JP2000214143A - Production of sham test piece for non-destructive inspection and non-destructive inspection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sham test piece for non-destructive inspection capable of easily and inexpensively obtaining a sham test piece having a grain boundary stress corrosion crack and a non-destructive inspection method applied to this technique. SOLUTION: An arbitrary region of a test piece 2 the same to a metal member constituting an actual machine plant is coated with a metal having a m.p. lower than that of the test piece 2 over an arbitrary range and, after welding heat is applied to the vicinity of the coated region, the coated region is cooled to generate a grain boundary stress corrosion crack within the range of the coated region. By this constitution, a sham examination object 1 for non- destructive inspection having a grain boundary stress corrosion crack near to a natural crack (flaw) generated in an actual machine can be obtained easily and inexpensively.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a simulated test specimen for non-destructive inspection used for non-destructive inspection of metal members constituting a nuclear power plant, and a non-destructive inspection of a real machine to which this technique is applied. It is about the method.

[0002]

2. Description of the Related Art Conventionally, there are various nondestructive inspections as one of required periodic inspections in a nuclear power plant or the like where a high safety is required for a nuclear power plant.

In this non-destructive inspection, a non-destructive inspection device equipped with a sensor such as an ultrasonic flaw detector is attached to an inspection site of an actual plant, for example, a welded portion of a pressure vessel or a pipe joint of a main steam line. Non-destructive inspection for defects such as cracks generated inside or inside the pipe which is not visible from the outside using ultrasonic waves etc., and one nuclear power plant is inspected during one inspection period. Tens to hundreds of inspection sites are to be inspected.

[0004]

By the way, in actually performing such a nondestructive inspection, a simulated test piece in which defects are artificially added to a test piece similar to an actual plant is manufactured in advance. Using this simulated test specimen, a preliminary inspection is performed for the purpose of confirming the performance of the non-destructive inspection device to be used and unifying and improving the inspection technology level. However, since the conventional simulated test piece used for such a preliminary inspection used a notch formed by machining to forcibly impart a crack to the surface of a test piece having a simple shape such as a metal flat plate, There is a drawback that high-precision and high-reliability preliminary inspection cannot be performed. That is,
The cracks that occur in the actual machine are intergranular stress corrosion cracks that occur along the crystal interface of the metal. For this purpose, a simulated test piece having cracks as close to natural grain boundary stress corrosion cracking as possible was required.

[0005] Therefore, for example, a specimen in which stainless steel having a high carbon content is welded is manufactured, and graphite fiber wool is adhered to the surface thereof and immersed in high-temperature and high-pressure water for a long time (several hundred to several thousand hours). Therefore, a method has been proposed in which a grain boundary stress corrosion cracking close to a natural defect is generated on the surface of a test specimen to form a simulated test specimen close to a natural state, but in this method, the specimen itself becomes a custom-made product. In addition, there is a disadvantage that the production cost is extremely high since a large amount of equipment and a long time are required for the production. Moreover, this method has a disadvantage that it is extremely difficult to freely control the length of the crack.

Accordingly, the present invention has been devised in order to effectively solve such problems, and a main object of the present invention is to provide a simulated test specimen having intergranular stress corrosion cracking close to actual natural cracking. And a non-destructive inspection method using the grain boundary stress corrosion cracking technology, which can easily and inexpensively obtain the same.

[0007]

Means for Solving the Problems In order to solve the above-mentioned problems, a first invention is to provide a test piece made of the same material and shape as a metal member constituting a part of an actual plant, with a grain boundary stress of an arbitrary size. In the method for producing a non-destructive test specimen having corrosion cracks, a paint containing a metal having a lower melting point than that of the test piece, such as zinc, tin, or lead, may be added to any part of the test piece. This is a method for producing a simulated test specimen for non-destructive inspection in which welding heat is applied to the vicinity of the applied portion and then cooled to generate intergranular stress corrosion cracking within the applied portion. .

[0008] This makes it possible to easily and inexpensively obtain a simulated test specimen for nondestructive inspection having a natural intergranular stress corrosion crack generated in an actual machine. Further, by arbitrarily setting the application range of the coating material containing the low-melting-point metal, it is possible to obtain a desired length of grain boundary stress corrosion cracking with good control.

Further, the second invention forms a simulated plant including the same structure as the non-destructive inspection site of the actual plant, and the non-destructive inspection site of the simulated plant includes a metal having a lower melting point than that of the simulated plant. The coating is applied over an arbitrary range, and after applying welding heat to the vicinity of the applied portion, the coating is cooled to generate intergranular stress corrosion cracking within the applied portion, and thereafter, a plurality of types of cracks are observed. After performing non-destructive inspection using the non-destructive inspection device, the non-destructive inspection site of the simulated plant was destroyed and the nature of the crack was actually measured. This is a nondestructive inspection method in which a nondestructive inspection site of the actual plant is inspected under the same conditions using a destructive inspection device.

As a result, the properties such as the length and depth of intergranular stress corrosion cracks generated at the nondestructive inspection site of the actual plant can be nondestructively inspected more accurately.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a preferred embodiment of the present invention will be described with reference to the accompanying drawings.

1 to 3 show an embodiment of a method for manufacturing a simulated test piece 1 for nondestructive inspection according to the present invention. In the drawings, reference numerals 2 and 2 denote circular test sections. The metal pipes 3 and 3 are grooves formed at the butted ends of the metal pipes 2 and 2, respectively.

[0013] As shown in FIG.
A metal material constituting the metal pipe 2, for example, SUS3 used in an actual machine
04 or a metal having a lower melting point than carbon steel, for example, a coating containing a low-melting point metal such as zinc may be applied to an arbitrary range (in the present embodiment, as shown in the filled-in portion in the figure, in the circumferential direction of the inner surface thereof). After forming the coating portion 5 by coating over the extended rectangular area, the grooves 3 of the metal pipes 2 are abutted to form a ring-shaped groove. As the low-melting-point metal, other than zinc (melting point: about 420 ° C.), low-melting-point metals such as tin and lead can be used. It is preferable to use tin, lead, or the like.

Next, as shown in FIG. 2, a welding rod 4 made of the same metal material as that of the metal pipe 2 is overlaid R on the ring-shaped groove 3 to perform joint welding. Then, the low-melting-point metal of the coating portion 5 is brittlely broken by “liquid metal embrittlement” by the welding heat generated around the groove 3, and the entire portion of the coating portion 5 has grains close to actual cracks. Interfacial stress corrosion cracking occurs.

SUS304TP, 125A × S
When the welding process was actually performed using the simulated test piece 1 including the pipe of the channel 160, as shown in FIG. 3, the grain boundary stress corrosion cracking C, that is, the metal crystal was formed along the coated portion 5 in the first pass. A continuous crack is generated along the surface, and the shape of the crack is a longitudinal crack C1 mainly generated in the circumferential direction within the coating range.
With the vertical cracks as starting points, the lateral cracks were formed as fine as branches and leaves on the left and right sides in the axial direction. Further, the range of the generated intergranular stress corrosion cracking C was about ± 1 mm with respect to the range of the coating portion 5 for the vertical crack C1, and the crack was surely generated along the range of the coating portion 5.

Therefore, by arbitrarily setting the range of the coating portion 5, it is possible to generate intergranular stress corrosion cracking of any length and width, and it is possible to control the length of this crack in mm. It becomes possible.

On the other hand, when the depth of the intergranular stress corrosion cracking C generated as described above was measured, the depth was about 2 mm at the deepest. Therefore, it has been found that the depth can be controlled in mm by applying a coating containing a low-melting-point metal to the cracks again after one-pass welding and then performing welding.

Therefore, in the method of the present invention, it is possible to easily obtain the simulated test piece 1 having intergranular stress corrosion cracking close to a natural defect in a relatively short time and at high temperature and high pressure conditions as in the conventional method. It can be obtained inexpensively and in a short time without requiring a long time. In addition, intergranular stress corrosion cracking C
Properties, that is, the length and depth can be controlled precisely in units of mm, so that it is possible to accurately obtain grain boundary stress corrosion cracking of any property, and to perform a preliminary test of nondestructive testing equipment And the level of nondestructive inspection technology can be understood and improved. still,
In the present embodiment, a description has been given of a case in which a metal test tube or other metal pipe is used as the simulation test body. However, the simulation test body is not limited to such a metal pipe, and may be a flat plate. Needless to say, it may be a curved plate shape.

FIG. 4 shows an embodiment of a non-destructive inspection method to which this intergranular stress corrosion cracking technique is applied.

That is, in the method of the present invention, first, at the time of nondestructive inspection of an actual plant, a simulated plant including the same structure as the nondestructive inspection site of the actual plant is formed in advance. For example, if the non-destructive inspection site of the actual plant is the pipe joint of the main steam line, only the vicinity of the simulated joint made of the same material and shape as the pipe joint or the main steam line including this simulated joint is formed. I do.

Next, a desired property, that is, a grain boundary stress that can be predicted to occur in an actual machine, is applied to the non-destructive inspection site of the simulated plant, for example, on the inner surface of the weld joint by the above-described grain boundary stress corrosion cracking method. After artificially generating corrosion cracks, the properties of the cracks are non-destructively inspected from the outside of the weld joint using a plurality of types of non-destructive inspection devices (such as UT devices).

At this time, if different inspection results are produced due to the type of the non-destructive inspection device to be used and the inspection method (for example, the scanning direction of the sensor or the emission direction of the ultrasonic wave), the simulation is performed. A non-destructive inspection device that destroys a non-destructive inspection site of a plant, measures the length, depth, and location of the grain boundary stress corrosion cracking accurately and obtains an inspection result that most closely resembles the actual properties. And the inspection method, the non-destructive inspection of the non-destructive inspection part of the actual plant is performed under exactly the same conditions as the simulation plant.

As a result, a non-destructive inspection device and an inspection method most suitable for a non-destructive inspection site of an actual plant can be adopted, so that non-destructive inspection of a non-destructive inspection site of an actual plant can be performed with high accuracy. can do.

[0024]

In summary, according to the present invention, a simulated non-destructive test specimen having intergranular stress corrosion cracking close to a natural crack (defect) generated in an actual machine can be obtained easily and at low cost. Since it is possible to control the properties of the intergranular stress corrosion cracking with high precision, it can greatly contribute to the preliminary inspection of non-destructive inspection equipment such as performance inspection and non-destructive inspection technology level. Such an excellent effect can be exhibited.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing one embodiment of a method for manufacturing a test sample according to the present invention.

FIG. 2 is a cross-sectional view showing one embodiment of a method for manufacturing a test sample according to the present invention.

FIG. 3 is a conceptual diagram showing stress corrosion cracking that has occurred in a coating portion.

FIG. 4 is a process chart showing an example of a nondestructive inspection method according to the method of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Mock test body 2 Metal pipe (test body) 3 Groove 4 Welding rod 5 Coating part R Overlay C Grain boundary stress corrosion cracking

Continuation of the front page (72) Inventor Akira Kato 1 Shinnakahara-cho, Isogo-ku, Yokohama-shi, Kanagawa Ishikawajima-Harima Heavy Industries, Ltd. F-term (reference) 2G047 AA07 AB07 AC02 BC07 BC14 EA16 GJ22

Claims (4)

[Claims] 1. A method for manufacturing a simulated non-destructive test specimen having an intergranular stress corrosion crack of an arbitrary size on the surface of a test specimen made of the same material and shape as a metal member constituting a part of an actual plant, A paint containing a metal having a lower melting point than that of the test piece is applied to an arbitrary portion of the test piece over an arbitrary range. A method for producing a simulated test piece for non-destructive inspection, characterized in that intergranular stress corrosion cracking is generated in the test piece. 2. The non-destructive test specimen according to claim 1, wherein stainless steel or carbon steel is used as the metal specimen, and zinc, tin, or lead is used as the low melting point metal. Production method. 3. A simulated plant including the same structure as the non-destructive inspection site of the actual plant is formed, and a paint containing a metal having a lower melting point than the simulated plant is applied to the non-destructive inspection site of the simulated plant. After applying the welding heat to the vicinity of the applied part, the applied part is cooled to generate intergranular stress corrosion cracking in the area of the applied part. After non-destructive inspection using
The nature of the crack was actually measured, and the non-destructive inspection part of the actual plant was subjected to non-destructive inspection under the same conditions using a non-destructive inspection device showing an inspection value closest to the actual measured value. A nondestructive inspection method characterized by the following. 4. The nondestructive inspection method according to claim 3, wherein zinc, tin, or lead is used as the low melting point metal.