JP2005024295A - Leakage flux flaw detection test - Google Patents

Leakage flux flaw detection test Download PDF

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Publication number
JP2005024295A
JP2005024295A JP2003187284A JP2003187284A JP2005024295A JP 2005024295 A JP2005024295 A JP 2005024295A JP 2003187284 A JP2003187284 A JP 2003187284A JP 2003187284 A JP2003187284 A JP 2003187284A JP 2005024295 A JP2005024295 A JP 2005024295A
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Japan
Prior art keywords
magnetic
magnetization
magnetic flux
flaw detection
leakage
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JP2003187284A
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Japanese (ja)
Inventor
Takahiro Koshihara
敬弘 腰原
Hiroharu Kato
宏晴 加藤
Akio Nagamune
章生 長棟
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Jfe Steel Kk
Jfeスチール株式会社
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Priority to JP2003187284A priority Critical patent/JP2005024295A/en
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Abstract

<P>PROBLEM TO BE SOLVED: To provide a leakage flux flaw detection method for easily setting the magnetization level and magnetization conditions, even if the steel type and the plate thickness change. <P>SOLUTION: When a ferromagnetic body metal specimen is magnetized by a magnetizer, a leakage flux signal, corresponding to the same position on the specimen, is measured under conditions, where the magnetization levels of the specimens are essentially different, by a plurality of magnetic sensors, where the installation positions are changed along the magnetization direction of the magnetizer; measurement results are computed, and defects are determined according to the computation result, and the magnetization conditions of the specimen in flaw detection are set by measuring the magnetic field near the surface of the specimen at a position, where at least one magnetic sensor is arranged, in advance, so that the magnetization conditions of the specimen in flaw detection are set; and a position where a sensor in charge of other magnetization levels is arranged, becomes the position, where a measured magnetic field becomes a desired value by measuring a magnetic field near the surface of the specimen magnetized by the magnetization conditions set. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【0001】
【発明の属する技術分野】本発明は、漏洩磁束探傷法における被検体の磁化条件および磁気センサ配置位置の調整方法に関し、更に詳しくは一つの磁化器に対して複数のセンサを配置し、各センサで得られる信号を演算し欠陥の検出性能を向上させる漏洩磁束探傷法におけるものに関する。
【0002】
【従来の技術】漏洩磁束探傷法は強磁性体を磁化したとき、内部欠陥から磁束が漏洩することを利用して探傷を行うもので、近年、簡便な構造で欠陥の検出性能に優れたものとして、磁化器の磁化方向に沿って設置位置を変えた複数の磁気センサにより、被検査体の磁化レベルが実質的に異なるような条件下で、被検体上の同一位置に対応する漏洩磁束信号を測定し、測定結果同士を演算し、その演算結果より欠陥判定を行うことを特徴とするものが開発され、特許文献1に記載されている。
【0003】
図4は特許文献1記載の漏洩磁束探傷法を説明する図で、図において21は鋼板、22、23は搬送ロール、24は磁気探傷装置、25は磁化器、26a、26bは磁気センサ、27は信号処理装置を示す。
【0004】
磁気探傷装置24は、磁化器25、磁気センサ26a、26b、信号処理装置27を有し、磁気センサ26aが磁化器25の磁化方向中心近傍に配置され、磁気センサ26bは磁化方向中心近傍から距離Sだけ離れた位置に配置されている。
【0005】
磁気センサ26aは鋼板21を挟んで反対側の磁化器25の磁極センタ上に配置され、強い磁化レベル条件(強磁化条件)による検出信号が得られ、一方、磁化器25の磁極センタから距離Sだけ離れている磁気センサ26bでは弱い磁化レベル条件(弱磁化条件)による検出信号が得られる。
【0006】
磁気センサ26a、26bは鋼板21の上方に間隔Lを有して配置され、かつ鋼板21の全面が検出できるように両者が板幅方向に直線的に配置される。鋼板21は搬送ローラ22、23により、ほぼ一定の速度Vで搬送される。
【0007】
信号処理装置27は、磁気センサ26a、26bからの検出信号をAD変換し、フィルタリング処理した後欠陥を判定するために必要な演算を行うもので、磁気センサ26a、26bの位置的なズレを解消して鋼板の同一個所における両者の信号が演算されるように処理する。
【0008】
特許文献1記載の発明では、磁化器から複数の磁気センサの各々までの距離を変化させることにより、鋼板に対する磁化条件を強弱に変化させた場合と同じ効果を得ている。
【0009】
磁化器25による鋼板21の磁化条件は、強磁化条件となる磁気センサ26aの検出信号が欠陥信号と雑音磁束信号の両者が大きくなる飽和磁化条件の近傍であり、且つ弱磁化条件となる磁気センサ26bの検出信号として、磁化レベルの弱化による欠陥信号レベルの変化が、雑音磁束信号レベルの変化度よりも大きくなるような磁化条件であって、更に磁気センサ26aの検出信号における雑音磁束信号が磁気センサ26bの検出信号においても存在するような磁化条件に設定される。
【0010】
【特許文献1】
特許第3266128号公報
【0011】
【発明が解決しようとする課題】
上述したように、一つの磁化器に対し、距離を変えて複数のセンサを配置し、各センサからの信号を演算し、欠陥検出性能を向上させる漏洩磁束探傷方法においては、複数のセンサで検出される雑音磁束信号の大きさがほぼ一定となるように被検体の磁化条件を調整する方法が用いられている。
【0012】
また、予め、標準サンプルを準備し、標準欠陥の欠陥信号を探傷して磁化条件を決定する方法を適用することも可能であるが、いずれも磁気センサの欠陥信号や雑音磁束信号などの検出信号が所定のレベルとなるように磁化条件を調整する方法のため、磁気センサの検出信号レベルに影響を及ぼす被検査体の鋼種、板厚などが変わり磁化条件を変更する際、標準サンプルを用いて適切な検出信号レベルが得られる磁化条件を決定するという手順が必要で、煩雑であった。
【0013】
そこで、本発明は被検体表面近傍での磁場を測定することにより、鋼種、板厚が変わった場合でも、容易に適切な磁化条件が設定可能な漏洩磁束探傷方法を提供することを課題とする。
【0014】
【課題を解決するための手段】
本発明者等は、検出信号のレベルが鋼板の内部磁束密度に依存すること及び鋼板を磁化した場合、磁場と磁束密度の関係がB−Hカーブとして求められることに着想を得て、磁化器による被検体の磁化条件を、被検体表面近傍で測定される磁場が所望の値、すなわち、鋼板の内部磁束密度を適正な検出信号レベルが得られるように調整する漏洩磁束探傷方法を完成した。
【0015】
本発明の課題は以下の手段により解決される。
【0016】
1.強磁性体金属被検体を磁化器により磁化し、被検体に存在する欠陥に起因して発生する漏洩磁束を、被検体の表面に配置した磁気センサで測定することにより、欠陥の検出を行う漏洩磁束探傷方法であって、強磁性体金属被検体を磁化器により磁化し、磁化器の磁化方向に沿って設置位置を変えた複数の磁気センサにより、被検査体の磁化レベルが実質的に異なるような条件下で、被検査体上の同一位置に対応する漏洩磁束信号を測定し、測定結果同士を演算し、その演算結果より欠陥判定を行う漏洩磁束探傷法において、少なくとも一の磁気センサが配置される位置における被検体表面近傍の磁場を予め測定することにより探傷時の被検査体の磁化条件を設定することを特徴とする漏洩磁束探傷方法。
【0017】
2.強磁性体金属被検体を磁化器により磁化し、被検体に存在する欠陥に起因して発生する漏洩磁束を、被検体の表面に配置した磁気センサで測定することにより、欠陥の検出を行う漏洩磁束探傷方法であって、強磁性体金属被検査体を磁化器により磁化し、磁化器の磁化方向に沿って設置位置を変えた複数の磁気センサにより、被検査体の磁化レベルが実質的に異なるような条件下で、被検査体の同一位置に対応する漏洩磁束信号を測定し、測定結果同士を演算し、その演算結果より欠陥判定を行う漏洩磁束探傷法において、少なくとも一の磁気センサが配置される位置で被検体表面近傍の磁場を予め測定することにより探傷時の被検査体の磁化条件を調整し、他の磁化レベルを担当するセンサが配置される位置は、前記設定された磁化条件により磁化された被検査体表面近傍の磁場を測定し、前記測定された磁場が所望の値となる位置とすることを特徴とする漏洩磁束探傷方法。
【0018】
3.2記載の漏洩磁束探傷方法において、少なくとも一の磁気センサが配置される位置で、被検査体表面近傍の磁場を予め測定することにより、その磁場の値を用いて磁化条件を設定して磁化レベルを設定する際、予め測定した被検体のB−Hカーブを用いることを特徴とする漏洩磁束探傷方法。
【0019】
4.2記載の漏洩磁束探傷方法において、少なくとも一の磁気センサが配置される位置で、被検査体表面近傍の磁化方向に平行な磁場を予め測定することにより、その磁場の値を用いて磁化条件を設定して磁化レベルを設定する際、予め測定した被検査体の雑音磁束信号を用いることを特徴とする漏洩磁束探傷方法。
【0020】
5.2記載の漏洩磁束探傷方法において、少なくとも一の磁気センサが配置される位置で、被検査体表面近傍の磁化方向に平行な磁場を予め測定することにより、その磁場の値を用いて磁化条件を設定して磁化レベルを設定する際、予め測定した基準欠陥信号を用いることを特徴とする漏洩磁束探傷方法。
【0021】
【発明の実施の形態】
本発明は、被検体を磁化した際に、磁気センサが配置される位置における前記被検体表面近傍の磁場を測定し、磁化条件を決定することを特徴とする漏洩磁束探傷方法である。
【0022】
本発明を一つの磁化器に対し、距離を変えて配置した複数のセンサからの信号を演算し、欠陥検出性能を向上させる漏洩磁束探傷方法に適用する場合は、被検体を磁化した際に、複数のセンサ位置のうち、一のセンサ位置において、前記被検体表面の磁化方向と平行な磁場を実際に測定し、前記測定される磁場が所望の値となるように探傷時の磁化条件を設定する。
【0023】
または、一のセンサ位置における磁場を所望の値となるように磁化条件を調整後、他の磁気センサの磁化レベルが所望のものとなるように、前記他の磁気センサの位置を、所望の磁場が得られる位置に移動することも可能である。
【0024】
図2は本発明の一実施例に係る漏洩磁束探傷法を説明する図で、図において1は鋼板、2、3は搬送ロール、4は磁気探傷装置、5は磁化器、6a,6bは磁気センサ、7は信号処理装置、8は磁化器電源、10は磁化コイル、11はセンサ移動機構を示す。
【0025】
磁気探傷装置4は、磁化器5、磁気センサ6a,6b、信号処理装置7を有し、磁気センサ6aが磁化器5の磁化方向中心近傍に配置され、磁気センサ6bは磁化方向中心近傍から距離Sだけ離れた位置に配置されている。
【0026】
磁化器5の中央位置に近い磁気センサ6aは磁気センサ6bに対し、より強く磁化されるので磁気センサ6aが強い方の磁化レベルを担当し、磁気センサ6bが弱い方の磁気レベルを担当する。
【0027】
図1は本発明における鋼板磁場の測定方法を模式的に示す図で、図において1は鋼板、5は磁化器、8は磁化器電源、9はガウスメータ、10は磁化コイルを示す。
【0028】
磁場の測定はガウスメータ9を用い、被検体(鋼板1)よりガウスメータ9が離れると、鋼板の内部磁束密度との相関性が損なわれるため、ガウスメータ9を被検体(鋼板1)の表面に接し、磁化器による磁場に平行方向となる磁場を測定できるように配置する。このとき、ガウスメータ9は安定して測定できるように鋼板表面に垂直に当てて、鋼板表面から2〜3mm程度の高さまでの極力表面に近い表面近傍に配置されるのが好ましい。
【0029】
磁化条件を調整する場合は、磁化器5の磁化電流、磁化器5と被検体との距離、磁化器5のヨーク間隔、形状、材質、磁化コイル10の巻数などを変えて行なう。
【0030】
本発明は、磁気センサ6a,6bの何れか一つまたは両者の各位置で磁場を測定し、所望の磁場となるように、すなわち欠陥検出に適した鋼板の内部磁束密度となるように、磁化条件および/またはセンサ位置を調整する。
【0031】
[調整方法1]
磁気センサ6a,6bの位置が予め固定されている場合は、被検体(鋼板1)を磁化した際に、鋼板表面上の磁気センサ6a,6bのいずれかの位置の鋼板表面近傍で磁場を測定し、前記磁場が所望の値となるように磁化条件を調整する。
【0032】
磁場を測定する磁気測定器は特に規定しないが、弱い磁化条件となる磁気センサ6bにおける磁場の値を所望の値に調整できるセンサであることが好ましい。
【0033】
尚、磁気センサは鋼板表面上に間隔Lを設けて設置するので、磁気センサ位置で鋼板の磁場を測定する場合は、その磁気センサ直下における鋼板表面近傍での磁場を測定する。
【0034】
[調整方法2]
磁気センサ6aの設置位置を、鋼板が磁化された際、鋼板の移動方向と平行となる方向の磁化が最大となるように磁化器5のヨーク先端を結んだ線の中心上に設定する。鋼板を磁化し、その位置での鋼板表面近傍の磁場をガウスメータで測定する。測定する磁場は鋼板表面の磁化方向と同方向とする。
【0035】
測定された磁場が所望の値となるように、磁化条件を磁化器により調整する。調整は例えば、磁化器電源8から磁化コイル10への磁化電流を変化させる。
【0036】
次に、ガウスメータを磁化器の磁化方向に沿って鋼板表面上を移動させ、磁気センサ6b用に予め設定した磁場の値が得られる位置を求め、前記位置の直上に磁気センサ6bをセンサ移動機構11などにより移動させる。
【0037】
尚、本発明では、予め被検体となる鋼板のB−Hカーブを求め、探傷用の内部磁束に対する磁場の値を求めておく。図3に示すB−Hカーブが得られる場合は、磁気センサ6aにおける磁化条件は、被検体の磁気飽和レベルの指標となる比微分透磁率が2となる磁場の値、45000A/mとし、磁気センサ6bにおける磁化条件は比微分透磁率が8.5となる磁場の値、25000A/mとすることが望ましい。
【0038】
また、本発明では、鋼板の磁化条件を調整する際、鋼板表面近傍での磁場の値の他に、更に、代表的な被検体の雑音磁束信号レベルや、標準欠陥の欠陥信号レベルを求めておき、これらの値も複数の磁気センサで適正となるように磁化条件を調整し、より適切な探傷条件とすることも可能である。
【0039】
【発明の効果】
本発明によれば、被検体を磁化する際、磁化条件を被検体の欠陥検出に適した内部磁束密度が得られるように調整することができるので、欠陥検出精度が向上する。また、探傷前に標準サンプルによる調整が不用なため、探傷時間の短縮が可能となり、産業上、極めて有用である。
【図面の簡単な説明】
【図1】本発明における鋼板表面の磁場測定方法を説明する図。
【図2】本発明が適用される漏洩磁束探傷装置の一例を示す図。
【図3】被検体(鋼板)のB−Hカーブの一例を示す図。
【図4】従来例を示す図。
【符号の説明】
1 鋼板
2 、3 搬送ローラ
4 磁気探傷装置
5 磁化器
6a,6b 磁気センサ
7 信号処理装置
8 磁化器電源
9 ガウスメータ
10 磁化コイル
11 センサ移動機構
21 鋼板
22、23 搬送ローラ
24 磁気探傷装置
25 磁化器
26a,26b 磁気センサ
27 信号処理装置
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for adjusting a magnetization condition of a subject and a magnetic sensor arrangement position in a leakage magnetic flux flaw detection method, and more specifically, a plurality of sensors are arranged for one magnetizer. The present invention relates to a leakage magnetic flux flaw detection method for calculating a signal obtained by the above and improving defect detection performance.
[0002]
BACKGROUND OF THE INVENTION Leakage magnetic flux flaw detection is a method for flaw detection utilizing the fact that magnetic flux leaks from internal defects when a ferromagnetic material is magnetized. In recent years, it has a simple structure and excellent defect detection performance. Leakage magnetic flux signal corresponding to the same position on the subject under the condition that the magnetization level of the object to be inspected is substantially different by a plurality of magnetic sensors whose installation positions are changed along the magnetization direction of the magnetizer Has been developed, and is described in Patent Document 1 in which a defect is determined based on the calculation result.
[0003]
FIG. 4 is a diagram for explaining the leakage magnetic flux flaw detection method described in Patent Document 1. In the figure, 21 is a steel plate, 22 and 23 are conveying rolls, 24 is a magnetic flaw detector, 25 is a magnetizer, 26a and 26b are magnetic sensors, 27 Indicates a signal processing device.
[0004]
The magnetic flaw detector 24 includes a magnetizer 25, magnetic sensors 26a and 26b, and a signal processing device 27. The magnetic sensor 26a is disposed near the center of the magnetization direction of the magnetizer 25, and the magnetic sensor 26b is a distance from the vicinity of the center of the magnetization direction. It is arranged at a position separated by S.
[0005]
The magnetic sensor 26a is disposed on the magnetic pole center of the magnetizer 25 on the opposite side across the steel plate 21, and a detection signal based on a strong magnetization level condition (strong magnetization condition) is obtained, while the distance S from the magnetic pole center of the magnetizer 25 is obtained. A magnetic sensor 26b that is far away can obtain a detection signal based on a weak magnetization level condition (weak magnetization condition).
[0006]
The magnetic sensors 26a and 26b are arranged above the steel plate 21 with a distance L, and both are linearly arranged in the plate width direction so that the entire surface of the steel plate 21 can be detected. The steel plate 21 is transported at a substantially constant speed V by the transport rollers 22 and 23.
[0007]
The signal processing device 27 performs AD conversion on the detection signals from the magnetic sensors 26a and 26b and performs a calculation necessary for determining a defect after filtering, and eliminates positional deviation of the magnetic sensors 26a and 26b. Then, processing is performed so that both signals at the same location of the steel plate are calculated.
[0008]
In invention of patent document 1, the same effect as the case where the magnetization conditions with respect to a steel plate are changed strongly is changed by changing the distance from a magnetizer to each of a plurality of magnetic sensors.
[0009]
The magnetizing condition of the steel plate 21 by the magnetizer 25 is a magnetic sensor in which the detection signal of the magnetic sensor 26a which is a strong magnetization condition is in the vicinity of a saturation magnetization condition where both a defect signal and a noise magnetic flux signal are large, and a weak magnetization condition. As a detection signal of 26b, the magnetization condition is such that the change of the defect signal level due to the weakening of the magnetization level is larger than the degree of change of the noise magnetic flux signal level, and the noise magnetic flux signal in the detection signal of the magnetic sensor 26a is further magnetic. The magnetization condition is set such that it also exists in the detection signal of the sensor 26b.
[0010]
[Patent Document 1]
Japanese Patent No. 3266128 [0011]
[Problems to be solved by the invention]
As described above, in a leakage magnetic flux flaw detection method in which a plurality of sensors are arranged at different distances with respect to one magnetizer, a signal from each sensor is calculated, and defect detection performance is improved, detection is performed by a plurality of sensors. A method is used in which the magnetization condition of the subject is adjusted so that the magnitude of the generated noise magnetic flux signal is substantially constant.
[0012]
In addition, it is possible to apply a method of preparing a standard sample in advance and detecting the defect signal of the standard defect to determine the magnetization condition. However, both detection signals such as the defect signal of the magnetic sensor and the noise magnetic flux signal Because the method of adjusting the magnetizing conditions so that the level of the sensor becomes a predetermined level, when changing the magnetizing conditions by changing the steel type, plate thickness, etc. of the test object that affects the detection signal level of the magnetic sensor, use a standard sample. The procedure of determining the magnetization condition for obtaining an appropriate detection signal level is necessary and complicated.
[0013]
SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a leakage magnetic flux flaw detection method capable of easily setting an appropriate magnetization condition even when the steel type and the plate thickness are changed by measuring a magnetic field in the vicinity of the subject surface. .
[0014]
[Means for Solving the Problems]
The inventors have taken the idea that the level of the detection signal depends on the internal magnetic flux density of the steel sheet and that when the steel sheet is magnetized, the relationship between the magnetic field and the magnetic flux density is obtained as a BH curve, The leakage magnetic flux flaw detection method has been completed in which the magnetic field measured in the vicinity of the subject surface is adjusted to a desired value, that is, the internal magnetic flux density of the steel plate to obtain an appropriate detection signal level.
[0015]
The problems of the present invention are solved by the following means.
[0016]
1. Leakage that detects a defect by magnetizing a ferromagnetic metal specimen with a magnetizer and measuring the leakage magnetic flux generated due to a defect present in the specimen with a magnetic sensor disposed on the surface of the specimen. A magnetic flux inspection method, in which a ferromagnetic metal object is magnetized by a magnetizer, and a plurality of magnetic sensors whose installation positions are changed along the magnetization direction of the magnetizer, the magnetization levels of the object to be inspected are substantially different. Under such conditions, at least one magnetic sensor is used in a leakage magnetic flux flaw detection method in which a leakage magnetic flux signal corresponding to the same position on the object to be inspected is measured, the measurement results are calculated, and a defect is determined from the calculation results. A leakage magnetic flux flaw detection method characterized by setting a magnetization condition of an object to be inspected at the time of flaw detection by measuring in advance a magnetic field in the vicinity of a subject surface at a position where the object is arranged.
[0017]
2. Leakage that detects a defect by magnetizing a ferromagnetic metal specimen with a magnetizer and measuring the leakage magnetic flux generated due to a defect present in the specimen with a magnetic sensor disposed on the surface of the specimen. A magnetic flux inspection method, in which a ferromagnetic metal object to be inspected is magnetized by a magnetizer, and the magnetic level of the object to be inspected is substantially reduced by a plurality of magnetic sensors whose installation positions are changed along the magnetization direction of the magnetizer. In a leakage magnetic flux flaw detection method in which leakage magnetic flux signals corresponding to the same position of an object to be inspected are measured under different conditions, measurement results are calculated, and defect determination is performed based on the calculation results, at least one magnetic sensor has The magnetic field in the vicinity of the surface of the subject is measured in advance at the position at which it is placed to adjust the magnetization conditions of the object to be inspected during flaw detection. On condition Magnetic flux leakage testing method to measure the magnetic field of the device under test near the surface, the measured magnetic field, characterized in that the position at which the desired value which is magnetized Ri.
[0018]
In the leakage magnetic flux flaw detection method according to 3.2, by measuring in advance a magnetic field in the vicinity of the surface of the object to be inspected at a position where at least one magnetic sensor is arranged, a magnetization condition is set using the value of the magnetic field. A leakage magnetic flux flaw detection method characterized by using a BH curve of a subject measured in advance when setting a magnetization level.
[0019]
In the leakage magnetic flux flaw detection method according to 4.2, a magnetic field parallel to the magnetization direction in the vicinity of the surface of the object to be inspected is measured in advance at a position where at least one magnetic sensor is arranged, and magnetization is performed using the value of the magnetic field. A leakage magnetic flux flaw detection method characterized by using a noise magnetic flux signal of an inspected object measured in advance when setting a magnetization level by setting conditions.
[0020]
5.2 In the leakage magnetic flux flaw detection method according to 5.2, by measuring in advance a magnetic field parallel to the magnetization direction in the vicinity of the surface of the object to be inspected at a position where at least one magnetic sensor is disposed, magnetization is performed using the value of the magnetic field. A leakage magnetic flux flaw detection method characterized by using a reference defect signal measured in advance when setting a magnetization level by setting conditions.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
The present invention is a leakage magnetic flux flaw detection method characterized in that when a subject is magnetized, a magnetic field in the vicinity of the subject surface at a position where the magnetic sensor is arranged is measured to determine a magnetization condition.
[0022]
When applying the present invention to a leakage magnetic flux flaw detection method for improving the defect detection performance by calculating signals from a plurality of sensors arranged at different distances with respect to one magnetizer, when magnetizing a subject, At one sensor position among a plurality of sensor positions, a magnetic field parallel to the magnetization direction of the subject surface is actually measured, and a magnetization condition at the time of flaw detection is set so that the measured magnetic field becomes a desired value. To do.
[0023]
Alternatively, after adjusting the magnetization condition so that the magnetic field at one sensor position becomes a desired value, the position of the other magnetic sensor is changed to a desired magnetic field so that the magnetization level of the other magnetic sensor becomes a desired value. It is also possible to move to a position where
[0024]
FIG. 2 is a diagram for explaining a leakage magnetic flux flaw detection method according to an embodiment of the present invention, in which 1 is a steel plate, 2 is a transport roll, 4 is a magnetic flaw detector, 5 is a magnetizer, and 6a and 6b are magnetic. A sensor, 7 is a signal processing device, 8 is a magnetizer power source, 10 is a magnetizing coil, and 11 is a sensor moving mechanism.
[0025]
The magnetic flaw detector 4 includes a magnetizer 5, magnetic sensors 6 a and 6 b, and a signal processing device 7. The magnetic sensor 6 a is disposed near the center of the magnetization direction of the magnetizer 5, and the magnetic sensor 6 b is a distance from the vicinity of the center of the magnetization direction. It is arranged at a position separated by S.
[0026]
Since the magnetic sensor 6a close to the center position of the magnetizer 5 is more strongly magnetized than the magnetic sensor 6b, the magnetic sensor 6a takes charge of the stronger magnetization level and the magnetic sensor 6b takes charge of the weaker magnetic level.
[0027]
FIG. 1 is a diagram schematically showing a method for measuring a magnetic field of a steel plate in the present invention. In the figure, 1 is a steel plate, 5 is a magnetizer, 8 is a magnetizer power source, 9 is a gauss meter, and 10 is a magnetizing coil.
[0028]
The measurement of the magnetic field uses a gauss meter 9, and when the gauss meter 9 moves away from the subject (steel plate 1), the correlation with the internal magnetic flux density of the steel plate is lost, so the gauss meter 9 is brought into contact with the surface of the subject (steel plate 1), It arrange | positions so that the magnetic field which becomes a direction parallel to the magnetic field by a magnetizer can be measured. At this time, the gauss meter 9 is preferably placed near the surface as close to the surface as possible to a height of about 2 to 3 mm from the surface of the steel plate so that it can be measured stably.
[0029]
When the magnetization conditions are adjusted, the magnetization current of the magnetizer 5, the distance between the magnetizer 5 and the subject, the yoke interval, the shape, the material, the number of turns of the magnetizing coil 10 and the like of the magnetizer 5 are changed.
[0030]
In the present invention, the magnetic field is measured at each position of one or both of the magnetic sensors 6a and 6b, so that the magnetic field becomes a desired magnetic field, that is, the internal magnetic flux density of the steel sheet suitable for defect detection. Adjust conditions and / or sensor position.
[0031]
[Adjustment method 1]
When the positions of the magnetic sensors 6a and 6b are fixed in advance, when the subject (steel plate 1) is magnetized, the magnetic field is measured in the vicinity of the steel plate surface at any position of the magnetic sensors 6a and 6b on the steel plate surface. Then, the magnetization condition is adjusted so that the magnetic field has a desired value.
[0032]
A magnetic measuring instrument that measures the magnetic field is not particularly defined, but it is preferably a sensor that can adjust the value of the magnetic field in the magnetic sensor 6b under weak magnetization conditions to a desired value.
[0033]
Since the magnetic sensor is installed on the surface of the steel plate with an interval L, when measuring the magnetic field of the steel plate at the magnetic sensor position, the magnetic field in the vicinity of the surface of the steel plate immediately under the magnetic sensor is measured.
[0034]
[Adjustment method 2]
The installation position of the magnetic sensor 6a is set on the center of the line connecting the yoke tips of the magnetizers 5 so that the magnetization in the direction parallel to the moving direction of the steel plate is maximized when the steel plate is magnetized. The steel plate is magnetized and the magnetic field near the steel plate surface at that position is measured with a gauss meter. The magnetic field to be measured is the same direction as the magnetization direction of the steel sheet surface.
[0035]
The magnetization condition is adjusted by a magnetizer so that the measured magnetic field becomes a desired value. In the adjustment, for example, the magnetizing current from the magnetizer power supply 8 to the magnetizing coil 10 is changed.
[0036]
Next, the gauss meter is moved on the surface of the steel sheet along the magnetization direction of the magnetizer to obtain a position at which a magnetic field value preset for the magnetic sensor 6b is obtained, and the magnetic sensor 6b is placed directly above the position. 11 and so on.
[0037]
In the present invention, the BH curve of the steel plate to be examined is obtained in advance, and the value of the magnetic field with respect to the internal magnetic flux for flaw detection is obtained. When the BH curve shown in FIG. 3 is obtained, the magnetization condition in the magnetic sensor 6a is set to 45000 A / m, which is a magnetic field value with a relative differential permeability of 2 as an index of the magnetic saturation level of the subject. The magnetization condition in the sensor 6b is preferably 25000 A / m, the value of the magnetic field at which the relative differential permeability is 8.5.
[0038]
Further, in the present invention, when adjusting the magnetization condition of the steel sheet, in addition to the value of the magnetic field in the vicinity of the steel sheet surface, the noise flux signal level of a typical subject and the defect signal level of the standard defect are obtained. In addition, it is possible to adjust the magnetization conditions so that these values are also appropriate for a plurality of magnetic sensors, and to make the flaw detection conditions more appropriate.
[0039]
【The invention's effect】
According to the present invention, when the subject is magnetized, the magnetization condition can be adjusted so as to obtain an internal magnetic flux density suitable for defect detection of the subject, so that the defect detection accuracy is improved. Further, since adjustment with a standard sample is unnecessary before flaw detection, flaw detection time can be shortened, which is extremely useful industrially.
[Brief description of the drawings]
FIG. 1 is a view for explaining a method of measuring a magnetic field on a steel sheet surface in the present invention.
FIG. 2 is a diagram showing an example of a leakage magnetic flux flaw detector to which the present invention is applied.
FIG. 3 is a diagram showing an example of a BH curve of a subject (steel plate).
FIG. 4 is a diagram showing a conventional example.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Steel plate 2, 3 Conveying roller 4 Magnetic flaw detector 5 Magnetizer 6a, 6b Magnetic sensor 7 Signal processing device 8 Magnetizer power supply 9 Gauss meter 10 Magnetizing coil 11 Sensor moving mechanism 21 Steel plate 22, 23 Conveying roller 24 Magnetic flaw detector 25 Magnetizer 26a, 26b Magnetic sensor 27 Signal processing device

Claims (5)

  1. 強磁性体金属被検体を磁化器により磁化し、被検体に存在する欠陥に起因して発生する漏洩磁束を、被検体の表面に配置した磁気センサで測定することにより、欠陥の検出を行う漏洩磁束探傷方法であって、強磁性体金属被検体を磁化器により磁化し、磁化器の磁化方向に沿って設置位置を変えた複数の磁気センサにより、被検査体の磁化レベルが実質的に異なるような条件下で、被検査体上の同一位置に対応する漏洩磁束信号を測定し、測定結果同士を演算し、その演算結果より欠陥判定を行う漏洩磁束探傷法において、少なくとも一の磁気センサが配置される位置における被検体表面近傍の磁場を予め測定することにより探傷時の被検査体の磁化条件を設定することを特徴とする漏洩磁束探傷方法。Leakage that detects a defect by magnetizing a ferromagnetic metal specimen with a magnetizer and measuring the leakage magnetic flux generated due to a defect present in the specimen with a magnetic sensor disposed on the surface of the specimen. A magnetic flux inspection method, in which a ferromagnetic metal object is magnetized by a magnetizer, and a plurality of magnetic sensors whose installation positions are changed along the magnetization direction of the magnetizer, the magnetization levels of the object to be inspected are substantially different. Under such conditions, at least one magnetic sensor is used in a leakage magnetic flux flaw detection method in which a leakage magnetic flux signal corresponding to the same position on the object to be inspected is measured, the measurement results are calculated, and a defect is determined from the calculation results. A leakage magnetic flux flaw detection method characterized by setting a magnetization condition of an object to be inspected at the time of flaw detection by measuring in advance a magnetic field in the vicinity of a subject surface at a position where the object is arranged.
  2. 強磁性体金属被検体を磁化器により磁化し、被検体に存在する欠陥に起因して発生する漏洩磁束を、被検体の表面に配置した磁気センサで測定することにより、欠陥の検出を行う漏洩磁束探傷方法であって、強磁性体金属被検査体を磁化器により磁化し、磁化器の磁化方向に沿って設置位置を変えた複数の磁気センサにより、被検査体の磁化レベルが実質的に異なるような条件下で、被検査体の同一位置に対応する漏洩磁束信号を測定し、測定結果同士を演算し、その演算結果より欠陥判定を行う漏洩磁束探傷法において、少なくとも一の磁気センサが配置される位置で被検体表面近傍の磁場を予め測定することにより探傷時の被検査体の磁化条件を調整し、他の磁化レベルを担当するセンサが配置される位置は、前記設定された磁化条件により磁化された被検査体表面近傍の磁場を測定し、前記測定された磁場が所望の値となる位置とすることを特徴とする漏洩磁束探傷方法。Leakage that detects a defect by magnetizing a ferromagnetic metal specimen with a magnetizer and measuring the leakage magnetic flux generated due to a defect present in the specimen with a magnetic sensor disposed on the surface of the specimen. A magnetic flux inspection method, in which a ferromagnetic metal object to be inspected is magnetized by a magnetizer, and the magnetic level of the object to be inspected is substantially reduced by a plurality of magnetic sensors whose installation positions are changed along the magnetization direction of the magnetizer. In a leakage magnetic flux flaw detection method in which leakage magnetic flux signals corresponding to the same position of an object to be inspected are measured under different conditions, measurement results are calculated, and defect determination is performed based on the calculation results, at least one magnetic sensor has The magnetic field in the vicinity of the surface of the subject is measured in advance at the position at which it is placed to adjust the magnetization conditions of the object to be inspected during flaw detection. On condition Magnetic flux leakage testing method to measure the magnetic field of the device under test near the surface, the measured magnetic field, characterized in that the position at which the desired value which is magnetized Ri.
  3. 請求項2記載の漏洩磁束探傷方法において、少なくとも一の磁気センサが配置される位置で、被検査体表面近傍の磁場を予め測定することにより、その磁場の値を用いて磁化条件を設定して磁化レベルを設定する際、予め測定した被検体のB−Hカーブを用いることを特徴とする漏洩磁束探傷方法。3. The leakage magnetic flux flaw detection method according to claim 2, wherein a magnetic field in the vicinity of the surface of the object to be inspected is measured in advance at a position where at least one magnetic sensor is arranged, and a magnetization condition is set using the value of the magnetic field. A leakage magnetic flux flaw detection method characterized by using a BH curve of a subject measured in advance when setting a magnetization level.
  4. 請求項2記載の漏洩磁束探傷方法において、少なくとも一の磁気センサが配置される位置で、被検査体表面近傍の磁化方向に平行な磁場を予め測定することにより、その磁場の値を用いて磁化条件を設定して磁化レベルを設定する際、予め測定した被検査体の雑音磁束信号を用いることを特徴とする漏洩磁束探傷方法。3. The leakage magnetic flux flaw detection method according to claim 2, wherein a magnetic field parallel to the magnetization direction in the vicinity of the surface of the object to be inspected is measured in advance at a position where at least one magnetic sensor is arranged, and magnetized using the value of the magnetic field. A leakage magnetic flux flaw detection method characterized by using a noise magnetic flux signal of an inspected object measured in advance when setting a magnetization level by setting conditions.
  5. 請求項2記載の漏洩磁束探傷方法において、少なくとも一の磁気センサが配置される位置で、被検査体表面近傍の磁化方向に平行な磁場を予め測定することにより、その磁場の値を用いて磁化条件を設定して磁化レベルを設定する際、予め測定した基準欠陥信号を用いることを特徴とする漏洩磁束探傷方法。3. The leakage magnetic flux flaw detection method according to claim 2, wherein a magnetic field parallel to the magnetization direction in the vicinity of the surface of the object to be inspected is measured in advance at a position where at least one magnetic sensor is arranged, and magnetized using the value of the magnetic field. A leakage magnetic flux flaw detection method characterized by using a reference defect signal measured in advance when setting a magnetization level by setting conditions.
JP2003187284A 2003-06-30 2003-06-30 Leakage flux flaw detection test Pending JP2005024295A (en)

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2007256274A (en) * 2006-02-24 2007-10-04 Jfe Steel Kk Method and device for detecting small surface irregularity defect
CN100432665C (en) * 2005-08-05 2008-11-12 营口市北方检测设备有限公司 Online detecting device and method for two-field leakage magnetic flux of defects on steel products surface
CN105300565A (en) * 2014-06-12 2016-02-03 国网山西省电力公司电力科学研究院 Method for measuring lifting force of magnetic crack detector
KR102287304B1 (en) 2021-02-09 2021-08-09 나우 주식회사 Adaptive magnetic particle detection device and magnetic particle detection method using the same

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN100432665C (en) * 2005-08-05 2008-11-12 营口市北方检测设备有限公司 Online detecting device and method for two-field leakage magnetic flux of defects on steel products surface
JP2007256274A (en) * 2006-02-24 2007-10-04 Jfe Steel Kk Method and device for detecting small surface irregularity defect
CN105300565A (en) * 2014-06-12 2016-02-03 国网山西省电力公司电力科学研究院 Method for measuring lifting force of magnetic crack detector
KR102287304B1 (en) 2021-02-09 2021-08-09 나우 주식회사 Adaptive magnetic particle detection device and magnetic particle detection method using the same

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