WO2003071256A1

WO2003071256A1 - Fluorescent magnetic flaw detector and fluorescent magnetic flaw detecting method

Info

Publication number: WO2003071256A1
Application number: PCT/JP2003/001642
Authority: WO
Inventors: Shuji Naito; Hideki Matsuda; Manabu Kuninaga
Original assignee: Nippon Steel Corporation
Priority date: 2002-02-19
Filing date: 2003-02-17
Publication date: 2003-08-28
Also published as: KR20040088504A; JP4184976B2; KR100667141B1; JPWO2003071256A1

Abstract

A fluorescent magnetic powder flaw detector capable of providing a sharp, bright, florescent-magnetic-powder-pattern image, and being free from complicated mechanisms, low in costs and excellent in maintainability, wherein the light source (26) of a ultraviolet irradiation device (25) uses strobe light, and an imaging device (30) consists of a CCD camera having at the front thereof a band-pass filter (32) for transmitting a fluorescence’s spectral band only and being added with the function of opening a shutter as much as the emission time of strobe light and with an image signal multiplying function. Accordingly, a clear fluorescent magnetic powder pattern can be obtained, and a higher relative speed between an object material of inspection and a flaw detector is made possible.

Description

Description Fluorescent magnetic particle flaw detector and fluorescent magnetic particle flaw detection method

The present invention relates to an automatic surface defect inspection apparatus for steel products, particularly to a fluorescent magnetic particle inspection apparatus and a fluorescent magnetic particle inspection method suitable for use in surface defect inspection of hot-rolled products and their welds. Background art

Because hot-rolled products such as hot-rolled steel strips, thick plates, steel pipes, and bar steel have scales and oil stains on their surfaces, and are coarser than cold-rolled products, it is difficult to automate surface defect inspection. is there. Therefore, in the past, the visual inspection of the inspector or the visual inspection by the magnetic particle flaw detection method when detection accuracy was required had been used.

Among the magnetic particle flaw detection methods described above, the fluorescent magnetic particle flaw detection method using fluorescent magnetic powder has an advantage that, when the fluorescent magnetic powder accumulated on the defective portion is irradiated with ultraviolet rays, disturbing factors such as surface scale are suppressed, and only the defective portion is exposed. There is. In recent years, there have been attempts to take advantage of this advantage by capturing the fluorescent magnetic powder pattern with a TV camera and processing it by signal processing to automate it. However, the fluorescence obtained by irradiating ultraviolet light is weaker than that of ordinary light illumination, so if the relative speed between the test object and the TV camera increases, the image blurs due to the image flow, A defect extending in a direction perpendicular to the traveling direction has a problem that the signal level is significantly reduced.

In order to address these problems, conventional equipment has a mirror swing mechanism to cancel the relative movement speed with respect to the inspection target, or a copy mechanism of a transport device to suppress the relative movement between the inspection target and the imaging device. Establishment I was One of the conventional automatic flaw detectors is to move the specimen in the longitudinal direction, and use a TV mirror to capture an image in synchronism with the movement of the imaging location via a scanning mirror to improve defect detection accuracy (See, for example, JP-A-4-65660). On the other hand, in other automatic flaw detectors, the material to be inspected is set aside, and a scanning mirror and a TV camera are installed on a carriage that travels in the longitudinal direction. In this way, images are taken with a TV camera to improve the accuracy of defect detection (see, for example, Japanese Patent Application Laid-Open No. Hei 5-273150).

The above prior art has several problems. As described in the official gazette of Japanese Patent Application Laid-Open No. 5-273150, it is necessary to generate a distance signal using a pulse generator or the like attached to a touch roll in order to achieve accurate synchronization. However, an error may occur due to slippage between the test sample and the touch roll. In addition, if the test object swings or is bent when the test object is conveyed, an image flow in a direction that cannot be followed by the vibrating mirror occurs. Even with the apparatus disclosed in Japanese Patent Application Laid-Open No. 4-65660, there are problems with relative swinging and bending of the material to be inspected. Furthermore, as the relative speed increases, the angle of deflection of the mirror increases, resulting in an image that looks the same as an oblique view, and inevitably results in an optically distorted image. Moreover, such a mechanical mechanism has problems such as complicatedness, high cost, and low maintainability when trying to improve the accuracy.

In order to solve these problems, it is only necessary to acquire a still image instantaneously, and this can be achieved by stroboscopic illumination in ordinary TV shooting and the like. However, the spectrum of ordinary flash pulp contains only a small amount of ultraviolet light components, and a small amount of magnetic powder gathers at the defect in magnetic particle flaw detection. Therefore, only weak fluorescent images are usually obtained, and sufficient sensitivity cannot be obtained with ordinary TV cameras and ultraviolet strobe lighting. T JP03 / 01642 Disclosure of the invention

The present invention solves the above-mentioned problems, can obtain a clear and bright fluorescent magnetic powder-like image, eliminates complicated mechanisms such as a mirror swing mechanism and a copying mechanism, and is inexpensive and excellent in maintainability. It is an object of the present invention to provide a fluorescent magnetic particle flaw detector. The gist of the present invention is as follows.

(1) A magnetizing device that magnetizes the surface of a steel material or a welded part of a steel material to be inspected, a magnetic particle liquid spray nozzle that sprays a magnetic powder solution on the surface of the material to be inspected, and ultraviolet light that irradiates the surface to be inspected In a fluorescent magnetic particle flaw detection device including an irradiation device, an imaging device for imaging a surface to be inspected, and an image processing device for processing an imaged screen to determine the presence or absence of a flaw,

A CCD having a band-pass filter on the front surface thereof for transmitting only a fluorescent spectrum band, and having a function of opening a shutter and a function of doubling a video signal for the emission time of the tropo light. A fluorescent magnetic particle flaw detection device characterized in that the relative speed between the material to be inspected and the flaw detection device can be increased by using a force camera.

(2) The magnetizing device provides a pair of electromagnets with four poles arranged so that the pair of electromagnets are symmetrical about an axis perpendicular to the surface to be inspected and the magnetic poles form the vertices of a square, and on one side of the square. By increasing the number of poles in the perpendicular direction by two at a time, the magnetic poles form a plurality of squares, and the magnetic poles arranged at the diagonal points of the newly formed square are each paired, effectively forming a pair of electromagnets. The fluorescent magnetic particle flaw detector according to (1), characterized in that it is a magnetizing device that generates a plurality of rotating magnetic fields on the surface to be inspected through a magnetized alternating current in which the phases of the electromagnets are shifted at the same frequency.

(3) The magnetizing device rotates a pair of electromagnets around an axis perpendicular to the surface to be inspected. In addition to providing four poles that are arranged axially symmetrically and with the magnetic poles forming the vertices of a square, four poles are added at regular intervals to one side of the square, and four poles are used to form multiple squares. By providing a yoke that short-circuits the magnetic poles at every four poles, the symmetry of each of the four magnetic poles is maintained, and two pairs of magnetized coils are used as diagonal magnetized coils. (1) The fluorescent magnetic particle flaw detector according to (1), wherein the magnetizing device generates a plurality of rotating magnetic fields on the surface to be inspected by passing a magnetized alternating current having the same frequency and a phase shifted.

(4) The magnetizing device has two poles, i.e., a pair of four poles, in which a pair of electromagnets are arranged symmetrically about an axis perpendicular to the surface to be inspected and the magnetic poles form rectangular or square vertices. Or two or more pairs, the diagonal poles or four poles of each 耝 electromagnet are short-circuited with a yoke, and the same frequency is applied to two pairs of magnetized coils wound around one pair of two poles. (1) The fluorescent magnetic powder according to (1), which is a magnetizing device that generates one or more rotating magnetic fields on the surface to be inspected through a magnetized alternating current having a phase shifted.

(5) A distance measuring device that measures the moving distance of each point on the surface to be inspected that moves relatively to the imaging position of the imaging device, and uses the moving distance information measured by the distance measuring device. The fluorescent magnetic particle flaw detector according to any one of (1) to (4), wherein surface flaws of the material to be inspected detected by mapping are mapped.

(6) Magnetizing the surface layer of the steel to be inspected or the welded portion of the steel member; magnetic powder spraying step for spraying the magnetic powder on the surface of the material to be inspected; and irradiating ultraviolet rays to the surface to be inspected A method for imaging a surface to be inspected, and an image processing step of processing an imaged screen to determine the presence or absence of a flaw.

The imaging step includes a pan that transmits only the fluorescent spectrum band.

Four By using a PT / JP03 / 01642 pass filter, opening the shutter for the duration of the stop light, and using a CCD camera with a video signal doubling function, A fluorescent magnetic particle flaw detection method characterized in that the relative speed of the flaw detector can be increased.

(7) The step of magnetizing comprises: providing a pair of electromagnets symmetrically about an axis perpendicular to the surface to be inspected and four poles arranged such that the magnetic poles form the vertices of a square; By increasing the number of poles by two in the direction perpendicular to one side, the magnetic poles form a plurality of squares, and the magnetic poles arranged at the diagonal points of the newly formed square are each paired, so that substantially one The magnetizing method generates a plurality of rotating magnetic fields on the surface to be inspected through a magnetized alternating current in which the phases are shifted by the same frequency to each electromagnet by the step of forming a pair of electromagnets. (6) The fluorescent magnetic particle flaw detection method described.

(8) The step of magnetizing comprises: providing a pair of electromagnets with four poles arranged so that the pair of electromagnets are symmetrical about an axis perpendicular to the surface to be inspected and the magnetic poles form the vertices of a square; The four poles are increased by four poles at regular intervals on one side of each of the four poles, arranged so that the four poles form a plurality of squares, and a yoke that shorts the poles is provided for each four poles. By maintaining the symmetry, the diagonal magnetized coils are paired, and two pairs of magnetized coils are passed through the magnetized alternating current phase-shifted at the same frequency. The fluorescent magnetic particle flaw detection method according to (6), wherein the method is a magnetization method for generating a rotating magnetic field.

(9) The step of magnetizing comprises: a pair of four poles in which two poles, i.e., a pair of electromagnets, are arranged symmetrically about an axis perpendicular to the surface to be inspected and the magnetic poles form rectangular or square vertices. It consists of two or more pairs, and the diagonal poles or four poles of each set of electromagnets are short-circuited with yoke, and the same frequency is applied to two pairs of magnetized coils wound around one pair of two poles. Rank The fluorescent magnetic particle flaw detection method according to (6), wherein the method is a magnetization method in which one or more rotating magnetic fields are generated on a surface to be inspected by a step of passing a magnetized alternating current having phases shifted.

(10) The step of measuring the moving distance of each point on the surface to be inspected, which moves relatively to the imaging position in the imaging step, is detected using the moving distance information measured by the distance measuring device. The fluorescent magnetic particle flaw detection method according to any one of (6) to (9), further comprising a step of masking a surface layer flaw of the material to be inspected.

As described above, the fluorescent magnetic particle flaw detector of the present invention is provided with the CCD camera having the function of opening the shutter for the emission time of the strobe light and the function of multiplying the video signal. As a result, a sharp image without blurring, which is equivalent to that during still shooting, can be obtained regardless of the relative movement or swinging direction. In addition, even a weak fluorescent image by an ultraviolet strobe can be photographed with sufficient sensitivity, and a clear bright fluorescent magnetic powder pattern image can be obtained. Therefore, the accuracy of defect detection is greatly improved.

Further, in the present invention, the magnetizing device is provided with four poles in which a pair of electromagnets are arranged axially symmetrically about an axis perpendicular to the surface to be inspected and the magnetic poles form the vertices of a square, and one side of the square is provided. By adding two poles at right angles to each other, the magnetic poles form a plurality of squares, and the magnetic poles arranged at the diagonal points of the newly formed square are paired, so that one pair is practically The magnet to be inspected has a configuration in which multiple rotating magnetic fields are generated on the surface to be inspected through a magnetized alternating current whose phases are shifted by the same frequency to each of the electromagnets. During successive passes, it is magnetized, so the magnetization time becomes longer, and a clear fluorescent magnetic powder pattern is formed even when the material to be inspected moves at high speed.

Further, in the present invention, the magnetizing device may include a pair of electromagnets on the test surface. In addition to providing four poles arranged symmetrically about the axis perpendicular to the axis 42 and with the magnetic poles forming the vertices of a square, increasing the number of poles by four at regular intervals on one side of the square The magnetic poles are arranged so as to form a plurality of squares, and a yoke that shorts the magnetic poles is provided for each of the four poles to maintain the symmetry of each of the four magnetic poles. Since a plurality of rotating magnetic fields are generated on the surface to be inspected by passing a magnetized alternating current having the same frequency and a phase shifted through the pair of magnetized coils, the material to be inspected is aligned with a plurality of aligned magnetic fields. While passing through the electromagnet sequentially, it is magnetized, so the magnetization time becomes longer, and a clear fluorescent magnetic powder pattern is formed even when the material to be inspected moves at high speed. Also, all rotating magnetic fields can be equalized without adjusting the number of coil turns, power supply voltage, and the like for each electromagnet. By equalizing the rotating magnetic field, the defect detection ability is improved.

Further, in the present invention, the magnetizing device is a four-pole one in which two poles, that is, a pair of magnetic stones are arranged symmetrically about an axis perpendicular to the surface to be inspected and the magnetic poles form rectangular or square vertices. It consists of one or more pairs of electromagnets, and the diagonal or four poles of each pair of electromagnets are short-circuited with a yoke, and two pairs of magnets are wound around one pair of magnetic poles. The magnetizing time may be extended by generating one or more rotating magnetic fields on the surface to be inspected through a magnetized alternating current whose phase is shifted by the coil at the same frequency.

Further, in the present invention, when it is necessary to determine the position of each flaw detected by the fluorescent magnetic particle flaw detector, each of the flaws on the surface to be inspected which moves relatively to the imaging position of the imaging device is required. A distance measuring instrument that measures the moving distance of a point with reference to a certain point on the surface to be inspected is incorporated into the fluorescent magnetic particle flaw detector, and the surface layer of the inspected material detected using the moving distance information measured by the distance measuring instrument Mapping flaws to facilitate subsequent flaw processing T JP03 / 01642 Yes. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 shows one embodiment of the present invention, and is a schematic side view of a fluorescent magnetic particle flaw detector.

FIG. 2 shows another embodiment of the present invention, and is a schematic side view of a fluorescent magnetic particle flaw detector.

FIG. 3 is a plan view of the fluorescent magnetic particle flaw detector shown in FIG.

FIG. 4 is a perspective view of an iron core of the magnetizing device of the fluorescent magnetic particle flaw detector according to the present invention.

FIG. 5 is a circuit diagram of a power supply and a magnetizing coil of the magnetizing device shown in FIG.

FIG. 6 is a graph of a magnetizing current supplied to the electromagnet of the fluorescent magnetic particle flaw detector according to the present invention.

FIG. 7 shows still another embodiment of the present invention, and is a schematic side view of a fluorescent magnetic particle flaw detector.

FIG. 8 is a plan view of the fluorescent magnetic particle flaw detector shown in FIG.

FIG. 9 is a circuit diagram of a power supply and a magnetized coil of the fluorescent magnetic particle flaw detector according to the present invention.

FIG. 10 is a drawing showing a partial cross section of another embodiment of the light source shown in FIG.

FIG. 11 is a diagram showing an embodiment in which the light source and the imaging device are arranged outside the magnetizer in the fluorescent magnetic particle flaw detector according to the present invention.

FIG. 12 is a view showing an example of an embodiment based on claim 4 of the present invention, in which an X-type or blind-type yoke is used to image outside with a magnetizer.

FIG. 13 is a diagram showing an example in which an image pickup position is measured by a moving distance measuring device and a defect position is recorded in the embodiment according to the fifth embodiment of the present invention. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention will be described with reference to the drawings.

FIG. 1 shows an embodiment of the present invention, and is a schematic configuration diagram of a fluorescent magnetic particle flaw detector. The fluorescent magnetic particle flaw detector includes a magnetizing device 10, a magnetic particle liquid spraying device 20, an ultraviolet irradiation device 25, an imaging device 30, and an image processing device 35.

The magnetizing device 10 comprises an electromagnet 11 in which a magnetizing coil 18 is wound around a leg 14 of a U-shaped iron core 12. DC is supplied to the magnetizing coil 18 from a DC power supply (not shown). The magnetizing coil 18 may be wound around a yoke 16 connecting the upper portions of the legs 14.

The magnetic powder liquid spraying device 20 includes a magnetic powder liquid injection nozzle 21 and a cleaning water supply nozzle 22. A magnetic powder tank is connected to the magnetic powder injection nozzle 21, and a water tank is connected to the washing water supply nozzle 22.

(Neither is shown) supplies a magnetic powder solution or washing water. Instead of the washing water supply nozzle 21, an air purge nozzle for ejecting air may be used. ·

The ultraviolet irradiation device 25 has an ultraviolet strobe light source 26. The ultraviolet light source 26 is, for example, a combination of a xenon flash lamp and a U340 filter. Xenon flash lamp bulbs are made of materials that transmit hard ultraviolet light. The emission time of the xenon flash lamp is about 10 S. The U340 filter emits and emits strobe light in a wide spectrum from hard ultraviolet rays to infrared rays, and transmits ultraviolet rays of about 310 to 390 nm, which are relatively safe for humans.

The image pickup device 30 is composed of a combination of an image pickup unit 31 composed of a CCD camera having a function of opening a shutter for a light emission time of the stop light and a function of multiplying a video signal, and a bandpass filter 32. here Uses an MCP CCD camera manufactured by Hamamatsu TV Co., Ltd. as the CCD camera. In this CCD camera, the optical image incident on the image intensifier is converted into photoelectrons on the photocathode. The photoelectrons are amplified several thousand times in the channel plate of the microphone opening, and become an optical image again on the phosphor screen. 'Shutter (gate) operation is controlled by the potential between the photocathode and the microchannel plate. When the microchannel plate potential is higher than the photocathode potential, the gate operation is turned on (the shutter is opened), and when the microchannel plate potential is lower, the gate operation is turned off.

The bandpass filter 32 transmits only the spectrum component of the fluorescent light. The irradiation light from the ultraviolet irradiation device 25 includes ultraviolet light for fluorescence excitation and, to a small extent, infrared light leaked from the U 340 filter. Since the imaging section 30 has wavelength sensitivity from the ultraviolet to the infrared region, it also captures the ultraviolet and infrared light. The pan-pass filter 32 enhances the ultraviolet and infrared rays to increase the S / N ratio of the image.

The image processing device 35 performs density correction, smoothing, binarization, and the like on the image signal from the imaging device 30 to determine whether there is a flaw. Criteria are created based on inspection data obtained in actual operations and stored in a table format in the image processing device.

In the fluorescent magnetic particle flaw detector configured as described above, the test object 1 is a drum-shaped welded structure obtained by bending and shaping a thick plate, and moves in the direction of the arrow. The part to be inspected is a welded part extending in the circumferential direction. The magnetizing device 10 DC magnetizes the magnetic flux so as to cross the weld. The fluorescent magnetic liquid is sprayed from the magnetic liquid spray nozzle 21 to the magnetized weld. If there is a defect in the surface layer of the material to be inspected 1, leakage magnetic flux is generated at the defect. The fluorescent magnetic powder in the magnetic powder liquid is attracted to the leakage magnetic flux and accumulates at the defective portion to form a fluorescent magnetic powder pattern. The cleaning water sprayed from the cleaning water supply nozzle 22 It flows down along the surface of 03 01642 to wash away excess magnetic powder. In general, the leakage magnetic flux at the defective portion is stronger than the leakage magnetic flux due to the unevenness of the non-defective portion. Therefore, when cleaning is performed at an appropriate flow rate, only the unnecessary magnetic powder at the non-defect portion is washed away. As a result, the SN ratio of the image captured by the imaging device 30 increases.

Ultraviolet light is emitted from above by the ultraviolet light source 26 to emit fluorescent magnetic powder accumulated at the defect. The emission time of the UV light source 26 is about 10 μsec as described above. The shutter of the above-mentioned CCD camera is adjusted so as to open for this light emission time. Usually, the frame rate of a CCD camera is 30 Hz, 33 ms e c. Therefore, the influence of the image flow and the illuminance of the surrounding environment is about 1 Z 3300. With such a short light emission time, the moving test object appears almost stationary, and a clear fluorescent magnetic powder pattern with no image flow can be imaged. As a result, it is possible to detect even minute cracks, which have conventionally been detected only when the test material is stationary, and the defect detection accuracy can be greatly improved.

2 to 5 show another embodiment of the present invention. Fig. 2 is a schematic side view of the fluorescent magnetic particle flaw detector, Fig. 3 is a plan view, Fig. 4 is a perspective view of an iron core of the magnetizing device, and Fig. 5 is a circuit diagram of a power supply and a magnetizing coil of the magnetizing device. In this embodiment, the same components as those shown in FIG. 1 are denoted by the same reference numerals, and detailed description thereof will be omitted.

In magnetic particle flaw detection, inspection standards sometimes require two-way magnetization in the direction of travel of the material to be inspected and in the direction perpendicular to the direction of travel. In such a case, the material to be inspected needs to be magnetized by a rotating magnetic field. In the fluorescent particle inspection apparatus of this embodiment, the magnetizing device generates a rotating magnetic field.

The fluorescent magnetic particle flaw detector includes a magnetizing device 40, a magnetic particle liquid spraying device 20, an ultraviolet irradiating device 25, an imaging device 30, and an image processing device 35. Magnetic powder liquid spraying device 20, ultraviolet irradiation device 25, imaging device 30, and image processing device Since 35 is the same as the device shown in FIG. 1, its description is omitted. The magnetizing device 40 includes three sets of magnetizers 41, 42, 43 provided with electromagnets and a power supply for supplying a magnetizing current to these magnetizers. The electromagnet core 60 has four U-shaped cores 61 to 64 arranged in a line at equal intervals. Both end portions of the first U-shaped iron core 61 and both end portions of the second U-shaped iron core 62 are connected to each other by a yoke 70 to form a first four-legged iron core 57. In addition, both ends of the second U-shaped iron core 62 and both ends of the third U-shaped iron core 63 are connected by yoke 70 to form a second quadruped iron core 58. Similarly, a third quadruple core 59 is formed. In the first quadruple iron core 57, the distance between the first U-shaped iron core 61 and the second U-shaped iron core 62 is equal to the distance between the legs 61A, B or 62A ', B' of the first U-shaped iron core 61. I'm sorry. Therefore, the four legs 61A, B, 62A ', B' are located at the vertices of the square. Similarly, in the second quadruple core 58 and the third quadruple core 59, the four legs are located at the vertices of the square.

Magnetizing coils 75Α, Β-78Α ', and Β' are wound around the legs 61 脚, Β-64Α ', and B', respectively. Of the magnetized coils 75 °, 〜 to 78 ′ ′, and B ′, one magnet is formed by the square-shaped magnetized coil facing in one diagonal direction, the U-shaped iron core and the yoke 70. For example, one electromagnet 51 is composed of the U-shaped iron cores 61 and 62, the yoke 70, and the magnetizing coils 75A and 76A 'in the first magnetizer 41, and the magnetizing coils 75Β and 76Β' are already used. One electromagnet 54 is configured. Similarly, the second magnetizer 42 forms electromagnets 52 and 55, and the third magnetizer 43 forms electromagnets 53 and 56, respectively.

The magnetizing device 40 has six sets of electromagnets including the three sets of electromagnets 51, 52, 53 and the three sets of electromagnets 54, 55, 56 thus configured. That is, four poles are provided in which a pair of electromagnets are arranged axially symmetrically about an axis perpendicular to the surface to be inspected and the magnetic poles form the vertices of a square. And By increasing the number of poles by two in the direction perpendicular to one side of the square, the magnetic poles are configured to form three squares, and the magnetic poles arranged at diagonal points of the newly formed square are paired with each other. As a pair of electromagnets.

FIG. 5 shows a circuit of the magnetizing coils 75Α to 78Β ′ and the power supply 80. An AC oscillator 81 is connected via a power amplifier 83 to the magnetizing coils 75 ° and 76A ′ and the magnetizing coils 77A and 78A ′ that are opposite to each other in the above-described square. An AC oscillator 81 is connected to the magnetizing coils 75B and 76B 'and the magnetizing coils 77B and 78B' which face each other in the diagonal direction via a 90 ° phase shifter 85 and a power amplifier 86. The power amplifiers 83 and 86 supply an alternating magnetizing current of a predetermined frequency to each of the magnetizing coils 75A to 78B according to a signal from the AC oscillator 81. The magnetizing coils 75B, 76B ', 77B, 78B' are supplied with an alternating magnetizing current 90 ° out of phase with respect to the magnetizing coils 75A, 76A ', 77A, 78A'. Fig. 6 shows the case where the magnets 51, 52, 53 are supplied with magnetized alternating current having the same frequency and a phase difference of 90 ° to the electromagnets 54, 55, 56. Note that a three-phase AC current power supply may be used and the phase difference may be 120 °.

In this embodiment, the number of magnetizers is three, but the number of magnetizers varies depending on the flaw detection conditions and the line speed (movement speed of the test object). For example, in magnetic particle inspection, it is recommended that the magnetic particle spray time be 5 seconds or more. Therefore, if the magnetic pole interval is lp [cm] and the line (inspected material) velocity is V [cm / sec], the transit time Tf of one magnetizer is Tf = lp / V. If n = 5 sec / Tf sec,

Integer greater than n + 2 magnetizers (magnetizer in purge section + magnetizer in imaging section)

Is preferably the number of magnetizers.

The magnetic powder spray nozzle 21 and the washing water supply nozzle 22 Are located in The ultraviolet irradiation device 25 and the imaging device 30 are arranged immediately above the third porcelain 43.

In the fluorescent magnetic particle flaw detector configured as described above, the slab 1 is sent in the direction of the arrow while being inclined with respect to the horizontal plane in order to wash away excess fluorescent magnetic powder with the washing water. The magnetizing device 40 is arranged so that the U-shaped iron cores 61 to 64 straddle the welding line 5. Since a magnetized alternating current having the same frequency and a phase difference of 90 ° is supplied to the electromagnets 54 to 56 for the electromagnets 51 to 53, a rotating magnetic field R is generated on the surface to be inspected for each magnetizer. The rotating magnetic field R has the same magnitude in the direction of the welding line and in the direction perpendicular thereto. The direction of rotation of the magnetic field of the second magnetizer 42 is opposite to the direction of rotation of the magnetic field of the first magnetizer 41 and the third magnetizer 43.

Since the rotating magnetic field R is an alternating magnetic field, it is demagnetized when the magnetized portion of the thick plate 1 moves away from the magnetic pole. However, in the magnetizing device 40 of this embodiment, since the magnetizing is performed for each magnetizer, the magnetic powder attached to the defective portion in the second magnetizer 42 is also held in the third magnetizer 43.

In general, it takes a certain amount of time for the magnetic powder in the sprayed magnetic powder liquid to move to the defect and accumulate to form a fluorescent magnetic powder pattern. Therefore, when a high-speed moving thick plate is subjected to magnetic particle flaw detection, the length of the magnetizing device must be increased according to the moving speed of the thick plate. On the other hand, to generate a rotating magnetic field as described above, the magnetic poles must be arranged at the vertices of a square. When the magnetic pole spacing of the magnetizing device is smaller, a high magnetic flux density is generated in the portion to be inspected between the magnetic poles.However, the spacing between the adjacent U-shaped iron cores becomes narrower, and sufficient time is not obtained to form the fluorescent magnetic powder pattern. . In this embodiment, since the three magnetizers 41, 42, and 43 magnetize each other, the magnetization time becomes longer, and a clear fluorescent magnetic powder pattern is formed even when the thick plate 1 moves at high speed. The number of magnetizers can be increased or decreased according to the feed speed of the test material or the flaw detection speed. 7 to 9 show still another embodiment of the present invention. FIG. 7 is a schematic side view of the fluorescent magnetic particle flaw detector, FIG. 8 is a plan view of the above-described device, and FIG. 9 is a circuit diagram of a power supply and a magnetizing coil of the magnetizing device.

The fluorescent magnetic particle flaw detector includes a magnetizing device 90, a magnetic particle liquid spraying device 20, an ultraviolet irradiating device 25, an imaging device 30, and an image processing device 35. Since the magnetic powder / liquid spraying device 20, the ultraviolet irradiation device 25, the imaging device 30, and the image processing device 35 are the same as those shown in FIG. 1, their description is omitted. The magnetizing device 90 includes three sets of magnetizers 91, 92, and 93 each having an electromagnet and a power supply for supplying a magnetizing current to these magnetizers. The iron core of the first magnetizer 91 is a first quadruple iron core 107 formed by connecting both end portions of the first U-shaped iron core 110 and both end portions of the second U-shaped iron core 111 with yoke 112, respectively. From The iron core of the second magnetizer 92 is formed of a second quadruple formed by connecting both end portions of the third U-shaped iron core 113 and both end portions of the fourth U-shaped iron core 114 with the yoke 115, respectively. It consists of 108 iron cores. Similarly, a third quadruple core 109 of the third magnetizer 93 is formed. In the first magnetizer 91, the distance between the first U-shaped iron core 110 and the second U-shaped iron core 111 is equal to the distance between the legs 110A, B or 111A ', B' of the first U-shaped iron core 110. I have. Therefore, the four legs 110A, B, 111A ', B are located at the vertices of the square. Similarly, in the second magnetizer 92 and the third magnetizer 93, the four legs are located at the vertices of the square.

The magnetizers 91, 92, and 93 are arranged such that the interval between the magnetic poles of adjacent magnetizers in the passing direction is equal to the interval between the magnetic poles of each magnetizer. For example, the distance between the magnetic pole of the leg 111B 'of the first magnetizer 91 and the magnetic pole of the leg 113A of the second magnetizer 92 is determined by the distance between the magnetic poles of the legs 110A and 111B' of the first magnetizer 91. equal. The number of magnetizers depends on the flaw detection conditions and the line speed (movement speed of the test object), as in the case of the device shown in Fig. 2. I can decide.

Magnetizing coils 121A, B to 126A ', B' are wound around each of the legs 110A, B to 117A ', B'. Among these magnetized coils 121A, B to 126A ', B', one magnetite is composed of the above-described square-shaped magnetized coil facing one diagonal direction, the U-shaped iron core, and the yoke. For example, the magnetizing device 90 in which the U-shaped iron cores 110 and 111, the iron core 112, and the magnetizing coils 121A and 122A 'make up one electromagnet 101 has three sets of electromagnets 101, 102, There are six sets of electromagnets, including 103 and three sets of electromagnets 104, 105, and 106. That is, four poles are provided in which a pair of electromagnets are arranged axially symmetrically about an axis perpendicular to the surface to be inspected and the magnetic poles form the vertices of a square. The poles are increased by 4 poles at right angles to one side of the square, so that the poles form three squares, and the newly formed poles at the diagonal points of the square are paired, respectively. By doing so, it is effectively a pair of electromagnets.

FIG. 9 shows the circuits of the magnetizing coils 121A to 126B 'and the power supply 130. An AC oscillator 131 is connected via a power amplifier 133 to the magnetizing coils 121 A and 122A ', the magnetizing coils 123A and 124A', and the magnetizing coils 125A and 126A 'which face one diagonal direction in the square. I have. AC oscillator 131 is connected to magnetizing coils 121B, 12 磁化 ', magnetizing coils 123B, 124B' and magnetizing coils 125B, 126B ', which face each other in the diagonal direction, via 90 ° phase shifter 135 and power amplifier 136. I have. The power amplifiers 133 and 136 supply an alternating magnetizing current of a predetermined frequency to each of the magnetizing coils 121A to 126B 'according to a signal from the AC oscillator 131. The magnetizing coils 121A, 122B ', 123B, 124B' and 125B, 126B 'have magnetizing coils 121A, 122A', 01642

Alternating magnetizing current with a 90 ° phase shift is supplied to 123A, 124A 'and 125A, 126A'.

In the fluorescent magnetic particle flaw detector configured as described above, the magnetizing device 90 is arranged so that the U-shaped iron cores 110, 111, 113, etc., straddle the welding line 5. Since a magnetized alternating current having the same frequency and a phase difference of 90 ° is supplied to the electromagnets 104 to 106 with respect to the electromagnets 101 to 103, a rotating magnetic field R is generated on the surface to be inspected for each magnetizer. The rotating magnetic field R has the same magnitude in the direction of the welding line and in the direction perpendicular thereto. The directions of rotation of the magnetic fields of the first magnetizer 91, the second magnetizer 92, and the third magnetizer 93 are the same.

Since the rotating magnetic field R is an alternating magnetic field, it is demagnetized when the magnetized portion of the thick plate 1 moves away from the magnetic pole. However, in the magnetizing device 90 according to the present embodiment, the magnetism is magnetized for each magnetizer, so that the magnetic powder attached to the defective portion in the second magnetizer 92 is also held in the third magnetizer 93. Also, in order to generate multiple rotating magnetic field strengths uniformly, it is necessary to equalize the magnetic flux flowing through all A-A 'pole pairs and BB' pole pairs. In this embodiment, if the number of turns of all the magnetized coils is made equal and a voltage is applied in parallel as shown in FIG. 9, the number of coil turns, power supply voltage, etc. are not adjusted for each magnetizer. All rotating magnetic fields can be equalized.

FIG. 10 shows another embodiment of the light source. The light source 140 includes a pair of LED panels 142 in which several tens of LEDs 144 that emit light in the ultraviolet region are arranged in a matrix. The LED panel 142 is provided between the leg 116A (not shown) and the leg 117 器 'of the third magnetizer 93 and the leg 116B (not shown) and the leg 117A' shown in FIG. They are located near the lower ends of these legs, with each in between. The LED 144 receives a pulse current from a power supply (not shown), emits light, and irradiates the inspection surface. With this LED light source 140, the strobe light source can be downsized, It can be placed near the expected position. Therefore, the lighting efficiency is high and the power supply is small.

FIG. 11 shows an embodiment in which the light source and the imaging device are outside the magnetizer. The magnetizer is an example using a yoke type (mouth type yoke). FIG. 12 shows an embodiment of claim 4, and FIG. 13 shows an embodiment of claim 5. Fig. 12 shows an example in which an image is taken outside of the magnet with an X-shaped or blind yoke. FIG. 13 shows an example in which the imaging position is measured by a moving distance measuring device and the defect position is recorded.

In the embodiment described above, the MCP type CCD camera combining the image intensifier with the shutter function and the CCD camera is used. However, basically, the shutter function, the video signal multiplication function and the MCP type CCD camera are used. Any type of ultra-high-sensitivity camera may be used. For example, an EB type CCD camera with a shirt function developed by Hamamatsu Photonics KK or an impact type CCD camera manufactured by Texas Instruments may be used. The LED light source shown in FIG. 10 is also applicable to the devices shown in FIGS. 1 and 2. Industrial applicability

The fluorescent magnetic particle flaw detector of the present invention is provided with a CCD camera having a function of opening the shutter for the strobe light emission time and a function of multiplying the video signal, so that it can move or swing relatively in any direction. Even with this, it is possible to obtain a clear and bright fluorescent magnetic powder pattern image without blurring, which is the same as in still photography. In addition, even a weak fluorescent image by an ultraviolet strobe can be imaged with sufficient sensitivity. As a result, the accuracy of defect detection has been greatly improved, and the accuracy of automatic inspection has become possible. Ultraviolet irradiators and imaging devices, such as mirror swing mechanisms and Eliminating the mechanism has reduced equipment costs and improved maintainability. In addition, the conventional fluorescent magnetic particle flaw detector required the provision of a dark room, but this is no longer necessary in indoor work environments. In this regard, equipment and work became simpler, such as inspection of welded parts of structures. Even when outdoors, fluorescent magnetic particle flaw detection can be performed with a ceiling covering that prevents direct sunlight.

In a fluorescent magnetic particle inspection system in which a magnetizing device is configured so that a rotating magnetic field is formed by a plurality of electromagnets having four magnetic poles arranged at the vertices of a square, the material to be inspected is magnetized while sequentially passing through a plurality of aligned electromagnets Therefore, the magnetization time becomes longer, and a clear fluorescent magnetic powder pattern is formed even when the test material moves at high speed.

Claims

The scope of the claims

1. A magnetizing device that magnetizes the surface layer of the steel material or the welded part of the steel material to be inspected, a magnetic powder spray nozzle that sprays the magnetic powder on the surface of the material to be inspected, and ultraviolet light that irradiates the surface to be inspected In a fluorescent magnetic particle flaw detection device including an irradiation device, an imaging device for imaging a surface to be inspected, and an image processing device for processing an imaged screen to determine the presence or absence of a flaw,

The imaging device has a band-pass filter on its front surface that transmits only the fluorescent spectrum band, and a function of opening the shutter only for the strobe light emission time and an image signal doubling function. A fluorescent magnetic particle flaw detector that uses a CCD force camera to increase the relative speed between the test material and the flaw detector.

2. The magnetizing device has four poles in which a pair of electromagnets are arranged symmetrically about an axis perpendicular to the surface to be inspected and the magnetic poles form the vertices of a square, and are perpendicular to one side of the square. By increasing the number of poles by two in each direction so that the magnetic poles form a plurality of squares, and making each pair of magnetic poles arranged at the diagonal point of the newly formed square, one pair of electromagnets 2. The fluorescent magnetic particle flaw detector according to claim 1, wherein the magnetizing device is configured to generate a plurality of rotating magnetic fields on a surface to be inspected by using a magnetized alternating current in which the phases of the electromagnets are shifted at the same frequency.

3. The magnetizing device provides a pair of electromagnets with four poles arranged such that the pair of electromagnets are symmetrical about an axis perpendicular to the surface to be inspected and the magnetic poles form the vertices of a square, and on one side of the square Four poles are added at intervals in the perpendicular direction, four poles are arranged so as to form a plurality of squares, and each four poles are targeted by providing a yoke that shorts the poles for every four poles By maintaining the characteristics, the diagonal magnetized coils are made into a pair, and the magnetized alternating current with the same frequency and phase shifted is passed through the two pairs of magnetized coils. 2. The fluorescent magnetic particle flaw detection apparatus according to claim 1, wherein the apparatus is a magnetizing apparatus that generates a plurality of rotating magnetic fields on a surface to be inspected.

4. The magnetizing device has two poles, i.e., a pair of four poles, in which a pair of electromagnets are arranged symmetrically about an axis perpendicular to the surface to be inspected and the magnetic poles are rectangular or square vertices. A pair or two or more pairs, the diagonal poles or four poles of each pair of electromagnets are short-circuited with a yoke, and the same frequency is applied to two pairs of magnetized coils wound on one pair of two poles. 2. The fluorescent magnetic powder according to claim 1, wherein the magnetizing device generates one or a plurality of rotating magnetic fields on the surface to be inspected through a magnetized alternating current having a phase shifted.

5. Equipped with a distance measuring device that measures the moving distance of each point on the surface to be inspected that moves relatively to the imaging position of the imaging device, using the moving distance information measured by the distance measuring device. The fluorescent magnetic particle flaw detector according to any one of claims 1 to 4, wherein the detected surface layer flaw of the test material is masked.

6. Magnetize the surface layer of the steel material or the welded part of the steel material to be inspected, magnetic powder liquid spraying step of spraying the magnetic powder liquid on the surface of the material to be inspected, and ultraviolet light to the surface to be inspected. A fluorescent magnetic particle flaw detection method, comprising: irradiating; imaging an inspected surface; and processing an imaged screen to determine whether there is a flaw.

In the imaging step, a band-pass filter that transmits only the fluorescent spectrum band is used, and a shutter is opened only for the emission time of the stop light, and a CCD with a video signal doubling function is added. A fluorescent magnetic particle flaw detection method characterized in that the relative speed between the material to be inspected and the flaw detector can be increased by a series of steps using a camera.

7. In the magnetizing step, a pair of electromagnets are arranged symmetrically about an axis perpendicular to the surface to be inspected and the magnetic poles form square vertices. Along with the step of providing four poles, two poles are added in the direction perpendicular to one side of the square so that the magnetic poles form a plurality of squares, and the magnetic poles arranged at diagonal points of the newly formed square are paired, respectively. By using a magnetizing method, a plurality of rotating magnetic fields are generated on the surface to be inspected through a magnetized alternating current in which the phases of the respective magnets are shifted at the same frequency by a step of substantially forming a pair of electromagnets. 7. The fluorescent magnetic particle flaw detection method according to claim 6, wherein:

8. The step of magnetizing includes providing a pair of electromagnets with four poles arranged so that the pair of electromagnets are symmetrical about an axis perpendicular to the surface to be inspected and the magnetic poles form a vertex of the square, and one side of the square. The poles of each four poles are increased by increasing the number of poles by four at regular intervals and by arranging the four poles so as to form a plurality of squares, and providing a yoke that shorts the poles every four poles. By maintaining the symmetry, a pair of diagonal magnetized coils is used, and two pairs of magnetized coils pass a magnetized alternating current whose phase is shifted at the same frequency. 7. The fluorescent magnetic particle flaw detection method according to claim 6, wherein the method is a magnetization method for generating a magnetic field.

9. The step of magnetizing comprises: a pair of four poles in which two poles, i.e., a pair of electromagnets, are arranged symmetrically about an axis perpendicular to the surface to be tested and the poles are rectangular or square vertices. It consists of two or more pairs, and the diagonal poles or four poles of each pair of electromagnets are short-circuited with a yoke, and the same frequency is applied to two pairs of magnetized coils wound around one pair of two poles. The fluorescent magnetic particle flaw detection method according to claim 6, wherein the method is a magnetization method that generates one or a plurality of rotating magnetic fields on a surface to be inspected by a step of passing a magnetization alternating current whose phase has been shifted by (1).

10. Measuring the moving distance of each point on the surface to be inspected, which moves relatively to the imaging position in the imaging step, and inspecting the object using the moving distance information measured by the distance measuring device. Pine surface flaws The method according to any one of claims 6 to 9, further comprising the step of: