JP2019020416A - Metal thin plate inspection device and method for inspecting metal thin plate - Google Patents

Abstract

To provide an inspection device and a method for inspection that can significantly increase the accuracy of detecting a fine defect by a simple device structure and can suppress outflow of defective items.SOLUTION: The metal thin plate inspection device for inspecting a metal thin plate includes: an inspection board on which a metal thin plate is to be put; a first light source unit for irradiating the surface of the inspection board with stripe light; and a second light source unit for irradiating the inspection board with light from a direction different from the direction from which the stripe light is emitted, the first light source desirably having a first light source for emitting light to the inspection board and a stripe pattern formation member between the first light source and the inspection board for irradiating the surface of the inspection board with a stripe pattern by light from the first light source.SELECTED DRAWING: Figure 1

Description

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

  The metal thin plate produced by rolling a metal material (hereinafter also simply referred to as a thin plate) has surface defects such as linear wrinkles during rolling, polishing and cutting, excessive ear waves, medium elongation, Shape defects such as rolling marks occur. As a method for checking the presence of this defect and inspecting the surface, a method is known in which the surface of the thin plate is irradiated with light and the surface defect is inspected from a change in reflected light. For example, in Patent Document 1, in order to quickly and surely identify fine scratches or the like generated on the surface of a metal or the like and perform a highly accurate surface inspection, the surface of the metal or the like that has been rolled or drawn is processed. In the optical surface inspection method for inspecting the uneven state, the illumination device that irradiates light having a stripe 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 is used. An optical surface inspection method for metal or the like is set so that the arrangement direction of the metal and the direction of rolling or drawing are the same.

JP 2002-202113 A

In recent years, the size and the number of defects on the surface of the thin plate that are allowed have been decreasing due to the demand for quality improvement from customers. For example, in a roll mark which is a defect in which a rolling roll pattern is transferred to the surface of a thin plate during rolling, it is necessary to detect even a very small defect such as a size of 0.5 mmφ or less depending on the required quality. Therefore, it is necessary for an expert to observe a plurality of times for a long time by visual inspection by an inspector, and further improvement in work efficiency and improvement in inspection accuracy are required. Patent Document 1 is an excellent invention that can easily inspect surface irregularity defects, but it may not be possible to detect minute defects or defects with very small irregularities, and there is room for further improvement. Is left. In addition, it is conceivable to introduce a high-precision inspection apparatus using an optical sensor or the like, but it is not preferable because the installation and installation of the apparatus requires a high cost.
SUMMARY OF THE INVENTION An object of the present invention is to provide a metal thin plate inspection apparatus and a metal thin plate inspection method that can be easily detected even if the shape defect or surface defect of the metal thin plate is minute.

One aspect of the present invention is a metal sheet inspection apparatus for inspecting a metal sheet,
An inspection table for placing a metal thin plate;
A first light source unit that emits striped light on the inspection table;
It is a metal thin plate inspection apparatus which has a 2nd light source which irradiates light toward the said inspection stand from the direction different from the said striped light.
Preferably, the first light source unit irradiates light toward the inspection table,
A striped pattern forming member that is disposed between the first light source and the inspection table and irradiates a striped pattern on the inspection table with light from the first light source.
Preferably, the inspection table can be inclined at a predetermined angle from a horizontal state.
Preferably, the second light source is located closer to the inspection table than the first light source unit.

Another aspect of the present invention is a method for inspecting a thin metal plate using the above-described inspection apparatus.
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 form of the irradiated stripe pattern Process,
And a second defect inspection step of inspecting the metal thin plate by irradiating the metal thin plate with light from the second light source.
Preferably, the metal thin 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 state of a thin metal plate can be inspected with a simple apparatus configuration. For example, it is possible to greatly improve the detection accuracy of minute defects, and to significantly suppress the outflow of defects.

It is a figure which shows an example of the test | inspection apparatus of this invention. It is a schematic diagram which shows the arrangement configuration of the inspection apparatus of this invention seen from the x direction of FIG. It is a figure which shows an example of the striped pattern formation member used for the test | inspection apparatus of this invention. It is a figure which shows the other example of the striped pattern formation member used for the test | inspection apparatus of this invention. It is the surface photograph of the metal thin plate at the time of the 1st defect inspection process implementation of this invention. It is the surface photograph of a metal thin plate at the time of 2nd defect inspection process implementation of this invention. It is the surface photograph of a metal thin plate at the time of the 1st defect inspection process of another this invention. It is the surface photograph of a metal thin plate which shows the B section enlarged part of FIG.

  Embodiments of the present invention will be described below. The present invention is not limited to the following embodiments, and can be appropriately combined and improved without departing from the technical idea of the present invention. First, the inspection apparatus of the present invention will be described. A schematic diagram of the inspection apparatus of the present embodiment is shown in FIGS. As shown in FIG. 1, the inspection apparatus of the present embodiment includes a first light source 1, a first light source unit 20 including a striped pattern forming member 4, a second light source 2, and an inspection table 3. The inspection table 3 and the striped pattern forming member 4 are attached to the frame 5. The frame body 5 is produced, for example, by combining pipes. The pipe used here can be a steel pipe coated with resin. In the case of visual inspection, the inspector can inspect the thin metal plate from the position with respect to the second light source. When performing an image inspection, an image photographing device such as a CCD camera may be installed and observed in a direction in which the light irradiated to the metal thin plate from the first light source and the second light source is reflected. Here, the “metal thin plate” preferably has a thickness of 1 mm or less. More preferably, it is 0.7 mm or less, More preferably, it is 0.5 mm or less. 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. In FIG. 1 and FIG. 2, which are 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 metal thin 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, and the surface state of the thin metal plate, for example, a shape defect or a surface defect is observed. The inspection table 3 preferably has a mounting surface on which a thin metal plate to be inspected can be mounted in a flat state, and can be inclined within a range of ± 30 ° from the horizontal state. . By this tilting mechanism, particularly when performing observation with the second light source 2 described later, the incident angle of light from the second light source 2 to the metal thin plate can be changed, so that the reflection characteristics of the surface of the metal thin plate are changed, A minute surface defect can be easily captured. Here, the + side inclination angle of the inspection table 3 in the present embodiment is such that the upper surface of the inspection table on the second light source installation side is located above the reference with respect to the upper surface of the inspection table in the horizontal state (example: FIG. 2) (the position of 3a in FIG. 2). Further, the minus side inclination angle of the inspection table 3 is an inclination angle (θ2 in the figure) when the upper surface of the inspection table on the second light source installation side is located below the reference (eg, position 3b in FIG. 2). ). Further, the inspection table 3 may be moved obliquely so that the right side is lowered or the left side is lowered as viewed from the y direction in order to adjust the visual field range.

  The first light source unit 20 in the inspection apparatus of the present embodiment includes a first light source 1 installed substantially vertically above the inspection table 3 and a striped pattern forming member 4 installed below the first light source 1. Has been. The light from the first light source 1 passes through the striped pattern forming member 4 to irradiate the striped pattern on the inspection table, and in particular, it is possible to detect shape defects such as swells and dents on the thin metal plate. The brightness of the first light source 1 can be appropriately changed depending on the material and surface state of the metal thin plate to be inspected, but if it is excessively bright, the stripe pattern may not be observed. For this reason, it is preferable to adjust the illuminance when the light from the first light source 1 is irradiated to the inspection table to 1100 lx (lux) or less. In addition, since the striped pattern cannot be confirmed 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 illuminance is 1000 lx, and a more preferable lower limit of illuminance is 900 lx. The first light source in this embodiment uses a straight tube fluorescent lamp.

  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 unit 10 and the installation interval of the light blocking unit 10 can be appropriately adjusted according to the material to be measured and the measurement environment. For example, glass or acrylic may be selected as the transparent member, and the light blocking portion may be a black vinyl tape or a black sheet printed on a transparent sheet. As a modification, a striped pattern forming member can be created by removing a member from a plate-like member that does not transmit light at a desired size and interval to form a light transmitting portion. The width L1 of the light blocking portion 10 and the interval L2 between the light blocking portions 10 of the stripe pattern forming member 4 may be formed with the same width and the same interval throughout the stripe 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 the present embodiment, for example, the width L1 of the light blocking portion can be set to 13 to 25 mm, and the interval L2 between the light blocking portions 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 interval L2 of 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 a defect can be selected depending on the material and surface state, so that the metal thin plate can be inspected more efficiently. You may adjust suitably the distance of the 1st light source 1 and the striped pattern formation member 4 in order to obtain desired illuminance. If the distance is too large, there is a possibility that the striped pattern irradiated on the inspection table cannot be clearly confirmed, so it 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. Moreover, in order to obtain desired illuminance, the distance between the inspection table 3 and the first light source 1 may be adjusted. For example, in the present embodiment, the distance can be set within a range of 500 to 1000 mm. In the present embodiment, the striped pattern forming member 4 is installed horizontally as shown in FIG. 2, but may be installed slightly tilted in order to change the irradiation condition of the striped pattern. Specifically, when a horizontally installed inspection table is used as a reference, it is preferable to incline within a range where the inclination angle γ is 5 ° or less. More preferably, it is 3 ° or less. Here, “the substantially vertical direction of the inspection table”, which is the installation location 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 by the line is 85 to 95 °. In this embodiment, the striped pattern forming member is used for irradiating the striped light on the inspection table. However, when the striped light can be irradiated only by the first light source, the striped pattern forming member is not installed. May be. An example of the first light source that does not require such a striped pattern forming member is one in which small LED chips are installed at equal intervals.

  In the inspection apparatus of the present embodiment, the second light source 2 is installed below the first light source unit 20 (and above the inspection table). The light source angle β in 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 is applied to the examination table from a different direction from the striped light from the first light source unit. The upper limit of the preferred light source angle is 50 °, more preferably 40 °, and even more preferably 35 °. The lower limit of the preferred light source angle is 0 °, more preferably 10 °, and even more preferably 20 °. The light source angle β in the second light source 2 is an angle between the center of the second light source and the center of the inspection table. Thus, by inspecting with the light source angle β set to be shallow, it is possible to detect minute surface defects such as linear wrinkles and muscle wrinkles that have a wrinkle depth of approximately 1 μm or less. At this time, the illuminance on the inspection table by the second light source is preferably adjusted to 700 to 1000 lx. This makes it easier to detect surface defects. The upper limit of the preferable illuminance is 950 lx, and the lower limit of the preferable illuminance is 800 lx. Here, the correlated color temperature of the second light source of the present embodiment is preferably set to 4000K or less. As a result, the hue of the second light source can be set to a warm color that is an advancing color, and therefore, it tends to be easier to capture minute surface defects as compared to a daylight white light source that is generally used. A preferred correlated color temperature is 3500K or less. The lower limit is not particularly set, and may be set to 2500K, for example. Preferably, you may set with 2700K which is the color temperature of a general incandescent lamp. In this embodiment, warm-color LED dimming illumination is used as the second light source. The position of the second light source in the horizontal direction (y direction in FIGS. 1 and 2) is such that it does not interfere with the first defect inspection process described later (the center of the first light source and the inspection table in FIG. 2). May be arranged in a direction toward a broken line connecting the two, and in that case, the horizontal position with the striped pattern forming member may partially overlap. Moreover, as shown in FIG. 2, you may install so that the horizontal direction position of a 2nd light source and a striped pattern formation member may not overlap.

  Subsequently, the inspection method of the present invention will be described. The inspection method of the present invention irradiates a thin metal plate placed on an inspection table with striped light from the first light source unit, and inspects a shape defect of the thin metal plate from the form of the irradiated stripe 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, the prepared thin metal plate to be inspected is placed on the inspection table, and the light from the first light source is transmitted to the striped pattern forming member in a state where the light from the second light source is not irradiated, so that the striped light is transmitted. Is inspected for a shape defect of the metal thin plate from the form of the irradiated stripe pattern. At this time, when it is difficult to see the striped pattern on the thin metal plate, the projection of the striped pattern can be adjusted by inclining the striped pattern forming member within a range of ± 5 °. Further, the inspection table may be inclined during the first defect inspection process. In the first defect inspection process, shape defects such as undulation, crease, dent, and roll mark of the metal thin plate can be mainly captured. When the shape defect as described above exists on the metal thin plate, the stripe defect is distorted as shown in FIG. 5, so that the shape defect can be easily captured.

<Second defect inspection process>
In the present embodiment, subsequently, the light from the second light source is irradiated to the metal thin plate in a state where the light from the first light source is not irradiated, and the defect of the metal thin plate is inspected. In the first defect inspection process, for example, it is difficult to detect a very shallow surface defect with a scratch depth of 1 μm or less, but the reflection characteristics change between the normal part and the defect part by this second defect inspection process. Therefore, the minute surface defects described above can also be captured. 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, and minute surface defects can be easily captured. In the present 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 having an arithmetic average roughness Ra of 0.2 μm or less and a maximum height Rz of 2.0 μm or less on the surface of the thin metal plate. If a thin metal plate that satisfies this condition is inspected, the reflection of the stripe pattern in the first defect inspection step becomes clearer, so that the accuracy of capturing defects can be further increased. The surface glossiness of the thin metal plate to be inspected in the present embodiment is preferably 100 or more and more preferably 105 or more at 85 ° glossiness. Thereby, the shape defect and surface defect detection accuracy in the first defect process and the second defect process can be further improved. The surface glossiness of the present invention may be evaluated using an existing gloss meter or the like.

  According to the inspection apparatus and the inspection method of the present invention, it is possible to improve the defect inspection accuracy at the time of visual inspection and to expect a significant reduction in the time required to find a defect. The present invention can be applied not only to visual inspection but also to image inspection using a photographing device such as a CCD camera.

  First, a sample for inspection was prepared. The sample used was a 0.1 mm-thick Fe-Ni alloy thin plate cut 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. 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 to 1.2 μm. Moreover, the glossiness (Gs (85 °)) based on JISZ8741 (1997) on the surface of the sample was measured in advance using a gloss meter, and as a result, it was confirmed to show a value of 110 to 120. Subsequently, the prepared sample was inspected using the inspection apparatus shown in FIG. First, the prepared sample was placed on the inspection table, and the first defect inspection process 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 is an average value obtained by measuring a 400 mm × 1000 mm range at the center of the examination table using an illuminometer. In addition, this average value shows the average of the measured values obtained by measuring five arbitrary positions in a measurement area of 400 mm × 1000 mm. A warm light source (correlated color temperature: 2700K to 3000K) is applied as the second light source.

  FIG. 5 shows a surface photograph of the metal thin plate when the first defect inspection process is performed. From FIG. 5, the striped pattern was irradiated to the surface of the metal thin plate, and the distortion of the striped pattern was observed in the part surrounded by the broken line. As a result of observing the portion where this distortion occurred in detail, it was confirmed that the dent was about 0.3 mm deep. In this way, it has been possible to detect even the minute shape defects that have been difficult to capture visually 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 could be captured in the first defect inspection process. Subsequently, the first light source was turned off, the second light source was turned on, and a second defect inspection process was performed. When performing the second defect inspection process, the metal thin plate was observed while changing the inspection table at hand within a range of ± 20 ° from the horizontal state. As a result, as shown in FIG. 6, it was possible to detect surface defects (locations surrounded by broken lines) that could not be detected in the first defect inspection process.

  As yet another example, the material of the thin plate was changed to martensitic stainless steel (equivalent to SUS420J2), and inspection was performed using the apparatus of the present invention. The sample had a thickness of 0.1 mm, and was cut into a width of about 45 mm and a length of 100 mm, and a plurality of the samples were placed on an inspection table for inspection. The setting items of the inspection apparatus were the same as those in Example 1. In addition, as a result of measuring the glossiness (Gs (85 °)) based on JISZ8741 (1997) on the sample surface in advance, it was also confirmed to show a value of 110-120. 7 and 8 show photographs of the surface of the thin metal plate when the first defect inspection process is performed. Note that FIG. 7 is an observation of two samples, and the black line between the two samples is the interval between the two samples. FIG. 8 is an enlarged photograph of part B in FIG. As shown in FIG. 8, by using the measuring apparatus of the present embodiment, it is possible to visually observe the sag portion (micro R shape) 16 formed on the edge of the thin metal plate. Usually, such a sag portion is difficult to visually observe because the formation region becomes smaller as the plate thickness becomes thinner. However, by applying the measuring apparatus and the measuring method of the present embodiment, the reflectance change of the sagging formation portion is more emphasized by the shadow of the stripe pattern, and the shape change can be easily observed visually. Further, by inspecting a plurality of samples placed on the inspection table, it was possible to inspect a plurality of production lots at the same time, and to inspect efficiently and accurately.

DESCRIPTION OF SYMBOLS 1 1st light source 2 2nd light source 3 Inspection stand 4 Striped pattern formation member 5 Frame 10 Light blocking part 16 Sagging part 20 1st light source part h1 Distance between 1st light source and striped pattern formation member Striped pattern formation member and inspection Distance to the table L1 Width of the light blocking part L2 Distance between the light blocking parts α First light source angle β Second light source angle γ Tilt angles θ1, θ2 of the striped pattern forming member

Claims (6)

In a thin metal plate inspection apparatus for inspecting a thin metal plate,
An inspection table for placing a metal thin plate;
A first light source unit that emits striped light on the inspection table;
A thin metal plate inspection apparatus comprising: a second light source that irradiates light toward the inspection table from a direction different from the striped light. The first light source unit is
A first light source that emits light toward the inspection table;
A striped pattern forming member that is disposed between the first light source and the inspection table and irradiates a striped pattern on the inspection table with light from the first light source. apparatus.   The metal sheet inspection apparatus according to claim 1, wherein the inspection table can be inclined at a predetermined angle from a horizontal state.   The thin metal plate inspection apparatus according to claim 1, wherein the second light source is located closer to the inspection table than the first light source unit. In the inspection method of a thin metal plate using the inspection apparatus according to any one of claims 1 to 4,
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 form of the irradiated stripe pattern Process,
Irradiating the metal thin plate with light from the second light source, and inspecting the metal thin plate, a second defect inspection step;
A method for inspecting a metal thin plate, comprising:   6. The method for inspecting a metal thin plate according to claim 5, wherein the metal thin plate has a thickness of 1 mm or less and a surface roughness of Ra ≦ 0.2 μm and Rz ≦ 2.0 μm.