JP2001141701A - Method for measuring coercive force - Google Patents
Method for measuring coercive forceInfo
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- JP2001141701A JP2001141701A JP32087499A JP32087499A JP2001141701A JP 2001141701 A JP2001141701 A JP 2001141701A JP 32087499 A JP32087499 A JP 32087499A JP 32087499 A JP32087499 A JP 32087499A JP 2001141701 A JP2001141701 A JP 2001141701A
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- Japan
- Prior art keywords
- magnetic field
- coercive force
- measured
- barkhausen noise
- magnetic
- Prior art date
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Abstract
Description
【０００１】[0001]
【発明の属する技術分野】本発明は、鋼板などの強磁性
体材料の保磁力を非破壊で測定する方法に関するもので
ある。The present invention relates to a method for non-destructively measuring a coercive force of a ferromagnetic material such as a steel plate.
【０００２】[0002]
【従来の技術】強磁性体材料においては、その磁気特
性、つまり磁気ヒステリシスループ（Ｂ−Ｈカーブ）を
知ることは品質管理上重要である。とりわけ、このヒス
テリシスループがＨ軸を横切る点である保磁力（ＨＣ）
は、強磁性体材料の特性を決定する極めて重要なパラメ
ータである。2. Description of the Related Art In ferromagnetic materials, it is important for quality control to know the magnetic properties, that is, the magnetic hysteresis loop (BH curve). In particular, the coercivity (HC) at which this hysteresis loop crosses the H axis
Is a very important parameter that determines the properties of the ferromagnetic material.
【０００３】例えば、 パーマロイのような、磁心として用いられる高透磁
率材料に関しては、鉄損を軽減させるために、保磁力が
小さいことが望まれる。 磁気テープのような磁気記録材料に関しては、一度
入力した信号が容易に消失しないように、保磁力が大き
いことが望まれる。 永久磁石に関しては、保磁力は反磁界に逆らって残
留磁束密度を保持しようとする抵抗の目安であり、残留
磁束密度と並んでその性能を左右する重要なパラメータ
である。 保磁力は、鉄鋼材料の結晶粒径、材料劣化、引張試
験値、降伏点といった種々の機械的性質と相関があるの
で、それらの推定に応用されている。For example, with respect to a high magnetic permeability material used as a magnetic core, such as permalloy, it is desired that the coercive force be small in order to reduce iron loss. With respect to a magnetic recording material such as a magnetic tape, it is desired that the coercive force be large so that once input signals are not easily lost. For a permanent magnet, the coercive force is a measure of the resistance to maintain the residual magnetic flux density against the demagnetizing field, and is an important parameter that affects the performance along with the residual magnetic flux density. The coercive force has been correlated with various mechanical properties such as the crystal grain size of steel materials, material deterioration, tensile test values, and yield points, and has been applied to their estimation.
【０００４】破壊試験においては、保磁力は以下のよう
な手順によって測定される。まず、被測定材料からドー
ナツ状の試料を切り出し、その試料に励磁コイルと検出
コイルを巻き付ける。次に、励磁コイルに励磁電流を流
すことで磁束が試料内を環状に通るようにする。そし
て、検出コイルにより磁化状態を調べ、Ｂ−Ｈカーブ
（ヒステリシスループ）を描かせ、Ｂ−ＨカーブがＨ軸
と交わる点から保磁力を得る。この方法では、強磁性体
材料の保磁力が正確かつ完全に求まるが、材料を破壊す
る破壊試験法であり、また測定に多大な時間と労力を要
するという問題点がある。In the destructive test, the coercive force is measured according to the following procedure. First, a donut-shaped sample is cut out from a material to be measured, and an exciting coil and a detection coil are wound around the sample. Next, an exciting current is passed through the exciting coil so that the magnetic flux passes through the sample in an annular shape. Then, the magnetization state is examined by the detection coil, a BH curve (hysteresis loop) is drawn, and a coercive force is obtained from a point where the BH curve intersects the H axis. According to this method, the coercive force of the ferromagnetic material can be accurately and completely determined, but it is a destructive test method for destroying the material, and there is a problem that measurement requires a great deal of time and labor.
【０００５】これに対し、非破壊的に保磁力を測定する
方法が、従来いくつか開発されており、特開平６−２１
３８７２号公報、特開平６−２６５５２５号公報、特開
平７−１２８２９４号公報等に開示されている。これら
の技術においては、図７に示すように、被測定強磁性体
７１の一方の面からＵ字型ヨーク７２を有する磁化コイ
ル７３を対面させ、磁化コイル７３に励磁電流発生器７
５からの励磁電流を流して被測定強磁性体７１を励磁す
る。すると、磁束変化により同一のＵ字型ヨークに設け
た磁気検出コイル７４に電圧が誘起されるので、この電
圧を検出電圧測定器７６で測定して演算装置７７に入力
する。演算装置７７では、この電圧が尖頭値をとった時
点の励磁電流値より保磁力を求めている。On the other hand, several methods for non-destructively measuring the coercive force have been developed in the past.
3872, JP-A-6-265525, JP-A-7-128294, and the like. In these techniques, as shown in FIG. 7, a magnetizing coil 73 having a U-shaped yoke 72 faces one surface of a ferromagnetic body 71 to be measured, and an exciting current generator 7 is connected to the magnetizing coil 73.
5 to excite the ferromagnetic body 71 to be measured. Then, a voltage is induced in the magnetic detection coil 74 provided on the same U-shaped yoke due to the change in magnetic flux. This voltage is measured by the detection voltage measuring device 76 and input to the arithmetic unit 77. The arithmetic unit 77 obtains the coercive force from the exciting current value at the time when this voltage takes a peak value.
【０００６】保磁力はヒステリシスループ上における磁
束密度のゼロクロス点と定義されるものであるが、これ
らの従来技術では、このときヒステリシスループの勾配
が最も急になることに着目し、ヒステリシスループの勾
配が最も急になる点の励磁電流値より保磁力を求めてい
ることになる。すなわち、磁気検出コイルの出力は磁束
密度の時間微分であるため、この値が極大値をとった時
点を検出することにより、ヒステリシスループの勾配が
最も急になる点を求めることができる。したがって、こ
の時点での励磁電流値を求めることで、保磁力に相当す
る値を求めることができる。The coercive force is defined as a zero-cross point of the magnetic flux density on the hysteresis loop. In these prior arts, attention is paid to the fact that the slope of the hysteresis loop becomes the steepest at this time. That is, the coercive force is determined from the exciting current value at the point where the steepest occurs. That is, since the output of the magnetic detection coil is the time derivative of the magnetic flux density, the point at which the gradient of the hysteresis loop becomes the steepest can be obtained by detecting the time when this value takes the maximum value. Therefore, a value corresponding to the coercive force can be obtained by obtaining the exciting current value at this time.
【０００７】[0007]
【発明が解決しようとする課題】しかしながら、このよ
うな従来の非破壊的な保磁力の測定方法には、以下のよ
うな問題点があった。すなわち、前述のように、これら
の測定方法においては、十分な励磁能力を得る目的で、
磁化器としてＵ字型のヨークにコイルを巻き付けたもの
が用いられ、また、磁気検出器としても十分な検出感度
を得る目的で同様にＵ字型のコアにコイルを巻き付けた
ものが用いられている。そのため、磁化器によって励磁
されるのは被測定強磁性体のみならず、磁化器のヨーク
材と磁気検出器のコアも含まれる。また、磁気検出器に
よって測定される磁気特性も、被測定強磁性体、磁化器
のヨーク材、磁気検出器のコアの特性が重なったものと
なる。However, such a conventional non-destructive method for measuring a coercive force has the following problems. That is, as described above, in these measurement methods, in order to obtain a sufficient exciting ability,
As a magnetizer, a coil wound around a U-shaped yoke is used, and as a magnetic detector, a coil wound around a U-shaped core for the purpose of obtaining sufficient detection sensitivity is also used. I have. Therefore, not only the ferromagnetic material to be measured but also the yoke material of the magnetizer and the core of the magnetic detector are excited by the magnetizer. Also, the magnetic characteristics measured by the magnetic detector are the same as those of the ferromagnetic material to be measured, the yoke material of the magnetizer, and the core of the magnetic detector.
【０００８】したがって、このような測定装置構成でヒ
ステリシスループを測定する場合、得られる特性は被測
定強磁性体の特性のみを反映したものではなく、それに
磁化器のヨーク材、磁気検出器コアの特性が加わった特
性となる。また、得られるヒステリシスループもこれら
の保磁力の特性だけが反映されたものでなく、飽和磁束
密度、透磁率、残留磁束密度などの特性や、反磁界の影
響が重畳された複雑なものとなる。Therefore, when measuring the hysteresis loop with such a measuring device configuration, the obtained characteristics do not reflect only the characteristics of the ferromagnetic material to be measured, but include the yoke material of the magnetizer and the magnetic detector core. This is the characteristic with the added characteristics. In addition, the obtained hysteresis loop does not reflect only the characteristics of the coercive force, but becomes a complicated one in which the characteristics of the saturation magnetic flux density, the magnetic permeability, the residual magnetic flux density, and the effects of the demagnetizing field are superimposed. .
【０００９】このように、従来の非破壊的測定系によっ
て得られたヒステリシスループからは、被測定強磁性体
材料の保磁力情報のみを抽出するのは極めて困難であ
り、保磁力計測の精度が極めて悪いといった問題があっ
た。As described above, it is extremely difficult to extract only the coercive force information of the ferromagnetic material to be measured from the hysteresis loop obtained by the conventional non-destructive measurement system, and the accuracy of the coercive force measurement is high. There was a problem that it was extremely bad.
【００１０】本発明はこのような事情に鑑みてなされた
もので、被測定強磁性体材料の保磁力情報のみを抽出す
ることができ、従って精度の良い測定が可能な、保磁力
の非破壊的測定方法を提供することを課題とする。The present invention has been made in view of such circumstances, and it is possible to extract only the coercive force information of a ferromagnetic material to be measured, and thus to perform accurate measurement. It is an object of the present invention to provide a dynamic measurement method.
【００１１】[0011]
【課題を解決するための手段】前記課題を解決するため
の第１の手段は、被測定強磁性体材料に印加する磁界の
強さを変化させてバルクハウゼンノイズの発生に要する
磁界の強さを求め、当該磁界の強さから強磁性体材料の
保磁力を求めることを特徴とする保磁力の測定方法（請
求項１）である。A first means for solving the above-mentioned problems is to change the strength of a magnetic field applied to a ferromagnetic material to be measured to change the strength of a magnetic field required for generating Barkhausen noise. And measuring the coercive force of the ferromagnetic material from the strength of the magnetic field (claim 1).
【００１２】バルクハウゼンノイズとは、強磁性体の磁
化に伴う磁壁の不連続移動によって発生する磁気ノイズ
である。図２に磁性材料の磁化過程を示す。同図内の左
図は磁化に伴う微視的な材料の変化を示したもので、右
図はそれに対応した磁化曲線を示したものである。(1)
→(2)→(3)という順番で磁化が進行し、磁性材料の結晶
は、磁区と呼ばれる磁化の揃った小領域に分割され、そ
の境界は磁壁と呼ばれる。Barkhausen noise is magnetic noise generated by discontinuous movement of domain walls due to magnetization of a ferromagnetic material. FIG. 2 shows the magnetization process of the magnetic material. The left figure in the figure shows a microscopic change of the material accompanying the magnetization, and the right figure shows a magnetization curve corresponding thereto. (1)
The magnetization progresses in the order of → (2) → (3), and the crystal of the magnetic material is divided into small domains with uniform magnetization called magnetic domains, and the boundaries are called domain walls.
【００１３】(1)は、磁性材料に外部磁場が与えられて
いない状態を示す。この状態では、微視的に見ると磁区
の磁化の状態がランダムになっており、材料全体として
は磁化されていないことになる。(1) shows a state in which no external magnetic field is applied to the magnetic material. In this state, when viewed microscopically, the state of magnetization of the magnetic domains is random, and the material as a whole is not magnetized.
【００１４】(2)は、外部磁化を少し与えた状態を示
す。磁区は外部磁場と同一の方向に磁化されたものが成
長し、それに伴い磁壁が移動する。この際、結晶内部に
ピニング因子があると、磁壁の移動が妨げられる。(2) shows a state in which external magnetization is slightly applied. The magnetic domain grows magnetized in the same direction as the external magnetic field, and the domain wall moves accordingly. At this time, if there is a pinning factor inside the crystal, the movement of the domain wall is hindered.
【００１５】(3)は、更に外部磁化を与えた状態を示
す。磁区は更に成長し、磁壁もピニング因子を乗り越
え、最後には結晶全体が同一の方向に磁化される。ここ
で、磁壁がピニング因子を乗り越える際に生じるノイズ
がバルクハウゼンノイズである。この現象は、右図にお
いては、拡大図に示すように、磁化曲線が階段状になる
ことで示される。(3) shows a state where external magnetization is further applied. The domains grow further, the domain walls also overcome the pinning factor, and finally the entire crystal is magnetized in the same direction. Here, the noise generated when the domain wall overcomes the pinning factor is Barkhausen noise. This phenomenon is shown in the right figure by the magnetization curve having a step shape as shown in the enlarged view.
【００１６】このように、強磁性体の磁区は磁化に伴っ
て成長し、この際磁壁が移動するが、ピニング因子があ
ると磁壁の移動が阻害され、磁界の増加に伴う磁束密度
の増加が不連続的となる。このときに発生するのがバル
クハウゼンノイズであり、図３に示したように、鋭いパ
ルス状のノイズとなって現れる。As described above, the magnetic domain of the ferromagnetic material grows with the magnetization, and the domain wall moves at this time, but the movement of the domain wall is hindered by a pinning factor, and the magnetic flux density increases with the increase of the magnetic field. It becomes discontinuous. What occurs at this time is Barkhausen noise, which appears as sharp pulse-shaped noise as shown in FIG.
【００１７】以上説明したように、バルクハウゼンノイ
ズは強磁性体の磁化に伴って発生するが、磁壁の移動が
激しくなる磁界の強さのところで、つまり図４に示すよ
うに微分透磁率が最大になる磁界で最も強く発生する。
ここで、微分透磁率が最大になる磁界の強さは、磁束密
度のゼロクロス点、つまり保磁力にほぼ一致する。その
ため、バルクハウゼンノイズが発生した時点での磁界の
強さを測定することで、被測定強磁性体材料の保磁力の
測定がを非破壊で簡便に行える。As described above, Barkhausen noise is generated with the magnetization of the ferromagnetic material. However, at the strength of the magnetic field at which the domain wall moves sharply, that is, as shown in FIG. The strongest magnetic field occurs.
Here, the strength of the magnetic field at which the differential magnetic permeability is maximized substantially coincides with the zero cross point of the magnetic flux density, that is, the coercive force. Therefore, by measuring the strength of the magnetic field when Barkhausen noise is generated, the coercive force of the ferromagnetic material to be measured can be easily and nondestructively measured.
【００１８】すなわち、バルクハウゼンノイズが発生し
た時点での磁界の強さと、破壊検査で測定された保磁力
との関係式を予め求めておき、測定においては、バルク
ハウゼンノイズが発生した時点での磁界の強さをこの関
係式に当てはめて、保磁力を測定すればよい。That is, the relational expression between the strength of the magnetic field at the time of the occurrence of Barkhausen noise and the coercive force measured by the destructive inspection is determined in advance. The coercive force may be measured by applying the strength of the magnetic field to this relational expression.
【００１９】先に述べたように、磁束密度の時間微分の
ピーク値に基づくこれまでの方法はいわばヒステリシス
ループを描写しようとするものであり、磁化器ヨーク、
磁気検出器コアのさまざまな磁気特性（保磁力、透磁
率、飽和磁束密度、残留磁束密度）の影響を受ける。一
方、本手段においては、バルクハウゼンノイズの発生す
る磁界の強さに基づいて保磁力を測定しているので、保
磁力以外の磁気特性は影響を与えない。したがって、本
手段において得られる情報は、保磁力に関するもののみ
となり、測定精度が良くなる。As described above, the conventional methods based on the peak value of the time derivative of the magnetic flux density try to describe a hysteresis loop, so to speak, the magnetizer yoke,
It is affected by various magnetic properties (coercive force, permeability, saturation magnetic flux density, residual magnetic flux density) of the magnetic detector core. On the other hand, in the present means, the coercive force is measured based on the strength of the magnetic field in which Barkhausen noise is generated, so that magnetic properties other than the coercive force have no effect. Therefore, the information obtained by this means is only information on the coercive force, and the measurement accuracy is improved.
【００２０】前記課題を解決するための第２の手段は、
被測定強磁性体材料に印加する磁界の強さを変化させ
て、磁界の増加過程、磁界の減少過程においてバルクハ
ウゼンノイズの発生に要する磁界の強さをそれぞれ求
め、当該磁界の絶対値の和から強磁性体材料の保磁力を
求めることを特徴とする保磁力の測定方法（請求項２）
である。A second means for solving the above-mentioned problem is as follows.
By changing the strength of the magnetic field applied to the ferromagnetic material to be measured, the strength of the magnetic field required to generate Barkhausen noise in the process of increasing and decreasing the magnetic field is obtained, and the sum of the absolute values of the magnetic field is determined. Determining a coercive force of the ferromagnetic material from the data (claim 2)
It is.
【００２１】被測定強磁性体材料には残留磁化の影響で
永久磁界が存在している可能性がある。この磁界は、磁
化器による磁界の印加に対しバイアスとして働く。その
ため、バルクハウゼンノイズの発生に要する磁界の値
は、図５に示すように磁界の増加過程と減少過程では異
なった値を示す。しかしながら、図５に示すように、磁
界が増加過程にあるときにバルクハウゼンノイズの発生
に要する磁界の値の絶対値と、磁界が減少過程にあると
きにバルクハウゼンノイズの発生に要する磁界の値の絶
対値との和は、残留磁界の有無や残留磁界の強さに関わ
らず一定の値となる。There is a possibility that a permanent magnetic field exists in the ferromagnetic material to be measured due to the influence of residual magnetization. This magnetic field acts as a bias to the application of the magnetic field by the magnetizer. Therefore, the value of the magnetic field required to generate Barkhausen noise differs between the process of increasing the magnetic field and the process of decreasing the magnetic field, as shown in FIG. However, as shown in FIG. 5, the absolute value of the magnetic field required to generate Barkhausen noise when the magnetic field is increasing and the value of the magnetic field required to generate Barkhausen noise when the magnetic field is decreasing. Is a constant value regardless of the presence or absence of the residual magnetic field and the strength of the residual magnetic field.
【００２２】よって、増加過程にある磁界を印加したと
きにバルクハウゼンノイズの発生に要する印加磁界と、
減少過程にある磁界を印加したときにバルクハウゼンノ
イズの発生に要する印加磁界とをそれぞれ求めて、それ
らの絶対値の和を求め、この絶対値の和と保磁力の関係
式をあらかじめ求めておき、被測定材料において、増加
過程にある磁界を印加したときにバルクハウゼンノイズ
が発生する印加磁界と、減少過程にある磁界を印加した
ときにバルクハウゼンノイズが発生する印加磁界とをそ
れぞれ求めて、それらの絶対値の和を求め、あらかじめ
求めた関係式に当てはめることにより、被測定強磁性体
材料の保磁力を非破壊で知ることができる。Therefore, when an increasing magnetic field is applied, the applied magnetic field required to generate Barkhausen noise is:
Obtain the applied magnetic field required for the generation of Barkhausen noise when applying a magnetic field in the process of decreasing, calculate the sum of their absolute values, and obtain the relational expression between the sum of the absolute values and the coercive force in advance. In the material to be measured, an applied magnetic field in which Barkhausen noise is generated when a magnetic field in an increasing process is applied, and an applied magnetic field in which Barkhausen noise is generated when a magnetic field in a decreasing process is applied, are obtained. The coercive force of the ferromagnetic material to be measured can be known in a non-destructive manner by calculating the sum of the absolute values and applying the sum to the relational expression obtained in advance.
【００２３】前記課題を解決するための第３の手段は、
前記第１の手段又は第２の手段であって、バルクハウゼ
ンノイズの発生に要する磁界の強さとして、バルクハウ
ゼンノイズの振幅が最大となるときの磁界の強さを採用
することを特徴とするもの（請求項３）である。A third means for solving the above-mentioned problem is:
The first means or the second means, wherein the strength of the magnetic field when the amplitude of the Barkhausen noise is maximized is adopted as the strength of the magnetic field required to generate Barkhausen noise. (Claim 3).
【００２４】前述のように、バルクハウゼンノイズは微
分透磁率が最大となるところで最も多く発生する。逆に
いえば、バルクハウゼンノイズが最も多く発生するとこ
ろが、微分透磁率が最大となる場所、すなわちＢ−Ｈカ
ーブがＨ軸にゼロクロスする場所である。よって、本手
段においては、バルクハウゼンノイズの発生に要する磁
界の強さとして、バルクハウゼンノイズの振幅が最大と
なるときの磁界の強さを採用し、そのときの磁界の強さ
を基にして保磁力を求めているので、保磁力を正確に求
めることができる。As described above, Barkhausen noise occurs most frequently where the differential magnetic permeability is maximum. Conversely, the place where Barkhausen noise is generated most is the place where the differential magnetic permeability is maximum, that is, the place where the BH curve crosses the H axis at zero. Therefore, in the present means, as the strength of the magnetic field required for the generation of Barkhausen noise, the strength of the magnetic field when the amplitude of the Barkhausen noise is maximum is adopted, and based on the strength of the magnetic field at that time. Since the coercive force is determined, the coercive force can be determined accurately.
【００２５】前記課題を解決するための第４の手段は、
前記第１の手段から第３の手段のいずれかであって、被
測定強磁性体材料に磁界を印加する磁化器のヨーク材、
及びバルクハウゼンノイズ測定に用いる磁気検出器のコ
ア材として、想定される被測定強磁性体材料の保磁力と
大きく異なる保磁力を有する材料を用いることを特徴と
するもの（請求項４）である。A fourth means for solving the above-mentioned problem is as follows.
Any one of the first to third means, wherein a yoke material of a magnetizer for applying a magnetic field to the ferromagnetic material to be measured;
And a material having a coercive force greatly different from a coercive force of a ferromagnetic material to be measured is used as a core material of a magnetic detector used for Barkhausen noise measurement (Claim 4). .
【００２６】ここで、本手段においては、計測に用いる
磁化器および磁気検出器の磁気特性によらない測定が行
える。つまり、バルクハウゼンノイズは磁壁の移動の激
しい領域でのみ発生するため、その出現する磁界の範囲
は狭い。そのため、磁化器ヨークおよび磁気検出器コア
の材料として、被測定強磁性体材料の保磁力として予想
される値と大きく異なる保磁力を有するものを選択すれ
ば、励磁コイルおよび検出コイルのコアから発生するバ
ルクハウゼンノイズと干渉せずに、被測定強磁性体材料
から発生するバルクハウゼンノイズに対応する磁界の強
さのみを測定することができる。Here, in this means, the measurement can be performed without depending on the magnetic characteristics of the magnetizer and the magnetic detector used for the measurement. That is, Barkhausen noise is generated only in a region where the domain wall moves sharply, and the range of the magnetic field that appears is narrow. Therefore, if a material having a coercive force that is significantly different from the expected coercive force of the ferromagnetic material to be measured is selected as the material of the magnetizer yoke and the magnetic detector core, the material generated from the cores of the excitation coil and the detection coil is generated. It is possible to measure only the strength of the magnetic field corresponding to the Barkhausen noise generated from the ferromagnetic material to be measured without interfering with the Barkhausen noise.
【００２７】[0027]
【発明の実施の形態】以下本発明の実施の形態について
図を用いて詳細に説明する。図１は、本発明の実施の形
態の１例である保磁力測定方法を実施するための測定装
置の概略構成を示す図である。図１において、１は被測
定材料、２は磁化器、３は磁気検出器、４は三角波発生
器、５は電力増幅器、６は信号増幅器、７はフィルタ
ー、８は演算処理装置、９は磁界検出器、１０は磁界信
号増幅器である。Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a diagram showing a schematic configuration of a measuring device for performing a coercive force measuring method which is an example of an embodiment of the present invention. In FIG. 1, 1 is a material to be measured, 2 is a magnetizer, 3 is a magnetic detector, 4 is a triangular wave generator, 5 is a power amplifier, 6 is a signal amplifier, 7 is a filter, 8 is an arithmetic processing unit, and 9 is a magnetic field. The detector 10 is a magnetic field signal amplifier.
【００２８】三角波形発生器４より発信される三角波信
号は、電力増幅器５により信号増幅されて、励磁電流と
して磁化器２の励磁コイルへ印加される。この磁化器
は、図示するようにＵ字型をしており、２つのヨークが
被測定材料１に近接して設置される。この磁化器２のほ
ぼ中央には、被測定材料１の面方向の漏洩磁束を検出す
るため磁気検出器３が設置されている。ここでは、磁気
検出器３としてＵ字型の磁気コイルを用いている。磁気
コイルで検出された信号は、信号増幅器６で増幅された
後、不要な成分を取り除くためフィルター７を通され、
バルクハウゼンノイズのみが抽出される。The triangular wave signal transmitted from the triangular waveform generator 4 is amplified by a power amplifier 5 and applied to an exciting coil of the magnetizer 2 as an exciting current. The magnetizer has a U-shape as shown in the figure, and two yokes are installed close to the material 1 to be measured. At a substantially center of the magnetizer 2, a magnetic detector 3 for detecting a leakage magnetic flux in the surface direction of the material 1 to be measured is provided. Here, a U-shaped magnetic coil is used as the magnetic detector 3. The signal detected by the magnetic coil is amplified by a signal amplifier 6 and then passed through a filter 7 to remove unnecessary components.
Only Barkhausen noise is extracted.
【００２９】また、被測定材料１の表面近傍に、被測定
材料１の表面方向の磁界を計測する磁界検出器９が設け
られており、その信号を磁界信号増幅器１０により増幅
して、被測定材料１に印加されている磁界を測定する。
演算処理装置８は、フィルター７で抽出されたバルクハ
ウゼンノイズの信号と磁界信号増幅器１０の出力信号と
により、バルクハウゼンノイズの発生に要する磁界の強
さを算出して保磁力に換算する。A magnetic field detector 9 for measuring a magnetic field in the direction of the surface of the material 1 to be measured is provided near the surface of the material 1 to be measured. The magnetic field applied to the material 1 is measured.
The arithmetic processing unit 8 calculates the strength of the magnetic field required for generating Barkhausen noise based on the signal of Barkhausen noise extracted by the filter 7 and the output signal of the magnetic field signal amplifier 10, and converts it into coercive force.
【００３０】被測定材料１への磁界の印加は磁化器２に
より行われるが、バルクハウゼンノイズの発生に要する
磁界の強さを調べるために、被測定材料１へ印加する磁
界の強さを変化させる必要がある。ここでは、磁界の強
さの変化を、磁化電流値を三角波状に増減させることで
行っている。The application of a magnetic field to the material 1 to be measured is performed by the magnetizer 2, and the intensity of the magnetic field applied to the material 1 to be measured is changed in order to check the strength of the magnetic field required to generate Barkhausen noise. Need to be done. Here, the intensity of the magnetic field is changed by increasing or decreasing the magnetizing current value in a triangular waveform.
【００３１】ここで、バルクハウゼンノイズは1〜10kHz
と高周波であるため、被測定材料１の表面近傍で発生し
たもののみが測定される。そのため、バルクハウゼンの
発生に要する磁界の強さは被測定材料表面近傍の値を知
ればよい。この値は隣接する空気層の磁界の強さと連続
となることから、被測定材料１の表面近傍に設置した磁
界検出器９により非破壊で磁界の強さを測定することが
できる。これにより、バルクハウゼンノイズの発生に要
する磁界の強さを知ることができる。Here, Barkhausen noise is 1 to 10 kHz.
And the high frequency, only those generated near the surface of the material 1 to be measured are measured. Therefore, the intensity of the magnetic field required to generate Barkhausen may be a value near the surface of the material to be measured. Since this value is continuous with the magnetic field strength of the adjacent air layer, the magnetic field strength can be measured nondestructively by the magnetic field detector 9 installed near the surface of the material 1 to be measured. This makes it possible to know the strength of the magnetic field required to generate Barkhausen noise.
【００３２】正確な測定を行うためには、一定の振幅の
磁界が被測定材料１に印加されるように制御することが
好ましい。材料内へ印加される磁界の強さは、材料の透
磁率や厚みによって変化するので、一定の振幅の磁界が
被測定材料１に印加されるようにするには、あらかじめ
求めておいた、材料の厚みおよび成分ごとの磁化器への
磁化電流値と磁界の強さとの校正曲線により、材料の厚
みおよび成分に応じて磁化器の磁化電流を制御するよう
にすることが好ましい。また、表面近傍に設置した磁界
検出器９により測定される磁界の強さの変化が一定にな
るよう、磁化器の磁化電流を制御するようにしてもよ
い。In order to perform accurate measurement, it is preferable to control so that a magnetic field having a constant amplitude is applied to the material 1 to be measured. Since the strength of the magnetic field applied into the material changes depending on the magnetic permeability and thickness of the material, in order to apply a magnetic field having a constant amplitude to the material 1 to be measured, a material determined in advance must be It is preferable to control the magnetizing current of the magnetizer according to the thickness and the component of the material by a calibration curve of the magnetizing current value to the magnetizer and the magnetic field strength for each thickness and component. Further, the magnetizing current of the magnetizer may be controlled so that the change in the strength of the magnetic field measured by the magnetic field detector 9 installed near the surface is constant.
【００３３】この実施の形態では、バルクハウゼンノイ
ズの発生に要する磁化器への磁化電流の強さから、バル
クハウゼンノイズの発生に要する磁界の強さを知り、そ
れから保磁力を演算するようにしているが、演算処理装
置８の動作として、バルクハウゼンノイズの振幅が最大
となるときの磁界の強さを検出し、これをバルクハウゼ
ンノイズの発生に要する磁界の強さと判断するような動
作を採用すれば、より正確で再現性の良い測定が可能と
なる。In this embodiment, the strength of the magnetic field required for generating Barkhausen noise is known from the strength of the magnetizing current to the magnetizer required for generating Barkhausen noise, and the coercive force is calculated based on the magnetic field strength. However, the operation of the arithmetic processing unit 8 employs an operation of detecting the strength of the magnetic field when the amplitude of the Barkhausen noise is maximized, and judging this as the strength of the magnetic field required to generate Barkhausen noise. Then, more accurate and highly reproducible measurement can be performed.
【００３４】また、演算処理装置８の動作を、図５に示
すように、増加過程にある磁界を印加したときにバルク
ハウゼンノイズの振幅が最大となる印加磁界と、減少過
程にある磁界を印加したときにバルクハウゼンノイズの
振幅が最大となる印加磁界とをそれぞれ求めて、それら
の絶対値の和を求め、これらの絶対値の和を、あらかじ
め求められた絶対値の和と保磁力との関係を示す式にあ
てはめて保磁力を算出する動作とすることにより、被測
定材料の残留磁気の影響を受けずに保磁力を算出するこ
とができるようになる。As shown in FIG. 5, the operation of the arithmetic processing unit 8 is divided into an applied magnetic field in which the amplitude of Barkhausen noise is maximized when a magnetic field in an increasing process is applied, and an applied magnetic field in a decreasing process. Then, the applied magnetic field at which the amplitude of the Barkhausen noise becomes maximum is obtained, the sum of their absolute values is obtained, and the sum of these absolute values is calculated by calculating the sum of the absolute value obtained in advance and the coercive force. By performing the operation of calculating the coercive force by applying to the equation indicating the relationship, the coercive force can be calculated without being affected by the remanence of the material to be measured.
【００３５】[0035]
【実施例】本発明の方法を使用して保磁力を測定した結
果の例を図６に示す。図１に示すような測定装置を使用
し、励磁電流として図５に示すような三角波を与えて測
定を行った。被測定対象材としては、保磁力が1500〜25
00A/mと比較的大きな工具鋼を用い、本発明法に基づい
て測定を行った後、リング状サンプルとして切り出し、
励磁コイルと検出コイルを巻いて求めたヒステリシスル
ープに基づいて保磁力を測定し、回帰分析により、真の
保磁力と本発明による測定値との関係を求めて図６に示
した。FIG. 6 shows an example of the result of measuring the coercive force using the method of the present invention. Using a measuring device as shown in FIG. 1, a measurement was performed by giving a triangular wave as shown in FIG. 5 as an exciting current. As the material to be measured, the coercive force is 1500 to 25
Using a relatively large tool steel of 00A / m, after measuring based on the method of the present invention, cut out as a ring sample,
The coercive force was measured based on a hysteresis loop obtained by winding the exciting coil and the detecting coil, and the relationship between the true coercive force and the measured value according to the present invention was obtained by regression analysis, and is shown in FIG.
【００３６】測定に際しては、被測定対象材の保磁力が
大きいことから、磁化器ヨーク材、磁気検出器コア材に
は保磁力の小さな軟鉄を用い、両者の干渉を避けるよう
配慮した。また、三角波の周波数は５Hzとし、バルクハ
ウゼンノイズの発生に要する磁界の強さは、バルクハウ
ゼンノイズが最大値を示す磁界の強さとして求めた。At the time of measurement, since the coercive force of the material to be measured is large, soft magnets having small coercive force were used for the magnetizer yoke material and the magnetic detector core material, and care was taken to avoid interference between the two. The frequency of the triangular wave was 5 Hz, and the strength of the magnetic field required to generate Barkhausen noise was determined as the strength of the magnetic field at which Barkhausen noise had a maximum value.
【００３７】そして、増加過程にある磁界を印加したと
きにバルクハウゼンノイズの振幅が最大となる印加磁界
と、減少過程にある磁界を印加したときにバルクハウゼ
ンノイズの振幅が最大となる印加磁界とをそれぞれ求め
て、それらの絶対値の和を求め、これらの絶対値の和と
保磁力とを対応させた。An applied magnetic field that maximizes the amplitude of Barkhausen noise when a magnetic field in the increasing process is applied, and an applied magnetic field that maximizes the amplitude of Barkhausen noise when the magnetic field in the decreasing process is applied And the sum of their absolute values was calculated, and the sum of these absolute values was made to correspond to the coercive force.
【００３８】図６より、真の保磁力と本発明法において
測定された保磁力相当値は良好な対応関係にあることが
わかる。ちなみに、回帰分析の結果、両者の間の誤差
は、標準偏差σで20A/mと非常に小さなものであった。FIG. 6 shows that there is a good correspondence between the true coercive force and the value corresponding to the coercive force measured in the method of the present invention. Incidentally, as a result of the regression analysis, the error between the two was very small with a standard deviation σ of 20 A / m.
【００３９】[0039]
【発明の効果】以上説明したように、本発明のうち請求
項１に係る発明においては、保磁力に関する情報のみを
使用して測定を行うことができるので、測定精度が向上
する。As described above, according to the first aspect of the present invention, since the measurement can be performed using only information on the coercive force, the measurement accuracy is improved.
【００４０】請求項２に係る発明においては、これに加
え、被測定対象材中の残留磁界の有無に係わらず正確な
保磁力の測定が可能となる。According to the second aspect of the invention, in addition to this, it is possible to accurately measure the coercive force regardless of the presence or absence of the residual magnetic field in the material to be measured.
【００４１】請求項３に係る発明においては、これらに
加え、さらに測定精度を向上させることができる。In the invention according to the third aspect, in addition to these, the measurement accuracy can be further improved.
【００４２】請求項４に係る発明においては、これらに
加え、励磁コイルおよび検出コイルのコアから発生する
バルクハウゼンノイズと干渉せずに、被測定強磁性体か
ら発生するバルクハウゼンノイズに対応する磁界の強さ
のみを測定することができる。In the invention according to claim 4, in addition to these, the magnetic field corresponding to the Barkhausen noise generated from the ferromagnetic material to be measured does not interfere with the Barkhausen noise generated from the cores of the excitation coil and the detection coil. Can be measured only.
【図１】本発明の実施の形態の１例である保磁力測定方
法を実施するための測定装置の概略構成を示す図であ
る。FIG. 1 is a diagram showing a schematic configuration of a measuring apparatus for performing a coercive force measuring method which is an example of an embodiment of the present invention.
【図２】バルクハウゼンノイズの発生機構を示す図であ
る。FIG. 2 is a diagram illustrating a mechanism of generating Barkhausen noise.
【図３】バルクハウゼンノイズの波形の例を示す図であ
る。FIG. 3 is a diagram illustrating an example of a waveform of Barkhausen noise.
【図４】磁気材料の磁化過程と保磁力の関係を示す図で
ある。FIG. 4 is a diagram showing a relationship between a magnetization process of a magnetic material and a coercive force.
【図５】残留磁場がある場合のバイアス磁界によが、バ
ルクハウゼノイズの発生に実用な励磁電流に及ぼす影響
を示す図である。FIG. 5 is a diagram showing the effect of a bias magnetic field in the presence of a residual magnetic field on a practical excitation current for generating Barkhause noise.
【図６】本発明により測定した保磁力と、従来の破壊検
査法により測定した保磁力（真の保磁力）の相関を示す
図である。FIG. 6 is a diagram showing a correlation between a coercive force measured by the present invention and a coercive force (true coercive force) measured by a conventional destructive inspection method.
【図７】従来の非破壊的保磁力測定装置の概要を示す図
である。FIG. 7 is a diagram showing an outline of a conventional nondestructive coercive force measuring device.
１…被測定材料 ２…磁化器 ３…磁気検出器 ４…三角波発生器 ５…電力増幅器 ６…信号増幅器 ７…フィルター ８…演算処理装置 ９…磁界検出器 １０…磁界信号増幅器 DESCRIPTION OF SYMBOLS 1 ... Material to be measured 2 ... Magnetizer 3 ... Magnetic detector 4 ... Triangular wave generator 5 ... Power amplifier 6 ... Signal amplifier 7 ... Filter 8 ... Arithmetic processing unit 9 ... Magnetic field detector 10 ... Magnetic field signal amplifier
Claims (4)
さを変化させてバルクハウゼンノイズの発生に要する磁
界の強さを求め、当該磁界の強さから強磁性体材料の保
磁力を求めることを特徴とする保磁力の測定方法。1. The strength of a magnetic field required for generating Barkhausen noise is obtained by changing the strength of a magnetic field applied to a ferromagnetic material to be measured, and the coercive force of the ferromagnetic material is determined from the strength of the magnetic field. A method for measuring a coercive force, which is to be determined.
さを変化させて、磁界の増加過程、磁界の減少過程にお
いてバルクハウゼンノイズの発生に要する磁界の強さを
それぞれ求め、当該磁界の絶対値の和から強磁性体材料
の保磁力を求めることを特徴とする保磁力の測定方法。2. The method according to claim 1, wherein the intensity of the magnetic field applied to the ferromagnetic material to be measured is changed to determine the intensity of the magnetic field required to generate Barkhausen noise in a process of increasing the magnetic field and a process of decreasing the magnetic field. A method for measuring the coercive force of a ferromagnetic material from the sum of the absolute values of
測定方法であって、バルクハウゼンノイズの発生に要す
る磁界の強さとして、バルクハウゼンノイズの振幅が最
大となるときの磁界の強さを採用することを特徴とする
保磁力の測定方法。3. The method for measuring a coercive force according to claim 1, wherein the strength of the magnetic field required to generate Barkhausen noise is defined as the strength of the magnetic field when the amplitude of Barkhausen noise is maximized. A method for measuring coercive force, characterized by employing strength.
項に記載の保磁力の測定方法であって、被測定強磁性体
材料に磁界を印加する磁化器のヨーク材、及びバルクハ
ウゼンノイズ測定に用いる磁気検出器のコア材として、
想定される被測定強磁性体材料の保磁力と大きく異なる
保磁力を有する材料を用いることを特徴とする保磁力の
測定方法。4. One of claims 1 to 3
The method of measuring the coercive force according to the paragraph, as a yoke material of a magnetizer that applies a magnetic field to the ferromagnetic material to be measured, and as a core material of a magnetic detector used for Barkhausen noise measurement,
A method for measuring a coercive force, characterized by using a material having a coercive force significantly different from a coercive force of a ferromagnetic material to be measured.
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|---|---|---|---|
| JP32087499A JP2001141701A (en) | 1999-11-11 | 1999-11-11 | Method for measuring coercive force |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP32087499A JP2001141701A (en) | 1999-11-11 | 1999-11-11 | Method for measuring coercive force |
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| Publication number | Priority date | Publication date | Assignee | Title |
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