JP2013185951A - Magnetic flaw detection probe - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an apparatus that can reduce the number of possessions of probes and shorten a probe exchange time since a conventional magnetic flaw detection probe has probes with different kinds of sensor attachment angles by defect shape kinds and each time a defect shape changes, the magnetic flaw detection probe is exchanged into a suitable probe kind.SOLUTION: The magnetic flaw probe is a magnetic flaw probe 6 in which a holder 3 holds a plurality of rectangular sensors 2. A sensor attachment angle α of the rectangular sensor with respect to the holder is two or more kinds.

Description

  The present invention relates to a probe for electromagnetic flaw detection, and in particular, is used for detecting defects existing locally in the circumferential direction of the outer surface of a long material (for example, steel pipe or steel bar) by a leakage magnetic flux flaw detection method or a eddy current flaw detection method. The present invention relates to an electromagnetic flaw detection probe incorporating a plurality of sensors.

  In Patent Document 1, an inductive leakage type magnetic flux probe provided with an annular detection coil (pickup coil) surrounding a magnetic flux generation part (bar magnet) is provided with a plurality of detection coils in the circumferential direction. It is described that the configuration is such that the induced electromotive force generated in the detection coil is individually guided to the flaw detector. As a result, the shape ratio of the defect relative to the entire length of the detection coil can be relatively increased. Therefore, the detection sensitivity of defects existing locally in the circumferential direction of the subject is greatly improved, and the reliability is increased. It is what you expect.

  In Patent Document 2, as a tube insertion type eddy current flaw detection probe, a plurality of sensor coils are arranged around a holder, the shape of the sensor coil is a linear rectangle, and the sensor coil is connected to the holder. It is described that it is arranged at a predetermined angle (45 °) with respect to the axial direction. As a result, the relative position between the sensor coil and the cracked scratch can be kept the same regardless of whether the crack is in the circumferential direction or the axial direction, and a constant detectability can be maintained regardless of the crack direction. Expect an effect.

JP-A-6-109706 Japanese Utility Model Publication No. 7-34366

  On the other hand, in the leakage magnetic flux flaw detection in which a ferromagnetic metal material, for example, a steel pipe is a test material and the outer surface is the test surface, as shown in FIGS. 2 (a) and 2 (b), on the outer surface of the steel pipe 10, A leakage magnetic flux flaw detector in which a magnet yoke 5 for applying a static magnetic field in which the arc direction of the length portion of the steel pipe 10 is the main direction of the lines of magnetic force is disposed in close proximity and the probe 1 is disposed between the NS poles of the magnet yoke 5 While rotating 11 in the tube circumferential direction or further moving in the longitudinal direction of the tube, the magnetic flux leakage from the scratch existing location in the test surface is detected by the probe 1, and the detected location is identified as the scratch existing location. The magnet yoke 5 may be in a form (electromagnet type) in which an exciting coil is wound around a magnetic core instead of the single magnet type in FIG.

  As shown in FIG. 2 (c), the probe 1 uses a rectangular sensor 2 formed of a coil (abbreviated rectangular coil) having a rectangular cross section in the coil radial direction as a sensor for detecting leakage magnetic flux. One or a plurality of these are held by the holder 3 so that the coil central axis of the rectangular sensor 2 is substantially perpendicular to the surface to be measured. The rectangular sensor 2 may be formed of a Hall element array that is a rectangular shape in which a plurality of Hall elements are arranged in a line instead of the rectangular coil. When the Hall element array is used, the Hall element is held so that the thickness direction thereof is substantially perpendicular to the surface to be covered.

  Further, in eddy current flaw detection in which the outer surface of a metal material (not limited to a ferromagnet is sufficient as a conductor) is a test surface, conventionally, a detection coil as a sensor is placed close to the test surface and AC is applied thereto. An electric current is applied and moved while generating an eddy current on the test surface by electromagnetic induction, and a change in the current value of the detection coil due to a change in the eddy current and a change in the magnetic field is detected. The surface location is identified as the location of the flaw. Instead of using the detection coil for eddy current induction and eddy current change detection as described above, the detection coil may be dedicated to detection, and an eddy current induction coil may be provided separately.

The detection coil is a coil having the same form as the rectangular sensor 2, and a probe is used in which one or a plurality of the detection coils are held by a holder in the same manner as in the case of detecting leakage magnetic flux.
In the conventional probe 1, as illustrated in FIG. 2C, the sensor mounting angle that is the mounting angle of the rectangular sensor 2 to the holder 3 is fixed to one angle. The sensor mounting angle is an angle α in the long side direction of the rectangular sensor 2 with respect to the holder longitudinal direction 101. The holder 3 of the probe 1 is usually arranged so that the holder longitudinal direction 101 is parallel to the specimen longitudinal direction 102.

  The electromagnetic flaw detection using the rectangular sensor is most effective when the inclination angle of the long side direction of the rectangular sensor with respect to the longitudinal direction of the flaw (defect) is 0 ° regardless of whether it is a leakage magnetic flux flaw detection or an eddy current flaw detection. The detection power (detection signal intensity) is large, and the detection power decreases as the inclination angle approaches 90 °. FIG. 3 is a diagram showing the results of investigating the influence of the relationship between the inclination of the artificial defect and the sensor mounting angle on the leakage flux detection force using a conventional probe. As shown in FIG. 3, when the angle θ = 0 ° between the extending direction of the artificial defect and the longitudinal direction of the steel pipe (test material longitudinal direction 102), the detection force is when the sensor mounting angle α = 0 ° of the probe. Maximum and decreases with increasing angle α. When θ = 10 °, the power shows a peak when α = 10 °.

  That is, in the conventional electromagnetic flaw detection probe, since the sensor mounting angle is fixed to one type, the detection power is greatly reduced depending on the defect shape (extending direction). Therefore, it is necessary to use a probe having a sensor mounting angle that matches a defect shape that is likely to occur. In reality, there are not one type of defect shape that is likely to occur in a product, but a plurality of types. Therefore, in order to cope with this, a plurality of types of probes having different sensor mounting angles must be held, and there is a problem that the cost of holding the probe is increased. However, since the type of defect shape that is likely to change depending on the product shape, it is necessary to replace the probe with a probe type that matches the defect shape type each time, and probe replacement time (inspection line stop time) occurs. As a result, there was a problem that productivity decreased.

  The present invention for solving the above-mentioned problems is an electromagnetic flaw detection probe in which a plurality of rectangular sensors are held by a single holder, wherein two or more types of sensor mounting angles of the rectangular sensors to the holder are used. This is a probe for electromagnetic flaw detection.

  According to the present invention, the number of probes can be reduced, the cost of possessing probes can be reduced, and the line stop time can be greatly shortened to improve productivity.

It is the schematic which shows the example of the probe of this invention. It is the schematic which shows the example of the conventional probe. It is a graph which shows the result of having investigated the influence of the inclination of the artificial defect and the sensor attachment angle which have on the leakage magnetic flux detection force using the conventional probe. Conventional It is the schematic which shows the sensor output chart example of the probes B and C of a prior art example, and the probe A of the example of this invention.

FIG. 1 is a schematic view showing an example of the probe of the present invention. In FIG. 1, 6 is a probe of the present invention, and the same or corresponding members as in FIG.
In the probe 6, two of the four rectangular sensors 2 have a sensor mounting angle α = 0 degrees, and the remaining two have α = 10 degrees.
As described above, since two or more types of sensor mounting angles in one probe are used, flaw detection can be performed with one probe for a plurality of types of defect shapes (defect extending directions). Accordingly, the number of possessed probes can be reduced. Further, even if the defect shape type changes, there is no need to replace the probe, and the productivity is improved.

  In the leakage magnetic flux flaw detection of two kinds of seamless steel pipes having an extension angle θ with respect to the longitudinal direction of the steel pipe, which is likely to occur, 0 degrees and 10 degrees, the sensor mounting angle α = 0 degrees in the form shown in FIG. The probe A of the present invention having two kinds of 10 degrees in combination, and two conventional probes B in the form shown in FIG. 2 in which one is α = 0 degrees and the other is α = 10 degrees. , C were used for flaw detection. FIG. 4 shows an example of the sensor output chart. In the conventional example, the probe B with α = 0 degrees shows a sufficient peak height for the defect with θ = 0 degrees, but the peak height is insufficient with respect to the defect with θ = 10 degrees. The probe C with α = 10 degrees shows a sufficient peak height for the defect with θ = 10 degrees, but the peak height is insufficient with respect to the defect with θ = 0 degrees. Therefore, after flaw detection was performed on one of the probes B and C, the probe had to be replaced with the other and flaw detected again. On the other hand, in the example of the present invention, the probe A showed a sufficient peak height for any defect of θ = 0 degrees and 10 degrees, and therefore, only one flaw detection was required.

  As described above, according to the present invention, the number of probes can be reduced as compared with the prior art, and it is not necessary to stop the line for probe replacement, thereby improving productivity.

1 Probe (conventional)
2 Rectangular sensor 3 Holder 5 Magnet yoke 6 Probe (present invention)
10 Steel pipe (test material)
11 Rotation 101 Holder longitudinal direction 102 Test material longitudinal direction

Claims (1)

  An electromagnetic flaw detection probe comprising a plurality of rectangular sensors held by a single holder, wherein two or more types of sensor mounting angles of the rectangular sensors to the holder are used.

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