JP2001264299A - Metal plate flaw detecting probe - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a metal plate flaw detecting probe widening a detection area for easily detecting a flaw over a wide range on the front and back faces and in the inside of a metal plate. SOLUTION: This flaw detecting probe 10 performing scanning along the surface of the metal plate 30 as a specimen is constructed so as to include a primary coil 12 and a pair of secondary coils 13, 14. As to a thin long coil former 11 arranged parallelly to the surface of the metal plate, the primary coil 12 is wound on a face facing the metal plate surface and on a face on the opposite side in the longitudinal direction so as to be excited by exciting current at a predetermined frequency. Between the metal plate surface and the primary coil, the secondary coils 13, 14 are wound around a shaft vertical to the metal plate surface adjacently to each other so as to be extended in the longitudinal direction of the primary coil and differentially connected to each other.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting flaws generated on the front surface, the back surface, and the inside of a metal product such as a flat metal plate, a metal plate having a curvature, or a metal body having the same cross-sectional shape and being continuous. The present invention relates to a metal plate flaw detection probe for inspection.

[0002]

2. Description of the Related Art For example, there is known a method of forming a pool by laying sand as a foundation of the pool and arranging a bottom plate made of an aluminum plate. In such a pool, an aluminum plate used as a bottom plate may be corroded by various substances contained in sand. When the aluminum plate is corroded, if left as it is, a hole is opened due to the corrosion and water leakage occurs. Here, the above-described corrosion cannot be observed from the front surface because it occurs from the back surface of the aluminum plate. On the other hand, for example, a probe for flaw detection as shown in FIG. 11 is used to search for thinning due to corrosion, scratches, or the like in the blade of an aircraft turbo engine or the aluminum wheel of an automobile.

[0003] In FIG. 11, a flaw detection probe 1 has a primary coil 2 disposed in an annular shape facing a metal plate (not shown) as a test object, and two cores inside the primary coil 2. 3 and a pair of secondary coils 4 wound around each other, and the two secondary coils 4 are differentially connected to each other.

According to the flaw detection probe 1 having such a configuration, when an exciting current having a predetermined frequency is applied to the primary coil 2, the magnetic field generated in the primary coil 2 acts on the metal plate to vortex the metal plate. An electric current is generated. Then, due to the eddy current, a current is generated in the secondary coil 4 by mutual induction.

In such a state, when the flaw detection probe 1 is scanned along the surface of the metal plate, the magnetic field generated by the primary coil 2 does not change if the metal plate does not lose its thickness due to corrosion, scratches, etc. The current generated in the secondary coil 4 is constant, but when the flaw detection probe 1 is applied to the thinned portion of the metal plate, the eddy current bypasses the thinned portion, and the eddy current changes. Thereby, the voltage generated in the secondary coil 4 changes. Therefore, the voltage output from the two secondary coils 4 that are differentially connected to each other fluctuates, and the fluctuation is detected by an appropriate means, whereby the surface, the back surface, or the inside of the metal plate as the test object is detected. Corrosion, scratches, etc. can be found.

[0006]

However, the flaw detection probe 1 having such a configuration is configured as a so-called pen type, and its detection range is very small. Therefore, it takes a lot of time to perform a wide range of flaw detection.

In view of the above, the present invention provides a metal plate flaw detection probe in which the detection range is enlarged so that flaw detection of a wide area on the front, back and inside of the metal plate can be easily performed. It is intended to be.

[0008]

According to the present invention, there is provided a flaw detection probe scanned along the surface of a metal plate as a test object, the probe being provided in parallel with the surface of the metal plate. The primary winding is wound in the longitudinal direction on the surface facing the surface of the metal plate and on the surface opposite to the surface of the metal plate, and is excited by an exciting current of a predetermined frequency, and between the surface of the metal plate and the primary coil. And at least one pair of secondary coils that are wound so as to extend in the longitudinal direction of the primary coil adjacent to each other around an axis perpendicular to the surface of the metal plate and that are differentially connected to each other. This is achieved by a metal plate flaw detection probe characterized in that:

[0009] In the metal plate flaw detection probe according to the present invention, the winding frame is preferably flat.

In the metal plate flaw detecting probe according to the present invention, preferably, the winding frame has a length L corresponding to a right-angled corner of the metal plate.
The primary coil and the secondary coil are provided on two adjacent surfaces of the bobbin facing the surface of the metal plate.

In the metal plate flaw detection probe according to the present invention, preferably, the winding frame is formed in an appropriate shape corresponding to the surface shape of the metal plate, and the primary coil and the secondary coil are formed on the surface of the metal plate. Are provided on the surface having the above-mentioned shape of the bobbin opposed to.

According to the above configuration, the magnetic field generated by the exciting current of a predetermined frequency flowing through the primary coil acts on the metal plate as the object to be tested, and an eddy current is generated in the metal plate. And corrosion on the front, back or inside of the metal plate,
If wall thinning such as a scratch occurs, the eddy current bypasses the thinned portion, and the eddy current changes due to the wall thinning. As a result, the voltage generated by the mutual induction in the secondary coil also changes, so that the occurrence of thinning can be detected by detecting a change in the output voltage of the secondary coil.

When the secondary coil is elongated in the longitudinal direction of the surface of the metal plate, the thinning is detected while scanning the metal plate flaw detection probe in a direction perpendicular to this direction. Accordingly, it is possible to detect the thinning with the width of the effective length in the longitudinal direction of the secondary coil.
Therefore, the detection area by one scan is significantly increased, and the inspection efficiency is greatly improved.

If the winding form is flat, the primary coil and the secondary coil extend long in the longitudinal direction of the winding form, so that a flat metal plate as a test object can be efficiently inspected. it can.

The bobbin is formed in an L-shape corresponding to a right-angled corner of the metal plate, and the primary coil and the secondary coil are formed by two adjacent surfaces of the bobbin facing the surface of the metal plate. When one of the two surfaces is brought into contact with the surface of the metal plate as the test object, the flat metal body can be inspected relatively efficiently, and By contacting the corners of the two surfaces with respect to the bent portion inside the metal plate as a body, flaw detection can be reliably performed up to the corners.

Further, the winding frame is formed in an appropriate shape corresponding to the surface shape of the metal plate, and the primary coil and the secondary coil have the same shape of the winding frame facing the surface of the metal plate. When provided on a surface having a metal plate, the surface of the winding frame is brought into contact with the surface of a metal plate to be tested, so that flaw detection can be performed over the entire range of a metal body having various shapes that are not flat. It can be performed relatively efficiently and reliably.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings. FIG. 1 shows a first embodiment of a metal plate flaw detection probe according to the present invention. In FIG. 1, a metal plate flaw detection probe 10 is disposed below a primary and elongated coil 11, a primary coil 12 wound on an upper surface and a lower surface with respect to the longitudinal direction of the reel 11, and a flat elongated winding frame 11. The pair of secondary coils 13 and 14, the protection plate 15 disposed below the secondary coils 13 and 14, the winding frame 11, the primary coil 12, the secondary coils 13 and 14, and the protection plate 15 It comprises a case 16 formed so as to cover from above, and a connector 17 attached to the outer surface of the case 16.

The winding frame 11 is made of, for example, a resin material, a metal, or a magnetic material, and has a central coil winding portion 11a in the width direction (vertical direction in FIG. 1A) and flange portions 11b on both sides thereof. , 11c. The size of the coil winding portion 11a is, for example, a length L1 of 80 mm,
The width W1 is 25 mm and the thickness D1 is 10 mm.

The primary coil 12 is an exciting coil. For example, a copper wire having a wire diameter of 0.35 mm is used, and is wound on the upper surface and the lower surface in the longitudinal direction of the bobbin 11 by 66 × 16 turns, for example. I have. Thereby, the primary coil 12
Has a length L2 of 92 mm and a thickness D2 of 22 mm in the illustrated case. Note that the width of the primary coil 12 is the same as the width W1 of the coil winding portion 11a of the winding frame 11 (2
5 mm).

The secondary coils 13 and 14 are detection coils, each having a wire diameter of 0.1, for example, as shown in FIG.
It is wound flat by, for example, 10 × 15 turns using a copper wire of 1 mm and attached to the lower surface of the primary coil 12 with an adhesive or the like. Thereby, each secondary coil 1
Each of 3, 3 has an outer length L3 of 66 mm, an inner length L4 of 60 mm, an outer width W3 of 8 mm, and an inner width W4 of 2 mm. The secondary coils 13, 1
The number of turns of 4 is not limited to the above-mentioned numerical value, and is appropriately selected so that its impedance becomes, for example, about 50Ω. Further, the secondary coils 13, 14
Are differentially connected to each other as described later.

The protective plate 15 is made of, for example, a high-hardness resin material or a stainless steel plate. The protective plate 15 protects the primary coil 12 and the secondary coils 13 and 14 and, when in use, is connected to the secondary coils 13 and 14 under test. Metal plate 30 as body
Is kept constant, and the thickness D3 thereof is, for example, 1 mm.

The connector 17 supplies an exciting current to the primary coil 12 and outputs a detection current from the secondary coils 13 and 14 to the outside.

The metal plate flaw detection probe 10 according to the present invention is configured as described above. In use, as shown in FIG. 3, the primary coil 12 supplies the exciting current to the power source 2 as shown in FIG.
Connected to 0. Further, the secondary coils 13 and 14 are differentially connected to each other, that is, connected to each other at one end and grounded, and the other ends are respectively connected to input terminals of the phase detector 22 via the adder 21. This phase detector 22
The detection signal from each of the secondary coils 13 and 14 is phase-detected to output an X component (H output) and a Y component (V output). In this case, the X component and the Y component output by adjusting the phase after the phase detection or the ratio between them is
It is a component that indicates the size and depth of flaws and corrosion generated on the metal plate 30. The voltage changes due to flaws described below all refer to voltage changes at the H output (X component) and the V output (Y component).

The metal plate flaw detection probe 10 has a protective plate 15, which is the lower surface thereof, brought into contact with the metal plate 30 at the time of flaw detection, for example, as shown by a chain line in FIG. Thus, the secondary coils 13 and 14 are maintained at a predetermined distance from the metal plate 30, for example, 1 mm.

Then, the metal plate 30 is detected by scanning the metal plate flaw detection probe 10 with respect to the metal plate 30 in a direction perpendicular to the longitudinal direction. At this time, the magnetic field generated by the primary coil 12 acts on the metal plate 30 located thereunder, and an eddy current is generated in the metal plate 30.
Then, due to the eddy current flowing through the metal plate 30, a voltage is generated in the secondary coils 13, 14 by mutual induction. As a result, the voltages generated in the secondary coils 13 and 14 are input to the phase detector 22 via the adder 21 as detection signals, and the H output (X component) and the V output (Y
Component) is output.

Here, when the metal plate 30 is not thinned, the above-described voltage fluctuations of the H output (X component) and the V output (Y component) hardly occur. On the other hand, the metal plate 30
If the thickness of the secondary coil 1 is reduced, the eddy current is bypassed in the thinned portion and the eddy current changes.
The voltage generated at 3, 3 fluctuates. Therefore, the H output (X component) and the V output (Y component) of the phase detector 22 also fluctuate, and it is possible to detect the presence of the thinned portion.

In this case, since each of the secondary coils 13 and 14 is wound on an elongated winding frame, the entire metal plate flaw detection probe 10 is configured to extend in the longitudinal direction.
For example, in the case of the secondary coils 13 and 14 shown in FIG. 2, the metal plate 3 has an effective length of about 50 mm in the longitudinal direction.
It is possible to detect a thinned portion of zero. Therefore, even when a flaw detection of a relatively large area is performed, the flaw detection efficiency is improved, and the flaw detection can be performed in a short time. In the metal plate flaw detection probe 10, each coil 1
Since the coils 3 and 14 are differentially connected to each other, the noises of the coils 13 and 14 cancel each other, and the detection of the thinned portion, that is, the accuracy of the flaw detection is improved.

Here, for the operation test of the metal plate flaw detection probe 10, an experimental example using a metal plate 31 having various artificially thinned portions processed will be described. This metal plate 31 is shown in FIG.
Various thinning portions as shown in FIG. That is, the metal plate 31 is a 300 mm square aluminum plate having a thickness of 3 mm, and two rows of thinned portions are formed on the back surface thereof. First, in FIG. 4A, thinner portions 32, 33, and 34 are formed in the upper row in order from the left, and thinner portions 35, 36, and 37 are similarly formed in the lower row. ing. Each of the thinned portions 32, 33, and 34 has a diameter of 5 mm.
Are filled with alumina, and the depth from the back surface of the metal plate 31 is
Is selected to be 80%, 50%, and 30% of the thickness. Further, the thinned portion 35 is constituted by a through hole having a diameter of 3 mm on the back side and a diameter of 1.5 mm on the front side. further,
The thinned portions 36 and 37 are each formed by a hole having a diameter of 5 mm, and the depth from the back surface of the metal plate 31 is
The thickness is selected to be 60% and 40% of the thickness of the metal plate 31, respectively.

When flaw detection is performed on the metal plate 31 having the thinned portions 32 to 37 using the present metal plate flaw detection probe 10 at an excitation frequency of 2 kHz, the H output from the phase detector 22 is obtained. (X component) and V output (Y component)
Output voltage changes as shown in the graphs of FIGS. That is, FIG. 5 shows a case where the thinned portions 35 and 32 are scanned in the direction of arrow X1 in FIG.
When scanning the thinned portions 36 and 33 in the direction of the arrow X2 in FIG. 4A and further scanning the thinned portions 37 and 34 in the direction of the arrow X3 in FIG. ) And the variation of the V output (Y component).

According to these graphs, for example, a thickness of 3 mm
In the case of the metal plate 31 made of an aluminum plate, even if it is the thinned portion 37 of 40% from the back surface,
% Corrosion (alumina),
It can be seen that the fluctuations of the H output (X component) and the V output (Y component) can be detected, and it is possible to detect not only the back surface of the metal body but also the front surface and inside flaws. In this case, the ratio (Y / X ratio) of the H output and the V output by the thinned portion 35 in FIG. 5A is represented by a graph shown in FIG. 8 on the XY plane. In that case, each part a to e of the output fluctuation
Respectively correspond to the positions indicated by the same reference numerals in the graph of FIG. 8, and the depth of the flaw of the thinned portion 35 can be evaluated by the inclination (phase difference) of the peak portions b and d. Then, the thinned portions 32 to 3 in each of FIGS.
The respective phase differences (slope) due to 7 have slopes indicated by dotted lines in FIG. Therefore, the actual metal plate 3
In the inspection of 0, 38, the obtained output fluctuation ratio (Y /
X), the flaw can be detected, and the depth of the flaw can be evaluated.

FIG. 9 shows a second embodiment of the metal plate flaw detection probe according to the present invention. In FIG. 9, the metal plate flaw detection probe 40 has substantially the same configuration as the metal plate flaw detection probe 10 shown in FIG. 1. In this case, instead of the winding frame 11, the side facing the metal plate is L-shaped. The primary coil 42 is wound along two L-shaped surfaces 41a and 41b of the winding frame 41, and the primary coil 42 is wound along the two surfaces 41a and 41b. Next coils 43 and 44 are attached.

Here, the winding frame 41 has a center coil winding portion 41c in the width direction and flange portions 41 on both sides thereof.
d, 41e, and the coil winding portion 11a has a cross section of a right-angled isosceles triangle as described above,
The length L5 of the two surfaces 41a and 41b is selected to be, for example, 40 mm. That is, the winding frame 41 is obtained by deforming the lower surface of the above-described winding frame 11 into a mountain shape in the longitudinal direction.

The primary coil 42 has, for example, a wire diameter of 0.3.
Using a 5 mm copper wire, for example, 66 × 16 turns,
It is wound along the longitudinal direction of the winding frame 41, that is, along the two surfaces 41a and 41b. Thus, in the illustrated case, the length L6 of the primary coil 42 in the longitudinal direction on each of the surfaces 41a and 41b is 52 mm. The width of the primary coil 12 is 25 mm, which is the same as the width of the coil winding portion 41c of the winding frame 41.
It is.

The secondary coils 43 and 44 are detection coils. As shown in FIG.
Using a 1 mm copper wire, it is wound flat at, for example, 10 × 15 turns, and then bent at a right angle at the center in the longitudinal direction to form two surfaces of the primary coil 42 (see FIG. 10A). (The left side surface and the lower surface) with an adhesive or the like. Accordingly, each of the secondary coils 43 and 44 has an outer length L7 of 33 mm from the corner, an inner length L8 of 30 mm, an outer width W5 of 8 mm, and an inner width W6 of 2 m.
m.

The metal plate flaw detection probe 4 having the above-described configuration.
According to No. 0, in use, the primary coil 42 is connected to the power supply 20 that supplies the exciting current, and the secondary coils 43 and 44 are differentially connected to each other, in the same manner as in the metal plate flaw detection probe 10 described above. That is, they are connected to each other at one end and grounded, and the other ends are respectively connected to the input terminals of the phase detector 22 via the adder 21.

When the flat metal plate 30 is to be flaw-detected, the metal plate flaw detection probe 40 is configured such that the protection plate 15 corresponding to the two surfaces 41a (or 41b) of the bobbin 41 has the front surface of the metal plate 30. Contacted against. As a result, half of the secondary coils 43 and 44 are separated from the metal plate 30 by a predetermined distance,
For example, it is kept at 1 mm.

The metal plate 30 is detected by scanning the metal plate flaw detection probe 40 with respect to the metal plate 30 in a direction perpendicular to the longitudinal direction. Here, when the metal plate 30 is not thinned, the voltage fluctuation of the H output (X component) and the V output (Y component) from the phase detector 22 hardly occurs. On the other hand, when the metal plate 30 has a reduced thickness, the voltage generated in the secondary coils 43 and 44 fluctuates.
Therefore, the H output (X component) of the phase detector 22 and V
The output (Y component) also fluctuates, and the presence of the thinned portion can be detected.

When flaw detection of a metal plate 38 having a right-angled corner is performed, as shown in FIG. 9A, the metal plate flaw detection probe 40 is provided with two surfaces 41a and 41a of a winding frame 41.
The protection plate 15 corresponding to b is in contact with two mutually perpendicular surfaces 38a and 38b of the metal plate 38, respectively. Thereby, the secondary coils 43 and 44 are maintained at a predetermined distance, for example, 1 mm, from the surfaces 38a and 38b of the metal plate 38, respectively.

The metal plate 38 is scanned by scanning the metal plate flaw detection probe 40 in a direction perpendicular to the longitudinal direction, that is, along the corners of the metal plate 38.
Flaw detection. Here, when the metal plate 38 is not thinned, voltage fluctuation of the H output (X component) and the V output (Y component) from the phase detector 22 hardly occurs. On the other hand, if the metal plate 38 has a reduced thickness, the secondary coil 4
The voltage generated at 3, 44 fluctuates.

Therefore, the H output of the phase detector 22 (X
Component) and the V output (Y component) also fluctuate, and the presence of the thinned portion can be detected. Here, in the case of the metal plate flaw detection probe 10 shown in FIG. 1, the secondary coils 13 and 14 have an ineffective portion on both sides in the longitudinal direction with respect to an effective length capable of detecting a thinned portion. ,
Both ends of the primary coil 12 protrude from both ends of the secondary coils 13 and 14 in the longitudinal direction, and furthermore, the protection plate 15 and the case 16 protrude, so that the metal plate 38 having a corner can be flawed in the corner area. Although it is difficult to perform the inspection, in the case of the metal plate flaw detection probe 40 shown in FIG. 9, it is possible to perform the flaw detection in the corner region of the metal plate 38 having such a corner.

Thus, the metal plate flaw detection probe 4
0, like the metal plate flaw detection probe 10,
A wide range of flaw detection can be performed by the effective length of the secondary coils 43 and 44 in the longitudinal direction, and flaw detection of a corner of the metal plate can also be performed.

In the embodiment described above, the metal plates 30, 31, and 38 to be tested are all aluminum plates having a thickness of 3 mm. However, the present invention is not limited to this. If it is up to the thickness, it is possible to detect flaws on the front surface, the back surface, and the inside thinned portion.
Further, a metal plate or a conductive plate made of another material may be used, and the thickness of the metal plate or the conductive plate is not limited to 3 mm. In these cases, depending on the material and thickness of the metal plate or conductive plate,
The frequency of the exciting current from power supply 20 is appropriately adjusted.

In the above-described embodiment, the winding frames 11, 41, the primary coils 12, 42, the secondary coils 13,
14, 43, 44 and the length of the protection plate 15,
Although the width, thickness, and the like are determined, it is apparent that the width, the thickness, and the like can be appropriately selected without being limited to these dimensions.
Further, in the above-described embodiment, the pair of secondary coils 13, 14 or 43, 44 is provided. However, the present invention is not limited to this, and a plurality of pairs of secondary coils may be provided. When the secondary coils of each pair are connected in parallel or switched, respectively, noise can be reduced by differential connection, and the output voltage can be increased,
The detection accuracy of the thinned portion can be improved.

[0044]

As described above, according to the present invention,
A magnetic field generated by an exciting current of a predetermined frequency flowing through the primary coil acts on a metal plate, which is an object to be tested, to generate an eddy current in the metal plate. If wall thinning such as a flaw occurs, the eddy current bypasses the thinned portion, and the eddy current changes due to the wall thinning. As a result, the voltage generated in the secondary coil due to mutual induction also changes, so that the occurrence of thinning can be detected by detecting a change in the output voltage of the secondary coil.

Here, since the secondary coil is elongated in the longitudinal direction of the surface of the metal plate, if thinning is detected while scanning the metal plate flaw detection probe in a direction perpendicular to this direction, The thinning can be detected based on the width of the effective length in the longitudinal direction of the next coil. Therefore,
The detection area by one scan is significantly increased, and the inspection efficiency is greatly improved.

As described above, according to the present invention, there is provided an extremely excellent metal plate flaw detection probe in which the detection range is enlarged so that flaw detection over a wide area on the back surface of the metal plate can be easily performed. You.

[Brief description of the drawings]

FIG. 1 shows a first embodiment of a metal plate flaw detection probe according to the present invention, in which (A) is a schematic side view, (B) is a schematic bottom view, and (C) is a schematic front view.

FIG. 2 is a bottom view of a secondary coil in the metal plate flaw detection probe of FIG. 1;

FIG. 3 is a circuit diagram showing an electrical configuration of the metal plate flaw detection probe of FIG. 1;

4A and 4B show a metal plate having a thinned portion for an operation test of a metal plate flaw detection probe, wherein FIG. 4A is a schematic bottom view, FIG. 4B is a cross-sectional view taken along line AA, and FIG. It is a B sectional view.

5 is a graph when the metal plate of FIG. 4 is scanned in the X1 direction by the metal plate flaw detection probe of FIG. 1 to detect a flaw,
(A) shows the V output and (B) shows the H output voltage change.

6A and 6B are graphs showing a V output and a H output voltage change, respectively, when the metal plate of FIG. 4 is scanned in the X2 direction by the metal plate flaw detection probe of FIG. 1 to perform flaw detection. It is.

FIG. 7 is a graph when the metal plate of FIG. 4 is scanned in the X3 direction by the metal plate flaw detection probe of FIG. 1 to perform flaw detection,
(A) shows the voltage change of the V output, and (B) shows the voltage change of the H output.

8 is a graph showing a Y / X ratio of a signal at each thinned portion in FIGS. 5 to 7. FIG.

9A and 9B show a second embodiment of a metal plate flaw detection probe according to the present invention, wherein FIG. 9A is a schematic side view, FIG. 9B is a schematic bottom view, and FIG. 9C is a schematic front view.

10A is a side view and FIG. 10B is a bottom view of the secondary coil in the metal plate flaw detection probe of FIG.

11A and 11B show a configuration of an example of a conventional metal plate flaw detection probe, in which FIG. 11A is a schematic side view, and FIG. 11B is a schematic bottom view.

[Explanation of symbols]

 10, 40 Metal plate flaw detection probe 11, 41 Winding frame 12, 42 Primary coil 13, 14, 43, 44 Secondary coil 15 Protection plate 16 Case 17 Connector 20 Power supply 21 Adder 22 Phase detector 30, 31, 38 Metal Plates 32, 33, 34, 35, 36, 37 Thinned portion

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hidetoshi Hosoe 3-12-22, Nishitsuga, Wakaba-ku, Chiba City, Chiba Prefecture (72) Inventor Shunichi Abe 4-6-10, Tsurumi-Chuo, Tsurumi-ku, Yokohama-shi, Kanagawa Prefecture No. 1 Building 302 Amic Co., Ltd. F-term (reference) 2G053 AA11 AA12 BA02 BA15 BC01 BC14 CA02 CA03 DA01 DB02

Claims (4)

[Claims] 1. A flaw detection probe scanned along a surface of a metal plate as a test object, wherein a winding frame disposed in parallel with the surface of the metal plate has a surface facing the surface of the metal plate; A primary coil wound longitudinally on the opposite surface and excited by an exciting current of a predetermined frequency; and between the surface of the metal plate and the primary coil, around an axis perpendicular to the surface of the metal plate. A metal plate flaw detection probe, comprising: at least one pair of secondary coils wound adjacently to extend in the longitudinal direction of the primary coil and differentially connected to each other. 2. The metal plate flaw detection probe according to claim 1, wherein the winding frame is flat. 3. The bobbin is formed in an L-shape corresponding to a right-angled corner of a metal plate, and the primary coil and the secondary coil are adjacent to the bobbin facing a surface of the metal plate. The metal plate flaw detection probe according to claim 1, wherein the probe is provided on two surfaces. 4. The winding frame is formed in an appropriate shape corresponding to the surface shape of the metal plate, and the primary coil and the secondary coil are formed in the same shape as the winding frame facing the surface of the metal plate. 2. The device according to claim 1, wherein the device is provided on a surface having
4. The metal plate flaw detection probe according to 4.