JP4929062B2 - Specimen and method for producing specimen - Google Patents

Description

  The present invention relates to a technique for imparting a defect to a weld.

  Patent Document 1 discloses a method for artificially introducing stress corrosion cracking into a welded portion of a metal pipe. Stress corrosion cracking may be described as SCC. In this method, an external force directed to the center of the metal tube is applied to a part of the outer surface of the metal tube, and a tensile stress is applied to the inner surface of the metal tube corresponding to the back side of the part. Then, stress corrosion cracking is introduced into the inner surface by bringing the corrosive fluid into contact with the inner surface to which the tensile stress is applied. In this method, the state in which the corrosive fluid is in contact with the inner surface is maintained for a long time, so that stress corrosion cracking occurs and grows with time. By continuing to keep the corrosive fluid in contact with the inner surface, stress corrosion cracking of the desired size is introduced.

  Patent document 2 is disclosing the technique which introduce | transduces the defect for an inspection into a fillet weld part. In this technique, by applying a residual stress to a fillet weld, stress corrosion cracks are generated in the fillet weld, and inspection defects based on the stress corrosion cracks are gradually grown.

  Patent Document 3 discloses a method capable of generating and propagating intergranular stress corrosion cracking by a simple means with respect to a test body that maintains the contact resistance by passivating. Intergranular stress corrosion cracking may be described as IGSCC. In this method, while applying a force to a nickel-based alloy specimen such as Alloy 182, the treatment liquid is brought into contact with each other to generate and propagate grain boundary type stress corrosion cracking. The treatment liquid is a 0.3 to 5% by weight potassium tetrathionate aqueous solution, and the temperature of the treatment liquid is preferably 5 to 50 ° C. and the pH value of the treatment liquid is 3 to 6. Also, it is disclosed that in nickel-base alloys, when stress acts on the sensitization in the vicinity of grain boundaries (Cr depletion phenomenon accompanying Cr carbide precipitation), grain boundary type stress corrosion cracking occurs and progresses. Yes. It has been disclosed that nickel-base alloys such as Alloy 182 are sensitized by stress relief annealing at temperatures around 600 ° C. and low temperature aging at temperatures 288-550 ° C.

  Patent Document 4 discloses a treatment liquid for generating and advancing grain boundary type stress corrosion cracking in a nickel-based alloy. The treatment liquid is an aqueous solution of potassium tetrathionate or sodium tetrathionate, the concentration of potassium tetrathionate or sodium tetrathionate is 0.3 to 6% by weight, the temperature of the treatment liquid is 5 to 60 ° C., and the pH value of the treatment liquid is 3 To 6 respectively. Further, it is disclosed that when NaCl or KCl is added to the treatment liquid, the time until grain boundary stress corrosion cracking occurs is shortened. In this case, the Cl concentration of the treatment liquid is preferably 0.06 to 6% by weight.

  Moreover, in patent document 4, in order to prolong the life of a nuclear power plant, the importance of evaluating the soundness of the equipment constituent material of a nuclear reactor, a reactor internal structure, and those welding parts is pointed out. Nickel-based alloys and stainless steel are often used as device constituent materials. Depending on conditions such as material, stress, and usage environment, the presence / absence of cracks due to intergranular stress corrosion cracking generated in equipment components, its size, shape, etc., can be detected and evaluated by nondestructive inspection in actual equipment. Application of ultrasonic flaw detection technology and eddy current flaw detection technology is considered as a means. In order to detect and evaluate cracks using these technologies, it is necessary to repeat the detection and evaluation of cracks using test specimens that reproduce various intergranular stress corrosion cracks occurring on actual machines in a laboratory. Is described. It is described that the technology to generate and propagate intergranular stress corrosion cracking is useful for the advancement of ultrasonic flaw detection technology, the development of inspection technology other than ultrasonic flaw detection, and the development of repair technology for Inconel (registered trademark) structures. ing.

  Note that fracture phenomena such as stress corrosion cracking are generally difficult to control. In particular, it is difficult to control the start point of fracture, such as the time point when stress corrosion cracking occurs. Therefore, the depth of the stress corrosion cracks obtained as a result varies greatly only by making the time for immersing the test specimen in the treatment liquid constant in order to form the stress corrosion cracks. In particular, it is difficult to form shallow stress corrosion cracks.

JP-A-9-137229 Japanese Patent Laid-Open No. 11-173958 JP 2002-333397 A Table 03/091709

  The objective of this invention is providing the manufacturing method of the test body and the test body in which the crack of desired depth is provided.

  Hereinafter, means for solving the problem will be described using the numbers used in (Best Mode for Carrying Out the Invention). These numbers are added to clarify the correspondence between the description of (Claims) and (Best Mode for Carrying Out the Invention). However, these numbers should not be used to interpret the technical scope of the invention described in (Claims).

  The test body according to the present invention comprises a first weld metal (3, 14-16, 32, 45) and a second weld metal (4, 17-19, 33, 46) coupled to the first weld metal. It has. A first crack (6 ', 23'-25', 37'-39 ', 48') is provided in the second weld metal. The tip in the depth direction of the first crack is located in a first boundary region (3a, 14a to 16a, 32a, 45a) between the first weld metal and the second weld metal. The first weld metal is a nickel-based alloy containing a first weight concentration of carbon and a second weight concentration of chromium. The second weld metal is a nickel-based alloy containing a third weight concentration of carbon and a fourth weight concentration of chromium. The third weight concentration is higher than the first weight concentration. The fourth weight concentration is lower than the second weight concentration.

  The first weld metal and the second weld metal have different carbon and chromium contents so that the crack sensitivity of the second weld metal is higher than the crack sensitivity of the first weld metal. Therefore, in the process of forming the first crack, the tip of the first crack stops at the first boundary region. Therefore, it is easy to control the depth of the first crack.

  It is preferable that a second crack (37 'to 39') is provided in the second weld metal. The tip in the depth direction of the second crack is located in the first boundary region. The first crack and the second crack are preferably opened on the surface (33a) of the second weld metal. The surface is inclined with respect to the first boundary region.

  Therefore, it is possible to simultaneously form the first crack and the second crack having different depths.

  The test body according to the present invention comprises a first weld metal (3, 14-16, 32, 45) and a second weld metal (4, 17-19, 33, 46) coupled to the first weld metal. It has. The second weld metal is provided with a first crack (6 ', 23' to 25 ', 37' to 39 ', 48') of stress corrosion cracking. The tip in the depth direction of the first crack is located in a first boundary region (3a, 14a to 16a, 32a, 45a) between the first weld metal and the second weld metal. There is a condition in which the crack susceptibility of the second weld metal to stress corrosion cracking is higher than the crack susceptibility of the first weld metal.

  If the first crack is formed under the above conditions, the tip of the first crack stops at the first boundary region. Therefore, it is easy to control the depth of the first crack. Note that the crack susceptibility can be evaluated by, for example, the time required for the occurrence of stress corrosion cracking and the rate of progress (advance speed in the depth direction of the tip of the stress corrosion cracking).

  The method for producing a specimen according to the present invention includes a step of melting and solidifying a first filler material to form a first weld metal (3, 14 to 16, 32, 45), and a second filler material being melted and solidified. Forming a second weld metal (4, 17-19, 33, 46) welded to the first weld metal, and stress corrosion cracking cracks (6 ′, 23′˜) on the second weld metal. 25 ', 37'-39', 48 '). The first filler metal is a nickel-based alloy containing a first weight concentration of carbon and a second weight concentration of chromium. The second filler metal is a nickel-based alloy containing a third weight concentration of carbon and a fourth weight concentration of chromium. The third weight concentration is higher than the first weight concentration. The fourth weight concentration is lower than the second weight concentration.

  The first weld metal and the second weld metal have different carbon and chromium contents so that the crack sensitivity of the second weld metal is higher than the crack sensitivity of the first weld metal. Therefore, in the process of crack formation, the crack tip stops at the boundary region between the first weld metal and the second weld metal. Therefore, it is easy to control the crack depth.

  The step of forming the crack includes forming a start notch (5, 20-22, 34-36, 47) on the surface of the second weld metal, and forming the crack starting from the start notch. Preferably, the method includes a step of cutting and a step of cutting the surface.

  It is possible to control the length and position of the crack by adjusting the length and position of the start notch. In addition, the start notch is removed by cutting the surface, leaving only a crack due to stress corrosion cracking.

  The method for producing a specimen according to the present invention includes a step of melting and solidifying a first filler material to form a first weld metal (3, 14 to 16, 32, 45), and a second filler material being melted and solidified. Forming a second weld metal (4, 17-19, 33, 46) welded to the first weld metal, and a start notch (5, 20-22, 34-) on the surface of the second weld metal. 36, 47), immersing the second weld metal in a treatment liquid while applying stress to the second weld metal, and shaving the surface. The first filler material is a first nickel-based alloy. The second filler material is a second nickel base alloy different from the first nickel base alloy. The crack susceptibility of the second nickel-base alloy to stress corrosion cracking under conditions immersed in the treatment liquid is higher than the crack susceptibility of the first nickel-base alloy to stress corrosion cracking under the conditions.

  Therefore, the crack sensitivity of the second weld metal in the treatment liquid is higher than the crack sensitivity of the first weld metal in the treatment liquid. Therefore, in the step of immersing, the stress corrosion crack progresses starting from the start notch, and the stress corrosion crack progress stops when the tip of the stress corrosion crack reaches the boundary region between the first weld metal and the second weld metal. . Therefore, it is easy to control the depth of stress corrosion cracking.

  ADVANTAGE OF THE INVENTION According to this invention, the test body to which the crack of desired depth is provided and the manufacturing method of a test body are provided.

  With reference to the accompanying drawings, the best mode for carrying out a test body and a method for manufacturing the test body according to the present invention will be described below.

(First embodiment)
1A and 1B show a top view and a cross-sectional view of a test body according to the first embodiment of the present invention. The test body according to the present embodiment includes a base material 1, a first weld metal 3, and a second weld metal 4. The base material 1 includes an upper surface 1a ′ and a groove portion 2 in which a groove opening in the upper surface 1a ′ is formed. The first weld metal 3 is coupled to the groove portion 2. The first weld metal 3 includes a boundary region 3a. The second weld metal 4 is coupled to the boundary region 3a. The boundary region 3 a is formed in a film shape along the boundary between the first weld metal 3 and the second weld metal 4. The second weld metal 4 has an upper surface 4 a on the opposite side of the first weld metal 3. The upper surface 4a and the upper surface 1a ′ form the same plane. A crack 6 ′ is formed in the second weld metal 4. The crack 6 'opens to the upper surface 4a, and the tip in the depth direction is located in the boundary region 3a.

  Next, the manufacturing method of the test body which concerns on this embodiment is demonstrated using Fig.2 (a)-(d).

  First, with reference to Fig.2 (a), the process of forming the groove part 2 in the base material 1, and the process of welding the 1st weld metal 3 to the groove part 2 are demonstrated. As the base material 1, for example, a stainless steel flat plate is used. The base material 1 has an upper surface 1a. The upper surface 1 a forms a groove portion 2 that opens in the upper surface 1 a in the base material 1. A first filler metal is welded to the groove portion 2 to form a first weld metal 3. The first weld metal 3 is located at the bottom portion of the groove portion 2. Here, the first filler material is a nickel-based alloy (example: Inconel) containing a first weight concentration of carbon and a second weight concentration of chromium. Therefore, the 1st weld metal 3 contains carbon and chromium similarly to the 1st filler metal.

  Next, with reference to FIG.2 (b), the process of welding the 2nd weld metal 4 to the 1st weld metal 3, and the process of forming the start notch 5 in the 2nd weld metal 4 are demonstrated. A second filler metal 4 having a height H1 is formed by welding the second filler metal to the first weld metal 3 (groove portion 2). Here, the second filler material is a nickel-based alloy (example: Inconel) containing a third weight concentration of carbon and a fourth weight concentration of chromium. Therefore, the second weld metal 4 contains carbon and chromium in the same manner as the second filler material. Since the third weight concentration is higher than the first weight concentration and the fourth weight concentration is lower than the second weight concentration, the second filler metal and the second weld metal 4 are more than the first filler material and the first weld metal 3. Is also susceptible to cracking. The second weld metal 4 is welded onto the first weld metal 3 and is located at the opening portion of the groove portion 2. The boundary region 3a as a portion of the first weld metal 3 coupled to the second weld metal 4 is located under the second weld metal 4 and has a film shape. A start notch 5 having a depth H2 is formed on the upper surface of the second weld metal 4. Here, the position where the start notch 5 is formed corresponds to the position where the crack 6 'is to be formed. The opening length of the start notch 5 corresponds to the opening length of the crack 6 '. When the target depth of the crack 6 'is H4, the value of the height H1 is preferably equal to the sum of the value of the target depth H4 and the value of the depth H2. Note that the value of the height H1 can be made larger than the sum of the value of the target depth H4 and the value of the depth H2.

  Next, with reference to FIG.2 (c), the process of extending the start notch 5 and forming the crack 6 is demonstrated. The second weld metal 4 is immersed in the treatment liquid while applying stress to the second weld metal 4. Then, the start notch 5 extends in the depth direction, and a crack 6 is formed. The shallow part of the crack 6 is a part formed as the start notch 5. The deep part of the crack 6 is a part formed by stress corrosion cracking. The tip in the depth direction of the crack 6 stops at the boundary region 3a.

  Next, the process of removing the shallow part of the crack 6 will be described with reference to FIG. The upper surface 1a and the upper surface of the second weld metal 4 are cut by a height H3 so that the deep part of the crack 6 remains as a crack 6 'having a depth H4. Here, the value of the height H3 is greater than or equal to the value of the depth H2. Therefore, the shallow part of the crack 6 is removed.

  Since the crack sensitivity of the second weld metal 4 is high and the crack sensitivity of the first weld metal 3 is low, when the tip of the crack 6 reaches the boundary region 3a in the process of forming the crack 6, the crack 6 progresses. Stop. Therefore, in the present embodiment, it is easy to accurately control the depth H4 of the crack 6 '.

(Second Embodiment)
3A and 3B show a top view and a cross-sectional view of a test body according to the second embodiment of the present invention. The test body according to the present embodiment includes a base material 10, first weld metals 14 to 16, and second weld metals 17 to 19. The base material 10 includes an upper surface 10a ′, a groove portion 11 in which a first groove opening in the upper surface 10a ′ is formed, and a groove portion 12 in which a second groove opening in the upper surface 10a ′ is formed, And a groove portion 13 formed with a third groove opening in the upper surface 10a ′. The first weld metal 14 is coupled to the groove portion 11. The first weld metal 14 includes a boundary region 14a. The second weld metal 17 is coupled to the boundary region 14a. The boundary region 14 a is formed in a film shape along the boundary between the first weld metal 14 and the second weld metal 17. The second weld metal 17 includes an upper surface 17 a on the opposite side of the first weld metal 14. A crack 23 ′ is formed in the second weld metal 17. The crack 23 'opens to the upper surface 17a, and the tip in the depth direction is located in the boundary region 14a. The first weld metal 15 is coupled to the groove portion 12. The first weld metal 15 includes a boundary region 15a. The second weld metal 18 is coupled to the boundary region 15a. The boundary region 15 a is formed in a film shape along the boundary between the first weld metal 15 and the second weld metal 18. The second weld metal 18 has an upper surface 18 a on the opposite side of the first weld metal 15. A crack 24 ′ is formed in the second weld metal 18. The crack 24 'opens to the upper surface 18a, and the tip in the depth direction is located in the boundary region 15a. The first weld metal 16 is coupled to the groove portion 13. The first weld metal 16 includes a boundary region 16a. The second weld metal 19 is coupled to the boundary region 16a. The boundary region 16 a is formed in a film shape along the boundary between the first weld metal 16 and the second weld metal 19. The second weld metal 19 includes an upper surface 19 a on the opposite side of the first weld metal 16. A crack 25 ′ is formed in the second weld metal 19. The crack 25 'opens to the upper surface 19a, and the tip in the depth direction is located in the boundary region 16a. The upper surface 17a, the upper surface 18a, the upper surface 19a, and the upper surface 10a ′ form the same plane.

  Next, the manufacturing method of the test body which concerns on this embodiment is demonstrated using Fig.4 (a)-(d).

  First, referring to FIG. 4A, the step of forming the groove portions 11 to 13 in the base material 10, the first weld metal 14 is welded to the groove portion 11, and the first welding is performed to the groove portion 12. The process of welding the metal 15 and welding the first weld metal 16 to the groove portion 13 will be described. As the base material 10, for example, a stainless steel flat plate is used. The base material 10 includes an upper surface 10a. Grooves 11 to 13 that open to the upper surface 10 a are formed in the base material 10. First, the first weld metal 14 is formed by welding the first filler metal to the groove portion 11. The first weld metal 14 is located at the bottom portion of the groove portion 11. Next, the first weld metal 15 is formed by welding the first filler material to the groove portion 12. The first weld metal 15 is located at the bottom portion of the groove portion 12. Further, the first filler metal is welded to the groove portion 13 to form the first weld metal 16. The first weld metal 16 is located at the bottom portion of the groove portion 13. Here, the first filler material is the same as the first filler material according to the first embodiment. Therefore, each of the first weld metals 14 to 16 includes carbon and chromium in the same manner as the first filler material.

  Next, referring to FIG. 4B, the second weld metal 17 is welded to the first weld metal 14, the second weld metal 18 is welded to the first weld metal 15, and the first weld metal 16 is welded to the first weld metal 16. 2 welding the weld metal 19, forming the start notch 20 in the second weld metal 17, forming the start notch 21 in the second weld metal 18, and forming the start notch 22 in the second weld metal 19. explain. First, a second weld metal 17 having a height H5 is formed by welding a second filler metal to the first weld metal 14 (groove portion 11). Next, a second weld metal 18 having a height H6 is formed by welding the second filler metal to the first weld metal 15 (groove portion 12). Further, the second weld metal 19 having a height H7 is formed by welding the second filler metal to the first weld metal 16 (groove portion 13). Here, the second filler material is the same as the second filler material according to the first embodiment. Therefore, the 2nd weld metals 17-19 contain carbon and chromium like the 2nd filler material. The second filler metal and the second weld metals 17 to 19 are more susceptible to cracking than the first filler material and the first weld metals 14 to 16. The second weld metal 17 is welded onto the first weld metal 14 and is located at the opening portion of the groove portion 11. The boundary region 14a as a portion of the first weld metal 14 coupled to the second weld metal 17 is located under the second weld metal 17 and has a film shape. Similarly, the second weld metal 18 is welded onto the first weld metal 15 and is located at the opening portion of the groove portion 12. A boundary region 15a as a portion of the first weld metal 15 coupled to the second weld metal 18 is located under the second weld metal 18 and has a film shape. Similarly, the second weld metal 19 is welded onto the first weld metal 16 and is located at the opening portion of the groove portion 13. A boundary region 16a as a portion of the first weld metal 16 coupled to the second weld metal 19 is located under the second weld metal 19 and has a film shape. Next, a start notch 20 having a depth H8 is formed on the upper surface of the second weld metal 17. Here, the position where the start notch 20 is formed corresponds to the position where the crack 23 'is to be formed. The length of the opening of the start notch 20 corresponds to the length of the opening of the crack 23 '. When the target depth of the crack 23 'is H10, the value of the height H5 is preferably equal to the sum of the value of the target depth H10 and the value of the depth H8. Note that the value of the height H5 can be made larger than the sum of the target depth H10 and the depth H8. Similarly, a start notch 21 having a depth H8 is formed on the upper surface of the second weld metal 18. Here, the position where the start notch 21 is formed corresponds to the position where the crack 24 'is to be formed. The length of the opening of the start notch 21 corresponds to the length of the opening of the crack 24 '. When the target depth of the crack 24 'is H11, the value of the height H6 is preferably equal to the sum of the value of the target depth H11 and the value of the depth H8. Note that the value of the height H6 can be made larger than the sum of the value of the target depth H11 and the value of the depth H8. Similarly, a start notch 22 having a depth H8 is formed on the upper surface of the second weld metal 19. Here, the position where the start notch 22 is formed corresponds to the position where the crack 25 'is to be formed. The length of the opening of the start notch 22 corresponds to the length of the opening of the crack 25 '. When the target depth of the crack 25 'is H12, the value of the height H7 is preferably equal to the sum of the value of the target depth H12 and the value of the depth H8. It is also possible to make the value of the height H7 larger than the sum of the value of the target depth H12 and the value of the depth H8. The heights H5 to H7 are different from each other.

  Next, referring to FIG. 4C, the start notch 20 is advanced to form a crack 23, the start notch 21 is advanced to form a crack 24, and the start notch 22 is advanced to form a crack 25. The process to perform is demonstrated. Each of the second weld metals 17 to 19 is immersed in the treatment liquid while applying stress to each of the second weld metals 17 to 19. Then, the start notch 20 extends in the depth direction to form a crack 23, the start notch 21 extends in the depth direction to form a crack 24, and the start notch 22 extends in the depth direction to form a crack 25. . The shallow portion of each of the cracks 23 to 25 is a portion formed as each of the start notches 20 to 22. The deep part of each of the cracks 23 to 25 is a part formed by stress corrosion cracking. The tip in the depth direction of each of the cracks 23 to 25 stops at each of the boundary regions 14a to 16a.

  Next, with reference to FIG. 4D, a process of removing the shallow portion of the crack 23, the shallow portion of the crack 24, and the shallow portion of the crack 25 will be described. A deep part of the crack 23 is left as a crack 23 'having a depth H10, a deep part of the crack 24 is left as a crack 24' having a depth H11, and a deep part of the crack 25 is left as a crack 25 'having a depth H12. The upper surface 10a, the upper surface of the second weld metal 17, the upper surface of the second weld metal 18, and the upper surface of the second weld metal 19 are scraped by a height H9 so as to be left as'. Here, the value of the height H9 is greater than or equal to the value of the depth H8. Therefore, the shallow part of the crack 23, the shallow part of the crack 24, and the shallow part of the crack 25 are removed.

  Since the crack susceptibility of the second weld metal 17-19 is high and the crack susceptibility of the first weld metal 14-16 is low, the tip of the crack 23-25 is the boundary region 14a-16a in the process of forming the crack 23-25. The cracks 23-25 stop growing. Therefore, in this embodiment, it is possible to form the cracks 23 ′ to 25 ′ having different target depths at a time.

(Third embodiment)
FIGS. 5A and 5B show a top view and a cross-sectional view of a test body according to the third embodiment of the present invention. The test body according to the present embodiment includes a base material 30, a first weld metal 32, and a second weld metal 33. The base material 30 includes an upper surface 30a ′ and a groove portion 31 in which a groove opening in the upper surface 30a ′ is formed. The first weld metal 32 is coupled to the groove portion 31. The first weld metal 32 includes a boundary region 32a. The second weld metal 33 is coupled to the boundary region 32a. The boundary region 32 a is formed in a film shape along the boundary between the first weld metal 32 and the second weld metal 33. The second weld metal 33 includes an upper surface 33 a on the opposite side of the first weld metal 32. The upper surface 33a and the upper surface 30a ′ form the same plane. The second weld metal 33 is formed with cracks 37 ′ to 39 ′. Each of the cracks 37 ′ to 39 ′ opens to the upper surface 33a, and the tip in the depth direction is located in the boundary region 32a. The opening length L1 of the crack 37 ′, the opening length L2 of the crack 38 ′, and the opening length L3 of the crack 39 ′ are different from each other. Further, since the upper surface 33a is inclined with respect to the boundary region 32a, and the cracks 37 ′ to 39 ′ are arranged along the inclination direction, the depth of the crack 37 ′ and the depth of the crack 38 ′. The depths of the cracks 39 'are different from each other.

  Next, the manufacturing method of the test body which concerns on this embodiment is demonstrated using Fig.6 (a)-(d).

  First, with reference to FIG. 6A, a process for forming the groove 31 on the base material 30 and a process for welding the first weld metal 32 to the groove 31 will be described. As the base material 30, for example, a stainless steel flat plate is used. The base material 30 includes an upper surface 30a. A groove 31 that opens to the upper surface 30 a is formed in the base material 30. A first filler metal is welded to the groove portion 31 to form a first weld metal 32. At this time, it forms so that the upper surface 32a of the 1st weld metal 32 may incline with respect to the upper surface 30a. The first weld metal 32 is located at the bottom portion of the groove portion 31. Here, the first filler material is the same as the first filler material according to the first embodiment. Therefore, the 1st weld metal 32 contains carbon and chromium similarly to the 1st filler metal.

  Next, with reference to FIG.6 (b), the process of welding the 2nd weld metal 33 to the 1st weld metal 32 and the process of forming the start notches 34-36 in the 2nd weld metal 33 are demonstrated. A second weld metal 33 is formed by welding a second filler metal to the first weld metal 32 (groove 31). The height of the second weld metal 33 continuously changes between a maximum height portion that is a height H13 and a minimum height portion that is a height H14. Here, the second filler material is the same as the second filler material according to the first embodiment. Therefore, the second weld metal 33 contains carbon and chromium in the same manner as the second filler material. The second filler metal and the second weld metal 33 are more susceptible to cracking than the first filler material and the first weld metal 32. The second weld metal 33 is welded onto the first weld metal 32 and is located at the opening portion of the groove portion 31. A boundary region 32a as a portion of the first weld metal 32 that is coupled to the second weld metal 33 is located under the second weld metal 33 and has a film shape. The boundary region 32a corresponds to the upper surface 32a. Start notches 34 to 36 having a depth H15 are formed on the upper surface of the second weld metal 33. Here, the positions where the start notches 34 to 36 are formed correspond to the positions where the cracks 37 ′ to 39 ′ are to be formed. The opening lengths of the start notches 34 to 36 correspond to the opening lengths L1 to L3 of the cracks 37 'to 39'.

  Next, with reference to FIG.6 (c), the process of extending the start notches 34-36 and forming the cracks 37-39 is demonstrated. The second weld metal 33 is immersed in the treatment liquid while applying stress to the second weld metal 33. Then, the start notch 34 extends in the depth direction to form a crack 37, the start notch 35 extends in the depth direction to form a crack 38, and the start notch 36 extends in the depth direction to form a crack 39. . The shallow part of each of the cracks 37 to 39 is a part formed as each of the start notches 34 to 36. The deep part of each of the cracks 37 to 39 is a part formed by stress corrosion cracking. The tip in the depth direction of each of the cracks 37 to 39 stops at the boundary region 32a.

  Next, with reference to FIG.6 (d), the process of removing the shallow part of the cracks 37-39 is demonstrated. The top surface 30a and the second weld are left so that a deep portion of the crack 37 remains as a crack 37 ', a deep portion of the crack 38 remains as a crack 38', and a deep portion of the crack 39 remains as a crack 39 '. The upper surface of the metal 33 is cut by a height H16. Here, the value of the height H16 is greater than or equal to the value of the depth H15. Therefore, the shallow part of the cracks 37 to 39 is removed. The height (interval between the boundary region 32a and the upper surface 33a) of the second weld metal 33 continuously changes between the maximum height portion that is the height H17 and the minimum height portion that is the height H18. is doing.

  Since the crack sensitivity of the second weld metal 33 is high and the crack sensitivity of the first weld metal 32 is low, when the tips of the cracks 37 to 39 reach the boundary region 32a in the process of forming the cracks 37 to 39, The progress of the cracks 37 to 39 stops. Therefore, in this embodiment, it is possible to form the cracks 37 ′ to 39 ′ having different target depths at a time.

  The lengths L1 to L3 may have the same value. Further, the first weld metal 32 and the second weld metal 33 according to the third embodiment may be applied to the first weld metal 14 to 16 and the second weld metal 17 to 19 according to the second embodiment. .

(Fourth embodiment)
7A and 7B show a front view and a cross-sectional view of a pipe test body according to the fourth embodiment of the present invention. Fig.7 (a) has shown the shape which looked at the piping test body which concerns on this embodiment from the axial direction. The pipe test body includes a metal pipe member 40, a first weld metal 45, and a second weld metal 46. The metal tube member 40 includes a first metal tube member 41, a second metal tube member 42, and a welding portion 43. The first metal tube member 41 and the second metal tube member 42 are arranged in the axial direction and are coupled to each other through the welded portion 43. The metal tube member 40 includes an inner side surface 40a facing the central axis. The welded portion 43 includes a groove portion 44 in which a groove that opens to the inner side surface 40a is formed. The first weld metal 45 is coupled to the groove portion 44. The boundary region 45 a is formed in a film shape along the boundary between the first weld metal 45 and the second weld metal 46. The second weld metal 46 has an upper surface 46 a on the opposite side of the first weld metal 45. The upper surface 46a and the inner side surface 40a form the same inner cylindrical surface. A crack 48 ′ is formed in the second weld metal 46. The crack 48 'opens to the upper surface 46a, and the tip in the depth direction is located in the boundary region 45a. The opening of the crack 48 'extends in the axial direction along the upper surface 46a.

  FIG. 8 shows a flowchart of a method for manufacturing a specimen according to the fourth embodiment of the present invention. The manufacturing method of the test body according to the present embodiment includes steps S1 to S12. Steps S1 to S12 will be described with reference to FIGS. 9A to 9F and FIG.

  First, step S1 will be described with reference to FIG. In step S <b> 1, each of the first metal tube member 41 and the second metal tube member 42 is machined, and the first metal tube member 41 and the second metal tube member 42 are welded via the welding portion 43. A metal tube member 40 is formed. The metal tube member 40 includes an inner side surface 40a facing the central axis.

  Next, step S2 will be described with reference to FIG. In step S <b> 2, the groove portion 44 that opens to the inner side surface 40 a is excavated in the welded portion 43. The groove portion 44 is formed only in a portion where a crack due to stress corrosion cracking is to be formed.

  Next, step S3 will be described with reference to FIG. In step S <b> 3, the first weld metal 45 is welded to the groove portion 44, and the second weld metal 46 is welded to the first weld metal 45. That is, the first filler metal is welded to the groove portion 44 to form the first weld metal 45, and the second weld metal is welded to the first weld metal 45 to form the second weld metal 46. The first weld metal 45 is located at the bottom portion of the groove portion 44. The second weld metal 46 is located at the opening portion of the groove portion 44. The height of the portion within the groove portion 44 of the second weld metal 46 (the portion radially outside the inner side surface 40a of the second weld metal 46) is indicated by H18, and the height of the second weld metal 46 is increased. The height of the portion (the portion located radially inward from the inner side surface 40a of the second weld metal 46) is indicated by H19. When the target depth of the crack 48 'is H21, the value of the height H18 is preferably equal to the value of the target depth H21. Here, the first filler material is the same as the first filler material according to the first embodiment. Therefore, the 1st weld metal 45 contains carbon and chromium similarly to the 1st filler metal. Here, the second filler material is the same as the second filler material according to the second embodiment. Therefore, the second weld metal 46 contains carbon and chromium in the same manner as the second filler material. The second filler metal and the second weld metal 46 are more susceptible to cracking than the first filler material and the first weld metal 45. A boundary region 45a as a portion of the first weld metal 45 coupled to the second weld metal 46 is located below the second weld metal 46 (outside in the radial direction) and has a film shape.

  Next, in step S4, the second weld metal 46 is sensitized by performing sensitization heat treatment. As the sensitizing heat treatment, for example, a stress relief annealing process at a temperature of about 600 ° C. or a low temperature aging process at a temperature of 288 to 550 ° C. can be applied. By sensitizing the second weld metal 46, stress corrosion cracks are easily generated and propagated in the second weld metal 46.

  Next, in step S5, a nondestructive inspection is performed to determine whether or not the weld 43, the first weld metal 45, and the second weld metal 46 are defective.

  Next, step S6 will be described with reference to FIG. In step S <b> 6, a start notch 47 having a depth H <b> 20 is provided on the inner side surface (top surface of the surplus portion) of the second weld metal 46 by an electric discharge machining method (EDM). The start notch 47 is provided so as to extend in the axial direction. The value of the depth H20 is preferably smaller than or equal to the value of the height H19.

  Next, step S7 will be described with reference to FIG. In step S <b> 7, a load 50 is applied to the metal pipe member 40, and a circumferential tensile stress 51 is applied to the second weld metal 46. As a method for applying the tensile stress 51, it is possible to use three-point / four-point bending. Then, the second weld metal 46 is immersed in the treatment liquid while applying the tensile stress 51 to the second weld metal 46. A polythionic acid solution is used as the treatment liquid. For example, in an aqueous solution of potassium tetrathionate or sodium tetrathionate, the concentration of potassium tetrathionate or sodium tetrathionate is 0.3 to 6% by weight, the temperature of the treatment liquid is 5 to 60 ° C., and the pH value of the treatment liquid is 3 to 6 Can be used. Here, if the treatment liquid contains 0.06 to 6% by weight of chlorine, the occurrence and development of stress corrosion cracking is accelerated.

  FIG.9 (e) has shown the piping test body after step S7. As a result of step S <b> 7, the start notch 47 advances and a crack 48 is formed. The shallow portion of the crack 48 is a portion formed as the start notch 47. The deep part of the crack 48 is a part formed by stress corrosion cracking. The tip of the crack 48 in the depth direction stops at the boundary region 45a.

  Next, step S8 will be described with reference to FIG. In step S <b> 8, the surplus portion (the portion located radially inward from the inner side surface 40 a of the second weld metal 46) is deleted. At this time, the shallow portion of the crack 48 is also removed. As a result of step S8, the deep part of the crack 48 is left as a crack 48 '.

  Next, in step S9, the depth H21 and the length L4 of the crack 48 'are examined. The depth H21 is investigated by an ultrasonic flaw detection technique. The length L4 is the axial length of the opening of the crack 48 '.

  When the value of the depth H21 is smaller than the target value, step S7 is additionally performed so that the value of the depth H21 becomes the target value. When the additional step S7 is performed, the portion of the pipe test body other than the crack 48 'is covered with silicon rubber or fluororubber so that only the crack 48' is immersed in the processing solution. .

  Next, in step S10, surface finishing of the welded portion 43 and the second weld metal 46 is performed.

  Next, in step S11, the depth H21 and the length L4 of the crack 48 'are measured.

  Next, in step S12, a pipe test body is completed.

  Since the crack sensitivity of the second weld metal 46 is high and the crack sensitivity of the first weld metal 45 is low, the progress of the crack 48 stops when the tip of the crack 48 reaches the boundary region 45a in step S7. Therefore, in the present embodiment, it is possible to accurately control the depth H21 of the crack 48 '.

  According to the first to fourth embodiments, a test body in which shallow stress corrosion cracks are formed and a test body in which stress corrosion cracks having different depths are formed in stages are provided. If a nondestructive flaw detector such as an ultrasonic flaw detector is calibrated using the specimens according to the first to fourth embodiments, it is possible to detect shallow stress corrosion cracks generated in an actual machine. In addition, it is possible to accurately measure the depth of stress corrosion cracking that has occurred in the actual machine.

FIG. 1A shows a top view of a test body according to the first embodiment of the present invention, and FIG. 1B shows a cross-sectional view of the test body according to the first embodiment. 2A to 2D are cross-sectional views of a test body for explaining a method for manufacturing the test body according to the first embodiment. FIG. 3A shows a top view of a specimen according to the second embodiment of the present invention, and FIG. 3B shows a cross-sectional view of the specimen according to the second embodiment. FIGS. 4A to 4D are cross-sectional views of a test body for explaining a method for manufacturing the test body according to the second embodiment. FIG. 5A shows a top view of a test body according to the third embodiment of the present invention, and FIG. 5B shows a cross-sectional view of the test body according to the second embodiment. FIGS. 6A to 6D are cross-sectional views of the test body for explaining the method for manufacturing the test body according to the third embodiment. Fig.7 (a) shows the front view of the test body which concerns on 4th Embodiment, FIG.7 (b) shows sectional drawing of the test body which concerns on 4th Embodiment. FIG. 8 shows a flowchart of a method for manufacturing a specimen according to the fourth embodiment of the present invention. FIGS. 9A to 9F are cross-sectional views of a test body for explaining a method for manufacturing the test body according to the fourth embodiment. FIG. 10: shows the front view of the test body for demonstrating the stress addition method which concerns on 4th Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Base material 1a, 1a '... Upper surface 2 ... Groove part 3 ... 1st weld metal 3a ... Boundary area | region 4 ... 2nd weld metal 4a ... Upper surface 5 ... Start notch 6 ... Crack 6' ... Crack (SCC)
DESCRIPTION OF SYMBOLS 10 ... Base material 10a, 10a '... Upper surface 11-13 ... Groove part 14-16 ... 1st weld metal 14a-16a ... Boundary area | region 17-19 ... 2nd weld metal 17a-19a ... Upper surface 20-22 ... Start notch 23-25, 23'-25 '... crack (SCC)
DESCRIPTION OF SYMBOLS 30 ... Base material 30a, 30a '... Upper surface 31 ... Groove part 32 ... 1st weld metal 32a ... Boundary area | region 33 ... 2nd weld metal 33a ... Upper surface 34-36 ... Start notch 37-39, 37'-39' ... Crack (SCC)
DESCRIPTION OF SYMBOLS 40 ... Metal pipe member 40a ... Inner side surface 41 ... 1st metal pipe member 42 ... 2nd metal pipe member 43 ... Welding part 44 ... Groove part 45 ... 1st weld metal 45a ... Boundary area 46 ... 2nd weld metal 46a ... Upper surface 47 ... start notches 48, 48 '... crack (SCC)
50 ... Load 51 ... Tensile stress

Claims (6)

A first weld metal;
A second weld metal coupled to the first weld metal;
A first crack is provided in the second weld metal;
The tip in the depth direction of the first crack is located in a first boundary region between the first weld metal and the second weld metal,
The first weld metal is a nickel-based alloy containing a first weight concentration of carbon and a second weight concentration of chromium;
The second weld metal is a nickel-based alloy containing a third weight concentration of carbon and a fourth weight concentration of chromium;
The third weight concentration is higher than the first weight concentration;
The fourth weight concentration is lower than the second weight concentration. A second crack is provided in the second weld metal;
The tip in the depth direction of the second crack is located in the first boundary region,
The first crack and the second crack open to the surface of the second weld metal;
The test body according to claim 1, wherein the surface is inclined with respect to the first boundary region. A first weld metal;
A second weld metal coupled to the first weld metal;
A first crack of stress corrosion cracking is provided in the second weld metal;
The tip in the depth direction of the first crack is located in a first boundary region between the first weld metal and the second weld metal,
A test specimen in which there is a condition that the crack sensitivity of the second weld metal to stress corrosion cracking is higher than the crack sensitivity of the first weld metal. Melting and solidifying the first filler material to form a first weld metal;
Forming a second weld metal welded to the first weld metal by melting and solidifying the second filler metal;
Forming a stress corrosion crack in the second weld metal,
The first filler material is a nickel-based alloy containing a first weight concentration of carbon and a second weight concentration of chromium,
The second filler material is a nickel-based alloy containing a third weight concentration of carbon and a fourth weight concentration of chromium,
The third weight concentration is higher than the first weight concentration;
The fourth weight concentration is lower than the second weight concentration. The step of forming the crack comprises:
Forming a start notch on the surface of the second weld metal;
Forming the crack starting from the start notch;
The method for manufacturing a test body according to claim 4, further comprising a step of cutting the surface. Melting and solidifying the first filler material to form a first weld metal;
Forming a second weld metal welded to the first weld metal by melting and solidifying the second filler metal;
Forming a start notch on the surface of the second weld metal;
Immersing the second weld metal in a treatment liquid while applying stress to the second weld metal;
Cutting the surface, and
The first filler material is a first nickel-based alloy,
The second filler material is a second nickel base alloy different from the first nickel base alloy,
The method for producing a test specimen, wherein the second nickel-based alloy has higher cracking susceptibility to stress corrosion cracking in the treatment solution than the first nickel-based alloy has cracking susceptibility to stress corrosion cracking.

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