JP2007040865A - Nondestructive measuring method for determining depth of hardened layer, unhardened state and foreign material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nondestructive measuring method for determining a depth of a hardened layer, an unhardened state and a foreign material of a steel product, which can carry out a precise measurement by using a simple and inexpensive apparatus. <P>SOLUTION: In the nondestructive measuring method for determining the depth of the hardened layer of the steel product, AC current having a frequency of 1 kHz or less is applied to a coil 2 into which a test piece 3 is inserted, or to the coil 2 disposed near the test piece 3, and an inductance value of the coil 2 is measured, thereby determining the depth of the hardened layer of the steel product. In order to determine the depth of the hardened layer of the steel product, a phase of impedance of the coil 2 may be measured instead of the inductance value. If the depth of the hardened layer is judged to be zero by using above method, the unhardened state of the steel product can be determined. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a nondestructive measurement method for determining a hardened layer depth, unquenched, and a different material of a steel material.

  Steel materials are used by being cured to the surface or the center by heat treatment depending on the application. When the steel material is a mass-produced product, the depth of the hardened layer is confirmed by a sampling inspection, and the current state is a destructive inspection for cutting the steel material. In some cases, non-destructive inspection by an eddy current method or the like is also attempted. In the nondestructive inspection such as the eddy current method, the depth of the hardened layer cannot be directly measured. Therefore, it is necessary to investigate the relationship between the hardened layer depth and the measured value of the nondestructive inspection in advance and prepare a calibration curve. The hardened layer depth is estimated by comparing the calibration curve with the nondestructive inspection measurement value of the test piece whose hardened layer depth is unknown.

  In the measurement of the hardened layer depth by the eddy current method, it is common to measure the hardened layer depth by inserting a test material into a through coil constituted by an excitation coil and a detection coil (for example, Non-Patent Document 1). . In this case, an eddy current is induced in the specimen by the exciting coil, and a voltage is induced in the detection coil by the eddy current. Since the state of the eddy current induced in the test material differs depending on the difference in the hardened layer depth of the test material, the hardened layer depth is estimated from the state of the voltage induced in the detection coil. In the measurement disclosed in Non-Patent Document 1, the hardened layer depth is estimated from the X value resulting from the phase lag of the voltage waveform induced in the detection coil.

  As another example of the measurement of the hardened layer depth by the eddy current method, there is a method by comparative measurement (for example, Non-Patent Document 2). In this case, a test piece for correction and a correction coil, and a test piece and a test coil to be inspected are used. Each of the correction coil and the test coil includes an exciting coil and a receiving coil, and a total of four coils are used. In this measurement, a difference between eddy currents induced in the test specimen for inspection and the test specimen for correction is detected, so that the X and Y signals (X: resistance component of the voltage vector, Y: reactance component of the voltage vector) ) And the quenching depth is estimated.

  In Non-Patent Document 3, the same eddy current measuring instrument as in the measurement method of Non-Patent Document 2 is used, and the hardened layer depth is estimated from the Y signal of the X and Y signals.

  In Non-Patent Document 4, measurement is performed using two excitation coils and a detection coil sandwiched between these coils, and analysis is performed using the conductivity and initial magnetization curve of each hardness of the steel material measured in advance. A method for estimating the hardened layer depth is disclosed.

  Non-Patent Document 5 discloses a method of estimating the hardened layer depth by measuring magnetic characteristics and electrical characteristics (inductance, impedance). However, the hardened layer depth has not yet been estimated.

Patent Document 1 uses a high frequency of 500 kHz or higher and uses a unique circuit in which the current value changes due to a change in inductance, so that the thickness of the hardened layer can be determined from the relationship between the current value of the circuit and the thickness of the hardened layer. A method of measuring is disclosed.
Akira Sakano, “Development of Quenching Quality Evaluation and Measurement Technology”, Preprint of Academic Lecture Meeting of the Society of Automotive Engineers of Japan, October 27, 2004, No.82-04, Suzuki Hitoshi, “Method of Estimating Hardened Layer Depth by Eddy Current Inspection Method”, Ken Automation Co., Ltd., August 5, 2003 Rov Kozar, 4 other authors, “Improving the Reliability of Eddy Current Testing as a Means of Induction Hardening Quality Control of Forged Axle Shafts” , Michigan Technological University Department of Materials Science Engineering, April 22, 2002 Yuji Goto, Ryuji Nomura, Atsushi Tanaka, Hiroaki Yano, Kengo Sakurai, “Numerical Analysis Evaluation Considering Variation of Magnetization Characteristics in Electromagnetic Inspection Method of Induction Hardening Depth”, Journal of Vocational Ability Development, 2001 Vol. 13 No.1 (25) Eiichi Inoue, “Study on Measurement Method of Surface Hardened Layer Depth of Non-destructive Surface Hardened Material—Carburized Quenching Material— (Preliminary Study)” Japanese Patent Publication No. 40-23956

However, the above-described eddy current method requires at least two coils, ie, an excitation coil and a detection coil. Generally, the measuring device is special and performs signal processing unique to each manufacturer, and the device is expensive.
Further, in the eddy current comparative measurement method as in Non-Patent Document 2, there is a problem that if the test piece inserted into the correction coil changes, the measurement value itself changes.
Further, in the measurement method according to Non-Patent Document 4, it is necessary to measure the electrical conductivity and the initial magnetization curve at each hardness of the steel material in advance, and much preparation and time are required.
In the measurement method according to Patent Document 1, it is necessary to manufacture an original measurement circuit and perform measurement after adjusting the circuit, and the measurement work is complicated.

  An object of the present invention is to provide a nondestructive measurement method for determining the depth of a hardened layer, unquenched, and different materials of a steel material that can be measured with high accuracy with a simple and inexpensive apparatus.

According to a first aspect of the present invention, there is provided a method for measuring a depth of a hardened layer of a steel material by passing an alternating current having a frequency of 1 kHz or less through a coil in which a test piece is inserted or a coil disposed in the vicinity of a test piece. This is a method of measuring the depth of the hardened layer of the steel material by measuring the inductance value.
In this case, for example, when the test piece is inserted into the coil or the test piece is arranged in the vicinity of the coil and an alternating current flows, the inductance value of the coil is measured with an LCR meter or the like, and the hardened layer depth and the inductance value are measured. Investigate the relationship and create a calibration curve. The inductance value of the test piece with the unknown hardened layer depth is collated with a calibration curve to obtain the hardened layer depth.

  According to this method, an AC current having a frequency of 1 kHz or less is passed through the coil, and the hardened layer depth of the steel material is obtained by measuring the inductance value of the coil. Therefore, a measurement in which one coil is connected to a commercially available LCR meter. Hardened layer depth can be measured only with the system. Therefore, it is not necessary to manufacture an original electronic circuit, and the measurement system becomes very simple and can be measured at low cost. Further, since the product can be measured by nondestructive inspection without cutting the product, it is not necessary to discard the product. Therefore, it is possible to inspect all the measurements of the depth of the hardened layer, which could only be done by sampling, so that products with an inappropriate hardened layer depth can be eliminated and the quality assurance accuracy of the product can be improved. it can. Furthermore, since 100% inspection is possible, it is useful for process management of the heat treatment process, and can be used to construct a more stable heat treatment process.

  The hardened layer depth nondestructive measuring method of the steel material according to the second invention of the present invention is the method of the first invention method, in which instead of the inductance value, the phase of the impedance of the coil is measured to measure the hardened layer depth of the steel material. This is a method for measuring the thickness. The cured layer depth can also be measured by measuring the impedance phase with an LCR meter or the like.

  A non-hardened nondestructive measuring method for steel according to a third aspect of the present invention is a method for determining whether the steel is unquenched by measuring an inductance value of a coil in the first inventive method. When the inductance value is collated with a calibration curve and the hardened layer depth is found to be 0 mm, the steel material can be determined to be unquenched.

  The non-hardened nondestructive measuring method for steel according to the fourth invention of the present invention is the method of determining the unhardened steel by measuring the phase of the coil impedance instead of the inductance value in the first invention method. It is a method to do. When the impedance phase is collated with a calibration curve and the hardened layer depth is found to be 0 mm, the steel material can be determined to be unquenched.

  In these second to fourth inventions as well, as described with respect to the first invention, measurement can be performed only with a measurement system in which one coil is connected to a commercially available LCR meter, and an original electronic circuit is manufactured. Therefore, the measurement system becomes very simple and can be measured or judged at low cost. Further, as described with respect to the first invention, it is possible to obtain each effect by being able to measure or determine by nondestructive inspection.

According to a fifth aspect of the present invention, a non-destructive measuring method for a dissimilar material of steel is such that an alternating current is passed through a coil in which a test piece is inserted or a coil disposed in the vicinity of the test piece, and the inductance value of the coil is measured. This is a method for judging a different steel material.
In this case, for example, the inductance value of the coil when the test piece is inserted into the coil or the test piece is arranged in the vicinity of the coil is measured in advance with an LCR meter or the like. Next, a steel material whose material is unknown is inserted into a coil, or placed in the vicinity of the coil and the inductance value is measured. If the inductance value is different from the known material, it is determined that the material is different.
Unlike the case of measuring the depth of the hardened layer, there is no need to worry too much about the penetration depth of the magnetic field. The degree of freedom is higher than when measuring.

The specific component amount nondestructive measuring method for a steel material according to a sixth aspect of the present invention is such that an alternating current is passed through a coil in which a test piece is inserted or a coil disposed in the vicinity of the test piece, and the inductance value of the coil is measured. Thus, the specific component amount in the steel material is determined.
In the case of this method, for example, with respect to a plurality of steel material test pieces whose specific component amounts are known in advance and different from each other in specific component amounts, an alternating current is passed through a coil in which the test piece is inserted or a coil disposed in the vicinity of the test piece. The relationship between each specific component amount and the inductance value of the coil is investigated by measuring the inductance value of the coil. In the same procedure, the inductance value of the coil is measured for a steel specimen having an unknown specific component amount, and the unknown specific component amount is obtained by comparing the inductance value with the measurement result.
In these fifth and sixth inventions as well, as described with respect to the first invention, measurement can be performed only with a measurement system in which one coil is connected to a commercially available LCR meter, and an original electronic circuit is manufactured. Therefore, the measurement system becomes very simple and can be determined inexpensively. Moreover, each effect by being able to measure by a nondestructive inspection can be acquired similarly to having demonstrated about 1st invention.

According to a first aspect of the present invention, there is provided a method for measuring a depth of a hardened layer of a steel material by passing an alternating current having a frequency of 1 kHz or less through a coil in which a test piece is inserted or a coil disposed in the vicinity of a test piece. This is a method of measuring the depth of the hardened layer of the steel material by measuring the inductance value of the steel material. Therefore, the depth of the hardened layer of the steel material can be accurately measured with a simple and inexpensive apparatus.
According to a second aspect of the present invention, there is provided a method for measuring a depth of a hardened layer of a steel material by passing an alternating current having a frequency of 1 kHz or less through a coil in which a test piece is inserted or a coil disposed in the vicinity of a test piece. This is a method for measuring the depth of the hardened layer of the steel material by measuring the phase of the impedance of the steel. Therefore, the depth of the hardened layer of the steel material can be accurately measured with a simple and inexpensive device.
In the non-hardened nondestructive measuring method of a steel material according to the third aspect of the present invention, an alternating current having a frequency of 1 kHz or less is passed through a coil in which a test piece is inserted or a coil disposed in the vicinity of the test piece, and the coil inductance By measuring the value, it is a method of determining whether the steel material has not been hardened. Therefore, it is possible to accurately determine whether the steel material has not been hardened with a simple and inexpensive device.
In the non-hardened nondestructive measuring method for steel material according to the fourth aspect of the present invention, an alternating current having a frequency of 1 kHz or less is passed through a coil in which a test piece is inserted or a coil disposed in the vicinity of the test piece, and the impedance of the coil In this method, the unquenched steel material can be accurately determined with a simple and inexpensive device.
In the non-destructive measuring method for dissimilar steel materials according to the fifth aspect of the present invention, the dissimilar steel material is determined by measuring the inductance value of the coil in which the test piece is inserted or the coil disposed in the vicinity of the test piece. Since this is a method, it is possible to accurately determine whether a steel material is a different material with a simple and inexpensive device.
The specific component amount nondestructive measurement method for steel according to the sixth aspect of the present invention is a method for determining the specific value in a steel by measuring the inductance value of a coil in which a test piece is inserted or a coil disposed in the vicinity of the test piece. Since it is a method of measuring the component amount, the specific component amount in the steel can be accurately measured with a simple and inexpensive apparatus.

  A first embodiment of the present invention will be described with reference to FIGS. As shown in FIG. 1, the hardened layer depth nondestructive measurement method of the steel material of this embodiment is a state in which a coil 2 is connected to the LCR meter 1 and a test piece 3 of a shaft-shaped steel material is inserted into the coil 2. In this method, an AC current having a frequency of 1 kHz or less is passed from the LCR meter 1 to the coil 2 and the inductance value L of the coil 2 at that time is measured by the LCR meter 1 to measure the hardened layer depth of the steel specimen 3. .

Specifically, in this hardened layer depth nondestructive measurement method, the inductance value L is measured by the measuring system having the above-described configuration for each of the plurality of steel material test pieces 3 having a known hardened layer depth and different hardened layer depths. Is measured in advance, the relationship between the hardened layer depth of each steel material test piece 3 and the measured inductance value L is investigated, and a calibration curve is created. The hardened layer depth may be obtained by destructive inspection after the inductance value L is measured by the measurement system. FIG. 2 shows an example of the calibration curve.
Next, with respect to the steel specimen 3 with the unknown hardened layer depth, the inductance value L is measured by the measurement system having the above configuration, and the unknown hardened layer depth is determined by checking the inductance value L with the calibration curve. Ask.
FIG. 3 is a schematic diagram showing the relationship between the impedance Z of the coil 2 and the resistance component R and reactance component ωL when an alternating current having an angular frequency ω is passed through the coil 2. In the hardened layer depth nondestructive measurement method, the inductance value L of the reactance component ωL is measured.

The calibration curve of FIG. 2 shows the result (primary regression equation) of investigating the relationship between the hardened layer depth and the inductance value L of the coil 2 when the frequency of the alternating current flowing through the coil 2 is 5 Hz in the measurement system of FIG. This linear regression equation is shown by a rough numerical example. The following equation is y = −1.50x + 110 (1)
Where x: inductance value (mH)
y: Hardened layer depth (mm)
The inductance value L of the coil 2 tends to decrease as the hardened layer depth increases. In this linear regression equation, the square value of the correlation coefficient R is as good as about 0.989, and a very high correlation is recognized.
In addition, when the hardened layer depth is obtained as 0 mm from this calibration curve, it can be determined that the steel specimen 3 is not quenched.

Here, the reason why the hardened layer depth can be obtained from the measured inductance value L will be described.
The inductance value L of the coil 2 is represented by the following equation when the number of turns is N: inductance value L = μαN ² (2)
Where μ: permeability around the coil α: coefficient determined by the shape of the coil.
From the equation (2), it can be seen that the change in the inductance value L of the coil 2 is caused by the change in the magnetic permeability μ around the coil. Since the magnetic permeability μ is different between the hardened layer portion and the uncured layer portion of the steel material, when the steel material test piece 3 is inserted into the coil 2, a change in the inductance value L according to the hardened layer depth occurs. Thereby, the hardened layer depth can be obtained from the inductance value L. However, unless the frequency of the current flowing through the coil 2 is appropriately selected, the hardened layer depth cannot be obtained correctly from the inductance value L.

  For example, when the depth of the hardened layer is measured to about 7 mm, it is necessary to use a low frequency of approximately 1 Hz to 15 Hz as the current flowing through the coil 2. The reason for this will be described below.

The difference in the magnetic permeability μ of the steel material test piece 3 is reflected in the inductance value L of the coil 2 through an alternating magnetic field generated from the coil 2. Therefore, when measuring the depth of the hardened layer, it is necessary to penetrate the AC magnetic field generated from the coil 2 deeper than the deepest portion of the hardened layer of the steel material test piece 3.
In the case of an AC magnetic field, the higher the frequency, the more it penetrates only near the surface of the conductor due to the skin effect, but how much the AC magnetic field penetrates into the inside of the conductor is generally expressed by the following equation penetration depth δ = 1 / (√ ( πfμσ)) …… (3)
However, π: Circumference ratio f: Frequency of magnetic field (coil current) μ: Conductivity of conductor σ: Conductivity of conductor is evaluated.

When the magnitude of the magnetic field outside the conductor is H _o , the penetration depth δ is a depth at which the magnitude H _X of the magnetic field inside the conductor is about 37% of H _o .
According to the results of the inventors measuring the magnetic permeability and electrical conductivity of the hardened layer of steel, the magnetic permeability was 1.005E-04 (H / m) and the electrical conductivity was 3.85E + 06 (S / m). FIG. 4 shows the result of calculating the penetration depth δ of the magnetic field using this permeability and conductivity. According to this result, when it is desired to measure the depth of the hardened layer up to 7 mm, a frequency lower than the frequency of 17 Hz when the penetration depth δ is 7 mm is an indication of the frequency to be used.

  5A to 5F show the results (primary regression equation) of examining the relationship between the hardened layer depth and the inductance value L of the coil 2 by changing the frequency of the current flowing through the coil 2. From this result, at a frequency of 15 Hz, there is a tendency that the inductance value L decreases as the hardened layer depth increases. At a frequency of 10 Hz or less, there is no problem even if the hardened layer depth is obtained from the inductance value L by a linear regression equation. It can be seen that

  In addition, when it is not necessary to measure the depth of the hardened layer to 7 mm deeply, for example, when measurement to a depth of 1 mm is sufficient, it is easily inferred that the optimum frequency becomes high. It is believed that there is.

  Thus, in the hardened layer depth nondestructive measuring method of the steel material of this embodiment, an alternating current having a frequency of 1 kHz or less is passed through the coil 2 in which the steel material test piece 3 is inserted, and the inductance value L of the coil 2 is measured. Therefore, the hardened layer depth can be measured only with a measurement system in which one coil 2 is connected to a commercially available LCR meter 1, and there is no need to manufacture an original electronic circuit. The measurement system becomes very simple and can be measured at low cost. In addition, since the product can be measured by nondestructive inspection without cutting the product, it is not necessary to dispose of the product, and it is possible to inspect all the cured layer depth measurements that could only be done by sampling. Products with an inappropriate depth can be eliminated, and the quality assurance accuracy of the product can be improved. Furthermore, since 100% inspection is possible, it is useful for process management of the heat treatment process, and can be used to construct a more stable heat treatment process.

Another embodiment of the present invention is shown in FIG. The steel layer hardened layer depth nondestructive measurement method is the same as the first embodiment shown in FIGS. 1 to 5 except that the inductance value L of the coil 2 is measured and the phase θ of the impedance Z of the coil 2 is determined. This is a method of measuring the hardened layer depth of the steel specimen 3 by measuring (FIG. 3).
The measurement system is the same as in FIG. 1, and the hardened layer depth of the steel material test piece 3 whose hardened layer depth is unknown is obtained by measuring the phase θ of the impedance Z with the LCR meter 1. As a preparation for this, the phase θ of the impedance Z of the coil 2 and the phase θ of the impedance Z of the coil 2 are measured for each of the plurality of steel specimens 3 whose hardening layer depths are known in advance by the measurement system. A calibration curve is created by investigating the relationship.

FIG. 6 shows an example of the calibration curve. This calibration curve shows the result (primary regression equation) of investigating the relationship between the hardened layer depth and the phase θ of the impedance Z of the coil 2 when the frequency of the alternating current flowing through the coil 2 is 5 Hz in the measurement system of FIG. This linear regression equation is expressed by the following equation: y = -11.08x + 124 (4)
Where x: phase of impedance (°)
y: Hardened layer depth (mm)
As the hardened layer depth increases, the phase θ of the impedance Z of the coil 2 tends to decrease. In this linear regression equation, the square value of the correlation coefficient R is as good as 0.999, and a very high correlation is recognized.

Thus, after investigating the relationship between the depth of the hardened layer and the phase θ of the impedance Z of the coil 2, a calibration curve (primary regression equation) was created, and the impedance of the coil 2 for the steel specimen 3 whose hardened layer was unknown. The phase θ of Z is measured, and the phase θ is compared with the calibration curve (primary regression equation) to determine the unknown hardened layer depth.
Also in this embodiment, when the hardened layer depth is determined to be 0 mm from the calibration curve, the steel material test piece 3 can be determined to be unquenched.

  In each of the above embodiments, the case where the inductance value L of the coil 2 and the phase θ of the impedance Z are measured in a state where the steel material test piece 3 is inserted into the coil 2 has been described. However, the steel material test piece 3 is huge. If it is difficult to insert the coil 2 into the coil 2 for reasons such as the above, the steel material test piece 3 may be disposed in the vicinity of the coil 2 as shown in FIG. Other configurations are the same as those of the previous embodiment, and the operations and effects are the same as those of the previous embodiment.

  FIG. 8 and FIG. 9 show an embodiment of the non-destructive measuring method for dissimilar steel materials according to the present invention. This foreign material nondestructive measurement method of steel material measures a foreign material of steel material by nondestructive inspection, and the same measurement system (FIG. 1) as the first embodiment is used. As a preparation for measuring the steel material test piece 3 whose material is unknown, the inductance value L of the coil 2 is measured for each of the plurality of steel material test pieces 3 whose material is known and different from each other by the above measurement system. The relationship of the inductance value L of the coil 2 is investigated. In the case of the first embodiment, in the above measurement, each steel material test piece 3 is inserted into the coil 2, an alternating current is passed from the LCR meter 1 to the coil 2, and the inductance value L of the coil 2 at this time is measured. Is the same. In this case as well, when each steel material test piece 3 cannot be inserted into the coil 2 due to its huge size, the steel material test piece 3 may be disposed in the vicinity of the coil 2 for measurement. FIG. 8 shows the relationship between each material obtained by the above measurement and the inductance value L of the coil 2.

Thus, after investigating the relationship between each material and the inductance value L, the inductance value L of the coil 2 is measured for the steel specimen 3 whose material is unknown, and the inductance value L is collated with the result of FIG. In order to find an unknown material. Since the inductance value L differs depending on the material, the material can be determined.
Even in the non-destructive measurement method for dissimilar steel materials according to this embodiment, a measurement system in which one coil is connected to a commercially available LCR meter, similarly to the nondestructive measurement method for the hardened layer depth of each steel material in the previous embodiments. It is possible to perform measurement with a simple measurement system, and it is not necessary to manufacture an original electronic circuit. Moreover, each effect similar to having demonstrated in 1st Embodiment by being able to measure by a nondestructive inspection can be acquired.

The SC material is called differently depending on the carbon content. For example, the SC material is called S15C when the carbon content is 0.15% and S35C when the carbon content is 0.35%. FIG. 9 shows an example of a calibration curve (primary regression equation) created by collectively gathering the relationship between the carbon content of the SC material and the inductance value L from the measurement results of FIG. This linear regression equation is expressed by the following equation: y = −2.43x + 14.8 (5)
Where x: inductance value (mH)
y: Carbon content (%)
The inductance value L of the coil 2 tends to decrease as the amount of carbon increases. In this linear regression equation, the square value of the correlation coefficient R is as good as 0.986, and a very high correlation is recognized.

Thus, after creating a calibration curve (primary regression equation) of the relationship between the amount of carbon and the inductance value L of the coil 2, the inductance value L of the coil 2 is measured for the steel material specimen 3 whose carbon amount is unknown, By comparing the inductance value L with the calibration curve (primary regression equation), the unknown carbon amount can be obtained.
In the non-destructive measurement method for the specific component amount of the steel material of this embodiment, one coil was connected to a commercially available LCR meter as in the nondestructive measurement method of the hardened layer depth of the steel material in the first embodiment. Measurements can be made only with the measurement system, and it is not necessary to manufacture an original electronic circuit. The measurement system is very simple and can be measured at low cost. Moreover, each effect similar to having demonstrated in 1st Embodiment by being able to measure by a nondestructive inspection can be acquired.

  Although the case where the amount of carbon contained in the SC material is measured has been described with reference to FIG. 8, the component amount of other substances that affect the magnetic permeability of the steel material contained in the steel material by measuring the inductance value L of the coil 2. Can be estimated by a similar method. Thus, the method based on the measurement of the inductance value L can also be used to estimate the amount of a certain component contained in the steel material.

In the case of performing the different material determination, unlike the case of measuring the hardened layer depth, it is not necessary to worry too much about the penetration depth of the magnetic field. The degree of freedom is higher than in the case of measuring the thickness. However, when the surface roughness of the steel material test piece 3 is rough, the penetration depth δ becomes very shallow if too much high frequency is used.
In addition, depending on the material to be discriminated, there are cases where it can be discriminated depending on the frequency, and attention is necessary.

FIG. 10 shows the results of measuring the inductance value L in the range of 1 Hz to 1000 Hz for the five types of materials shown in FIG. From the figure, it can be seen that, depending on the frequency, even if the materials are different, the inductance value L may be equal and may not be discriminated. The inductance value L shown in FIGS. 8 and 9 is the inductance value L when the frequency is 8 Hz. In this case, the above five types of materials can be discriminated.
For this reason, unlike the case of measurement of the hardened layer depth, when different materials are determined, the frequency is not selected from the penetration depth δ of the magnetic field, but the inductance value L of those materials is determined. All need to select a different frequency. However, if there are many materials to be identified, it may be difficult to determine the inductance values of all the materials at one frequency. In that case, comprehensive determination is performed using the inductance values L of a plurality of frequencies. You may make it do.

It is a schematic block diagram which shows an example of the measurement system used for the hardened layer depth nondestructive measuring method of the steel materials concerning 1st Embodiment of this invention. It is a figure which shows an example of the calibration curve calculated | required by the same measuring method. It is a schematic diagram which shows the relationship between the impedance of the coil in the same measuring method, its resistance component, and reactance component. It is a graph which shows the relationship between the penetration depth of a magnetic field, and a frequency. It is a figure which shows each example of the calibration curve corresponding to each frequency. It is a figure which shows an example of the analytical curve calculated | required by the hardened layer depth nondestructive measuring method of the steel materials concerning other embodiment of this invention. It is a schematic block diagram which shows another example of the measurement system used for the hardened layer depth nondestructive measuring method of the steel material of this invention. It is a figure which shows the relationship between the material calculated | required by the different material nondestructive measuring method of the steel materials concerning other embodiment of this invention, and an inductance. It is a figure which shows an example of the calibration curve calculated | required by the specific component amount nondestructive measuring method of the steel materials concerning other embodiment of this invention. It is a graph which shows the change according to the frequency of the inductance value of the coil by each material.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... LCR meter 2 ... Coil 3 ... Steel material test piece

Claims (6)

  Curing of steel material that measures the hardened layer depth of steel material by passing an alternating current with a frequency of 1 kHz or less through a coil in which the test piece is inserted or a coil arranged in the vicinity of the test piece and measuring the inductance value of the coil Layer depth nondestructive measurement method.   A steel material for measuring the depth of the hardened layer of the steel material by passing an alternating current having a frequency of 1 kHz or less through a coil in which the test piece is inserted or a coil disposed in the vicinity of the test piece and measuring the phase of the impedance of the coil. Hardened layer depth nondestructive measurement method.   An unquenched steel material that determines whether the steel material has not been hardened by passing an alternating current with a frequency of 1 kHz or less through a coil in which the test piece has been inserted or a coil disposed in the vicinity of the test piece, and measuring the inductance value of the coil Nondestructive measurement method.   An AC current having a frequency of 1 kHz or less is passed through a coil in which the test piece is inserted or a coil disposed in the vicinity of the test piece, and the phase of the impedance of the coil is measured to determine whether the steel material is not hardened. Quenching nondestructive measurement method.   A non-destructive measuring method for different materials of steel, in which an alternating current is passed through a coil in which a test piece is inserted or a coil disposed in the vicinity of the test piece and the inductance value of the coil is measured to determine the different materials of the steel.   Nondestructive amount of specific component of steel, measuring the amount of specific component in steel by measuring the inductance value of the coil by passing an alternating current through the coil in which the test piece is inserted or the coil placed near the test piece Measurement method.

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