JP6659444B2 - Magnetic property measuring probe, magnetic property measuring system, magnetic property measuring method and deterioration evaluation method - Google Patents

Description

  An embodiment of the present invention relates to a technique for measuring magnetic properties of a measurement target.

  A metal material used in a severe environment such as high temperature, high pressure or high radiation deteriorates with a structural change or segregation in which impurities are unevenly distributed. For example, when evaluating the deterioration of various devices used in a power plant or the like, a method of evaluating the deterioration of a metal material without destroying members or the like constituting the device, that is, a so-called non-destructive evaluation is desired.

  In such non-destructive evaluation, there is a method of examining a change in magnetic properties of a metal material constituting a device to be measured. For example, a ferromagnetic material exhibiting magnetic hysteresis may be used as a metal material of a device for a power plant. The magnetic properties of a ferromagnetic material change in accordance with segregation in which impurities are unevenly distributed and a change in structure.

  Magnetic properties include various parameters represented by magnetization curves, such as coercive force, residual magnetic flux density, initial magnetic permeability, and the like. The value indicating such magnetic properties has a correlation with the mechanical properties of the metal material, and it has been proposed to evaluate the deterioration of the metal material using such parameters. For example, it is known that there is a correlation between Vickers hardness and coercive force.

  Techniques for measuring such magnetic properties include a coil through which an exciting current flows, a so-called yoke around which an exciting coil is wound, to form a magnetic path in a predetermined region including an outer surface (hereinafter referred to as a surface layer) of an object to be measured. There is a technique of forming and measuring a magnetic flux or the like near the surface layer. In this technique, both ends of the yoke are brought into close contact with the outer surface of the object to be measured to form a magnetic path on the surface layer.

Japanese Unexamined Patent Publication No. Hei.

Fumiya Ito et al., "Hardness and magnetic properties change during cold rolling and recovery of low carbon steel," Proc. Of the 38th Annual Meeting of the Magnetic Society of Japan, 2014, p.38

  As described above, in order to measure the magnetic characteristics, it is necessary to estimate the strength of a magnetic field for magnetizing the surface layer to be measured, that is, the so-called magnetizing force. Such a magnetizing force is generally estimated based on the coil diameter, length, number of windings, exciting current, and magnetic permeability of the yoke of the exciting coil. In a system for measuring magnetic properties (hereinafter, referred to as a magnetic property measurement system), generally, based on the magnetizing force in the surface layer, the strength of the magnetization (or magnetic flux density) in the surface layer and the strength of the magnetic field are measured. Curve (magnetizing force), a so-called magnetization curve. Parameters indicating magnetic properties, such as coercive force, residual magnetic flux density, and initial magnetic permeability, are usually obtained in the process of obtaining a magnetization curve.

  By the way, the outer surface of the measurement target may not be a completely flat surface but a three-dimensionally curved shape. In such a case, both end surfaces of the yoke may not be able to adhere to the outer surface of the measurement target, and a gap may be formed between the end surface of the yoke and the outer surface of the measurement target even when the yoke is pressed against the measurement target.

  A magnetic pole is generated near such a gap, and a magnetic field having a direction opposite to a magnetic field applied to magnetize the surface layer to be measured, that is, a so-called “anti-magnetic field” is generated. The demagnetizing field also occurs inside the yoke and the surface layer to be measured.

  The generation of such a demagnetizing field causes a difference between the magnetizing force for actually magnetizing the surface layer to be measured and the magnetizing force calculated based on the exciting current or the like to increase. There is a demand for a magnetic property measurement system that measures the magnetic properties by estimating the magnetizing force on the surface layer to be measured with high accuracy even when a demagnetizing field is generated.

  The embodiment of the present invention has been made in view of the above circumstances, and provides a technique for calculating the magnetizing force for magnetizing the surface layer of a measurement target with higher accuracy and measuring the magnetic characteristics of the measurement target. The purpose is to do.

In order to achieve the above-described object, a magnetic property measuring probe according to an embodiment of the present invention includes a yoke that forms a magnetic path together with the measurement target when both end surfaces are close to the outer surface of the measurement target, and a winding around the yoke. An exciting coil that excites the yoke so as to form the magnetic path by receiving the supply of an exciting current, and is wound so as to surround at least one radially outer side of the both end faces, A magnetizing force detection coil capable of detecting a time change of a magnetic flux passing through the both end surfaces, and disposed between the both end surfaces, and configured to be in contact with the outer surface of the measurement target, including the outer surface and detectable magnetic sensor flux density or magnetization in a direction from one to the other of the both end surfaces in the surface layer, a magnetic characteristic measuring probe wherein the magnetizing force detecting coil, said end surfaces It is wound so as to surround the radial outer side of the formed gap between at least one said measured outer surface, characterized in that it is and disposed an outer surface and engageable in said measurement object .

  In addition, the magnetic characteristic measurement system according to the embodiment of the present invention includes a yoke that forms a magnetic path together with the measurement target when both end surfaces are close to the outer surface of the measurement target, and is wound around the yoke, and has an exciting current. And an exciting coil that excites the yoke so that the magnetic path is formed, and is wound so as to surround at least one radially outer side of the both end faces, and is formed of a magnetic flux passing through the both end faces. One of the two end faces on the surface layer including the outer face, the magnetizing force detection coil capable of detecting a time change and being disposed between the both end faces, and configured to be in contact with the outer face of the measurement target. A magnetic sensor capable of detecting a magnetic flux density or magnetization in a direction from the other to the other, an exciter for supplying an exciting current of a predetermined frequency to the exciting coil, and a magnetic sensor on the surface layer based on the frequency of the exciting current. To calculate the demagnetizing field coefficient in the direction parallel to the magnetic path, calculate the end magnetizing force that is the strength of the magnetic field on at least one of the end faces of the yoke, and the magnetic flux density from the magnetic sensor or A processing device for calculating an effective magnetizing force, which is the strength of a magnetic field for magnetizing the surface layer, based on the magnetization, the demagnetizing coefficient, and the end magnetizing force.

  Further, the magnetic characteristic measuring method of the embodiment of the present invention is characterized in that the yoke forming a magnetic path together with the object to be measured and the exciting current being wound around the yoke when both end surfaces are close to the outer surface of the object to be measured. And an exciting coil that excites the yoke so that the magnetic path is formed, and is wound so as to surround at least one radially outer side of the both end faces, and is formed of a magnetic flux passing through the both end faces. One of the two end faces on the surface layer including the outer face, the magnetizing force detection coil capable of detecting a time change and being disposed between the both end faces, and configured to be in contact with the outer face of the measurement target. And a magnetic sensor capable of detecting a magnetic flux density or magnetization in a direction from the other side to the other side, and a magnetic property measuring probe for measuring a magnetic property of the surface layer by pressing a magnetic property measuring probe against the outer surface of the measurement object. A method, wherein a processing device that obtains and processes a signal from the magnetic property measurement probe, calculates a demagnetizing field coefficient in a direction parallel to the magnetic path in the surface layer based on a frequency of the exciting current, An end magnetizing force, which is a magnetic field strength at at least one of the two end faces of the yoke, is calculated, and the surface layer is determined based on a magnetic flux density or magnetization from the magnetic sensor, the demagnetizing factor, and the end magnetizing force. The method is characterized in that an effective magnetizing force which is the strength of a magnetic field for magnetizing is calculated.

  Further, in the deterioration evaluation method of the embodiment of the present invention, the yoke which forms a magnetic path together with the measurement object when both end surfaces are close to the outer surface of the measurement object, and which is wound around the yoke, the excitation current An excitation coil that excites the yoke so that the magnetic path is formed by receiving the supply; and an exciting coil that is wound so as to surround at least one radially outer side of the both end faces, and that a time of a magnetic flux passing through the both end faces is provided. A magnetizing force detection coil capable of detecting a change, disposed between the both end surfaces, and configured to be in contact with the outer surface of the measurement object, from one of the two end surfaces in the surface layer including the outer surface A magnetic sensor capable of detecting the magnetic flux density or magnetization in the direction toward the other, and measuring the magnetic properties of the surface layer by pressing a magnetic property measuring probe against the outer surface of the measurement target, and It is a deterioration evaluation method for evaluating the deterioration of the measurement object based on, by a processing device that acquires and processes a signal from the magnetic property measurement probe, the magnetic path in the surface layer based on the frequency of the excitation current Calculate the demagnetizing field coefficient in the parallel direction, calculate the end magnetizing force that is the strength of the magnetic field on at least one of the two end faces of the yoke, and calculate the magnetic flux density or magnetization from the magnetic sensor and the demagnetizing field coefficient. And calculating an effective magnetizing force that is the strength of a magnetic field that tends to magnetize the surface layer based on the end magnetizing force, and a magnetic flux density in a direction parallel to a magnetic path in the surface layer corresponding to the effective magnetizing force. Acquiring a magnetic history that is a history of magnetization, calculating a parameter indicating a magnetic characteristic of the measurement target based on the magnetic history, and evaluating deterioration of the measurement target based on the magnetic characteristics. That.

  According to the embodiment of the present invention, it is possible to measure the magnetic properties of the measurement target by calculating the magnetizing force for magnetizing the surface layer of the measurement target with high accuracy, and to evaluate the deterioration of the measurement target. Become.

1 is a schematic diagram illustrating a schematic configuration of a magnetic characteristic measurement system according to an embodiment. It is sectional drawing of the probe for magnetic property measurement of embodiment. FIG. 4 is a perspective view illustrating a positional relationship between first and second yokes and a magnetic sensor in the magnetic characteristic measuring probe according to the embodiment. It is a block diagram explaining each function of the magnetic property measuring system of an embodiment. FIG. 3 is a diagram illustrating an example of a magnetization curve acquired by the magnetic characteristic measurement system according to the embodiment, and is a diagram illustrating parameters indicating magnetic characteristics.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The present invention is not limited by the embodiments described below, and various changes can be made without departing from the gist of the present invention.

[First Embodiment]
An object to be measured by the magnetic property measurement system of the present embodiment will be described with reference to FIG. FIG. 1 is a schematic diagram illustrating a schematic configuration of a magnetic characteristic measurement system according to the present embodiment.

  As shown in FIG. 1, the measurement target 5 of the magnetic property measurement system 1 is a device such as a power plant, and FIG. 1 shows a reactor pressure vessel as an example of the measurement target 5. At least the vicinity of the outer surface 6 of the measurement target 5 is made of a metal material, and more specifically, is made of a magnetic material showing magnetic history (magnetic hysteresis), that is, a so-called ferromagnetic material. Such metal materials include, for example, ferritic steel materials such as carbon steel and low alloy steel.

  Next, the configuration of the magnetic characteristic measuring probe 10 of the present embodiment will be described with reference to FIGS. FIG. 2 is a cross-sectional view of the probe for measuring magnetic properties according to the present embodiment. FIG. 3 is a perspective view illustrating the positional relationship between the first and second yokes and the magnetic sensor in the magnetic characteristic measuring probe of the present embodiment. In FIG. 3, the illustration of the first excitation coil and the second excitation coil is omitted.

  As shown in FIG. 2, the magnetic characteristic measuring probe 10 of the present embodiment extends in a substantially U-shape, and has a magnetic path together with the measuring object 5 when both end surfaces are close to the outer surface 6 of the measuring object 5. It has yokes 12 and 22 to be formed. Specifically, the magnetic property measuring probe 10 includes a yoke (hereinafter, referred to as a first yoke) 12 for forming a first magnetic path (indicated by a dashed line C1 in the figure) together with the measurement object 5, and a measurement object 5 and a yoke (hereinafter, referred to as a second yoke) 22 for forming a second magnetic path.

  The magnetic characteristic measuring probe 10 includes an exciting coil (hereinafter, referred to as a first exciting coil) 15 wound around a first yoke 12 and an exciting coil (hereinafter, referred to as a second exciting coil) wound around a second yoke 22. 25 (referred to as an exciting coil). The first exciting coil 15 is wound around the central portion 12c of the first yoke 12, and receives an exciting current (AC current) having a predetermined frequency from an exciter 31 (see FIG. 1). Similarly, the second excitation coil 25 is wound around the central portion 22c of the second yoke 22, and receives an excitation current.

  The first excitation coil 15 excites a certain area (hereinafter, referred to as a surface layer) 5a including the outer surface 6 of the first yoke 12 and the measurement object 5, and the surface layer 5a and the first yoke 12 A first magnetic path indicated by a chain line C1 is formed. In other words, the surface layer 5a is a region of the measurement target 5 where a magnetic path is formed and magnetized. Similarly, the second excitation coil 25 excites the second yoke 22 and the measurement target 5 to form a second magnetic path (indicated by a point C2 in FIG. 2).

  The central portion 22c of the second yoke 22 intersects the central portion 12c of the first yoke 12 at a predetermined interval in a direction perpendicular to the outer surface 6 (indicated by an arrow Z in FIG. 2). In the present embodiment, the second excitation coil 25 intersects the first excitation coil 15 at a predetermined interval. The second yoke 22 is configured such that its central portion 22c and the second excitation coil 25 are located closer to the measurement target 5 than the central portion 12c of the first yoke 12 and the first excitation coil 15.

  Both end surfaces 13 and 14 of the first yoke 12 and both end surfaces 23 and 24 of the second yoke 22 are arranged on substantially the same (virtual) plane, as shown in FIG. The plane is a plane parallel to each of the dashed-dotted arrow X and the arrow Y in FIG. In FIG. 3, an arrow X indicates a direction from one end surface 13 of the first yoke 12 to the other end surface 14, and is hereinafter referred to as a “first direction”. The arrow Y indicates a direction from one end surface 23 of the second yoke 22 to the other end surface 24, and is hereinafter referred to as a “second direction”. The second direction is orthogonal to the first direction. Further, a direction perpendicular to each of the first direction and the second direction is referred to as a “third direction” and is indicated by an arrow Z in each drawing.

  As shown in FIG. 2, when the both end surfaces 13 and 14 of the first yoke 12 are close to the outer surface 6, a substantially cylindrical gap 7 is formed between one end surface 13 and the outer surface 6, and the other is formed. A substantially cylindrical gap 8 is formed between the end face 14 and the outer face 6. Similarly, when both end surfaces 23, 24 of the second yoke 22 are close to the outer surface 6, a gap (see FIG. 3) is also provided between the end surface 23 and the outer surface 6 and between the end surface 24 and the outer surface 6 shown in FIG. (Not shown).

  As shown by a dashed-dotted line C1 in FIG. 2, the first magnetic path includes a surface layer 5a of the measurement object 5, gaps 7 and 8 between the surface layer 5a and the first yoke 12, and the first yoke 12. Pass. As shown by a point C2 in FIG. 2, the second magnetic path includes a second yoke 22, a surface layer 5a of the measurement target 5, and a gap (not shown) between the surface layer 5a and the second yoke 22. Pass through. In the surface layer 5a, the first magnetic path and the second magnetic path are orthogonal to each other.

  The generation of magnetic poles on the end surface of the yoke or the surface layer sandwiching such an air gap causes the inside of the yoke and the surface layer 5a of the object 5 to be measured to be opposite to the magnetic field applied to magnetize the surface layer 5a. A magnetic field is formed. In consideration of the generation of such a demagnetizing field, it is necessary to calculate a magnetizing force for magnetizing the surface layer 5a (hereinafter, referred to as an effective magnetizing force).

  Further, in the present embodiment, in order to evaluate the anisotropy of the magnetic properties of the measurement object, the strength of the magnetic field in the first direction (indicated by the arrow X in FIG. 3) along the first magnetic path on the surface layer 5a is determined. It is required to calculate a certain first effective magnetizing force and a second effective magnetizing force which is the strength of a magnetic field in the second direction (indicated by an arrow Y in FIG. 3) along the second magnetic path on the surface layer 5a. .

  Therefore, as shown in FIG. 2, the magnetic property measuring probe 10 according to the present embodiment employs a coil (hereinafter, referred to as a magnetizing force detecting coil) for detecting the strength of a magnetic field for magnetizing the measurement object 5, that is, the magnetizing force. 17, 18, 27, 28). Specifically, magnetizing force detecting coils 17 and 18 for detecting a magnetizing force when a first magnetic path (indicated by a dashed-dotted line C1) is formed in the first yoke 12 and the surface layer 5a; Magnetizing force detecting coils 27 and 28 for detecting a magnetizing force when a magnetic path (indicated by a point C2) is formed.

  The magnetizing force detecting coils 17 and 18 are provided corresponding to both end surfaces 13 and 14 of the first yoke 12, respectively. The magnetizing force detecting coil 17 is wound so as to surround the corresponding end face 13 radially outside. In the present embodiment, the magnetizing force detecting coil 17 surrounds not only the end face 13 but also the gap 7 on the measurement object 5 side from the end face 13. On the other hand, the magnetizing force detecting coil 18 is wound so as to surround a radially outer side of the end face 14, and more specifically, in addition to the end face 14, the gap 8 on the measurement object 5 side from the end face 14. Is enclosed. When the first magnetic path shown by the dashed line C1 in FIG. 2 is formed, the magnetizing force detecting coils 17 and 18 respond to the time change (dφ / dt) of the magnetic flux passing through the corresponding end faces 13 and 14, respectively. A voltage is generated. These voltages are used for calculating the first effective magnetizing force.

  Similarly, the magnetizing force detecting coils 27 and 28 are provided corresponding to both end surfaces 23 and 24 of the second yoke 22, as shown in FIGS. The magnetizing force detecting coil 27 is wound so as to surround the radially outside of a gap (not shown) on the measurement object 5 side from the end face 23 in addition to the end face 23 (see FIG. 3). The magnetizing force detecting coil 28 is wound so as to surround a radially outside of a gap (not shown) on the measurement object 5 side from the end face 24 in addition to the end face 24 (see FIG. 3). When the second magnetic path indicated by a point C2 in FIG. 2 is formed, the magnetizing force detecting coils 27 and 28 apply a voltage corresponding to the time change (dφ / dt) of the magnetic flux passing through the corresponding end faces 23 and 24, respectively. Occurs. These voltages are used for calculating the second effective magnetizing force.

  The magnetic property measuring probe 10 of the present embodiment has a magnetic sensor 20 for detecting the intensity of magnetization in the surface layer 5a of the measurement target 5 shown in FIG. In the present embodiment, the magnetic sensor 20 converts a voltage corresponding to a magnetic flux density in a first direction (indicated by an arrow X in FIGS. 2 and 3) and a magnetic flux density in a second direction (indicated by an arrow Y in FIG. 3). It is configured to generate a corresponding voltage and a voltage corresponding to the magnetic flux density in a third direction (indicated by an arrow Z in FIGS. 2 and 3) perpendicular to the first direction. That is, the magnetic sensor 20 is configured as a so-called three-axis (three-dimensional) magnetic flux sensor.

  Such a magnetic sensor (magnetic flux sensor) 20 can be realized by, for example, a sensor using a Hall element. In addition, as the magnetic sensor 20, an MI sensor using a magnetic impedance element may be used.

  In the present embodiment, the magnetic sensor 20 responds to the magnetic flux densities in the first direction and the second direction, as well as in third directions perpendicular to these directions (indicated by arrows Z in FIGS. 2 and 3). It is configured as a so-called three-dimensional (three-axis) magnetic sensor capable of detecting a voltage.

  The magnetic sensor 20 is disposed between both end surfaces 13 and 14 of the first yoke 12 as shown in FIG. 2 and between both end surfaces 23 and 24 of the second yoke 22 as shown in FIG. I have. More specifically, the magnetic sensor 20 is disposed between the end faces 13 and 14 of the first yoke 12 and between the end faces 23 and 24 of the second yoke 22.

  The magnetic sensor 20 is configured to contact the outer surface 6 of the measurement target 5. The magnetic characteristic measuring probe 10 of the present embodiment moves the magnetic sensor 20 in the third direction Z on the measurement object 5 side (the arrow Z shown in the drawing) so that the magnetic sensor 20 contacts the outer surface 6 of the measurement object 5. (Opposite side). The spring 19 has one end connected to the magnetic sensor 20 and the other end connected to the body 11 of the probe 10 for measuring magnetic properties. As the spring 19, for example, a compression coil spring is used.

  The voltage according to the magnetic flux density of the surface layer 5a detected by the magnetic sensor 20 is detected by a detector 35 described later. In the present embodiment, the voltage output from the magnetic sensor 20 according to the magnetic flux density in each of the first direction, the second direction, and the third direction is detected by the detector 35.

  The components constituting the magnetic characteristic measuring probe 10 described above, ie, the yokes 12, 22, the exciting coils 15, 25, and the magnetizing force detecting coils 17, 18, 27, 28 are composed of a body 11 (see FIG. 2). And are integrally connected through. The magnetic sensor 20 is connected to the body 11 via a spring 19.

  In addition, the body 11 can use various materials, for example, can be comprised with a synthetic resin. It is also preferable that the magnetic property measuring probe 10 has a so-called resin molded structure in which each component is molded by a synthetic resin body 11.

  When the magnetic property measuring probe 10 thus configured is pressed against the outer surface 6 of the measuring object 5 as shown in FIG. 1, as shown in FIG. The coils for use 17, 18, 27, and 28 and the magnetic sensor 20 are configured to contact the outer surface 6 of the measurement target 5. The magnetic characteristic measuring probe 10 is configured such that a gap is formed between the end surfaces of the yokes 12 and 22 and the outer surface 6 and radially inward of the magnetizing force detecting coils 17, 18, 27 and 28. Have been.

  As described above, the magnetic property measurement probe 10 of the present embodiment includes the yoke 12 that forms the magnetic path C1 together with the measurement target 5 by bringing the both end faces 13 and 14 close to the outer surface 6 of the measurement target 5; An exciting coil 15 wound around the yoke 12 and supplied with an exciting current to excite the yoke 12 so as to form the magnetic path C1, and wound around the radially outer sides of both end faces 13 and 14. And magnetizing force detecting coils 17 and 18 which can detect a temporal change of a magnetic flux passing through the both end faces 13 and 14. In addition, it is arranged between both end surfaces 13 and 14 and is configured so as to be in contact with the outer surface 6 of the measurement object 5. The probe 10 for measuring magnetic characteristics is provided on both end surfaces 13 a of the surface layer 5 a including the outer surface 6. , 14 from one side to the other.

  The strength of the magnetic field (that is, the end magnetizing force) based on the voltage from the magnetizing force detecting coils 17 and 18 wound radially outward of both end surfaces 13 and 14 of the yoke 12 and the end surfaces 13 and 14, respectively. A demagnetizing field is generated inside the both end faces 13 and 14 of the yoke 12 and in the surface layer 5a based on the magnetic flux density B or the magnetization M in the surface layer 5a from the magnetic sensor 20 disposed between the two. Also, it is possible to calculate the effective magnetizing force for magnetizing the surface layer 5a with relatively high accuracy. The method for calculating the effective magnetizing force according to the present embodiment will be described in detail below.

  Each function of the magnetic characteristic measurement system of the present embodiment will be described with reference to FIGS. FIG. 4 is a block diagram illustrating each function of the magnetic property measurement system of the present embodiment. In FIG. 4, the flow of the electric signal or data is indicated by a broken arrow.

  In the following description, a case where the first yoke 12 and the first exciting coil 15 form a first magnetic path on the surface layer 5a of the measurement target 5 will be described for easy understanding. A description of the case where the second magnetic path is formed by the second yoke 22 and the second excitation coil 25 will be omitted as appropriate.

  As shown in FIGS. 1 and 4, the magnetic characteristic measuring system 1 acquires and processes an electric signal from the magnetic characteristic measuring probe 10 in addition to the magnetic characteristic measuring probe 10 described above (hereinafter, referred to as an apparatus). (Hereinafter simply referred to as “processing device”) 50. In the present embodiment, the processing device 50 obtains a signal (a voltage corresponding to a temporal change in magnetic flux) from the magnetizing force detecting coils 17, 18, 27, and 28 via the detector 33, and outputs the signal from the magnetic sensor 20. A signal (magnetic flux signal) is obtained via the detector 35. Further, the processing device 50 acquires a reference signal including the frequency of the exciting current from the exciter 31.

  In addition, the magnetic characteristic measurement system 1 includes a storage device 70 that can store various constants and variables, and an output device 80 that outputs a calculation result of the processing device 50. The storage device 70 and the output device 80 are electrically connected to the processing device 50 via the communication line 40, and are configured to be able to exchange various data.

  In this embodiment, the storage device 70 may be a so-called main storage device such as a memory, or an auxiliary storage device such as a hard disk. In addition, as the output device 80, a display device that displays data in a visible form, that is, a so-called display is used. The output device 80 may use a plotter (plotting device) or a printer (printing device).

  Further, the magnetic characteristic measuring system 1 has an exciter 31 capable of supplying an exciting current to the exciting coils 15 and 25 (see FIG. 4) of the magnetic characteristic measuring probe 10 described above. Further, the magnetic characteristic measuring system 1 includes a detector 33 for detecting voltages generated in the magnetizing force detecting coils 17, 18, 27, and 28, respectively, and a signal (a voltage in the present embodiment) relating to a magnetic flux from the magnetic sensor 20. Is detected. A signal relating to the magnetizing force (that is, the strength of the magnetic field) from the magnetizing force detecting coils 17, 18, 27, 28 is sent to the processing device 50 via the detector 33. On the other hand, a signal (hereinafter, referred to as a magnetic flux signal) from the magnetic sensor 20 regarding the magnetic flux (that is, the intensity of magnetization) is sent to the processing device 50 via the detector 35.

  The exciter 31 includes a power supply (not shown), and is configured to be able to supply an exciting current having a desired frequency and a desired amplitude to each of the first exciting coil 15 and the second exciting coil 25. The exciter 31 supplies an exciting current, and a signal indicating the frequency of the exciting current (hereinafter, referred to as a reference signal) is acquired by the detector 33 and the processing device 50.

  When the exciter 31 supplies an exciting current to the first exciting coil 15 in a state where the above-described probe 10 for measuring magnetic properties is pressed against the outer surface 6 of the measuring object 5 (see FIGS. 1 and 2), FIG. As described above, the first magnetic path (indicated by a dashed line C1 in the figure) passing through the first yoke 12, the gap 7, the surface layer 5a of the measurement target 5, and the gap 8 is formed. Similarly, when the exciter 31 supplies an exciting current to the second exciting coil 25, a second magnetic path passing through the second yoke 22, the surface layer 5a, and a gap (not shown) is formed.

  The detector 33 is a device that detects a voltage (AC signal) generated in each of the magnetizing force detecting coils 17, 18, 27, and 28. The detector 33 preferably has a function of removing a noise component unrelated to the magnetizing force from each voltage of the magnetizing force detecting coils 17, 18, 27, and 28. A detector capable of synchronous detection (phase detection) can be used as the detector 33, and a so-called lock-in amplifier is used in the present embodiment.

  In the present embodiment, the detector 33 extracts a component having the same frequency as the reference signal from each voltage of the magnetizing force detecting coils 17, 18, 27, and 28 to remove noise. The detector 33 has a band-pass filter for removing noise, specifically, a low-pass filter.

  The detector 33 of the present embodiment multiplies each voltage of the magnetizing force detecting coils 17, 18, 27, and 28, that is, an AC signal, by a reference signal indicating the frequency of the exciting current, thereby obtaining the same frequency as the reference signal. Is converted into a DC signal and passed through a low-pass filter. Other components having a different frequency from the reference signal, that is, noise, are converted into an AC signal, and thus are removed by the low-pass filter.

  In this way, the detector 33 detects the voltage (AC) of each of the magnetizing force detecting coils 17, 18, 27, and 28, removes noise unrelated to the magnetizing force, and removes the corresponding magnetic flux. It is converted into a voltage (direct current) according to the time change (dφ / dt). These voltages are acquired by the processing device 50.

  On the other hand, the detector 35 detects a voltage according to the magnetic flux density of the surface layer 5a from the magnetic sensor 20. The detector 35 has a function of converting the voltage from the magnetic sensor 20 into a signal indicating the magnetic flux density B on the surface layer 5a. The relationship between the voltage of the magnetic sensor 20 and the magnetic flux density B is stored in a storage unit (not shown) of the detector 35 in advance. The detector 35 of the present embodiment further has a function of converting the magnetic flux density B into a magnetization intensity M (hereinafter, simply referred to as “magnetization”) which is a magnetic moment per unit volume. When the magnetic sensor 20 is a Hall sensor, for example, a data logger can be used as the detector 35.

  The detector 35 of the present embodiment converts a voltage corresponding to the magnetic flux density B1 in the first direction (indicated by an arrow X in FIGS. 2 and 3) on the surface layer 5a into a signal indicating the magnetization M1 in the first direction. A voltage corresponding to the magnetic flux density B2 in the second direction (indicated by an arrow Y in FIG. 3) is converted into a signal indicating the magnetization M2 in the second direction. The signals indicating the magnetizations M1 and M2 are acquired by the processing device 50.

  Next, details of the function of the processing device 50 of the magnetic characteristic measurement system of the present embodiment and a magnetic characteristic measurement method using the system will be described with reference to FIGS. FIG. 5 is a diagram illustrating an example of a magnetization curve obtained by the magnetic characteristic measurement system according to the present embodiment, and is a diagram illustrating parameters indicating magnetic characteristics.

  The processing device 50 calculates a demagnetizing coefficient in a predetermined direction on the surface layer 5a based on a reference signal from the exciter 31, that is, the frequency of the exciting current (hereinafter, referred to as a demagnetizing factor calculating unit) 51, Function of calculating the “end magnetizing force”, which is the strength of the magnetic field on the end face, based on the time change (dφ / dt) of the magnetic flux passing through the end face of the yoke from the heater 33 (hereinafter referred to as an end magnetizing force calculation unit and 53).

  In addition, the processing device 50 calculates an effective magnetizing force for magnetizing the surface layer 5a based on the demagnetizing coefficient, the end magnetizing force (average value), and the magnetization M (or the magnetic flux density B) (hereinafter, referred to as a function). A function of acquiring a history of magnetization M or a magnetic flux density B in a predetermined direction on the surface layer 5a corresponding to the effective magnetizing force (hereinafter referred to as a magnetic history acquisition unit) 57; have.

  The end magnetizing force calculation unit 53 acquires from the detector 33 a voltage (DC) corresponding to a time change (dφ / dt) of the magnetic flux from the magnetizing force detecting coil 17 passing through the end face 13. The end magnetizing force calculation unit 53 calculates the magnetic flux φ passing through the end face 13 by integrating the value of the voltage with time. Further, the magnetic flux density B is calculated based on the magnetic flux φ and the area S of the end face 13. Based on the magnetic flux density B and the magnetic permeability μ of the first yoke 12, the strength of the magnetic field on the end face 13, that is, the so-called end magnetizing force [A / m] is calculated.

  The end magnetizing force calculated in this way includes the magnetoresistance component of the air gap 7 on the measurement object 5 side from the end face 13. Similarly, the end magnetizing force on the end surface 14 of the first yoke 12 is calculated. This end magnetizing force also includes the magnetoresistance component of the air gap 8 located on the measurement object 5 side from the end face 14.

  In the present embodiment, the end magnetizing force calculator 53 calculates an average value of the end magnetizing force of the end face 13 and the end magnetizing force of the end face 14 (hereinafter, referred to as a first end magnetizing force). Similarly, the end magnetizing force calculator 53 calculates the second yoke based on the time change (dφ / dt) of the magnetic flux passing from the magnetizing force detecting coils 27 and 28 through the end faces 23 and 24 (see FIG. 3). 22 and a second end magnetizing force corresponding to the second magnetic path are calculated. The calculated first and second end magnetizing forces are sent to the effective magnetizing force calculator 55.

  On the other hand, the demagnetizing coefficient calculating unit 51 acquires a reference signal including information on the frequency of the exciting current from the exciter 31. The demagnetizing factor calculating unit 51 calculates a “diamagnetic field coefficient” in a direction parallel to a magnetic path formed on the surface layer 5a based on the frequency of the exciting current and various preset constants. The details will be described below.

  The demagnetizing factor is a coefficient for a uniformly magnetized object, and is a coefficient that, when multiplied by the magnetization M, gives “strength of self-demagnetizing field”. When a magnetic path is formed in the surface layer 5a of the measurement object 5 and the surface layer 5a is magnetized, a so-called self-demagnetization effect occurs in which a demagnetizing field acts in a direction opposite to the direction of the magnetization M. The strength of the self-demagnetizing field is proportional to a value obtained by multiplying the magnetization M in the surface layer 5a by the demagnetizing coefficient N.

  The demagnetizing factor calculating unit 51 determines the depth of the portion where the magnetic path is effectively formed based on the frequency of the exciting current and the conductivity [S / m] and the relative permeability [H / m] of the measurement target 5. Now, the so-called “skin depth” is calculated. Note that the conductivity and the relative magnetic permeability of the measurement target 5 are stored in the storage device 70 (see FIG. 1) in advance.

  Skin depth is the depth to which a magnetic field in a medium penetrates and is also referred to as "penetration depth". In addition, as for the skin depth, when the magnetic permeability of the surface layer 5a may be considered to be constant, the strength of the magnetic field is a predetermined ratio (about 37%) with respect to the outer surface 6a. An example of the skin depth is shown in FIG.

  The demagnetizing factor calculation unit 51 calculates a demagnetizing factor based on the skin depth. In the present embodiment, first, based on the skin depth, the demagnetizing factor calculation unit 51 determines the shape of the portion (surface layer 5a) where the magnetic path is effectively formed in the measurement target 5 (hereinafter, referred to as a permeation shape). Is calculated. For example, when only the first magnetic path (see FIG. 2) is formed in the measurement target 5, the penetrating shape is an envelope that envelopes both the end faces 13 and 14 of the first yoke 12 (in FIG. 3, a two-dot chain line). 2), the outer surface 6a is extruded inside the measurement object 5 by the skin depth indicated by D in FIG. In this example, the outer surface 6a has an elliptical shape extending in a first direction indicated by an arrow X in the figure, and the penetrating shape extends in the first direction, and an end in the direction is rounded. It has a substantially rectangular parallelepiped shape.

  The demagnetizing factor calculation unit 51 can calculate the demagnetizing factor in a predetermined direction based on the penetration shape calculated based on the skin depth. The demagnetizing field coefficient in a predetermined direction corresponding to the permeation shape can be obtained, for example, by performing a simulation or the like.

  In the present embodiment, the demagnetizing factor calculation unit 51 determines one demagnetizing factor from a plurality of demagnetizing factors set in advance corresponding to the permeation shape. The plurality of permeation shapes and the demagnetizing field coefficients respectively corresponding to these permeation shapes are obtained in advance and stored in the storage device 70 (see FIG. 1) as a database in advance.

  The demagnetizing factor calculation unit 51 determines, from among the plurality of penetration shapes stored in the storage device 70 in advance, the one closest to the penetration shape calculated based on the skin depth, and corresponds to the determined penetration shape. The demagnetizing coefficient is obtained from the storage device 70. In this way, the demagnetizing factor calculation unit 51 calculates the skin depth based on the frequency (variable) of the exciting current, the conductivity and the relative magnetic permeability (constant) of the measurement object 5, and calculates the skin depth. , And determines the demagnetizing field coefficient corresponding to the permeation shape.

  In the present embodiment, the demagnetizing coefficient N1 when only the first magnetic path is formed on the surface layer 5a (hereinafter referred to as the first demagnetizing coefficient) N1 and the demagnetizing coefficient N1 when only the second magnetic path is formed A demagnetizing coefficient (hereinafter, referred to as a second demagnetizing coefficient) N2 is calculated. These demagnetizing factors N1 and N2 are sent out and used for calculating the corresponding effective magnetizing force.

  The effective magnetizing force calculation unit 55 adds the end magnetizing force (average value) calculated by the end magnetizing force calculating unit 53 and the demagnetizing coefficient calculated by the demagnetizing factor calculating unit 51, Is obtained. The effective magnetizing force calculator 55 calculates an effective magnetizing force [A / m] for magnetizing the surface layer 5a based on the edge magnetizing force, the magnetization M, and the demagnetizing field coefficient.

  The effective magnetizing force [A / m] calculated in this manner is corrected in consideration of the magnetic resistance generated by the air gap between the end face of the yoke and the measurement object 5 and the influence of the demagnetizing field on the surface layer 5a. Value.

  In the present embodiment, the effective magnetizing force calculator 55 calculates the first effective magnetizing force based on the first end portion magnetizing force corresponding to the first magnetic path and the first demagnetizing field coefficient. Further, a second effective magnetizing force is calculated based on the second end magnetizing force corresponding to the second magnetic path and the second demagnetizing field coefficient. The effective magnetization force and the above-described magnetization M (or magnetic flux density B) change according to the excitation current supplied from the exciter 31 to the excitation coils 15 and 25, respectively.

  The magnetic history acquisition unit 57 acquires a change in the exciting current, that is, a history of the magnetization M (or the magnetic flux density B) according to the change in the magnetic field strength (effective magnetizing force) in the surface layer 5a of the measurement target 5, that is, a so-called magnetic history. I do. The magnetic history (magnetization M or magnetic flux density B) is stored in the storage device 70 (see FIG. 1) in association with the effective magnetization force, and output to the output device 80.

  In the present embodiment, the magnetic history obtaining unit 57 obtains data in which the magnetic flux detected by the magnetic sensor 20 is converted into the magnetization M by the detector 35. More specifically, the first magnetic path is formed. The history of the magnetization M1 in the first direction at the time of the formation and the history of the magnetization M2 in the second direction when the second magnetic path is formed are acquired.

  The magnetic history acquisition unit 57 of the present embodiment acquires, as the magnetic history, a magnetization curve indicating the relationship between the magnetization M (or the magnetic flux density B) and the effective magnetization force H that is the strength of the magnetic field as shown in FIG. . First, after completely demagnetizing at least the surface layer 5a of the measurement target 5, the magnetic history acquiring unit 57 gradually reduces the effective magnetizing force H from zero (shown by point 0 in the figure) to a saturated state shown by point a in the figure. A magnetic history, that is, a so-called initial magnetization curve during the increase is acquired. At the point a, the surface layer 5a reaches saturation magnetization + Ms (that is, saturation magnetic flux density + Bs). The effective magnetizing force + Hmax is the strength of the magnetic field at which the surface layer 5a reaches the saturation magnetization + Ms (that is, the saturation magnetic flux density + Bs).

  The processing device 50 can calculate the initial permeability of the surface layer 5a by determining the slope (indicated by a two-dot chain line Pi in the figure) of the initial magnetization curve at zero (point 0). Further, the processing device 50 obtains a maximum gradient (indicated by a two-dot chain line Pmax in the figure) connecting zero (point 0) and a point on the initial magnetization curve, thereby obtaining the maximum permeability of the surface layer 5a. Can be calculated.

  In addition, the magnetic history acquisition unit 57 determines the magnetization remaining when the effective magnetizing force (magnetic field strength) H shown at point c in the figure from the saturated state shown by point a in FIG. (That is, the residual magnetic flux density Br) is obtained.

  Further, an effective magnetizing force is applied in a direction opposite to the point a (negative direction), and is applied to the surface layer 5a when the magnetization M (that is, the magnetic flux density B) becomes zero as shown by a point d in the figure. The magnetic history acquisition unit 57 acquires an effective magnetizing force, that is, a so-called coercive force Hc. It is known that the coercive force Hc has a correlation with the hardness of the surface layer 5a (for example, Vickers hardness Hv).

  The magnetic history acquisition unit 57 determines that the effective magnetizing force passes from + Hmax indicated by the point a in FIG. 5 to zero indicated by the point c, −Hmax indicated by the point e, zero indicated by the point f, and a positive value indicated by the point g. Then, a history of the magnetization M (or the magnetic flux density B) up to + Hmax indicated by the point a again, that is, a so-called hysteresis loop is acquired.

  That is, the magnetization curve acquired by the magnetic history acquisition unit 57 includes a hysteresis loop in addition to the above-described initial magnetization curve. One cycle of the hysteresis loop corresponds to one cycle of the frequency of the exciting current.

  It is also preferable that the magnetic history acquisition unit 57 acquires a plurality of hysteresis loops by changing the amplitude of the exciting current, that is, the effective magnetizing force applied to the surface layer 5a. In addition, by gradually reducing the amplitude of the exciting current to converge to zero, the surface layer 5a can be demagnetized using the above-described magnetic characteristic measuring probe 10.

  In the present embodiment, the magnetic history acquisition unit 57 performs the first magnetization indicating the relationship between the first effective magnetization force H1 applied to the surface layer 5a when the first magnetic path is formed and the magnetization M1 in the first direction. A curve and a second magnetization curve indicating a relationship between the second effective magnetization force H2 applied when the second magnetic path is formed and the magnetization M2 in the second direction are acquired. The data of the magnetic history including the first magnetization curve and the second magnetization curve is stored in the storage device 70 (see FIG. 1) and output to the output device 80. The magnetic history data is displayed on a display, for example.

  In the present embodiment, the processing device 50 calculates the magnetic characteristics of the measurement target 5 in the surface layer 5a based on the acquired magnetic history. The processing device 50 controls the coercive force Hc, the residual magnetization Mr (or the residual magnetic flux density Br), the saturation magnetization Ms (or the saturated magnetic flux density Bs), and the initial permeability for each of the first magnetization curve and the second magnetization curve as the magnetic history. It is possible to calculate typical parameters indicating the magnetic characteristics of the measurement object 5, such as the magnetic susceptibility (see the two-dot chain line Pi in FIG. 5), the maximum magnetic permeability (see the two-dot chain line Pmax in FIG. 5), and the area in the hysteresis loop. it can. It is also preferable that the output device 80 displays a parameter indicating these magnetic characteristics together with the first magnetization curve and the second magnetization curve.

  The processing device 50 may calculate a difference, a ratio, and the like between the first magnetization curve and the second magnetization curve, and output the difference and the ratio to the output device 80. By outputting such a difference or ratio, the difference in magnetic characteristics between the first direction (see arrow X in FIG. 3) and the second direction (see arrow Y in FIG. 3) on the surface layer 5a of the measurement target 5, that is, what is called Anisotropy can be evaluated.

  In the deterioration evaluation method of the present embodiment, the processing device 50 evaluates the deterioration of the measurement target 5 based on the calculated magnetic characteristics. Specifically, the magnetic characteristics of the measurement target 5 measured by the magnetic characteristic measuring system 1 are compared with the magnetic characteristics previously measured by the substantially same magnetic characteristic measuring system. The previously measured data of the magnetic properties is stored in the storage device 70 in advance, for example.

  In the deterioration evaluation method according to the present embodiment, the processing device 50 acquires the magnetic history of the surface layer 5a as described above, and calculates the coercive force Hc as the magnetic characteristic of the measurement target 5. The processing device 50 compares the value measured this time with the value measured before (past) for the coercive force Hc on the surface layer 5a of the same measurement target 5. For example, for the same surface layer 5a of the measurement target 5, the coercive force Hc measured this time is compared with the coercive force measured before to check the change in the coercive force Hc.

  The coercive force Hc generally has a correlation with Vickers hardness. By examining in advance the relationship between the coercive force Hc and the Vickers hardness of the material constituting the measurement object 5, it is possible to know the change in Vickers hardness, that is, the degree of aging of the metal material constituting the measurement object 5. Can be.

  The magnetic characteristics for evaluating the deterioration of the measurement target are not limited to the coercive force Hc. It is also possible to evaluate the deterioration of the measurement object 5 based on the residual magnetization Mr (or residual magnetic flux density Br), the saturation magnetization Ms (or saturated magnetic flux density Bs), the initial magnetic permeability, the maximum magnetic permeability, the area in the hysteresis loop, and the like. It is possible.

  According to the present embodiment, when the measurement target 5 such as a rolled material or a welded portion is configured so that segregation of impurities or a crystal structure occurs in a specific direction, the probe 10 of the magnetic property measurement Either the first direction in which both end surfaces 13 and 14 of one yoke 12 are arranged, or the second direction (see FIG. 3) in which both end surfaces 23 and 24 of second yoke 22 are arranged, By adjusting to, the magnetic properties of the surface layer 5a of the measurement object 5 can be calculated with higher accuracy, and the deterioration of the metal material forming the measurement object can be evaluated with higher accuracy.

[Other embodiments]
In the embodiment described above, the detector 33 that detects the voltage of the magnetizing force detecting coils 17, 18, 27, and 28 is a lock-in amplifier. It is not limited. The detector 33 may be a data logger having the functions described above.

  In the above-described embodiment, the voltage corresponding to the magnetic flux of the surface layer 5a from the magnetic sensor 20 is converted into a signal indicating the magnetization M by the detector 35 and sent to the processing device 50. The method by which the processing device 50 acquires the data from is not limited to this mode. For example, the voltage corresponding to the magnetic flux from the magnetic sensor 20 may be converted into a signal indicating the magnetic flux density B by the detector 35 and sent to the processing device 50.

  In this case, the magnetic history obtaining unit 57 and the effective magnetizing force calculating unit 55 of the processing device 50 obtain the magnetic flux densities B1 and B2 from the detector 35 instead of the magnetizations M1 and M2. The effective magnetizing force calculator 55 may calculate the effective magnetizing force based on the magnetic flux density, the end magnetizing force, and the demagnetizing field coefficient.

  In the above-described embodiment, the magnetic property measuring probe 10 includes two yokes 12 and 22, and excitation coils 15 and 25 and magnetizing force detecting coils 17, 18, 27 and 28 corresponding to the yokes 12 and 22. However, the magnetic property measuring probe according to the present invention is not limited to this embodiment. The probe for measuring magnetic properties has at least one yoke, and an excitation coil and a magnetizing force detection coil may be provided corresponding to the yoke. For example, the yoke, the exciting coil, and the magnetizing force detecting coil may be provided in one set or three or more sets.

  The magnetizing force detecting coils 17, 18, 27, and 28 of the above-described embodiment are wound around the respective ends 13, 14, 23, and 24 of the two yokes 12, 22 in the radial direction. However, the magnetizing force detecting coil according to the present invention is not limited to this mode. The magnetizing force detecting coil according to the present invention may be wound so as to surround at least one radially outer side of both end surfaces of each yoke. For example, the coils for detecting the magnetizing force may be provided only radially outside one end surface 13 of the first yoke 12 and one end surface 23 of the second yoke 22.

  Further, in the above-described embodiment, the magnetizing force detecting coils 17, 18, 27, and 28 have not only the corresponding end faces 13, 14, 23, and 24 but also the end faces 13, 14, 23, and 24 and the measurement object Is wound so as to surround the radially outer side of the gap between the outer surface 6 and the outer surface 6. However, the position where the magnetizing force detecting coil according to the present invention is arranged is limited to this embodiment. is not. The magnetizing force detection coil according to the present invention only needs to be wound radially outward of at least one end face of each yoke. For example, a gap may be hardly formed between the end surface of the yoke and the outer surface of the measurement object.

  Further, in the above-described embodiment, the measurement target 5 is made of a ferromagnetic material having a relative magnetic permeability of greater than 1, but the metal material forming the measurement target according to the present invention is not limited to this. Not something. What is necessary is that the surface layer including the outer surface is made of a metal material (other than a non-magnetic material) exhibiting magnetic hysteresis.

1 Magnetic property measurement system, 5 measurement target (reactor pressure vessel), 5a surface layer (measurement target)
6, 6a Outer surface (measurement target), 7, 8 air gap, 10 Magnetic property measurement probe, 11 Body, 12 First yoke (yoke), 12c Central part (First yoke), 13, 14 End surface (First yoke) , 15 First excitation coil (excitation coil), 17, 18 Magnetizing force detection coil (first magnetic path detection coil), 19 spring (compression coil spring), 20 magnetic sensor (three-dimensional (three-axis) magnetic sensor) , 22 second yoke (yoke), 22c central part (second yoke)
23, 24 end face (second yoke), 25 second excitation coil (excitation coil), 27, 28 magnetizing force detection coil (second magnetic path detection coil), 31 exciter (power supply), 33 detector 35 detection , 40 communication line, 50 processing unit, 51 demagnetizing factor calculation unit (processing unit)
53 end magnetizing force calculating unit (processing device), 55 effective magnetizing force calculating unit (processing device), 57 magnetic history acquiring unit (processing device), 70 storage device, 80 output device

Claims (8)

A yoke that forms a magnetic path together with the measurement target by having both end surfaces close to the outer surface of the measurement target,
An exciting coil wound around the yoke and exciting the yoke so as to form the magnetic path by receiving supply of an exciting current;
A magnetizing force detection coil wound so as to surround at least one radially outer side of the both end faces and capable of detecting a time change of a magnetic flux passing through the both end faces,
It is arranged between the both end surfaces, and is configured to be in contact with the outer surface of the measurement object, and can detect a magnetic flux density or a magnetization in a direction from one of the two end surfaces to the other in the surface layer including the outer surface. Magnetic sensor,
A magnetic property measurement probe comprising:
The magnetizing force detection coil is wound so as to surround a radial outside of a gap formed between at least one of the both end surfaces and the outer surface of the measurement target, and the outer surface of the measurement target. A probe for measuring magnetic properties, which is arranged so as to be able to abut . The yoke is
A first yoke forming a first magnetic path together with the measurement object;
A second yoke that forms a second magnetic path orthogonal to a first magnetic path on the surface layer of the measurement target together with the measurement target,
The excitation coil,
A first exciting coil wound around the first yoke and exciting the first yoke so as to form a first magnetic path;
A second exciting coil wound around the second yoke to excite the second yoke so that a second magnetic path is formed;
The magnetizing force detection coil is provided corresponding to at least one of both end surfaces of the first yoke and at least one of both end surfaces of the second yoke, respectively.
The magnetic sensor can detect a magnetic flux density in a first direction from one of both end faces of the first yoke toward the other and a magnetic flux density in a second direction from one of both end faces of the second yoke to the other. The probe for measuring magnetic properties according to claim 1, wherein the probe is configured as follows .   A yoke that forms a magnetic path together with the measurement target by having both end surfaces close to the outer surface of the measurement target,
  An exciting coil wound around the yoke and exciting the yoke so as to form the magnetic path by receiving supply of an exciting current;
  A magnetizing force detection coil wound so as to surround at least one radially outer side of the both end faces and capable of detecting a time change of a magnetic flux passing through the both end faces,
  It is arranged between the both end surfaces, and is configured to be in contact with the outer surface of the measurement object, and can detect a magnetic flux density or a magnetization in a direction from one of the two end surfaces to the other in the surface layer including the outer surface. Magnetic sensor,
  An exciter that supplies an exciting current having a predetermined frequency to the exciting coil;
  A demagnetizing field coefficient in a direction parallel to the magnetic path is calculated on the surface layer based on a frequency of the exciting current, and an end magnetizing force that is a magnetic field strength on at least one of the both end faces of the yoke is calculated. And a processing device that calculates an effective magnetizing force that is the strength of a magnetic field that attempts to magnetize the surface layer based on the magnetic flux density or magnetization from the magnetic sensor, the demagnetizing coefficient, and the end magnetizing force,
A magnetic characteristic measuring system comprising: The processing device calculates the skin depth of the surface layer on which the magnetic path is effectively formed among the measurement targets based on the frequency and the preset conductivity and relative magnetic permeability of the measurement target. Calculate the demagnetizing factor based on the skin depth
The magnetic characteristic measuring system according to claim 3, wherein: The processing device calculates, based on the skin depth, a permeation shape that is a shape of a surface layer in which a magnetic path is effectively formed among the measurement targets, and calculates the demagnetizing field coefficient based on the permeation shape. magnetic characteristic measuring system according to claim 4, characterized in <br/> that. A plurality of penetrating shapes and a demagnetizing coefficient corresponding to each of the penetrating shapes are further provided with a storage device that is stored in advance,
The processing device determines a penetration shape closest to the calculated penetration shape among a plurality of penetration shapes stored in advance in the storage device, and calculates a demagnetizing field coefficient corresponding to the determined penetration shape in the storage device. The magnetic characteristic measurement system according to claim 5, wherein the magnetic characteristic measurement system obtains from the following .   When both end surfaces are close to the outer surface of the measurement target, the yoke is formed around the yoke to form a magnetic path together with the measurement target, and the yoke is wound around the yoke so that the excitation current is supplied to form the magnetic path. An exciting coil that excites the yoke, a coil for magnetizing force detection that is wound so as to surround at least one radially outer side of the both end faces, and that can detect a time change of a magnetic flux passing through the both end faces; It is arranged between both end surfaces, and is configured to be in contact with the outer surface of the measurement object, and can detect a magnetic flux density or a magnetization in a direction from one of the both end surfaces to the other in the surface layer including the outer surface. A magnetic sensor, comprising: a magnetic property measuring method for measuring a magnetic property of the surface layer by pressing a magnetic property measuring probe including the probe against the outer surface of the measurement object,
  By a processing device that acquires and processes a signal from the magnetic property measurement probe,
  Calculating a demagnetizing factor in a direction parallel to the magnetic path in the surface layer based on the frequency of the exciting current,
  Calculating the end magnetizing force that is the strength of the magnetic field on at least one of the two end faces of the yoke,
  An effective magnetizing force, which is the strength of a magnetic field for magnetizing the surface layer, is calculated based on the magnetic flux density or magnetization from the magnetic sensor, the demagnetizing coefficient, and the end magnetizing force.
A method for measuring magnetic properties, characterized in that:   When both end surfaces are close to the outer surface of the object to be measured, the yoke is formed around the yoke to form a magnetic path together with the object to be measured. An exciting coil for exciting the yoke, a magnetizing force detecting coil wound so as to surround at least one radially outer side of the both end faces, and capable of detecting a time change of a magnetic flux passing through the both end faces; It is arranged between both end faces, and is configured to be in contact with the outer surface of the measurement target, and can detect a magnetic flux density or magnetization in a direction from one of the two end faces to the other in the surface layer including the outer surface. A magnetic sensor, and a magnetic property measurement probe having the magnetic property of the surface layer measured by pressing the probe against the outer surface of the measurement target, and evaluating the deterioration of the measurement target based on the magnetic property. A law,
  By a processing device that acquires and processes a signal from the magnetic property measurement probe,
  Calculating a demagnetizing factor in a direction parallel to the magnetic path in the surface layer based on the frequency of the exciting current,
  Calculating the end magnetizing force that is the strength of the magnetic field on at least one of the two end faces of the yoke,
  Based on the magnetic flux density or magnetization from the magnetic sensor and the demagnetizing coefficient and the end magnetizing force, calculate an effective magnetizing force that is the strength of a magnetic field that attempts to magnetize the surface layer,
  Acquire a magnetic history which is a history of magnetic flux density or magnetization in a direction parallel to a magnetic path in the surface layer corresponding to the effective magnetizing force,
  Based on the magnetic history, calculate a parameter indicating the magnetic characteristics of the measurement target,
  Evaluate the degradation of the measurement target based on the magnetic properties
A deterioration evaluation method characterized by the following.

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