JP2010032352A - Eddy current flaw detecting method and eddy current flaw detector - Google Patents
Eddy current flaw detecting method and eddy current flaw detector Download PDFInfo
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本発明は、管、丸ビレット、丸棒など、断面略円形の被探傷材に存在する欠陥を検出する渦流探傷方法及び装置に関する。特に、本発明は、検出コイル間の差動信号についての校正作業の手間を軽減することにより、高能率で探傷可能な渦流探傷方法及び装置に関する。 The present invention relates to an eddy current flaw detection method and apparatus for detecting defects existing in a flaw detection material having a substantially circular cross section, such as a tube, a round billet, and a round bar. In particular, the present invention relates to an eddy current flaw detection method and apparatus capable of flaw detection with high efficiency by reducing the labor of calibration for differential signals between detection coils.
管、丸ビレット、丸棒などの表面に存在する欠陥を検出する方法として、従来より渦流探傷方法が用いられている。 Conventionally, an eddy current flaw detection method has been used as a method for detecting defects existing on the surface of a tube, a round billet, a round bar, and the like.
渦流探傷方法に用いられるプローブコイルとしては、いわゆる自己比較方式のプローブコイルと、いわゆる標準比較方式のプローブコイルとが知られている。自己比較方式のプローブコイルは、少なくとも１対の検出コイル（被探傷材に誘起された渦電流を検出するコイル）を具備し、被探傷材に対向配置された各検出コイルでの検出信号の差（各検出コイル間の差動信号）を出力するように構成されている。標準比較方式のプローブコイルは、少なくとも１対の検出コイルを具備し、一方の検出コイルを被探傷材に対向配置し、他方の検出コイルを標準となるものに対向配置して各検出コイルでの検出信号の差を出力するように構成されている。自己比較方式のプローブコイルを用いれば、標準比較方式のプローブコイルを用いる場合に比べて、プローブコイルの相対移動に伴う被探傷材とプローブコイルとのリフトオフ変動等に起因したノイズ信号が抑制され、Ｓ／Ｎ比が大きくなるため、微小な欠陥を検出できるという利点がある。このため、渦流探傷方法には、自己比較方式のプローブコイルが広く用いられている。 As a probe coil used in the eddy current flaw detection method, a so-called self-comparison type probe coil and a so-called standard comparison type probe coil are known. The self-comparison type probe coil includes at least one pair of detection coils (coils for detecting eddy currents induced in the material to be detected), and the difference in detection signals between the detection coils arranged opposite to the material to be detected. It is configured to output (differential signals between the detection coils). The probe coil of the standard comparison system has at least one pair of detection coils, one detection coil is disposed opposite to the material to be inspected, and the other detection coil is disposed opposite to the standard detection coil. The detection signal difference is output. If a self-comparison probe coil is used, noise signals caused by lift-off fluctuations between the material to be inspected and the probe coil accompanying relative movement of the probe coil are suppressed, compared to the case of using a standard comparison probe coil. Since the S / N ratio increases, there is an advantage that minute defects can be detected. For this reason, self-comparison probe coils are widely used in the eddy current flaw detection method.
自己比較方式のプローブコイルを用いた渦流探傷技術としては、例えば、特許文献１〜４に記載の技術が提案されている。 As an eddy current flaw detection technique using a self-comparison probe coil, for example, techniques disclosed in Patent Documents 1 to 4 have been proposed.
特許文献１には、被検査材の軸方向に沿って並設され、それぞれが被検査材の軸方向の磁力線を生じるように励磁される１対のコイルから構成され、該１対のコイルに誘導する電圧差に基づいて被検査材を探傷する渦流探傷センサが開示されている。この渦流探傷センサは、自己比較方式のプローブコイルに相当する。そして、この渦流探傷センサを被検査材の軸方向に螺旋状に相対移動させることによって被検査材は探傷される。また、特許文献１には、未探傷領域が生じないように、複数の渦流探傷センサを被検査材の軸方向に千鳥状に２列に配置する構成が開示されている。 Patent Document 1 includes a pair of coils that are juxtaposed along the axial direction of the material to be inspected, and are each excited so as to generate magnetic lines of force in the axial direction of the material to be inspected. An eddy current flaw detection sensor that flaws a material to be inspected based on an induced voltage difference is disclosed. This eddy current flaw detection sensor corresponds to a self-comparison type probe coil. Then, the material to be inspected is detected by moving the eddy current flaw detection sensor in a spiral manner in the axial direction of the material to be inspected. Further, Patent Document 1 discloses a configuration in which a plurality of eddy current flaw detection sensors are arranged in two rows in a staggered manner in the axial direction of a material to be inspected so that an undetected region does not occur.
特許文献２には、円筒形高透磁率磁芯材料の表面に巻いた励磁巻線の表面に、その円周方向全域にわたり複数個の偏平な検出コイルを千鳥状に配置し、外部を保持体で覆った渦流探傷用内挿型プローブが開示されている。各検出コイルは、未探傷領域が生じないように、内挿型プローブの軸方向から見てラップする部分を有する。そして、この内挿型プローブを管内面に挿入し、管軸方向に移動させて、隣接する１対の検出コイル間の差動信号により管内面が探傷される。この１対の検出コイルが、自己比較方式のプローブコイルに相当する。 In Patent Document 2, a plurality of flat detection coils are arranged in a zigzag pattern on the surface of an excitation winding wound around the surface of a cylindrical high permeability magnetic core material, and the outside is a holding body. An eddy current flaw-detecting interpolated probe covered with the above is disclosed. Each detection coil has a portion that wraps when viewed from the axial direction of the insertion probe so that an undetected region does not occur. Then, the insertion type probe is inserted into the inner surface of the tube and moved in the tube axis direction, and the inner surface of the tube is detected by a differential signal between a pair of adjacent detection coils. This pair of detection coils corresponds to a self-comparison probe coil.
特許文献３には、断面円形の被検査材の表面に対して垂直磁場を形成するセンサコイルを、被検査材の軸心を中心とする同心円上に多数配設し（具体的には、千鳥状に２列に配列し）、相隣するセンサコイルを１対として順次通電すると共に、センサコイルを被検査材の軸長方向へ相対移動させる渦流探傷装置が開示されている。このセンサコイルを被検査材の軸長へ相対移動させて、隣接する１対のセンサコイル間の差動信号により被検査材が探傷される。この１対のセンサコイルが、自己比較方式のプローブコイルに相当する。 In Patent Document 3, a large number of sensor coils that form a vertical magnetic field with respect to the surface of a material to be inspected having a circular cross section are arranged on a concentric circle centered on the axis of the material to be inspected (specifically, staggered). An eddy current flaw detector is disclosed in which adjacent sensor coils are sequentially energized as a pair, and the sensor coils are relatively moved in the axial length direction of the material to be inspected. This sensor coil is moved relative to the axial length of the material to be inspected, and the material to be inspected is detected by a differential signal between a pair of adjacent sensor coils. The pair of sensor coils corresponds to a self-comparison probe coil.
特許文献４には、円柱状ボビンの外周に、コイル長が７０ｍｍ以下に巻装した１対の検出コイルの端部がボビンの軸方向から見て重複するように、検出コイルを複数対千鳥状に配置した内挿プローブを用いて、内管内壁全面を探傷する二重管の内挿渦流探傷方法が開示されている。この内挿プローブを管軸方向に移動させて、１対の検出コイル間の差動信号により二重管が探傷される。この１対の検出コイルが、自己比較方式のプローブコイルに相当する。
特許文献１に記載の技術は、被探傷材の軸方向に千鳥状に２列に配置した複数の検出コイルを被探傷材の軸方向に螺旋状に相対移動させることにより、１回の走査（相対移動）で未探傷領域を生じさせることなく被探傷材を探傷可能としている。また、特許文献２〜４に記載の技術は、被探傷材の周方向に千鳥状に２列に配置した複数の検出コイルを被探傷材の軸方向に相対移動させることにより、１回の走査（相対移動）で未探傷領域を生じさせることなく被探傷材を探傷可能としている。 In the technique described in Patent Document 1, a plurality of detection coils arranged in two rows in a staggered manner in the axial direction of the flaw detection material are relatively moved spirally in the axial direction of the flaw detection material. The flaw detection material can be detected without causing an undetected region by relative movement. Further, in the techniques described in Patent Documents 2 to 4, one scanning is performed by relatively moving a plurality of detection coils arranged in two rows in a staggered manner in the circumferential direction of the flaw detection material in the axial direction of the flaw detection material. The flaw detection material can be detected without causing an undetected region by (relative movement).
特許文献１〜４の何れの技術についても、複数の検出コイルを千鳥状に配置することによって探傷領域を広げている点で、探傷能率は向上するといえる。しかしながら、従来、検出コイル間の差動信号の検出感度及び位相の校正は、差動信号を得る１対の検出コイル毎に行っているため、検出コイルの数が増えれば増えるほど、校正作業に手間を要する。従って、探傷精度を高めるために、検出コイル間の差動信号についての校正作業の頻度を高めると、その分だけ、探傷能率が低下するという問題がある。 In any of the techniques of Patent Documents 1 to 4, it can be said that the flaw detection efficiency is improved in that the flaw detection area is widened by arranging a plurality of detection coils in a staggered manner. However, conventionally, the calibration of the detection sensitivity and phase of the differential signal between the detection coils is performed for each pair of detection coils that obtain the differential signal. Therefore, as the number of detection coils increases, the calibration work increases. It takes time. Therefore, if the frequency of the calibration work for the differential signal between the detection coils is increased in order to increase the flaw detection accuracy, there is a problem that the flaw detection efficiency is lowered accordingly.
本発明は、斯かる従来技術の問題点に鑑みてなされたものであり、断面略円形の被探傷材に存在する欠陥を検出する渦流探傷方法及び装置であって、検出コイル間の差動信号の校正作業の手間を軽減することにより、高能率で探傷可能な渦流探傷方法及び装置を提供することを課題とする。 The present invention has been made in view of the problems of the prior art, and is an eddy current flaw detection method and apparatus for detecting a defect present in a flaw detection material having a substantially circular cross section, and a differential signal between detection coils. It is an object of the present invention to provide an eddy current flaw detection method and apparatus that can perform flaw detection with high efficiency by reducing the labor of calibration work.
前記課題を解決するため、本発明は、長手方向に直線状に配列された偶数個の検出コイルからなる検出コイル列が、短手方向に隣接する検出コイルの端部同士が短手方向から見て互いに重なり合うように、短手方向に２列配列されて構成される検出コイル群を、各検出コイルの長手方向が断面略円形の被探傷材の軸方向に沿うように該被探傷材に対向配置して、該被探傷材に存在する欠陥を検出する渦流探傷方法であって、以下の各ステップを含むことを特徴とする渦流探傷方法を提供する。
（１）校正ステップ：校正用の被探傷材に、該校正用被探傷材の軸方向に延びる人工きずであって、前記検出コイル群を構成する長手方向及び短手方向に隣接する２対の検出コイルの長さ以上に延びる人工きずを設け、前記検出コイル群を前記人工きずに対向配置して、前記校正用被探傷材の周方向に前記検出コイル群を相対移動させることにより、短手方向に隣接する検出コイル間の差動信号の検出感度及び位相を校正する。
（２）調整ステップ：前記検出コイル群を用いて得られる検出対象欠陥についての長手方向に隣接する検出コイル間の差動信号の最大振幅及び位相と、前記校正ステップで用いる人工きずについての短手方向に隣接する検出コイル間の差動信号の最大振幅及び位相との予め取得した関係に基づき、長手方向に隣接する検出コイル間の差動信号の検出感度及び位相を調整する。
（３）探傷ステップ：前記調整ステップで調整した後の前記検出コイル群を被探傷材に対向配置し、前記検出コイル群を被探傷材の軸方向に螺旋状に相対移動させて、長手方向に隣接する検出コイル間の差動信号に基づき、前記被探傷材に存在する欠陥を検出する。
In order to solve the above-described problems, the present invention provides a detection coil array composed of an even number of detection coils arranged linearly in the longitudinal direction, and the ends of the detection coils adjacent in the lateral direction are viewed from the lateral direction. The detection coil group constituted by two rows arranged in the short direction so as to overlap each other is opposed to the material to be inspected so that the longitudinal direction of each detection coil is along the axial direction of the material to be inspected having a substantially circular cross section. Provided is an eddy current flaw detection method that is arranged and detects defects present in the material to be flawed, and includes the following steps.
(1) Calibration step: two pairs of artificial flaws extending in the axial direction of the calibration flaw detection material adjacent to each other in the longitudinal direction and the short direction constituting the detection coil group. By providing an artificial flaw extending beyond the length of the detection coil, the detection coil group is disposed opposite to the artificial flaw, and the detection coil group is relatively moved in the circumferential direction of the calibration flaw detection material. The detection sensitivity and phase of the differential signal between the detection coils adjacent in the direction are calibrated.
(2) Adjustment step: The maximum amplitude and phase of the differential signal between the detection coils adjacent in the longitudinal direction with respect to the detection target defect obtained using the detection coil group, and the shortness of the artificial flaw used in the calibration step Based on the previously acquired relationship between the maximum amplitude and phase of the differential signal between the detection coils adjacent in the direction, the detection sensitivity and phase of the differential signal between the detection coils adjacent in the longitudinal direction are adjusted.
(3) Flaw detection step: The detection coil group adjusted in the adjustment step is disposed opposite to the flaw detection material, and the detection coil group is moved relatively in a spiral shape in the axial direction of the flaw detection material, and in the longitudinal direction. A defect present in the flaw detection material is detected based on a differential signal between adjacent detection coils.
本発明で用いる検出コイル群は、長手方向に直線状に配列された偶数個の検出コイルからなる検出コイル列が、短手方向に隣接する検出コイルの端部同士が短手方向から見て互いに重なり合うように、短手方向に２列配列されて構成される。そして、この検出コイル群が、各検出コイルの長手方向が断面略円形の被探傷材の軸方向に沿うように該被探傷材に対向配置され、被探傷材に存在する欠陥が検出される。換言すれば、本発明で用いる検出コイル群は、被探傷材に対向配置された状態で、被探傷材の軸方向に千鳥状に２列（被探傷材の周方向に２列）に配置した複数の検出コイルを備え、被探傷材の周方向に隣接する検出コイルの端部同士が被探傷材の周方向から見て互いに重なり合うように構成されている。そして、本発明の探傷ステップにおいて、検出コイル群を被探傷材に対向配置し、検出コイル群を被探傷材の軸方向に螺旋状に相対移動させて、長手方向（被探傷材の軸方向）に隣接する検出コイル間の差動信号に基づき、被探傷材に存在する欠陥を検出するため、１回の走査（相対移動）で未探傷領域を生じさせることなく被探傷材を探傷可能である。 In the detection coil group used in the present invention, a detection coil array composed of an even number of detection coils arranged in a straight line in the longitudinal direction is connected to each other when the ends of the detection coils adjacent in the lateral direction are viewed from the lateral direction. Two rows are arranged in the lateral direction so as to overlap. Then, this detection coil group is disposed opposite the flaw detection material so that the longitudinal direction of each detection coil is along the axial direction of the flaw detection material having a substantially circular cross section, and a defect present in the flaw detection material is detected. In other words, the detection coil groups used in the present invention are arranged in two rows in a staggered manner in the axial direction of the flaw detection material (two rows in the circumferential direction of the flaw detection material) in a state of being opposed to the flaw detection material. A plurality of detection coils are provided, and the ends of the detection coils adjacent in the circumferential direction of the flaw detection material are configured to overlap each other when viewed from the circumferential direction of the flaw detection material. In the flaw detection step of the present invention, the detection coil group is arranged opposite to the flaw detection material, and the detection coil group is relatively moved in a spiral shape in the axial direction of the flaw detection material, and the longitudinal direction (the axial direction of the flaw detection material). Since the defect existing in the flaw detection material is detected based on the differential signal between the detection coils adjacent to the flaw detection material, the flaw detection material can be flawed without causing an unflawed area in one scan (relative movement). .
そして、本発明の校正ステップでは、校正用の被探傷材に、検出コイル群を構成する長手方向（被探傷材の軸方向）及び短手方向（被探傷材の周方向）に隣接する２対の検出コイルの長さ以上に延びる人工きずを設け、検出コイル群を人工きずに対向配置して、校正用被探傷材の周方向に検出コイル群を相対移動させることにより、短手方向（被探傷材の周方向）に隣接する検出コイル間の差動信号の検出感度及び位相が校正される。換言すれば、人工きずを探傷する際に得られる短手方向（被探傷材の周方向）に隣接する検出コイル間の差動信号（きず信号）の最大振幅が予め決めた所定値となるように、差動信号の検出感度（差動信号の増幅率）が調整される。また、人工きず以外の部位を探傷する際に得られる短手方向（被探傷材の周方向）に隣接する検出コイル間の差動信号（リフトオフ変動等に起因したノイズ信号）の位相と、上記きず信号の位相とを弁別し易いように、差動信号の位相が調整される。本発明の校正ステップによれば、校正用被探傷材の周方向に検出コイル群を相対移動させることにより、短手方向（被探傷材の周方向）に隣接する検出コイル間の差動信号の検出感度及び位相を、少なくとも２対の検出コイル分だけ同時に校正できるため、従来のように１対の検出コイル毎に校正する場合に比べて、校正作業の手間を軽減することができ、探傷能率を高めることが可能である。なお、人工きずの長さが、検出コイル群を構成する長手方向（被探傷材の軸方向）及び短手方向（被探傷材の周方向）に隣接する２対の検出コイルの長さと同等であり、且つ、検出コイル群が、長手方向（被探傷材の軸方向）及び短手方向（被探傷材の周方向）に隣接する４対以上の検出コイルを備える場合には、いずれか隣接する２対の検出コイルを人工きずに対向配置して校正した後、検出コイル群を校正用被探傷材の軸方向に相対移動させ、残りの隣接する２対の検出コイルを人工きずに対向配置して校正を行えばよい。 Then, in the calibration step of the present invention, two pairs adjacent to the calibrated flaw detection material are adjacent to the longitudinal direction (axial direction of the flaw detection material) and the short direction (circumferential direction of the flaw detection material) constituting the detection coil group. An artificial flaw extending beyond the length of the detection coil is provided, the detection coil group is disposed opposite to the artificial flaw, and the detection coil group is moved relative to the circumferential direction of the calibration flaw detection material, thereby reducing the short direction (covered). The detection sensitivity and phase of the differential signal between the detection coils adjacent in the circumferential direction of the flaw detection material are calibrated. In other words, the maximum amplitude of the differential signal (flaw signal) between the detection coils adjacent in the short direction (circumferential direction of the flaw detection material) obtained when flaw detection is performed on the artificial flaw is set to a predetermined value. In addition, the detection sensitivity of the differential signal (the amplification factor of the differential signal) is adjusted. Further, the phase of the differential signal (noise signal due to lift-off fluctuations, etc.) between the detection coils adjacent in the short direction (circumferential direction of the flaw detection material) obtained when flaw detection is performed on parts other than artificial flaws, and the above The phase of the differential signal is adjusted so that the phase of the flaw signal can be easily distinguished. According to the calibration step of the present invention, the differential signal between the detection coils adjacent in the short direction (circumferential direction of the flaw detection material) is moved by relatively moving the detection coil group in the circumferential direction of the flaw detection material for calibration. Since the detection sensitivity and phase can be calibrated at the same time for at least two pairs of detection coils, it is possible to reduce the time and effort of calibration compared to the case of calibrating each pair of detection coils as in the past, and the flaw detection efficiency. It is possible to increase. The length of the artificial flaw is equivalent to the length of two pairs of detection coils adjacent in the longitudinal direction (the axial direction of the flaw detection material) and the short direction (the circumferential direction of the flaw detection material) constituting the detection coil group. If the detection coil group includes four or more pairs of detection coils adjacent in the longitudinal direction (axial direction of the material to be detected) and the short direction (circumferential direction of the material to be detected), either of them is adjacent. After calibrating with two pairs of detection coils facing each other without artificial flaws, the detection coil group is relatively moved in the axial direction of the flaw to be calibrated, and the remaining two pairs of adjacent detection coils are disposed facing each other without artificial flaws. And calibrate.
ただし、上記の校正ステップでは、短手方向（被探傷材の周方向）に隣接する検出コイル間の差動信号について校正しており、探傷ステップで実際に探傷する際に用いる長手方向（被探傷材の軸方向）に隣接する検出コイル間の差動信号について校正するものではない。このため、本発明では、前記検出コイル群を用いて得られる検出対象欠陥（例えば、被探傷材の表面が窪んだピット状きずや貫通きずなどの微小きず）についての長手方向に隣接する検出コイル間の差動信号の最大振幅及び位相と、校正ステップで用いる人工きずについての短手方向に隣接する検出コイル間の差動信号の最大振幅及び位相との関係を予め取得しておく。そして、本発明の調整ステップにおいて、この予め取得した関係に基づき、長手方向に隣接する検出コイル間の差動信号の検出感度及び位相を調整する。これにより、校正ステップにおいて、短手方向（被探傷材の周方向）に隣接する検出コイル間の差動信号の検出感度及び位相を校正しさえすれば、前記予め取得した関係に基づき、長手方向に隣接する検出コイル間の差動信号の検出感度及び位相を容易に調整可能である。なお、検出対象欠陥が微小きずである場合、この微小きずについての長手方向に隣接する検出コイル間の差動信号の振幅は、微小きずがいずれか一方の検出コイルの中心に対向する位置にあるときに最大となる。このため、微小きずについての長手方向に隣接する検出コイル間の差動信号の最大振幅を得るには、被探傷材の軸方向についての検出コイル群の相対位置を微妙に調整する必要が生じ、手間を要する。しかしながら、微小きずについての長手方向に隣接する検出コイル間の差動信号の最大振幅及び位相と、校正ステップで用いる人工きずについての短手方向に隣接する検出コイル間の差動信号の最大振幅及び位相との関係が変化しないとすれば、この関係を取得するために、微小きずについての長手方向に隣接する検出コイル間の差動信号の最大振幅を一度だけ取得すればよい。すなわち、微小きずについての長手方向に隣接する検出コイル間の差動信号の最大振幅を取得し、この最大振幅及び位相と、校正ステップで用いる人工きずについての短手方向に隣接する検出コイル間の差動信号の最大振幅及び位相との関係を取得した後は、人工きずを用いて短手方向（被探傷材の周方向）に隣接する検出コイル間の差動信号についてのみ校正すればよいため、校正作業の手間を軽減することができ、探傷能率を高めることが可能である。 However, in the calibration step, the differential signal between the detection coils adjacent in the short direction (circumferential direction of the flaw detection material) is calibrated, and the longitudinal direction (flaw to be detected) used in actual flaw detection in the flaw detection step. It does not calibrate the differential signal between the detection coils adjacent in the axial direction of the material. For this reason, in this invention, the detection coil adjacent to the longitudinal direction about the detection target defect (for example, micro flaws, such as a pit-like flaw and the penetration flaw which the surface of the to-be-examined material was dented) obtained using the said detection coil group The relationship between the maximum amplitude and phase of the differential signal between and the maximum amplitude and phase of the differential signal between the detection coils adjacent in the short direction of the artificial flaw used in the calibration step is acquired in advance. In the adjustment step of the present invention, the detection sensitivity and phase of the differential signal between the detection coils adjacent in the longitudinal direction are adjusted based on the previously acquired relationship. As a result, in the calibration step, as long as the detection sensitivity and phase of the differential signal between the detection coils adjacent in the short direction (circumferential direction of the flaw detection material) are calibrated, the longitudinal direction is based on the previously acquired relationship. It is possible to easily adjust the detection sensitivity and phase of the differential signal between the detection coils adjacent to each other. When the defect to be detected is a minute flaw, the amplitude of the differential signal between the detection coils adjacent in the longitudinal direction of the minute flaw is at a position where the minute flaw is opposed to the center of one of the detection coils. Sometimes it becomes maximum. For this reason, in order to obtain the maximum amplitude of the differential signal between the detection coils adjacent in the longitudinal direction with respect to the minute flaw, it is necessary to finely adjust the relative position of the detection coil group in the axial direction of the flaw detection material, It takes time. However, the maximum amplitude and phase of the differential signal between the detection coils adjacent in the longitudinal direction for the minute flaw and the maximum amplitude and phase of the differential signal between the detection coils adjacent in the short direction of the artificial flaw used in the calibration step If the relationship with the phase does not change, in order to acquire this relationship, the maximum amplitude of the differential signal between the detection coils adjacent in the longitudinal direction with respect to minute flaws need only be acquired once. That is, the maximum amplitude of the differential signal between the detection coils adjacent in the longitudinal direction with respect to the minute flaws is obtained, and the maximum amplitude and phase between the detection coils adjacent in the short direction with respect to the artificial flaw used in the calibration step. After obtaining the relationship between the maximum amplitude and phase of the differential signal, it is only necessary to calibrate the differential signal between adjacent detection coils in the short direction (circumferential direction of the flaw detection material) using an artificial flaw. Thus, it is possible to reduce the labor of calibration work and to increase the flaw detection efficiency.
以上のように、本発明に係る方法によれば、検出コイル間の差動信号の校正作業の手間が軽減され、探傷効率を高めることが可能である。なお、本発明における「長手方向」及び「短手方向」とは、それぞれ検出コイル群を構成する各検出コイルの長手方向及び短手方向を意味する。また、本発明における「長手方向及び短手方向に隣接する２対の検出コイルの長さ」とは、長手方向及び短手方向に隣接する２対の検出コイルの長手方向の総長さを意味する。 As described above, according to the method of the present invention, the labor for calibrating the differential signal between the detection coils can be reduced, and the flaw detection efficiency can be increased. In the present invention, the “longitudinal direction” and the “short direction” mean the long direction and the short direction of each detection coil constituting the detection coil group, respectively. Further, “the length of two pairs of detection coils adjacent in the longitudinal direction and the short direction” in the present invention means the total length in the longitudinal direction of two pairs of detection coils adjacent in the longitudinal direction and the short direction. .
好ましくは、前記人工きずは、前記検出コイル群の長さ以上に前記校正用被探傷材の軸方向に延びるものとされる。 Preferably, the artificial flaw extends in the axial direction of the calibration flaw detection material more than the length of the detection coil group.
斯かる好ましい方法によれば、検出コイル群を人工きずに対向配置して、校正用被探傷材の周方向に検出コイル群を一回相対移動させるだけで、全ての検出コイル間の差動信号について校正することが可能である。すなわち、校正ステップを実行する際に、検出コイル群を校正用被探傷材の軸方向に相対移動させる必要が無いため、校正作業の手間がより一層軽減され、より一層探傷効率を高めることが可能である。なお、本発明における「検出コイル群の長さ」とは、検出コイル群を構成する全ての検出コイルの長手方向の総長さを意味する。 According to such a preferable method, the detection coil groups are arranged to face each other without artificial flaws, and the differential signals between all the detection coils are simply moved once in the circumferential direction of the flaw detection material for calibration. Can be calibrated. In other words, when performing the calibration step, it is not necessary to move the detection coil group relative to the calibration flaw detection material in the axial direction, so that the labor of the calibration work can be further reduced and the flaw detection efficiency can be further increased. It is. The “length of the detection coil group” in the present invention means the total length in the longitudinal direction of all the detection coils constituting the detection coil group.
また、前記課題を解決するため、本発明は、長手方向に直線状に配列された偶数個の検出コイルからなる検出コイル列が、短手方向に隣接する検出コイルの端部同士が短手方向から見て互いに重なり合うように、短手方向に２列配列されて構成される検出コイル群であって、各検出コイルの長手方向が断面略円形の被探傷材の軸方向に沿うように該被探傷材に対向配置された検出コイル群と、前記検出コイル群における長手方向に隣接する検出コイル間の差動信号と、短手方向に隣接する検出コイル間の差動信号とを切り替えて出力する切り替え手段と、前記切り替え手段によって出力された差動信号の検出感度及び位相を調整する調整手段と、前記検出コイル群を被探傷材の軸方向及び周方向に相対移動させる移動手段とを備えることを特徴とする渦流探傷装置としても提供される。 In order to solve the above-mentioned problem, the present invention provides a detection coil array composed of an even number of detection coils arranged linearly in the longitudinal direction, and the ends of the detection coils adjacent in the lateral direction are in the lateral direction. The detection coil groups are arranged in two rows in the short direction so as to overlap each other when viewed from the top, and the detection coil is arranged so that the longitudinal direction of each detection coil is along the axial direction of the flaw detection material having a substantially circular cross section. A detection coil group arranged opposite to the flaw detection material, a differential signal between detection coils adjacent in the longitudinal direction in the detection coil group, and a differential signal between detection coils adjacent in the short direction are switched and output. A switching unit; an adjusting unit that adjusts the detection sensitivity and phase of the differential signal output by the switching unit; and a moving unit that relatively moves the detection coil group in the axial direction and the circumferential direction of the flaw detection material. Special It is provided as an eddy-current flaw detection device according to.
本発明に係る装置によれば、切り替え手段によって短手方向に隣接する検出コイル間の差動信号を出力し、移動手段によって検出コイル群を被探傷材の周方向に相対移動させながら、調整手段によって短手方向に隣接する検出コイル間の差動信号の検出感度及び位相を調整することにより、前述した本発明に係る方法の校正ステップを実行することが可能である。また、切り替え手段によって長手方向に隣接する検出コイル間の差動信号を出力し、調整手段によって長手方向に隣接する検出コイル間の差動信号の検出感度及び位相を調整することにより、前述した本発明に係る方法の調整ステップを実行することが可能である。さらに、切り替え手段によって長手方向に隣接する検出コイル間の差動信号を出力し、移動手段によって検出コイル群を被探傷材の軸方向及び周方向に同時に（すなわち、螺旋状に）相対移動させることにより、前述した本発明に係る方法の探傷ステップを実行することが可能である。 According to the apparatus of the present invention, the adjustment means outputs the differential signal between the detection coils adjacent in the short direction by the switching means, and relatively moves the detection coil group in the circumferential direction of the flaw detection material by the moving means. By adjusting the detection sensitivity and phase of the differential signal between the detection coils adjacent in the short direction by the above, it is possible to execute the calibration step of the method according to the present invention described above. Further, the switching means outputs a differential signal between the detection coils adjacent in the longitudinal direction, and the adjustment means adjusts the detection sensitivity and phase of the differential signal between the detection coils adjacent in the longitudinal direction. It is possible to carry out the adjusting step of the method according to the invention. Further, a differential signal between detection coils adjacent in the longitudinal direction is output by the switching means, and the detection coil group is relatively moved simultaneously (ie, spirally) in the axial direction and the circumferential direction of the flaw detection material by the moving means. Thus, the flaw detection step of the method according to the present invention described above can be executed.
本発明によれば、検出コイル間の差動信号についての校正作業の手間を軽減することにより、管、丸ビレット、丸棒など、断面略円形の被探傷材に存在する欠陥を高能率で探傷可能である。 According to the present invention, it is possible to efficiently detect defects existing in a material having a substantially circular cross section, such as a tube, a round billet, and a round bar, by reducing the labor of calibration for differential signals between detection coils. Is possible.
以下、添付図面を適宜参照しつつ、本発明の一実施形態について、被探傷材が管である場合を例に挙げて説明する。 DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings, taking as an example a case where a flaw detection material is a pipe.
＜１．渦流探傷装置の構成＞
図１は、本発明の一実施形態に係る渦流探傷装置の概略構成を示す模式図である。図１に示すように、本実施形態に係る渦流探傷装置１００は、検出コイル群１と、信号処理部２とを備えている。また、渦流探傷装置１００は、検出コイル群１を管Ｐの軸方向及び周方向に相対移動させる移動手段（図示せず）を備える。
<1. Configuration of Eddy Current Flaw Detector>
FIG. 1 is a schematic diagram showing a schematic configuration of an eddy current flaw detector according to an embodiment of the present invention. As shown in FIG. 1, the eddy current flaw detector 100 according to the present embodiment includes a detection coil group 1 and a signal processing unit 2. Further, the eddy current flaw detection apparatus 100 includes a moving means (not shown) that relatively moves the detection coil group 1 in the axial direction and the circumferential direction of the tube P.
検出コイル群１は、長手方向（図１のＸ方向）に直線状に配列された偶数個（本実施形態では４つ）の検出コイル１１からなる検出コイル列が、短手方向に２列配列されて構成されている。具体的には、検出コイル１１ａ、１１ｃ、１１ｅ、１１ｇからなる検出コイル列と、検出コイル１１ｂ、１１ｄ、１１ｆ、１１ｈからなる検出コイル列とが、短手方向（図１のＹ方向）に配列されている。そして、これらの検出コイル列は、短手方向に隣接する検出コイル１１の端部同士が短手方向から見て互いに重なり合うように配列されている。この検出コイル群１は、各検出コイル１１の長手方向が管Ｐの軸方向に沿うように管Ｐの外面に対向配置されている。なお、未探傷領域を生じさせることなく管Ｐを探傷するため、検出コイル１１の長手方向の配列ピッチ（例えば、検出コイル１１ａの中心と検出コイル１１ｂの中心との長手方向の離間距離）は、検出コイル１１で欠陥の検出が可能な有効長さＬＥ以下とされる。換言すれば、検出コイル１１は、その配列ピッチが有効長さＬＥ以下となるように、端部同士が短手方向から見て互いに重なり合うように配列されている。 The detection coil group 1 includes two detection coil rows each including an even number (four in this embodiment) of detection coils 11 arranged linearly in the longitudinal direction (X direction in FIG. 1). Has been configured. Specifically, the detection coil array composed of the detection coils 11a, 11c, 11e, and 11g and the detection coil array composed of the detection coils 11b, 11d, 11f, and 11h are arranged in the short direction (Y direction in FIG. 1). Has been. These detection coil arrays are arranged so that ends of the detection coils 11 adjacent in the short direction overlap each other when viewed from the short direction. This detection coil group 1 is disposed opposite to the outer surface of the tube P so that the longitudinal direction of each detection coil 11 is along the axial direction of the tube P. In order to detect the tube P without generating an undetected region, the arrangement pitch in the longitudinal direction of the detection coils 11 (for example, the separation distance in the longitudinal direction between the center of the detection coil 11a and the center of the detection coil 11b) is: The detection coil 11 is set to an effective length LE or less capable of detecting a defect. In other words, the detection coils 11 are arranged so that the ends overlap each other when viewed from the short direction so that the arrangement pitch is equal to or less than the effective length LE.
本実施形態に係る検出コイル１１は、周縁に導線が巻回されており、管Ｐに誘起された渦電流によって生じる管Ｐの外面に垂直な方向の交流磁界の変化を検出すると共に、管Ｐの外面に垂直な方向に交流磁界を作用させて渦電流を誘起する励磁コイルの機能を兼ねた、いわゆる自己誘導型コイルとされている。 The detection coil 11 according to the present embodiment has a conducting wire wound around the periphery thereof, detects a change in an alternating magnetic field in a direction perpendicular to the outer surface of the tube P caused by an eddy current induced in the tube P, and also detects the tube P This is a so-called self-inductive coil that also functions as an exciting coil that induces an eddy current by applying an alternating magnetic field in a direction perpendicular to the outer surface of the coil.
ここで、検出コイル１１の寸法が小さいほど、ピット状きずや貫通きずなどの微小きずを検出し易いため、これら微小きずの検出能を高めるには、検出コイル１１の寸法を小さくすることが好ましい。一方、後述のように、検出コイル１１を管Ｐの軸方向に螺旋状に相対移動させて探傷するに際し、管Ｐの周方向１回転当たりの各検出コイル１１の探傷幅（管Ｐの探傷領域の軸方向寸法）を広くする方が、探傷能率は向上する。このため、検出対象欠陥が微小きずである場合には、検出コイル１１として、長手方向（管Ｐの軸方向）の寸法と短手方向（管Ｐの周方向）の寸法との比が比較的大きな細長形状の検出コイルを用いることが好ましい。例えば、検出対象欠陥が内径２ｍｍのピット状きずである場合には、検出コイル１１の短手方向の寸法（具体的には、欠陥の検出が可能な有効幅ＷＥ）は、好ましくは２ｍｍ以下、より好ましくは１ｍｍ以下とされる。また、検出コイル１１の長手方向の寸法（欠陥の検出が可能な有効長さＬＥ）は、好ましくは４ｍｍ以上とされる。 Here, as the size of the detection coil 11 is smaller, it is easier to detect minute flaws such as pit-like flaws and penetrating flaws. Therefore, in order to improve the detection ability of these minute flaws, it is preferable to reduce the size of the detection coil 11. . On the other hand, as described later, when the detection coil 11 is relatively moved spirally in the axial direction of the tube P to perform flaw detection, the flaw detection width of each detection coil 11 per rotation in the circumferential direction of the tube P (flaw detection region of the tube P). The flaw detection efficiency is improved by increasing the axial dimension). For this reason, when the defect to be detected is a minute flaw, the ratio of the dimension in the longitudinal direction (the axial direction of the tube P) and the dimension in the lateral direction (the circumferential direction of the tube P) is relatively small as the detection coil 11 It is preferable to use a large elongated detection coil. For example, when the defect to be detected is a pit-shaped flaw having an inner diameter of 2 mm, the dimension in the short direction of the detection coil 11 (specifically, the effective width WE capable of detecting the defect) is preferably 2 mm or less, More preferably, it is 1 mm or less. Further, the dimension in the longitudinal direction of the detection coil 11 (effective length LE capable of detecting a defect) is preferably 4 mm or more.
本実施形態に係る信号処理部２は、切り替え手段２１（２１ａ〜２１ｄ）と、発信器２２と、増幅器２３（２３ａ〜２３ｄ）と、同期検波器２４（２４ａ〜２４ｄ）と、位相回転器２５（２５ａ〜２５ｄ）と、バンドパスフィルタ２６（２６ａ〜２６ｄ）と、Ａ／Ｄ変換器２７（２７ａ〜２７ｄ）と、検出部２８（２７ａ〜２７ｄ）とを備える。なお、本実施形態の増幅器２３及び位相回転器２５が、本発明における「切り替え手段によって出力された差動信号の検出感度及び位相を調整する調整手段」に相当する。 The signal processing unit 2 according to this embodiment includes a switching unit 21 (21a to 21d), a transmitter 22, an amplifier 23 (23a to 23d), a synchronous detector 24 (24a to 24d), and a phase rotator 25. (25a to 25d), a band pass filter 26 (26a to 26d), an A / D converter 27 (27a to 27d), and a detector 28 (27a to 27d). The amplifier 23 and the phase rotator 25 of the present embodiment correspond to “adjusting means for adjusting the detection sensitivity and phase of the differential signal output by the switching means” in the present invention.
発信器２２は、各検出コイル１１に所定周波数の交流電流を供給する。これにより、前述のように、各検出コイル１１から管Ｐの外面に垂直な方向に作用する交流磁界が生じ、管Ｐに渦電流が誘起される。そして、管Ｐに誘起された渦電流によって生じる管Ｐの外面に垂直な方向の交流磁界の変化が各検出コイル１１で検出され、検出信号として出力される。 The transmitter 22 supplies an alternating current having a predetermined frequency to each detection coil 11. As a result, an alternating magnetic field acting in a direction perpendicular to the outer surface of the tube P is generated from each detection coil 11 as described above, and an eddy current is induced in the tube P. And the change of the alternating magnetic field of the direction perpendicular | vertical to the outer surface of the pipe | tube P produced by the eddy current induced in the pipe | tube P is detected by each detection coil 11, and is output as a detection signal.
切り替え手段２１は、検出コイル群１における長手方向に隣接する検出コイル１１間の差動信号と、短手方向に隣接する検出コイル１１間の差動信号とを切り替えて出力する機能を有する。本実施形態では、検出コイル群１が８つの検出コイル１１ａ〜１１ｈからなることに応じて、４つの切り替え手段２１ａ〜２１ｄが設けられている。具体的には、切り替え手段２１ａには、検出コイル１１ａ、１１ｂ、１１ｃでの検出信号がそれぞれ入力される。そして、切り替え手段２１ａは、長手方向に隣接する検出コイル１１ａ、１１ｃでの検出信号の差を差動信号として出力するか、或いは、短手方向に隣接する検出コイル１１ａ、１１ｂでの検出信号の差を差動信号として出力するかを切り替える。 The switching means 21 has a function of switching and outputting a differential signal between the detection coils 11 adjacent in the longitudinal direction in the detection coil group 1 and a differential signal between the detection coils 11 adjacent in the short direction. In the present embodiment, four switching means 21a to 21d are provided in accordance with the detection coil group 1 including eight detection coils 11a to 11h. Specifically, detection signals from the detection coils 11a, 11b, and 11c are input to the switching unit 21a, respectively. The switching means 21a outputs the difference between the detection signals in the detection coils 11a and 11c adjacent in the longitudinal direction as a differential signal, or the detection signal in the detection coils 11a and 11b adjacent in the short direction. Switches whether to output the difference as a differential signal.
同様にして、切り替え手段２１ｂには、検出コイル１１ｂ、１１ｃ、１１ｄでの検出信号がそれぞれ入力される。そして、切り替え手段２１ｂは、長手方向に隣接する検出コイル１１ｂ、１１ｄでの検出信号の差を差動信号として出力するか、或いは、短手方向に隣接する検出コイル１１ｃ、１１ｄでの検出信号の差を差動信号として出力するかを切り替える。切り替え手段２１ｃには、検出コイル１１ｅ、１１ｆ、１１ｇでの検出信号がそれぞれ入力される。そして、切り替え手段２１ｃは、長手方向に隣接する検出コイル１１ｅ、１１ｇでの検出信号の差を差動信号として出力するか、或いは、短手方向に隣接する検出コイル１１ｅ、１１ｆでの検出信号の差を差動信号として出力するかを切り替える。切り替え手段２１ｄには、検出コイル１１ｆ、１１ｇ、１１ｈでの検出信号がそれぞれ入力される。そして、切り替え手段２１ｄは、長手方向に隣接する検出コイル１１ｆ、１１ｈでの検出信号の差を差動信号として出力するか、或いは、短手方向に隣接する検出コイル１１ｇ、１１ｈでの検出信号の差を差動信号として出力するかを切り替える。 Similarly, detection signals from the detection coils 11b, 11c, and 11d are input to the switching unit 21b. Then, the switching means 21b outputs the difference between the detection signals in the detection coils 11b and 11d adjacent in the longitudinal direction as a differential signal, or the detection signal in the detection coils 11c and 11d adjacent in the short direction. Switches whether to output the difference as a differential signal. Detection signals from the detection coils 11e, 11f, and 11g are input to the switching unit 21c. The switching unit 21c outputs the difference between the detection signals in the detection coils 11e and 11g adjacent in the longitudinal direction as a differential signal, or the detection signal in the detection coils 11e and 11f adjacent in the short direction. Switches whether to output the difference as a differential signal. Detection signals from the detection coils 11f, 11g, and 11h are input to the switching unit 21d, respectively. The switching means 21d outputs the difference between the detection signals in the detection coils 11f and 11h adjacent in the longitudinal direction as a differential signal, or the detection signal in the detection coils 11g and 11h adjacent in the short direction. Switches whether to output the difference as a differential signal.
なお、切り替え手段２１としては、切り替え回路等を具備し、適宜の制御信号に基づいて、切り替え回路が、出力する差動信号を自動的に切り替える構成の他、押しボタンスイッチ等を押すことにより、電気的接続を機械的に切り替え、出力する差動信号を手動で切り替える構成を採用することも可能である。 The switching means 21 includes a switching circuit and the like, and the switching circuit automatically switches the differential signal to be output based on an appropriate control signal, and by pressing a push button switch or the like, It is also possible to adopt a configuration in which electrical connection is mechanically switched and a differential signal to be output is manually switched.
増幅器２３は、切り替え手段２１から出力された差動信号を増幅した後、同期検波器２４に出力する。本実施形態では、４つの切り替え手段２１ａ〜２１ｄが設けられていることに応じて、４つの増幅器２３ａ〜２３ｄが設けられている。 The amplifier 23 amplifies the differential signal output from the switching unit 21 and then outputs it to the synchronous detector 24. In the present embodiment, four amplifiers 23a to 23d are provided in response to the four switching means 21a to 21d being provided.
同期検波器２４は、発振器２２から出力される参照信号に基づき、増幅器２３の出力信号を同期検波する。本実施形態では、４つの増幅器２３ａ〜２３ｄが設けられていることに応じて、４つの同期検波器２４ａ〜２４ｄが設けられている。具体的に説明すれば、発振器２２から各同期検波器２４ａ〜２４ｄに向けて、各検出コイル１１に供給する交流電流と同一の周波数で同一の位相を有する第１参照信号と、該第１参照信号の位相を９０°だけ移相した第２参照信号とが出力される。そして、同期検波器２４ａ〜２４ｄは、増幅器２３ａ〜２３ｄの出力信号から、第１参照信号の位相と同位相の信号成分（第１信号成分）及び第２参照信号の位相と同位相の信号成分（第２信号成分）を分離・抽出する。分離・抽出された第１信号成分及び第２信号成分は、それぞれ位相回転器２５に出力される。 The synchronous detector 24 synchronously detects the output signal of the amplifier 23 based on the reference signal output from the oscillator 22. In the present embodiment, four synchronous detectors 24a to 24d are provided in response to the four amplifiers 23a to 23d. More specifically, a first reference signal having the same phase as the alternating current supplied to each detection coil 11 from the oscillator 22 toward each of the synchronous detectors 24a to 24d, and the first reference A second reference signal whose phase is shifted by 90 ° is output. Then, the synchronous detectors 24a to 24d receive signal components having the same phase as the phase of the first reference signal (first signal component) and signal components having the same phase as the phase of the second reference signal from the output signals of the amplifiers 23a to 23d. (Second signal component) is separated and extracted. The separated and extracted first signal component and second signal component are each output to the phase rotator 25.
位相回転器２５は、同期検波器２４から出力された第１信号成分及び第２信号成分の位相を互いに同一の所定量だけ回転（移相）し、例えば、第１信号成分をＸ信号、第２信号成分をＹ信号として、バンドパスフィルタ２６に出力する。本実施形態では、４つの同期検波器２４ａ〜２４ｄが設けられていることに応じて、４つの位相回転器２５ａ〜２５ｄが設けられている。なお、位相回転器２５から出力されるＸ信号及びＹ信号は、互いに直交する２軸（Ｘ軸、Ｙ軸）で表されるＸ−Ｙベクトル平面においていわゆるリサージュ波形と称される信号波形（すなわち、振幅をＺ、位相をθとして極座標（Ｚ、θ）で表した検出コイル１１間の差動信号波形（正確には、増幅器２３によって増幅した後の差動信号波形））を、Ｘ軸及びＹ軸にそれぞれ投影した成分に相当することになる。 The phase rotator 25 rotates (shifts) the phase of the first signal component and the second signal component output from the synchronous detector 24 by the same predetermined amount, for example, the first signal component is the X signal, The two signal components are output to the band pass filter 26 as a Y signal. In the present embodiment, four phase rotators 25a to 25d are provided in response to the four synchronous detectors 24a to 24d being provided. The X signal and Y signal output from the phase rotator 25 are signal waveforms (that is, so-called Lissajous waveforms) on the XY vector plane represented by two axes (X axis and Y axis) orthogonal to each other (that is, , The differential signal waveform between the detection coils 11 expressed in polar coordinates (Z, θ) with the amplitude Z and the phase θ (more precisely, the differential signal waveform after amplification by the amplifier 23), This corresponds to the component projected on the Y axis.
バンドパスフィルタ２６は、位相回転器２５から出力されたＸ信号及びＹ信号から所定の帯域の周波数成分のみを透過させて、Ａ／Ｄ変換器２７に出力する。本実施形態では、４つの位相回転器２５ａ〜２５ｄが設けられていることに応じて、４つのバンドパスフィルタ２６ａ〜２６ｄが設けられている。 The band pass filter 26 transmits only the frequency component of a predetermined band from the X signal and the Y signal output from the phase rotator 25 and outputs them to the A / D converter 27. In the present embodiment, four band pass filters 26a to 26d are provided in response to the four phase rotators 25a to 25d being provided.
Ａ／Ｄ変換器２７は、バンドパスフィルタ２６の出力信号をＡ／Ｄ変換し、検出部２８に出力する。本実施形態では、４つのバンドパスフィルタ２６ａ〜２６ｄが設けられていることに応じて、４つのＡ／Ｄ変換器２７ａ〜２７ｄが設けられている。 The A / D converter 27 performs A / D conversion on the output signal of the bandpass filter 26 and outputs it to the detection unit 28. In the present embodiment, four A / D converters 27a to 27d are provided in accordance with the four band pass filters 26a to 26d.
検出部２８は、Ａ／Ｄ変換器２７の出力データ（すなわち、バンドパスフィルタ２６によって所定の周波数成分のみが透過されたＸ信号及びＹ信号をＡ／Ｄ変換したデジタルデータ。以下、Ｘ信号データ及びＹ信号データという）に基づいて、管Ｐに存在する欠陥を検出する。具体的に説明すれば、検出部２８は、入力されたＸ信号データ及びＹ信号データに基づき、検出コイル１１間の差動信号（正確には、増幅器２３によって増幅し、バンドパスフィルタ２６によって所定の帯域の周波数成分のみを透過させた後の差動信号）の振幅Ｚ及び位相θを演算する。Ｘ信号データの値をＸ、Ｙ信号データの値をＹとすると、振幅Ｚ及び位相θは、下記の式（１）及び（２）によって演算される。
Ｚ＝（Ｘ２＋Ｙ２）１／２ ・・・ （１）
θ＝ｔａｎ−１（Ｙ／Ｘ） ・・・ （２）
The detection unit 28 outputs data from the A / D converter 27 (that is, digital data obtained by A / D-converting the X signal and the Y signal having only a predetermined frequency component transmitted by the band-pass filter 26. Hereinafter, the X signal data. And a defect existing in the tube P based on the Y signal data). More specifically, the detection unit 28 is based on the input X signal data and Y signal data, and a differential signal between the detection coils 11 (precisely, the signal is amplified by the amplifier 23 and is predetermined by the band pass filter 26). The amplitude Z and the phase θ of the differential signal after transmitting only the frequency component of the band (2) are calculated. When the value of the X signal data is X and the value of the Y signal data is Y, the amplitude Z and the phase θ are calculated by the following equations (1) and (2).
Z = (X 2 + Y 2 ) 1/2 (1)
θ = tan −1 (Y / X) (2)
次に、検出部２８は、前記演算した振幅Ｚが予め定めたしきい値よりも大きいか否かを判定する。振幅Ｚが予め定めたしきい値以下である場合、検出部２８は、この振幅Ｚを有する差動信号は欠陥での差動信号ではないと判定する。一方、振幅Ｚが予め定めたしきい値よりも大きい場合には、検出部２８は、この振幅Ｚを有する差動信号は欠陥での差動信号であると判定し、必要に応じて、欠陥を検出したことを知らせる所定のアラームを出力する。 Next, the detection unit 28 determines whether or not the calculated amplitude Z is greater than a predetermined threshold value. When the amplitude Z is equal to or smaller than a predetermined threshold value, the detection unit 28 determines that the differential signal having the amplitude Z is not a differential signal due to a defect. On the other hand, when the amplitude Z is larger than the predetermined threshold, the detection unit 28 determines that the differential signal having the amplitude Z is a differential signal at the defect, and if necessary, the defect A predetermined alarm is output informing that it has been detected.
なお、本実施形態では、検出部２８が振幅Ｚの大小によって欠陥の有無を判定する構成について説明したが、これに限るものではなく、検出部２８が、Ｘ信号データの値あるいはＹ信号データの値の何れかの大小によって欠陥の有無を判定する構成を採用することも可能である。 In the present embodiment, the configuration in which the detection unit 28 determines the presence / absence of a defect based on the magnitude of the amplitude Z has been described. However, the present invention is not limited to this, and the detection unit 28 may determine the value of the X signal data or the Y signal data. It is also possible to adopt a configuration in which the presence / absence of a defect is determined based on any value.
検出コイル群１を管Ｐの軸方向及び周方向に相対移動させる移動手段（図示せず）としては、例えば、管Ｐを載置して周方向に回転させるローラと、管Ｐを載置して軸方向に搬送するローラとを組み合わせた構成を挙げることができる。また、前記移動手段としては、管Ｐを載置して周方向に回転させるローラと、検出コイル群１を管Ｐの軸方向に移動させる一軸駆動機構とを組み合わせた構成を挙げることもできる。 As moving means (not shown) for relatively moving the detection coil group 1 in the axial direction and the circumferential direction of the tube P, for example, a roller for placing the tube P and rotating it in the circumferential direction, and a tube P are placed. Thus, a configuration in which a roller for conveying in the axial direction is combined can be given. Further, as the moving means, a configuration in which a roller on which the tube P is placed and rotated in the circumferential direction and a uniaxial driving mechanism that moves the detection coil group 1 in the axial direction of the tube P can be combined.
＜２．渦流探傷方法の説明＞
以下、上述した構成を有する渦流探傷装置１００を用いた本発明の一実施形態に係る渦流探傷方法について説明する。本実施形態に係る渦流探傷方法は、校正ステップと、調整ステップと、探傷ステップとを含む。以下、各ステップについて順次説明する。
<2. Explanation of eddy current flaw detection method>
Hereinafter, an eddy current flaw detection method according to an embodiment of the present invention using the eddy current flaw detection apparatus 100 having the above-described configuration will be described. The eddy current flaw detection method according to the present embodiment includes a calibration step, an adjustment step, and a flaw detection step. Hereinafter, each step will be described sequentially.
＜２−１．校正ステップ＞
図２に示すように、校正ステップでは、校正用の管Ｐ１（実際に探傷を行って製品として出荷される管Ｐと寸法や材質が同じである管）に、該校正用管Ｐ１の軸方向に延びる人工きずであって、検出コイル群１１を構成する長手方向及び短手方向に隣接する２対の検出コイル１１の長さＬ２以上に延びる人工きずＮ（例えば、長尺のノッチきず）を設ける。図２に示す例では、好ましい態様として、検出コイル群１の長さＬ１以上に延びる人工きずＮを設けている。なお、人工きずＮの幅（校正用管Ｐ１の周方向についての寸法）は、好ましくは、検出コイル１１の有効幅ＷＥ（図１参照）以下とされる。
<2-1. Calibration step>
As shown in FIG. 2, in the calibration step, the calibration pipe P1 (the pipe P1 that has the same dimensions and material as the pipe P1 that is actually subjected to flaw detection and shipped as a product) is moved in the axial direction of the calibration pipe P1. An artificial flaw N (for example, a long notch flaw) extending beyond the length L2 of two pairs of detection coils 11 adjacent to each other in the longitudinal direction and the short direction constituting the detection coil group 11. Provide. In the example shown in FIG. 2, as a preferred mode, an artificial flaw N extending beyond the length L1 of the detection coil group 1 is provided. The width of the artificial flaw N (the dimension in the circumferential direction of the calibration tube P1) is preferably set to be equal to or smaller than the effective width WE (see FIG. 1) of the detection coil 11.
そして、本ステップでは、検出コイル群１を人工きずＮに対向配置して、移動手段（図示せず）により校正用管Ｐ１の周方向に検出コイル群１を相対移動させることにより、短手方向に隣接する検出コイル１１間の差動信号の検出感度及び位相を校正する。以下、これについて具体的に説明する。 In this step, the detection coil group 1 is arranged opposite to the artificial flaw N, and the detection coil group 1 is relatively moved in the circumferential direction of the calibration tube P1 by a moving means (not shown), thereby The detection sensitivity and phase of the differential signal between the adjacent detection coils 11 are calibrated. This will be specifically described below.
まず、図１に示す切り替え手段２１を動作させ、切り替え手段２１が、短手方向に隣接する検出コイル１１での検出信号の差を差動信号として出力する状態にする。具体的には、切り替え手段２１ａが、短手方向に隣接する検出コイル１１ａ、１１ｂでの検出信号の差を差動信号として出力し、切り替え手段２１ｂが、短手方向に隣接する検出コイル１１ｃ、１１ｄでの検出信号の差を差動信号として出力し、切り替え手段２１ｃが、短手方向に隣接する検出コイル１１ｅ、１１ｆでの検出信号の差を差動信号として出力し、切り替え手段２１ｄが、短手方向に隣接する検出コイル１１ｇ、１１ｈでの検出信号の差を差動信号として出力する状態にする。 First, the switching unit 21 shown in FIG. 1 is operated so that the switching unit 21 outputs a difference between detection signals from the detection coils 11 adjacent in the short direction as a differential signal. Specifically, the switching unit 21a outputs a difference between detection signals in the detection coils 11a and 11b adjacent in the short direction as a differential signal, and the switching unit 21b detects the detection coil 11c in the short direction. The difference between the detection signals at 11d is output as a differential signal, the switching means 21c outputs the difference between the detection signals at the detection coils 11e and 11f adjacent in the short direction as a differential signal, and the switching means 21d The difference between the detection signals in the detection coils 11g and 11h adjacent in the short direction is set to a state of outputting as a differential signal.
次に、人工きずＮに対向配置した検出コイル群１の各検出コイル１１に発信器２２から交流電流を供給し、検出コイル群１を校正用管Ｐ１の周方向に相対移動させて探傷する。これにより、各検出コイル１１から各検出コイル１１に対向する校正用管Ｐ１の部位についての検出信号が出力される。そして、各切り替え手段２１から短手方向に隣接する検出コイル１１での検出信号の差が差動信号として出力される。人工きずＮを探傷する際に各切り替え手段２１から出力される差動信号（きず信号）は、人工きずＮが一方の検出コイル列（検出コイル１１ａ、１１ｃ、１１ｅ、１１ｇ）の短手方向中央に対向する位置にあるとき、或いは、人工きずＮが他方の検出コイル列（検出コイル１１ｂ、１１ｄ、１１ｆ、１１ｈ）の短手方向中央に対向する位置にあるときに、その振幅が最大となる。そして、このきず信号の最大振幅が増幅後に予め決めた所定値となるように、各増幅器２３の増幅率を調整する。具体的には、各検出部２８で演算されるきず信号の最大振幅Ｚが予め決めた所定値となるように、各増幅器２３の増幅率を調整する。以上のようにして、短手方向に隣接する検出コイル１１間の差動信号の検出感度を校正する。 Next, an alternating current is supplied from the transmitter 22 to each of the detection coils 11 of the detection coil group 1 disposed so as to face the artificial flaw N, and the detection coil group 1 is relatively moved in the circumferential direction of the calibration tube P1 for flaw detection. As a result, a detection signal is output from each detection coil 11 for the portion of the calibration tube P1 that faces each detection coil 11. And the difference of the detection signal in the detection coil 11 adjacent to the transversal direction from each switching means 21 is output as a differential signal. The differential signal (flaw signal) output from each switching means 21 when flaw detection is performed on the artificial flaw N is the center in the short direction of one of the detection coil arrays (detection coils 11a, 11c, 11e, 11g). When the artificial flaw N is at a position facing the center in the short direction of the other detection coil array (detection coils 11b, 11d, 11f, 11h), the amplitude becomes maximum. . Then, the amplification factor of each amplifier 23 is adjusted so that the maximum amplitude of the flaw signal becomes a predetermined value after amplification. Specifically, the amplification factor of each amplifier 23 is adjusted so that the maximum amplitude Z of the flaw signal calculated by each detector 28 becomes a predetermined value. As described above, the detection sensitivity of the differential signal between the detection coils 11 adjacent in the lateral direction is calibrated.
また、校正用管Ｐ１の人工きずＮ以外の部位を探傷する際、すなわち、いずれの検出コイル列に対向する位置にも人工きずＮがない場合に各切り替え手段２１から出力される差動信号（リフトオフ変動等に起因したノイズ信号）の位相と、上記きず信号の位相とを弁別し易いように、差動信号の位相を調整する。具体的には、各検出部２８で演算されるきず信号の位相θが予め決めた所定値となるように、各位相回転器２５における位相の回転量（移相量）を調整する。以上のようにして、短手方向に隣接する検出コイル１１間の差動信号の位相を校正する。 Further, when a portion other than the artificial flaw N of the calibration pipe P1 is detected, that is, when there is no artificial flaw N at a position facing any of the detection coil rows, a differential signal ( The phase of the differential signal is adjusted so that the phase of the noise signal due to lift-off fluctuation or the like can be easily distinguished from the phase of the flaw signal. Specifically, the phase rotation amount (phase shift amount) in each phase rotator 25 is adjusted so that the phase θ of the flaw signal calculated by each detection unit 28 becomes a predetermined value. As described above, the phase of the differential signal between the detection coils 11 adjacent in the lateral direction is calibrated.
図４（ａ）は、以上に説明した校正ステップによって、短手方向に隣接する一対の検出コイル１１間の差動信号の検出感度及び位相を校正する際に得られる信号波形（リサージュ波形、Ｘ信号波形、Ｙ信号波形）の一例を示す。なお、図４（ａ）に示す例では、校正用管Ｐ１として、外径１６０ｍｍ、肉厚７ｍｍ、長さ３００ｍｍのステンレス鋼管（ＳＵＳ３０４）を用いた。また、この校正用管Ｐ１に、人工きずＮとして、幅０．５ｍｍ、深さ０．５ｍｍ、長さ１００ｍｍのノッチきずを設けた。そして、有効幅ＷＥが１ｍｍ、有効長さＬＥが４ｍｍの検出コイル１１からなる検出コイル群１１をリフトオフ２ｍｍで校正用管Ｐ１の外面に対向配置し、校正用管Ｐ１を周方向に３０ｍ／ｍｉｎで回転させることにより、校正用管Ｐ１の周方向に検出コイル群１を相対移動させた。なお、発信器２２から供給する交流電流の周波数は１３０ｋＨｚとし、バンドパスフィルタ２６の透過周波数帯域は２０〜４００Ｈｚとした。 FIG. 4A shows a signal waveform (Lissajous waveform, X) obtained by calibrating the detection sensitivity and phase of the differential signal between the pair of detection coils 11 adjacent in the short direction by the calibration step described above. An example of a signal waveform and a Y signal waveform is shown. In the example shown in FIG. 4A, a stainless steel pipe (SUS304) having an outer diameter of 160 mm, a thickness of 7 mm, and a length of 300 mm is used as the calibration pipe P1. Further, this calibration pipe P1 was provided with a notch defect having a width of 0.5 mm, a depth of 0.5 mm and a length of 100 mm as an artificial defect N. Then, a detection coil group 11 composed of detection coils 11 having an effective width WE of 1 mm and an effective length LE of 4 mm is opposed to the outer surface of the calibration pipe P1 with a lift-off of 2 mm, and the calibration pipe P1 is 30 m / min in the circumferential direction. The detection coil group 1 was relatively moved in the circumferential direction of the calibration tube P1. The frequency of the alternating current supplied from the transmitter 22 was 130 kHz, and the transmission frequency band of the bandpass filter 26 was 20 to 400 Hz.
図４（ａ）に示す例では、きず信号の最大振幅Ｚが５０ｄＢ（１００％）となるように、増幅器２３の増幅率を調整すると共に、きず信号の位相θが０°となるように、位相回転器２５における位相の回転量（移相量）を調整している。 In the example shown in FIG. 4A, the amplification factor of the amplifier 23 is adjusted so that the maximum amplitude Z of the scratch signal is 50 dB (100%), and the phase θ of the scratch signal is 0 °. The amount of phase rotation (phase shift amount) in the phase rotator 25 is adjusted.
＜２−２．調整ステップ＞
前述した校正ステップを実行した後、調整ステップを実行する。調整ステップを実行するに際しては、検出コイル群１を用いて得られる検出対象欠陥（例えば、被探傷材の表面が窪んだピット状きずや貫通きずなどの微小きず）についての長手方向に隣接する検出コイル１１間の差動信号の最大振幅及び位相と、前述した校正ステップで用いる人工きずＮについての短手方向に隣接する検出コイル１１間の差動信号の最大振幅及び位相との関係を予め取得しておく。
<2-2. Adjustment steps>
After the calibration step described above is executed, the adjustment step is executed. When executing the adjustment step, detection of adjacent defects in the longitudinal direction with respect to a detection target defect obtained by using the detection coil group 1 (for example, a fine flaw such as a pit-shaped flaw or a penetrating flaw in which the surface of the flaw detection material is recessed) The relationship between the maximum amplitude and phase of the differential signal between the coils 11 and the maximum amplitude and phase of the differential signal between the detection coils 11 adjacent in the short direction of the artificial flaw N used in the calibration step described above is acquired in advance. Keep it.
上記の関係を取得する際には、図３に示すように、管Ｐに検出対象欠陥Ｄ（人工きず又は自然きず）を設け、検出コイル群１をこの管Ｐに対向配置する。次に、検出対象欠陥Ｄが、長手方向に隣接する検出コイル１１のうち何れか一方の検出コイル１１（図３に示す例では、検出コイル１１ａ）の長手方向中央に対向する位置となるように、移動手段によって検出コイル群１を相対移動させる。そして、移動手段により管Ｐの周方向に検出コイル群１を相対移動させることにより、検出対象欠陥Ｄについての長手方向に隣接する検出コイル１１間の差動信号の最大振幅及び位相を取得する。以下、より具体的に説明する。 When obtaining the above relationship, as shown in FIG. 3, a detection target defect D (artificial flaw or natural flaw) is provided in the pipe P, and the detection coil group 1 is disposed opposite to the pipe P. Next, the detection target defect D is positioned so as to face the center in the longitudinal direction of one of the detection coils 11 adjacent in the longitudinal direction (the detection coil 11a in the example shown in FIG. 3). The detection coil group 1 is relatively moved by the moving means. Then, the maximum amplitude and phase of the differential signal between the detection coils 11 adjacent to each other in the longitudinal direction with respect to the detection target defect D are obtained by relatively moving the detection coil group 1 in the circumferential direction of the tube P by the moving means. More specific description will be given below.
まず、図１に示す切り替え手段２１を動作させ、切り替え手段２１が、長手方向に隣接する検出コイル１１での検出信号の差を差動信号として出力する状態にする。具体的には、切り替え手段２１ａが、長手方向に隣接する検出コイル１１ａ、１１ｃでの検出信号の差を差動信号として出力し、切り替え手段２１ｂが、長手方向に隣接する検出コイル１１ｂ、１１ｄでの検出信号の差を差動信号として出力し、切り替え手段２１ｃが、長手方向に隣接する検出コイル１１ｅ、１１ｇでの検出信号の差を差動信号として出力し、切り替え手段２１ｄが、長手方向に隣接する検出コイル１１ｆ、１１ｈでの検出信号の差を差動信号として出力する状態にする。 First, the switching unit 21 shown in FIG. 1 is operated so that the switching unit 21 outputs a difference between detection signals in the detection coils 11 adjacent in the longitudinal direction as a differential signal. Specifically, the switching means 21a outputs the difference between detection signals in the detection coils 11a and 11c adjacent in the longitudinal direction as a differential signal, and the switching means 21b is detected in the detection coils 11b and 11d adjacent in the longitudinal direction. The switching means 21c outputs the difference between the detection signals in the detection coils 11e and 11g adjacent in the longitudinal direction as a differential signal, and the switching means 21d in the longitudinal direction. The difference between the detection signals in the adjacent detection coils 11f and 11h is set to a state of outputting as a differential signal.
次に、検出対象欠陥Ｄを長手方向に隣接する検出コイル１１ａ、１１ｃのうち何れか一方の検出コイルの長手方向中央に対向する位置とした状態で、管Ｐに対向配置した検出コイル群１の各検出コイル１１に発信器２２から交流電流を供給し、検出コイル群１を管Ｐの周方向に相対移動させて探傷する。これにより、切り替え手段２１ａから長手方向に隣接する検出コイル１１ａ、１１ｃでの検出信号の差が差動信号として出力される。検出対象欠陥Ｄを探傷する際に切り替え手段２１ａから出力される差動信号（きず信号）は、検出対象欠陥Ｄが検出コイル１１ａ、１１ｃのうち何れか一方の検出コイルの中心に対向する位置にあるときに、その振幅が最大となる。そして、このきず信号の最大振幅及び位相を取得する。具体的には、検出部２８ａで演算されるきず信号の最大振幅Ｚ及び位相θを取得する。 Next, the detection coil group 1 disposed opposite to the tube P in a state where the detection target defect D is positioned at the position facing the longitudinal center of one of the detection coils 11a and 11c adjacent in the longitudinal direction. An alternating current is supplied to each detection coil 11 from the transmitter 22, and the detection coil group 1 is relatively moved in the circumferential direction of the tube P to detect flaws. Thereby, the difference between the detection signals in the detection coils 11a and 11c adjacent in the longitudinal direction from the switching unit 21a is output as a differential signal. The differential signal (flaw signal) output from the switching means 21a when detecting the defect D to be detected is at a position where the defect D to be detected faces the center of one of the detection coils 11a and 11c. At some point, the amplitude is maximum. Then, the maximum amplitude and phase of the flaw signal are acquired. Specifically, the maximum amplitude Z and phase θ of the flaw signal calculated by the detection unit 28a are acquired.
同様にして、検出対象欠陥Ｄを長手方向に隣接する検出コイル１１ｂ、１１ｄのうち何れか一方の検出コイルの長手方向中央に対向する位置とした状態で、検出コイル群１を管Ｐの周方向に相対移動させて探傷し、検出部２８ｂで演算されるきず信号の最大振幅Ｚ及び位相θを取得する。また、検出対象欠陥Ｄを長手方向に隣接する検出コイル１１ｅ、１１ｇのうち何れか一方の検出コイルの長手方向中央に対向する位置とした状態で、検出コイル群１を管Ｐの周方向に相対移動させて探傷し、検出部２８ｃで演算されるきず信号の最大振幅Ｚ及び位相θを取得する。さらに、検出対象欠陥Ｄを長手方向に隣接する検出コイル１１ｆ、１１ｈのうち何れか一方の検出コイルの長手方向中央に対向する位置とした状態で、検出コイル群１を管Ｐの周方向に相対移動させて探傷し、検出部２８ｄで演算されるきず信号の最大振幅Ｚ及び位相θを取得する。 Similarly, the detection coil group 1 is set in the circumferential direction of the tube P in a state where the detection target defect D is positioned opposite to the longitudinal center of one of the detection coils 11b and 11d adjacent in the longitudinal direction. To detect the maximum amplitude Z and phase θ of the flaw signal calculated by the detector 28b. In addition, the detection coil group 1 is relatively positioned in the circumferential direction of the tube P in a state where the detection target defect D is located at a position facing the longitudinal center of one of the detection coils 11e and 11g adjacent in the longitudinal direction. The flaw detection is performed by moving, and the maximum amplitude Z and the phase θ of the flaw signal calculated by the detection unit 28c are acquired. Further, the detection coil group 1 is set in the circumferential direction of the tube P in a state where the detection target defect D is set to a position facing the longitudinal center of one of the detection coils 11f and 11h adjacent in the longitudinal direction. The flaw detection is performed by moving, and the maximum amplitude Z and the phase θ of the flaw signal calculated by the detection unit 28d are acquired.
以上のようにして、検出対象欠陥Ｄについての長手方向に隣接する検出コイル１１間の差動信号の最大振幅及び位相を取得する。なお、検出対象欠陥Ｄについての長手方向に隣接する検出コイル１１間の差動信号の最大振幅及び位相を取得するに際しては、切り替え手段２１によって出力する差動信号を切り替える点を除き、増幅器２３の増幅率や位相回転器２５における位相の回転量（移相量）などは前述した校正ステップで調整した後の条件と同一の条件として探傷を行う。 As described above, the maximum amplitude and phase of the differential signal between the detection coils 11 adjacent in the longitudinal direction for the detection target defect D are acquired. When obtaining the maximum amplitude and phase of the differential signal between the detection coils 11 adjacent to each other in the longitudinal direction with respect to the defect D to be detected, the differential of the amplifier 23 is changed except that the differential signal output by the switching means 21 is switched. The amplification factor and the amount of phase rotation (phase shift amount) in the phase rotator 25 are subjected to flaw detection under the same conditions as those adjusted in the calibration step described above.
図４（ｂ）、（ｃ）は、以上に説明した検出対象欠陥Ｄについての長手方向に隣接する一対の検出コイル１１間の差動信号の最大振幅及び位相を取得する際に得られる信号波形（リサージュ波形、Ｘ信号波形、Ｙ信号波形）の一例を示す。なお、図４（ｂ）に示す例では、検出対象欠陥Ｄとして、内径２．６ｍｍの貫通きずを設けた。また、図４（ｃ）に示す例では、検出対象欠陥Ｄとして、内径５ｍｍ、深さ０．５ｍｍのピット状きずを設けた。その他の条件については、図４（ａ）に示す例と同様の条件で探傷した。 4B and 4C are signal waveforms obtained when obtaining the maximum amplitude and phase of the differential signal between the pair of detection coils 11 adjacent to each other in the longitudinal direction for the detection target defect D described above. An example (Lissajous waveform, X signal waveform, Y signal waveform) is shown. In the example shown in FIG. 4B, a through defect having an inner diameter of 2.6 mm is provided as the detection target defect D. In the example shown in FIG. 4C, a pit-shaped flaw having an inner diameter of 5 mm and a depth of 0.5 mm is provided as the detection target defect D. For other conditions, flaw detection was performed under the same conditions as in the example shown in FIG.
図４（ｂ）に示す例では、検出対象欠陥Ｄについての長手方向に隣接する検出コイル１１間の差動信号の最大振幅Ｚは、人工きずＮについての短手方向に隣接する検出コイル１１間の差動信号の最大振幅Ｚに対し、４ｄＢだけ大きくなるという関係を有する。また、検出対象欠陥Ｄについての長手方向に隣接する検出コイル１１間の差動信号の位相θは、人工きずＮについての短手方向に隣接する検出コイル１１間の差動信号の位相θに対し、１６０°だけ大きくなるという関係を有する。また、図４（ｃ）に示す例では、検出対象欠陥Ｄについての長手方向に隣接する検出コイル１１間の差動信号の最大振幅Ｚは、人工きずＮについての短手方向に隣接する検出コイル１１間の差動信号の最大振幅Ｚに対し、１ｄＢだけ小さくなるという関係を有する。また、検出対象欠陥Ｄについての長手方向に隣接する検出コイル１１間の差動信号の位相θは、人工きずＮについての短手方向に隣接する検出コイル１１間の差動信号の位相θに対し、１８０°だけ大きくなるという関係を有する。 In the example shown in FIG. 4B, the maximum amplitude Z of the differential signal between the detection coils 11 adjacent in the longitudinal direction with respect to the detection target defect D is between the detection coils 11 adjacent in the short direction with respect to the artificial flaw N. The maximum amplitude Z of the differential signal is increased by 4 dB. Further, the phase θ of the differential signal between the detection coils 11 adjacent in the longitudinal direction with respect to the defect D to be detected is the phase θ of the differential signal between the detection coils 11 adjacent in the short direction with respect to the artificial flaw N. , 160 °, and the relationship becomes larger by 160 °. In the example shown in FIG. 4C, the maximum amplitude Z of the differential signal between the detection coils 11 adjacent in the longitudinal direction for the detection target defect D is the detection coil adjacent in the short direction for the artificial flaw N. The maximum amplitude Z of the differential signal between 11 is reduced by 1 dB. Further, the phase θ of the differential signal between the detection coils 11 adjacent in the longitudinal direction with respect to the defect D to be detected is the phase θ of the differential signal between the detection coils 11 adjacent in the short direction with respect to the artificial flaw N. , 180 degrees.
上記のようにして、検出対象欠陥Ｄについての長手方向に隣接する検出コイル１１間の差動信号の最大振幅及び位相と、人工きずＮについての短手方向に隣接する検出コイル１１間の差動信号の最大振幅及び位相との関係を予め取得する。 As described above, the maximum amplitude and phase of the differential signal between the detection coils 11 adjacent in the longitudinal direction with respect to the detection target defect D, and the differential between the detection coils 11 adjacent in the short direction with respect to the artificial flaw N The relationship between the maximum amplitude and phase of the signal is acquired in advance.
そして、調整ステップでは、予め取得した上記の関係に基づき、長手方向に隣接する検出コイル間の差動信号の検出感度及び位相を調整する。例えば、図４（ｂ）に示す例では、検出対象欠陥Ｄについての長手方向に隣接する検出コイル１１間の差動信号の最大振幅Ｚが、人工きずＮについての短手方向に隣接する検出コイル１１間の差動信号の最大振幅Ｚと同等の振幅となるように、増幅器２３の増幅率を校正ステップでの調整後の増幅率よりも４ｄＢだけ小さくなるように調整する。また、検出対象欠陥Ｄについての長手方向に隣接する検出コイル１１間の差動信号の位相θが、人工きずＮについての短手方向に隣接する検出コイル１１間の差動信号の位相θと同等の位相となるように、位相回転器２５における位相の回転量（移相量）を校正ステップでの調整後の回転量（移相量）よりも１６０°だけ小さくなるように調整する。また、図４（ｃ）に示す例では、検出対象欠陥Ｄについての長手方向に隣接する検出コイル１１間の差動信号の最大振幅Ｚが、人工きずＮについての短手方向に隣接する検出コイル１１間の差動信号の最大振幅Ｚと同等の振幅となるように、増幅器２３の増幅率を校正ステップでの調整後の増幅率よりも１ｄＢだけ大きくなるように調整する。また、検出対象欠陥Ｄについての長手方向に隣接する検出コイル１１間の差動信号の位相θが、人工きずＮについての短手方向に隣接する検出コイル１１間の差動信号の位相θと同等の位相となるように、位相回転器２５における位相の回転量（移相量）を校正ステップでの調整後の回転量（移相量）よりも１８０°だけ小さくなるように調整する。 In the adjustment step, the detection sensitivity and phase of the differential signal between the detection coils adjacent in the longitudinal direction are adjusted based on the above-obtained relationship. For example, in the example shown in FIG. 4B, the maximum amplitude Z of the differential signal between the detection coils 11 adjacent to the detection target defect D in the longitudinal direction is adjacent to the short direction of the artificial flaw N. The amplification factor of the amplifier 23 is adjusted to be 4 dB smaller than the amplification factor after the adjustment in the calibration step so that the amplitude is equal to the maximum amplitude Z of the differential signal between the two. Further, the phase θ of the differential signal between the detection coils 11 adjacent in the longitudinal direction for the defect D to be detected is equivalent to the phase θ of the differential signal between the detection coils 11 adjacent in the short direction for the artificial flaw N. The phase rotation amount (phase shift amount) in the phase rotator 25 is adjusted to be 160 ° smaller than the rotation amount (phase shift amount) after the adjustment in the calibration step. In the example shown in FIG. 4C, the maximum amplitude Z of the differential signal between the detection coils 11 adjacent in the longitudinal direction for the detection target defect D is the detection coil adjacent in the short direction for the artificial flaw N. The amplification factor of the amplifier 23 is adjusted so as to be larger by 1 dB than the amplification factor after the adjustment in the calibration step so that the amplitude becomes equal to the maximum amplitude Z of the differential signal between 11. Further, the phase θ of the differential signal between the detection coils 11 adjacent in the longitudinal direction for the defect D to be detected is equivalent to the phase θ of the differential signal between the detection coils 11 adjacent in the short direction for the artificial flaw N. The phase rotation amount (phase shift amount) in the phase rotator 25 is adjusted so as to be smaller by 180 ° than the rotation amount (phase shift amount) after the adjustment in the calibration step.
＜２−３．探傷ステップ＞
探傷ステップでは、前述した調整ステップで調整した後の渦流探傷装置１００の検出コイル群１を管Ｐに対向配置し、移動手段により検出コイル群１を管Ｐの軸方向に螺旋状に相対移動させる。そして、長手方向に隣接する検出コイル１１間の差動信号に基づき、管Ｐに存在する欠陥を検出する。具体的には、前述のように、検出部２８が演算した振幅Ｚが予め定めたしきい値よりも大きいか否かによって、欠陥の有無を判定する。
<2-3. Flaw detection step>
In the flaw detection step, the detection coil group 1 of the eddy current flaw detection apparatus 100 that has been adjusted in the adjustment step described above is disposed opposite to the tube P, and the detection coil group 1 is relatively moved in the axial direction of the tube P by the moving means. . And the defect which exists in the pipe | tube P is detected based on the differential signal between the detection coils 11 adjacent to a longitudinal direction. Specifically, as described above, the presence or absence of a defect is determined based on whether or not the amplitude Z calculated by the detection unit 28 is greater than a predetermined threshold value.
１・・・検出コイル群
２・・・信号処理部
１１・・・検出コイル
２１・・・切り替え手段
２２・・・発信器
２３・・・増幅器（調整手段）
２４・・・同期検波器
２５・・・位相回転器（調整手段）
２６・・・バンドパスフィルタ
２７・・・Ａ／Ｄ変換器
２８・・・検出部
１００・・・渦流探傷装置
Ｐ・・・管
DESCRIPTION OF SYMBOLS 1 ... Detection coil group 2 ... Signal processing part 11 ... Detection coil 21 ... Switching means 22 ... Transmitter 23 ... Amplifier (adjustment means)
24 ... Synchronous detector 25 ... Phase rotator (adjustment means)
26: Band pass filter 27: A / D converter 28: Detection unit 100: Eddy current flaw detector P: Tube
Claims (3)
校正用の被探傷材に、該校正用被探傷材の軸方向に延びる人工きずであって、前記検出コイル群を構成する長手方向及び短手方向に隣接する２対の検出コイルの長さ以上に延びる人工きずを設け、前記検出コイル群を前記人工きずに対向配置して、前記校正用被探傷材の周方向に前記検出コイル群を相対移動させることにより、短手方向に隣接する検出コイル間の差動信号の検出感度及び位相を校正する校正ステップと、
前記検出コイル群を用いて得られる検出対象欠陥についての長手方向に隣接する検出コイル間の差動信号の最大振幅及び位相と、前記校正ステップで用いる人工きずについての短手方向に隣接する検出コイル間の差動信号の最大振幅及び位相との予め取得した関係に基づき、長手方向に隣接する検出コイル間の差動信号の検出感度及び位相を調整する調整ステップと、
前記調整ステップで調整した後の前記検出コイル群を被探傷材に対向配置し、前記検出コイル群を被探傷材の軸方向に螺旋状に相対移動させて、長手方向に隣接する検出コイル間の差動信号に基づき、前記被探傷材に存在する欠陥を検出する探傷ステップとを含むことを特徴とする渦流探傷方法。 2 in the short direction so that the ends of the detection coils adjacent to each other in the short direction overlap each other when viewed from the short direction. A group of detection coils arranged in a row is arranged facing the flaw detection material so that the longitudinal direction of each detection coil is along the axial direction of the flaw detection material having a substantially circular cross section, and exists in the flaw detection material. An eddy current flaw detection method for detecting defects,
The calibration flaw detection material is an artificial flaw extending in the axial direction of the calibration flaw detection material, and is longer than the length of two pairs of detection coils adjacent in the longitudinal direction and the short direction constituting the detection coil group The detection coils adjacent to each other in the short-side direction are provided by disposing an artificial flaw extending to the surface, disposing the detection coil group oppositely to the artificial flaw, and relatively moving the detection coil group in the circumferential direction of the calibration flaw detection material. A calibration step for calibrating the detection sensitivity and phase of the differential signal between,
The detection coil adjacent in the short direction of the maximum amplitude and phase of the differential signal between the detection coils adjacent in the longitudinal direction for the detection target defect obtained using the detection coil group and the artificial flaw used in the calibration step An adjustment step for adjusting the detection sensitivity and phase of the differential signal between the detection coils adjacent in the longitudinal direction, based on a previously acquired relationship between the maximum amplitude and phase of the differential signal between,
The detection coil group that has been adjusted in the adjustment step is disposed to face the flaw detection material, and the detection coil group is relatively moved in a spiral shape in the axial direction of the flaw detection material, so that the detection coils adjacent to each other in the longitudinal direction are moved. And a flaw detection step for detecting a defect present in the flaw detection material based on a differential signal.
前記検出コイル群における長手方向に隣接する検出コイル間の差動信号と、短手方向に隣接する検出コイル間の差動信号とを切り替えて出力する切り替え手段と、
前記切り替え手段によって出力された差動信号の検出感度及び位相を調整する調整手段と、
前記検出コイル群を被探傷材の軸方向及び周方向に相対移動させる移動手段とを備えることを特徴とする渦流探傷装置。 2 in the short direction so that the ends of the detection coils adjacent to each other in the short direction overlap each other when viewed from the short direction. A group of detection coils arranged in a row, each of the detection coils arranged in opposition to the flaw detection material so that the longitudinal direction of each detection coil is along the axial direction of the flaw detection material having a substantially circular cross section;
Switching means for switching and outputting a differential signal between detection coils adjacent in the longitudinal direction in the detection coil group and a differential signal between detection coils adjacent in the short direction;
Adjusting means for adjusting the detection sensitivity and phase of the differential signal output by the switching means;
An eddy current flaw detector comprising: moving means for relatively moving the detection coil group in the axial direction and the circumferential direction of the flaw detection material.
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