Electron beam welding method for multi-layer thin-wall sleeve of nuclear waste glass curing smelting furnace electrode

Abstract

The invention provides an electron beam welding method for a multi-layer thin-wall sleeve of a nuclear waste glass curing smelting furnace electrode, and belongs to the technical field of heat-resisting alloy electron beam welding. The method comprises the following steps: processing a joint; butting joints; welding construction; wherein the welding beam adopted in the welding construction is gradually changed from large to small. According to the method, a variable-power welding strategy is adopted, welding beams are gradually reduced in the welding process, the outer pipe can be thoroughly welded in the initial welding stage and cannot be thoroughly welded in the middle and later welding stages, and therefore the welding quality and the performance of a welded joint are improved. The method is not only suitable for welding of a multi-layer thin-wall sleeve of a nuclear waste glass curing smelting furnace electrode, but also suitable for electron beam welding of other nickel-based or iron-based high-temperature alloy parts and the like, and is suitable for popularization and application in the field of heat-resisting alloy electron beam welding.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of heat-resistant alloy electron beam welding, and more particularly relates to an electron beam welding method for a nuclear waste glass solidification furnace electrode multilayer thin-wall sleeve. BACKGROUND

[0002] With the rapid development of China's nuclear industry, the most harmful high-level radioactive waste generated in the reprocessing process of nuclear fuel cycle and direct disposal of spent fuel is increasing rapidly by 600 tons per year, facing the severe problem of no place to store. Spent liquid waste has high radiation level, long half-life period and high biological toxicity, and its treatment and disposal has become a worldwide concern. As one of the hundred major engineering projects, high-level waste treatment has been raised to the national level. As the most effective and mature high-level waste treatment technology in the world, glass solidification has been paid great attention at home and abroad. China will adopt the process route of "glass solidification-geological disposal" for high-level waste treatment, and glass solidification technology is the primary problem to be solved. The ceramic furnace glass solidification technology by Joule heating is the most advanced waste liquid treatment method in the world at present, and only a few countries in the world have mastered this technology. In recent years, China has made significant progress in the design and manufacture of nuclear waste glass solidification furnaces. The electrode is the core component of the glass solidification furnace, and the electrode generates Joule heat to realize glass heating, waste liquid evaporation, denitration, calcination, melting and other processes.

[0003] Because different parts in the electrode manufacturing process are connected by electron beam welding, the welding quality directly affects the electrical conductivity and sealing performance of the electrode, determines the service performance and safety performance of the furnace electrode, and the service life of the electrode determines the service life of the furnace. Due to structural reasons, different pipe fittings or components must be connected by electron beam welding process during the manufacturing process of the electrode, plus the numerous specifications of the electrode joints, and electron beam welding itself also involves a variety of process parameters, and the welding quality directly affects the electrical conductivity and mechanical properties at the joint. Therefore, electron beam welding is a key technology in the manufacturing process of the electrode, and the localization manufacturing of the glass solidification furnace first needs to solve the problem of the electron beam welding process of the electrode.

[0004] In order to realize temperature measurement, cooling, power supply and other functions, the nuclear waste glass solidification furnace electrode adopts a multi-layer sleeve design. Taking a certain type of furnace electrode as an example, the outer diameter of the cooling pipe is 32 mm, the outer diameter of the thermocouple pipe is 12.5 mm, the thickness is 2.5 mm, and the gap between the two pipes is very small, only 7.25 mm. During the electron beam welding operation, as the welding proceeds, the temperature of the thin-walled pipe joint part rises rapidly. If the welding power is kept constant, two problems are likely to occur: one is that the power is too large, although the pipe wall is welded normally at the beginning of welding, but as the welding proceeds, the temperature of the pipe rises rapidly, and in the later stage of welding, the electron beam burns through the cooling pipe to the thermocouple pipe, causing damage to the thermocouple pipe base metal; the other is that the power is too small, although the outer pipe wall can be welded normally due to the increase in temperature after welding, but at the beginning of welding, the electron beam cannot weld through the outer pipe wall due to the fact that the temperature has not risen significantly, resulting in incomplete penetration defects. In addition, due to the length of the multi-layer sleeve being close to 1 meter, if not properly controlled during electron beam welding, problems such as not meeting the design requirements of coaxiality may occur, which seriously affects the service life and safety performance of the electrode. SUMMARY

[0005] The purpose of the present application is to provide a nuclear waste glass solidification furnace electrode multi-layer thin-walled sleeve electron beam welding method, which solves the problems of burning through or incomplete penetration during electron beam welding.

[0006] In order to achieve the above-mentioned purpose, the present application provides a nuclear waste glass solidification furnace electrode multi-layer thin-walled sleeve electron beam welding method, which comprises: joint processing; joint butt joint; welding construction; Among them, the welding beam used in the welding construction gradually changes from large to small.

[0007] Optionally, the welding beam is 5mA~15mA.

[0008] Optionally, the welding beam gradually changes from 6.5mA to 5.0mA.

[0009] Optionally, the acceleration voltage used in the welding construction is 100kV~200kV; The welding speed used in the welding construction is 500mm / min~800mm / min.

[0010] Optionally, the welding construction is carried out in a vacuum welding chamber.

[0011] Optionally, the vacuum degree of the vacuum welding chamber is ≤1´10 -4 mbar.

[0012] Optionally, the joint processing comprises: processing both joints into flat heads.

[0013] Optionally, the joint processing further comprises: processing each of the pair of joints into a sharp edge.

[0014] Optionally, the joint butt joint comprises: fixing the outer tube and the inner tube to be welded coaxially.

[0015] Optionally, the fixing the outer tube and the inner tube to be welded coaxially comprises: using a wedge-shaped tool to fix the relative positions of the inner tube and the outer tube. The wedge-shaped tool is provided with a through hole coaxial with the wedge-shaped tool, the inner diameter of the through hole is the same as the outer diameter of the inner tube, the through hole is used for sleeving the outer periphery of the inner tube, the outer periphery of the wedge-shaped tool is tapered, the outer diameter of one end of the wedge-shaped tool is smaller than the inner diameter of the outer tube, the outer diameter of the other end of the wedge-shaped tool is larger than the inner diameter of the outer tube, one end of the wedge-shaped tool is used for inserting into the outer tube, and the outer periphery of the wedge-shaped tool is used for cooperating with the inner periphery of the outer tube to limit.

[0016] The method provided by the present application is suitable for the welding of the multi-layer thin-wall sleeve of the nuclear waste glass solidification furnace electrode, and can be used for the 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 heat-resistant alloy electron beam welding.

[0017] Other features and advantages of the present application will be described in detail in the following specific embodiment part. BRIEF DESCRIPTION OF DRAWINGS

[0018] The above and other objects, features and advantages of the present application will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings in which like reference characters refer to like parts throughout the several views, and in which:

[0019] Figure 1 A flow chart of the electron beam welding method of the multi-layer thin-wall sleeve of the nuclear waste glass solidification furnace electrode according to the embodiment 1 of the present application is shown.

[0020] Figure 2 A schematic structural diagram of the multi-layer thin-wall sleeve to be welded according to the embodiment 1 of the present application is shown.

[0021] Figure 3A schematic structural view of the wedge-shaped tool of the embodiment 1 of the present application is shown.

[0022] Figure 4 A schematic structural view of the combination structure of the wedge-shaped tool, the inner tube and the outer tube of the embodiment 1 of the present application is shown.

[0023] Figure 5 A microstructure detection result view of the welded joint of the embodiment 1 of the present application is shown.

[0024] Figure 6 A recessed defect view of the outer surface of the inner tube base material of the comparative example 1 of the present application is shown.

[0025] Figure 7 A recessed defect view of the inner wall of the inner tube of the comparative example 1 of the present application is shown.

[0026] Explanation of reference signs: 1, inner tube; 2, outer tube; 3, weld; 4, wedge-shaped tool; 5, through hole. DETAILED DESCRIPTION

[0027] The preferred embodiments of the present application will be described in more detail below. Although the preferred embodiments of the present application are described below, it should be understood that the present application can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided so that the present application is more complete and complete, and the scope of the present application is fully conveyed to those skilled in the art.

[0028] The present application provides a nuclear waste glass solidification furnace electrode multilayer thin-walled sleeve electron beam welding method, which comprises: joint processing; joint docking; welding construction; wherein the welding beam current used in the welding construction gradually changes from large to small.

[0029] Specifically, for the thin-walled multilayer sleeve of the furnace electrode, the gap is small, and problems such as burning through or not welding through are prone to occur during electron beam welding. The present method adopts a variable power welding strategy, gradually reduces the welding beam current during welding, can weld through the outer tube at the early stage of welding, and will not burn through the outer tube at 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 heat-resistant alloy electron beam welding.

[0030] Optionally, the welding beam current is 5mA-15mA.

[0031] Preferably, the welding beam current gradually changes from 6.5mA to 5.0mA.

[0032] Specifically, the beam current range and the gradual change mode determined through experiments and research can ensure that the electron beam welding can achieve the best welding effect in the beam current range. For the welding of the electrode multi-layer thin-wall sleeve of the nuclear waste glass solidification furnace, the appropriate beam current range and the gradual change parameters can effectively ensure the weld penetration, the weld forming quality and the mechanical properties of the welded joint, while avoiding welding defects caused by excessive or insufficient beam current, such as incomplete penetration and overheating damage.

[0033] Optionally, the acceleration voltage used in the welding construction is 100kV~200kV. The welding speed used in the welding construction is 500mm / min~800mm / min.

[0034] Specifically, the acceleration voltage affects the energy and penetration ability of the electron beam, and appropriate acceleration voltage can ensure 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 the welding heat input. By reasonably matching the acceleration voltage and the welding speed, the welding efficiency can be improved, the welding deformation can be reduced, and the size of the heat affected zone in the welding process can be controlled, further optimizing the performance of the welded joint.

[0035] The acceleration voltage, the welding speed and the welding beam current and other parameters can also be determined according to the specific welding equipment and the welding specifications and requirements.

[0036] Optionally, the welding construction is carried out in a vacuum welding chamber.

[0037] Specifically, the vacuum welding environment can effectively avoid the interference of oxygen, nitrogen and other gases 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 prolong the service life of the welded part.

[0038] Preferably, the vacuum degree of the vacuum welding chamber is ≤1´10 -4 mbar.

[0039] The welding vacuum degree can also be determined according to the specific welding equipment and the welding specifications and requirements.

[0040] Optionally, the joint processing includes: processing both joints into flat heads.

[0041] Specifically, in the traditional welding method, the stop structure such as the step / groove is usually used, which increases the local material thickness, causes heat accumulation when the electron beam is scanned, and easily causes overburning or deformation. In this method, flat head butt joint is used to ensure uniform heat distribution around the whole circumference; in addition, the flat head butt joint has a continuous stress path and no cross-section mutation, which is beneficial to improve the joint strength Optionally, the joint processing further includes: processing the pair of joints into sharp edges.

[0042] Specifically, the sharp edge can reduce the heat capacity, so that the electron beam energy is concentrated on the ridge line, instantaneously melts and forms a stable molten pool, and avoids incomplete fusion or burn-through caused by heat diffusion.

[0043] Optionally, the joint butt joint includes: coaxially fixing the outer pipe and the inner pipe to be welded.

[0044] Preferably, coaxially fixing the outer pipe and the inner pipe to be welded includes: using a wedge-shaped tool to fix the relative positions of the inner pipe and the outer pipe; The wedge-shaped tool has a through hole coaxial with the wedge-shaped tool, the inner diameter of the through hole is the same as the outer diameter of the inner pipe, the through hole is used to be sleeved on the outer periphery of the inner pipe, the outer periphery of the wedge-shaped tool is tapered, the outer diameter of one end of the wedge-shaped tool is smaller than the inner diameter of the outer pipe, the outer diameter of the other end of the wedge-shaped tool is larger than the inner diameter of the outer pipe, one end of the wedge-shaped tool is used to be inserted into the outer pipe, and the outer periphery of the wedge-shaped tool is used to cooperate with the inner periphery of the outer pipe to limit.

[0045] Specifically, the traditional welding method is prone to problems of misalignment of the outer pipe and the inner pipe, and the method uses a wedge-shaped tool to fix the relative positions of the outer pipe and the inner pipe to ensure coaxiality and post-weld dimensional tolerance. In implementation, the wedge-shaped tool is first sleeved on the outer periphery of the inner pipe, and then the wedge-shaped tool is slid towards the outer pipe, so that one end of the wedge-shaped tool is inserted into the outer pipe, and the inner periphery of the outer pipe is in contact with the tapered surface of the outer periphery of the wedge-shaped tool, thereby achieving accurate coaxial fixing of the inner pipe and the outer pipe, and ensuring that the coaxiality and post-weld dimensional tolerance after welding meet the requirements.

[0046] Embodiment

[0047] In this embodiment, the outer pipe 2 to be welded is an electrode cooling pipe with an outer diameter of 32 mm, a wall thickness of 2.5 mm, and a material of 690 alloy, and the position of the weld 3 to be welded is as shown in Figure 2 The inner pipe 1 is a thermocouple tube with an outer diameter of 12.5 mm, a wall thickness of 2.5 mm, and a material of 690 alloy; and the welding equipment is an EK310C-EG150-15B electron beam welder.

[0048] In this embodiment, as shown in Figure 1 The electron beam welding process is as follows: S1, joint processing. Process the pair of joints into flat heads and sharp edges. After processing, clean before welding, and use acetone to repeatedly wipe the weld and the surrounding area within 25 mm.

[0049] S2, joint butt joint. During the butt joint process, the wedge-shaped tool 4 is used to fix the relative positions of the outer pipe 2 and the inner pipe 1. The structure of the wedge-shaped tool 4 is as shown in Figure 3As shown, the combined structure of the clamping wedge-shaped tool 4, the inner tube 1 and the outer tube 2 after clamping is as shown in FIG. 3. 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.

[0050] S3, welding construction. The welding operation is performed by a certified welder, and the welding parameters include: the vacuum degree of the vacuum welding chamber is ≤1´10 -4 mbar, the acceleration voltage is 150 kV, the welding speed is 600 mm / min, the welding current is 6.5 mA, and is gradually adjusted to 5.0 mA during welding.

[0051] After welding, the weld 3 is inspected. The size inspection finds that the coaxiality of the outer tube 2 and the inner tube 1 after welding meets the design requirements; the metallographic detection of the welded joint is as shown in FIG. 4. Figure 5 As shown, the weld 3 has a dense structure, and no welding cracks, bubbles or inclusions are found, which meets the control requirements of the I-level joint internal quality in the GJB1718A-2005 standard; the coloring detection result of the welded joint is: “no excessive discontinuity display trace, qualified”, which meets the I-level requirement in the NB / T47013.5-2015 standard.

[0052] The results of the embodiment prove that the electrode electron beam welded joint quality can reach the I-level standard in the national standard by using the method of the embodiment, and the coaxiality of the multi-layer sleeve can meet the requirements of electrode manufacturing.

[0053] Comparative Example 1 In the comparative example, the outer tube 2 to be welded is an electrode cooling tube with an outer diameter of 32 mm and a wall thickness of 2.5 mm, and the material is 690 alloy; the inner tube 1 is a thermocouple tube with an outer diameter of 12.5 mm and a wall thickness of 2.5 mm, and the material is 690 alloy; and the welding equipment is an EK310C-EG150-15B electron beam welder.

[0054] In the comparative example, the electron beam welding process is as follows: S1, joint processing. Both joints are processed into flat heads and sharp edges. After processing, pre-welding cleaning is performed, and acetone is repeatedly wiped on the welding bead and the surrounding area within 25 mm.

[0055] S2, joint butt joint. During the butt joint process, the relative position of the outer tube 2 and the inner tube 1 is clamped and fixed by using the wedge-shaped tool 4.

[0056] S3, welding construction. The welding operation is performed by a certified welder, and the welding parameters include: the vacuum degree of the vacuum welding chamber is ≤1´10 -4 mbar, the acceleration voltage is 150 kV, the welding speed is 600 mm / min, and the welding current remains unchanged at 6.5 mA.

[0057] Post-weld inspection of the weld 3 found that the electron beam penetrated the outer tube 2 and damaged the inner tube 1. As shown in FIG. 2, the base metal outer surface of the inner tube 1 is concave; as shown in FIG. 3, the inner wall of the inner tube 1 has a weld bead protrusion. Figure 6 Figure 7

[0058] The results of the present comparative example demonstrate that without using the method of the present application, the electron beam penetrated the cooling tube and damaged the internal thermocouple tube, and failed to meet the quality control requirements for electrode manufacturing.

[0059] Comparative Example 2 In the present comparative example, the outer tube 2 to be welded is an electrode cooling tube with an outer diameter of 32 mm, a wall thickness of 2.5 mm, and a material of 690 alloy; the inner tube 1 is a thermocouple tube with an outer diameter of 12.5 mm, a wall thickness of 2.5 mm, and a material of 690 alloy; and the welding equipment is an EK310C-EG150-15B electron beam welder.

[0060] In the present comparative example, the electron beam welding process is as follows: S1, joint processing. Both joints are processed into flat heads and sharp edges. After processing, pre-weld cleaning is performed, and acetone is repeatedly wiped on the weld bead and the surrounding area within 25 mm.

[0061] S2, joint docking. During the docking process, the wedge-shaped tool 4 is used to fix the relative positions of the outer tube 2 and the inner tube 1.

[0062] S3, welding operation. The welding operation is performed by a certified welder, and the welding parameters include: vacuum degree of the vacuum welding chamber ≤1´10 -4 mbar, acceleration voltage 150 kV, welding speed 600 mm / min, and welding beam current remains at 5.0 mA.

[0063] Post-weld inspection of the weld 3 found that the outer tube 2 was penetrated and the internal thermocouple tube was not damaged during the later welding stage, but the electron beam failed to penetrate the outer tube 2 during the initial welding stage, resulting in a lack of penetration defect.

[0064] The results of the present comparative example demonstrate that without using the method of the present application, the electron beam failed to penetrate the outer tube 2 during the initial welding stage, resulting in a lack of penetration defect, and failed to meet the quality control requirements for electrode manufacturing.

[0065] The above has described various embodiments of the present application, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and changes are obvious 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.

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.

9. 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 connection includes: fixing the outer tube (2) to be welded to the inner tube (1) coaxially.

10. 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 method of coaxially fixing the outer tube (2) to be welded and the inner tube (1) 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 around 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). The outer circumference of the wedge-shaped tool (4) is used to cooperate with the inner circumference of the outer tube (2) for limiting.

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