Surface roughness evaluation method and surface roughness evaluation device

Abstract

To make it possible to more reliably evaluate whether or not the surface roughness of a metal to be evaluated is within the target surface roughness.SOLUTION: The surface roughness evaluation method is for evaluating whether the surface roughness of a metal to be evaluated is the target surface roughness. When the surface of the metal to be evaluated is illuminated with illumination light from an illumination device 10, an area including the intersection point with the irradiation axis of the illumination device is defined as a bright area ARA-1 and an area adjacent to the bright area ARA-1 and relatively lower in brightness than the bright area ARA-1 as a dark area ARA-2. In the bright area ARA-1, the luminance ratio, which is the ratio of areas with a brightness level equal to or higher than a preset brightness level, is calculated, and the average luminance of the dark area ARA-2 is calculated as the luminance of the dark area. When the luminance ratio is less than a first preset threshold and the dark luminance is greater than a second threshold value, the surface roughness of the metal to be evaluated is evaluated as the target surface roughness.SELECTED DRAWING: Figure 13

Description

[Technical Field]

[0001] The present invention relates to a surface roughness evaluation technique for evaluating whether a metal surface to be evaluated has a target surface roughness. The present invention is suitable for evaluating the surface roughness of a metal surface that has been roughened by a surface treatment, i.e., for evaluating the surface treatment that has been performed. The present invention is also applicable to metal surfaces that have not been subjected to surface treatment. [Background technology]

[0002] When a predetermined surface roughness is to be imparted to the metal surface as the final product shape, the metal surface may be subjected to shot blasting or other surface treatments. For example, the pipe end thread portion formed on the pipe end of an oil country tubular good is formed by cutting using an NC thread cutting machine. As shown in Figure 1, this pipe end thread portion 1 is composed of a thread portion (hereinafter also referred to as the thread portion main body 1A), a seal portion 1B, a shoulder portion 1C, and an inner surface portion 1D. Generally, the thread portion main body 1A and the seal portion 1B together are referred to as the outer surface portion 1E. Furthermore, the thread shape of the pipe end thread portion 1 of a pipe can be, for example, a round head thread, a trapezoidal thread, or a hook thread.

[0003] The threaded portion of the pipe end produced as described above is usually roughened by subjecting the metal surface to a blast treatment (surface treatment). Here, oil well tubular goods are connected to each other by, for example, applying a compound to the threaded portion of the pipe end and tightening the joint. If the threaded portion is not blasted, seizing may occur during tightening. To prevent this, blasting media is sprayed onto the entire threaded portion of the pipe end at a constant pressure to roughen the surface of the threaded portion.

[0004] The blasting treatment is carried out, for example, by spraying blasting media 4 such as SUS beads and alumina onto the pipe end thread portion 1 using an apparatus such as that shown in Figure 2. For example, as shown in Figure 2, the blasting media 4 is sprayed from two nozzles 5A, 5B tilted toward the axial side of the oil country tubular good 2 in opposite directions from a direction H perpendicular to the axis of the oil country tubular good 2. Then, the oil country tubular good 2 is moved in the pipe axial direction (longitudinal direction) while being rotated about its axis, thereby blasting the entire metal surface of the pipe end thread portion 1. Conventionally, the roughened surface has been visually inspected to determine the quality of the surface treatment, but visual inspection of each individual pipe poses a problem, hindering the productivity of oil country tubular goods manufacturing.

[0005] Although the subject is not oil country tubular goods, there is a method described in Patent Document 1, for example, as an evaluation method for a surface-treated metal surface that does not require visual inspection. Patent Document 1 describes a surface defect inspection method for detecting surface defects (visual abnormalities) on a metal plate. In this method, an imaging target area on the surface of the metal plate is irradiated with illumination light, and the light reflected from the imaging target area is captured. The captured image is then binarized, and surface defects on the metal plate to be evaluated are detected in bright areas of the binarized image based on predetermined judgment rules. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 2019-184559 Summary of the Invention [Problem to be solved by the invention]

[0007] Patent Document 1 describes that the state of defects present in the surface of a metal plate can be determined by illuminating the surface of the metal plate and capturing an image of only the bright areas that are obtained. However, the inventors have confirmed that when a surface treatment is applied to a metal surface on which irregularities such as the thread shape of the threaded portion at the end of an oil country tubular good are formed, the accuracy of the image assessment described in Patent Document 1 is poor. That is, on a metal surface having a surface shape such as a threaded portion, the brightness of bright areas varies due to the influence of shadows and reflections caused by the irregularities on the metal surface. For this reason, when the method described in Patent Document 1 was used to test a metal surface such as a threaded portion at a pipe end, which is inevitably affected by surface irregularities, it was not possible to clearly evaluate whether the surface was in an unblasted state or blasted as a whole.

[0008] The present invention has been made with the above points in mind, and aims to make it possible to more reliably evaluate whether the surface roughness of the metal surface being evaluated is the target surface roughness. [Means for solving the problem]

[0009] Here, one aspect of the present invention is not primarily intended to detect surface defects locally (pinpoint) in a region of a surface-treated metal surface, but rather has as its primary objective the evaluation of whether the metal surface being evaluated as a whole has a predetermined target surface roughness.

[0010] To solve the problem, one aspect of the present invention is a surface roughness evaluation method for evaluating whether the surface roughness of a metal surface to be evaluated is a target surface roughness, in which illumination light is irradiated onto the metal surface to be evaluated using a lighting device, the metal surface to be evaluated where the illumination light hits is imaged, bright areas that are areas with a brighter brightness and dark areas that are lower in brightness than the bright areas are defined in the image, and the surface roughness of the metal surface to be evaluated is evaluated based on the brightness of the bright areas and the brightness of the dark areas.

[0011] Another aspect of the present invention is a surface roughness evaluation method for evaluating a metal surface having an area with a surface shape that has a predetermined uneven shape, and evaluating whether the surface roughness of the metal surface meets a target surface roughness.The method involves irradiating the metal surface of the uneven area with illumination light using a lighting device, capturing an image of the metal surface to be evaluated where the illumination light hits, determining bright areas in the captured image that are areas with a brighter brightness within the uneven area, calculating a brightness ratio that is the proportion of areas in the bright areas that have a brightness equal to or greater than a predetermined brightness, and evaluating the surface roughness of the metal surface to be evaluated based on the brightness ratio. [Effects of the Invention]

[0012] According to the aspects of the present invention, it is possible to evaluate whether or not the metal surface to be evaluated has a target surface roughness. Furthermore, according to the aspects of the present invention, it is possible to more reliably evaluate the surface roughness even for a metal surface on which a predetermined uneven shape (such as a thread shape) is formed. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 3 is a cross-sectional view illustrating the configuration of a pipe end thread portion. [Figure 2] FIG. 1 is a schematic diagram showing an example of an apparatus for performing blasting treatment on a threaded portion of a pipe end. [Figure 3] FIG. 10 is a schematic diagram showing the relationship between the pipe and the nozzle when the blasting process is performed normally. [Figure 4] 10A and 10B are diagrams illustrating an example of blasting a screw when a nozzle 5A is clogged. [Figure 5] 10A and 10B are diagrams illustrating an example of blasting a screw when a nozzle 5B is clogged. [Figure 6] FIG. 10 is a schematic diagram showing the relationship between the pipe and the nozzle when the nozzle 5B is clogged during blasting. [Figure 7] 1 is a diagram showing an example of the configuration of a surface roughness evaluation device according to an embodiment of the present invention. [Figure 8]FIG. 10 is a diagram showing the relative positions of a camera 11A and a lighting device 10A. [Figure 9] FIG. 2 is a diagram illustrating the configuration of a calculation processing unit. [Figure 10] FIG. 10 is a diagram showing an image of a threaded portion before blasting. [Figure 11] FIG. 10 is a diagram showing an image of the outer surface (screw body and seal portion) that has been subjected to blast processing. [Figure 12] FIG. 10 is a diagram showing an image of the outer surface (the main body of the threaded portion and the seal portion) when the blast is thin. [Figure 13] FIG. 10 is a diagram showing an example of an image of the outer surface (screw body and seal portion) to be evaluated, illustrating bright and dark areas. [Figure 14] FIG. 2 is a diagram illustrating a configuration of an evaluation calculation unit. [Figure 15] FIG. 10 is a diagram illustrating an example of a processing flow of a first evaluation unit. [Figure 16] FIG. 10 is a diagram illustrating an example of a processing flow of a second evaluation unit. [Figure 17] This figure explains the difference in reflected light due to surface roughness. (a) shows the case where the surface roughness is small and there is a lot of specular reflection, and (b) shows the case where the surface roughness is large and there is a lot of diffuse reflected light. [Figure 18] FIG. 10 is a diagram showing an example of setting conditions for a device, etc. [Figure 19] FIG. 10 is a diagram of an image showing the occurrence of halation on the inner surface due to non-blasting. [Figure 20] 10A and 10B are diagrams illustrating a method of correcting the position in the horizontal direction (lateral direction). [Figure 21] 10A and 10B are diagrams illustrating a method of correcting the position in the vertical direction (up and down direction). [Figure 22] FIG. 1 is a diagram showing an example of blast defects at a threaded portion of a pipe end and an evaluation method. [Figure 23] FIG. 10 is a diagram showing the results of evaluation tests in Examples. DETAILED DESCRIPTION OF THE INVENTION

[0014] Next, an embodiment based on the present invention will be described with reference to the drawings. In this embodiment, the metal surface to be evaluated is a metal surface that has been subjected to a surface treatment and has a rough surface. That is, the evaluation of surface roughness is used as an example of the evaluation of the surface treatment. However, the present disclosure is also applicable to metal surfaces that have not been subjected to a surface treatment.

[0015] (Surface treatment) In this embodiment, blasting is exemplified as a surface treatment method for increasing (roughening) the surface roughness of a metal surface. However, the surface treatment method for roughening a surface to which the present disclosure is applicable is not limited to blasting, and other methods such as chemical treatment may also be used. In the following description, an example will be given in which the metal surface to be evaluated is the surface of the pipe end thread portion 1 of an oil country tubular good.

[0016] (Pipe end thread 1) As described above, the pipe end thread portion 1 formed on the pipe end of the oil country tubular good is formed by cutting with an NC thread cutting machine. In this state, the metal surface of the pipe end thread portion 1 has a surface roughness of, for example, Ra: 1.7 μm or less. The surface of the pipe end thread portion 1 to be evaluated is composed of the thread portion main body 1A, the seal portion 1B, the shoulder portion 1C, and the inner surface portion 1D (the inner diameter surface near the pipe end face), as shown in Figure 1. Generally, the thread portion main body 1A and the seal portion 1B together are referred to as the outer surface portion 1E. The threaded portion main body 1A is an area having a concave-convex shape in which a thread shape (thread crests and valleys) is formed as a predetermined concave-convex shape. The present disclosure is applicable if the concave-convex shape of the metal surface to be evaluated is known in advance. The present disclosure is particularly effective for complex surface shapes that produce shadows. The present disclosure is applicable when the concave-convex shape is formed in a predetermined pattern on the metal surface to be evaluated, but is also applicable when the concave-convex shape is formed in an irregular shape. However, it is more versatile when targeting a metal surface having a concave-convex shape formed in a predetermined pattern.

[0017] (blasting) In this embodiment, a blast treatment (surface treatment) is performed on the metal surface of the pipe end thread portion 1 formed as described above. Figure 2 shows the configuration of the blast injection unit and its surroundings in a blasting device 3 used for blasting. This blasting device 3 is configured to perform blasting by injecting blasting media 4, such as SUS beads and alumina, into the pipe end thread portion 1 within a closed space (box). Two types of nozzles, nozzle 5A and nozzle 5B, are used to inject the blasting media 4. As shown in Figure 2, the injection axes of nozzles 5A and 5B are tilted in opposite directions from the direction perpendicular to the axial direction H (normal direction) of the OCTG. This ensures reliable blasting of the bottom surface of the thread portion. In Figure 2, reference numeral 6 denotes an inner plug that prevents the blasting media 4 from entering the OCTG 2. The blasting device 3 also includes a rotation drive unit (not shown) that rotates the oil well pipe 2 about its axis, and an advancing / retracting mechanism (not shown) that moves the oil well pipe 2 back and forth in the axial direction (longitudinal direction).

[0018] Then, while rotating the oil country tubular good 2 around its axis, it is moved in the axial direction (longitudinal direction) as shown in Figure 3, while spraying blasting media 4 from two nozzles 5A, 5B onto the pipe end thread portion 1. This blasts the thread portion main body 1A, seal portion 1B, shoulder portion 1C, and inner surface portion 1D (inner diameter surface of the pipe end) that make up the pipe end thread portion 1. In other words, this process increases the surface roughness of the entire metal surface of the pipe end thread portion 1, excluding the inner surface of the steel pipe. It is not necessary to roughen the inner surface 1D, but when the shoulder portion 1C is roughened, the inner diameter surface near the end of the pipe is also roughened.

[0019] If nozzle 5A becomes clogged and cannot spray blasting media 4, depending on the thread shape of thread body 1A, thread root corner B may not be blasted, as shown in Figure 4. However, in this case, spraying from nozzle 5B will blast flat portion 1F, which is seal portion 1B and shoulder portion 1C (see Figure 3). For this reason, if flat portion 1F has been blasted, it can be determined that symbol A in Figure 4 has been blasted.

[0020] In blasting, when the workpiece surface has portions with different orientations, as shown in A and B in Figure 4, it can be difficult to blast the entire workpiece surface using nozzles facing the same direction. With such complex metal surface shapes, there are the following risks: The nozzle may become clogged, causing the media to not hit the workpiece sufficiently, or the media may collide with each other from two directions, reducing the media impact pressure, resulting in a risk of not achieving the desired roughness. This is a problem that can occur not only in the threaded end of an oil well tubular good, but also in any other inspection of a workpiece with significantly different surface orientations, and this embodiment is particularly effective.

[0021] On the other hand, if the nozzle 5B is clogged and the blasting media 4 cannot be sprayed, depending on the thread shape, the thread root corner A may not be blasted, as shown in Figure 5. In this case, as can be seen from Figure 5, the shoulder portion 1C remains unblasted, and the pipe becomes a defective blasted product.

[0022] (Surface roughness evaluation device) The surface roughness evaluation device of this embodiment is a device for evaluating the surface roughness of a metal surface. This device is also applicable to areas with a surface shape having multiple irregularities, such as the threaded portion 1 of a pipe end. This disclosure is highly effective when evaluating the effectiveness of a process for increasing the surface roughness of an area where multiple irregularities form multiple shadows. Specifically, the surface roughness evaluation device of this embodiment is a device for evaluating whether a metal surface has a target surface roughness, i.e., a desired surface roughness, achieved by a blasting process or the like. In other words, the surface roughness evaluation device of this embodiment is a device for evaluating the surface roughness of a metal surface to evaluate whether the blasting process was performed properly.

[0023] <Metal surface (area) to be evaluated> In this embodiment, the metal surface to be evaluated is divided into two regions: a first metal surface region MT1 and a second metal surface region MT2 (see FIG. 1). The surface roughness (simply referred to as roughness) of each surface is evaluated separately for each of the regions MT1 and MT2.

[0024] The first metal surface region MT1 is a metal surface region formed by the outer surface portion 1E, which is made up of the thread portion main body 1A and the seal portion 1B and forms the outer diameter surface of the pipe end thread portion 1. The thread portion main body 1A and the seal portion 1B may be treated as separate regions and evaluated individually. This first metal surface region MT1 is primarily intended to evaluate the metal surface of the thread portion main body 1A. The thread portion main body 1A forms a metal surface on which a predetermined uneven shape is formed.

[0025] The second metal surface region MT2 is a metal surface region formed by a flat portion 1F consisting of a shoulder portion 1C and an inner surface portion 1D (inner diameter surface near the pipe end face). In this embodiment, evaluation is performed on the inner surface portion 1D, taking into account interference with the blasting device 3. This is because if the inner surface portion 1D has been blasted, the shoulder portion 1C can be considered to have been blasted as well. Note that the shoulder portion 1C can be directly evaluated by acquiring an image from an outer position in the axial direction of the oil country tubular good 2. The inner surface portion 1D consists of a flat metal surface. Note that this embodiment is an example in which a surface roughness evaluation device is provided as part of the blasting device 3 equipment.

[0026] <Device configuration> As shown in Figures 7 and 9, the surface roughness evaluation device of this embodiment includes an illumination device 10, an imaging device (camera 11), a setting unit 22, an arithmetic processing unit 12 consisting of a computer capable of image processing, and a position correction unit.

[0027] <Lighting device 10> As shown in FIG. 4, the lighting device 10 includes a lighting device 10A for the first metal surface region MT1 and a lighting device 10B for the second metal surface region MT2. The lighting device 10A is configured to irradiate the threaded portion main body 1A and the seal portion 1B with illumination light from above (for example, in a direction perpendicular to the axis) onto the pipe end threaded portion 1. For example, the lighting device 10A is configured with a plurality of LEDs arranged in the tube axis direction, with LEDs being an example of the light source. In other words, the lighting device 10A is configured to be able to uniformly illuminate the outer surface of the pipe end threaded portion 1. In this case, multiple lighting axes 10P of the lighting device 10A are set to be arranged in a straight line along the tube axis direction. The lighting device 10B is configured to irradiate illumination light onto a lower portion in the circumferential direction of the inner diameter surface near the tube end. There are no particular limitations on the light sources of the lighting device 10.

[0028] <Imaging device> The imaging device is composed of cameras 11. The cameras 11 include a camera 11A for the first metal surface area MT1 and a camera 11B for the second metal surface area MT2. The camera 11A is arranged with its imaging axis 11P facing, for example, an illumination axis 10P near the center of an array of multiple illumination axes 10P arranged in the axial direction (see Figure 8), and is capable of imaging the illumination area irradiated with illumination light by the illumination device 10A. The camera 11A is disposed so as to be able to capture an image of an area irradiated with laser light, which will be described later, in the tube axis direction. The camera 11B captures an image of an area including the inner diameter surface of the tube end irradiated with illumination light by the illumination device 10B. The image to be acquired may be a monochrome image or a color image. It should be noted that the lighting and imaging are performed in a dark environment, i.e., the image acquisition process is performed in a dark room (behind a blackout curtain) that forms a closed space.

[0029] <Position correction section> The position correction unit includes the laser light irradiation device 13 and a correction processing unit 21. As shown in Fig. 9, the correction processing unit 21 includes a horizontal direction correction processing unit 21A and a vertical direction position correction unit 21B. The laser beam irradiation device 13 irradiates the outer diameter surface of the pipe near the threaded portion main body 1A on the pipe end side with laser beams along the circumferential direction from a direction assumed to be perpendicular to the pipe axis. The irradiation position is set to the imaging range of the camera 11A.

[0030] The horizontal direction correction processor 21A performs image processing such as binarization on the captured image of the pipe end thread portion 1 to detect the position of the pipe end face in the image. Then, based on the detected pipe end face position (its horizontal center position), it corrects the horizontal (lateral) position of the pipe end thread portion 1 in the image. For example, it corrects the frame position of the image itself or each region, such as a bright region, so that the reference pipe axis position coincides with the center axis of the actual pipe end thread portion 1 in the image. Based on the image including the laser light captured by the camera 11A, the vertical position correction unit 21B detects the positions of the upper and lower ends of the pipe in the image based on the change in the density of the laser light, and performs vertical position correction.

[0031] Here, camera 11A captures the image from diagonally above the pipe, as shown in Figure 8. Therefore, if the pipe end thread portion 1 is displaced horizontally or vertically, the actual pipe end thread portion 1 is captured in the image at a position displaced from the hypothetical pipe axis (reference axis). Correction processing unit 21 detects this displacement and corrects the image so that the axis of the actual pipe end thread portion 1 coincides with the reference axis. Alternatively, the position of the reference axis is corrected to the axis of the actual pipe end thread portion 1. When camera 11A captures an image from directly above, the effect of vertical displacement is small. However, camera 11B captures an image of a lower circumferential position near the pipe end face from an obliquely upward position, so if vertical displacement occurs, it may not be possible to capture the target imaging area. For this reason, horizontal and vertical corrections are necessary. Here, the positions of the bright area ARA-1, the dark area ARA-2, etc. are defined based on the position of the reference axis.

[0032] <Settings section 22> The setting unit 22 obtains a specified value for setting a bright area ARA-1 and a dark area ARA-2 for an image. "About setting light and dark areas" Generally, the surface roughness (roughness) and brightness (brightness of the captured image) are bright when the roughness is small, and dark when the roughness is large. Also, when the light source is close and the light is irradiated at an angle close to perpendicular to the object being inspected, that is, perpendicular to the irradiation axis, the image is bright and halation is likely to occur, and when the point in question is far from the light source and the irradiation angle is shallower than perpendicular, the image is dark. In surface treatment processes, polishing processes such as buffing result in small roughness, but roughness increases after processing in processes that roughen the surface such as shot blasting.

[0033] In this embodiment, if a test specimen that can measure the surface roughness at each part and has an appropriate surface roughness in advance can be used to determine the range of image information such as satisfactory brightness of light and dark areas, it is possible to determine whether the product has the specified surface roughness based on the image information alone when it is produced. In the case of threaded parts for oil well tubular goods, where the surface shapes change in a complex manner, using multiple lights, cameras, etc. is highly effective, as it allows the desired surface roughness to be obtained on each surface.

[0034] Here, the illumination area is defined as the area illuminated by illumination light from the illumination device 10. For example, since the illumination device 10A illuminates the outer surface 1E of the pipe end thread portion 1 from above, the illumination area is, for example, approximately the upper half of the circumference of the pipe (see FIG. 8).

[0035] The bright area ARA-1 is a relatively bright area selected from within the illumination area. In this embodiment, the bright area ARA-1 is selected from an area including a position intersecting with the illumination axis of the illumination device. In this embodiment, the bright area ARA-1 is set as an area including all areas where halation occurs due to illumination light on the surface before surface treatment, for example.

[0036] Here, when illumination light is shone on the metal surface of the outer surface 1E of the pipe end thread portion 1 before surface treatment, halation HA occurs at the position where it intersects with the irradiation axis and in the vicinity thereof, i.e., at positions where the illumination light hits strongly, as shown in Figure 10. Then, the maximum width HH (the width in the pipe circumferential direction) of the portion where halation HA occurs is determined and stored in advance. This maximum width HH can be the same value if the diameter of the oil country tubular goods 2 is approximately the same. Instead of the maximum width HH, the width of the average value detected along the axial direction of the position of halation HA may also be used. However, the maximum width HH is set so that the portion where halation occurs is not included as much as possible in the dark area described below.

[0037] Then, as shown in Figure 13, the setting unit 22 determines the width position in the pipe circumferential direction based on the stored maximum width HH, with the position where it intersects with the illumination axis of the lighting device as the center, and defines a rectangular area along the longitudinal direction that contains the entire seal portion 1B and thread portion main body 1A as the bright area ARA-1. Note that the thread main body occupies the majority of the bright area ARA-1. Here, in Figure 13, there are positions where the bright area ARA-1 intersects with multiple illumination axes 10P along the widthwise center position of the bright area ARA-1. In this embodiment, the bright portion main body region ARA-1A is a region of the bright portion region ARA-1 that is slightly narrower in width in the circumferential direction while keeping the position where it intersects with the irradiation axis as its center.

[0038] The setting unit 22 also sets the region adjacent to the bright region ARA-1 in the tube circumferential direction and having a relatively lower brightness than the bright region ARA-1 as the dark region ARA-2 (see Figure 13). The dark region ARA-2 is also set as a rectangular region having the same length in the tube longitudinal direction as the bright region ARA-1. The lengths may be different. In this embodiment, the dark region ARA-2 is set as a region having a narrower width than the bright region ARA-1. The bright region ARA-1 and the dark region ARA-2 do not need to be the same size or shape. This is because information such as brightness is converted into the ratio of the area of ​​regions with a specific brightness or higher to the entire evaluation range as an index of brightness for evaluating roughness, or is calculated as the average brightness of a specific region.

[0039] Here, the width of the bright area region ARA-1 may be set to, for example, 1 / 3 of the diameter of the tube without determining the maximum width HH in advance. If it is about 1 / 3 of the diameter, it can be estimated that it includes the area where the halation occurs. Furthermore, the width of the dark area region ARA-2 is set to, for example, 1 / 4 of the diameter of the tube.

[0040] Furthermore, the setting unit 22 stores, as the halation luminance, the luminance of the portion where the halation occurs, or a luminance obtained by reducing the luminance of the halation by a safety margin, for example. The above description is about the settings for the outer surface portion 1E (first metal surface region MT1). The settings for the flat portion 1F (second metal surface region MT2) can also be set in the same way as described above.

[0041] The pair of bright area ARA-1 and dark area ARA-2 used in each evaluation is selected from areas with similar metal surface shapes. When evaluating the surface roughness of a flat area, the pair of bright area ARA-1 and dark area ARA-2 is selected and set from the flat area that has been surface treated. In addition, for the main body of the thread, the pair of bright area ARA-1 and dark area ARA-2 is selected and set from the area where the thread shape (concave-convex shape) is formed. It is preferable to select and set the pair of bright area ARA-1 and dark area ARA-2 from areas where the surface shape conditions (concave-convex conditions, etc.) of the metal surface before surface treatment are the same or similar conditions.

[0042] <Evaluation calculation unit 20> As shown in FIG. 14, the evaluation calculation unit 20 includes an image area confirmation unit 20A, a brightness ratio calculation unit 20B, a dark area brightness calculation unit 20C, a bright area brightness calculation unit 20D, a comparison brightness calculation unit 20E, an image brightness confirmation unit 20F, and an evaluation unit 20G.

[0043] [Image area confirmation unit 20A] The image area confirmation unit 20A constitutes a part of the processing of the setting unit. The image area confirmation unit 20A detects and sets the frames of the bright area area ARA-1, the bright area main area ARA-1A, and the dark area ARA-2 for the image captured by the camera 11A based on the position where the image area confirmation unit 20A intersects with the lighting axis 10P of the lighting device 10A and the respective specified values ​​that define the bright area area ARA-1, the bright area main area ARA-1A, and the dark area ARA-2 set by the setting unit 22 (see Figure 13). The image area confirmation unit 20A performs the same process for the second metal surface area MT2. That is, the position where the area intersects with the illumination axis 10P of the illumination device 10B and its vicinity are set as the bright area area ARA-1, and the area selected from its periphery is set as the dark area area ARA-2. Because the second metal surface area MT2 is not a metal surface with a predetermined uneven shape, it is not necessary to set a separate bright area main body area ARA-1A. The following explanation will be given using the first metal surface area MT1 as an example.

[0044] The image region confirmation unit 20A detects the bright region ARA-1 and the bright main region ARA-1A based on the maximum width HH, for example, with the position where the region intersects with the illumination axis 10P as the widthwise center position. In addition, it sets the frame of the dark region ARA-2 at a position adjacent to the bright region ARA-1 in the tube circumferential direction. Here, it is assumed that the captured image has been corrected by the processing of the correction processing unit 21 so that the position of the pipe end thread portion in the image coincides with the axis of the pipe (reference axis) that serves as a reference.

[0045] [Brightness ratio calculation unit 20B] The luminance ratio calculation unit 20B calculates a luminance ratio, which is the ratio of an area having a luminance equal to or greater than a preset luminance (halation luminance) within the bright area ARA-1. As mentioned above, the halation brightness is the brightness at the position of the halation on a metal surface that has not been blasted. For safety reasons, the halation brightness may be set to a brightness slightly lower than the brightness of the halation. Note that, as long as the amount of light from the illumination is constant, the halation brightness may be the brightness of the halation measured when the metal surface made of the same material has a low surface roughness. The luminance ratio is calculated, for example, as the ratio of the number of pixels having halation luminance or more to the total number of pixels in the bright area ARA-1 in the image.

[0046] [Dark area luminance calculation unit 20C] The dark area luminance calculation unit 20C obtains the average luminance of the dark area ARA-2 as the dark area luminance. [Bright area luminance calculation unit 20D] The bright portion luminance calculation unit 20D calculates the average luminance of the bright portion main body region ARA-1A as the bright portion luminance. The bright area luminance calculation unit 20D may calculate the average luminance of the bright area region ARA-1 as the bright area luminance. In this embodiment, the average luminance of the bright area main body region ARA-1A is calculated to make the luminance of the bright area clearer. In the second metal surface region MT2, the average luminance of the bright area region ARA-1 is calculated as the bright area luminance. [Comparative luminance calculation unit 20E] The comparative luminance calculation unit 20E calculates the difference in luminance between the calculated bright area luminance and the dark area luminance as the luminance difference.

[0047] [Image brightness check section 20F] The image brightness checking unit 20F evaluates whether or not the brightness of the bright area is equal to or less than a preset lower limit threshold value. When the image brightness confirmation unit 20F judges that the brightness of the bright area is equal to or less than the lower threshold C, it judges that the apparatus is not properly maintained and suspends the process. The above-mentioned device failure is a detection of a device failure such as a decrease in the amount of light from the lighting device 10 or a decrease in brightness due to a dirty lens of the camera 11, for example. The lower limit threshold C may be set by experiment or the like. [Evaluation Section 20G] The evaluation unit 20G performs an evaluation process to determine whether the metal surface to be evaluated has the target surface roughness. The evaluation section 20G includes a first evaluation section 20G1 for the first metal surface region MT1 and a second evaluation section 20G2 for the second metal surface region MT2.

[0048] [First evaluation unit 20G1] The processing of the first evaluation unit 20G1 will be described with reference to the flow of FIG. In step S10, first evaluation unit 20G1 evaluates whether the luminance ratio is less than a first threshold (upper threshold). If the luminance ratio is less than the first threshold (upper threshold), the process proceeds to step S20. On the other hand, if the brightness ratio is equal to or greater than the first threshold (upper threshold), the brightness ratio is deemed too high and the blasting process is evaluated as abnormal (poor). For example, this is an abnormality when the blasting process is not performed. It is also an abnormality when the blasting process is thin and the surface roughness is smaller than the target surface roughness. In step S20, it is evaluated whether the dark area luminance is greater than a preset second threshold (lower limit luminance). If the dark area luminance is greater than the preset second threshold (lower limit luminance), the process proceeds to step S30.

[0049] On the other hand, if the dark area brightness is equal to or less than a preset second threshold (lower limit brightness B), it is evaluated as a blasting process abnormality. For example, this abnormality occurs when the pipe end thread portion 1 to be evaluated is not installed. Here, the metal surface to be evaluated can be evaluated to have the target surface roughness by the evaluation in step S10 alone, but the evaluation in step S20 is performed in order to further increase the evaluation accuracy.

[0050] FIG. 10 shows an example of an unblasted state, and FIG. 11 shows an example of a blasted state. FIG. 12 shows an example of a state where the blasting is light. As can be seen from FIGS. 10 to 12, the dark area luminance is higher in the blasted state than in the unblasted state. Therefore, the second threshold value can be set to a value higher than the dark area luminance in the unblasted state. More preferably, the second threshold value can be set to a luminance that is lower than the dark area luminance measured in the blasted state by a safety margin. Alternatively, the second threshold value can be set to, for example, an intermediate value between the luminance in the unblasted state and the luminance in the blasted state. In other words, the second threshold value can be determined by experiment or other means.

[0051] Then, when the process proceeds to step S30, the metal surface to be evaluated can be evaluated as having the target surface roughness. In step S30, it is evaluated whether the difference in brightness between the bright area brightness and the dark area brightness exceeds a preset third threshold value. If the difference in brightness between the bright area brightness and the dark area brightness exceeds the preset third threshold value, the evaluation is changed to indicate that the surface roughness of the metal surface being evaluated is smaller than the target surface roughness, and the blasting process is evaluated as abnormal.

[0052] If the difference in brightness between the bright area brightness and the dark area brightness is equal to or less than a third preset threshold value, the surface roughness is evaluated as being the target, and the blasting process is evaluated as passing. Here, in Figure 10, which shows the unblasted image, the difference in brightness was 162. In Figure 11, which shows the blasted image, the difference in brightness was 76. Furthermore, in Figure 12, which shows the lightly blasted image, the difference in brightness was 141. In this case, the third threshold is set to, for example, 90, which is larger than 76, taking into account variations (safety margin).

[0053] In the above example, from the perspective shown in Figure 22, the first camera evaluates items other than (2), and the second camera evaluates part (2), and an example is introduced in which thresholds for three conditions are used for judgment. From the above, it is possible to set the number of conditions and values ​​of each threshold value in advance through experiments or the like, depending on the surface shape of the target metal surface.

[0054] [Second evaluation unit 20G2] The processing of the second evaluation unit 20G2 will be described with reference to the flow of FIG. In step S100, the second evaluation unit 20G2 evaluates whether the luminance ratio is less than a first threshold (upper limit threshold) and the dark area luminance is greater than a preset second threshold (lower limit luminance). If the condition is satisfied, the process proceeds to step S110. On the other hand, if the conditions are not satisfied, it is evaluated as a blasting abnormality, such as the pipe end thread portion 1 to be treated not being positioned or the blasting treatment being insufficient.

[0055] In step S110, it is evaluated whether the difference in brightness between the bright area brightness and the dark area brightness exceeds a preset third threshold value. If the difference in brightness between the bright area brightness and the dark area brightness exceeds the preset third threshold value, the evaluation is changed to indicate that the surface roughness of the metal surface being evaluated is smaller than the target surface roughness, and the blasting process is evaluated as abnormal. This means that when the difference in brightness between the bright area brightness and the dark area brightness is equal to or less than a third preset threshold value, the surface roughness of the metal surface to be evaluated can be evaluated as the target surface roughness. The surface roughness of the metal surface to be evaluated may be evaluated based on this evaluation alone.

[0056] If the difference in brightness between the bright area brightness and the dark area brightness is equal to or less than a third preset threshold value, the surface roughness is evaluated as being the target, and the blasting process is evaluated as passing. Here, the above threshold values ​​may be determined by experiment, etc. Also, the first evaluation unit 20G1 and the second evaluation unit 20G2 may have different evaluation threshold values, that is, may be set individually for each evaluation unit. If the first evaluation section 20G1 evaluates the blasting to be passable and the second evaluation section 20G2 evaluates the blasting to be passable for the entire pipe end threaded portion 1.

[0057] (Operation etc.) After various studies, the inventors found that it is impossible to clearly evaluate the quality of the blasting treatment of the thread body 1A by using only the average brightness of the bright area (bright area brightness) or the average brightness of the area away from the irradiation axis (dark area brightness) through image processing. Furthermore, if the sum of the brightness of the bright area and the brightness of the dark area, that is, the average brightness of the entire illuminated area, is calculated, the values ​​for both unblasted and blasted areas will be the same, making it impossible to clearly evaluate. In this embodiment, the reason for using the luminance ratio in the bright area ARA-1 is as follows. be.

[0058] The brightness ratio differs from the evaluation using the average brightness in the bright area ARA-1, which was set as the area including the position where halation occurred before blasting. The brightness ratio evaluates the degree to which brightness above a certain level (brightness that appears bright) has decreased in the bright area ARA-1. The brightness ratio evaluates, for example, the degree to which halation has decreased. In particular, on metal surfaces with uneven shapes, there are clear differences in brightness even within the bright area ARA-1, and the area where halation occurs can be clearly evaluated from the ratio. The ratio of light and dark is affected by a preset uneven shape, so the halation brightness may be set based on the brightness ratio on a metal surface that has been normally subjected to blast processing, for example.

[0059] Here, consider a case where one of the two blast injection nozzles 5A, 5B becomes clogged during blasting. In this case, there is a risk that a small corner of the thread base will remain unblasted (see Figures 4 and 5). In this case, the bright area luminance, dark area luminance, and the difference between the bright area luminance and dark area luminance will each change slightly, but because the changes are so small, it is difficult to clearly evaluate. In contrast, the luminance ratio changes significantly relative to such defects. Therefore, it is possible to evaluate whether a part of the thread is unblasted by checking whether the luminance ratio is below the first threshold.

[0060] However, in the case of a flat surface without any irregularities such as a screw shape, such as the second metal surface region MT2, it is estimated that accuracy will be reduced by simply checking whether the luminance ratio is less than the first threshold value. For this reason, in this embodiment, the evaluation accuracy is improved by evaluating whether the dark area luminance is equal to or greater than the second threshold value.

[0061] Next, the reason for evaluating whether the dark area luminance is equal to or greater than the second threshold value will be explained. First, we will explain a metal surface that has not been blasted. Such a metal surface has a low degree of roughness, and when illuminated, halation occurs and the area where the surface intersects with the illumination axis 10P and its vicinity (the area where light corresponding to the bright area ARA-1 hits strongly) is bright. However, even in the area where the illumination light hits, the area away from the area where the illumination axis 10P intersects (the dark area ARA-2) is significantly darker and has low brightness. That is, as shown in Figure 17(a), when illumination is applied to a surface with little unevenness (low surface roughness), only specularly reflected light is captured by the camera 11. As a result, only the area where the specularly reflected light hits (the bright area) is halated, and the surrounding area other than the halated area is captured very darkly.

[0062] On the other hand, after surface treatment, the metal surface has a large surface roughness. Therefore, when such a surface is illuminated, the rough surface causes a small amount of diffuse reflected light to be captured by the camera 11 from multiple directions, as shown in Figure 17(b). As a result, the brightness of the area directly illuminated is reduced, and the peripheral area (dark area ARA-2) away from the position where the illumination axis 10P intersects appears relatively bright in the image. In this way, when the dark area luminance is equal to or greater than the second threshold, it can be determined that the blast processing is being performed.

[0063] This tendency is particularly pronounced on curved surfaces such as threaded portions at pipe ends. That is, as can be seen from Figure 10, which shows the unblasted state, the roughness of the threaded surface is low in the unblasted state, so the illumination light from the lighting device is strongly reflected only near the illumination axis 10P. On the other hand, the roughness of the blasted threaded surface is high, so as shown in Figure 11, the light from the lighting device is diffusely reflected, allowing the entire pipe end to be imaged brightly. Note that in Figure 12, where the blasting is thin, the average brightness of the dark area ARA-2 is lower than in Figure 11. In this way, it is possible to evaluate the surface roughness by whether the dark area brightness is above the second threshold.

[0064] Furthermore, because the oil country tubular goods 2 are long, bending of the oil country tubular goods 2 may cause the pipe end thread portion 1 to be displaced laterally (horizontally) or vertically (vertically) relative to the pipe axis. If there is a displacement, this will have an adverse effect on the above evaluation using the image, so in this embodiment, a correction is made to the position of the pipe end thread portion 1 in the image. The correction in this embodiment involves, for example, processing the image itself so that the axis of the oil country tubular goods (reference axis) coincides with the axis of the actual pipe end thread portion 1.

[0065] For the reasons described above, this embodiment can be applied to metal surfaces that have a predetermined irregular shape, such as a thread shape, such as the threaded portion 1 at the end of an oil country tubular good 2. Furthermore, the quality of surface treatments such as blasting can be evaluated automatically by a device rather than by visual inspection. As a result, this embodiment improves productivity and makes it possible to prevent mass rejection of pipes due to poor blasting.

[0066] In this embodiment, evaluation is performed by partially sampling the outer surface portion 1E portion (the upper part of the thread main body 1A and the upper part of the seal portion 1B) located on the upper side of the entire circumference of the outer surface portion 1E of the pipe end thread portion 1. In other words, the blast treatment of the entire pipe end thread portion 1 is evaluated by this partial evaluation. Furthermore, the main purpose of this embodiment is not to detect defects in the surface treatment on the metal surface being evaluated, but to evaluate whether the metal surface being evaluated as a whole has the desired target surface roughness.

[0067] "Application to threaded end sections of oil country tubular goods" Hereinafter, examples of setting conditions and the like when the device and method of this embodiment are applied to the pipe end thread portion 1 will be further described. (Example of device configuration and processing) The following provides a supplementary explanation of an example of the conditions and processing of the device configuration of this embodiment. 18 shows an example of the conditions for the camera 11A, the camera 11B, and the laser light irradiation device 13 used in this embodiment. (a) shows an example of the conditions for the camera 11A, (b) shows the conditions for the camera 11B, and (c) shows an example of the conditions for the laser light irradiation device 13.

[0068] <Optimal conditions for imaging> The pipe end thread portion 1 preferably has a width (length in the x-axis direction) of, for example, 30 mm to 300 mm. The lighting devices 10A and 10B emit white light with a power consumption of, for example, 16 to 46 W. The correlated color temperature is, for example, 5600K. An example of the camera 11 specifications is shown below (Figure 18(a)). Type: 2M Gray Image sensor: Interline type, 1 / 1.8-inch CCD fixed image sensor Number of pixels: 1600 pixels horizontally x 1200 pixels vertically Pixel size: 4.4 μm × 4.4 μm, Frame rate: up to 30 frames per second

[0069] Here, the acquisition of each image, that is, the imaging, is performed, for example, as follows. 0.5 msec after camera 11A starts capturing images, lighting device 10A emits illumination light for 1 msec. The exposure time (shutter speed) of camera 11A is, for example, 20 msec. After that, a margin of time of, for example, 80 msec is provided. The margin of time is provided to prevent the light emitted by lighting device 10A from being captured by imaging camera 11B, which will capture the next image. After a margin of time has been provided, an image is captured by camera 11B. 0.5 msec after camera 11B starts capturing images, lighting device 10B emits light for 1 msec. The exposure time (shutter speed) of camera 11B is, for example, 10 msec.

[0070] The reason why the exposure time (shutter speed) of the camera 11A is set to 20 msec longer than the exposure time (shutter speed) of the camera 11B, 10 msec, is as follows: This is to clearly capture on the image the irradiation position RR of the laser light emitted from the laser light irradiation device 13 for correcting the vertical position of the pipe end bend of the oil country tubular good 2. The laser light emitted from the laser light emitting device 13 for correcting the vertical position of the bent tube end may be kept on all the time, or may be kept on only when imaging is being performed.

[0071] <An example of how to determine the "bright area luminance" threshold> The threshold value of the bright area luminance is set to detect a decrease in the amount of light of the lighting device 10A. When comparing the "lower limit value of the bright area luminance in the unblasted state" with the "lower limit value of the bright area luminance in the blasted state," the bright area luminance in the blasted state is always lower due to diffuse reflection of light. From this, the threshold value of the bright part luminance is, for example, a value obtained by multiplying the lower limit value of the bright part luminance after blasting, which has been determined in advance, by a coefficient T (0.5 ≤ T ≤ 0.9). The coefficient T is a safety factor for adding a safety margin. By this, it becomes possible to evaluate normally. The coefficient T is preferably 0.7 ≤ T ≤ 0.8. When 0.9 < T, there are many false detections. When T < 0.5, there is a possibility that the discovery of the decrease in the light quantity of the lighting device 10A may be delayed.

[0072] <An example of a method for determining the threshold value (the second threshold value) of "dark part luminance"> The threshold value of the dark part luminance is mainly for detecting a case where the blasting process is thin or a state where the pipe end screw part 1 is not installed. Obtain "the dark part luminance when blasting is performed at the air pressure for passing during blasting" and "the dark part luminance when blasting is performed at an air pressure for failing by deliberately reducing the air pressure during blasting". Then, as the threshold value of the dark part luminance, for example, set the intermediate value of the two dark part luminances.

[0073] When actually carried out, it was a pass when blasting was performed at an air pressure of 0.24 Mpa, and a fail when blasting was performed at an air pressure of 0.23 Mpa. The dark part luminance of the qualified product blasted at an air pressure of 0.24 Mpa was 25, and the dark part luminance of the unqualified product blasted at an air pressure of 0.23 Mpa was 11. Then, for example, set 18, which is the intermediate value between 25 and 11, as the threshold value of the dark part luminance. When an upper limit threshold value is required, for example, by setting 255 as the upper limit threshold value, it becomes possible to evaluate the pass or fail normally.

[0074] [[ID=十六]] [[ID=十七]]<An example of a method for determining the threshold value (the third threshold value) of "bright part luminance - dark part luminance"> The threshold value of "bright part luminance - dark part luminance" is mainly for the purpose of detecting a case where the blasting process is thin. Obtain "bright part luminance - dark part luminance" when blasting is performed at a qualified air pressure and "bright part luminance - dark part luminance" when the air pressure during blasting is deliberately reduced to an unqualified air pressure. Then, set the intermediate value of the two as, for example, the threshold value (the third threshold value) of "bright part luminance - dark part luminance".

[0075] In actual testing, the blasting process was successful when the air pressure was 0.24 MPa, but failed when the air pressure was 0.23 MPa. The "bright area luminance - dark area luminance" of a passing product blasted at an air pressure of 0.24 MPa was 52, while the "bright area luminance - dark area luminance" of a failing product blasted at an air pressure of 0.23 MPa was 82. Then, for example, 67, the midpoint between 52 and 82, is set as the third threshold. If a lower limit for the "bright area luminance - dark area luminance" threshold is required, for example, setting 0 as the lower threshold will enable normal pass / fail evaluation. If there is a discrepancy between the evaluation using the thresholds set as described above and the operator's judgment for each threshold, the evaluation accuracy can be improved by fine-tuning the set thresholds each time.

[0076] <Camera 11A: Regarding blast quality evaluation based on brightness ratio on outer surface 1E> In an unblasted thread, the surface roughness is low, and halation occurs in areas directly hit by the light emitted from the lighting device 10A. If the number of pixels where this halation is captured is equal to or greater than a set threshold, it can be detected as a large number of halated pixels. In this case, the operator will determine that "halation has occurred, so the blasting process has failed."

[0077] Conversely, if the number of pixels where halation is present is less than the set threshold, it can be detected as a large number of pixels without halation. In this case, the operator will determine that "since no halation has occurred, the blast processing has been passed." If the ratio of pixels judged to have "failed the blasting process due to the occurrence of halation" is a brightness ratio smaller than the brightness ratio when the image has not been blasted, the image can be evaluated as having been blasted. In other words, the brightness ratio can be used to evaluate whether the image has been blasted or not.

[0078] Here, when the lighting device 10A is used to illuminate the outer surface 1E of the pipe end thread portion 1 of the oil country tubular good 2, the thread crest, thread root, thread side, black scale portion on the outer surface of the pipe, and seal portion 1B are not evaluated individually, but such evaluation is not necessary.

[0079] One method for evaluating the surface roughness of the crest and root of a thread (the quality of the blasting treatment) is to measure (evaluate) the surface roughness of the seal portion 1B and evaluate the quality of the blasting treatment. This is an evaluation that considers the surface roughness of the seal portion 1B to be equivalent to the surface roughness of the crest and root of the thread. In other words, as shown in Figure 2, the blasting treatment is performed on the entire end of the OCTG 2 with a constant pressure while rotating the OCTG 2. Therefore, in one blasting treatment, it is safe to consider the surface roughness of areas other than the seal portion 1B to be equivalent to the surface roughness of the seal portion 1B.

[0080] <An example of a method for determining the luminance ratio threshold for the outer surface 1E> The brightness ratio threshold for the outer surface 1E can be used to detect cases where the thread base corner of the hook is not blasted, where the thread part containing black scale is not blasted, and where there is no blasting treatment.

[0081] [When the hook thread bottom corner B is not blasted (Fig. 4)] When nozzle 5A is clogged, as shown in Figure 4, there is a risk that the thread bottom corner B will not be blasted. For this reason, halation is detected and is detected as the halation area ratio (the ratio of pixels where halation occurs). Based on this, for example, the intermediate value between the halation area ratio and the halation area ratio of a blasted, acceptable product is set as the brightness ratio threshold.

[0082] In actual testing, when nozzle 5A is clogged, as in Figure 4, thread bottom corner B is not blasted, and the detected halation area is 82. The area value is expressed in units of pixels (same below). The intermediate value 41 between this halation area value 82 and the halation area of ​​a blasted, acceptable product, 0, is set as the threshold. If a lower limit for the threshold is required, setting 0 as the lower limit threshold will enable normal pass / fail evaluation.

[0083] [When the non-hook thread bottom corner A is not blasted (Fig. 5)] When nozzle 5B is clogged, as shown in Figure 5, thread bottom corner A is not blasted. Therefore, halation is detected and detected as the halation area ratio (ratio of pixel count). For this reason, for example, the intermediate value between the halation area ratio and the halation area ratio of a blasted, acceptable product is set as the threshold (upper limit threshold).

[0084] In actual testing, when nozzle 5B is clogged, as in the case of Figure 7, the thread bottom corner A is not blasted, so the detected halation area is 94. For example, the intermediate value 47 between the halation area value 94 and the halation area of ​​a blasted, acceptable product, 0, can be set as the threshold value (upper threshold value). If a lower limit is required, setting 0 as the lower threshold value will enable normal pass / fail evaluation. If there is a discrepancy between the evaluation using the threshold values ​​set as above and the judgment of the operator, the evaluation accuracy can be improved by fine-tuning the set threshold values ​​each time.

[0085] <Example of blast quality evaluation based on brightness ratio on inner surface 1D> As can be seen from Figure 6(b), when the nozzle 5B is clogged as described above, the shoulder portion 1C and the inner surface 1D are always left unblasted. In this case, the surface roughness of the inner surface 1D is reduced, and halation occurs on the inner surface 1D where light emitted from the lighting device 10B hits (see Figure 19). Note that the symbol HA in Figure 19 indicates the location where halation occurs.

[0086] If the number of pixels in the image where halation occurs is equal to or greater than the set threshold, the number of halated pixels is detected as being large. In this case, the operator will determine that "halation has occurred and the blast processing has failed." Conversely, if the number of pixels where halation is present is less than the set threshold, it is detected as having a large number of pixels without halation. In this case, the operator will determine that "since no halation has occurred, the blast processing has been passed."

[0087] Then, by setting a threshold value that is lower than the brightness ratio, which is the percentage of pixels that are judged to have "failed the blasting process due to the occurrence of halation," it is possible to evaluate whether the surface has been blasted or not. This evaluation can be used to detect whether the thread bottom corner A and shoulder 1C have not been blasted (see Figures 4 and 5). In this embodiment, when illuminated obliquely from above, the shoulder portion 1C is the end face of the tube, and reflected light cannot be detected. Therefore, the surface roughness of the inner surface portion 1D is used for evaluation.

[0088] <Example of a method for determining the luminance ratio threshold of the inner surface portion 1D> The threshold value of the brightness ratio on the inner surface portion 1D can mainly detect cases where the non-hook portion of the thread bottom corner has not been blasted. When nozzle 5B is clogged, the shoulder portion 1C and inner surface portion 1D are always left unblasted, as shown in Figure 6. Therefore, halation is detected on inner surface portion 1D, and the state can be detected by the brightness ratio, which is the ratio of the halation area. Then, for example, the intermediate value between the halation area ratio and the halation area ratio of a blasted, acceptable product is set as the threshold value.

[0089] In actual testing, when nozzle 5B is clogged, as in Figure 6, shoulder portion 1C and inner surface portion 1D are always left unblasted. In this case, the halation area on inner surface portion 1D is detected to be 52. Then, for example, the threshold value is set to 26, which is the intermediate value between the halation area value 52 and the halation area of ​​a blasted, acceptable product, which is 0. If a lower limit for the threshold is required, setting 0 as the lower limit threshold allows for normal pass / fail evaluation. If there is a discrepancy between the evaluation using the threshold set as described above and the operator's judgment, the evaluation accuracy can be improved by fine-tuning the set threshold each time.

[0090] <Example of position correction (horizontal and vertical directions) for pipe end thread part 1> Since long tubes are transported and processed, slight misalignment of the tube end position in the horizontal direction occurs with respect to the tube axis, which requires horizontal (lateral) position correction for each tube. Furthermore, due to the influence of different pipe curvatures for each pipe, the position of the pipe end thread portion 1 in the vertical direction will be displaced from the reference position for each pipe, so it is necessary to perform position corrections in the horizontal and vertical directions for each pipe.

[0091] [Horizontal direction] Horizontal position correction is performed using image processing. The method for correcting minute misalignments in the horizontal pipe end position is as follows. Within an evaluation frame like the one shown in Figure 20, detection is performed from right to left, that is, from the side farthest from the pipe end toward the pipe end, and the change in shade from black to white is detected using image processing to recognize the pipe end. Then, based on the recognized pipe end position (the center position in the width direction), the horizontal (lateral) position of the pipe end thread portion 1 is corrected.

[0092] [Vertical direction] The vertical position correction is performed by using a laser beam emitted from the laser beam irradiation device 13 and performing image processing. The bending of the pipe changes the vertical position of the pipe end thread portion 1. For example, in small diameter oil country tubular goods (OCG) pipes with an outer diameter of less than 73.1 mm, the bending of the pipe end of the oil country tubular goods (OCG) pipe 2 is large, changing by up to 4 mm / 300 mm. Therefore, laser irradiation is performed as a measure to correct the vertical position.

[0093] As shown in Figure 21, a laser beam is irradiated from diagonally above toward a position in the pipe axis direction slightly away from the pipe end thread portion 1 of the OCTG 2. The laser beam is irradiated in a vertical direction toward the side surface of the pipe. Then, image processing of an image including the laser beam irradiation position RR is performed to recognize the boundary between black and white shading where the laser beam stops within the evaluation frame as the upper and lower edges Eg1 and Eg2 of the pipe end thread portion 1. By recognizing the upper and lower edges Eg1 and Eg2 of the pipe end thread portion 1 in this way, even if the pipe end thread portion 1 is bent in the vertical direction, it is possible to follow the bend and accurately recognize the actual axis of the pipe end thread portion 1. Then, vertical position correction is performed based on the recognized upper and lower edges Eg1 and Eg2. In addition, for oil country tubular goods 2 exceeding the small diameter size (73.1 mm or more), the rigidity of the tubular goods increases and positional deviation tends to be small. However, since minute deviations do occur, it is preferable to perform correction by irradiating a laser for vertical position correction.

[0094] <Example of blasting defect pattern and evaluation method> An example of a defect pattern occurring in the pipe end thread portion 1 of an oil country tubular good 2 is shown in FIG. The names of blast defects that may occur in this pipe end thread portion 1, their causes, locations where defects occur, and examples of evaluation methods will be explained below.

[0095] (1) When the blast is thin The cause of the defect was "a drop in air pressure during blasting (holes in the hose joint, wear on the nozzle injection hole, etc.)." The areas where the blasting defect occurred were "outer surface 1E (threaded part, seal part 1B) and shoulder part 1C." The evaluation method is, for example, to image the outer surface 1E with the camera 11A and then evaluate whether the dark area luminance is outside the range of a set threshold value, or to image the outer surface 1E with the camera 11A and then evaluate whether the difference between the bright area luminance and the dark area luminance is outside the range of a set threshold value.

[0096] (2) If the non-hook thread corner is not blasted The cause of the defect was "Nozzle 5B clogging." The blasting defects occurred in "Outer surface 1E (non-hook part screw bottom corner) and shoulder 1C." The evaluation method is, for example, to capture an image of the inner surface portion 1D with a camera 11B, binarize the halation portion, and evaluate whether the total value of the halation (halation area ratio: brightness ratio) is outside the range of a set threshold.

[0097] (3) If the bottom corner of the hook thread is not blasted However, the cause of the defect was "Nozzle 5A clogging." The location of the blast defect was "Outer surface 1E (hook part screw bottom corner)." The evaluation method is, for example, to capture an image of the outer surface 1E with a camera 11A, binarize the halation area, and evaluate whether the total value of the halation (halation area ratio: brightness ratio) is outside the range of a set threshold.

[0098] (4) In the case where the threaded part including the black scale has not been blasted The cause of the defect was "the nozzle fixing jig shifted, causing the nozzle angle to shift significantly (occurs only when changing sizes)." The evaluation method is, for example, to capture an image of the outer surface 1E with a camera 11A, then binarize the halation area, and evaluate whether the total value of the halation (halation area ratio: brightness ratio) is outside the range of a set threshold.

[0099] (5) "No blast" The cause of the defect was "a significant drop in air pressure (perforated hose joint, worn nozzle injection hole, etc.)." The evaluation method is, for example, to image the outer surface portion 1E with the camera 11A and then evaluate whether the luminance of dark areas is outside the range of a set threshold. Also, to image the outer surface portion 1E with the camera 11A and then evaluate whether the difference between the luminance of bright areas and the luminance of dark areas is outside the range of a set threshold. Also, to image the outer surface portion 1E with the camera 11A and then binarize the halation areas, and then evaluate whether the total value of the halation (halation area ratio: luminance ratio) is outside the range of a set threshold.

[0100] (6) When there is no object to be imaged The cause of the defect is "the tube is pushed out of the field of view (for example, caused by installing the wrong size inner plug when changing sizes)." The evaluation method is, for example, to image the outer surface 1E with the camera 11A and then evaluate whether the dark area luminance is outside the range of a set threshold. Also, to image the outer surface 1E with the camera 11A and then evaluate whether the difference between the bright area luminance and the dark area luminance is outside the range of a set threshold. Furthermore, the reduction in the amount of light of the lighting device 10 can be evaluated by capturing an image of the outer surface 1E with the camera 11A and then checking whether the luminance of the bright areas is outside the range of a set threshold value.

[0101] By carrying out the evaluation process as described above, the device of this embodiment can detect all blasting defects based on the surface roughness of the pipe end thread portion 1 of the oil country tubular good 2. This makes it possible to automatically evaluate the quality of blasting of the pipe end thread portion 1 of an oil country tubular good 2, for example.

[0102] (Variation) The above description has been given by way of example of evaluation of the surface roughness of a processed metal surface in the case where the roughness after processing is higher than before processing due to surface processing such as blasting of the metal surface. The present disclosure can also be applied to evaluating the surface roughness of a processed metal surface when the roughness after processing, such as buffing, is lower than before processing. In this case, based on the concept described above, for example, if the difference in brightness between the bright area brightness and the dark area brightness exceeds a preset third threshold, the metal surface being evaluated is evaluated as having the target surface roughness. The third threshold can be determined by conducting experiments according to the target surface roughness or by measuring a metal surface after surface processing has been completed normally.

[0103] (others) The present disclosure may also have the following configuration. (1) A surface roughness evaluation method for evaluating whether the surface roughness of a metal surface to be evaluated is a target surface roughness, comprising: The lighting device irradiates the metal surface to be evaluated with light, taking an image of the metal surface to be evaluated that is illuminated by the illumination light; In the captured image, a bright area having a high luminance and a dark area having a lower luminance than the bright area are respectively determined, Evaluating the surface roughness of the metal surface to be evaluated based on the luminance of the bright region and the luminance of the dark region. A surface roughness evaluation method comprising:

[0104] (2) The average luminance of the bright area is calculated as the bright area luminance. The average luminance of the dark area is calculated as the dark area luminance. When the difference in brightness between the bright area brightness and the dark area brightness is equal to or less than a third threshold value set in advance, the metal surface to be evaluated is evaluated as having a target surface roughness. (3) A luminance ratio, which is the ratio of an area having a luminance equal to or greater than a predetermined value, is calculated in the bright area. Based on the brightness ratio, the surface roughness of the metal surface to be evaluated is evaluated.

[0105] (4) If the brightness ratio is less than a first threshold value set in advance, the metal surface to be evaluated is evaluated to have a target surface roughness. (5) The above-mentioned preset luminance is the luminance of the part where halation occurs when halation occurs on the metal surface to be evaluated, or a luminance that is smaller than that luminance by a safety margin. (6) determining a dark area in the captured image that is lower in brightness than the bright area; The average luminance of the dark area is calculated as the dark area luminance. Based on the brightness ratio and the brightness of the dark area, the surface roughness of the metal surface to be evaluated is evaluated.

[0106] (7) When the brightness ratio is less than a preset first threshold value and the dark area brightness is greater than a preset second threshold value, the metal surface to be evaluated is evaluated as having a target surface roughness. (8) The second threshold value is a luminance greater than the average luminance of the dark area when halation occurs over the entire bright area. (9) The average luminance of the bright area is calculated as the bright area luminance. If the difference in brightness between the bright area brightness and the dark area brightness exceeds a third threshold value set in advance, the evaluation of the metal surface being evaluated is changed from having the target surface roughness to having a surface roughness smaller than the target surface roughness.

[0107] (10) A surface roughness evaluation method for evaluating whether a metal surface having a region with a predetermined uneven surface shape meets a target surface roughness, the method comprising: an illumination device irradiates the metal surface in the region having the concave and convex shape with illumination light; taking an image of the metal surface to be evaluated that is illuminated by the illumination light; A bright area is determined as an area with high brightness within the area having the concave and convex shape in the captured image, A luminance ratio, which is the ratio of an area having a luminance equal to or higher than a predetermined value, is calculated in the bright area. Evaluating the surface roughness of the metal surface to be evaluated based on the brightness ratio. A surface roughness evaluation method comprising:

[0108] (11) If the brightness ratio is less than a first threshold value set in advance, the metal surface to be evaluated is evaluated to have a target surface roughness. (12) The above-mentioned preset luminance is the luminance of the part where halation occurs when halation occurs on the metal surface to be evaluated, or a luminance that is smaller than that luminance by a safety margin. (13) determining a dark area in the captured image, the dark area being lower in brightness than the bright area in the area having the concave and convex shape; The average luminance of the dark area is calculated as the dark area luminance. When the brightness ratio is less than the first threshold value and the dark area brightness is greater than a preset second threshold value, the metal surface to be evaluated is evaluated as having a target surface roughness.

[0109] (14) The second threshold value is a luminance greater than the average luminance of the dark area when halation occurs over the entire bright area. (15) The average luminance of the bright area is calculated as the bright area luminance. If the brightness ratio is less than the first threshold, and the dark area brightness is greater than a preset second threshold, and further, the difference in brightness between the bright area brightness and the dark area brightness is equal to or less than a preset third threshold, the metal surface being evaluated is evaluated as having the target surface roughness. (16) The preset concave-convex shape is a screw shape. (17) The metal surface to be evaluated is a metal surface that has been roughened by surface treatment. (18) The bright region is a region including a portion where halation occurs when the illuminating light is irradiated onto the metal surface before the surface treatment is performed. (19) The preset brightness is the brightness at the position of halation that occurs when the illumination light is irradiated onto the metal surface before the surface treatment is performed, or a brightness that is smaller than that brightness by a safety margin.

[0110] (20) The metal surface to be evaluated is a threaded portion at the end of an oil well pipe, The position of the tube end is detected by image processing of the captured image of the tube end. The horizontal position of the tube end in the image is corrected based on the detected tube end position. (21) Irradiating a laser beam along the circumferential direction of the tube, and capturing an image of the tube irradiated with the laser beam; The vertical position of the tube is detected based on the position of the laser light in the captured image. The vertical position of the pipe end in the image is corrected based on the detected vertical position of the pipe.

[0111] (22) A surface roughness evaluation device for evaluating whether the surface roughness of a metal surface to be evaluated is a target surface roughness, comprising: an illumination device that irradiates illumination light onto the metal surface to be evaluated; an imaging device that captures an image of an illumination area that is an area illuminated by the illumination light; a setting unit that sets a bright area having a high luminance and a dark area having a low luminance, the bright area being selected from the illumination area in the captured image; and an evaluation unit that evaluates the surface roughness of the metal surface to be evaluated based on the luminance of the bright region and the luminance of the dark region; A surface roughness evaluation device comprising:

[0112] (23) a bright area luminance calculation unit that calculates the average luminance of the bright area as the bright area luminance; a dark area luminance calculation unit that calculates an average luminance of the dark area as the dark area luminance, When the difference in luminance between the bright area luminance and the dark area luminance is equal to or less than a third threshold value set in advance, the evaluation unit evaluates that the metal surface to be evaluated has a target surface roughness. (24) A brightness ratio calculation unit is provided to calculate a brightness ratio, which is a ratio of an area having a brightness equal to or greater than a predetermined value in the bright area, The evaluation unit evaluates the surface roughness of the metal surface to be evaluated based on the brightness ratio. (25) When the brightness ratio is less than a first threshold value set in advance, the evaluation unit evaluates that the metal surface to be evaluated has a target surface roughness.

[0113] (26) The above-mentioned preset luminance is the luminance of the part where halation occurs when halation occurs on the metal surface to be evaluated, or a luminance that is smaller than that luminance by a safety margin. (27) The setting unit sets a dark area in the captured image that has a lower brightness than the bright area, Further, a dark area luminance calculation unit is provided to calculate an average luminance of the dark area as the dark area luminance, The evaluation unit evaluates the surface roughness of the metal surface to be evaluated based on the brightness ratio and the dark area brightness.

[0114] (28) The evaluation unit evaluates the metal surface to be evaluated as having the target surface roughness when the brightness ratio is less than a predetermined first threshold and the dark area brightness is greater than a predetermined second threshold. (29) The second threshold value is a luminance greater than the average luminance of the dark area when halation occurs over the entire bright area. (30) A bright area luminance calculation unit is provided to calculate the average luminance of the bright area as the bright area luminance, If the difference in brightness between the bright area brightness and the dark area brightness exceeds a third threshold value set in advance, the evaluation unit changes the evaluation of the metal surface being evaluated from having a target surface roughness to having a surface roughness smaller than the target surface roughness.

[0115] (31) A surface roughness evaluation device for evaluating whether a metal surface having a region with a predetermined uneven surface shape is a target surface roughness, the device comprising: an illumination device that irradiates illumination light onto the metal surface of the uneven area; an imaging device that captures an image of an illumination area that is an area illuminated by the illumination light; a setting unit that sets a bright area, which is an area selected from the illumination area in the captured image and is an area with a bright luminance among the area having the concave and convex shape; a brightness ratio calculation unit that calculates a brightness ratio, which is the ratio of an area having a brightness equal to or higher than a predetermined value, in the bright area; an evaluation unit that evaluates the surface roughness of the metal surface to be evaluated based on the brightness ratio; A surface roughness evaluation device comprising:

[0116] (32) When the brightness ratio is less than a first threshold value set in advance, the evaluation unit evaluates that the metal surface to be evaluated has the target surface roughness. (33) The preset brightness is the brightness of the portion where halation occurs when halation occurs on the metal surface to be evaluated, or a brightness that is smaller than that brightness by a safety margin. (34) The setting unit determines a dark area in the area having the concave and convex shape in the captured image, the dark area having a lower brightness than the bright area, Further, a dark area luminance calculation unit is provided to calculate an average luminance of the dark area as the dark area luminance, The evaluation unit evaluates the metal surface to be evaluated as having a target surface roughness when the brightness ratio is less than a preset first threshold value and the dark area brightness is greater than a preset second threshold value.

[0117] (35) The second threshold value is a luminance greater than the average luminance of the dark area when halation occurs over the entire bright area. (36) A bright area luminance calculation unit is provided to calculate the average luminance of the bright area as the bright area luminance, The evaluation unit evaluates the metal surface to be evaluated as having the target surface roughness if the brightness ratio is less than the first threshold value, the dark area brightness is greater than a predetermined second threshold value, and the brightness difference between the bright area brightness and the dark area brightness is less than or equal to a predetermined third threshold value. (37) The preset concave-convex shape is a screw shape. (38) The metal surface to be evaluated is a metal surface that has been roughened by surface treatment. (39) The bright region is defined as a region including a portion where halation occurs when the illuminating light is irradiated onto the metal surface before the surface treatment is performed. (40) The preset luminance is the luminance at the position of the halation generated when the illumination light is applied to the metal surface before the surface treatment, or the luminance reduced by a safety margin from that luminance.

Example

[0118] Automated evaluation was performed on the pipe end thread portion 1 of the oil well pipe 2 to determine whether it was non-blasted or blasted using image processing. As the devices, an image processing device PV200 manufactured by Panasonic and a laser light irradiation device LDU20515LZ3-A manufactured by Takekuma Optronics were used. Here, the surface condition, surface roughness (hereinafter referred to as Ra), and quality evaluation are as shown in Fig. 23. Note that when it is non-blasted, Ra is 1.7 μ or less. Also, the target surface roughness was set to 2.1 μ or more and 3.8 μm or less.

[0119] First, assuming the possible patterns shown in Fig. 22, an evaluation test using only the camera 11A was carried out. The normal injection pressure P in the blasting process was 0.24 Mpa ≤ P ≤ 0.44 Mpa, preferably 0.29 Mpa ≤ P ≤ 0.39 Mpa.

[0120] When P < 0.24 Mpa, it is equivalent to the non-blasted state. If it is non-blasted, seizure occurs between the thread portion and the joint when the joint is tightened, resulting in a defective product due to blasting. Also, when 0.44 Mpa < P, the surface of the pipe end thread portion 1 becomes excessively rough, and the friction coefficient increases. As a result, seizure occurs between the thread portion and the joint when the joint is tightened, resulting in a non-conforming product. This can be detected by setting a range for the target surface roughness.

[0121] The results of the above evaluation test are shown in Fig. 23. Initially, in level D, we thought that we could capture the outer surface 1E from the front using only camera 11A and obtain halation of the seal part 1B and thread body 1A for all thread types. However, we found that the blast condition of the thread root corner A could be either unblasted or blasted depending on the value of angle θ1 shown in Figures 4 and 5.

[0122] <Prerequisites> The prerequisites for the thread shape of the pipe end threaded portion are described below (see Figures 4 and 5). θ3=40° (Nozzles are generally fixed at 40°) θ4=40° (40° is common) θ5=θ4÷2 →θ5=40°÷2=20° θ6=θ3-θ5 →θ6=40°-20°=20° Due to alternate angles, θ1=θ6 When θ1>20°, preferably θ1>22°, blasting occurs and diffuse reflected light is imaged. When θ1≦20°, the thread root corner A is not blasted and remains unblasted.

[0123] <Example> X thread θ1=15° → Thread bottom corner A is not blasted and remains unblasted. Y-screw θ1=25° → Thread bottom corner A is blasted and becomes in a blasted state. Furthermore, in the case of level D, if the nozzle 5B is clogged, the shoulder 1C and inner surface 1D will always be left unblasted (Fig. 6(b)), resulting in a defective blasted product. If this case overlaps with the case where the thread bottom corner A has already been blasted, a quality evaluation using only the camera 11A and lighting device 10A will result in the rejected product being sent to the next process. That is, it was found that the quality of the blasting state of the shoulder portion 1C and the inner surface portion 1D cannot be determined by the camera 11A and the lighting device 10A alone.

[0124] Next, a camera 11B and an illumination device 10B capable of capturing an image of the inner surface 1D were added. An evaluation test was then conducted using the camera 11A, the illumination device 10A, the camera 11B, and the illumination device 10B. In this case, halation on the inner surface 1D was confirmed when the shoulder portion 1C and the inner surface 1D of level D were not blasted. That is, in level D, considering the influence of nozzle 5B being clogged, we consider the following. That is, we consider the case where the shoulder portion 1C and inner surface portion 1D are not blasted, and the case shown in Figure 6 where the thread bottom corner portion A has been blasted overlap. Even in this case, halation on the inner surface portion 1D can be confirmed with camera 11B, and the pipe can be evaluated as having a blast defect.

[0125] Furthermore, in small-diameter oil country tubular goods (outer diameter less than 73.1 mm), the pipe end of the oil country tubular goods 2 is bent significantly, and in this case, the vertical position changes by a maximum of 4.0 mm / 300 mm. For this reason, a laser light irradiation device 13 was introduced to correct the vertical position. The principle was to irradiate the side surface of the pipe near the pipe end thread 1 with laser light, and the points where the laser light is interrupted are recognized as the top and bottom edges of the pipe through image processing evaluation based on the difference in density.

[0126] Although the positional deviation tends to be smaller for oil country tubular goods 2 exceeding the small diameter size (73.1 mm or more), a minute deviation still occurs, so the laser light irradiation device 13 for correcting the position in the vertical direction is necessary. As described above, by combining the camera 11A, the lighting device 10A, the camera 11B, the lighting device 10B, and the laser light irradiation device 13, it is possible to automatically evaluate the quality of the blasting of the pipe end thread portion 1 of the oil country pipe 2. [Explanation of symbols]

[0127] 1 Pipe end thread 1A Threaded body 1B Seal part 1C Shoulder section 1D inner part 1E External part 1F flat area 2 Oil country tubing 5A, 5B Blast injection nozzle 10,10A10B Lighting device 10P lighting axis 11, 11A, 11B Camera (imaging device) 11P imaging axis 12 Processing unit 13 Laser light irradiation device 20 Evaluation calculation unit 20A Image area confirmation section 20B Luminance ratio calculation section 20C Dark area luminance calculation section 20D Brightness calculation section 20E comparative brightness calculation section 20F Image brightness confirmation section 20G Evaluation Unit 20G1 First Evaluation Section 20G2 Second Evaluation Section 21 Correction processing unit 21A Horizontal position correction section 21B Vertical position correction section 22 Setting section ARA-1 Light area ARA-1A light area main body area (light area) ARA-2 Dark region HA Halation HH maximum width MT1 First metal surface area MT2 Second metal surface area

Claims

1. A surface roughness evaluation method for evaluating whether a metal surface having a region with a predetermined uneven surface shape meets a target surface roughness, comprising: an illumination device irradiates the metal surface in the region having the concave and convex shape with illumination light; taking an image of the metal surface to be evaluated that is illuminated by the illumination light; A bright area is determined as an area with high brightness within the area having the concave and convex shape in the captured image, A luminance ratio, which is the ratio of an area having a luminance equal to or higher than a predetermined value, is calculated in the bright area. Evaluating the surface roughness of the metal surface to be evaluated based on the brightness ratio. A surface roughness evaluation method comprising:

2. If the brightness ratio is less than a predetermined first threshold value, the metal surface to be evaluated is evaluated to have a target surface roughness.

2. The surface roughness evaluation method according to claim 1, wherein the surface roughness evaluation method comprises:

3. The preset luminance is the luminance of the portion where halation occurs when halation occurs on the metal surface to be evaluated, or a luminance obtained by reducing the luminance by a safety margin.

3. The surface roughness evaluation method according to claim 1 or 2.

4. A dark area having a lower brightness than the bright area is determined in the area having the concave and convex shape in the captured image; The average luminance of the dark area is calculated as the dark area luminance. When the brightness ratio is less than a predetermined first threshold value and the dark area brightness is greater than a predetermined second threshold value, the metal surface to be evaluated is evaluated to have a target surface roughness.

3. The surface roughness evaluation method according to claim 1 or 2.

5. The second threshold value is a luminance greater than an average luminance of the dark area when halation occurs in the entire bright area.

5. The surface roughness evaluation method according to claim 4, wherein the surface roughness evaluation method comprises:

6. The average luminance of the bright area is calculated as the bright area luminance. When the brightness ratio is less than the first threshold value, the dark area brightness is greater than a preset second threshold value, and further, the brightness difference between the bright area brightness and the dark area brightness is equal to or less than a preset third threshold value, the metal surface to be evaluated is evaluated to have a target surface roughness.

5. The surface roughness evaluation method according to claim 4, wherein the surface roughness evaluation method comprises:

7. The preset concave-convex shape is a thread shape.

3. The surface roughness evaluation method according to claim 1 or 2.

8. The metal surface to be evaluated is a metal surface that has been roughened by surface treatment.

3. The surface roughness evaluation method according to claim 1 or 2.

9. The bright region is a region including a portion where halation occurs when the illumination light is irradiated onto the metal surface before the surface treatment is performed.

9. The surface roughness evaluation method according to claim 8.

10. The preset luminance is the luminance at the position of halation that occurs when the illuminating light is irradiated onto the metal surface before the surface treatment is performed, or a luminance that is smaller than the luminance by a safety margin.

10. The surface roughness evaluation method according to claim 9, wherein the surface roughness evaluation method is

11. The metal surface to be evaluated is a threaded portion at the end of an oil well pipe, The position of the tube end is detected by image processing of the captured image of the tube end. The horizontal position of the pipe end in the image is corrected based on the detected pipe end position.

8. The surface roughness evaluation method according to claim 7, wherein the surface roughness evaluation method is a surface roughness evaluation method.

12. A laser beam is irradiated along the circumferential direction of the pipe, and an image of the pipe irradiated with the laser beam is taken. The vertical position of the tube is detected based on the position of the laser light in the captured image. The vertical position of the end of the pipe in the image is corrected based on the detected vertical position of the pipe.

8. The surface roughness evaluation method according to claim 7, wherein the surface roughness evaluation method is a surface roughness evaluation method.

13. A surface roughness evaluation device is used to evaluate a metal surface having a region whose surface shape is a predetermined uneven shape, and evaluates whether the surface roughness of the metal surface is a target surface roughness, which is a target surface roughness, an illumination device that irradiates illumination light onto the metal surface of the uneven area; an imaging device that captures an image of an illumination area that is an area illuminated by the illumination light; a setting unit that sets a bright area, which is an area selected from the illumination area in the captured image and is an area with a bright luminance among the area having the concave and convex shape; a brightness ratio calculation unit that calculates a brightness ratio, which is the ratio of an area having a brightness equal to or higher than a predetermined value, in the bright area; an evaluation unit that evaluates the surface roughness of the metal surface to be evaluated based on the brightness ratio; A surface roughness evaluation device comprising:

14. the evaluation unit evaluates that the metal surface to be evaluated has the target surface roughness when the brightness ratio is less than a predetermined first threshold value; 14. The surface roughness evaluation device according to claim 13, further comprising:

15. The preset luminance is the luminance of the portion where halation occurs when halation occurs on the metal surface to be evaluated, or a luminance obtained by reducing the luminance by a safety margin.

15. The surface roughness evaluation device according to claim 14.

16. the setting unit determines a dark area in the area having the concave and convex shape in the captured image, the dark area having a lower brightness than the bright area; Further, a dark area luminance calculation unit is provided to calculate an average luminance of the dark area as the dark area luminance, the evaluation unit evaluates the metal surface to be evaluated as having a target surface roughness when the brightness ratio is less than a predetermined first threshold value and the dark area brightness is greater than a predetermined second threshold value; 14. The surface roughness evaluation device according to claim 13.

17. The second threshold value is a luminance greater than an average luminance of the dark area when halation occurs in the entire bright area.

17. The surface roughness evaluation device according to claim 16.

18. A bright area luminance calculation unit is provided to calculate an average luminance of the bright area as the bright area luminance, the evaluation unit evaluates the metal surface to be evaluated as having a target surface roughness when the brightness ratio is less than the first threshold value, the dark area brightness is greater than a preset second threshold value, and further, the brightness difference between the bright area brightness and the dark area brightness is equal to or less than a preset third threshold value; 17. The surface roughness evaluation device according to claim 16.

19. The preset concave-convex shape is a thread shape. The surface roughness evaluation device according to any one of claims 13 to 18.

20. The metal surface to be evaluated is a metal surface that has been roughened by surface treatment. The surface roughness evaluation device according to any one of claims 13 to 18.

21. The bright region is a region including a portion where halation occurs when the illumination light is irradiated onto the metal surface before the surface treatment is performed.

21. The surface roughness evaluation device according to claim 20.

22. The preset luminance is the luminance at the position of halation that occurs when the illuminating light is irradiated onto the metal surface before the surface treatment is performed, or a luminance that is smaller than the luminance by a safety margin.

21. The surface roughness evaluation device according to claim 20.

Images