KR20210108120A - Testing apparatus of measuring starting time of stress corrosion cracking and thereof method - Google Patents

Abstract

One embodiment of the present invention is to provide a testing apparatus for measuring the start time of stress corrosion cracking, and a method therefor, configured to evaluate the stress corrosion cracking characteristics of highly corrosion-resistant structural materials and parts used in a high-temperature and high-pressure water environment such as a nuclear power plant so as to increase the number and types of specimens which can be tested simultaneously when acquiring lifetime data and shorten the testing time. The testing apparatus for measuring a start time of stress corrosion cracking in accordance with one embodiment of the present invention comprises: a pressure unit which fixes a specimen to a pressure boundary between a high-pressure side and a low-pressure side; a solution storage unit provided in a solution circulation line and configured to store a solution supplied to the high-pressure side of the pressure unit; a high-pressure pump which supplies the solution stored in the solution storage unit to the high-pressure side of the pressure unit and circulates the solution back to the solution storage unit; a heating unit provided to be included in the pressure unit and configured to heat the internal temperature of the pressure unit to a set temperature; and a pressure gauge which is connected to the low-pressure side of the pressure unit, detects the pressure at the low-pressure side of the pressure unit when the surface of a specimen exposed to high temperature and high pressure water environment ruptures due to stress corrosion cracking.

Description

Test apparatus and method for measuring stress corrosion cracking initiation time

The present invention relates to a stress corrosion cracking initiation time measurement test apparatus and method.

Various material deteriorations occur in nickel-based alloys and stainless steel structural materials and parts used in high-temperature, high-pressure water environments such as nuclear power plants and thermal power plants. In particular, in the case of stress corrosion cracking, if a small defect occurs during operation, it is difficult to detect it before damage or failure of the equipment. Therefore, it is necessary to predict the onset time of stress corrosion cracking and the probability of failure of equipment and parts, and to operate the equipment safely by replacing or maintaining parts and equipment during the planned preventive maintenance period.

To this end, a predictive model is being developed based on the data that evaluated the stress corrosion cracking characteristics of these materials in various environments and conditions. Conventionally, a method of determining whether stress corrosion cracking occurs and measuring the stress corrosion cracking initiation time by periodically inspecting the corrosion state after exposing a small number of specimens to a corrosive environment for a long period of time is used. However, as the stress corrosion cracking resistance is improved through the development of new materials and the improvement of existing materials, and the occurrence time is prolonged, it may take a long time to acquire data using the conventional evaluation method and develop a predictive model based on this.

As a related prior document, Korean Patent No. 1,083,183 discloses "a method of manufacturing a specimen for non-destructive test performance verification for stress corrosion cracking generated in a heater sleeve nozzle penetration pipe used in a high-temperature and high-pressure environment of a nuclear power plant", Japanese Patent Laid-Open Patent 2009 -085811 discloses "a test piece for detecting stress corrosion cracking and a device for detecting stress corrosion cracking", and Korean Patent Publication No. 1994-0016855 discloses a "test device for measuring stress corrosion cracking susceptibility".

Korean Patent 1,083,183 Japanese Patent Laid-Open Patent 2009-085811 Korean Patent Publication 1994-0016855

The embodiment of the present invention evaluates the stress corrosion cracking characteristics of highly corrosion-resistant structural materials and parts used in high-temperature and high-pressure water environments such as nuclear power plants, and increases the number and types of samples that can be tested simultaneously when acquiring life data, and increases the test period It is to provide a test apparatus and method for measuring the stress corrosion cracking initiation time that can shorten the time.

In addition to the above problems, the embodiment according to the present invention may be used to achieve other problems not specifically mentioned.

The stress corrosion cracking initiation time measurement test apparatus according to an embodiment of the present invention is a solution for storing a solution supplied to the high-pressure side of the pressure part, which is provided in the pressure part for fixing the specimen to the pressure boundary of the high-pressure side and the low-pressure side, and the solution circulation line A storage unit, a high-pressure pump that supplies the solution stored in the solution storage unit to the high-pressure side of the pressure unit and circulates it back to the solution storage unit, a heating unit that is provided to include the pressure unit and heats the internal temperature of the pressure unit to a set temperature, and low pressure of the pressure unit It includes a pressure gauge for detecting the pressure on the low pressure side of the pressure part when it is connected to the side and ruptures due to stress corrosion cracking on the surface of the specimen exposed to a high temperature and high pressure water environment.

The embodiment of the present invention provides test conditions that can reproduce the same deterioration mechanism as the stress corrosion cracking that occurs in the operating environment of structural materials and parts so as to improve the efficiency of the stress corrosion cracking initiation time test, and based on the test data and this It has the effect of increasing the reliability of the predictive model developed with

1 is a view showing a stress corrosion cracking initiation time measurement test apparatus according to an embodiment of the present invention.
2 is a view showing a pressure unit according to an embodiment of the present invention.
3 is a view showing a specimen rupture process in the stress corrosion cracking initiation time measurement test method according to an embodiment of the present invention.

With reference to the accompanying drawings, the embodiments of the present invention will be described in detail so that those of ordinary skill in the art to which the present invention pertains can easily implement them. The present invention may be embodied in many different forms and is not limited to the embodiments described herein. In order to clearly explain the present invention in the drawings, parts irrelevant to the description are omitted, and the same reference numerals are used for the same or similar components throughout the specification. In addition, in the case of a well-known known technology, a detailed description thereof will be omitted.

Throughout the specification, when a part "includes" a certain element, it means that other elements may be further included, rather than excluding other elements, unless otherwise stated.

Hereinafter, the stress corrosion cracking initiation time measurement test apparatus will be described in detail with reference to the drawings. 1 is an overall configuration diagram of a test apparatus for testing stress corrosion cracking initiation time measurement according to an embodiment of the present invention, and FIG. 2 is a view showing a pressure unit according to an embodiment of the present invention. 1 and 2, the stress corrosion cracking initiation time measurement test apparatus according to an embodiment of the present invention includes a pressure unit 100, a solution storage unit 110, a high pressure pump 120, a heating unit 140, And it includes a pressure gauge 150, and when stress corrosion cracking occurs on the surface of the specimen 10 exposed to a high temperature and high pressure water environment, the stress corrosion cracking time is measured in real time by measuring the pressure change at which the specimen 10 is ruptured. can be measured accurately.

The pressure unit 100 forms a pressure boundary between the high pressure side and the low pressure side, and may fix the specimen 10 to the pressure boundary between the high pressure side and the low pressure side. The pressure unit 100 includes a low-pressure side housing 102 and a high-pressure side housing 103 . Here, the specimen 10 may be formed of a thin high corrosion-resistant material such as a nickel-based alloy and stainless steel. And the specimen 10 may be formed in a disk shape. The specimen 10 is coupled between the low pressure side housing 102 and the high pressure side housing 103, respectively, and one surface is affected by the low pressure side, and the other surface is affected by the high pressure side. The low pressure side housing 102 has a low pressure side inner diameter A of a preset size. In addition, the high-pressure side housing 103 has a high-pressure side inner diameter B of a preset size and is coupled to the low-pressure side housing 102 with the specimen 10 interposed therebetween to fix the specimen 10 . Here, in order to prevent the stress corrosion cracking generation time from being changed by the deformation of the specimen 10, the high pressure side inner diameter (B) may be formed larger than the low pressure side inner diameter (A). In FIG. 1, when the pressure part 100 is connected in series or in parallel, the number of specimens 10 that can be tested at the same time increases, so that a more efficient stress corrosion cracking initiation time measurement test is possible.

The low-pressure side housing 102 and the high-pressure side housing 103 may include sealing means to maintain a pressure difference using various methods such as a screw thread method or a bolt method. For example, the pressure unit 100 may further include a metal gasket 104 and a fixing pin 105 to minimize deformation of the specimen 10 and maintain high-pressure sealing. The metal gasket 104 is provided between the bonding surface of the specimen 10 and the high-pressure side housing 103 to prevent deformation of the specimen 10 and maintain high-pressure sealing. The fixing pin 105 is coupled to the surface of the specimen 10 and may serve to fix the metal gasket 104 to prevent rotational deformation. When the low-pressure side housing 102 and the high-pressure side housing 103 are screwed together in a threaded manner, a fixing pin 105 for fixing the metal gasket 104 so as not to induce rotational deformation on the surface of the specimen 10 by rotational force. ) may be further included. Also, at both ends of the pressure unit 100 , the pipe connection unit 106 may be connected to the low pressure side housing 102 and the high pressure side housing 103 , respectively.

The solution storage unit 110 is provided on the high-pressure side of the pressure unit 100 and is provided in the solution circulation line 12 provided to simulate the same water environment as the conditions of use of the specimen 10 to the high-pressure side of the pressure unit 100 . It is possible to store the solution supplied to the The solution storage unit 110 is provided in the solution circulation line 12 and may include a storage tank having an inlet through which the solution is introduced and an outlet through which the solution is discharged.

The high-pressure pump 120 is provided between the solution storage unit 110 and the pressure unit 100 in the solution circulation line 12 to supply the solution stored in the solution storage unit 110 to the high-pressure side of the pressure unit 100 and again It functions to circulate to the solution storage unit 110 . In order to simulate the same water environment as the conditions of use of the specimen 10 on the high-temperature and high-pressure side of the specimen 10, the solution stored in the solution storage unit 110 is transferred to the solution circulation line 12 using the high-pressure pump 120. It is sequentially supplied to the provided preheating unit 130 , the heating unit 140 , and the pressure unit 100 , and then circulated back to the solution storage unit 110 . The solution circulation line 12 may further include a preheating unit 130 provided between the high-pressure pump 120 and the pressure unit 100 to further heat the pressure unit 100 . When it is necessary to further increase the temperature inside the pressure unit 100 even when the heating unit 140 is driven, the preheating unit 130 may be used.

The heating unit 140 may be provided so that the pressure unit 100 is included therein to heat the internal temperature of the pressure unit 100 to a set temperature. By using the heating unit 140, the temperature inside the pressure unit 100 may be heated according to the operating temperature condition.

The pressure gauge 150 may include a pressure detection sensor connected to the low pressure side of the pressure unit 100 to detect the low pressure side pressure of the pressure unit 100 . As described above, when pressure is continuously applied to the high-temperature and high-pressure side of the specimen 10 in a state where the specimen 10 is fixed to the pressure boundary between the high-pressure side and the low-pressure side of the pressure unit 100 , the high-temperature and high-pressure side of the specimen 10 is Stress corrosion cracking occurs on the side surface. And when the high temperature and high pressure burst pressure PB(S) of the specimen 10 is lower than the pressure difference ΔP, the time for the specimen 10 to rupture and the high temperature and low pressure side pressure P1 through the pressure gauge 150 increases It is measured as the time to rupture.

As described above, in the stress corrosion cracking initiation time measurement test apparatus according to an embodiment of the present invention, one side of the specimen 10 formed of a high corrosion resistance material is exposed to a high temperature and high pressure water environment, and the opposite surface of the specimen 10 is high temperature Maintain for a long time after exposure to low pressure atmospheric environment. In this state, when stress corrosion cracking occurs on the surface of the specimen 10 exposed to a high-temperature and high-pressure water environment, the specimen 10 ruptures and the high-temperature and low-pressure pressure increases, so the pressure gauge 150 is used to measure it in real time. Thus, the stress corrosion cracking time can be accurately measured.

3 is a conceptual diagram illustrating the operating principle of the stress corrosion cracking initiation time measurement test method according to an embodiment of the present invention, and is a view showing the rupture process of the specimen 10 in a high-temperature and high-pressure water environment. And the portion of the pressure unit 100 to which the specimen 10 is coupled in FIG. 3 is an enlarged dotted line portion including the specimen 10 in FIG. 2 . Prior to describing the test method for measuring stress corrosion cracking initiation time according to an embodiment of the present invention, the specimen 10 is formed of a high corrosion resistance material such as a nickel-based alloy and stainless steel, and one side of the specimen 10 is subjected to high temperature and high pressure. It is assumed that the environment is exposed, and the opposite surface of the specimen 10 is maintained for a preset time in a state exposed to a high temperature and low pressure atmospheric environment. In this state, referring to FIG. 3 , in the initial step S310 , in which the pressures on the high-pressure side and the low-pressure side of the pressure unit 100 are the same, the specimen 10 may maintain its original flat plate. When a high pressure (P2, P2 > P1) is applied to the high-pressure side in a state where the pressures on the high-pressure side and the low-pressure side of the pressure unit 100 are the same, the pressure difference between the high-pressure side and the low-pressure side (ΔP, P2 - P1) causes the specimen ( 10) is deformed to form a convex curvature toward the low pressure side (S320). At this time, by adjusting the thickness of the specimen 10 and the inner diameter (A) of the low pressure side, the burst pressure (PB) is designed to be higher than the pressure difference (ΔP), so that mechanical rupture does not occur. However, if stress corrosion cracking occurs in the tensile stress portion of the surface of the specimen 10 in a high-temperature water environment on the high-pressure side during long-term maintenance, the rupture pressure of the specimen 10 is lowered. Therefore, as the depth of the stress corrosion cracking increases, the time of the stress corrosion cracking can be known when the rupture pressure PB becomes lower than the pressure difference ΔP (S330). As the stress corrosion cracking continues, the specimen 10 ruptures, and the pressure P1 on the high temperature and low pressure side increases to the pressure P2 on the high temperature and high pressure side (S340). In this state, the pressure P1 on the high temperature and low pressure side is measured in real time using the pressure gauge 150 to accurately measure the time of occurrence of stress corrosion cracking from the time the pressure increases.

The burst pressure PB of the specimen 10 may be calculated using Equations 1 and 2.

[Equation 1]

PB = (2tσ) / R

where t = thickness of the specimen, σ = tensile strength of the specimen, R = radius of curvature after deformation of the specimen,

[Equation 2]

-1]/(1+δ)PB = (8tσ) / D × [

-1]/(1+δ)

D = Specimen exposed diameter (same as the inner diameter of the low pressure side), δ = Elongation of the specimen (with a value between 0 and 1)

Since the burst pressure PB of the specimen 10 calculated in Equations 1 and 2 is the initial burst pressure PB(0) of the specimen 10 without stress corrosion cracking, the condition of Equation 3 must be satisfied. do.

[Equation 3]

PB(0) > ΔP = (P2 - P1)

When stress corrosion cracking occurs on the surface of the high temperature and high pressure side of the specimen 10 Compared to the initial burst pressure (PB(0)) of the specimen 10 without stress corrosion cracking, it is usually reduced to 1/2 level. Therefore, as shown in Equation 4, if the high-temperature and high-pressure bursting pressure (PB(S)) of the specimen 10 is designed to be lower than the pressure difference ΔP, stress corrosion cracking occurs and the depth is 1/ of the thickness of the specimen 10 When grown to 2, the specimen 10 is ruptured.

[Equation 4]

PB(S) = 1/2 PB(0) < ΔP

In Equations 1 and 2, all variables should be physical properties at the temperature at which the experiment is performed. And as an experimental design condition, in order to fix the specimen 10, the diameter of the specimen 10 should be greater than the inner diameter of the high-pressure side (B). When the low-pressure housing 102 and the high-pressure housing 103 are fastened to fix the specimen 10 , deformation may also occur in the contact portion between the specimen 10 and the metal gasket 104 . In order to prevent the stress corrosion cracking time from being changed by this deformation, the inner diameter of the low pressure side (A) should be sufficiently smaller than the inner diameter of the high pressure side (B). In addition, a relationship between the size ratio of the high pressure side inner diameter (B) and the low pressure side inner diameter (A) and the thickness of the specimen 10 can be set. For example, (B-A)/2 can be designed to be more than three times the thickness of the specimen 10.

As described above, the stress corrosion cracking initiation time measurement test apparatus and method according to an embodiment of the present invention evaluates the stress corrosion cracking characteristics of highly corrosion-resistant structural materials and components used in high-temperature and high-pressure water environments such as nuclear power plants and acquires life data In doing so, the number and types of samples that can be tested simultaneously can be increased. And it is possible to measure the stress corrosion cracking time in real time and accurately measure the time, shortening the test period and greatly improving the efficiency. In addition, in improving the test efficiency, it is possible to increase the reliability of the test data and the predictive model developed based on the test data and this by providing test conditions that can reproduce the same deterioration mechanism as the stress corrosion cracking occurring in the operating environment of structural materials and parts.

Although preferred embodiments of the present invention have been described above, the present invention is not limited thereto, and it is possible to carry out various modifications within the scope of the claims, the detailed description of the invention, and the accompanying drawings, and this is also It goes without saying that they fall within the scope of the present invention.

10 ; Psalm 12; solution circulation line
100 ; pressure part 102 ; low pressure housing
103; high pressure side housing 104 ; metal gasket
105 ; fixing pin 110 ; solution reservoir
120 ; high pressure pump 130 ; preheating part
140 ; heating unit 150 ; pressure gauge

Claims (9)

A pressure part that fixes the specimen at the pressure boundary between the high-pressure side and the low-pressure side;
A solution storage unit provided in the solution circulation line to store the solution supplied to the high pressure side of the pressure unit;
a high-pressure pump for supplying the solution stored in the solution storage unit to the high-pressure side of the pressure unit;
A heating unit provided to be included in the pressure unit to heat the internal temperature of the pressure unit to a set temperature, and
A pressure gauge connected to the low pressure side of the pressure unit to detect the pressure on the low pressure side of the pressure unit when the surface of the specimen exposed to a high temperature and high pressure water environment ruptures due to stress corrosion cracking.
A stress corrosion cracking initiation time measurement test device comprising a. In claim 1,
the pressure part
A low pressure side housing having a low pressure side inner diameter (A) of a preset size, and
A high-pressure housing having a high-pressure-side inner diameter (B) formed to be different from the low-pressure-side inner diameter (A) and coupled to the low-pressure-side housing with the specimen interposed therebetween to fix the specimen
A stress corrosion cracking initiation time measurement test device comprising a. In claim 2,
The high-pressure side inner diameter (B) is a stress corrosion cracking start time measurement test apparatus that is formed larger than the low pressure side inner diameter (A). In claim 2,
The stress corrosion cracking initiation time measurement test apparatus further comprising a metal gasket provided between the joint surface of the specimen and the high-pressure side housing to prevent deformation of the specimen and maintain high-pressure sealing. In claim 4,
Stress corrosion cracking initiation time measurement test apparatus further comprising a fixing pin coupled to the surface of the specimen for fixing the metal gasket to prevent rotational deformation. In claim 1,
The pressure part is a stress corrosion cracking start time measurement test apparatus provided in plurality in the solution circulation line. In claim 1,
The specimen is a stress corrosion cracking initiation time measurement test device comprising at least one of a nickel-based alloy or stainless steel. A specimen preparation step of preparing a specimen in the pressure part forming the boundary between the low-pressure side and the high-pressure side;
A specimen pressurizing step of forming a high-temperature and high-pressure water environment on the high-pressure side of the pressure part based on the specimen;
A specimen rupture step of rupturing the specimen due to stress corrosion cracking of the specimen exposed to a high-temperature and high-pressure water environment, and
Stress corrosion cracking start time measurement test method comprising the step of measuring the stress corrosion cracking start time of measuring the rupture state of the specimen in real time using a pressure gauge connected to the low pressure side of the pressure part. In claim 8,
The step of measuring the stress corrosion cracking initiation time is
Stress corrosion cracking occurs on the surface of the high-temperature and high-pressure side of the specimen, and the high-temperature and high-pressure bursting pressure (PB(S)) of the specimen is the pressure of the low-pressure side pressure (P1) of the specimen and the high-pressure side pressure (P2) of the specimen When it is lower than the difference (ΔP), the specimen is ruptured, and the time at which the low pressure side pressure (P1) of the specimen increases through the manometer is measured as the rupture time.

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