Surface inspection method and device for metal rods

Abstract

To provide a surface inspection method and device for a metallic rod-like material capable of accurately inspecting a surface flaw of the metallic rod-like material.SOLUTION: Provided is a surface inspection method and device 10 for a metallic rod-like material 11 for inspecting the peripheral surface of the metallic rod-like material 11 while moving the metallic rod-like material in its longitudinal direction, the surface inspection device including ring-like light emitting means 12, imaging means 13, and image processing means 14. The surface inspection method includes, while inserting the metallic rod-like material 11 into a through-hole 18 formed in the ring-like light emitting means 12, projecting visible light from the ring-like light emitting means 12 toward the peripheral surface of the metallic rod-like material, photographing reflected light caused by the projection of the visible light toward the peripheral surface of the metallic rod-like material 11 by the imaging means 13, and processing the image photographed by the imaging means 13 by the image processing means 14 to inspect the peripheral surface of the metallic rod-like material 11.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a surface inspection method and a surface inspection device for metal bars such as steel bars (bars such as deformed steel bars and round steel bars, wire rods, and shaped steel) and steel pipes. [Background technology]

[0002] For example, automated inspection methods for metal bar materials such as round steel and deformed steel bars (hereinafter also referred to as bar steel) have included eddy current inspection, magnetic leakage flux inspection, shape inspection using the light cutting method, and image inspection using self-luminous photography, which takes advantage of the fact that when the material is red-hot, the temperature drops locally only in the defective area, resulting in a difference in brightness. However, due to the recent increase in quality requirements and the shortage of personnel engaged in inspection, it has become clear that conventional inspection methods have limitations in their applicability.

[0003] Eddy current testing and magnetic leakage flux testing require a separate probe for each product size, placing a significant burden on workers. While they can achieve high detection accuracy for sharp cracks with V-shaped cross sections, they are difficult to detect peeling flaws and dents. Furthermore, with deformed steel bars (deformed reinforcing bars), it is difficult to distinguish between changes in shape due to knots or roll marks and changes due to flaws, making these methods virtually useless for inspection (see, for example, Patent Document 1). Due to its characteristics, shape inspection using the light cutting method cannot detect defects unless there is a clear change in unevenness, it cannot detect crack-like defects, the sampling cycle is at most 10 kHz, so it cannot be applied to high-speed conveyance speeds, and it is very expensive, so it is not very effective and not cost-effective for flaw detection purposes.

[0004] On the other hand, the image processing method (image inspection using self-luminous photography), which is currently the mainstream method for hot image inspection, detects defects from brightness differences caused by temperature differences, boasts extremely high detection performance for scab-like defects and has become popular as an alternative to eddy current inspection, especially in the manufacturing process of the deformed steel bars mentioned above. However, large scabs are likely to peel off due to the high resistance they encounter during transport. Therefore, defects that appear as chips due to the scabs peeling off are often impossible to detect, even if they are large. The inability to detect defects that significantly affect mechanical strength is a significant drawback compared to other inspection methods. Furthermore, the ability to detect linear defects is limited, and narrow-aperture linear defects cannot be detected. Furthermore, since the method captures self-luminous material, only a vague outline is obtained, making it difficult to make a final judgment by visual inspection of the detected image. Therefore, workers must inspect the actual product before bundling the deformed steel bars. While inspection is typically performed before bundling, the inspection process is dangerous due to residual heat of several hundred degrees Celsius immediately after rolling and poor footing, such as on a chain conveyor. In some cases, inspection of linear defects is abandoned, and if multiple linear defects are detected in a steel product, all products rolled from the same billet are destroyed.

[0005] In image inspection using reflected light photography, by capturing reflected light, it is possible to check objects using the same principle as living organisms visually checking objects that do not emit light themselves. Therefore, even in hot inspection, it is possible to obtain images that look the same as if the product were visually checked after cooling. This is a significant advantage over conventional flaw detection methods, which could not directly obtain information on the appearance of flaws, such as changes in brightness due to changes in current value or temperature differences, and therefore could not make a final pass / fail judgment on flaws until the actual product was inspected. In the case of image flaw detection using reflected light photography, workers can judge pass / fail by checking the image of the detected flaw on the inspection system screen. Naturally, the detected image can be saved on the system. This eliminates the need to check the actual product after detection and take images of the flaw with a digital camera or other device for record purposes, as is the case with conventional inspection methods. This significantly reduces the burden on workers and time lost, and also makes it possible to accurately identify and remove detected defects, contributing to improved yields. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-199830 Summary of the Invention [Problem to be solved by the invention]

[0007] However, it is not easy to uniformly irradiate the surface of a bar having a circular cross section (circular, elliptical, etc.) with curvature with visible light. Because the above-mentioned bar steel has a curvature, a lot of reflected light is obtained from the vertex closest to the light source's light-emitting surface, but the light is diffused on both sides of the vertex, resulting in a difference in the level of reflected light obtained when photographed with a camera.In addition, it is difficult to install lighting equipment in the high-temperature environment of hot inspection, and even in cold inspection, when the transport speed of the inspection object is relatively high, there is a limit to the lighting equipment that can ensure the amount of light necessary to photograph with a short exposure time.For these reasons, image flaw detection using the reflected light method has not become widespread. The above phenomenon also occurs in section steel with irregularities, such as deformed steel bars, and section steel with no recesses on the surface, such as square steel bars that do not have a curvature of a polygonal cross section.

[0008] The present invention has been made in view of the above circumstances, and has as its object to provide a surface inspection method and apparatus for metal bar materials that can inspect the surface defects of metal bar materials with high accuracy. [Means for solving the problem]

[0009] A first aspect of the present invention provides a method for inspecting the surface of a metal bar, which method includes: a step A of moving the metal bar in the longitudinal direction of the metal bar and inserting the metal bar into a through-hole formed in a ring-shaped light-emitting means, while irradiating visible light from the ring-shaped light-emitting means onto the peripheral surface of the metal bar; a step B of irradiating the peripheral surface of the metal bar with visible light and capturing reflected light with an imaging means; and step C, in which the image captured by the imaging means is processed by image processing means to inspect the peripheral surface of the metal bar. In this way, by moving the metal rod while it is inserted through the through hole of the ring-shaped light-emitting means and irradiating visible light from the ring-shaped light-emitting means onto the peripheral surface of the metal rod, visible light can be uniformly irradiated onto the entire peripheral surface of the metal rod (for example, a curved bar).

[0010] In the surface inspection method for metal bar material according to the first invention, the metal bar material is heated bar steel, and the ring-shaped light-emitting means preferably has a light source that generates visible light with a higher brightness than the bar steel and a ring-shaped irradiation unit equipped with the through hole, and the light source is preferably positioned at a position away from the bar steel, and the visible light generated by the light source is irradiated toward the surrounding surface of the bar steel via the ring-shaped irradiation unit. In this way, the light source and the ring-shaped irradiation unit are separated, and the light source is located away from the steel section, so the light-emitting element, which is generally considered to be heat-sensitive, is not affected by the radiant heat emitted from the high-temperature steel section. Furthermore, because the light source can be configured to a scale that allows for a large visible light output, it is possible to irradiate powerful visible light at a level that is suitable for extremely short exposure times, even when photographing steel sections being transported at high speed, from a close distance via the ring-shaped irradiation unit. The ring-shaped irradiation unit (ring-shaped light-emitting means) can be configured as a continuous, integrated unit in the circumferential direction, but if a ring-shaped irradiation unit corresponding to a large inspection object (metal rod-shaped material) cannot be manufactured with the above configuration, it is also possible to manufacture, for example, multiple arc-shaped or linear divided pieces and combine (connect) them in the circumferential direction to form a ring shape.

[0011] In the surface inspection method for metal bar material according to the first invention, it is preferable that the ring-shaped irradiation unit is housed in a heat-resistant case, and that visible light is irradiated onto the peripheral surface of the bar through a slit formed on the side of the heat-resistant case facing the bar, and that gas is sprayed from the slit. In this way, by housing the ring-shaped irradiation unit in a heat-resistant case and injecting gas onto the bar steel through this heat-resistant case, it is possible to cool the ring-shaped irradiation unit that has been heated by the heat generated by light emission and the heat from the bar steel, prevent the adhesion of scale and water droplets, and further blow away scale and water droplets that interfere with surface inspection by image processing.

[0012] In the surface inspection method for metal bar material according to the first invention, the reflected light captured by the imaging means may be light that is visible light irradiated from the ring-shaped light emitting means and reflected by the surrounding surface of the metal bar material, and light that is reflected from the surrounding surface of the metal bar material by irradiating a portion of that light again onto the surrounding surface of the metal bar material using a reflecting member. In this way, by using a reflective member, the reflected visible light becomes diffused light (the brightness of the light is reduced) and is irradiated again onto the metal bar, making it possible to make changes caused by slight irregularities formed on the surface of the metal bar less noticeable. Furthermore, by using a reflective member, light can be irradiated onto the metal bar having irregularities such as deformed steel bars, on the side opposite to the side where visible light is directly irradiated from the ring-shaped light-emitting means, so that the surrounding surface of the metal bar can be photographed evenly without creating shadows due to the shape of the object to be inspected, such as knots in deformed steel bars, and blind spots in inspection using image processing can be eliminated.

[0013] A second invention for achieving the above object is a surface inspection device for metal rods, which inspects the peripheral surface of a metal rod while moving the metal rod in the longitudinal direction of the metal rod, and comprises: a ring-shaped light emitting means having a through hole formed therein and configured to irradiate visible light toward a peripheral surface of the metal bar inserted into the through hole; an imaging means for imaging reflected light generated by irradiating the peripheral surface of the metal bar with visible light; and image processing means for processing the image captured by the imaging means to inspect the peripheral surface of the metal bar.

[0014] In the surface inspection device for metal bar material according to the second invention, the metal bar material is heated bar steel, and the ring-shaped light-emitting means preferably has a light source that generates visible light with a higher brightness than the bar steel and a ring-shaped irradiation unit equipped with the through hole, the light source being positioned at a distance from the ring-shaped irradiation unit, and the visible light generated by the light source being irradiated toward the surrounding surface of the bar steel via the ring-shaped irradiation unit.

[0015] In the surface inspection device for metal bar material according to the second invention, it is preferable that the ring-shaped irradiation unit is housed in a heat-resistant case, a slit is formed on the side of the heat-resistant case facing the bar steel, visible light is irradiated through the slit, and gas is ejected from the slit.

[0016] In the surface inspection device for metal bar material according to the second invention, it is preferable to have a reflecting member that is arranged at a position different from the ring-shaped light-emitting means and that re-irradiates a portion of the light that is reflected by the surrounding surface of the metal bar material from the visible light irradiated from the ring-shaped light-emitting means onto the surrounding surface of the metal bar material. [Effects of the Invention]

[0017] The surface inspection method and surface inspection device for metal bar material according to the present invention irradiates visible light from a ring-shaped light-emitting means toward the peripheral surface of the metal bar material, so that visible light can be uniformly irradiated onto the entire peripheral surface of the metal bar material, and by capturing the reflected light with an imaging means, the captured image can be processed with an image processing means to inspect the peripheral surface of the metal bar material. This allows the metal bar to be inspected for surface defects with high accuracy. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is an explanatory diagram illustrating a state in which a surface inspection device for a metal bar according to an embodiment of the present invention is used; [Figure 2]1A is a front view of the ring-shaped irradiation unit of the ring-shaped light-emitting means used in the metal bar surface inspection device and the heat-resistant case that houses it, and FIG. 1B is a cross-sectional view taken along the arrow aa in FIG. 1A. [Figure 3] 10A and 10B are explanatory diagrams illustrating a state in which a surface inspection device for a metal bar according to a modified example is used. [Figure 4] 10 is an explanatory diagram showing another state of use of the surface inspection device for metal bars. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0019] Next, embodiments of the present invention will be described with reference to the accompanying drawings to facilitate understanding of the present invention. As shown in Figures 1, 2(A) and (B), a surface inspection device for metal bar material (hereinafter also referred to simply as a surface inspection device) 10 according to one embodiment of the present invention is an apparatus capable of accurately inspecting surface defects of a section steel bar (an example of a metal bar material) 11, and has a ring-shaped (annular) light-emitting means 12, a line scan camera (an example of an imaging means) 13, and a computer (PC: an example of an image processing means) 14. A detailed explanation is provided below.

[0020] The bar steel 11 to be inspected by the metal bar surface inspection device 10 is, for example, in a heated, high-temperature state (for example, a surface temperature of about 1000° C.) and is continuously conveyed from the final rolling stand. Specifically, these include steel bars such as deformed steel bars and round steel bars, wire rods, and shaped steel bars, and their cross-sectional shapes are circular, elliptical, polygonal, and other shapes that have no recesses on the surface and bulge outward, and are available in high temperature and room temperature (low temperature) states. Note that deformed steel bars are steel bars with ridges formed on the outer periphery of a circular cross-sectional steel bar body, and these ridges have a repeated shape of irregularities (which may be spiral) called "ribs" or "nodes," for example. The inspection object may also be a steel pipe (an example of a metal bar).

[0021] The ring-shaped light-emitting means 12 emits visible light toward the surrounding surface of the bar 11, and can be installed on a conveying line downstream of the final stand in the rolling process of the bar 11, a conveying line in the finishing process, or in a manufacturing process or inspection process where the bar 11 is conveyed. This ring-shaped light-emitting means 12 has a ring-shaped irradiation section (also called a ring light guide) 15 that irradiates visible light, a light source (also called a light-emitting device) 16 that generates the visible light irradiated from this ring-shaped irradiation section 15, and an optical fiber 17 that connects this light source 16 to the ring-shaped irradiation section 15.By inserting the bar steel 11 into a through hole 18 formed in the ring-shaped irradiation section 15 and moving (transporting) the bar steel 11 in the longitudinal direction, visible light can be irradiated from the ring-shaped irradiation section 15 toward the surrounding surface of the bar steel 11.

[0022] The ring-shaped irradiation unit 15 is housed in a heat-resistant case 19, as shown in FIGS. The heat-resistant case 19 is ring-shaped and has a continuous space 20 formed therein in which the ring-shaped irradiation unit 15 is disposed, and includes an outer cylindrical portion 21, an inner cylindrical portion 22 that is smaller in diameter than the outer cylindrical portion 21 and is disposed inside the outer cylindrical portion 21 with its axis aligned, and annular lid portions 23 and 24 that are attached and fixed from both sides in the axial direction so that the space 20 is formed between the outer cylindrical portion 21 and the inner cylindrical portion 22. As a result, the inner cylindrical portion 22 is located within a through-hole 18 formed in the ring-shaped irradiation unit 15. The ring-shaped irradiation unit 15 is attached and fixed to a support column (support portion) 25 in the space 20 that is attached and fixed to the lid portion 23 on one axial side of the heat-resistant case 19 (downstream side in the movement direction (conveyance direction) of the section steel 11).

[0023] On the other axial side of the heat-resistant case 19, facing the section steel 11 (upstream side in the moving direction (conveying direction) of the section steel 11, the same applies below), a slit (gap) 26 is formed between the inner cylindrical portion 22 and the lid portion 24, continuing in the circumferential direction of the heat-resistant case 19. This allows visible light generated by the light source 16 to be irradiated from the ring-shaped irradiation portion 15 through the slit 26 in the heat-resistant case 19 onto the peripheral surface of the section steel 11. The heat-resistant case 19 is also provided with an air supply section 27 that supplies compressed air (an example of gas) from, for example, a compressor (not shown) into the space 20. This allows visible light to be irradiated onto the section steel 11 through the slit 26, and compressed air to be ejected therefrom. The shape of the slit 26 is formed so that the visible light and compressed air are irradiated onto the peripheral surface of the bar 11 from the downstream side to the upstream side in the direction of movement, and the compressed air is sprayed onto the peripheral surface of the bar 11 from the downstream side to the upstream side in the direction of movement, but the slit 26 can also be formed so that the visible light is irradiated onto the peripheral surface of the bar 11 from the upstream side to the downstream side in the direction of movement, or even so that both are performed.

[0024] The light source 16 generates visible light to be irradiated onto the section steel 11, and the visible light can be generated by, for example, an LED element or a xenon lamp. The light source 16 has a very strong light-emitting capability, and can generate visible light with a higher luminance (stronger light) than the section steel 11 in a high-temperature state, for example. The ring-shaped irradiation unit 15 and the light source 16 are separated, and as shown in FIG. 1, the light source 16 is disposed at a position away from the ring-shaped irradiation unit 15 (for example, at a position where it is not affected by the heat of the section steel 11 in a high-temperature state). This makes it possible to apply the light source 16 to hot section steel conveying lines, where application of ordinary lighting equipment has been difficult, and makes it possible to irradiate red-hot section steel at around 1000°C with strong visible light from a close distance. Furthermore, because the light source 16 has very strong light-emitting capability, it is advantageous for taking images with an extremely short exposure time using the line scan camera 13, even in cold inspections (for example, section steel conveyed at high speeds of about 1 m / s or more).

[0025] As described above, the ring-shaped light-emitting means 12 is configured with the ring-shaped irradiation unit 15 and the light source 16 separated from each other, but a configuration in which these are integrated, for example, a ring illumination in which light-emitting elements such as LEDs are arranged in a ring shape, can also be used as the ring-shaped light-emitting means. For example, when applied to cold inspection or when a heat-resistant case having sufficient cooling capacity can be provided even in hot inspection, the above-mentioned ring illumination may be used. In particular, when an area camera, which will be described later, is used as the imaging means, it is effective to use the above-mentioned ring lighting, which can uniformly irradiate visible light over a certain range in the axial direction, or a ring-shaped flash lighting, which can momentarily irradiate powerful visible light, as the ring-shaped light-emitting means.

[0026] As shown in FIG. 3, a reflecting member 28 can be disposed upstream of the ring-shaped irradiation unit 15 in the moving direction of the bar steel 11 (at a position different from the ring-shaped irradiation unit 15). The reflecting member 28 is made of, for example, a stainless steel pipe or a white resin pipe, and is capable of receiving the section steel 11. That is, the inner diameter of the reflecting member 28 is larger than the outer diameter of the section steel 11, and it is preferable that the reflecting member be made of a steel pipe when the section steel is in a high-temperature state, and that the reflecting member be made of a resin pipe when the section steel is in a room-temperature state. This reflecting member 28 has a diameter that expands toward the ring-shaped irradiation section 15 on the side facing the ring-shaped irradiation section 15, and is configured to reflect a portion of the light (reflected light) that is irradiated from the ring-shaped irradiation section 15 and reflected by the surrounding surface of the bar steel 11, and to irradiate it again onto the surrounding surface of the bar steel 11 as diffused light.

[0027] The visible light irradiated by the ring-shaped irradiation unit 15 is reflected by the bar steel 11 (reflected light), which is direct light, and therefore the reflected light from the fine irregularities on the surface of the bar steel 11 is emphasized and captured by the line scan camera 13, which can cause erroneous detection. Therefore, by installing a reflecting member 28 so as to face the direction of irradiation of the visible light, irradiating the surface of the section steel 11 with diffused light reflected from the reflecting member 28, and photographing the light reflected from the surrounding surface of the section steel 11 with the line scan camera 13, it becomes possible to reduce the influence of light reflected from fine irregularities on the surface of the section steel 11. This is particularly effective for section steel made of a material with a strong metallic luster. Furthermore, as shown in Figure 4, when inspecting deformed steel bars, the backside of the knots is cast in shadow when visible light is irradiated from one side, so by efficiently using light from the reflective member, it is possible to inspect the surface of the backside of the knots as well.

[0028] The line scan camera 13 photographs (takes an image of) reflected light that is generated when visible light is irradiated onto the surface surrounding the bar steel 11. The line scan camera 13 is a line sensor camera in which imaging elements (light receiving elements) are arranged in a one-dimensional line, and is arranged so that the linearly arranged imaging elements are perpendicular to the axis of the section steel 11. Although one line scan camera 13 may be used, it is preferable to arrange a plurality of line scan cameras 13 at equal angular positions in the circumferential direction around the axis of the section steel 11 so that the entire circumference of the section steel 11 can be photographed without any gaps. This line scan camera 13 is effective for use in continuously photographing the object to be inspected while it is being transported, but there is no problem with the inspection function if an area camera (an example of an imaging means) is used instead of or together with the line scan camera, and either or both of the line scan camera and area camera can be selected as appropriate depending on the application.

[0029] The computer 14 has a memory unit, an image processing unit, an error detection unit, a judgment unit, and a display (display unit), and performs the processes performed by these units and the controls of the ring-shaped light emitting means 12 and the line scan camera 13 according to a program pre-set in the computer 14, and processes image data of the bar steel 11 photographed by the line scan camera 13 to inspect the peripheral surface of the bar steel 11. The computer is a conventionally known computer equipped with RAM, CPU, ROM, I / O, and a bus connecting these elements, but is not limited to this. A brief explanation is given below.

[0030] The storage unit performs processing to store image data of the bar steel 11 photographed by the line scan camera 13 and transmitted to the computer 14 . The image processing unit processes the image data of the bar 11 stored in the storage unit, and performs processing to clearly show the areas on the surface of the bar 11 that have and do not have defects. The error detection unit compares the bar 11 obtained by processing in the image processing unit with a bar having no surface flaws, and performs processing to detect errors (differences). The determination unit performs a process of evaluating the surface condition of the bar 11 based on the error (difference) detected by the error detection unit. Specifically, for example, an operator uses a keyboard or mouse to input an error value that serves as a criterion for determining whether or not a flaw has occurred. As a result, if the error detected by the error detection section is larger than the input value, the determination section determines that there is a flaw, and if the error is equal to or smaller than the input value, the determination section determines that there is no flaw. The determination of the presence or absence of defects is not limited to the above-described process as long as the presence or absence of defects can be detected, but can also be performed by other processes, or, for example, can be performed by an operator using an image obtained by the image processing unit of computer 14.

[0031] Next, a method for inspecting the surface of a metal bar according to one embodiment of the present invention will be described with reference to FIGS. 1, 2(A) and 2(B). The surface inspection device 10 for metal bars is located downstream of the final stand of the rolling process for producing section steel 11. The section steel 11 is inserted into a through hole 18 formed in a ring-shaped irradiation unit 15 of the ring-shaped light emitting means 12 and transported at high speed in the longitudinal direction of the section steel 11 so as to pass through the axial center position of the ring-shaped irradiation unit 15 (for example, moving at a high speed of about 1 m / sec or more). As a result, while the section steel 11 is being manufactured in the rolling process, the manufactured section steel 11 is continuously moved relative to the ring-shaped irradiation unit 15, and visible light generated by the light source 16 can be irradiated from the ring-shaped irradiation unit 15 toward the peripheral surface of the section steel 11. As the section steel 11 passes through the axis of the ring-shaped irradiation unit 15 as described above, the distance from the emission position of the visible light to the section steel 11 becomes nearly constant in the circumferential direction of the section steel 11, and it becomes possible to uniformly irradiate the visible light onto the surface of, for example, a cylindrical section steel having a curve (the above is process A).

[0032] Next, the reflected light generated by irradiating the peripheral surface of the bar steel 11 with visible light is photographed by the line scan camera 13. As described above, the section steel 11 produced in the rolling process is in a red-hot state at around 1000°C, and therefore, by having the light source 16 generate visible light with a higher brightness than the section steel 11, the reflected light can be captured by the line scan camera 13 without being affected by the spontaneous emission of light emitted from the high-temperature section steel 11. Furthermore, even when capturing an image of section steel 11 being transported at high speed, the reflected light can be captured by the line scan camera 13 by irradiating the section steel 11 with strong visible light at a level that can be handled with an extremely short exposure time from a close distance. In particular, by housing the ring-shaped irradiation unit 15 in a heat-resistant case 19, it is possible to cool the ring-shaped irradiation unit 15 that has been heated by the heat generated by light emission and the heat from the steel bar 11, and it is also possible to prevent scale and water droplets from adhering to it, and further to blow away scale and water droplets that would interfere with surface inspection by image processing.

[0033] 3, the reflected visible light is diffused (reduces the brightness of the light) and is irradiated again onto the section steel 11, and this reflected light is also photographed by the line scan camera 13, making it possible to make less noticeable changes due to slight irregularities formed on the surface of the section steel 11, for example. In this case, the section steel 11 passes through the axis of the reflecting member 28, as in the case of the ring-shaped irradiation unit 15 described above, and so the distance from the reflection position of the reflecting member 28 to the section steel 11 becomes nearly constant in the circumferential direction of the section steel 11, making it possible to irradiate the reflected light (diffused light) uniformly onto the surface of the section steel 11, which has a curved cylindrical shape, for example. Furthermore, by using the reflecting member 28, as shown in Figure 4, it is possible to irradiate the deformed steel bar with light on the side opposite to the side where visible light is directly irradiated from the ring-shaped irradiation unit, so that the surrounding surface of the deformed steel bar can be photographed evenly without creating shadows due to the shape of the object to be inspected, and blind spots in inspection using image processing can be eliminated. The acquired image data is transmitted to the computer 14 (this completes step B).

[0034] The image data transmitted to the computer 14 is stored in the storage unit and then processed in the image processing unit. Specifically, the image data of the section steel 11 stored in the storage unit is processed to clearly show the areas on the surface of the section steel 11 that have and do not have defects. Then, the error detection unit compares the bar steel 11 obtained by processing in the image processing unit with bar steel without surface defects to detect errors (differences), and the judgment unit performs processing to evaluate the condition of the surrounding surface of the bar steel 11 based on the errors (differences) detected in the error detection unit. As a result, if the error detected by the error detection section is larger than the input value, the determination section determines that there is a flaw, and if the error is equal to or smaller than the input value, the determination section determines that there is no flaw. The determination of the presence or absence of defects is not limited to the above-described process as long as the presence or absence of defects can be detected, but can also be performed by other processes, or, for example, can be performed by an operator using an image obtained by the image processing unit of computer 14. Here, the bar steel that is determined to have no defects is shipped to, for example, a contractor, and the bar steel that is determined to have defects is returned to the bar steel manufacturing process again (these are the steps of process C). [Example]

[0035] Next, examples carried out to confirm the effects of the present invention will be described. Here, the surface inspection method for metal bar material of the present invention was applied (using a surface inspection device) to conduct tests to detect surface defects in deformed steel bars (bar steel) for approximately three months, in combination with existing eddy current flaw detection. As a result, large defects that resembled chips, thought to have occurred due to the scab portion peeling off, were detected on average about once every five operating days. These types of defects cannot be detected using conventional inspection methods, and it is presumed that a certain number of defects that are likely to affect mechanical strength are leaking out under conventional inspection environments. Therefore, in the case of deformed steel bars that are used as they are without machining, there is a possibility that defects may be left unnoticed during construction work. From the above, it is believed that the introduction of the metal bar surface inspection method and surface inspection device of the present invention will not only improve the quality of bar steel, but will also contribute to society in a wide range of areas, such as improving the earthquake resistance of building structures.

[0036] Although the present invention has been described above with reference to the embodiments, the present invention is not limited to the configurations described in the above embodiments and includes other embodiments and modifications that can be considered within the scope of the claims. For example, the scope of the present invention also includes a case in which the surface inspection method and surface inspection device for metal bars of the present invention are configured by combining some or all of the above embodiments and modifications. In the above embodiment, the case where a bar is used as the inspection object of the present invention has been described, but the structure and material of the bar are not particularly limited as long as it is a metal bar-shaped material.

[0037] Furthermore, in the above embodiment, the heat-resistant case is described as being composed of an outer cylindrical portion, an inner cylindrical portion, and two lid portions, but there is no particular limitation as long as it can accommodate the ring-shaped irradiation unit and prevent damage due to heat. If the ring-shaped irradiating unit is not affected by heat or is only slightly affected by heat, it is not necessary to use a heat-resistant case. In this case, the ring-shaped light-emitting means may be configured such that the ring-shaped irradiating unit and the light source are not separated (integrated).

[0038] In the above embodiment, the case where the visible light is irradiated onto the peripheral surface of the section steel while the section steel is continuously moved relative to the ring-shaped irradiation unit has been described, but the visible light may also be irradiated while the section steel is moved intermittently (while repeatedly moving and stopping). In this case, the visible light may be irradiated either while the section steel is moving or while it is stopped. Furthermore, in the above embodiment, the slits for irradiating visible light and spraying compressed air are described as being formed continuously in the circumferential direction of the heat-resistant case, but they may also be formed at a preset pitch. Also, the slits for irradiating visible light and spraying compressed air may be provided separately, or only the slits for irradiating visible light may be formed on the heat-resistant case, and the means for spraying compressed air may be provided separately from the heat-resistant case. [Explanation of symbols]

[0039] 10: Metal bar surface inspection device, 11: Bar steel (metal bar), 12: Ring-shaped light emitting means, 13: Line scan camera (imaging means), 14: Computer (image processing means), 15: Ring-shaped irradiation unit, 16: Light source, 17: Optical fiber, 18: Through hole, 19: Heat-resistant case, 20: Space, 21: Outer cylindrical portion, 22: Inner cylindrical portion, 23, 24: Lid, 25: Support, 26: Slit, 27: Air supply unit, 28: Reflective member

Claims

1. a step A in which a red-hot metal bar is moved in the longitudinal direction of the metal bar and inserted into a through-hole formed in a ring-shaped light-emitting means, while irradiating visible light from the ring-shaped light-emitting means onto the peripheral surface of the metal bar; a step B of irradiating the peripheral surface of the metal bar with visible light and capturing reflected light with an imaging means; and a step C of processing the image captured by the imaging means with an image processing means to inspect the peripheral surface of the metal bar-shaped material, the ring-shaped light-emitting means includes a light source that generates visible light with a brightness higher than that of the metal rod in a red-hot state, a ring-shaped irradiation unit having the through-hole, and an optical fiber that connects the light source and the ring-shaped irradiation unit; The ring-shaped irradiation unit is housed in a heat-resistant case, and visible light is irradiated onto the peripheral surface of the metal bar through slits formed continuously in the circumferential direction of the heat-resistant case on the side of the heat-resistant case facing the metal bar, A method for inspecting the surface of a metal bar, characterized in that the light source is positioned at a position away from the metal bar in a red-hot state and at a position away from the ring-shaped irradiation unit.

2. 2. The method for inspecting the surface of a metal bar according to claim 1, wherein the metal bar is a steel bar, and visible light generated by the light source is irradiated onto the peripheral surface of the steel bar via the ring-shaped irradiation unit.

3. 2. A method for inspecting the surface of a metal bar according to claim 1, wherein gas is injected from said slit.

4. A method for inspecting the surface of a metal bar according to any one of claims 1 to 3, characterized in that the reflected light captured by the imaging means is light that is visible light irradiated from the ring-shaped light-emitting means and reflected by the surrounding surface of the metal bar, and light that is reflected from the surrounding surface of the metal bar by irradiating a portion of the light again onto the surrounding surface of the metal bar using a reflecting member.

5. 1. An apparatus for inspecting the peripheral surface of a metal bar while moving the metal bar in a red-hot state in the longitudinal direction of the metal bar, comprising: a ring-shaped light emitting means having a through hole formed therein and configured to irradiate visible light toward a peripheral surface of the metal bar inserted into the through hole; an imaging means for imaging reflected light generated by irradiating the peripheral surface of the metal bar with visible light; and image processing means for processing the image captured by the imaging means to inspect the peripheral surface of the metal bar, the ring-shaped light-emitting means includes a light source that generates visible light with a brightness higher than that of the metal rod in a red-hot state, a ring-shaped irradiation unit having the through-hole, and an optical fiber that connects the light source and the ring-shaped irradiation unit; The ring-shaped irradiation unit is housed in a heat-resistant case, and visible light is irradiated onto the peripheral surface of the metal bar through slits formed continuously in the circumferential direction of the heat-resistant case on the side of the heat-resistant case facing the metal bar, A surface inspection device for metal rods, characterized in that the light source is positioned at a position away from the metal rod in a red-hot state and at a position away from the ring-shaped irradiation unit.

6. 6. The surface inspection device for metal bar material according to claim 5, wherein the metal bar material is a steel bar, and the visible light generated by the light source is irradiated toward the peripheral surface of the steel bar via the ring-shaped irradiation unit.

7. 6. The surface inspection apparatus for metal bars according to claim 5, wherein gas is ejected from said slit.

8. The surface inspection device for metal bar material according to any one of claims 5 to 7, characterized in that it has a reflecting member arranged at a position different from the ring-shaped light-emitting means, which re-irradiates a portion of the light that is reflected by the peripheral surface of the metal bar material when the visible light is irradiated from the ring-shaped light-emitting means onto the peripheral surface of the metal bar material.

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