JP2002156366A - Inspection method of spherical graphitic cast iron member - Google Patents
Inspection method of spherical graphitic cast iron memberInfo
- Publication number
- JP2002156366A JP2002156366A JP2000351141A JP2000351141A JP2002156366A JP 2002156366 A JP2002156366 A JP 2002156366A JP 2000351141 A JP2000351141 A JP 2000351141A JP 2000351141 A JP2000351141 A JP 2000351141A JP 2002156366 A JP2002156366 A JP 2002156366A
- Authority
- JP
- Japan
- Prior art keywords
- cast iron
- spheroidal graphite
- graphite cast
- iron member
- ferrite phase
- 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
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Landscapes
- Investigating Or Analyzing Materials By The Use Of Magnetic Means (AREA)
Abstract
Description
【０００１】[0001]
【発明の属する技術分野】本発明は、球状黒鉛鋳鉄部材
の検査方法及び検査装置に関する。The present invention relates to a method and an apparatus for inspecting a spheroidal graphite cast iron member.
【０００２】[0002]
【従来の技術】自動車部品、特にサスペンションやナッ
クル等の大きな負荷や強い衝撃のかかる自動車部品は、
球状黒鉛鋳鉄で形成されるが、軽量化のために小型化及
び薄肉化が要求され、引張強さ及び伸びが大きい球状黒
鉛鋳鉄部材の開発が望まれている。そこで本出願人は、
特開平９−２９６２１５号公報に記載の如く、Ｍｎ、Ｃ
ｕ、Ｓｎ、Ｓｂ及びＰｂからなる群から選ばれた少なく
とも一種のパーライト安定化元素を含有し、フェライト
化率が６０％以上で少なくとも０．５ｍｍの厚さを有す
る表層部と、基地の大部分がパーライト相からなる内部
とを有し、引張強さや耐衝撃性等が良好な球状黒鉛鋳鉄
部材を開発した。2. Description of the Related Art Automobile parts, especially automobile parts that are subjected to large loads or strong impacts such as suspensions and knuckles,
Although formed of spheroidal graphite cast iron, miniaturization and thinning are required for weight reduction, and development of a spheroidal graphite cast iron member having large tensile strength and elongation is desired. Therefore, the applicant has
As described in JP-A-9-296215, Mn, C
a surface layer part containing at least one pearlite stabilizing element selected from the group consisting of u, Sn, Sb and Pb, having a ferrite conversion rate of 60% or more and a thickness of at least 0.5 mm; Has developed a spheroidal graphite cast iron member having a pearlite phase inside and excellent tensile strength and impact resistance.
【０００３】更に本出願人は、特願平２０００−１９８
８５号にて、肉厚が１ｃｍ以下の薄肉部を有する球状黒
鉛鋳鉄部材において、質量比で、Ｃ：３．４〜３．９
％、Ｓｉ：１．９〜２．６％、Ｐ：０．０５％以下、
Ｓ：０．０２％以下、Ｍｇ：０．０２〜０．０６％、Ｃ
ｕ：０．５〜１％、及び残部実質的にＦｅ及び不可避的
不純物からなり、基地のフェライト化率が６０％以上の
表層部と基地の大部分がパーライト相からなる内部とを
有し、前記表層部の厚さが実質的に全鋳肌面にわたって
０．０５〜０．４５ｍｍの範囲内にあり、薄肉部を有し
ていても、引張強さ及び極低温での耐衝撃性に優れた球
状黒鉛鋳鉄部材を開発した。[0003] Further, the present applicant has disclosed Japanese Patent Application No. 2000-198.
No. 85, in a spheroidal graphite cast iron member having a thin portion having a thickness of 1 cm or less, C: 3.4 to 3.9 in mass ratio.
%, Si: 1.9 to 2.6%, P: 0.05% or less,
S: 0.02% or less, Mg: 0.02 to 0.06%, C
u: 0.5 to 1%, the balance substantially consisting of Fe and unavoidable impurities, and having a surface layer portion in which the ferrite conversion ratio of the matrix is 60% or more and an inside in which most of the matrix is formed of a pearlite phase, The thickness of the surface layer portion is substantially in the range of 0.05 to 0.45 mm over the entire casting surface, and has excellent tensile strength and impact resistance at cryogenic temperatures even with a thin portion. Spheroidal graphite cast iron members were developed.
【０００４】上述した２種類の球状黒鉛鋳鉄部材は、引
張強さ及び耐衝撃性を確保するために、表層部のフェラ
イト相の厚さを厳密に管理する必要がある。検査手法と
しては、製品から試料を切出し顕微鏡で組織を観察する
破壊検査や、超音波音速測定による非破壊検査などがま
ず考えられる。しかし、破壊検査では検査結果を得るま
でに時間がかかり、用途によっては球状黒鉛鋳鉄部材を
別部材と組み立てた後で結果が分かり万一不合格の場合
は、最終製品とした後に、分解して全数検査しなければ
ならないという問題点がある。一方、超音波音速測定に
よる非破壊検査は、非破壊で直接測定できるという簡便
さはあるが、球状黒鉛鋳鉄部材表層部のフェライト相の
有無やその厚さ、更にフェライト相の内部のパーライト
相の有無までは判別できないという問題点がある。In the above two types of spheroidal graphite cast iron members, it is necessary to strictly control the thickness of the ferrite phase in the surface layer in order to secure tensile strength and impact resistance. As an inspection method, a destructive inspection in which a sample is cut out from a product and the tissue is observed with a microscope, a nondestructive inspection by ultrasonic sound velocity measurement, and the like can be considered. However, in the destructive inspection, it takes time to obtain the inspection result, and depending on the application, the result is ascertained after assembling the spheroidal graphite cast iron member with another member, and if it does not pass, it is disassembled after it is final product There is a problem that 100% inspection is required. On the other hand, the nondestructive inspection by ultrasonic sound velocity measurement has the simplicity that it can be directly measured nondestructively, but the presence or absence of the ferrite phase on the surface layer of the spheroidal graphite cast iron member, its thickness, and the pearlite phase inside the ferrite phase. There is a problem that it is not possible to determine the presence or absence.
【０００５】一方、上記以外の非破壊検査の手法とし
て、渦電流を用いる検査方法がある。例えば特開平１０
−２０６３９５号公報には、試験コイルに励磁電流を誘
導し、その励磁電流によって測定試料に渦電流を生成さ
せ、試験コイルに生じるインピーダンスの変化を検出す
ること及び励磁電流の周波数を変化させて測定試料にお
ける低周波数側及び高周波数側の少なくとも２つのイン
ピーダンスの測定値を対比することによって、金属組織
の変化、特に焼入れ鋼の加工において発生する加工変質
層を検出し、測定試料を破断することなく表面硬化処理
部品の硬化層深さを測定することが記載されている。On the other hand, as a nondestructive inspection method other than the above, there is an inspection method using an eddy current. For example, JP-A-10
JP-A-206395 discloses that an exciting current is induced in a test coil, an eddy current is generated in a measurement sample by the exciting current, a change in impedance generated in the test coil is detected, and a frequency of the exciting current is changed to perform measurement. By comparing the measured values of at least two impedances on the low frequency side and the high frequency side of the sample, a change in the metallographic structure, particularly a work-affected layer that occurs in the processing of quenched steel, is detected without breaking the measured sample. Measuring the hardened layer depth of a surface hardened part is described.
【０００６】渦電流の浸透深さは被検査材（導電体）の
導電率と、透磁率及び励磁電流の周波数の積の平方根に
反比例することはよく知られている（「渦流探傷試験
３」〔（社）日本非破壊検査協会１９８４年発行〕参
照）。浸透深さは、周波数が低くなるにつれ深くなるの
で、複数の周波数を使用すれば焼入深さなどの金属組織
の変化度合いを検出できることは容易に理解できる。It is well known that the depth of penetration of an eddy current is inversely proportional to the conductivity of the material to be inspected (conductor) and the square root of the product of the magnetic permeability and the frequency of the exciting current ("Eddy Current Testing 3"). [See Japan Non-Destructive Inspection Association (1984)]. Since the penetration depth increases as the frequency decreases, it can be easily understood that a plurality of frequencies can be used to detect the degree of change in the metal structure such as the quenching depth.
【０００７】[0007]
【発明が解決しようとする課題】しかしながら、上記特
開平１０−２０６３９５号公報に記載の検出方法では、
焼入れ鋼の切削加工または研削加工によって生じた最表
面の加工変質層の有無やその程度を検出することはでき
ても、焼入とは逆の、表層部に軟質のフェライト相が薄
く形成され、その内部が硬質のパーライト相で形成され
ている球状黒鉛鋳鉄部材のフェライト相の厚さを検出す
ることはできない。即ち、球状黒鉛鋳鉄は、均一の組織
に近い鋼と比べ、黒鉛と基地組織からなる組織のばらつ
きが比較的大きい材料である。このため、上記公報に記
載されているように励磁電流の周波数を低周波から高周
波までの広い範囲（１００ｋＨｚ〜６ＭＨｚ）で変化さ
せ、渦電流の浸透深さを変えただけでは、組織のばらつ
きによる渦電流のばらつきが大きく、組織差を正確に判
別することができないと考えられる。However, in the detection method described in Japanese Patent Application Laid-Open No. H10-206395,
Even if it is possible to detect the presence and degree of a work-affected layer on the outermost surface caused by cutting or grinding of quenched steel, the reverse of quenching, a soft ferrite phase is formed thinly on the surface layer, The thickness of the ferrite phase of a spheroidal graphite cast iron member having a hard pearlite phase inside cannot be detected. That is, spheroidal graphite cast iron is a material having a relatively large variation in the structure composed of graphite and a base structure, as compared with steel having a uniform structure. For this reason, as described in the above publication, the frequency of the exciting current is changed in a wide range from low frequency to high frequency (100 kHz to 6 MHz) and the penetration depth of the eddy current is merely changed to cause a variation in tissue. It is considered that the variation of the eddy current is large and the tissue difference cannot be accurately determined.
【０００８】本発明の課題は、球状黒鉛鋳鉄部材の表層
部のフェライト相の有無やその厚さ、更にフェライト相
の内部のパーライト相の有無を、非破壊で迅速にかつ正
確に検出することができる検査方法を提供することであ
る。An object of the present invention is to detect non-destructively, quickly and accurately the presence or absence of a ferrite phase in the surface layer of a spheroidal graphite cast iron member, and the presence or absence of a pearlite phase inside the ferrite phase. It is to provide an inspection method that can be performed.
【０００９】[0009]
【課題を解決するための手段】本発明者らは、フェライ
ト相とパーライト相では磁気特性に差異があることに注
目し、球状黒鉛鋳鉄部材の表面に接触または近接して配
置したコイルに低周波の励磁電流を複数個流して磁界を
発生させ、球状黒鉛鋳鉄部材に渦電流を生成させた。そ
の結果、励磁電流の周波数及び磁界の強さを適宜選択す
ることで、渦電流によりコイルに生じるインピーダンス
が、球状黒鉛鋳鉄部材表層部のフェライト相の有無やそ
の厚さ、更にフェライト相の内部のパーライト相の有無
で大きく異なることを見出し、本発明に想到した。The present inventors have noticed that there is a difference in magnetic properties between the ferrite phase and the pearlite phase, and have applied a low-frequency coil to a coil placed in contact with or close to the surface of a spheroidal graphite cast iron member. A plurality of exciting currents were passed to generate a magnetic field, and an eddy current was generated in the spheroidal graphite cast iron member. As a result, by appropriately selecting the frequency of the exciting current and the strength of the magnetic field, the impedance generated in the coil due to the eddy current causes the presence or absence of the ferrite phase on the surface layer of the spheroidal graphite cast iron member, its thickness, and the internal The present inventors have found that they differ greatly depending on the presence or absence of the pearlite phase, and have reached the present invention.
【００１０】即ち、本発明の球状黒鉛鋳鉄部材表層部の
検査方法は、球状黒鉛鋳鉄部材の表面に接触または近接
して配置したコイルに１００ｋＨｚ未満の周波数をもつ
複数個の励磁電流を流すことにより発生した磁界によ
り、前記部材に渦電流を生成させ、この各周波数につい
て渦電流により前記コイルに生じるインピーダンス変化
を検出することにより、前記球状黒鉛鋳鉄部材の表層部
のフェライト相の有無及び／またはフェライト相の厚さ
を検知することを特徴とする。In other words, the method for inspecting the surface layer of a spheroidal graphite cast iron member according to the present invention is characterized in that a plurality of exciting currents having a frequency of less than 100 kHz are passed through a coil arranged in contact with or close to the surface of the spheroidal graphite cast iron member. An eddy current is generated in the member by the generated magnetic field, and an impedance change generated in the coil due to the eddy current at each frequency is detected, whereby the presence or absence of a ferrite phase and / or a ferrite phase in the surface layer of the spheroidal graphite cast iron member is detected. It is characterized by detecting the thickness of the phase.
【００１１】本発明において、励磁電流は６種類以上
で、その周波数が２０Ｈｚ〜３２ｋＨｚの範囲にあるこ
とが好ましく、さらに励磁電流は２０Ｈｚ〜２０ｋＨｚ
の範囲に２つ以上の周波数をもつことがより好ましい。In the present invention, it is preferable that the excitation current has six or more types and the frequency is in the range of 20 Hz to 32 kHz, and the excitation current is 20 Hz to 20 kHz.
It is more preferable to have two or more frequencies in the range.
【００１２】本発明においては、コイルに励磁電流を流
すことにより磁界の強さを１０〜２０００Ａ／ｍにする
ことが好ましい。In the present invention, it is preferable that the intensity of the magnetic field be 10 to 2000 A / m by passing an exciting current through the coil.
【００１３】本発明において、表層部のフェライト相が
表面から２ｍｍ以下の深さまで存在し、それより内部の
大部分がパーライト相である球状黒鉛鋳鉄部材のフェラ
イト相の厚さを高精度に検出することができる。In the present invention, the thickness of the ferrite phase of the spheroidal graphite cast iron member in which the ferrite phase in the surface layer is present at a depth of 2 mm or less from the surface and most of the inside is the pearlite phase is detected with high accuracy. be able to.
【００１４】[0014]
【発明の実施の形態】以下、本発明の詳細を図面により
説明する。図１は、本発明を実施するための検査装置の
一例を示す構成図である。図１において、検査装置１０
は、球状黒鉛鋳鉄部材２０の表面２０ａに接触または近
接して配置した試験コイル１１を内蔵するプローブ１２
と、試験コイル１１のインピーダンスの変化を取出すた
めに、試験コイル１１と可変抵抗器（図示せず）とから
構成されているブリッジ回路１４と、基準信号を生成す
る発振回路１５と、ブリッジ回路１４の出力電圧を増幅
する増幅器１６と、増幅器１６の出力と移相器１３の出
力を比較する位相検波回路１７と、ＣＲＴなどの表示装
置１８とからなる。DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram showing an example of an inspection device for implementing the present invention. In FIG. 1, an inspection device 10
Is a probe 12 having a built-in test coil 11 disposed in contact with or in close proximity to the surface 20a of the spheroidal graphite cast iron member 20.
A bridge circuit 14 composed of the test coil 11 and a variable resistor (not shown) for extracting a change in impedance of the test coil 11; an oscillation circuit 15 for generating a reference signal; An amplifier 16 amplifies the output voltage of the phase shifter 13, a phase detection circuit 17 for comparing the output of the amplifier 16 with the output of the phase shifter 13, and a display device 18 such as a CRT.
【００１５】上記試験コイル１１としては、単一のコイ
ルで励磁と検出を兼ねる自己誘導形コイルを用いること
ができ、製作が容易であるという利点を有するが、検出
精度の点からは、励磁コイルと磁束による起電力を取出
すための検出コイルをもった相互誘導形コイルを用いる
ことが望ましい。この励磁コイルは電力増幅器を介して
発振回路に接続され、検出コイルは前置増幅器に接続さ
れる。前記発振回路１５は、公知のものを使用できる
が、発振精度が高くかつ安定性も高い水晶発振回路が好
適である。また本発明では、複数の周波数を用いるの
で、発振回路１５とブリッジ回路１４との間に分周回路
（図示せず）を接続して、発振回路１５で得られた一つ
の周波数を分周することにより検査に必要な複数の周波
数を作成すればよい。さらに増幅器１６としては、比較
的広い範囲の信号を均一に増幅する広帯域増幅器を用い
ることが望ましい。As the test coil 11, a self-induction type coil which performs both excitation and detection with a single coil can be used, which has the advantage of being easy to manufacture. It is desirable to use a mutual induction coil having a detection coil for extracting an electromotive force due to magnetic flux. The excitation coil is connected to the oscillation circuit via a power amplifier, and the detection coil is connected to a preamplifier. As the oscillation circuit 15, a known one can be used, but a crystal oscillation circuit having high oscillation accuracy and high stability is preferable. Further, in the present invention, since a plurality of frequencies are used, a frequency dividing circuit (not shown) is connected between the oscillation circuit 15 and the bridge circuit 14 to divide one frequency obtained by the oscillation circuit 15. Thus, a plurality of frequencies necessary for the inspection may be created. Further, as the amplifier 16, it is desirable to use a broadband amplifier that uniformly amplifies a signal in a relatively wide range.
【００１６】上記検査装置１０の動作は次の通りであ
る。発振回路１５で発振された基準信号は、ブリッジ回
路１４と移相器１３に加えられる。球状黒鉛鋳鉄部材２
０に渦電流が生成すると、ブリッジ回路１４のバランス
が崩れ（ブリッジが不平衡となり）、球状黒鉛鋳鉄部材
２０の表面２０ａに存在するフェライト相の厚さに応じ
て試験コイル１１のインピーダンスが変化し、このイン
ピーダンスの変化に応じた電圧が出力される。出力電圧
は極めて小さいので、増幅器１６により、その振幅が増
幅される。移相器１３では、そこに入力された基準信号
は、同一の周波数で任意の位相をもつ信号として出力さ
れる。増幅器１６の出力と移相器１３の出力は、位相検
波回路１７で比較され、搬送ノイズなどの不要信号が除
去される（これによりＳＮ比が向上する）。位相検波回
路１７の出力には、被測定物の材質、形状、寸法等の変
化に起因するノイズが含まれていることが多いので、必
要に応じ、図示しないフィルター回路（例えばバンドパ
スフィルター）を介して、表示装置１８にて表示され
る。The operation of the inspection apparatus 10 is as follows. The reference signal oscillated by the oscillation circuit 15 is applied to the bridge circuit 14 and the phase shifter 13. Spheroidal graphite cast iron member 2
When an eddy current is generated at zero, the balance of the bridge circuit 14 is lost (the bridge becomes unbalanced), and the impedance of the test coil 11 changes according to the thickness of the ferrite phase present on the surface 20a of the spheroidal graphite cast iron member 20. A voltage corresponding to the change in the impedance is output. Since the output voltage is extremely small, the amplitude is amplified by the amplifier 16. In the phase shifter 13, the reference signal input thereto is output as a signal having the same frequency and an arbitrary phase. The output of the amplifier 16 and the output of the phase shifter 13 are compared in a phase detection circuit 17, and unnecessary signals such as carrier noise are removed (this improves the SN ratio). Since the output of the phase detection circuit 17 often includes noise due to changes in the material, shape, dimensions, and the like of the device under test, a filter circuit (not shown) (for example, a band-pass filter) may be provided as necessary. Via the display device 18.
【００１７】上記検査装置１０による球状黒鉛鋳鉄部材
２０の表面２０ａに存在するフェライト相の検出動作の
詳細を図２により説明する。図２は、図１の検査装置１
０で、試験コイル１１を励磁して球状黒鉛鋳鉄部材２０
に渦電流を生成させる状況の模式図である。導電体の表
面に接触または近接して配置した試験コイル１１に励磁
電流ｉ（交流電流）を流すと、導電体内に渦電流が誘導
され、この渦電流は試験コイル１１に近い表面に集中し
て流れる（表皮効果）。また、渦電流の時間的な遅れを
示す位相は導電体の内部ほど大きくなる。ここで導電体
に発生した交流磁束の密度は、導電体の表面ほど高く、
表面から内部に入るほど低くなることは知られている。The detection operation of the ferrite phase present on the surface 20a of the spheroidal graphite cast iron member 20 by the inspection apparatus 10 will be described in detail with reference to FIG. FIG. 2 shows the inspection apparatus 1 of FIG.
0, the test coil 11 is excited and the spheroidal graphite cast iron member 20 is excited.
FIG. 4 is a schematic diagram of a situation in which an eddy current is generated in the circumstance. When an exciting current i (alternating current) is applied to the test coil 11 placed in contact with or close to the surface of the conductor, an eddy current is induced in the conductor, and the eddy current concentrates on the surface near the test coil 11. Flow (skin effect). Further, the phase indicating the time delay of the eddy current becomes larger inside the conductor. Here, the density of the AC magnetic flux generated in the conductor is higher on the surface of the conductor,
It is known that it gets lower from the surface to the inside.
【００１８】従って、図２に示すように、球状黒鉛鋳鉄
部材２０の表面２０ａから表層部２１を経て内部２２ま
で磁束が到達する周波数で試験コイル１１を励磁する
と、試験コイル１１のインピーダンスＺは表層部２１の
フェライト相を流れる渦電流Ｅｆと、表層部２１より内
部２２のパーライト相を流れる渦電流Ｅｐの両方に影響
された値となる。交流磁束Φは励磁電流ｉに比例し、励
磁電流ｉは周波数ｆにより変化することは知られてい
る。Accordingly, as shown in FIG. 2, when the test coil 11 is excited at a frequency at which the magnetic flux reaches the interior 22 through the surface layer 21 from the surface 20a of the spheroidal graphite cast iron member 20, the impedance Z of the test coil 11 becomes equal to the surface layer. The value is influenced by both the eddy current Ef flowing through the ferrite phase of the portion 21 and the eddy current Ep flowing from the surface layer portion 21 through the pearlite phase inside 22. It is known that the AC magnetic flux Φ is proportional to the exciting current i, and the exciting current i changes with the frequency f.
【００１９】なお、図１の検査装置の回路構成によれ
ば、上記インピーダンスＺは抵抗分（Ｒ）とインダクタ
ンス分（２πｆＬ）の和で表され、励磁電流ｉはインピ
ーダンスＺに反比例する。交流磁束Φと磁界の強さＨは
比例することから、周波数ｆが変化すれば、磁界の強さ
Ｈも変化することになる。According to the circuit configuration of the inspection apparatus shown in FIG. 1, the impedance Z is represented by the sum of the resistance (R) and the inductance (2πfL), and the exciting current i is inversely proportional to the impedance Z. Since the AC magnetic flux Φ is proportional to the magnetic field strength H, if the frequency f changes, the magnetic field strength H also changes.
【００２０】そして、励磁電流ｉの周波数を、例えば２
０Ｈｚ〜１ｋＨｚと低くして、球状黒鉛鋳鉄部材２０の
内部２２まで交流磁束Φを浸透させると、試験コイル１
１のインピーダンスは内部２２のパーライト相の特性を
反映する。一方、試験コイル１１の励磁電流ｉの周波数
を、例えば１６ｋＨｚ〜３２ｋＨｚと高くすると、試験
コイル１１が作る交流磁束Φは表面に集中し、試験コイ
ル１１のインピーダンスは表層部２１のフェライト相の
特性を反映したものとなる。従って、励磁電流ｉの周波
数として数十Ｈｚ〜数十ｋＨｚの範囲で２つ以上、例え
ば６つの異なる値を選択すれば、球状黒鉛鋳鉄部材２０
の表層部にフェライト相が存在するか否か、及びその厚
さを検出することができる。The frequency of the exciting current i is, for example, 2
When the AC magnetic flux Φ penetrates into the interior 22 of the spheroidal graphite cast iron member 20 by lowering the frequency to 0 Hz to 1 kHz, the test coil 1
The impedance of 1 reflects the characteristics of the pearlite phase inside 22. On the other hand, when the frequency of the exciting current i of the test coil 11 is increased to, for example, 16 kHz to 32 kHz, the AC magnetic flux Φ generated by the test coil 11 is concentrated on the surface, and the impedance of the test coil 11 is determined by the characteristics of the ferrite phase of the surface layer 21. Will be reflected. Therefore, if two or more, for example, six different values are selected as the frequency of the exciting current i in the range of several tens Hz to several tens kHz, the spheroidal graphite cast iron member 20 is selected.
It is possible to detect whether or not a ferrite phase exists in the surface layer portion of No. 3 and its thickness.
【００２１】本発明において、高精度で表層部のフェラ
イト相の厚さ検出するためには、周波数とともに磁界の
強さの選択も重要である。一般に鋳鉄や鋼のような磁性
体に渦電流を誘導させた場合、渦電流の浸透深さは、そ
の材料の導電率によってはほとんど影響されず、透磁率
に大きく依存するので、球状黒鉛鋳鉄のように組織のば
らつきが比較的大きい、即ち渦電流のばらつきが大きい
材料に渦電流を誘導させて組織の良否を判別する場合
は、周波数の変化により、できるだけ透磁率の差が大き
くなるような磁界の強さを選択すれば、組織のばらつき
の影響を受けずに、組織の良否を判別することができ
る。In the present invention, in order to detect the thickness of the ferrite phase in the surface layer portion with high accuracy, it is important to select not only the frequency but also the strength of the magnetic field. Generally, when an eddy current is induced in a magnetic material such as cast iron or steel, the penetration depth of the eddy current is hardly affected by the conductivity of the material and largely depends on the magnetic permeability. As described above, when determining the quality of a tissue by inducing an eddy current in a material having a relatively large variation in the tissue, that is, a material having a large variation in the eddy current, a magnetic field in which a difference in magnetic permeability is as large as possible due to a change in frequency. Is selected, the quality of the tissue can be determined without being affected by the variation of the tissue.
【００２２】図３は、表層部２１及びその内部２２とも
実質的にフェライト相からなる通常の機械的強度を有す
る球状黒鉛鋳鉄部材（フェライト基地球状黒鉛鋳鉄（Ｊ
ＩＳ）ＦＣＤ３７０相当材）、及び表層部２１及びその
内部２２とも実質的にパーライト相からなる通常の機械
的強度を有する球状黒鉛鋳鉄部材（パーライト基地球状
黒鉛鋳鉄（ＪＩＳ）ＦＣＤ６００相当材）の磁界の強さ
と比透磁率の関係を示す図である。FIG. 3 shows a spheroidal graphite cast iron member (ferrite based spheroidal graphite cast iron (J
IS) material equivalent to FCD370) and the spheroidal graphite cast iron member (material equivalent to pearlite-based spheroidal graphite cast iron (JIS) FCD600) having a normal mechanical strength in which both the surface layer portion 21 and the inside 22 thereof substantially consist of a pearlite phase. It is a figure which shows the relationship between intensity | strength and relative magnetic permeability.
【００２３】図３から、磁界の強さが２０００Ａ／ｍよ
りも大きいと、フェライト相とパーライト相とで比透磁
率の差が小さくなり、組織のばらつきの影響で材質の判
別が困難になるが、磁界の強さが１０〜２０００Ａ／ｍ
の範囲、好ましくは４００〜６００Ａ／ｍの範囲では、
フェライト相とパーライト相とでは比透磁率の差が大き
く異なるので、組織のばらつきの影響があったとしても
フェライト相とパーライト相の判別を行うことができ
る。FIG. 3 shows that when the strength of the magnetic field is greater than 2000 A / m, the difference in the relative permeability between the ferrite phase and the pearlite phase becomes small, and it becomes difficult to determine the material due to the influence of the structure variation. , The magnetic field strength is 10 to 2000 A / m
, Preferably in the range of 400 to 600 A / m,
Since the difference in the relative magnetic permeability between the ferrite phase and the pearlite phase is significantly different, the ferrite phase and the pearlite phase can be distinguished even if there is an effect of the variation in the structure.
【００２４】以下に示す４種類の球状黒鉛鋳鉄部材を準
備し、図１の検査装置１０により、フェライト相の検出
を行った。ＦＣＤ４５０及びＦＣＤ５００は、表層部２
１及びその内部２２とも実質的にフェライト相の通常の
機械的強度を有する球状黒鉛鋳鉄部材であり、ＦＣＤ６
００は、前述の表層部２１及びその内部２２とも実質的
にパーライト相の通常の機械的強度を有する球状黒鉛鋳
鉄部材である。The following four types of spheroidal graphite cast iron members were prepared, and a ferrite phase was detected by the inspection apparatus 10 shown in FIG. FCD450 and FCD500 have a surface layer 2
1 and its interior 22 are substantially spheroidal graphite cast iron members having a normal mechanical strength of a ferrite phase.
Reference numeral 00 denotes a spheroidal graphite cast iron member having a normal mechanical strength of the pearlite phase in both the surface layer portion 21 and the inside 22 thereof.
【００２５】表層部２１にフェライト相を有し、表層部
２１の内部２２の大部分がパーライト相である球状黒鉛
鋳鉄部材２０は、以下のようにして作製した。先ず、質
量比で、Ｃ：３．４〜３．９％、Ｓｉ：１．９〜２．６
％、Ｐ：０．０５％以下、Ｓ：０．０２％以下、Ｍｇ：
０．０２〜０．０６％、Ｃｕ：０．５〜１％、及び残部
実質的にＦｅ及び不可避的不純物からなる組成で、肉厚
が１ｃｍ以下の薄肉部を有する部材を鋳造した。その
後、（１）基地全体が実質的にオーステナイト化する温
度で保持し、（２）表層部２１のフェライト化が内部２
２のパーライト化より先に起こる冷却速度で冷却し、
（３）表層部２１の基地がフェライト相のままで内部２
２のパーライト化が起こる温度に保持し、（４）内部２
２のパーライト化が完了した直後に冷却する熱処理を施
した。そして、表層部２１をフェライト化率が６０％以
上の基地として全鋳肌面にわたって０．０５〜０．４５
ｍｍ厚さのフェライト相と、表層部２１の内部２２の大
部分をパーライト相とした。A spheroidal graphite cast iron member 20 having a ferrite phase in the surface layer portion 21 and a large part of the interior 22 of the surface layer portion 21 being a pearlite phase was produced as follows. First, C: 3.4-3.9%, Si: 1.9-2.6 by mass ratio.
%, P: 0.05% or less, S: 0.02% or less, Mg:
A member having a composition of 0.02 to 0.06%, Cu: 0.5 to 1%, and a balance substantially composed of Fe and unavoidable impurities, and having a thin portion having a thickness of 1 cm or less was cast. Thereafter, (1) the temperature is maintained at a temperature at which the entire substrate substantially turns into austenite, and (2) the ferrite of the surface layer portion 21
Cooling at a cooling rate that occurs prior to the pearlitization of 2,
(3) The base 2 of the surface layer 21 remains in the ferrite phase while the inside 2
(4) The internal temperature is maintained at a temperature at which pearlitization occurs.
Immediately after the pearlitization of No. 2 was completed, a heat treatment for cooling was performed. Then, the surface layer portion 21 is formed into a matrix having a ferrite conversion rate of 60% or more, and the surface portion 21 has a thickness of 0.05 to 0.45 over the entire casting surface.
The ferrite phase having a thickness of 1 mm and most of the interior 22 of the surface layer 21 were formed as a pearlite phase.
【００２６】図４は、励磁電流ｉの周波数と渦流強度指
示値の関係を示す図である。試験コイル１１により発生
する磁界の強さは周波数によって変化し、本実験では１
０〜２０００Ａ／ｍの範囲で変化させた。渦流強度指示
値は、ＦＣＤ６００のインピーダンスに対する他の球状
黒鉛鋳鉄部材のインピーダンスの比率である。FIG. 4 is a diagram showing the relationship between the frequency of the exciting current i and the eddy current strength instruction value. The strength of the magnetic field generated by the test coil 11 varies with the frequency.
It was changed in the range of 0 to 2000 A / m. The eddy current strength indication value is a ratio of the impedance of another spheroidal graphite cast iron member to the impedance of FCD600.
【００２７】図４から、検査の周波数が０．２５ｋＨｚ
〜３２ｋＨｚの範囲では、表層部２１にフェライト相を
有する球状黒鉛鋳鉄部材２０は、その渦流強度指示値は
８ｋＨｚの周波数のときに極大値を示す分布を有し、表
層部２１及びその内部２２とも実質的にフェライト相の
球状黒鉛鋳鉄部材（ＦＣＤ４５０、ＦＣＤ５００）や、
表層部２１及びその内部２２とも実質的にパーライト相
の球状黒鉛鋳鉄部材（ＦＣＤ６００）の渦流強度指示値
の分布と比較して、大きく異なっており、表層部２１の
フェライト相の有無が検出可能であることが分かる。従
って、表層部２１のフェライト相の有無は、０．５〜３
２ｋＨｚ、好ましくは４〜１６ｋＨｚの範囲にある２種
類以上（好ましくは３種類以上）の各周波数について渦
流強度指示値を求めることによって検出可能である。FIG. 4 shows that the test frequency is 0.25 kHz.
In the range of up to 32 kHz, the spheroidal graphite cast iron member 20 having the ferrite phase in the surface layer portion 21 has a distribution in which the eddy current strength indicated a maximum value at a frequency of 8 kHz, and both the surface layer portion 21 and the inside 22 thereof Substantially ferritic spheroidal graphite cast iron members (FCD450, FCD500),
The surface layer portion 21 and the inside 22 thereof are substantially different from the distribution of the eddy current intensity indicated value of the spheroidal graphite cast iron member (FCD600) substantially having the pearlite phase, and the presence or absence of the ferrite phase in the surface layer portion 21 can be detected. You can see that there is. Therefore, the presence or absence of the ferrite phase in the surface layer portion 21 is 0.5 to 3
It can be detected by obtaining an eddy current intensity indication value for each of two or more (preferably three or more) frequencies in the range of 2 kHz, preferably 4 to 16 kHz.
【００２８】次に、球状黒鉛鋳鉄部材として、表層部に
フェライト相がない（ＪＩＳ）ＦＣＤ６００材と、熱処
理条件を変えた以外はこのＦＣＤ６００材と同様の条件
で製造し、内部２２はパーライト相のままで、表層部２
１のフェライト相の厚さを０.２〜１．３ｍｍの範囲で
変化させた８種類の球状黒鉛鋳鉄部材とを準備した。各
球状黒鉛鋳鉄部材２０について励磁電流ｉの周波数と渦
流強度指示値との関係を求めた。その結果を図５に示
す。なお、図５に示す渦流強度指示値は、表層部２１の
フェライト相の厚さが１．３ｍｍの球状黒鉛鋳鉄部材の
インピーダンスに対する他の球状黒鉛鋳鉄部材のインピ
ーダンスの比率である。Next, as a spheroidal graphite cast iron member, an FCD600 material having no ferrite phase in the surface layer (JIS) and a material similar to the FCD600 material except that the heat treatment conditions were changed, and the inside 22 was made of a pearlite phase. As it is, surface layer 2
Eight types of spheroidal graphite cast iron members in which the thickness of the ferrite phase No. 1 was changed in the range of 0.2 to 1.3 mm were prepared. For each spheroidal graphite cast iron member 20, the relationship between the frequency of the exciting current i and the indicated eddy current intensity value was determined. The result is shown in FIG. The eddy current strength indication value shown in FIG. 5 is the ratio of the impedance of another spheroidal graphite cast iron member to the impedance of a spheroidal graphite cast iron member having a ferrite phase thickness of 1.3 mm in the surface layer portion 21.
【００２９】図５から、何れの球状黒鉛鋳鉄部材でも、
０．２５ｋＨｚと低い周波数（交流磁束Φの浸透深さが
深い）では渦流強度指示値がほぼ同じ値を示すことか
ら、フェライト相の厚さは異なっていても、内部２２の
組織は同一のパーライト相であると判断できる。また、
周波数が４ｋＨｚ以上では渦流強度指示値の分布は、フ
ェライト相の厚さによって変化することから、この渦流
強度指示値の分布を求めれば球状黒鉛鋳鉄部材２０のフ
ェライト相の厚さを検出できることが分かる。即ち、検
査の周波数が０．２５〜３２ｋＨｚの範囲で、６種類以
上の異なった周波数の励磁電流ｉを試験コイル１１に流
すことにより、表層部２１のフェライト相の厚さが０．
０〜１．２ｍｍの球状黒鉛鋳鉄部材２０の渦流強度指示
値の分布が異なっており、表層部２１のフェライト相の
厚さを特定できることが分かる。また、図４の結果も考
慮すると、表層部２１のフェライト相の厚さを高精度で
検出可能とするためには、試験コイル１１に８回通電
し、各励磁電流の周波数ｆn（但しnは７以下の整数）を
ｆn+1＝２×ｆn（但し、ｆ1＝０．２５ｋＨｚ）の関係
を満足するように選択することが望ましい。FIG. 5 shows that any of the spheroidal graphite cast iron members
At a frequency as low as 0.25 kHz (the penetration depth of the AC magnetic flux Φ is deep), the eddy current intensity indicated values are almost the same. Therefore, even if the thickness of the ferrite phase is different, the structure of the inside 22 is the same pearlite. It can be judged that it is a phase. Also,
When the frequency is 4 kHz or more, the distribution of the eddy current intensity value changes depending on the thickness of the ferrite phase. Therefore, it is found that the thickness of the ferrite phase of the spheroidal graphite cast iron member 20 can be detected by obtaining the distribution of the eddy current intensity value. . That is, when the frequency of the inspection is in the range of 0.25 to 32 kHz, the exciting current i of six or more different frequencies is passed through the test coil 11 so that the thickness of the ferrite phase of the surface layer portion 21 is set to 0.1.
The distribution of the indicated value of the eddy current intensity of the spheroidal graphite cast iron member 20 of 0 to 1.2 mm is different, and it can be seen that the thickness of the ferrite phase of the surface layer portion 21 can be specified. In consideration of the results of FIG. 4 as well, in order to enable the thickness of the ferrite phase of the surface layer portion 21 to be detected with high accuracy, the test coil 11 is energized eight times and the frequency f n of each excitation current (where n Is preferably an integer of 7 or less) so as to satisfy the relationship of f n + 1 = 2 × f n (where f 1 = 0.25 kHz).
【００３０】[0030]
【発明の効果】以上詳細に説明のとおり、本発明の球状
黒鉛鋳鉄部材の検査方法によれば、球状黒鉛鋳鉄部材表
層部のフェライト相の有無やその厚さ、更にフェライト
相の内部のパーライト相の有無を、非破壊で迅速にかつ
正確に検査できる。As described above in detail, according to the method for inspecting a spheroidal graphite cast iron member of the present invention, the presence or absence and thickness of a ferrite phase in the surface layer of a spheroidal graphite cast iron member, and the pearlite phase inside the ferrite phase are further improved. Can be quickly and accurately inspected for non-destruction.
【図１】本発明を実施する検査装置の一例を示す構成図
である。FIG. 1 is a configuration diagram illustrating an example of an inspection device that implements the present invention.
【図２】本発明の原理を示す模式図である。FIG. 2 is a schematic view illustrating the principle of the present invention.
【図３】基地組織の異なる２種類の球状黒鉛鋳鉄部材の
磁界の強さと比透磁率の関係を示す図である。FIG. 3 is a diagram showing the relationship between the magnetic field strength and the relative magnetic permeability of two types of spheroidal graphite cast iron members having different base structures.
【図４】各種球状黒鉛鋳鉄部材の励磁電流の周波数と渦
流強度指示値との関係を示す図である。FIG. 4 is a diagram showing the relationship between the frequency of the exciting current of various spheroidal graphite cast iron members and the eddy current strength instruction value.
【図５】表層部にフェライト相を有する球状黒鉛鋳鉄部
材の励磁電流の周波数と渦流強度指示値との関係を示す
図である。FIG. 5 is a diagram showing a relationship between a frequency of an exciting current of a spheroidal graphite cast iron member having a ferrite phase in a surface layer portion and an eddy current strength indication value.
１０：球状黒鉛鋳鉄部材の検査装置 １１：試験コイル １２：プローブ １３：移相器 １４：ブリッジ回路 １５：発振回路 １６：増幅器 １７：位相検波回路 １８：表示装置 ２０：球状黒鉛鋳鉄部材 ２０ａ：表面 ２１：表層部 ２２：内部 ｉ：励磁電流 Ｅｆ：フェライト相を流れる渦電流 Ｅｐ：パーライト相を流れる渦電流 Φ：交流磁束 10: Inspection device for spheroidal graphite cast iron member 11: Test coil 12: Probe 13: Phase shifter 14: Bridge circuit 15: Oscillation circuit 16: Amplifier 17: Phase detection circuit 18: Display device 20: Spheroidal graphite cast iron member 20a: Surface 21: Surface layer 22: Inside i: Excitation current Ef: Eddy current flowing in ferrite phase Ep: Eddy current flowing in pearlite phase Φ: AC magnetic flux
Claims (5)
接して配置したコイルに１００ｋＨｚ未満の周波数をも
つ複数個の励磁電流を流すことにより発生した磁束によ
り、前記部材に渦電流を生成させ、この各周波数につい
て渦電流により前記コイルに生じるインピーダンス変化
を検出することにより、前記球状黒鉛鋳鉄部材の表層部
のフェライト相の有無及び／またはフェライト相の厚さ
を検知することを特徴とする球状黒鉛鋳鉄部材の検査方
法。An eddy current is generated in said member by a magnetic flux generated by flowing a plurality of exciting currents having a frequency of less than 100 kHz through a coil arranged in contact with or in close proximity to the surface of a spheroidal graphite cast iron member, A spheroidal graphite characterized by detecting the presence or absence of a ferrite phase and / or the thickness of a ferrite phase in a surface layer of the spheroidal graphite cast iron member by detecting an impedance change generated in the coil due to the eddy current at each frequency. Inspection method for cast iron parts.
〜３２ｋＨｚの範囲に６個以上の周波数をもつことを特
徴とする請求項１に記載の球状黒鉛鋳鉄部材の検査方
法。2. An exciting current flowing through the coil is 20 Hz.
The method for inspecting a spheroidal graphite cast iron member according to claim 1, wherein the spheroidal graphite cast iron member has six or more frequencies in a range of -32 kHz.
〜２０ｋＨｚの範囲に２個以上の周波数をもつことを特
徴とする請求項２に記載の球状黒鉛鋳鉄部材の検査方
法。3. An exciting current flowing through the coil is 20 Hz.
3. The method for inspecting a spheroidal graphite cast iron member according to claim 2, wherein two or more frequencies are in a range of 20 kHz to 20 kHz.
１０〜２０００Ａ／ｍの範囲にあることを特徴とする請
求項１乃至請求項３の何れか１項に記載の球状黒鉛鋳鉄
部材の検査方法。4. The strength of a magnetic field generated by an exciting current is
The method for inspecting a spheroidal graphite cast iron member according to any one of claims 1 to 3, wherein the inspection temperature is in a range of 10 to 2000 A / m.
ライト相が表面から２ｍｍ以下の深さまで存在し、それ
より内部がパーライト相を主体とする球状黒鉛鋳鉄部材
のフェライト相の厚さ検知することを特徴とする球状黒
鉛鋳鉄部材の検査方法。5. In the spheroidal graphite cast iron member, the ferrite phase of the surface layer portion is present to a depth of 2 mm or less from the surface, and the thickness of the ferrite phase of the spheroidal graphite cast iron member mainly composed of a pearlite phase is detected. A method for inspecting a spheroidal graphite cast iron member, comprising:
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2000351141A JP2002156366A (en) | 2000-11-17 | 2000-11-17 | Inspection method of spherical graphitic cast iron member |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2000351141A JP2002156366A (en) | 2000-11-17 | 2000-11-17 | Inspection method of spherical graphitic cast iron member |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JP2002156366A true JP2002156366A (en) | 2002-05-31 |
Family
ID=18824251
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP2000351141A Pending JP2002156366A (en) | 2000-11-17 | 2000-11-17 | Inspection method of spherical graphitic cast iron member |
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| Country | Link |
|---|---|
| JP (1) | JP2002156366A (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2007510916A (en) * | 2003-11-10 | 2007-04-26 | フラウンホファー ゲセルシャフトツール フェールデルンク ダー アンゲヴァンテン フォルシュンク エー．ファオ． | A method for quantitative determination of the width of the soft zone region of partially cured workpieces. |
| JP2014500476A (en) * | 2010-12-21 | 2014-01-09 | 新東工業株式会社 | Surface characteristic evaluation apparatus and surface characteristic evaluation method |
| EP3286558A4 (en) * | 2015-02-04 | 2018-07-11 | Texas Instruments Incorporated | Spectrographic material analysis using multi-frequency inductive sensing |
| CN110823997A (en) * | 2019-10-29 | 2020-02-21 | 万向钱潮股份有限公司 | Nondestructive measurement device and method for core ferrite of shaft part |
-
2000
- 2000-11-17 JP JP2000351141A patent/JP2002156366A/en active Pending
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2007510916A (en) * | 2003-11-10 | 2007-04-26 | フラウンホファー ゲセルシャフトツール フェールデルンク ダー アンゲヴァンテン フォルシュンク エー．ファオ． | A method for quantitative determination of the width of the soft zone region of partially cured workpieces. |
| JP2014500476A (en) * | 2010-12-21 | 2014-01-09 | 新東工業株式会社 | Surface characteristic evaluation apparatus and surface characteristic evaluation method |
| EP3286558A4 (en) * | 2015-02-04 | 2018-07-11 | Texas Instruments Incorporated | Spectrographic material analysis using multi-frequency inductive sensing |
| US10338055B2 (en) | 2015-02-04 | 2019-07-02 | Texas Instruments Incorporated | Spectrographic material analysis based on inductive sensing |
| CN110823997A (en) * | 2019-10-29 | 2020-02-21 | 万向钱潮股份有限公司 | Nondestructive measurement device and method for core ferrite of shaft part |
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