JP6524884B2 - Inner surface inspection method of tubular body - Google Patents
Inner surface inspection method of tubular body Download PDFInfo
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- JP6524884B2 JP6524884B2 JP2015207312A JP2015207312A JP6524884B2 JP 6524884 B2 JP6524884 B2 JP 6524884B2 JP 2015207312 A JP2015207312 A JP 2015207312A JP 2015207312 A JP2015207312 A JP 2015207312A JP 6524884 B2 JP6524884 B2 JP 6524884B2
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本発明は、超音波を用いた管状体の内面検査方法に関する。特に、本発明は、管の熱間押出機に設けられ、素材を水圧で押圧するためのシリンダなど、ステンレス鋼製の管状体の内面の微小な凹凸を簡易に検出可能な管状体の内面検査方法に関する。 The present invention relates to a method of inspecting the inner surface of a tubular body using ultrasonic waves. In particular, the present invention provides an inner surface inspection of a tubular body provided in a pipe hot extruder and capable of easily detecting minute irregularities on the inner surface of a stainless steel tubular body such as a cylinder for pressing a material with water pressure. On the way.
従来より、高合金等の難加工材を素材とする継目無管に好適な製造方法として、熱間押出法が知られている（例えば、特許文献１参照）。
この熱間押出法は、一般的に、熱間押出機が備えるダイスに向けて素材（中空ビレット）を押圧し、ダイスとマンドレルとの間で素材を押出成形することで、継目無管を製造する方法である。熱間押出機には、素材を水圧で押圧するために、耐食性に優れるステンレス鋼製のシリンダ（メインシリンダ）が設けられている。
Conventionally, a hot extrusion method is known as a manufacturing method suitable for a seamless pipe made of a difficult-to-process material such as a high alloy as a raw material (see, for example, Patent Document 1).
This hot extrusion method generally produces a seamless pipe by pressing a material (hollow billet) toward a die included in a hot extruder and extruding the material between the die and a mandrel. How to The hot extrusion machine is provided with a stainless steel cylinder (main cylinder) excellent in corrosion resistance in order to press the material by water pressure.
上記のシリンダは、長期間使用しているうちに、内部に流通する高圧水に異物（例えば、シリンダに高圧水を供給・排出するための配管内面に形成された酸化スケールの落下物）が混入し、熱間押出機の停機時にその異物が主としてシリンダ内面の下部に堆積する。この異物の堆積によってシリンダ内面に微小な凹凸（以下、適宜、これを「内面微小凹凸」と称する）が生じる場合がある。 In the above-mentioned cylinder, while being used for a long time, foreign matter (for example, fallen matter of oxidized scale formed on the inner surface of a pipe for supplying and discharging high pressure water to the cylinder) is mixed in high pressure water flowing inside When the hot extruder stops, the foreign matter mainly deposits on the lower part of the inner surface of the cylinder. Due to the deposition of the foreign matter, there may be a case where minute unevenness (hereinafter, appropriately referred to as “inner minute unevenness”) is generated on the inner surface of the cylinder.
シリンダの内面微小凹凸は、例えば、ＩＴＶカメラなどの撮像手段をシリンダ内に挿入し、撮像画を目視観察することでも検出可能である。
しかしながら、撮像手段をシリンダに対して挿脱するには、熱間押出機を停機して、シリンダ内部から高圧水を排出する他、撮像手段の挿脱動作に干渉する付帯設備を取り外す必要もあり、非常に手間を要する。
このため、シリンダの外面側から内面の微小凹凸を簡易に検出できる方法が望まれている。
上記と同様の課題は、熱間押出機に設けられたシリンダに限らず、ステンレス鋼製の管状体全般に共通するものだと考えられる。
The inner surface micro unevenness of the cylinder can also be detected by, for example, inserting an imaging device such as an ITV camera into the cylinder and visually observing the imaged image.
However, in order to insert and remove the imaging means with respect to the cylinder, it is necessary to stop the hot extruder and discharge high pressure water from the inside of the cylinder and also to remove incidental equipment that interferes with the insertion and removal operation of the imaging means. Very time-consuming.
For this reason, a method is desired which can easily detect minute irregularities on the inner surface from the outer surface side of the cylinder.
The same problem as described above is considered not to be limited to the cylinder provided in the hot extruder, but common to all stainless steel tubular bodies.
管状体の内面検査方法としては、例えば、特許文献２〜５のような方法が提案されているものの、いずれもステンレス鋼製の管状体の内面微小凹凸を簡易に検出する上で効果的な方法ではない。
また、特許文献６には、高い周波数のパルス成分と低い周波数のパルス成分とを有する超音波を被検体に送信し、被検体からのエコー信号をフーリエ変換して周波数解析することで、被検体の粗さを計測する方法が提案されている。しかしながら、ステンレス鋼製の管状体は、超音波の高周波成分が大幅に減衰する上、結晶粒度が均一でないために減衰率にバラツキも生じる。このため、特許文献６に提案されている周波数解析によって、ステンレス鋼製の管状体の内面微小凹凸を検出することは難しい。
As methods for inspecting the inner surface of a tubular body, for example, methods such as Patent Documents 2 to 5 have been proposed, but any method is effective in easily detecting the inner surface micro unevenness of a stainless steel tubular body. is not.
Further, in Patent Document 6, an ultrasonic wave having a pulse component of high frequency and a pulse component of low frequency is transmitted to a subject, and an echo signal from the subject is subjected to Fourier transform to analyze the frequency. A method has been proposed to measure the roughness of However, in the stainless steel tubular body, the high frequency component of the ultrasonic wave is significantly attenuated and, in addition, the grain size is not uniform, and the attenuation factor also varies. For this reason, it is difficult to detect the inner surface micro unevenness of the stainless steel tubular body by the frequency analysis proposed in Patent Document 6.
本発明は、上記のような従来技術の問題点を解決するためになされたものであり、ステンレス鋼製の管状体の内面の微小な凹凸を簡易に検出可能な管状体の内面検査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 as described above, and provides a method for inspecting the inner surface of a tubular body that can easily detect minute irregularities on the inner surface of the stainless steel tubular body. To be a task.
前記課題を解決するため、本発明者らは鋭意検討した結果、以下の（Ａ）〜（Ｃ）に記載の知見を得て、本発明を完成した。
（Ａ）管状体の内面を垂直探傷したときの底面エコー信号の強度が内面微小凹凸によって減衰する。
（Ｂ）上記内面微小凹凸による底面エコー信号の強度の減衰は微弱であるため、管状体の偏芯や偏肉、内面肌の影響を受けやすい。管状体の偏芯や偏肉、内面肌の影響を低減するには、管状体の周方向の微分処理を施して評価することが効果的である。
（Ｃ）多数の測定箇所で得られた底面エコー信号の微分強度に統計処理（平均値や標準偏差を算出する処理）を施して得られた統計値の大小によって内面微小凹凸を検出可能（健全な内面と識別可能）である。
MEANS TO SOLVE THE PROBLEM As a result of earnestly examining, in order to solve the said subject, the present inventors acquired the knowledge as described in the following (A)-(C), and completed this invention.
(A) The intensity of the bottom echo signal when the inner surface of the tubular body is subjected to vertical flaw detection is attenuated by the inner surface micro unevenness.
(B) Since the attenuation of the intensity of the bottom surface echo signal due to the inner surface micro unevenness is weak, it is easily affected by the eccentricity, uneven thickness and inner skin of the tubular body. In order to reduce the influence of eccentricity, uneven thickness, and inner skin of the tubular body, it is effective to apply differential treatment in the circumferential direction of the tubular body for evaluation.
(C) It is possible to detect the inner surface micro unevenness by the magnitude of the statistical value obtained by performing statistical processing (processing to calculate the average value and the standard deviation) on the differential intensity of the bottom echo signal obtained at many measurement points (Identifiable from the inside).
すなわち、本発明は、以下の第１〜第５ステップを含むことを特徴とする管状体の内面検査方法を提供する。
（１）第１ステップ：ステンレス鋼製の管状体の外面に対向して超音波探触子を配置する。
（２）第２ステップ：前記超音波探触子を前記管状体の周方向に沿って相対的に移動させると共に、前記超音波探触子から前記管状体の内面に対して略垂直に超音波を送信し、前記管状体の内面から反射した底面エコーを前記超音波探触子で受信して、前記管状体の周方向についての底面エコー信号の強度分布を取得する。
（３）第３ステップ：前記第２ステップで取得した底面エコー信号の強度分布に前記管状体の周方向の微分処理を施して、底面エコー信号の微分強度分布を取得する。
（４）第４ステップ：前記超音波探触子を前記管状体の軸方向に沿って相対的に移動させて前記第２ステップ及び前記第３ステップを繰り返し実行することで、又は、前記超音波探触子として前記管状体の軸方向に沿って複数の振動子を具備するアレイ超音波探触子を用いることで、前記管状体の軸方向に沿って複数の底面エコー信号の微分強度分布を取得する。
（５）第５ステップ：前記第４ステップで取得した複数の底面エコー信号の微分強度分布に統計処理を施し、該統計処理によって得られた統計値の大小に基づき、前記管状体の内面の凹凸を検出する。
That is, the present invention provides a method for inspecting the inner surface of a tubular body including the following first to fifth steps.
(1) First step: The ultrasonic probe is placed opposite to the outer surface of the stainless steel tubular body.
(2) Second step: The ultrasonic probe is relatively moved along the circumferential direction of the tubular body, and from the ultrasonic probe to the ultrasonic wave substantially perpendicular to the inner surface of the tubular body And the bottom surface echo reflected from the inner surface of the tubular body is received by the ultrasonic probe to acquire the intensity distribution of the bottom surface echo signal in the circumferential direction of the tubular body.
(3) Third step: The intensity distribution of the bottom surface echo signal obtained in the second step is subjected to differentiation processing in the circumferential direction of the tubular body to obtain a differential intensity distribution of the bottom surface echo signal.
(4) Fourth step: By relatively moving the ultrasonic probe along the axial direction of the tubular body and repeatedly executing the second step and the third step, or the ultrasonic wave By using an array ultrasonic probe including a plurality of transducers along the axial direction of the tubular body as a probe, differential intensity distributions of a plurality of bottom echo signals along the axial direction of the tubular body are obtained. get.
(5) Fifth step: The differential intensity distribution of the plurality of bottom surface echo signals acquired in the fourth step is subjected to statistical processing, and the unevenness of the inner surface of the tubular body based on the magnitude of the statistical value obtained by the statistical processing To detect
本発明によれば、第１ステップ〜第４ステップを実行することにより、ステンレス鋼製の管状体の軸方向に沿って複数の底面エコー信号の微分強度分布を取得することが可能である。換言すれば、管状体の周方向及び軸方向について、複数点の底面エコー信号の微分強度を取得することが可能である。そして、第５ステップにおいて、複数の底面エコー信号の微分強度分布に統計処理を施し（管状体の周方向及び軸方向について得られた複数点の底面エコー信号の微分強度に統計処理を施し）、得られた統計値の大小に基づき、管状体の内面の微小凹凸を検出することが可能である。
本発明によれば、機械的動作としては、管状体の外面に対向して超音波探触子を配置し（第１ステップ）、管状体の周方向及び軸方向に相対的に超音波探触子を移動させる（第２ステップ及び第４ステップ）だけで良いため、撮像手段を挿脱する場合に比べて手間が掛からず、管状体の内面の微小凹凸を簡易に自動検出することが可能である。
According to the present invention, it is possible to acquire the differential intensity distribution of a plurality of bottom echo signals in the axial direction of the stainless steel tubular body by executing the first to fourth steps. In other words, it is possible to obtain differential intensities of bottom echo signals at a plurality of points in the circumferential direction and the axial direction of the tubular body. Then, in the fifth step, statistical processing is performed on the differential intensity distributions of the plurality of bottom surface echo signals (the differential processing of the bottom surface echo signals of the plurality of points obtained in the circumferential direction and the axial direction of the tubular body is performed); It is possible to detect the micro unevenness of the inner surface of the tubular body based on the magnitude of the obtained statistical value.
According to the present invention, as the mechanical operation, the ultrasonic probe is disposed to face the outer surface of the tubular body (first step), and the ultrasonic probe is relatively performed in the circumferential direction and the axial direction of the tubular body. Since it is sufficient to move the child (the second and fourth steps), it takes less time and effort than in the case of inserting and removing the imaging means, and it is possible to easily and automatically detect micro unevenness on the inner surface of the tubular body is there.
本発明において、前記第４ステップで取得した前記管状体の軸方向に沿った複数の底面エコー信号の微分強度分布の各波形を、横軸を前記管状体の周方向位置とし、縦軸を前記管状体の軸方向位置として、重ねて表示することが好ましい。 In the present invention, each waveform of the differential intensity distribution of the plurality of bottom surface echo signals along the axial direction of the tubular body obtained in the fourth step has a horizontal axis as a circumferential position of the tubular body and a vertical axis is the above It is preferable to overlap and display as an axial direction position of a tubular body.
上記の好ましい方法によれば、底面エコー信号の微分強度分布の各波形を目視で確認し易いため、統計値の大小に基づく内面微小凹凸の自動検出に加えて、目視判断も併用することで、内面微小凹凸の検出精度が高まることが期待できる。 According to the above preferred method, each waveform of the differential intensity distribution of the bottom surface echo signal can be easily confirmed visually, so by using visual judgment in addition to automatic detection of the inner surface micro unevenness based on the magnitude of the statistical value, It can be expected that the detection accuracy of the inner surface micro unevenness is enhanced.
本発明によれば、ステンレス鋼製の管状体の内面の微小な凹凸を簡易に且つ自動的に検出可能である。 According to the present invention, minute irregularities on the inner surface of a stainless steel tubular body can be detected easily and automatically.
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説明する。
図１は、本発明の一実施形態に係る管状体の内面検査方法を実施するための装置構成を概略的に説明する説明図である。図１（ａ）は管状体の軸方向から見た正面図を、図１（ｂ）は平面図を示す。
図１に示すように、本実施形態に係る内面検査方法を実施するために用いる装置は、超音波探触子１と、超音波探触子１に接続された信号処理手段２とを備えている。また、後述のように、超音波探触子１をステンレス鋼製の管状体Ｐの周方向及び軸方向に相対的に移動させるための機構部（図示せず）も備えている。
Hereinafter, an embodiment of the present invention will be described with reference to the attached drawings as appropriate.
FIG. 1 is an explanatory view schematically illustrating an apparatus configuration for carrying out a method for inspecting an inner surface of a tubular body according to an embodiment of the present invention. FIG. 1 (a) shows a front view of the tubular body seen from the axial direction, and FIG. 1 (b) shows a plan view.
As shown in FIG. 1, the apparatus used to carry out the inner surface inspection method according to the present embodiment comprises an ultrasonic probe 1 and signal processing means 2 connected to the ultrasonic probe 1. There is. Further, as described later, a mechanical portion (not shown) for relatively moving the ultrasonic probe 1 in the circumferential direction and the axial direction of the stainless steel tubular body P is also provided.
本実施形態の超音波探触子１としては、内面微小凹凸（管状体Ｐの過酸洗によって生じる管状体Ｐの内面の微小な凹凸）の検出精度を高めるべく、例えば、単一の振動子を具備し、探傷周波数１０ＭＨｚで、焦点距離１インチのラインフォーカス型の超音波探触子が好適に用いられる。なお、超音波探触子１の焦点距離は、管状体Ｐの肉厚に応じて適宜選択すれば良い。 As the ultrasonic probe 1 according to the present embodiment, for example, a single transducer is used to enhance the detection accuracy of the inner surface micro unevenness (micro unevenness of the inner surface of the tubular body P generated by peracid washing of the tubular body P). A line focus type ultrasonic probe having a flaw detection frequency of 10 MHz and a focal length of 1 inch is preferably used. The focal length of the ultrasonic probe 1 may be appropriately selected according to the thickness of the tubular body P.
制御・信号処理手段２は、超音波探触子１から超音波を送信させるためのパルス信号を供給するパルサーや、エコーを受信した超音波探触子１から出力されるエコー信号を増幅するレシーバなど、超音波の送受信を制御する機能を果たす部分と、後述のように超音波探触子１から出力される底面エコー信号に基づき、管状体Ｐの周方向についての底面エコー信号の強度分布や微分強度分布を作成したり、底面エコー信号の微分強度分布に統計処理を施すなど、各種の信号処理を実行する機能を果たす部分とを備えている。 The control / signal processing means 2 is a pulser for supplying a pulse signal for transmitting an ultrasonic wave from the ultrasonic probe 1 or a receiver for amplifying an echo signal output from the ultrasonic probe 1 having received an echo. The intensity distribution of the bottom echo signal in the circumferential direction of the tubular body P based on the portion that controls the transmission and reception of ultrasonic waves and the bottom echo signal output from the ultrasonic probe 1 as described later. It has a portion that performs various signal processing functions, such as creating a differential intensity distribution or performing statistical processing on the differential intensity distribution of the bottom echo signal.
機構部としては、管状体Ｐの周方向に超音波探触子１を回転させる機構と、管状体Ｐを軸方向に搬送する機構とを備えたものを例示できる。ただし、これに限るものではなく、超音波探触子１の方を管状体Ｐの周方向及び軸方向の双方に移動させる機構や、管状体Ｐの方を周方向に回転させ軸方向に搬送する機構を採用することも可能である。 As a mechanism part, the thing provided with the mechanism which rotates the ultrasonic probe 1 to the circumferential direction of the tubular body P, and the mechanism which conveys the tubular body P in an axial direction can be illustrated. However, the present invention is not limited to this, and a mechanism for moving the ultrasonic probe 1 in both the circumferential direction and the axial direction of the tubular body P, and the tubular body P being rotated in the circumferential direction and conveyed in the axial direction It is also possible to adopt a mechanism that
以上に説明した構成を有する装置を用いて、本実施形態に係る内面検査方法では、図１に示すように、管状体Ｐの外面に対向して超音波探触子１を配置する（本発明の第１ステップに相当）。 In the inner surface inspection method according to the present embodiment, using the device having the configuration described above, the ultrasonic probe 1 is disposed to face the outer surface of the tubular body P, as shown in FIG. Equivalent to the first step of
次に、機構部によって超音波探触子１を管状体Ｐの周方向に沿って相対的に移動させると共に、超音波探触子１から管状体Ｐの内面に対して略垂直に超音波を送信し、管状体Ｐの内面から反射した底面エコーＢを超音波探触子１で受信して底面エコー信号を出力し、制御・信号処理手段２が管状体Ｐの周方向についての底面エコー信号の強度分布を作成する（本発明の第２ステップに相当）。
具体的には、制御・信号処理手段２は、管状体Ｐの周方向について所定のピッチ毎に、超音波探触子１で受信したエコーのうち、底面エコーＢ（本実施形態では、表面エコーＳを受信してから最初に受信した第１底面エコー）に相当する底面エコー信号の強度を検出することで、管状体Ｐの周方向についての底面エコー信号の強度分布を作成する。本実施形態では、管状体Ｐの１周当たり３００点の底面エコー信号の強度を検出して強度分布を作成している。
Next, the ultrasonic probe 1 is relatively moved along the circumferential direction of the tubular body P by the mechanism section, and the ultrasonic wave from the ultrasonic probe 1 substantially perpendicularly to the inner surface of the tubular body P The ultrasound echo probe 1 receives the bottom echo B reflected from the inner surface of the tubular body P and outputs a bottom echo signal, and the control / signal processing means 2 produces a bottom echo signal in the circumferential direction of the tubular P Of the intensity distribution of H. (corresponding to the second step of the present invention).
Specifically, the control / signal processing means 2 generates a bottom surface echo B (surface echo in the present embodiment) among the echos received by the ultrasonic probe 1 at predetermined pitches in the circumferential direction of the tubular body P. The intensity distribution of the bottom echo signal in the circumferential direction of the tubular body P is created by detecting the strength of the bottom echo signal corresponding to the first bottom echo received first after receiving S. In the present embodiment, the intensity distribution is created by detecting the intensity of the bottom surface echo signal of 300 points per one turn of the tubular body P.
次に、制御・信号処理手段２は、作成した底面エコー信号の強度分布に管状体Ｐの周方向の微分処理を施して、底面エコー信号の微分強度分布を作成する（本発明の第３ステップに相当）。
具体的には、制御・信号処理手段２は、底面エコー信号の強度分布を構成する複数の点の各強度に対して、注目点から所定の点数の範囲内での強度の最大値から最小値を減算し、この減算結果を当該注目点の微分強度とする演算を、注目点を順次ずらして実行することにより、底面エコー信号の微分強度を作成している。本実施形態では、底面エコー信号の強度分布を構成する３００点の各強度に対して、注目点から５点の範囲内（約０．５ｍｍピッチ毎に底面エコー信号を検出する場合、２．５ｍｍの範囲内）での強度の最大値から最小値を減算して底面エコー信号の微分強度を作成している。
Next, the control / signal processing means 2 performs differential processing on the generated intensity distribution of the bottom surface echo signal in the circumferential direction of the tubular body P to create a differential intensity distribution of the bottom surface echo signal (third step of the present invention) Equivalent to
Specifically, control / signal processing means 2 sets the maximum value to the minimum value of the intensities within the range of a predetermined number of points from the point of interest for each of the intensities of the plurality of points constituting the intensity distribution of the bottom surface echo signal. The differential intensity of the bottom surface echo signal is created by performing an operation of sequentially subtracting the target point by subtracting the target value and the subtraction result as the differential intensity of the target point. In the present embodiment, for each intensity of 300 points constituting the intensity distribution of the bottom surface echo signal, within the range of 5 points from the attention point (2.5 mm when the bottom surface echo signal is detected every about 0.5 mm pitch) The minimum value is subtracted from the maximum value of the intensity in the range of) to create the differential intensity of the bottom echo signal.
次に、機構部によって超音波探触子１を管状体Ｐの軸方向に沿って相対的に移動させて制御・信号処理手段２が上記の動作（本発明の第２ステップ及び第３ステップに相当する動作）を繰り返し実行することで、制御・信号処理手段２は、管状体Ｐの軸方向に沿って複数の底面エコー信号の微分強度分布を作成する（本発明の第４ステップに相当）。
本実施形態では、管状体Ｐの軸方向に１ｍｍピッチで計２０点の底面エコー信号の微分強度分布を作成している。したがって、底面エコー信号の微分強度として、管状体Ｐの周方向に約３００点で軸方向に２０点の計約６０００点の微分強度が生成されることになる。
なお、本実施形態では、機構部によって超音波探触子１を管状体Ｐの軸方向に沿って相対的に移動させる方法を採用しているが、本発明はこれに限るものではなく、超音波探触子１として管状体Ｐの軸方向に沿って複数の振動子を具備するアレイ超音波探触子を用いてもよい。超音波探触子１として２０個以上の振動子を具備するアレイ超音波探触子を用いれば、超音波探触子１を管状体Ｐの軸方向に沿って相対的に移動させなくても、本実施形態と同様に、少なくとも約６０００点の微分強度を生成することが可能である。
Next, the ultrasonic probe 1 is relatively moved along the axial direction of the tubular body P by the mechanism section, and the control / signal processing means 2 performs the above operation (in the second step and the third step of the present invention). By repeatedly executing the corresponding operation, the control / signal processing means 2 creates differential intensity distributions of a plurality of bottom surface echo signals along the axial direction of the tubular body P (corresponding to the fourth step of the present invention) .
In this embodiment, a differential intensity distribution of bottom echo signals of a total of 20 points is created at a pitch of 1 mm in the axial direction of the tubular body P. Therefore, as the differential intensity of the bottom surface echo signal, a total of about 6000 differential intensities of 20 points in the axial direction are generated at about 300 points in the circumferential direction of the tubular body P.
In the present embodiment, although the method of relatively moving the ultrasonic probe 1 along the axial direction of the tubular body P by the mechanism unit is adopted, the present invention is not limited to this, and An array ultrasonic probe having a plurality of transducers along the axial direction of the tubular body P may be used as the acoustic probe 1. If an array ultrasonic probe having 20 or more transducers is used as the ultrasonic probe 1, the ultrasonic probe 1 does not have to be relatively moved along the axial direction of the tubular body P As in the present embodiment, it is possible to generate at least about 6000 differential intensities.
図２〜図４は、本実施形態に係る内面検査方法によって取得される底面エコー信号の微分強度分布の例を示す図である。なお、図２〜図４に示す結果は、実際に熱間押出機に設けられたシリンダの偏芯や偏肉を再現するために、過酸洗によって内面微小凹凸を再現したステンレス鋼製の管を用いて得られた結果である。後述する図５〜図７に示す結果も同様である。図２〜図４の各図の（ａ）は管状体Ｐの内面をＩＴＶカメラで撮像した撮像画を、各図の（ｂ）は各図の（ａ）に示す管状体Ｐの内面について作成した底面エコー信号の微分強度分布（管状体Ｐの軸方向について２０点作成した底面エコー信号の微分強度分布をそのまま重ねて表示したもの）を、各図の（ｃ）は各図の（ａ）に示す管状体Ｐの内面について作成した底面エコー信号の強度分布（管状体Ｐの軸方向について２０点作成した底面エコー信号の強度分布（微分処理を施す前）をそのまま重ねて表示したもの）を示す。図２は管状体Ｐの内面に内面微小凹凸が存在しない健全な内面の例を、図３は管状体Ｐの内面に局部的に内面微小凹凸が存在する例を、図４は管状体Ｐの内面全体に内面微小凹凸が存在する例を示す。 2 to 4 are diagrams showing examples of the differential intensity distribution of the bottom echo signal acquired by the inner surface inspection method according to the present embodiment. It should be noted that the results shown in FIGS. 2 to 4 are stainless steel tubes in which the inner surface micro unevenness is reproduced by peracid washing in order to reproduce eccentricity and uneven thickness of the cylinder actually provided in the hot extruder. Is the result obtained using The results shown in FIGS. 5 to 7 described later are the same. (A) in each of FIGS. 2 to 4 is a captured image obtained by imaging the inner surface of the tubular body P with an ITV camera, and (b) in each of the figures is created for the inner surface of the tubular P shown in (a) of each figure. (C) of each figure is a diagram showing the differential intensity distribution of the bottom surface echo signal (the differential intensity distribution of the bottom surface echo signal prepared at 20 points in the axial direction of the tubular body P is superimposed and displayed as it is) The intensity distribution of the bottom surface echo signal created for the inner surface of the tubular body P shown in (The intensity distribution of the bottom surface echo signal created at 20 points in the axial direction of the tubular body P (before being subjected to differentiation) is displayed as it is) Show. 2 shows an example of a sound inner surface where there is no inner surface micro unevenness on the inner surface of the tubular body P, FIG. 3 shows an example where an inner surface micro unevenness exists locally on the inner surface of the tubular body P, FIG. An example in which inner surface micro unevenness exists on the entire inner surface is shown.
図３（ａ）及び図４（ａ）から分かるように、ＩＴＶカメラで撮像した撮像画において、内面微小凹凸が存在する部位では、その周辺部位に比べて暗く（黒っぽく）撮像されている。
そして、図２（ｂ）〜図４（ｂ）から分かるように、内面微小凹凸が存在する場合（図３（ｂ）及び図４（ｂ））には、存在しない場合（図２（ｂ））に比べて、底面エコー信号の微分強度が管状体Ｐの周方向について局部的に大きくなったり、全体的に大きくなったりすることがわかる。したがい、複数の底面エコー信号の微分強度分布に統計処理を施し、その統計値の大小を評価すれば、内面微小凹凸が検出可能（健全な内面と識別可能）となることが期待できる。
なお、図２（ｃ）〜図４（ｃ）から分かるように、微分処理を施さない底面エコー信号の強度分布には、図２（ｂ）〜図４（ｂ）に比べて、管状体Ｐの偏芯や偏肉に起因した強度のムラが生じている。このため、内面微小凹凸の検出精度を高めるには、本実施形態に係る内面検査方法のように、微分処理を施して評価することが効果的である。
As can be seen from FIGS. 3A and 4A, in the image captured by the ITV camera, in the portion where the inner surface micro unevenness exists, the image is darker (blacker) than in the peripheral portion.
Then, as can be seen from FIGS. 2 (b) to 4 (b), in the case where there is an inner surface micro unevenness (FIG. 3 (b) and FIG. 4 (b)), there is no case (FIG. 2 (b)) It can be understood that the differential intensity of the bottom surface echo signal is locally increased in the circumferential direction of the tubular body P or is generally increased as compared with the above. Accordingly, if the differential intensity distribution of the plurality of bottom echo signals is subjected to statistical processing and the magnitude of the statistical value is evaluated, it can be expected that the inner surface micro unevenness can be detected (distinguishable from the sound inner surface).
As can be seen from FIGS. 2 (c) to 4 (c), in the intensity distribution of the bottom surface echo signal not subjected to the differentiation process, compared with FIGS. 2 (b) to 4 (b) Inconsistencies in strength due to eccentricity and uneven thickness occur. For this reason, in order to improve the detection accuracy of the inner surface micro unevenness, it is effective to perform differentiation processing and evaluation as in the inner surface inspection method according to the present embodiment.
本実施形態に係る内面検査方法では、上述のようにして作成した複数の底面エコー信号の微分強度分布（本実施形態では約６０００点の微分強度）に統計処理を施し、該統計処理によって得られた統計値の大小に基づき、内面微小凹凸を検出している（本発明の第５ステップに相当）。 In the inner surface inspection method according to the present embodiment, statistical processing is performed on the differential intensity distributions of the plurality of bottom surface echo signals (the differential intensities of about 6000 points in the present embodiment) created as described above, The inner surface micro unevenness is detected based on the magnitude of the statistical value (corresponding to the fifth step of the present invention).
図５は、本実施形態に係る内面検査方法において底面エコー信号の微分強度分布に施す各種の統計処理を評価した結果の一例を示す。図５（ａ）は平均値を評価した結果を、図５（ｂ）は標準偏差を評価した結果を、図５（ｃ）は平均値×標準偏差を評価した結果を示す。図５（ａ）〜図５（ｃ）の横軸に示す「黒比率」は、管状体Ｐの内面を撮像したＩＴＶカメラの撮像画像において、黒っぽく撮像された領域（内面微小凹凸に対応する領域）を視認し、その領域が撮像画像全体に占める割合を数値化したものである。この黒比率の大小が、概ね目視による管状体Ｐの内面状態の評価に対応するものとなる。すなわち、図５に示す結果は、種々の内面状態を有する複数の管状体Ｐ（黒比率の異なる複数の管状体Ｐ）のそれぞれに対して、前述のように約６０００点の微分強度を取得し、この微分強度から得られた各種の統計値との相関を評価した結果である。
図５に示すように、平均値、標準偏差、平均値×標準偏差のいずれの統計値も、黒比率に対して一定以上の相関係数（Ｒ２）を有することがわかった。したがい、いずれかの統計値を単独で、或いは、いずれかの統計値を組み合わせて、その大小に基づき、内面微小凹凸を検出すれば、目視評価と同等の精度で内面微小凹凸を検出可能であることが期待できる。
FIG. 5 shows an example of the result of evaluating various statistical processes applied to the differential intensity distribution of the bottom surface echo signal in the inner surface inspection method according to the present embodiment. FIG. 5 (a) shows the result of evaluation of the average value, FIG. 5 (b) shows the result of evaluation of the standard deviation, and FIG. 5 (c) shows the result of evaluation of average value × standard deviation. The “black ratio” indicated by the horizontal axis in FIGS. 5A to 5C is a blackly imaged area (an area corresponding to the inner surface micro unevenness in the image taken by the ITV camera which imaged the inner surface of the tubular body P ), And the ratio of the area to the entire captured image is quantified. The magnitude of the black ratio roughly corresponds to the visual evaluation of the inner surface state of the tubular body P. That is, the results shown in FIG. 5 indicate that, for each of a plurality of tubular bodies P (a plurality of tubular bodies P having different black ratios) having various inner states, differential intensities of about 6000 points are obtained as described above. It is the result of having evaluated correlation with various statistics value obtained from this differential intensity.
As shown in FIG. 5, it was found that all the statistical values of the mean value, the standard deviation, and the mean value × the standard deviation have a correlation coefficient (R 2 ) of a certain value or more with respect to the black ratio. Therefore, if the inner surface micro unevenness is detected based on the magnitude of either of the statistical values alone or by combining any of the statistical values, the inner surface unevenness can be detected with the same accuracy as visual evaluation. Can be expected.
図６は、本実施形態に係る内面検査方法において、統計値として平均値×標準偏差を用いた場合の内面微小凹凸の検出結果と目視評価結果とを対比した結果の一例を示す。具体的には、図６において「自動判定」の欄に示す結果は、種々の内面状態を有する複数（１９本）の管状体Ｐ（黒比率の異なる複数の管状体Ｐ）のそれぞれに対して、前述のように約６０００点の微分強度を取得し、この微分強度から得られた平均値×標準偏差が１３以上である場合（「×」で示すデータ）には、内面微小凹凸が存在すると判定し、１３未満である場合（「〇」で示すデータ）には、内面微小凹凸が存在しないか、存在したとしても極めて軽微であるため使用上の問題が無い（実質的に内面微小凹凸が存在しないものとして扱える）と判定した結果である。一方、図６において「目視判定」の欄に示す結果は、ＩＴＶカメラの撮像画像を目視して、内面微小凹凸の有無を評価した結果である。目視によって内面微小凹凸が存在すると判定した試験材のデータには「×」を、内面微小凹凸が存在しないか、存在したとしても極めて軽微であるため使用上の問題が無いと判定した場合の試験材のデータには「〇」を付けている。
図６に示すように、本実施形態に係る内面検査方法による内面微小凹凸の自動判定（検出）結果と目視判定の結果は一致している。したがって、本実施形態に係る内面検査方法によれば、複数の底面エコー信号の微分強度分布に統計処理を施して得られた統計値の大小に基づき、目視評価と同等の精度で内面微小凹凸を検出可能であることが分かった。
FIG. 6 shows an example of the result of comparison of the detection result of the inner surface micro unevenness and the visual evaluation result in the case of using an average value × standard deviation as a statistical value in the inner surface inspection method according to the present embodiment. Specifically, the result shown in the column of “automatic determination” in FIG. 6 is obtained for each of a plurality of (19) tubular bodies P (a plurality of tubular bodies P having different black ratios) having various inner surface states. As described above, when the differential intensity of about 6000 points is acquired, and the average value x standard deviation obtained from this differential intensity is 13 or more (data shown by "x"), it is assumed that the inner surface micro unevenness exists If it is judged that it is less than 13 (data indicated by "o"), there is no internal micro-concavities or no problem in use because it is extremely minor if it exists (substantially, internal micro-concavities are It is a result of judging that it can be treated as nonexistent. On the other hand, the result shown in the column of "visual judgment" in FIG. 6 is the result of visually observing the captured image of the ITV camera and evaluating the presence or absence of the inner surface micro unevenness. "X" is the data of the test material that was judged to have internal micro-concavities by visual inspection, and no internal micro-concavities exist, or even if it is extremely small, it is extremely minor, so it is judged that there is no problem in use The material data is marked with "o".
As shown in FIG. 6, the result of the automatic determination (detection) of the inner surface micro unevenness by the inner surface inspection method according to the present embodiment and the result of the visual determination are identical. Therefore, according to the inner surface inspection method according to the present embodiment, based on the magnitude of the statistical value obtained by performing statistical processing on the differential intensity distribution of the plurality of bottom surface echo signals, the inner surface micro unevenness is obtained with the same accuracy as visual evaluation. It was found to be detectable.
なお、本実施形態に係る内面検査方法において、管状体Ｐの軸方向に沿った複数の底面エコー信号の微分強度分布の各波形を、横軸を管状体Ｐの周方向位置とし、縦軸を管状体Ｐの軸方向位置として、重ねて表示することが好ましい。具体的には、制御・信号処理手段２がモニターを具備し、制御・信号処理手段２が作成した複数の底面エコー信号の微分強度分布の各波形をモニターに上記の態様で表示することが好ましい。
図７は、複数の底面エコー信号の微分強度分布の各波形の表示例を示す。図７（ａ）は前述の図３に示す例に対応する表示例であり、図７（ｂ）は前述の図４に示す例に対応する表示例である。
図７に示すような表示を行えば、底面エコー信号の微分強度分布の各波形をオペレータが目視で確認し易いため、前述した統計値の大小に基づく内面微小凹凸の自動検出に加えて、目視判断も併用することで、内面微小凹凸の検出精度が高まることが期待できる。
In the inner surface inspection method according to the present embodiment, each waveform of the differential intensity distribution of the plurality of bottom surface echo signals along the axial direction of the tubular body P has the horizontal axis as the circumferential position of the tubular body P, and the vertical axis It is preferable to overlap and display as the axial direction position of the tubular body P. Specifically, it is preferable that the control and signal processing means 2 be equipped with a monitor and each waveform of the differential intensity distribution of the plurality of bottom surface echo signals created by the control and signal processing means 2 be displayed on the monitor in the above manner. .
FIG. 7 shows a display example of each waveform of differential intensity distribution of a plurality of bottom echo signals. FIG. 7 (a) is a display example corresponding to the example shown in FIG. 3 described above, and FIG. 7 (b) is a display example corresponding to the example shown in FIG. 4 described above.
If the display as shown in FIG. 7 is performed, the operator can easily confirm each waveform of the differential intensity distribution of the bottom surface echo signal, so in addition to the automatic detection of the inner surface micro unevenness based on the magnitude of the statistical value described above It can be expected that the detection accuracy of the inner surface micro unevenness is enhanced by using the judgment together.
１・・・超音波探触子
２・・・制御・信号処理手段
Ｐ・・・管状体
1 ··· Ultrasonic probe 2 ··· Control and signal processing means P ··· Tubular body
Claims (2)
前記超音波探触子を前記管状体の周方向に沿って相対的に移動させると共に、前記超音波探触子から前記管状体の内面に対して略垂直に超音波を送信し、前記管状体の内面から反射した底面エコーを前記超音波探触子で受信して、前記管状体の周方向についての底面エコー信号の強度分布を取得する第２ステップと、
前記第２ステップで取得した底面エコー信号の強度分布に前記管状体の周方向の微分処理を施して、底面エコー信号の微分強度分布を取得する第３ステップと、
前記超音波探触子を前記管状体の軸方向に沿って相対的に移動させて前記第２ステップ及び前記第３ステップを繰り返し実行することで、又は、前記超音波探触子として前記管状体の軸方向に沿って複数の振動子を具備するアレイ超音波探触子を用いることで、前記管状体の軸方向に沿って複数の底面エコー信号の微分強度分布を取得する第４ステップと、
前記第４ステップで取得した複数の底面エコー信号の微分強度分布に統計処理を施し、該統計処理によって得られた統計値の大小に基づき、前記管状体の内面の凹凸を検出する第５ステップと、
を含むことを特徴する管状体の内面検査方法。 Placing the ultrasound probe against the outer surface of the stainless steel tubular body;
The ultrasonic probe is relatively moved along the circumferential direction of the tubular body, and the ultrasonic probe transmits ultrasonic waves substantially perpendicularly to the inner surface of the tubular body, and the tubular body A second step of receiving the bottom echo reflected from the inner surface of the inner surface by the ultrasonic probe to obtain an intensity distribution of the bottom echo signal in the circumferential direction of the tubular body;
A third step of performing differentiation processing in a circumferential direction of the tubular body on the intensity distribution of the bottom surface echo signal acquired in the second step, and acquiring a differential intensity distribution of the bottom surface echo signal;
By relatively moving the ultrasonic probe along the axial direction of the tubular body and repeatedly executing the second step and the third step, or the tubular body as the ultrasonic probe A fourth step of acquiring differential intensity distributions of a plurality of bottom echo signals along the axial direction of the tubular body by using an array ultrasonic probe having a plurality of transducers along the axial direction of
A fifth step of performing statistical processing on differential intensity distributions of the plurality of bottom surface echo signals acquired in the fourth step, and detecting unevenness of the inner surface of the tubular body based on the magnitude of the statistical value obtained by the statistical processing; ,
A method of inspecting the inner surface of a tubular body, comprising:
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