JPH0875675A - Method and device for magnetic particle inspection - Google Patents

Abstract

PURPOSE: To provide a magnetic particle inspection device, which can readily detect the position of an edge at a low cost. CONSTITUTION: A phosphor 9, which is longer than the width of a corner steel piece 1, is provided at the lower side of the corner steel piece 1 so that the angle with respect to the ground GND forms 60 deg. with an interval of 100mm being provided. An imaging device 5a, which photographs the surface of the corner steel piece 1, and an imaging device 5b, which photographs the corner part at the upper side of the corner steel piece 1, are provided. Ultraviolet-ray irradiation devices 4 and 4 are provided at both sides of the imaging device 5b at the inclination of the specified angle. The left end and the right end of the image part in the direction of the X axis expressing the phosphor are detected by the projection in the direction of the X axis from the binary coded image obtained from the imaging devices 5a and 5b. The upper end and the lower end of the upper end part and the upper end and the lower end of the lower end part in the direction of the Y axis are detected by the projection in the direction of the Y axis. The specified operation is performed, and the process starting position and the process finishing position are obtained. Thus, a window is set.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic particle flaw detection method for detecting flaws on the surface of a steel slab and an apparatus used for carrying out the flaw detection method.

[0002]

2. Description of the Related Art Magnetic powder flaw detection, eddy current flaw detection, leakage magnetic flux flaw detection and the like have been used for a long time as a method of inspecting a surface flaw of a steel slab. For round steel slabs with a circular cross-sectional shape, automatic flaw detectors utilizing these methods have been developed, which has greatly contributed to productivity improvement. However, since the square steel has a square cross-section, automation is difficult, and the magnetic particle flaw detection method is the mainstream. In the magnetic particle flaw detection method, the test material is magnetized, the fluorescent magnetic particles attached to the surface defects are irradiated with ultraviolet rays, and the defects are detected by the fluorescence. In the old days, defects were detected by visually observing the fluorescence, but in recent years, automation has been advanced, and automatic flaw detectors have been put to practical use.

FIG. 6 is a schematic diagram showing the structure of a flaw detection apparatus using the magnetic particle flaw detection method. In the figure, reference numeral 1 denotes a square steel piece made of a ferromagnetic material, which is conveyed in the direction indicated by the white arrow in the figure. A magnetizing device 2 for magnetizing the square steel piece 1 and a magnetic powder liquid spray nozzle 3 for spraying the fluorescent magnetic powder liquid are provided on the upstream side of the square steel piece 1 in the conveying direction. Further, on the downstream side, an ultraviolet illuminator 4 that irradiates the square steel piece 1 with ultraviolet rays and an imaging device 5 that images the surface of the square steel piece 1 are installed.
The image signal obtained by the image pickup device 5 is subjected to image processing such as binarization by the image processing device 6, and processing for detecting flaws is performed by the data processing device 7. Further, the automatic flaw removal device Etc. to a predetermined device.

When the square steel piece 1 has a defect, a leakage magnetic flux is generated in the defective portion and magnetic particles adhere to the defect. When this defective portion to which the magnetic particles are attached is irradiated with ultraviolet rays from the ultraviolet lighting device 4, the magnetic particles emit fluorescence. By picking up this fluorescence with the image pickup device 5 and processing the obtained image with the image processing device 6 and the data processing device 7, defects on the surface of the square steel piece 1 are automatically detected.

The image processing device 6 extracts the image portion to be processed from the image captured from the image pickup device 5. In the case of a square steel slab, the edge position of the steel slab is detected and the extracted image is determined based on that position. . As a result, it is possible to limit the position of the flaw on the steel slab, and it is possible to easily carry out processing by a predetermined device such as a subsequent automatic flaw removing device. Here, as a method of detecting the edge position, a method of detecting the position with a rangefinder and a method of detecting the edge position with visible light have been proposed. For example, "33rd Quality Control Committee ND
I Subcommittee, September 21-22, 1989 "proposes a device that irradiates a square steel piece with a dedicated visible light source and detects the edge position with a camera.

[0006]

However, in the case of the conventional magnetic particle flaw detector, a dedicated device for detecting the edge position is additionally provided, which is problematic in terms of cost and maintenance.
The present invention has been made in view of such circumstances, only by adding a phosphor to the conventional device, it is possible to detect the edge position without providing another dedicated device, the reliability is improved. An object is to provide a possible magnetic particle flaw detector.

[0007]

According to the magnetic particle flaw detection method of the present invention, a fluorescent magnetic powder is attached to the surface of a magnetized steel slab, and the fluorescent magnetic powder is irradiated with excitation light to image the fluorescent light emitted from the magnet and the flaw is detected. In the method for flaw detection, the phosphor protruding from the steel piece is installed on the back side of the steel piece, and the steel piece and the phosphor that are irradiated with excitation light are imaged, and among the imaged images, the steel It is characterized in that a position where the image portion which is the shadow of the piece and which shows the phosphor is divided is obtained, and the position of the edge of the steel piece is detected based on this position.

The magnetic particle flaw detector according to the present invention is an apparatus for flaw detection by attaching fluorescent magnetic powder to the surface of a magnetized steel slab and irradiating the fluorescent magnetic powder with excitation light to image fluorescence emitted thereby. Phosphor provided so as to protrude in the width direction of the steel piece on the back side of the steel piece, means for imaging the steel piece and the phosphor irradiated with excitation light, among the captured images, It is characterized by further comprising means for obtaining a position where an image portion which is a shadow of the steel piece and which shows the phosphor is divided, and means for detecting a position of an edge of the steel piece based on this position.

[0009]

According to the present invention, the phosphor is provided on the back side of the steel piece, and the phosphor is imaged together with the steel piece to determine the position where the image portion showing the phosphor is divided. The edge position of the piece is detected. Therefore, it is not necessary to separately provide a dedicated device for detecting the edge position by the method of obtaining the distance from the edge of the image to the steel piece unlike the conventional method. Further, the edge position detection in the present invention can be performed by simple image processing.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to the drawings showing the embodiments. FIG. 1 is a schematic side view showing an arrangement configuration of a magnetic particle flaw detector according to the present invention. In the figure, reference numeral 1 denotes a square steel piece made of a ferromagnetic material, which is conveyed in the direction indicated by the white arrow in the figure. A magnetizing device 2 for magnetizing the square steel piece 1 and a magnetic powder liquid spray nozzle 3 for spraying the fluorescent magnetic powder liquid are provided on the upstream side of the square steel piece 1 in the conveying direction. Further, on the downstream side, an ultraviolet illuminator 4 that irradiates the square steel piece 1 with ultraviolet rays and an imaging device 5 that images the surface of the square steel piece 1 are installed. The image signal obtained by the imaging device 5 is
Image processing such as binarization is performed by the image processing device 6, processing for detecting a flaw is performed by the data processing device 7, and the data is further given to a predetermined device such as an automatic flaw removing device. There is.

When the square steel piece 1 has a defect, a leakage magnetic flux is generated in the defective portion, and magnetic particles adhere to the defect. When this defective portion to which the magnetic particles are attached is irradiated with ultraviolet rays from the ultraviolet lighting device 4, the magnetic particles emit fluorescence. By picking up this fluorescence with the image pickup device 5 and processing the obtained image with the image processing device 6 and the data processing device 7, defects on the surface of the square steel piece 1 are automatically detected.

FIG. 2 is a sectional view taken along line II-II in FIG. The phosphor 9 longer than the width of the square steel piece 1 is located below the conveying path of the square steel piece 1 with the square steel piece 1 at a distance of 100 mm from the ground GN.
It is installed so that the angle θ with respect to D is 60 °. An image pickup device 5a for picking up an image of the surface of the square steel piece 1 facing the face facing the phosphor 9 and an image pickup device 5b for picking up the upper corner portion are provided. Further, ultraviolet illuminators 4 and 4 are provided on both sides of the image pickup device 5b so as to be inclined at a predetermined angle.

FIG. 3 is a block diagram showing the configuration of the image processing apparatus 6 shown in FIG. The image processing device 6 includes an image capturing unit 61 that captures an image obtained by the imaging device 5, a binarizing unit 62 that binarizes the captured image, and a projection of the binarized image in the X-axis direction. X-axis direction projection unit 63 that performs the above-mentioned operation, and Y-axis direction projection unit 6 that performs the projection of the binarized image in the Y-axis direction.
4, an edge detection unit 65 that detects the edge position of the square steel piece 1 from the projection in the X-axis direction and the projection in the Y-axis direction, and performs a predetermined arithmetic process based on the detected edge position and is used for flaw detection. Window setting unit 66 for setting windows to limit extracted images
With.

FIG. 4 shows the image signal from the image pickup device 5a.
It is explanatory drawing which shows the binarized image. The upper end and the lower end of the phosphor 9 are not shaded by the square steel piece 1 and are shown as shown by hatching in FIG. FIG. 4 (a) shows two-dimensionally, FIG. 4 (b) shows one-dimensionally in the X-axis direction (longitudinal direction of the square steel piece 1), and FIG. 4 (c) shows Y-axis direction ( The width direction of the square steel piece 1) is shown one-dimensionally.

The left end where the image portion of the phosphor 9 appears in the X-axis direction is X-left, and the right end is X-right.
In the Y-axis direction, the position indicating the upper side of the image is Y0, and the position indicating the lower side is Y-size. X-left,
In the image between X-right, the upper end in the Y-axis direction where the image portion of the upper end of the phosphor 9 appears is Y-top-1, and the lower end is Y.
-top. Further, the upper end where the image portion of the lower end of the phosphor 9 appears is referred to as Y-bottom, and the lower end is referred to as Y-bottom-1. The processing start position Y-start is below the Y-top by a preset value s, and the processing end position Y-end is above the Y-bottom by the set value s. The processing width W is from the processing start position Y-start to the processing end position Y-end.

Next, the operation of the device of the present invention will be described. FIG. 5 is a flowchart showing a processing procedure in the image processing device 6 of the device of the present invention. First, the image processing unit 6
1, the image signal is captured from the image pickup device 5a (step S1), and the threshold value set in advance by the binarization unit 62 is set to 2
The value is converted (step S2). Next, the X-axis direction projection unit 63 performs projection in the X-axis direction, and the edge detection unit 65 performs left end X-left and right end X-r in the X-axis direction.
ight is detected (step S3). Further, the Y-axis direction projection unit 64 performs Y-axis direction projection, and the edge detection unit 65 outputs the upper end Y-t of the upper end in the Y-axis direction.
op-1, bottom Y-top and bottom Y-bottom, bottom Y
-Bottom-1 is detected (step S4).

The window setting section 66 includes an edge detecting section 6
The lower end Y-top of the upper end detected at 5 and the upper end Y of the lower end
-bottom is fetched, the processing start position Y-start is calculated by performing the calculation of "Y-top + s" (step S5), and "Y-bot
"tom-s" is calculated to obtain the processing end position Y-end (step S6). This sets the window. This data and flaw data are given to the data processing unit 7.

The data processing unit 7 extracts an image portion within the set window and performs image processing such as flaw detection. By the automatic edge detection of the square steel piece 1 using such a phosphor 9, the edge position can be accurately detected even if the position of the square steel piece 1 changes. Therefore, if the distance from the window periphery is measured, the position of the flaw in the square steel piece 1 can be accurately limited. Further, since the present invention is realized by a configuration in which the phosphor 9 is simply installed in the conventional device,
A large-scale device dedicated to edge detection is unnecessary, and cost reduction and reliability improvement can be achieved.

[0019]

As described above, according to the present invention, the phosphor is provided on the back side of the steel piece, and the phosphor is imaged together with the steel piece, and the image portion showing the phosphor is separated at the position. The edge position of the steel slab can be detected by determining Therefore, it is not necessary to separately provide a dedicated device for detecting the edge position by a method such as obtaining the distance from the edge of the image to the steel piece as in the conventional art, and cost reduction and reliability improvement can be achieved. The present invention has excellent effects.

[Brief description of drawings]

FIG. 1 is a schematic side view showing an arrangement configuration of a magnetic particle flaw detector according to the present invention.

FIG. 2 is a sectional view taken along line II-II in FIG.

FIG. 3 is a block diagram showing the configuration of the image processing apparatus shown in FIG.

FIG. 4 is an explanatory diagram showing a screen obtained by binarizing an image signal by the image pickup apparatus shown in FIG.

FIG. 5 is a flowchart showing a processing procedure in the image processing apparatus of the apparatus of the present invention.

FIG. 6 is a schematic diagram showing a configuration of a flaw detection device by a magnetic particle flaw detection method.

[Explanation of symbols]

 1 Square Steel Piece 2 Magnetizing Device 3 Magnetic Particle Liquid Dispersing Nozzle 4 Ultraviolet Illuminator 5, 5a, 5b Imaging Device 6 Image Processing Device 7 Data Processing Device 9 Phosphor 61 Image Capture Unit 62 Binarization Unit 63 X-axis Direction Projection Unit 64 Y-axis direction projection unit 65 Edge detection unit 66 Window setting unit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shuji Matsumoto 4-53-3 Kitahama, Chuo-ku, Osaka City, Osaka Prefecture Sumitomo Metal Industries, Ltd.

Claims (2)

[Claims] 1. A method of adhering a fluorescent magnetic powder to the surface of a magnetized steel piece, irradiating the fluorescent magnetic powder with excitation light to image fluorescence emitted to detect flaws, and a flaw protruding from the steel piece. Is installed on the back surface side of the steel piece, and the steel piece and the phosphor that are irradiated with excitation light are imaged, and in the imaged image, the image part that is the shadow of the steel piece and shows the phosphor is divided. The method for detecting magnetic particles is characterized in that the position of the edge of the steel slab is detected based on this position. 2. An apparatus for adhering a fluorescent magnetic powder to the surface of a magnetized steel slab and irradiating the fluorescent magnetic powder with excitation light to image the fluorescent light emitted to detect flaws in the surface of the steel slab. A phosphor provided so as to protrude in the width direction of the steel piece, a means for imaging the steel piece and the phosphor irradiated with excitation light, and a shadow of the steel piece in the captured image, and A magnetic particle flaw detector comprising: a means for obtaining a position where an image portion showing a phosphor is divided, and a means for detecting a position of an edge of the steel piece based on the position.