JP6565411B2 - Inner surface inspection method for tubular body - Google Patents
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- JP6565411B2 JP6565411B2 JP2015143648A JP2015143648A JP6565411B2 JP 6565411 B2 JP6565411 B2 JP 6565411B2 JP 2015143648 A JP2015143648 A JP 2015143648A JP 2015143648 A JP2015143648 A JP 2015143648A JP 6565411 B2 JP6565411 B2 JP 6565411B2
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Description
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、内部に高圧水が流通する管状体の内面の腐食状態を簡易に評価可能な管状体の内面検査方法に関する。 The present invention relates to a method for inspecting an inner surface of a tubular body using ultrasonic waves. In particular, the present invention relates to a tubular body that is provided in a hot extruder for a tube and that can easily evaluate the corrosion state of the inner surface of a tubular body through which high-pressure water circulates, such as a cylinder for pressing a material with water pressure. The present invention relates to an inner surface inspection method.
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、内部に高圧水が流通する水平方向に延びるシリンダ（メインシリンダ）が設けられている。
Conventionally, a hot extrusion method is known as a production method suitable for a seamless pipe made of a difficult-to-work material such as a high alloy (for example, see Patent Document 1).
This hot extrusion method generally produces a seamless pipe by pressing the material (hollow billet) toward the die of the hot extruder and extruding the material between the die and the mandrel. It is a method to do. The hot extruder is provided with a horizontally extending cylinder (main cylinder) through which high-pressure water circulates in order to press the material with 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腐食が生じ、腐食が進展することで、シリンダ内面に微小クラックが発生する。この状態でシリンダ内部に高圧水が流通すると、微小クラックに応力集中が生じて、亀裂が進展し、やがては破壊して高圧水がシリンダ外部に漏れるおそれがある。このため、シリンダ内面の腐食状態を適宜評価することが重要である。 While the above cylinder has been in use for a long time, foreign matter (for example, fallen oxide scale formed on the inner surface of the piping for supplying and discharging high pressure water to the cylinder) gets mixed into the high pressure water circulating inside. However, when the hot extruder is stopped, the foreign matter accumulates mainly on the lower part of the inner surface of the cylinder. The accumulation of the foreign matter causes corrosion on the inner surface of the cylinder, and the progress of the corrosion causes micro cracks on the inner surface of the cylinder. When high-pressure water flows inside the cylinder in this state, stress concentration occurs in the microcracks, the cracks develop, and eventually, the high-pressure water may leak to the outside of the cylinder. For this reason, it is important to appropriately evaluate the corrosion state of the cylinder inner surface.
シリンダの内面の腐食状態は、例えば、ＩＴＶカメラなどの撮像手段をシリンダ内に挿入し、撮像画をオペレータが目視観察することでも評価可能である。
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腐食状態を簡易に評価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、内部に高圧水が流通する管状体全般に共通するものだと考えられる。
The corrosion state of the inner surface of the cylinder can be evaluated by, for example, inserting an imaging means such as an ITV camera into the cylinder and visually observing the captured image by the operator.
However, in order to insert / remove the image pickup 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 / removal operation of the image pickup means It takes a lot of work.
Therefore, a method that can easily evaluate the corrosion state of the inner surface from the outer surface side of the cylinder is desired.
The same problem as described above is not limited to the cylinder provided in the hot extruder, but is considered to be common to all tubular bodies in which high-pressure water flows.
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、いずれも内部に高圧水が流通する管状体の内面の腐食状態を簡易に評価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、内部に高圧水が流通する管状体は、耐圧性の観点より、大きな肉厚を有するのが通常である。また、耐腐食性の観点より、超音波減衰の大きなステンレス鋼から形成されている場合も多い。内部に高圧水が流通する管状体が大きな肉厚を有するステンレス鋼製である場合、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、内部に高圧水が流通する管状体の内面の腐食状態を評価することは難しい。
As methods for inspecting the inner surface of a tubular body, for example, methods such as Patent Documents 2 to 5 have been proposed. However, in any case, in order to easily evaluate the corrosion state of the inner surface of a tubular body in which high-pressure water flows. It is not an effective method.
In Patent Document 6, an ultrasonic wave having a high-frequency pulse component and a low-frequency pulse component is transmitted to a subject, and an echo signal from the subject is Fourier-transformed to perform frequency analysis. A method for measuring the roughness of the surface has been proposed. However, the tubular body in which high-pressure water circulates normally has a large thickness from the viewpoint of pressure resistance. Further, from the viewpoint of corrosion resistance, it is often formed from stainless steel having a large ultrasonic attenuation. When the tubular body in which high-pressure water circulates is made of stainless steel having a large thickness, the high-frequency component of the ultrasonic wave is significantly attenuated, and the attenuation rate varies because the crystal grain size is not uniform. For this reason, it is difficult to evaluate the corrosion state of the inner surface of the tubular body in which high-pressure water flows through 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、内部に高圧水が流通する管状体など、管状体の内面の腐食状態を簡易に評価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 above-described problems of the prior art, and is a tubular body that can easily evaluate the corrosion state of the inner surface of the tubular body, such as a tubular body in which high-pressure water flows. It is an object of the present invention to provide an inner surface inspection method.
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の腐食によって減衰する。
（Ｂ）上記腐食による底面エコー信号の強度の減衰は、管状体の偏芯、偏肉、内面肌の影響を受けやすい。これら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腐食状態（腐食の程度）を評価可能（健全な内面と識別可能）である。
In order to solve the above-mentioned problems, the present inventors diligently studied, and as a result, obtained the knowledge described in the following (A) to (C) and completed the present invention.
(A) The intensity of the bottom echo signal when the inner surface of the tubular body is flaw-detected is attenuated by corrosion of the inner surface.
(B) The attenuation of the intensity of the bottom echo signal due to the corrosion is easily affected by eccentricity, thickness deviation, and inner skin of the tubular body. In order to reduce these influences, it is effective to perform evaluation by performing differential processing in the circumferential direction of the tubular body.
(C) Corrosion state (degree of corrosion) is determined by the magnitude of statistical values obtained by applying statistical processing (processing to calculate average value and standard deviation) to differential intensities of bottom echo signals obtained at many measurement points. Evaluable (can be distinguished from a healthy inner surface).
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：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腐食状態を評価する。
That is, this invention provides the inner surface inspection method of the tubular body characterized by including the following 1st-5th steps.
(1) 1st step: An ultrasonic probe is arrange | positioned facing the outer surface of a tubular body.
(2) Second step: The ultrasonic probe is moved relatively along the circumferential direction of the tubular body, and the ultrasonic wave is substantially perpendicular to the inner surface of the tubular body from the ultrasonic probe. The bottom echo reflected from the inner surface of the tubular body is received by the ultrasonic probe, and the intensity distribution of the bottom echo signal in the circumferential direction of the tubular body is acquired.
(3) Third step: The differential distribution in the circumferential direction of the tubular body is applied to the intensity distribution of the bottom echo signal acquired in the second step to acquire the differential intensity distribution of the bottom echo signal.
(4) Fourth step: By repeatedly 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 having a plurality of transducers along the axial direction of the tubular body as a probe, a differential intensity distribution of a plurality of bottom surface echo signals can be obtained along the axial direction of the tubular body. get.
(5) Fifth step: Statistical processing is performed on the differential intensity distributions of the plurality of bottom surface echo signals obtained in the fourth step, and corrosion of the inner surface of the tubular body is performed based on the magnitude of the statistical value obtained by the statistical processing. Assess the condition.
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、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、管状体の内面の腐食状態を評価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、管状体の内面の腐食状態を簡易に且つ自動的に評価することが可能である。
According to the present invention, it is possible to obtain differential intensity distributions of a plurality of bottom surface echo signals along the axial direction of the tubular body by executing the first step to the fourth step. In other words, it is possible to obtain differential intensities of the bottom surface 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 distribution of the plurality of bottom surface echo signals (statistic processing is performed on the differential strengths of the bottom surface echo signals at a plurality of points obtained in the circumferential direction and the axial direction of the tubular body), Based on the magnitude of the obtained statistical value, it is possible to evaluate the corrosion state of the inner surface of the tubular body.
According to the present invention, as a mechanical operation, an ultrasonic probe is arranged facing the outer surface of the tubular body (first step), and the ultrasonic probe is relatively relative to the circumferential direction and the axial direction of the tubular body. Since it is only necessary to move the child (second step and fourth step), it is less time-consuming than when the imaging means is inserted and removed, and the corrosion state of the inner surface of the tubular body is easily and automatically evaluated. Is possible.
本発明は、前記管状体が、内部に高圧水が流通する管状体である場合に好適に用いられる。より具体的には、例えば、前記管状体が、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である場合に特に好適である。 The present invention is suitably used when the tubular body is a tubular body in which high-pressure water flows. More specifically, for example, it is particularly suitable when the tubular body is a cylinder that is provided in a hot extruder of a tube and presses the material with water pressure.
本発明を管の熱間押出機に設けられたシリンダに適用する場合、必ずしも熱間押出機を停機する必要はなく、シリンダ内部に高圧水が流通している状態で評価することも可能である。 When the present invention is applied to a cylinder provided in a hot extruder for pipes, it is not always necessary to stop the hot extruder, and it is possible to evaluate in a state where high-pressure water is circulating inside the cylinder. .
本発明によれば、管状体の内面の腐食状態を簡易に評価可能であり、特に、内部に高圧水が流通する管状体に対して好適に用いられる。 According to the present invention, it is possible to easily evaluate the corrosion state of the inner surface of the tubular body, and it is particularly suitable for a tubular body in which high-pressure water circulates.
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に接続された制御・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を管状体Ｐの周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。管状体Ｐは、熱間押出機に設けられたシリンダなど、内部に高圧水が流通する管状体である。本実施形態に係る内面検査方法を実施する際、管状体Ｐの内部に高圧水が流通している状態でも良いし、高圧水が排出されている状態であっても良い。
Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings as appropriate.
FIG. 1 is an explanatory diagram schematically illustrating an apparatus configuration for carrying out a tubular body inner surface inspection method according to an embodiment of the present invention. Fig.1 (a) shows the front view seen from the axial direction of the tubular body, FIG.1 (b) shows a top view.
As shown in FIG. 1, an apparatus used to carry out the inner surface inspection method according to the present embodiment includes an ultrasonic probe 1 and control / signal processing means 2 connected to the ultrasonic probe 1. I have. As will be described later, a mechanism (not shown) for moving the ultrasonic probe 1 relatively in the circumferential direction of the tubular body P is also provided. The tubular body P is a tubular body in which high-pressure water circulates, such as a cylinder provided in a hot extruder. When the inner surface inspection method according to the present embodiment is performed, the high-pressure water may be circulated inside the tubular body P, or the high-pressure water may be discharged.
本実施形態の超音波探触子１としては、管状体Ｐの軸方向に沿って複数の振動子１１を具備するアレイ超音波探触子が好適に用いられる。本実施形態の超音波探触子１は、管状体Ｐの軸方向に沿った寸法が１ｍｍでそれに直交する方向の寸法が２０ｍｍの振動子１１を管状体Ｐの軸方向に沿って３２個具備しており、探傷周波数は７ＭＨｚとされている。 As the ultrasonic probe 1 of the present embodiment, an array ultrasonic probe including a plurality of transducers 11 along the axial direction of the tubular body P is preferably used. The ultrasonic probe 1 of the present embodiment includes 32 transducers 11 having a dimension along the axial direction of the tubular body P of 1 mm and a dimension perpendicular to the axis of 20 mm along the axial direction of the tubular body P. The flaw detection frequency is 7 MHz.
制御・信号処理手段２は、超音波探触子１（超音波探触子１が具備する各振動子１１）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（超音波探触子１が具備する各振動子１１）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 includes a pulser that supplies a pulse signal for transmitting an ultrasonic wave from the ultrasonic probe 1 (each transducer 11 included in the ultrasonic probe 1), and an ultrasonic wave that has received an echo. A portion that functions to control transmission / reception of ultrasonic waves, such as a receiver that amplifies an echo signal output from the ultrasonic probe 1 (each transducer 11 included in the ultrasonic probe 1), and an ultrasonic wave as described later. Based on the bottom echo signal output from the acoustic probe 1, the intensity distribution or differential intensity distribution of the bottom echo signal in the circumferential direction of the tube P is created, or statistical processing is performed on the differential intensity distribution of the bottom echo signal. And a portion performing a function of executing various signal processing.
機構部としては、管状体Ｐの周方向に超音波探触子１を回転させる機構を例示できる。ただし、これに限るものではなく、管状体Ｐの方を周方向に回転させる機構を採用することも可能である。 As a mechanism part, the mechanism which rotates the ultrasonic probe 1 to the circumferential direction of the tubular body P can be illustrated. However, it is not restricted to this, It is also possible to employ | adopt the mechanism which rotates the direction of the tubular body P to the circumferential direction.
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 apparatus having the above-described configuration, as shown in FIG. 1, the ultrasonic probe 1 is disposed facing the outer surface of the tubular body P (the present invention). Equivalent to the first step).
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。底面エコー信号の強度分布は、各振動子１１から出力される底面エコー信号毎に作成される。本実施形態では、内径が約１３００ｍｍの管状体Ｐの周方向について１ｍｍピッチ毎に約２５０点〜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 moved relatively along the circumferential direction of the tubular body P by the mechanism portion, and ultrasonic waves are emitted from the ultrasonic probe 1 substantially perpendicularly to the inner surface of the tubular body P. The bottom echo B transmitted and reflected from the inner surface of the tubular body P is received by the ultrasonic probe 1 to output a bottom echo signal, and the control / signal processing means 2 controls the bottom echo signal in the circumferential direction of the tubular body P. Is created (corresponding to the second step of the present invention).
Specifically, the control / signal processing means 2 is a bottom echo B (in this embodiment, a surface echo) of echoes received by the ultrasonic probe 1 at a predetermined pitch 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 intensity of the bottom echo signal corresponding to the first bottom echo received first after receiving S. The intensity distribution of the bottom echo signal is created for each bottom echo signal output from each transducer 11. In the present embodiment, the intensity distribution is created by detecting the intensity of the bottom echo signals of about 250 to 300 points for every 1 mm pitch in the circumferential direction of the tubular body P having an inner diameter of about 1300 mm.
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）。底面エコー信号の微分強度分布は、各振動子１１から出力される底面エコー信号毎に作成される。
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２５０点〜３００点の各強度に対して、注目点から５点の範囲内（５ｍｍの範囲内に相当）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 a differential process in the circumferential direction of the tubular body P on the created intensity distribution of the bottom echo signal to create a differential intensity distribution of the bottom echo signal (third step of the present invention). Equivalent). The differential intensity distribution of the bottom echo signal is created for each bottom echo signal output from each transducer 11.
Specifically, the control / signal processing means 2 calculates the intensity from the maximum value to the minimum value within a predetermined number of points from the point of interest for each intensity of a plurality of points constituting the intensity distribution of the bottom echo signal. The differential intensity of the bottom echo signal is created by subtracting and substituting the result of the subtraction for the differential intensity of the target point. In the present embodiment, for each intensity of 250 to 300 points constituting the intensity distribution of the bottom echo signal, the maximum value of the intensity within the range of 5 points from the attention point (corresponding to the range of 5 mm) is minimized. The differential intensity of the bottom echo signal is created by subtracting the value.
本実施形態では、超音波探触子１として、管状体Ｐの軸方向に沿って３２個の振動子１１を具備するアレイ超音波探触子を用いているため、前述のように、各振動子１１から出力される底面エコー信号毎に底面エコー信号の微分強度分布を作成することで、管状体Ｐの軸方向に沿って複数（３２点）の底面エコー信号の微分強度分布を作成することになる（本発明の第４ステップに相当）。
上記のように、本実施形態では、管状体Ｐの軸方向に約１ｍｍピッチ（振動子１１の寸法）で計３２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２５０〜３００点で軸方向に３２点の計約８０００点〜９６００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、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いるが、本発明はこれに限るものではない。超音波探触子１として、単一の振動子を具備する超音波探触子を用い、この超音波探触子１を機構部によって管状体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、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ことも可能である。
In the present embodiment, as the ultrasonic probe 1, an array ultrasonic probe including 32 transducers 11 along the axial direction of the tubular body P is used. Creating differential intensity distributions of a plurality of (32 points) bottom surface echo signals along the axial direction of the tubular body P by creating a differential intensity distribution of the bottom surface echo signals for each bottom surface echo signal output from the child 11. (Corresponding to the fourth step of the present invention).
As described above, in this embodiment, the differential intensity distribution of the bottom surface echo signals of a total of 32 points is created at a pitch of about 1 mm (dimension of the transducer 11) in the axial direction of the tubular body P. Therefore, as the differential intensity of the bottom echo signal, a total differential intensity of about 8000 to 9600 points, which is about 250 to 300 points in the circumferential direction of the tubular body P and 32 points in the axial direction, is generated.
In the present embodiment, an array ultrasonic probe having a plurality of transducers along the axial direction of the tubular body P is used as the ultrasonic probe 1, but the present invention is not limited to this. Absent. An ultrasonic probe having a single vibrator is used as the ultrasonic probe 1, and the ultrasonic probe 1 is relatively moved along the axial direction of the tubular body P by the mechanism portion. The control / signal processing means 2 repeatedly executes the above-described operations (operations corresponding to the second step and the third step of the present invention), so that the differential intensities of a plurality of bottom surface echo signals along the axial direction of the tubular body P are obtained. It is also possible to create a distribution.
図２〜図５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。各図の（ａ）は管状体Ｐ（具体的には、熱間押出機に設けられたシリンダ）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３２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３２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は熱間押出機に設置してから約１２年経過したシリンダ（以下、適宜、「旧シリンダ」と称する）の内面下部で腐食が進展している状態の例を、図３は旧シリンダの内面上部で腐食が軽微である状態の例を、図４は熱間押出機に設置してからまだ１年程度しか経過していないシリンダ（以下、適宜、「新シリンダ」と称する）の内面下部で腐食が軽微である状態の例を、図５は新シリンダの内面上部で腐食が生じていない例を示す。
2-5 is a figure which shows the example of the differential intensity distribution of the bottom face echo signal acquired by the inner surface inspection method which concerns on this embodiment. (A) in each figure is an image obtained by imaging the inner surface of the tubular body P (specifically, a cylinder provided in the hot extruder) with an ITV camera, and (b) in each figure is (a) in each figure. The differential intensity distribution of the bottom echo signal created on the inner surface of the tubular body P shown in () (the differential intensity distribution of the bottom echo signal created 32 points in the axial direction of the tubular body P is displayed as it is) is shown in each figure. (C) is the intensity distribution of the bottom echo signal created for the inner surface of the tubular body P shown in FIG. (A) (the intensity distribution of the bottom echo signal created for 32 points in the axial direction of the tubular body P (before differential processing is performed). ) Is displayed as it is.
FIG. 2 shows an example of a state in which corrosion has progressed in the lower part of the inner surface of a cylinder (hereinafter referred to as “old cylinder” where appropriate) that has passed about 12 years since installation in the hot extruder, and FIG. FIG. 4 shows an example of a state where the corrosion is slight at the upper part of the inner surface of the cylinder. FIG. 4 shows the inner surface of a cylinder (hereinafter referred to as “new cylinder” where appropriate) that has only passed about one year since it was installed in the hot extruder. FIG. 5 shows an example in which corrosion does not occur in the upper part of the inner surface of the new cylinder.
図２（ｂ）〜図５（ｂ）から分かるように、腐食が進展している場合（図２（ｂ））には、腐食が軽微な場合（図３（ｂ）及び図４（ｂ））や腐食が無い場合（図５（ｂ））に比べて、底面エコー信号の微分強度が全体的に大きくなり、変動も大きいことがわかる。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、腐食状態（腐食の程度）を評価可能（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５（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５（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、腐食状態を精度良く評価するには、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. 2B to 5B, when the corrosion is progressing (FIG. 2B), the corrosion is slight (FIGS. 3B and 4B). ) And the case where there is no corrosion (FIG. 5B), the differential intensity of the bottom surface echo signal is increased as a whole, and the fluctuation is large. Therefore, by applying statistical processing to the differential intensity distribution of multiple bottom echo signals and evaluating the magnitude of the statistical value, it is expected that the corrosion state (degree of corrosion) can be evaluated (can be distinguished from a healthy inner surface). it can.
As can be seen from FIGS. 2 (c) to 5 (c), the intensity distribution of the bottom surface echo signal that is not subjected to the differentiation process has a tubular body P as compared to FIGS. 2 (b) to 5 (b). There is unevenness in strength due to eccentricity and thickness deviation. For this reason, in order to accurately evaluate the corrosion state, it is effective to perform the evaluation by performing a differential process 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８０００点〜９６００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、腐食状態を評価している（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 (in the present embodiment, differential intensities of about 8000 to 9600 points) of the plurality of bottom surface echo signals created as described above, and the statistical processing is performed. The corrosion state is evaluated based on the magnitude of the statistical value obtained by (corresponding to the fifth step of the present invention).
図６は、本実施形態に係る内面検査方法によって腐食状態を評価した結果の一例を示す。図６において「〇」でプロットしたデータは統計値として平均値を用いた場合を、「△」でプロットしたデータは統計値として標準偏差を用いた場合を示す。図６に示す結果は、前述の図２〜図５を参照して説明した旧シリンダの内面下部及び内面上部と新シリンダの内面下部及び内面上部において、それぞれ複数の領域で統計値を算出してプロットしたものである。
図６に示すように、平均値及び標準偏差のいずれの統計値も、腐食が進展している場合と、腐食が軽微な場合と、腐食が無い場合とで、その値に有意差が生じている。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、管状体Ｐの内面の腐食状態を評価可能であることが分かった。
FIG. 6 shows an example of the result of evaluating the corrosion state by the inner surface inspection method according to the present embodiment. In FIG. 6, data plotted with “◯” indicates a case where an average value is used as a statistical value, and data plotted with “Δ” indicates a case where a standard deviation is used as a statistical value. The results shown in FIG. 6 are obtained by calculating statistical values in a plurality of regions in the lower inner surface and upper inner surface of the old cylinder and the lower inner surface and upper inner surface of the new cylinder described with reference to FIGS. It is a plot.
As shown in FIG. 6, the statistical values of the average value and the standard deviation are significantly different between the case where the corrosion is progressing, the case where the corrosion is minor, and the case where there is no corrosion. Yes. Therefore, according to the inner surface inspection method according to the present embodiment, it is possible to evaluate the corrosion state of the inner surface of the tubular body P 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. It turns out that.
１・・・超音波探触子
２・・・制御・信号処理手段
Ｐ・・・管状体
DESCRIPTION OF SYMBOLS 1 ... Ultrasonic probe 2 ... Control and signal processing means P ... Tubular body
Claims (3)
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腐食状態を評価する第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。 A first step of placing an ultrasound probe opposite the outer surface of the tubular body;
The ultrasonic probe is moved relatively along the circumferential direction of the tubular body, and ultrasonic waves are transmitted from the ultrasonic probe substantially perpendicular 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 tube with the ultrasonic probe and obtaining the intensity distribution of the bottom echo signal in the circumferential direction of the tubular body;
A third step of performing differential processing in the circumferential direction of the tubular body on the intensity distribution of the bottom echo signal acquired in the second step, and acquiring a differential intensity distribution of the bottom echo signal;
The ultrasonic probe is relatively moved along the axial direction of the tubular body, and the second step and the third step are repeatedly executed, or the tubular body is used as the ultrasonic probe. A fourth step of acquiring differential intensity distributions of a plurality of bottom surface echo signals along the axial direction of the tubular body by using an array ultrasonic probe comprising a plurality of transducers along the axial direction of
Fifth step of performing statistical processing on the differential intensity distributions of the plurality of bottom surface echo signals acquired in the fourth step and evaluating the corrosion state of the inner surface of the tubular body based on the magnitude of the statistical value obtained by the statistical processing When,
A method for inspecting an inner surface of a tubular body, comprising:
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