steel pipe 200 is 101.6 mm (FIG. 13), the pipe thickness of the ERW steel pipe 200 is 3.4 mm (FIGS. 9 and 13), and the pipe making speed of the ERW steel pipe 200 is 40 m / min. Is entered.

  Subsequently, in step S2, the transmission / reception condition setting unit 142 performs processing for setting the transmission / reception conditions based on the subject condition input in step S1. Here, as the transmission / reception conditions, for example, the transmission / reception timing of the ultrasonic beam 131 for flaw detection and the ultrasonic beam 132 for coupling check, the transmission frequency of these ultrasonic beams, and the ultrasonic waves used for transmission / reception of these ultrasonic beams The delay time of the transmission timing of each channel of the ultrasonic transducer group for flaw detection is set so that the transducer 121 and the flaw detection ultrasonic beam 131 are converged at the welded portion 210 (welded surface).

  In this embodiment, since the thickness of the ERW steel pipe 200 is 3.4 mm, the phased array probe 120 having the maximum SN ratio (200) in FIG. Pitch p is 0.5 mm, and the frequency of ultrasonic waves to be transmitted is 5 MHz). At this time, in this embodiment, in step S2, the transmission / reception condition setting unit 142 is used for flaw detection on the pipe thickness of the welded steel pipe 200 (the thickness of the welded part 210 (welded surface)) and the welded part 210 (welded surface). Based on the effective beam diameter of the ultrasonic beam 131, the number N of divisions for dividing the tube thickness direction region of the welded portion 210 (welded surface) into N pieces (N is an integer of 1 or more) is set. The number N of divisions corresponds to the number of scans related to ultrasonic flaw detection in the direction of the tube thickness in the welded portion 210 (welded surface). Specifically, in this embodiment, the pipe thickness of the welded steel pipe 200 is 3.4 mm, and the effective beam diameter of the ultrasonic beam for flaw detection with respect to the welded portion 210 (welded surface) is 1.6 mm (FIG. 9B). “3” is set as the division number N. As shown in FIG. 10, the transmission / reception condition setting unit 142 sets the ultrasonic transducer group for flaw detection in the phased array probe 120 to the ultrasonic transducer group for flaw detection near the inner surface, as shown in FIG. (Third flaw detection ultrasonic transducer group (Nth flaw detection ultrasonic transducer group)) 123, near the central portion flaw detection ultrasonic transducer group (second flaw detection ultrasonic transducer group) 124, and The ultrasonic vibration group constituting the flaw detection ultrasonic transducer group is divided (divided) into three groups of the outer surface vicinity flaw detection ultrasonic transducer group (first flaw detection ultrasonic transducer group). A coupling check ultrasonic transducer group 122 configured by a plurality of ultrasonic transducers different from the child is set.

  Subsequently, in step S3, the transmission unit 144 controls the ultrasonic transducer for coupling check of the phased array probe 120 based on the transmission / reception conditions set by the transmission / reception condition setting unit 142 under the control of the transmission / reception control unit 143. The ultrasonic beam 132 for coupling check is transmitted from the group 122 substantially perpendicularly to the outer surface 200G of the ERW steel pipe 200.

  Subsequently, in step S <b> 4, the receiving unit 145 controls the reflected coupling check ultrasonic beam 132 for coupling check based on the transmission / reception conditions set by the transmission / reception condition setting unit 142 under the control of the transmission / reception control unit 143. Received via the ultrasonic transducer group 122. Thereafter, the coupling check ultrasonic beam 132 received by the reception unit 145 is processed by the reception signal processing unit 146.

  Subsequently, in step S5, the water determination unit 148 determines whether or not the coupling is problematic based on the coupling check ultrasonic beam 132 received in step S4. Specifically, the water determination unit 148 determines whether or not the space between the phased array probe 120 (strictly speaking, the acoustic lens 110) and the outer surface 200G of the ERW steel pipe 200 is filled with water without air or the like. By determining, it is determined whether or not the coupling is problematic.

  As a result of the determination in step S5, when it is determined in the coupling check that there is a problem with the coupling (in the case of S5 / NO), the process proceeds to step S6.

  In step S6, the recording / display unit 149 displays a warning indicating that there is a problem with the coupling. By performing this warning display, the user performs maintenance of the equipment, and after the maintenance of the equipment, the processing is performed from the beginning of the flowchart of FIG. 15 by the user's operation.

  On the other hand, as a result of the determination in step S5, when it is determined in the coupling check that there is no problem in coupling (in the case of S5 / YES), the process proceeds to step S7. If there is no problem in the coupling, the defect inspection process of the welded part 210 is started.

  In step S7, the transmission unit 144 is controlled by the transmission / reception control unit 143 based on the transmission / reception conditions set by the transmission / reception condition setting unit 142 from the ultrasonic transducer group for flaw detection of the phased array probe 120. The flaw detection ultrasonic beam 131 is incident on the outer surface 200G of the sewn steel pipe 200 at an oblique angle. The transmitting unit 144 directly enters the welded ultrasonic wave beam 131 incident on the welded part 210 (welded surface) substantially perpendicularly without being reflected by the inner surface 200N of the welded steel pipe 200. And the ultrasonic beam 131 for flaw detection is transmitted so that it may converge on the welding part 210 (welding surface).

  Subsequently, in step S8, the receiving unit 145 controls the reflected ultrasonic beam 131 for flaw detection based on the transmission / reception conditions set by the transmission / reception condition setting unit 142 under the control of the transmission / reception control unit 143. Receive via the ultrasonic transducer group. Thereafter, the flaw detection ultrasonic beam 131 received by the receiving unit 145 is processed by the received signal processing unit 146.

  Subsequently, in step S <b> 9, for example, the transmission / reception control unit 143 determines whether or not all defect inspections have been performed in the depth direction (tube thickness direction) of the welded part 210.

  Here, in the present embodiment, as shown in FIG. 10, as a group of ultrasonic transducers for flaw detection, the vicinity of the inner surface 200N of the welded portion 210 (welded surface) of the ERW steel pipe 200 (that is, the third region (the first region) N region)) near the inner surface ultrasonic transducer group (third ultrasonic ultrasonic beam for flaw detection (Nth ultrasonic beam for flaw detection)) 131N for transmitting near the inner surface ultrasonic transducer group (Third flaw detection ultrasonic transducer group (Nth flaw detection ultrasonic transducer group)) 123 and the vicinity of the center portion of the pipe thickness of the welded portion 210 (welded surface) of the ERW steel pipe 200 (that is, the first flaw detection ultrasonic transducer group). 2), an ultrasonic transducer group near the central portion for transmitting the ultrasonic beam near the central portion (second ultrasonic beam for flaw detection) 131C (second ultrasonic transducer group for flaw detection). ) 124 and the vicinity of the outer surface 200G of the welded portion 210 (welded surface) of the ERW steel pipe 200 (immediately , First surface) ultrasonic transducer group near the outer surface for transmitting the ultrasonic beam for near-surface flaw detection (first flaw detection ultrasonic beam) 131G (first flaw detection ultrasonic vibration) (Child group) 125 is composed of different ultrasonic transducers. Therefore, in the present embodiment, in step S9, in the depth direction (tube thickness direction) of the welded portion 210 (weld surface), defect inspection using the ultrasonic beam 131N near the inner surface and ultrasonic beam for flaw detection near the center portion are performed. It is determined whether or not the defect inspection by 131C and the defect inspection by the ultrasonic beam 131G for detecting near the outer surface have been performed.

  As a result of the determination in step S9, if not all defect inspection has been performed for each region in the depth direction of the welded portion 210 (welded surface) (in the case of S9 / NO), the region where defect inspection has not yet been performed. The process returns to step S7 to perform the defect inspection.

  On the other hand, as a result of the determination in step S9, if all the flaw detection is performed in the depth direction of the welded portion 210 (in the case of S9 / YES), the process proceeds to step S10.

  In step S10, for example, the transmission / reception control unit 143 determines whether or not all defect inspections have been performed in the tube axis direction 220 of the ERW steel pipe 200.

  Here, in the present embodiment, as described above, it is assumed that the tube-axis direction beam focusing diameter is generally 1 mm due to the focusing of the ultrasonic beam in the tube axis direction 220 by the acoustic lens 110. On the other hand, the length in the tube axis direction 220 is input in step S1. Therefore, in the present embodiment, in step S10, it is determined whether or not defect inspection has been performed for the entire region in the tube axis direction 220 of the ERW steel tube 200 based on these pieces of information.

  As a result of the determination in step S10, when defect inspection is not performed for the entire region in the tube axis direction 220 of the ERW steel pipe 200 (S10 / NO), the tube axis direction of the ERW steel pipe 200 that has not yet been subjected to defect inspection. The process returns to step S7 to perform the defect inspection of the area 220.

  On the other hand, as a result of the determination in step S10, when defect inspection is performed for the entire region in the tube axis direction 220 of the ERW steel pipe 200 (in the case of S10 / YES), the process proceeds to step S11.

  Subsequently, in step S11, the defect determination unit 147 determines whether or not there is a defect in the welded portion 210 (welded surface) of the ERW steel pipe 200 based on the flaw detection ultrasonic beam 131 received in step S8. Processing to determine is performed. Furthermore, when the defect determination unit 147 determines that a defect exists in the welded part 210 (welded surface), the defect determination unit 147 also performs processing for specifying the position and size.

  In the previous stage of defect determination by the defect determination unit 147, for example, the received signal processing unit 146 sets the positive maximum amplitude to A and the negative maximum amplitude to B with respect to the waveform of the received ultrasonic beam 131 for flaw detection. Each is detected as (B is a negative value), and A-B is processed as a signal C at the waveform detection position.

  Subsequently, in step S12, the recording / display unit 149 performs a process of displaying the defect determination result in step S11. For example, the recording / display unit 149 creates a two-dimensional map of the signal C as the defect determination result, for example, with the x-axis direction as the position in the tube axis direction 220 and the y-axis direction as the depth position of the welded part 210. Display.

  Hereinafter, an example of a two-dimensional map will be described. First, before explaining the two-dimensional map, an example of a received waveform of the flaw detection ultrasonic beam will be described.

FIG. 16 is a diagram illustrating an example of a reception waveform of a reflected ultrasonic beam for flaw detection according to the first embodiment of this invention. Here, FIGS. 16A and 16B are analyzed under the condition that the number of sections N is 5 larger than 3 in order to improve the resolution in the thickness direction of the ERW steel pipe 200. The resolution is 1 mm, and the resolution in the tube thickness direction is 0.68 mm corresponding to 1/5 of the tube thickness (3.4 mm). In FIG. 16A, a defect 211 having a thickness of 0.2 mm is provided around the central part in the tube thickness direction, and the ultrasonic beam for flaw detection is focused on the defect 211 in the central part among the five sections, and the reflected supersonic beam is focused. It is an example of the received waveform of a sound wave. FIG. 16B shows an example of a received waveform of the reflected ultrasonic wave in which the defect 211 is not provided in the central part in the tube thickness direction and the flaw detection ultrasonic beam is focused on the central part among the five sections. In the received waveforms shown in FIGS. 16A and 16B, S ₁ indicates the reflected ultrasonic wave from the outer surface 200G of the electric resistance welded steel pipe 200, and in the received waveform shown in FIG. 16A, F ₁ indicates the reflected ultrasonic wave from the defect 211. ing. That is, as in the received waveform shown in FIG. 16B, if there is no defect 211, F ₁ is not detected.

Next, an example of a two-dimensional map will be described. FIG. 17 is a diagram illustrating an example of a two-dimensional map according to the first embodiment of this invention. The two-dimensional map shown in FIG. 17 is obtained by analyzing the pipe thickness direction of the electric resistance welded steel pipe 200 in five sections in the same manner as in FIG. 16A described above. The defect 211 is provided in the central part of each. In FIG. 17, the x-axis direction is the position in the tube axis direction 220, the y-axis direction is the position in the tube thickness direction of the ERW steel pipe 200 (the depth position of the welded portion 210), and the signal C described above has seven stages ( 6 <C,..., C ≦ 1). For example, the reflected ultrasonic wave F ₁ from the defect 211 shown in FIG. 16A has a positive maximum amplitude A of about 3.2 and a negative maximum amplitude B of about −3.6. C = A−B = 3.2 − (− 3.6) = 6.8. For this reason, in FIG. 17, the center part of the pipe thickness direction of the ERW steel pipe 200 divided into five sections is 6 <C. By displaying such a two-dimensional map, it is possible to specify the position of the defect 211 in the welded part 210 of the ERW steel pipe 200.

  When the process of step S12 ends, the process of the flowchart in FIG. 15 ends.

According to the defect detection apparatus 100 according to the present embodiment, since the 70 ° flaw detection method using the phased array probe 120 is performed, it is possible to detect a minute defect of about 0.2 mm, and the tube Even in the case of a small diameter ERW steel pipe 200 having a thickness of 7.5 mm or less and a pipe diameter of 5 inches or less, improvement in defect detection accuracy can be realized (FIG. 8).
(Second Embodiment)
In the first embodiment described above, as shown in FIG. 10, as an ultrasonic transducer group for flaw detection of the phased array probe 120, in the vicinity of the inner surface 200N of the welded portion 210 (welded surface) of the ERW steel pipe 200 ( That is, the inner surface for transmitting the ultrasonic beam for near-inner surface flaw detection (third flaw detection ultrasonic beam (Nth flaw detection ultrasonic beam)) 131N to the third region (Nth region). The near-surface flaw detection ultrasonic transducer group (third flaw detection ultrasonic transducer group (Nth flaw detection ultrasonic transducer group)) 123 and the pipe thickness of the welded portion 210 (welded surface) of the ERW steel pipe 200 Near the center (ie, the second region) of the ultrasonic transducer group near the center for transmitting the ultrasonic beam for near-center flaw detection (second ultrasonic beam for flaw detection) 131C (second region) Of ultrasonic transducers for flaw detection) 124 and welded portion 210 of ERW steel pipe 200 Ultrasonic transducer for flaw detection near the outer surface for transmitting an ultrasonic wave for flaw detection near the outer surface (first flaw detection ultrasonic beam) 131G near the outer surface 200G of the welding surface) (that is, the first region). The case where the group (first flaw detection ultrasonic transducer group) 125 is configured by different ultrasonic transducers is illustrated. In the present invention, the present invention is not limited to this mode. One flaw detection ultrasonic transducer group is set in the phased array probe 120, and the ultrasonic flaw detection ultrasonic transducer group is used to set ultrasonic waves. By sequentially switching the transmission direction, the third region (Nth region), the second region, and the first region in the tube thickness direction in the welded portion 210 are respectively third. An ultrasonic beam 131N near the inner surface which is an ultrasonic beam for flaw detection (Nth ultrasonic beam for flaw detection), an ultrasonic beam 131C for flaw detection near the center which is a second ultrasonic beam for flaw detection, and A mode in which the outer surface near-surface detection ultrasonic beam 131G, which is the first ultrasonic inspection beam, is sequentially transmitted is also applicable. In this case, the reflected ultrasonic beam 131N near the inner surface, the reflected ultrasonic beam 131C near the central portion, and the reflected outer surface flaw detected through the single ultrasonic transducer group. Each ultrasonic beam 131G is received.

In the case of the present embodiment, the phased array probe 120 is provided with one flaw detection ultrasonic transducer group (for example, 16 ch) and one coupling check ultrasonic transducer group 122 (for example, 4 ch). become.
(Third embodiment)
In the first and second embodiments described above, the flaw detection ultrasonic transducer group and the coupling check ultrasonic transducer group 122 are configured by different ultrasonic transducers. In the present invention, the present invention is not limited to this embodiment, and the ultrasonic transducer for flaw detection is performed by all of the plurality of ultrasonic transducers among the plurality of ultrasonic transducers 121 arranged in the phased array probe 120. A configuration in which a group is formed and the ultrasonic transducer group for coupling check 122 is included in the ultrasonic transducer group for flaw detection is also applicable.

  In the case of the present embodiment, for example, 16 ultrasonic transducers 121 (16ch) are provided in the phased array probe 120, and all of the 16 ultrasonic transducers 121 are used as an ultrasonic transducer group for flaw detection. All or a part (for example, 4ch) of the 16 ultrasonic transducers 121 are set as a coupling check ultrasonic transducer group 122.

That is, in this embodiment, the ultrasonic wave 132 for coupling check is transmitted from the phased array probe 120 to the outer surface 200G of the electric resistance welded steel pipe 200 by sequentially switching the transmission direction of the ultrasonic waves. , For third flaw detection with respect to the third region (Nth region), the second region, and the first region in the tube thickness direction in the welded portion 210 (welded surface), respectively. An ultrasonic beam 131N near the inner surface that is an ultrasonic beam (Nth ultrasonic beam for flaw detection), an ultrasonic beam 131C near the center that is a second ultrasonic beam for flaw detection, and the first A configuration is adopted in which the outer surface vicinity ultrasonic detecting beam 131G which is an ultrasonic detecting beam is sequentially transmitted. In this case, the reflected ultrasonic beam 132 for coupling check, the reflected ultrasonic beam 131N near the inner surface, the reflected ultrasonic beam 131C near the center, and the reflected through the phased array probe 120, The reflected ultrasonic wave 131G for flaw detection near the outer surface is received.
(Other embodiments)
The present invention can also be realized by executing the following processing. That is, software (program) that realizes the function of the control processing apparatus 140 according to the embodiment of the present invention described above is supplied to a system or apparatus via a network or various storage media, and a computer (or CPU or CPU) of the system or apparatus is supplied. MPU or the like) reads out and executes a program. This program and a computer-readable recording medium storing the program are included in the present invention.

  The above-described embodiments of the present invention are merely examples of the implementation of the present invention, and the technical scope of the present invention should not be construed in a limited manner. . That is, the present invention can be implemented in various forms without departing from the technical idea or the main features thereof. The entire disclosure of Japanese Patent Application No. 2012-150685 is incorporated herein by reference. All documents, patent applications, and technical standards mentioned in this specification are to the same extent as if each individual document, patent application, and technical standard were specifically and individually described to be incorporated by reference, Incorporated herein by reference.

DESCRIPTION OF SYMBOLS 100: Defect detection apparatus, 110: Acoustic lens, 120: Phased array probe, 121: Ultrasonic transducer, 131: Ultrasonic beam for flaw detection, 132: Ultrasonic beam for coupling check (Ultrasonic beam for water determination) 140: Control processing device, 141: Subject condition input unit, 142: Transmission / reception condition setting unit, 143: Transmission / reception control unit, 144: Transmission unit, 145: Reception unit, 146: Reception signal processing unit, 147: Defect determination Part, 148: water judgment part, 149: recording / display part, 200: ERW steel pipe, 200G: outer surface, 200N: inner surface, 210: welded part

Claims (18)

A defect detection device for detecting defects present on a weld surface formed along the pipe axis direction of a welded steel pipe,
A phased array probe installed outside the outer surface of the welded steel pipe and arranged with a plurality of ultrasonic transducers;
From the group of ultrasonic transducers for flaws including a part or all of the plurality of ultrasonic transducers, an ultrasonic beam for flaw detection incident on the welded steel pipe from the outer surface of the welded steel pipe is generated inside the welded steel pipe. The ultrasonic beam for flaw detection is transmitted so as to be directly incident on the welding surface substantially vertically without being reflected by the surface and to converge on the welding surface, and the thickness of the welded steel pipe and the welding surface A plurality of regions along the tube thickness direction of the weld surface based on the effective beam diameter determined based on the displacement distribution inside the tube thickness direction of the welded steel tube of the ultrasonic beam for flaw detection in Transmitting means for transmitting the ultrasonic beam for flaw detection a plurality of times so that the ultrasonic beam for flaw detection is sequentially incident on each of the divided areas of the welding surface;
Receiving means for receiving the reflected ultrasonic beam for flaw detection via the flaw detection ultrasonic transducer group;
Defect determining means for determining whether or not there is a defect on the weld surface based on the ultrasonic beam for flaw detection received by the receiving means;
A defect detection apparatus including:   The defect detection apparatus according to claim 1, wherein the welded steel pipe is a small-diameter ERW steel pipe having a pipe diameter of 5 inches or less and a pipe thickness of 7.5 mm or less. Between the phased array probe and the outer surface of the welded steel pipe, water exists as a medium through which the ultrasonic beam for flaw detection propagates,
The transmitter further includes a water determination ultrasonic beam substantially perpendicular to the outer surface of the welded steel pipe from a water determination ultrasonic transducer group including a part or all of the plurality of ultrasonic transducers. Send
The receiving means further receives the reflected ultrasonic beam for water determination via the ultrasonic transducer group for water determination,
Water determination means for determining whether the space between the phased array probe and the outer surface of the welded steel pipe is filled with water based on the water determination ultrasonic beam received by the reception means. The defect detection apparatus of Claim 1 or 2 containing.   When the water determining unit determines that the space between the phased array probe and the outer surface of the welded steel pipe is filled with water, the transmitting unit determines from the flaw detection ultrasonic transducer group as described above. The defect detection apparatus according to claim 3, wherein an ultrasonic beam for flaw detection is transmitted.   A focusing lens provided between the phased array probe and the outer surface of the welded steel pipe so as to correspond to the phased array probe and for focusing the flaw detection ultrasonic beam in the tube axis direction; The defect detection apparatus of any one of Claims 1 thru | or 4 containing.   The transmitting means divides a plurality of ultrasonic transducers included in the flaw detection ultrasonic transducer group into N groups according to the number N of sections of the weld surface in the tube thickness direction, 5. The defect detection according to claim 1, wherein the flaw detection ultrasonic beam is sequentially transmitted from each of the divided groups so that the flaw detection ultrasonic beam sequentially enters each of the divided areas of the weld surface. 6. apparatus. A focusing lens provided between the phased array probe and the outer surface of the welded steel pipe so as to correspond to the phased array probe and for focusing the flaw detection ultrasonic beam in the tube axis direction; Including
In the focusing lens, the radius of curvature of the curved surface along the tube axis direction changes along the arrangement direction of the plurality of ultrasonic transducers, and extends from the phased array probe to the welding surface. The defect detection apparatus according to claim 6, wherein the radius of curvature increases in a direction in which a propagation distance of the ultrasonic beam for flaw detection increases. Before Symbol transmission means such that said the flaw ultrasonic beams to divided each regions of the weld surface is sequentially incident ultrasonic transducer for a single flaw comprising a portion of said plurality of ultrasonic transducers The defect detection apparatus according to claim 1, wherein the ultrasonic wave for flaw detection is transmitted by sequentially switching the transmission direction from the group. Before Symbol transmission means such that said the flaw ultrasonic beams to divided each regions of the weld surface is sequentially incident, the transmission direction from said plurality of ultrasonic comprises all vibrators wound group of ultrasound transducers Are sequentially switched to transmit the ultrasonic beam for flaw detection, and from the water determination ultrasonic transducer group including a part of the plurality of ultrasonic transducers, to the outer surface of the welded steel pipe, The defect detection apparatus according to claim 3, wherein an ultrasonic beam is transmitted.   A focusing lens provided between the phased array probe and the outer surface of the welded steel pipe so as to correspond to the phased array probe and for focusing the flaw detection ultrasonic beam in the tube axis direction; The defect detection apparatus of Claim 9 containing.   The transmitting means rounds the pipe thickness of the welded steel pipe by the effective beam diameter of the flaw-detecting ultrasonic beam on the weld surface, and rounds up the first decimal place to the pipe thickness of the weld surface. The defect detection apparatus according to claim 1, wherein the defect detection apparatus is set as the number of sections in the direction. The effective beam diameter corresponds to a range in which the displacement is 0.5 or more when a maximum value of displacement inside the welded steel pipe due to vibration of the ultrasonic beam for flaw detection is 1. The defect detection apparatus of any one of thru | or 11. Using a phased array probe installed outside the outer surface of the welded steel pipe and arranged with a plurality of ultrasonic transducers, defects present on the weld surface formed along the pipe axis direction of the welded steel pipe are removed. A defect detection method by a defect detection device to detect,
Based on the pipe thickness of the welded steel pipe and the effective beam diameter determined based on the internal displacement distribution of the ultrasonic beam for flaw detection on the welded surface in the pipe thickness direction of the welded steel pipe, An area segmentation step for segmenting into a plurality of areas along the thickness direction;
From the group of ultrasonic transducers for flaws including a part or all of the plurality of ultrasonic transducers, an ultrasonic beam for flaw detection incident on the welded steel pipe from the outer surface of the welded steel pipe is generated inside the welded steel pipe. A plurality of times so that the ultrasonic beam for flaw detection is incident on the welding surface substantially perpendicularly without being reflected on the surface, is focused on the welding surface, and is incident on each divided region of the welding surface. A first transmission step of transmitting the flaw detection ultrasonic beam over a period of time;
A first reception step of receiving the reflected ultrasonic beam for flaw detection via the flaw detection ultrasonic transducer group;
A defect determination step of determining whether or not a defect exists on the weld surface based on the ultrasonic beam for flaw detection received in the first reception step;
A defect detection method including:   The defect detection method according to claim 13, wherein the welded steel pipe is a small-diameter ERW steel pipe having a pipe diameter of 5 inches or less and a pipe thickness of 7.5 mm or less. Between the phased array probe and the outer surface of the welded steel pipe, water exists as a medium through which the ultrasonic beam for flaw detection propagates,
Second transmission for transmitting a water determination ultrasonic beam from a water determination ultrasonic transducer group including a part or all of the plurality of ultrasonic transducers substantially perpendicularly to the outer surface of the welded steel pipe. Steps,
A second receiving step of receiving the reflected ultrasonic beam for water determination via the ultrasonic transducer group for water determination;
Water determination for determining whether the space between the phased array probe and the outer surface of the welded steel pipe is filled with water based on the water determination ultrasonic beam received in the second reception step Steps,
The defect detection method according to claim 13 or 14, further comprising: Using a phased array probe installed outside the outer surface of the welded steel pipe and arranged with a plurality of ultrasonic transducers, defects present on the weld surface formed along the pipe axis direction of the welded steel pipe are removed. A program for causing a computer to execute a defect detection method by a defect detection device to detect,
Based on the pipe thickness of the welded steel pipe and the effective beam diameter determined based on the internal displacement distribution of the ultrasonic beam for flaw detection on the welded surface in the pipe thickness direction of the welded steel pipe, An area segmentation step for segmenting into a plurality of areas along the thickness direction;
From the group of ultrasonic transducers for flaws including a part or all of the plurality of ultrasonic transducers, an ultrasonic beam for flaw detection incident on the welded steel pipe from the outer surface of the welded steel pipe is generated inside the welded steel pipe. A plurality of times so that the ultrasonic beam for flaw detection is incident on the welding surface substantially perpendicularly without being reflected on the surface, is focused on the welding surface, and is incident on each divided region of the welding surface. A first transmission step of transmitting the flaw detection ultrasonic beam over a period of time;
A first reception step of receiving the reflected ultrasonic beam for flaw detection via the flaw detection ultrasonic transducer group;
A defect determination step of determining whether or not a defect exists on the weld surface based on the ultrasonic beam for flaw detection received in the first reception step;
A program that causes a computer to execute. Between the phased array probe and the outer surface of the welded steel pipe, water exists as a medium through which the ultrasonic beam for flaw detection propagates,
Second transmission for transmitting a water determination ultrasonic beam from a water determination ultrasonic transducer group including a part or all of the plurality of ultrasonic transducers substantially perpendicularly to the outer surface of the welded steel pipe. Steps,
A second receiving step of receiving the reflected ultrasonic beam for water determination via the ultrasonic transducer group for water determination;
Water determination for determining whether the space between the phased array probe and the outer surface of the welded steel pipe is filled with water based on the water determination ultrasonic beam received in the second reception step Steps,
The program according to claim 16, further causing the computer to execute.   A computer-readable storage medium storing the program according to claim 16 or 17.

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