A pressure resistance welding pressurizing device and welding method for end plugs of nuclear fuel rods

Abstract

The present invention provides a pressure resistance welding pressurizing device and a welding method for the end plug of a nuclear fuel rod. The device includes a upsetting electric cylinder, a pressure sensor, a floating joint, a guiding and adjusting mechanism, a displacement sensor, an end plug seat, an electrode rod, a cladding tube, a welding chamber, and a pneumatic actuator. The upsetting electric cylinder is installed on a base, one end of the upsetting electric cylinder is connected to a servo motor which provides the execution power, and the other end is connected to the floating joint. The floating joint faces the electrode rod. The electrode rod is installed on the guiding and adjusting mechanism, and a pressure sensor is installed at one end of the electrode rod in contact with the floating joint. The pressure sensor is used to be connected to a controller. The end plug seat is installed at the other end of the hollow electrode rod, and a negative pressure is provided inside the electrode rod to adsorb the end plug seat. The present invention provides a pressure resistance welding pressurizing device for the end plug of a nuclear fuel rod, which can achieve precise and rapid pressure and precise and rapid position control in the welding mode where the power-on and pressurization for the end plug pressure resistance welding are in the millisecond level.

Description

Technical Field

[0001] The present invention belongs to the technical field of nuclear energy utilization equipment, and particularly relates to a device for applying pressure in resistance welding and a welding method. Background Art

[0002] The structure of the zirconium tube is as Figure 1 shown. Its function is to store nuclear fuel and isolate the nuclear fuel from the medium outside the rod. The main structure is composed of a tube in the middle and end plugs through welding. Among them, the most mainstream connection methods currently are the initial traditional fusion welding and the pressure resistance welding adopted by French USW and Russian VVER. The welding principles of the two are similar as Figure 2 shown. In the figure, 101 - end plug electrode, 102 - pneumatic actuator, 103 - extended cladding tube, 104 - welding chamber, 105 - welding electrode, 106 - sealing ring, 107 - cladding tube fixture (collet).

[0003] The process of pressure resistance welding is as follows: The end plug and the pipe are positioned and a pre-pressure is applied (forming a local contact surface) - the welding current is switched on and the welding pressure is applied (heating and plastic forming near the contact surface to complete the welded joint).

[0004] The welded joint is required to have a smooth outer surface without machining; an extruded weld bead formed on the inner surface indicates that the weld has sufficient plastic deformation to achieve reliable connection.

[0005] The formation of the weld requires pressure and current (providing heat to form a temperature field suitable for joint forming). Under the condition that the machining dimensions and shapes of the contact surface and the pre-pressure are certain, the contact form of the contact surface determines that the contact resistance is an important factor directly affecting the welding temperature field. The existing end plug pressure resistance welding using a pneumatic power source has the following defects:

[0006] (1) Slow response, and the precise coordination between the applied pressure, speed, displacement and current cannot be achieved.

[0007] (2) Air leakage of the piston, lubrication and maintenance required between the piston and the cylinder block, etc., resulting in unstable output force and increased maintenance work.

[0008] However, in the prior art, when attempting to replace the pneumatic actuator with an electric actuator, the components of the original pneumatic actuator cannot respond in a timely manner, resulting in the inability to obtain the desired welding effect of the fuel rod end plug. Therefore, the existing welding method still remains in the pneumatic actuator mode. Summary of the Invention

[0009] The purpose of the present invention is to solve the defects existing in the above-mentioned prior art, and provide a pressure resistance welding pressurization device and a welding method for the end plug of a nuclear fuel rod, which can achieve precise and rapid control and precise and rapid position control in the welding method where the power-on and pressurization of the end plug pressure resistance welding are in milliseconds.

[0010] The present invention adopts the following technical solution:

[0011] A pressure resistance welding pressurizing device for the end plug of a nuclear fuel rod, comprising a upsetting electric cylinder, a pressure sensor, a floating joint, a guiding and adjusting mechanism, a displacement sensor, an end plug seat, an electrode rod, a cladding tube, a welding chamber, and a pneumatic actuator.

[0012] The upsetting electric cylinder is installed on a base, one end of the upsetting electric cylinder is connected to a servo motor which provides the execution power, and the other end is connected to the floating joint. The floating joint faces the electrode rod. The electrode rod is installed on the guiding and adjusting mechanism, and a pressure sensor is installed at the end of the electrode rod in contact with the floating joint. The pressure sensor is used to be connected to a controller. The end plug seat is installed at the other end of the hollow electrode rod, and a negative pressure is provided inside the electrode rod for adsorbing the end plug seat. A displacement sensor for measuring the displacement of the end plug seat is installed on one side of the end plug seat, and the displacement sensor is used to be connected to the controller;

[0013] The guiding and adjusting mechanism includes linear guides and slide rails. The 2 linear guides are arranged in a diagonal balance, one end of each is installed on the base, and the other end of each is installed on the welding chamber. The cross-section of the slide rail is circular, and the slide rail is sleeved on the linear guides arranged in parallel diagonally.

[0014] The cladding tube is fixed on the pneumatic actuator on the other side. Three clamping parts are arranged on the top of the pneumatic actuator for clamping and fixing the cladding tube and ensuring the end is flush. The pneumatic actuator provides the power for the cladding tube to move towards the welding chamber.

[0015] The pneumatic actuator includes 3 clamping parts, namely a front clamping part, a middle clamping part, and a rear clamping part. The front clamping part is movably installed on the front clamping part mounting seat, the middle clamping part is installed on the moving slide rail, and the rear clamping part is installed on the optical rod guide rail. The front clamping part mounting seat, the moving slide rail, and the optical rod guide rail are respectively installed on their own bases.

[0016] Inside the welding chamber, there are a welding chamber, welding electrodes, a sealing ring, and a cladding tube fixture. The welding chamber, welding electrodes, sealing ring, and cladding tube fixture are arranged in sequence from left to right in the welding chamber. The welding chamber is the position for welding the end plug seat and the cladding tube. The welding electrodes are used to energize the cladding tube, corresponding to the electrode rod, to achieve precise welding. The sealing ring is an inflatable rubber ring for isolating the air on one side of the cladding tube. The cladding tube fixture is used for fixing the cladding tube in the welding chamber.

[0017] The cladding tube fixture may be a pneumatic chuck of a milling machine of a CNC system.

[0018] On the top surface of the welding chamber 9, there are also air extraction holes for air extraction and air supplement holes for supplementing a protective atmosphere.

[0019] The controller is connected to the welding power source and the servo motor. The welding power source has two control modes: constant current and constant power.

[0020] A further technical solution is that an inflatable sealing ring is arranged at one side entrance of the end plug seat 6 at the 40th end of the welding chamber, which is used to wrap the electrode rod 7 during welding to isolate the air in the end plug seat 6.

[0021] A further technical solution is that a sensor for measuring displacement is installed on the leftmost clamping part of the pneumatic actuator. The displacement sensor is connected to the controller and is used to control the position of the cladding tube moving towards the welding chamber.

[0022] In addition, the welding method of the present invention is as follows:

[0023] Step 1. Install the end plug seat at one end of the electrode rod. The electrode rod adsorbs the end plug seat through negative pressure, and install the cladding tube on the clamping part of the pneumatic actuator, and keep the ends flush.

[0024] Step 2. The pneumatic actuator moves towards the welding chamber. Use the displacement sensor to measure the displacement of the cladding tube. When it moves to the welding position, use the cladding tube fixture to clamp the cladding tube.

[0025] Step 3. The controller controls the servo motor to make the upsetting cylinder move towards the welding chamber side until the end plug seat enters the predetermined position in the welding chamber.

[0026] Step 4. Inflate the sealing ring on the side of the cladding tube and the sealing ring on the side of the electrode rod. After a period of time, use the air extraction hole at the top of the welding chamber to extract the air in the welding chamber. After a period of time, then fill the welding chamber with a protective atmosphere at a certain air pressure.

[0027] Step 5. The controller controls the welding power source to energize the electrode rod and the welding electrode, and controls the servo motor to continue to provide the power for upsetting to the right. During the execution process, the quality of the welding is grasped in real time through the pressure sensor and the displacement sensor, and the welding method is adjusted.

[0028] A further solution is that the protective atmosphere is low-pressure helium.

[0029] A further solution is that the welding power source has two control modes: constant current and constant power.

[0030] The beneficial effects of the present invention:

[0031] 1. The upsetting cylinder of the present invention uses a servo motor as the power source. The pressure during the welding process is controlled, the response speed is fast, and the pressure control accuracy is high. It can combine the welding current combination process to realize the process experiments and product development of multiple materials and specifications.

[0032] The traditional USW welding equipment uses a cylinder as the upsetting mechanism. The cylinder is simple to implement and has a low cost. However, the pressure during the welding process cannot respond quickly to changes (the response speed of pressure changes is not fast enough). It is very difficult to achieve a multi-segment pressure curve.

[0033] 2. The end plug electrode rod of the present invention is guided by a symmetric structure linear guide rail; while the USW welding equipment uses a frame structure and uses the bottom linear guide rail as the guide. The linear guide rail is installed on one side, and there is a problem of uneven force during welding upsetting.

[0034] 3. During welding of the present invention, the cladding tube is not clamped by vacuum adsorption, and welding is not carried out under a high-pressure atmosphere. Instead, a pneumatic sleeve jaw chuck (cladding tube fixture) is used to clamp the end plug. During welding, a low-pressure helium gas is filled around the welding chamber area to form a protective atmosphere to achieve the purpose of protecting the weld.

[0035] On the other hand, continue to use negative pressure to adsorb the end plug seat, and use an inflatable sealing ring (rubber ring) that can block the electrode rod to seal the electrode rod. A pressure sensor and a displacement sensor are designed to position the end plug seat, so that the end plug of the welded fuel rod will not be deformed, while the USW directly uses a two-stage sealing ring for the electrode rod.

[0036] 4. The VVER fuel rod (cladding tube) is clamped by a sleeve jaw, but the electrode (welding electrode) is in the form of a three-lobe claw. At the same time, different welding power supplies have very high requirements for electrode material matching and are not suitable for use.

[0037] Currently, in the prior art, the AFA3G electrode block structure is adopted. In the specific structure of the AFA3G fuel rod clamping mechanism, the electrode block (welding electrode) is composed of two arc-shaped surfaces, and the power supply uses medium-frequency inversion, and the technology maturity is high.

[0038] Both the VVER fuel rod and the AFA3G fuel rod have the problem that the electrode block is the clamping block.

[0039] The present invention uses a pneumatic sleeve jaw mechanism, which is a standardized product on the market, similar to the CNC machine head milling cutter chuck. The chuck has multiple lobes, large friction force, large effective contact area, good profile, and is not easy to damage the cladding tube, realizing the separate design of the welding electrode and the cladding tube fixture.

[0040] 5. The cladding tube is realized by an inflatable sealing ring. Before the cladding tube is fed in, the inflatable sealing ring does not feed gas. The inner ring of the sealing ring shrinks under the elastic action of the material, and the inner ring diameter becomes larger, so that the cladding tube can enter smoothly; when the cladding tube is in place, gas is filled into the sealing ring, and the inner ring of the sealing ring is tightened to form a good sealing surface with the cladding tube.

[0041] 6. The present invention utilizes a controller to preset variable adjustments for the current and pressure curves during the welding process, enabling the equipment to have more excellent process performance;

[0042] The welding method and principle of the present invention will create new technical highlights in terms of structure and product performance:

[0043] The configured welding power supply has two control modes: constant current and constant power;

[0044] The configured welding system has a high-response-speed pressure control technology for precisely adjusting pre-weld pre-pressure, constant pressure during welding, and post-weld pressure holding;

[0045] The high-response pressure control speed is combined with the high-response current control during welding to meet the process requirements of different materials and specifications.

[0046] In the device of the present invention, the pneumatic actuator is changed to an electric actuator, solving the problem that the original accessory components cannot respond in time to the electric actuator welding method. Through comprehensive analysis, the present invention has found the conditions for the welding method that can quickly respond to the electric actuator - it is necessary to ensure the sealing during welding, the magnitude of the welding current, the magnitude of the welding pressure, and the magnitude of the displacement, and there is a correlation between these factors, which is a combined factor. Therefore, in order to ensure the sealing during welding, the magnitude of the welding current, the magnitude of the welding pressure, and the magnitude of the displacement factors, the clamping and sealing of the cladding tube and the clamping and sealing of the end plug seat are realized, and the control of the welding pressure and displacement are all interrelated. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 is a structural schematic diagram of a zirconium tube;

[0048] Figure 2 is a structural schematic diagram of a typical foreign pressure resistance welding equipment;

[0049] Figure 3 is a schematic diagram of the welding process principle of the improved electric actuator pressure welding;

[0050] Figure 4 is a structural diagram of the present invention (excluding the pneumatic actuator);

[0051] Figure 5 is a structural diagram of the pneumatic actuator of the present invention;

[0052] Figure 6 is the front view of the pneumatic actuator;

[0053] Figure 7 is the top view of the pneumatic actuator;

[0054] Figure 8 is the side view of the pneumatic actuator.

[0055] In the figure: 1 - upsetting electric cylinder, 2 - pressure sensor, 3 - floating joint, 4 - guiding and adjusting mechanism, 6 - end plug seat, 7 - electrode rod, 8 - cladding tube, 9 - welding chamber;

[0056] 40 - welding chamber, 50 - welding electrode, 60 - sealing ring, 70 - cladding tube fixture;

[0057] 101 - front clamping part, 102 - middle clamping part, 103 - rear clamping part;

[0058] 104 - front clamping part mounting seat, 105 - moving slide rail, 106 - optical rod guide rail. Specific embodiments

[0059] To make the objectives, technical solutions and advantages of the present invention clearer, the technical solutions in the present invention will be clearly and completely described below. Obviously, the described embodiments are some but not all of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art without making creative efforts based on the embodiments in the present invention belong to the scope of protection of the present invention.

[0060] As Figure 3 、 4 shown, a pressure resistance welding pressurizing device for the end plug of a nuclear fuel rod according to the present invention

[0061] comprises an upsetting electric cylinder 1, a pressure sensor 2, a floating joint 3, a guiding and adjusting mechanism 4, a displacement sensor, an end plug seat 6, an electrode rod 7, a cladding tube 8, a welding chamber 9, and a pneumatic actuator.

[0062] The upsetting electric cylinder 1 is installed on a base. One end of the upsetting electric cylinder 1 is connected to a servo motor which provides the driving force, and the other end is connected to the floating joint 3. The floating joint 3 faces the electrode rod 7. The electrode rod 7 is installed on the guiding and adjusting mechanism 4. A pressure sensor 2 is installed at the end of the electrode rod 7 in contact with the floating joint 3. The pressure sensor 2 is used to be connected to a controller for sensing the magnitude of the upsetting pressure. The end plug seat 6 is installed at the other end of the hollow electrode rod 7, and a negative pressure is provided inside the electrode rod 7 for adsorbing the end plug seat 6. A displacement sensor for measuring the displacement of the end plug seat 6 is installed on one side of the end plug seat 6, and the displacement sensor is used to be connected to the controller.

[0063] The guiding and adjusting mechanism 4 comprises linear guide rails and slide rails. Two linear guide rails are arranged in a diagonal balance. One end of each is installed on the base, and the other end of each is installed on the welding chamber 9. The cross-section of the slide rail is circular, and the slide rail is sleeved on the linear guide rails arranged in parallel diagonally.

[0064] The cladding tube 8 is fixed to the pneumatic actuator on the other side. Three clamping parts are arranged on the top of the pneumatic actuator for clamping and fixing the cladding tube 8 and ensuring the end alignment. The pneumatic actuator provides the power for the cladding tube 8 to move towards the welding chamber 9.

[0065] As Figures 5 - 8 shown, the pneumatic actuator includes three clamping parts, namely the front clamping part 101, the middle clamping part 102, and the rear clamping part 103. The front clamping part 101 is movably installed on the front clamping part mounting seat 104, the middle clamping part 102 is installed on the moving slide rail 105, and the rear clamping part 103 is installed on the optical rod guide rail 106. The front clamping part mounting seat 104, the moving slide rail 105, and the optical rod guide rail 106 are respectively installed on their respective bases.

[0066] Inside the welding chamber 9, there are a welding chamber 40, welding electrodes 50, a sealing ring 60, and a cladding tube fixture 70. The welding chamber 40, welding electrodes 50, sealing ring 60, and cladding tube fixture 70 are arranged in the welding chamber from left to right in sequence. The welding chamber 40 is the position for welding the end plug seat 6 and the cladding tube 8. The welding electrodes 50 are used to energize the cladding tube 8, corresponding to the electrode rod 7 to achieve precise welding. The sealing ring 60 is an inflatable rubber ring used to isolate the air on one side of the cladding tube 8. The cladding tube fixture 70 is used to fix the cladding tube 8 inside the welding chamber 9.

[0067] Six high-precision displacement sensors are installed on the welding chamber 9 in three directions. Before the cladding tube 8 enters, the displacement sensors are in the retracted state, leaving the passage for the cladding tube 8 to enter. When the cladding tube 8 enters, the sensing heads of the displacement sensors contact the cladding tube 8, and at the same time, the position data can be determined as the displacement data of the cladding tube 8 inside the welding chamber 9. When the end plug seat 6 side enters, this is used as a reference basis and determination result for adjusting the end plug seat 6.

[0068] The cladding tube fixture 70 may be a pneumatic chuck of a CNC system milling machine.

[0069] On the top surface of the welding chamber 9, there are also air extraction holes for air extraction and air supplement holes for supplementing the protective atmosphere.

[0070] The controller is connected to the welding power supply and the servo motor. The welding power supply has two control modes: constant current and constant power.

[0071] A further technical solution is that an inflatable sealing ring is arranged at the entrance on the side of the end plug seat 6 of the welding chamber 40, which is used to wrap the electrode rod 7 during welding to isolate the air of the end plug seat 6.

[0072] A further technical solution is that a displacement measuring sensor is installed on the leftmost clamping part of the pneumatic actuator, and the displacement sensor is connected to the controller to control the position of the cladding tube moving towards the welding chamber.

[0073] The operation method of the present invention is as follows:

[0074] Step 1. Install the end plug seat 6 at one end of the electrode rod 7. The electrode rod 7 adsorbs the end plug seat 6 through negative pressure, and install the cladding tube 8 on the clamping part of the pneumatic actuator, and keep the ends flush.

[0075] Step 2. The pneumatic actuator moves towards the welding chamber 9. Use a displacement sensor to measure the displacement of the cladding tube 8. When it moves to the welding position, clamp the cladding tube 8 with the cladding tube fixture 70.

[0076] Step 3. The controller controls the servo motor to make the upsetting cylinder 1 move towards the welding chamber 9 until the end plug seat 6 enters the predetermined position inside the welding chamber 9.

[0077] Step 4. Inflate the sealing rings on the side of the cladding tube 8 and the sealing rings on the side of the electrode rod 7. After a period of time, extract the air in the welding chamber 9 through the air extraction holes at the top of the welding chamber 9. After a period of time, then fill the welding chamber 9 with a protective atmosphere at a certain air pressure.

[0078] Step 5. The controller controls the welding power supply to energize the electrode rod 7 and the welding electrode 50, and controls the servo motor to continue to provide the power for upsetting to the right. During the execution process, the quality of the welding is grasped in real time through the pressure sensor and the displacement sensor, and the welding method is adjusted.

[0079] A further solution is that the protective atmosphere is low-pressure helium gas, and the low-pressure helium gas is helium gas ≤ 15 MPa.

[0080] A further solution is that the welding power supply has two control modes of constant current and constant power.

[0081] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present invention, rather than limiting it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A welding method using a nuclear fuel rod end plug pressure resistance welding pressurizing device, characterized in that: The following steps are involved: Step 1. Install the end plug seat on one end of the electrode rod. The electrode rod absorbs the end plug seat through negative pressure. Install the cladding tube on the clamping part of the pneumatic actuator and keep the ends flush. Step 2. The pneumatic actuator moves toward the welding chamber, and a displacement sensor is used to measure the displacement of the cladding tube. When the actuator moves to the welding position, the cladding tube is clamped with a cladding tube fixture. Step 3. The controller controls the servo motor to move the upsetting electric cylinder toward the side of the welding chamber until the end plug seat enters the predetermined position in the welding chamber; Step 4. Inflate the sealing ring on one side of the cladding tube and the sealing ring on the side of the electrode rod. After a period of time, use the exhaust hole on the top of the welding room to extract the air in the welding room. After a period of time, fill the welding room with a protective atmosphere at a certain pressure. Step 5. The controller controls the welding power supply to energize the electrode rod and the welding electrode, and controls the servo motor to continue to provide power for upsetting to the right. During this process, the pressure sensor and displacement sensor are used to monitor the welding quality in real time and adjust the welding method. In step 4, the protective atmosphere is low-pressure helium, and the welding power supply has two control modes: constant current and constant power; Among them, a nuclear fuel rod end plug pressure resistance welding pressurizing device includes an upsetting electric cylinder, a pressure sensor, a floating joint, a guide adjustment mechanism, a displacement sensor, an end plug seat, an electrode rod, a cladding tube, a welding chamber, and a pneumatic actuator; The upsetting electric cylinder is installed on the base. One end of the upsetting electric cylinder is connected to the servo motor, which provides the executing power. The other end is connected to the floating joint. The floating joint faces the electrode rod. The electrode rod is installed on the guide adjustment mechanism. One end of the guide adjustment mechanism is installed on the base, and the other end is installed on the welding chamber. A pressure sensor is installed on the end of the electrode rod that contacts the floating joint. The pressure sensor is used to connect to the controller. The end plug seat is installed on the other end of the hollow electrode rod, and negative pressure is provided in the electrode rod to adsorb the end plug seat. A displacement sensor for measuring the displacement of the end plug seat is installed on one side of the end plug seat. The displacement sensor is used to connect to the controller. The cladding tube is fixed on the pneumatic actuator on the other side. A clamping part is arranged on the top of the pneumatic actuator to clamp and fix the cladding tube and ensure that the ends are flush. The pneumatic actuator provides the power for the cladding tube to move toward the welding chamber. The guide adjustment mechanism includes a linear guide rail and a slide rail. The two linear guide rails are arranged in a diagonal balance, one end of each is mounted on the base, and the other end is mounted on the welding chamber. The cross section of the slide rail is circular, and the slide rail is sleeved on the linear guide rails arranged in parallel with the diagonal line. The welding room includes welding room, welding electrodes, sealing ring, cladding tube fixture, cladding tube fixture, Welding chamber, welding electrode, sealing ring, cladding tube fixture. The cladding tube fixture is arranged in the welding chamber from left to right. The welding electrode is used to energize the cladding tube to achieve precise welding. The sealing ring is an inflatable rubber ring used to isolate the air on one side of the cladding tube. The cladding tube fixture is used to fix the cladding tube in the welding chamber. The cladding tube fixture is a pneumatic chuck for the milling machine of the CNC system; The top surface of the welding chamber is also provided with an exhaust hole for exhausting air and an air supply hole for replenishing the protective atmosphere; The controller is connected to the welding power supply and the servo motor; An inflatable sealing ring is arranged at the inlet of one side of the end plug seat of the welding chamber to wrap the electrode rod during welding and isolate the air from the end plug seat; A displacement sensor for measuring displacement is installed on the leftmost clamping part of the pneumatic actuator. The displacement sensor is connected to the controller and is used to control the position of the cladding tube moving toward the welding chamber.

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