JPH0384451A - Eddy current flaw detecting method - Google Patents
Eddy current flaw detecting methodInfo
- Publication number
- JPH0384451A JPH0384451A JP22133689A JP22133689A JPH0384451A JP H0384451 A JPH0384451 A JP H0384451A JP 22133689 A JP22133689 A JP 22133689A JP 22133689 A JP22133689 A JP 22133689A JP H0384451 A JPH0384451 A JP H0384451A
- Authority
- JP
- Japan
- Prior art keywords
- test material
- magnetic
- longitudinal direction
- flaw detection
- magnetization
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
- 238000000034 method Methods 0.000 title description 18
- 238000012360 testing method Methods 0.000 claims abstract description 84
- 239000000463 material Substances 0.000 claims abstract description 80
- 230000005291 magnetic effect Effects 0.000 claims abstract description 59
- 238000001514 detection method Methods 0.000 claims abstract description 46
- 230000005415 magnetization Effects 0.000 claims abstract description 38
- 239000004020 conductor Substances 0.000 claims description 9
- 230000003313 weakening effect Effects 0.000 claims description 5
- 230000005381 magnetic domain Effects 0.000 abstract description 9
- 230000035699 permeability Effects 0.000 abstract description 8
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical group [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 abstract description 4
- 229920006395 saturated elastomer Polymers 0.000 abstract description 3
- 230000005389 magnetism Effects 0.000 abstract description 2
- 230000003247 decreasing effect Effects 0.000 abstract 1
- 229910000831 Steel Inorganic materials 0.000 description 8
- 239000010959 steel Substances 0.000 description 8
- 230000001360 synchronised effect Effects 0.000 description 8
- 230000007423 decrease Effects 0.000 description 6
- 238000010586 diagram Methods 0.000 description 5
- 230000035945 sensitivity Effects 0.000 description 4
- 238000007796 conventional method Methods 0.000 description 3
- 230000007547 defect Effects 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 230000005284 excitation Effects 0.000 description 2
- 230000004907 flux Effects 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 230000005674 electromagnetic induction Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000000605 extraction Methods 0.000 description 1
- 239000003302 ferromagnetic material Substances 0.000 description 1
- 239000003292 glue Substances 0.000 description 1
- 239000003550 marker Substances 0.000 description 1
- 238000012544 monitoring process Methods 0.000 description 1
- 238000009659 non-destructive testing Methods 0.000 description 1
- 230000035515 penetration Effects 0.000 description 1
Landscapes
- Investigating Or Analyzing Materials By The Use Of Magnetic Means (AREA)
Abstract
Description
本発明は、棒鋼や鋼管等の試験材を非破壊検査する際に
好適な、渦流探傷方法に関する。The present invention relates to an eddy current flaw detection method suitable for nondestructively testing test materials such as steel bars and steel pipes.
棒鋼や鋼管等の試験材を、渦流探傷方法を採用して非破
壊検査する場合がある。この渦流探傷方法においては、
試験コイルを用いて電磁誘導により試験材に渦流を発生
させ、傷のある部分でその渦流が変化することを検出し
て探傷する。
試験材が鋼等の強磁性体の場合には、試験材の磁気的特
性の不均一や、その磁気的特性の不均一により、透磁率
が一定とならないことが原因して雑音が発生する場合が
ある。
このような雑音は、探傷信号の信号／雑音（Ｓ／Ｎ）を
低下させ、検出感度、精度を低下させてしまうため、何
らかの対策が必要である。
そこで、この雑音を防止する対策として、従来、磁気飽
和装置が用いられている。この磁気飽和装置は、例えば
第８図に示すように、円環状の直流磁気飽和コイル１０
を有しており、探傷する際には、まず、試験材、例えば
パイプ材１２がそのコイル１０中央部を貫通するように
、且つ、当該パイプ材１２の両端方向に隔離し°て設け
る０次いで、この磁気飽和コイル１０に直流励磁電流を
通電してパイプ材１２を直流磁化させる。この場合、電
流の向きと磁束の向きは例えば第８図中に示す関係にな
る。
今、磁気飽和コイル１０による磁化を強くすれば、磁気
的性質の差異によらずにパイプ材１２の全ての部分を磁
気飽和状態として、どの部分においても透磁率を−様な
値μ０にすることができる。
即ち、直流磁化する前の試験材においては、例えば第９
図（Ａ）に示すように、微小な磁区の磁極の向きが揃っ
ておらず、全体として互いに打消し合う状態となってい
るが、直流磁気飽和により、第９図（Ｂ）に示すように
ほとんどの微小磁区の磁極が長手方向に向くようになる
。これにより、透磁率は−様な値μＧとなるように見え
る。
このように、磁気飽和した状態で、第８図のように、２
つの試験コイル（検出コイルとも称する）１４に交流信
号を入力して発振させ、２つの試験コイル１４に出力差
があるときに欠陥があると判定する。There are cases where test materials such as steel bars and steel pipes are subjected to non-destructive testing using the eddy current testing method. In this eddy current flaw detection method,
A test coil is used to generate a vortex in the test material through electromagnetic induction, and flaws are detected by detecting changes in the vortex at the flawed area. When the test material is a ferromagnetic material such as steel, noise may occur due to non-uniform magnetic properties of the test material or non-uniform magnetic permeability due to non-uniform magnetic properties. There is. Such noise lowers the signal/noise (S/N) of the flaw detection signal and lowers the detection sensitivity and accuracy, so some kind of countermeasure is required. Therefore, as a measure to prevent this noise, a magnetic saturation device has conventionally been used. This magnetic saturation device includes, for example, an annular DC magnetic saturation coil 10 as shown in FIG.
When performing flaw detection, first, a test material, for example, a pipe material 12, is provided so that it passes through the center of the coil 10, and is spaced apart toward both ends of the pipe material 12. A DC excitation current is applied to this magnetic saturation coil 10 to magnetize the pipe material 12 with DC magnetization. In this case, the direction of current and the direction of magnetic flux have the relationship shown in FIG. 8, for example. Now, if the magnetization by the magnetic saturation coil 10 is strengthened, all parts of the pipe material 12 will be brought into a magnetic saturation state regardless of differences in magnetic properties, and the magnetic permeability in any part will be set to a negative value μ0. I can do it. That is, in the test material before DC magnetization, for example, the 9th
As shown in Figure (A), the directions of the magnetic poles of minute magnetic domains are not aligned, and they cancel each other out as a whole, but due to DC magnetic saturation, as shown in Figure 9 (B), The magnetic poles of most of the microdomains become oriented in the longitudinal direction. As a result, the magnetic permeability appears to be a −-like value μG. In this way, in a magnetically saturated state, as shown in Figure 8, 2
An alternating current signal is input to two test coils (also referred to as detection coils) 14 to cause them to oscillate, and when there is an output difference between the two test coils 14, it is determined that there is a defect.
【発明が達成しようとする課１１１
しかしながら、前記のように磁気飽和装置を用いて渦流
探傷を行う際に、直流励磁電流を増加させた場合、その
雑音は低下するが、例えば第１０図の渦流探傷による記
録計の指示のように、雑音の低下と共に傷信号の低下も
生じ、第１１図のようにＳ／Ｎが低下してしまうため検
出能力が低下するという問題点が生じる。なお、前記記
録計では、例えば直径１１４．ｌｕ、厚さ２１１１の鋼
管に人工傷として直径２１１の穴を深さ５０％まで開け
たものを探傷した結果を記録しである。
本発明は、前記従来の問題点を解消すべくなされたもの
で、雑音の減少及びＳ／Ｎの向上を合わせて図り、欠陥
検出能力を向上させ得る渦流探傷方法を提供することを
課題とする。
【課題を達成するための手段】
本発明は、試験材をその＾平方向に直交する方向に交流
磁化すると共に、その磁気力を徐々に弱めて、前記試験
材の前記直交する方向への磁気力を弱める工程と、前記
磁気力が弱められた試験材を、その長手方向に直流磁化
して磁気飽和させて、渦流探傷する工程とを含むことに
より、前記課題を達成したものである。
又、本発明において、試験材の交流磁化を、試験材をそ
の長手方向に直交する方向から挾むように交流磁化コイ
ル付鉄心を対向させて設け、当該コイルに交流電流を通
電することにより行うことができる。
又、本発明において、試験材の交流磁化を、試験材の長
手方向端部に電極を設けて、当該電極間に交流電圧を印
加して試験材に通電することにより行うことができる。
更に又、本発明において、中空の試験材の交流磁化を、
当該試験材の中空孔中に導体棒を貫通させ、当該導体棒
に交流電流を通電することにより行うことができる。Problem to be achieved by the invention 111 However, when performing eddy current flaw detection using a magnetic saturation device as described above, when the DC excitation current is increased, the noise decreases; As indicated by a recorder during flaw detection, as the noise decreases, so does the flaw signal, and as shown in FIG. 11, the S/N ratio decreases, resulting in a problem that the detection ability decreases. Note that the recorder has a diameter of 114 mm, for example. This is a record of the results of flaw detection on a steel pipe with a thickness of 2111 mm, in which a hole with a diameter of 211 mm was drilled to a depth of 50% as an artificial flaw. The present invention has been made to solve the above-mentioned conventional problems, and an object of the present invention is to provide an eddy current flaw detection method that can reduce noise and improve S/N, and improve defect detection ability. . [Means for Achieving the Object] The present invention magnetizes a test material with alternating current in a direction perpendicular to its horizontal direction, and gradually weakens the magnetic force, thereby increasing the magnetism of the test material in the orthogonal direction. The above object has been achieved by including a step of weakening the force, and a step of subjecting the test material whose magnetic force has been weakened to direct current magnetization in the longitudinal direction to magnetically saturate it and performing eddy current flaw detection. In addition, in the present invention, AC magnetization of the test material can be performed by placing iron cores with AC magnetization coils facing each other so as to sandwich the test material from a direction perpendicular to the longitudinal direction thereof, and applying an AC current to the coils. can. Furthermore, in the present invention, alternating current magnetization of the test material can be performed by providing electrodes at longitudinal ends of the test material and applying an alternating current voltage between the electrodes to energize the test material. Furthermore, in the present invention, the AC magnetization of the hollow test material is
This can be carried out by passing a conductor rod through the hollow hole of the test material and passing an alternating current through the conductor rod.
前出第８図に示したようにパイプ材１２等の試験材を直
流磁気飽和させると、前出第９図（Ｂ）に示すように、
微小磁区のほとんどにおいて、その磁極は試験材１２の
長手方向を向くが、一部の微小磁区では長手方向を向か
ず、磁極の向きに不均一が生じる。直流磁化電流を増加
した場合、この不均一な磁極の向きによる磁気的特性、
透磁率の不均一が起因してＳ／Ｎが低下してしまう。
そこで、発明者は試験材の磁気的特性や透磁率を均一化
するべく種々検討した。その結果、予め、例えば交流電
流を試験材の長手方向に流してその電流を徐々に弱くす
ることにより、試験材の長手方向に直交する方向への磁
力を弱くすることを着想した。
即ち、磁化する前の試験材においては、第１図（Ａ）に
示すように、各微小磁区において磁極の向きが全体とし
て互いに打ち消し合うように並んでいたものが、前記直
交する方向に交流磁化すると共に、その磁化する力を徐
々に弱めた場合、第１図（Ｂ）に示すように、当該直交
する方向への磁気力が弱まる。
前記直交する方向への磁気力が弱められた試験材を、そ
の長手方向に直流磁化して磁気飽和させれば、第１図（
Ｃ）に示すように、当該微小磁区の磁極の向きはほぼ完
全に長手方向に揃うこととなる。これにより、試験材の
磁気的特性や透磁率が均一化する。
従って、磁気的特性や透磁率の均一化することから、雑
音が減少する。直流磁化を強めて傷信号を大きくしても
雑音が増大しないため、Ｓ／Ｎが向上し、高精度な探傷
が可能になる。
なお、前記試験材を、長手方向に直交する方向に交流磁
化する際には、例えば第２図（Ａ）に示すように、試験
材１２を、その長平方向に直交する方向から挾むように
交流磁化コイル１６付鉄心１７を対向させて設け、当該
コイル１６に交流電流を通電することにまり交播磁界を
試験材１２に供給して交流磁化することができる。この
ようにすれば、試験材の所望箇所を所望の強さで交流磁
化することができる。なお、この交流磁化法は、極間法
という。
又、例えば第２図（Ｂ）に示すように、試験材１２の長
手方向端部に電極１８を設けて、当該電極１８間に交流
電圧を印加して試験材１２に交流電流を通電し、試験材
１２自身で磁束を発生させて交流磁化することができる
。このようにすれば、電極１８のみを設けて交流磁化で
きるため、比較的簡単な設備、手順で済み、経済性が高
い、なお、この交流磁化法を軸通電法という。
又、例えば第２図（Ｃ）に示すように、試験材１２が中
空のものである場合には、その中空孔中に導体棒２０を
貫通させ、当該導体棒２０の両端に設けたｔ＃ｌ１８等
を介して導体棒２０に交流電流を通電し、試験材１２を
交流磁化することができる。このようにすれば、試験材
の内側から外側へかけて確実に交流磁化することができ
る。なお、この交流磁化法を電流貫通法という。
又、交流磁化する際に各を極間に印加する電圧、電流に
商用周波数のものを用いるようにすれば特別な電源回路
がいらないため、装置の全体構成が簡略化できる。When the test material, such as the pipe material 12, is subjected to direct current magnetic saturation as shown in Fig. 8 above, as shown in Fig. 9 (B) above,
In most of the minute magnetic domains, the magnetic poles are oriented in the longitudinal direction of the test material 12, but in some minute magnetic domains, the magnetic poles are not oriented in the longitudinal direction, resulting in non-uniformity in the direction of the magnetic poles. When the DC magnetizing current is increased, the magnetic properties due to the uneven orientation of the magnetic poles,
The S/N decreases due to non-uniform magnetic permeability. Therefore, the inventor conducted various studies to make the magnetic properties and magnetic permeability of the test materials uniform. As a result, we came up with the idea of weakening the magnetic force in the direction orthogonal to the longitudinal direction of the test material by, for example, passing an alternating current in the longitudinal direction of the test material and gradually weakening the current. In other words, in the test material before magnetization, as shown in FIG. 1(A), the magnetic poles in each minute magnetic domain were aligned so that they canceled each other as a whole, but instead of being magnetized by AC magnetization in the orthogonal direction. At the same time, when the magnetizing force is gradually weakened, the magnetic force in the perpendicular direction is weakened, as shown in FIG. 1(B). If the test material whose magnetic force in the perpendicular direction is weakened is magnetically saturated by direct current magnetization in its longitudinal direction, the result shown in Fig. 1 (
As shown in C), the magnetic poles of the minute magnetic domains are almost completely aligned in the longitudinal direction. This makes the magnetic properties and magnetic permeability of the test material uniform. Therefore, since the magnetic properties and permeability are made uniform, noise is reduced. Even if the DC magnetization is strengthened to increase the flaw signal, noise does not increase, so the S/N ratio improves and highly accurate flaw detection becomes possible. When the test material is subjected to AC magnetization in a direction perpendicular to the longitudinal direction, for example, as shown in FIG. Iron cores 17 with coils 16 are provided to face each other, and by passing an alternating current through the coils 16, an alternating magnetic field can be supplied to the test material 12 to cause alternating current magnetization. In this way, a desired portion of the test material can be magnetized with alternating current with a desired intensity. Note that this alternating current magnetization method is called the pole spacing method. For example, as shown in FIG. 2(B), an electrode 18 is provided at the longitudinal end of the test material 12, and an alternating current voltage is applied between the electrodes 18 to supply an alternating current to the test material 12. The test material 12 itself can generate magnetic flux and be magnetized with alternating current. In this way, AC magnetization can be performed by providing only the electrode 18, which requires relatively simple equipment and procedures, and is highly economical.This AC magnetization method is referred to as the axial energization method. For example, as shown in FIG. 2(C), when the test material 12 is hollow, the conductor rod 20 is passed through the hollow hole, and the t# provided at both ends of the conductor rod 20 is inserted. An alternating current is applied to the conductor rod 20 through the conductor rod 118, etc., and the test material 12 can be magnetized with alternating current. In this way, alternating current magnetization can be reliably carried out from the inside to the outside of the test material. Note that this alternating current magnetization method is called a current penetration method. Further, if commercial frequency voltages and currents are applied between the poles during AC magnetization, a special power supply circuit is not required, and the overall configuration of the device can be simplified.
以下、図面を参照して本発明の実施例を詳細に説明する
。
この実施例は、第３図に示すような構成の渦流探傷装置
である。
第３図に示すように、この渦流探傷装置には、探傷前に
、予め試験材１２に電［１１８を介して交流電流を通電
し、その長手方向に直交する方向に交流磁化するための
交流磁化部２１と、前記試験材１２へ探傷信号を送信し
、受信するための一対の試験コイル（検出コイル）１４
と、各試験コイル１４をその回路中に含み、各コイル１
４の出力ずれ×から生じる不平衡から傷信号を出力する
ブリッジ２２と、当該ブリッジ２２へ適切な周波数の交
流電圧を印加するための発振器２４と、傷以外の要因に
より生じるブリッジの不平衡を自動的に修正するための
自動平衡器２６と、前記ブリッジ２２の傷信号出力を増
幅するための増幅器２８と、増幅された傷信号をモニタ
するためのメータ３０と、出力された傷信号中に含まれ
る試験材１２の搬送振動により生ずる雑音を位相回折に
よる検波して除去するための同期検波器３２と、当該同
期検波器３２の位相を任意に推移させるための移相器３
４と、検波後の傷信号を第４図に示すように、Ｘ方向を
傷成分としＹ方向をノイズ成分として、例えばリサージ
ュ図形で表示するための陰極線管（ＣＲＴ＞３６と、検
波された傷信号から低い周波数の雑音を除去するための
フィルタ３８と、低周波数の雑音が除去された傷信号か
ら低レベルの雑音（ベースノイズ）を除去するためのり
ジエクション４０と、雑音除去後の！Ｉ傷信号ら、傷が
所定値以上大きいか否かを判断して、警報を出力する警
報器４２とを備える。
なお、リジェクション４０から構成される装置号は、記
録装置に記録したり、選別装置に入力して試験材１２の
マーキングを行うようにすることができる。又、図示し
ないが、この渦流探傷装置には前出第８図に示した直流
磁気飽和装置が設けられている。
以下、実施例の作用を説明する。
まず、試験材１２に交流通電して長手方向に直交する方
向への交流磁化を行う、この際、流す電流は徐々に低下
させて、前出第２図（Ｂ）に示すように、前記試験材１
２の前記直交する方向への磁化力を弱めていく、なお、
通電する電流は商用周波数とすることができる。
この交流通電により、前出第１図（Ｂ）に示すように、
試験材１２の長手方向に直交する方向への磁気力が減少
し、各磁区の磁気力は長手方向に揃う、この場合に、通
電する交流電流は例えば３Ａとすることができ、その後
、例えば５秒間の間で３ＡからＯＡに徐々に電流を低下
させていくことができる。
次いで、交流磁化により前記磁気力が弱められた試験材
１２に対して直流磁気飽和コイル１０で直流磁化し、発
振器２４からブリッジ２２に交流電圧を供給する。試験
コイル１４を含むブリッジ２２は試験材１２の傷の存在
を平衡のくずれから検出して傷信号を出力する。増幅器
２８はこのブリッジ２２の出刃傷信号を適切な大きさに
増幅する。増幅された出刃傷信号は同期検波器３２へ入
力され、当該同期検波器３２はその大刃傷信号を移相器
３４から加えられる制御信号によって位相回折して検波
し、傷信号以外の雑音を抑制する。
更に、フィルタ３８はその検波後の傷信号の低周波数雑
音を除去し、リジェクション４０は、傷信号以外の低レ
ベル雑音を除去する。
この探傷装置のオペレータは、前記移相器３４により同
期検波器３２の制御信号の位相を調整すると共に、ＣＲ
Ｔ３６により、傷信号に含まれる傷成分とノイズ成分を
ベクトル的に観測し、傷の大きさを把握できる。なお、
この探傷装置の出力信号は記録装置や選別装置あるいは
マーカに伝達されて、後の工程の指令となる。
次に、本発明を採用して探傷した結果を説明する。
この場合、同期検波器の位相を変えて、傷成分（ｘｒｌ
ｊ、分）をチャート高さとしている。又、比較のため、
試験材を交流磁化せずに渦流探傷（従来方法）した結果
を第５図に示す、又、本発明方法で探傷した結果を第６
図に示す。
いずれの場合も試験材は外径３１．８１の鋼管であり、
人工傷として幅０．３■、深さ０．１５旧、長さ２５ｉ
ｎのノツチを形成しである。又、試験コイル１４への印
加電流は３Ａであり、その周波数は８に七であった。
従来方法においては、探傷結果は、第５図に示すように
なった。この場合、試験材には直径１■の貫通したドリ
ルホールも合わせて形成した。同期検波器の位相が変化
するに従って、前記ドリルホールについては精度良くチ
ャート高さとして傷成分が表わされているが、前記ノツ
チについては、傷成分が全体的にベースノイズに隠れて
しまい、精度の良い探傷結果が得られていない、又、感
度はＳ／Ｎで２４−２．４＝２１．６ｄＢであった。
これに対して、本発明方法により探傷した結果は第６図
に示すようになった。この場合、試験材には深さ０．２
１１１のノツチを設けたが、位相の変化によって、この
０．２１１のノツチのみならず、０．１５＋１１１のノ
ツチも、ベースノイズに隠れることなく精度良くチャー
ト高さに表われた。又、感度はＳ／Ｎで２７−１．５＝
２５．５ｄＢであり、感度が向上していることが確認さ
れる。
又、試験材の探傷を行っている際に、探傷装置の同期検
波器の位相が零度における、（Ｓ信号のチャート高さの
例を第７図に示す、この第７図は、探傷開始から終了ま
での一連の傷信号をチャート高さで示している。第７図
において、リジェクションのレベルを２０１１１にして
も、０．２１と０゜１５ｎｎのノツチの検出結果は得ら
れ、精度良く探傷できることがわかる。又、第７図のよ
うに警報レベルを設け、それ以上の信号が生じた場合警
報を出力するようにできる。
なお、前記実施例においては、試験材として鋼管等を例
示したが、本発明により探傷可能な試験材はこれに限定
されず、他の、例えばＩｉｇ、線材でも同様に実施する
ことができる。
又、前記実施例においては、試験材を交流磁化する方法
として、直接試験材に交流電流を通電する方法（軸通電
法）を用いていたが、交流磁化する方法はこれに限定さ
れるものではなく、他の例えば前出第２図（Ａ）、（Ｃ
）に示した極間法や電流貫通法を用いることができる。Embodiments of the present invention will be described in detail below with reference to the drawings. This embodiment is an eddy current flaw detection device having a configuration as shown in FIG. As shown in FIG. 3, this eddy current flaw detection device is equipped with an alternating current (AC) system in which an alternating current is applied to the test material 12 through an electric wire 118 before flaw detection, and AC magnetization is performed in a direction perpendicular to the longitudinal direction of the test material 12. a magnetization section 21 and a pair of test coils (detection coils) 14 for transmitting and receiving flaw detection signals to the test material 12;
and each test coil 14 in its circuit, each coil 1
A bridge 22 that outputs a flaw signal due to the unbalance caused by the output deviation × of 4, an oscillator 24 that applies an AC voltage of an appropriate frequency to the bridge 22, and an automatic bridge unbalance that occurs due to factors other than flaws. an automatic balancer 26 for correcting flaw signals; an amplifier 28 for amplifying the flaw signal output of the bridge 22; a meter 30 for monitoring the amplified flaw signal; A synchronous detector 32 for detecting and removing noise generated by the transport vibration of the test material 12 by phase diffraction, and a phase shifter 3 for arbitrarily shifting the phase of the synchronous detector 32.
4, the flaw signal after detection is shown in Fig. 4, with the flaw component in the X direction and the noise component in the Y direction. A filter 38 for removing low-frequency noise from the signal, a glue extraction 40 for removing low-level noise (base noise) from the signal from which the low-frequency noise has been removed, and a filter 40 for removing low-level noise (base noise) from the signal after the noise removal. It is equipped with an alarm device 42 that outputs an alarm after determining whether or not the damage is larger than a predetermined value. can be inputted to mark the test material 12. Although not shown, this eddy current flaw detection device is equipped with the DC magnetic saturation device shown in FIG. 8 above. The operation of the example will be explained. First, alternating current is applied to the test material 12 to cause alternating current magnetization in a direction perpendicular to the longitudinal direction. At this time, the applied current is gradually reduced and ), the test material 1
2, the magnetizing force in the orthogonal direction is weakened,
The current applied may be at a commercial frequency. Due to this alternating current energization, as shown in Figure 1 (B) above,
The magnetic force in the direction perpendicular to the longitudinal direction of the test material 12 decreases, and the magnetic force of each magnetic domain becomes uniform in the longitudinal direction. In this case, the applied alternating current can be, for example, 3 A, and then, for example, The current can be gradually reduced from 3A to OA in seconds. Next, the test material 12 whose magnetic force has been weakened by AC magnetization is subjected to DC magnetization by the DC magnetic saturation coil 10, and an AC voltage is supplied from the oscillator 24 to the bridge 22. The bridge 22 including the test coil 14 detects the presence of flaws in the test material 12 from imbalance and outputs a flaw signal. The amplifier 28 amplifies the cut signal of the bridge 22 to an appropriate magnitude. The amplified knife flaw signal is input to the synchronous detector 32, which detects the large knife flaw signal through phase diffraction using a control signal applied from the phase shifter 34, thereby suppressing noise other than the flaw signal. do. Further, the filter 38 removes low frequency noise from the detected flaw signal, and the rejection 40 removes low level noise other than the flaw signal. The operator of this flaw detection apparatus adjusts the phase of the control signal of the synchronous detector 32 using the phase shifter 34, and
By T36, the flaw component and the noise component included in the flaw signal can be observed vectorwise, and the size of the flaw can be grasped. In addition,
The output signal of this flaw detection device is transmitted to a recording device, a sorting device, or a marker, and becomes a command for a subsequent process. Next, the results of flaw detection using the present invention will be explained. In this case, by changing the phase of the synchronous detector, the flaw component (xrl
j, minutes) is the chart height. Also, for comparison,
Figure 5 shows the results of eddy current flaw detection (conventional method) without alternating current magnetization of the test material, and Figure 6 shows the results of flaw detection using the method of the present invention.
As shown in the figure. In both cases, the test material was a steel pipe with an outer diameter of 31.81 mm.
As an artificial wound, the width is 0.3cm, the depth is 0.15cm, and the length is 25cm.
A notch of n is formed. Further, the current applied to the test coil 14 was 3A, and its frequency was 7 in 8. In the conventional method, the flaw detection results were as shown in FIG. In this case, a drill hole with a diameter of 1 cm was also formed in the test material. As the phase of the synchronous detector changes, the flaw component is accurately expressed as the chart height for the drill hole, but for the notch, the flaw component is entirely hidden by the base noise, resulting in poor accuracy. Good flaw detection results were not obtained, and the sensitivity was 24-2.4=21.6 dB in terms of S/N. On the other hand, the results of flaw detection using the method of the present invention are shown in FIG. In this case, the test material has a depth of 0.2
A notch of 0.111 was provided, but due to the change in phase, not only the notch of 0.211 but also the notch of 0.15+111 was accurately displayed in the chart height without being hidden by the base noise. Also, the sensitivity is S/N = 27-1.5
25.5 dB, confirming that the sensitivity has improved. Also, when performing flaw detection on a test material, when the phase of the synchronous detector of the flaw detection device is zero, an example of the chart height of the (S signal) is shown in Fig. 7. A series of flaw signals up to the end is shown by chart height. In Fig. 7, even if the rejection level is set to 20111, detection results for notches of 0.21 and 0°15 nn can be obtained, and flaw detection can be performed with high accuracy. In addition, an alarm level can be set as shown in Fig. 7, and an alarm can be output when a signal higher than the level is generated.In addition, in the above embodiment, steel pipes etc. were used as the test material. The test material that can be tested by the present invention is not limited to this, and the test can be similarly performed with other materials such as Iig and wire rods.In addition, in the above embodiments, as a method of alternating current magnetization of the test material, direct Although a method of passing an alternating current through the test material (axial energization method) was used, the method of alternating current magnetization is not limited to this, and other methods such as those shown in Fig. 2 (A) and (C) may also be used.
) can be used.
以上説明した通り、本発明によれば、渦流探傷する際の
雑音が減少して、Ｓ／Ｎが向上するため、欠陥検出能力
の向上が図れる。従って、生産工程における生産材や製
品の信頼性、品質の向上を図ることができる等の優れた
効果が得られる。As described above, according to the present invention, noise during eddy current flaw detection is reduced and S/N is improved, so that defect detection ability can be improved. Therefore, excellent effects such as improving the reliability and quality of production materials and products in the production process can be obtained.
第１図は、本発明の詳細な説明するための、試験材にお
ける磁化前後における微小磁区磁極の向きを示す平面図
、
第２図（Ａ）〜（Ｃ）は、交流磁化の方法例を示す側面
図、
第３図は、本発明の実施例に係る渦流探傷装置の構成を
示す、一部斜視図を含むブロック図、第４図は、前記装
置で表示される傷信号図形の例を示す平面図、
第５図は、従来方法により探傷した結果例を示す線図、
第６図、第７図は、本発明法により探傷した結果例を示
す線図、
第８図は、従来の探傷装置の構成例を示す断面図及び関
面図、
第９図は、前記探傷装置で磁化した場合の各磁区におけ
る磁極の向きの変化を示す平面図、第１０図は、直流励
磁電流を変化させた場合の傷信号と雑音の例を示す線図
、
第１１図は、同じ＜Ｓ／Ｈの例を示す線図である。
１０・・・磁気飽和コイル、
１２・・・試験材、 １４・・・試験コイル、
６・・・交流磁化コイル、
８・・・電極、
１・・・交流磁化部、
２・・・ブリッジ、
６・・・自動平衡器、
２・・・同期検波器、
４・・・位相器、
６・・・陰極線管（ＣＲＴ）
８・・・フィルタ、
０・・・リジェクション。
１７・・・鉄心、
２０・・・導体棒、
２４・・・発振器、FIG. 1 is a plan view showing the orientation of minute magnetic domain magnetic poles before and after magnetization in a test material for detailed explanation of the present invention, and FIG. 2 (A) to (C) show an example of the method of AC magnetization. FIG. 3 is a block diagram including a partial perspective view showing the configuration of an eddy current flaw detection device according to an embodiment of the present invention, and FIG. 4 shows an example of a flaw signal figure displayed by the device. A plan view, FIG. 5 is a diagram showing an example of the results of flaw detection using the conventional method, FIGS. 6 and 7 are diagrams showing an example of the results of flaw detection using the method of the present invention, and FIG. A cross-sectional view and a relationship diagram showing an example of the configuration of the device, FIG. 9 is a plan view showing changes in the direction of magnetic poles in each magnetic domain when magnetized by the flaw detection device, and FIG. Figure 11 is a diagram showing an example of the flaw signal and noise in the case of <S/H. 10... Magnetic saturation coil, 12... Test material, 14... Test coil,
6...AC magnetization coil, 8...electrode, 1...AC magnetization section, 2...bridge, 6...automatic balancer, 2...synchronous detector, 4...phase shifter , 6... Cathode ray tube (CRT) 8... Filter, 0... Rejection. 17... Iron core, 20... Conductor bar, 24... Oscillator,
Claims (4)
すると共に、その磁気力を徐々に弱めて、前記試験材の
前記直交する方向への磁気力を弱める工程と、 前記磁気力が弱められた試験材を、その長手方向に直流
磁化して磁気飽和させ、渦流探傷する工程とを含むこと
を特徴とする渦流探傷方法。(1) A step of AC magnetizing a test material in a direction perpendicular to its longitudinal direction and gradually weakening the magnetic force to weaken the magnetic force of the test material in the perpendicular direction; and the step of weakening the magnetic force. An eddy current flaw detection method comprising the steps of subjecting the test material to direct current magnetization in its longitudinal direction to magnetic saturation and performing eddy current flaw detection.
をその長手方向に直交する方向から挾むように交流磁化
コイル付鉄心を対向させて設け、当該コイルに交流電流
を通電することにより行うことを特徴とする渦流探傷方
法。(2) In claim 1, the alternating current magnetization of the test material is carried out by providing cores with alternating current magnetization coils facing each other so as to sandwich the test material from a direction perpendicular to the longitudinal direction of the test material, and applying an alternating current to the coil. An eddy current flaw detection method characterized by:
の長手方向端部に電極を設けて、当該電極間に交流電圧
を印加して試験材に通電することにより行うことを特徴
とする渦流探傷方法。(3) Claim 1 is characterized in that the alternating current magnetization of the test material is performed by providing electrodes at the longitudinal ends of the test material and applying an alternating current voltage between the electrodes to energize the test material. Eddy current flaw detection method.
当該試験材の中空孔中に導体棒を貫通させ、当該導体棒
に交流電流を通電することにより行うことを特徴とする
渦流探傷方法。(4) In claim 1, the AC magnetization of the hollow test material is
An eddy current flaw detection method characterized by passing a conductor rod through a hollow hole of the test material and passing an alternating current through the conductor rod.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP22133689A JPH0384451A (en) | 1989-08-28 | 1989-08-28 | Eddy current flaw detecting method |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP22133689A JPH0384451A (en) | 1989-08-28 | 1989-08-28 | Eddy current flaw detecting method |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH0384451A true JPH0384451A (en) | 1991-04-10 |
Family
ID=16765211
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP22133689A Pending JPH0384451A (en) | 1989-08-28 | 1989-08-28 | Eddy current flaw detecting method |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH0384451A (en) |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS51115697A (en) * | 1975-04-03 | 1976-10-12 | Kanetsuu Kogyo Kk | Eliminating method of residual magnetism |
| JPS5246532A (en) * | 1975-10-11 | 1977-04-13 | Omron Tateisi Electronics Co | Control circuitfor cmbustion system |
| JPS61264251A (en) * | 1985-05-17 | 1986-11-22 | Hitachi Metals Ltd | Eddy current flaw inspecting method and its device |
-
1989
- 1989-08-28 JP JP22133689A patent/JPH0384451A/en active Pending
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS51115697A (en) * | 1975-04-03 | 1976-10-12 | Kanetsuu Kogyo Kk | Eliminating method of residual magnetism |
| JPS5246532A (en) * | 1975-10-11 | 1977-04-13 | Omron Tateisi Electronics Co | Control circuitfor cmbustion system |
| JPS61264251A (en) * | 1985-05-17 | 1986-11-22 | Hitachi Metals Ltd | Eddy current flaw inspecting method and its device |
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