Inspection method, inspection device, and manufacturing method of metal products

Abstract

To provide an inspection method which can easily determine whether at least any of water and aqueous processing liquid being a cause of the quality defect remains in a metal product in which an oil film of rust preventive oil is formed on a surface thereof.SOLUTION: There is provided an inspection method which targets a metal product in which an oil film of rust preventive oil is formed on a surface thereof as an inspection object, inspects whether at least any of water and aqueous processing liquid remains in the inspection object, and includes the following steps (S1) and (S2). Step (S1) is the step of imaging the inspection object with an infrared imaging device that can detect the infrared ray with a wavelength equal to or greater than 8 μm. Step (S2) is the step of determining whether at least any of water and aqueous processing liquid remains in the inspection object on the basis of the concentration difference of each pixel corresponding to the inspection object in the image acquired in step (S1).SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an inspection method and an inspection device, and a method for manufacturing a metal product using the inspection method. [Background technology]

[0002] Metal products manufactured through multiple processing steps are usually subjected to a rust prevention process in which an oil film made of rust-preventive oil is formed on the surface of the metal to prevent oxidation and deterioration of the metal surface. In the machining process for manufacturing metal products, an aqueous machining fluid is used in processes such as cutting, and water is used in the cleaning process. The aqueous machining fluid and water can cause rust, which may lead to poor quality of the metal product. Therefore, in the rust prevention process, measures such as using an anti-rust oil with excellent water displacement properties are taken to remove the aqueous machining fluid and water from the metal surface (for example, Patent Document 1, etc.). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-219744 Summary of the Invention [Problem to be solved by the invention]

[0004] However, it is difficult to completely prevent quality defects in metal products caused by water-based machining fluids and water simply by improving the water displacement properties of rust-preventive oils, and other measures are thought to be necessary. Specifically, it is thought to be effective to determine on the production line after the rust-prevention process whether or not water-based machining fluids and water remain on metal products on which an oil film of rust-preventive oil has formed on the surface, and to take measures such as repeating the rust-prevention process on metal products on which water-based machining fluids and water remain. However, at present, there is no established simple method for making such a judgment on the production line after the rust prevention process has been completed.

[0005] Therefore, an object of the present invention is to provide an inspection method and inspection device that can easily determine whether or not at least one of water and water-based machining fluid, which are the cause of quality defects, remains on a metal product on the surface of which an oil film made of rust-preventive oil has been formed, and a method for manufacturing a metal product using the inspection method. [Means for solving the problem]

[0006] The present inventors have conducted extensive research to solve the above problems, and as a result have found that in images taken with an infrared imaging device capable of detecting infrared rays with wavelengths of 8 μm or more, metal products on which an oil film made of rust-preventive oil has been formed can be clearly distinguished from water and aqueous machining fluid remaining on the metal products by the shade of pixels. After further research, the present inventors have completed the present invention.

[0007] According to the present invention, the following [1] to [3] are provided. [1] An inspection method for inspecting a metal product having an oil film made of rust-preventive oil formed on its surface to determine whether or not at least one of water and water-based machining fluid remains on the inspection object, the inspection method comprising the following steps (S1) and (S2): Step (S1): A step of capturing an image of the inspection object using an infrared imaging device capable of detecting infrared rays with a wavelength of 8 μm or more. Step (S2): A step of determining whether or not at least one of water and water-based machining fluid remains in the object to be inspected based on the shade of each pixel corresponding to the object to be inspected for the image acquired in step (S1). [2] An inspection device that inspects a metal product having an oil film formed on its surface by rust-preventive oil as an inspection object to determine whether or not at least one of water and water-based machining fluid remains on the inspection object, an infrared imaging device capable of detecting infrared rays with a wavelength of 8 μm or more, which images the inspection object; a determination unit that determines whether or not at least one of water and water-based machining fluid remains in the inspection object based on the density of each pixel corresponding to the inspection object in the image acquired by the infrared imaging device; An inspection device comprising at least: [3] A method for manufacturing a metal product having an oil film made of rust-preventive oil formed on its surface, comprising a step of carrying out the inspection method described in [1] above. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide an inspection method and inspection device that can easily determine whether or not at least one of water and water-based machining fluid, which are the cause of quality defects, remains on a metal product on the surface of which an oil film made of rust-preventive oil has been formed, as well as a method for manufacturing a metal product using the inspection method. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 2 is a flow chart showing an example of an inspection method according to the present embodiment. [Figure 2] FIG. 1 is a schematic diagram illustrating an example of an inspection device according to an embodiment of the present invention. [Figure 3] In Example 1, water, a water-based machining fluid, and an anti-rust oil were dropped onto an SPCC-SD steel plate, and images were taken with an infrared camera. (A) is the raw measurement data, and (B) is the thermal conversion image. [Figure 4] In Example 1, water, a water-based machining fluid, and an anti-rust oil were dropped onto an SPCC-SD steel sheet, and then anti-rust oil was dropped onto the areas where the water and water-based machining fluid were dropped. Images were then captured with an infrared camera. (A) is the raw measurement data, and (B) is the thermal conversion image. [Figure 5] 10 shows images acquired in Example 2. The top row shows raw measurement data, and the bottom row shows thermal conversion images. [Figure 6] 10 is an image obtained in Example 3. DETAILED DESCRIPTION OF THE INVENTION

[0010] [Inspection method and inspection system] The inspection method of this embodiment is an inspection method for inspecting a metal product having an oil film made of rust-preventive oil formed on its surface to determine whether or not at least one of water and water-based machining fluid remains on the inspection object, and includes the following steps (S1) and (S2). Step (S1): A step of capturing an image of the inspection object using an infrared imaging device capable of detecting infrared rays with a wavelength of 8 μm or more. Step (S2): A step of determining whether or not at least one of water and water-based machining fluid remains in the object to be inspected based on the shade of each pixel corresponding to the object to be inspected in the image acquired in step (S1).

[0011] As shown in FIG. 1, the inspection method of this embodiment is carried out by, after the above-mentioned step (S1), performing image processing (S21), determining whether water or water-based machining fluid remains (S22), and displaying the determination result (S23) as the above-mentioned step (S2).

[0012] The inspection method of this embodiment can be implemented, for example, by the following inspection device. That is, the inspection device of this embodiment is an inspection device that inspects a metal product having an oil film formed on its surface by rust-preventive oil as an inspection object, and inspects whether or not at least one of water and water-based machining fluid remains on the surface of the inspection object, an infrared imaging device capable of detecting infrared rays with a wavelength of 8 μm or more, which images the inspection object; a determination unit that determines whether or not at least one of water and a water-based machining fluid remains on the surface of the inspection object based on the shade of each pixel corresponding to the inspection object in the image acquired by the infrared imaging device; At least the following is provided.

[0013] An example of the inspection device of this embodiment is shown in FIG. The inspection device 1 shown in FIG. 2 includes an infrared imaging device 2 and a determination unit 3. The determination unit 3 includes a processing unit 31, a storage unit 32, an input unit 33, and an output unit . The infrared imaging device 2, processing unit 31, storage unit 32, input unit 33, and output unit 34 are all connected via a bus 40. However, these connections are not limited to wired connections via the bus 40, and may of course be wireless connections. Furthermore, image data captured by the infrared imaging device 2 may be input to the determination unit 3 via a storage medium such as a USB memory, an SD card, or a microSD card.

[0014] The processing unit 31 reads out basic programs such as an operating system program and application programs such as an image processing program that are stored in advance, and controls the entire inspection device 1 in accordance with these various programs. The storage unit 32 is, for example, a semiconductor storage device, a magnetic tape device, a magnetic disk device, an optical disk device, or the like, and stores various programs and various data used in the processing by the processing unit 31. The input unit 33 is, for example, a keyboard, a mouse, or a touch panel, and an operator can use the input unit 33 to input letters, numbers, symbols, etc., and to operate and execute the operating system and various application programs, etc. When operated by the operator, the input unit 33 generates a signal corresponding to the operation. The generated signal is then supplied to the processing unit 31 as an instruction from the operator. The output unit 34 is, for example, a liquid crystal display or an organic EL (Electro-Luminescence) display, and displays an image and a determination result according to the data input from the processing unit 31. The output unit 34 may also be a device that prints images, characters, etc. on a display medium such as paper.

[0015] The inspection method and inspection device of this embodiment will be described in detail below with reference to FIGS.

[0016] <Inspection object> In this embodiment, the object to be inspected is a metal product having an oil film made of anti-rust oil formed on its surface, and which may have at least one of water and water-based machining fluid remaining on it. Metal products on which an oil film made from anti-rust oil has been formed undergo various processes prior to the anti-rust process, including cleaning and cutting processes, etc. If the water or water-based machining fluid used in these processes remains on the metal product when the oil film made from anti-rust oil is formed, rust will form on the metal product, resulting in a deterioration in quality. The inspection method and inspection device of this embodiment can determine whether or not at least one of water and water-based machining fluid, which may cause a deterioration in the quality of metal products, remains.

[0017] (metal products) The metal product is not particularly limited as long as it is obtained by processing a metal material (preferably a steel material) and is shipped after forming an oil film with a rust-preventive oil. Examples include various steel plates such as cold-rolled steel plates and hot-rolled steel plates; bearings; gears; camshafts; cylinders; steel pipes; and steel balls.

[0018] (rust prevention oil) The rust-preventive oil for forming an oil film on a metal product is not particularly limited, but examples include rust-preventive oils classified as fingerprint-removing type, solvent-diluted type, petrolatum type, lubricating oil type, and volatile type according to JIS K2246-1994. Among these, from the viewpoint of minimizing the amount of water and water-based machining fluid remaining on metal products on which an oil film made of anti-rust oil has been formed, reducing the number of products judged to be defective by the inspection method and inspection device of this embodiment, and improving product yield, it is preferable that the anti-rust oil be a solvent-diluted type 3, No. 1 anti-rust oil or a solvent-diluted type 3, No. 2 anti-rust oil, which are anti-rust oils with excellent water displacement properties. In addition, the thickness of the oil film formed on the metal product by the rust-preventive oil is preferably 30 mm or less, more preferably 20 mm or less, even more preferably 10 mm or less, and even more preferably 5 mm or less, from the viewpoint of further improving the detection performance of water and water-based machining fluid using the inspection method and inspection device of this embodiment.

[0019] (Water and water-based machining fluids) The water to be detected in this embodiment originates from rinse water or the like used in a cleaning process or the like, which is a process preceding the rust prevention process for metal products. The aqueous machining fluid to be detected in this embodiment is a liquid containing water used in a cutting process or the like, which is a process preceding the rust prevention process for metal products. Examples of aqueous machining fluids include liquids obtained by diluting emulsion-type, soluble-type, or solution-type water-soluble cutting fluids with water.

[0020] <Process (S1)> In step (S1), an image of an object to be inspected is captured by an infrared imaging device. In this embodiment, in step (S2), an image obtained by imaging the object to be inspected using an infrared imaging device is used to inspect whether or not at least one of water and water-based machining fluid remains on the metal product being inspected. Because infrared imaging devices are small, inspection equipment can be made compact, making them easy to incorporate into metal product manufacturing lines. Furthermore, because infrared imaging devices can capture images of a wide area at once, measurement time can be significantly reduced compared to measurements using a microscope, etc.

[0021] The infrared imaging device used is one that can detect infrared rays with wavelengths of 8 μm or more. If infrared rays with wavelengths of 8 μm or more cannot be detected, it becomes difficult to distinguish between a metal product on which an oil film made of rust-preventive oil has been formed and the water and water-based machining fluid remaining on the metal product based on the shade of the pixels. Here, from the viewpoint of making it easier to distinguish between a metal product on which an oil film made of anti-rust oil has been formed and the water and water-based machining fluid remaining on the metal product by the shade of the pixels, the wavelength of infrared light that can be detected by the infrared imaging device is preferably 8 μm to 50 μm, more preferably 8 μm to 25 μm, even more preferably 8 μm to 20 μm, and even more preferably 8 μm to 14 μm. In addition, the number of pixels of the infrared imaging device is preferably 300,000 or more (640 x 480 or more) from the viewpoint of making it easier to distinguish between the metal product on which an oil film made of rust-preventive oil has been formed and the water and water-based machining fluid remaining on the metal product by the shade of the pixels. Examples of infrared imaging devices include the SMART HUNTER-IR EK model (detection wavelength range 8 μm to 14 μm) manufactured by Hutec Corporation, the Gobi+ series (detection wavelength range 8 μm to 12 μm) manufactured by Xenics, the Dione 640 CAM series (detection wavelength range 8 μm to 14 μm) manufactured by Xenics, and the VIM-640G2 (detection wavelength range 8 μm to 14 μm) manufactured by Vision Sensing Co., Ltd.

[0022] Infrared imaging devices can reflect the infrared absorption and emissivity of an object in the captured image, and do not require a light source, which is also advantageous in making the inspection device more compact. In this embodiment, in order to minimize noise in the image obtained by imaging, it is preferable that ultraviolet light and visible light are reduced as much as possible during imaging. Therefore, in this embodiment, it is preferable that step (S1) is performed in a light-shielded space. Specifically, it is preferable that the inspection object is placed in a box made of, for example, a black material, and the inspection object placed in the box is imaged using an infrared imaging device.

[0023] Furthermore, from the viewpoint of facilitating improved detection accuracy for water and water-based machining fluids, it is preferable that in step (S1), the temperature of the measurement environment is adjusted so that the surface temperature of the object to be inspected is preferably 0°C or higher and 40°C or lower, more preferably 10°C or higher and 30°C or lower, even more preferably 15°C or higher and 25°C or lower, and even more preferably 20°C or higher and 25°C or lower. Furthermore, from the viewpoint of suppressing variations in the test results, it is preferable that in step (S1), the temperature of the measurement environment is maintained constant, and the surface temperature between the test objects is maintained constant.

[0024] If it is necessary to image not only the front surface of the object under inspection but also other surfaces (for example, the side or back surface), the infrared imaging device may be movable. Also, the stage on which the object under inspection is placed may be movable. Alternatively, the object under inspection may be rotatably held by a robot arm or the like.

[0025] The image acquired in step (S1) is subjected to step (S2), and it is determined whether or not at least one of water and water-based machining fluid remains on the object to be inspected.

[0026] <Process (S2)> In step (S2), it is determined whether or not at least one of water and water-based machining fluid remains in the object to be inspected, based on the shade of each pixel corresponding to the object to be inspected, for the image acquired in step (S1).

[0027] In the image acquired in step (S1), among the areas corresponding to the metal product on which an oil film made of anti-rust oil has been formed, there is a clear difference in shading between an area (1) where water and water-based machining fluid are not present and an area (2) where water or water-based machining fluid is present. In detail, the area (2) where water or water-based machining fluid is present is displayed with a darker pixel density than the area (1) where water or water-based machining fluid is not present. In this embodiment, this phenomenon is utilized to determine whether or not at least one of water and water-based machining fluid remains on the inspection object.

[0028] The flow of step (S2) will be explained based on the inspection device 1 of FIG. The image acquired by the infrared imaging device 2 (the image acquired in step (S1)) is input and stored in the memory unit 32, and then image processing is performed in the processing unit 31 (S21). Next, the processing unit 31 uses the image processing results to determine whether or not at least one of water and water-based machining fluid remains in the object to be inspected based on the shade of each pixel corresponding to the object to be inspected (S22). The determination result is sent to the output unit 34 and output by the output unit 34 (S23).

[0029] As the image processing (S21), in order to make the determination (S22) easier, for example, the density of each pixel in the image is converted into a numerical value. Specifically, the density of each pixel in the image is converted into a gradation value. A threshold value capable of distinguishing between an area (1) where water and water-based machining fluid are not present and an area (2) where water or water-based machining fluid is present is stored in advance in the memory unit 32, and if there is a pixel having a gradation value greater than the threshold value, it is determined that at least one of water and water-based machining fluid remains in the object being inspected.

[0030] In order to improve the accuracy of detecting water and water-based machining fluid, it is preferable to convert the captured image data into a thermal equivalent image. By converting the captured image into a thermal equivalent image, it is possible to more clearly distinguish between an area (1) where water and water-based machining fluid are not present and an area (2) where water or water-based machining fluid is present. When converting to a thermal conversion image, the number of pixels of the thermal conversion image is preferably 19,200 pixels or more, more preferably 50,000 pixels or more, and even more preferably 100,000 pixels or more, from the viewpoint of making it easier to clearly distinguish between the area (1) where water and water-based processing fluid are not present and the area (2) where water or water-based processing fluid is present.

[0031] In order to more easily improve the detection accuracy of water and water-based machining fluid, it is preferable to carry out step (S2) using the standard sample (A) as a reference. Specifically, a metal product having an oil film made of anti-rust oil formed on its surface and no remaining water or water-based machining fluid is used as the reference sample (A). The rust preventive oil and metal products that make up the reference sample (A) shall be of the same type as the test object. Then, the pixel density (C A) and sets a threshold value (T1) based on the threshold value (T1), and if there are pixels in the image of the object to be inspected acquired in step (S1) that have a density greater than the threshold value (T1), it is determined that at least one of water and water-based machining fluid remains in the object to be inspected. It is preferable that the measured temperature (surface temperature of reference sample (A)) when the reference sample (A) is imaged using an infrared imaging device and the measured temperature (surface temperature of the object to be inspected) when the object to be inspected is imaged using an infrared imaging device are as close as possible, and it is more preferable that they are the same temperature. As described above, when the gradation value is used in the judgment (S22), the density (C A ) is converted into a gradation value, and a threshold value (T1) is set based on the gradation value.

[0032] The threshold value (T1) is set taking into consideration the range of pixel densities in the entire region corresponding to the reference sample (A), measurement noise, and the like. Preferably, the maximum value of the pixel density (C) in the entire area corresponding to the reference sample (A) is A-MAX ) is set as the threshold (T1).

[0033] In addition, from the viewpoint of further improving the detection accuracy of water and water-based machining fluid, it is preferable to carry out step (S2) using standard samples (B) and (C) as references in addition to standard sample (A). Specifically, a metal product having an oil film made of anti-rust oil formed on its surface and no remaining water or water-based machining fluid is used as the reference sample (A). A defective metal product with an oil film made of anti-rust oil formed on its surface and water remaining on it is used as the reference sample (B). A defective metal product with an oil film made of rust-preventive oil formed on its surface and with residual water-based machining fluid is used as the reference sample (C). The rust preventive oil and metal products that make up standard sample (A), standard sample (B), and standard sample (C) shall be of the same type as the object being inspected. Furthermore, from the viewpoint of improving the accuracy of water detection, the reference sample (B) is preferably a sample in which water exists between the surface of the metal product and the oil film of the rust preventive oil. Similarly, from the viewpoint of improving the accuracy of water detection, the reference sample (C) is preferably a sample in which a water-based machining fluid exists between the surface of the metal product and the oil film of the rust preventive oil. The water-based working fluid used for the reference sample (C) is preferably the same type as the water-based working fluid used in the manufacturing process of the metal product to be inspected. Then, the pixel density (C A ), the pixel density (C B ), and the pixel density (C c ), a threshold value (T2) that satisfies both the following formulas (f1) and (f2) is set. C A <T2<C B (f1) C A <T2<C C (f2) If there are pixels in the image of the object to be inspected acquired in step (S1) that have a density higher than the threshold value (T2), it is determined that at least one of water and water-based machining fluid remains on the surface of the object to be inspected. It is preferable that the measured temperature when the reference sample (A) is imaged using the infrared imaging device (surface temperature of the reference sample (A)), the measured temperature when the reference sample (B) is imaged using the infrared imaging device (surface temperature of the reference sample (B)), the measured temperature when the reference sample (C) is imaged using the infrared imaging device (surface temperature of the reference sample (C)), and the measured temperature when the object to be inspected is imaged using the infrared imaging device (surface temperature of the object to be inspected) are as close as possible, and it is more preferable that they are the same temperature. As described above, when the gradation value is used in the judgment (S22), the density (C A), the pixel density of the remaining water part of the reference sample (B) (C B ), and the pixel density of the water-based machining fluid remaining part of the reference sample (C) (C c ) is converted into a gradation value, and a threshold value (T2) is set based on the gradation value.

[0034] The threshold value (T2) is determined based on the range of pixel densities in the entire region corresponding to the reference sample (A), the range of pixel densities in the entire region corresponding to the reference sample (B), and the range of pixel densities in the entire region corresponding to the water-based machining fluid remaining region of the reference sample (C). c ) range, measurement noise, etc. Preferably, the maximum value of the pixel density (C) in the entire area corresponding to the reference sample (A) is A-MAX ), the minimum pixel density of the entire water-retaining area of ​​the reference sample (B) (C B-MIN ), the minimum pixel density of the entire water-based machining fluid remaining part of the reference sample (C) (C C-MIN The threshold value (T2) is set so that the following expressions (f1-1) and (f2-2) are satisfied. C A-MAX <T2<C B-MIN ···(f1-1) C A-MAX <T2<C C-MIN (f2-1)

[0035] The determination result obtained by the processing unit 31 is displayed on the output unit 34 together with the image.

[0036] If an inspection object is determined to contain at least one of water and water-based machining fluid by the inspection method and inspection device of this embodiment, the object can be removed from the production line and treated appropriately, such as by repeating the rust prevention process, to make it a non-defective product. Therefore, the inspection method and inspection device of this embodiment can improve the yield of metal products. Therefore, in this embodiment, there is provided a method for manufacturing a metal product having an oil film made of rust-preventive oil formed on its surface, which includes a step of carrying out the inspection method of this embodiment.

[0037] It should be noted that the above-described embodiments are preferred examples of the present invention, and the present invention is not necessarily limited to these, and it goes without saying that various modifications and changes are possible within the scope that does not deviate from the gist of the present invention. For example, the determination based on the shading of the image is not limited to a method using gradation values, and it is of course also possible to adopt a method using binary data or a method using contour data.

[0038] [One aspect of the present invention provided] In one aspect of the present invention, the following [1] to [8] are provided. [1] An inspection method for inspecting a metal product having an oil film made of rust-preventive oil formed on its surface to determine whether or not at least one of water and water-based machining fluid remains on the inspection object, the inspection method comprising the following steps (S1) and (S2): Step (S1): A step of capturing an image of the inspection object using an infrared imaging device capable of detecting infrared rays with a wavelength of 8 μm or more. Step (S2): A step of determining whether or not at least one of water and water-based machining fluid remains in the object to be inspected based on the shade of each pixel corresponding to the object to be inspected for the image acquired in step (S1). [2] The step (S2) A non-defective metal product having an oil film formed on its surface by the rust-preventive oil and free from residual water and water-based machining fluid is used as a reference sample (A), The density (C) of the pixels of the reference sample (A) in the image acquired by imaging the reference sample (A) with the infrared imaging device A ) based on which a threshold (T1) is set, The inspection method according to the above-mentioned [1], wherein, when there is a pixel having a density higher than the threshold value (T1) among the pixels corresponding to the object to be inspected in the image acquired in the step (S1), it is determined that at least one of water and water-based machining fluid remains in the object to be inspected. [3] The step (S2) A non-defective metal product having an oil film made of the rust-preventive oil formed on its surface and free from residual water and water-based machining fluid is designated as a reference sample (A), a defective metal product having an oil film made of the rust-preventive oil formed on its surface and free from residual water is designated as a reference sample (B), and a defective metal product having an oil film made of the rust-preventive oil formed on its surface and free from residual water-based machining fluid is designated as a reference sample (C), The pixel density (C) of the reference sample (A) in the image obtained by imaging the reference sample (A) with the infrared imaging device A ), the pixel density (C B ), and the pixel density (C c ) based on the above, a threshold value (T2) is set that satisfies both of the following formulas (f1) and (f2), C A <T2<C B (f1) C A <T2<C C (f2) The inspection method according to the above-mentioned [1], wherein, when there is a pixel having a density higher than the threshold value (T2) among the pixels corresponding to the object to be inspected in the image acquired in the step (S1), it is determined that at least one of water and water-based machining fluid remains in the object to be inspected. [4] The inspection method according to any one of [1] to [3] above, wherein a thermal conversion image is used as the image captured by the infrared imaging device. [5] The inspection method according to any one of the above [1] to [4], wherein the step (S1) is carried out in a light-shielded space. [6] The inspection method according to any one of [1] to [5] above, wherein the thickness of the oil film on the metal product is 30 mm or less. [7] An inspection device that inspects a metal product having an oil film formed on its surface by rust-preventive oil as an inspection object to determine whether or not at least one of water and water-based machining fluid remains on the inspection object, an infrared imaging device capable of detecting infrared rays with a wavelength of 8 μm or more, which images the inspection object; a determination unit that determines whether or not at least one of water and water-based machining fluid remains in the inspection object based on the density of each pixel corresponding to the inspection object in the image acquired by the infrared imaging device; An inspection device comprising at least: [8] A method for manufacturing a metal product having an oil film made of rust-preventive oil formed on its surface, comprising a step of carrying out the inspection method according to any one of [1] to [6] above. [Example]

[0039] The present invention will be specifically described with reference to the following examples, although the present invention is not limited to the following examples.

[0040] The infrared imaging device and test liquid used in Examples 1 and 2 are shown below. (1) Infrared imaging device An infrared camera (manufactured by Hutec Corporation, product name: SMART HUNTER-IR EK model, model number: EKFV-SAU3000-00, frame rate adjusted (frame rate: 50 fps)) was used. This infrared camera has a detection wavelength range of 8 to 14 μm and a pixel count of 640 × 480 pixels. (2) Test solution Water: Ion-exchanged water was used. "Water-based machining fluid": Daphne Alpha Cool WR (soluble type, manufactured by Idemitsu Kosan Co., Ltd.) was diluted with tap water and left to stand at room temperature (23°C) for one day. The concentration of Daphne Alpha Cool WR in the liquid was 5% by mass. "Rust preventive oil": Daphne Super Coat WR (manufactured by Idemitsu Kosan Co., Ltd., classified as solvent-diluted type 3, No. 2 under JIS K2246-1994) was left to stand at room temperature (23°C) for one day before use.

[0041] [Example 1] The following tests were conducted using SSPC-SD steel plates as metal products. The SSPC-SD steel plates had no anti-rust oil film formed on them, and were left to stand at room temperature (23°C) for one day before being subjected to the test. In the following explanation, "SSPC-SD steel plate" may also be abbreviated to "steel plate." The following tests were carried out in an environment at room temperature (23°C).

[0042] One drop each of water and water-based machining fluid was dropped onto the surface of the steel plate using a dropper at four locations, and one drop each of rust-preventive oil was dropped onto two locations using a dropper, after which images were taken using an infrared camera. Figure 3(A) shows the raw measurement image, and Figure 3(B) shows the thermal conversion image.

[0043] The results shown in Figures 3(A) and 3(B) reveal the following. It can be seen that the pixels in the area where water or water-based machining fluid was dropped are clearly darker than the pixels in the area where anti-rust oil was dropped. This shows that, in a steel plate on which an oil film was formed with anti-rust oil, it is possible to clearly distinguish between areas where water or water-based machining fluid is present and areas where water or water-based machining fluid is present, based on the image captured by the infrared imaging device.

[0044] Next, one drop each of water and water-based machining fluid was dropped onto the surface of the steel plate using a dropper at four locations, and one drop of rust-preventive oil was dropped onto two locations using a dropper. Of these samples, one drop of rust-preventive oil was then dropped onto two of the locations where water had been dropped and two of the locations where water-based machining fluid had been dropped, and images were taken using an infrared camera. Figure 4(A) shows the raw measurement image, and Figure 4(B) shows the thermal conversion image.

[0045] The results shown in Figure 4 reveal the following: It can be seen that, although there is a slight change in the size of the spots in the pixels of the areas where anti-rust oil has been dropped on top of the areas where water or water-based machining fluid has been dropped, the density is clearly higher than that of the pixels of the areas where only anti-rust oil has been dropped on the steel plate. From this, it can be seen that, in a steel plate on which an oil film has been formed by anti-rust oil, it is possible to clearly distinguish, in the image taken by the infrared imaging device, between areas where water and water-based machining fluid are not present and areas where water covered with anti-rust oil or water-based machining fluid covered with anti-rust oil is present.

[0046] [Example 2] The metal product used was a thrust bearing outer ring (outer ring φ100 mm, recess depth approximately 5 mm) and the following tests were carried out. The thrust bearing outer rings were not coated with an anti-rust oil film and were left to stand at room temperature (23°C) for one day before testing. In the following explanation, "thrust bearing outer ring" will sometimes be abbreviated to "bearing." The following tests were carried out in an environment at room temperature (23°C).

[0047] (1) Processing A The bearing, on which an oil film was formed using anti-rust oil, was placed on a resin stage and then photographed using an infrared camera. (2) Processing B One drop of water-based machining fluid was dropped into each of two recesses on the bearing that had undergone treatment A, and then an image was taken using an infrared camera.

[0048] The obtained images are shown in Figure 5. In Figure 5, the upper row is the raw measurement image, and the lower row is the thermal conversion image.

[0049] The results shown in Figure 5 reveal the following: From the image after process B, it can be seen that in the bearing on which an oil film is formed using anti-rust oil, the areas where water and water-based machining fluid are not present and the areas where water-based machining fluid is present can be clearly distinguished from the image taken by the infrared imaging device.

[0050] [Example 3] We investigated whether it was possible to distinguish between areas where an oil film made of rust-preventive oil was formed and areas where water was present when the thickness of the oil film made of rust-preventive oil became thick. Specifically, water or rust-preventive oil was added to a cylindrical glass container with an inner diameter of 52 mm, and the thickness of the water or rust-preventive oil (height from the bottom of the glass container) was calculated based on the amount added. Images were then taken using an infrared camera.

[0051] The resulting image is shown in FIG.

[0052] The results shown in Figure 6 reveal the following: As the thickness of the rust-preventive oil increases, the pixels in the area where the rust-preventive oil is present become slightly darker, but the density of the pixels is lighter than the pixels when the water thickness is extremely thin at 1.9 mm. Therefore, it can be seen that even when the oil film made of rust-preventive oil is relatively thick, it is possible to clearly distinguish between areas where water or water-based machining fluid is not present and areas where water is present in the image captured by the infrared imaging device.

Claims

1. An inspection method for inspecting a metal product having an anti-rust oil film formed on its surface with a thickness of 30 mm or less, and for inspecting whether or not at least one of water and water-based machining fluid remains on the inspection object, the inspection method comprising the following steps (S1) and (S2): Step (S1): A step of capturing an image of the inspection object using an infrared imaging device capable of detecting infrared rays with a wavelength of 8 μm or more and 14 μm or less. Step (S2): A step of determining whether or not at least one of water and water-based machining fluid remains in the object to be inspected based on the shade of each pixel corresponding to the object to be inspected for the image acquired in step (S1).

2. The step (S2) A non-defective metal product having an oil film formed on its surface by the rust-preventive oil and free from residual water and water-based machining fluid is used as a reference sample (A), The pixel density (C) of the reference sample (A) in the image acquired by imaging the reference sample (A) with the infrared imaging device Ａ ) and setting a threshold (T1) based on 2. The inspection method according to claim 1, wherein, when there is a pixel having a density higher than the threshold value (T1) among the pixels corresponding to the object to be inspected in the image acquired in the step (S1), it is determined that at least one of water and water-based machining fluid remains in the object to be inspected.

3. The step (S2) A non-defective metal product having an oil film made of the rust-preventive oil formed on its surface and free from residual water and water-based machining fluid is designated as a reference sample (A), a defective metal product having an oil film made of the rust-preventive oil formed on its surface and free from residual water is designated as a reference sample (B), and a defective metal product having an oil film made of the rust-preventive oil formed on its surface and free from residual water-based machining fluid is designated as a reference sample (C), The pixel density (C) of the reference sample (A) in the image obtained by imaging the reference sample (A) with the infrared imaging device Ａ ), the pixel density (C) of the remaining water portion of the reference sample (B) in the image obtained by imaging the reference sample (B) with the infrared imaging device. Ｂ ), and the pixel density (C ｃ ) based on the above, a threshold value (T2) that satisfies both of the following formulas (f1) and (f2) is set, C Ａ <T2<C Ｂ ・・・(f1) C Ａ <T2<C Ｃ ・・・(f2) 2. The inspection method according to claim 1, wherein, when there is a pixel having a density higher than the threshold value (T2) among the pixels corresponding to the object to be inspected in the image acquired in the step (S1), it is determined that at least one of water and water-based machining fluid remains in the object to be inspected.

4. 4. The inspection method according to claim 1, wherein a thermal conversion image is used as the image captured by the infrared imaging device.

5. The inspection method according to any one of claims 1 to 4, wherein the step (S1) is carried out in a light-shielded space.

6. 6. The inspection method according to claim 1, wherein the thickness of the oil film on the metal product is 20 mm or less.

7. An inspection device for inspecting a metal product having an oil film of 30 mm or less formed on its surface by rust-preventive oil, to determine whether or not at least one of water and water-based machining fluid remains on the inspection object, an infrared imaging device that captures an image of the inspection object and is capable of detecting infrared rays with a wavelength of 8 μm or more and 14 μm or less; a determination unit that determines whether or not at least one of water and water-based machining fluid remains in the inspection object based on the density of each pixel corresponding to the inspection object in the image acquired by the infrared imaging device; An inspection device comprising at least:

8. A method for manufacturing a metal product having an oil film made of rust-preventive oil formed on its surface, comprising a step of carrying out the inspection method according to any one of claims 1 to 6.

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