Laser welding device and method for cross spiral core filling rod and cross end plug

Abstract

A laser welding device and method for a cross-shaped spiral core filling rod and a cross-shaped end plug aim at achieving reliable connection of a special-shaped thin-wall cladding and the end plug, and the device comprises a welding clamp, a front tool, a stepped cross-shaped front end plug, a cross-shaped spiral simulation fuel rod, a stepped cross-shaped rear end plug and a rear tool. The rear end of the cross-shaped spiral simulation fuel rod is connected with the rear tool through a stepped cross-shaped rear end plug; the front end of the cross-shaped spiral simulation fuel rod is connected with the rear end of the stepped cross-shaped front end plug, and the front end of the stepped cross-shaped front end plug is connected with the welding clamp through the front tool. The welding method adopts step-by-step spot welding: firstly fixing the front end plug, and rotating a welding clamp to perform spot welding for four times; the same process is repeated for rear end plug welding; according to the method, the welding seam with narrow welding seam, high surplus height and good air tightness can be formed on the thin-walled tube, the phenomenon that the thin-walled tube is easy to burn through during welding due to mismatching of assembly gaps and non-uniform solder accumulation in the welding process is avoided, and poor tightness and overlarge spacing of the welding seam in the welding process are prevented.

Description

Technical Field

[0001] This invention relates to the field of nuclear fuel assembly design and manufacturing technology, specifically to a laser welding device and process for a cross-shaped spiral simulated fuel rod and cross-shaped end plug, which is applicable to experimental research, thermal-hydraulic testing or new fuel design verification of nuclear reactor fuel assemblies. Background Technology

[0002] Fuel assemblies are the core components of nuclear reactors, and their performance directly affects the reactor's safety and operational efficiency. Traditional fuel rods typically consist of fuel pellets, cladding tubes, and end plugs, with a simple circular cavity internal structure. The cladding and end plugs are welded using vacuum electron beam welding. However, with the development of new fuel designs, especially for experimental research, thermal-hydraulic testing, or new fuel verification, fuel rods with complex internal structures have emerged, such as cruciform helical cored rods. These fuel rods typically employ thin-walled, irregularly shaped cladding structures to achieve better thermal-hydraulic performance or simulate special fuel behaviors, but their manufacturing process faces numerous challenges.

[0003] Currently, the welding technology for thin-walled cladding of complex structures still faces the following problems: 1. Numerous welding defects: Due to the complexity of the irregular thin-walled cladding structure, traditional welding methods are prone to defects such as weld penetration and weld leakage, which affect the sealing performance and structural integrity of the fuel rods; 2. Large heat-affected zone: Traditional welding methods are prone to causing cladding deformation or material performance degradation, affecting the long-term stability of fuel rods; 3. Insufficient sealing: The welding of the complex geometry of the casing and the end plug requires extremely high assembly precision. The uniformity and consistency of the weld seam are difficult to guarantee by traditional welding processes, which increases the risk of leakage and affects the safety of the simulated fuel rods.

[0004] Therefore, it is necessary to develop a high-precision welding process with low thermal damage to solve the problem of reliable connection between irregular thin-walled cladding and end plugs, and to ensure the manufacturing quality and safety of fuel rods with complex internal structures. Summary of the Invention

[0005] This invention addresses the problem of reliable connection between irregularly shaped thin-walled shells and end plugs, avoids burn-through in thin-walled welding due to mismatched assembly gaps and uneven solder accumulation during welding, and prevents thinning of the weld seam, poor airtightness, and excessive spacing during welding. Therefore, it proposes a laser welding device and method for cross-shaped spiral filler rods and cross-shaped end plugs.

[0006] The technical solution adopted by the present invention to solve the above problems is as follows: This invention proposes a laser welding device for a cross-shaped spiral filler rod and a cross-shaped end plug, including a welding fixture, a front tooling, a front end plug, a rear end plug, and a rear tooling. The rear end of the cross-shaped spiral simulated fuel rod is connected to the rear tooling through the rear end plug; the front end of the cross-shaped spiral simulated fuel rod is connected to the rear end of the front end plug, and the front end of the front end plug is connected to the welding fixture through the front tooling.

[0007] The cross-shaped spiral simulated fuel rod is a thin-walled hollow tube with a cross-shaped petal cross-section. The inner wall of the tube is fitted with a front plug and a rear plug. The radius of the rounded corner of each petal of the cross-shaped spiral simulated fuel rod ranges from 0.5 to 1.5 mm, the radius of the groove between two adjacent petals is 1.0 to 3.0 mm, and the diameter at the apex is 6 to 10 mm. The tube length of the cross-shaped spiral simulated fuel rod is 1000 to 15000 mm, and the tube wall thickness is 0.05 to 0.3 mm. Its outer surface is threaded with a pitch of 400 to 900 mm.

[0008] Furthermore, the front plug and the rear plug have the same structure. The front plug is coaxially arranged with a first cylindrical segment, a second cylindrical segment, and a ten-segment field, connected sequentially from left to right. The diameter of the first cylindrical segment is smaller than that of the second cylindrical segment, and the diameter of the second cylindrical segment is smaller than that of the ten-segment field. The first cylindrical segment is inserted into the clamping hole at the rear end of the front tooling. The outer surface shape of the ten-segment field matches the inner wall shape of the cross-shaped spiral simulated fuel rod. The cross-section of the ten-segment field of the front plug is a cross-shaped petal. The radius of the rounded corner of each petal of the front plug is 0.5-1.5mm, and the radius of the groove between two adjacent petals is 1.0-3.0mm.

[0009] The ten fields are distributed along the axial direction with a first step and a second step. The diameter of the first step is larger than that of the second step, forming a stepped transition. A process boss is provided between the first step and the second step. The second step is embedded in the inner groove of the cross-shaped spiral simulated fuel rod. The first step is flush with the outer wall end face of the cross-shaped spiral simulated fuel rod.

[0010] Furthermore, the depth to which the front plug is inserted into the cross-shaped spiral simulated fuel rod is 0.6-9.0 mm, and the depth to which the rear plug is inserted into the cross-shaped spiral simulated fuel rod is the same as that of the front plug.

[0011] Furthermore, the rear tooling includes a pole and a mounting plate, which are rotatably connected by a shaft and a bearing; the mounting plate is provided with a cross-shaped mounting groove that mates with the rear end plug.

[0012] This invention also proposes a laser welding method for a cross-shaped spiral filler rod and a cross-shaped end plug, the welding method comprising the following steps: Step 1: Insert the rear end of the front plug into the front end of the cross-shaped spiral simulated fuel rod. The front end of the front plug is fixed to the welding fixture by the front tooling. Install the rear end of the cross-shaped spiral simulated fuel rod on the cross-shaped mounting groove of the rear tooling by the rear plug. Step 2: Align the laser welding focus with the joint between the cross-shaped spiral simulated fuel rod and the front plug, and complete the spot welding fixation; Step 3: Spot weld the four sides of the joint between the cross-shaped spiral simulated fuel rod and the front plug to form a semi-finished cross-shaped spiral simulated fuel rod. Step 4: Separate the front plug from the front fixture; separate the rear plug from the rear fixture; insert the rear plug into the front fixture and the front plug into the rear fixture; Step 5: Align the laser welding focus with the joint between the cross-shaped spiral simulated fuel rod and the rear plug, and complete the spot welding fixation; Step 6: Spot weld the four surfaces at the junction of the cross-shaped spiral simulated fuel rod and the rear plug; Step 7: Set the program to continuously weld one revolution, and exceed the stroke of one revolution by 3mm to 10mm to form the required shaped cross-spiral simulated fuel rod and end plug metal tubing.

[0013] In step 1, the front plug and the cross-shaped spiral simulated fuel rod are aligned to achieve a gap fit, and the first step and the outer wall of the cross-shaped spiral simulated fuel rod are kept horizontal and flush.

[0014] Step 3 involves the following specific steps: 3.1 Adjust the assembled cross-shaped spiral simulated fuel rod and front plug to be horizontal, so that the apex of the two symmetrical cross-shaped petals is located on the horizontal plane, and spot weld the two sides of the apex of the cross-shaped petals through the laser welding focus; 3.2 Rotate the welding fixture 90 degrees clockwise so that the third petal and the second petal of the second side are on the horizontal plane, and perform spot welding on the same side of the petal of the second horizontal plane; 3.3 Repeat step 3.2 twice to complete the welding of the third and fourth sides of the petal apex of the cross-shaped petals.

[0015] In step seven, the welding speed is 2-10 mm / s; the leakage rate of the formed cross-shaped spiral simulated fuel rod and the front and rear end plugs must be less than 1×10. -9 Pa·m 3 / s.

[0016] The beneficial effects of this invention are: 1. In this invention, before laser welding, two end plugs are fixed to both ends of a cross-shaped spiral simulated fuel rod by laser spot welding. The distance and angle between the spot welds are controlled, and the material is locally aggregated by melting the end plugs in a stepped manner. 2. In the continuous welding process, the cross-shaped spiral simulated fuel rod and the end plug are fixed by spot welding, which ensures that the gap between the cross-shaped spiral simulated fuel rod and the end plug is uniform and achieves small weld spacing and high air tightness.

[0017] 3. This invention can be applied to thermal hydraulic testing, irradiation simulation, or fluid dynamics research. It can form a narrow weld with low reinforcement and good airtightness on thin-walled tubes. It is an effective method to avoid the phenomenon of easy burn-through in thin-walled welding caused by mismatched assembly gaps and uneven weld accumulation during the welding process, and to prevent the thinning of the weld wall thickness, poor airtightness, and excessive spacing during the welding process. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the pre-welding state of a cross-spiral simulated fuel rod and end plug laser welding device according to the present invention; Figure 2 This is a schematic diagram of the assembly state of the front plug and the cross-spiral simulated fuel rod of the laser welding device for the cross-spiral simulated fuel rod and the end plug according to the present invention. Figure 3 This is a schematic diagram of the first welding state of the front plug and the cross-shaped spiral simulated fuel rod of the present invention; Figure 4 This is a schematic diagram of the second welding state between the front plug and the cross-shaped spiral simulated fuel rod of the present invention; Figure 5 This is a schematic diagram of the welding completion state of a cross-spiral simulated fuel rod and end plug laser welding device according to the present invention; Figure 6 A schematic diagram of the cross-shaped mounting groove for the subsequent tooling; Figure 7 This is a schematic diagram of the front / rear end plugs; Figure 8 This is a schematic diagram of the physical structure of a cross-shaped spiral simulated fuel rod. Figure 9 The image shows a physical sample of a simulated fuel rod with a cross-shaped spiral, produced using the welding apparatus and process method described in this application.

[0019] In the figure, 1-welding fixture, 2-front tooling, 3-front plug, 3-1 first cylindrical section, 3-2 second cylindrical section; 3-3 cross-shaped field; 4-laser welding focus, 5-cross-shaped spiral simulated fuel rod, 6-rear plug, 7-rear tooling; 7-1-upright rod; 7-2-mounting plate; 7-3-cross-shaped contour mounting groove; 8-semi-finished cross-shaped spiral simulated fuel rod; 9-formed cross-shaped spiral simulated fuel rod. Detailed Implementation

[0020] Specific implementation method one: as follows Figure 1As shown, the laser welding device for a cross-shaped spiral filler rod and a cross-shaped end plug described in this embodiment includes a welding fixture 1, a front tooling 2, a front end plug 3, a rear end plug 6, and a rear tooling 7. The cross-shaped spiral simulated fuel rod 5 is a thin-walled hollow tube with a cross-shaped petal cross-section. The rear end of the cross-shaped spiral simulated fuel rod 5 is connected to the rear tooling 7 through the rear end plug 6. The front end of the cross-shaped spiral simulated fuel rod 5 is connected to the rear end of the front end plug 3, and the front end of the front end plug 3 is connected to the welding fixture 1 through the front tooling 2.

[0021] The cross-shaped spiral simulated fuel rod 5 is a spiral twisted rod with a thin-walled hollow tube in cross-shaped petals in cross-shaped cross-section. A pre-fabricated groove with a depth of 0.6-9.0 mm is located at the center of the tube. The inner wall of the tube mates with the front plug 3 and the rear plug 6. The radius of the rounded corner of each petal of the cross-shaped spiral simulated fuel rod 5 ranges from 0.5-1.5 mm, the radius of the groove between two adjacent petals is 1.0-3.0 mm, and the diameter at the apex is 6-10 mm. The tube length of the cross-shaped spiral simulated fuel rod 5 is 1000-15000 mm, and the wall thickness is 0.05-0.3 mm. Its outer surface is threaded with a pitch of 400-900 mm.

[0022] The shape and diameter of the two end plugs with ten-segment cross-shaped sections are similar to those of the cross-shaped spiral simulated fuel rod 5 to avoid uneven welding and poor airtightness. The front plug 3 and the rear plug 6 have the same structure. The front plug 3 is coaxially arranged with a first cylindrical section 3-1, a second cylindrical section 3-2, and ten-segment cross-shaped sections 3-3, connected from left to right. The diameter of the first cylindrical section 3-1 is smaller than that of the second cylindrical section 3-2, and the diameter of the second cylindrical section 3-2 is smaller than that of the ten-segment cross-shaped sections 3-3. The first cylindrical section 3-1 is inserted into the clamping hole at the rear end of the front tooling 2, and the second cylindrical section 3-2 serves as a limiting element. The outer surface shape of the ten-segment cross-shaped sections 3-3 matches the inner wall shape of the cross-shaped spiral simulated fuel rod 5. The ten-segment cross-shaped sections 3-3 of the front plug 3 have a cross-shaped petal cross-section. The radius of the rounded corner of each petal of the front plug 3 is 0.5-1.5mm, and the radius of the groove between two adjacent petals is 1.0-3.0mm. The ten-section field 3-3 is axially distributed with a first step 3-3-1 and a second step 3-3-2. The diameter of the first step 3-3-1 is larger than the diameter of the second step 3-3-2, forming a stepped transition. A process boss 3-3-1 is provided between the first step 3-3-1 and the second step 3-3-2. The process boss 3-3-1 melts during laser welding and acts as welding wire to fill the weld gap. The second step 3-3-2 is embedded in the inner groove of the fuel rod 5. The first step 3-3-1 is flush with the outer wall end face of the cross-shaped spiral simulating the fuel rod 5. The laser focus 4 is aligned with the process boss 3-3-1.

[0023] The front plug 3 is inserted into the cross-shaped spiral simulated fuel rod 5 to a depth of 0.6-9.0 mm, and the rear plug 6 is inserted into the cross-shaped spiral simulated fuel rod 5 to the same depth as the front plug 3.

[0024] The rear tooling 7 includes a vertical rod 7-1 and a mounting plate 7-2, which are rotatably connected via a shaft and bearings. The mounting plate 7-2 is provided with a cross-shaped mounting groove 7-3 that mates with the rear end plug 6. The cross-shaped mounting groove 7-3 is used for the installation and positioning of the front and rear end plugs, and the vertical rod 7-1 provides support for the pre-welded cross-shaped spiral simulated fuel rod 5.

[0025] Specific Implementation Method Two: Combining Figure 1 This embodiment describes a laser welding method for a cross-shaped spiral filler rod and a cross-shaped end plug, based on the welding apparatus of specific embodiment one. The welding method includes the following steps: Step 1: Insert the tenth segment 3-3 of the front plug 3 into the front end of the cross-shaped spiral simulated fuel rod 5. The first cylindrical segment 3-1 of the front plug 3 is fixed to the welding fixture 1 through the front tooling 2. The rear end of the cross-shaped spiral simulated fuel rod 5 is installed on the cross-shaped mounting groove 7-3 of the rear tooling 7 through the rear plug 6. The front plug 3 and the cross-shaped spiral simulated fuel rod 5 are in a state of gap fit, and the first step 3-3-1 and the outer wall of the cross-shaped spiral simulated fuel rod 5 are kept horizontal and flush.

[0026] Step 2: Align the laser welding focus 4 with the joint between the cross-shaped spiral simulated fuel rod 5 and the front plug 3 (i.e., the process boss 3-3-1) and complete the spot welding fixation; this prevents uneven stress and uneven heat conduction during the subsequent spot welding and fixing process from causing twisting and gaps. Step 3: Spot weld the four surfaces at the junction of the cross-shaped spiral simulated fuel rod 5 and the front plug 3 to form the semi-finished cross-shaped spiral simulated fuel rod 8; the specific operation is as follows: 3.1 Adjust the assembled cross-shaped spiral simulated fuel rod 5 and front plug 3 to be horizontal, so that the apex of the two symmetrical cross-shaped petals is located on the horizontal plane, and spot weld the two sides of the apex of the cross-shaped petals through the laser welding focus 4. 3.2 The welding fixture 1 rotates 90 degrees clockwise, thereby rotating the front plug 3 and the cross-shaped spiral simulated fuel rod 5 90 degrees, so that the second side third petal and the second petal are on the horizontal plane, and spot welding is performed on the same side of the second horizontal petal. The rotation of the welding fixture 1 is driven by an external motor, which transmits power to the cross-shaped spiral simulated fuel rod 5 to be welded by clamping the front tooling 2, so as to realize the rotation of the cross-shaped spiral simulated fuel rod 5. The rear plug 6 and the mounting plate 7-1 rotate together with the cross-shaped spiral simulated fuel rod 5.

[0027] 3.3 Repeat step 3.2 twice to complete the welding of the third and fourth sides of the petal apex of the cross-shaped petals.

[0028] The above steps complete the welding of the petal apexes on the four sides of the cross-shaped spiral simulated fuel rod 5 to the front plug 3, totaling eight weld points. The steps for spot welding the four sides of the joint between the cross-shaped spiral simulated fuel rod 5 and the rear plug 6 are the same as in step 3.

[0029] Step 4: Separate the front plug 3 from the front fixture 2; separate the rear plug 6 from the rear fixture 7; insert the rear plug 6 into the front fixture 2 and the front plug 3 into the rear fixture 7; Step 5: Align the laser welding focus 4 with the joint between the cross-shaped spiral simulated fuel rod 5 and the rear end plug 6 to complete spot welding and fixation; the rear end plug 6 and the cross-shaped spiral simulated fuel rod 5 achieve a state of gap matching, and keep the first step of the rear end plug 6 level with the outer wall of the cross-shaped spiral simulated fuel rod 5.

[0030] Step 6: Repeat the operation of step 3 to spot weld the four surfaces at the junction of the cross-shaped spiral simulated fuel rod 5 and the rear plug 6. Step 7: Set the program to continuously weld one revolution, exceeding the welding stroke by 3mm to 10mm, to form the required cross-spiral simulated fuel rod and end plug metal tubing, i.e., forming the cross-spiral simulated fuel rod 9. Preferably, the welding speed is 2-10mm / s; the leakage rate of the cross-spiral simulated fuel rod 5 and the front and rear end plugs should be less than 1×10⁻⁶. -9 Pa·m 3 / s.

[0031] Example: The following is a specific implementation method for laser welding a cross-shaped spiral simulated fuel rod to an end plug using a 316L thin-walled tubing material with a characteristic inner bore diameter of φ9.0mm and a wall thickness of 0.25mm. The method includes the following steps: Step 1: Install the cross-shaped spiral simulated fuel rod 5 and the front plug 3 (e.g., Figure 2 As shown), the front fixture 2 is installed on the welding fixture 1. The tail end of the cross-shaped spiral simulated fuel rod 5 is installed on the cross-shaped mounting groove 7-3 of the rear fixture 7 through the rear end plug 6. After installation, the interfaces at both ends of the cross-shaped spiral simulated fuel rod 5 and the front end plug 3 are adjusted, and the end plug is inserted into the twisted cross-shaped spiral simulated fuel rod 5. The front end plug 3 and the cross-shaped spiral simulated fuel rod 5 reach a state of gap fit, and the first step 3-3-1 and the outer wall of the cross-shaped spiral simulated fuel rod 5 are kept horizontal and flush.

[0032] Step 2: Align the laser welding focus 4 with one end of the joint between the step of the front plug 3 and the cross-shaped spiral simulated fuel rod 5, and complete the spot welding fixation (e.g., Figure 3 (as shown) Step 3: Spot weld the four surfaces at the junction of the cross-shaped spiral simulated fuel rod 5 and the front plug 3 to form a semi-finished cross-shaped spiral simulated fuel rod (e.g., Figure 4 (As shown); the specific operation is as follows: 3.1 Adjust the assembled cross-shaped spiral simulated fuel rod 5 and front plug 3 to be horizontal, so that the apex of the two symmetrical cross-shaped petals is located on the horizontal plane, and spot weld the two sides of the apex of the cross-shaped petals through the laser welding focus 4. 3.2 The welding fixture 1 rotates 90 degrees clockwise, thereby driving the front plug 3 and the cross-shaped spiral simulated fuel rod 5 to rotate 90 degrees, so that the second side third petal and the second petal are on the horizontal plane, and spot welding is performed on the same side of the second horizontal petal; the rotation of the welding fixture 1 is driven by an external motor, which transmits power to the cross-shaped spiral simulated fuel rod 5 to be welded by clamping the front tooling 2, so as to realize the rotation of the cross-shaped spiral simulated fuel rod 5. The rear plug 6 and the mounting plate 7-1 rotate together with the cross-shaped spiral simulated fuel rod 5.

[0033] 3.3 Repeat step 3.2 twice to complete the welding of the third and fourth sides of the petal apex of the cross-shaped petals.

[0034] Step 4: Separate the front plug 3 from the front fixture 2; separate the rear plug 6 from the rear fixture 7; insert the rear plug 6 into the front fixture 2 and the front plug 3 into the rear fixture 7; Step 5: Align the laser welding focus 4 with the joint between the cross-shaped spiral simulated fuel rod 5 and the rear plug 6 to complete spot welding and fixation; the rear plug 6 and the cross-shaped spiral simulated fuel rod 5 should achieve a state of gap matching and remain horizontal and flush.

[0035] Step 6: Repeat the operation in Step 3, and spot weld the four surfaces at the junction of the cross-shaped spiral simulated fuel rod 5 and the rear plug 6 (e.g., Figure 5 (as shown) Step 7: Set the program to continuously weld one revolution, exceeding the welding revolution by 3mm to 10mm, forming the required cross-shaped spiral to simulate the metal tubing of the fuel rod and end plug, such as... Figure 8 As shown; Figure 8 This is a schematic diagram of the formed cross-shaped spiral simulated fuel rod physical structure. Figure 9 The image shows a simulated fuel rod with a cross-shaped spiral, which was produced using the welding apparatus and process method described in this application. Measurements showed that the airtightness met the accuracy requirements and no welding defects were generated.

[0036] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent substitutions, and improvements made to the above embodiments without departing from the scope of the present invention, based on the technical essence of the present invention and within the spirit and principles of the present invention, shall still fall within the protection scope of the present invention.

Claims

1. A laser welding device for a cross-shaped spiral filler rod and a cross-shaped end plug, characterized in that: The welding device includes a welding fixture (1), a front tooling (2), a front plug (3), a rear plug (6), and a rear tooling (7). The cross-shaped spiral simulated fuel rod (5) has a cross-shaped petal-shaped thin-walled hollow tube. The rear end of the cross-shaped spiral simulated fuel rod (5) is rotatably connected to the rear tooling (7) through the rear plug (6). The front end of the cross-shaped spiral simulated fuel rod (5) is connected to the rear end of the front plug (3). The front end of the front plug (3) is connected to the welding fixture (1) through the front tooling (2).

2. The laser welding device for a cross-shaped spiral filler rod and a cross-shaped end plug as described in claim 1, characterized in that: The front plug (3) has the same structure as the rear plug (6). The front plug (3) is coaxially arranged by a first cylindrical section (3-1), a second cylindrical section (3-2), and a ten-segment section (3-3), which are connected in sequence from left to right. The diameter of the first cylindrical section (3-1) is smaller than that of the second cylindrical section (3-2), and the diameter of the second cylindrical section (3-2) is smaller than that of the ten-segment section (3-3). The first cylindrical section (3-1) is inserted into the clamping hole at the rear end of the front tooling (2), and the outer surface shape of the ten-segment section (3-3) matches the inner wall shape of the cross-shaped spiral simulated fuel rod (5).

3. The laser welding device for a cross-shaped spiral filler rod and a cross-shaped end plug according to claim 2, characterized in that: The cross-section of the ten-segment (3-3) of the front plug (3) is a cross-shaped petal. The radius of the rounded corner of each petal of the front plug (3) is 0.5-1.5mm, and the radius of the groove between two adjacent petals is 1.0-3.0mm.

4. The laser welding device for a cross-shaped spiral filler rod and a cross-shaped end plug according to claim 2, characterized in that: The ten fields (3-3) are distributed along the axial direction with a first step (3-3-1) and a second step (3-3-2). The diameter of the first step (3-3-1) is larger than the diameter of the second step (3-3-2), forming a stepped transition. A process boss (3-3-3) is provided between the first step (3-3-1) and the second step (3-3-2). The second step (3-3-2) is embedded in the inner groove of the cross-shaped spiral simulated fuel rod (5). The first step (3-3-1) is flush with the end face of the cross-shaped spiral simulated fuel rod (5).

5. The laser welding device for a cross-shaped spiral filler rod and a cross-shaped end plug according to claim 1, characterized in that: The front plug (3) is inserted into the cross-shaped spiral simulated fuel rod (5) to a depth of 0.6-9.0 mm, and the rear plug (6) is inserted into the cross-shaped spiral simulated fuel rod (5) to the same depth as the front plug (3).

6. The laser welding device for a cross-shaped spiral filler rod and a cross-shaped end plug according to claim 1, characterized in that: The rear tooling (7) includes a pole (7-1) and a mounting plate (7-2). The pole (7-1) and the mounting plate (7-2) are rotatably connected by a shaft and a bearing. The mounting plate (7-2) is provided with a cross-shaped mounting groove (7-3) that mates with the rear end plug (6).

7. A laser welding method for a cross-shaped spiral filler rod and a cross-shaped end plug, implemented based on the welding apparatus described in any one of claims 1-6, characterized in that, The welding method includes the following steps: Step 1: Insert the tenth segment (3-3) of the front plug (3) into the front end of the cross-shaped spiral simulated fuel rod (5). The first cylindrical segment (3-1) of the front plug (3) is fixed to the welding fixture (1) by the front tooling (2). The rear end of the cross-shaped spiral simulated fuel rod (5) is installed on the cross-shaped mounting groove (7-3) of the rear tooling (7) by the rear plug (6). Step 2: Align the laser welding focus (4) with the joint of the cross-shaped spiral simulated fuel rod (5) and the front plug (3) to complete spot welding fixation; Step 3: Spot weld the four sides of the joint between the cross-shaped spiral simulated fuel rod (5) and the front plug (3) to form a semi-finished cross-shaped spiral simulated fuel rod; Step 4: Separate the front plug (3) from the front fixture (2); separate the rear plug (6) from the rear fixture (7); insert the rear plug (6) into the front fixture (2) and the front plug (3) into the rear fixture (7); Step 5: Align the laser welding focus (4) with the joint of the cross-shaped spiral simulated fuel rod (5) and the rear plug (6) to complete the spot welding fixation; Step 6: Spot weld the four surfaces of the joint between the cross-shaped spiral simulated fuel rod (5) and the rear plug (6); Step 7: Set the program to continuously weld one revolution, and exceed the stroke of one revolution by 3mm to 10mm to form the required shaped cross-spiral simulated fuel rod and end plug metal tubing.

8. The laser welding method for a cross-shaped spiral filler rod and a cross-shaped end plug according to claim 7, characterized in that, In step 1, the front plug (3) and the cross-shaped spiral simulated fuel rod (5) are aligned with the gap, and the first step (3-3-1) and the outer wall of the cross-shaped spiral simulated fuel rod (5) are kept horizontal and flush.

9. A laser welding method for a cross-shaped spiral filler rod and a cross-shaped end plug according to claim 7, characterized in that, Step 3 involves the following specific steps: 3.1 Adjust the assembled cross-shaped spiral simulated fuel rod (5) and front plug (3) to be horizontal so that the apex of the two symmetrical cross-shaped petals is located on the horizontal plane, and spot weld the two sides of the apex of the cross-shaped petals through the laser welding focus (4); 3.2 Welding fixture (1) Rotate 90 degrees clockwise so that the third petal and the second petal of the second side are on the horizontal plane, and spot weld on the same side of the petal of the second horizontal plane; 3.3 Repeat step 3.2 twice to complete the welding of the third and fourth sides of the petal apex of the cross-shaped petals.

10. A laser welding method for a cross-shaped spiral filler rod and a cross-shaped end plug according to claim 7, characterized in that, In step 7, the welding speed is 2-10 mm / s; the leakage rate of the formed cross-spiral simulated fuel rod (5) and the front and rear end plugs is less than 1×10. -9 Pa·m 3 / s.

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