JP5153274B2 - Inspection equipment for inspection objects - Google Patents

Description

The present invention relates to a device you flaw detection surface of the inspection object, such as a metal pipe or a metal rod.

  Conventionally, the eddy current flaw detection method has been used as a method for nondestructively inspecting the presence or absence of a flaw present on the surface of an inspection object such as a metal tube or a metal rod.

  FIG. 17 is a view showing a conventional eddy current flaw detection probe 80.

  As shown in FIG. 17, the conventional eddy current flaw detection probe 80 is wound around the outer peripheral surface of a cylindrical bobbin 81 to form three solenoidal coils 82, 83a, 83b. Among these, one coil 82 is an exciting coil, and the other two coils 83a and 83b are detection coils. A test is performed by penetrating a metal tube or a metal rod, which is an inspection object, into the bobbin 81.

  In such a bobbin type eddy current flaw detection probe 80, a vortex is formed on the surface of the inspection object placed inside the bobbin 81 in the winding direction of the coil 82, that is, in the circumferential direction of the inspection object (perpendicular to the axis). Current flows. When a flaw such as a crack along the axial direction exists on the surface of the inspection object, the current path for the eddy current is cut off and changed. This change is detected as a change in impedance of the detection coils 83a and 83b wound in the vicinity of the exciting coil 82.

  Further, when it is desired to detect flaws on the inner surface of the metal tube, a method of inserting such an eddy current probe 80 into the tube is used. This method is defined in “Eddy Current Testing II, 5, Test Coil” edited by Japan Nondestructive Inspection Association.

In addition, arrange two or more small pancake coils so that eddy currents are generated in the axial direction or in a spiral shape of the test object, and a defect interrupts the eddy currents so that impedance changes occur in the coils. An eddy current flaw detection probe is proposed (Patent Document 1).
JP-A-9-43204

  According to the conventional eddy current flaw detection probe 80 shown in FIG. 17, it is possible to realize a high-speed inspection in a non-contact manner with a relatively simple configuration, but it is in the same direction as the eddy current flowing on the surface of the inspection object. Even if there is a flaw, that is, a flaw in the circumferential direction, the current path of the eddy current is not significantly obstructed, so that there is a problem that detection of the flaw in the circumferential direction is extremely difficult.

  In other words, in the eddy current flaw detection probe 80 using a penetration type coil that has been widely used in the past, the axial direction flaw and the circumferential direction of a long-shaped inspection object manufactured by a rolling process such as a metal tube or a metal rod It was difficult to simultaneously detect flaws and flaws having a fine pore shape.

  Further, in the method of arranging a plurality of small pancake coils shown in Patent Document 1, it is not easy to arrange a large number of pancake coils close to the inspection object, and the apparatus is complicated and expensive. There's a problem.

The present invention has been made in view of the above-described problems, and can easily apply a two-direction magnetic field to an inspection object with a simple configuration and can detect a flaw in any direction. and to provide a probe KizuSo location of the object.

An apparatus according to the present invention includes an exciting coil in which two coils having a rectangular cross section are arranged orthogonal to each other, a current supply device that supplies an alternating current having a phase difference of 90 degrees to the two coils, It includes a magnetic sensing element in which the two coils are arranged in a position intersecting the said exciting coil, wherein the inspection object two coils are arranged so as to be through, the exciting the exciting coil A rotating device is provided for rotating around the inspection object passing through the coil.
Alternatively, a plurality of the excitation coils are used, and the plurality of excitation coils are arranged so as to be shifted from each other by a predetermined rotation angle around the inspection object. The magnetic detection element is arranged so as to detect scratches in different angular ranges on the outer peripheral surface.

According to the present invention, it is possible to easily apply a magnetic field in two directions to an inspection object with a simple configuration, and it is possible to detect and detect flaws in any direction of the inspection object. Moreover, even when the inspection object has a large diameter, it is possible to perform flaw detection on the entire periphery of the inspection object.

[First Embodiment]
FIG. 1 is a diagram showing the structure of the eddy current flaw detection probe 3 according to the first embodiment of the present invention, FIG. 2 is a diagram showing waveforms of currents flowing through the coils 11 and 12 of the eddy current flaw detection probe 3, and FIG. FIG. 17 is a diagram showing the state of eddy currents on the surface of the metal plate induced by the flaw detection probe 3, and FIG. 17 is a diagram showing the positions of the dimensions of the coils 21 and 22.

  1A is a front view of the eddy current flaw detection probe 3, FIG. 1B is a right side view of the eddy current flaw detection probe 3, and FIG. 1C is a bottom view of the eddy current flaw detection probe 3.

  In FIG. 1, an eddy current flaw detection probe 3 includes an exciting coil 11 in which two coils 21 and 22 having a rectangular cross section are arranged orthogonal to each other, and magnetic detection arranged at a position where the two coils 21 and 22 intersect. It consists of element 12. A rotating magnetic field is generated by flowing alternating currents having a phase difference of 90 degrees to the two coils 21 and 22 to detect flaws on the surface of the metal inspection object WK existing in the vicinity of the two coils 21 and 22. To do.

  Each of the coils 21 and 22 is obtained by winding an electric wire around a bobbin made of a nonmagnetic material such as synthetic resin, ceramic, or paper. Such a bobbin can have various structures or configurations such as a rectangular parallelepiped shape, a shape in which an elongated rectangular parallelepiped shape is orthogonal, and a combination in which two rectangular frames are orthogonal.

  The two coils 21 and 22 each have a rectangular long side L2 that is three or more times as long as the short side L1, and the lengths L3 of the coils 21 and 22 are three times shorter than the rectangular short side L1. 1 to 3/5. However, other dimensions may be used. For the short side L1, the long side L2, and the length L3 of the coils 21 and 22, see FIG.

  As the magnetic detection element 12, a search coil, a Hall element, a flux gate element, a GMR element, an MI element, a thin film planar coil, and other elements are used. The magnetic detection element 12 may be arranged at two positions where the two coils 21 and 22 cross each other.

  For the inspection of the inspection object WK, the two coils 21 and 22 are supplied with alternating currents J1 and J2, which are sine waves having a phase difference of 90 degrees.

  That is, the current SA1 shown in FIG. 2 flows through one coil 21 and the current J2 shown in FIG. Apply SB. In this way, by causing the currents J1 and J2 having a phase difference of 90 degrees to flow through the coils 21 and 22, a rotating magnetic field is generated at the intersection of the coils 21 and 22.

  When the intersecting portion of the coils 21 and 22 is brought close to the metal plate as the inspection object WK1, as shown in FIG. 3, the eddy current Z1 due to the current J1 of the coil 21 and the current of the coil 22 are formed on the surface of the metal plate WK1. Eddy currents Z2 due to J2 flow respectively. These eddy currents Z1 and Z2 are orthogonal to each other. Since the magnitudes of the eddy currents Z1 and Z2 change according to the currents J1 and J2, they change in a sine wave shape. As a result, when the eddy currents Z1 and Z2 are combined, a rotating eddy current is obtained.

In any case, since the eddy currents Z1 and Z2 orthogonal to each other flow on the surface of the metal plate WK1, it is possible to easily detect flaws along the directions orthogonal to the directions of the eddy currents Z1 and Z2. It becomes.
[Second Embodiment]
Next, the eddy current flaw detection probe 3B according to the second embodiment that enables inspection of a long inspection object WK such as a metal tube or a metal rod will be described.

  FIG. 4 is a view showing an eddy current flaw detection probe 3B according to the second embodiment, and FIG. 5 and FIG. 6 are views showing an eddy current flowing on the surface of the inspection object WK2 by the eddy current flaw detection probe 3B.

  As shown in FIG. 4, the exciting coil 11B has a circular hole 13 in the center of the coils 21 and 22 so that the tubular or rod-shaped inspection object WK2 can penetrate the two coils 21 and 22. Is provided.

  An eddy current corresponding to the current flowing through the coils 21 and 22 flows on the surface of the inspection object WK2 inserted through the two coils 21 and 22 by passing through the hole 13. For example, when alternating currents having the same phase are passed through the two coils 21 and 22, eddy currents Z3 and Z4 flow in directions orthogonal to each other as shown in FIG. In this case, since the coils 21 and 22 are wound in a direction of 45 degrees with respect to the axial center direction (axial direction) of the inspection object WK2, as a flaw on the surface of the inspection object WK2, On the other hand, flaws along the directions of ± 45 degrees and ± 135 degrees are detected by the magnetic detection element 12 with the maximum sensitivity. However, in general, since there are many flaws of 0 degree (± 25 degrees) and 90 degrees (± 25 degrees) with respect to the axial direction, the eddy currents Z3 and Z4 in the direction shown in FIG. The signal detected by the detection element 12 cannot be evaluated satisfactorily.

  Therefore, as shown in FIG. 2 of the first embodiment, an alternating current having a phase difference of 90 degrees is supplied to the two coils 21 and 22 to generate a rotating eddy current on the surface of the inspection object WK2. Let

  That is, as shown in FIG. 6, due to the rotating magnetic field generated by the coils 21 and 22, an eddy current whose direction of flow changes with time, that is, a rotating eddy current Z5 flows on the surface of the inspection object WK2. The rotating eddy current Z5 can detect a flaw in any direction. That is, the rotating eddy current Z5 acts so that an equivalent signal can be obtained in the magnetic detection element 12 for any flaw in any direction. As a result, a signal having the same amplitude is obtained as an output signal of the magnetic detection element 12 with respect to both an axial flaw and a circumferential flaw on the surface of the inspection object WK2 such as a metal tube or a metal rod.

Further, in the past, flaw detection was not possible for tubes and rods having a rectangular or hexagonal cross section, but in this embodiment, inspection objects WK of those shapes can be easily flawed as above. Become.
[Third Embodiment]
Next, a case where a tube (square tube) having a rectangular cross-sectional shape is used as the inspection object WK3 will be described.

  FIG. 7 is a diagram showing an eddy current flaw detection probe 3C according to the third embodiment.

  In FIG. 7, the eddy current flaw detection probe 3 </ b> C is configured by arranging two eddy current flaw detection probes 3 </ b> C <b> 1 and 3 </ b> C <b> 2 having the same structure on the same axis and rotated at an angle of 90 degrees.

  Each of the eddy current flaw detection probes 3C1 and 3C2 has an exciting coil 11C in which two coils 21 and 22 are arranged so as to be orthogonal to each other, and two magnetic detection elements 12C arranged at the crossing position thereof. Each exciting coil 11C is provided with a hole 13C having a rectangular cross section so that the inspection object WK3 can be inserted therethrough.

  Thus, in the eddy current flaw detection probe 3C, a plurality of excitation coils 11C are used, and the respective excitation coils 11C are arranged so as to be shifted from each other by a predetermined rotation angle, here 90 degrees, around the inspection object WK3. ing. In each excitation coil 11C, two magnetic detection elements 12 are arranged so as to detect scratches in different angular ranges on the outer peripheral surface of the inspection object WK3.

  In each of the eddy current flaw detection probes 3C1 and 3C2, a rotating magnetic field is generated by passing alternating currents having a phase difference of 90 degrees through the two coils 21 and 22, and flaws on the four peripheral surfaces of the square of the inspection object WK3. Is detected. That is, the left and right surfaces of the inspection object WK3 are inspected by the eddy current flaw detection probe 3C1, and the upper and lower surfaces of the inspection object WK3 are inspected by the eddy current flaw detection probe 3C2. As described above, according to the eddy current flaw detection probe 3C, it is possible to simultaneously inspect flaws on the entire circumference of the inspection object WK3.

Two eddy current flaw detection probes 3C1 and 3C2 are used when the inspection object WK3 is a square, but three eddy current flaw detection probes 3C1, 3C2 and 3C3 may be used when the inspection object WK3 is a hexagon.
[Fourth Embodiment]
As is clear from the above description, according to the eddy current flaw detection probes 3 to 3C of the present embodiment, it is possible to magnetize the inspection object WK in two directions even though it is a penetration coil or an insertion probe. There are advantages.

  In general, since the position where the detection coil is arranged is limited to the intersection of the exciting coils, a round inspection as shown in FIG. 4 is performed except for a rectangular inspection object WK as shown in FIG. In the case of the object WK, there are only two places where the magnetic detection element 12 can be arranged with respect to one set of coils 21, 22, that is, one excitation coil 11.

  Therefore, in order to perform flaw detection on the entire circumference of the inspection object WK, a large number of exciting coils 11 or eddy current flaw detection probes 3 are arranged in the axial direction, and a constant value calculated from the detection range of each magnetic detection element 12 is used. It is necessary to take measures such as disposing them at different angles.

  However, in this case, when the inspection object WK has a large diameter, for example, when the outer diameter is 50 mm, the detection range of the single eddy current flaw detection probe 3 is about 4 mm. As a result, 40 eddy current flaw detection probes 3 are required for flaw detection on the entire circumference.

  Therefore, in this case, the total length of the 40 eddy current flaw detection probes 3 arranged is 400 mm in total length even if the length of one eddy current flaw detection probe 3 is about 10 mm. A portion having a length of 400 mm is deeply damaged at the same time. However, since this does not mean that the entire circumference of a specific portion in the axial direction is flawed at a time, it becomes sensitive to the backlash signal even though the number of eddy current flaw detection probes 3 is large, and during the rolling process. It is not suitable for on-line inspection of the inspection object WK.

  Therefore, in order to apply the eddy current flaw detection probe 3 to such online flaw detection, a method of rotating the eddy current flaw detection probe 3 is effective. Next, a flaw detector using such a rotary drive device will be described as a fourth embodiment.

  FIG. 8 is a diagram showing a configuration of the flaw detection apparatus 1 using a rotation drive device.

  In FIG. 8, the eddy current flaw detection probe 3 </ b> D is held in a cylindrical probe holder 34. The probe holder 34 is rotatably supported by two bearing rollers 32 and 33 that are rotatably provided on the base 31. A rotation drive device 35 including a motor, a gear, and the like is in contact with the surface of the probe holder 34, and the probe holder 34 is rotated by the rotation of the rotation drive device 35. With the rotation of the probe holder 34, the eddy current flaw detection probe 3D rotates integrally. An output signal from the eddy current flaw detection probe 3D is taken out using, for example, a slip ring (not shown).

  The inspection object WK4 passes through the hole 13D provided in the center of the eddy current flaw detection probe 3D and moves (runs) in the axial direction thereof, and the outer periphery of the inspection object WK4 is flaw detected by the eddy current flaw detection probe 3D. Is done. At that time, since the eddy current flaw detection probe 3D also rotates, the entire circumference of the inspection object WK4 is flawed.

  Any of the eddy current flaw detection probes 3 to 3C described above may be used as the eddy current flaw detection probe 3D. The hole 13D may be enlarged with a margin so as not to interfere with the traveling inspection object WK4.

In this method, only the magnetic detection elements 12 provided at two locations of the eddy current flaw detection probe 3D contribute to the detection of flaws. Therefore, the effective detection region (rotation angle region) has, for example, an outer diameter of 20 mm. In the case of a tube, since it is about ± 15 degrees per magnetic detection element 12, only 60 degrees / 360 degrees can be obtained in one rotation of the eddy current flaw detection probe 3D in a normal case. Therefore, it is necessary to increase the rotational speed of the eddy current flaw detection probe 3D. When the inspection object WK4 has a large diameter of 40 mm or more, it is effective to increase the effective flaw detection range by swinging a plurality of eddy current flaw detection probes 3D within a predetermined angle range.
〔Concrete example〕
Now, an example of specific dimensions of the eddy current flaw detection probes 3 to 3D will be described.

  In the eddy current testing probes 3 to 3D described above, the coils 21 and 22 have an axial length L3 of about 4 mm, a width (rectangular long side) L2 of about 16 mm, and a height (rectangular short side). ) L1 is about 10 mm. Note that the width L2 may be about three times or more than the height L1. The magnetic detection element 12 is a planar coil having a diameter of about 3 mm, a thickness of about 50 μm, and a number of turns of about 70. The magnetic detection element 12 is affixed to the lower side of the winding at the crossing portion (4 × 4 mm portion) of the two coils 21 and 22.

  The number of turns of the coils 21 and 22 is, for example, about 100 to 200 times, and the frequency of the current flowing through the coils 21 and 22 is about several KHz to several hundred KHz, or several hundred KHz to several GHz. As a current supply device for supplying such a current, a circuit that outputs AC voltages SA and SB having two sine waveforms having different phases and the same amplitude can be used. In this case, the output voltage is, for example, about several volts to several tens of volts.

  FIG. 9 shows the detection results of the drill holes and EDM slits processed into the plate-like inspection object WK using this eddy current flaw detection probe. In FIG. 9, the position in the length direction of the inspection object WK is shown on the x-axis, and the output signal based on the magnetic detection element 12 at each position is shown on the y-axis.

  As shown in FIG. 9A, an output signal having a differential waveform by the drill hole is obtained at the position of the drill hole (position of the scale of about 18). Further, as shown in FIG. 9B, an output signal having a differential waveform by the EDM slit is obtained at the position of the EDM slit (the position of the scale of about 18). Thus, the flaw signal similar to the conventional probe was obtained using the eddy current flaw detection probe 3.

  Moreover, the detection result of the drill hole which inserted the aluminum pipe | tube whose outer diameter is 8 mm as a test object WK using the same eddy current flaw detection probe as the upper part, and was processed into the aluminum pipe | tube was shown in FIGS.

  That is, FIG. 10 shows output signals according to drill diameters of 1.5 mm, 0.7 mm, 0.5 mm, and 1.0 mm.

  FIG. 11 shows the result of examining the positional relationship with the magnetic detection element 12 without providing a 1.0 mm drill hole in the same aluminum tube. In FIG. 11, the case where the drill hole passes through the center of the magnetic detection element 12 is indicated by a solid line, and the case where the drill hole passes through a position shifted from the center of the magnetic detection element 12 by about 5 degrees is indicated by a broken line. .

  According to this, when the drill hole is deviated from the center of the magnetic detection element 12 by about 5 degrees, the magnitude of the output signal is reduced by about 20%.

  Therefore, by rotating the inspection object WK using the flaw detection apparatus 1 described in the fourth embodiment above, as shown in FIG. 12, the drill hole is located at any position in the circumferential direction of the inspection object WK. Can be detected satisfactorily.

  Further, as described in the fourth embodiment, a large number of, for example, six eddy current flaw detection probes 3 are used, and the respective eddy current flaw detection probes 3 are arranged with their rotational angle positions shifted by 30 degrees. The case will be described.

  FIG. 13 is a view showing the eddy current flaw detection probe 3E in which six eddy current flaw detection probes 3E1 to 3E6 are arranged with their rotational angle positions shifted from each other, and FIG. 14 is a view of an aluminum tube as the inspection object WK5. The figure which shows the position of the flaw KZ provided in the outer periphery, FIG. 15 is a figure which shows the detection result by the flaw provided in the test object WK5.

  As shown in FIG. 13, when six eddy current flaw detection probes are arranged with their rotational angle positions shifted, the same state is obtained as when twelve magnetic detection elements 12 are arranged at intervals of 30 degrees in the circumferential direction. . Therefore, if there is a flaw at any angular position on the outer periphery of the inspection object WK5 that passes through the central hole 13E of the eddy current flaw detection probe 3E, the flaw KZ can be detected as shown in FIG.

  Using the eddy current flaw detection probe 3E shown in FIG. 13 to inspect the flaws on the outer peripheral surface of the copper pipe at high speed by driving the copper pipe as the inspection object WK5 through the hole 13E and driving it with a roller. Is possible.

  In addition, as the inspection object WK5, it is possible to inspect the surface of a flat metal plate and other various shapes of metal.

  The eddy current flaw detection probes 3, 3B, 3C, 3D, and 3E described above also correspond to the flaw detection apparatus according to the present invention.

  As a circuit for processing a signal output from the magnetic detection element 12, various known circuit configurations in which an amplifier circuit, a synchronous detection circuit, a differentiation circuit, an arithmetic circuit, a memory circuit, an output circuit, and the like are combined are used. Is possible. In that case, the outputs of the plurality of magnetic detection elements 12 may be connected in series and input to one amplifier circuit.

  According to the eddy current flaw detection probes 3 to 3E or the flaw detection apparatus 1 of the above-described embodiments, it is possible to easily apply a two-direction magnetic field to the inspection target WK with a simple configuration. It is possible to detect and detect flaws in such a direction.

  In each of the above-described embodiments, the structure, configuration, shape, size, number of coils 21 and 22, the excitation coil 11, the magnetic detection element 12, the eddy current probe 3 to 3E, or the entire or each part of the flaw detection apparatus 1, The material, circuit configuration, voltage, frequency, and the like can be changed as appropriate within the spirit of the present invention.

It is a figure which shows the structure of the probe for eddy current flaw detection of 1st Embodiment which concerns on this invention. It is a figure which shows the waveform of the electric current sent through the coil of a probe for eddy current flaw detection. It is a figure which shows the mode of the eddy current which flows with the probe for eddy current flaw detection. It is a figure which shows the probe for eddy current flaw detection of 2nd Embodiment. It is a figure which shows the mode of the eddy current which flows into the surface of a test target object. It is a figure which shows the mode of the eddy current which flows into the surface of a test target object. It is a figure which shows the probe for eddy current flaw detection of 3rd Embodiment. It is a figure which shows the structure of the flaw detection apparatus using a rotational drive apparatus. It is a figure which shows the detection result of the flaw processed into the plate-shaped test target object. It is a figure which shows the detection result of the flaw processed into the aluminum pipe. It is a figure which shows the detection result of the flaw processed into the aluminum pipe. It is a figure which shows the detection result of the flaw processed into the aluminum pipe. It is a figure which shows the apparatus using six probes for eddy current flaw detection. It is a figure which shows the position of the flaw provided in the outer periphery of an aluminum pipe. It is a figure which shows the detection result by the flaw provided in the aluminum pipe. It is a figure which shows the position of each dimension of a coil with a rectangular cross section. It is a figure which shows the conventional probe for eddy current flaw detection.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Flaw detection apparatus 3, 3B-3E Eddy current flaw detection probe 11 Excitation coil 12 Magnetic detection element 13 Hole 21, 22 Coil 35 Rotation drive apparatus (rotation apparatus)
WK Inspection object SA, SB Voltage (current supply device)

Claims (3)

An exciting coil in which two coils having a rectangular cross section are arranged perpendicular to each other;
A current supply device for supplying an alternating current having a phase difference of 90 degrees to the two coils; a magnetic detection element disposed at a position where the two coils intersect;
Have
The exciting coil, the two coils of inspection object is disposed so as to be through,
A rotating device is provided for rotating the excitation coil around the inspection object passing through the excitation coil.
An inspection object inspection device characterized by the above. An exciting coil in which two coils having a rectangular cross section are arranged perpendicular to each other;
A current supply device for supplying an alternating current having a phase difference of 90 degrees to the two coils; a magnetic detection element disposed at a position where the two coils intersect;
Have
The exciting coil, the two coils of inspection object is disposed so as to be through,
A plurality of the exciting coils are used,
The plurality of exciting coils are arranged to be shifted from each other by a predetermined rotation angle around the inspection object,
In each excitation coil, the magnetic detection element is arranged so as to detect scratches in different angular ranges on the outer peripheral surface of the inspection object.
An inspection object inspection device characterized by the above. The magnetic detection element is any one of a search coil, a Hall element, a fluxgate element, a GMR element, an MI element, or a thin film planar coil.
The flaw detection apparatus for an inspection object according to claim 1 or 2.

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