JP5615161B2 - Quenching range detection method and quenching range inspection method - Google Patents

Quenching range detection method and quenching range inspection method Download PDF

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JP5615161B2
JP5615161B2 JP2010287075A JP2010287075A JP5615161B2 JP 5615161 B2 JP5615161 B2 JP 5615161B2 JP 2010287075 A JP2010287075 A JP 2010287075A JP 2010287075 A JP2010287075 A JP 2010287075A JP 5615161 B2 JP5615161 B2 JP 5615161B2
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徳義 高岡
徳義 高岡
佳孝 三阪
佳孝 三阪
川嵜　一博
一博 川嵜
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Description

本件発明は、渦電流測定法を利用してワーク（鉄鋼材）の焼入範囲を非破壊で検出する焼入範囲検出方法及び焼入範囲検査方法に関し、特に、焼入範囲と未焼入範囲との境界位置を判定可能な焼入範囲検出方法及び焼入範囲検査方法に関する。   The present invention relates to a quenching range detection method and a quenching range inspection method for non-destructively detecting the quenching range of a work (steel material) using an eddy current measurement method, and in particular, a quenching range and an unquenched range. It is related with the quenching range detection method and quenching range inspection method which can determine the boundary position with.

高周波焼入れ等により部分的に焼入れが施された焼入鋼材が種々の装置部品材料等として広く使用されている。このような焼入鋼材については、その品質保証のため、焼入鋼材に形成された焼入硬化層が、所定の硬化深さや焼入範囲で形成されているか否かを検査するために、硬化深さや焼入範囲の測定又は検出が行われる。   Hardened steel materials that are partially quenched by induction hardening or the like are widely used as various device component materials. For such a hardened steel material, in order to assure its quality, the hardened hardened layer formed on the hardened steel material is hardened in order to inspect whether or not it is formed at a predetermined hardening depth or hardened range. Measurement or detection of depth and quenching range is performed.

例えば、特許文献１には、渦電流測定法を利用して、焼入硬化層の硬化深さを測定する方法が開示されている。また、この特許文献１には、焼入鋼材の表面上で焼入範囲を測定することが行われている。焼入範囲の測定に際して、焼入鋼材の表面における焼入組織と未焼入組織の境界点、すなわち焼入範囲と未焼入範囲との境界位置が求められている。   For example, Patent Document 1 discloses a method of measuring the hardening depth of a hardened hardening layer using an eddy current measurement method. In Patent Document 1, the quenching range is measured on the surface of the hardened steel material. When measuring the quenching range, the boundary point between the quenched structure and the unquenched structure on the surface of the quenched steel material, that is, the boundary position between the quenched range and the unquenched range is required.

また、特許文献２には、強磁性体材料を交番磁化するときに生じるバルクハウゼン効果雑音が焼入れにより変化することを利用して、部分焼入れした材料の焼入部と非焼入部のバルクハウゼン効果雑音の平均信号レベルを基準電圧と比較することにより、部分焼入れした強磁性体材料の焼入部と非焼入部との境界、すなわち焼入範囲と未焼入範囲との境界位置を測定する方法が記載されている。   Further, Patent Document 2 discloses that the Barkhausen effect noise generated when the ferromagnetic material is alternately magnetized is changed by quenching, so that the Barkhausen effect noise between the quenched part and the non-quenched part of the partially quenched material is disclosed. Describes a method for measuring the boundary position between a hardened part and a non-hardened part of a partially quenched ferromagnetic material, that is, a boundary position between a hardened range and an unquenched range, by comparing the average signal level of the material with a reference voltage. Has been.

特開２００９−１０９３５８号公報JP 2009-109358 A 特開平５−２６４５０８号公報Japanese Patent Laid-Open No. 5-264508

ところで、上記特許文献１においても指摘されているように、渦電流測定法により得られた測定結果には、測定位置周辺の影響が含まれて平均化されてしまう。このため、渦電流測定により得られた測定結果だけでは、焼入範囲と未焼入範囲との境界位置を精度良く特定することが困難であった。そこで、上記特許文献１に記載の方法では、表面硬度計を用いて、焼入鋼材の表面の硬度を測定し、この硬度測定結果により、渦電流測定法により得られた測定結果を補完し、焼入範囲と未焼入範囲との境界位置を求める構成としている。しかしながら、当該特許文献１に開示の方法では、渦電流測定装置に加えて、硬度計を要し、焼入範囲と未焼入範囲との境界位置を判定するための装置構成が複雑化するとともに、計算量も増加するという課題がある。   By the way, as pointed out also in the said patent document 1, the measurement result obtained by the eddy current measuring method includes the influence around a measurement position, and is averaged. For this reason, it has been difficult to accurately identify the boundary position between the quenching range and the non-quenching range only by the measurement result obtained by the eddy current measurement. Therefore, in the method described in Patent Document 1, the hardness of the surface of the hardened steel material is measured using a surface hardness meter, and the measurement result obtained by the eddy current measurement method is complemented by this hardness measurement result, The boundary position between the quenching range and the non-quenching range is obtained. However, in the method disclosed in Patent Document 1, a hardness meter is required in addition to the eddy current measuring device, and the device configuration for determining the boundary position between the quenching range and the unquenched range is complicated. There is a problem that the calculation amount increases.

一方、特許文献２に記載の方法では、バルクハウゼン効果雑音の平均信号レベルを求めて、基準電圧と比較することにより、焼入範囲と未焼入範囲との境界位置を判定しているため、特許文献１に開示の方法と比較すると装置構成は単純である。しかしながら、例えば、材質、形状及び焼入範囲が同一のワークであっても、各ワークを製造したときの材料ロット、熱処理ロット、測定環境の温度変化等の種々の要因によって、各ワークについて得られるバルクハウゼン効果雑音の平均信号レベルは異なる恐れがある。しかしながら、特許文献２には、当該平均信号レベルにバラツキがある場合、基準電圧値をどのように定めるかについての開示はない。当該平均信号レベルにバラツキの大きな材料を検出対象ワークとする場合、各ワークについて得られたバルクハウゼン効果雑音の平均信号レベルと所定の値である基準電圧値とを比較しても、焼入範囲と未焼入範囲との境界位置を精度良く判定するのは困難である。   On the other hand, in the method described in Patent Document 2, since the average signal level of the Barkhausen effect noise is obtained and compared with the reference voltage, the boundary position between the hardened range and the unhardened range is determined. Compared with the method disclosed in Patent Document 1, the apparatus configuration is simple. However, even if the workpiece has the same material, shape, and quenching range, it can be obtained for each workpiece due to various factors such as the material lot when each workpiece is manufactured, the heat treatment lot, and the temperature change of the measurement environment. The average signal level of Barkhausen effect noise can be different. However, Patent Document 2 does not disclose how to determine the reference voltage value when the average signal level varies. When a material with a large variation in the average signal level is used as a workpiece to be detected, the quenching range can be obtained by comparing the average signal level of the Barkhausen effect noise obtained for each workpiece with a reference voltage value that is a predetermined value. It is difficult to accurately determine the boundary position between the unquenched range and the unquenched range.

そこで、本件発明は、渦電流測定方法を利用して、各ワークの渦電流測定結果のバラツキが大きい場合であっても、ワークの焼入範囲と未焼入範囲との境界位置を非破壊で簡易に、且つ、精度よく判定することができる焼入範囲検出方法及び焼入範囲検査方法を提供することを目的とする。   Therefore, the present invention uses the eddy current measurement method to non-destruct the boundary position between the workpiece quenching range and the unquenched range even if the eddy current measurement results of each workpiece vary greatly. It is an object of the present invention to provide a quenching range detection method and a quenching range inspection method that can be easily and accurately determined.

上記目的を達成するために、本件発明に係る焼入範囲検出方法は、ワークの表面に渦電流を発生させる励磁コイルと、前記渦電流に関する検出信号を検出するための検出コイルとを備えた渦電流センサを用い、焼入範囲の検出対象とする対象ワークの焼入範囲とこれに隣接する未焼入範囲とを前記渦電流センサにより連続的に走査し、前記焼入範囲と前記未焼入範囲との境界領域における前記検出信号の信号変化率に基づいて、当該対象ワークの表面における焼入範囲と未焼入範囲との境界位置を判定して、ワークの焼入範囲を検出する焼入範囲検出方法であって、以下の点を特徴とする。 In order to achieve the above object, a quenching range detection method according to the present invention includes an excitation coil that generates an eddy current on the surface of a workpiece, and a vortex provided with a detection coil for detecting a detection signal related to the eddy current. The current sensor is used to continuously scan the quenching range of the target work to be detected as a quenching range and the unquenched range adjacent thereto by the eddy current sensor, and the quenching range and the unquenched range. Quenching that detects the quenching range of the workpiece by determining the boundary position between the quenching range and the unquenched range on the surface of the target workpiece based on the signal change rate of the detection signal in the boundary region with the range The range detection method is characterized by the following points.

すなわち、本件発明に係る焼入範囲検出方法では、前記焼入範囲を前記渦電流センサで走査したときに、前記検出信号が定常的な値を示す領域を焼入定常領域とし、前記未焼入範囲を前記渦電流センサで走査したときに、前記検出信号が定常的な値を示す領域を未焼入定常領域とし、前記境界領域は、前記焼入定常領域と前記未焼入定常領域との間の領域とし、前記検出信号の信号変化率は、前記焼入定常領域における前記検出信号の定常値と、前記未焼入定常領域における前記検出信号の定常値とを基準として求めたものであり、前記境界領域において、前記検出信号の信号変化率が予め定めた判定値になる位置を前記対象ワークの焼入範囲と未焼入範囲との境界位置として判定する。 That is, in the quenching range detection method according to the present invention, when the quenching range is scanned by the eddy current sensor, a region where the detection signal shows a steady value is set as a quenching steady region, and the unquenched region is detected. When the range is scanned by the eddy current sensor, a region where the detection signal shows a steady value is defined as an unquenched steady region, and the boundary region is defined by the quenching steady region and the unquenched steady region. The signal change rate of the detection signal is obtained based on the steady value of the detection signal in the quenching steady region and the steady value of the detection signal in the unquenched steady region. In the boundary region, a position where the signal change rate of the detection signal becomes a predetermined determination value is determined as a boundary position between the quenching range and the unquenched range of the target workpiece .

本件発明に係る焼入範囲検出方法において、前記信号変化率を百分率で表した場合に、前記判定値は２０％〜９０％の範囲内で定めた所定の値である請求項２に記載の焼入範囲検出方法。   The quenching range detection method according to the present invention, wherein, when the signal change rate is expressed as a percentage, the determination value is a predetermined value defined within a range of 20% to 90%. Entry range detection method.

本件発明に係る焼入範囲検出方法において、複数の検証用ワークを用いて、各検証用ワークの前記境界領域における前記検出信号の信号変化率と、各検証用ワークの焼入範囲と未焼入範囲との境界位置との相関性を予め検証しておき、前記判定値は当該相関性に基づき定めた値であることが好ましい。   In the quenching range detection method according to the present invention, using a plurality of verification workpieces, the signal change rate of the detection signal in the boundary region of each verification workpiece, the quenching range of each verification workpiece and unquenched It is preferable that the correlation with the boundary position with the range is verified in advance, and the determination value is a value determined based on the correlation.

前記検出信号は、前記検出コイルのインピーダンスに関する値であることが好ましい。このとき、当該検出コイルのインピーダンスの抵抗成分を検出信号としてもよいし、リアクタンス成分を検出信号としてもよい。   The detection signal is preferably a value related to the impedance of the detection coil. At this time, the resistance component of the impedance of the detection coil may be a detection signal, or the reactance component may be a detection signal.

また、上記目的を達成するために、本件発明に係る焼入範囲検査方法は、前記対象ワークの焼入範囲を検出し、この検出結果に基づいて、前記対象ワークに焼入れを施すべき範囲に、焼入れが施されているか否かを判定することを特徴とする。   Further, in order to achieve the above object, the quenching range inspection method according to the present invention detects the quenching range of the target workpiece, and based on the detection result, in the range where the target workpiece is to be quenched, It is characterized by determining whether quenching is performed.

本件発明によれば、焼入範囲の検出対象とする対象ワークの焼入範囲と未焼入範囲とを渦電流センサにより連続的に走査することで、焼入範囲と未焼入範囲の境界領域における検出コイルに生じた検出信号の信号変化を検出することができる。そして、検出コイルの検出信号の信号変化率に基づいて、対象ワークの焼入範囲と未焼入範囲との境界位置を非破壊で簡易に判定することができる。また、検出コイルの検出信号の絶対値に基づいて対象ワークの表面における焼入範囲と未焼入範囲との境界位置を判定するのではなく、信号変化率に基づいて、対象ワークの表面における焼入範囲と未焼入範囲との境界位置を判定するため、材料ロットや熱処理ロット、或いは、測定環境の温度変化等の要因によって、対象ワーク毎に検出コイルの検出信号の絶対値が変化する場合であっても、検出信号のバラツキによらず、各対象ワークの表面における焼入組織と未焼入組織との境界を精度よく判定することができる。   According to the present invention, by continuously scanning the quenching range and the unquenched range of the target workpiece as the detection target of the quenching range by the eddy current sensor, the boundary region between the quenching range and the unquenched range The signal change of the detection signal generated in the detection coil at can be detected. Then, based on the signal change rate of the detection signal of the detection coil, the boundary position between the hardened range and the unhardened range of the target workpiece can be easily determined without destruction. In addition, the boundary position between the quenching range and the unquenched range on the surface of the target workpiece is not determined based on the absolute value of the detection signal of the detection coil, but the quenching on the surface of the target workpiece is determined based on the signal change rate. When the absolute value of the detection signal of the detection coil changes for each target workpiece due to factors such as material lots, heat treatment lots, or temperature changes in the measurement environment to determine the boundary position between the hardened range and the unquenched range Even so, the boundary between the hardened structure and the unhardened structure on the surface of each target workpiece can be accurately determined regardless of the variation in the detection signal.

本件発明に係る焼入範囲検出方法及び焼入範囲検査方法の一例を示す概略図である。It is the schematic which shows an example of the quenching range detection method and quenching range inspection method which concern on this invention. 本件発明に係る渦電流センサの構成を模式的に示した図である。It is the figure which showed typically the structure of the eddy current sensor which concerns on this invention. 検出コイルのインピーダンスと、その抵抗成分Ｒとリアクタンス成分ωＬとの関係を示す模式図である。It is a schematic diagram which shows the relationship between the impedance of a detection coil, its resistance component R, and reactance component (omega) L. 対象ワークを渦電流センサで走査したときの検出コイルの検出信号Ｚ（１）、検出信号Ｘ（２）、検出信号Ｙ（３）の測定値の推移の一例を示す図である。It is a figure which shows an example of transition of the measured value of detection signal Z (1) of the detection coil, detection signal X (2), and detection signal Y (3) when a target workpiece is scanned with an eddy current sensor. 対象ワークの他の形状例（ａ）と、このときに得られる検出信号の推移を簡略化して示した略図（ｂ）である。It is the schematic (b) which simplified and showed other shape examples (a) of the object workpiece | work, and transition of the detection signal obtained at this time. 本件発明に係る検証用ワークを用いた検証方法の一例を示す概略図である。It is the schematic which shows an example of the verification method using the workpiece | work for verification which concerns on this invention. 各検証用ワークを渦電流センサで走査したときの検出信号Ｘ（抵抗成分Ｒ）の測定値の推移を示す図である。It is a figure which shows transition of the measured value of detection signal X (resistance component R) when each verification workpiece | work is scanned with an eddy current sensor. 各検証用ワークを渦電流センサで走査したときの検出信号Ｙ（リアクタンス成分ωＬ）の測定値の推移を示す図である。It is a figure which shows transition of the measured value of detection signal Y (reactance component (omega) L) when each verification workpiece | work is scanned with an eddy current sensor. 各検証用ワークを渦電流センサで走査したときの検出信号Ｘ（抵抗成分Ｒ）の測定値の推移を信号変化率の推移として表した図である。It is a figure showing change of a measured value of detection signal X (resistance component R) when each verification work is scanned with an eddy current sensor as change of a signal change rate. 各検証用ワークを渦電流センサで走査したときの検出信号Ｙ（リアクタンス成分ωＬ）の測定値の推移を信号変化率の推移として表した図である。It is a figure showing change of a measured value of detection signal Y (reactance component ωL) when each verification work is scanned with an eddy current sensor as change of signal change rate. 検出信号Ｘの信号変化率が５０％になる位置を評価位置としたときの、評価位置と各検証用ワークの焼入範囲と未焼入範囲との境界位置との相関を検証するための図である。The figure for verifying the correlation between the evaluation position and the boundary position between the quenching range and the unquenched range of each verification work when the position where the signal change rate of the detection signal X is 50% is set as the evaluation position. It is. 検出信号Ｙの信号変化率が５０％になる位置を評価位置としたときの、評価位置と各検証用ワークの焼入範囲と未焼入範囲との境界位置との相関を検証するための図である。The figure for verifying the correlation between the evaluation position and the boundary position between the quenching range and the unquenched range of each verification work when the position where the signal change rate of the detection signal Y is 50% is set as the evaluation position. It is. 評価位置を信号変化率が０％〜１００％の範囲内で変化させた際の各評価位置における相関係数を示す図である。It is a figure which shows the correlation coefficient in each evaluation position at the time of changing an evaluation position within the range whose signal change rate is 0%-100%.

以下、本件発明に係る焼入範囲検出方法及び焼入範囲検査方法の好ましい実施の形態を図面を参照しながら説明する。本件発明では、図１に示す渦電流センサ１０を用い、この渦電流センサ１０でワークＷの焼入範囲２０とこれに隣接する未焼入範囲３０とを連続的に走査し、ワークＷの焼入範囲２０と未焼入範囲３０との境界領域における渦電流センサ１０の検出信号の信号変化率に基づいて、ワークＷの焼入範囲２０と未焼入範囲３０との境界位置を判定する方法を採用している。また、本件発明に係る焼入範囲検査方法は、本件発明に係る焼入範囲検出方法を利用して、対象ワークの焼入範囲２０を検出し、この検出結果に基づいて、対象ワークに焼入れを施すべき範囲に、焼入れが施されているか否かを判定するものである。本件発明に係る焼入範囲検出方法及び焼入範囲検査方法は、渦電流測定法を利用して、ワークＷの表面における焼入範囲２０と未焼入範囲３０との境界位置を非破壊で簡易に、且つ、精度よく判定することができる。   Hereinafter, preferred embodiments of a quenching range detection method and a quenching range inspection method according to the present invention will be described with reference to the drawings. In the present invention, the eddy current sensor 10 shown in FIG. 1 is used, and the eddy current sensor 10 continuously scans the quenching range 20 of the workpiece W and the unquenched range 30 adjacent thereto to quench the workpiece W. Method for determining the boundary position between the quenching range 20 and the unquenched range 30 of the workpiece W based on the signal change rate of the detection signal of the eddy current sensor 10 in the boundary region between the quenching range 20 and the unquenched range 30 Is adopted. Further, the quenching range inspection method according to the present invention detects the quenching range 20 of the target workpiece using the quenching range detection method according to the present invention, and quenches the target workpiece based on the detection result. It is determined whether or not the range to be subjected to quenching. The quenching range detection method and quenching range inspection method according to the present invention use the eddy current measurement method to easily and nondestructively demarcate the boundary position between the quenching range 20 and the unquenched range 30 on the surface of the workpiece W. In addition, it can be determined with high accuracy.

ワーク： まず、ワークＷについて説明する。本実施の形態では、対象ワークは、焼入れが施された鉄鋼材とする。例えば、鋼材として、機械構造用炭素鋼材（以下、「ＳＣ材」）は、種々の装置部品等の構造部材として用いられ、熱処理等により機械的性質を改善して使用される。また、ＳＣ材は種々の装置部品に用いられることから、その用途に応じて、熱処理が施される面積や位置も多様である。本件発明は、このような部分焼入れが施された部分焼入鋼材の焼入範囲２０を検出する際に特に好適に用いることができる。また、本件発明を用いれば、部分焼入鋼材の製造ラインにおいて、焼入工程後に、焼入範囲２０の全数検査をインラインで行うことが可能になる。 Work: First, the work W will be described. In the present embodiment, the target workpiece is a steel material that has been quenched. For example, as a steel material, a carbon steel material for machine structure (hereinafter referred to as “SC material”) is used as a structural member such as various apparatus parts, and is used by improving mechanical properties by heat treatment or the like. Moreover, since SC material is used for various apparatus components, the area and position where heat treatment is performed vary depending on the application. The present invention can be particularly suitably used when detecting the quenching range 20 of the partially quenched steel material subjected to such partial quenching. Moreover, if this invention is used, it will become possible to perform the total inspection of the quenching range 20 in-line after a quenching process in the production line of a partially hardened steel material.

ワーク形状： 本件発明において、ワークＷの形状は特に限定されるものではない。図１には、ワークＷの一例として鋼棒の断面を示している。図１にハッチングで示すＡ位置からＢ位置の間の領域は、次に説明する焼入範囲２０を示している。すなわち、図１には、外周部分の表面に焼入れが施された鋼棒の断面を示しており、鋼棒の断面部分に付すべきハッチングは省略している。 Work Shape: In the present invention, the shape of the work W is not particularly limited. FIG. 1 shows a cross section of a steel bar as an example of the workpiece W. A region between the A position and the B position indicated by hatching in FIG. 1 indicates a quenching range 20 described below. That is, FIG. 1 shows a cross section of a steel bar whose surface is quenched, and the hatching to be applied to the cross section of the steel bar is omitted.

焼入範囲２０： 本実施の形態において、焼入範囲２０とは、ワークＷの焼入工程において、熱処理が施されることにより、焼入硬化層が形成された領域を指す。当該焼入範囲２０は、ワークＷの金属組織が変化して焼入組織として存在する領域である。 Quenching range 20: In the present embodiment, the quenching range 20 refers to a region in which a hardened and hardened layer is formed by heat treatment in the quenching process of the workpiece W. The quenching range 20 is an area where the metal structure of the workpiece W changes and exists as a quenched structure.

未焼入範囲３０： 一方、未焼入範囲３０とは、上記焼入範囲２０に隣接し、熱処理が施されていない領域をいう。当該未焼入範囲３０は、母材の金属組織が変化せずに未焼入組織として存在する領域である。 Unquenched range 30: On the other hand, the unquenched range 30 refers to a region adjacent to the quenched range 20 and not subjected to heat treatment. The unquenched range 30 is an area where the metal structure of the base material does not change and exists as an unquenched structure.

境界領域： 焼入範囲２０と未焼入範囲３０との境界領域とは、互いに隣接する焼入範囲２０と未焼入範囲３０との境界位置付近の領域を指すが、具体的には後述する。 Boundary region: The boundary region between the quenching range 20 and the unquenched range 30 refers to a region in the vicinity of the boundary position between the quenching range 20 and the unquenched range 30 that are adjacent to each other. .

渦電流センサ１０： 次に、図２を参照して渦電流センサ１０の構成を説明する。渦電流センサ１０は、ワークＷの表面に渦電流Ｃを発生させる励磁コイル１１と、ワークＷの表面に発生した前記渦電流Ｃに関する検出信号を検出するための検出コイル１２とを備えている。励磁コイル１１と、検出コイル１２とは、それぞれ所定の位置関係になるようにして図１に示したケース内に収容される。渦電流センサ１０は、図示しない治具により、ワークＷの表面に対して、一定のギャップ（リフトオフ）Ｇを空けて配置される。また、渦電流センサ１０は、上記治具によりワークＷに対して、一定速度で相対移動可能に構成されている。従って、渦電流センサ１０によりワークＷの表面を走査した場合、渦電流センサ１０が走査基準位置から走査部位まで移動する際に要した走査時間に基づいて、ワークＷの表面における走査部位を簡易に特定することができる。 Eddy Current Sensor 10: Next, the configuration of the eddy current sensor 10 will be described with reference to FIG. The eddy current sensor 10 includes an exciting coil 11 that generates an eddy current C on the surface of the workpiece W, and a detection coil 12 that detects a detection signal related to the eddy current C generated on the surface of the workpiece W. The excitation coil 11 and the detection coil 12 are accommodated in the case shown in FIG. 1 so as to have a predetermined positional relationship. The eddy current sensor 10 is arranged with a certain gap (lift-off) G with respect to the surface of the workpiece W by a jig (not shown). The eddy current sensor 10 is configured to be relatively movable with respect to the workpiece W at a constant speed by the jig. Therefore, when the surface of the workpiece W is scanned by the eddy current sensor 10, the scanning site on the surface of the workpiece W can be easily determined based on the scanning time required when the eddy current sensor 10 moves from the scanning reference position to the scanning site. Can be identified.

図２に模式的に示すように、励磁コイル１１は、ワークＷの表面に対してコイル軸が垂直になるようにしてケース内に収容される。励磁コイル１１の両端には、交流電源１３が接続されている。この交流電源１３により、励磁コイル１１には所定の周波数の交流電流が供給される。検出コイル１２は、そのコイル軸が、励磁コイル１１のコイル軸と一致するようにして、巻線が巻かれている。検出コイル１２の両端には、検出コイル１２の電気的なパラメータを検出信号として測定するための測定装置１４が接続されている。   As schematically shown in FIG. 2, the exciting coil 11 is accommodated in the case so that the coil axis is perpendicular to the surface of the workpiece W. An AC power supply 13 is connected to both ends of the exciting coil 11. The AC power supply 13 supplies an AC current having a predetermined frequency to the exciting coil 11. The detection coil 12 is wound with its coil axis aligned with the coil axis of the excitation coil 11. A measuring device 14 for measuring the electrical parameters of the detection coil 12 as a detection signal is connected to both ends of the detection coil 12.

焼入範囲２０の検出原理： ここで、図２を参照しながら、渦電流測定法を利用した本件発明に係る焼入範囲２０の検出原理を説明する。交流電源１３は、励磁コイル１１に対して所定の周波数の交流電流を供給する。但し、交流電源１３から励磁コイル１１に供給する交流電流の周波数は、焼入範囲２０の検出対象とする対象ワークに応じて、適宜、適切な周波数を選定することができる。励磁コイル１１に交流電流を供給すると、励磁コイル１１によりワークＷの表面に対して垂直な磁束Ｍが発生する。そして、ワークＷの表面には、この磁束Ｍを中心とする環状の渦電流Ｃが発生する。ワークＷの表面に渦電流Ｃが発生すると、この渦電流Ｃにより図示しない磁束が発生する。この磁束の一部は、検出コイル１２を貫通する。その結果、電磁誘導により、検出コイル１２の両端には誘起電圧が生じる。この検出コイル１２の両端に生じた誘起電圧に関する電気的なパラメータは、ワークＷの表面に発生した渦電流Ｃの状態を反映する。そこで、測定装置１４により、この検出コイル１２の電気的なパラメータを測定することで、渦電流センサ１０の走査部位においてワークＷの表面に発生した渦電流Ｃの状態を検出することができる。 Detection principle of quenching range 20: Here, the detection principle of the quenching range 20 according to the present invention using the eddy current measurement method will be described with reference to FIG. The AC power supply 13 supplies an AC current having a predetermined frequency to the exciting coil 11. However, the frequency of the alternating current supplied from the alternating current power supply 13 to the exciting coil 11 can be appropriately selected according to the target work to be detected in the quenching range 20. When an alternating current is supplied to the exciting coil 11, a magnetic flux M perpendicular to the surface of the workpiece W is generated by the exciting coil 11. An annular eddy current C around the magnetic flux M is generated on the surface of the workpiece W. When an eddy current C is generated on the surface of the workpiece W, a magnetic flux (not shown) is generated by the eddy current C. A part of this magnetic flux penetrates the detection coil 12. As a result, an induced voltage is generated at both ends of the detection coil 12 by electromagnetic induction. The electrical parameter related to the induced voltage generated at both ends of the detection coil 12 reflects the state of the eddy current C generated on the surface of the workpiece W. Therefore, the state of the eddy current C generated on the surface of the workpiece W at the scanning portion of the eddy current sensor 10 can be detected by measuring the electrical parameters of the detection coil 12 by the measuring device 14.

検出信号： 検出信号は、ワークＷの表面に発生した渦電流Ｃに関する信号である。本実施の形態では、上述した通り、検出コイル１２の両端に生じた誘起電圧に関する電気的なパラメータを検出信号とする。ここで、磁性体である鉄鋼材を焼入れると、焼入組織の硬度は未焼入組織の硬度に比して高くなる一方、焼入組織の透磁率は未焼入組織の透磁率に比して低下する。つまり、焼入組織が形成された部位では、未焼入組織を有する部位に比して、励磁コイル１１により励磁されにくくなる。従って、焼入れを行ったワークＷの表面を渦電流センサ１０で走査したときに、未焼入組織に比して、焼入組織が形成された部位では、ワークＷの表面で発生する渦電流Ｃが小さくなり、検出コイル１２の両端に生じる誘起電圧も小さくなる。このように検出コイル１２の両端に生じる誘起電圧は、ワークＷの表面の透磁率を介して、ワークＷの表面硬度を反映する。本実施の形態は、検出信号として、検出コイル１２のインピーダンスに関する信号を採用する。 Detection signal: The detection signal is a signal related to the eddy current C generated on the surface of the workpiece W. In the present embodiment, as described above, an electrical parameter related to the induced voltage generated at both ends of the detection coil 12 is used as a detection signal. Here, when the steel material, which is a magnetic material, is quenched, the hardness of the hardened structure is higher than the hardness of the unquenched structure, while the permeability of the hardened structure is higher than the permeability of the unhardened structure. Then drop. That is, in the site | part in which the hardened structure | tissue was formed, it becomes difficult to be excited by the exciting coil 11 compared with the site | part which has a non-hardened structure | tissue. Therefore, when the surface of the workpiece W that has been quenched is scanned by the eddy current sensor 10, the eddy current C generated on the surface of the workpiece W is compared with the unquenched tissue in the region where the quenched structure is formed. And the induced voltage generated at both ends of the detection coil 12 is also reduced. Thus, the induced voltage generated at both ends of the detection coil 12 reflects the surface hardness of the workpiece W via the magnetic permeability of the surface of the workpiece W. In the present embodiment, a signal related to the impedance of the detection coil 12 is employed as the detection signal.

検出コイル１２のインピーダンス： 図３に、励磁コイル１１に角周波数ωの交流電流を流したときの検出コイル１２のインピーダンス（Ｚ）と、その抵抗成分Ｒ（実数部）と、リアクタンス成分ｊωＬ（虚数部）の関係を模式的に示す。
但し、インピーダンス（Ｚ）は下記式で表される。
Ｚ＝Ｒ＋ｊωＬ・・・（式） Impedance of the detection coil 12: FIG. 3 shows the impedance (Z) of the detection coil 12 when an alternating current having an angular frequency ω flows through the excitation coil 11, its resistance component R (real part), and reactance component jωL (imaginary number). Part) is schematically shown.
However, impedance (Z) is represented by the following formula.
Z = R + jωL (formula)

このように、インピーダンスは、抵抗成分Ｒとリアクタンス成分ｊωＬの和として表される。本実施の形態では、検出信号として、図３に示すようにインピーダンス平面に表したときの、抵抗成分Ｒを表すＸ値（実数軸値）と、リアクタンス成分ｊωＬを表すＹ値（虚数軸値）とを採用する。以下、インピーダンスの抵抗成分Ｒを表す検出信号を検出信号Ｘと称する。また、インピーダンスのリアクタンス成分ｊωＬを表す検出信号を検出信号Ｙと称する。本実施の形態では、測定装置１４によりこれらの検出信号Ｘ及び検出信号Ｙをそれぞれの電圧値として測定している。但し、検出信号は、検出信号Ｘ及び検出信号Ｙの双方を測定する必要はなく、少なくともいずれか一方を測定すればよい。また、検出コイル１２のインピーダンス自体を検出信号として用いることもできる。   Thus, the impedance is expressed as the sum of the resistance component R and the reactance component jωL. In this embodiment, as a detection signal, an X value (real number value) representing the resistance component R and a Y value (imaginary number value) representing the reactance component jωL when represented on the impedance plane as shown in FIG. And adopt. Hereinafter, the detection signal representing the resistance component R of the impedance is referred to as a detection signal X. A detection signal representing the reactance component jωL of the impedance is referred to as a detection signal Y. In the present embodiment, the detection device X measures the detection signal X and the detection signal Y as respective voltage values. However, it is not necessary to measure both the detection signal X and the detection signal Y, and it is sufficient to measure at least one of the detection signals. Further, the impedance itself of the detection coil 12 can be used as a detection signal.

検出信号Ｘ： ここで、インピーダンス平面におけるＸ値は、励磁コイル１１に印加された交流電圧に対して、渦電流Ｃにより検出コイル１２の両端に生じた誘起電圧の位相差に起因する値となる。この位相差は、ワークＷに形成された焼入硬化層の硬化深さと相関のある値と考えられている。すなわち、ワークＷに形成された焼入硬化層の硬化深さが深くなると、透磁率の低い焼入組織が深く分布することになり、励磁コイル１１に印加した交流電圧に対して、検出コイル１２の両端に生じた誘起電圧の位相ズレが増加する。これに対して、ワークＷに形成された焼入硬化層の硬化深さが浅くなると、透磁率の低い焼入組織の分布が浅くなるため、位相ズレは減少する。未焼入組織は、硬化深さがゼロであると考ることができるから、位相差に起因するＸ値の信号変化に基づいて、焼入範囲２０と未焼入範囲３０との境界位置を判定することができる。 Detection signal X: Here, the X value on the impedance plane is a value resulting from the phase difference of the induced voltage generated at both ends of the detection coil 12 by the eddy current C with respect to the AC voltage applied to the excitation coil 11. . This phase difference is considered to be a value having a correlation with the curing depth of the quenched and hardened layer formed on the workpiece W. That is, when the hardening depth of the hardened hardened layer formed on the workpiece W is deepened, a hardened structure having a low magnetic permeability is deeply distributed, and the detection coil 12 is detected with respect to the AC voltage applied to the exciting coil 11. The phase shift of the induced voltage generated at both ends of the increases. On the other hand, when the hardening depth of the hardened hardened layer formed on the workpiece W becomes shallower, the distribution of the hardened structure having a low magnetic permeability becomes shallower, so that the phase shift decreases. Since the unhardened structure can be considered to have a hardening depth of zero, the boundary position between the hardened range 20 and the unquenched range 30 is determined based on the signal change in the X value due to the phase difference. Can be determined.

検出信号Ｙ： 一方、インピーダンス平面におけるＹ値は、検出コイル１２の両端に生じた誘起電圧の振幅値を表す。走査部位の透磁率が高くなると、渦電流発生に伴う磁束が増すため、検出コイル１２の両端に生じる誘起電圧の振幅値も増大する。これに対して、走査部位の透磁率が低くなると、渦電流発生に伴う磁束が減るため、検出コイル１２の両端に生じる誘起電圧の振幅値も減少する。従って、誘起電圧の振幅値を表すＹ値は、走査部位の透磁率、すなわち、走査部位の表面硬度を反映する値といえる。従って、Ｙ値の信号変化に基づく表面硬度の差異から、焼入範囲２０と未焼入範囲３０との境界位置を判定することができる。以下、インピーダンスのリアクタンス成分を表す検出信号を検出信号Ｙと称する。 Detection signal Y: On the other hand, the Y value on the impedance plane represents the amplitude value of the induced voltage generated at both ends of the detection coil 12. When the magnetic permeability of the scanning region is increased, the magnetic flux accompanying the generation of eddy current increases, so that the amplitude value of the induced voltage generated at both ends of the detection coil 12 also increases. On the other hand, when the magnetic permeability at the scanning portion is lowered, the magnetic flux accompanying the generation of eddy current is reduced, so that the amplitude value of the induced voltage generated at both ends of the detection coil 12 is also reduced. Therefore, the Y value representing the amplitude value of the induced voltage can be said to be a value reflecting the magnetic permeability of the scanning region, that is, the surface hardness of the scanning region. Therefore, the boundary position between the quenching range 20 and the unquenched range 30 can be determined from the difference in surface hardness based on the signal change of the Y value. Hereinafter, the detection signal representing the reactance component of the impedance is referred to as a detection signal Y.

検出信号の変化： 渦電流センサ１０により、ワークＷの焼入範囲２０と未焼入範囲３０とを連続的に走査したとき、検出信号Ｘ及び検出信号Ｙのいずれを測定した場合であってもこれらの測定値の変化は概ね同様の傾向を示す。図４に、ワークＷを走査したときの検出信号Ｘ及び検出信号Ｙを電圧値として測定したときの測定値の推移を示す。また、図４には、このときの検出コイル１２のインピーダンスの推移を検出信号Ｚとして併せて示している。なお、図４における検出信号Ｚについても電圧換算値を示している。図４に示す測定例は、Ｓ４５Ｃ材からなる直径２０ｍｍ、長さ１００ｍｍの円柱状の鋼材であって、その外周を部分的に熱処理を施した試験片に対して、渦電流センサ１０で走査したときに得られた各検出信号の変化を示したものである。横軸は、渦電流センサ１０のワークＷの表面上の走査部位を走査開始位置からの走査時間として示したものである。また、縦軸は、測定値を示している。焼入組織が分布する領域と、未焼入組織が分布する領域とを比較すると、各領域の透磁率の差異から、図４に示すように、焼入組織が分布する領域に対して、未焼入組織が分布する領域の方がいずれの検出信号も高い値を示す。また、図４に示すように、いずれの検出信号も焼入範囲２０側で定常的な値を示したのち、焼入範囲２０と未焼入範囲３０との境界領域においてその値を変動させながら、未焼入範囲３０において再び定常的な値を示すようになる。 Change in detection signal: When the eddy current sensor 10 continuously scans the quenching range 20 and the non-quenching range 30 of the workpiece W, even when either the detection signal X or the detection signal Y is measured. These changes in measured values show a similar tendency. FIG. 4 shows the transition of the measured value when the detection signal X and the detection signal Y when the workpiece W is scanned are measured as voltage values. FIG. 4 also shows the transition of the impedance of the detection coil 12 at this time as a detection signal Z. In addition, the voltage conversion value is also shown about the detection signal Z in FIG. The measurement example shown in FIG. 4 is a columnar steel material having a diameter of 20 mm and a length of 100 mm made of S45C material, and the outer periphery of the test piece was scanned with the eddy current sensor 10 on a partially heat-treated test piece. The change of each detection signal obtained at times is shown. The horizontal axis shows the scanning part on the surface of the workpiece W of the eddy current sensor 10 as the scanning time from the scanning start position. The vertical axis represents the measured value. Comparing the region where the hardened structure is distributed with the region where the unhardened structure is distributed, the difference in the magnetic permeability of each region shows that the region where the hardened structure is distributed as shown in FIG. In the region where the hardened structure is distributed, all the detection signals show higher values. Further, as shown in FIG. 4, after each detection signal shows a steady value on the quenching range 20 side, the value is changed in the boundary region between the quenching range 20 and the unquenched range 30. In the unquenched range 30, a steady value is again shown.

焼入定常領域： ここで、焼入定常領域とは、焼入範囲２０を渦電流センサ１０で走査したときに、検出信号が定常的な値を示す領域をいう。ここで、「検出信号が定常的な値を示す領域」とは、焼入範囲２０を渦電流センサ１０で走査したときの検出信号の測定値を走査部位に対してプロットしたときに、所定の関数式（Ｙ＝ｆ（ｘ）＋ｙ１）で表される近似曲線（但し、近似直線を含む）を引くことができる領域であると定義することができる。また、当該領域における検出信号の定常的な値を「焼入定常値」と称する。図４に示す測定例では、焼入範囲２０内において、走査部位によらず「検出信号の測定値が定常的に略一定の値を示す領域」があり、この領域が焼入定常領域となる。そして、当該領域では、上記関数式において「ｆ（ｘ）＝０」の「Ｙ＝ｙ１」で表される近似曲線を引くことができる。また、この場合、焼入定常値は「ｙ１」で表わされ、この値は当該領域内における検出信号の測定値の平均値に相当する。 Quenching steady region: Here, the quenching steady region refers to a region where the detection signal shows a steady value when the quenching range 20 is scanned by the eddy current sensor 10. Here, the “region where the detection signal shows a steady value” means a predetermined value when the measurement value of the detection signal when the quenching range 20 is scanned with the eddy current sensor 10 is plotted against the scanning region. It can be defined as an area where an approximate curve (including an approximate straight line) represented by a functional expression (Y = f (x) + y 1 ) can be drawn. In addition, a steady value of the detection signal in the region is referred to as a “quenching steady value”. In the measurement example shown in FIG. 4, there is a “region in which the measurement value of the detection signal constantly shows a substantially constant value” in the quenching range 20 regardless of the scanning region, and this region is a quenching steady region. . In this area, an approximate curve represented by “Y = y 1 ” of “f (x) = 0” in the above functional expression can be drawn. In this case, the quenching steady value is represented by “y 1 ”, and this value corresponds to the average value of the measurement values of the detection signal in the region.

未焼入定常領域： 一方、未焼入定常領域とは、焼入定常領域と同様に、未焼入範囲３０を渦電流センサ１０で走査したときに、検出信号が定常的な値を示す領域をいい、未焼入範囲３０を渦電流センサ１０で走査したときの検出信号の測定値を走査部位に対してプロットしたときに、所定の関数式（Ｇ＝ｇ（ｘ）＋ｙ２）で表される近似曲線を引くことができる領域をいう。また、当該領域における検出信号の定常的な値を「未焼入定常値」と称する。図４に示す測定例では、焼入範囲２０と同様に、未焼入範囲３０内において、走査部位によらず検出信号の測定値が定常的に略一定の値を示す領域があり、この領域が未焼入定常領域となる。そして、当該領域では、焼入定常領域と同様に「ｇ（ｘ）＝０」の「Ｙ＝ｙ２」で表される近似曲線を引くことができる。また、この場合、未焼入定常値は「ｙ２」で表わされ、焼入定常値と同様に、この値は当該領域内における検出信号の測定値の平均値に相当する。 Unquenched steady region: On the other hand, the unquenched steady region is a region where the detection signal shows a steady value when the unquenched range 30 is scanned by the eddy current sensor 10, as in the steady quenched region. When the measured value of the detection signal when the unquenched range 30 is scanned by the eddy current sensor 10 is plotted against the scanning region, it is expressed by a predetermined function equation (G = g (x) + y 2 ). An area where an approximated curve can be drawn. Further, the steady value of the detection signal in the region is referred to as “unquenched steady value”. In the measurement example shown in FIG. 4, similarly to the quenching range 20, there is a region in which the measurement value of the detection signal constantly shows a substantially constant value regardless of the scanning portion in the unquenched range 30. Becomes the unquenched steady region. In this region, an approximate curve represented by “Y = y 2 ” of “g (x) = 0” can be drawn as in the steady quenching region. Further, in this case, the unquenched steady value is represented by “y 2 ”, and this value corresponds to the average value of the measurement values of the detection signal in the region, similarly to the steady quench value.

ところで、図４に示す測定例のように、渦電流センサ１０の走査範囲において、ワークWの形状やワークの硬化層深さが略一定である場合、焼入定常領域では、走査部位によらず検出信号の測定値が略一定の値を示した。しかしながら、本件発明において、「検出信号が定常的な値を示す領域」は、図４に示す測定例のように「検出信号の測定値が定常的に略一定の値を示す領域」のみを意味するのではなく、上述した通り、「検出信号の測定値を走査部位に対してプロットしたときに、所定の関数式（Ｙ＝ｆ（ｘ）＋ｙ１、Ｇ＝ｇ（ｘ）＋ｙ２）で表される近似曲線（但し、近似直線を含む）を引くことができる領域」を意味する。 Incidentally, as in the measurement example shown in FIG. 4, when the shape of the workpiece W and the hardened layer depth of the workpiece are substantially constant in the scanning range of the eddy current sensor 10, the quenching steady region does not depend on the scanning portion. The measured value of the detection signal showed a substantially constant value. However, in the present invention, the “region where the detection signal shows a steady value” means only the “region where the measurement value of the detection signal shows a constant value at a constant level” as in the measurement example shown in FIG. Instead, as described above, “when the measured value of the detection signal is plotted with respect to the scanning region, a predetermined function formula (Y = f (x) + y 1 , G = g (x) + y 2 ) It means a region where an approximated curve (however, an approximate straight line is included) can be drawn.

例えば、図５（ａ）に示すワークＷ１のように、渦電流センサ１０の走査面と、ワークＷ１の表面との間の距離が、渦電流センサ１０の走査部位に応じて変化する場合、図５（ｂ）に示すように検出信号（例えば、検出信号Ｘ）の測定値も走査部位によって変化する。しかしながら、焼入範囲２０を走査したときに得られた検出信号の測定値を走査部位に対してプロットしたときに、図５（ｂ）に示すように、所定の関数式（Ｙ＝ｆ（ｘ）＋ｙ１、但し、図示例ではｆ（ｘ）＝ａ×ｘであり、ａは定数である。）で表される近似曲線Ｌ１を引くことができる領域がある。従って、図５に示す例では、当該領域が焼入定常領域となる。同様に、未焼入範囲３０を走査したときに得られた検出信号の測定値を走査部位に対してプロットしたときにも、所定の関数式（Ｇ＝ｇ（ｘ）＋ｙ２、但し、図示例では、ｇ（ｘ）＝ｂ×ｘであり、ｂは定数である。）で表せる近似曲線Ｌ２を引くことの出来る領域がある。従って、当該領域が未焼入定常領域となる。但し、図４及び図５に示す例では、焼入定常領域及び未焼入定常領域において、近似曲線はいずれも一次関数式で表されたが、近似曲線を表す関数式は一次関数式に限るものではなく、二次関数式以上の高次の関数式であってもよいのは勿論である。すなわち、本件発明では、焼入範囲２０及び未焼入範囲３０において、検出信号の測定値が変化する場合であっても、当該測定値の変化がワークＷの形状等の変化に伴う定性的な変化の範囲内である限り、本件発明では検出信号が定常的な値を示すものとして取り扱う。そして、検出信号の測定値が上記各近似曲線から外れた値を示す領域、すなわち、検出信号の測定値がワークＷの形状等の変化の範囲を超えて変動する領域を、次に説明する境界領域とする。 For example, when the distance between the scanning surface of the eddy current sensor 10 and the surface of the workpiece W 1 changes according to the scanning part of the eddy current sensor 10 as in the workpiece W 1 shown in FIG. As shown in FIG. 5B, the measured value of the detection signal (for example, the detection signal X) also changes depending on the scanning site. However, when the measurement value of the detection signal obtained when scanning the quenching range 20 is plotted against the scanning region, as shown in FIG. 5B, a predetermined function formula (Y = f (x ) + Y 1 However, in the illustrated example, f (x) = a × x, where a is a constant.) There is a region where an approximate curve L 1 represented by: Therefore, in the example shown in FIG. 5, the region is a quenching steady region. Similarly, when the measurement value of the detection signal obtained when the unquenched range 30 is scanned is plotted with respect to the scanning region, a predetermined function formula (G = g (x) + y 2 , provided that FIG. in示例a g (x) = b × x , b is an area that can draw the approximate curve L 2 representable is a constant.). Therefore, this region becomes an unquenched steady region. However, in the examples shown in FIGS. 4 and 5, in the quenching steady region and the unquenched steady region, the approximate curves are both expressed by linear function equations, but the function equations representing the approximate curves are limited to linear function equations. Needless to say, it may be a higher-order function expression than a quadratic function expression. That is, in the present invention, even when the measurement value of the detection signal changes in the quenching range 20 and the non-quenching range 30, the change in the measurement value is qualitatively accompanied by a change in the shape of the workpiece W or the like. As long as it is within the range of change, the present invention treats the detection signal as indicating a steady value. A region where the measurement value of the detection signal shows a value deviating from each of the approximate curves, that is, a region where the measurement value of the detection signal fluctuates beyond the range of change of the shape of the workpiece W, etc. This is an area.

境界領域： 次に、境界領域について説明する。境界領域とは、上述した様に、焼入範囲２０と未焼入範囲３０との境界位置付近の領域を指し、具体的には上記焼入定常領域と上記未焼入定常領域との間の領域をいう。焼入定常領域及び未焼入定常領域では、検出信号の測定値はそれぞれ定常的な値を示すことから、各領域に分布する金属組織の透磁率はそれぞれ略一定であり、各領域における焼入硬化層の硬化層深さは略一定（若しくはゼロ）或いは、設計上の変動の範囲内の値を示すことが分かる。一方、境界領域では、図４に示すように、検出信号の測定値が変動する。これは、当該境界領域においてワークＷの表面硬度やワークＷに形成された金属硬化層の硬化層深さも変動しているためである。本件発明では、渦電流センサ１０で焼入範囲２０と未焼入範囲３０とを連続的に走査することにより、焼入定常領域と未焼入定常領域とを明らかにするとともに、当該境界領域における検出信号の信号変化に基づいて、焼入範囲２０と未焼入範囲３０との境界位置を判定する方法を採用している。当該観点から、この境界領域は、焼入範囲２０と未焼入範囲３０との境界位置を判定するための判定領域である。 Boundary area: Next, the boundary area will be described. As described above, the boundary region refers to a region near the boundary position between the quenching range 20 and the unquenched range 30, and specifically, between the quenching steady region and the unquenched steady region. An area. In the quenching steady region and the non-quenched steady region, the measured values of the detection signals show steady values, respectively, and the magnetic permeability of the metal structure distributed in each region is substantially constant, and the quenching in each region It can be seen that the cured layer depth of the cured layer is substantially constant (or zero) or shows a value within a range of design variation. On the other hand, in the boundary region, as shown in FIG. 4, the measurement value of the detection signal varies. This is because the surface hardness of the work W and the hardened layer depth of the metal hardened layer formed on the work W also vary in the boundary region. In the present invention, the quenching range 20 and the unquenched range 30 are continuously scanned by the eddy current sensor 10 to clarify the quenching steady region and the unquenched steady region, and in the boundary region. A method of determining the boundary position between the quenching range 20 and the unquenched range 30 based on the signal change of the detection signal is employed. From this viewpoint, this boundary region is a determination region for determining the boundary position between the quenching range 20 and the unquenched range 30.

しかしながら、材質、形状、焼入範囲２０が互いに同じワークＷであっても、当該ワークＷを製造したときの材料ロットや熱処理ロットが異なる場合、母材の金属組織や、焼入組織の透磁率、導電率等に誤差があることが想定される。また、検出信号を測定するときのワークＷの表面温度や、雰囲気温度が異なると、同じ材質等から成るワークＷであっても、その抵抗率、すなわち導電率が変化することが想定される。このように透磁率や導電率等の変化を招く外乱要因は種々存在するため、検出信号の測定値（絶対値）そのものを用いて、ワークＷの焼入範囲２０と未焼入範囲３０との境界位置を判定した場合、ワークＷの焼入範囲２０と未焼入範囲３０との境界位置を精度よく判定するのは困難である。   However, even if the workpiece W has the same material, shape, and quenching range 20, if the material lot or heat treatment lot when the workpiece W is manufactured is different, the metal structure of the base material or the permeability of the quenched structure It is assumed that there is an error in conductivity and the like. Further, if the surface temperature of the workpiece W when measuring the detection signal and the ambient temperature are different, it is assumed that the resistivity, that is, the conductivity, of the workpiece W made of the same material changes. Since there are various disturbance factors that cause changes in the magnetic permeability, conductivity, and the like in this way, the measured value (absolute value) of the detection signal itself is used to determine whether the workpiece W has a hardened range 20 and an unquenched range 30. When the boundary position is determined, it is difficult to accurately determine the boundary position between the quenching range 20 and the unquenched range 30 of the workpiece W.

そこで、本件発明では、検出信号の測定値を用いるのではなく、検出信号の測定値を信号変化率に変換して、当該信号変化率が予め定めた判定値（閾値）になった位置を焼入範囲２０と未焼入範囲３０との境界位置と判定する方法を採用している。すなわち、検出信号の測定値を信号変化率に変換し、検出信号の信号変化率を用いて焼入範囲２０と未焼入範囲３０との境界位置を判定することにより、材料ロットや熱処理ロット、あるいは測定環境の温度変化等の種々の外乱要因による影響を排除して、ワークＷの焼入範囲２０と未焼入範囲３０との境界位置を精度よく判定することが可能になった。   Therefore, in the present invention, instead of using the measurement value of the detection signal, the measurement value of the detection signal is converted into a signal change rate, and the position where the signal change rate becomes a predetermined determination value (threshold) is calculated. A method of determining the boundary position between the quenching range 20 and the unquenched range 30 is employed. That is, by converting the measurement value of the detection signal into a signal change rate, and determining the boundary position between the quenching range 20 and the unquenched range 30 using the signal change rate of the detection signal, the material lot and the heat treatment lot, Alternatively, it is possible to accurately determine the boundary position between the quenching range 20 and the unquenched range 30 of the workpiece W by eliminating the influence of various disturbance factors such as temperature changes in the measurement environment.

信号変化率： ここで、信号変化率は、検出信号の測定値を焼入定常値と未焼入定常値を基準とした信号変化率として表したものである。このように、検出信号の測定値を焼入定常値と未焼入定常値との間の変化の割合に変換することにより、外乱要因の影響を排除して、検出信号の信号変化率を境界領域における金属組織等の変化の程度として捉えることができる。従って、ワークＷの用途や材質等に応じて、焼入範囲２０と未焼入範囲３０との境界位置を表す所定の値を判定値として予め定めておくことにより、対象ワークを走査したときの信号変化率と、この判定値とを比較することにより、対象ワークに形成された焼入範囲２０と未焼入範囲３０との境界位置を簡易に、且つ、精度よく判定することができる。但し、図４に示す場合は上述した様に、焼入定常値及び未焼入定常値はそれぞれ切片「ｙ１」、「ｙ２」の値で表され、これらの値を基準にして、境界領域において得られた検出信号の測定値を信号変換率に変換することができる。一方、図５（ｂ）に例示する場合のように、近似曲線が傾き（ａ≠０、ｂ≠０）を有する一次関数式あるいは、二次関数以上の関数式で表される場合は、次のようにして信号変換率を求める。走査部位「Ｓｘ」における検出信号Ｘの測定値が「Ｘｓ」であった場合、各近似曲線Ｌ１、Ｌ２を表す関数式のｆ（ｘ）、ｇ（ｘ）にそれぞれ「ｘ＝Ｓｘ」を代入し、そのときに得られる「Ｙｓ」、「Ｇｓ」の値を基準にして、当該測定値「ＸＳ」を信号変換率に変換することができる。 Signal change rate: Here, the signal change rate represents the measured value of the detection signal as a signal change rate based on the quenching steady value and the unquenched steady value. In this way, by converting the measured value of the detection signal into the rate of change between the quenching steady value and the unquenched steady value, the influence of disturbance factors is eliminated and the signal change rate of the detection signal is bounded. It can be understood as the degree of change in the metal structure or the like in the region. Accordingly, when a predetermined value representing the boundary position between the quenching range 20 and the unquenched range 30 is set in advance as a determination value according to the use or material of the workpiece W, the target workpiece is scanned. By comparing the signal change rate with this determination value, the boundary position between the quenching range 20 and the unquenched range 30 formed on the target workpiece can be easily and accurately determined. However, in the case shown in FIG. 4, as described above, the quenching steady value and the unquenched steady value are represented by the values of the intercepts “y 1 ” and “y 2 ”, respectively. The measurement value of the detection signal obtained in the region can be converted into a signal conversion rate. On the other hand, when the approximate curve is expressed by a linear function expression having a slope (a ≠ 0, b ≠ 0) or a function expression of a quadratic function or more as in the case illustrated in FIG. Thus, the signal conversion rate is obtained. When the measured value of the detection signal X at the scanning region “S x ” is “X s ”, “x =” is given to each of f (x) and g (x) of the functional expressions representing the approximate curves L 1 and L 2. Substituting S x ”, the measured value“ X S ”can be converted into a signal conversion rate based on the values of“ Y s ”and“ G s ”obtained at that time.

判定値： 判定値は、焼入範囲２０と未焼入範囲３０との境界位置を判定するために用いる所定の値であり、ワークＷの用途や材質等に応じて、適宜、適切な値を選定することができる。ところで、現時点において、ワークＷの表面における焼入範囲２０と未焼入範囲３０との境界位置に関する規格はない。そこで、本件発明では、焼入範囲２０と未焼入範囲３０との境界位置として、焼入組織と未焼入組織との物理的又は化学的性質の差異が区別できない位置と定義する。判定値は、この境界位置における検出信号の信号変化率に相当する。 Determination value: The determination value is a predetermined value used to determine the boundary position between the quenching range 20 and the non-quenching range 30, and an appropriate value is appropriately selected according to the use or material of the workpiece W. Can be selected. By the way, at present, there is no standard regarding the boundary position between the quenching range 20 and the unquenched range 30 on the surface of the workpiece W. Therefore, in the present invention, the boundary position between the quenching range 20 and the unquenched range 30 is defined as a position where the difference in physical or chemical properties between the quenched structure and the unquenched structure cannot be distinguished. The determination value corresponds to the signal change rate of the detection signal at this boundary position.

判定値の設定： 具体的に判定値を設定する際には、複数の検証用ワークＷＮを用いて、各検証用ワークＷＮの境界領域における検出信号の信号変化率と、各検証用ワークＷＮの焼入範囲２０と未焼入範囲３０との境界位置との相関性を予め検証しておくことが好ましい。そして、この相関性に基づいて、判定値を設定することが好ましい。具体的には、複数の検証用ワークＷＮを用いて、各検証用ワークＷＮを渦電流センサ１０で焼入範囲２０とこれに隣接する未焼入範囲３０を連続的に走査したときの検出信号の信号の推移に基づいて、焼入範囲２０と未焼入範囲３０との境界位置として適切であり、且つ、信号変化率の推移により精度よく当該境界位置を判定可能な値にすることが好ましい。 Setting the determination value: When setting the specific determination value, using a plurality of verification workpiece W N, the signal rate of change of the detection signal in the boundary region of each verification workpiece W N, the verification work it is preferable to previously verify the correlation between the boundary position between the W quenching range 20 to non quenching range 30 N. And it is preferable to set a determination value based on this correlation. Specifically, when a plurality of verification workpieces W N are used and each verification workpiece W N is continuously scanned by the eddy current sensor 10 between the quenching range 20 and the unquenched range 30 adjacent thereto. Based on the signal transition of the detection signal, the boundary position between the quenching range 20 and the unquenched range 30 is appropriate, and the boundary position is set to a value that can be accurately determined by the transition of the signal change rate. Is preferred.

検証方法： 具体的な検証方法として、例えば、判定値を０％〜１００％の範囲で変化させて、各判定値において焼入範囲２０と未焼入範囲３０との境界位置として判定した位置（以下、評価位置とする）と、検証用ワークＷＮの実際の焼入範囲２０と未焼入範囲３０との境界位置との相関性を検証する方法が一例として挙げられる。本件発明者が行った実験結果によると、信号変化率を百分率で表したときに、判定値を２０％〜９０％の範囲の値とした場合、上記判定位置と実際の境界位置との相関性がよく、精度よく対象ワークの焼入範囲２０を検出することができる。特に、Ｓ４５Ｃ材については、判定値を２０％〜９０％の範囲内の値とすると、判定位置と実際の境界位置との相関性が良好であった。また、判定値の値を２０％未満あるいは９０％を超える値にした場合、図４に示すように、渦電流センサ１０で境界領域を走査した場合に、判定値と同じ信号変化率となる位置が２箇所以上存在する場合があり、焼入範囲２０と未焼入範囲３０との境界位置を一意的に判定するのが困難になる。これらの観点から、信号変化率を百分率で表したとき、判定値は２０％〜９０％の範囲内で定めた所定の値とすることが妥当である。 Verification method: As a specific verification method, for example, a determination value is changed in a range of 0% to 100%, and each determination value is determined as a boundary position between the quenching range 20 and the non-quenching range 30 ( hereinafter, to) and the evaluation position, a method of verifying the actual correlation between the boundary position between the quenching range 20 to non quenching range 30 of the verification work W N as an example. According to the results of experiments conducted by the present inventors, when the signal change rate is expressed as a percentage, if the determination value is in the range of 20% to 90%, the correlation between the determination position and the actual boundary position Therefore, the quenching range 20 of the target workpiece can be detected with high accuracy. In particular, for the S45C material, the correlation between the determination position and the actual boundary position was good when the determination value was within a range of 20% to 90%. Further, when the judgment value is less than 20% or more than 90%, as shown in FIG. 4, when the boundary region is scanned by the eddy current sensor 10, the position where the signal change rate is the same as the judgment value. May exist in two or more places, and it becomes difficult to uniquely determine the boundary position between the quenching range 20 and the unquenched range 30. From these viewpoints, when the signal change rate is expressed as a percentage, it is appropriate that the determination value is a predetermined value determined within a range of 20% to 90%.

焼入範囲検査方法： 以上のようにして得た焼入範囲２０の検出結果に基づいて、対象ワークに焼入れを施すべき範囲に、焼入れが施されているか否かを判定することができる。このとき、例えば、対象ワークについて判定された境界位置が、対象ワークの焼入範囲２０と未焼入範囲３０との境界位置として適切な位置であるか否かを判定すればよい。 Hardening range inspection method: Based on the detection result of the quenching range 20 obtained as described above, it is possible to determine whether or not the target workpiece is to be quenched in the range to be quenched. At this time, for example, it may be determined whether or not the boundary position determined for the target workpiece is an appropriate position as the boundary position between the quenching range 20 and the unquenched range 30 of the target workpiece.

以上説明した本実施の形態は、本件発明の一態様であり、本件発明の趣旨を逸脱しない範囲で適宜変更可能であるのは勿論である。また、入力装置、記憶装置、演算装置、出力装置等を有するコンピュータを測定装置１４に接続し、測定装置１４から入力装置を介して入力された検出信号の測定値を、演算装置により信号変化率に変換すると共に、この信号変化率を記憶装置に予め記憶された判定値と比較し、信号変化率が判定値になった走査部位を焼入範囲２０と未焼入範囲３０との境界位置と判定する焼入範囲検出装置として構成してもよい。また、このとき、演算装置により、判定された境界位置が、対象ワークの焼入範囲２０と未焼入範囲３０との境界位置として適切な位置であるか否かを、記憶装置に予め記憶された管理値としての境界位置と比較して、焼入範囲２０の良否を判定し、その判定結果を出力装置を介して出力するようにしてもよい。このとき、コンピュータには、各ステップを実行させるための本件発明に係るプログラムがインストールされるのは勿論である。また、プログラムは、検出信号の測定値の入力を受け付けるステップと、焼入範囲と未焼入範囲との境界領域における前記検出信号の測定値を、信号変化率に変換するステップと、前記検出信号の信号変化率の変化に基づいて、当該対象ワークの表面における焼入範囲と未焼入範囲との境界位置を判定させるステップとを、コンピュータに実行させるものであれば、本件発明の趣旨を逸脱しない範囲で適宜変更可能である。   The present embodiment described above is an aspect of the present invention, and it is needless to say that the embodiment can be appropriately changed without departing from the gist of the present invention. In addition, a computer having an input device, a storage device, an arithmetic device, an output device, etc. is connected to the measuring device 14, and the measurement value of the detection signal input from the measuring device 14 through the input device is converted into a signal change rate by the arithmetic device. And the signal change rate is compared with a determination value stored in advance in the storage device, and the scanning portion where the signal change rate becomes the determination value is determined as the boundary position between the quenching range 20 and the unquenched range 30. You may comprise as a quenching range detection apparatus to determine. At this time, whether or not the determined boundary position is an appropriate position as the boundary position between the quenching range 20 and the unquenched range 30 of the target workpiece is stored in advance in the storage device. Compared with the boundary position as the management value, the quality of the quenching range 20 may be determined, and the determination result may be output via the output device. At this time, of course, the computer according to the present invention for executing each step is installed in the computer. Further, the program receives the input of the measurement value of the detection signal, converts the measurement value of the detection signal in the boundary region between the quenching range and the unquenched range into a signal change rate, and the detection signal If the computer executes the step of determining the boundary position between the quenching range and the non-quenching range on the surface of the target workpiece based on the change in the signal change rate of the target, it deviates from the gist of the present invention. It is possible to change appropriately within the range not to be.

以下、実際に複数の検証用ワークＷＮを用いて、各検証用ワークＷＮの境界領域における検出信号の信号変化率と、各検証用ワークＷＮの焼入範囲２０と未焼入範囲３０との境界位置との相関性を検証した検証結果に関する実施例について説明する。但し、以下に説明する実施例に本件発明が限定されるものではない。 Hereinafter, actually using a plurality of verification workpiece W N, the signal rate of change of the detection signal in the boundary region of each verification workpiece W N, Not quenched range and quenching the range 20 of the verification work W N 30 An example relating to the verification result of verifying the correlation with the boundary position between the two will be described. However, the present invention is not limited to the embodiments described below.

検証用ワークＷＮ： まず、検証用ワークＷＮについて説明する。図５に示すように、本実施例では焼入範囲２０の異なる６個（Ｎ個）の検証用ワークＷＮを用意した。各検証用ワークＷＮは、焼入範囲２０の検出対象とする対象ワークに対応するものであり、対象ワークと素材や形状が一致するものを用意する。本実施例では、Ｓ４５Ｃ材から成る直径２０ｍｍ、長さ１００ｍｍの鋼棒を検証用ワークＷＮとして用いた。この６個の検証用ワークＷＮに対して、それぞれ異なる領域に誘導加熱コイルにより移動焼入れを行った。誘導加熱コイルの移動加熱領域は、図４に示すＡ位置を移動開始位置とし、Ｂｎ位置（ｎ＝Ｎ−１）を移動終了位置とした。各検証用ワークＷＮに対する焼入れ条件は、誘導加熱コイルの移動加熱領域（熱処理範囲）が異なる以外は同一の条件を採用した。検証用ワークＷＮのうち、いずれか一の検証用ワークＷＮの熱処理範囲は、焼入範囲２０の検出対象とする対象ワークの熱処理範囲と同じ領域になるようにした。 Verification Work W N : First, the verification work W N will be described. As shown in FIG. 5, in this embodiment, six (N) verification workpieces W N having different quenching ranges 20 were prepared. Each verification work W N corresponds to a target work that is a detection target of the quenching range 20, and a work whose material and shape coincide with the target work is prepared. In this example, a steel bar made of S45C and having a diameter of 20 mm and a length of 100 mm was used as the verification work W N. The six verification workpieces W N were transferred and quenched by induction heating coils in different areas. In the movement heating region of the induction heating coil, the position A shown in FIG. 4 was set as the movement start position, and the position Bn (n = N−1) was set as the movement end position. The quenching conditions for each verification workpiece W N were the same except that the moving heating region (heat treatment range) of the induction heating coil was different. Of verification workpiece W N, heat treatment range of any one of the verification work W N was set to be in the same region as the heat treatment range of the target workpiece to be detected in the hardening range 20.

基準ワークＷ０と比較ワークＷｎ： 検証用ワークＷＮのうち、いずれか一の検証用ワークＷＮの熱処理範囲は、焼入範囲２０の検出対象とする対象ワークの熱処理範囲と同じ領域になるようにした。この検証用ワークＷＮを基準ワークＷ０とした。そして、基準ワークＷ０以外の検証用ワークＷＮを比較ワークＷｎとした。各比較ワークＷｎの熱処理範囲の端部位置であるＢｎ位置は、基準ワークＷ０の端部位置Ｂ０位置からＤｎｍｍ離間する位置にある。本実施例では、第一比較ワークＷ１のＢ１位置は、Ｂ０位置からＤ１＝０．５ｍｍ離間した位置とした。第二比較ワークＷ２のＢ２位置は、Ｂ０位置からＤ２＝１．５ｍｍ離間した位置とした。第三比較ワークＷ３のＢ４位置は、Ｂ０位置からＤ３＝２．０ｍｍ離間した位置とした。第四比較ワークＷ４のＢ４位置は、Ｂ０位置からＤ４＝２．５ｍｍ離間した位置とした。第五比較ワークＷ５のＢ５位置は、Ｂ０位置からＤ５＝３．０ｍｍ離間した位置とした。但し、これらの各Ｂｎ位置は任意に設定することができる。 Reference work W 0 and compares the workpiece W n: out of the verification work W N, heat treatment range of any one of the verification work W N is the same region as the thermal treatment range of the target workpiece to be detected in the hardening range 20 It was made to become. This verification work W N was set as a reference work W 0 . A verification work W N other than the reference work W 0 was used as a comparison work W n . The B n position, which is the end position of the heat treatment range of each comparative workpiece W n , is at a position that is separated from the end position B 0 position of the reference workpiece W 0 by D n mm. In the present embodiment, the B 1 position of the first comparison work W 1 is a position that is separated from the B 0 position by D 1 = 0.5 mm. The B 2 position of the second comparison workpiece W 2 was a position that was separated from the B 0 position by D 2 = 1.5 mm. The B 4 position of the third comparison workpiece W 3 was set at a position separated from the B 0 position by D 3 = 2.0 mm. The B 4 position of the fourth comparison work W 4 was set to a position spaced by D 4 = 2.5 mm from the B 0 position. B 5 position of the fifth comparative work W 5 were from B 0 position and D 5 = 3.0 mm spaced locations. However, each of these Bn positions can be set arbitrarily.

走査条件： 次に、渦電流センサ１０による走査条件を説明する。渦電流センサ１０により上述の各検証用ワークＷＮの焼入範囲２０と未焼入範囲３０とを連続して走査する。このとき、図５に示すように、検証用ワークＷＮの長尺方向（軸方向）を走査方向とし、走査速度は２ｍｍ／秒とした。また、焼入範囲２０側から未焼入範囲３０側に向かって走査するものとした。渦電流センサ１０の構成は、図２において説明したものと同様の構成を有している。励磁コイル１１と検出コイル１２の外径はそれぞれ２．９ｍｍとした。また、検出信号を測定するための測定周波数は３２ｋＨｚとした。すなわち、交流電源１３から励磁コイル１１に供給する交流電流の周波数を３２ｋＨｚとした。また、検出信号は検出コイル１２のインピーダンスに関する信号とし、具体的には、図３を参照しながら説明した検出信号Ｘと検出信号Ｙとをそれぞれ測定した。 Scanning conditions: Next, scanning conditions by the eddy current sensor 10 will be described. Continuously scans the non-hardening range 30 and quenching the range 20 of the verification work W N described above by the eddy current sensor 10. At this time, as shown in FIG. 5, the longitudinal direction (axial direction) of the verification work W N was set as the scanning direction, and the scanning speed was set to 2 mm / second. Further, scanning was performed from the quenching range 20 side toward the non-quenching range 30 side. The configuration of the eddy current sensor 10 is the same as that described in FIG. The outer diameters of the excitation coil 11 and the detection coil 12 were each 2.9 mm. The measurement frequency for measuring the detection signal was 32 kHz. That is, the frequency of the alternating current supplied from the alternating current power supply 13 to the exciting coil 11 was set to 32 kHz. Further, the detection signal was a signal related to the impedance of the detection coil 12, and specifically, the detection signal X and the detection signal Y described with reference to FIG. 3 were measured.

検出信号の測定値： 渦電流センサ１０により、各検出用ワークＷ（基準ワークＷ０及び比較ワークＷｎ）を走査したときの、検出信号Ｘ及び検出信号Ｙの測定値の推移をそれぞれ図５及び図７に示す。図６及び図７は、渦電流センサ１０の走査部位に対して、当該走査部位における検出信号Ｘ及び検出信号Ｙのそれぞれの測定値をプロットしたものである。但し、図６及び図７において、走査部位は、予め定めた走査基準位置からの距離を走査時間として表している。渦電流センサ１０は、一定の速度（２ｍｍ／秒）で各検証用ワークＷＮの表面を走査するため、渦電流センサ１０が走査基準位置から走査部位に達するまでに要した走査時間により、各検証用ワークＷＮの表面上の走査部位を特定することができる。本実施例では、基準ワークＷ０の焼入定常領域と境界領域との境界位置を走査基準位置とした。 Measurement of the detection signal: by the eddy current sensor 10, when scanned each detection workpiece W (reference work W0 and Comparative workpiece W n), the detection signal X and FIG. 5, respectively and the change of the measured value of the detection signal Y As shown in FIG. 6 and 7 plot the measured values of the detection signal X and the detection signal Y at the scanning portion with respect to the scanning portion of the eddy current sensor 10. However, in FIG. 6 and FIG. 7, the scanning part represents the distance from the predetermined scanning reference position as the scanning time. Since the eddy current sensor 10 scans the surface of each verification work W N at a constant speed (2 mm / second), each eddy current sensor 10 has a scanning time required to reach the scanning site from the scanning reference position. The scanning part on the surface of the verification work W N can be specified. In this embodiment, the boundary position between the quenching constant region and the boundary region of the reference workpiece W 0 and the scan reference position.

焼入定常値と未焼入定常値： 図６に示すように、渦電流センサ１０が焼入範囲２０を走査している間に、検出信号Ｘの測定値が、０．００Ｖ〜−０．１０Ｖ程度の定常的な値を示す領域が見られた。この領域を焼入定常領域とする。また、当該焼入定常領域における検出信号Ｘの測定値の平均値を焼入定常値とする。また、渦電流センサ１０が未焼入範囲３０を走査している間に、検出信号Ｘの測定値が１．０Ｖ〜１．３０Ｖ程度の定常的な値を示す領域が見られた。この領域を未焼入定常領域とする。このときの未焼入定常領域における検出信号Ｘの測定値の平均値を未焼入定常値とする。 Hardened steady value and unquenched steady value: As shown in FIG. 6, while the eddy current sensor 10 scans the quenching range 20, the measured value of the detection signal X is 0.00V to −0. A region showing a steady value of about 10 V was observed. This region is a quenching steady region. Further, an average value of measured values of the detection signal X in the quenching steady region is set as a quenching steady value. In addition, while the eddy current sensor 10 was scanning the unquenched range 30, there was a region where the measured value of the detection signal X showed a steady value of about 1.0V to 1.30V. This region is defined as an unquenched steady region. The average value of the measurement values of the detection signal X in the unquenched steady region at this time is defined as the unquenched steady value.

また、図７に示すように、検出信号Ｙは、検出信号Ｘと同様の推移を示した。検出信号Ｙについても渦電流センサ１０が焼入範囲２０及び未焼入範囲３０を走査している間に、検出信号Ｙの測定値が定常的な値を示す領域がそれぞれ見られた。これらの領域をそれぞれ焼入定常領域、未焼入定常領域とし、その間の領域を境界領域とする。また、各領域における検出信号Ｙの測定値の平均値をそれぞれ焼入定常値、未焼入定常値とする。   Further, as shown in FIG. 7, the detection signal Y showed the same transition as the detection signal X. As for the detection signal Y, while the eddy current sensor 10 scans the quenching range 20 and the non-quenching range 30, areas where the measured value of the detection signal Y shows a steady value were respectively observed. These regions are defined as a quenching steady region and an unquenched steady region, respectively, and a region between them is defined as a boundary region. Further, the average value of the measured values of the detection signal Y in each region is set as a quenching steady value and an unquenched steady value, respectively.

信号変化率： 図６及び図７に示すように、各検証用ワークＷＮについて得た検出信号Ｘ、Ｙの焼入定常値及び未焼入定常値はそれぞれ異なっている。これは、上述した通り、種々の外乱要因によるものと考えられる。そこで、これらの外乱要因による影響を排除するために、各検証用ワークＷＮについて測定した検出信号Ｘ、Ｙについて、それぞれ焼入定常値を０％、未焼入定常値を１００％として、境界領域における検出信号Ｘの測定値を信号変化率に変換した。各検証用ワークＷＮの検出信号Ｘに関するグラフを図８に示す。また、検出信号Ｙに関するグラフを図９に示す。 Signal change: As shown in FIGS. 6 and 7, the detection signal X, quenching constant value and non-quenching constant value of Y obtained for each verification workpiece W N are different from each other. As described above, this is considered to be caused by various disturbance factors. Therefore, in order to eliminate the influence of these disturbance factors, the detection signals X and Y measured for each verification workpiece W N are each set to a boundary where the quenching steady value is 0% and the unquenched steady value is 100%. The measured value of the detection signal X in the region was converted into a signal change rate. A graph relating to the detection signal X of each verification work W N is shown in FIG. A graph relating to the detection signal Y is shown in FIG.

判定値と評価位置： 次に、判定値を設定するために、これらの各検証用ワークＷＮの境界領域における検出信号の信号変化率と、各検証用ワークＷＮの焼入範囲２０と未焼入範囲３０との境界位置との相関性を検証する。このとき、仮の判定値として判定値を０％〜１００％の範囲で５％ずつ変化させて、この仮の判定値を用いて判定した焼入範囲２０と未焼入範囲３０との境界位置（評価位置）と、各検証用ワークＷＮの焼入範囲２０と未焼入範囲３０との実際の境界位置との相関性を検証した。ここで、破壊検査を行って各検証用ワークＷＮの焼入範囲２０と未焼入範囲３０との境界位置を求めることができるが、本実施例では誘導加熱コイルの移動範囲に基づいて各検証用コイルの焼入範囲２０と非焼入範囲２０との境界位置を定めた。高周波焼入れでは、誘導加熱コイルによる熱処理範囲と焼入範囲２０とは高い相関性を有する。各比較ワークＷｎの熱処理範囲の端部位置であるＢｎ位置は、基準ワークＷ０の端部位置Ｂ０位置からＤｎｍｍ離間する位置にある。従って、各比較ワークＷｎの焼入範囲２０と未焼入れ範囲との境界位置は、基準ワークＷの焼入範囲２０と未焼入範囲３０との境界位置とそれぞれＤｎｍｍに対応する位置関係を有するはずである。従って、仮の判定値が判定値として適切である場合、各比較ワークＷの評価位置は、基準ワークＷの評価位置に対して、Ｄｎｍｍに対応する位置関係となるはずである。本実施例では、このような観点に基づき、検証を行った。 Judgment value the evaluation position: Next, in order to set a determination value, the signal change rates of these detection signals in the boundary region of each verification workpiece W N, and quenching the range 20 of the verification work W N Not The correlation with the boundary position with the quenching range 30 is verified. At this time, the boundary value between the quenching range 20 and the unquenched range 30 determined using the temporary determination value by changing the determination value by 5% in the range of 0% to 100% as the temporary determination value. and (evaluation position), to verify the correlation between the actual boundary position between the quenching range 20 of the verification work W N and green input range 30. Here, it is possible to determine the boundary position between the quenching range 20 to non quenching range 30 of performing destructive testing each verification workpiece W N, in the present embodiment based on the moving range of the induction heating coil each The boundary position between the quenching range 20 and the non-quenching range 20 of the verification coil was determined. In the induction hardening, the heat treatment range by the induction heating coil and the quenching range 20 have a high correlation. The B n position, which is the end position of the heat treatment range of each comparative workpiece W n , is at a position that is separated from the end position B 0 position of the reference workpiece W 0 by D n mm. Thus, the boundary position between the quenching range 20 and not quenched range of each comparison workpiece W n, the boundary position and the positional relationship corresponding to D n mm each of the quenching range 20 of the reference workpiece W with non-quenching range 30 Should have. Therefore, when the provisional determination value is appropriate as the determination value, the evaluation position of each comparative workpiece W should be in a positional relationship corresponding to D n mm with respect to the evaluation position of the reference workpiece W. In this example, verification was performed based on such a viewpoint.

検証結果： 図１０及び図１１に、判定値を仮に５０％としたときの検証結果を示す。図１０及び図１１において、縦軸はそれぞれ基準ワークＷの評価位置から各検出用ワークＷの評価位置までの距離（ｍｍ）を表している。また、横軸は基準ワークＷの焼入範囲２０と未焼入範囲３０との境界位置に対応するＢ０位置から、比較ワークＷの焼入範囲２０と未焼入範囲３０との境界位置に対応するＢｎ位置までの距離（Ｄｎ）を表している。図１０及び図１１において、それぞれ近似曲線（回帰直線）を引いた。検出信号Ｘについては、ｙ＝１．０２７ｘ＋０．０１５７の近似曲線が得られた。このときの相関係数ｒ＝０．９９８であった。一方、検出信号Ｙについては、ｙ＝０．９３３７ｘ−０．０１５の近似曲線が得られた。このときの相関係数は、ｒ＝０．９９５１であった。 Verification Result: FIG. 10 and FIG. 11 show the verification result when the judgment value is assumed to be 50%. 10 and 11, each vertical axis represents a distance (mm) from the evaluation position of the reference workpiece W to the evaluation position of each detection workpiece W. Also, the horizontal axis corresponding B 0 located at the boundary position between the quenching range 20 to non quenching range 30 of the reference workpiece W, the boundary position between the quenching range 20 comparison workpiece W with non-quenching range 30 It represents the distance (D n ) to the corresponding B n position. In FIGS. 10 and 11, approximate curves (regression lines) are drawn. For the detection signal X, an approximate curve of y = 1.027x + 0.0157 was obtained. The correlation coefficient r at this time was 0.998. On the other hand, for the detection signal Y, an approximate curve of y = 0.9337x−0.015 was obtained. The correlation coefficient at this time was r = 0.9951.

各評価位置と相関係数： 上記と同様の方法により、信号変化率を変化させて検証を行った。結果を図１２に示す。図１２において、横軸は評価位置を判定したときの判定値を示している。縦軸は、そのときの評価位置と実際の焼入範囲２０と未焼入範囲３０との境界位置との相関係数を示している。図１２に示すように、検出信号Ｘについてみると、信号変化率が２０％未満の位置で、焼入範囲２０と未焼入範囲３０との境界位置を判定した場合、相関係数が低くなることが分かる。一方、検出信号Ｙは、信号変化率が１０％になる位置で焼入範囲２０と未焼入範囲３０との境界位置を判定した場合であっても、相関係数は０．９９５であり、相関性は良好である。しかしながら、図９に示すように、検証用ワークＷＮによっては、信号変化率が２０％未満の領域では２箇所以上の走査部位で同じ信号変化率を示す場合があり、焼入範囲２０と未焼入範囲３０との境界位置を一意的に判定するのが困難になる。従って、焼入範囲２０と未焼入範囲３０との境界位置を判定する際に用いる判定値としての信号変化率は２０％以上とすることが好ましい。一方、信号変化率が９０％を超える位置で焼入範囲２０と未焼入範囲３０との境界位置を判定すると、検出信号Ｘ及び検出信号Ｙのいずれについても相関係数の低下が見られる。また、信号変化率が９０％を超える領域において検出信号Ｙの相関係数の低下の度合いは低い。しかしながら、図９に示すように、検出信号Ｙは信号変化率が９０％を超える領域で、２箇所以上の走査部位で同じ信号変化率を示す場合がある。このため、焼入範囲２０と未焼入範囲３０との境界位置を一意的に判定するのが困難になる。また、信号変化率が２０％〜９０％の領域で焼入範囲２０と未焼入範囲３０との境界位置を判定すると、高い相関性が得られることが分かる。以上の検証結果より、判定値として用いる信号変化率の値は、２０％〜９０％の間で判定するのが好ましく、また、当該範囲内において判定値を設定することにより、精度よく対象ワークの焼入範囲２０の検出が可能であることが分かる。 Each evaluation position and correlation coefficient: Verification was performed by changing the signal change rate by the same method as described above. The results are shown in FIG. In FIG. 12, the horizontal axis indicates the determination value when the evaluation position is determined. The vertical axis represents the correlation coefficient between the evaluation position at that time and the boundary position between the actual quenching range 20 and the unquenched range 30. As shown in FIG. 12, regarding the detection signal X, when the boundary position between the quenching range 20 and the unquenched range 30 is determined at a position where the signal change rate is less than 20%, the correlation coefficient is low. I understand that. On the other hand, the detection signal Y has a correlation coefficient of 0.995 even when the boundary position between the quenching range 20 and the unquenched range 30 is determined at a position where the signal change rate becomes 10%. The correlation is good. However, as shown in FIG. 9, depending on the verification work W N , in the region where the signal change rate is less than 20%, the same signal change rate may be shown in two or more scanning parts, and the quenching range 20 and the non-hardening range 20 are not. It becomes difficult to uniquely determine the boundary position with the quenching range 30. Therefore, it is preferable that the signal change rate as a determination value used when determining the boundary position between the quenching range 20 and the unquenched range 30 is 20% or more. On the other hand, when the boundary position between the quenching range 20 and the unquenched range 30 is determined at a position where the signal change rate exceeds 90%, a decrease in the correlation coefficient is observed for both the detection signal X and the detection signal Y. Further, the degree of decrease in the correlation coefficient of the detection signal Y is low in the region where the signal change rate exceeds 90%. However, as shown in FIG. 9, the detection signal Y may show the same signal change rate in two or more scanning regions in a region where the signal change rate exceeds 90%. For this reason, it becomes difficult to uniquely determine the boundary position between the quenching range 20 and the unquenched range 30. It can also be seen that when the boundary position between the quenching range 20 and the unquenched range 30 is determined in a region where the signal change rate is 20% to 90%, high correlation is obtained. From the above verification results, it is preferable that the signal change rate value used as the determination value is determined between 20% and 90%, and by setting the determination value within the range, the target workpiece can be accurately determined. It can be seen that the quenching range 20 can be detected.

本件発明は、渦電流測定法を利用してワークＷ（鉄鋼材）の焼入範囲２０を非破壊で検出することができ、特に焼入範囲２０と未焼入範囲３０との境界位置を簡易に、且つ、精度よく判定することができる。また、本件発明では、コンピュータを用いて、コンピュータ処理により自動的に対象ワークの焼入範囲２０と未焼入範囲３０との境界位置を判定することができ、焼入範囲２０の良否を精度よく判定することが可能である。このため、焼入鋼材の製造ラインにおいて、インラインで、焼入範囲２０の検出及び焼入範囲２０の全数検査を行うことができ、焼入鋼材の品質保証を良好に行うことができる。焼入範囲２０が不良な鉄鋼材が組付工程等に回されるのを防止し、不良品の発生を防止し、無駄な廃材が出るのを防止することができる。   In the present invention, the quenching range 20 of the workpiece W (steel material) can be detected nondestructively using the eddy current measurement method, and in particular, the boundary position between the quenching range 20 and the unquenched range 30 can be simplified. In addition, it can be determined with high accuracy. Further, in the present invention, a boundary position between the quenching range 20 and the unquenched range 30 of the target workpiece can be automatically determined by computer processing using a computer, and the quality of the quenching range 20 can be accurately determined. It is possible to determine. For this reason, in the production line of a hardened steel material, the detection of the quenching range 20 and the total inspection of the quenching range 20 can be performed in-line, and the quality assurance of the hardened steel material can be performed well. It is possible to prevent a steel material having a poor quenching range 20 from being sent to the assembly process or the like, to prevent generation of defective products, and to prevent useless waste materials from being produced.

１０・・・渦電流センサ
１１・・・励磁コイル
１２・・・検出コイル
２０・・・焼入範囲
３０・・・未焼入範囲
Ｗ ・・・ワーク
ＷＮ・・・検証用ワーク 10 ... eddy current sensor 11 ... exciting coil 12 ... detection coil 20 ... hardening range 30 ... green input range W ... workpiece W N ... verification work

Claims (4)

ワークの表面に渦電流を発生させる励磁コイルと、前記渦電流に関する検出信号を検出するための検出コイルとを備えた渦電流センサを用い、焼入範囲の検出対象とする対象ワークの焼入範囲とこれに隣接する未焼入範囲とを前記渦電流センサにより連続的に走査し、前記焼入範囲と前記未焼入範囲との境界領域における前記検出信号の信号変化率に基づいて、当該対象ワークの表面における焼入範囲と未焼入範囲との境界位置を判定して、ワークの焼入範囲を検出する焼入範囲検出方法であって、
前記焼入範囲を前記渦電流センサで走査したときに、前記検出信号が定常的な値を示す領域を焼入定常領域とし、
前記未焼入範囲を前記渦電流センサで走査したときに、前記検出信号が定常的な値を示す領域を未焼入定常領域とし、
前記境界領域は、前記焼入定常領域と前記未焼入定常領域との間の領域とし、
前記検出信号の信号変化率は、前記焼入定常領域における前記検出信号の定常値と、前記未焼入定常領域における前記検出信号の定常値とを基準として求めたものであり、
前記境界領域において、前記検出信号の信号変化率が予め定めた判定値になる位置を前記対象ワークの焼入範囲と未焼入範囲との境界位置として判定すること、
を特徴とする焼入範囲検出方法。 Using an excitation coil for generating an eddy current in the surface of the word over click, the eddy current sensor and a detection coil for detecting a detection signal related to the eddy currents, bake target workpiece to be detected in the quenching range The eddy current sensor continuously scans the quenching range and the unquenched range adjacent thereto, and based on the signal change rate of the detection signal in the boundary region between the quenched range and the unquenched range, A quenching range detection method for detecting a quenching range of a workpiece by determining a boundary position between a quenching range and an unquenched range on the surface of the target workpiece ,
When the quenching range is scanned by the eddy current sensor, a region where the detection signal shows a steady value is a quenching steady region,
When the unquenched range is scanned with the eddy current sensor, the region where the detection signal shows a steady value is an unquenched steady region,
The boundary region is a region between the quenching steady region and the unquenched steady region,
The signal change rate of the detection signal is obtained based on the steady value of the detection signal in the quenching steady region and the steady value of the detection signal in the unquenched steady region,
In the boundary region, determining a position where the signal change rate of the detection signal becomes a predetermined determination value as a boundary position between the quenching range and the unquenched range of the target workpiece,
A quenching range detection method characterized by: 前記信号変化率を百分率で表した場合に、前記判定値は２０％〜９０％の範囲内で定めた所定の値である請求項１に記載の焼入範囲検出方法。 2. The quenching range detection method according to claim 1 , wherein when the signal change rate is expressed as a percentage, the determination value is a predetermined value determined within a range of 20% to 90%. 複数の検証用ワークを用いて、各検証用ワークの前記境界領域における前記検出信号の信号変化率と、各検証用ワークの焼入範囲と未焼入範囲との境界位置との相関性を予め検証しておき、前記判定値は当該相関性に基づき定めた値である請求項１又は請求項２に記載の焼入範囲検出方法。 Using a plurality of verification workpieces, the correlation between the signal change rate of the detection signal in the boundary region of each verification workpiece and the boundary position between the quenching range and the unquenched range of each verification workpiece is previously determined. 3. The quenching range detection method according to claim 1 , wherein the determination value is a value determined based on the correlation. 請求項１〜請求項３のいずれか一項に記載の焼入範囲検出方法を用いて、前記対象ワークの焼入範囲を検出し、この検出結果に基づいて、前記対象ワークに焼入れを施すべき範囲に、焼入れが施されているか否かを判定することを特徴とする焼入範囲検査方法。 The quenching range of the target workpiece should be detected using the quenching range detection method according to any one of claims 1 to 3 , and the target workpiece should be quenched based on the detection result. A quenching range inspection method characterized by determining whether or not the range has been quenched.
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