Test specimen and preparation method thereof

Abstract

The present disclosure belongs to the field of nuclear power technology, and specifically relates to a test specimen and its preparation method. In the present disclosure, there is a gap between the first test block and the second test block, and the gap is divided into a first gap area and a second gap area from top to bottom. The first gap area is a V-shaped gap that is wide at the top and narrow at the bottom, and the second gap area has a uniform width; the first feeler gauge is embedded in the position where the first gap area and the second gap area are connected, and the second feeler gauge is embedded in the lower end of the second gap; the first test block, the second test block and the second feeler gauge are fixedly connected by welding, and the first feeler gauge can be taken out of the gap. After the first feeler gauge is taken out of the gap, brazing can be used to form a brazed seam between the upper end of the second feeler gauge and the bottom end of the first gap area, and the top of the brazed seam has a crack of a preset depth. The present disclosure can ensure the stability of the test process conditions and ensure that the specimen can be reliably tested under higher fracture strength test conditions.

Description

Technical Field

[0001] The invention belongs to the technical field of nuclear power, and in particular relates to a test sample and a preparation method thereof. Background Art

[0002] Compact tensile specimens (CT) are a commonly used specimen structure for studying the stress corrosion resistance of metallic materials. They can be used to test and measure stress corrosion cracking rates in various media. However, in related technologies, the specimen structure is manufactured as a single piece. Testing the stress corrosion resistance of brazed joints requires the preparation of specialized brazed joint compact tensile specimens.

[0003] Because the gap between brazed joints is extremely narrow, typically only around 0.1mm, precise control of the gap is required to reduce test variables. Furthermore, brazed joints generally have low fracture strength, making them prone to premature fracture under high-fracture-strength test conditions. This can lead to insufficient test time and compromised test results reliability. Therefore, there is an urgent need to enhance the reliability of test specimens under high-fracture-strength test conditions. Summary of the Invention

[0004] In order to overcome the problems existing in the related art, a test specimen and a preparation method thereof are provided.

[0005] According to one aspect of an embodiment of the present disclosure, there is provided a test specimen, the test specimen comprising: a first test block, a second test block, a first feeler gauge, and a second feeler gauge;

[0006] There is a gap between the first test block and the second test block, and the gap is divided into a first gap area and a second gap area from top to bottom. The first gap area is a V-shaped gap that is wide at the top and narrow at the bottom. The second gap area has a uniform width. The lower end of the first gap area is connected to the second gap area, and the width of the first gap area is greater than that of the second gap area.

[0007] The first feeler gauge is embedded in the position where the first gap area and the second gap area are connected, and the second feeler gauge is embedded in the lower end of the second gap;

[0008] The first test block, the second test block and the second feeler gauge are fixedly connected by electron beam welding. The first feeler gauge can be removed from the gap. After the first feeler gauge is removed from the gap, a brazed seam can be formed between the electron beam weld and the bottom end of the first gap area by brazing, and a crack of a preset depth is provided at the top of the brazed seam.

[0009] In a possible implementation, the distance between the electron beam weld and the bottom end of the first gap area is between 4 and 5 mm.

[0010] In a possible implementation, the depth of the crack at the top of the weld is between 1 and 2 mm.

[0011] In a possible implementation, a width of the second gap is between 50 and 150 micrometers.

[0012] In a possible implementation, the roughness of the opposing surfaces of the first test block and the second test block is between 1.6 and 3.2 Ra.

[0013] In a possible implementation, the first feeler gauge and the second feeler gauge are rectangular, and the first feeler gauge and the second feeler gauge are radially arranged in the gap.

[0014] According to another aspect of the present disclosure, a method for preparing a test sample is provided. The method is applied to prepare the above-mentioned test sample, and the method includes:

[0015] Selecting a first feeler gauge and a second feeler gauge of preset thickness, and embedding the first feeler gauge at a position where the first gap area connects with the second gap area, and embedding the second feeler gauge at a lower end of the second gap area, so that a preset distance exists between the first feeler gauge and the second feeler gauge;

[0016] The first test block, the second test block, and the second feeler gauge are fixedly connected by electron beam welding to form a test specimen. The penetration of the electron beam welding should reach a preset depth. The first feeler gauge is removed from the first gap area, and the test specimen is cleaned.

[0017] After the test sample is cleaned, a stopper is injected into the bottom of the first gap region using a syringe, so that the injected stopper penetrates into the second gap region to a preset depth;

[0018] After applying brazing material to the edge of the gap between the second gap area and the first gap area, placing the test sample in a vacuum brazing furnace for brazing treatment;

[0019] After taking out of the furnace, clean off the residual solder stopper and grind the surface of the test sample to make it smooth.

[0020] The beneficial effects of the present disclosure are as follows: the present disclosure realizes precise control of the gap between the first test block and the second test block by using the first feeler gauge and the second feeler gauge, and the second feeler gauge is respectively welded to the first test block and the second test block, thereby increasing the stability of the connection between the first test block and the second test block on the one hand, and reducing the length of the brazing weld on the other hand, thereby ensuring the stability of the test process conditions and ensuring that the specimen can be reliably tested under higher fracture strength test conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is a perspective view of a test specimen according to an exemplary embodiment.

[0022] In the picture:

[0023] 1. First test block; 2. Second test block; 3. First feeler gauge; 4. Second feeler gauge; 5. First gap area; 6. Second gap area; DETAILED DESCRIPTION

[0024] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0025] Figure 1 FIG is a perspective view of a test specimen according to an exemplary embodiment. Figure 1 As shown, the test specimen includes: a first test block 1, a second test block 2, a first feeler gauge 3 and a second feeler gauge 4;

[0026] The first test block 1 and the second test block 2 are arranged opposite to each other, and there is a gap between the first test block 1 and the second test block 2. The gap is divided into a first gap area 5 and a second gap area 6 from top to bottom. The first gap area 5 is a V-shaped gap that is wide at the top and narrow at the bottom. The second gap area 6 has a uniform width. The width of the second gap area 6 can be set according to the width of the brazing seam required for the brazing test. The lower end of the first gap area 5 is connected to the second gap area 6. The width of the first gap area 5 is greater than the width of the second gap area 6.

[0027] The first feeler gauge 3 is embedded in the position where the first gap area 5 and the second gap area 6 are connected, and the second feeler gauge 4 is embedded in the lower end of the second gap;

[0028] The first test block 1, the second test block 2 and the second feeler gauge 4 are fixedly connected by welding, and the first feeler gauge 3 can be removed from the gap. After the first feeler gauge 3 is removed from the gap, a brazing seam can be formed between the upper end of the second feeler gauge 4 and the bottom end of the first gap area 5 by brazing, and the top of the brazing seam has a crack of a preset depth.

[0029] The present disclosure achieves precise control of the gap between the first test block and the second test block by using a first feeler gauge and a second feeler gauge. The second feeler gauge is welded to the first test block and the second test block respectively. On the one hand, the stability of the connection between the first test block and the second test block is increased, and on the other hand, the length of the brazing weld is reduced, thereby ensuring the stability of the test process conditions and ensuring that the specimen can be reliably tested under higher fracture strength test conditions.

[0030] In a possible implementation, the distance between the electron beam weld and the bottom end of the first gap area is between 4 and 5 mm.

[0031] In a possible implementation, the depth of the crack at the top of the weld is between 1 and 2 mm.

[0032] In a possible implementation, a width of the second gap is between 50 and 150 micrometers.

[0033] In a possible implementation, the roughness of the opposing surfaces of the first test block and the second test block is between 1.6 and 3.2 Ra.

[0034] In a possible implementation, the first feeler gauge and the second feeler gauge are rectangular, and the first feeler gauge and the second feeler gauge are radially arranged in the gap.

[0035] In one possible implementation, a method for preparing a test sample is provided. The method is applied to prepare the above-mentioned test sample, and the method includes:

[0036] Selecting a first feeler gauge and a second feeler gauge of preset thickness, and embedding the first feeler gauge at a position where the first gap area connects with the second gap area, and embedding the second feeler gauge at a lower end of the second gap area, so that a preset distance exists between the first feeler gauge and the second feeler gauge;

[0037] The first test block, the second test block, and the second feeler gauge are fixedly connected by electron beam welding to form a test specimen. The penetration of the electron beam welding should reach a preset depth. The first feeler gauge is removed from the first gap area, and the test specimen is cleaned.

[0038] After the test sample is cleaned, a stopper is injected into the bottom of the first gap region using a syringe, so that the injected stopper penetrates into the second gap region to a preset depth;

[0039] After applying brazing material to the edge of the gap between the second gap area and the first gap area, placing the test sample in a vacuum brazing furnace for brazing treatment;

[0040] After taking out of the furnace, clean off the residual solder stopper and grind the surface of the test sample to make it smooth.

[0041] In an application example, a vacuum brazing specimen of 304L stainless steel and BNi-7 brazing material is used as an example to illustrate the following:

[0042] The gap between the brazed joints to be controlled is 100μm. First, use 304L stainless steel to make a symmetrical first test block and a second test block. The surface roughness of the brazing seam between the first test block and the second test block should be controlled at 1.6~3.2Ra. Select a standard feeler gauge with a thickness of 100μm, use tin snips to cut two small pieces of about 1cm long, and place them at the top and bottom of the gap between the first test block and the second test block respectively. Align the two test blocks, and use a small vise to clamp the first test block, the second test block and the feeler gauge together. Electron beam butt welding is performed on the gap at the bottom of the first test block and the second test block. The penetration depth of the electron beam weld is made to be about 10mm, so that the first test block, the second test block and the first feeler gauge are welded and fixed. After the electron beam welding is completed, remove the fixture, use pliers to remove the first feeler gauge, and place the test sample in an ultrasonic cleaner to clean the sample. Then, using a dispensing needle with an inner diameter of approximately 1mm and a syringe, inject aluminum oxide solder stopper along the brazing seam at the bottom of the first gap area, maintaining a certain pressure to ensure that the solder stopper penetrates approximately 2mm into the second gap area (also called the brazing seam). Apply an appropriate amount of BNi-7 brazing filler metal to the edge of the brazing seam, and then place the specimen into the furnace for vacuum brazing. After exiting the furnace, use an ultrasonic cleaner to clean off any remaining solder stopper. Then, polish the sides and bottom of the test specimen on a metallographic specimen grinder and polisher to create a compact tensile specimen suitable for stress corrosion testing.

[0043] While various embodiments of the present disclosure have been described above, the foregoing description is intended to be illustrative, non-exhaustive, and not limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is selected to best explain the principles of the embodiments, their practical applications, or technical improvements to existing technologies, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A method for preparing a test sample, characterized in that: The test specimen includes: a first test block, a second test block, a first feeler gauge and a second feeler gauge; There is a gap between the first test block and the second test block, and the gap is divided into a first gap area and a second gap area from top to bottom. The first gap area is a V-shaped gap that is wide at the top and narrow at the bottom. The second gap area has a uniform width. The lower end of the first gap area is connected to the second gap area, and the width of the first gap area is greater than that of the second gap area. The first feeler gauge is embedded in the position where the first gap area and the second gap area are connected, and the second feeler gauge is embedded in the lower end of the second gap area; The first test block, the second test block, and the second feeler gauge are fixedly connected by an electron beam weld, and the first feeler gauge can be removed from the gap. After the first feeler gauge is removed from the gap, a brazed seam can be formed between the electron beam weld and the bottom end of the first gap region by brazing, and a crack of a preset depth is formed at the top of the brazed seam; The method for preparing the test sample comprises: Selecting a first feeler gauge and a second feeler gauge of preset thickness, and embedding the first feeler gauge at a position where the first gap area connects with the second gap area, and embedding the second feeler gauge at a lower end of the second gap area, so that a preset distance exists between the first feeler gauge and the second feeler gauge; The first test block, the second test block, and the second feeler gauge are fixedly connected by electron beam welding to form a test specimen. The penetration of the electron beam welding should reach a preset depth. The first feeler gauge is removed from the first gap area, and the test specimen is cleaned. After the test sample is cleaned, a stopper is injected into the bottom end of the first gap region using a syringe, so that the injected stopper penetrates into the second gap region to a preset depth; After applying brazing material to the edge of the gap between the second gap area and the first gap area, placing the test sample in a vacuum brazing furnace for brazing treatment; After taking out of the furnace, clean off the remaining solder stopper and grind the surface of the test sample to make it smooth.

2. The method according to claim 1, characterized in that The distance between the electron beam weld and the bottom end of the first gap area is between 4 and 5 mm.

3. The method according to claim 1, characterized in that The depth of the crack at the top of the weld is between 1 and 2 mm.

4. The method according to claim 1, wherein The width of the second gap is between 50 and 150 micrometers.

5. The method according to claim 1, wherein The roughness of the opposing surfaces of the first test block and the second test block ranges from 1.6 to 3.2 Ra.

6. The method according to claim 1, characterized in that The first feeler gauge and the second feeler gauge are rectangular and are radially arranged in the gap.

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