Method for electron beam welding of a multilayer thin-walled sleeve for electrodes of a nuclear waste glass solidification furnace

Abstract

The application provides a kind of nuclear waste glass solidification furnace electrode multilayer thin-walled sleeve electron beam welding method, belongs to the technical field of electron beam welding of heat-resistant alloy.The method comprises: joint processing;Joint butt joint;Welding construction;Wherein, the welding beam current gradually changes from large to small is used in welding construction.This method uses variable power welding strategy, gradually reduces the welding beam current during welding, can weld through the outer tube in the early stage of welding, and will not weld through the outer tube in the middle and late stages of welding, thereby improving the welding quality and the performance of the welded joint.The method is not only suitable for the welding of nuclear waste glass solidification furnace electrode multilayer thin-walled sleeve, but also can be used for electron beam welding of other nickel-based or iron-based high-temperature alloy parts, and is suitable for popularization and application in the field of electron beam welding of heat-resistant alloy.

Description

Technical Field

[0001] This invention belongs to the field of electron beam welding technology for heat-resistant alloys, and more specifically, relates to an electron beam welding method for multi-layer thin-walled sleeve electrodes of nuclear waste glass curing furnaces. Background Technology

[0002] With the rapid development of my country's nuclear industry, the amount of highly hazardous high-level radioactive waste generated in the reprocessing of nuclear fuel and the direct disposal of spent fuel is increasing rapidly, growing at a rate of 600 tons per year, posing a serious problem of insufficient storage capacity. Due to its high radioactivity levels, long half-life, and high biotoxicity, the treatment and disposal of high-level radioactive waste has become a global concern. High-level radioactive waste treatment, as one of the top 100 national projects, has been elevated to a national level. Vitrification, currently the most effective and mature high-level radioactive waste treatment technology in the world, has received significant attention both domestically and internationally. my country's process route for high-level radioactive waste treatment will adopt "vitrification-geological disposal," with vitrification technology being the primary issue to be addressed. Joule-heated ceramic furnace vitrification technology is currently the most advanced waste treatment method internationally, mastered by only a few countries. In recent years, my country has made significant progress in the design and manufacturing of nuclear waste vitrification furnaces. Electrodes are the core components of vitrification furnaces. By applying electricity to the molten glass through the electrodes, Joule heat is generated to achieve a series of processes including glass heating, waste evaporation, denitrification, calcination, and melting.

[0003] Because different components are connected by electron beam welding during electrode manufacturing, the welding quality directly affects the electrode's conductivity and sealing performance, determining the furnace electrode's serviceability and safety. The electrode's service life determines the furnace's lifespan. Due to structural reasons, electron beam welding is necessary to connect different pipes or components during electrode manufacturing. Furthermore, there are numerous electrode joint specifications, and electron beam welding itself involves various process parameters. The welding quality directly affects the conductivity and mechanical properties at the joint. Therefore, electron beam welding is a key technology in electrode manufacturing, and the localization of glass curing furnace manufacturing first requires solving the electron beam welding process for electrodes.

[0004] To achieve multiple functions such as temperature measurement, cooling, and power supply, the electrodes of nuclear waste glass solidification furnaces employ a multi-layer sleeve design. Taking a certain type of furnace electrode as an example, the cooling tube has an outer diameter of 32mm, the thermocouple tube has an outer diameter of 12.5mm, and both are 2.5mm thick. Furthermore, the gap between the two tubes is very small, only 7.25mm. During electron beam welding, the temperature at the joint of the thin-walled tube rises rapidly as welding progresses. If a constant welding power is maintained, two problems are likely to occur: one is excessive power. Although the tube wall welds normally in the early stages, the temperature of the tube rises rapidly as welding progresses. In the later stages of welding, the electron beam burns through the cooling tube and reaches the thermocouple tube, causing damage to the thermocouple tube base material. The other is insufficient power. Although the temperature rises during the later stages of welding, the electron beam can penetrate the outer tube wall normally, but in the early stages of welding, the temperature has not yet risen significantly, and the electron beam cannot penetrate the outer tube wall, resulting in incomplete penetration defects. In addition, since the length of the multi-layer sleeve is close to 1 meter, if the electron beam welding process is not properly controlled, problems such as coaxiality not meeting design requirements can easily occur, seriously affecting the service life and safety performance of the electrodes. Summary of the Invention

[0005] The purpose of this invention is to provide an electron beam welding method for multilayer thin-walled sleeve electrodes of nuclear waste glass curing furnaces, which solves the problem of burn-through or incomplete penetration that easily occurs during the electron beam welding process.

[0006] To achieve the above objectives, the present invention provides an electron beam welding method for multilayer thin-walled sleeve electrodes in a nuclear waste glass curing furnace, the method comprising:

[0007] Connector processing;

[0008] Connector mating;

[0009] Welding construction;

[0010] The welding beam used in the welding process gradually decreases from large to small.

[0011] Optionally, the welding beam current is 5mA to 15mA.

[0012] Optionally, the welding beam current is gradually varied from 6.5 mA to 5.0 mA.

[0013] Optionally, the accelerating voltage used in the welding process is 100kV~200kV;

[0014] The welding speed used in the welding process is 500 mm / min to 800 mm / min.

[0015] Optionally, the welding process is performed in a vacuum welding chamber.

[0016] Optionally, the vacuum degree of the vacuum welding chamber is ≤1×10⁻⁶. -4mbar.

[0017] Optionally, the joint processing includes processing both joints into flat ends.

[0018] Optionally, the joint processing further includes processing both of the joints into sharp edges.

[0019] Optionally, the joint connection includes: fixing the outer tube to be welded and the inner tube coaxially.

[0020] Optionally, the step of coaxially fixing the outer tube to be welded with the inner tube includes: using a wedge-shaped tool to fix the relative position of the inner tube and the outer tube;

[0021] The wedge-shaped tooling has a through hole coaxial with itself. The inner diameter of the through hole is the same as the outer diameter of the inner tube. The through hole is used to fit around the outer circumference of the inner tube. The outer circumference of the wedge-shaped tooling is conical. The outer diameter of one end of the wedge-shaped tooling is smaller than the inner diameter of the outer tube, and the outer diameter of the other end of the wedge-shaped tooling is larger than the inner diameter of the outer tube. One end of the wedge-shaped tooling is used to insert into the outer tube, and the outer circumference of the wedge-shaped tooling is used to cooperate with the inner circumference of the outer tube for limiting.

[0022] The beneficial effects of this invention are that, addressing the problems of burn-through or incomplete penetration during electron beam welding of thin-walled, multi-layered sleeves for nuclear waste glass curing furnace electrodes due to their thin walls and small gaps, a method for electron beam welding of these sleeves is provided. This method includes: joint processing; joint butt welding; and welding construction. During welding construction, the welding beam current gradually decreases from high to low. This method employs a variable power welding strategy, gradually reducing the welding beam current during the welding process. It achieves penetration of the outer tube in the initial stage of welding and avoids burn-through in the middle and later stages, thereby improving welding quality and joint performance. This method is not only applicable to the welding of thin-walled, multi-layered sleeves for nuclear waste glass curing furnace electrodes but can also be used for electron beam welding of other nickel-based or iron-based high-temperature alloy components, making it suitable for widespread application in the field of heat-resistant alloy electron beam welding.

[0023] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0024] The above and other objects, features and advantages of the present invention will become more apparent from the more detailed description of exemplary embodiments of the invention in conjunction with the accompanying drawings, wherein the same reference numerals generally represent the same components in the exemplary embodiments of the invention.

[0025] Figure 1 A flowchart of the electron beam welding method for multilayer thin-walled sleeve electrodes of nuclear waste glass curing furnace according to Embodiment 1 of the present invention is shown.

[0026] Figure 2 A schematic structural diagram of a multilayer thin-walled sleeve to be welded according to Embodiment 1 of the present invention is shown.

[0027] Figure 3 A schematic structural diagram of the wedge-shaped tooling of Embodiment 1 of the present invention is shown.

[0028] Figure 4 A schematic diagram of the combined structure of the wedge-shaped tooling, inner tube, and outer tube of Embodiment 1 of the present invention is shown.

[0029] Figure 5 The metallographic test results of the welded joint in Embodiment 1 of the present invention are shown.

[0030] Figure 6 A diagram showing a concave defect on the outer surface of the inner tube base material in Comparative Example 1 of the present invention is provided.

[0031] Figure 7 The diagram shows a weld protrusion and concave defect on the inner wall of the inner tube in Comparative Example 1 of the present invention.

[0032] Explanation of reference numerals in the attached figures:

[0033] 1. Inner tube; 2. Outer tube; 3. Weld; 4. Wedge-shaped tool; 5. Through hole. Detailed Implementation

[0034] Preferred embodiments of the invention will now be described in more detail. While preferred embodiments of the invention are described below, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that the invention will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

[0035] This invention provides a method for electron beam welding of multilayer thin-walled sleeve electrodes in nuclear waste glass curing furnaces, the method comprising:

[0036] Connector processing;

[0037] Connector mating;

[0038] Welding construction;

[0039] The welding beam used in the welding process gradually decreases from large to small.

[0040] Specifically, addressing the issues of burn-through or incomplete penetration during electron beam welding of multilayer sleeves for furnace electrodes due to their thin walls and small gaps, this method employs a variable power welding strategy. The welding beam current is gradually reduced during welding, ensuring penetration of the outer tube in the initial stages and preventing burn-through in the later stages, thereby improving welding quality and joint performance. This method is not only suitable for welding multilayer thin-walled sleeves for nuclear waste glass curing furnace electrodes but can also be used for electron beam welding of other high-temperature alloy components such as nickel-based or iron-based alloys, making it suitable for widespread application in the field of electron beam welding of heat-resistant alloys.

[0041] Optionally, the welding current is 5mA~15mA.

[0042] Preferably, the welding beam current gradually changes from 6.5 mA to 5.0 mA.

[0043] Specifically, the beam current range and gradient method determined through experiments and research ensure that electron beam welding achieves optimal welding results within this beam current range. For welding special structures and materials such as multilayer thin-walled sleeves for electrodes in nuclear waste glass curing furnaces, appropriate beam current range and gradient parameters can effectively guarantee weld penetration, weld formation quality, and the mechanical properties of the weld joint, while avoiding welding defects caused by excessive or insufficient beam current, such as incomplete penetration and overheating damage.

[0044] Optionally, the accelerating voltage used in welding is 100kV~200kV;

[0045] The welding speed used in the welding construction is 500mm / min to 800mm / min.

[0046] Specifically, the accelerating voltage affects the energy and penetration capability of the electron beam. A suitable accelerating voltage ensures that the electron beam can effectively melt the welding material and form a good weld. The welding speed determines the total amount and distribution of welding heat input. By properly matching the accelerating voltage and welding speed, welding efficiency can be improved and welding deformation reduced while ensuring welding quality. It also helps to control the size of the heat-affected zone during the welding process and further optimize the performance of the welded joint.

[0047] Parameters such as acceleration voltage, welding speed, and welding beam current can also be determined based on the specific welding equipment, welding specifications, and requirements.

[0048] Alternatively, welding can be performed in a vacuum welding chamber.

[0049] Specifically, a vacuum welding environment can effectively avoid interference from gases such as oxygen and nitrogen in the air on the welding process, prevent adverse reactions such as oxidation and nitriding in the welding area, further improve the purity and performance stability of the welded joint, and extend the service life of the welded components.

[0050] Preferably, the vacuum degree of the vacuum welding chamber is ≤1×10⁻⁶. -4 mbar.

[0051] The welding vacuum level can also be determined based on the specific welding equipment, welding specifications, and requirements.

[0052] Optionally, the joint processing includes processing both joints into flat ends.

[0053] Specifically, traditional welding methods often employ stop structures such as steps / grooves, which increase local material thickness, leading to heat accumulation during electron beam scanning and potentially causing overheating or deformation. This method uses a flat-end butt joint, ensuring uniform heat distribution across the entire circumference. Furthermore, the flat-end butt joint provides a continuous stress path without abrupt changes in cross-section, which helps improve joint strength.

[0054] Optionally, the joint processing also includes processing both joints into sharp edges.

[0055] Specifically, sharp edges can reduce heat capacity, allowing the electron beam energy to be concentrated on the edge, achieving instantaneous melting and forming a stable molten pool, avoiding incomplete fusion or burn-through due to heat diffusion; the sharp edge flat design can be precisely aligned, avoiding excessive gaps that could lead to electron beam penetration failure or weld depression.

[0056] Optionally, the joint mating includes: coaxially fixing the outer tube to be welded to the inner tube.

[0057] Preferably, fixing the outer tube to be welded and the inner tube coaxially includes: using a wedge-shaped tool to fix the relative positions of the inner tube and the outer tube;

[0058] The wedge-shaped fixture has a through hole coaxial with itself. The inner diameter of the through hole is the same as the outer diameter of the inner tube. The through hole is used to fit around the outer circumference of the inner tube. The outer circumference of the wedge-shaped fixture is conical. The outer diameter of one end of the wedge-shaped fixture is smaller than the inner diameter of the outer tube, and the outer diameter of the other end of the wedge-shaped fixture is larger than the inner diameter of the outer tube. One end of the wedge-shaped fixture is used to insert into the outer tube, and the outer circumference of the wedge-shaped fixture is used to cooperate with the inner circumference of the outer tube for limiting.

[0059] Specifically, traditional welding methods are prone to misalignment between the outer and inner tubes. This method uses a wedge-shaped fixture to fix the relative positions of the outer and inner tubes, ensuring coaxiality and post-weld dimensional tolerances. During implementation, the wedge-shaped fixture is first fitted onto the outer circumference of the inner tube. Then, the wedge-shaped fixture is slid towards the outer tube, so that one end of the wedge-shaped fixture is inserted into the outer tube, and the inner circumference of the outer tube contacts the outer conical surface of the wedge-shaped fixture. This achieves precise coaxial fixation of the inner and outer tubes, ensuring that the coaxiality and post-weld dimensional tolerances meet the requirements.

[0060] Example

[0061] In this embodiment, the outer tube 2 to be welded is an electrode cooling tube with an outer diameter of 32mm, a wall thickness of 2.5mm, and is made of 690 alloy. The location of the weld 3 to be welded is as follows: Figure 2 As shown; Inner tube 1 is a thermocouple tube with an outer diameter of 12.5mm, a wall thickness of 2.5mm, and a material of 690 alloy; The welding equipment is an EK310C-EG150-15B electron beam welder.

[0062] In this embodiment, as Figure 1 As shown, the electron beam welding process is as follows:

[0063] S1. Joint Machining. Machin both joints to flat ends and sharp edges. After machining, perform pre-welding cleaning by repeatedly wiping the weld bead and surrounding area within 25mm with acetone.

[0064] S2. Joint Assembly. During the assembly process, a wedge-shaped fixture 4 is used to fix the relative positions of the outer tube 2 and the inner tube 1. The structure of the wedge-shaped fixture 4 is as follows: Figure 3 As shown, the combined structure of the wedge-shaped tool 4, inner tube 1, and outer tube 2 after the clamping and fixing is as follows: Figure 4 As shown, the inner diameter of the through hole 5 is 12.5 mm, the outer diameter of one end of the wedge-shaped tool 4 is 24 mm, the outer diameter of the other end of the wedge-shaped tool 4 is 40 mm, and the outer diameter of the middle part of the wedge-shaped tool 4 is 32 mm.

[0065] S3. Welding Operation. Welding operations shall be performed by certified welders. Welding parameters include: vacuum level of the vacuum welding chamber ≤ 1×10⁻⁶. -4 mbar, accelerating voltage 150kV, welding speed 600mm / min, welding beam current 6.5mA, which is gradually adjusted to 5.0mA as welding progresses.

[0066] Post-welding inspection of weld 3 was conducted. Dimensional inspection revealed that the coaxiality of the outer tube 2 and inner tube 1 met design requirements; metallographic examination of the welded joint showed... Figure 5 As shown, weld 3 has a dense structure with no welding cracks, bubbles, or inclusions, meeting the control requirements for the internal quality of Class I joints in GJB1718A-2005 standard; the dye penetrant test result of the weld joint is: "No traces of excessive discontinuity are found, qualified", meeting the Class I requirements in NB / T47013.5-2015 standard.

[0067] The results of this embodiment confirm that the method of this embodiment can ensure that the quality of the electrode electron beam welding joint meets the Class I standard in the national standard, and ensure that the coaxiality of the multilayer sleeve meets the electrode manufacturing requirements.

[0068] Comparative Example 1

[0069] In this comparative example, the outer tube 2 to be welded is an electrode cooling tube with an outer diameter of 32mm, a wall thickness of 2.5mm, and is made of 690 alloy; the inner tube 1 is a thermocouple tube with an outer diameter of 12.5mm, a wall thickness of 2.5mm, and is made of 690 alloy; the welding equipment is an EK310C-EG150-15B electron beam welder.

[0070] In this comparative example, the electron beam welding process is as follows:

[0071] S1. Joint Machining. Machin both joints to flat ends and sharp edges. After machining, perform pre-welding cleaning by repeatedly wiping the weld bead and surrounding area within 25mm with acetone.

[0072] S2. Connecting the joints. During the connection process, wedge-shaped tool 4 is used to fix the relative positions of the outer tube 2 and the inner tube 1.

[0073] S3. Welding Operation. Welding operations shall be performed by certified welders. Welding parameters include: vacuum level of the vacuum welding chamber ≤ 1×10⁻⁶. -4 mbar, accelerating voltage 150kV, welding speed 600mm / min, welding beam current kept constant at 6.5 mA.

[0074] Post-welding inspection of weld 3 revealed that the electron beam penetrated the outer tube 2 and damaged the inner tube 1. For example... Figure 6 As shown, the outer surface of the base material of the inner tube 1 is concave; as Figure 7 As shown, weld bead protrusions appear on the inner wall of inner tube 1.

[0075] The results of this comparative example confirm that failure to use the method of the present invention resulted in the electron beam penetrating the cooling tube and damaging the internal thermocouple tube, thus failing to meet the quality control requirements for electrode manufacturing.

[0076] Comparative Example 2

[0077] In this comparative example, the outer tube 2 to be welded is an electrode cooling tube with an outer diameter of 32mm, a wall thickness of 2.5mm, and is made of 690 alloy; the inner tube 1 is a thermocouple tube with an outer diameter of 12.5mm, a wall thickness of 2.5mm, and is made of 690 alloy; the welding equipment is an EK310C-EG150-15B electron beam welder.

[0078] In this comparative example, the electron beam welding process is as follows:

[0079] S1. Joint Machining. Machin both joints to flat ends and sharp edges. After machining, perform pre-welding cleaning by repeatedly wiping the weld bead and surrounding area within 25mm with acetone.

[0080] S2. Connecting the joints. During the connection process, wedge-shaped tool 4 is used to fix the relative positions of the outer tube 2 and the inner tube 1.

[0081] S3. Welding Operation. Welding operations shall be performed by certified welders. Welding parameters include: vacuum level of the vacuum welding chamber ≤ 1×10⁻⁶. -4 mbar, accelerating voltage 150kV, welding speed 600mm / min, welding beam current kept constant at 5.0 mA.

[0082] Weld 3 was inspected after welding. In the later stage of welding, the outer tube 2 was fully penetrated without damaging the internal thermocouple tube. However, in the early stage of welding, the electron beam failed to penetrate the outer tube 2, resulting in incomplete penetration.

[0083] The results of this comparative example confirm that failure to use the method of the present invention resulted in the electron beam failing to penetrate the outer tube 2 in the initial stage of welding, leading to incomplete penetration defects and failing to meet the quality control requirements for electrode manufacturing.

[0084] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they 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.

Claims

1. A method for electron beam welding of multilayer thin-walled sleeve electrodes in a nuclear waste glass curing furnace, characterized in that, The method includes: Connector processing; Connector mating; Welding construction; The welding beam used in the welding process gradually decreases from large to small. The joint connection includes: fixing the outer tube (2) to be welded and the inner tube (1) coaxially; fixing the outer tube (2) to be welded and the inner tube (1) coaxially includes: using a wedge-shaped tool (4) to fix the relative position of the inner tube (1) and the outer tube (2); the wedge-shaped tool (4) is provided with a through hole (5) coaxial with the wedge-shaped tool (4), the inner diameter of the through hole (5) is the same as the outer diameter of the inner tube (1), the through hole (5) is used to fit on the outer circumference of the inner tube (1), the outer circumference of the wedge-shaped tool (4) is conical, the outer diameter of one end of the wedge-shaped tool (4) is smaller than the inner diameter of the outer tube (2), the outer diameter of the other end of the wedge-shaped tool (4) is larger than the inner diameter of the outer tube, one end of the wedge-shaped tool (4) is used to insert into the outer tube (2), and the outer circumference of the wedge-shaped tool (4) is used to cooperate with the inner circumference of the outer tube (2) for limiting.

2. The electron beam welding method for multi-layer thin-walled sleeve electrodes of nuclear waste glass curing furnace according to claim 1, characterized in that, The welding beam current is 5mA~15mA.

3. The electron beam welding method for multi-layer thin-walled sleeve electrodes of nuclear waste glass curing furnace according to claim 2, characterized in that, The welding beam current gradually changes from 6.5 mA to 5.0 mA.

4. The electron beam welding method for multi-layer thin-walled sleeve electrodes of nuclear waste glass curing furnace according to claim 2, characterized in that, The accelerating voltage used in the welding process is 100kV~200kV; The welding speed used in the welding process is 500 mm / min to 800 mm / min.

5. The electron beam welding method for multi-layer thin-walled sleeve electrodes of nuclear waste glass curing furnace according to claim 1, characterized in that, The welding process is carried out in a vacuum welding chamber.

6. The electron beam welding method for multi-layer thin-walled sleeve electrodes of nuclear waste glass curing furnace according to claim 5, characterized in that, The vacuum degree of the vacuum welding chamber is ≤1×10⁻⁶. -4 mbar.

7. The electron beam welding method for multi-layer thin-walled sleeve electrodes of nuclear waste glass curing furnace according to claim 1, characterized in that, The joint processing includes processing both joints into flat ends.

8. The electron beam welding method for multi-layer thin-walled sleeve electrodes of nuclear waste glass curing furnace according to claim 7, characterized in that, The joint processing also includes processing both of the joints into sharp edges.

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