JPH03108657A - Apparatus for detecting heterogeneous layer in metal - Google Patents

Abstract

PURPOSE:To detect a shape of a heterogeneous layer with high accuracy by detecting an infiltration depth based on difference between an output of a reference coil and an output of a detecting coil facing the heterogeneous layer. CONSTITUTION:A reference coil 4 and a detecting coil 5 are placed on a body 3 facing a work receiving base 2 on a base 1 along an X direction at a distance where the work receiving base 2 is reciprocally moved in the X direction by a motor 6. An output of the reference coil 4 and an output of the detecting coil 5 are transferred to a phase detecting circuit 14, which detects a shift in phases as voltage. Then the detected voltage is amplified by a differential amplifier 15 to be sent to a peak value holding circuit 16 where the peak voltage value is held. Then a data memory circuit 17 stores a frequency when the voltage exhibits the peak value. In a control and arithmetic circuit 10, a depth of a welded part A is calculated by the frequency sent from the circuit 17, and the depth and a relative position are combined to have a shape and a size of a heterogeneous layer in metal, in this case the welded part A, displayed 18 to permit determination of quality of the welding.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is directed to the structure, hardening, and other physical properties of heat-treated parts such as quenched layers, carburized layers, and alloyed layers and welded parts that are different from those of the base material. This invention relates to a device that non-destructively and non-contact detects the shape, size, etc. of a metallic heterogeneous layer.

[Conventional technology]

Various devices are known as devices for nondestructively inspecting metals.

For example, an ultrasonic flaw detector detects defects such as cracks inside metal by emitting ultrasonic waves toward the metal surface and receiving the reflected ultrasonic waves.

Equipped with a solenoid coil, variable frequency oscillator, and calculation section.
An eddy current flaw detection device that detects the depth of carburized and hardened layers by passing a current of the same frequency through a solenoid coil and measuring the magnitude of the eddy current generated between the solenoid coil and the metal surface.

etc. are known.

[Problem to be solved by the invention]

The former device is not only suitable for inspecting defects such as cracks inside the metal, but also unable to inspect the shape and size of foreign layers inside the safe. The sensor must be brought into contact with the sensor through the metal surface, and inspection must be performed while supplying a medium to the metal surface, which is cumbersome. In addition, when inspecting a high-temperature part such as a weld, the sensor may be damaged due to thermal effects.

With the latter device, the carburization depth is detected by moving one solenoid coil along the metal surface and detecting changes in magnetic permeability, etc. of the part facing the solenoid coil, so the detection accuracy is not only not very good. , shape of carburized layer・
I can't judge the size.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a detection device for a foreign layer inside a safe, which can solve the above-mentioned problems.

[Means and effects for solving the problem] A reference coil facing the base material of the object to be detected, a detection coil that moves relative to the heterogeneous layer, and the frequency of the alternating current given to each coil is made variable. a mechanism, a means for detecting the output difference of each coil and a frequency at which the output difference is maximum, and a means for outputting the shape of the heterogeneous layer based on the frequency and the relative position. This is a layer detection device, which allows the shape of a heterogeneous layer of an object to be detected to be detected with high accuracy.

〔Example〕

FIG. 1 is an explanatory diagram of the device, in which a base 1 has a workpiece holder 2.
is provided to be able to freely reciprocate in the X direction, and a reference coil 4 and a detection coil 5 are arranged at intervals in the X direction on the main body 3 facing the workpiece pedestal 2. 2
is reciprocated in the X direction by the motor 6.

For example, a feed screw rod is rotated by the motor 6, and the feed rod is screwed into a nut member provided on the workpiece pedestal 2.

A workpiece 7, which is an object to be detected having a heterogeneous layer, is set on the workpiece pedestal 2, and this workpiece 7 is mounted on two plates 7, for example.
A and 7a are spot welded using a laser beam, and the shape and size of the welded portion A is detected.

The control/arithmetic circuit 10 sends a drive signal to the motor drive 11, which causes the motor 6 to rotate, so that the control/arithmetic circuit 10 can sense the movement stroke of the workpiece pedestal 2.

For example, the rotation of the motor 6 is detected by an encoder, a coder, a potentiometer, etc. and sent to the control/arithmetic circuit 10,
The motor 6 may be a step motor and the number of pulses sent to the step motor may be adjusted. , By doing this, the reference coil 4 and the detection coil 5
This allows the control/arithmetic circuit 10 to detect the stroke of movement of the workpiece 7 with respect to the different layer of the workpiece 7, that is, the relative position.

Note that the main body 3 may be reciprocated in the X direction by the motor 6, and the workpiece pedestal 2 may be kept stationary.

The control/arithmetic circuit 10 sends a signal to the sweep circuit 12, the sweep circuit 12 sends a variable signal to the frequency scattering oscillator 13, and AC power of different frequencies is sent to the reference coil 4 and detection coil 5.

The output sides of the reference coil 4 and the detection coil 5 are sent to a phase detection circuit 14 to detect the phase shift as a voltage, and the detected voltage is amplified by a differential amplifier 15 and sent to a peak value hold circuit 16. The data storage circuit 17 holds the peak voltage value and stores the frequency when the voltage is at its peak value.
The stored frequency is sent to the control/arithmetic circuit 10 to determine the depth of the weld A from the frequency, and the depth and the relative position are combined to determine the heterogeneous layer in the safe, in this case the weld A. The shape and size are displayed on the display section 18.

In order to determine the welding depth from the frequency, the relationship between the frequency and the welding depth can be determined in advance through experiments and converted into data, and the converted value can be stored in the memory section of the control/arithmetic circuit 10, or by theoretical calculation. What is necessary is to provide calculation means for converting the frequency into the weld depth.

Next, the detection principle will be explained.

The reference coil 4 is always located at the base material 7b of the workpiece 7, and the detection coil 5 is configured to move relatively over the base material 7b and the welding part A.

When the reference coil 4 and the detection coil 5 are excited by applying an alternating current (alternating current) with a predetermined frequency, an eddy current is generated, and a magnetic flux proportional to the depth at which the eddy current penetrates into the workpiece 7 is generated. The depth of penetration of the eddy current into the workpiece 7 is determined by the magnetic permeability and conductivity values of the workpiece 7 and the frequency.

In other words, based on the eddy current flaw detection principle, δ-1/J-yrx7TXσ.

However, δ is penetration depth, f is frequency, μ is magnetic permeability, and σ is electrical conductivity.

Because of this, when the reference coil 4 and the detection coil 5 are facing the base material 7b of the workpiece 7 as shown in FIG. 2, the penetration depth is the same, so the reference coil 4 and the detection coil 5 are The magnitude of the magnetic flux of the coil 5 is the same, and the difference in output between the two is zero.

As shown in FIG. 3, the reference coil 4 is connected to the base material 7b of the workpiece 7.
When the detection coil 5 faces the weld A, the penetration depth differs due to the difference in magnetic permeability and conductivity between the base metal 7b and the weld A, and a difference occurs in the output between the two.

Here, according to the above formula, if the frequency is changed, the penetration depth will be different, so if the frequency of the alternating current to the reference coil 4 and the detection coil 5 is changed at the same timing in the state shown in FIG. The output difference of the detection coil 5 is different,
The output difference is maximum at a certain frequency.

Therefore, the frequency at which the output difference is maximum can be detected, and the depth of the weld A can be detected based on that frequency as described above.

For example, when the depth and distance of the welded part A shown in Fig. 4 were actually measured, the results were as shown in Fig. 5, and the output difference between the reference coil 4 and the detection coil 5 at this time was the maximum. The frequency and penetration depth are as shown in Figure 6.

Thereby, the frequency at which the output difference between the reference coil 4 and the detection coil 5 becomes maximum can be detected, and the welding depth can be detected based on that frequency.

Next, the operation of detecting the shape and size of the welded portion A of the workpiece 7 using the apparatus shown in FIG. 1 will be explained.

The motor 6 moves the work pedestal 2 in the X direction and moves the work 7 with respect to the reference coil 4 and the detection coil 5 at every predetermined stroke, and each time the output difference between the reference coil 4 and the detection coil 5 is measured. Detect.

At this time, when the reference coil 4 and the detection coil 5 are facing the base material 7b of the workpiece 7, the output difference is zero,
When the detection coil 5 corresponds to the welding part A, a difference in output occurs.

This output difference appears as a phase shift between the input frequency of the alternating current and the detection frequency as shown in FIG.
The signal is amplified and sent to the peak value hold circuit 17.

At the same time, if an output difference occurs, the work pedestal 2 is held still and the sweep circuit 12 sends a variable signal to the frequency oscillator 13 to make the frequency variable, and the frequency when the voltage is maximum is set to the peak value hold circuit. 16 and stored in the data storage circuit 17.

When the above operations are completed, the workpiece pedestal 2 is again moved by a predetermined stroke, and the frequency is made variable as described above, and the frequency at which the detected voltage is maximum is stored.

In this way, the frequency at which the detected voltage for each predetermined stroke is maximum is detected and stored, and when the detected voltage becomes zero, the motor 6 is stopped and the workpiece 7 is stopped.

After this, the welding depth is determined based on the frequency mentioned above,
Based on the welding depth and the stroke of the workpiece 7, the shape and size of the welded part A are displayed as shown in FIG. 8, for example.

Next, a specific example will be explained.

Two plates 7a made of carbon steel with a thickness of 0.5 mm.

7a was spot welded using a laser beam.

As a result, when the workpiece 7 is well welded as shown in FIG. 9(a), the display on the display section 18 becomes as shown in FIG. 10(a), and when the workpiece 7 is welded successfully as shown in FIG. 9(b), 10th in case of
As shown in Fig. (b), it is possible to judge whether the welding is good or bad on the display section 18.

When determining the quality of the heat-treated layer B of a workpiece whose surface has been annularly heat-treated on the cylinder rod 20 as shown in FIG. Since it can be displayed as follows, it is possible to judge whether the heat treatment is good or bad.

FIG. 13 shows a second embodiment, in which a different layer width detection sensor 30 is provided between the reference coil 4 and the detection coil 5.

The heterogeneous layer width detection sensor 30, as shown in FIG. The change in the magnetic flux 33 due to the difference in magnetic permeability between the base material 7b of the workpiece 7 and the welded part A is detected as a voltage change of the magnetoresistive element 31, and the voltage change is detected by the amplifier 34. control/
It is designed to be input to the arithmetic circuit 10.

With this configuration, the width of the foreign layer such as the welded part of the workpiece 7 can be detected by the foreign layer width detection sensor 30, so that the width of the foreign layer is smaller than the diameter of the detection coil 5, and the width of the foreign layer is smaller than the diameter of the detection coil 5. Even when it is difficult to detect the width of a heterogeneous layer using the coil 5 as described above, the heterogeneous layer width detection sensor 30 can be used.
The width of the heterogeneous layer can be detected, and the shape and size can be detected.

In addition, when the welding method and heat treatment method are determined, the shape (depth and width ratio) of the heterogeneous layer may be constant, and in this case, the heterogeneous layer width detection sensor 30 detects the heterogeneous layer width. Depth can be determined by detecting.

Alternatively, a displacement meter may be provided to detect the distortion of the workpiece 7, and the shape of the detected heterogeneous layer may be corrected based on the distortion of the workpiece 7 detected by the deformation needle.

In this way, even if the workpiece 7 is thin and distorted due to welding or heat treatment, the shape of the foreign layer can be detected accurately.

According to each of the above embodiments, the workpiece pedestal 2 or the main body 3 is moved in the X direction, but it may be moved in the X direction and the Y direction.

〔Effect of the invention〕

(1) The penetration depth is detected based on the difference between the output of the reference coil 4 facing the base material of the object to be detected and the output of the detection coil 5 facing the foreign layer. Since the shape of the foreign layer is detected based on the relative position of the detection coil 5, the shape of the foreign layer can be detected with high accuracy.

Furthermore, since each coil is not in contact with the object to be detected, it is unlikely to be affected by heat.

2) Even if the diameter of the foreign layer is smaller than the diameter of the detection coil 5, the width of the foreign layer can be detected by the foreign width detection sensor 30, so the shape of the foreign layer can be detected accurately.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention; Fig. 1 is an explanatory diagram of the entire device, Figs. 2 and 3 are explanatory diagrams of the detection operation, Fig. 4 is an enlarged view of the welded part, and Fig. 5 is the welding depth. Figure 6 is a diagram showing the relationship between penetration depth and frequency, Figure 7 is an explanatory diagram of output difference detection, Figure 8 is a front view of a display example, Figure 9 (a), (
b) is a welding state diagram, FIGS. 10(a) and (b) are illustrations of the display state, FIG. 11 is a perspective view of the cylinder rod, FIG. 12 is an illustration of the detection display state, and FIG. 13 is an illustration of the display state. FIG. 14 is an explanatory diagram of the entire apparatus of the second embodiment, and FIG. 14 is an explanatory diagram of the heterogeneous layer width detection sensor.

Claims (2)

[Claims] (1) A reference coil 4 facing a base material of a metal object to be detected having a heterogeneous layer, a detection coil 5 that moves relative to the heterogeneous layer, and a detection coil 5 relative to the heterogeneous layer. a mechanism for applying an alternating current to the reference coil 4 and the detection coil 5 and varying the frequency; and an output of the reference coil 4 and the detection coil 5. An apparatus for detecting a heterogeneous layer in metal, comprising: means for storing a frequency when the difference is maximum; and means for calculating and outputting the shape of the heterogeneous layer based on the frequency and the relative position. (2) The apparatus for detecting a heterogeneous layer in a metal according to claim 1, wherein the heterogeneous layer width detection sensor 30 including a magnetoresistive element 31 and a permanent magnet 32 is provided movably relative to the heterogeneous layer.