JP4175181B2 - Magnetic flux leakage flaw detector - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a leakage magnetic flux inspection apparatus that is installed in a line for manufacturing a magnetic material, particularly a thin steel plate (thin plate), and detects an internal defect and a surface defect of a material to be detected, and in particular, a sensitivity of a magnetic sensor for detecting leakage magnetic flux Calibration can be performed easily and with high accuracy.
In general, a magnetic sensor used for flaw detection on a thin plate is configured such that a plurality of magnetic sensors are continuously arranged so that flaw detection over a wide area is possible while moving the thin plate relative to the magnetic sensor. The present invention makes it possible to easily calibrate the sensitivity of the plurality of magnetic sensors (detecting elements).
[0002]
[Prior art]
In a line for producing a thin plate such as a tin plate, a galvanized iron plate, a surface-treated steel plate, etc., introduction of a leakage magnetic flux type flaw detection apparatus is proceeding (see Patent Document 1).
The principle of leakage magnetic flux flaw detection will be described with reference to FIG.
As shown in FIG. 7, direct current excitation is applied to the thin plate 1 that is the material to be inspected to saturate the magnetic flux 7 from the internal defect 3 in the thin plate 1, and the magnetic flux 7 is disturbed by the defect (this disturbance is mainly It is known that the magnetic flux 7 leaks from the magneto-resistive element, that is, the magnetic sensor 11 arranged with the magnetic sensing surface 11a facing the thin plate. And converted into an electrical signal for detection (see Patent Document 1, Patent Document 2, etc.).
[0003]
Next, a typical example of a leakage magnetic flux flaw detector applied to a thin plate will be described with reference to FIG.
In FIG. 8, a thin plate 1 that is a flaw detection material is wound around a nonmagnetic roll 2 and conveyed.
A magnetizing yoke 6 having an exciting coil 5 is disposed on the nonmagnetic roll 2 and excites the transported thin plate 1 to generate a leakage magnetic flux. Then, the leakage magnetic flux is detected by the magnetic sensor 11, and the defect of the thin plate is detected. A large number of magnetic sensors 11 are arranged in the vertical direction (that is, the width direction of the thin plate) on the paper surface of FIG. 8 to cover flaw detection on the entire surface of the thin plate 1. For example, in the case of a leakage magnetic flux flaw detector installed on a cold-rolled steel plate line having a width of about 500 mm, more than 300 magnetic sensors are arranged in the width direction. A magnetic sensor head 10 is constructed by integrating a magnetizing yoke 6 having an exciting coil 5 and a magnetic sensor 11.
[0004]
A detection signal which is an output of a signal detected by the magnetic sensor 11 is amplified by the amplifier 12 and further output as an inspection signal, and the defect determination means 13 makes a defect determination using the inspection signal as an input.
By the way, when using a leakage magnetic flux flaw detector having a large number of magnetic sensors, it is necessary to perform a calibration work for periodically checking and adjusting changes in sensitivity of each sensor. For this sensitivity calibration, an actual defect sample to be detected is used, or a simulated sample or a simulated magnetic input that provides an equivalent inspection output is used. Based on these simulated inputs, Check the sensitivity of each sensor and adjust the gain. Conventional sensitivity adjustment methods and apparatuses having a sensitivity adjustment function include the following, which have already been put into practical use.
(1) A coil that generates a constant alternating magnetic field and an alternating current power source are arranged on the non-magnetic sensing surface 11b side of the detection element (magnetic sensor), and the inspection output obtained by the magnetic field of the coil is adjusted to a constant sensitivity ( (See Patent Document 3).
(2) A calibration coil (copper wire) that generates a magnetic field is wound around the detection element (magnetic sensor), and the inspection output obtained by the magnetic field of the coil is adjusted to a constant sensitivity (see Patent Document 4).
(3) An off-line sensitivity calibration device is installed near the magnetic sensing surface 11a side of the magnetic sensor to move or rotate the saddle sample that generates a leakage flux equivalent to the inspection target at the same speed as the inspection speed. The sensitivity is adjusted so that the obtained inspection output is constant (see Patent Document 5). In addition, a natural defect and the artificial defect used as an equivalent test output, for example, a drill hole and a concave pit, are used for a saddle sample. In addition, a test method using a magnetic metal wire in place of the artificial cage has been put into practical use (see Patent Document 6).
(4) A calibration magnetism generator is embedded on the surface of a calibration roll for sensitivity calibration, a simulated magnetic field is generated while rotating the roll, and the gain of the apparatus is adjusted (see Patent Document 7).
[0005]
[Patent Document 1]
Japanese Patent Laid-Open No. 56-61645 [Patent Document 2]
JP 2002-195984 A [Patent Document 3]
JP-A-3-134555 [Patent Document 4]
JP-A-5-10926 [Patent Document 5]
Japanese Patent Laid-Open No. 11-108899 [Patent Document 6]
Japanese Patent Laid-Open No. 58-135954 [Patent Document 7]
JP-A-11-211698 [0006]
[Problems to be solved by the invention]
However, in order to arrange the calibration coil on the magnetic sensing surface 11a side of the detection element (magnetic sensor) as in (1) above, it is necessary to move the flaw detection device to the offline side.
In the above (2), the calibration coil (copper wire) is wound around each of a large number of detection elements (magnetic sensors) arranged in a row, so that the structure becomes complicated. It is necessary to separate them from each other, and there is a possibility that a dead zone occurs and the detection ability is lowered.
[0007]
In the above (3) and (4), it is necessary to move the flaw detection apparatus to the off-line side and prepare a large off-line facility for calibration.
In addition, since the flaw detection apparatus needs to be calibrated in as short a time as possible and returned to operation, it is necessary to reduce the work time required for the movement and detachment of the apparatus or for calibration.
[0008]
The present invention provides a leakage magnetic flux flaw detector capable of performing sensitivity calibration in a short time at an online position without moving the flaw detector to the offline side.
[0009]
[Means for Solving the Problems]
The present invention relates to a magnetic flux leakage inspection apparatus applied to a magnetic material, when comprising a conductor capable of generating a magnetic flux which simulates the leakage magnetic flux from the magnetic material, conductor line is the conductor pairs, in a row The non-magnetic sensing surfaces of the plurality of magnetic sensors arranged in a row are arranged on the side of the non-magnetic sensing surface opposite to the magnetic sensing surface so as not to sandwich the plurality of magnetic sensors arranged in parallel with the pair of conductors. in parallel, to solve the above problems by leakage flux flaw detection apparatus and a current direction flowing through the conductor pair is formed by the different parallel wires.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
A preferred embodiment of a leakage magnetic flux flaw detector having a sensitivity calibration function of the present invention will be described with reference to FIG. In addition, the same number is attached | subjected to the same member as the conventional leakage magnetic flux flaw detector demonstrated in FIG. 9, and description for the second time is abbreviate | omitted. Moreover, in FIG. 1, although description of the nonmagnetic roll 2 formed by winding the thin plate 1 is omitted, the nonmagnetic roll 2 is not essential to the present invention.
[0011]
In the embodiment shown in FIG. 1 of the present invention, the leakage magnetic flux from the magnetic material is simulated for sensitivity calibration on the nonmagnetic sensing surface 11b of the magnetic sensor 11 arranged in the width direction of the magnetic material (thin plate 1). It is characterized by comprising a conducting wire 15 for generating a magnetic flux. In order to avoid interference with the thin plate 1 and the nonmagnetic roll 2 on the magnetic sensing surface 11a side by arranging a sensitivity calibration lead wire constituting the main part of the calibration device on the nonmagnetic sensing surface 11b side Can be calibrated without evacuating to the offline side.
[0012]
The conducting wire 15 is preferably a conducting wire pair parallel to the nonmagnetic sensing surface 11b side of the magnetic sensor 11 and having different current directions. In particular, the magnetic sensor 11 is arranged in a row in the width direction of the thin plate 1, and the conducting wire 15 is a one-turn coil that is a pair of parallel conducting wires in parallel with the magnetic sensor 11 arranged in a row. It is preferable that
As described above, by arranging the conducting wire 15 as a parallel conducting wire of the one-turn coil, the magnetic flux 20 shown in FIG. 2 is generated, and the magnetic flux 20 crosses the magnetic sensor 11 vertically. Then, the magnetic flux 20 traversing the magnetic sensor 11 is adjusted to a level equivalent to the sensing level on the magnetic sensing surface 11a side for detecting the leakage magnetic flux generated due to the defect by adjusting the current flowing through the conducting wire 15. It is easy.
[0013]
Needless to say, the conductor 15 may be arranged as a coil having two or more turns, but the structure becomes complicated.
As already described, when the leakage magnetic flux flaw detector is installed in the cold-rolled steel plate line, the number of channels of the magnetic sensor 11 exceeds 300 in the width direction. For this reason, usually, as shown in FIG. 3 or FIG. 5, about 20 sensors are gathered in one sensor block 17, and the sensor block 17 is mounted on the sensor holder 18. Here, the sensor block 17 is provided with a connection pin 17a connected to the magnetic sensor 11, and the connection pin 17a is inserted into the connection hole 18a of the sensor holder 18. The connection hole 18a is connected to the amplifier 12.
[0014]
As shown in FIG. 4, if the conductor 15 is embedded in the vicinity of the back surface opposite to the magnetic sensing surface 11a of the magnetic sensor 11 in the sensor block 17, the conductor due to interference between the conductor 15 and the thin plate 1 etc. It is possible to avoid failures caused by deformation of the material. However, in this case, it is necessary to connect the conducting wires 15 between the sensor blocks 17.
Further, even if the lead wire 15 is routed to the non-magnetic sensing surface 11b side of the magnetic sensor 11 as shown in FIG. 5, it functions as a one-turn coil equivalent to the already described embodiment for each magnetic sensor. Further, it is apparent that a calibration lead may be individually arranged on the non-magnetic sensing surface 11b side for each magnetic sensor.
[0015]
In the present invention, the simulation signal input to the conductor 15 may be a time / signal intensity profile when an actual defect passes online. Various defects can be simulated by arbitrarily selecting the peak value of the input voltage (or current).
As an example, an input simulation signal is shown in FIG. In the figure, a signal corresponding to a defect of 2 msec is input every 100 msec. The signal strength is 1A. The waveform of the simulation signal is preferably a rectangular wave (FIG. 6A) that is easy to reproduce and easy to generate, or a half-wave sine wave. FIG. 6B shows how a detection signal having a signal intensity of 2 V is obtained from the magnetic sensor. The sensitivity can be easily calibrated with high accuracy by adjusting the gain of the amplifier so that the detection signal matches the intensity of the target inspection signal.
[0016]
【The invention's effect】
The present invention also eliminates the need to pull the flaw detection device off-line. In addition, sensitivity calibration of a large number of magnetic sensors exceeding 300 was performed almost simultaneously, and the time required for sensitivity calibration could be greatly reduced.
[Brief description of the drawings]
FIG. 1 is a schematic diagram (a) showing a configuration of a leakage magnetic flux flaw detector having a sensitivity calibration function of the present invention, and an AA view (b) thereof.
FIG. 2 is a schematic diagram showing a magnetic flux distribution when the sensitivity calibration function of the present invention is applied.
FIG. 3 is a schematic diagram showing an example of arrangement of sensitivity calibration lead wires in a leakage magnetic flux flaw detector.
FIG. 4 is a schematic view showing an example in which a sensitivity calibration lead is incorporated and arranged in a sensor holder.
FIG. 5 is a schematic view showing another arrangement example of the sensitivity calibration lead wire incorporated in the sensor holder.
FIG. 6 is a schematic diagram of a time / signal intensity profile showing a suitable example (a) of a simulated signal input to a sensitivity calibration lead and a detection signal (b) from the sensor in that case.
FIG. 7 is a diagram for explaining the principle of leakage magnetic flux flaw detection.
FIG. 8 is a schematic diagram showing a typical example of a leakage magnetic flux flaw detector.
[Explanation of symbols]
1 Thin steel plate (thin plate)
2 Nonmagnetic roll 3 Internal defect 5 Excitation coil 6 Magnetization yoke 7 Leakage magnetic flux
10 Magnetic sensor head
11 Magnetic sensor
11a Magnetic sensing surface
11b Non-magnetic sensing surface
12 Amplifier
13 Defect judgment means
15 Coil conductor
17 Sensor block
17a connection pin
18 Sensor holder
18a Connection hole
20 Magnetic flux

Claims (1)

A leakage magnetic flux flaw detector applied to a magnetic material,
In providing a conductor that can generate magnetic flux imitating leakage magnetic flux from the magnetic material, the conductor is a conductor pair, so that a plurality of magnetic sensors arranged in parallel in a row are not sandwiched between the conductor pairs. Parallel conductors arranged on the non-magnetic sensing surface side opposite to the magnetic sensing surface and parallel to the non-magnetic sensing surfaces of the plurality of magnetic sensors arranged in a row and having different current directions flowing in the pair of conductors. A leakage magnetic flux flaw detector characterized by comprising

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