JP4055278B2 - Method for manufacturing non-destructive test specimen and non-destructive test method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for manufacturing a non-destructive inspection simulation specimen used when performing non-destructive inspection of a metal member constituting a nuclear power plant, and a non-destructive inspection method for an actual machine to which this technology is applied.
[0002]
[Prior art]
Conventionally, there are various non-destructive inspections as one of the periodic inspections required in nuclear power plants that require high safety such as nuclear power plants.
[0003]
This non-destructive inspection is performed by attaching a non-destructive inspection device equipped with a sensor such as an ultrasonic flaw detector to an inspection site of an actual plant, for example, a welded part of a pressure vessel or a pipe joint part of a main steam line. This is a non-destructive inspection for defects such as cracks that have occurred inside the pipe or on the inside of pipes that cannot be seen from the outside. ~ Several hundreds of sites are being tested.
[0004]
[Problems to be solved by the invention]
By the way, in actually performing such nondestructive inspection, a simulated test body in which a defect is artificially given to a test body approximating an actual plant is manufactured in advance and used with this simulated test body. Preliminary inspections are being conducted for the purpose of confirming the performance of non-destructive inspection equipment and unifying and improving the inspection technology level. However, since the conventional mock test body used for such preliminary inspection used a forcible notch by machining on the surface of a simple test body such as a metal flat plate, There was a drawback that high-precision and high-reliability preliminary inspection could not be performed. In other words, cracks that occur in actual machines are intergranular stress corrosion cracks that occur along the crystal interface of the metal, and their properties differ greatly from cracks that are forcibly applied by machining. In order to do this, a simulated specimen with cracks that are as close to the natural intergranular stress corrosion cracking as possible was required.
[0005]
Therefore, for example, a test body in which stainless steel with a high carbon content is welded is manufactured, graphite fiber wool is pasted on the surface, and this is immersed in high-temperature and high-pressure water for a long time (hundreds to thousands of hours). A method has been proposed for generating a simulated specimen close to the natural state by generating intergranular stress corrosion cracks close to natural defects on the surface of the body. In this method, the specimen itself is a custom-made product and manufactured. However, since a lot of equipment and a long time are required, the production cost is extremely high. Moreover, this method has a drawback that it is extremely difficult to freely control the length of the crack.
[0006]
Therefore, the present invention has been devised in order to effectively solve such problems, and its main purpose is to easily provide a simulated specimen having intergranular stress corrosion cracking close to actual natural cracking and The present invention provides a novel non-destructive test specimen that can be obtained at low cost and a non-destructive test method that applies this intergranular stress corrosion cracking technique.
[0007]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the first invention is a nondestructive inspection having an intergranular stress corrosion cracking of an arbitrary dimension on the surface of a tubular test body made of the same material and shape as a metal member constituting a part of an actual plant. In the method for manufacturing a mock test specimen for use, a rectangular range extending in the circumferential direction of the inner surface of the test specimen is coated with a paint containing a metal having a melting point lower than that of the test specimen on the inner surface side of one butt end of the test specimen. was applied over this after adding coating vicinity to welding heat, it cooled allowed by non-destructive inspection simulative test product, characterized in that so as to generate intergranular stress corrosion cracking in the coating unit range It is a manufacturing method.
[0008]
This makes it possible to easily and inexpensively obtain a non-destructive test simulation specimen having natural intergranular stress corrosion cracking that occurs in an actual machine. Moreover, the grain boundary stress corrosion cracking of a desired length can be obtained with good control by arbitrarily setting the application range of the paint containing the low melting point metal.
[0009]
Further, the second invention forms a simulated plant having the same structure as the non-destructive inspection site of the actual plant, and has a lower melting point than that of the simulated plant on the inner surface of the simulated pipe joint that is the non-destructive inspection site of the simulated plant. The paint containing the metal is applied over a rectangular range extending in the circumferential direction of the inner surface of the simulated pipe joint, and welding heat is applied to the vicinity of the application portion, and then cooled, and the particles are placed in the application portion range. After generating field stress corrosion cracking and then nondestructively inspecting the nature of the crack using multiple types of nondestructive inspection equipment, actually measure the nature of the crack and best approximate this actual measurement value. This is a nondestructive inspection method in which a nondestructive inspection portion of the actual plant is nondestructively inspected under the same conditions using a nondestructive inspection apparatus that indicates an inspection value.
[0010]
As a result, it is possible to more accurately perform the non-destructive inspection of the properties such as the length and depth of the intergranular stress corrosion cracking occurring at the non-destructive inspection site of the actual plant.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Next, a preferred embodiment for carrying out the present invention will be described with reference to the accompanying drawings.
[0012]
First, FIGS. 1 to 3 show an embodiment of a method for producing a non-destructive inspection simulation test body 1 according to the present invention. In FIG. Pipes 3 are grooves formed at the butt ends of the metal pipes 2, 2, respectively.
[0013]
As shown in FIG. 1, first, a metal material constituting the metal pipe 2, such as SUS304 or carbon steel used in an actual machine, has a lower melting point on the inner surface side of one end of the metal pipe 2. A coating containing a low melting point metal such as zinc, for example, in an arbitrary range (in this embodiment, a rectangular range extending in the circumferential direction of the inner surface as shown in the illustrated filled portion). Then, the application portion 5 is formed by coating, and then the grooves 3 and 3 of the metal pipes 2 and 2 are butted together to form a ring-shaped groove. As the low melting point metal, in addition to zinc (melting point: about 420 ° C.), a low melting point metal such as tin or lead can be used, and the base material for the paint containing the low melting point metal is used. As such, it is preferable to use tin, lead or the like.
[0014]
Next, as shown in FIG. 2, joint welding is performed on the ring-shaped groove 3 by overlaying a welding rod 4 made of the same metal material as the metal pipe 2. Then, the low melting point metal of the application part 5 is brittlely broken by “liquid metal embrittlement” by the welding heat generated around the groove 3, and grains close to actual cracks over the entire range of the application part 5. Field stress corrosion cracking occurs.
[0015]
Then, when the welding process was actually performed using the simulated specimen 1 composed of SUS304TP, 125A × Sch160 piping, as shown in FIG. 3, the intergranular stress corrosion cracking along the coating part 5 was performed in the first pass. C, that is, continuous cracks occur along the metal crystal plane, and the shape of the cracks is mainly vertical cracks C1 occurring in the circumferential direction within the coating range, and branching leaves on the left and right in the axial direction starting from the vertical cracks. It consisted of fine lateral cracks. Moreover, the range of the generated intergranular stress corrosion cracking C was about ± 1 mm with respect to the range of the coated portion 5 with respect to the longitudinal crack C1, and the crack was reliably generated along the range of the coated portion 5.
[0016]
Therefore, by setting the range of the coating portion 5 arbitrarily, it is possible to generate an intergranular stress corrosion cracking having an arbitrary length and width, and to control the crack length in mm units. .
[0017]
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 point. For this reason, it was found that the depth can be controlled in units of mm by performing coating after coating a coating containing a low melting point metal again on the crack after one pass welding.
[0018]
Therefore, according to the method of the present invention, the simulated test body 1 having intergranular stress corrosion cracking close to natural defects can be obtained in a relatively short time, and the high temperature and high pressure conditions and the long time can be obtained as in the conventional method. Therefore, it can be obtained inexpensively and in a short time. In addition, since the properties of the intergranular stress corrosion cracking C, that is, the length and depth can be accurately controlled in mm units, it is possible to obtain the intergranular stress corrosion cracking of any property with high accuracy. It can greatly contribute to the performance inspection of a certain nondestructive inspection device and the grasp and improvement of the nondestructive inspection technology level. In the present embodiment, the simulation test body has been described using a metal pipe such as a main steam line. However, the simulation test body is not limited to such a metal pipe. Needless to say, a flat plate or curved plate may be used.
[0019]
Next, FIG. 4 shows one embodiment of a nondestructive inspection method applying this intergranular stress corrosion cracking technique.
[0020]
That is, according to the method of the present invention, first, when performing a 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 a pipe joint part of the main steam line, only the vicinity of the simulated pipe joint part made of the same material and shape as the pipe joint part or the main steam line including this simulated joint part Form.
[0021]
Next, at the non-destructive inspection site of this simulation plant, for example, the inner surface of the weld joint is subjected to the desired properties, that is, the intergranular stress corrosion cracking that can be predicted to occur in the actual machine by the above-described intergranular stress corrosion cracking application method. After the generation, the cracks are nondestructively inspected from the outside of the weld joint using a plurality of types of nondestructive inspection devices (UT device or the like).
[0022]
At this time, if different inspection results are obtained due to the type of non-destructive inspection apparatus used or the inspection method (for example, the scanning direction of the sensor or the direction of ultrasonic wave emission), Non-destructive inspection equipment and inspection method that destroyed the destructive inspection site, actually measured the length, depth, part, etc. of the intergranular stress corrosion cracks, and obtained the test results that most closely approximated the actual properties And nondestructive inspection of the nondestructive inspection site of the actual plant under the same conditions as the simulation plant.
[0023]
As a result, the most suitable nondestructive inspection device and inspection method for the nondestructive inspection site of the actual plant can be adopted, so that the nondestructive inspection of the nondestructive inspection site of the actual plant can be reliably performed with high accuracy. it can.
[0024]
【The invention's effect】
In short, according to the present invention, it is possible to easily and inexpensively obtain a non-destructive test specimen having intergranular stress corrosion cracking close to natural cracks (defects) generated in an actual machine, and the intergranular stress corrosion. Since it is possible to control the properties of cracks with high accuracy, it has excellent effects such as the ability to greatly contribute to the performance inspection of non-destructive inspection equipment, which is a preliminary test, and the understanding and improvement of the level of non-destructive inspection technology. It can be demonstrated.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an embodiment of a method for producing a simulated specimen according to the present invention.
FIG. 2 is a cross-sectional view showing an embodiment of a method for manufacturing a simulated specimen 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 diagram showing an example of a nondestructive inspection method according to the method of the present invention.
[Explanation of symbols]
1 Simulated specimen 2 Metal piping (test specimen)
3 Groove 4 Welding rod 5 Application part R Overlay C Intergranular stress corrosion cracking

Claims (4)

In a method for producing a simulated specimen for nondestructive inspection having an intergranular stress corrosion cracking of an arbitrary size on the surface of a tubular specimen having the same material and shape as a metal member constituting a part of an actual plant, A paint containing a metal having a melting point lower than that of the test specimen is applied to one butt end inner surface over a rectangular area extending in the circumferential direction of the inner surface of the test specimen, and welding heat is applied in the vicinity of the application section. A method for producing a simulated specimen for nondestructive inspection, characterized in that, after adding, cooling is performed to cause intergranular stress corrosion cracking in the range of the coated portion.   The method for producing a nondestructive 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. Forming a simulated plant including the same structure as the non-destructive inspection site of actual plant, the simulated pipe joint portion inner surface is non-destructive inspection site of the simulated plant, the simulated paint containing a low melting point of the metal than the simulated plant Applying over a rectangular range extending in the circumferential direction of the inner surface of the pipe joint , applying welding heat in the vicinity of this applied part, cooling and generating intergranular stress corrosion cracking in the applied part range, Then, after the non-destructive inspection of the crack properties using multiple types of non-destructive inspection equipment, the crack properties were actually measured, and the non-destructive inspection showed the inspection value closest to this actual measurement value. A nondestructive inspection method characterized in that a nondestructive inspection site of the actual plant is nondestructively inspected under the same conditions using an apparatus.   4. The nondestructive inspection method according to claim 3, wherein zinc, tin, or lead is used as the low melting point metal.

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