JPH0454446A - Eddy current flaw detecting device - Google Patents

Abstract

PURPOSE:To accurately detect a lengthwise flaw of a body to be inspected which has section other than circular one by using an adjusting means which holds a probe and the surface of the body to be inspected at a constant distance. CONSTITUTION:A cam 15 makes one rotation when a rotary frame 12 makes one rotation. Then the outer peripheral shape of the cam 15 is made to correspond to the sectional shape of the body 11 to be inspected and then the probe 13 makes a scan plotting a track as shown by a dotted line. Namely, the probe 13 is held at the constant distance to the opposite surface of the body 11 to be inspected at any angle of rotation of the rotary frame 12. Then if there is a flaw on the surface of the body 11 to be inspected, an induced current which flows through the coil of the probe 13 varies, so that the flaw is detected.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an eddy current flaw detection device for detecting flaws on the surface of a long object made of a metal material.

[Background of the invention]

Eddy current flaw detection is one of the methods for detecting flaws on the surface of a long object made of metal materials such as steel and aluminum. What is the eddy current flaw detection method? When a coil carrying an alternating current is brought close to a conductor such as metal, an induced current called an eddy current is generated in the coil, but if there is a defect such as a flaw on the surface of the conductor,
This method utilizes the phenomenon that the way the eddy current flows through the coil changes. Specifically, the eddy current flaw detection method described above is carried out by scanning a coil called a probe over a fixed distance over the surface of a test object made of a metal material.

[Conventional technology]

Conventionally, when testing the surface of a long object with a circular cross section made of a metal material using the eddy current flaw detection method, as shown in FIG. 12, in a plane perpendicular to the axis A of the object (1),
A probe (3) is supported on a rotating frame (2) that surrounds the subject (1) and rotates around the axis A, and
A device was used in which the probe (3) was scanned by keeping the probe (3) at a fixed distance from the surface facing the object (1) by rotating the rotating frame (2) while feeding the probe (3) in the axial direction. .

However, for example, in the case of a test object whose cross section is square with R (R) at the four corners, the distance between the probe and the facing surface of the test object is not constant according to the above device, so as shown in FIG. While sending the subject (11) in the direction of the arrow a, the N surface part (11)A is a circle whose diameter is the width W of the surface part (11)A in a plane parallel to the surface part (11)A at a predetermined distance. Flaws are detected by a probe (3) A that is scanned on the orbit (as indicated by the arrow), and the rounded corner part (11) B has a saddle-shaped probe ( 3) A method of flaw detection has been taken in which B is placed at a certain distance from the surface of the rounded corner (11) 8.

[Problem to be solved by the invention]

However, in the above-mentioned conventional eddy current flaw detection device, the probe (3)A is scanned on a circular trajectory along the surface portion (11)A of the object (11).
There are parts where the scanning direction of probe (3) A does not intersect at right angles to the linear flaws in the longitudinal direction of the probe (3), and the flaws in the axial direction cannot be detected accurately. The scanning direction is completely parallel to the linear flaw in the longitudinal direction of the object (11), so the linear flaw cannot be detected. To do this, a total of 8 probes, 4 probes (3) A and 4 probes (3) B, are required.
Four scanning means are required to rotate the .

As described above, in conventional eddy current flaw detection equipment, when one flaw detection equipment is to be applied to a test object having a cross-sectional shape other than circular, it is necessary to use a large number of probes,
Moreover, it is necessary to provide a scanning means for the probe, making the mechanism of the apparatus complicated. Therefore, instead of using a flaw detection device having such a complicated mechanism, it has been desired to be able to detect flaws on the entire surface of the object using a flaw detection device having a simple structure and having a small number of probes.

[Means to solve the problem]

As a means to solve the above-mentioned conventional problems, the present invention surrounds a long object (11) made of a metal material in a plane orthogonal to the axis A of the object (11) and rotates around the axis. Rotating frames (12), (22), (32) and probes (13), (2) movably attached to the rotating frames (12), (22), (32) on the radial line of the axis A; 23), (33), the probe (13), (23), (33), and the analyte (1).
1) An eddy current flaw detection device is provided, which comprises adjusting means for moving the probes (13), (23), and (33) so as to maintain a constant distance from the opposing surface (see Figs. 1 to 3). 6), the adjusting means includes a cam (1) having a shape corresponding to the cross-sectional shape of the subject (11).
5), (25) according to the probe (13), (
means for moving the probe (23) on the radiation of the axis A of the subject (11), a means for moving the probe (33) on the radiation by a movement motor (33)J, and a swinging motor (33)D This provides means for making the distal end surface of the probe (33) parallel to the surface facing the subject (11).

[Operation] In a plane perpendicular to the axis A of the elongated object (11) made of a metal material, the rotating frame (1) surrounding the object (1)
2) If we rotate , (22) and (32), we get
Probes (13), (23), attached to the rotating frames (12), (22), (32),
(33) also rotates around the subject (11) about the axis A. Then, the adjustment means adjusts the probe (13
), (23), (33) in the radial direction of the axis A, the probes (13), (23),
(33) and the opposing surface of the subject (11) is maintained constant.

When the adjusting means is a cam (15), (25), the probe (13), (23) moves on the radiation line following the shape of the cam, and the adjusting means is moved by a moving motor (3).
3) In the case of the swing motor (33) D, the movement motor (33) J is controlled by the motor control section (36).
is actuated to move the probe (33) on the radiation, and the swing motor (33)D moves the probe (33) to an axis (33) parallel to the axis of the long subject (11).
Rotate around C.

〔Effect of the invention〕

Therefore, in the present invention, since longitudinal flaws in a specimen having a cross-sectional shape other than circular can be accurately detected using a single probe, the structure of the flaw detection device is extremely simple and highly practical. becomes.

〔Example〕

A first embodiment of the present invention is shown in FIGS. 1 and 2. FIG. In the figure, (12) is a ring-shaped rotating frame, and the rotating frame (12) is rotatably supported by a fixed plate (14) via a shaft tube (12)A. ) is rotated in the direction of arrow C around -A through the shaft tube (12)A by a drive device (not shown). The rotating frame (12
) A bracket (12)B is extended from the front surface of the probe (13), and a rod (13)A of the probe (13) is slidably supported on the bracket (12)H, thus allowing the probe (13) to is movable on the ray of axis A. And the probe (13) is connected to a spring (13).
It is urged in the direction of arrow d by H.

A rotating shaft (15) A is further rotatably supported on the rotating frame (12), and a cam (15) is attached to the rotating shaft (15) A on the front side of the rotating frame (12). , gear (15) B is attached to the rear side, and the gear (
15) B meshes with the ring gear (14) A attached to the front surface of the stationary plate (14).

In the flaw detection apparatus having the above configuration, in order to detect flaws on the surface of an elongated test object (11) made of metal such as steel or aluminum and having a square cross section with round corners, the test object (11) is moved to the rotary frame (12).
into the shaft tube (12) A, and the rotary frame (12) is rotated in the direction of arrow C via the shaft tube (12) A by a drive device (not shown). The axis A of the rotating frame (12) coincides with the axis of the subject (11), and the rotating frame (12)
It thus rotates in a plane perpendicular to axis A. When the rotating frame (12) is rotated, the gear (14) meshing with the ring gear (14) A of the stationary plate (14) is rotated.
15) Cam (15) via B and rotating shaft (15) A
rotates in the direction of arrow e in FIG. The ring gear (14)
If the gear ratio between A and the gear (15) B is 1:1, the cam (15) will rotate once when the rotating frame (12) rotates once. As the cam (15) rotates, the probe (13) moves on the radial line of the axis A as the rod (13) A is pushed against the outer periphery of the cam (15).

By making the outer peripheral shape of the cam (15) correspond to the cross-sectional shape of the subject (11), the probe (13) is scanned along a trajectory as shown by the dotted line in FIG. That is, the probe (13) maintains a constant distance from the opposing surface of the subject (11) at any rotation angle of the rotating frame (12). If a flaw exists on the surface of the object (11), the flaw is detected by fluctuations in the induced current flowing through the coil, which is the probe (13).

In FIGS. 3 and 4 showing a second embodiment of the present invention, (22) is a ring-shaped rotating frame.

The rotating frame (22) is connected to the fixed platen (2) via the shaft cylinder (22)A.
4), and the rotating frame (22) is rotated in the direction of arrow f about the axis A via the shaft tube (22) A by a drive device (not shown). A bracket (22)B is extended from the front surface of the rotating frame (22), and a probe (23) is attached to the bracket (22)H.
) is slidably supported on the rod (23)A, so that the probe (23) is movable in the radial direction of the axis A. The probe (23) is urged in the direction of arrow g by a spring (23)B.

A ring-shaped cam (25) is arranged on the front side of the rotating frame (22), and the cam (25) is supported by a fixed mold (24) via an arm (26). A roller (23) D rotatably supported by a bearing (23) C attached to the tip of the rod (23) A of the probe (23) is in contact with the inner periphery of the probe (23).

In the flaw detection device having the above configuration, the object (11) is fed into the shaft tube (22) A of the rotary frame (22) as in the first embodiment, and the shaft tube (22) is moved by a drive device (not shown).
The rotating frame (22) is rotated in the direction of arrow f via A. The axis A of the rotating frame (22) coincides with the axis of the subject (11), and the rotating frame (22) rotates in a plane perpendicular to the axis A, as in the first embodiment. The rotating frame (22)
As the rod (23) of the probe (23) rotates, the rod (23
)A moves on the radial line of axis A by being pushed by the inner periphery of the cam (25) via rollers (23)D.

By making the inner peripheral shape of the cam (25) correspond to the cross-sectional shape of the subject (11), the probe (23) is scanned along a trajectory as shown in the dotted line in Figure 3, ) to detect flaws on the surface of the object (11).

In FIG. 0 showing the third embodiment of the present invention in FIGS. 5 and 6, (32) is a ring-shaped rotating frame, and the rotating frame (32) is fixed via a shaft cylinder (32) A. The rotary frame (32) is rotatably supported by a disk (34), and the rotary frame (32) is rotated in the direction indicated by the arrow around the axis A via the shaft tube (32) A by a drive device (not shown). The rotating frame (32
) The probe (33) and motor control unit (
36) is arranged, and a sensor (35) is arranged on the back side a little further forward in the direction of movement of the subject (11), and the probe (33) has a pinion (33) B attached to it and is connected to the axis A.
It is rotatably supported by a support frame (33)A via an axis (33)C parallel to the above, and a swinging motor (33)D is further supported by the support frame (33)A. A worm gear (33)E that meshes with the pinion (33)B of the probe (33) is attached to the shaft of the swing motor (33)D. The support frame (33)A has the rotation frame (
32) It is movably attached to the front surface via a guide rail (33)F on the radial line of the axis A, and the support frame (33)
) A screw (33) G is extended from the top surface of A.

The screw (33)G is a bearing (33)H, (33)
I is movably supported on the ray. Furthermore, a moving motor (33) J is mounted on the front of the rotating frame (32).
is attached, and the pinion (33)K of the shaft of the moving motor (33)J is connected to the bearings (33)N and (33)P with the shaft (33)M attached to the front surface of the rotating frame (32). It meshes with a pinion (33) Q that is coaxial with a worm gear (33) L that is rotatably supported. The sensor (35) is connected to the input side of the motor control section (36),
Motors (33)D and (33)J are connected to the output side of the motor control section (36).

In the flaw detection apparatus having the above configuration, the object (11) is fed into the shaft tube (32)A of the rotating frame (32) as in the first and second embodiments, and the shaft tube is driven by a drive device (not shown). (32) Rotate the rotating frame (32) in the direction of the arrow via A. The motor control unit (36) controls the subject (
The motors (33)D and (33)J are driven according to a program set according to the cross-sectional shape and size of the motor (33)D and (33)J. Depending on the drive of the motor (33)D, the worm gear (
33)E, probe (33) via pinion (33)B
) rotates in the direction of arrow i in Figure 5 to perform a swinging motion,
Depending on the drive of the motor (33) J, the pinion (33)
K, (33) Q, worm gear (33) L, and screw (33) G, along the guide rail (33) F, the probe (33) moves in the direction of arrow j (axis A) in FIGS. (on the radiation of). Therefore, the probe (33) is moved to the subject (1) by the motor (33)J.
The distal end surface of the probe (33) is kept parallel to the opposing surface of the subject (11) by the motor (33)D. However, when the cross-sectional shape and dimensions of the object (11) deviate from the setting program of the motor control section (36), the sensor (35) measures the distance to the opposing surface of the object (11), and the motor control section ( The moving motor (33)J is operated via the probe (36) to correct the distance between the probe (33) and the facing surface of the subject (11). Note that a vortex type sensor is usually used as the sensor (35).

In this example, as described above, the probe (33) is connected to the subject (
In addition to maintaining a constant distance from the opposing surface of the object (11), the tip of the probe (33) is parallel to the opposing surface of the object (11), so flaws on the surface of the object (11) can be detected with extremely high accuracy. be done.

In this embodiment, for example, if the length L of the negative side of the object (11) is 150 m and the radius R of the rounded corner is 25 m, the rotating part of the rotating frame (32) and the probe (33) in the direction of arrow j The amount of movement and the amount of swing in the direction of arrow i are set as shown in FIG. In the figure, a rotation angle of 0° means that the sensor (35) shown in FIG. 5 is located directly above the subject (11). As shown in Fig. 7, the probe (33) performs a reciprocating motion of a stroke of 20 degrees in the j direction at every 90 degrees of rotation angle, and ±3
It is set to perform a 4° oscillation, and the subject (
If the feed rate (flaw detection speed) of 11) is 10 m/min, the number of channels is 4, and the flaw detection pitch is 101, then the rotation speed of the rotating frame (32) is approximately 4 rps, and the motion frequency is 167. Therefore, the moving speed in the j direction is 660
■/s, the swing speed in the i direction is 22oO°/s.

The probe (33) used in the present invention has a pair of left and right iron cores (331)A and (331)H made of a magnetic material such as ferrite or silicon steel, each having a coil attached to its outer periphery, as shown in Figure 8 (A). (332)A and (332)B are fitted, and the outside thereof is covered with a cover (333), but in order to omit the swinging mechanism and perform flaw detection with high accuracy, the As shown in the figure, the tip surface of the probe (33), that is, the iron cores (331)A, (331)B, are chamfered in an arc shape on both the left and right edges (334)A, (334).
)B L, or linear chamfers (335)A, (335)B as shown in FIG. 10, or circular chamfers (334)A, (334)A, as shown in FIG.
Following (334)B, linear (335)A, (33
5) B may be chamfered, and the cover (333) may cover the lower ends of the iron cores (331)A and (331)H. 4. Brief description of the drawings Figures 1 and 2 show a first embodiment of the present invention, with Figure 1 being a front view and Figure 2 taken along line A-A in Figure 1.
3 and 4 show a second embodiment of the present invention, FIG. 3 is a front view, and FIG. 5 and 6 show a third embodiment of the present invention, with FIG. 5 being a front view and FIG.
The figures are an upper half view of the CC cross section in FIG. 5, FIG. 7 is a graph showing the amount of movement of the sensor with respect to the rotating part, and FIG. 8A.

The mouth is an explanatory diagram of a probe, FIG. 9 is an explanatory diagram of another embodiment of the probe, FIG. 10 is an explanatory diagram of yet another embodiment of the probe, and FIG. 11 is an explanatory diagram of yet another embodiment of the probe. , FIG. 12 is a longitudinal cross-sectional view of a conventional example, and FIG. 13 is a partial plan view of another conventional example.

In the figure, (11)...subject.

(12), (22), (32)... Rotating frame, (13), (23), (33)...
Probe, (15), (25)...cam, (
33) D...Motor for swinging (33) J...Motor for movement A...Shaft Fig. 3 Patent applicant Daido Steel Co., Ltd.←B No. 40 No. 5 Fig. 11 334A 34B Specification

Claims (1)

[Scope of Claims] 1. A rotating frame that surrounds the long subject made of a metal material and rotates around the axis in a plane orthogonal to the axis of the long subject, and a rotating frame that surrounds the subject and rotates around the axis; An eddy current flaw detection device 2 characterized by comprising a probe movably mounted on the top, and an adjusting means for moving the probe so as to maintain a constant distance between the probe and the surface facing the object. The adjusting means is a cam having a shape corresponding to the cross-sectional shape of the subject, and the probe moves on the radial line of the axis by the cam as the rotating frame rotates. The eddy current flaw detection device 3 includes a moving motor for moving the probe on a radiation line of the axis, and a swinging motor for rotating the probe about an axis parallel to the axis of the test object. The eddy current flaw detection device 4 according to claim 1, further comprising a motor control unit that operates the swinging motor so that the probe tip surface and the object-facing surface are parallel to each other, in the probe tip surface. The eddy current flaw detection device according to claim 1 or 2, wherein chamfered portions are formed over both left and right edges.