JPH02167453A - Method and device for pressure-reduction dye penetrant flaw detection - Google Patents

Abstract

PURPOSE:To detect a microdefect by dipping a sample body in a penetrant under reduce pressure and putting the sample body back under atmospheric pressure. CONSTITUTION:The sample body 1 which is a turbine rotor is mounted on a sample mounting basket 3 in a pressure-reduced container 2 and after a leak valve 4 is closed, the pressure in the container 2 is reduced by a vacuum pump 5 to remove the air in the surface defect part 7 of the sample body 1. Then, the basket 3 is dipped in the water-washable fluorescent penetrant 9 held at the lower part in the container 2. Then the valve 4 is opened to produce the atmospheric pressure in the container 2 and the basket 3 is lifted to the upper part in the container 2 from the penetrant 9 to take the sample body 1 out. This sample body 1 is washed to remove excessive liquid 9 sticking on the surface and after the defect part 7 is colored, the blade section of the rotor is observed through a stereoscopic microscope to detect the size of the defect. The penetrant 9 penetrates every place of the defect part 7 with the force produced when air enters the defect when the container 2 is put back to the atmospheric pressure and the microdefect is accurately detected.

Description

Detailed Description of the Invention [Industrial Application Fields] The present invention relates to a method for detecting defects in a specimen by immersing the specimen in a penetrating liquid while exposing the specimen to a reduced pressure after heating; Regarding equipment.

[Prior Art] Penetrant testing methods have been widely used to detect defects in intermediate materials and products such as metals, synthetic resins, and ceramics.

In this test method, the specimen is immersed in a penetrating solution such as a dye penetrating solution or a fluorescent penetrating solution, and the penetrating solution is infiltrated into the defects in the specimen.The penetrating solution on the surface is then washed, and a developer is used to form capillary tubes. This was done by sucking out the penetrating liquid and creating an indicator pattern, which was then observed visually or under magnification.
All these operations were performed under atmospheric pressure. especially,
Fluorescent penetrant testing is capable of detecting surface defects of approximately 1,107 tons, and is important as a method for detecting surface defects in structural ceramic parts, for example, but it can also be used under extremely harsh conditions such as in ceramic gas turbines. For parts that are used below and require high reliability, the smaller 10J
It is desired that micro defects of the order of Lm or less can be detected.

[Problem to be solved by the invention] However, in the conventional penetrant testing method described above,
Since the specimen is immersed in the penetrating liquid under normal pressure, when the size of the defect is small, as shown in Figure 2, the specimen
The penetrating liquid 9 is blocked by the air 8 in the defect 7.
It is unable to penetrate into the interior and only closes the opening 10 of the defect. Therefore, with conventional penetrant testing, there is a limit to the size of defects that can be detected.
There was a problem that it was about 0 gm or more. Furthermore, since the size of the defect on the surface of the sample is small and the penetrating liquid does not sufficiently penetrate into the defect, the cleaning process washes away the penetrating liquid inside the defect, making it impossible to detect the defect.

Furthermore, since the infiltration takes place using capillary action, the infiltration time is as long as 10 to 15 minutes.

[Means for Solving the Problems] Therefore, as a result of intensive studies in view of the above-mentioned conventional problems, the present inventor placed the sample body under reduced pressure to remove air within the defect, and then immersed it in a penetrating liquid, and It was discovered that when the specimen is returned to the flame pressure after immersion, the penetrating liquid penetrates into even the smallest defects in the specimen, making it possible to detect the defects, and has thus arrived at the present invention.

That is, according to the present invention, in a penetrant flaw detection method in which a sample is immersed in a penetrating liquid and the defective portion of the sample is tested by immersing the penetrating liquid, the sample is exposed to reduced pressure. A reduced-pressure penetrant testing method is provided, which is characterized in that the specimen is immersed in a penetrating liquid and then placed under atmospheric pressure.

Further, according to the present invention, in a penetrant tester that performs flaw detection by immersing a sample in a penetrating liquid and immersing the defective part of the sample in the penetrating liquid, the air in the defective part of the sample is removed. There is also provided a reduced-pressure penetrant flaw detection apparatus, characterized in that it is equipped with a reduced-pressure container for holding the permeate and a vacuum device for reducing the pressure in the reduced-pressure container.

In the present invention, after putting the sample into the vacuum container, the inside of the vacuum container is preferably kept at zero. The degree of vacuum is set to 1 mmHg or more, and the sample body from which the defective part has been deaerated is immersed in a penetrant liquid for flaw detection, preferably for io seconds or more.

Further, it is desirable that the sample body is permeated at a temperature of 30 to 40°C.

After immersing the sample in the osmotic liquid, either: 1. Bring the pressure of the vacuum container to atmospheric pressure while the sample is immersed in the osmotic solution, or 2. to atmospheric pressure.

In both methods (■) and (■) above, the pressure inside the defect is reduced by placing the specimen under reduced pressure, and the force of air entering the defect when the pressure is released to atmospheric pressure is used to draw the penetrating liquid into the defect. The penetrating solution penetrates into every corner of the defect, completely penetrating into even the smallest details that the penetrating solution did not penetrate during immersion. Furthermore, the penetration time is shortened to 2 to 3 minutes.

[Examples] Hereinafter, the present invention will be explained in more detail with reference to illustrated examples, but the present invention is not limited to these examples.

FIG. 1 is a schematic diagram showing an embodiment of a reduced pressure penetrant flaw detection apparatus according to the present invention.

A sample body 1 made of a ceramic molded body is placed on a cup 3 which extends from the central ceiling of the vacuum container 2 and is movable up and down. A penetrating liquid 9 for flaw detection is held in the lower part of the reduced pressure container 2. Further, a vacuum pump 5 is connected to the reduced pressure container 2 to reduce the pressure inside the reduced pressure container 2. Further, a heater 11 is installed around the inside of the vacuum container 2 to keep the permeate at a predetermined temperature.

In the above configuration, the sample l, which is a φ90II11 turbine rotor, is placed on the sample mounting cap 3 in the vacuum container 2 heated to 30°C, and then, after closing the leak valve 4, the vacuum pump 5 is operated. to reduce the pressure inside the vacuum container 2 to 0.
The temperature was lowered to 1 mmHg, and the air inside the sample surface defect 7 was removed. Next, the sample body 1 was placed in the water-washable fluorescent penetrant liquid 9 held at the bottom of the vacuum container 2, and the heel 3 was immersed in a downward motion and held in that state for 10 seconds.

Next, the leak valve 4 of the reduced pressure container 2 is opened to return the pressure inside the reduced pressure container 2 to atmospheric pressure, and the basket 3 carrying the sample l is lifted up from the permeate 9 into the reduced pressure container 2, and the sample l is removed. I took it out. After cleaning the sample 1 to remove excess penetrating liquid 9 adhering to the surface of the sample 1 and coloring the defect 7, the cross section of the rotor blade was observed with a stereomicroscope to determine the size of the defect. Detected.

As a result, defects larger than approximately 5gm can be detected,
Accurate detection results were obtained as shown in the stereoscopic micrograph of FIG. 3(a).

On the other hand, using the same turbine rotor sample body as in the example, the sample body was treated under the same conditions as in the example except that the sample body was not subjected to depressurization treatment in a vacuum container, and the obtained sample body was observed. Only defects larger than 20 gm could be detected, resulting in detection results with poor accuracy as shown in the stereoscopic micrograph of FIG. 3(b).

From the above results, it can be seen that the reduced pressure penetrant testing method of the present invention is superior to the conventional method in detecting minute defects.

[Effects of the Invention] As explained above, the present invention provides the following effects.

In the reduced pressure penetrant testing method according to claim 1, the sample is first placed under reduced pressure to remove air in defects in the sample, then immersed in a penetrating liquid, and then the sample is returned to atmospheric pressure. This allows the penetrating liquid to penetrate into every corner of the specimen, making it possible to detect smaller micro-defects compared to the conventional method, which uses only capillary action to penetrate the penetrating liquid into the specimen. .

By using the reduced-pressure penetrant flaw detection apparatus according to the second aspect of the present invention, the penetrating liquid can be sufficiently penetrated into every corner of the sample body, and minute defects can be detected with high precision.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram showing an embodiment of the reduced pressure penetrant tester according to the present invention, and Figs. 2 (a), (b), and (c) are explanations showing the process of penetration of the penetrant into the defective part of the specimen. Figure 3(a) is a stereoscopic micrograph (280x magnification) of an inspection example using the low-pressure penetrant testing method of the present invention, showing the particle structure of ceramics, and Figure 3(b) is an inspection example using the conventional method. This is a stereoscopic micrograph (magnification = 80x) showing the grain structure of the ceramic.

Claims (2)

[Claims] (1) In a penetrant testing method in which flaws are detected by immersing a sample in a penetrating liquid and immersing the defective part of the sample in the penetrating liquid, the sample is immersed in the penetrating liquid while being exposed to reduced pressure. A reduced pressure penetrant testing method characterized by immersing the sample body and then placing the sample body under atmospheric pressure. (2) In a penetrant tester that performs flaw detection by immersing a sample in a penetrating liquid and immersing the defective part of the sample in the penetrating liquid, the air in the defective part of the sample is degassed and the A reduced-pressure penetrant flaw detection device comprising: a reduced-pressure container for holding a penetrant; and a vacuum device for reducing the pressure inside the reduced-pressure container.