JP2003075358A - Optical flaw-detection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely detect not only a latelally cracked flaw existing in the periphery of an angle part in a rolled angle steel material but also a micro pin-hole flaw. SOLUTION: In this method for flaw-detecting the angle part C of the rolled material optically, the periphery of the angle part C in a rolled material is irradiated with a light source 11 at least from its rolled tip side at a prescribed angle, an image of the irradiated portion is image-picked up at the prescribed angle by an image pick-up camera 12, and the surface flaw in the angle part C of the rolled material is detected by a flaw detecting means 22, based on the obtained picked-up image.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an optical flaw detection method. More specifically, it relates to an optical flaw detection method for detecting lateral crack flaws and pinhole flaws existing around the corners of a rolled square steel material.

[0002]

2. Description of the Related Art Conventionally, the material of mechanical structural parts such as bolts is a prismatic steel material (square steel material) cut into a predetermined length after roll forming, and a cross-sectional shape suitable for manufacturing bolts and the like. It is rolled and shipped.

Here, when the square steel material is made of a non-magnetic material, a side surface may be scratched in the longitudinal direction in the rolling process, and lateral cracks and minute pinhole scratches may be generated around the corners. If there are scratches on the steel material, problems such as deterioration of the strength of bolts that will be manufactured later will occur.Therefore, not only the product inspection before shipping products such as bolts but also the presence of surface scratches at the steel material stage is inspected. ing.

As a method for inspecting the surface damage of the steel material, for example, as shown in FIG. 7, when an induction current is applied to the induction coil 101 arranged around the steel material W ', the temperature around the damage of the steel material W'is An induction heating flaw detection method is known in which flaw detection is performed by utilizing the change.

In the induction heating flaw detection method, however, it is difficult to detect these flaws (lateral cracks) Ky in the same direction as the direction of the induced current and the small temperature change around the minute pinhole flaw Kp, so that these flaws are difficult to detect. Is.

Japanese Unexamined Patent Publication (Kokai) No. 6-109652 discloses that when a flat wire is moved with the fine wire abutting the corner of the flat wire with a predetermined tension, the scratch existing at the corner passes through the fine wire. A flaw detection device has been proposed which detects a flaw in a corner portion of a flat wire rod from a change in tension of a thin wire, and Japanese Patent Application Laid-Open No. 5-126760 discloses irradiating a continuously fed wire rod with light.
An optical flaw detection device has been proposed which detects a surface flaw based on a captured image obtained by capturing the irradiated portion with a CCD camera.

However, in the flaw detector proposed in Japanese Patent Application Laid-Open No. 6-109652, the tension hardly changes even when the minute pinhole flaw Kp passes through the fine wire, so that the minute pinhole flaw Kp is detected. Is difficult. The optical flaw detector proposed in Japanese Patent Laid-Open No. 5-126760 pays attention to the fact that when a flaw is present, the irradiation light is diffusely reflected by the flaw and the output signal of the CCD camera is disturbed. However, if a minute pinhole is scratched, signal disturbance is small and detection is difficult.

It should be noted that the applicant, as already shown in FIG.
The ultrasonic wave is transmitted from the probe 102 to the corner area of the steel material W ′ at a predetermined angle so that the ultrasonic wave propagates in the longitudinal direction of the steel material W ′, and the flaw detection is performed by detecting the reflected wave reflected by the flaw. An ultrasonic bevel flaw detection method has been proposed (Patent Application 200
0-314893).

However, even with this ultrasonic oblique flaw detection method, there is a problem in that minute pinhole scratches Kp are difficult to detect because of small reflection of ultrasonic waves.

[0010]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and not only lateral cracks existing around the corners of a rolled square steel product but also minute pinhole scratches. It is an object of the present invention to provide an optical flaw detection method capable of surely detecting even.

[0011]

A first mode of the optical flaw detection method of the present invention is an optical flaw detection method for optically flaw detection of a rolled material corner portion, and at least the periphery of the rolled material corner portion has its rolling tip. It is characterized in that irradiation is performed from a side at a predetermined angle, the irradiated portion is imaged at a predetermined angle, and a surface flaw of a rolled material corner portion is detected based on the obtained captured image.

A second embodiment of the optical flaw detection method of the present invention is an optical flaw detection method for optically flaw detection of a rolled material corner portion,
Alternately irradiate around the corner of the rolled material from the front and back at a predetermined angle,
It is characterized in that the irradiated portion is imaged at a predetermined angle, and surface scratches at the corners of the rolled material are detected based on the obtained captured image.

In the optical flaw detection method of the present invention, it is preferable that the irradiation angle is in the range of 30 to 80 degrees and the imaging angle is in the range of 45 to 90 degrees.

Further, in the optical flaw detection method of the present invention, it is preferable that the portion where the amount of decrease in brightness exceeds the threshold value is a flaw.

Further, in the optical flaw detection method of the present invention, it is preferable that the rolled material is a material such as stainless steel which is difficult to process.

[0016]

Since the present invention is constructed as described above, not only lateral cracks existing around the corners of the rolled material but also minute pinholes can be reliably detected.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described based on the embodiments with reference to the accompanying drawings, but the present invention is not limited to such embodiments.

Embodiment 1 FIG. 1 shows a schematic view of an optical flaw detector (hereinafter, simply referred to as flaw detector) to which the optical flaw detection method according to Embodiment 1 of the present invention is applied. It is suitable for use in flaw detection of the corners of rolled square steel (material to be inspected) made of magnetic material, especially difficult-to-machine material such as stainless steel.

As shown in FIG. 1, the flaw detection apparatus S has a flaw detection section 10 for picking up an image around the corner C of the material W to be inspected and a flaw detection section 10.
A control detection unit 20 that controls the
The output means 30 for outputting the flaw detection result serves as a main component. Here, the output means 30 is, for example, a printer, C
It is used as an RT display.

As shown in FIG. 1, the flaw detection portion 10 faces the other one of the first and second flaw detection portions 10A and 10B for picking up images around one of the opposite corners C1 and C2 of the material W to be inspected, respectively. It is composed of third and fourth flaw detection units 10C and 10D that image the periphery of the corners C3 and C4, respectively. As shown in FIG. 2, each of the flaw detection parts 10 illuminates the periphery of the corresponding corner part C obliquely from the rolling tip side of the material W to be inspected.
And around the corner C illuminated by the light source 11 to be inspected material W
And a CCD camera (image pickup means) 12 for picking up an image from a direction perpendicular to the longitudinal direction of the steel sheet or an oblique direction of the rolling rear end side.

Here, the first and second flaw detectors 10A, 1
The 0B light source 11 and the CCD camera 12 are arranged such that their optical axes or light receiving axes are located on the same plane as the diagonal surfaces of the corner portions C1 and C2, and the third and fourth flaw detection portions 1 are arranged.
The 0C and 10D light sources 11 and the CCD camera 12 are arranged such that their optical axes or light receiving axes are located on the same plane as the diagonal surfaces of the corner portions C3 and C4.

Specifically, as shown in FIG. 2 (a), the light source 11 uses the optical axis 11a as the material to be inspected when the material W to be inspected is conveyed in the longitudinal direction with the rolling tip as the leading end. It is disposed so as to be inclined toward the downstream side of W in the transport direction. On the contrary, Fig. 2 (b)
As shown in (1), when the material W to be inspected is conveyed in the longitudinal direction with the trailing end of the rolling as the leading end, the optical axis 11a is arranged with the optical axis 11a inclined toward the upstream side in the conveyance direction of the material to be inspected W.

The angle θ ₁₁ between the optical axis 11a and the longitudinal direction of the material W to be inspected is 30 ° to 80 °. Also,
The irradiation range of the light source 11 is adjusted so as not to affect the imaging of the adjacent flaw detection unit 10. For example, the irradiation is adjusted so as to irradiate the vicinity of the central portion on both side surfaces of the corner portion C.

The CCD camera 12 is specifically shown in FIG.
As shown in (a), when the material W to be inspected is conveyed in the longitudinal direction with the leading end of the rolling as the leading end, the light receiving shaft 12a is upstream of the light source 11 and is perpendicular to the conveying direction or upstream in the conveying direction. Corner C that is tilted and illuminated by the light source 11
It is arranged at a position where the surrounding area can be imaged. On the contrary, Fig. 2
As shown in (b), when the material W to be inspected is conveyed in the longitudinal direction with the rolled rear end as the leading end, the light receiving shaft 12a is located downstream of the light source 11 in the direction perpendicular to the conveying direction or on the downstream side in the conveying direction. Corner C illuminated by the light source 11 tilted to
It is arranged at a position where the surrounding area can be imaged.

Here, the angle θ ₁₂ formed by the light receiving shaft 12a and the longitudinal direction of the material W to be inspected is 45 ° to 90 °. Further, the CCD camera 12 is adjusted so that its imaging range is included in the irradiation range of the light source 11. That is, if there is no scratch on the surface of the inspection object W, the CCD camera 12
The entire image pickup range is designed to have high brightness.

The control detector 20 includes flaw detectors 10A to 10D.
The control means 21 controls the light source 11 and the CCD camera 12 and the flaw detection means 22 that detects a flaw based on the image captured by the CCD camera 12.

The control means 21 causes the light source 11 to irradiate the corner C of the material W to be inspected and causes the CCD camera 12 to image the corner C illuminated by the light source 11 over the entire length of the material W to be inspected.

The scratch detecting means 22 is a scratch K existing around the corner of the material W to be inspected based on the image picked up by the CCD camera 12.
Is to detect. In the case of difficult-to-machine materials such as stainless steel, lateral cracking grooves and pinhole scratches that occur around the corners of roll-formed square steel are formed obliquely toward the extended tip side, as exaggeratedly shown in FIG. It Therefore, this scratch K
Is obliquely irradiated from the rolling tip side by the light source 11,
A shadow is formed on the scratched portion, and as shown in FIG.
The portion of the captured image (output signal) corresponding to the scratch K has much lower brightness than the surrounding area.

Therefore, the flaw detecting means 22 sets an appropriate threshold value for extracting a low-luminance portion corresponding to the flaw K from the picked-up image, and designates a portion of the picked-up image in which the amount of decrease in luminance exceeds the threshold value as a flaw portion. To detect. Here, this threshold value is appropriately set based on, for example, an image pickup signal at the time of flaw detection of an artificial flaw.

The control detection unit 20 having such a function
Is realized, for example, by storing a program corresponding to the functions of the control means 21 and the flaw detection means 22, that is, a control program and a flaw detection program in a computer equipped with the output means 30.

As described above, according to the present embodiment, the periphery of the corner of the material to be inspected is obliquely irradiated from the rolling front side of the material to be inspected, and the irradiation location is a direction perpendicular to the longitudinal direction of the material to be inspected. Or because the flaw is detected based on the imaged image obtained by imaging from the rolling rear end side of the inspected material,
Not only lateral cracks existing around the corners of the material to be inspected but also minute pinholes can be reliably detected.

Embodiment 2 FIG. 4 shows a schematic view of an optical flaw detector (hereinafter, simply referred to as flaw detector) to which an optical flaw detection method according to Embodiment 2 of the present invention is applied. This flaw detection device S1 is a modification of the flaw detection unit 10 (10A to 10D) of the flaw detection device S of the first embodiment. Even if the inspection material is mixed, the flaw detection can be performed. Specifically, as shown in FIGS. 4 and 5, the light source 13 is arranged so as to face the light source 11 of each flaw detection unit 10, and the control means 21 corresponds to the control means 21A. Is.

In the light source 13, for example, the light source 11 has an optical axis 11a.
If the light source 11 is inclined toward the downstream side in the transport direction, the light source 11
Upstream of the optical axis 13a, the optical axis 13a is upstream in the transport direction.
It is installed at an angle. Here, the optical axis 13a and the inspection object W
Angle θ with the longitudinal direction of₁₃Is the optical axis 11a and the inspection material W
Angle θ with the longitudinal direction of₁₁Is equal to and also light
The distance between the light source 11 and the light source 13 is equal to the optical axis 11a and the optical axis 1
3a and 3a are adjusted to intersect at a corner C.
In the present embodiment, the optical axis 13a and the longitudinal direction of the material W to be inspected
Angle θ with the direction₁₃Is the longitudinal direction of the optical axis 11a and the inspected material W
Angle θ with the direction ₁₁Is equal to, but the angle θ₁₃Is always
The angle θ₁₁Need not be the same as.

The CCD camera 12 of the present embodiment includes a light source 1
The light receiving shaft 12a is arranged at an intermediate position between the light source 13 and the light source 13 so as to be orthogonal to the longitudinal direction of the inspection target material W.

The control means 21A includes flaw detectors 10A to 10D.
The light source 11, the CCD camera 12 and the light source 13 are controlled. Specifically, the light sources 11 and 13 are alternately irradiated, and the CCD is irradiated for each of the light sources 11 and 13.
The operation of taking an image with the camera 12 is performed at predetermined intervals. Here, the predetermined interval is a corner C
In each of the case where the light is irradiated by the light source 11 and the case where the light is irradiated by the light source 13, it is appropriately set according to the transport speed of the material W to be inspected so that the image can be taken over the entire length of the material W to be inspected.

In the present embodiment, however, whether the material W to be inspected is conveyed with the leading edge of the rolling or the trailing edge of the rolling being the leading edge, the periphery of the corner is inspected by either the light source 11 or the light source 13. Since the material W is obliquely irradiated from the rolling tip side, it is possible to detect a scratch existing around the corner of the material W to be inspected from a captured image when the light source 11 or the light source 13 is irradiated. it can.

The remaining structure, operation and effect of the second embodiment are similar to those of the first embodiment.

[0038]

EXAMPLES Hereinafter, the present invention will be described more specifically based on more specific examples.

Examples 1 to 4 As inspection samples, 3.0 mm × on each corner.
2.0 mm, 1.0 mm x 2.0 mm, 0.5 mm x
Four square steel materials having pinhole scratches of 1.5 mm and 0.5 mm × 1.0 mm were prepared (Examples 1 to 4).

FIG. 6 shows an image pickup result obtained by obliquely irradiating the periphery of the corner where pinhole scratches exist in Examples 1 to 4 from the rolling front side and imaging the rolling rear side obliquely. here,
In Examples 1 to 4, the angle between the optical axis of the light source and the longitudinal direction of the test sample was 45 °, and the angle between the light receiving axis of the CCD camera and the longitudinal direction of the test sample was 90 °.
It is said that.

From FIG. 6, it can be seen that in the picked-up images of Examples 1 to 4, the brightness of the portion corresponding to the pinhole scratch is much lower than that of the surrounding area. That is, by irradiating the periphery of the corner of a square steel product from the rolling front side obliquely and imaging from the oblique direction of the rolling rear end side, the diameter is 1.0 m.
It is understood that even an extremely small pinhole scratch of mφ can be detected.

Although the present invention has been described based on the embodiments and examples, the present invention is not limited to the embodiments and examples, and various modifications can be made. For example, in the embodiment, the material to be inspected (square steel material) is a non-magnetic material, but it may be a magnetic material. Further, in the embodiment, the flaw detection is performed while conveying the inspected material in the longitudinal direction, but the inspected material is kept stationary, and the flaw detection part is moved along the longitudinal direction of the inspected material. It may be performed.

[0043]

As described in detail above, according to the present invention,
An excellent effect that not only lateral cracks existing around the corners of the rolled material but also minute pinholes can be reliably detected is obtained.

[Brief description of drawings]

FIG. 1 is a schematic diagram of an optical flaw detection apparatus to which an optical flaw detection method according to a first embodiment of the present invention is applied.

FIG. 2 is a view of the flaw detection part of the same device as seen from the direction of the arrow shown in FIG. 1, in which FIG. 2 (a) shows the case where the material to be inspected is conveyed in the longitudinal direction with the rolling tip as the leading end, The same (b) shows the case where the material to be inspected is conveyed in the longitudinal direction with the trailing end of the rolling as the leading end.

FIG. 3 is a graph showing an imaging result obtained by imaging an area around a corner where a pinhole scratch exists.

FIG. 4 is a schematic diagram of an optical flaw detection apparatus to which an optical flaw detection method according to a second embodiment of the present invention is applied.

5 is a view of the flaw detection unit of the same device as seen from the direction of the arrow shown in FIG.

6A and 6B are graphs showing imaging results obtained by obliquely irradiating the inspection samples of Examples 1 to 4 from the rolling front side and imaging from the rolling rear end side in an oblique direction, in which FIG. ,
The same (b) shows Example 2, the same (c) shows Example 3, and the same (d) shows Example 4.

FIG. 7 is an explanatory diagram of an induction heating flaw detection method.

FIG. 8 is an explanatory diagram of an ultrasonic oblique flaw detection method according to the applicant's previous proposal.

[Explanation of symbols]

10 flaw detection section 11, 13 Light source 12 CCD camera (imaging means) 20 Control detector 21 Control means 22 Scratch detection means 30 Output means S Optical flaw detector W Inspected material (square steel material)

Claims (5)

[Claims] 1. An optical flaw detection method for optically detecting a corner of a rolled material, which comprises irradiating the periphery of the rolled material at a predetermined angle from at least the leading end side of the rolling, and irradiating the irradiated portion with a predetermined angle. The optical flaw detection method is characterized in that the surface flaw of the corner portion of the rolled material is detected based on the obtained picked-up image. 2. An optical flaw detection method for optically detecting a corner of a rolled material, which comprises alternately irradiating the periphery of the rolled material at a predetermined angle from the front and rear,
An optical flaw detection method, characterized in that an image of the irradiated portion is picked up at a predetermined angle, and a surface flaw at a corner of a rolled material is detected based on the obtained picked-up image. 3. The optical flaw detection method according to claim 1, wherein the irradiation angle is in the range of 30 degrees to 80 degrees and the imaging angle is in the range of 45 degrees to 90 degrees. 4. The optical flaw detection method according to claim 1, wherein a portion where the amount of decrease in luminance exceeds a threshold value is used as a flaw. 5. The optical flaw detection method according to claim 1, wherein the rolled material is a hard-to-machine material such as stainless steel.