Small fatigue test device and test method capable of realizing low-oxygen liquid lead bismuth environment

Abstract

The invention relates to a small fatigue test device and test method capable of realizing a low-oxygen liquid lead bismuth environment, the device is applied to a uniaxial fatigue testing machine, and the device comprises a liquid lead bismuth test unit, a gas circuit unit, a thermocouple connecting pipeline and an oxygen concentration detection unit; carrying out a mechanical test on the threaded sample through the liquid lead bismuth test unit, the gas circuit unit and the thermocouple connecting pipeline; the oxygen concentration is detected through the liquid lead bismuth test unit, the gas circuit unit, the thermocouple connecting pipeline and the oxygen concentration detection unit. The device can be directly adapted to a uniaxial fatigue testing machine, the gauge length section of the threaded sample is wrapped in the liquid lead bismuth environment, the low-oxygen lead bismuth environment and the testing performance can be guaranteed on the premise of reducing the size, and the device has the advantages of being compact in structure, low in cost, low in lead bismuth consumption, fast in oxygen reduction, high in adaptability, easy to operate and the like; and the mechanical test requirements in a low-oxygen liquid lead bismuth environment can be met.

Description

Technical Field

[0001] This invention relates to the field of nuclear engineering technology, specifically to a small-scale fatigue testing device and method capable of creating a low-oxygen liquid lead-bismuth environment. Background Technology

[0002] Nuclear energy possesses core advantages such as zero greenhouse gas emissions, high energy density, and stable baseload power supply, making it a key technological direction for addressing energy shortages and climate change. Among them, the lead-cooled fast reactor (LBE) in Generation IV nuclear power reactors is considered one of the core development directions for future advanced nuclear energy systems due to its inherent high safety, low nuclear waste generation, and high fuel utilization efficiency. Liquid lead-bismuth alloy (LBE) has become the preferred coolant for LBE due to its high boiling point, strong chemical inertness, small neutron absorption cross section, excellent thermal conductivity and heat capacity, and ability to effectively shield fission products.

[0003] However, the corrosion and embrittlement of in-reactor structural materials by liquid lead-bismuth alloys during service is a core bottleneck restricting the commercial application of lead-cooled fast reactors. Existing research shows that the corrosion rate of liquid lead-bismuth materials is highly correlated with the ambient oxygen concentration. Therefore, precisely controlling the oxygen concentration in the liquid lead-bismuth environment and studying the fatigue performance of structural materials in a low-oxygen liquid lead-bismuth environment is crucial for revealing the failure mechanism of lead-bismuth-induced materials and guiding material selection. While current mechanical testing devices in lead-bismuth environments can control oxygen concentration and perform related mechanical tests, their multiple loading and oxygen control systems result in a large overall structure, high cost, and demanding operational requirements, making them unsuitable for conventional mechanical testing devices.

[0004] To address the above technical issues, a small-scale fatigue testing device and method capable of achieving a low-oxygen liquid lead-bismuth environment are proposed. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a small-scale fatigue testing device and method that can realize a low-oxygen liquid lead-bismuth environment. It can be directly adapted to a uniaxial fatigue testing machine, and the gauge length of the threaded specimen is wrapped in the liquid lead-bismuth environment. While reducing the volume, it can ensure the low-oxygen lead-bismuth environment and test performance. It has the advantages of compact structure, low cost, low lead-bismuth consumption, fast oxygen reduction, strong adaptability and simple operation, and can meet the mechanical testing requirements in a low-oxygen liquid lead-bismuth environment.

[0006] The technical problem solved by this invention is achieved through the following technical solution: A small-scale fatigue testing device capable of operating in a low-oxygen liquid lead-bismuth environment includes a liquid lead-bismuth testing unit, a gas path unit, thermocouple connection pipelines, and an oxygen concentration detection unit; mechanical tests are conducted on threaded specimens through the liquid lead-bismuth testing unit, the gas path unit, and the thermocouple connection pipelines; and the oxygen concentration is detected through the liquid lead-bismuth testing unit, the gas path unit, the thermocouple connection pipelines, and the oxygen concentration detection unit. The liquid lead-bismuth testing unit includes a heating device, a metal cavity, and an upper cover for the metal cavity. The metal cavity includes a lead-bismuth storage tank and a vacuum bellows. The lead-bismuth storage tank stores liquid lead-bismuth, and the vacuum bellows is welded to the outer circumference of the lead-bismuth storage tank to ensure dynamic sealing during loading. A threaded specimen is inserted into the lead-bismuth storage tank. The threads at the upper and lower ends of the threaded specimen are connected to the threaded holes of the upper cover of the metal cavity and the threaded holes of the lead-bismuth storage tank, respectively. The upper cover and the metal cavity are clamped and fixed by several clamps to form a sealed space enclosing the gauge length of the threaded specimen. A heating device is installed outside the metal cavity to heat the metal cavity. The upper and lower clamping sections of the threaded specimen are clamped on the fixtures of a uniaxial fatigue testing machine for mechanical testing. The gas circuit unit includes an inlet pipe, an outlet pipe, a one-way valve, and a CF flange. One end of the inlet pipe is installed on the upper cover of the metal cavity, and the other end is connected to an external gas cylinder through the CF flange. One end of the outlet pipe is installed on the upper cover of the metal cavity, and the other end is connected to a one-way valve. One end of the thermocouple connection pipe is installed on the upper end cap of the metal cavity, and the other end is connected to the thermocouple through a KF flange. The oxygen concentration detection unit includes an oxygen concentration sensor, a sensor CF flange, a transfer tube, a ceramic rod, and a bottom seal. The transfer tube is connected to the threaded hole of the upper end cover of the metal cavity. The bottom seal is connected to the threaded hole of the lead-bismuth storage tank. The oxygen concentration sensor is mounted on the transfer tube through the sensor CF flange. The ceramic rod at the lower end of the oxygen concentration sensor extends into the metal cavity to detect the oxygen concentration inside the metal cavity.

[0007] Furthermore, the heating device has an openable structure, consisting of two semicircles that are closed by a buckle, forming an internal insulation cavity with a heating wire. The metal cavity is placed inside the insulation cavity, and a circular hole at the bottom of the insulation cavity is used for the lower clamping section of the threaded sample to pass through. The thermocouple is connected to a temperature controller, which controls the on / off state of the heating wire inside the heating device to keep the temperature inside the metal cavity within the range of 30℃-600℃.

[0008] Furthermore, the upper end face of the metal cavity upper end cover and the lower end face of the upper end boss of the vacuum bellows are both provided with clamp grooves for installing clamps, and the metal cavity upper end cover and the metal cavity are clamped and fixed by several clamps.

[0009] Furthermore, a metal-wound graphite gasket is installed between the upper end cover of the metal cavity and the metal cavity, and a seal is formed by pre-tightening with several clamps.

[0010] Furthermore, copper gaskets are respectively provided at the threaded connections between the threaded sample and the threaded holes of the upper end cover of the metal cavity and the threaded holes of the lead-bismuth storage tank to ensure that a local seal is formed between the metal cavity, the upper end cover of the metal cavity and the threaded sample, which encloses the gauge length section of the threaded sample.

[0011] Furthermore, the air inlet pipe and the air outlet pipe are arranged at 180° intervals on the upper end cover of the metal cavity to ensure sufficient gas flow.

[0012] Furthermore, the length of the air intake pipe extending into the metal cavity is half the depth to which it is submerged in the lead-bismuth liquid surface A.

[0013] Furthermore, the clamps mentioned herein consist of four clamps, with the four clamps spaced 90° apart.

[0014] A test method for a small fatigue testing device capable of creating a low-oxygen liquid lead-bismuth environment includes the following steps: Step 1, Preliminary Experiment: (1) Connect the bottom seal to the threaded hole of the lead-bismuth storage tank, fill the lead-bismuth storage tank with solid lead-bismuth blocks, install a metal-wound graphite gasket between the metal cavity and the upper end cover of the metal cavity, install 4 clamps in the clamp slot, each clamp is spaced 90° apart, use a torque wrench to pre-tighten the 4 clamps spaced 90° apart, and clamp and fix the upper end cover of the metal cavity and the metal cavity by clamping and fixing them; (2) Install the oxygen concentration sensor on the adapter pipe through the sensor CF flange. The ceramic rod at the lower end of the oxygen concentration sensor is inserted into the metal cavity. High-purity argon gas is continuously introduced into the metal cavity for 30 minutes through the gas inlet pipe to expel the oxygen inside the metal cavity. (3) Turn on the heating device outside the metal cavity, control the heating through the temperature controller, heat the solid lead bismuth block filled in the lead bismuth storage tank to 180°C, so that the solid lead bismuth block melts into liquid and the liquid lead bismuth reaches the height of liquid level A. (4) A hydrogen-argon mixture containing 5% H2 is introduced into the metal cavity through the inlet pipe at a flow rate of 25 ml / min to reduce the oxygen concentration in the liquid lead-bismuth. The one-way valve at the outlet pipe is used to release gas. (5) The thermocouple monitors and maintains the temperature up to the test temperature of 350℃, with a temperature error of less than ±1℃. The oxygen concentration sensor feeds back the signal to the PLC. The test shows that after 9.6 hours of ventilation, the low oxygen lead-bismuth concentration range is less than 10-8 wt.%. (6) Remove the oxygen concentration sensor, sensor CF flange, connecting pipe and bottom seal, and clean the inside of the lead bismuth storage tank; Step Two, Formal Experiment: 1) The lower clamping section 503 of the threaded sample 5 is threadedly connected to the threaded hole 304 of the lead-bismuth storage tank. The lead-bismuth storage tank is filled with solid lead-bismuth blocks. The upper clamping section 501 of the threaded sample is threadedly connected to the threaded hole 404 of the upper end cover of the metal cavity. A copper gasket is installed at the threaded connection to ensure the threaded connection is sealed. 2) A metal-wound graphite gasket is installed between the metal cavity and the upper end cover of the metal cavity. Four clamps are installed in the clamp slots, with each clamp spaced 90° apart. A torque wrench is used to pre-tighten the four clamps spaced 90° apart. The upper end cover of the metal cavity and the metal cavity are clamped and fixed by the clamps to form a sealed space that encloses the gauge length section of the threaded sample. 3) The upper and lower clamping sections of the threaded specimen are clamped on the fixture of the uniaxial fatigue testing machine, and high-purity argon gas is continuously introduced into the metal cavity through the air inlet pipe to expel the oxygen inside the metal cavity. 4) Turn on the heating device outside the metal cavity, control the heating through the temperature controller, and heat the solid lead-bismuth block filled in the lead-bismuth storage tank to 180°C, so that the solid lead-bismuth block melts into liquid and the liquid lead-bismuth reaches the height of liquid level A. 5) A hydrogen-argon mixture containing 5% H2 is introduced into the metal cavity through the inlet pipe at a flow rate of 25 ml / min to reduce the oxygen concentration in the liquid lead-bismuth. The gas is discharged through the one-way valve at the outlet pipe. 6) The thermocouple is used to monitor and maintain the temperature to the required test temperature of 350℃, with a temperature error of less than ±1℃. After 9.6 hours of ventilation, the oxygen lead-bismuth concentration range is less than 10-8 wt.%, and the uniaxial fatigue testing machine is turned on to conduct the test.

[0015] The advantages and positive effects of this invention are: 1. This invention provides a small-scale fatigue testing device for low-oxygen liquid lead-bismuth environments, comprising a liquid lead-bismuth testing unit, a gas path unit, thermocouple connection pipelines, and an oxygen concentration detection unit. Mechanical tests are performed on threaded specimens using the liquid lead-bismuth testing unit, gas path unit, and thermocouple connection pipelines. Oxygen concentration is detected using the same components. Without modifying a uniaxial fatigue testing machine, this invention effectively achieves mechanical testing in a low-oxygen liquid lead-bismuth environment, while also reducing the amount of lead-bismuth used and increasing the oxygen reduction rate.

[0016] 2. This invention enables a small-scale fatigue testing device for a low-oxygen liquid lead-bismuth environment. The metal cavity includes a lead-bismuth storage tank and a vacuum bellows. The lead-bismuth storage tank stores liquid lead-bismuth, and the vacuum bellows is welded to the outer circumference of the lead-bismuth storage tank to ensure dynamic sealing during loading. A threaded specimen is inserted into the lead-bismuth storage tank. The threads at the upper and lower ends of the threaded specimen are connected to the threaded holes of the upper end cover of the metal cavity and the threaded holes of the lead-bismuth storage tank, respectively. The upper end cover of the metal cavity and the metal cavity are clamped and fixed by several clamps to form a sealed space that encloses the gauge length of the threaded specimen. The upper clamping section of the threaded specimen is threaded to the threaded hole of the upper end cover of the metal cavity, and the lower clamping section of the threaded specimen is threaded to the threaded hole of the lead-bismuth storage tank. A copper gasket ensures a sealing effect at the threaded connection. The metal cavity structure is sealed to the threaded specimen via threads and gaskets. Liquid lead bismuth only acts on the gauge length of the threaded specimen, while the vacuum bellows ensures dynamic sealing during loading. This structure is suitable for most cylindrical specimens and provides a test method for a specimen that is locally filled with a liquid lead bismuth environment.

[0017] 3. The present invention can realize a small fatigue testing device in a low-oxygen liquid lead-bismuth environment. The upper end face of the metal cavity upper end cover and the lower end face of the upper end boss of the vacuum bellows are provided with clamp grooves for installing clamps. The metal cavity upper end cover and the metal cavity are clamped and fixed by several clamps.

[0018] 4. This invention enables a small-scale fatigue testing device for low-oxygen liquid lead-bismuth environments, miniaturizing the liquid lead-bismuth environment testing system, significantly reducing equipment costs, simplifying equipment structure, and, when combined with a heating device and gas path unit, meeting the testing requirements of low-oxygen liquid lead-bismuth environments. It can also be adapted to a uniaxial fatigue testing machine, expanding mechanical testing in various enclosed environments. Attached Figure Description

[0019] Figure 1 This is a three-dimensional structural diagram of the liquid lead-bismuth test unit, gas circuit unit, and thermocouple connection pipeline of the small fatigue test device for realizing a low-oxygen liquid lead-bismuth environment according to the present invention. Figure 2 This is a schematic diagram of the three-dimensional structure of the gas circuit unit, thermocouple connection pipeline and metal cavity upper cover of the small fatigue testing device of the present invention, which can realize a low-oxygen liquid lead-bismuth environment. Figure 3 This is a three-dimensional structural diagram of the metal cavity of the small fatigue testing device for realizing a low-oxygen liquid lead-bismuth environment according to the present invention. Figure 4 This is a three-dimensional structural diagram of the heating device of the small fatigue testing device for realizing a low-oxygen liquid lead-bismuth environment according to the present invention. Figure 5This is a cross-sectional schematic diagram of the combination of the liquid lead-bismuth test unit, the gas circuit unit, and the thermocouple connection pipeline of the small fatigue test device that can realize a low-oxygen liquid lead-bismuth environment according to the present invention. Figure 6 This is a three-dimensional structural diagram of the liquid lead-bismuth test unit, gas circuit unit, thermocouple connection pipeline and oxygen concentration detection unit of the small fatigue test device for realizing a low-oxygen liquid lead-bismuth environment according to the present invention. Figure 7 This is a cross-sectional schematic diagram showing the combination of the liquid lead-bismuth test unit, gas circuit unit, thermocouple connection pipeline and oxygen concentration detection unit of the small fatigue test device for realizing a low-oxygen liquid lead-bismuth environment according to the present invention. Figure 8 The oxygen concentration test curve is shown in the test method of the small fatigue testing device of the present invention, which can realize a low-oxygen liquid lead-bismuth environment. In the diagram: 1-Heating device; 101-Heating wire; 102-Insulation cavity; 103-Box buckle; 2-Clamp; 3-Metal cavity; 301-Vacuum bellows; 302-Lead-bismuth storage tank; 303-Metal wound graphite gasket; 304-Threaded hole of lead-bismuth storage tank; 4-Upper end cover of metal cavity; 401-Thermocouple connection pipeline; 402-Inlet pipeline; 403-CF flange; 404-Upper end cover of metal cavity. Threaded end cap hole; 405-Clamping groove; 406-One-way valve; 407-Outlet pipe; 408-KF flange; 409-Thermocouple; 5-Threaded sample; 501-Upper clamping section; 502-Copper gasket; 503-Lower clamping section; 504-Gazelle section; 6-Oxygen concentration sensor; 601-Sensor CF flange; 602-Transfer pipe; 603-Ceramic rod; 604-Bottom seal. Detailed Implementation

[0020] The present invention will be further described in detail below through specific embodiments. The following embodiments are merely descriptive and not limiting, and should not be used to limit the scope of protection of the present invention.

[0021] like Figures 1 to 7 As shown, a small fatigue testing device for a low-oxygen liquid lead-bismuth environment is used in conjunction with a uniaxial fatigue testing machine. The device includes a liquid lead-bismuth testing unit, a gas path unit, a thermocouple connection pipe 401, and an oxygen concentration detection unit. Mechanical tests are performed on threaded specimens 5 through the liquid lead-bismuth testing unit, the gas path unit, and the thermocouple connection pipe 401. The oxygen concentration is detected through the liquid lead-bismuth testing unit, the gas path unit, the thermocouple connection pipe 401, and the oxygen concentration detection unit.

[0022] The liquid lead-bismuth test unit includes a heating device 1, a metal cavity 3, and a metal cavity upper cover 4. Both the metal cavity 3 and the metal cavity upper cover 4 are made of corrosion-resistant 410 stainless steel. The metal cavity 3 includes a lead-bismuth storage tank 302 and a vacuum bellows 301. The lead-bismuth storage tank 302 stores liquid lead-bismuth, and the vacuum bellows 301 is welded to the outer periphery of the lead-bismuth storage tank 302 to ensure dynamic sealing during the loading process. A threaded specimen 5 is inserted into the lead-bismuth storage tank 302, and the threads at the upper and lower ends of the threaded specimen 5 are respectively connected to… The upper end cover 4 of the metal cavity is connected to the threaded hole 404 of the lead-bismuth storage tank 302. The upper end cover 4 of the metal cavity and the metal cavity 3 are clamped and fixed by several clamps 2 to form a closed space that encloses the gauge length section 504 of the threaded sample 5. A heating device 1 is provided outside the metal cavity 3 to heat the metal cavity 3. The upper clamping section 501 and the lower clamping section 503 of the threaded sample 5 are clamped on the fixture of the uniaxial fatigue testing machine for mechanical testing.

[0023] The upper clamping section 501 of the threaded specimen 5 is threadedly connected to the threaded hole 404 of the upper end cover of the metal cavity, and the lower clamping section 503 of the threaded specimen 5 is threadedly connected to the threaded hole 304 of the lead-bismuth storage tank. The sealing effect of the threaded connection is ensured by the copper gasket 502, so that the gauge section 504 of the threaded specimen 5 is completely enclosed in the metal cavity 3. The threaded specimen 5 conforms to the ASTM-E466 standard.

[0024] Both the upper end face of the metal cavity cap 4 and the lower end face of the upper boss of the vacuum bellows 301 are provided with clamp grooves 405 for installing clamps 2. The metal cavity cap 4 and the metal cavity 3 are clamped and fixed by several clamps 2, which consist of four clamps 2 spaced 90° apart. A metal-wound graphite gasket 303 is installed between the metal cavity cap 4 and the metal cavity 3. The four clamps 2 are pre-tightened at 90° intervals using a torque wrench to form a seal.

[0025] The heating device 1 has an openable structure, consisting of two semicircles. The two semicircles are closed by a box buckle 103, forming an insulation cavity 102 inside, which is equipped with a heating wire 101. The metal cavity 3 is placed inside the insulation cavity 102, and the metal cavity 3 is heated from the circumference. The insulation cavity 102 can ensure the heating effect well and is easy to disassemble and assemble. The round hole at the bottom of the insulation cavity 102 is used to pass through the lower clamping section 503 of the threaded sample 5.

[0026] The gas circuit unit includes an inlet pipe 402, an outlet pipe 407, a one-way valve 406, and a CF flange 403, providing a stable gas environment for the low-oxygen liquid lead-bismuth environment. One end of the inlet pipe 402 is installed on the upper cover 4 of the metal cavity, and the other end is connected to an external gas cylinder via the CF flange 403, allowing the introduction of argon and a hydrogen-argon mixture into the metal cavity 3. One end of the outlet pipe 407 is installed on the upper cover 4 of the metal cavity, and the other end is connected to the one-way valve 406, used to discharge the mixed gas from the metal cavity 3, while preventing gas backflow and maintaining a positive pressure environment of 0.1 MPa within the metal cavity 3. The inlet pipe 402 and the outlet pipe 407 are spaced 180° apart on the upper cover 4 of the metal cavity, ensuring sufficient residence time of the gas inside the metal cavity 3. Liquid level A is the liquid level of liquid lead and bismuth in lead-bismuth storage tank 302, which can submerge the gauge section 504 of the threaded sample 5. The air inlet pipe 402 extends into the metal cavity 3 to a height above 1 / 2 of the liquid lead and bismuth level, ensuring that the liquid lead and bismuth are in full contact with the hydrogen-argon mixture.

[0027] One end of the thermocouple connection pipe 401 is installed on the upper end cap 4 of the metal cavity, and the other end is connected to the thermocouple 409 through the KF flange 408. Thermocouple 409 is connected to thermocouple connection pipe 401 through KF flange 408 to form a KF vacuum seal. Thermocouple 409 transmits the temperature in the metal cavity 3 to the temperature controller. The temperature controller controls the on and off of heating wire 101 in heating device 1 to stabilize the temperature between 30℃ and 600℃, with a temperature error of ±1℃.

[0028] like Figures 6 to 7 As shown, the oxygen concentration detection unit includes an oxygen concentration sensor 6, a sensor CF flange 601, an adapter pipe 602, a ceramic rod 603, and a bottom seal 604. The adapter pipe 602 is connected to the threaded hole 404 of the upper end cover of the metal cavity 4, and the bottom seal 604 is connected to the threaded hole 304 of the lead-bismuth storage tank 302. The oxygen concentration sensor 6 is installed on the adapter pipe 602 through the sensor CF flange 601 to ensure a sealed environment inside the metal cavity 3. The ceramic rod 603 at the lower end of the oxygen concentration sensor 6 extends into the metal cavity 3, below the lead-bismuth liquid surface A, to detect the oxygen concentration inside the metal cavity 3. The oxygen concentration sensor 6 continuously detects the oxygen concentration without accompanying the test process. It detects the oxygen content of the liquid lead-bismuth in the metal cavity 3 through independent testing and transmits the data to the PLC to determine how long it takes for the liquid lead-bismuth in the metal cavity 3 to reach a low oxygen concentration range. The oxygen concentration test curve is shown in Figure 6. Figure 8 As shown, after 9.6 hours of introducing the mixed gas, the lead-bismuth concentration in the metal cavity 3 reached a low oxygen level of less than 10-8 wt.

[0029] As an optional implementation, the threaded specimen 5 can be replaced with a round bar specimen of other specifications, which is suitable for a variety of specimen types and loading conditions.

[0030] As an extended implementation method, the liquid lead-bismuth test unit can be set up with a variety of gas and corrosive environments, such as argon environment, acidic solution, and other liquid metal corrosion, to meet the environmental requirements of various tests.

[0031] Working principle of this invention: Mechanical tests were conducted on the threaded specimen 5 using the liquid lead-bismuth test unit, the gas circuit unit, and the thermocouple connection pipe 401. The vacuum bellows 301 of the metal cavity 3 is welded to the outer periphery of the lead-bismuth storage tank 302. The lower clamping section 503 of the threaded sample 5 is threadedly connected to the threaded hole 304 of the lead-bismuth storage tank, and a copper gasket 502 is installed at the threaded connection. The lead-bismuth storage tank 302 is filled with solid lead-bismuth blocks. The upper clamping section 501 of the threaded sample 5 is threadedly connected to the threaded hole 404 of the upper end cover of the metal cavity, and a copper gasket 502 is installed at the threaded connection. A metal-wound graphite washer 303 is installed between the upper end cover 4 of the metal cavity and the metal cavity 3. Four clamps 2 are installed in the clamp slots 405, with each clamp 2 spaced 90° apart. A torque wrench is used to pre-tighten the four clamps 2 spaced 90° apart, clamping and fixing the upper end cover 4 of the metal cavity and the metal cavity 3 by the clamps 2, forming a sealed space that encloses the gauge section 504 of the threaded sample 5. A heating device 1 is installed on the outside of the metal cavity 3.

[0032] One end of the inlet pipe 402 is installed on the upper cover 4 of the metal cavity, and the other end is connected to an external gas cylinder via a CF flange 403, for introducing argon and hydrogen-argon mixture into the metal cavity 3; one end of the outlet pipe 407 is installed on the upper cover 4 of the metal cavity, and the other end is connected to a one-way valve 406, for discharging the mixed gas in the metal cavity 3; one end of the thermocouple connection pipe 401 is installed on the upper cover 4 of the metal cavity, and the other end is connected to a thermocouple 409 via a KF flange 408, and the thermocouple 409 is connected to a temperature controller. The inlet pipe 402 and the outlet pipe 407 are spaced 180° apart on the upper cover 4 of the metal cavity, and the thermocouple connection pipe 401 is located between the inlet pipe 402 and the outlet pipe 407.

[0033] Thermocouple 409 transmits the temperature in the metal cavity 3 to the temperature controller, which controls the temperature of the metal cavity 3 by controlling the on / off state of the heating wire 101 in the heating device 1.

[0034] The upper clamping section 501 and lower clamping section 503 of the threaded specimen 5 are clamped on the fixture of the uniaxial fatigue testing machine for mechanical testing.

[0035] Oxygen concentration is detected using the liquid lead-bismuth test unit, gas circuit unit, thermocouple connection pipe 401, and oxygen concentration detection unit. The vacuum bellows 301 of the metal cavity 3 is welded to the outer periphery of the lead-bismuth storage tank 302. The bottom seal 604 is threadedly connected to the threaded hole 304 of the lead-bismuth storage tank. Solid lead-bismuth blocks are filled inside the lead-bismuth storage tank 302. The adapter pipe 602 is connected to the threaded hole 404 of the upper end cover of the metal cavity. The oxygen concentration sensor 6 is installed on the adapter pipe 602 through the sensor CF flange 601. The ceramic rod 603 at the lower end of the oxygen concentration sensor 6 extends into the metal cavity 3. A metal-wound graphite gasket 303 is installed between the upper end cover 4 of the metal cavity and the metal cavity 3. Four clamps 2 are installed in the clamp slots 405, with each clamp 2 spaced 90° apart. A torque wrench is used to pre-tighten the four clamps 2 spaced 90° apart, and the upper end cover 4 of the metal cavity and the metal cavity are clamped and fixed by the clamps 2. A heating device is installed on the outside of the metal cavity 3.

[0036] One end of the inlet pipe 402 is installed on the upper cover 4 of the metal cavity, and the other end is connected to an external gas cylinder via a CF flange 403, for introducing argon and hydrogen-argon mixture into the metal cavity 3; one end of the outlet pipe 407 is installed on the upper cover 4 of the metal cavity, and the other end is connected to a one-way valve 406, for discharging the mixed gas in the metal cavity 3; one end of the thermocouple connection pipe 401 is installed on the upper cover 4 of the metal cavity, and the other end is connected to a thermocouple 409 via a KF flange 408, and the thermocouple 409 is connected to a temperature controller. The inlet pipe 402 and the outlet pipe 407 are spaced 180° apart on the upper cover 4 of the metal cavity, and the thermocouple connection pipe 401 is located between the inlet pipe 402 and the outlet pipe 407.

[0037] Thermocouple 409 transmits the temperature in the metal cavity 3 to the temperature controller. The temperature controller controls the temperature of the metal cavity 3 by controlling the on and off of the heating wire 101 in the heating device 1, thereby liquefying the solid lead-bismuth blocks filled in the lead-bismuth storage tank 302.

[0038] The oxygen content of liquid lead-bismuth in the metal cavity 3 is detected by oxygen concentration sensor 6 and the data is transmitted to PLC to determine that the low oxygen lead-bismuth concentration range in the metal cavity 3 is less than 10-8 wt.%.

[0039] A test method for a small-scale fatigue testing device capable of creating a low-oxygen liquid lead-bismuth environment is described below: Step 1, Preliminary Experiment: (1) Connect the bottom seal 604 to the threaded hole 304 of the lead-bismuth storage tank, fill the lead-bismuth storage tank 302 with solid lead-bismuth blocks, install a metal wound graphite gasket 303 between the metal cavity 3 and the upper end cover 4 of the metal cavity, install 4 clamps 2 in the clamp slot 405, each clamp 2 is spaced 90° apart, use a torque wrench to pre-tighten the 4 clamps 2 spaced 90° apart, and clamp and fix the upper end cover 4 of the metal cavity and the metal cavity 3 by clamping and fixing them with clamps 2; (2) Install the oxygen concentration sensor 6 on the adapter pipe 602 through the sensor CF flange 601. The ceramic rod 603 at the lower end of the oxygen concentration sensor 6 is inserted into the metal cavity 3. High-purity argon gas is continuously introduced into the metal cavity 3 through the gas inlet pipe 402 for 30 minutes to remove the oxygen inside the metal cavity 3. (3) Turn on the heating device 1 outside the metal cavity 3 and control the heating through the temperature controller to heat the solid lead bismuth block filled in the lead bismuth storage tank 302 to 180°C, so that the solid lead bismuth block melts into liquid and the liquid lead bismuth reaches the height of liquid level A. (4) A hydrogen-argon mixture containing 5% H2 is introduced into the metal cavity 3 through the inlet pipe 402 at a flow rate of 25 ml / min to reduce the oxygen concentration in the liquid lead-bismuth. Gas is discharged from the one-way valve 406 at the outlet pipe 407, indicating that the gas circulation is good. (5) Thermocouple 409 monitors and maintains the temperature up to the test temperature of 350℃, with a temperature error of less than ±1℃. Oxygen concentration sensor 6 feeds the signal back to PLC. The test shows that after 9.6 hours of ventilation, the low oxygen lead-bismuth concentration range is less than 10-8 wt.%. (6) Remove oxygen concentration sensor 6, sensor CF flange 601, connecting pipe and bottom seal 604, and clean the inner cavity of lead bismuth storage tank 302; Step Two, Formal Experiment: 1) The lower clamping section 503 of the threaded sample 5 is threadedly connected to the threaded hole 304 of the lead-bismuth storage tank. The lead-bismuth storage tank 302 is filled with solid lead-bismuth blocks. The upper clamping section 501 of the threaded sample 5 is threadedly connected to the threaded hole 404 of the upper end cover of the metal cavity. A copper gasket 502 is installed at the threaded connection to ensure the threaded connection is sealed. 2) A metal-wound graphite gasket 303 is installed between the metal cavity 3 and the upper end cover 4 of the metal cavity. Four clamps 2 are installed in the clamp slots 405, with each clamp 2 spaced 90° apart. A torque wrench is used to pre-tighten the four clamps 2 spaced 90° apart. The upper end cover 4 of the metal cavity and the metal cavity 3 are clamped and fixed by the clamps 2 to form a closed space that encloses the gauge length section 504 of the threaded sample 5. 3) The upper clamping section 501 and lower clamping section 503 of the threaded specimen 5 are clamped on the fixture of the uniaxial fatigue testing machine, and high-purity argon gas is continuously introduced into the metal cavity 3 through the air inlet pipe 402 to expel the oxygen inside the metal cavity 3. 4) Turn on the heating device 1 outside the metal cavity 3, and control the heating through the temperature controller to heat the solid lead-bismuth block filled in the lead-bismuth storage tank 302 to 180°C, so that the solid lead-bismuth block melts into liquid and the liquid lead-bismuth reaches the height of liquid level A. 5) A hydrogen-argon mixture containing 5% H2 is introduced into the metal cavity 3 through the inlet pipe 402 at a flow rate of 25 ml / min to reduce the oxygen concentration in the liquid lead-bismuth. Gas is discharged from the one-way valve 406 at the outlet pipe 407, indicating that the gas circulation is good. 6) Thermocouple 409 monitors and maintains the temperature to the required test temperature of 350℃, with a temperature error of less than ±1℃. After ventilating for 9.6 hours, the oxygen lead-bismuth concentration range is less than 10-8wt.%, and the uniaxial fatigue testing machine is turned on to conduct the test.

[0040] Although embodiments and drawings of the present invention have been disclosed for illustrative purposes, those skilled in the art will understand that various substitutions, variations and modifications are possible without departing from the spirit and scope of the present invention and the appended claims. Therefore, the scope of the present invention is not limited to the contents disclosed in the embodiments and drawings.

Claims

1. A small-scale fatigue testing device capable of creating a low-oxygen liquid lead-bismuth environment, characterized in that: It includes a liquid lead-bismuth test unit, a gas path unit, a thermocouple connection pipe (401), and an oxygen concentration detection unit; mechanical tests are performed on threaded specimens (5) through the liquid lead-bismuth test unit, the gas path unit, and the thermocouple connection pipe (401); and the oxygen concentration is detected through the liquid lead-bismuth test unit, the gas path unit, the thermocouple connection pipe (401), and the oxygen concentration detection unit. The liquid lead-bismuth test unit includes a heating device (1), a metal cavity (3), and a metal cavity upper cover (4). The metal cavity (3) includes a lead-bismuth storage tank (302) and a vacuum bellows (301). The lead-bismuth storage tank (302) is used to store liquid lead-bismuth. The vacuum bellows (301) is welded to the outer periphery of the lead-bismuth storage tank (302) to ensure dynamic sealing during the loading process. A threaded sample (5) is inserted into the lead-bismuth storage tank (302). The threads at the upper and lower ends of the threaded sample (5) are respectively connected to the upper end of the metal cavity of the metal cavity upper cover (4). The threaded hole (404) of the cover is connected to the threaded hole (304) of the lead-bismuth storage tank (302). The upper end cover (4) of the metal cavity and the metal cavity (3) are clamped and fixed by several clamps (2) to form a closed space that encloses the gauge length section (504) of the threaded specimen (5). A heating device (1) is provided outside the metal cavity (3) to heat the metal cavity (3). The upper clamping section (501) and lower clamping section (503) of the threaded specimen (5) are clamped on the fixture of the uniaxial fatigue testing machine for mechanical testing. The gas circuit unit includes an inlet pipe (402), an outlet pipe (407), a one-way valve (406), and a CF flange (403). One end of the inlet pipe (402) is installed on the upper end cover (4) of the metal cavity, and the other end is connected to an external gas cylinder through the CF flange (403). One end of the outlet pipe (407) is installed on the upper end cover (4) of the metal cavity, and the other end is connected to the one-way valve (406). One end of the thermocouple connection pipe (401) is installed on the upper end cap (4) of the metal cavity, and the other end is connected to the thermocouple (409) through the KF flange (408). The oxygen concentration detection unit includes an oxygen concentration sensor (6), a sensor CF flange (601), a transfer tube (602), a ceramic rod (603), and a bottom seal (604). The transfer tube (602) is connected to the threaded hole (404) of the upper end cover of the metal cavity (4). The bottom seal (604) is connected to the threaded hole (304) of the lead-bismuth storage tank (302). The oxygen concentration sensor (6) is installed on the transfer tube (602) through the sensor CF flange (601). The ceramic rod (603) at the lower end of the oxygen concentration sensor (6) extends into the metal cavity (3) to detect the oxygen concentration in the metal cavity (3).

2. The small-scale fatigue testing device capable of realizing a low-oxygen liquid lead-bismuth environment according to claim 1, characterized in that: The heating device (1) is an openable structure, consisting of two semicircles. The two semicircles are closed by a box buckle (103), forming an insulation cavity (102) inside, and a heating wire (101) is provided. The metal cavity (3) is placed inside the insulation cavity (102). The bottom hole of the insulation cavity (102) is used to pass through the lower clamping section (503) of the threaded sample (5). The thermocouple (409) is connected to the temperature controller. The temperature controller controls the opening and closing of the heating wire (101) in the heating device (1) to keep the temperature inside the metal cavity (3) in the range of 30℃-600℃.

3. The small-scale fatigue testing device capable of realizing a low-oxygen liquid lead-bismuth environment according to claim 1, characterized in that: The upper end face of the metal cavity upper end cover (4) and the lower end face of the upper end boss of the vacuum bellows (301) are both provided with clamp grooves (405) for installing clamps (2). The metal cavity upper end cover (4) and the metal cavity (3) are clamped and fixed by several clamps (2).

4. A small-scale fatigue testing device capable of creating a low-oxygen liquid lead-bismuth environment according to claim 1, characterized in that: A metal-wound graphite gasket (303) is installed between the upper end cap (4) of the metal cavity and the metal cavity (3), and a seal is formed by pre-tightening with several clamps (2).

5. A small-scale fatigue testing device capable of creating a low-oxygen liquid lead-bismuth environment according to claim 1, characterized in that: Copper gaskets (502) are respectively provided at the threaded connection points of the threaded specimen (5) with the threaded hole (404) of the upper end cover of the metal cavity and the threaded hole (304) of the lead-bismuth storage tank, to ensure that a local seal is formed between the metal cavity (3), the upper end cover (4) of the metal cavity and the threaded specimen (5) to cover the gauge length section of the threaded specimen (5).

6. A small-scale fatigue testing device capable of realizing a low-oxygen liquid lead-bismuth environment according to claim 1, characterized in that: The air inlet pipe (402) and air outlet pipe (407) are arranged at 180° intervals on the upper end cover (4) of the metal cavity to ensure sufficient gas flow.

7. A small-scale fatigue testing device capable of realizing a low-oxygen liquid lead-bismuth environment according to claim 1, characterized in that: The length of the air intake pipe (402) extending into the metal cavity (3) is half the depth of its immersion in the lead-bismuth liquid surface A.

8. A small-scale fatigue testing device capable of realizing a low-oxygen liquid lead-bismuth environment according to claim 1, characterized in that: The clamps (2) mentioned above are 4 clamps (2) with a 90° interval between them.

9. A test method for a small fatigue testing device capable of achieving a low-oxygen liquid lead-bismuth environment as described in any one of claims 1-6, characterized in that: Includes the following steps: Step 1, Preliminary Experiment: (1) Connect the bottom seal (604) to the threaded hole (304) of the lead-bismuth storage tank, fill the lead-bismuth storage tank (302) with solid lead-bismuth blocks, install a metal-wound graphite gasket (303) between the metal cavity (3) and the upper end cover (4) of the metal cavity, install 4 clamps (2) in the clamp slot (405), each clamp is spaced 90° apart, use a torque wrench to pre-tighten the 4 clamps (2) spaced 90° apart, and clamp and fix the upper end cover (4) of the metal cavity and the metal cavity (3) by clamps (2); (2) Install the oxygen concentration sensor (6) on the adapter pipe (602) through the sensor CF flange (601). The ceramic rod (603) at the lower end of the oxygen concentration sensor (6) is inserted into the metal cavity (3). High-purity argon gas is continuously introduced into the metal cavity (3) for 30 minutes through the gas inlet pipe (402) to remove the oxygen inside the metal cavity (3). (3) Open the heating device (1) outside the metal cavity (3), control the heating through the temperature controller, and heat the solid lead bismuth block filled in the lead bismuth storage tank (302) to 180°C, so that the solid lead bismuth block melts into liquid and the liquid lead bismuth reaches the height of liquid level A. (4) A hydrogen-argon mixture containing 5% H2 is introduced into the metal cavity (3) through the inlet pipe (402) at a flow rate of 25 ml / min to reduce the oxygen concentration in the liquid lead-bismuth. The one-way valve (406) at the outlet pipe (407) releases gas. (5) The thermocouple (409) monitors and maintains the temperature up to 350℃, with a temperature error of less than ±1℃. The oxygen concentration sensor (6) feeds the signal back to the PLC. The test shows that after 9.6 hours of ventilation, the low oxygen lead-bismuth concentration range is less than 10-8 wt.%. (6) Remove the oxygen concentration sensor (6), sensor CF flange (601), connecting pipe and bottom seal (604), and clean the inside of the lead bismuth storage tank (302); Step Two, Formal Experiment: 1) The lower clamping section (503) of the threaded sample (5) is threaded to the threaded hole (304) of the lead-bismuth storage tank. The lead-bismuth storage tank (302) is filled with solid lead-bismuth blocks. The upper clamping section (501) of the threaded sample (5) is threaded to the threaded hole (404) of the upper end cover of the metal cavity. A copper gasket (502) is installed at the threaded connection to ensure the threaded connection is sealed. 2) A metal-wound graphite gasket (303) is installed between the metal cavity (3) and the upper end cover (4) of the metal cavity. Four clamps (2) are installed in the clamp slots (405), with each clamp (2) spaced 90° apart. A torque wrench is used to pre-tighten the four clamps (2) spaced 90° apart. The upper end cover (4) of the metal cavity and the metal cavity (3) are clamped and fixed by the clamps (2) to form a sealed space that wraps the gauge length section of the threaded sample (5). 3) The upper clamping section (501) and lower clamping section (503) of the threaded specimen (5) are clamped on the fixture of the uniaxial fatigue testing machine, and high-purity argon gas is continuously introduced into the metal cavity (3) through the air inlet pipe (402) to expel the oxygen inside the metal cavity (3). 4) Turn on the heating device (1) outside the metal cavity (3), control the heating through the temperature controller, and heat the solid lead bismuth block filled in the lead bismuth storage tank (302) to 180°C, so that the solid lead bismuth block melts into liquid and the liquid lead bismuth reaches the height of liquid level A. 5) A hydrogen-argon mixture containing 5% H2 is introduced into the metal cavity (3) through the inlet pipe (402) at a flow rate of 25 ml / min to reduce the oxygen concentration in the liquid lead-bismuth. The one-way valve (406) at the outlet pipe (407) releases gas. 6) The thermocouple (409) monitors and maintains the temperature to the required test temperature of 350℃, with a temperature error of less than ±1℃. After 9.6 hours of ventilation, the low oxygen lead-bismuth concentration range is less than 10-8wt.%, and the uniaxial fatigue testing machine is turned on to carry out the test.

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