JP3200424B2 - Defect inspection method by infrared thermography - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for inspecting defects of a material or a product by infrared thermography, and more particularly to an infrared thermography using a paint which has high emissivity of infrared rays, has excellent detection accuracy, can be easily removed, and is quick-drying. A defect inspection method.

[0002]

2. Description of the Related Art A defect inspection method using infrared thermography of this type can be used for nondestructively inspecting various defects such as corrosion of a steel plate of an automobile and a flaw inside a structure. For example, when an object to be inspected is irradiated with a heat pulse using a flash lamp or the like, the heat conduction speed due to the heat pulse changes due to corrosion or flaws, and this change is reflected in the surface temperature of the object to be inspected. By capturing the surface temperature of the inspection object with an infrared camera and outputting the temperature distribution as a temperature distribution, it is possible to specify the presence or absence of a defect, its location, and the degree of the defect in a non-destructive state.

In such a defect inspection method using infrared thermography, it is desirable to apply a paint having a high infrared emissivity to the surface of the inspection object in order to improve the detection accuracy of the surface temperature of the inspection object by the infrared camera. You. As such a paint, an acrylic lacquer paint has been conventionally used.

[0004]

However, since the conventional acrylic lacquer paint is an oil-based paint, it is difficult to remove the paint film after inspection. Therefore, there is a problem that the inspection object cannot be used again.

[0005] In addition, there is a problem that the base material may be damaged due to its oiliness, and the range of application is limited. Further, since it takes time from application of the paint to drying, there is a problem that workability is poor.

The present invention has been made in view of such problems of the prior art, and has high infrared emissivity, excellent detection accuracy, can be easily removed, and uses an infrared thermography using a quick-drying paint. It is an object of the present invention to provide a defect inspection method according to the present invention.

[0007]

(1) In order to achieve the above object, a defect inspection method using infrared thermography according to the present invention provides an infrared camera which acquires a thermal image of an inspection object given a temperature field using an infrared camera. In the defect inspection method using thermography, a coating containing a carbon-based black pigment, a solvent containing alcohols and aliphatic hydrocarbons, and a dispersant is applied to the surface of the inspection object. Acquiring a thermal image through the thermal image.

In the defect inspection method using infrared thermography according to the present invention, a paint containing a carbon black pigment, a solvent containing alcohols and aliphatic hydrocarbons, and a dispersant is applied to the surface of the inspection object. This paint has a high infrared emissivity and is black, so it has high infrared detection accuracy on the surface of the test object, and since it contains no resin, it is quick-drying. It can be easily removed after inspection and has excellent workability. Further, since the solvent as a volatile component contains alcohols and aliphatic hydrocarbons as main components, there is very little danger of immersing the test object, and therefore, the solvent can be applied to a wide range of test objects.

(2) In the above invention, examples of the black pigment contained in the paint include triiron tetroxide, biotite, graphite, carbon black and the like. Graphite or carbon black is preferred, and carbon black is particularly preferred. Is more preferred.

Since ferric oxide has a large specific gravity, its dispersibility in a solvent is relatively poor, and biotite cannot be said to be good in its dispersibility in a solvent. When the aerosolization is performed, nozzle clogging may occur.

The dispersibility of graphite is good.
Also excellent in removing film. However, due to the dark gray color, the infrared emissivity is slightly lower than that of carbon black. On the other hand, carbon black is excellent in all of dispersibility, redispersibility, removability of a coating film and infrared emissivity, and furthermore, the risk of nozzle clogging is extremely small.

As the solvent contained in the paint, for example, M
Examples include alcohols such as EK denatured alcohol, normal propanol and ethyl alcohol, aliphatic hydrocarbons such as normal heptane and cyclohexane.

The dispersant contained in the paint is for dispersing the above-mentioned black pigment in a solvent, and is not particularly limited. Examples thereof include polyoxyethylene sorbitan ester, polyoxyethylene sorbitan laurate, alkyl allyl ether, and polyallyl ether. Nonionic (nonionic) surfactants such as oxyethylene alkyl ether can be exemplified.

(3) In the above invention, the mixing ratio of the pigment, the solvent and the dispersing agent contained in the coating material is not particularly limited.
Less than 0% by weight, the solvent is 70% by weight or more and less than 99% by weight,
Preferably, the dispersant is less than 5% by weight.

When the amount of the black pigment is 30% by weight or more, it is difficult to form a uniform coating film and to remove the coating film, and when the amount is less than 1% by weight, a thin black coating film is formed and infrared emissivity is reduced. . On the other hand, when the content of the dispersant is 5% by weight or more, it becomes difficult to remove the coating film.

(4) In the above invention, it is more preferable that the paint is applied by aerosolization using LPG or the like as a spray gas from the viewpoint of workability.

[0017]

According to the present invention, since the surface of the object to be inspected has a high infrared emissivity, can be easily removed, and is applied with a quick-drying paint, the inspection is performed. The detection accuracy is excellent, and the accuracy of specifying the presence / absence of a defect, a part, a range, a degree, etc. is improved. Further, since the inspection can be performed in a short time after the application of the paint, the work efficiency is excellent. Furthermore, since the coating film can be easily removed after the inspection and there is no possibility of damaging the inspection object, the invention can be applied to a completed product or an inspection object of any material.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. First, an example of an inspection system using a defect inspection method using infrared thermography according to the present invention will be described.

FIG. 1 is a conceptual diagram showing a defect inspection system using a defect inspection method by infrared thermography according to the present invention. A flash lamp 13 for providing a temperature field and an infrared camera 12 for detecting infrared radiation emitted from the surface of the steel plate 2 to detect a temperature distribution on the surface of the steel plate 2 are provided.

The infrared camera 12 is arranged substantially at the center of the housing 11 so that infrared light from the steel plate 2 can be obtained without bias. The flash lamp 13 is used for the steel plate 2.
Are arranged on both sides of the infrared camera 12 so that a uniform heat pulse is applied to the infrared camera 12.

The image data obtained by the infrared camera 12 is sent to an image processing device 14 composed of a personal computer or the like, where it is processed and then a desired image is displayed on a display 15.

The defect inspection system 1 can be applied to, for example, inspection of the corrosion state of a steel plate 2 of a completed vehicle.

In this case, first, a coating material for improving the emissivity of infrared rays is applied to the surface of the steel plate 2 to form a coating film 3. This paint is made by adding a carbon black pigment such as carbon black or graphite, together with a dispersant such as a nonionic surfactant, to a solvent containing alcohols and aliphatic hydrocarbons. Spray 2 Since this paint is quick-drying, the inspection can be started in a short time after spraying, and since there is no risk of attacking the steel plate 2 or the overcoat film formed thereon, The site is not restricted.
Further, since the coating film 3 can be easily removed by using water or a blackboard eraser after the inspection, the defect inspection can be performed even for a completed vehicle. Further, since the emissivity of infrared rays is high, the influence of disturbance can be reduced, and the detection accuracy of infrared rays is improved.

After the coating film 3 is formed, the flash lamp 13 is operated to generate a heat pulse, and a temperature field is applied to the steel plate 2. At this time, if the corroded portion 21 exists on the back surface of the steel plate 2 as shown in the figure, the transmission speed of the heat pulse heat inside the steel plate changes, and the corroded portion 21
The surface temperature of the part where the corroded portion 21 exists becomes higher, and the surface temperature of the part where the corroded portion 21 does not exist becomes relatively lower. This temperature distribution is acquired by the infrared camera 12 and the image processing device 14
, The presence or absence and location of the corroded portion 21, the degree of corrosion (corrosion depth), and the like can be displayed on the display 15. When the inspection is completed, the coating film 3 is removed using water, a blackboard eraser, or the like.

[0025]

Next, the present invention will be described in more detail. Example 1 First, a paint to be applied to the surface of the steel plate 2 as an inspection object was prepared. This paint is made of carbon black (carbon black MA10 manufactured by Mitsubishi Chemical Corporation) as a carbon black pigment.
0) 10% by weight and polyoxyethylene sorbitan ester as a dispersant (Nonion LT manufactured by NOF Corporation)
-221) 2% by weight was added to 57% by weight of MEK-denatured alcohol, 2% by weight of normal propanol and 29% by weight of normal heptane as solvents, and sufficiently stirred and dispersed using a dissolver or the like. The obtained coating material was aerosolized using LPG as a filling gas, and then sprayed on a steel plate to form a coating film 3. The coating thickness of the coating film 3 is about 25
μm.

The steel sheet 2 on which the coating film 3 is formed is set in the defect inspection system 1 shown in FIG. 1, and the infrared emissivity of the coating film 3 is visually evaluated based on the thermal image acquired by the infrared camera 12. did. A sample with a high infrared emissivity and a very good one was marked with “◎”, a good one with “○”, a slightly poor one with “△”, and a very poor one with “x”.

Further, the dispersibility of the pigment when the paint was aerosolized was visually evaluated, and those with extremely good dispersibility were evaluated as “◎”, those with good dispersibility as “○”, those with slightly poor dispersibility as “△”, Very poor grades were marked "x".

Further, it was observed whether nozzle clogging occurs when the paint is aerosolized and sprayed. The case where no nozzle clogging occurred was evaluated as “「 ”, and the case where nozzle clogging occurred occurred as“ X ”.

The state of the coating film 3 formed on the surface of the steel sheet 2 was visually observed to evaluate its uniformity. The coating film 3 was evaluated as “○” when it was uniform, and “X” when unevenness was observed and uneven.

After a thermal image was obtained by the infrared camera 12, the coating film 3 was removed by washing with water, and the workability of removing the coating film at this time was evaluated. Those that could be removed very easily are "◎",
Those that could be easily removed were marked with “○”, those that were difficult to remove were marked with “△”, and those that couldn't be removed were marked with “x”.

Table 1 shows the results of the infrared emissivity, pigment dispersibility, nozzle clogging, uniformity of the coating film, and removability of the coating film.

Example 2 Graphite as a carbon-based black pigment (CPB-6 manufactured by Chuetsu Graphite Co., Ltd.) was used as a coating material applied to the surface of the steel sheet 2.
20% by weight and polyoxyethylene sorbitan ester as a dispersant (Nonion LT-2 manufactured by NOF Corporation)
21) 2% by weight was added to 51% by weight of MEK-modified alcohol as a solvent, 2% by weight of normal propanol and 25% by weight of normal heptane, and sufficiently stirred and dispersed using a dissolver or the like. The obtained coating material was aerosolized using LPG as a filling gas, and then sprayed on a steel plate to form a coating film 3. The coating thickness of the coating film 3 is about 25 μm
Met.

The paint and the coating film were evaluated for infrared emissivity, pigment dispersibility, nozzle clogging, uniformity of the coating film, and removability of the coating film in the same manner as in Example 1. Table 1 shows the results.

Example 3 As a coating material to be applied to the surface of the steel sheet 2, 2% by weight of carbon black as a carbon-based black pigment (MB manufactured by Orient Chemical Industry Co., Ltd.) and 4% by weight of magnesium carbonate (4A manufactured by Kyowa Chemical Industry Co., Ltd.) %, Erosil (Ezil # 200 manufactured by Japan Aerosil Co., Ltd.) 1% by weight and Carplex (Carplex # 6 manufactured by Shionogi & Co., Ltd.)
7) 3% by weight of polyoxyethylene sorbitan laurate as a dispersant (Newco.
L # 25) 1% by weight and alkyl acetalized polyvinyl alcohol (BL-1 manufactured by Sekisui Chemical Co., Ltd.)
% By weight and 70% by weight of ethyl alcohol as a solvent
And 18% by weight of normal heptane, and sufficiently stirred and dispersed using a dissolver or the like. The obtained coating material was aerosolized using LPG as a filling gas, and then sprayed on a steel plate to form a coating film 3. The coating thickness of the coating film 3 is about 5
It was 0 μm.

The paint and the coating film were evaluated in the same manner as in Example 1 for infrared emissivity, pigment dispersibility, nozzle clogging, uniformity of the coating film, and removability of the coating film. Table 1 shows the results.

[0036]

[Table 1]

COMPARATIVE EXAMPLE 1 As a paint applied to the surface of the steel sheet 2, iron trioxide (BL-500, manufactured by Titanium Industry Co., Ltd.) 10 as a black pigment was used.
% By weight and a polyoxyethylene sorbitan ester as a dispersant (Nonion LT-22 manufactured by NOF Corporation)
1) 2% by weight was added to 57% by weight of MEK-denatured alcohol as a solvent, 2% by weight of normal propanol and 29% by weight of normal heptane, and sufficiently stirred and dispersed using a dissolver or the like. The obtained coating material was aerosolized using LPG as a filling gas, and then sprayed on a steel plate to form a coating film 3. The coating thickness of the coating film 3 is about 25 μm
Met.

When the pigment dispersibility of the paint and the coating film was evaluated in the same manner as in Example 1, the dispersibility was extremely poor, and the paint and the paint could not be used. Therefore, other evaluations were not performed (see Table 2).

Comparative Example 2 As a paint to be applied to the surface of the steel sheet 2, biotite as a black pigment (color mica HC-
8372) 15% by weight and 2% by weight of polyoxyethylene sorbitan ester (Nonion LT-221 manufactured by NOF CORPORATION) as a dispersant, 52% by weight of MEK-modified alcohol as a solvent, 2% by weight of normal propanol and normal It was added to 29% by weight of heptane, and sufficiently stirred and dispersed using a dissolver or the like. The obtained coating material was aerosolized using LPG as a filling gas, and then sprayed on a steel plate to form a coating film 3. The coating thickness of the coating film 3 was about 25 μm.

When the paint and the coating film were evaluated for nozzle clogging in the same manner as in Example 1, nozzle clogging occurred. Therefore, other evaluations were not performed (see Table 2).

[0041]

[Table 2]

From the above, the paints of Examples 1 to 3 improve the emissivity of infrared rays, are excellent in workability such as quick drying and removability, and are suitable for defect inspection by infrared thermography. confirmed.

The embodiments and examples described above have been described in order to facilitate understanding of the present invention, but are not intended to limit the present invention. Therefore, each element disclosed in the above embodiments and examples is intended to include all design changes and equivalents belonging to the technical scope of the present invention.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram showing an example of an inspection system using a defect inspection method using infrared thermography according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Defect inspection system 11 ... Housing 12 ... Infrared camera 13 ... Flash lamp 14 ... Image processing apparatus 15 ... Display 2 ... Steel plate (inspection object) 21 ... Corrosion part 3 ... Coating

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tadashi Komai Nissan Motor Co., Ltd. (2) Takaracho, Kanagawa-ku, Yokohama, Kanagawa Prefecture (72) Inventor Jun Kubo 2 Takaracho, Kanagawa-ku, Yokohama, Kanagawa Nissan Motor Co., Ltd. (72) Inventor Hidetake Harada 1-22-13 Oi, Shinagawa-ku, Tokyo Ishikawa Island Inspection & Measurement Co., Ltd. (72) Inventor Kunishi Hanasaki 1-44 Shinmeicho, Saiwai-ku, Kawasaki-shi, Kanagawa Prefecture Nippon Oil & Fat Co., Ltd. In the factory (72) Inventor Koji Uemura 1055 Takada, Kashiwa-shi, Chiba Pref. Eisin Chemical Co., Ltd. Chiba factory (58) Fields investigated (Int. Cl. ⁷ , DB name) G01N 21/91 C09D 1/00 WPI (DIALOG) )

Claims (8)

(57) [Claims] 1. A defect inspection method using infrared thermography in which a thermal image of an inspection object given a temperature field is acquired by an infrared camera, wherein a carbon black pigment, alcohols, A defect inspection method by infrared thermography, comprising applying a paint containing a solvent containing an aliphatic hydrocarbon and a dispersant, and acquiring a thermal image through the paint film. 2. The defect inspection method by infrared thermography according to claim 1, wherein the carbon-based black pigment mainly contains carbon black or graphite. 3. The paint according to claim 1, wherein said carbon black pigment is 1% by weight or more and less than 30% by weight, and said solvent is 70% by weight or more.
The defect inspection method by infrared thermography according to claim 1 or 2, wherein the content of the dispersant is less than 9% by weight and the content of the dispersant is less than 5% by weight. 4. The defect inspection method according to claim 1, wherein the paint is aerosolized and applied. 5. A paint used for defect inspection using infrared thermography in which a thermal image of an inspection object given a temperature field is obtained by an infrared camera, comprising: a carbon black pigment; an alcohol; A paint used for defect inspection by infrared thermography, comprising a solvent containing hydrogen and a dispersant. 6. The paint for use in defect inspection by infrared thermography according to claim 5, wherein said carbon-based black pigment contains carbon black or graphite as a main component. 7. The carbon-based black pigment is 1% by weight or more and less than 30% by weight, the solvent is 70% by weight or more and less than 99% by weight,
The dispersant is contained in an amount of less than 5% by weight.
A paint used for defect inspection by the infrared thermography described in the above. 8. An aerosol sprayer comprising the paint according to claim 5 and an aerosol filling gas.