CN105823661A - Method for preparing simulated stress corrosion crack with controllable crack size and conductivity - Google Patents

Abstract

A simulated stress corrosion crack preparation method that can control crack size and conductivity. First, two stainless steel test blocks are processed. According to the size of the real stress corrosion crack, a pit of a certain size and shape is pre-buried on the surface to be welded of one of the test blocks. Defects, then select high-temperature-resistant materials with appropriate conductivity to fill in the pre-embedded pits based on the electrical conductivity of the real cracks, and then use solid-state welding technology to weld the two test blocks together to obtain a welded test piece. Cut off the welded test piece and pre-embed it. The part above the defect area can be processed into a surface defect specimen and used for eddy current testing experiments to simulate the real stress corrosion crack; the simulated specimen prepared by the method of the present invention can be used for stress corrosion crack specimens with complex actual shapes and difficult preparation. An effective alternative, it has the advantages of simple operation, low cost, and adjustable crack size and conductivity. It can be widely used in the detection capability certification system of quantitative eddy current detection methods for stress corrosion cracks.

Description

Preparation method of simulated stress corrosion cracks with controllable crack size and electrical conductivity

technical field

The invention relates to the field of preparation of stress corrosion crack simulation test pieces, in particular to a preparation method of simulated stress corrosion cracks which can control the crack size and electrical conductivity.

Background technique

Austenitic stainless steel materials sensitive to stress corrosion are widely used in nuclear power plants, and the existence of tensile stress and corrosive environment in nuclear power structures makes stress corrosion cracks widely exist in key parts of nuclear power plants, such as heat exchange tube sheets of steam generators Expansion part, welding part of main cooling tube platform, etc. The existence of stress corrosion cracks poses a huge threat to the safe operation of nuclear power structures, and considering economic benefits, it is necessary to evaluate the size of cracks, so the quantitative nondestructive testing of stress corrosion cracks is extremely important. At present, the testing ability certification system is proposed in the world, and the testing instrument system and testing personnel are integrated for specific testing targets. my country is also actively discussing the introduction of a testing capability certification system for quantitative non-destructive testing of stress corrosion cracks. However, one of the key technologies is to have typical stress corrosion crack test pieces. Stress corrosion cracking is different from other cracks in that the crack region has a partial electrical conductivity weaker than that of the base material, and the cracking process is very complicated. Therefore, the existing artificial production methods are not only time-consuming, laborious and expensive, but also difficult to control the size of the crack. The prepared stress corrosion cracks often require destructive experiments to determine the final size and shape, and the electrical conductivity of the crack area cannot be artificially regulated. In summary, the development of stress corrosion crack simulation specimens with controllable size and electrical conductivity has important practical value for the certification system of quantitative nondestructive testing capabilities for stress corrosion cracks.

In view of this, the present invention proposes a simulated stress corrosion crack preparation method that can control the crack size and electrical conductivity, which can realize the regulation and control of the crack size and electrical conductivity, and the prepared simulated specimen can detect real stress corrosion cracks in the sense of eddy current testing. Make effective simulations.

Contents of the invention

In order to solve the above-mentioned existing artificial stress corrosion crack test piece preparation difficulties, the size of the prepared crack and the uncontrollable electrical conductivity of the crack area, the object of the present invention is to provide a simulated stress corrosion cracking that can control the crack size and electrical conductivity The preparation method can regulate the crack size and electrical conductivity and simulate and replace the stress corrosion cracked specimen in the sense of eddy current detection. This method has the advantages of simple operation, easy implementation, low cost, and known simulated crack size and electrical conductivity. It can be widely used in the certification system of stress corrosion crack quantitative non-destructive testing capability.

To achieve the above object, the present invention adopts the following technical solutions:

A method for preparing simulated stress corrosion cracks with adjustable crack size and electrical conductivity, comprising the following steps:

Step 1: The design and processing of embedded defects and the filling of high-temperature-resistant dielectric materials with specific conductivity, the specific steps are as follows:

1) Process and prepare the first cuboid stainless steel test piece 6 and the second cuboid stainless steel test piece 7 with the same size, and the first surface to be welded 8 of the first cuboid stainless steel test piece 6 and the second cuboid stainless steel test piece 7 Two, the surface 9 to be welded is polished to make it smooth and smooth, and the parallelism between the upper and lower surfaces of the first cuboid stainless steel test block 6 and the second cuboid stainless steel test block 7 is good for welding in addition;

2) Use TOFD ultrasonic testing equipment to measure the depth of the real stress corrosion crack, and use a microscope to observe the length and width of the crack to obtain the parameter information of the real stress corrosion crack size;

3) according to the size and the shape of the real stress corrosion crack measured in step 2), in step 1) prepare the pre-buried pit defect 1 of the same shape on the first surface 8 to be welded of the first cuboid stainless steel test piece 6, pre-process The length and width of the buried pit defect 1 correspond to the length and depth of the real stress corrosion crack respectively, and the depth of the pre-buried pit defect 1 is set according to the width of the real stress corrosion crack, and the second cuboid stainless steel test block 7 does not Any embedded defect processing;

4) In step 3), the different areas along the width direction of the pre-buried pit defect 1 are the first area 2, the second area 3, the third area 4 and the fourth area 5, respectively filled with high temperature resistant materials with different conductivity Dielectric material, the thickness of the filling material is the same as the depth of the pre-buried pit defect 1, so that the surface is smooth and the test block to be welded is obtained;

Step 2: Preparation of simulated stress corrosion cracks based on solid phase welding technology, the specific steps are as follows:

1) The second cuboid stainless steel test block 7 prepared in step 1) of step 1 and the test block to be welded prepared in step 4) are used in solid phase welding technology, under a pressure of 8 to 12 MPa at 10 and a temperature of 1000 to 1200 ° C Keep for 0.5 to 2 hours under high temperature conditions to realize the welding of two test blocks and obtain welding test pieces;

2) Cut the part 12 of the welded test piece obtained in step 1) above the embedded defect, and process the welded test piece into a surface defect test piece 11, which is convenient for eddy current testing, so as to obtain the real stress corrosion cracking in the sense of eddy current testing Simulated specimens with equivalent detection signals.

The solid-phase welding technique described in step 2 (1) is hot isostatic pressure diffusion bonding or uniaxial pressurized diffusion welding.

The high-temperature-resistant dielectric material described in step 1-4) is a conductive ceramic or a high-temperature-resistant conductive composite material.

Compared with the prior art, the present invention has the following advantages:

1) The method of the present invention can prepare a simulated test piece equivalent to a real stress corrosion crack detection signal in the sense of eddy current detection, and the method has the advantages of simple operation, easy realization, and low processing cost;

2) The simulated stress corrosion crack test piece prepared by the present invention has the characteristics of known and controllable crack size and electrical conductivity, and can be widely used in the quantitative nondestructive testing capability certification system for stress corrosion cracks, and has universal applicability.

Description of drawings

Fig. 1 is a schematic diagram of processing simulated stress corrosion cracks by using solid state welding technology in the present invention.

Figure 2 shows the real stress corrosion cracked specimen.

Figure 3 is a schematic diagram of surface defect processing.

detailed description

As shown in Figure 1, the principle of the present invention is to pre-embed defects on the surface of a test block to be welded, and then fill high-temperature resistant media with different conductivity in different regions of the defects, and then do not use this for the other test block. After processing, the two test blocks are welded together by solid-state welding technology, and the welded part contains defects with a certain size and conductivity weaker than the base material, so as to simulate the real stress corrosion cracked test piece in the sense of eddy current testing.

The method of the present invention will be further described in detail with reference to FIG. 1 , FIG. 2 and FIG. 3 .

Step 1: The design and processing of embedded defects and the filling of high-temperature-resistant dielectric materials with specific conductivity, the specific steps are as follows:

1) Process and prepare the first cuboid stainless steel test piece 6 and the second cuboid stainless steel test piece 7 with the same size, and the first surface to be welded 8 of the first cuboid stainless steel test piece 6 and the second cuboid stainless steel test piece 7 Two, the surface 9 to be welded is polished to make it smooth and smooth, and the parallelism between the upper and lower surfaces of the first cuboid stainless steel test block 6 and the second cuboid stainless steel test block 7 is good for welding in addition;

2) Use TOFD ultrasonic testing equipment to measure the depth of the real stress corrosion crack as shown in Figure 2, and use a microscope to observe the length and width of the crack to obtain the parameter information of the real stress corrosion crack size;

3) according to the size and the shape of the real stress corrosion crack measured in step 2), in step 1) prepare the pre-buried pit defect 1 of the same shape on the first surface 8 to be welded of the first cuboid stainless steel test piece 6, pre-process The length and width of the buried pit defect 1 correspond to the length and depth of the real stress corrosion crack respectively, and the depth of the pre-buried pit defect 1 is set according to the width of the real stress corrosion crack, and the second cuboid stainless steel test block 7 does not Any embedded defect processing;

4) In step 3), the different regions of the pre-buried pit defect 1 along the width direction are the first region 2, the second region 3, the third region 4 and the fourth region 5, respectively filled with high-temperature resistant media with different conductivity material, and the electrical conductivity of the filling medium gradually increases in order to simulate the change trend of crack electrical conductivity with the crack depth increasing. The thickness of the filling material is the same as the depth of the pre-buried pit defect 1, so that the surface is smooth, and the obtained Test block to be welded.

Step 2: Preparation of simulated stress corrosion cracks based on solid phase welding technology, the specific steps are as follows:

1) The second cuboid stainless steel test block 7 prepared in step 1) of step 1 and the test block to be welded prepared in step 4) are used in solid phase welding technology, under a pressure of 8 to 12 MPa at 10 and a temperature of 1000 to 1200 ° C Keep for 0.5 to 2 hours under high temperature conditions to realize the welding of two test blocks and obtain welding test pieces;

2) As shown in Figure 3, cut the part 12 above the embedded defect of the welding test piece in step 1), and process it into a surface defect test piece 11, which is convenient for eddy current testing, thereby obtaining the real stress in the sense of eddy current testing. Corrosion crack detection signal equivalent simulated specimen.

It should be noted that in the actual process, step 1 and step 4) can be divided into more detailed areas along the width direction of the pre-buried pit, and the conductivity of the filled material can be changed more finely, which has achieved better simulation results.

Claims (3)

1. the simulation stress corrosion cracking (SCC) preparation method of controllable crackle size and electrical conductivity, it is characterised in that: comprise the steps:

Step 1: the Design and Machining of pre-buried defect and the filling of the high-temperature resistant medium material of specific conductivity, specifically comprises the following steps that

1) the first cuboid rustless steel test block (6) and second cuboid rustless steel test block (7) of two consistent size is prepared in processing, and the first surface to be welded (8) of the first cuboid rustless steel test block (6) and the second surface to be welded (9) of the second cuboid rustless steel test block (7) are carried out grinding process and make it bright and clean smooth, additionally processed makes the depth of parallelism of upper and lower surface of the first cuboid rustless steel test block (6) and the second cuboid rustless steel test block (7) good to weld；

2) utilize TOFD ultrasonic detection equipment to record the degree of depth of true stress corrosion cracking, and utilize the length and width of microscopic crackle, it is thus achieved that the parameter information of true stress corrosion cracking size；

3) according to step 2) in the size and shape of true stress corrosion cracking measured, in step 1) prepare the pre-buried pit defect (1) processing same shape on the first surface to be welded (8) of the first cuboid rustless steel test block (6), the length and width of pre-buried pit defect (1) corresponds respectively to length and the degree of depth of true stress corrosion cracking, the degree of depth of pre-buried pit defect (1) is then set according to the width of true stress corrosion cracking, and the second cuboid rustless steel test block (7) does not carry out the processing of any pre-buried defect；

4) in step 3) in pre-buried pit defect (1) zones of different in the width direction be respectively first area (2), second area (3), the 3rd region (4) and the 4th region (5) place and fill the high-temperature resistant medium material of different conductivity respectively, the thickness of packing material is identical with the degree of depth of pre-buried pit defect (1), so that surfacing, obtain test block to be welded；

Step 2: prepared by simulation stress corrosion cracking (SCC) based on Solid-phase welding technology, specifically comprise the following steps that

1) by the step 1 of step 1) the second cuboid rustless steel test block (7) and step 4 of preparing) test block to be welded for preparing, utilize Solid-phase welding technology, keep 0.5～2 hour under pressure (10) 8～12MPa and the hot conditions of 1000～1200 DEG C, the welding of two test blocks can be realized, it is thus achieved that welding piece；

2) by step 1) more than the pre-buried defect of welding piece that obtains part (12) cuts, welding piece is processed into surface defect test specimen (11), it is convenient for EDDY CURRENT, thus obtains imitation specimen of equal value with true stress corrosion cracking detection signal in EDDY CURRENT meaning.

Controllable crackle size the most according to claim 1 and the simulation stress corrosion cracking (SCC) preparation method of electrical conductivity, it is characterised in that: the 1 of step 2) described in Solid-phase welding technology be high temperature insostatic pressing (HIP) diffusion connect or an axle pressurization Diffusion Welding.

Controllable crackle size the most according to claim 1 and the simulation stress corrosion cracking (SCC) preparation method of electrical conductivity, it is characterised in that: the 4 of step 1) described in high-temperature resistant medium material be conductivity ceramics or high temperature resistant conducing composite material.