JP7110777B2 - Metal thin plate inspection device and metal thin plate inspection method - Google Patents

Description

The present invention relates to a thin metal sheet inspection apparatus capable of inspecting shape defects, surface defects, and the like of thin metal sheets, and a method of inspecting a thin metal sheet using the thin metal sheet inspection apparatus.

A thin metal plate (hereinafter also simply referred to as a thin plate) produced by rolling a metal material has surface defects such as linear scratches during rolling, polishing, and cutting, excessive edge waves, medium elongation, Shape defects such as rolling marks occur. As a method of checking the presence or absence of such defects and inspecting the surface, a method of irradiating the surface of a thin plate with light and inspecting for surface defects from changes in reflected light is known. For example, in Patent Literature 1, in order to quickly and reliably identify fine scratches that occur on the surface of a metal or the like during processing and perform a highly accurate surface inspection, the surface of the rolled or drawn metal or the like In an optical surface inspection method for inspecting unevenness, an illumination device is used to irradiate light having a striped pattern in which bright portions and dark portions are alternately arranged at equal intervals on the surface of a metal or the like to be inspected, and the striped pattern is obtained. Disclosed is an optical surface inspection method for metals, etc., in which the direction of arrangement of the metal and the direction of rolling or drawing are set to be the same.

Japanese Patent Application Laid-Open No. 2002-202113

In recent years, the size and number of allowable defects on the surface of a thin plate tend to decrease due to demands for quality improvement from customers. For example, in the case of roll marks, which are defects in which a roll pattern is transferred to the surface of a thin plate during rolling, it is necessary to detect very small defects such as 0.5 mmφ or less, depending on the required quality. Therefore, visual inspection by an inspector requires even an experienced inspector to make multiple observations for a long period of time, and there is a demand for further improvement in work efficiency and inspection accuracy. Patent document 1 is an excellent invention that can easily inspect surface unevenness defects, but it may not be possible to detect minute defects or defects with very small unevenness, so there is room for further improvement is left. It is also conceivable to introduce a high-precision inspection device using an optical sensor or the like, but it is not preferable because the introduction and installation of the device is expensive.
SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a thin metal sheet inspection apparatus and a thin metal sheet inspection method that can easily detect even minute shape defects and surface defects of a metal sheet.

One aspect of the present invention is a thin metal plate inspection apparatus for inspecting a thin metal plate,
an inspection table for placing the thin metal plate;
a first light source unit that irradiates striped light onto the inspection table;
and a second light source for irradiating the inspection table with light from a direction different from the striped light.
Preferably, the first light source unit includes a first light source that emits light toward the inspection table;
a striped pattern forming member disposed between the first light source and the inspection table for irradiating a striped pattern on the inspection table with the light from the first light source.
Preferably, the examination table can be tilted at a predetermined angle from a horizontal state.
Preferably, the second light source is positioned closer to the examination table than the first light source section.

Another aspect of the present invention provides a method for inspecting a thin metal plate using the inspection apparatus described above,
A first defect inspection in which a thin metal plate for inspection is placed on the inspection table, the thin metal plate is irradiated with striped light from the first light source unit, and the thin metal plate is inspected from the shape of the irradiated striped pattern. process and
and a second defect inspection step of inspecting the thin metal plate by irradiating the thin metal plate with light from the second light source.
Preferably, the thin metal plate has a thickness of 1 mm or less and a surface roughness of Ra≦0.2 μm and Rz≦2.0 μm.

According to the present invention, the surface condition of a thin metal plate can be inspected with a simple device configuration. For example, it is possible to greatly improve the detection accuracy of minute defects, and to greatly suppress the outflow of defects.

It is a figure which shows an example of the inspection apparatus of this invention. FIG. 2 is a schematic diagram showing the arrangement configuration of the inspection apparatus of the present invention viewed from the x direction of FIG. 1; It is a figure which shows an example of the striped pattern formation member used for the inspection apparatus of this invention. FIG. 4 is a diagram showing another example of the striped pattern forming member used in the inspection apparatus of the present invention; It is a surface photograph of the metal thin plate at the time of implementation of the first defect inspection step of the present invention. It is a surface photograph of the metal thin plate at the time of the second defect inspection process implementation of this invention. It is a surface photograph of the metal thin plate at the time of implementation of the 1st defect inspection process of another this invention. FIG. 8 is a photograph of the surface of the thin metal plate, showing an enlarged portion of part B in FIG. 7 ;

Embodiments of the present invention are described below. The present invention is not limited to the following embodiments, and appropriate combinations and improvements are possible without departing from the technical idea of the invention. First, the inspection apparatus of the present invention will be explained. Schematic diagrams of the inspection apparatus of this embodiment are shown in FIGS. 1 and 2. FIG. The inspection apparatus of this embodiment has a first light source 1, a first light source unit 20 composed of a striped pattern forming member 4, a second light source 2, and an inspection table 3, as shown in FIG. , the inspection table 3 and the striped pattern forming member 4 are attached to the frame 5 . The frame 5 is made by combining pipes, for example. A steel pipe or the like coated with a resin can be used as the pipe used here. In the case of visual inspection, the inspector can inspect the thin metal plate from a position facing the second light source. When performing an image inspection, an image capturing device such as a CCD camera may be installed in the direction in which the light emitted from the first light source and the second light source onto the thin metal plate is reflected, and observation may be performed. Here, the "metal thin plate" preferably has a thickness of 1 mm or less. It is more preferably 0.7 mm or less, more preferably 0.5 mm or less. Note that the z-direction in the present invention indicates the arrangement direction of the first light source 1, the striped pattern forming member 4, and the inspection table 3. As shown in FIG. In FIGS. 1 and 2 of the present embodiment, since the above members are arranged in the vertical direction, the z direction is the vertical direction.

The inspection apparatus of this embodiment has an inspection table 3 for placing a thin metal plate to be inspected. The thin metal plate placed on the inspection table is irradiated with light from a first light source or a second light source, which will be described later, to observe the surface condition of the thin metal plate, for example, shape defects and surface defects. The inspection table 3 preferably has a mounting surface on which the thin metal plate to be inspected can be placed in a flat state, and is configured to be tilted within a range of ±30° from the horizontal state. . This tilting mechanism makes it possible to change the incident angle of the light from the second light source 2 with respect to the thin metal plate, particularly when performing observation with the second light source 2, which will be described later. It is possible to facilitate capture of minute surface defects. Here, the + side inclination angle of the inspection table 3 in this embodiment is such that the upper surface of the inspection table on the side where the second light source is installed is located above the reference with the upper surface of the inspection table in a horizontal state as a reference (eg, FIG. 2) is the inclination angle (θ1 in FIG. 2). The − side tilt angle of the inspection table 3 is the tilt angle (θ2 ). In addition, the inspection table 3 may be moved obliquely so that the right side or the left side of the y-direction is lowered in order to adjust the visual field range or the like.

The first light source unit 20 in the inspection apparatus of this embodiment is composed of the first light source 1 installed above the inspection table 3 in the substantially vertical direction and the striped pattern forming member 4 installed below the first light source 1. It is The light from the first light source 1 is transmitted through the striped pattern forming member 4 to irradiate a striped pattern on the inspection table, and it is possible to detect shape defects such as undulations and dents on the thin metal plate. The brightness of the first light source 1 can be appropriately changed according to the material and surface condition of the thin metal plate to be inspected, but if it is too bright, there is a possibility that the striped pattern cannot be observed. Therefore, it is preferable to adjust the illuminance to 1100 lx (lux) or less when the inspection table is irradiated with the light from the first light source 1 . Since the striped pattern cannot be recognized even if the inspection table is too dark, the lower limit of the illuminance on the inspection table by the light from the first light source 1 can be set to 700 lx. A more preferable upper limit of the illuminance is 1000 lx, and a more preferable lower limit of the illuminance is 900 lx. A straight tube fluorescent lamp is used as the first light source in this embodiment.

The striped pattern forming member 4 of the present embodiment can be produced by forming the light blocking portion 10 on a transparent member that transmits light. The width of the light blocking section 10 and the installation interval of the light blocking section 10 can be appropriately adjusted according to the material of the object to be measured and the measurement environment. For the transparent member, for example, glass or acrylic may be selected, and for the light shielding portion, a black vinyl tape or a transparent sheet with a black pattern printed thereon may be used. As a modified example, a striped pattern forming member can be produced by removing a member from a plate-like member that does not transmit light at desired sizes and intervals to form light transmitting portions. The width L1 of the light blocking portion 10 of the striped pattern forming member 4 and the interval L2 of the light blocking portion 10 may be formed with the same width and the same interval throughout the striped pattern forming member as shown in FIG. As shown, the width and interval of the light blocking portion may be changed depending on the position. In this embodiment, for example, the width L1 of the light blocking portion can be set to 13 to 25 mm, and the interval L2 of the light blocking portion can be set to 5 to 13 mm. A preferable width L1 of the light blocking portion is 15 to 23 mm, and a preferable distance L2 between the light blocking portions is 7 to 11 mm. If the striped pattern forming member of FIG. 4 is used, a striped pattern that easily captures defects can be selected depending on the material and surface condition, so that the thin metal plate can be inspected more efficiently. The distance between the first light source 1 and the striped pattern forming member 4 may be appropriately adjusted to obtain a desired illuminance. If the distance is too large, there is a possibility that the striped pattern irradiated onto the inspection table cannot be clearly confirmed, so the distance can be set to 100 mm or less. The lower limit is not particularly set, and the light source and the striped pattern forming member may be brought into close contact with each other. Also, the distance between the inspection table 3 and the first light source 1 may be adjusted in order to obtain a desired illuminance. In this embodiment, the striped pattern forming member 4 is installed horizontally as shown in FIG. 2, but it may be installed with a slight inclination in order to change the irradiation condition of the striped pattern. Specifically, when a horizontally installed examination table is used as a reference, it is preferable that the tilt angle γ is within a range of 5° or less. More preferably, it is 3° or less. Here, the "substantially vertical direction of the inspection table", which is the installation position of the first light source 1, connects the horizontal inspection table, the center of the first light source 1, and the center of the inspection table 3 as shown in the figure. The angle (first light source angle) α formed with the line is 85 to 95°. In this embodiment, the striped pattern forming member is used to irradiate the inspection table with striped light. may An example of a first light source that does not require such a striped pattern forming member is one in which small LED chips are arranged at regular intervals.

In the inspection apparatus of this embodiment, the second light source 2 is installed below the above-described first light source section 20 (and above the inspection table). The light source angle β of the second light source 2 is set to be smaller than the light source angle of the first light source, as shown in FIG. That is, the light from the second light source irradiates the inspection table from a direction different from that of the striped light from the first light source. The upper limit of the light source angle is preferably 50°, more preferably 40°, and even more preferably 35°. The lower limit of the light source angle is preferably 0°, more preferably 10°, and even more preferably 20°. The light source angle β in the second light source 2 is the angle between the center of the second light source and the center of the inspection table. By setting the light source angle β to be shallow in this way, it is possible to detect minute surface defects such as linear flaws and streak flaws with extremely shallow flaw depths of about 1 μm or less. At this time, it is preferable to adjust the illuminance on the inspection table by the second light source to 700 to 1000 lx. This makes it easier to detect surface defects. A preferable upper limit of illuminance is 950 lx, and a preferable lower limit of illuminance is 800 lx. Here, it is preferable to set the correlated color temperature of the second light source in this embodiment to 4000K or less. As a result, the hue of the second light source can be a warm color, which is an advanced color, so that minute surface defects tend to be captured more easily than with a generally used daylight white light source. A preferred correlated color temperature is 3500K or less. Note that the lower limit is not particularly set, and may be set to 2500K, for example. Preferably, it may be set to 2700K, which is the color temperature of a general incandescent lamp. In this embodiment, a warm-color LED dimming illumination is used as the second light source. The position of the second light source in the horizontal direction (the y direction in FIGS. 1 and 2) is set to the central side of the device (the center of the first light source in FIG. ), and in that case, the horizontal position with the striped pattern forming member may partially overlap. Further, as shown in FIG. 2, the second light source and the striped pattern forming member may be installed so that their horizontal positions do not overlap.

Next, the inspection method of the present invention will be described. The inspection method of the present invention includes a first defect inspection step of irradiating a thin metal plate placed on an inspection table with striped light from a first light source, and inspecting the shape defect of the thin metal plate from the form of the irradiated striped pattern. and a second defect inspection step of irradiating the thin metal plate with light from the second light source and inspecting the thin metal plate for defects.

<First defect inspection process>
First, a prepared thin metal plate to be inspected is placed on an inspection table, and the light from the first light source is transmitted through the striped pattern forming member in a state where the light from the second light source is not irradiated. is irradiated onto the thin metal plate, and the shape defect of the thin metal plate is inspected from the form of the irradiated striped pattern. At this time, if the striped pattern is difficult to see on the thin metal plate, it is possible to adjust the appearance of the striped pattern by inclining the striped pattern forming member within a range of ±5°. Also, the inspection table may be tilted during the first defect inspection step. In this first defect inspection step, shape defects such as waviness, folds, dents, and roll marks of the thin metal plate can be captured. If a shape defect as described above exists on the thin metal plate, the striped pattern is distorted as shown in FIG. 5, so the shape defect can be easily captured.

<Second defect inspection process>
In the present embodiment, the thin metal plate is subsequently irradiated with light from the second light source while the light from the first light source is not applied, and the thin metal plate is inspected for defects. In the first defect inspection process, it is difficult to detect a very shallow surface defect, for example, a scratch depth of 1 μm or less. Therefore, even the minute surface defects described above can be caught. In this second defect inspection step, it is preferable to observe the thin metal plate while changing the angle of the inspection table within a range of ±30°. As a result, the reflection characteristics of the surface of the thin metal plate can be changed, making it easier to catch minute surface defects. In this embodiment, the first defect inspection process and the second defect inspection process are performed in this order, but the second defect inspection process may be performed first.

The inspection method of the present embodiment is preferably applied to a thin metal plate whose surface has an arithmetic mean roughness Ra of 0.2 μm or less and a maximum height Rz of 2.0 μm or less. By inspecting a thin metal plate that satisfies this condition, the reflection of the striped pattern in the first defect inspection step becomes clearer, so it is possible to further improve the accuracy of detecting defects. The surface glossiness of the thin metal plate to be inspected in this embodiment is preferably 100 or more, more preferably 105 or more at 85° glossiness. Thereby, the shape defect detection accuracy and the surface defect detection accuracy in the first defect process and the second defect process can be further improved. Incidentally, the surface glossiness of the present invention may be evaluated using an existing gloss meter or the like.

According to the inspection apparatus and inspection method of the present invention, it is possible to improve the accuracy of defect inspection during visual inspection, and to greatly reduce the time required to discover defects. Moreover, the present invention can be applied not only to visual inspection but also to image inspection using an imaging device such as a CCD camera.

First, a sample for inspection was prepared. The sample used was obtained by cutting an Fe—Ni alloy thin plate having a thickness of 0.1 mm into a width of 45 mm and a length of 100 mm. Here, the "length" direction is the rolling direction, and the "width" direction is the direction perpendicular to the rolling direction. As a result of measuring the surface roughness of this sample in advance, it was confirmed that the surface roughness Ra was about 0.06 to 0.1 μm and the maximum height Rz was about 0.6 μm to 1.2 μm. It was also confirmed that the glossiness (Gs (85°)) of the sample surface based on JISZ8741 (1997) was measured in advance using a gloss meter and showed a value of 110-120. Subsequently, the prepared samples were inspected using the inspection apparatus shown in FIG. First, the prepared sample was placed on the inspection table, and the first defect inspection step was performed. Table 1 shows various setting conditions of the inspection apparatus used in the examples. The distance h1 between the first light source and the striped pattern forming member indicates the maximum vertical distance, and the distance h2 between the striped pattern forming member and the inspection table indicates the maximum vertical distance when the inspection table is installed horizontally. The illuminance when the first light source is turned on and when the second light source is turned on are average values obtained by measuring a range of 400 mm×1000 mm in the center of the examination table using an illuminometer. This average value indicates the average of measured values obtained by measuring five arbitrary points in a measurement area of 400 mm×1000 mm. A warm color light source (correlated color temperature: 2700K to 3000K) is applied to the second light source.

FIG. 5 shows a photograph of the surface of the thin metal plate during the first defect inspection step. From FIG. 5, a striped pattern was irradiated on the surface of the thin metal plate, and distortion of the striped pattern was observed in the area enclosed by the dashed line. As a result of detailed observation of the distorted portion, it was confirmed that the dent had a depth of about 0.3 mm. Thus, it was possible to detect even minute shape defects, which were difficult to catch by visual inspection, by using the apparatus of the present invention. Although not shown in the photograph, a roll mark of 0.3 mmφ×3 μm in height was also caught in this first defect inspection process. Subsequently, after turning off the first light source, the second light source was turned on, and the second defect inspection step was performed. During the second defect inspection step, the thin metal plate was observed while moving the inspection table at hand within a range of ±20° from the horizontal state. As a result, as shown in FIG. 6, surface defects (areas surrounded by broken lines) that could not be detected in the first defect inspection process could be detected.

As another example, the material of the thin plate was changed to martensitic stainless steel (corresponding to SUS420J2), and the inspection was performed using the apparatus of the present invention. A sample having a thickness of 0.1 mm was cut into a size of about 45 mm in width and 100 mm in length. The setting items of the inspection apparatus were the same as those in the first embodiment. As a result of measuring the glossiness (Gs (85°)) of the sample surface based on JISZ8741 (1997) in advance, it was confirmed that a value of 110 to 120 was exhibited. 7 and 8 show photographs of the surface of the thin metal plate during the first defect inspection step. In addition, FIG. 7 is obtained by observing two samples, and the black linear portion between them is the space between the two samples. 8 is an enlarged photograph of the B portion of FIG. As shown in FIG. 8, by using the measuring apparatus of the present embodiment, it became possible to visually observe the sagging portion (fine R shape) 16 formed at the edge of the thin metal plate. Generally, the thinner the plate thickness is, the smaller the formation area of such a sagging portion is, making it difficult to visually observe it. However, by applying the measuring apparatus and measuring method of the present embodiment, the change in reflectance of the sag forming portion was emphasized by the shade of the striped pattern, and the change in shape could be easily observed visually. In addition, by placing a plurality of samples on the inspection table and inspecting them, it was possible to simultaneously inspect a plurality of production lots, and to perform the inspections efficiently and accurately.

1 first light source 2 second light source 3 inspection table 4 striped pattern forming member 5 frame 10 light shielding portion 16 sagging portion 20 first light source portion h1 distance h2 between first light source and striped pattern forming member striped pattern forming member and inspection Distance from table L1 Width of light blocking portion L2 Spacing of light blocking portion α First light source angle β Second light source angle γ Inclination angles θ1 and θ2 of striped pattern forming member Inclination angle of inspection table

Claims (5)

In a thin metal plate inspection device for inspecting a thin metal plate,
an inspection table for placing a thin metal plate , which can be tilted at a predetermined angle from a horizontal state ;
a first light source unit that irradiates striped light onto the inspection table;
and a second light source that irradiates light with a correlated color temperature of 4000 K or less toward the inspection table from a direction different from the striped light. The first light source unit
a first light source that emits light toward the inspection table;
2. The thin metal plate inspection system according to claim 1, further comprising: a striped pattern forming member arranged between said first light source and said inspection table for irradiating a striped pattern on the inspection table with light from said first light source. device . 3. The thin metal plate inspection apparatus according to claim 1, wherein said second light source is positioned closer to said inspection table than said first light source unit. In a method for inspecting a thin metal plate using the inspection apparatus according to any one of claims 1 to 3 ,
A first defect inspection in which a thin metal plate for inspection is placed on the inspection table, the thin metal plate is irradiated with striped light from the first light source unit, and the thin metal plate is inspected from the shape of the irradiated striped pattern. process and
and a second defect inspection step of inspecting the thin metal plate by irradiating the thin metal plate with light from the second light source. 5. The method of inspecting a thin metal plate according to claim 4 , wherein the thin metal plate has a thickness of 1 mm or less and a surface roughness of Ra≦0.2 μm and Rz≦2.0 μm.

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