JP4363699B2 - Method for detecting carburized layer and measuring thickness thereof - Google Patents

Method for detecting carburized layer and measuring thickness thereof Download PDF

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JP4363699B2
JP4363699B2 JP12682099A JP12682099A JP4363699B2 JP 4363699 B2 JP4363699 B2 JP 4363699B2 JP 12682099 A JP12682099 A JP 12682099A JP 12682099 A JP12682099 A JP 12682099A JP 4363699 B2 JP4363699 B2 JP 4363699B2
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carburized layer
metal tube
reflected
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JP2000321041A (en
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政廣 中林
正 林
美年 四辻
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Idemitsu Kosan Co Ltd
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    • G01N29/04—Analysing solids
    • G01N29/11—Analysing solids by measuring attenuation of acoustic waves
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Description

【０００１】
【発明の属する技術分野】
本発明は、石油化学プラントの炉内配管等の金属管の内，外面の浸炭層の検出及びその厚さの測定を非破壊試験で行う方法に関する。
【０００２】
【従来の技術】
従来、石油化学プラントの代表例であるエチレン製造装置，重油脱硫装置，ＢＴＸ装置等の加熱炉や反応塔の配管（加熱炉管等）は、外側からの加熱や内側の高温流体の通流等によって高温加熱されるため、低合金鋼９Ｃｒ−１ＭＯ，２（１／２）Ｃｒ−１ＭＯ，インコロイ８００，ＳＵＳ３２１ＨＴＦ等の金属管で形成される。
【０００３】
そして、これらの高温加熱される金属管にあっては、使用によって管の内，外面に浸炭層が発生し、次第にその層が厚くなって劣化するため、定期的な検査等で浸炭層の発生（有無）及びその厚さを監視し、その結果に応じて管の取換え等の措置をとる必要がある。
【０００４】
ところで、この種の金属管は長く、しかも、プラント内等に多数配設されるため、それらの浸炭状況を、１本ずつ切断，研削等して破壊検査することは、検査効率や費用の面から極めて不経済である。
【０００５】
そこで、従来はこの種の金属管の浸炭状況を、とりあえず電磁誘導式の浸炭計で計測して非破壊検査し、その結果に基づき、疑わしい場合に切断，研削等して浸炭層の発生の検出及びその厚さの測定を行っている。
【０００６】
【発明が解決しようとする課題】
前記従来の電磁誘導式の浸炭計は、浸炭層が磁性層であることに着目して浸炭状況を計測するものであり、計測可能な金属管がインコロイやＳＵＳ等の非磁性体の金属管に限られ、いわゆる鋼管等の磁性体の金属管については計測することができない。
【０００７】
しかも、浸炭計の計測では磁性層の厚さを知ることは困難であり、内側にフィンを付けた押出管のような内径の不均一な金属管や溶接部分を有する金属管の計測も困難である。
【０００８】
すなわち、従来は磁性管や内径が不均一な管等の浸炭層の発生を、非破壊試験で知ることができず、しかも、浸炭層の厚さについては、磁性管，非磁性管を問わず、非破壊検査で知ることができない問題点がある。
【０００９】
本発明は、石油化学プラント等のこの種の金属管につき、磁性管，非磁性管を問わず、その内，外面の浸炭層の発生の検出及び厚さの測定が、非破壊試験で行えるようにすることを課題とする。
【００１０】
【課題を解決するための手段】
前記の課題を解決するために、本発明のベースになる浸炭層の検出方法においては、金属管の外面に間隔をとって超音波斜角探傷試験用の送信側探触子と受信側探触子とを設け、
超音波Ｖ透過法の試験により、送信側探触子から出射されて金属管の管面等で反射し、受信側探触子に反射パルスとして受信された超音波の受信レベル及び路程長を測定し、
受信側探触子が受信する反射パルスのうちの金属管の内面で反射した最も大きい内面反射パルスの受信レベルが最大になるように、両探触子の間隔を初期間隔に設定した後、
両探触子の間隔を初期間隔より狭くし、
金属管の内面側の浸炭層と，この浸炭層より金属管の外面側の非浸炭層との界面で反射した内面反射パルスの短路程側の隣接反射パルスの受信の有無を検出し、
短路程側の隣接反射パルスの受信により、金属管の内面側の浸炭層の発生を検出する。
【００１１】
この場合、超音波Ｖ透過法の試験により、金属管の外面の送信側探触子から内面側に斜めに出射された超音波は、金属管の内面で反射するだけでなく、内面側に浸炭層が発生していると、この浸炭層とその外面側の非浸炭層との界面でも反射する。
【００１２】
そして、これらの超音波の反射パルスにおいては、内面反射パルスが他の反射パルスより著しく大きく、また、内面側の浸炭層と非浸炭層との界面での反射パルスの管内の路程長（伝播距離）は内面反射パルスの路程長より短くなる。
【００１３】
そのため、最初に受信側又は送信側の探触子を、最も大きい内面反射パルスの受信レベルが最大になる位置に移動し、両探触子の間隔を初期間隔に設定すると、受信側探触子が内面反射パルスの受信点（到達点）に位置する。
【００１４】
そして、受信側又は送信側の探触子をその間隔が狭くなるように移動すると、内面側に浸炭層が発生し、この層とその外面側の非浸炭層との界面での反射パルスがあるときに、この反射パルスが内面反射パルスの短路程側の隣接反射パルスとして受信側探触子に受信される。
【００１５】
したがって、この短路程側の隣接反射パルスの受信により、金属管の内面側に浸炭層が発生していることを、切断，研削等することなく、現場の非破壊試験で検出することができ、この場合金属管が磁性管や内径が不均一な管等であっても、確実に内面側の浸炭層の発生を検出することができる。
【００１６】
つぎに、本発明のベースになる浸炭層の厚さの測定方法においては、送信側探触子と受信側探触子との間隔を初期間隔にして内面反射パルスの路程長を求めた後、
両探触子の間隔を初期間隔より狭くし、
金属管の内面側の浸炭層と，この浸炭層より金属管の外面側の非浸炭層との界面で反射した内面反射パルスの短路程側の隣接反射パルスを受信したときに、短路程側の隣接反射パルスの受信レベルが最も大きくなる路程長を内側浸炭層反射パルスの路程長として求め、
内面反射パルスの路程長と内側浸炭層反射パルスの路程長との差の１／２に超音波の屈折角の余弦関数値の係数を乗算して金属管の内面側に発生した浸炭層の厚さを測定する。
【００１７】
この場合、内面反射パルスの路程長及びその短路程側の隣接反射パルスの路程長の１／２に超音波の屈折角の余弦関数値の係数を乗算すると、それぞれ反射面から金属管の外面までの距離（長さ）になる。
【００１８】
そして、内面反射パルスの路程長の１／２に前記の余弦関数値の係数を乗算した長さは金属管の内面から外面までの厚さになり、短路程側の隣接反射パルスの路程長の１／２に前記の余弦関数値の係数を乗算した長さは金属管の浸炭層より外面側の非浸炭層の厚さになる。
【００１９】
したがって、両反射パルスの路程長の差の１／２に前記の余弦関数値の係数を乗算した長さから、金属管の内面側の浸炭層の厚さを求めて測定することができ、このとき、金属管が非磁性管等であっても正確に内面側の浸炭層の厚さを測定することができる。
【００２０】
つぎに、請求項１の本発明の浸炭層の検出方法においては、両探触子の間隔を初期間隔に設定した後、
両探触子の間隔を初期間隔より広くし、
金属管の内面で反射して外面で再反射し、金属管の外面側の浸炭層と，該浸炭層より内面側の非浸炭層との界面で再々反射した内面反射パルスの長路程側の隣接反射パルスの受信の有無を検出し、
長路程側の隣接反射パルスの受信により、金属管の外面側の浸炭層の発生を検出する。
【００２１】
この場合、金属管の外面側に浸炭層が発生すると、金属管の内面反射パルスは金属管の外面で再反射し、その再反射パルスが前記界面で外面側に再々反射し、この再々反射の反射パルスが内面反射パルスの長路程側の隣接反射パルスとして受信側探触子で受信される。
【００２２】
そのため、両探触子の間隔を初期間隔に設定した後、受信側探触子又は送信側探触子をその間隔が広くなるように移動すると、外面側に浸炭層が発生しているときに、金属管の内面で一旦反射し、外面で再反射した後、浸炭層とその内面側の非浸炭層との界面で再々反射した超音波の反射パルスが内面反射パルスの長路程側の隣接反射パルスとして受信側探触子に受信される。
【００２３】
したがって、この長路程側の隣接反射パルスの受信により、金属管の外面側に浸炭層が発生していることを非破壊試験で検出することができ、この場合、金属管が磁性管や内径が不均一な管であっても、確実に外面側の浸炭層の発生を検出することができる。
【００２４】
つぎに、請求項２の本発明の浸炭層の厚さの測定方法においては、両探触子の間隔を初期間隔にして内面反射パルスの路程長を求めた後、
両探触子の間隔を初期間隔より広くし、
金属管の内面で反射して外面で再反射し、金属管の外面側の浸炭層と，該浸炭層より金属管の内面側の非浸炭層との界面で再々反射した内面反射パルスの長路程側の隣接反射パルスを受信したときに、長路程側の隣接反射パルスの受信レベルが最も大きくなる路程長を外面側浸炭層反射パルスの路程長として求め、
この外面側浸炭層反射パルスの路程長と内面反射パルスの路程長との差の１／２に超音波の屈折角の余弦関数値の係数を乗算して金属管の外面側に発生した浸炭層の厚さを測定する。
【００２５】
この場合、両探触子が初期間隔のときの内面反射パルスの路程長及びその長路程側の隣接反射パルスの路程長の１／２に超音波の屈折角の余弦関数値の係数を乗算すると、内面から金属管の外面までの距離（長さ），この距離に外面側の浸炭層の厚さを加えた距離になる。
【００２６】
したがって、長路程側の隣接反射パルスと内面反射パルスとの路程長の差の１／２に前記の余弦の係数を乗算した長さから、金属管の外面側の浸炭層の厚さを求めて測定することができ、このとき、金属管が非磁性管等であっても正確に内面側の浸炭層の厚さを測定することができる。
【００２７】
つぎに、請求項３の本発明の浸炭層の検出方法においては、両探触子の間隔を初期間隔に設定した後、
金属管の内面側の浸炭層の発生の検出により、両探触子の間隔を初期間隔より狭くし、
金属管の内面側の浸炭層と，該浸炭層より前記金属管の外面側の非浸炭層との界面で反射した内面反射パルスの短路程側の隣接反射パルスの受信の有無を検出し、
短路程側の隣接反射パルスの受信により、金属管の内面側の浸炭層の発生を検出し、
金属管の外面側の浸炭層の発生の検出により、両探触子の間隔を初期間隔より広くし、
金属管の内面で反射して外面で再反射し、金属管の外面側の浸炭層と，該浸炭層より金属管の内面側の非浸炭層との界面で再々反射した内面反射パルスの長路程側の隣接反射パルスの受信の有無を検出し、
長路程側の隣接反射パルスの受信により、金属管の外面側の浸炭層の発生を検出する。
【００２８】
したがって、この場合はベースになる検出方法と請求項１の検出方法とを組合わせた検出方法により、金属管の内面側及び外面側の浸炭層の発生を非破壊試験で正確に検出することができる。
【００２９】
つぎに、請求項４の浸炭層の厚さの測定方法においては、両探触子の間隔を初期間隔にして内面反射パルスの路程長を求めた後、
金属管の内面側に発生した浸炭層の厚さの測定により、両探触子の間隔を初期間隔より狭くし、
金属管の内面側の浸炭層と，該浸炭層より金属管の外面側の非浸炭層との界面で反射した内面反射パルスの短路程側の隣接反射パルスを受信したときに、短路程側の隣接反射パルスの受信レベルが最も大きくなる路程長を内面側浸炭層反射パルスの路程長として求め、
内面反射パルスの路程長と内面側浸炭層反射パルスの路程長との差の１／２に超音波の屈折角の余弦関数値の係数を乗算して金属管の内面側に発生した浸炭層の厚さを測定し、
金属管の外面側に発生した浸炭層の厚さの測定により、両探触子の間隔を初期間隔より広くし、
金属管の内面で反射して外面で再反射し、金属管の外面側の浸炭層と，該浸炭層より金属管の内面側の非浸炭層との界面で再々反射した内面反射パルスの長路程側の隣接反射パルスを受信したときに、長路程側の隣接反射パルスの受信レベルが最も大きくなる路程長を外面側浸炭層反射パルスの路程長として求め、
外面側浸炭層反射パルスの路程長と内面反射パルスの路程長との差の１／２に超音波の屈折角の余弦関数値の係数を乗算して金属管の外面側に発生した浸炭層の厚さを測定する。
【００３０】
したがって、この場合はベースになる測定方法と請求項２の測定方法とを組合わせた測定方法により、金属管の内面側及び外面側に発生した浸炭層の厚さを非破壊検査で正確に測定することができる。
【００３１】
【発明の実施の形態】
本発明の実施の形態につき、図１ないし図１０を参照して説明する。
図１は例えばＢＴＸ装置の加熱炉の鋼管等の金属管１の管軸方向（長手方向）の断面図であり、図中の２は金属管１の内面側に発生した浸炭層（内面側浸炭層）、３は金属管１の外面側に発生した浸炭層（外面側浸炭層）、４は浸炭層２，３間の金属管１の非浸炭層である。
【００３２】
５，６は金属管１の外面１′に管軸方向に間隔をとって設けられた超音波斜角探傷試験用の送信側探触子，受信側探触子である。
【００３３】
そして、金属管１の浸炭状況の検査（保守点検）はＢＴＸ装置の運転が停止等されて金属管１に熱が加わらないときに現地で実施される。
【００３４】
このとき、金属管１は加熱炉等に縦向き又は横向きに配設され、探触子５，６が１組の場合、図１に実線及び破線で示したように、探触子５，６の設置位置を金属管１の各検査部位の外面１′に順に移動して検査が行われる。
【００３５】
つぎに、具体的な検査について説明する。
まず、探触子５，６を用いた超音波Ｖ透過法の試験により、反射パルスと呼ばれる超音波の反射エコーの計測から、金属管１の内面側浸炭層２の検出及び厚さの測定を行う。
【００３６】
この場合、図１の一部の拡大図である図２に示すように、探触子５，６の間隔を、最初に、金属管１の内面１″で反射した超音波の反射パルス（内面反射パルスＶ0）の受信レベルが最大になる初期間隔Ｙ0に調整して設定する。
ところで、送信側探触子５は超音波を図２の屈折角θで出射する。
【００３７】
そして、この屈折角θは３０°，４５°，６０°，７０°等に適当に設定してよいが、いわゆるＵ字管等の場合も考慮して種々実験したところ、４５°にすることが汎用性等の面から最も好ましいことが判明した。
【００３８】
なお、検出及び測定を精度よく行うため、屈折角θはいわゆる公称屈折角でなく、予め実験等で測定した実測角である。
【００３９】
また、探触子５，６は図示省略された本体装置の制御，監視により、超音波の送受信が制御，監視される。
【００４０】
そして、その送受信結果に基づく本体装置のマイクロコンピュータ等の演算処理により、斜角探傷法のうちのタンデム法を変形した周知のＶ透過法で反射パルスを測定し、金属管１の音速及びその超音波の出射（送信）から受信までの時間計測等に基づき、例えば図２の矢印線に示す送信側探触子５から受信側探触子６に至るまでの超音波の伝播路の長さを、反射パルスの路程長として求める。
【００４１】
さらに、この路程長と受信レベルとの関係を示す図３のような波形のグラフを、モニタ表示器等に画面表示する。
【００４２】
図３は内面反射パルスＶ0の場合の画面表示を示し、路程長Ｌ0の１／２の往路又は復路の路程長をビーム路程長Ｗ0 とし、ビーム路程長を横軸，受信レベルを表わす任意単位のエコー高さ（％）を縦軸にして内面反射パルスＶ0 を画面表示したものである。
【００４３】
そして、送信側探触子５から出射された超音波は、実際には、内面１″だけでなく、浸炭層２，３と非浸炭層４との界面Ｆ1，Ｆ2でも反射するが、内面１″で反射した内面反射パルスＶ0 のレベルが他のパルスより著しく大きくなる。
【００４４】
そこで、初期間隔Ｙ0 に調整する場合、モニタ表示器の画面表示をみながら、受信ゲインを調整しつつ送信側探触子５，受信側探触子６のいずれか一方又は両方を、表示された最も大きい反射パルスが最大レベルになるように、すなわち図３のように内面反射パルスＶ0 が最も大きく表示されるように、近づく方向又は離れる方向に少しずつ移動して超音波の送受信をくり返し、位置決めする。
【００４５】
なお、図３においては内面反射パルスＶ0 の受信レベルが最大であることが分り易いように、最大レベルのときに１００％でなく、８０％になるように表示したものであり、この場合、他の反射パルスについてはレベルが小さく、画面には現れない。
【００４６】
つぎに、内面側浸炭層２が発生している場合、この浸炭層２とその外面側の非浸炭層４との界面Ｆ1 でも超音波が反射し、その反射パルス（短路程側の隣接反射パルスＶ1）の路程長Ｌ1は、図４からも明らかなように内面反射パルスＶ0 の路程長Ｌ0 より浸炭層２の厚さに相当する数ミリメートル程度の微小な長さだけ短くなる。
【００４７】
そこで、モニタ表示器の表示画面をみながら、受信ゲインを調整しつつ探触子５，６のいずれか一方又は両方を近づく方向に移動して両探触子５，６の間隔を初期間隔Ｙ0 から少しずつ狭くし、図５に示すように、表示画面の内面反射パルスＶ0の短路程側近傍に隣接反射パルスＶ1が明瞭に分離して出現し、反射パルスＶ1 が検出されるか否かを観察する。
【００４８】
なお、本発明の反射パルスＶ0，Ｖ1等は横波のパルスであるが、実際には横波のパルスの他に、縦波のパルス等の疑似エコーと呼ばれる反射パルスも発生し、これらの反射パルスもモニタ表示等に画面表示される場合がある。
【００４９】
しかし、横波の反射パルスＶ0，Ｖ1等と疑似エコーの反射パルスとは探触子５，６の間隔を変えたときの表示変化等から区別することができ、しかも、疑似エコーの反射パルスは反射パルスＶ1 より短路程側に群パルス状に発生する。
【００５０】
そこで、図５等にあっては、本発明を分り易くするため、疑似エコーの反射パルスは省略して表している。
【００５１】
そして、隣接反射パルスＶ1 が明瞭に分離して検出されると、この検出によって内面側浸炭層２の発生が検出される。
【００５２】
つぎに、本形態ではその厚さを検出するため、隣接反射パルスＶ1 が最大レベルになるように探触子５，６の間隔を初期間隔Ｙ0から狭くして間隔Ｙ1にする。
【００５３】
このとき、図２からも明らかなように、内面反射パルスＶ0の路程長Ｌ0の１／２をＷ0とすると、その余弦関数値Ｗ0・cosθが金属管１の内面１″から外面１′までの厚さｔ0になる。
【００５４】
さらに、図４からも明らかなように、隣接反射パルスＶ1の路程長Ｌ1の１／２をＷ1とすると、その余弦関数値Ｗ1・cosθが界面Ｆ1から外面までの厚さ（ｔ0−ｔ1）になる。
【００５５】
したがって、内面側浸炭層２の厚さｔ1 は、路程長Ｌ0，Ｌ1の差の１／２に屈折角θの余弦関数値cosθの係数Ｋを乗算するつぎの数１の式から求められて測定される。
【００５６】
【数１】
ｔ1＝（（Ｌ0−Ｌ1）／２）・Ｋ＝（Ｗ0−Ｗ1）・cosθ
【００５７】
そして、金属管１の端面を示した図６の内面側浸炭層２の厚さｔ1 につき、数１の式から求めた測定値の精度を確かめたところ、実際に切断して確認した値（検証厚）と、数１の式から求めた値（測定厚）とにつき、図７の各○印の結果が得られた。
【００５８】
この図７によると、例えば実測の検証厚０．５mmに対して数１の式から求めた測定厚はその＋０．３mm〜−０．２mmの範囲になり、誤差が少なく、数１の式から金属管１の内面側浸炭層２の厚さｔ1 を非破壊試験で精度よく求めて測定できることが確かめられた。
【００５９】
つぎに、探触子５，６を用いた金属管１の外面側浸炭層３の検出及び厚さの測定について説明する。
【００６０】
ところで、金属管１等にあっては、管内の高温流体の通流によって浸炭層が内面側に発生し、加熱炉管等の管外から熱が加わるものについては、内面側だけでなく、外面側にも浸炭層（外面側浸炭層３）が発生する。
【００６１】
そして、この外面側浸炭層３の有無を検出する場合も、最初に内面反射パルスＶ0の受信に基づき、探触子５，６の設置間隔を初期間隔Ｙ0に設定する。
【００６２】
つぎに、外面側浸炭層３が発生している場合、探触子５から出射された超音波は、図８に示すように一部は外面側浸炭層３と非浸炭層４との界面Ｆ2 ，非浸炭層４と内面側浸炭層２との界面Ｆ1 で反射するが、大部分は金属管１の内面１″で反射する。
【００６３】
そして、界面Ｆ２で反射した超音波は金属管１の外面１′で再反射し、その後、界面Ｆ２での反射と外面１′での反射とをくり返し、探触子６に到達するまでに著しく減衰する。
【００６４】
また、界面Ｆ1で反射した超音波（内面側浸炭層反射パルスＶ1）は外面１′の内面反射パルスＶ0の到達点より探触子５に近い地点で受信される。
【００６５】
一方、内面１″で反射した超音波は内面反射パルスＶ０であることから他の反射パルスより著しく大きく、この内面反射パルスＶ０が外面１′で再反射して界面Ｆ２で再々反射すると、内面１″の内面反射パルスＶ０の到達点より外面側浸炭層３の厚さに応じた路程（距離）離れた地点で十分な大きさの反射パルスとして受信することができる。
【００６６】
そして、この反射パルスが内面反射パルスＶ0 の長路程側の隣接反射パルスＶ2であり、探触子５，６を初期間隔Ｙ0 に設置した後、モニタ表示器の表示画面をみながら、受信ゲインを調整しつつ探触子５，６のいずれか一方又は両方を離れる方向に移動して両探触子５，６の間隔を初期間隔から少しずつ広くし、図９に示すように、モニタ表示器の表示画面の内面反射パルスＶ0 の長路程側近傍に隣接反射パルスＶ2が明瞭に分離して出現し、反射パルスＶ2が検出されるか否かを観察する。
【００６７】
そして、隣接反射パルスＶ2 が明瞭に分離して検出されることにより、外面側浸炭層３の発生が検出される。
【００６８】
つぎに、外面側浸炭層３の厚さを検出するため、隣接反射パルスＶ2 が最も大きく受信されるように、探触子５，６の間隔を初期間隔Ｙ0から広くして間隔Ｙ2にする。
【００６９】
このとき、隣接反射パルスＶ２の出射から受信までの全路程長Ｌ２は、図８からも明らかなように、内面反射パルスＶ０の路程長Ｌ０（＝２・Ｗ０＝２・Ｗ２ａ）に、外面１′で再反射して界面Ｆ２で再々反射する路程長２・Ｗ２ｂを加算した長さＬ０＋２・Ｗ２ｂ（＝２（Ｗ２ａ＋Ｗ２ｂ））になる。
【００７０】
そして、金属管１の厚さｔ0は（Ｌ0／２）・cosθ（＝Ｗ0・cosθ＝Ｗ2a・cosθ）であり、外面側浸炭層３の厚さｔ2は（２・Ｗ2b／２）・cosθ（＝Ｗ2b・cosθ）である。，
【００７１】
そのため、外面側浸炭層３の厚さｔ2 は、路程長Ｌ2，Ｌ1の差の１／２に係数Ｋ（＝cosθ）を乗算するつぎの数２の式から求められて測定される。
【００７２】
【数２】
ｔ2＝（（Ｌ2−Ｌ0）／２）・Ｋ＝（Ｗ2−Ｗ0）・cosθ＝Ｗ2b・cosθ
【００７３】
そして、図６の外面側浸炭層３の厚さｔ2 につき、数２の式から求めた測定値の精度を確かめたところ、図７と同様の図１０の結果が得られ、この図１０から明らかなように、数２の式から外面側浸炭層３の厚さｔ2 を精度よく求めて測定できる。
【００７４】
したがって、探触子５，６を用いた超音波Ｖ透過法の試験により、金属管１の内面側浸炭層２，外面側浸炭層３の発生の検出及びその厚さの測定が、金属管１を切断，研削等することなく確実に精度よく行える。
【００７５】
そして、従来の電磁誘導式の浸炭計を用いた場合のような金属管１の材質や内面形状等による制限がなく、磁性管，非磁性管を問わず、どのような金属管であっても、現場での非破壊試験で精度よく、しかも、経済的に効率よく浸炭層２，４の発生を検出し、その厚さを測定することができる。
【００７６】
なお、浸炭層の有無が表示画面から容易に分かり、しかも、その厚さが数１，数２の式から簡単に求められるため、浸炭層２，３の検出や厚さの測定に超音波の反射エコーについての高度の熟練等を要しない利点もある。
【００７７】
ところで、金属管によっては内面側浸炭層２又は外面側浸炭層３についてのみ、浸炭層の発生の検出又はこの検出とその厚さの測定を行うようにしてもよい。また、探触子５，６を複数組用いて複数の金属管の検出，測定又は１本の金属管の複数個所の検出，測定を一度に行うようにしてもよい。
【００７８】
さらに、探触子５，６が送受する超音波の屈折角θは４５°に限られるものでなく、３０°，４５°，６０°，７０°等の種々の角度であっても、同様に適用できるのは勿論である。
【００７９】
そして、本発明は熱が加わる種々の金属管の浸炭層の発生の検出及びその厚さの測定に適用できる。
【００８０】
【発明の効果】
本発明は、以下に記載する効果を奏する。
まず、ベースになる検出方法の場合は、最初に受信側又は送信側の探触子６，５を、金属管１の内面１″の内面反射パルスＶ０の受信レベルが最大になる位置に移動し、両探触子５，６の間隔を初期間隔Ｙ０に設定すると、受信側探触子６が内面反射パルスＶ０の受信点（到達点）に位置し、つぎに受信側又は送信側の探触子６，５をその間隔が狭くなるように移動すると、内面側に浸炭層２が発生し、この層２とその外面側の非浸炭層４との界面Ｆ１での反射パルスがあるときに、この反射パルスを内面反射パルスＶ０の短路程側の隣接反射パルスＶ１として受信側探触子６で受信することができる。
【００８１】
そして、この短路程側の隣接反射パルスＶ1 の受信により、金属管１の内面側に浸炭層２が発生していることを、切断，研削等することなく、現場の非破壊試験で検出することができ、この場合、金属管１が磁性管や内径が不均一な管等であっても、確実に内面側の浸炭層２の発生を検出して浸炭状況を把握することができる。
【００８２】
また、ベースになる測定方法の場合は、内面側の浸炭層２の検出時、反射パルスＶ０，Ｖ１の路程長Ｌ０，Ｌ１の差の１／２（Ｗ０−Ｗ１）に屈折角θの余弦関数値の係数を乗算した長さ（Ｗ０−Ｗ１）ｃｏｓθから金属管１の浸炭層２の厚さｔ１ を求めて測定することができ、このとき、金属管１が非磁性管等であっても正確に内面側の浸炭層２の厚さを測定して浸炭状況を一層正確に把握することができ、その結果に基づいて管の取換え等の必要な補修等を適切に行うことができる。
【００８３】
そして、請求項１の検出方法の場合は、探触子５，６の間隔を初期間隔Ｙ０に設定した後、受信側又は送信側の探触子６，５をその間隔が広くなるように移動すると、外面側に浸炭層３が発生しているときに、金属管１の内面１″で一旦反射し、外面１′で再反射した後、浸炭層３とその内面側の非浸炭層４との界面Ｆ２で再々反射した超音波の反射パルスが内面反射パルスＶ０の長路程側の隣接反射パルスＶ２として受信側探触子６で受信することができる。
【００８４】
したがって、この長路程側の隣接反射パルスＶ2 の受信により、金属管１の外面側に浸炭層３が発生していることを切断，研削等することなく、現場の非破壊試験で検出することができ、この場合、金属管１が磁性管や内径が不均一な管であっても、確実に外面側の浸炭層３の発生を検出して浸炭状況を把握することができる。
【００８５】
また、請求項２の測定方法の場合は、外面側の浸炭層３の検出時、長路程側の隣接反射パルスＶ２と内面反射パルスＶ０との路程長Ｌ２，Ｌ０の差の１／２（（Ｗ２−Ｗ０）に屈折角θの余弦関数値の係数を乗算した長さ（Ｗ２−Ｗ０）ｃｏｓθから金属管１の外面側の浸炭層３の厚さｔ２を求めて測定することができ、このとき、金属管１が非磁性管等であっても正確に外面側の浸炭層３の厚さを測定して浸炭状況を一層正確に把握することができる。
【００８６】
つぎに、請求項３の検出方法の場合は、ベースになる検出方法と請求項１の検出方法とを組合わせた検出方法により、金属管１の内面側及び外面側の浸炭層２，３の発生を現場の非破壊試験で確実に検出して浸炭状況を把握することができる。
【００８７】
また、請求項４の測定方法の場合は、ベースになる測定方法と請求項２の測定方法とを組合わせた測定方法により、金属管１の内面側及び外面側に発生した浸炭層２，３の厚さｔ１，ｔ２を非破壊試験で正確に測定して内面側及び外面側の浸炭状況を一層正確に把握することができる。
【図面の簡単な説明】
【図１】本発明の実施の１形態の金属管の管軸方向の切断面図である。
【図２】図１の金属管の内面反射パルスの反射の説明図である。
【図３】図２の内面反射パルスの受信波形の説明図である。
【図４】図１の金属管の内面側浸炭層反射パルスの反射の説明図である。
【図５】図４の内面側浸炭層反射パルスの受信波形図である。
【図６】図１の金属管の端面図である。
【図７】図１の金属管の内面側浸炭層の厚さの測定結果の１例の説明図である。
【図８】図１の金属管の外面側浸炭層反射パルスの反射の説明図である。
【図９】図８の外面側浸炭層反射パルスの受信波形図である。
【図１０】図１の金属管の外面側浸炭層の厚さの測定結果の１例の説明図である。
【符号の説明】
１ 金属管
１′ 外面
１″ 内面
２ 内面側浸炭層
３ 外面側浸炭層
５ 送信側探触子
６ 受信側探触子
Ｆ1，Ｆ2 界面
Ｌ0，Ｌ1，Ｌ2 路程長
Ｖ0 内面反射パルス
Ｖ1 内面側浸炭層反射パルス
Ｖ2 外面側浸炭層反射パルス
Ｙ0 初期間隔
ｔ0，ｔ1，ｔ2 厚さ
θ 屈折角[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for detecting a carburized layer on the outer surface of a metal pipe such as a pipe in a furnace of a petrochemical plant and measuring its thickness by a nondestructive test.
[0002]
[Prior art]
Conventionally, heating furnaces such as ethylene production equipment, heavy oil desulfurization equipment, BTX equipment, etc., which are representative examples of petrochemical plants, pipes (heating furnace tubes, etc.) are heated from the outside and flow of high-temperature fluid inside. Therefore, it is made of a metal tube such as low alloy steel 9Cr-1MO, 2 (1/2) Cr-1MO, Incoloy 800, SUS321HTF.
[0003]
In these high-temperature heated metal tubes, carburized layers are formed on the inner and outer surfaces of the tube by use, and the layers gradually become thicker and deteriorate. It is necessary to monitor the presence / absence and its thickness, and take measures such as replacing the pipe according to the result.
[0004]
By the way, since this kind of metal pipe is long and many are arranged in the plant etc., it is inspected in terms of inspection efficiency and cost to perform destructive inspection by cutting, grinding, etc. one by one. Is extremely uneconomical.
[0005]
Therefore, in the past, the carburization status of this type of metal tube was measured with a non-destructive inspection for the time being with an electromagnetic induction type carburizing meter, and based on the results, the occurrence of carburized layers was detected by cutting, grinding, etc. when in doubt. And the thickness is measured.
[0006]
[Problems to be solved by the invention]
The conventional electromagnetic induction type carburization meter measures the carburization state by paying attention to the fact that the carburized layer is a magnetic layer, and the measurable metal tube is a non-magnetic metal tube such as Incoloy or SUS. However, measurement is not possible for magnetic metal pipes such as steel pipes.
[0007]
Moreover, it is difficult to know the thickness of the magnetic layer by carburization meter measurement, and it is also difficult to measure metal pipes with non-uniform inner diameters such as extruded pipes with fins inside and welded parts. is there.
[0008]
That is, conventionally, the occurrence of a carburized layer such as a magnetic tube or a tube having a non-uniform inner diameter cannot be known by a nondestructive test, and the thickness of the carburized layer is not limited to a magnetic tube or a nonmagnetic tube. There is a problem that cannot be known by non-destructive inspection.
[0009]
The present invention is capable of detecting the occurrence of carburized layers on the outer surface and measuring the thickness of these types of metal tubes, such as petrochemical plants, regardless of whether they are magnetic tubes or non-magnetic tubes, by nondestructive testing. The challenge is to make it.
[0010]
[Means for Solving the Problems]
To solve the above problems ,Book Invention Become a base In the method for detecting the carburized layer, a transmitting probe and a receiving probe for an ultrasonic oblique flaw detection test are provided at intervals on the outer surface of the metal tube,
The ultrasonic wave transmission method is used to measure the reception level and path length of ultrasonic waves that are emitted from the transmitter probe, reflected from the tube surface of a metal tube, etc., and received as reflected pulses by the receiver probe. And
After setting the interval between both probes to the initial interval so that the reception level of the largest internal reflection pulse reflected by the inner surface of the metal tube among the reflected pulses received by the receiving probe is maximized,
The distance between the two probes is narrower than the initial distance,
Detecting the presence or absence of reception of adjacent reflected pulses on the short path side of the internal reflection pulse reflected at the interface between the carburized layer on the inner surface side of the metal tube and the non-carburized layer on the outer surface side of the metal tube from this carburized layer;
The occurrence of a carburized layer on the inner surface side of the metal tube is detected by receiving the adjacent reflected pulse on the short path side.
[0011]
In this case, the ultrasonic wave obliquely emitted from the transmitting probe on the outer surface of the metal tube to the inner surface side by the ultrasonic V transmission method test is not only reflected on the inner surface of the metal tube but also carburized on the inner surface side. When a layer is generated, it is also reflected at the interface between the carburized layer and the non-carburized layer on the outer surface side.
[0012]
In these ultrasonic reflected pulses, the internal reflection pulse is significantly larger than the other reflection pulses, and the path length (propagation distance) of the reflection pulse at the interface between the carburized layer and the non-carburized layer on the inner surface side is increased. ) Is shorter than the path length of the internal reflection pulse.
[0013]
Therefore, when the probe on the reception side or the transmission side is first moved to a position where the reception level of the largest internal reflection pulse is maximized, and the interval between the two probes is set to the initial interval, the reception side probe Is located at the reception point (arrival point) of the internal reflection pulse.
[0014]
When the probe on the reception side or the transmission side is moved so that the interval is narrowed, a carburized layer is generated on the inner surface side, and there is a reflected pulse at the interface between this layer and the non-carburized layer on the outer surface side. Sometimes, this reflection pulse is received by the receiving probe as an adjacent reflection pulse on the short path side of the internal reflection pulse.
[0015]
Therefore, by receiving this adjacent reflection pulse on the short path side, it is possible to detect that a carburized layer is generated on the inner surface side of the metal tube by a nondestructive test in the field without cutting, grinding, In this case, even if the metal tube is a magnetic tube or a tube having a non-uniform inner diameter, it is possible to reliably detect the occurrence of the carburized layer on the inner surface side.
[0016]
Next ,Book Invention Become a base In the method of measuring the thickness of the carburized layer, after obtaining the path length of the internal reflection pulse with the interval between the transmitter probe and the receiver probe as the initial interval,
The distance between the two probes is narrower than the initial distance,
When the adjacent reflected pulse on the short path side of the internal reflection pulse reflected at the interface between the carburized layer on the inner surface side of the metal tube and the non-carburized layer on the outer surface side of the metal tube from the carburized layer is received, Obtain the path length at which the reception level of the adjacent reflected pulse is the largest as the path length of the inner carburized layer reflected pulse,
The thickness of the carburized layer generated on the inner surface side of the metal tube by multiplying 1/2 of the difference between the path length of the inner reflection pulse and the inner carburized layer reflection pulse by the coefficient of the cosine function value of the ultrasonic refraction angle. Measure.
[0017]
In this case, when the path length of the internal reflection pulse and the path length of the adjacent reflection pulse on the short path side are multiplied by the coefficient of the cosine function value of the refraction angle of the ultrasonic wave, each from the reflection surface to the outer surface of the metal tube Distance (length).
[0018]
The length obtained by multiplying 1/2 of the path length of the inner reflection pulse by the coefficient of the cosine function value is the thickness from the inner surface to the outer surface of the metal tube, and is the length of the adjacent reflection pulse on the short path side. The length obtained by multiplying 1/2 by the coefficient of the cosine function value is the thickness of the non-carburized layer on the outer surface side of the carburized layer of the metal pipe.
[0019]
Therefore, the thickness of the carburized layer on the inner surface side of the metal tube can be obtained from the length obtained by multiplying the difference between the path lengths of both reflected pulses by the coefficient of the cosine function value, and this can be measured. When the metal tube is a non-magnetic tube or the like, the thickness of the carburized layer on the inner surface side can be accurately measured.
[0020]
Next, the claim 1 In the method for detecting a carburized layer according to the present invention, after setting the interval between the probes to the initial interval,
The distance between the two probes is wider than the initial distance,
Adjacent on the long path side of the internal reflection pulse reflected on the inner surface of the metal tube, re-reflected on the outer surface, and re-reflected at the interface between the carburized layer on the outer surface side of the metal tube and the non-carburized layer on the inner surface side of the carburized layer Detects the presence or absence of reflection pulse reception,
The occurrence of a carburized layer on the outer surface side of the metal tube is detected by receiving the adjacent reflected pulse on the long path side.
[0021]
In this case, when a carburized layer is generated on the outer surface side of the metal tube, the inner-surface reflection pulse of the metal tube is re-reflected on the outer surface of the metal tube, and the re-reflection pulse is re-reflected on the outer surface side at the interface. The reflected pulse is received by the receiving probe as an adjacent reflected pulse on the long path side of the internal reflection pulse.
[0022]
Therefore, after setting the interval between both probes to the initial interval, when the receiving side probe or the transmitting side probe is moved so that the interval becomes wide, when the carburized layer is generated on the outer surface side After reflection on the inner surface of the metal tube and re-reflection on the outer surface, the reflected pulse of the ultrasonic wave reflected again at the interface between the carburized layer and the non-carburized layer on the inner surface side is adjacently reflected on the long path side of the inner surface reflection pulse. The pulse is received by the receiving probe as a pulse.
[0023]
Therefore, it is possible to detect in a nondestructive test that a carburized layer is generated on the outer surface side of the metal tube by receiving the adjacent reflected pulse on the long path side. In this case, the metal tube has a magnetic tube or an inner diameter. Even if it is a non-uniform pipe | tube, generation | occurrence | production of the carburized layer of an outer surface side can be detected reliably.
[0024]
Next, the claim 2 In the method for measuring the thickness of the carburized layer of the present invention, after obtaining the path length of the internal reflection pulse with the interval between the probes as the initial interval,
The distance between the two probes is wider than the initial distance,
The long path of the internal reflection pulse reflected at the inner surface of the metal tube and re-reflected at the outer surface, and re-reflected at the interface between the carburized layer on the outer surface side of the metal tube and the non-carburized layer on the inner surface side of the metal tube from the carburized layer. When the adjacent reflection pulse on the side is received, the path length at which the reception level of the adjacent reflection pulse on the long path side is the largest is obtained as the path length of the outer surface side carburized layer reflection pulse,
Carburized layer generated on the outer surface side of the metal tube by multiplying 1/2 of the difference between the path length of the outer surface side carburized layer reflection pulse and the inner surface reflection pulse by the coefficient of the cosine function value of the ultrasonic refraction angle. Measure the thickness.
[0025]
In this case, when the path length of the internal reflection pulse when the two probes are at the initial interval and the path length of the adjacent reflection pulse on the long path side are multiplied by the coefficient of the cosine function value of the ultrasonic refraction angle, The distance (length) from the inner surface to the outer surface of the metal tube is the distance obtained by adding the thickness of the carburized layer on the outer surface side to this distance.
[0026]
Therefore, the thickness of the carburized layer on the outer surface side of the metal tube is obtained from the length obtained by multiplying the difference of the path length between the adjacent reflected pulse on the long path side and the inner surface reflected pulse by the cosine coefficient. At this time, even if the metal tube is a non-magnetic tube or the like, the thickness of the carburized layer on the inner surface side can be accurately measured.
[0027]
Next, the claim 3 In the method for detecting a carburized layer according to the present invention, after setting the interval between the probes to the initial interval,
By detecting the occurrence of a carburized layer on the inner surface side of the metal tube, the distance between the two probes is made smaller than the initial distance,
Detecting the presence or absence of reception of adjacent reflected pulses on the short path side of the inner surface reflected pulse reflected at the interface between the carburized layer on the inner surface side of the metal tube and the non-carburized layer on the outer surface side of the metal tube from the carburized layer;
By receiving adjacent reflected pulses on the short path side, the occurrence of a carburized layer on the inner surface side of the metal tube is detected,
By detecting the occurrence of a carburized layer on the outer surface of the metal tube, the distance between both probes is made wider than the initial distance,
The long path of the internal reflection pulse reflected at the inner surface of the metal tube and re-reflected at the outer surface, and re-reflected at the interface between the carburized layer on the outer surface side of the metal tube and the non-carburized layer on the inner surface side of the metal tube from the carburized layer. Detect the presence or absence of reception of the adjacent reflection pulse on the side,
The occurrence of a carburized layer on the outer surface side of the metal tube is detected by receiving the adjacent reflected pulse on the long path side.
[0028]
So in this case Become a base Detection method and claims 1 By the detection method combined with this detection method, it is possible to accurately detect the occurrence of carburized layers on the inner surface side and the outer surface side of the metal tube by a non-destructive test.
[0029]
Next, the claim 4 In the method of measuring the thickness of the carburized layer, after obtaining the path length of the internal reflection pulse with the interval between the probes as the initial interval,
By measuring the thickness of the carburized layer generated on the inner surface side of the metal tube, the distance between the two probes is made smaller than the initial distance,
When the adjacent reflected pulse on the short path side of the inner surface reflected pulse reflected at the interface between the carburized layer on the inner surface side of the metal tube and the non-carburized layer on the outer surface side of the metal tube from the carburized layer is received, Obtain the path length at which the reception level of the adjacent reflection pulse is the largest as the path length of the inner side carburized layer reflection pulse,
The half of the difference between the path length of the inner reflection pulse and the inner carburized layer reflection pulse is multiplied by the coefficient of the cosine function value of the refraction angle of the ultrasonic wave, and the carburized layer generated on the inner surface side of the metal tube Measure the thickness,
By measuring the thickness of the carburized layer generated on the outer surface side of the metal tube, the distance between both probes is wider than the initial distance,
The long path of the internal reflection pulse reflected at the inner surface of the metal tube and re-reflected at the outer surface, and re-reflected at the interface between the carburized layer on the outer surface side of the metal tube and the non-carburized layer on the inner surface side of the metal tube from the carburized layer. When the adjacent reflection pulse on the side is received, the path length at which the reception level of the adjacent reflection pulse on the long path side is the largest is obtained as the path length of the outer surface side carburized layer reflection pulse,
The carburized layer generated on the outer surface side of the metal tube is multiplied by a factor of the cosine function value of the refraction angle of the ultrasonic wave by 1/2 of the difference between the path length of the outer surface side carburized layer reflected pulse and the inner surface reflected pulse. Measure the thickness.
[0030]
So in this case Become a base Measurement method and claims 2 By the measurement method combined with this measurement method, the thickness of the carburized layer generated on the inner surface side and the outer surface side of the metal tube can be accurately measured by nondestructive inspection.
[0031]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described with reference to FIGS.
FIG. 1 is a cross-sectional view in the tube axis direction (longitudinal direction) of a metal tube 1 such as a steel tube of a heating furnace of a BTX apparatus, and 2 in the figure is a carburized layer (inner surface side carburization generated on the inner surface side of the metal tube 1. Layer) 3 is a carburized layer (outer surface side carburized layer) generated on the outer surface side of the metal tube 1, and 4 is a non-carburized layer of the metal tube 1 between the carburized layers 2 and 3.
[0032]
Reference numerals 5 and 6 denote a transmission side probe and a reception side probe for an ultrasonic oblique angle flaw detection test provided on the outer surface 1 'of the metal tube 1 at intervals in the tube axis direction.
[0033]
Then, the inspection (maintenance inspection) of the carburization state of the metal pipe 1 is performed on site when the operation of the BTX apparatus is stopped and the metal pipe 1 is not heated.
[0034]
At this time, when the metal tube 1 is disposed vertically or horizontally in a heating furnace or the like and the probes 5 and 6 are one set, the probes 5 and 6 are indicated by solid lines and broken lines in FIG. The inspection is performed by sequentially moving the installation position of the metal tube 1 to the outer surface 1 ′ of each inspection portion of the metal tube 1.
[0035]
Next, specific inspection will be described.
First, by the ultrasonic V transmission method test using the probes 5 and 6, the detection of the inner side carburized layer 2 of the metal tube 1 and the measurement of the thickness are performed from the measurement of the reflection echo of the ultrasonic wave called the reflection pulse. Do.
[0036]
In this case, as shown in FIG. 2 which is an enlarged view of a part of FIG. 1, the interval between the probes 5 and 6 is first reflected by an ultrasonic reflected pulse (inner surface) reflected by the inner surface 1 ″ of the metal tube 1. Reflected pulse V 0 ) Initial interval Y that maximizes the reception level 0 Adjust and set to.
By the way, the transmitting probe 5 emits ultrasonic waves at a refraction angle θ in FIG.
[0037]
The refraction angle θ may be appropriately set to 30 °, 45 °, 60 °, 70 °, etc., but when various experiments are performed in consideration of a so-called U-tube or the like, it can be set to 45 °. It turned out to be most preferable in terms of versatility.
[0038]
In order to perform detection and measurement with high accuracy, the refraction angle θ is not a so-called nominal refraction angle, but an actual measurement angle measured in advance through experiments or the like.
[0039]
Further, the probes 5 and 6 are controlled and monitored for transmission / reception of ultrasonic waves by control and monitoring of the main unit (not shown).
[0040]
Then, the reflected pulse is measured by a known V transmission method, which is a modification of the tandem method of the oblique flaw detection method, by the arithmetic processing of the microcomputer of the main unit based on the transmission / reception result, and the sound velocity of the metal tube 1 and its super Based on the time measurement from emission (transmission) to reception of the sound wave, for example, the length of the propagation path of the ultrasonic wave from the transmission side probe 5 to the reception side probe 6 shown by the arrow line in FIG. The path length of the reflected pulse is obtained.
[0041]
Further, a waveform graph as shown in FIG. 3 showing the relationship between the path length and the reception level is displayed on a monitor display or the like.
[0042]
3 shows the internal reflection pulse V 0 Shows the screen display in the case of 0 1/2 of the forward or return path length is the beam path length W 0 The internal reflection pulse V with the beam path length as the horizontal axis and the echo height (%) in arbitrary units representing the reception level as the vertical axis 0 Is displayed on the screen.
[0043]
The ultrasonic wave emitted from the transmitting probe 5 is actually not only the inner surface 1 ″ but also the interface F between the carburized layers 2 and 3 and the non-carburized layer 4. 1 , F 2 Even though it is reflected, the internal reflection pulse V reflected from the internal surface 1 ″ 0 Is significantly higher than other pulses.
[0044]
Therefore, the initial interval Y 0 In the case of adjusting to, the largest reflected pulse displayed on either or both of the transmitting side probe 5 and the receiving side probe 6 is adjusted while adjusting the reception gain while observing the screen display of the monitor display. In order to reach the maximum level, that is, as shown in FIG. 0 Is moved little by little in the direction of approaching or moving away so as to repeat the transmission / reception of ultrasonic waves, and positioning is performed.
[0045]
In FIG. 3, the internal reflection pulse V 0 In order to make it easy to understand that the reception level of the signal is the maximum, the display is made so that it becomes 80% instead of 100% at the maximum level. Does not appear.
[0046]
Next, when the inner surface side carburized layer 2 is generated, the interface F between the carburized layer 2 and the non-carburized layer 4 on the outer surface side thereof. 1 However, the ultrasonic wave is reflected and the reflected pulse (adjacent reflected pulse V on the short path side) 1 ) Path length L 1 As shown in FIG. 4, the internal reflection pulse V 0 No way length L 0 Further, the length becomes shorter by a minute length of about several millimeters corresponding to the thickness of the carburized layer 2.
[0047]
Therefore, while looking at the display screen of the monitor display, adjusting one or both of the probes 5 and 6 while adjusting the reception gain, the distance between the probes 5 and 6 is set to the initial interval Y. 0 As shown in FIG. 5, the internal reflection pulse V of the display screen is gradually reduced. 0 Near the short path side of the adjacent reflected pulse V 1 Appear clearly separated and the reflected pulse V 1 Observe whether or not is detected.
[0048]
The reflected pulse V of the present invention 0 , V 1 Is a transverse wave pulse, but in fact, in addition to the transverse wave pulse, a reflected pulse called a pseudo echo such as a longitudinal wave pulse is also generated, and these reflected pulses may be displayed on the monitor display. is there.
[0049]
However, the reflected pulse V of the transverse wave 0 , V 1 And the reflected pulse of the pseudo echo can be distinguished from the display change when the interval between the probes 5 and 6 is changed, and the reflected pulse of the pseudo echo is the reflected pulse V 1 It occurs in the form of group pulses on the shorter path side.
[0050]
Therefore, in FIG. 5 and the like, the reflection pulse of the pseudo echo is omitted for easy understanding of the present invention.
[0051]
And the adjacent reflection pulse V 1 Is clearly separated and detected, the generation of the inner side carburized layer 2 is detected by this detection.
[0052]
Next, in this embodiment, in order to detect the thickness, the adjacent reflection pulse V 1 Set the interval between the probes 5 and 6 to the initial interval Y so that the 0 Narrower from Y 1 To.
[0053]
At this time, as is apparent from FIG. 0 No way length L 0 1/2 of W 0 Then, the cosine function value W 0 Cos θ is the thickness t from the inner surface 1 ″ to the outer surface 1 ′ of the metal tube 1 0 become.
[0054]
Further, as is apparent from FIG. 4, the adjacent reflected pulse V 1 No way length L 1 1/2 of W 1 Then, the cosine function value W 1 ・ Cosθ is interface F 1 To the outer surface (t 0 -T 1 )become.
[0055]
Therefore, the thickness t of the inner surface side carburized layer 2 1 Is the path length L 0 , L 1 ½ of the difference between the two and the coefficient K of the cosine function value cos θ of the refraction angle θ is obtained from the following equation 1 and measured.
[0056]
[Expression 1]
t 1 = ((L 0 -L 1 ) / 2) ・ K = (W 0 -W 1 ) ・ Cosθ
[0057]
And the thickness t of the inner surface side carburized layer 2 in FIG. 6 showing the end face of the metal tube 1 1 When the accuracy of the measured value obtained from the equation (1) was confirmed, the value actually verified by cutting (validation thickness) and the value (measured thickness) obtained from the equation (1) were as shown in FIG. The result of each ◯ mark was obtained.
[0058]
According to FIG. 7, for example, the measured thickness obtained from the equation (1) with respect to the actual verification thickness of 0.5 mm is in the range of +0.3 mm to -0.2 mm, and there is little error. Thickness t of inner side carburized layer 2 of metal tube 1 1 It was confirmed that it can be measured with high accuracy by nondestructive testing.
[0059]
Next, detection of the outer side carburized layer 3 of the metal tube 1 using the probes 5 and 6 and measurement of the thickness will be described.
[0060]
By the way, in the case of the metal pipe 1 or the like, the carburized layer is generated on the inner surface side due to the flow of the high-temperature fluid in the pipe, and heat is applied from the outside of the tube such as the heating furnace tube as well as the inner surface side. A carburized layer (outer surface side carburized layer 3) is also generated on the side.
[0061]
And also when detecting the presence or absence of this outer surface side carburized layer 3, first, the inner surface reflection pulse V 0 , The installation interval of the probes 5 and 6 is set to the initial interval Y. 0 Set to.
[0062]
Next, when the outer surface side carburized layer 3 is generated, a part of the ultrasonic wave emitted from the probe 5 is an interface F between the outer surface side carburized layer 3 and the non-carburized layer 4 as shown in FIG. 2 , Interface F between the non-carburized layer 4 and the inner side carburized layer 2 1 However, most of the light is reflected by the inner surface 1 ″ of the metal tube 1.
[0063]
And interface F 2 The ultrasonic waves reflected by the outer surface 1 of the metal tube 1 ′ At the interface F 2 Reflection and exterior 1 ′ Is repeatedly attenuated until the probe 6 is reached.
[0064]
Also, interface F 1 Reflected by the ultrasonic wave (carburized layer reflection pulse V on the inner surface side) 1 ) Is the inner surface reflection pulse V of the outer surface 1 '. 0 Is received at a point closer to the probe 5 than the arrival point.
[0065]
On the other hand, the ultrasonic wave reflected by the inner surface 1 ″ is reflected by the inner surface reflection pulse V. 0 Therefore, the internal reflection pulse V is significantly larger than the other reflection pulses. 0 Is re-reflected by the outer surface 1 'and the interface F 2 And re-reflect Inside Internal reflection pulse V of surface 1 ″ 0 Can be received as a sufficiently large reflected pulse at a point distant from the point reached by the path length (distance) corresponding to the thickness of the outer surface side carburized layer 3.
[0066]
And this reflection pulse is the internal reflection pulse V 0 Adjacent reflection pulse V on the long path side of 2 The probes 5 and 6 are set at the initial interval Y. 0 And then moving the probe 5 or 6 away from the probe 5 or 6 while adjusting the reception gain while viewing the display screen of the monitor display. As shown in FIG. 9, the internal reflection pulse V of the display screen of the monitor display is gradually increased from the initial interval. 0 Adjacent reflected pulse V near the long path side of 2 Appear clearly separated and the reflected pulse V 2 Observe whether or not is detected.
[0067]
And the adjacent reflection pulse V 2 Is clearly separated and detected, the occurrence of the outer surface side carburized layer 3 is detected.
[0068]
Next, in order to detect the thickness of the outer side carburized layer 3, the adjacent reflected pulse V 2 So that the distance between the probes 5 and 6 is the initial distance Y. 0 Wide from Y 2 To.
[0069]
At this time, the adjacent reflection pulse V 2 Total path length L from emission to reception 2 As is clear from FIG. 8, the internal reflection pulse V 0 No way length L 0 (= 2 · W 0 = 2W 2a ), Outer surface 1 ′ Re-reflects at interface F 2 The length of the road that reflects again at 2W 2b L added to 0 + 2 · W 2b (= 2 (W 2a + W 2b ))become.
[0070]
And the thickness t of the metal tube 1 0 Is (L 0 / 2) ・ cosθ (= W 0 ・ Cosθ = W 2a Cos θ) and the thickness t of the outer surface side carburized layer 3 2 Is (2.W 2b / 2) ・ cosθ (= W 2b Cos θ). ,
[0071]
Therefore, the thickness t of the outer surface side carburized layer 3 2 Is the path length L 2 , L 1 Is obtained by the following equation (2) and multiplied by a coefficient K (= cos θ).
[0072]
[Expression 2]
t 2 = ((L 2 -L 0 ) / 2) ・ K = (W 2 -W 0 ) ・ Cosθ ＝ W 2b ・ Cosθ
[0073]
And thickness t of the outer surface side carburized layer 3 in FIG. 2 When the accuracy of the measured value obtained from the equation 2 is confirmed, the result of FIG. 10 similar to FIG. 7 is obtained. As is apparent from FIG. 10, the outer side carburized layer 3 is obtained from the equation 2. Thickness t 2 Can be obtained and measured accurately.
[0074]
Therefore, the detection of the occurrence of the inner surface side carburized layer 2 and the outer surface side carburized layer 3 of the metal tube 1 and the measurement of the thickness thereof by the ultrasonic V transmission method test using the probes 5 and 6 are performed. Can be reliably and accurately performed without cutting or grinding.
[0075]
And there is no restriction | limiting by the material, inner surface shape, etc. of the metal pipe 1 like the case where the conventional electromagnetic induction type carburization meter is used, regardless of a magnetic pipe or a non-magnetic pipe, any metal pipe can be used. In addition, the occurrence of the carburized layers 2 and 4 can be detected accurately and economically efficiently in a nondestructive test in the field, and the thickness thereof can be measured.
[0076]
In addition, since the presence or absence of the carburized layer can be easily determined from the display screen, and the thickness can be easily obtained from the equations (1) and (2), ultrasonic waves can be used for detecting the carburized layers 2 and 3 and measuring the thickness. There is also an advantage that a high degree of skill in reflection echo is not required.
[0077]
By the way, depending on the metal pipe, only the inner surface side carburized layer 2 or the outer surface side carburized layer 3 may be detected to detect the occurrence of the carburized layer or to measure the thickness thereof. Alternatively, a plurality of sets of probes 5 and 6 may be used to detect and measure a plurality of metal tubes or to detect and measure a plurality of locations of one metal tube at a time.
[0078]
Furthermore, the refraction angle θ of the ultrasonic waves transmitted and received by the probes 5 and 6 is not limited to 45 °, and similarly, even at various angles such as 30 °, 45 °, 60 °, and 70 °. Of course, it can be applied.
[0079]
The present invention can be applied to the detection of the occurrence of carburized layers of various metal tubes to which heat is applied and the measurement of the thickness thereof.
[0080]
【The invention's effect】
The present invention has the following effects.
First, Become a base In the case of the detection method, first, the receiving side or transmitting side probes 6 and 5 are connected to the metal tube 1. Inside Internal reflection pulse V of surface 1 ″ 0 Move to a position where the reception level of the probe becomes maximum, and the interval between the probes 5 and 6 is set to the initial interval 0 When set to, the receiving side probe 6 is subjected to the internal reflection pulse V. 0 Next, when the probes 6 and 5 on the receiving side or the transmitting side are moved so that the interval between them is narrowed, a carburized layer 2 is generated on the inner surface side. Interface F with the non-carburized layer 4 on the outer surface side 1 When there is a reflection pulse at, this reflection pulse is converted to the internal reflection pulse V. 0 Adjacent reflected pulse V on the short path side 1 Can be received by the receiving side probe 6.
[0081]
And the adjacent reflected pulse V on the short path side 1 , The occurrence of the carburized layer 2 on the inner surface side of the metal tube 1 can be detected by on-site nondestructive testing without cutting or grinding. In this case, the metal tube 1 is magnetic. Even if it is a pipe or a pipe with an uneven inner diameter, it is possible to reliably detect the occurrence of the carburized layer 2 on the inner surface side and grasp the carburization status.
[0082]
Also, Become a base In the case of the measurement method, when detecting the carburized layer 2 on the inner surface side, the reflected pulse V 0 , V 1 No way length L 0 , L 1 1/2 of the difference between (W 0 -W 1 ) Multiplied by the coefficient of the cosine function value of the refraction angle θ (W 0 -W 1 ) From cos θ, the thickness t of the carburized layer 2 of the metal tube 1 1 At this time, even if the metal tube 1 is a non-magnetic tube or the like, the thickness of the carburized layer 2 on the inner surface side can be accurately measured to more accurately grasp the carburization status. Based on the result, necessary repairs such as tube replacement can be appropriately performed.
[0083]
And , Claims 1 In the case of this detection method, the interval between the probes 5 and 6 is set to the initial interval Y. 0 When the probe 6 or 5 on the reception side or the transmission side is moved so that the interval is widened, the inner surface 1 of the metal tube 1 is formed when the carburized layer 3 is generated on the outer surface side. ″ Reflected once, outer surface 1 ′ After re-reflection, the interface F between the carburized layer 3 and the non-carburized layer 4 on the inner surface side thereof 2 The reflected pulse of the ultrasonic wave reflected again by the internal reflection pulse V 0 Adjacent reflection pulse V on the long path side of 2 Can be received by the receiving side probe 6.
[0084]
Therefore, the adjacent reflected pulse V on the long path side is 2 , The occurrence of the carburized layer 3 on the outer surface side of the metal tube 1 can be detected by on-site nondestructive testing without cutting, grinding, etc. In this case, the metal tube 1 is a magnetic tube. Even if the pipe has a non-uniform inner diameter, it is possible to reliably detect the carburization state by detecting the occurrence of the carburized layer 3 on the outer surface side.
[0085]
Claims 2 In the case of this measurement method, when detecting the carburized layer 3 on the outer surface side, the adjacent reflected pulse V on the long path side is detected. 2 And internal reflection pulse V 0 Path length L with 2 , L 0 1/2 of the difference between ((W 2 -W 0 ) Multiplied by the coefficient of the cosine function value of the refraction angle θ (W 2 -W 0 ) Thickness t of the carburized layer 3 on the outer surface side of the metal tube 1 from cos θ 2 At this time, even if the metal tube 1 is a non-magnetic tube or the like, the thickness of the carburized layer 3 on the outer surface side can be accurately measured to more accurately grasp the carburization status. .
[0086]
Next, the claim 3 For the detection method of Become a base Detection method and claims 1 By the detection method combined with this detection method, the occurrence of the carburized layers 2 and 3 on the inner surface side and the outer surface side of the metal tube 1 can be reliably detected by a non-destructive test in the field, and the carburization status can be grasped.
[0087]
Claims 4 For the measurement method of Become a base Measurement method and claims 2 The thickness t of the carburized layers 2 and 3 generated on the inner surface side and the outer surface side of the metal tube 1 by the measurement method combined with 1 , T 2 Can be accurately measured in a non-destructive test, and the carburization status of the inner surface side and the outer surface side can be grasped more accurately.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view in the tube axis direction of a metal tube according to an embodiment of the present invention.
FIG. 2 is an explanatory diagram of reflection of an inner surface reflection pulse of the metal tube of FIG. 1;
3 is an explanatory diagram of a reception waveform of the internal reflection pulse of FIG. 2;
4 is an explanatory diagram of reflection of an inner surface side carburized layer reflection pulse of the metal tube of FIG. 1; FIG.
5 is a reception waveform diagram of the inner-side carburized layer reflection pulse of FIG. 4;
6 is an end view of the metal tube of FIG. 1. FIG.
7 is an explanatory diagram of an example of the measurement result of the thickness of the inner surface side carburized layer of the metal pipe of FIG. 1;
8 is an explanatory diagram of reflection of an outer surface side carburized layer reflection pulse of the metal tube of FIG. 1; FIG.
9 is a reception waveform diagram of the outer-surface carburized layer reflection pulse of FIG. 8. FIG.
10 is an explanatory diagram of an example of a measurement result of a thickness of an outer surface side carburized layer of the metal pipe of FIG. 1;
[Explanation of symbols]
1 Metal tube
1 'exterior
1 ″ inner surface
2 Inside carburized layer
3 Carburized layer on the outer surface
5 Transmitter probe
6 Receiver probe
F 1 , F 2 interface
L 0 , L 1 , L 2 Path length
V 0 Internal reflection pulse
V 1 Inner side carburized layer reflection pulse
V 2 External side carburized layer reflection pulse
Y 0 Initial interval
t 0 , T 1 , T 2 thickness
θ Refraction angle

Claims (4)

加熱炉，反応塔の配管等の熱が加わる金属管の外面側の浸炭層の発生を検出する浸炭層の検出方法において、
前記金属管の外面に間隔をとって超音波斜角探傷試験用の送信側探触子と受信側探触子とを設け、
超音波Ｖ透過法の試験により、前記送信側探触子から出射されて前記金属管の管面等で反射し、前記受信側探触子に反射パルスとして受信された超音波の受信レベル及び路程長を測定し、
前記受信側探触子が受信した反射パルスのうちの前記金属管の内面で反射した最も大きい内面反射パルスの受信レベルが最大になるように、前記両探触子の間隔を初期間隔に設定した後、
前記両探触子の間隔を前記初期間隔から広くし、
前記金属管の内面で反射して外面で再反射し、前記金属管の外面側の浸炭層と，該浸炭層より前記金属管の内面側の非浸炭層との界面で再々反射した前記内面反射パルスの長路程側の隣接反射パルスの受信の有無を検出し、
前記長路程側の隣接反射パルスの受信により、前記金属管の外面側の浸炭層の発生を検出する
ことを特徴とする浸炭層の検出方法。In the method for detecting a carburized layer, which detects the occurrence of a carburized layer on the outer surface side of a metal pipe to which heat is applied, such as a heating furnace and piping of a reaction tower,
A transmission side probe and a reception side probe for ultrasonic oblique flaw detection tests are provided at intervals on the outer surface of the metal tube,
The ultrasonic reception level and path length of the ultrasonic wave emitted from the transmitting probe and reflected by the tube surface of the metal tube and received as a reflected pulse by the receiving probe by the ultrasonic V transmission test. Measure the length
The interval between the probes is set to the initial interval so that the reception level of the largest internal reflection pulse reflected by the inner surface of the metal tube among the reflection pulses received by the reception side probe is maximized. rear,
The interval between the two probes is increased from the initial interval,
Reflecting on the inner surface of the metal tube and re-reflecting on the outer surface, the inner surface reflection reflected again on the interface between the carburized layer on the outer surface side of the metal tube and the non-carburized layer on the inner surface side of the metal tube from the carburized layer. Detect the presence or absence of reception of adjacent reflected pulses on the long path side of the pulse,
The detection of the carburized layer on the outer surface side of the metal pipe is detected by reception of the adjacent reflected pulse on the long path side. 加熱炉，反応塔の配管等の熱が加わる金属管の外面側に発生した浸炭層の厚さを測定する浸炭層の厚さの測定方法において、
前記金属管の外側面に間隔をとって超音波斜角探傷試験用の送信側探触子と受信側探触子とを設け、
超音波Ｖ透過法の試験により、前記送信側探触子から出射されて前記金属管の管面等で反射し、前記受信側探触子に反射パルスとして受信された超音波の受信レベル及び路程長を測定し、
前記受信側探触子が受信した反射パルスのうちの前記金属管の内面で反射した最も大きい内面反射パルスの受信レベルが最大になるように、前記両探触子の間隔を初期間隔にして内面反射パルスの路程長を求めた後、
前記両探触子の間隔を前記初期間隔から広くし、
前記金属管の内面で反射して外面で再反射し、前記金属管の外面側の浸炭層と，該浸炭層より前記金属管の内面側の非浸炭層との界面で再々反射した前記内面反射パルスの長路程側の隣接反射パルスを受信したときに、前記長路程側の隣接反射パルスの受信レベルが最も大きくなる路程長を外面側浸炭層反射パルスの路程長として求め、
前記外面側浸炭層反射パルスの路程長と前記内面反射パルスの路程長との差の１／２に超音波の屈折角の余弦関数値の係数を乗算して前記金属管の外面側に発生した浸炭層の厚さを測定する
ことを特徴とする浸炭層の厚さの測定方法。In the method of measuring the thickness of the carburized layer, which measures the thickness of the carburized layer generated on the outer surface side of the metal pipe to which heat is applied such as the heating furnace and the piping of the reaction tower,
A transmission side probe and a reception side probe for ultrasonic oblique flaw detection tests are provided at intervals on the outer surface of the metal tube,
The ultrasonic reception level and path length of the ultrasonic wave emitted from the transmitting probe and reflected by the tube surface of the metal tube and received as a reflected pulse by the receiving probe by the ultrasonic V transmission test. Measure the length
Among the reflected pulses received by the receiving side probe, the inner surface is set with the interval between the probes as an initial interval so that the reception level of the largest inner surface reflected pulse reflected by the inner surface of the metal tube is maximized. After determining the path length of the reflected pulse,
The interval between the two probes is increased from the initial interval,
Reflecting on the inner surface of the metal tube and re-reflecting on the outer surface, the inner surface reflection reflected again on the interface between the carburized layer on the outer surface side of the metal tube and the non-carburized layer on the inner surface side of the metal tube from the carburized layer. When the adjacent reflected pulse on the long path side of the pulse is received, the path length at which the reception level of the adjacent reflected pulse on the long path side becomes the largest is obtained as the path length of the outer surface side carburized layer reflected pulse,
Generated on the outer surface side of the metal tube by multiplying 1/2 of the difference between the path length of the outer surface side carburized layer reflection pulse and the path length of the inner surface reflection pulse by the coefficient of the cosine function value of the ultrasonic refraction angle. A method for measuring the thickness of a carburized layer, characterized by measuring the thickness of the carburized layer. 加熱炉，反応塔の配管等の熱が加わる金属管の内面側及び外面側の浸炭層の発生を検出する浸炭層の検出方法において、
前記金属管の外面に間隔をとって超音波斜角探傷試験用の送信側探触子と受信側探触子とを設け、
超音波Ｖ透過法の試験により、前記送信側探触子から出射されて前記金属管の管面等で反射し、前記受信側探触子に反射パルスとして受信された超音波の受信レベル及び路程長を測定し、
前記受信側探触子が受信した反射パルスのうちの前記金属管の内面で反射した最も大きい内面反射パルスの受信レベルが最大になるように、前記両探触子の間隔を初期間隔に設定した後、
前記金属管の内面側の浸炭層の発生の検出により、前記両探触子の間隔を前記初期間隔から狭くし、
前記金属管の内面側の浸炭層と，該浸炭層より前記金属管の外面側の非浸炭層との界面で反射した前記内面反射パルスの短路程側の隣接反射パルスの受信の有無を検出し、
前記短路程側の隣接反射パルスの受信により、前記金属管の内面側の浸炭層の発生を検出し、
前記金属管の外面側の浸炭層の発生の検出により、前記両探触子の間隔を前記初期間隔から広くし、
前記金属管の内面で反射して外面で再反射し、前記金属管の外面側の浸炭層と，該浸炭層より前記金属管の内面側の非浸炭層との界面で再々反射した前記内面反射パルスの長路程側の隣接反射パルスの受信の有無を検出し、
前記長路程側の隣接反射パルスの受信により、前記金属管の外面側の浸炭層の発生を検出する
ことを特徴とする浸炭層の検出方法。In the detection method of the carburized layer for detecting the occurrence of the carburized layer on the inner surface side and the outer surface side of the metal tube to which heat is applied such as the heating furnace and the piping of the reaction tower,
A transmission side probe and a reception side probe for ultrasonic oblique flaw detection tests are provided at intervals on the outer surface of the metal tube,
The ultrasonic reception level and path length of the ultrasonic wave emitted from the transmitting probe and reflected by the tube surface of the metal tube and received as a reflected pulse by the receiving probe by the ultrasonic V transmission test. Measure the length
The interval between the probes is set to the initial interval so that the reception level of the largest internal reflection pulse reflected by the inner surface of the metal tube among the reflection pulses received by the reception side probe is maximized. rear,
By detecting the occurrence of a carburized layer on the inner surface side of the metal tube, the interval between the probes is reduced from the initial interval,
The presence or absence of reception of adjacent reflected pulses on the short path side of the inner surface reflected pulse reflected at the interface between the carburized layer on the inner surface side of the metal tube and the non-carburized layer on the outer surface side of the metal tube from the carburized layer is detected. ,
By detecting the adjacent reflected pulse on the short path side, the occurrence of a carburized layer on the inner surface side of the metal tube is detected,
By detecting the occurrence of a carburized layer on the outer surface side of the metal tube, the interval between the probes is increased from the initial interval,
Reflecting on the inner surface of the metal tube and re-reflecting on the outer surface, the inner surface reflection reflected again on the interface between the carburized layer on the outer surface side of the metal tube and the non-carburized layer on the inner surface side of the metal tube from the carburized layer. Detect the presence or absence of reception of adjacent reflected pulses on the long path side of the pulse,
The detection of the carburized layer on the outer surface side of the metal pipe is detected by reception of the adjacent reflected pulse on the long path side. 加熱炉，反応塔の配管等の熱が加わる金属管の内面側及び外面側に発生した浸炭層の厚さを測定する浸炭層の厚さの測定方法において、
前記金属管の外面に間隔をとって超音波斜角探傷試験用の送信側探触子と受信側探触子とを設け、
超音波Ｖ透過法の試験により、前記送信側探触子から出射されて前記金属管の管面等で反射し、前記受信側探触子に反射パルスとして受信された超音波の受信レベル及び路程長を測定し、
前記受信側探触子が受信した反射パルスのうちの前記金属管の内面で反射した最も大きい内面反射パルスの受信レベルが最大になるように、前記両探触子の間隔を初期間隔にして内面反射パルスの路程長を求めた後、
前記金属管の内面側に発生した浸炭層の厚さの測定により、前記両探触子の間隔を前記初期間隔より狭くし、
前記金属管の内面側の浸炭層と，該浸炭層より前記金属管の外面側の非浸炭層との界面で反射した前記内面反射パルスの短路程側の隣接反射パルスを受信したときに、前記短路程側の隣接反射パルスの受信レベルが最も大きくなる路程長を内面側浸炭層反射パルスの路程長として求め、
前記内面反射パルスの路程長と前記内面側浸炭層反射パルスの路程長との差の１／２に超音波の屈折角の余弦関数値の係数を乗算して前記金属管の内面側に発生した浸炭層の厚さを測定し、
前記金属管の外面側に発生した浸炭層の厚さの測定により、前記両探触子の間隔を前記初期間隔より広くし、
前記金属管の内面で反射して外面で再反射し、前記金属管の外面側の浸炭層と，該浸炭層より前記金属管の内面側の非浸炭層との界面で再々反射した前記内面反射パルスの長路程側の隣接反射パルスを受信したときに、前記長路程側の隣接反射パルスの受信レベルが最も大きくなる路程長を外面側浸炭層反射パルスの路程長として求め、
前記外面側浸炭層反射パルスの路程長と前記内面反射パルスの路程長との差の１／２に超音波の屈折角の余弦関数値の係数を乗算して前記金属管の外面側に発生した浸炭層の厚さを測定する
ことを特徴とする浸炭層の厚さの測定方法。In the method for measuring the thickness of the carburized layer, which measures the thickness of the carburized layer generated on the inner surface side and outer surface side of the metal tube to which heat is applied, such as the heating furnace and the piping of the reaction tower,
A transmission side probe and a reception side probe for ultrasonic oblique flaw detection tests are provided at intervals on the outer surface of the metal tube,
The ultrasonic reception level and path length of the ultrasonic wave emitted from the transmitting probe and reflected by the tube surface of the metal tube and received as a reflected pulse by the receiving probe by the ultrasonic V transmission test. Measure the length
Among the reflected pulses received by the receiving side probe, the inner surface is set with the interval between the probes as an initial interval so that the reception level of the largest inner surface reflected pulse reflected by the inner surface of the metal tube is maximized. After determining the path length of the reflected pulse,
By measuring the thickness of the carburized layer generated on the inner surface side of the metal tube, the distance between the probes is made smaller than the initial distance,
When the adjacent reflected pulse on the short path side of the inner surface reflected pulse reflected at the interface between the carburized layer on the inner surface side of the metal tube and the non-carburized layer on the outer surface side of the metal tube from the carburized layer, Obtain the path length at which the reception level of the adjacent reflected pulse on the short path side is the largest as the path length of the inner side carburized layer reflected pulse,
Generated on the inner surface side of the metal tube by multiplying 1/2 of the difference between the path length of the inner surface reflection pulse and the path length of the inner surface side carburized layer reflection pulse by the coefficient of the cosine function value of the ultrasonic refraction angle. Measure the thickness of the carburized layer,
By measuring the thickness of the carburized layer generated on the outer surface side of the metal tube, the distance between the probes is wider than the initial distance,
Reflecting on the inner surface of the metal tube and re-reflecting on the outer surface, the inner surface reflection reflected again on the interface between the carburized layer on the outer surface side of the metal tube and the non-carburized layer on the inner surface side of the metal tube from the carburized layer. When the adjacent reflected pulse on the long path side of the pulse is received, the path length at which the reception level of the adjacent reflected pulse on the long path side becomes the largest is obtained as the path length of the outer surface side carburized layer reflected pulse,
Generated on the outer surface side of the metal tube by multiplying 1/2 of the difference between the path length of the outer surface side carburized layer reflection pulse and the path length of the inner surface reflection pulse by the coefficient of the cosine function value of the ultrasonic refraction angle. A method for measuring the thickness of a carburized layer, characterized by measuring the thickness of the carburized layer.
JP12682099A 1999-05-07 1999-05-07 Method for detecting carburized layer and measuring thickness thereof Expired - Lifetime JP4363699B2 (en)

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