JPS62174651A - Method and device for deciding hardness of magnetic body - Google Patents

Abstract

PURPOSE:To decide the hardness of a magnetic body accurately without reference to variation in the temperature of test environment by arranging the 1st and the 2nd magnetic sensors nearby a reference magnetic body and the object magnetic body. CONSTITUTION:The 1st magnetic sensor 8 is arranged nearby the reference magnetic body 26 whose hardness is already know and the 2nd magnetic sensor 10 is arranged nearby the magnetic body 26 to be decided. Then, primary coils 8A and 10A of the magnetic sensors 8 and 10 are fed with electricity from an AC signal source to induce electromotive force at secondary coils 8B and 10B. At this time, the specific gain control mechanism of a variable gain amplifier 6 is operated so that the read value of a voltmeter 20 based upon the electromotive force of the secondary coil 8B of the magnetic sensor 8 is constant. Namely, variations in magnetic permeability of both magnetic bodies 24 and 26 with the temperature of the test environment are compensated by adjusting the primary currents to hold the secondary electromotive force constant, and consequently the difference in permeability that both magnetic bodies 24 and 25 have originally, i.e. difference in hardness is compared without reference to the environmental temperature to decide the hardness of the object magnetic body 26.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method and apparatus for determining the hardness of a magnetic material, and particularly to a method for determining the hardness of steel materials, etc. using an eddy current magnetic method, which is a type of non-destructive testing. The present invention relates to a method for determining the hardness of a magnetic material and an apparatus therefor.

[Conventional technology]

In general, structural materials used in automobiles and the like are subjected to predetermined surface treatments to obtain the necessary strength, and carburizing and quenching has been widely used as one of these treatments.

Eddy current magnetic methods (also referred to as eddy current methods) are often used for non-destructive testing of carburized and hardened metal structural materials. In this eddy current magnetic method, a magnetic sensor including, for example, a magnetically fed primary coil and a secondary coil is arranged near a structural material as a magnetic body to be measured, and the secondary coil is set at a predetermined frequency. Detects the electromotive force induced in the secondary coil when an alternating current of Then, use this detected value as a basis of known hardness! l#
The carburization depth (hardness), which is proportional to the magnetic permeability of the structural material, is measured or determined by comparing it with data regarding magnetic materials.

[Problem that the invention seeks to solve]

However, when testing using the above-described conventional method, the surrounding test environment temperature (i.e., the temperature of the magnetic material) may vary, for example, in the morning and evening.

Because the temperature changes greatly, as seen in the temperature difference between winter and summer,
As a result, physical constants such as magnetic permeability and resistance of the magnetic material to be measured change greatly, and as a result, the secondary voltage (V2) based on the detected value from the magnetic sensor changes as shown in Figure 3 (here, the parameter l is Since the carburization depth varies as shown in (indicating the carburization depth), there was an inconvenience that the accuracy and reproducibility of hardness measurements were significantly reduced.

In addition, in this case, if the change in detected value V2 due to changes in environmental temperature exceeds the change in detected value V2 due to the degree of carburization, it becomes impossible to even determine the relative hardness. Therefore, in a test environment where the temperature changes significantly over time, there is an inconvenience that, for example, it becomes impossible to perform a 100% test on a production line.

[Purpose of the invention]

The present invention improves the disadvantages of the prior art, and particularly provides a method and apparatus for determining the hardness of a magnetic material, which can accurately determine the hardness of a magnetic material regardless of changes in the temperature of the test environment. is its purpose.

Means for Solving Problem C] Therefore, the present invention is provided with first and second magnetic sensors capable of detecting an electric signal corresponding to the hardness of the magnetic material by applying an alternating current signal. A first magnetic sensor is disposed close to a reference magnetic body having a known hardness, a second magnetic sensor is disposed close to a magnetic body to be determined, and then the second (7) magnetic sensor In a method for determining the hardness of a magnetic material, the value of the electric signal detected from the first magnetic material is compared with the output of the first magnetic sensor, and thereby the hardness of the magnetic material to be determined relative to the reference magnetic material is determined. ,
The electric signal detected by the first magnetic sensor is controlled so that the value of the electric signal is always constant even if the environmental temperature changes.
This method attempts to achieve the above object by adjusting the value of the AC signal applied to the second magnetic sensor and applying the adjusted AC signal to the second magnetic sensor.

[Embodiments of the invention]

[First Embodiment] Hereinafter, a first embodiment of the present invention will be described based on FIG. 1.

In FIG. 1, 2 indicates an AC signal source.

This AC signal source 2 has a predetermined frequency (here, for example, 3
An oscillation circuit 4 that generates an alternating current signal (20 (Hz)), and amplifies the output signal from this oscillation circuit 4.
It is comprised of a variable gain amplifier 6 whose gain can be changed as necessary. Here, the oscillation circuit 4
is a sine wave signal as an AC signal with a distortion factor of 0.01, for example.
The sine wave signal from the variable gain amplifier 6 is transmitted to the first magnetic sensor 8 and the second magnetic sensor 10, which are installed in parallel at the next stage. It is now output.

Above 1st. The second magnetic sensors 8 and 10 have primary and secondary coils 8A and 8B, or IOA and IOB, respectively, and the primary and secondary coils are magnetically coupled to each other. Therefore, each partial coil 8A is controlled by the output from the variable gain amplifier 6.

When a sinusoidal alternating current 11 flows at 10A, the secondary coil 8B responds by electromagnetic induction.

A secondary electromotive force V2 is induced at both ends of each of 10B. And the first. Each electromotive force V2 induced by the second magnetic sensors 8 and 10 is applied to the first magnetic sensor provided at the next stage. Each signal is output to the second display means 12.14 separately.

In this case, since the frequency of the AC signal from the AC signal source 2 is low frequency, the first. Second magnetic sensor 8,1
0 is disposed close to a magnetic material such as metal, an eddy current flows to the inside of the magnetic material.

Since the energy of some of the coils is partially absorbed by this eddy current generation, the electromotive force induced in the secondary coil becomes larger than that in the air. In other words, the generated eddy current depends on the type, shape, and conductivity of the magnetic material.
It changes depending on the magnitude of physical constants such as magnetic permeability, and therefore,
For example, when the shape of the magnetic body is the same, if the magnetic permeability is different, the electromotive force induced in the secondary coil will be different. Moreover, it is generally known that the carburization depth, ie, the hardness of the surface of the magnetic material, is in a proportional relationship with the above-mentioned magnetic permeability.

On the other hand, the first display means 12 includes an amplifier 16 for voltage amplification and a voltmeter 20 that displays the output of the amplifier 16. Further, the second display means 14 is similarly constituted by an amplifier 18 and a voltmeter 22. Therefore, the secondary electromotive force as the detection signal obtained as described above is ultimately transmitted to the voltmeter 20.
22, each item is displayed separately.

Next, the effects of the first embodiment will be explained.

Now, a round bar-shaped metal material (hereinafter referred to as "test work") 24 as a magnetic material to be determined has been subjected to carburizing and quenching treatment.
The case of determining the hardness, that is, the degree of carburization depth, will be described below.

First, the first magnetic sensor 8 has a carburizing depth of, for example, 0.9.
4 (dragon) (i.e. hardness is known), its shape,
A base Y$ magnetic body (hereinafter referred to as "master work") 26 having the same material etc. as the metal material 24 is set, and a second
Set the magnetic sensor 10 at the test work 2°4.

In this case, it is assumed that after the carburizing and quenching process, the test workpiece 24 is cooled to room temperature and is the same as the temperature of the master workpiece 26 (that is, the temperature of the test environment).

Therefore, the AC signal source 2 is driven, and each first . Part of the coil 8A and IOA of the second magnetic sensor 8.10 are energized. As a result, as mentioned above, each secondary coil 8B,
An electromotive force is induced in the IOB. At this time, the operator manually operates the variable gain amplifier 6 so that the reading value 2 of the voltmeter 20 based on the electromotive force of the secondary coil 8B of the first magnetic sensor 8 becomes a constant value (for example, 215 (mv)).
A predetermined gain control mechanism (e.g., a variable resistor) is operated. In other words, both workpieces 24 due to temperature changes in the test environment.
．． 26 magnetic permeability changes are compensated for by the magnitude of the primary current,
Keep the secondary electromotive force constant. Then, the reading value (2) of the voltmeter 22 of the second display means 14 at this time is compared with the constant value (2).

In other words, this means that both workpieces 2
This means that the reading values Vt + vz' due to the difference in i3m ratio (i.e., carburization depth) inherent in 4.26 are compared with each other. Therefore, by using this method, the carburization depth of the test work 24 can be adjusted to the master work 26.
carburization depth of 0.94 [drunk]), is it the same or not?
Or, if they are different, the percentage difference can be easily determined or measured.

Further, in a production line, the test workpieces 24 can be replaced one after another and their hardnesses can be similarly determined. Thereby, even if the environmental temperature that determines the temperature of both works 24 and 26 changes over time, the hardness can be determined almost independently of the temperature change.

[Second Embodiment] Next, a second embodiment of the present invention will be described based on FIG. 2. Here, the same reference numbers are used for the same components as in the first embodiment described above.

This second embodiment attempts to automatically perform the feedback operation for the AC signal source 2, which was manually performed in the first embodiment.

In FIG. 2, the amplifier in the first display means 12, the device 1
The output of the differential amplifier 30 is also connected to the comparison input terminal of the differential amplifier 30. The other reference input terminal of the differential amplifier 30 is applied with a reference voltage V2 (here, for example, 215 (mv)) outputted by a reference voltage generator 32.

Further, the feedback signal from the output end of the differential amplifier 30 is applied to the gain control end of the variable gain amplifier 34 in the AC signal source 2.

Therefore, when driving this device, the reference voltage v2 and the output 2' of the amplifier 16 are compared point by point, and a control feedback signal based on the difference is used to control the variable gain amplifier 34.
Its gain is automatically controlled to adjust its output.

Here, the above-mentioned differential amplifier 30. Reference voltage generator 32
An applied signal control means 36 for controlling the gain of the AC signal source 2 is configured by the following.

The other configurations and functions are the same as those of the first embodiment described above, and the determination of the hardness of the test workpiece 24 is performed in the same manner.

As described above, according to the second embodiment, the same effects as those of the first embodiment described above can be obtained, and
Each 1st. Since the primary current of the second magnetic sensor 8-10 is automatically controlled, the hardness determination operation is significantly simplified, and work efficiency can be further improved.

In addition, in each of the above embodiments, the test work 24 is a round bar-shaped metal material, but the present invention is not necessarily limited to this, and can be similarly applied to magnetic materials of other shapes. It is something. In addition, the reference voltage ■2 is
It may be set as appropriate according to the known carburization depth of the reference magnetic material.

〔Effect of the invention〕

Since the present invention is configured and functions as described above, it is possible to compare the hardness of the magnetic material with a reference value and determine it almost independently of the environmental temperature, that is, the temperature of the magnetic material. Even on a production line where changes occur from moment to moment, unlike conventional methods, it is possible to easily determine the hardness of all products using a non-destructive method, thereby significantly improving quality control. An excellent method and device for determining the hardness of a magnetic material can be provided.

Furthermore, in the device according to claim 3, since the reference value is automatically adjusted to a predetermined value, the operation for discrimination can be significantly simplified, thereby making it possible to perform hardness discrimination. The effect is that the process can be carried out efficiently and accurately.

[Brief explanation of drawings]

FIG. 1 is a block diagram according to the first embodiment of the present invention, and FIG.
The figure is a block diagram according to the second embodiment of the present invention, and FIG. 3 is a diagram showing an example of the relationship between the secondary voltage based on the secondary electromotive force of the magnetic sensor and the environmental temperature. 2... AC signal source, 8... First magnetic sensor, 10... Second magnetic sensor, 12...
...First display means, 14...Second display means, 24...Magnetic material to be determined (test work)
, 26...Reference magnetic body (master work), 3
6... Applied signal control means.

Claims (3)

[Claims] (1) Equipped with first and second magnetic sensors capable of detecting an electric signal corresponding to the hardness of the magnetic material by applying an alternating current signal; and a second magnetic sensor is arranged close to the magnetic substance to be determined, and then the value of the electric signal detected from the second magnetic sensor is transferred to the first magnetic substance. In a method for determining the hardness of a magnetic body, the hardness of the magnetic body to be determined is determined relative to the reference magnetic body by comparing the hardness with a magnetic sensor output, the value of the electric signal detected by the first magnetic sensor being , so that the first temperature remains constant even if the environmental temperature changes.
A method for determining the hardness of a magnetic material, comprising adjusting the value of an alternating current signal applied to the second magnetic sensor, and applying the adjusted alternating current signal to the second magnetic sensor. (2) An AC signal source configured to output an AC signal of a predetermined frequency and to be able to adjust its output value as necessary; A first magnetic sensor that detects the hardness of the reference magnetic body by applying an alternating current signal from a signal source and outputs an electrical signal at a predetermined level, and a first display that displays the sensor output from the first magnetic sensor. and a means for detecting the hardness of the magnetic substance to be determined by applying the same signal as the alternating current signal that is disposed close to the magnetic substance to be determined and applied to the first magnetic sensor. a second magnetic sensor that outputs an electrical signal of a predetermined level corresponding to the
A second magnetic sensor displaying the sensor output from this second magnetic sensor.
An apparatus for determining the hardness of a magnetic material, characterized in that it is also equipped with a display means. (3) An alternating current signal source configured to output an alternating current signal of a predetermined frequency and whose output value can be adjusted as necessary; A first magnetic sensor that detects the hardness of the reference magnetic body by applying an alternating current signal from a signal source and outputs an electric signal of a predetermined level corresponding to the hardness, and a sensor output from the first magnetic sensor is displayed. the hardness of the magnetic material to be determined by applying the same signal as the AC signal that is disposed close to the magnetic material to be determined and applied to the first magnetic sensor. a second magnetic sensor that detects and outputs an electric signal at a predetermined level corresponding to the detected electric signal;
A second magnetic sensor displaying the sensor output from this second magnetic sensor.
display means, and applied signal control means for feedback-controlling the alternating current signal source and automatically adjusting the detected value of the first magnetic sensor to a constant level regardless of environmental temperature. Hardness determination device for magnetic materials.