Reactor core fuel outer sleeve welding positioning device and friction stir welding method thereof

Abstract

The invention provides a reactor core fuel outer sleeve welding positioning device and a friction stir welding method thereof.The positioning device comprises a first clamping block and a second clamping block, the opposite side faces of the first clamping block and the second clamping block are provided with a first V-shaped groove and a second V-shaped groove correspondingly, and when a reactor core fuel outer sleeve is in a welding state, the first V-shaped groove and the second V-shaped groove are clamped; the first V-shaped groove and the second V-shaped groove can jointly clamp the side wall, in the welding direction, of the hexagonal pipe and the side wall, in the welding direction, of the hexagonal adapter. The welding positioning device further comprises two axial limiting assemblies. The axial limiting assemblies are located at the ends of the reactor core fuel outer sleeve respectively and connected with the first clamping block and the second clamping block so that axial movement of the reactor core fuel outer sleeve can be limited. When the reactor core fuel outer sleeve is welded in a friction stir welding mode, it is guaranteed that the outer sleeve is reliably limited in all directions, dislocation or cracking of all components is prevented, and the welding quality is guaranteed.

Description

Technical Field

[0001] The invention belongs to the technical field of nuclear reactor material welding, and in particular relates to a core fuel outer casing welding positioning device and a stir friction welding method thereof. Background Art

[0002] The core fuel jacket of a nuclear reactor is usually made of multiple hexagonal tubes welded together. Iron Horse Steel has good mechanical properties and excellent resistance to radiation swelling and stress corrosion, making it the preferred material for the core jacket. Multiple hexagonal tubes are connected by connectors, and this structure becomes the weakest part of the entire fuel assembly structure due to the effect of welding thermal cycles.

[0003] Fusion welding techniques such as argon arc welding and laser welding are the most commonly used welding methods for hexagonal tubes (CN 116408546A). However, due to the high alloy content of iron horse steel (usually the mass fraction of Cr is 9-12%), the use of fusion welding welds is not only prone to generate defects such as pores, cracks, weld bumps, and undercuts, which reduce the quality of weld formation, but also prone to δ ferrite phase transformation at high temperatures, and generate a large amount of martensite, which deteriorates the plastic toughness of the joint. In addition, the significant heat-affected zone is also prone to cause the fourth type of cracks in the joint during high-temperature service, which seriously reduces the service life of the core fuel assembly.

[0004] As a solid-phase connection technology, friction stir welding can be carried out in a temperature range far below the melting point of the material, effectively inhibiting the generation of pores and cracks in the joint and reducing residual stress. Since the friction stir welding tool applies severe plastic deformation and forging to the weld, the joint is not only free of defects such as weld nodules and undercuts, but also can achieve significant microstructure refinement, thereby obtaining higher strength and plastic toughness.

[0005] However, the current friction stir welding technology of Tiema Steel hexagonal tubes is developing very slowly. The main factor hindering its development is the lack of supporting friction stir welding methods. This is related to the high positioning requirements of the workpiece in friction stir welding and the high requirements of the friction stir welding tools suitable for steel materials. Since the material does not melt during the welding process, the workpiece is undoubtedly subjected to the strong friction, extrusion and forging effects of the friction stir welding tools. If the technical solution of the bench spot welding positioning-ring welding welding (CN 101332529 B) in the existing technical solution is adopted, the strong external force applied by the welding tool during friction stir welding is not only easy to cause the workpiece to warp and deform and displace, resulting in assembly dislocation, but also may cause the workpiece to be displaced as a whole, seriously affecting the quality of the weld and the safety of production and manufacturing. Therefore, there is an urgent need for a device that can reliably and accurately position the workpiece during the friction stir welding process. Summary of the invention

[0006] Therefore, the present invention provides a core fuel outer casing welding positioning device and a stir friction welding method thereof, which can solve the technical problem in the prior art that there is a lack of a welding positioning device that can withstand the strong friction, extrusion and forging effects of the stir friction welding tool when stir friction welding is performed on the core fuel outer casing.

[0007] In order to solve the above problems, the present invention provides a core fuel jacket welding positioning device, comprising a first clamping block and a second clamping block, the first clamping block and the second clamping block are arranged opposite to each other, and a first V-shaped groove is formed on the side of the first clamping block facing the second clamping block, and a second V-shaped groove is formed on the side of the second clamping block facing the first clamping block, the notch opening angles of the first V-shaped groove and the second V-shaped groove are both 120°, two sections of hexagonal tubes of the core fuel jacket and a hexagonal adapter between the two sections of the hexagonal tubes, when the core fuel jacket is in a welding state, the first V-shaped groove and the second V-shaped groove can jointly form a clamp for the side walls of the hexagonal tube and the hexagonal adapter in the welding direction, and the welding positioning device also includes two groups of axial limit assemblies, each of the axial limit assemblies is respectively located at the end position of the core fuel jacket and is connected to the first clamping block and the second clamping block to limit the axial movement of the core fuel jacket.

[0008] In some embodiments, the axial limiting assembly includes a limiting bar, one end of which is detachably connected to the first clamping block, and the other end of which is detachably connected to the second clamping block.

[0009] In some embodiments, both side elevations of the first clamping block and the second clamping block parallel to the welding direction are configured with axial limiting through holes, the limiting strip is connected to the corresponding axial limiting through holes via a first threaded fastener, and both ends of the first threaded fastener have threaded sections, and the maximum spacing between the two threaded sections is greater than the depth of the axial limiting through hole; and / or,

[0010] The first clamping block and the second clamping block are detachably positioned and assembled on the welding machine platform.

[0011] In some embodiments, the first clamping block and the second clamping block are respectively constructed with fixing grooves penetrating the top and bottom surfaces thereof, and the fixing grooves extend along a horizontal direction perpendicular to the welding direction. The welding positioning device also includes a second threaded fastener, and the first clamping block and the second clamping block are respectively positioned and assembled with the welding machine platform via the corresponding second threaded fasteners.

[0012] In some embodiments, welding guide plates are detachably connected to the top surfaces of the first clamping block and the second clamping block, respectively. When the core fuel outer casing is in a welding state, the top surface of the welding guide plate and the top surface of the core fuel outer casing are on the same horizontal plane, and the material of the welding guide plate is the same as that of the hexagonal tube and the hexagonal adapter.

[0013] In some embodiments, the bottom side surface of the welding guide plate has an arc notch that matches the arc of the edge of the hexagonal tube and the hexagonal adapter. When the core fuel outer casing is in a welding state, the arc notch fits and covers the arc of the edge of the hexagonal tube and the hexagonal adapter.

[0014] In some embodiments, the first V-shaped groove has a first evacuation groove on its groove wall, and its position corresponds to the position of the hexagonal adapter. The second V-shaped groove has a second evacuation groove on its groove wall, and its position corresponds to the position of the hexagonal adapter. The groove widths of the first evacuation groove and the second evacuation groove are w, the axial width of the docking section of the hexagonal adapter is d, and the diameter of the stirring head of the stir friction welding tool is D, w>d+D+δ to accommodate the protruding portion of the flash formed by welding, and δ is the axial width of the single-sided flash.

[0015] The present invention also provides a friction stir welding method for a core fuel outer casing, comprising the following steps:

[0016] Outer sleeve assembly and positioning step: respectively butting the two sections of the hexagonal tube to be welded on the overlapping sections at both ends of the hexagonal adapter to form an outer sleeve butt assembly, positioning and assembling the outer sleeve butt assembly in the above-mentioned core fuel outer sleeve welding positioning device, and positioning and assembling the core fuel outer sleeve welding positioning device and the welding machine platform;

[0017] Welding steps: Use a stir friction welding tool to stir friction weld the butt joint gaps of the outer sleeve butt joint assembly exposed on the top surface area of ​​the core fuel outer sleeve welding positioning device, and after completing the welding of each butt joint gap on the side, replace another unwelded butt joint gap of the outer sleeve butt joint assembly to expose the top surface area of ​​the core fuel outer sleeve welding positioning device, until all the butt joint gaps on the six sides of the outer sleeve butt joint assembly are welded.

[0018] In some embodiments, when the core fuel outer sleeve welding positioning device includes a welding guide plate, before welding the butt joint gap, each welding guide plate is assembled on the first clamping block and the second clamping block, and when welding the butt joint gap, the welding starting point and the end point are respectively located on the portion of the welding guide plate located above the first clamping block and the second clamping block, and before replacing the unwelded butt joint gap to expose the top surface area, the welding guide plate welded as a whole with the outer sleeve butt joint assembly is removed; and / or,

[0019] During the welding process, the advancing side of the friction stir welding tool is close to the hexagonal adapter, and / or the rotation axis of the friction stir welding tool is located within the butt joint surface of the corresponding outer sleeve butt joint assembly to be welded.

[0020] In some embodiments, when the first V-shaped groove has a first clearance groove and the second V-shaped groove has a second clearance groove, after all the butt joint gaps on the six sides of the outer sleeve butt joint assembly are welded, the weld flash formed on each side is removed by processing; and / or,

[0021] The rotation speed of the friction stir welding tool is 50-550 rpm, the translation speed of the friction stir welding tool is 20-100 mm / min, and industrial pure argon is used as the shielding gas during the translation process. The shielding gas pipe outlet diameter is 6-12 mm and the flow rate is 2-5 liters / min.

[0022] The core fuel outer casing welding positioning device and the friction stir welding method thereof provided by the present invention have the following beneficial effects:

[0023] The first V-shaped groove of the first clamping block and the second V-shaped groove of the second clamping block form a stable and reliable clamping of the opposite side walls of the hexagonal core fuel outer sleeve, which effectively resists the strong force (generated by friction, extrusion and forging) of the welding tool in the welding direction (WD) during stir friction welding. Due to the design of the V-shaped groove, effective limitation of the outer sleeve in the normal direction (ND) is achieved. At the same time, the axial limiting components respectively located at the end positions of the outer sleeve are used to achieve reliable limitation of the outer sleeve in the lateral direction (TD), so that the core fuel outer sleeve can be used in the stir friction welding process. When welding is performed by welding, the outer sleeve is guaranteed to achieve all-round reliable limitation, and the misalignment or cracking between the butted components due to the extrusion of the welding tool during the welding process is prevented, and it can be stably in the target position, thereby effectively ensuring the welding quality; compared with the bench-type hexagonal tube welding device used in the prior art, it has the advantages of simple structure, large load-bearing capacity and high limiting accuracy; in this technical solution, the first clamping block and the second clamping block are used as assembly carriers for other components, the structural design is reasonable, and it has the characteristics of high clamping efficiency, small space occupation and strong shape and position control ability. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the implementation methods of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for the implementation methods or the description of the prior art. The drawings described below are only exemplary, and for ordinary technicians in this field, other implementation drawings can be derived from the provided drawings without creative work.

[0025] Figure 1 1 is a schematic diagram of the three-dimensional structure of a core fuel outer casing welding positioning device according to an embodiment of the present invention (the figure shows an outer casing butt assembly and a corresponding welder-related structure), in which WD indicates a welding direction, ND indicates a normal direction, and TD indicates a lateral direction (lateral translation direction);

[0026] Figure 2 yes Figure 1 A schematic diagram of the three-dimensional structure of the first clamping block and the second clamping block;

[0027] Figure 3 yes Figure 1 A schematic diagram of the three-dimensional structure of the hexagonal adapter of the outer sleeve;

[0028] Figure 4 It is a schematic diagram of assembling the hexagonal adapter of the outer sleeve and the hexagonal tube of the present invention;

[0029] Figure 5(a) is a schematic diagram of the state when the friction stir welding tool of the present invention is welding the butt joint gap between the right hexagonal tube and the hexagonal adapter, in which AS shows the forward side of the welding tool, and the arrow in the figure shows the rotation direction of the welding tool, which is clockwise in a top view; Figure 5 (b) is a schematic diagram of the state when the friction stir welding tool of the present invention is welding the butt joint gap between the left hexagonal tube and the hexagonal adapter, in which AS shows the forward side of the welding tool, and the arrow in the figure shows the rotation direction of the welding tool, which is counterclockwise in a top view;

[0030] Figure 6 This is the front macroscopic morphology of the welded joint prepared by the welding device and welding process of the present invention (friction stir welding tool speed 500 rpm, translation speed 50 mm / min, shielding gas flow rate 3 L / min) in Example 1 of the present invention;

[0031] Figure 7 This is the front macroscopic morphology of the welded joint prepared by the welding device and welding process of the present invention (friction stir welding tool speed 600 rpm, translation speed 50 mm / min, shielding gas flow 3 liters / min) in Comparative Example 4 of the present invention.

[0032] The accompanying drawings are marked as follows:

[0033] 11. First clamping block; 111. First V-shaped groove; 12. Second clamping block; 121. Second V-shaped groove; 21. Limiting strip; 31. Axial limiting through hole; 32. First threaded fastener; 41. Fixing groove; 42. Second threaded fastener; 5. Welding guide plate; 51. Arc notch; 52. Third threaded fastener; 53. Threaded hole; 101. Hexagonal tube; 102. Hexagonal adapter; 1021. Butt joint section; 1022. Overlap section; 200. Friction stir welding tool; 201. Stirring head; 300. Welding machine platform. DETAILED DESCRIPTION

[0034] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0035] In the description of the present invention, it is necessary to understand that the directions or positional relationships indicated by directional words such as "front, back, up, down, left, right", "lateral, vertical, perpendicular, horizontal" and "top, bottom" are usually based on the directions or positional relationships shown in the drawings. They are only for the convenience of describing the present invention and simplifying the description. Unless otherwise specified, these directional words do not indicate or imply that the devices or elements referred to must have a specific direction or be constructed and operated in a specific direction. Therefore, they cannot be understood as limiting the scope of protection of the present invention. The directional words "inside and outside" refer to the inside and outside relative to the contours of each component itself.

[0036] For ease of description, spatially relative terms such as "above", "above", "on the upper surface of", "above", etc. may be used here to describe the spatial positional relationship between a device or feature and other devices or features as shown in the figure. It should be understood that spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation described in the figure. For example, if the device in the accompanying drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below other devices or structures". Thus, the exemplary term "above" can include both "above" and "below". The device can also be positioned in other different ways (rotated 90° or in other orientations), and the spatially relative descriptions used here are interpreted accordingly.

[0037] In addition, it should be noted that the use of terms such as "first" and "second" to limit components is only for the convenience of distinguishing the corresponding components. If not otherwise stated, the above terms have no special meaning and therefore cannot be understood as limiting the scope of protection of the present invention.

[0038] See also Figures 1 to 7 As shown, according to an embodiment of the present invention, a core fuel jacket welding positioning device is provided, comprising a first clamping block 11 and a second clamping block 12, wherein the first clamping block 11 and the second clamping block 12 are arranged opposite to each other, and a first V-shaped groove 111 is formed on the side of the first clamping block 11 facing the second clamping block 12, and a second V-shaped groove 121 is formed on the side of the second clamping block 12 facing the first clamping block 11, and the notch opening angles of the first V-shaped groove 111 and the second V-shaped groove 121 are both 120°, two sections of hexagonal tubes 101 of the core fuel jacket and a hexagonal adapter 102 between the two sections of the hexagonal tubes 101, when the core fuel jacket is in a welding state, the first V-shaped groove 111 and the second V-shaped groove 121 can jointly form a hexagonal tube 101 and the hexagonal adapter 102 in the welding direction ( Figure 1The welding positioning device further comprises two sets of axial limit assemblies (not labeled in the figure), each of which is located at the end of the core fuel outer sleeve and is connected to the first clamping block 11 and the second clamping block 12 to limit the axial movement of the core fuel outer sleeve (i.e. Figure 1 The direction indicated by TD in the chart).

[0039] In this technical solution, the first V-shaped groove 111 of the first clamping block 11 and the second V-shaped groove 121 of the second clamping block 12 form a stable and reliable clamping of the opposite side walls of the hexagonal core fuel outer sleeve, which effectively resists the strong force (generated by friction, extrusion and forging) of the welding tool in the welding direction (WD) during stir friction welding. Due to the design of the V-shaped groove, effective limitation of the outer sleeve in the normal direction (ND) is achieved. At the same time, axial limiting components respectively located at the end positions of the outer sleeve are used to achieve reliable limitation of the outer sleeve in the lateral direction (TD), so that the core fuel outer sleeve can be used in the process of adopting When friction stir welding is used for welding, the outer sleeve is ensured to achieve all-round reliable positioning, and the misalignment or cracking between the butted components due to the extrusion of the welding tool during the welding process is prevented. The target position can be stably maintained, thereby effectively ensuring the welding quality. Compared with the bench-type hexagonal tube welding device used in the prior art, it has the advantages of simple structure, large load-bearing capacity and high positioning accuracy. In this technical solution, the first clamping block 11 and the second clamping block 12 are used as assembly carriers for other components, and the structural design is reasonable, with the characteristics of high clamping efficiency, small space occupation and strong shape and position control ability.

[0040] In some embodiments, the axial limiting assembly includes a limiting strip 21, one end of which is detachably connected to the first clamping block 11, and the other end of which is detachably connected to the second clamping block 12. The limiting strip 21 is made of a strip of metal with a certain thickness, width, and length.

[0041] In this technical solution, both ends of the length of the limiting strip 21 are detachably connected to the first clamping block 11 and the second clamping block 12 respectively, which can further simplify the structural design of the positioning device.

[0042] See Figure 1 As shown, the limiting strip 21 is arranged in the region above the central horizontal plane of the end of the core fuel outer sleeve, and can form a reliable axial limit for the top region of the welded outer sleeve.

[0043] See Figure 2 As shown, in a specific embodiment, the first clamping block 11 and the second clamping block 12 have two side elevations (i.e. Figure 2 An axial limiting through hole 31 is constructed on both the front side and the rear side in the orientation shown, and the axial limiting through hole 31 passes through the two side elevations. The limiting strip 21 passes through and is connected to the corresponding axial limiting through hole 31 via a first threaded fastener 32, and both ends of the first threaded fastener 32 have thread segments, and the maximum spacing between the two thread segments (that is, the spacing between the outer side end edges of the two thread segments) is greater than the depth of the axial limiting through hole 31. At the same time, the minimum spacing between the two thread segments (that is, the spacing between the inner side end edges of the two thread segments) is The depth of the axial limit hole 31 is not greater than that of the first threaded fastener 32. Specifically, a double-headed stud can be used. In this way, when positioning, the corresponding nuts can be screwed at the two ends of the double-headed stud respectively, so that the limit strip 21 is fixed on the two side elevations of the two clamping blocks. At the same time, since the maximum spacing between the threaded sections at both ends of the first threaded fastener 32 is greater than the depth of the axial limit hole 31, the welding positioning device of the present invention can be applied to outer sleeves with larger axial lengths, that is, the applicable working conditions of the welding positioning device are improved, and the device is more versatile. It is worth noting that the above design can also reduce the position accuracy requirements of the outer sleeve and the clamping block in the length direction (axial direction).

[0044] In a feasible embodiment, the first clamping block 11 and the second clamping block 12 are assembled and positioned on a separate platform carrier, so that the welding positioning device of the present invention is assembled to form a relatively complete and independent structure. In another specific embodiment, the first clamping block 11 and the second clamping block 12 are detachably positioned and assembled on the welding machine platform 300. It can be understood that the welding machine platform 300 is a part of the welding equipment. In this way, the welding positioning device of the present invention does not need to be separately configured with the aforementioned platform carrier, but directly uses the welding machine platform 300 of the welding equipment as its positioning and loading platform, which can further simplify the device structure and reduce the device manufacturing cost. For details, see Figure 1 As shown, generally speaking, the welding machine platform 300 has a corresponding T-shaped slot, so that the first clamping block 11 and the second clamping block 12 can be fixedly assembled at the position corresponding to the aforementioned T-shaped slot by using corresponding fasteners.

[0045] See Figure 2 As shown, in a preferred embodiment, the first clamping block 11 and the second clamping block 12 are respectively configured with a fixing groove 41 penetrating the top surface and the bottom surface thereof, and the fixing groove 41 extends along a horizontal direction perpendicular to the welding direction (i.e. Figure 1The welding positioning device further comprises a second threaded fastener 42. The first clamping block 11 and the second clamping block 12 are respectively positioned and assembled with the welding machine platform 300 via the corresponding second threaded fastener 42. The second threaded fastener 42 may also be implemented by a stud.

[0046] In this technical solution, the fixing groove 41 extends along the TD direction, and its specific length should generally at least span the distance between the two T-slots on the aforementioned welding machine platform 300, so that at least two groups of the aforementioned second threaded fasteners 42 can be simultaneously arranged in one fixing groove 41 to achieve reliable fixation of the corresponding clamping block, further ensuring that the position of the outer sleeve is reliable and stable during the welding process. In order to further ensure the connection reliability between the clamping block and the welding machine platform 300, generally speaking, a corresponding washer is clamped and arranged between the fastening nut at the end of the second threaded fastener 42 and the matching surface of the clamping block or the welding machine platform 300.

[0047] See Figure 1 As shown, as a preferred embodiment, the top surfaces of the first clamping block 11 and the second clamping block 12 are detachably connected with welding guide plates 5, respectively. When the core fuel outer sleeve is in a welding state, the top surface of the welding guide plate 5 is on the same horizontal plane as the top surface of the core fuel outer sleeve. The material of the welding guide plate 5 is the same as that of the hexagonal tube 101 and the hexagonal adapter 102, both of which are iron horse steel. In a specific embodiment, the material of the aforementioned clamping block and the limit strip 21 is steel. Specifically, corresponding threaded holes 53 are respectively constructed on the top surfaces of the first clamping block 11 and the second clamping block 12, and second threaded fasteners 52, such as bolts, are screwed into the corresponding threaded holes 53 to achieve the connection and fixation of each welding guide plate 5 with the corresponding clamping block.

[0048] In this technical solution, by respectively arranging a welding guide plate 5 which can be detachably connected to the corresponding clamping block at the starting end and the ending end of the welding direction of the aforementioned core fuel outer casing, it is possible to effectively avoid the inherent forming defects of stir friction welding, such as unbonded areas at the welding head and tail ends (outside the welding tool stroke) and keyholes at the tail end of the weld (formed after the welding tool is pulled out), that is, the presence of unbonded areas and keyhole defects at the head and tail ends of the weld obtained after welding, thereby improving the welding manufacturing quality.

[0049] In some embodiments, the bottom side surface of the welding guide plate 5 has an arc notch 51 that matches the arc edges of the hexagonal tube 101 and the hexagonal adapter 102. When the core fuel outer casing is in a welding state, the arc notch 51 fits and covers the arc edges of the hexagonal tube 101 and the hexagonal adapter 102, that is, the shape of the arc notch 51 is the same as the shape of the arc edges of the hexagonal tube 101 and the hexagonal adapter 102.

[0050] In this technical solution, by setting an arc notch 51 on the bottom side surface of the welding guide plate 5, that is, the side facing the hexagonal tube 101, it can be ensured that the welding guide plate 5 fits and covers the edge of the welding plane of the hexagonal tube 101 and the hexagonal adapter 102 to ensure smooth welding.

[0051] In some embodiments, the first V-shaped groove 111 has a first paving groove (not shown in the figure) on its groove wall, and the position of the first paving groove corresponds to the position of the hexagonal adapter 102. The second V-shaped groove 121 has a second paving groove (not shown in the figure) on its groove wall, and the position of the second paving groove corresponds to the position of the hexagonal adapter 102. The groove widths of the first paving groove and the second paving groove are w, the axial width of the docking section of the hexagonal adapter 102 is d, and the diameter of the stirring head 201 of the friction stir welding tool 200 is D, w>d+D+δ to accommodate the burr protrusion formed by welding, δ is the axial width of the unilateral burr, and the units of the aforementioned physical parameters are, for example, mm. The specific value of the aforementioned δ is reasonably selected according to welding parameters such as the rotation speed and downward pressure of the stirring head 201. In this way, after the corresponding side surfaces of the hexagonal tube 101 and the hexagonal adapter 102 are welded, when switching to the other side for welding, there is no need to machine the burr protrusion formed on the welded side surface, but the burr protrusion can be accommodated in each first clearance groove and the second clearance groove, ensuring that the first clamping block 11 and the second clamping block 12 can reliably clamp the opposite side walls of the outer sleeve, ensuring uniform application of the clamping force, and preventing the clamping deformation caused by the burr protrusion.

[0052] According to an embodiment of the present invention, a friction stir welding method for a core fuel outer casing is also provided, comprising the following steps:

[0053] The outer sleeve assembly and positioning step: the two sections of the hexagonal tube 101 to be welded are respectively connected to the overlapping sections 1022 at both ends of the hexagonal adapter 102 to form an outer sleeve docking assembly. At this time, the docking section 1021 of the hexagonal adapter 102 is clamped between the two sections of the hexagonal tube 101. The outer sleeve docking assembly is positioned and assembled in the above-mentioned core fuel outer sleeve welding positioning device, and the core fuel outer sleeve welding positioning device is positioned and assembled with the welding machine platform 300. Specifically, the first clamping block 11 of the core fuel outer sleeve welding positioning device is first fixedly connected to the welding machine platform 300, and then the two adjacent side surfaces of the assembled outer sleeve docking assembly are fitted and placed in the first V-shaped groove 111. Then, the second clamping block 12 is connected to the welding machine platform 300 and moved close to one side of the first clamping block 11 until the second V-shaped groove 121 is fitted with the other two adjacent side surfaces of the outer sleeve to lock the position of the second clamping block 12. In this process, it should be ensured that the length center plane of the outer sleeve docking assembly is roughly coincident with (or nearly coincident with) the length center plane of the first clamping block 11. Then, the axial limit assembly is installed at the two end positions of the outer sleeve docking assembly and the position of the limit bar 21 is locked by screwing the corresponding fastening nut. In this way, the core fuel outer sleeve welding positioning device realizes reliable limitation of the axial (ie TD), welding direction (ie WD) and normal (ie ND) positions of the outer sleeve docking assembly;

[0054] Welding step: using a friction stir welding tool 200 to perform friction stir welding on the butt joint gaps of the outer sleeve butt joint assembly exposed on the top surface area of ​​the core fuel outer sleeve welding positioning device, and after completing the welding of each butt joint gap on the side, replace another unwelded butt joint gap of the outer sleeve butt joint assembly to be exposed on the top surface area of ​​the core fuel outer sleeve welding positioning device, until all the butt joint gaps on the six sides of the outer sleeve butt joint assembly are welded. It can be understood that there are two butt joint gaps on each side of the outer sleeve, so the friction stir welding for each side needs to be performed twice;

[0055] Furthermore, when the core fuel outer sleeve welding positioning device includes a welding guide plate 5, before welding the butt joint gap, each welding guide plate 5 is assembled on the first clamping block 11 and the second clamping block 12. When welding the butt joint gap, the welding starting point and the end point are respectively located on the portion of the welding guide plate 5 located on the first clamping block 11 and the second clamping block 12, which can effectively avoid the inherent forming defects of stir friction welding such as unbonded areas at the welding head and tail ends (outside the welding tool stroke) and keyholes at the weld tail end (formed after the welding tool is pulled out), that is, unbonded areas and keyhole defects exist at the weld head and tail ends after welding, thereby improving the welding manufacturing quality. Afterwards, before replacing the unwelded butt joint gap to expose it to the top surface area, the welding guide plate 5 welded as one with the outer sleeve butt assembly is removed to ensure reliable positioning of the outer sleeve by the welding positioning device.

[0056] In this technical solution, since the core fuel outer sleeve welding positioning device of the present invention is used to reliably fix the position of the outer sleeve docking assembly, the position change and component warping deformation caused by excessive force on the outer sleeve during the stir friction welding process are effectively prevented, thereby effectively ensuring the welding manufacturing quality; since the stir friction welding technology is used to achieve the welding of the aforementioned core fuel outer sleeve, the problems of pores, cracks, weld nodules, undercuts and other defects that are prone to occur in the traditional melting welding process can be avoided, and the welding manufacturing quality can be significantly improved.

[0057] During the welding process, the rotation axis of the friction stir welding tool 200 (that is, the rotation axis of the stirring head 201) is located within the butt joint surface of the outer sleeve butt joint assembly corresponding to the welding. Figure 5 As described, (a) in the figure shows that the rotation axis of the stirring head 201 coincides with the right side docking surface of the hexagonal adapter 102, thereby realizing welding of the right side docking gap, and (b) in the figure shows that the rotation axis of the stirring head 201 coincides with the left side docking surface of the hexagonal adapter 102, thereby realizing welding of the left side docking gap. During the specific welding, the stirring head 201 rotates with a certain rotation direction and speed and is pressed into the docking surface of the hexagonal tube 101 and the hexagonal adapter 102 and moves along the length direction of the docking gap, finally forming a weld with a well-formed surface and no internal defects.

[0058] The forward side (i.e. Figure 5 The area indicated by AS in the figure is close to the hexagonal adapter 102, which can effectively prevent the overlapping surface area of ​​the hexagonal tube 101 from moving up due to the stirring friction, leaving unbonded areas in the weld and reducing the welding quality. Figure 5(a) When welding, the tool is rotated clockwise (from a top view) to weld the left side of the joint (i.e. Figure 5 (b)) When welding is performed, the tool is rotated counterclockwise (from a top-down perspective), that is, the front side of the welding tool is close to the hexagonal adapter 102. This is because the material on the forward side of the weld is prone to upward movement along the normal direction (i.e., ND), and the interface between the hexagonal tube 101 and the hexagonal adapter 102 is an L-shape composed of a butt surface (butt section) and a lap surface (lap section). If the rotation direction of the welding tool is selected so that the forward side of the welding tool is away from the hexagonal adapter 102, the lap surface (i.e., the lap position area corresponding to the lap section 1022 of the hexagonal adapter 102) of the hexagonal tube 101 on the forward side of the weld is prone to upward movement, resulting in residual unbonded areas in the weld, thereby reducing the welding manufacturing quality.

[0059] In some embodiments, when the first V-groove 111 has a first clearance groove and the second V-groove 121 has a second clearance groove, after all the docking gaps on the six sides of the outer sleeve docking assembly are welded, the weld flash formed on each side is processed and removed. In this way, it is only necessary to process and remove the weld flash according to actual needs after all the docking gaps of the outer sleeve are welded.

[0060] In a preferred embodiment, the rotation speed of the friction stir welding tool 200 is 50-550 rpm, the translation speed of the friction stir welding tool 200 is 20-100 mm / min, and industrial pure argon is used as the shielding gas during the translation process, the shielding gas pipe outlet diameter is 6-12 mm, and the flow rate is 2-5 liters / min. When the rotation speed is lower than the aforementioned parameter range, the translation speed (that is, the travel speed of the welding tool) is higher than the aforementioned parameter range, the shielding gas flow rate and the pipe outlet diameter are greater than the aforementioned parameter range, the welding heat input is insufficient, the weld is difficult to soften, holes and tunnel defects are easily generated, and the stirring needle is easy to break and fail; when the rotation speed is higher than the aforementioned parameter range, the translation speed is lower than the aforementioned parameter range, the shielding gas flow rate and the pipe outlet diameter are less than the aforementioned parameter range, the welding heat input is too large, the weld temperature is too high, the heat is excessively accumulated, the weld is prone to spatter, severe flash or collapse, the stirring head is severely mechanically and chemically worn, the weld residual stress is large, the structural toughness is low, and cold cracks are prone to occur.

[0061] The following specific embodiments and comparative examples further illustrate the welding process technology scheme and beneficial effects of the present invention.

[0062] Embodiment 1:

[0063] For 3 mm thick 12Cr-1Mo alloy (i.e. a specific material of the aforementioned iron horse steel) hexagonal tube ( Figure 3) for friction stir welding, and the hexagonal tube to be welded (that is, the aforementioned outer sleeve butt assembly) is fastened and constrained ( Figure 1 ), adjust the axis (i.e. the aforementioned rotation axis, the same below) of the stirring tool assembly (i.e. the aforementioned friction stir welding tool 200) to coincide with the butt joint surface of the hexagonal tube (i.e. the aforementioned hexagonal tube 101) and the adapter (i.e. the aforementioned hexagonal adapter 102), the rotation speed of the stirring tool assembly during welding is 550 rpm, the translation speed is 100 mm / min, industrial pure argon is used as the shielding gas during the translation of the stirring tool assembly, the gas pipe outlet diameter is 10 mm, and the flow rate is 5 liters / min. The rotation direction of the stirring tool changes with the position of the butt joint interface, such as Figure 5 As shown in the figure, when welding the right side of the adapter, the tool is rotated clockwise, and when welding the left side of the adapter, the tool is rotated counterclockwise. Figure 6 As shown, the joint surface is well formed and no obvious welding defects are found.

[0064] Comparative Example 1

[0065] The difference from Example 1 is that the rotation speed of the stirring tool assembly in this comparative example does not adopt the prescribed parameter range, and the specific method is as follows:

[0066] The composition, size and mechanical properties of the welded hexagonal tube were the same as those in Example 1, and the welding device and tooling assembly process were the same as those in Example 1. The rotation speed of the stirring tool assembly was 40 rpm, the translation speed was 100 mm / min, and the rest of the welding process was the same as that in Example 1. Due to the low heat input, the material was difficult to soften, flow and fill, and obvious plowing defects appeared on the weld surface and tunnel defects appeared at the bottom.

[0067] Example 2

[0068] The iron horse steel hexagonal tube with the same composition, size and mechanical properties as in Example 1 was used. The welding device and tooling assembly process were the same as in Example 1. The stirring tool assembly used in the welding process was the same as in Example 1, the rotation speed of the stirring tool assembly was 50 rpm, the translation speed was 20 mm / min, and the rest of the welding process was the same as in Example 1. The surface of the obtained joint was well formed, and no obvious welding defects were found.

[0069] Comparative Example 2

[0070] The difference from Example 2 is that the translation speed of the stirring tool assembly in this comparative example does not adopt the prescribed parameter range, and the specific method is as follows:

[0071] The composition, size and mechanical properties of the welded hexagonal tube are the same as those in Example 1. The welding device and tooling assembly process used are the same as those in Example 1. The rotation speed of the stirring tool assembly is 550 rpm, the translation speed is 150 mm / min, and the rest of the welding process is the same as that in Example 1. Although there are no obvious defects on the weld surface, due to the excessively fast translation speed of the stirring tool assembly, the heat input at the bottom of the weld is too low, and the material is difficult to fully flow and fill, resulting in holes and tunnel defects at the bottom of the weld.

[0072] Example 3

[0073] A 3 mm thick 9Cr-1Mo alloy (i.e., a specific material of the aforementioned Tiema Steel) hexagonal tube was subjected to friction stir welding. The hexagonal tube to be welded was tightened and constrained using the same welding device and tooling assembly process as in Example 1, and the axis of the stirring tool assembly was adjusted to coincide with the docking surface of the hexagonal tube and the adapter. The stirring tool assembly used in the welding process is the same as in Example 1. The rotation speed of the stirring tool assembly is 100 rpm, and the translation speed is 50 mm / min. During the translation of the stirring tool assembly, industrial pure argon is used as the shielding gas. The diameter of the gas pipe outlet is 6 mm, and the flow rate is 2 liters / min. The rotation direction of the stirring tool varies with the position of the docking interface, such as Figure 5 As shown in the figure, when welding the right side of the transition joint, the tool rotation direction is clockwise, and when welding the left side of the transition joint, the tool rotation direction is counterclockwise. The surface of the obtained joint is well formed, and no obvious welding defects are found.

[0074] Comparative Example 3

[0075] The difference from Example 3 is that the protective air pipe outlet diameter and flow rate used in this comparative example are not within the specified parameter range. The specific method is as follows:

[0076] The composition, size and mechanical properties of the welded hexagonal tube are the same as those in Example 3. The welding device and tooling assembly process used are the same as those in Example 1. Industrial pure argon is used as the shielding gas during the translation of the stirring tool assembly, the gas pipe outlet diameter is 15 mm, the flow rate is 7 liters / minute, and the rest of the welding process is the same as in Example 3. Due to the strong convection effect of the shielding gas, a large amount of heat input is conducted out of the weld, resulting in too low welding heat input, making it difficult for the material to fully flow and fill, and furrow defects appear locally on the weld surface, and holes and tunnel defects appear at the bottom of the weld.

[0077] Example 4

[0078] The iron horse steel hexagonal tube with the same composition, size and mechanical properties as in Example 3 was used. The welding device and tooling assembly process were the same as in Example 1. During the welding process, the rotation speed of the stirring tool assembly was 550 rpm, the translation speed was 100 mm / min, and the rest of the welding process was the same as in Example 1. The surface of the obtained joint was well formed, and no obvious welding defects were found.

[0079] Comparative Example 4

[0080] The difference from Example 4 is that the stirring tool used in this comparative example rotates in a different direction. The specific method is as follows:

[0081] The composition, size and mechanical properties of the welded hexagonal tube are the same as those in Example 3. The welding device and tooling assembly process used are the same as those in Example 1. When welding the right side butt joint of the adapter, the tool rotation direction is counterclockwise, and when welding the left side butt joint of the adapter, the tool rotation direction is clockwise. The rest of the welding process is the same as that in Example 4. Since the rotation direction of the stirring tool does not match the position of the butt joint interface, holes and tunnel defects appear on the forward side of the bottom of the weld when welding the right side butt joint of the adapter. Under the action of welding residual stress, cracks initiate at the tunnel defects after the weld cools and extend to the weld surface, eventually forming cold cracks, such as Figure 7 shown.

[0082] It is easy for those skilled in the art to understand that, without conflict, the advantageous technical features of the above-mentioned methods can be freely combined and superimposed.

[0083] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principle of the present invention shall be included in the protection scope of the present invention. The above description is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and variations can be made without departing from the technical principles of the present invention. These improvements and variations should also be regarded as the protection scope of the present invention.

Claims

1. A core fuel outer casing welding positioning device, characterized in that: The invention comprises a first clamping block (11) and a second clamping block (12), wherein the first clamping block (11) and the second clamping block (12) are arranged opposite to each other, and a first V-shaped groove (111) is formed on the side of the first clamping block (11) facing the second clamping block (12), and a second V-shaped groove (121) is formed on the side of the second clamping block (12) facing the first clamping block (11), and the notch opening angles of the first V-shaped groove (111) and the second V-shaped groove (121) are both 120 degrees, and two hexagonal tubes (101) of the core fuel outer sleeve and the two sections are connected to each other. The hexagonal adapter (102) between the hexagonal tubes (101) is in a welding state, and the first V-shaped groove (111) and the second V-shaped groove (121) can jointly form a clamp for the side walls of the hexagonal tube (101) and the hexagonal adapter (102) in the welding direction. The welding positioning device also includes two groups of axial limit assemblies, each of which is located at the end position of the core fuel outer sleeve and is connected to the first clamping block (11) and the second clamping block (12) to limit the axial movement of the core fuel outer sleeve.

2. The core fuel outer casing welding positioning device according to claim 1, characterized in that: The axial limiting assembly comprises a limiting strip (21), one end of the limiting strip (21) is detachably connected to the first clamping block (11), and the other end of the limiting strip (21) is detachably connected to the second clamping block (12).

3. The core fuel outer casing welding positioning device according to claim 2, characterized in that: The first clamping block (11) and the second clamping block (12) are both provided with axial limit through holes (31) on two side elevations parallel to the welding direction, the limit strip (21) is connected to the corresponding axial limit through hole (31) via a first threaded fastener (32), and both ends of the first threaded fastener (32) have threaded sections, and the maximum spacing between the two threaded sections is greater than the depth of the axial limit through hole (31); and / or, The first clamping block (11) and the second clamping block (12) are detachably positioned and assembled on the welding machine platform (300).

4. The core fuel outer casing welding positioning device according to claim 3, characterized in that: The first clamping block (11) and the second clamping block (12) are respectively configured with a fixing groove (41) penetrating the top surface and the bottom surface thereof, and the fixing groove (41) extends along a horizontal direction perpendicular to the welding direction. The welding positioning device also includes a second threaded fastener (42), and the first clamping block (11) and the second clamping block (12) are respectively positioned and assembled with the welding machine platform (300) via the corresponding second threaded fastener (42).

5. The core fuel outer casing welding positioning device according to any one of claims 1 to 4, characterized in that: A welding guide plate (5) is detachably connected to the top surface of the first clamping block (11) and the second clamping block (12), respectively. When the core fuel outer casing is in a welding state, the top surface of the welding guide plate (5) is on the same horizontal plane as the top surface of the core fuel outer casing. The material of the welding guide plate (5) is the same as that of the hexagonal tube (101) and the hexagonal adapter (102).

6. The core fuel outer casing welding positioning device according to claim 5, characterized in that: The bottom side surface of the welding guide plate (5) has an arc notch (51) that matches the arc of the edge of the hexagonal tube (101) and the hexagonal adapter (102); when the core fuel outer casing is in a welding state, the arc notch (51) fits and covers the arc of the edge of the hexagonal tube (101) and the hexagonal adapter (102).

7. The core fuel outer casing welding positioning device according to claim 1, characterized in that: The first V-shaped groove (111) has a first paving groove on its groove wall, and the position of the first paving groove corresponds to the position of the hexagonal adapter (102). The second V-shaped groove (121) has a second paving groove on its groove wall, and the position of the second paving groove corresponds to the position of the hexagonal adapter (102). The groove widths of the first paving groove and the second paving groove are w, the axial width of the butt joint section of the hexagonal adapter (102) is d, and the diameter of the stirring head (201) of the friction stir welding tool (200) is D, w>d+D+δ to accommodate the burr protrusion formed by welding, and δ is the axial width of the burr on one side.

8. A friction stir welding method for a core fuel outer casing, characterized in that: The steps include: Outer sleeve assembly and positioning step: respectively butting the two sections of the hexagonal tube (101) to be welded onto the overlapping sections (1021) at both ends of the hexagonal adapter (102) to form an outer sleeve butt assembly, positioning and assembling the outer sleeve butt assembly in the core fuel outer sleeve welding positioning device according to any one of claims 1 to 7, and positioning and assembling the core fuel outer sleeve welding positioning device and the welding machine platform (300); Welding step: using a friction stir welding tool (200) to perform friction stir welding on the butt joint gaps of the outer sleeve butt joint assembly exposed on the top surface area of ​​the core fuel outer sleeve welding positioning device, and after completing the welding of each butt joint gap on the side, replacing another unwelded butt joint gap of the outer sleeve butt joint assembly exposed on the top surface area of ​​the core fuel outer sleeve welding positioning device, until all the butt joint gaps on the six sides of the outer sleeve butt joint assembly are welded.

9. The friction stir welding method according to claim 8, characterized in that: When the core fuel outer sleeve welding positioning device includes a welding guide plate (5), before welding the butt joint gap, each welding guide plate (5) is assembled on the first clamping block (11) and the second clamping block (12); when welding the butt joint gap, the welding starting point and the end point are respectively located on the portion of the welding guide plate (5) located above the first clamping block (11) and the second clamping block (12); and before replacing the unwelded butt joint gap to expose the top surface area, the welding guide plate (5) welded as a whole with the outer sleeve butt joint assembly is removed; and / or, During the welding process, the advancing side of the friction stir welding tool (200) is close to the hexagonal adapter (102), and / or the rotation axis of the friction stir welding tool (200) is located within the butt joint surface of the corresponding outer sleeve butt joint assembly to be welded.

10. The friction stir welding method according to claim 9, characterized in that: When the first V-shaped groove (111) has a first clearance groove and the second V-shaped groove (121) has a second clearance groove, after all the butt joint gaps on the six sides of the outer sleeve butt joint assembly are welded, the weld flash formed on each side is removed by processing; and / or, The rotation speed of the friction stir welding tool (200) is 50-550 revolutions per minute, the translation speed of the friction stir welding tool (200) is 20-100 millimeters per minute, and industrial pure argon is used as a shielding gas during the translation process, the shielding gas pipe outlet diameter is 6-12 millimeters, and the flow rate is 2-5 liters per minute.

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