JP4359892B2 - Ultrasonic flaw detection method - Google Patents
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Description
本発明は、管材の超音波探傷方法に関し、特に被検査管の管軸方向から傾斜する方向に延びるいわゆる斜めきずを精度良く且つ効率良く検出可能な超音波探傷方法に関する。 The present invention relates to an ultrasonic flaw detection method for a tube material, and more particularly to an ultrasonic flaw detection method capable of accurately and efficiently detecting so-called oblique flaws extending in a direction inclined from the tube axis direction of a tube to be inspected.
従来より、鋼管等の管材に発生したきずを非破壊的に検出する方法として超音波探傷方法が広く用いられている。斯かる超音波探傷方法は、垂直方向から又は斜め方向から超音波を管材内部に入射し、管材内部や表面に存在するきずからの反射エコーを検出してきずの存在を検知する方法である。 Conventionally, an ultrasonic flaw detection method has been widely used as a method for nondestructively detecting flaws generated in a pipe material such as a steel pipe. Such an ultrasonic flaw detection method is a method in which ultrasonic waves are incident on the inside of a pipe material from a vertical direction or an oblique direction, and reflection echoes from flaws existing inside or on the surface of the pipe material are detected to detect the presence of flaws.
ここで、超音波探傷方法によってきずを確実に検出するには、きずにおける超音波の反射率を大きくするべく、超音波がきずの延びる方向に対して垂直に入射し垂直に反射するように超音波の入射角を選定することが重要である。鋼管の超音波探傷は、管軸方向又は管周方向に延びるきずを検出することを目的として行うのが一般的であるため、超音波がきずの延びる方向に対して垂直に入射し垂直に反射するように、鋼管の管周方向又は管軸方向に超音波を入射して探傷を行っている。しかしながら、管軸方向から傾斜する方向に延びる斜めきずが存在する場合には、管周方向や管軸方向から超音波を入射しても、斜めきずの延びる方向に対して垂直に入射し垂直に反射しないため、前記斜めきずが有害であったとしてもこれを検出することができないという問題がある。 Here, in order to reliably detect flaws by the ultrasonic flaw detection method, in order to increase the reflectivity of the ultrasonic waves in the flaws, the ultrasonic waves are incident perpendicularly to the extending direction of the flaws and reflected vertically. It is important to select the incident angle of the sound wave. Ultrasonic flaw detection of steel pipes is generally performed for the purpose of detecting flaws extending in the tube axis direction or pipe circumferential direction, so that ultrasonic waves are incident perpendicularly to the direction in which the flaws extend and reflected vertically. As described above, flaw detection is performed by injecting ultrasonic waves in the pipe circumferential direction or the pipe axis direction of the steel pipe. However, when there are oblique flaws extending in a direction inclined from the tube axis direction, even if ultrasonic waves are incident from the tube circumferential direction or the tube axis direction, they are incident perpendicularly to the direction in which the oblique flaws extend. Since there is no reflection, there is a problem that even if the oblique flaw is harmful, it cannot be detected.
そこで、上記のような斜めきずを検出する方法として、従来より、管周方向の入射角を設定した後に、管軸方向に入射方向を傾斜させて斜めきずを検出する方法が提案されている（特許文献１、２参照）。 Therefore, as a method for detecting the oblique flaw as described above, a method for detecting the oblique flaw by inclining the incident direction in the tube axis direction after setting the incident angle in the tube circumferential direction has been proposed ( (See Patent Documents 1 and 2).
より具体的に説明すれば、特許文献１には、管周斜角超音波探傷において、超音波ビームを入射方向を含む管軸平行面内で傾斜させて（５°≦傾斜角度α≦２０°）入射する方法が提案されている。 More specifically, Patent Document 1 discloses that in ultrasonic flaw detection around a tube circumference, an ultrasonic beam is tilted in a tube axis parallel plane including the incident direction (5 ° ≦ tilt angle α ≦ 20 °). ) A method of incidence has been proposed.
また、特許文献２には、管周方向に超音波を入射させる場合の入射角を設定した後に、超音波の入射点を頂点とし、該入射点における垂線を中心軸とする一つの円錐の側面上に超音波の照射方向ベクトルが存在するように超音波の照射方向を変更する方法が提案されている。
しかしながら、特許文献１に記載の方法は、単に超音波ビームの傾斜角度αをスリットきずの傾き（管軸方向と成す角度）θの約半分にして５°〜２０°の範囲で設定することを提案するのみであって、管軸方向に対して特定の傾斜角度を有する斜めきずを検出するための明確な指標を与えるものではない。また、特許文献１に記載の方法によれば、斜めきずの延びる方向に対して超音波を垂直な方向に入射させることが可能ではあるものの、超音波ビームを傾斜させることにより、入射角が変化する（これにより屈折角も変化する）ため、これに起因して斜めきずからの反射エコーが過大又は過小となり、きずの大きさに対応した適正な反射エコーが得られないという問題がある。 However, the method described in Patent Document 1 simply sets the inclination angle α of the ultrasonic beam to about half of the inclination (angle formed with the tube axis direction) θ of the slit flaw and sets it within a range of 5 ° to 20 °. It is only proposed and does not give a clear index for detecting oblique flaws having a specific inclination angle with respect to the tube axis direction. Further, according to the method described in Patent Document 1, although it is possible to make an ultrasonic wave incident in a direction perpendicular to the direction in which the oblique flaw extends, the incident angle changes by tilting the ultrasonic beam. As a result, the refraction angle also changes, and as a result, the reflected echo from the oblique flaw becomes excessive or small, and there is a problem that an appropriate reflected echo corresponding to the size of the flaw cannot be obtained.
また、特許文献２に記載の方法によれば、特許文献１に記載の方法のように超音波の入射角が変化することはなく、超音波の照射方向を変更しても入射角を一定に保つことができる（これにより屈折角も一定に保つことができる）ため、きずの大きさに対応した適正な反射エコーを得ることが可能である。また、検出したい斜めきずの傾斜角度と一致するように超音波の照射方向を変更すればよい（管周方向を基準にした超音波の照射方向を旋回する角度と、検出したい斜めきずの傾斜角度とを合致させればよい）ため、管軸方向に対して特定の傾斜角度を有する斜めきずを検出するための明確な指標が与えられる。 Further, according to the method described in Patent Document 2, the incident angle of the ultrasonic wave does not change as in the method described in Patent Document 1, and the incident angle is kept constant even when the ultrasonic wave irradiation direction is changed. Since the refraction angle can be kept constant (by this, the refraction angle can be kept constant), it is possible to obtain an appropriate reflection echo corresponding to the size of the flaw. In addition, the ultrasonic irradiation direction should be changed to match the inclination angle of the oblique flaw to be detected (the angle of turning the ultrasonic irradiation direction based on the tube circumferential direction and the inclination angle of the oblique flaw to be detected. Therefore, a clear index for detecting oblique flaws having a specific inclination angle with respect to the tube axis direction is given.
しかしながら、特許文献２に記載の方法を実施するには、超音波の入射点における垂線を中心軸とする一つの円錐の側面上に超音波の照射方向ベクトルを存在させるための複雑な機構を有する探触子ホルダーを用いる必要があるため、その設定に時間が掛かるのみならず、高度な熟練を要するという欠点がある。また、オンラインで高速に超音波探傷を行うには、処理能力向上のために多数の超音波探触子を配設する必要がある。しかしながら、多数の超音波探触子について同時に超音波の照射方向を変更できる（各超音波探触子から照射される超音波の照射方向ベクトルが、超音波の入射点における垂線を中心軸とする一つの円錐の側面上に存在するように変更できる）機構を実現することは、極めて困難であり、各超音波探触子毎に機構を設ける必要があることから、設定に膨大な時間を要する他、設備コストも膨大となるという問題もある。 However, in order to carry out the method described in Patent Document 2, an ultrasonic irradiation direction vector is present on the side surface of one cone having a perpendicular at the ultrasonic incident point as a central axis. Since it is necessary to use a probe holder, it takes time to set the probe holder, and there is a disadvantage that a high degree of skill is required. Further, in order to perform ultrasonic flaw detection at high speed online, it is necessary to arrange a large number of ultrasonic probes in order to improve the processing capability. However, the ultrasonic irradiation direction can be changed simultaneously for a large number of ultrasonic probes (the ultrasonic irradiation direction vector irradiated from each ultrasonic probe has a perpendicular line at the ultrasonic incident point as the central axis. It is extremely difficult to realize a mechanism that can be changed so that it exists on the side of one cone. Since it is necessary to provide a mechanism for each ultrasonic probe, it takes a lot of time for setting. In addition, there is a problem that the equipment cost becomes enormous.
以上に説明したように、従来より提案されている斜めきずの検出方法は、きず検出精度或いは検査効率（超音波入射方向の設定の容易さ）の点で問題があった。 As described above, the conventional methods for detecting oblique flaws have been problematic in terms of flaw detection accuracy or inspection efficiency (easiness of setting the ultrasonic incident direction).
本発明は、斯かる従来技術の問題点を解決するべくなされたものであり、被検査管の管軸方向から傾斜する方向に延びる斜めきずを精度良く且つ効率良く検出可能な超音波探傷方法を提供することを課題とする。 The present invention has been made to solve the problems of the prior art, and provides an ultrasonic flaw detection method capable of accurately and efficiently detecting oblique flaws extending in a direction inclined from the tube axis direction of a tube to be inspected. The issue is to provide.
前記課題を解決するべく、本発明は、被検査管の管軸方向から傾斜する方向に延びる斜めきずを検出する超音波探傷方法であって、被検査管の管周方向に超音波を入射させた場合において、被検査管内面及び外面にそれぞれ設けた管軸方向に延びる人工きずからの反射エコーの強度が略同等となるように、超音波の管周方向の入射角Ａを決定する第１ステップと、検出したい斜めきずの管軸方向からの傾斜角度をθとした場合、以下の式（１）及び式（２）を満足するように、超音波の管周方向の入射角α及び管軸方向の入射角βを算出する第２ステップと、前記算出した管周方向の入射角α及び管軸方向の入射角βに従って超音波の入射方向を設定し被検査管を探傷する第３ステップと、を含むことを特徴とする超音波探傷方法を提供するものである。
ｔａｎθ＝ｓｉｎβ／ｓｉｎα ・・・（１）
（ｓｉｎα）２＋（ｓｉｎβ）２＝（ｓｉｎＡ）２ ・・・（２）
In order to solve the above-described problems, the present invention provides an ultrasonic flaw detection method for detecting an oblique flaw extending in a direction inclined from the tube axis direction of a tube to be inspected, which makes ultrasonic waves incident in the tube circumferential direction of the tube to be inspected. In this case, the incident angle A of the ultrasonic wave in the tube circumferential direction is determined so that the intensities of the reflected echoes from the artificial flaws extending in the tube axis direction respectively provided on the inner surface and the outer surface of the tube to be inspected are substantially equal. When the step and the inclination angle of the oblique flaw to be detected from the tube axis direction are θ, the incident angle α of the ultrasonic wave in the tube circumferential direction and the tube so as to satisfy the following expressions (1) and (2): A second step of calculating the incident angle β in the axial direction, and a third step of setting the incident direction of the ultrasonic wave in accordance with the calculated incident angle α in the tube circumferential direction and the incident angle β in the tube axis direction to detect the inspection tube. Providing an ultrasonic flaw detection method characterized by comprising: It is.
tan θ = sin β / sin α (1)
(Sin α) 2 + (sin β) 2 = (sin A) 2 (2)
斯かる発明によれば、後述するように、特定の傾斜角度θを有する斜めきずに対して垂直に超音波を入射し垂直に反射させることができると共に、被検査管に入射した超音波の屈折角を一定に保つことができるため、斜めきずを精度良く検出することが可能である。また、人工きずを設けた被検査管を用いて管周方向の入射角Ａを決定した後は、計算によって管周方向の入射角α及び管軸方向の入射角βを算出し、当該算出した管周方向の入射角α及び管軸方向の入射角βに従って斜めきずに対する超音波の入射方向を設定すればよいため、超音波入射方向の設定が容易であり効率良く検査することが可能である。 According to such an invention, as will be described later, it is possible to vertically reflect an ultrasonic wave with respect to an oblique flaw having a specific inclination angle θ and to reflect the vertical wave, and to refract the ultrasonic wave incident on the inspection tube. Since the corner can be kept constant, it is possible to detect oblique flaws with high accuracy. In addition, after determining the incident angle A in the tube circumferential direction using the test tube provided with the artificial flaw, the incident angle α in the tube circumferential direction and the incident angle β in the tube axis direction are calculated by calculation, and the calculation is performed. Since it is only necessary to set the incident direction of the ultrasonic wave with respect to the oblique flaw according to the incident angle α in the tube circumferential direction and the incident angle β in the tube axis direction, the setting of the ultrasonic incident direction is easy and the inspection can be performed efficiently. .
なお、本発明における「管周方向の入射角」とは、被検査管の管周方向に超音波を入射させた状態における管軸方向から見た超音波の入射方向と超音波の入射点を通る被検査管の法線との成す角度を意味し、一般的な鋼管の斜角超音波探傷方法での入射角に相当する。本発明においては、管軸方向に延びる人工きずを検出するための管周方向の入射角をＡとし、傾斜角度θを有する斜めきずを検出するための管周方向の入射角をαとしている。また、「管軸方向の入射角」とは、斜めきずを検出するために、管軸に平行な面内で超音波の入射方向を傾斜させる角度を意味し、管周方向から見た傾斜後の超音波の入射方向と超音波の入射点を通る被検査管の法線との成す角度を意味する。本発明においては、傾斜角度θを有する斜めきずを検出するための管軸方向の入射角をβとしている。 The “incidence angle in the tube circumferential direction” in the present invention refers to the incident direction of ultrasonic waves and the incident point of ultrasonic waves as viewed from the tube axis direction in a state where ultrasonic waves are incident in the tube circumferential direction of the tube to be inspected. This means the angle formed with the normal line of the tube to be inspected, and corresponds to the incident angle in the general oblique ultrasonic inspection method for steel pipes. In the present invention, the incident angle in the tube circumferential direction for detecting artificial flaws extending in the tube axis direction is A, and the incident angle in the tube circumferential direction for detecting oblique flaws having the inclination angle θ is α. The “incidence angle in the tube axis direction” means an angle for inclining the incident direction of ultrasonic waves in a plane parallel to the tube axis in order to detect oblique flaws. Means the angle formed by the incident direction of the ultrasonic wave and the normal line of the tube to be inspected passing through the ultrasonic incident point. In the present invention, the incident angle in the tube axis direction for detecting oblique flaws having an inclination angle θ is β.
好ましくは、前記第２ステップにおいて算出した超音波の管周方向の入射角α及び管軸方向の入射角βに従って超音波の入射方向を設定し、被検査管内面及び外面にそれぞれ設けた管軸方向からの傾斜角度が前記θである人工きずからの反射エコーを検出するステップと、前記管軸方向の入射角βを当該入射角β近傍で変更し、前記検出した各人工きずからの反射エコーの強度が略同等となる管軸方向の入射角β’を決定するステップとをさらに含み、前記第３ステップにおいて、前記算出した管周方向の入射角α及び前記決定した管軸方向の入射角β’に従って超音波の入射方向を設定し被検査管を探傷するように構成される。 Preferably, the ultrasound incident direction is set according to the incident angle α in the tube circumferential direction and the incident angle β in the tube axis direction calculated in the second step, and the tube axes respectively provided on the inner surface and the outer surface of the tube to be inspected. Detecting a reflected echo from an artificial flaw whose inclination angle from the direction is θ, and changing the incident angle β in the tube axis direction in the vicinity of the incident angle β, and detecting the reflected echo from each detected artificial flaw And determining the incident angle β ′ in the tube axis direction in which the intensities are substantially equal, and in the third step, the calculated incident angle α in the tube circumferential direction and the determined incident angle in the tube axis direction An ultrasonic wave incident direction is set in accordance with β ′, and the inspection tube is flaw-detected.
斯かる構成によれば、単に計算によって算出した管軸方向の入射角β（及び管周方向の入射角α）のみに従って探傷時の超音波の入射方向を設定するのではなく、算出した管軸方向の入射角β（及び管周方向の入射角α）に従って探傷時の超音波の入射方向をいったん設定した後、被検査管の内外面にそれぞれ設けた傾斜角度がθである人工きずからの反射エコーを実際に検出し、両反射エコーの強度が略同等となるように管軸方向の入射角βを微調（微調後の入射角はβ’であり、β’＝βとなることもあり得る）するため、斜めきずをより一層精度良く検出し得ることが期待できる。また、仮にβ’＝βとなれば、設定した入射角βの妥当性を検証できるという点でも好ましい。 According to such a configuration, instead of setting the incident direction of the ultrasonic wave at the time of flaw detection according to only the incident angle β in the tube axis direction (and the incident angle α in the tube circumferential direction) calculated by calculation, the calculated tube axis After setting the incident direction of the ultrasonic wave at the time of flaw detection according to the incident angle β in the direction (and the incident angle α in the tube circumferential direction), from the artificial flaw where the inclination angle provided on the inner and outer surfaces of the test tube is θ The reflected echo is actually detected, and the incident angle β in the tube axis direction is finely tuned so that the intensities of both reflected echoes are approximately the same (the incident angle after fine adjustment is β ′, and β ′ = β may be obtained) Therefore, it can be expected that oblique flaws can be detected with higher accuracy. Further, if β ′ = β, it is preferable that the validity of the set incident angle β can be verified.
なお、前記構成においては管軸方向の入射角βを微調しているが、管周方向の入射角αを微調しても同様の作用効果を奏することが可能である。すなわち、前記第２ステップにおいて算出した超音波の管周方向の入射角α及び管軸方向の入射角βに従って超音波の入射方向を設定し、被検査管内面及び外面にそれぞれ設けた管軸方向からの傾斜角度が前記θである人工きずからの反射エコーを検出するステップと、前記管周方向の入射角αを当該入射角α近傍で変更し、前記検出した各人工きずからの反射エコーの強度が略同等となる管周方向の入射角α’を決定するステップとをさらに含み、前記第３ステップにおいて、前記決定した管周方向の入射角α’及び前記算出した管軸方向の入射角βに従って超音波の入射方向を設定し被検査管を探傷するように構成することも可能である。 In the above-described configuration, the incident angle β in the tube axis direction is finely adjusted. However, even if the incident angle α in the tube circumferential direction is finely adjusted, the same effect can be obtained. That is, the ultrasonic incident direction is set according to the incident angle α in the tube circumferential direction and the incident angle β in the tube axis direction calculated in the second step, and the tube axis directions provided on the inner surface and the outer surface of the tube to be inspected, respectively. Detecting a reflected echo from an artificial flaw whose inclination angle is θ, and changing the incident angle α in the tube circumferential direction in the vicinity of the incident angle α, and detecting the reflected echo from each detected artificial flaw A tube circumferential direction incident angle α ′ having substantially the same intensity, and in the third step, the determined tube circumferential direction incident angle α ′ and the calculated tube axis direction incident angle. It is also possible to configure to inspect the inspection tube by setting the incident direction of the ultrasonic wave according to β.
また、好ましくは、前記第３ステップにおいて、被検査管を探傷するための超音波探触子として管軸方向に沿って複数の振動子を配設したアレイ型超音波探触子を用い、前記複数の振動子の発振タイミングを電気的に制御することにより前記管軸方向の入射角（アレイ型超音波探触子の場合、ステアリング角と称される）βを設定するように構成される。 Preferably, in the third step, an array type ultrasonic probe in which a plurality of transducers are arranged along the tube axis direction is used as an ultrasonic probe for flaw detection of the tube to be inspected. The incident angle (referred to as a steering angle in the case of an array-type ultrasonic probe) β in the tube axis direction is set by electrically controlling the oscillation timing of a plurality of transducers.
或いは、前述のように、算出した管軸方向の入射角（ステアリング角）βを微調した管軸方向の入射角（ステアリング角）β’（及び管周方向の入射角α）に従って探傷時の超音波の入射方向を設定する場合には、前記第３ステップにおいて、被検査管を探傷するための超音波探触子として管軸方向に沿って複数の振動子を配設したアレイ型超音波探触子を用い、前記複数の振動子の発振タイミングを電気的に制御することにより前記管軸方向の入射角（ステアリング角）β’を設定することが好ましい。 Alternatively, as described above, the superposition at the time of flaw detection is made according to the incident angle (steering angle) β ′ (and the incident angle α in the tube circumferential direction) in the tube axis direction obtained by finely adjusting the calculated incident angle (steering angle) β in the tube axis direction. When setting the incident direction of the sound wave, in the third step, an array type ultrasonic probe in which a plurality of transducers are arranged along the tube axis direction as an ultrasonic probe for flaw detection of the tube to be inspected. It is preferable to set the incident angle (steering angle) β ′ in the tube axis direction by electrically controlling the oscillation timings of the plurality of vibrators using a touch element.
上記の構成によれば、アレイ型超音波探触子を用いて各振動子の発振タイミングを電気的に制御することにより管軸方向の入射角（ステアリング角）β（又はβ’）を設定する（管周方向の入射角αはアレイ型超音波探触子全体の管周方向の傾き又は管軸中心からの芯ずれ量を機械的に制御すればよい）ため、超音波入射方向の設定がより一層容易となり、より一層効率良く検査することが可能である。 According to the above configuration, the incident angle (steering angle) β (or β ′) in the tube axis direction is set by electrically controlling the oscillation timing of each transducer using the array-type ultrasonic probe. (The incident angle α in the tube circumferential direction may be mechanically controlled by the inclination in the tube circumferential direction of the entire array-type ultrasonic probe or the amount of misalignment from the tube axis center). It becomes much easier and it is possible to perform inspection more efficiently.
本発明に係る超音波探傷方法によれば、特定の傾斜角度θを有する斜めきずに対して垂直に超音波を入射し垂直に反射させることができると共に、被検査管に入射した超音波の屈折角を一定に保つことができるため、斜めきずを精度良く検出することが可能である。また、人工きずを設けた被検査管を用いて管周方向の入射角Ａを決定した後は、計算によって管周方向の入射角α及び管軸方向の入射角βを算出し、当該算出した管周方向の入射角α及び管軸方向の入射角βに従って超音波の入射方向を設定すればよいため、超音波入射方向の設定が容易であり効率良く検査することが可能である。 According to the ultrasonic flaw detection method according to the present invention, it is possible to vertically reflect an ultrasonic wave with respect to an oblique flaw having a specific inclination angle θ and to reflect it vertically, and to refract the ultrasonic wave incident on the inspection tube. Since the corner can be kept constant, it is possible to detect oblique flaws with high accuracy. In addition, after determining the incident angle A in the tube circumferential direction using the test tube provided with the artificial flaw, the incident angle α in the tube circumferential direction and the incident angle β in the tube axis direction are calculated by calculation, and the calculation is performed. Since the incident direction of the ultrasonic wave only needs to be set according to the incident angle α in the tube circumferential direction and the incident angle β in the tube axis direction, the setting of the ultrasonic wave incident direction is easy and efficient inspection can be performed.
以下、添付図面を適宜参照しつつ、本発明に係る超音波探傷方法の一実施形態について説明する。 Hereinafter, an embodiment of an ultrasonic flaw detection method according to the present invention will be described with reference to the accompanying drawings as appropriate.
図１は、本発明の一実施形態に係る超音波探傷方法を説明するための説明図であり、図１（ａ）は管軸方向に延びる人工きずを検出するための設定方法を説明する側面図を、図１（ｂ）は図１（ａ）の正面図を示す。また、図１（ｃ）は斜めきずを検出するための設定方法を説明する側面図を、図１（ｄ）は図１（ｃ）の正面図を示す。さらに、図１（ｅ）は図１（ｃ）に示す超音波の入射面を含むＩ−Ｉ断面図を、図１（ｆ）は図１（ｃ）に示す斜めきずを検出するための超音波の進行方向に沿ったＩＩ−ＩＩ断面図を示す。 FIG. 1 is an explanatory diagram for explaining an ultrasonic flaw detection method according to an embodiment of the present invention, and FIG. 1A is a side view for explaining a setting method for detecting an artificial flaw extending in the tube axis direction. FIG. 1 (b) shows a front view of FIG. 1 (a). 1C is a side view for explaining a setting method for detecting oblique flaws, and FIG. 1D is a front view of FIG. 1C. Further, FIG. 1 (e) is an II cross-sectional view including the ultrasonic incident surface shown in FIG. 1 (c), and FIG. 1 (f) is an ultrasonic wave for detecting the oblique flaw shown in FIG. 1 (c). II-II sectional drawing along the advancing direction of a sound wave is shown.
本実施形態に係る超音波探傷方法においては、先ず最初に、超音波探触子１から被検査管Ｐの管周方向（図１（ａ）の管軸を表す直線Ｔに直交する方向）に超音波を入射させた場合において、被検査管Ｐ内面及び外面にそれぞれ設けた規格や客先要求で規定された管軸方向（図１の直線Ｔの方向）に延びる人工きずＬｉ、Ｌｏからの反射エコーの強度が略同等となるように、超音波の管周方向の入射角Ａを決定する第１ステップが実行される。管周方向の入射角Ａは、管軸方向から見た（すなわち図１（ｂ）の視点から見た）超音波の入射方向と超音波の入射点を通る被検査管Ｐの法線Ｎ０との成す角度である。 In the ultrasonic flaw detection method according to the present embodiment, first, in the tube circumferential direction of the tube P to be inspected (direction perpendicular to the straight line T representing the tube axis in FIG. 1A) from the ultrasonic probe 1. When ultrasonic waves are incident, from the artificial flaws Li and Lo extending in the tube axis direction (the direction of the straight line T in FIG. 1) defined by the standards and customer requirements provided on the inner and outer surfaces of the pipe P to be inspected, respectively. The first step of determining the incident angle A of the ultrasonic wave in the tube circumferential direction is performed so that the intensity of the reflected echo is substantially equal. The incident angle A in the tube circumferential direction is an ultrasonic incident direction viewed from the tube axis direction (that is, viewed from the viewpoint of FIG. 1B) and the normal line N0 of the test tube P passing through the ultrasonic incident point. This is the angle formed by
次に、検出したい内外面斜めきずＯｉ、Ｏｏの管軸方向からの傾斜角度をθとした場合、以下の式（１）及び式（２）を満足するように、超音波の管周方向の入射角α及び管軸方向の入射角βを計算によって算出する第２ステップが実行される。
ｔａｎθ＝ｓｉｎβ／ｓｉｎα ・・・（１）
（ｓｉｎα）２＋（ｓｉｎβ）２＝（ｓｉｎＡ）２ ・・・（２）
Next, when the inclination angle of the inner and outer surface oblique flaws Oi and Oo to be detected from the tube axis direction is θ, the ultrasonic circumferential direction of the ultrasonic wave is satisfied so as to satisfy the following equations (1) and (2). A second step is performed in which the incident angle α and the incident angle β in the tube axis direction are calculated.
tan θ = sin β / sin α (1)
(Sin α) 2 + (sin β) 2 = (sin A) 2 (2)
ここで、超音波の管周方向の入射角αは、被検査管Ｐの管周方向に超音波を入射させた状態における管軸方向から見た超音波の入射方向と超音波の入射点を通る被検査管Ｐの法線との成す角度を意味し、これは、図１（ｄ）に示すように、管軸方向から見た超音波の入射方向と超音波の入射点Ｕを通る被検査管Ｐの法線Ｎとの成す角度に相当する。なお、図１（ｂ）の入射角Ａと図１（ｄ）の入射角αは、上記式（１）及び式（２）によってαが計算されるため、Ａ≠αとなるのが一般的である。 Here, the incident angle α in the tube circumferential direction of the ultrasonic wave is determined by the incident direction of the ultrasonic wave and the incident point of the ultrasonic wave as viewed from the tube axis direction in a state where the ultrasonic wave is incident in the tube circumferential direction of the test tube P. This means the angle formed with the normal line of the inspection tube P that passes through, as shown in FIG. 1 (d), and this is the direction of the ultrasonic wave viewed from the tube axis direction and the ultrasonic wave incident point U. This corresponds to the angle formed with the normal line N of the inspection tube P. Note that the incident angle A in FIG. 1B and the incident angle α in FIG. 1D are generally set to A ≠ α because α is calculated by the above formulas (1) and (2). It is.
また、管軸方向の入射角βは、被検査管Ｐの管周方向に超音波を入射させた状態（管周方向の入射角αで超音波を入射させた初期状態）から当該初期状態の超音波の入射方向を含む管軸に平行な面内で超音波の入射方向を傾斜させる角度を意味し、図１（ｅ）に示すように、傾斜後の超音波の入射方向と超音波の入射点Ｕを通る被検査管Ｐの法線Ｎとの成す角度に相当する。 In addition, the incident angle β in the tube axis direction is changed from a state in which ultrasonic waves are incident in the tube circumferential direction of the tube P to be inspected (an initial state in which ultrasonic waves are incident at an incident angle α in the tube circumferential direction) to the initial state. This means the angle by which the incident direction of the ultrasonic wave is inclined in a plane parallel to the tube axis including the incident direction of the ultrasonic wave, and as shown in FIG. 1 (e), the incident direction of the ultrasonic wave after the inclination and the ultrasonic wave This corresponds to an angle formed with the normal line N of the inspection tube P passing through the incident point U.
上記第２ステップを実行した後、最後に、前記算出した管周方向の入射角α及び管軸方向の入射角βに従って超音波の入射方向を設定し被検査管Ｐを探傷する。換言すれば、最初に被検査管Ｐの管周方向に超音波を入射させた状態で超音波探触子１の管周方向の傾き又は管軸中心からの芯ずれ量を調整して管周方向の入射角がαとなるように設定し、次に、当該初期状態の超音波の入射方向を含む管軸に平行な面内で超音波探触子１の管軸方向の傾きを調整して管軸方向の入射角がβとなるように設定（管周方向の入射角αと管軸方向の入射角βの設定は順序を逆にすることも可能である。すなわち、管軸方向の入射角βを設定した後に管周方向の入射角αを設定することも可能である）し、この状態で被検査管Ｐを探傷することになる。上記のように、管周方向の入射角α及び管軸方向の入射角βを設定することで、斜めきずを精度良く検出することができる。なお、管周方向の入射角α及び管軸方向の入射角βを設定するには、超音波探触子１が単一の振動子を具備する一般的な探触子である場合には、前述した特許文献１に記載されたような機構を好適に用いることが可能である。超音波探触子１がアレイ型超音波探触子である場合については後述する。 After executing the second step, finally, the inspected pipe P is flawed by setting the incident direction of ultrasonic waves according to the calculated incident angle α in the tube circumferential direction and incident angle β in the tube axis direction. In other words, in the state in which ultrasonic waves are first incident in the tube circumferential direction of the tube P to be inspected, the tube probe is adjusted by adjusting the inclination of the ultrasonic probe 1 in the tube circumferential direction or the amount of misalignment from the tube axis center. The angle of incidence is set to α, and then the inclination of the ultrasonic probe 1 in the tube axis direction is adjusted in a plane parallel to the tube axis including the incident direction of the ultrasonic wave in the initial state. Therefore, the incident angle in the tube axis direction is set to be β (the setting of the incident angle α in the tube circumferential direction and the incident angle β in the tube axis direction can be reversed. It is also possible to set the incident angle α in the tube circumferential direction after setting the incident angle β), and the tube to be inspected P is flawed in this state. As described above, by setting the incident angle α in the tube circumferential direction and the incident angle β in the tube axis direction, oblique flaws can be detected with high accuracy. In order to set the incident angle α in the tube circumferential direction and the incident angle β in the tube axis direction, when the ultrasonic probe 1 is a general probe having a single transducer, A mechanism such as that described in Patent Document 1 described above can be suitably used. The case where the ultrasonic probe 1 is an array type ultrasonic probe will be described later.
以下、上記式（１）及び（２）によって算出した管周方向の入射角α及び管軸方向の入射角βに従って超音波の入射方向を設定すれば、管軸方向からの傾斜角度がθである内外面斜めきずＯｉ、Ｏｏを精度良く検出できる理由について説明する。 Hereinafter, if the incident direction of the ultrasonic wave is set according to the incident angle α in the tube circumferential direction and the incident angle β in the tube axis direction calculated by the above equations (1) and (2), the inclination angle from the tube axis direction is θ. The reason why certain inner and outer surface oblique flaws Oi and Oo can be accurately detected will be described.
まず最初に、被検査管Ｐの管周方向に超音波を入射角αで入射させた状態（初期状態）において、超音波探触子１と被検査管Ｐとの間に存在する接触媒質（例えば、水）における音速をＶｗ、被検査管Ｐ中における横波音速をＶｓとし、管周方向の屈折角をγ１（図１（ｄ）参照）とすれば、スネルの法則により、以下の式（３）が成立する。
ｓｉｎγ１＝ｓｉｎα・Ｖｓ／Ｖｗ ・・・（３）
First, a contact medium (between the ultrasonic probe 1 and the test tube P) in a state (initial state) in which an ultrasonic wave is incident at an incident angle α in the tube circumferential direction of the test tube P ( For example, if the sound velocity in water is Vw, the transverse wave velocity in the test tube P is Vs, and the refraction angle in the tube circumferential direction is γ1 (see FIG. 1 (d)), the following formula ( 3) is established.
sinγ1 = sinα · Vs / Vw (3)
一方、音速Ｖｓで被検査管Ｐ中を伝搬する超音波の管周方向の速度ベクトル成分をＶＬ（図１（ｃ）及び（ｄ）参照）とすれば、以下の式（４）が成立する。
ＶＬ＝Ｖｓ・ｓｉｎγ１ ・・・（４）
On the other hand, if the velocity vector component in the tube circumferential direction of the ultrasonic wave propagating through the inspection pipe P at the sound velocity Vs is VL (see FIGS. 1C and 1D), the following equation (4) is established. .
VL = Vs · sinγ1 (4)
従って、上記式（４）に式（３）を代入すれば、以下の式（５）が成立することになる。
ＶＬ＝ｓｉｎα・Ｖｓ２／Ｖｗ ・・・（５）
Therefore, if the formula (3) is substituted into the above formula (4), the following formula (5) is established.
VL = sin α · Vs 2 / Vw (5)
次に、前記初期状態の超音波の入射方向を含む管軸に平行な面内で入射角βだけ超音波探触子１を管軸方向に傾斜させた場合には、管軸方向についてもスネルの法則に従った超音波の屈折が生じることになる。すなわち、管軸方向の屈折角をγ２（図１（ｅ）参照）とすれば、スネルの法則により、以下の式（６）が成立する。
ｓｉｎγ２＝ｓｉｎβ・Ｖｓ／Ｖｗ ・・・（６）
Next, when the ultrasonic probe 1 is inclined in the tube axis direction by an incident angle β in a plane parallel to the tube axis including the incident direction of the ultrasonic wave in the initial state, the snell in the tube axis direction is also obtained. The refraction of the ultrasonic wave according to the law of will occur. That is, if the refraction angle in the tube axis direction is γ2 (see FIG. 1 (e)), the following equation (6) is established according to Snell's law.
sinγ2 = sinβ · Vs / Vw (6)
一方、音速Ｖｓで被検査管Ｐ中を伝搬する超音波の管軸方向の速度ベクトル成分をＶＴ（図１（ｃ）及び（ｅ）参照）とすれば、以下の式（７）が成立する。
ＶＴ＝Ｖｓ・ｓｉｎγ２ ・・・（７）
On the other hand, if the velocity vector component in the tube axis direction of the ultrasonic wave propagating through the inspection tube P at the sound velocity Vs is VT (see FIGS. 1C and 1E), the following equation (7) is established. .
VT = Vs · sinγ2 (7)
従って、上記式（７）に式（６）を代入すれば、以下の式（８）が成立することになる。
ＶＴ＝ｓｉｎβ・Ｖｓ２／Ｖｗ ・・・（８）
Therefore, if the equation (6) is substituted into the equation (7), the following equation (8) is established.
VT = sin β · Vs 2 / Vw (8)
以上に説明したように、管周方向の入射角α及び管軸方向の入射角βに従って超音波の入射方向を設定すれば、斜めきずを検出するために被検査管Ｐ中を伝搬する超音波の速度ベクトルＶＣ（図１（ｃ）及び（ｆ）参照）は、管周方向の速度ベクトル成分ＶＬと管軸方向の速度ベクトル成分ＶＴとが合成されたものとなる。従って、屈折角φ（図１（ｃ）参照）と速度ベクトル成分ＶＬ及びＶＴとの間には、以下の式（９）に示す関係が成立することになる。
ｔａｎφ＝ＶＬ／ＶＴ ・・・（９）
As described above, if the incident direction of the ultrasonic wave is set according to the incident angle α in the tube circumferential direction and the incident angle β in the tube axis direction, the ultrasonic wave propagating through the tube P to be detected in order to detect an oblique flaw. The velocity vector VC (see FIGS. 1C and 1F) is obtained by combining the velocity vector component VL in the tube circumferential direction and the velocity vector component VT in the tube axis direction. Therefore, the relationship shown in the following equation (9) is established between the refraction angle φ (see FIG. 1C) and the velocity vector components VL and VT.
tanφ = VL / VT (9)
ここで、特定の傾斜角度θを有する斜めきずに対して垂直に超音波を入射する（垂直に反射させる）には、幾何学的な関係より、以下の式（１０）が成立すればよい。
φ＝θ ・・・（１０）
Here, in order to make an ultrasonic wave incident perpendicularly (reversely reflect) to an oblique flaw having a specific inclination angle θ, the following equation (10) may be satisfied from a geometrical relationship.
φ = θ (10)
従って、上記式（９）の左辺に式（１０）を代入し、式（９）の右辺に式（５）及び式（７）を代入して整理すれば、前述した式（１）が成立することになる。換言すれば、式（１）を満足するように管周方向の入射角α及び管軸方向の入射角βを設定することにより、特定の傾斜角度θを有する斜めきずに対して垂直に超音波を入射し垂直に反射させることができるようになる。 Therefore, if the formula (10) is substituted into the left side of the formula (9) and the formulas (5) and (7) are substituted into the right side of the formula (9) and rearranged, the above formula (1) is established. Will do. In other words, by setting the incident angle α in the tube circumferential direction and the incident angle β in the tube axis direction so as to satisfy the expression (1), the ultrasonic waves are perpendicular to an oblique flaw having a specific inclination angle θ. Can be incident and reflected vertically.
次に、被検査管Ｐの管軸方向に延びる人工きずＬｉ、Ｌｏを検出するために管周方向に超音波を入射角Ａで入射させた状態において、超音波探触子１と被検査管Ｐとの間に存在する接触媒質における音速をＶｗ、被検査管Ｐ中における横波音速をＶｓとし、管周方向の屈折角をγ（図１（ｂ）参照）とすれば、スネルの法則により、以下の式（１１）が成立する。
ｓｉｎγ＝ｓｉｎＡ・Ｖｓ／Ｖｗ ・・・（１１）
Next, in order to detect artificial flaws Li and Lo extending in the tube axis direction of the tube to be inspected P, the ultrasonic probe 1 and the tube to be inspected in a state where ultrasonic waves are incident at an incident angle A in the tube circumferential direction. Assuming that the sound velocity in the contact medium existing between P and V is Vw, the transverse wave velocity in the test tube P is Vs, and the refraction angle in the tube circumferential direction is γ (see FIG. 1B), Snell's law The following formula (11) is established.
sinγ = sinA · Vs / Vw (11)
一方、音速Ｖｓで被検査管Ｐ中を伝搬する超音波の管周方向の速度ベクトル成分をＶＡ（図１（ｂ）参照）とすれば、以下の式（１２）が成立する。
ＶＡ＝Ｖｓ・ｓｉｎγ ・・・（１２）
On the other hand, if the velocity vector component in the tube circumferential direction of the ultrasonic wave propagating through the test tube P at the sound velocity Vs is VA (see FIG. 1B), the following equation (12) is established.
VA = Vs · sinγ (12)
従って、上記式（１２）に式（１１）を代入すれば、以下の式（１３）が成立することになる。
ＶＡ＝ｓｉｎＡ・Ｖｓ２／Ｖｗ ・・・（１３）
Therefore, if the formula (11) is substituted into the formula (12), the following formula (13) is established.
VA = sinA · Vs 2 / Vw (13)
ここで、斜めきずを精度良く検出するには、斜めきずに対する超音波の屈折角γ３（図１（ｆ）参照）を、管軸方向に延びる人工きずを検出する時と同じ屈折角γに設定しなければならない。換言すれば、管軸方向に延びる人工きずＬｉ、Ｌｏに対する超音波の速度ベクトルＶＡと斜めきずＯｉ、Ｏｏに対する速度ベクトルＶＣとを同じ値にしなければならない。すなわち、以下の式（１４）を満足させる必要がある。
ＶＣ＝ＶＡ ・・・（１４）
Here, in order to detect oblique flaws with high accuracy, the ultrasonic refraction angle γ3 (see FIG. 1 (f)) with respect to the oblique flaws is set to the same refraction angle γ as when detecting artificial flaws extending in the tube axis direction. Must. In other words, the ultrasonic velocity vector VA for the artificial flaws Li and Lo extending in the tube axis direction and the velocity vector VC for the oblique flaws Oi and Oo must have the same value. That is, it is necessary to satisfy the following expression (14).
VC = VA (14)
また、上述したように、斜めきずを検出するために被検査管Ｐ中を伝搬する超音波の速度ベクトルＶＣは、管周方向の速度ベクトル成分ＶＬと管軸方向の速度ベクトル成分ＶＴとが合成されたものとなるため、ＶＣとＶＴ及びＶＬとの間には、以下の式（１５）に示す関係が成立する。
ＶＴ２＋ＶＬ２＝ＶＣ２ ・・・（１５）
Further, as described above, the velocity vector VC of the ultrasonic wave propagating through the inspected pipe P in order to detect an oblique flaw is a combination of the velocity vector component VL in the tube circumferential direction and the velocity vector component VT in the tube axis direction. Therefore, the relationship shown in the following formula (15) is established between VC, VT, and VL.
VT 2 + VL 2 = VC 2 (15)
従って、上記式（１５）の右辺に式（１４）を代入すれば、下記の式（１６）が成立する。
ＶＴ２＋ＶＬ２＝ＶＡ２ ・・・（１６）
Therefore, the following formula (16) is established by substituting the formula (14) into the right side of the formula (15).
VT 2 + VL 2 = VA 2 (16)
さらに、上記式（１６）の左辺に式（５）及び式（８）を代入し、式（１６）の右辺に式（１３）を代入して整理すれば、前述した式（２）が成立することになる。換言すれば、式（２）を満足するように管周方向の入射角α及び管軸方向の入射角βを設定することにより、被検査管Ｐに入射した超音波の屈折角を一定に保つことができるようになる。 Further, if the formula (5) and the formula (8) are substituted into the left side of the formula (16) and the formula (13) is substituted into the right side of the formula (16) and rearranged, the above formula (2) is established. Will do. In other words, by setting the incident angle α in the tube circumferential direction and the incident angle β in the tube axis direction so as to satisfy the expression (2), the refraction angle of the ultrasonic wave incident on the test tube P is kept constant. Will be able to.
以上に説明したように、本実施形態に係る超音波探傷方法によれば、上記式（１）及び式（２）を満足する管周方向の入射角α及び管軸方向の入射角βに従って入射方向を設定した超音波で被検査管Ｐを探傷するため、特定の傾斜角度θを有する斜めきずＯｉ、Ｏｏに対して垂直に超音波を入射し垂直に反射させることができると共に、被検査管Ｐに入射した超音波の屈折角を一定に保つ（γ＝γ３）ことができるため、斜めきずを精度良く検出することが可能である。また、人工きずを設けた被検査管Ｐを用いて管周方向の入射角Ａを決定した後は、計算によって管周方向の入射角α及び管軸方向の入射角βを算出し、当該算出した管周方向の入射角α及び管軸方向の入射角βに従って超音波の入射方向を設定すればよいため、超音波入射方向の設定が容易であり効率良く検査することが可能である。 As described above, according to the ultrasonic flaw detection method according to the present embodiment, the incidence is performed in accordance with the incident angle α in the tube circumferential direction and the incident angle β in the tube axis direction that satisfy the expressions (1) and (2). Since the inspection pipe P is flaw-detected with ultrasonic waves having a set direction, ultrasonic waves can be incident perpendicularly to the oblique flaws Oi and Oo having a specific inclination angle θ and reflected vertically, and the inspection pipe Since the refraction angle of the ultrasonic wave incident on P can be kept constant (γ = γ3), oblique flaws can be detected with high accuracy. In addition, after determining the incident angle A in the tube circumferential direction using the test tube P provided with the artificial flaw, the incident angle α in the tube circumferential direction and the incident angle β in the tube axis direction are calculated by calculation, and the calculation is performed. The ultrasonic incident direction may be set according to the incident angle α in the tube circumferential direction and the incident angle β in the tube axis direction, so that the ultrasonic incident direction can be easily set and can be inspected efficiently.
なお、斜めきずＯｉ、Ｏｏをより一層精度良く検出するために（或いは、設定した管軸方向の入射角βの妥当性を検証するために）、以下のような手順で超音波探傷を行うことも可能である。すなわち、先ず最初に、前述した式（１）及び（２）によって算出した超音波の管周方向の入射角α及び管軸方向の入射角βに従って超音波の入射方向を設定した後、被検査管Ｐの内面及び外面にそれぞれ設けた傾斜角度が前記θである人工きずＯｉ、Ｏｏからの反射エコーを検出する。そして、管軸方向の入射角βを当該入射角β近傍で変更し、前記検出した各人工きずからの反射エコーの強度が略同等となる管軸方向の入射角β’を決定する。最後に、前記算出した管周方向の入射角α及び前記決定した管軸方向の入射角β’に従って超音波の入射方向を設定し被検査管を探傷するという手順である。また、逆に管軸方向の入射角βを固定して管周方向の入射角αを当該入射角α近傍で変更し、各人工きずからの反射エコーの強度が略同等となる入射角α’を決定しても良い。 In order to detect oblique flaws Oi and Oo with higher accuracy (or to verify the validity of the set incident angle β in the tube axis direction), ultrasonic flaw detection is performed in the following procedure. Is also possible. That is, first, after setting the incident direction of the ultrasonic wave according to the incident angle α in the tube circumferential direction and the incident angle β in the tube axis direction calculated by the above formulas (1) and (2), Reflected echoes are detected from artificial flaws Oi and Oo having inclination angles θ provided on the inner and outer surfaces of the tube P, respectively. Then, the incident angle β in the tube axis direction is changed in the vicinity of the incident angle β, and the incident angle β ′ in the tube axis direction at which the intensity of the reflected echo from each detected artificial flaw is substantially equal is determined. Finally, according to the calculated incident angle α in the tube circumferential direction and the determined incident angle β ′ in the tube axis direction, the incident direction of the ultrasonic wave is set and the tube to be inspected is detected. Conversely, the incident angle β in the tube axis direction is fixed, the incident angle α in the tube circumferential direction is changed in the vicinity of the incident angle α, and the incident angle α ′ at which the intensity of the reflected echo from each artificial flaw becomes substantially equal. May be determined.
上記の構成によれば、単に計算によって算出した管軸方向の入射角β（及び管周方向の入射角α）のみに従って探傷時の超音波の入射方向を設定するのではなく、被検査管の内外面にそれぞれ設けた傾斜角度がθである人工きずからの反射エコーを参照して入射角β又はαを微調（微調後の入射角はβ’又はα’であり、β’＝β又はα’＝αとなることもあり得る）するため、斜めきずをより一層精度良く検出し得ることが期待できる。 According to the above configuration, the incident direction of the ultrasonic wave at the time of flaw detection is not set according to only the incident angle β in the tube axis direction (and the incident angle α in the tube circumferential direction) calculated simply by calculation. Finely adjust the incident angle β or α with reference to the reflected echo from the artificial flaw with an inclination angle θ provided on the inner and outer surfaces (the incident angle after fine adjustment is β ′ or α ′, and β ′ = β or α Therefore, it is expected that oblique flaws can be detected with higher accuracy.
また、本実施形態に係る超音波探触子１は、単一の振動子を具備する一般的な探触子とすることも可能であるものの、より一層検査効率を高めるには、管軸方向に沿って複数の振動子を配設したアレイ型超音波探触子を用いることが好ましい。 Moreover, although the ultrasonic probe 1 according to the present embodiment can be a general probe having a single transducer, in order to further increase the inspection efficiency, the tube axis direction It is preferable to use an array-type ultrasonic probe in which a plurality of transducers are arranged along.
斯かるアレイ型超音波探触子を用いれば、管軸方向の入射角（アレイ型超音波探触子の場合、ステアリング角と称される）β（又はβ’）を設定するための機械的な機構が不要であり（ただし、アレイ型超音波探触子全体の管周方向の傾き又は管軸中心からの芯ずれ量を機械的に制御するための機構は必要）、各振動子の発振タイミングを電気的に制御する（例えば、特開２００３−４７０９号公報参照）ことによって管軸方向の入射角（ステアリング角）β（又はβ’）を容易に設定することができるため、より一層効率良く検査することが可能である。 By using such an array type ultrasonic probe, a mechanical for setting an incident angle (or a steering angle in the case of an array type ultrasonic probe) β (or β ′) in the tube axis direction. (However, a mechanism for mechanically controlling the tilt of the entire array-type ultrasonic probe in the tube circumferential direction or the amount of misalignment from the tube axis center is necessary.) Since the timing is electrically controlled (see, for example, Japanese Patent Laid-Open No. 2003-4709), the incident angle (steering angle) β (or β ′) in the tube axis direction can be easily set. It is possible to inspect well.
以下、実施例及び比較例を示すことにより、本発明の特徴をより一層明らかにする。 Hereinafter, the features of the present invention will be further clarified by showing examples and comparative examples.
＜実施例１＞
図１に示す超音波探触子１として被検査管（鋼管）Ｐの管軸方向に沿って複数の振動子を配設したアレイ型超音波探触子を用い、鋼管Ｐの管周方向に超音波を入射させると共に、超音波探触子１の管軸中心からの芯ずれ量を機械的に調整したところ、鋼管Ｐ内面及び外面にそれぞれ設けた管軸方向に延びる人工きずＬｉ、Ｌｏからの反射エコーの強度が略同等となる管周方向の入射角Ａは１８°であった。
<Example 1>
As an ultrasonic probe 1 shown in FIG. 1, an array type ultrasonic probe in which a plurality of transducers are arranged along the tube axis direction of a tube (steel pipe) P to be inspected is used. When the ultrasonic wave is incident and the amount of misalignment from the tube axis center of the ultrasonic probe 1 is mechanically adjusted, the artificial flaws Li and Lo extending in the tube axis direction respectively provided on the inner surface and the outer surface of the steel pipe P are used. The incident angle A in the tube circumferential direction at which the reflected echo intensities are substantially equal was 18 °.
次に、特定の傾斜角度θ＝２２．５°を有する斜めきずを検出するのに適した探傷条件を計算により算出した。すなわち、前述した式（１）及び式（２）に対してＡ＝１８°、θ＝２２．５°を代入し、式（１）及び式（２）を解くことにより超音波の管周方向の入射角α及び管軸方向の入射角βを算出した。その結果、α＝１６．６°、β＝６．８°であった。 Next, flaw detection conditions suitable for detecting oblique flaws having a specific inclination angle θ = 22.5 ° were calculated by calculation. That is, by substituting A = 18 ° and θ = 22.5 ° into the above-described formulas (1) and (2) and solving the formulas (1) and (2), the circumferential direction of the ultrasonic wave The incident angle α and the incident angle β in the tube axis direction were calculated. As a result, α = 16.6 ° and β = 6.8 °.
次に、超音波探触子１の管軸中心からの芯ずれ量を機械的に調整することにより、管周方向の入射角を上記α（＝１６．６°）に設定した。そして、当該入射角αを固定したまま、超音波探触子１を構成する各振動子の発振タイミングを電気的に制御することにより、管軸方向の入射角βを種々の値に変更した。そして、鋼管Ｐ内面及び外面のそれぞれに管軸方向からの傾斜角度θが２２．５°である斜めきず（人工きず）を設け、上記各探傷条件（入射角αと入射角βの組合せ）のそれぞれについて、斜めきずからの反射エコーを検出しその強度を評価した。 Next, the incident angle in the tube circumferential direction was set to α (= 16.6 °) by mechanically adjusting the amount of misalignment from the tube axis center of the ultrasonic probe 1. The incident angle β in the tube axis direction was changed to various values by electrically controlling the oscillation timing of each transducer constituting the ultrasonic probe 1 while fixing the incident angle α. And each of the inner surface and the outer surface of the steel pipe P is provided with oblique flaws (artificial flaws) whose inclination angle θ from the pipe axis direction is 22.5 °, and the above flaw detection conditions (combination of incident angle α and incident angle β) About each, the reflective echo from the diagonal flaw was detected and the intensity | strength was evaluated.
図２は、管周方向の入射角αを１６．６°に設定する一方、管軸方向の入射角βを種々の値に設定した各探傷条件について検出された斜めきずからの反射エコーの強度を評価した結果を示すグラフである。図２の横軸は管軸方向の入射角β（°）を、縦軸は検出された斜めきずからの反射エコーの強度の相対値（％）（超音波探傷器（図１では図示省略）のモニタ画面で表示され得る反射エコーの最大強度を１００％とした）を示す。なお、図中、「○」でプロットしたデータは鋼管Ｐの外面に設けた斜めきずＯｏの反射エコー強度を、「□」でプロットしたデータは鋼管Ｐの内面に設けた斜めきずＯｉの反射エコー強度を示す。後述する図３及び図４についても同様である。 FIG. 2 shows the intensity of reflected echo from an oblique flaw detected for each flaw detection condition in which the incident angle α in the tube circumferential direction is set to 16.6 ° and the incident angle β in the tube axis direction is set to various values. It is a graph which shows the result of having evaluated. The horizontal axis in FIG. 2 is the incident angle β (°) in the tube axis direction, and the vertical axis is the relative value (%) of the intensity of the reflected echo detected from the oblique flaw (ultrasonic flaw detector (not shown in FIG. 1)). The maximum intensity of the reflected echo that can be displayed on the monitor screen is 100%). In the figure, the data plotted with “◯” indicates the reflected echo intensity of the oblique flaw Oo provided on the outer surface of the steel pipe P, and the data plotted with “□” indicates the reflected echo of the oblique flaw Oi provided on the inner surface of the steel pipe P. Indicates strength. The same applies to FIGS. 3 and 4 described later.
図２に示すように、鋼管Ｐの内面及び外面のそれぞれに設けた斜めきずからの反射エコーの強度が同程度となるには、入射角βを７°程度に設定する必要があり、これは前記計算によって算出した入射角β＝６．８°に一致することが分かった。また、図２に示すように、入射角βを７°程度に設定すれば、反射エコーの強度は比較的大きくなる（５０％以上）ため、当該反射エコーに基づいて斜めきずを検出することが可能であった。以上のように、本実施例に係る超音波探傷方法によれば、被検査管Ｐの内面及び外面に設けた斜めきず（θ＝２２．５°）の双方を精度良く検出できることが分かった。 As shown in FIG. 2, in order for the intensity of the reflected echo from the oblique flaw provided on each of the inner surface and the outer surface of the steel pipe P to be approximately the same, it is necessary to set the incident angle β to about 7 °. It was found that the incident angle β calculated by the equation was equal to 6.8 °. Further, as shown in FIG. 2, when the incident angle β is set to about 7 °, the intensity of the reflected echo becomes relatively large (50% or more), so that an oblique flaw can be detected based on the reflected echo. It was possible. As described above, according to the ultrasonic flaw detection method according to the present example, it has been found that both oblique flaws (θ = 22.5 °) provided on the inner surface and the outer surface of the test tube P can be detected with high accuracy.
＜実施例２＞
実施例１と同様に入射角Ａを１８°に設定する一方、特定の傾斜角度θ＝４５°を有する斜めきずを検出するのに適した探傷条件を計算により算出した。その結果、α＝１２．６°、β＝１２．６°であった。
<Example 2>
While the incident angle A was set to 18 ° as in Example 1, flaw detection conditions suitable for detecting oblique flaws having a specific inclination angle θ = 45 ° were calculated by calculation. As a result, α = 12.6 ° and β = 12.6 °.
次に、超音波探触子１を構成する各振動子の発振タイミングを電気的に制御することにより、管軸方向の入射角を上記β（＝１２．６°）に設定した。そして、当該入射角βを固定したまま、超音波探触子１の管軸中心からの芯ずれ量を機械的に調整することにより、管周方向の入射角αを種々の値に変更した。そして、鋼管Ｐ内面及び外面のそれぞれに管軸方向からの傾斜角度θが４５°である斜めきず（人工きず）を設け、上記各探傷条件（入射角αと入射角βの組合せ）のそれぞれについて、斜めきずからの反射エコーを検出しその強度を評価した。 Next, by electrically controlling the oscillation timing of each transducer constituting the ultrasonic probe 1, the incident angle in the tube axis direction was set to β (= 12.6 °). Then, the incident angle α in the tube circumferential direction was changed to various values by mechanically adjusting the misalignment amount from the tube axis center of the ultrasonic probe 1 with the incident angle β fixed. And each of the above-mentioned flaw detection conditions (combination of incident angle α and incident angle β) is provided on each of the inner surface and the outer surface of the steel pipe P with oblique flaws (artificial flaws) whose inclination angle θ from the tube axis direction is 45 °. The reflected echo from the oblique flaw was detected and its intensity was evaluated.
図３は、管軸方向の入射角βを１２．６°に設定する一方、管周方向の入射角αを種々の値に設定した各探傷条件について検出された斜めきずからの反射エコーの強度を評価した結果を示すグラフである。図３の横軸は管周方向の入射角α（°）を、縦軸は図２と同様に検出された斜めきずからの反射エコーの強度の相対値（％）を示す。図３に示すように、鋼管Ｐの内面及び外面のそれぞれに設けた斜めきずからの反射エコーの強度が同程度となるには、入射角αを１３°程度に設定する必要があり、これは前記計算によって算出した入射角α＝１２．６°に略一致することが分かった。また、図３に示すように、入射角αを１３°程度に設定すれば、反射エコーの強度は比較的大きくなる（４５％以上）ため、当該反射エコーに基づいて斜めきずを検出することが可能であった。以上のように、本実施例に係る超音波探傷方法によれば、被検査管Ｐの内面及び外面に設けた斜めきず（θ＝４５°）の双方を精度良く検出できることが分かった。 FIG. 3 shows the intensity of reflected echo from oblique flaws detected for each flaw detection condition in which the incident angle β in the tube axis direction is set to 12.6 ° and the incident angle α in the tube circumferential direction is set to various values. It is a graph which shows the result of having evaluated. The horizontal axis in FIG. 3 indicates the incident angle α (°) in the tube circumferential direction, and the vertical axis indicates the relative value (%) of the intensity of the reflected echo detected from the oblique flaw as in FIG. As shown in FIG. 3, in order for the intensity of the reflected echo from the oblique flaws provided on the inner surface and the outer surface of the steel pipe P to be approximately the same, it is necessary to set the incident angle α to about 13 °. It was found that the incident angle α calculated substantially by the above equation was approximately equal to 12.6 °. In addition, as shown in FIG. 3, when the incident angle α is set to about 13 °, the intensity of the reflected echo becomes relatively large (45% or more), so that an oblique flaw can be detected based on the reflected echo. It was possible. As described above, according to the ultrasonic flaw detection method according to the present example, it has been found that both oblique flaws (θ = 45 °) provided on the inner surface and the outer surface of the test tube P can be detected with high accuracy.
＜比較例＞
実施例１と同様に管周方向の入射角Ａを１８°に設定する一方、特許文献１に記載の方法と同様に、当該入射角Ａを固定したまま、超音波探触子１を構成する各振動子の発振タイミングを電気的に制御することにより、管軸方向の入射角（ステアリング角）βを種々の値に変更した。そして、鋼管Ｐ内面及び外面のそれぞれに管軸方向からの傾斜角度θが２２．５°である斜めきず（人工きず）と、傾斜角度θが４５°である斜めきず（人工きず）とを設け、上記各探傷条件（入射角Ａと入射角βの組合せ）のそれぞれについて、斜めきずからの反射エコーを検出した。
<Comparative example>
While the incident angle A in the tube circumferential direction is set to 18 ° as in the first embodiment, the ultrasonic probe 1 is configured with the incident angle A fixed as in the method described in Patent Document 1. The incident angle (steering angle) β in the tube axis direction was changed to various values by electrically controlling the oscillation timing of each vibrator. Then, an oblique flaw (artificial flaw) having an inclination angle θ of 22.5 ° from the pipe axis direction and an oblique flaw (artificial flaw) having an inclination angle θ of 45 ° are provided on each of the inner surface and the outer surface of the steel pipe P. For each of the flaw detection conditions (combination of incident angle A and incident angle β), reflected echoes from oblique flaws were detected.
図４は、管周方向の入射角Ａを１８°に設定する一方、管軸方向の入射角βを種々の値に設定した各探傷条件について検出された、管軸方向に延びる人工きずＬｉ、Ｌｏからの反射エコーの強度と斜めきずＯｉ、Ｏｏからの反射エコーの強度を評価した結果を示すグラフである。図４の横軸は管軸方向の入射角（ステアリング角）β（°）を、縦軸は検出された各きずからの反射エコーの強度の相対値（％）を示す。図４に示すように、人工きずＬｉ、Ｌｏからの反射エコーの強度（β＝０°）５０％に対し、θ＝２２．５°、４５°の斜めきずからの反射エコーの強度は小さい値となることが分かった。より具体的には、θ＝２２．５°の斜めきずを検出するために設定した入射角β≒９°のときの反射エコーの強度は略２０％以下であり、θ＝４５°の斜めきずを検出するために設定した入射角β＝１８°のときの反射エコーの強度は略５％以下であり、双方の設定ではいずれの斜めきずも精度良く検出できないことが分かった。 FIG. 4 shows an artificial flaw Li extending in the tube axis direction detected for each flaw detection condition in which the incident angle A in the tube circumferential direction is set to 18 °, while the incident angle β in the tube axis direction is set to various values. It is a graph which shows the result of having evaluated the intensity | strength of the reflective echo from Lo, and the intensity | strength of the reflective echo from the diagonal flaw Oi and Oo. The horizontal axis in FIG. 4 indicates the incident angle (steering angle) β (°) in the tube axis direction, and the vertical axis indicates the relative value (%) of the intensity of the reflected echo detected from each flaw. As shown in FIG. 4, the intensity of the reflected echo from the oblique flaws of θ = 22.5 ° and 45 ° is small with respect to the intensity (β = 0 °) of the reflected echo from the artificial flaws Li and Lo of 50%. I found out that More specifically, the intensity of the reflected echo is approximately 20% or less at an incident angle β≈9 ° set to detect an oblique flaw of θ = 22.5 °, and a diagonal flaw of θ = 45 °. The intensity of the reflected echo at an incident angle β = 18 ° set to detect γ is approximately 5% or less, and it has been found that neither oblique flaw can be detected accurately with both settings.
１・・・超音波探触子
Ｐ・・・被検査管
Ａ・・・管周方向の入射角
α・・・管周方向の入射角
β・・・管軸方向の入射角（ステアリング角）
θ・・・斜めきずの傾斜角
DESCRIPTION OF SYMBOLS 1 ... Ultrasonic probe P ... Tube to be inspected A ... Incident angle in the tube circumferential direction α ... Incident angle in the tube circumferential direction β ... Incident angle in the tube axis direction (steering angle)
θ ・ ・ ・ Inclination angle of oblique flaw
Claims (5)
被検査管の管周方向に超音波を入射させた場合において、被検査管内面及び外面にそれぞれ設けた管軸方向に延びる人工きずからの反射エコーの強度が略同等となるように、超音波の管周方向の入射角Ａを決定する第１ステップと、
検出したい斜めきずの管軸方向からの傾斜角度をθとした場合、以下の式（１）及び式（２）を満足するように、超音波の管周方向の入射角α及び管軸方向の入射角βを算出する第２ステップと、
前記算出した管周方向の入射角α及び管軸方向の入射角βに従って超音波の入射方向を設定し被検査管を探傷する第３ステップと、
を含むことを特徴とする超音波探傷方法。
ｔａｎθ＝ｓｉｎβ／ｓｉｎα ・・・（１）
（ｓｉｎα）２＋（ｓｉｎβ）２＝（ｓｉｎＡ）２ ・・・（２） An ultrasonic flaw detection method for detecting oblique flaws extending in a direction inclined from a tube axis direction of a test tube,
Ultrasonic waves so that the intensity of reflected echoes from artificial flaws extending in the tube axis direction provided on the inner surface and outer surface of the tube to be inspected are substantially equal when ultrasonic waves are incident in the tube circumferential direction of the tube to be inspected. A first step of determining an incident angle A in the tube circumferential direction;
When the inclination angle of the oblique flaw to be detected from the tube axis direction is θ, the incident angle α of the ultrasonic tube in the tube circumferential direction and the tube axis direction so as to satisfy the following equations (1) and (2): A second step of calculating the incident angle β;
A third step of setting the incident direction of the ultrasonic wave according to the calculated incident angle α in the tube circumferential direction and the incident angle β in the tube axis direction and flaw-inspecting the test tube;
An ultrasonic flaw detection method comprising:
tan θ = sin β / sin α (1)
(Sin α) 2 + (sin β) 2 = (sin A) 2 (2)
前記管軸方向の入射角βを当該入射角β近傍で変更し、前記検出した各人工きずからの反射エコーの強度が略同等となる管軸方向の入射角β’を決定するステップとをさらに含み、
前記第３ステップにおいて、前記算出した管周方向の入射角α及び前記決定した管軸方向の入射角β’に従って超音波の入射方向を設定し被検査管を探傷することを特徴とする請求項１に記載の超音波探傷方法。 The ultrasonic incident direction is set in accordance with the incident angle α in the tube circumferential direction and the incident angle β in the tube axis direction calculated in the second step, and the ultrasonic wave is incident from the tube axis direction provided on the inner surface and the outer surface of the tube to be inspected, respectively. Detecting a reflected echo from an artificial flaw having an inclination angle of θ,
A step of changing the incident angle β in the tube axis direction in the vicinity of the incident angle β, and determining an incident angle β ′ in the tube axis direction at which the intensity of the reflected echo from each detected artificial flaw is substantially equal. Including
The inspected tube is flawed in the third step by setting an incident direction of ultrasonic waves according to the calculated incident angle α in the tube circumferential direction and the determined incident angle β ′ in the tube axis direction. 2. The ultrasonic flaw detection method according to 1.
前記管周方向の入射角αを当該入射角α近傍で変更し、前記検出した各人工きずからの反射エコーの強度が略同等となる管周方向の入射角α’を決定するステップとをさらに含み、
前記第３ステップにおいて、前記決定した管周方向の入射角α’及び前記算出した管軸方向の入射角βに従って超音波の入射方向を設定し被検査管を探傷することを特徴とする請求項１に記載の超音波探傷方法。 The ultrasonic incident direction is set in accordance with the incident angle α in the tube circumferential direction and the incident angle β in the tube axis direction calculated in the second step, and the ultrasonic wave is incident from the tube axis direction provided on the inner surface and the outer surface of the tube to be inspected. Detecting a reflected echo from an artificial flaw having an inclination angle of θ,
Changing the incident angle α in the tube circumferential direction in the vicinity of the incident angle α, and determining the incident angle α ′ in the tube circumferential direction at which the intensity of the reflected echo from each detected artificial flaw is substantially equal. Including
The inspected tube is flawed in the third step by setting an incident direction of ultrasonic waves according to the determined incident angle α ′ in the tube circumferential direction and the calculated incident angle β in the tube axis direction. 2. The ultrasonic flaw detection method according to 1.
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| CN100578213C (en) * | 2007-12-18 | 2010-01-06 | 宝钢集团常州轧辊制造公司 | Fault detection method of roller body chamfering |
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| CN104634874B (en) * | 2015-02-06 | 2018-08-24 | 宝钢轧辊科技有限责任公司 | Large forged back -up roll body of roll working lining defect inspection method |
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