JP2014106165A - Magnetic field visualization sensor and probe for magnetic flaw detection - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic field visualization sensor having a function capable of discriminating a magnetic flux leaking from a magnetizer to a magnetic sensor from a magnetic flux leaking to the outside of a specimen due to a defect in the specimen, and visualizing the defect on the spot and a probe for magnetic flaw detection including the magnetic field visualization sensor.SOLUTION: A probe for magnetic flaw detection includes: a magnetizer for magnetizing a specimen; a magnetic detection part for detecting a magnetic field generated due to a defect; and a light emitting element corresponding to the magnetic detection part. The probe for magnetic flaw detection includes a function for determining the lighting of the light emitting element in accordance with the arithmetic result of an output signal from the magnetic detection part.

Description

  The present invention relates to a magnetic field visualization sensor and a magnetic flaw detection probe.

  Conventionally, with magnetic materials, if there is a defect inside or on the surface, there may be a problem in quality such as strength. Therefore, various non-destructive methods such as X-ray transmission method and ultrasonic flaw detection method are used for quality control or quality assurance. Inspection is being conducted. In particular, an electromagnetic technique such as a magnetic particle inspection method or a leakage magnetic flux inspection method is often used for detecting defects near the surface or detecting defects on the surface and inside of a thin steel plate.

  In the magnetic particle flaw detection method, the test body is magnetized with a magnetizer or the like in which a coil is wound around a ferromagnetic core, and the magnetic powder coated with a fluorescent material is attached to the magnetic pole generated on the scratched surface of the test body surface. This is a flaw detection method in which a wound is detected by irradiating with an ultraviolet irradiation lamp and causing it to emit light. This flaw detection method is excellent in detecting surface defects and has an advantage that the defects can be visually recognized on the spot, but has low detectability of the internal defects below the surface. Next, the leakage magnetic flux flaw detection method is superior to the magnetic particle flaw detection method in terms of detectability of subsurface intrinsic defects. However, the leakage magnetic flux flaw detection method uses a sensor of a system that outputs a magnetic signal by detecting a magnetic field such as a Hall element or a magnetoresistive element as a magnetic sensor, and the defect cannot be visually recognized on the spot.

  Therefore, in the inspection of the internal defects under the surface of the magnetic material, by adding a function for visually detecting the defects on the spot to the magnetic field detection sensor used for the leakage magnetic flux flaw detection method, the magnetic particle flaw detection method is also provided. A simple test can be performed. As a magnetic sensor having such a function, there is, for example, Japanese Patent No. 4316974 (Patent Document 1). The sensor disclosed in Patent Document 1 is a sensor that forms a hole transport layer and a light emitting layer between electrodes, detects a change in light emission intensity due to a direct magnetic field intensity, and detects a magnetic field.

Japanese Patent No. 4316974

  On the other hand, as shown in FIG. 2A, the leakage magnetic flux 14 is generated from the side surfaces of the magnetic poles 13a and b of the magnetizer 30 in which a coil (not shown) is wound around the ferromagnetic core 5 used in the leakage magnetic flux flaw detection method. It always occurs. For this reason, in the case of a sensor that directly observes the change in the light emission intensity due to the magnetic field intensity as shown in Japanese Patent No. 4316974, this is caused by the leakage magnetic flux 14 from the side surfaces of the magnetic poles 13a and b and the defects inside the specimen 8. As a result, the magnetic flux leaking out of the test body 8 cannot be distinguished.

  Further, as shown in FIG. 2B, a method in which a magnetic shield 15 is provided between the magnetic poles 13a and b of the magnetizer 30 to block the leakage magnetic flux 14 from the side surfaces of the magnetic poles 13a and b can be considered. However, since the magnetic shield 15 is provided, the magnetic flux 12 in the test body 8 leaks to the magnetic shield 15 as the leakage magnetic flux 16, so that the magnetic field strength of the test body 8 is weakened and the detectability of defects is lowered. There was a problem.

  The present invention has been made to solve this problem. The magnetic flux leaking from the magnetizer to the magnetic sensor and the magnetic flux leaking outside the test body due to the defect in the test object are identified, and the defect is further detected. An object of the present invention is to provide a magnetic field visualizing sensor having a function of being visually recognized in the field and a magnetic flaw detection probe including the magnetic field visualizing sensor.

  The present invention is a magnetic flaw detection probe comprising a magnetizer for magnetizing a specimen, a magnetic detection unit for detecting a magnetic field generated due to a defect, and a light emitting element corresponding to the magnetic detection unit, A function of determining lighting of the light emitting element based on a calculation result of an output signal from the magnetic detection unit is provided.

  According to the present invention, a magnetic field visualization sensor having a function of discriminating a magnetic flux leaking from a magnetizer to a magnetic sensor and a magnetic flux leaking outside the test body due to a defect in the test body, and further allowing the defect to be visually recognized on the spot, and It is possible to provide a magnetic flaw detection probe including a magnetic field visualization sensor.

It is a figure which shows the magnetic field visualization sensor of this invention. It is a figure which shows the flow of the magnetic flux between a test body and a magnetizer. It is a figure which shows the probe for magnetic testing of this invention. (A) It is AA sectional drawing of FIG. (B) It is AA sectional drawing of FIG. 3 which provided the horizontal hole under the surface of the test body. It is a block diagram of a signal processing part. (A) It is a figure which shows the sensor signal of a Hall element at the time of magnetizing a test body in FIG. 4 (a), and the lighting condition of LED. (B) It is a figure which shows the sensor signal of a Hall element at the time of magnetizing a test body in FIG.4 (b), and the lighting condition of LED. (A) It is a figure which shows the sensor signal which subtracted the sensor signal of FIG. 6 (a) from FIG.6 (b), and the lighting condition of LED. (B) It is a figure which shows the lighting condition of the sensor signal and LED which processed the position difference process of the sensor signal of Fig.7 (a). It is a figure which shows one form of the block diagram of a signal processing part. (A) It is a figure which shows the lighting condition of LED which performed the process of the direction identification part to the sensor signal of Fig.7 (a). (B) It is a figure which shows the lighting condition of LED which performed the process of the direction identification part to the sensor signal of FIG.7 (b). It is AA sectional drawing of the probe for magnetic flaw detection which combined the Hall element and LED of the magnetic field visualization sensor into one. It is a figure which shows one form of the block diagram of the signal processing part which added the function which records a sensor signal synchronizing with an encoder signal.

  The present invention relates to inspection of a magnetic material, and relates to a sensor for turning on a light emitting element at a position where a magnetic field is detected and clearly indicating a magnetic field generation position, and a probe for magnetic flaw detection having the sensor. Examples of the present invention will be described below.

  A magnetic field visualization sensor and a magnetic flaw detection probe, which are a preferred embodiment of the present invention, will be described below with reference to FIGS.

  FIG. 1 shows a magnetic field visualization sensor. As a magnetic sensor, a magnetic detection unit is arranged in a two-dimensional array on one outer surface of a U-shaped substrate, and light emitting elements are arranged on the opposite outer surface at positions corresponding to the magnetic detection units. In FIG. 1, the magnetic detection unit is a Hall element 1, and the light emitting element is constituted by an LED 2. A cable of the hall element 1 and the LED 2 is connected to the signal processing unit 4 to constitute a magnetic field visualization sensor 10. Of course, a magnetoresistive element such as an AMR sensor or a TMR sensor may be used as the magnetic sensor used in the magnetic field visualization sensor 10, and an organic EL or liquid crystal may be used as the light emitting element. Further, the arrangement of the magnetic sensors and the light emitting elements may be a one-dimensional array, and the U-shaped substrate 3 may be configured by combining two independent substrates.

  FIG. 3 shows a magnetic flaw detection probe 20 using the magnetic field visualization sensor 10. A magnetizer 30 is provided on the magnetic material test body 8, and the magnetic field visualization sensor 10 is disposed between the magnetic poles of the magnetizer 30. The magnetizer 30 has a structure in which a coil 6 is wound around a ferromagnetic core 5. The test body 8 is magnetized by the power supply 7 connected to the magnetizer 30. FIG. 4A shows a central cross section (AA cross-sectional view) of the magnetic flaw detection probe 20 in the depth direction. FIG. 4B shows a view in which a horizontal hole 9 is provided below the surface of the test body 8. The magnetic field visualization sensor 10 detects the magnetic field caused by the defect, turns on the LED 2, and processes the process until the defect is visually recognized. The one row of Hall elements 1 and LED 2 shown in FIGS. It explains using.

  6 (a) and 6 (b) show the sensor signals 400 and 500 and the holes when the specimen 8 is magnetized by the magnetizer 30 and the Hall element 1 detects the magnetic field in FIGS. 4 (a) and 4 (b). The lighting state of the LED 2 corresponding to the element 1 is shown. The direction of magnetization is the same as in FIG. 2, and the Hall element 1 outputs a positive signal with respect to the magnetic flux in the Z-axis direction, and outputs a negative signal with respect to the magnetic flux in the reverse direction with respect to the Z-axis. As shown in FIG. 6 (a), even in a healthy part where there is no defect in the test body, the magnetic flux leaks from the magnetic pole side surface of the magnetizer 30 to the surface of the test body 8, and thus the sensor signal is detected.

  FIG. 5 is a block diagram of the signal processing unit 4 that determines whether the LED 2 is turned on. When the sensor signal 100 recorded by the sensor signal recording unit 110 is directly processed by the threshold processing unit 160 with the threshold shown in FIG. 6A, the LEDs 2 are all turned on except for the center 2f. Even if the same processing is performed under the conditions given the horizontal holes in FIG. 6B, the LEDs 2 are all turned on except for the center 2f. Therefore, the magnetic field visualization sensor 10 in which the LED 2 is lit only in the lateral hole is realized by the procedure described below.

  First, the sensor signal 400 of the Hall element 1 when the healthy part of the specimen 8 shown in FIG. 6A is magnetized is recorded in the sensor signal recording unit 110 shown in FIG. The signal 400 (initial signal) is stored in the initial signal storage unit 120. Thereafter, all of the sensor signals 500 recorded from the specimen to be tested for defects are subtracted from the initial signal stored in the initial signal storage unit 120 in the initial signal subtracting unit 130. FIG. 7A shows the result of subtracting the sensor signal 400 of FIG. 6A stored as the initial signal from the sensor signal 500 of FIG. 6B. This sensor signal 600 is stored in the processing signal storage unit 150. Here, the threshold value processing unit 160 processes the sensor signal 600 with the threshold value shown in FIG. 7A, and outputs the sensor signal exceeding the threshold value (2d, 2e, 2g, 2h) corresponding to the magnetic detection unit. ) Is lit. In this way, there is one LED 2f that is extinguished at the center, and if the same number of LEDs 2d, 2e, 2g, and 2h are lit, and the outer LEDs 2c and 2i are off, the LED 2 that is lit It can be seen that there is a defect between and the defect is in the vicinity of the LED 2f.

  Further, as shown in FIG. 7 (b), the sensor signal 600 shown in FIG. 7 (a) is taken by the position difference processing unit 140 shown in FIG. As a result, differential information is obtained, and defect detectability is improved. When the sensor signal 700 is processed by the threshold processing unit 160 with the threshold shown in FIG. 7B, 2e, 2f, and 2g are turned on. Since the sensor signal subjected to the difference processing has a peak at the center like the sensor signal 700, it can be understood that the center of the lit LED 2, in the case of FIG. 7B, is the position closest to the defect.

  As described above, according to this embodiment, the light-emitting element corresponding to the magnetic sensor that can visually recognize the surface of the test piece of the magnetic material and the scratch under the surface is provided on the spot, and the output signal of the magnetic sensor is processed. The magnetic field visualization sensor and the magnetic field visualization sensor have a signal processing function for discriminating between the noise signal of the magnetic flux leaked from the magnetizer and the magnetic field signal caused by the defect and lighting only the magnetic sensor that detected the magnetic field signal caused by the defect. It is possible to provide a probe for magnetic testing provided with

  Example 2 of the signal processing unit 4 of the magnetic field visualization sensor 10 is shown in FIGS. A direction identifying unit 170 is provided after the initial signal subtracting unit 130 to identify the direction of the magnetic flux passing through the Hall element. FIG. 9A shows the result of adding the processing of the direction identification unit 170 to the sensor signal 600 of FIG. In FIG. 9 (a), the direction of the detected magnetic field is represented by shading when the LEDs 2d, 2e and the LEDs 2g, 2h are turned on. As another expression method, the LEDs 2d, 2e are turned on, and the LEDs 2g and 2h are turned on. It can also be realized by flashing. Another possible method is to arrange LEDs 2 of different colors with respect to the Hall element 1 and change the color of the LEDs 2 that are lit depending on the direction of the detected magnetic field. As shown in FIG. 9 (a), the direction of the magnetic flux changes before and after the defect such as the horizontal hole 9. Therefore, if the direction of the magnetic flux can be identified by the lighting state of the LED 2, the detectability of the defect is improved.

  Similarly, FIG. 9B shows the result of adding the process of the direction identifying unit 170 to the sensor signal 700 of FIG. Also in this case, since the sign of the sensor signal is inverted before and after the LED 2f, the LEDs 2e and 2g are turned on differently from the LED 2f as shown in FIG. 9B. Therefore, the detectability of defects improves as in the case of FIG. Further, as a method for improving the detectability of defects, there is a method in which a signal strength identifying unit 180 is added after the threshold processing unit 160 as shown in FIG. After identifying the direction of the magnetic field, the signal strength identifying unit 180 changes the shade and color of the LED according to the signal strength to represent a more detailed magnetic field distribution. Further, by using a smaller Hall element 1 and narrowing the interval between the Hall elements 1, the resolution of magnetic field detection is improved, and the defect detectability is also improved.

  A third embodiment is shown in FIGS. One Hall element 1 and one LED 2 are installed on the U-shaped substrate 3, and the U-shaped substrate 3 is reciprocally scanned on the same line, and synchronized with a signal 800 of an encoder (not shown) during forward scanning. The sensor signal 100 of the Hall element 1 is recorded in the sensor signal recording unit 110 of the signal processing unit 4. Subsequent processing from the initial signal subtracting unit 130 to the threshold processing unit 160 is performed in the same manner as in the first and second embodiments, and the lighting determination is performed on the sensor signal 100 at the position of each encoder signal 800. When the U-shaped substrate 3 reaches the position where the LED 2 is lit (in synchronization with the position of the encoder signal) during the backward scan after completion of the lighting determination at each position, the LED 2 is lit. By improving the resolution of the encoder by such a method, the resolution of the magnetic field to be detected is improved, and the defect detectability can be further improved.

The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the invention described in the claims, and it goes without saying that these are also included in the present invention. Specifically, the Hall element 1, the LED 2, the U-shaped substrate 3, and the signal processing unit 4 are configured according to the present invention in accordance with the magnetic characteristics of the steel material to be measured, the size of the defect to be detected and the leakage magnetic flux distribution. Adjustments can be made as appropriate without departing from the spirit of the invention.

  DESCRIPTION OF SYMBOLS 1 ... Hall element, 2 ... LED, 3 ... U-shaped board | substrate, 4 ... Signal processing part, 5 ... Core, 6 ... Coil, 7 ... Power supply, 8 ... Test body, 9 ... Side hole, 10 ... Magnetic field visualization sensor, 13a, b ... magnetic pole, 15 ... magnetic shield, 20 ... probe for flaw detection, 30 ... magnetizer

Claims (6)

  A magnetometer for magnetizing a test body, a magnetic detection unit for detecting a magnetic field generated due to a defect, and a probe for magnetic testing including a light emitting element corresponding to the magnetic detection unit, from the magnetic detection unit A probe for magnetic flaw detection, comprising a function of determining whether the light emitting element is turned on or off based on the calculation result of the output signal.   In Claim 1, From the detection signal obtained from the initial signal memory | storage part which memorize | stores beforehand the detection signal which the said magnetic detection part detected when the healthy part of the said test body was magnetized, and the test body which tests the presence or absence of a defect A probe for magnetic testing, comprising: an initial signal subtracting unit that subtracts the initial signal; and a threshold processing unit that processes the sensor signal output from the initial signal subtracting unit and a threshold value.   3. The probe for magnetic flaw detection according to claim 1, wherein the threshold value processing unit has a function of lighting the light emitting element corresponding to the magnetic detection unit that outputs a sensor signal exceeding a threshold value.   4. The probe for magnetic flaw detection according to claim 3, further comprising a direction identification unit that identifies a direction of a magnetic flux penetrating the magnetic detection unit based on a sensor signal output from the initial signal subtraction unit.   In Claim 1, the said magnetic detection part and the said light emitting element are reciprocated scanned between the magnetic poles of the said magnetizer, the sensor signal from the said magnetic detection part is recorded synchronizing with an encoder signal at the time of an outward scan, A probe for magnetic flaw detection, comprising a function of determining lighting and lighting the light emitting element in synchronization with the position of the encoder signal during backward scanning. A magnetic field visualization sensor used for a magnetic flaw detection probe using a magnetizer for magnetizing a specimen,
A magnetic field visualization sensor comprising a magnetic detection unit for detecting a magnetic field generated due to a defect and a light emitting element corresponding to the magnetic detection unit, wherein the light emission is performed according to a calculation result of an output signal from the magnetic detection unit. Magnetic field visualization sensor with a function to determine lighting of the element.