JPH09178710A - Flaw detecting element for eddy current flaw detection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily detect the direction of a detect being present in a metal to-be-tested and obtain much information on the defect for accurately repairing and drastically reducing period. SOLUTION: In a flaw detecting element, two square coils 2 and 3 which cross at right angle are provided inside an excitation coil 103. By constituting the flaw detecting element as in the above, eddy current in the metal to-be-tested 110 is generated concentrically with the excitation coil 103 and the influence of eddy current which changes depending on the direction of defect can occur only in either detection coil 2 or 3 determined by the direction of defect. Therefore, by configuring two detection coils so that each outputs the difference each other, the direction where a signal is generated becomes opposite to the direction of defect, thus judging the direction of defect from that (polarity) of the detected signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flaw detector for an eddy current flaw detector which confirms the soundness of, for example, a metal flat plate.

[0002]

2. Description of the Related Art An eddy current flaw detector is generally used as a device for confirming the soundness of a metal flat plate or the like. This conventional eddy current flaw detector has a detection coil 1 as shown in FIG.
01, a dummy coil 102, an exciting coil 103, a flaw detector 120 having a display screen 121, and a connection cable 130 connecting the two.

FIG. 6 shows an electrical connection state of the eddy current flaw detector having such a structure. In FIG. 5 and FIG. 6, 110 is a target metal to be inspected, 111 is a defect near the surface of the metal to be inspected, 131 is a magnetic field generated by the exciting coil 103, and 132 is metal due to the magnetic field 131 generated by the exciting coil 103. Eddy current flowing in the body, 133 is a magnetic field generated by the eddy current 132, 141 is the flaw detector 12
0 is an internal oscillator.

A connection cable 130 is connected to the exciting coil 103.
, An alternating current having a constant amplitude and a constant frequency flows from the oscillator 141. When an alternating current flows through the exciting coil 103, the magnetic field 13
1 occurs. This magnetic field 131 is applied to the detection coil 101,
An eddy current 132 is generated in the subject metal 110 by interlinking with the dummy coil 102 and the subject metal 110. This eddy current 132 is generated when the metal 110 is healthy.
It occurs concentrically with 03. The eddy current 132 also generates a magnetic field 133, and this magnetic field 133 is also generated by the detection coil 1
Link with 01.

By interlinking these alternating magnetic fields 131 and 133 with the detection coil 101, the detection coil 10
An alternating voltage is induced in 1. Since the alternating magnetic field 131 interlinks with the dummy coil 102, an alternating voltage is also induced in the dummy coil 102. The detection coil 101 and the dummy coil 102 form a bridge circuit inside the flaw detector 120, and when the flaw detector is located in the sound portion of the object metal 110,
The voltages induced in the detection coil 101 and the dummy coil 102 cancel each other out and are adjusted so that no output is generated.

In FIG. 5, an arrow 151 indicates the scanning direction X of the flaw detector, and an arrow 152 indicates the scanning direction Y of the flaw detector.
The flaw detector is scanned on the surface of the subject in the directions of these arrows X and Y to detect the flaw of the subject metal 110.

When a defect 111 is present in the object metal 110, the flow of the eddy current 132 changes as compared with the case where there is no defect. At this time, the magnetic field 13 generated by the eddy current 132
3 also changes as compared with the case where there is no defect, the voltage induced in the detection coil 101 also changes, and this change in the voltage is processed by the flaw detector 120 and displayed on the screen 121 of the flaw detector 120. When actually applied, the flaw detector is connected to the object metal 11.
The surface 0 is scanned in the directions of arrows 151 and 152, and a signal waveform 123 appearing on the screen 121 of the flaw detector 120 at this time, that is, a signal waveform 123 obtained by processing a voltage induced in the detection coil 101 is observed. Flaw detector is object metal 1
10, the voltage induced in the detection coil 101 and the dummy coil 102 is adjusted so as to cancel each other out, so that the signal waveform 123 on the screen 121 of the flaw detector 120 has a dot. And it is determined that there is no defect.

Therefore, the screen 121 of the flaw detector 120 is moved while moving the flaw detector on the subject metal 110 as described above.
By observing, the presence or absence of a defect can be determined, and the soundness of the test metal 110 can be known.

[0009]

However, in the above-described flaw detector using the conventional flaw detector, since the eddy current in the metal to be tested flows concentrically with the exciting coil of the flaw detector, a signal due to the defect is not detected. There is a problem that the defect occurs regardless of the direction and the direction of the defect is not known.

The present invention has been made in order to solve the above problems, and can easily detect the direction of a defect existing in a metal to be inspected, obtain a lot of information about the defect, and perform accurate repair. It is an object of the present invention to provide a flaw detector for an eddy current flaw detector which enables a significant reduction in period.

[0011]

A flaw detector for an eddy current flaw detector according to the present invention comprises an exciting coil excited by a signal from an eddy current flaw detector, and a first coil arranged inside the exciting coil at a right angle. A first and a second detection coil, and when the first and the second detection coils are located in a sound portion of the metal to be inspected, the magnetic field due to the eddy current generated in the metal to be inspected is evenly received, When the first and second detection coils scan over the defect of the metal to be inspected, the first or second detection coil induced voltage is generated corresponding to the direction of the defect. And

(Operation) When the metal to be inspected is scanned by the flaw detector, an eddy current generated by the exciting coil in the metal to be inspected is generated concentrically with the exciting coil. When there is a defect on the metal to be inspected, the effect of the eddy current that changes depending on the direction of the defect occurs only in one detection coil determined by the direction of the defect. Therefore, it becomes possible to determine the defect direction by the direction (polarity) of the signal induced in the first and second detection coils.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram of an eddy current inspection device according to an embodiment of the present invention. In FIG. 1, 10
Reference numeral 3 denotes an exciting coil of the flaw detector, which generates an alternating magnetic field by the alternating current from the flaw detector 120. Exciting coil 10
A first detection coil 2 and a second detection coil 3, which are rectangular, for example, are arranged inside 3 so that they are orthogonal to each other. In the detection coils 2 and 3, the voltage induced by the magnetic field of the exciting coil 103 and the change of the magnetic field due to the change of the eddy current in the subject metal 110 changes. The induced voltage of the detection coils 2 and 3 is sent to the flaw detector 120, and the difference between the induced voltages is processed and displayed as a signal waveform 52 on the screen 121.

Reference numeral 120 is the same eddy current flaw detector as in the conventional flaw detector, and 130 is a cable for connecting between the flaw detector 120 and the coil. 111 is the subject metal 110
132 is an eddy current flowing through the metal 110 to be inspected, 133 is a magnetic field generated by the eddy current, arrow 151 is the scanning direction X of the flaw detector, and arrow 152 is the scanning direction Y of the flaw detector.

Next, the operation of the above embodiment will be described with reference to FIGS. 2, 3 and 4. FIG. 2 is a diagram for explaining the operation of the flaw detector according to the present invention. FIG. 3 is a diagram for explaining the signal waveform of the same flaw detector, and FIG.
(B) is a signal waveform when the flaw passes through the defect. In FIG. 3, 125 is a screen 121 of the flaw detector 120.
The signal waveform when there is no defect observed in 1., 126 is the signal waveform when the flaw crosses the defect, 55 is the left peak point of the signal waveform, and 56 is the right peak point of the signal waveform.

FIG. 4 is a diagram for explaining the direction of the defect and the direction of the signal waveform. In FIG. 4A, reference numeral 61 indicates that the first detection coil 2 crosses the defect in the direction parallel to the coil 2. In the case of the signal waveform, reference numeral 62 indicates the direction in which the signal waveform 61 starts to be generated. Reference numeral 63 in FIG. 6B shows a signal waveform when the second detection coil 3 crosses a defect in a direction parallel to the coil 3, and reference numeral 64 shows a direction in which the signal waveform 63 starts to be generated.

FIG. 2 shows how the flow of the eddy current 132 flowing in the metal 110 under test is affected by the defect 111,
The change of the induced voltage of the 1st detection coil 2 and the 2nd detection coil 3 which accompanies it is shown.

FIG. 2A shows an eddy current and a magnetic field generated by the eddy current when the flaw detector is provided on a sound metal body. When there is a flaw detector on a sound metal body, the eddy current 132 flows in a perfect circle, and the magnetic field 13 generated by the eddy current is generated.
3 are evenly generated around the detection coils 2 and 3, and the magnetic field 133 generated by these eddy currents is such that the left and right magnetic fields interlink with the respective detection coils 2 and 3 in opposite directions. Therefore, the voltages induced in the respective detection coils 2 and 3 do not cancel each other and do not occur. Therefore, no voltage is induced in each of the detection coils 2 and 3 even if the flaw detector scans the sound part of the subject metal 110. If there is no induced voltage like this,
Even if the signal processing is performed inside the flaw detector 120, the signal waveform 125 is displayed at the origin of the screen 121 of the flaw detector 120 as shown in FIG.

FIG. 2B shows an example in which the defect 111 approaches the right side of the detection coil 2. In this case, the eddy current 132 flowing in the metal body does not form a perfect circle as shown in the figure, and the flow becomes parallel to the defect 111 in the vicinity of the defect 111. Therefore, the magnetic field 133 generated by the eddy current 132
Is not even on the left and right with respect to the detection coil 2, and the magnetic field on the right side of the detection coil 2 strongly interlinks with the detection coil 2 and induces a voltage of constant polarity in the detection coil 2.

Although the detection coil 3 is omitted in FIGS. 2B, 2C and 2D, the detection coil 2 is shown in FIG.
The case where the defect 111 exists in the direction parallel to is described. In this case, the magnetic field generated by the eddy current generated by the change in the flow of the eddy current due to the existence of the defect 111 is equal to the left and right with respect to the detection coil 3. This is because the voltage is not induced.

As shown in FIG. 2B, when the defect 111 approaches in the direction parallel to the detection coil 2, a voltage having a constant polarity is induced in the detection coil 2. At this time, no voltage is induced in the detection coil 3. The voltages induced in the detection coil 2 and the detection coil 3 are subtracted from each other inside the flaw detector 120. However, since the voltage is not induced in the detection coil 3, the voltage itself induced in the detection coil 2 is subjected to signal processing and flaw detection is performed. A shake occurs in the signal waveform 126 on the screen 121 of the container 120.

FIG. 2C shows the detection coil 2 and the coil 2.
It is a figure explaining the case where the center of the defect 111 parallel to is in agreement. In this case, in order to simplify the drawing, the detection coil 2
Was omitted. As shown in FIG. 2C, the detection coil 2
And the center of the defect 111 coincide with each other, the eddy current 132 becomes an ellipse, and the magnetic field 133 generated by the eddy current 132 is generated.
Unlike in the case of FIG. 2A, the periphery is not uniform. However, this magnetic field 133 becomes equal to the left and right with respect to the detection coil 2, and the left and right magnetic fields interlink with the detection coil 2 in opposite directions. Therefore, the induced voltages of the detection coil 2 cancel each other out and no output is generated. Therefore,
In the case of FIG. 2C, no voltage is induced in the detection coils 2 and 3, and no voltage is generated by subtraction of these, and even if this is processed by the internal circuit of the flaw detector 120, the signal waveform There is no wobbling. In this case, the signal waveform is the flaw detector 120.
Is displayed on the origin of the screen 121.

Contrary to FIG. 2B, FIG. 2D shows an example in which the defect 111 is close to the left side of the detection coil 2. In this case, the eddy current 132 is opposite to that in FIG.
It becomes parallel to the defect 111 on the left side. Therefore, the detection coil 2
The magnetic field 133 on the left side of is strongly interlinked with the detection coil 2 and a voltage is induced. In this case, the direction in which the magnetic field 133 interlinks with the detection coil 2 is opposite to that in FIG. 2B, and the polarity of the voltage induced by the detection coil 2 is opposite to that in FIG. 2B. The induced voltage of the opposite polarity is subjected to signal processing in the internal circuit of the flaw detector 120 and appears as a shake on the screen 121 of the flaw detector 120. In this case, the shake is opposite to that in the case of FIG. 2B.

Now, the defect 11 is present in the direction parallel to the detection coil 2.
1 exists and when the detection coil 2 moves in the direction of arrow 151 of FIG.
As shown in FIG. 2B, the detection coil 2 is approached from the right side, then the centers of the detection coil 2 and the defect 111 are aligned as shown in FIG. 2C, and then the detection coil 2 is detected as shown in FIG. 2D. The defect 111 moves away from the coil 2 from the left side. In this case, as described above, the voltage is induced in FIG. 2B and FIG. 2D, but the polarity of the induced voltage is opposite, and this is processed by the internal circuit of the flaw detector 120. On the screen 121 of the flaw detector 120, the shake appears opposite to that in FIGS. 2B and 2D.

That is, when the flaw detector is scanned across the detection coil 2, as shown in FIG. 3B, the defect 111 approaches the detection coil 2 from the origin, which is in a sound state and in which no shake occurs. By doing so, the signal waveform swings in the direction of the peak point 55 on the left side of the signal waveform, and the defect 111 coincides with the detection coil 2 to return to the origin where no shake occurs, and then the defect 111 moves to the left side of the detection coil 2. When present, the signal waveform is generated such that it swings in the direction of the peak point 56 on the right side of the signal waveform, and when the defect 111 moves away from the detection coil 2, the defect returns to the origin where there is no vibration. That is, when the flaw detector traverses the defect 111 in the direction parallel to the detection coil 2, the target point of FIG.
The signal waveform 126 as shown in (b) is displayed on the screen 1 of the flaw detector 120.
Appears on 21.

As described above, this signal waveform 126
The direction of has a constant relationship with the direction in which the flaw moves when other conditions are constant. The same applies to the case where there is a defect in the direction parallel to the second detection coil 3, and when the detection coil 3 is scanned across the defect in the direction parallel to the coil 3, FIG. A signal waveform similar to that shown in () is generated.

However, as described above, since the voltage induced in the detection coil 2 and the voltage induced in the detection coil 3 are subtracted from each other, the detection coil 3 crosses a defect in a direction parallel to the coil 3. The signal waveform when scanned by
It appears in the opposite polarity (in the opposite direction) when the detection coil 2 is scanned across a defect in a direction parallel to the coil 2 as in FIG.

That is, when the detection coil 2 is scanned across a defect in a direction parallel to the coil 2 as shown in FIG. 4A, a signal waveform 61 appears in a direction 62 in which a signal starts to be generated. . Further, as shown in FIG. 4B, when the detection coil 3 is scanned across a defect in a direction parallel to the coil 3, a signal waveform 63 appears in a direction 64 in which a signal starts to be generated.

As described above, according to the present invention, the direction of the signal waveform obtained differs depending on the direction of the defect, and the direction of the defect can be known by discriminating the difference in the direction of the signal waveform.

[0030]

As described above in detail, according to the present invention, it becomes possible to easily detect the direction of the defect existing in the metal to be inspected, and the information for the repair necessary in the next step can be obtained. As a result, the number of repairs can be accurately performed, and the repair period can be significantly shortened.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a flaw detector and an eddy current flaw detector according to an embodiment of the present invention.

FIG. 2 is a view for explaining the operation of the flaw detector in the embodiment.

FIG. 3 is an exemplary view for explaining a signal waveform of the flaw detector in the embodiment.

FIG. 4 is a view for explaining a direction of a defect and a direction of a signal waveform in the embodiment.

FIG. 5 is an explanatory view showing a conventional flaw detector and an eddy current flaw detector.

FIG. 6 is a configuration diagram of a conventional flaw detector and eddy current flaw detector.

[Explanation of symbols]

 2 1st detection coil 3 2nd detection coil 52 Signal waveform 55 Left peak point of signal waveform 56 Right peak point of signal waveform 103 Excitation coil 110 Specimen metal 125 Signal waveform when there is no defect 126 Signal waveform when a defect is crossed 120 Flaw detector 121 Flaw detector screen 130 Connection cable 132 Eddy current flowing in a metal body 133 Magnetic field generated by eddy current

Claims (1)

[Claims] 1. An exciting coil that is excited by a signal from an eddy current flaw detector, and first and second detection coils that are arranged orthogonal to each other inside the exciting coil.
When the second detection coil is located in the sound part of the object metal, the magnetic field due to the eddy current generated in the object metal is evenly received, and the first and second detection coils are defective in the object metal. A flaw detector for an eddy current flaw detector, characterized in that, when scanning above, the first or second detection coil induced voltage is generated corresponding to the direction of the defect.