A device and method for welding the bottom ring seam of a small pressure-bearing storage tank of different heights

Abstract

The application relates to the field of welding and provides a device suitable for welding of bottom ring seams of small pressure-bearing storage tanks with different heights, which comprises a base, a mandrel assembly, an inner support assembly and a narrow embracing outer pressing assembly; when the device is clamped to the small pressure-bearing storage tank with different heights, the inner support assembly, the mandrel assembly and the outer clamping tool matched with the small pressure-bearing storage tank are assembled; the inner support assembly can be axially adjusted based on the position of a welding seam through an adjusting pad of the mandrel assembly, so that the welding of the bottom ring seams of the pressure-bearing storage tanks with different heights is adapted; the inner support assembly is designed in a split type, can be manually disassembled and taken out through a front bottom manhole flange hole after the bottom welding is completed, and the application further discloses a method suitable for welding of bottom ring seams of small pressure-bearing storage tanks with different heights. The application solves the problem that the inner support assembly cannot be taken out after the bottom welding is completed, realizes the clamping that the inner support assembly can be disassembled and taken out through the manhole flange hole, the supporting height is adjustable and the joint is not warped, and guarantees the welding quality.

Description

Technical Field

[0001] This invention belongs to the field of welding technology and relates to a clamping device and method for friction stir welding of the bottom sealing of a small pressure tank. Background Technology

[0002] Pressure tank structures are widely used in aerospace, new energy vehicles, and special transportation industries. With the rapid and high-quality development of my country's industrial manufacturing capabilities, the lightweighting, increasing complexity, and improving the connection performance of pressure tank structures have become essential requirements for enhancing product competitiveness. Therefore, lightweight high-strength alloys, such as aluminum and magnesium alloys, are increasingly used in pressure tanks. Controlling deformation, stress, and reducing defects during the manufacturing process has become crucial. Friction stir welding (FSW) is a novel solid-state joining technology. Compared with traditional welding methods, this method offers advantages such as low heat input, high joint strength coefficient, minimal welding deformation, simple pre-weld cleaning, and no need for shielding gas or welding wire. It is particularly suitable for welding lightweight alloys with poor hot workability, such as aluminum and magnesium alloys. Currently, FSW is maturely applied in welding butt joints of flat plates or large-diameter cylindrical sections.

[0003] When welding aluminum alloys using friction stir welding, the internal support mechanism and clamping fixture have a significant impact on the weld joint formation quality. Due to the lack of suitable internal support mechanisms and clamping fixtures, the mandrel diameter of the fixture is designed to be relatively large to ensure the rigid support of the weld joint. However, the bottom manhole flange hole is small, making it difficult to remove the internal support fixture after welding. Therefore, the bottom ring weld of current small aluminum alloy pressure tank structures mainly uses fusion welding. When welding aluminum alloy ring welds using fusion welding, the large heat input results in poor microstructure and properties in the weld area, large residual stress and deformation, and susceptibility to hot cracking defects. In addition, existing clamping fixtures are difficult to adapt to the weld position adjustment requirements of tanks of different heights, and there is a lack of effective external clamping mechanisms to prevent warping and deformation of the thin-walled ring joint, leading to weld formation defects.

[0004] Existing friction stir welding fixtures for circumferential welds are mostly suitable for large pressure tanks or large-diameter cylindrical structures with large end openings. For small pressure tanks, if a large-diameter integral internal support mandrel is used, it is difficult to remove it through the bottom manhole flange after welding. Therefore, a split clamping structure is needed that can provide sufficient internal support rigidity and can be disassembled and removed through the manhole flange after welding. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a clamping device and method for friction stir welding of the bottom sealing of a small pressure tank. This method enables the internal support component to be disassembled and removed through the manhole flange hole, the support height to be adjustable, and the joint to be warped, thus ensuring the welding quality of the annular workpiece bottom sealing circumferential weld.

[0006] To achieve the above objectives, the present invention employs the following technical solutions: A device for sealing the bottom circumferential seam of small pressure tanks of different heights, comprising: The base has a hollow cylindrical structure in the middle, with a keyway structure on the inner wall for driving the spindle assembly to rotate at a constant speed. The outer wall has a pre-set threaded through hole for fixing and connecting the spindle assembly. The upper part is composed of an inner circle and an outer circle connected by strips. The outer circle matches the manhole flange hole of the small pressure tank. The space between the strips is used to reserve operating space for removing the inner support assembly. The mandrel assembly includes a lower rod, an upper rod, and an adjusting pad. The lower rod is a stepped cylindrical structure that is connected to the base and supports the inner support assembly. The upper rod is a stepped cylindrical structure that is connected to the lower rod and fixes the inner support assembly. The adjusting pad adjusts the axial height of the inner support assembly. The inner support assembly adopts a split design, including a chassis, a large support block assembly, a small support block assembly, a small guide rail, a side top block, and locking screws. The chassis is sleeved on the spindle assembly. The small guide rail and the side top block are connected to the chassis. The large support block assembly and the small support block assembly can move along the small guide rail. The large support block assembly and the small support block assembly are alternately distributed, and their outer edges form a circular inner support to support the inner wall of the weld. The side top block acts on the end face of the large support block assembly or the small support block assembly through the locking screw to restrict and fit against the inner wall of the weld. Moreover, each component of the inner support assembly can be disassembled and removed through the manhole flange hole. The narrow-shaped encircling external pressure assembly includes a segmented external pressure sleeve that surrounds both sides of the weld and applies radial clamping force to both sides of the weld to prevent warping and deformation of the joint.

[0007] By combining a split, detachable inner support assembly with an axially adjustable mandrel assembly, the contradiction between rigid support and tooling removal is resolved. At the same time, with the external pressure clamping assembly surrounding both sides of the weld, the clamping effect of removable inner support, adjustable support height, and no warping of the joint is achieved, ensuring the welding quality of the bottom sealing ring seam of the small pressure tank.

[0008] Furthermore, the adjusting pad is fitted onto the lower rod, and the axial height of the inner support assembly is adjusted by changing the number or thickness of the adjusting pad.

[0009] Furthermore, the lower rod, from bottom to top, comprises: a first cylindrical section with a key block that engages with the keyway structure of the base; a second cylindrical section with distributed through holes that engage with pre-set threaded through holes on the outer wall of the base; a third cylindrical section for supporting the inner support assembly; a fourth cylindrical section with a key block for engaging and driving the inner support assembly; and a fifth cylindrical section with a threaded rod at the top for connecting to the upper rod. The lower rod is designed as a stepped cylindrical structure, with each cylindrical section undertaking specific functions such as engaging with the base, fixed connection, supporting the inner support, driving rotation, and connecting to the upper rod.

[0010] Furthermore, the upper rod comprises, from bottom to top, the following: a first cylindrical section with a concentric cylindrical cavity that corresponds to and engages with the lower rod; a second cylindrical section with a threaded hole that engages with and connects to the lower rod; a third cylindrical section; and a fourth cylindrical section with a lead screw at the end for connecting a nut, and a small through hole at the bottom for easy assembly and disassembly of the rod.

[0011] The upper rod is designed as a stepped cylindrical structure, with each cylindrical segment undertaking specific functions such as mating with the lower rod, threaded connection, transition, and nut locking. This allows the upper rod to reliably connect with the lower rod while providing a structural basis for the axial clamping of the upper pressure ring and nut.

[0012] Furthermore, the spindle assembly also includes a transition pad, which is fitted onto the third cylindrical section of the lower rod and located below the adjustment pad.

[0013] Furthermore, the mandrel assembly also includes an upper pressure ring and a nut. The upper pressure ring is sleeved on the top of the fourth cylindrical section of the upper rod, and the nut engages with the lead screw at the end of the fourth cylindrical section for locking. Tightening the nut causes the upper pressure ring to axially press against the cylindrical section of the small pressure tank, ensuring a tight fit between the weld seam of the cylindrical section and the front bottom section. The engagement of the nut and the upper pressure ring at the top of the fourth cylindrical section provides a uniform axial clamping force, driving the joint between the cylindrical section and the front bottom section to fit tightly, effectively eliminating assembly gaps and ensuring weld formation quality. Furthermore, the segmented external pressure sleeve is composed of multiple segments connected by screws to form a ring structure, so that the force on both sides of the weld is uniform.

[0014] The present invention also provides a method for sealing the bottom circumferential seam of small pressure tanks of different heights, comprising the following steps: S1: Threaded connection welding positioner and base, insert the lower rod into the base and screw it in, adjust the position of the front bottom section so that the threaded holes around the manhole flange hole are aligned with the threaded holes on the upper part of the base, and then screw the base and the front bottom section together. S2: Connect the chassis and the small guide rail and screw them together. Connect the small guide rail and the side top block and screw them together. Slide the large support block assembly and the small support block assembly alternately into the small guide rail. The locking screw passes through the side top block. Place the transition pad, the adjusting pad and the inner support assembly onto the lower rod in sequence. Connect the upper rod and the lower rod. Fix the inner support assembly by tightening the thread. S3: Adjust the position of the cylinder section so that it fits onto the circular inner support formed by the large support block assembly and the small support block assembly and aligns with the front bottom section. Fit the upper pressure ring onto the upper rod. Use the screwing force of the nut to make the joint position of the cylinder section and the front bottom section fit tightly. Set narrow ring-type external pressure components on both sides of the weld and tighten them to achieve clamping and fixing. S4: The stir welding spindle, carrying the retractable stirring head, applies the set rotation speed and welding pressure to the area to be welded and then remains stationary. The welding positioner, carrying the front bottom section, mandrel assembly, inner support assembly, and cylinder section, rotates at the set speed. The stir welding spindle, carrying the retractable stirring head, continuously applies the welding joint to promote the welding of the contact surfaces of the cylinder section and the front bottom section. After one rotation, the stirring needle is retracted to achieve keyless stir friction welding and then withdrawn from the weld area. S5: Remove the narrow-shaped encircling external pressure assembly, remove the locking screws and side top blocks and retract the small support block assembly, separate the small guide rail and chassis and remove the disassembled parts through the manhole flange hole at the bottom of the front bottom section, retract the large support block assembly and the corresponding small guide rail, remove the nut and upper pressure ring, and remove the small pressure tank from the upper rod direction.

[0015] Further in S2, the locking screw passes through the side top block and contacts the end face of the large support block assembly or the small support block assembly but does not apply force, keeping the positions of each component in the inner support assembly facing downwards toward the front bottom section, while ensuring that the area to be welded is located at the center of the circular inner support composed of the large support block assembly and the small support block assembly.

[0016] The present invention has the following advantages: (1) The present invention uses friction stir welding technology to weld the bottom ring seam of small pressure tanks, avoiding the disadvantages of poor microstructure, large residual stress and deformation, and hot cracking defects that occur in the fusion welding method. It is particularly suitable for welding metals with poor hot working properties such as aluminum alloys and magnesium alloys.

[0017] (2) The welding clamping fixture of the present invention can clamp a small pressure tank with a height variation of 400mm under a certain diameter by selecting accessories such as large and small support block components, small guide rails, side top blocks, chassis and upper and lower rods. With the extension of the upper and lower rods, it can also clamp a larger pressure tank, realizing the widespread application of the fixture.

[0018] (3) The present invention controls the position of the inner support mechanism by using a small guide rail and an adjustment pad, so that the large and small support block components in the inner support mechanism support the position of the weld joint, ensuring the normal operation of the friction stir welding process.

[0019] (4) The pressure tank internal support mechanism and clamping fixture of the present invention have an ingenious structure. By adopting the close cooperation between the large and small support block components, the small guide rail and the side top block, it can not only provide sufficient internal support for the bottom sealing weld during the friction stir welding process, but also make it easy to disassemble the fixture after welding to ensure production efficiency. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the working state of keyless friction stir welding for sealing the bottom of a small pressure tank according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the base according to an embodiment of the present invention; Figure 3 This is a schematic diagram of the mandrel assembly according to an embodiment of the present invention; Figure 4 This is a schematic diagram of the internal support component according to an embodiment of the present invention; Figure 5 This is a schematic diagram of the overall assembly structure of the small pressure tank according to an embodiment of the present invention; In the diagram: 1. Welding positioner; 2. Base; 3. Front bottom section; 4. Spindle assembly; 5. Inner support assembly; 6. Narrow-shaped encircling external pressure assembly; 7. Stir welding spindle; 8. Cylindrical section; 4-1. Lower rod; 4-2. Transition pad; 4-3. Adjusting pad; 4-4. Upper rod; 4-5. Upper pressure ring; 4-6. Nut; 5-1. Chassis; 5-2. Small guide rail; 5-3. Side top block; 5-4. Large support block assembly; 5-5. Small support block assembly; 5-6. Locking screw; 6-1. Split-type external pressure sleeve. Detailed Implementation

[0021] The present invention will now be described in detail with reference to the accompanying drawings.

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0023] Taking the keyless friction stir welding of the bottom sealing of a 2219 aluminum alloy pressure tank with an inner diameter of 800mm, a wall thickness of 5mm, and a height of 1200mm as an example, a specific implementation method is given: Example 1 like Figure 1 , Figure 2 , Figure 3 , Figure 4 and Figure 5 As shown, this embodiment of the invention provides a clamping device for welding the bottom circumferential seam of a small pressure tank. The clamping device mainly includes four core components: a base 2, a spindle assembly 4, an inner support assembly 5, and a narrow-shaped encircling external pressure assembly 6. Through the specific combination and synergistic cooperation of each component, the contradiction between rigid support and narrow opening withdrawal during the bottom circumferential seam welding of a small pressure tank is resolved, and the warping and deformation of the joint are effectively prevented.

[0024] The lower outer edge of the base 2 has evenly distributed threaded holes for connecting the positioner 1, with a lower diameter of 260mm. The middle part is a hollow cylindrical structure with pre-set threaded through holes on its outer wall for fixing and connecting the mandrel assembly 4. The inner wall has a keyway structure for driving the mandrel assembly 4 to rotate at a uniform speed during the welding process. According to the cantilever beam formula, the height is set to 60mm to ensure sufficient operating space and maintain sufficient rigidity when manually disassembling the mandrel assembly 4 and the inner support assembly 5. The upper part consists of an inner circle and an outer circle connected by three strips, which provides sufficient space while ensuring rigidity. The outer circle structure dimensions and the distribution of threaded holes match the manhole flange holes in the front bottom section 3. The inner circle and outer circle diameters are 60mm and 120mm, respectively. The base 2 serves as the basic support and positioning platform for the entire clamping device. The hollow cylindrical structure in its middle not only provides a stable support for the installation of the mandrel assembly 4, but the keyway structure on the inner wall also ensures that the mandrel assembly 4 can be precisely driven during the welding rotation without relative slippage or speed fluctuation. The inner and outer circles and connecting ribs on the upper part of the base ensure the support rigidity while creating a disassembly operation space, allowing the individual components of the inner support assembly to be removed through the manhole flange after welding.

[0025] The main components of the mandrel assembly 4 include a lower rod 4-1, a transition pad 4-2, an adjusting pad 4-3, an upper rod 4-4, an upper pressure ring 4-5, and a nut 4-6. The lower rod 4-1 has a stepped cylindrical structure with five stages from bottom to top. The first stage has two rows of key blocks that engage with the base 2. The second stage has through holes that engage with pre-set threaded holes on the outer wall of the base 2. The third stage connects the transition pad 4-2, the adjusting pad 4-3, and the inner support assembly 5. The fourth stage has two rows of key blocks to engage with and drive the inner support assembly 5 to rotate at a constant speed during welding. The fifth stage has a threaded rod at the top for connecting to the upper rod 4-4. The transition pad 4-2 is fitted over the top of the third stage of the lower rod 4-1 to house the adjusting pad 4-3 and the inner support assembly 5. The adjusting pad 4-3 is fitted over the lower rod 4-1 and placed above the transition pad 4-2, with two 2mm thick adjusting pads 4-3 placed on top. The inner support assembly 5 is directly opposite the circumferential weld. The upper rod 4-4 is also designed as a stepped cylindrical structure with four steps from bottom to top. The first-step cylinder has a concentric cylindrical cavity with dimensions corresponding to the fourth-step cylinder of the lower rod 4-1. The second-step cylinder has a threaded hole that mates with the fifth-step cylindrical threaded rod of the lower rod 4-1. This connects the two rods and drives the upper rod axially through the threaded tightening force to fix the inner support assembly 5. The end of the fourth-step cylinder is a lead screw for connecting the nut 4-6. A small through hole is arranged below to facilitate the mounting of the rod, allowing for the assembly and disassembly of the upper rod 4-4 and the lower rod 4-1. The upper pressure ring 4-5 is locked to the top of the upper rod 4-4 by the nut 4-6, ensuring a tight fit between the circumferential weld between the barrel section 8 and the front bottom section 3, thus guaranteeing welding quality.

[0026] Because the axial position of the bottom sealing ring seam often varies significantly among small pressure tanks of different heights, if the mandrel height is fixed, the inner support assembly will not be able to accurately align with the inner wall of the weld, leading to support failure. By setting adjustment shims on the mandrel assembly, operators can flexibly change the configuration of the adjustment shims according to the actual weld height of the tank, thereby accurately raising or lowering the circular support surface of the inner support assembly to the plane where the weld is located.

[0027] The lower rod, serving as the lower section of the spindle assembly, bears the main shaft. Its stepped cylindrical structure distributes different functional requirements to each cylindrical section, achieving modular division of labor and precise positioning of structural functions. The first cylindrical section has a key block that engages with the keyway structure on the inner wall of the base, ensuring that the lower rod does not rotate relative to the base and allowing the rotational driving force of the base to be reliably transmitted to the lower rod, driving the inner support assembly to rotate at a uniform speed. The second cylindrical section has through holes that engage with pre-set threaded through holes on the outer wall of the base, anchoring the lower rod to the base with fasteners and providing axial fixation. The third cylindrical section supports the inner support assembly, with transition pads and adjusting pads fitted onto this section, providing a stable foundation for the inner support assembly and height adjustment. The fourth cylindrical section has a key block to engage and drive the inner support assembly to rotate at a uniform speed during welding, ensuring the rotational accuracy of friction stir welding. The fifth cylindrical section has a threaded rod at the top, which engages with the threaded hole of the upper rod to achieve threaded engagement and axial tightening of the upper and lower rods.

[0028] The upper rod, serving as the upper section of the mandrel assembly and acting as the clamping spindle, features a stepped cylindrical structure that forms a symmetrical modular division of labor with the lower rod. The first cylindrical section has a concentric cylindrical cavity whose dimensions correspond to and match the fourth cylindrical section of the lower rod, ensuring concentricity and positioning accuracy during connection. The second cylindrical section has a threaded hole that connects to the threaded rod at the top of the fifth cylindrical section of the lower rod, achieving reliable connection and axial clamping through threaded engagement. The third cylindrical section serves as a transition section, connecting the threaded connection section and the clamping functional section. The end of the fourth cylindrical section is a lead screw used to connect a nut to lock the upper pressure ring, and a small through hole at the bottom facilitates the insertion of a tool for disassembling and assembling the upper and lower rods.

[0029] The main components of the inner support assembly 5 include a chassis 5-1, a small guide rail 5-2, a side top block 5-3, a large support block assembly 5-4, a small support block assembly 5-5, and a locking screw 5-6. The chassis 5-1 is fitted onto the lower rod 4-1 in a four-stage cylindrical shape, and is placed on the adjusting pad 4-3 and the transition pad 4-2. Threaded holes are distributed around the chassis, connecting it to the small guide rail 5-2 and the side top block 5-3. The small guide rail 5-2 is equipped with sliding blocks, allowing the large support block assembly 5-4 or the small support block assembly 5-5 to move freely along the sliding direction. The side top block 5-3 and the locking screw 5-6 engage through a transmission thread, acting on the end face of the large support block assembly 5-4 or the small support block assembly 5-5, restricting and ensuring the support block assembly fits tightly against the inner wall of the weld, guaranteeing effective support during the welding process. The large support block assembly 5-4 and the small support block assembly 5-5 are alternately distributed, forming a circular inner support with a diameter of 790mm along their outer edges. With the cooperation of the narrow-shaped encircling external pressure assembly 6, this effectively prevents excessive deformation during the sealing weld of the pressure tank, ensuring weld quality. The modular design with a specific combination structure solves the industry problem that traditional integral internal support tooling cannot be removed from the narrow manhole flange hole after bottom sealing welding. The narrow-shaped circumferential external pressure assembly 6 mainly consists of a segmented external pressure sleeve 6-1. This assembly comprises four segmented external pressure sleeves 6-1 with a 90-degree arc, connected by nuts. The segmented structure ensures uniform force distribution on both sides of the circumferential weld, guaranteeing weld quality. The segmented external pressure sleeves are arranged around both sides of the weld, ensuring the clamping force is tightly attached to the weld area, preventing torque attenuation or uneven force distribution due to excessive distance. During welding, the upsetting force and heat input of friction stir welding can easily cause warping deformation of the circumferential joint of the thin-walled tank. Especially when the inner support assembly provides radial support, if there is a lack of corresponding external clamping constraint, the tank wall may still experience localized bulging or warping. The narrow-shaped circumferential external pressure assembly applies radial clamping force from the outside through the segmented external pressure sleeves, counteracting the supporting force of the internal support block, firmly clamping the weld area between the inner and outer pressures, thereby effectively suppressing the warping tendency of the joint.

[0030] Example 2 This invention provides a method for keyless friction stir welding to seal the bottom of small pressure tanks of varying heights. The method includes the following steps: S1: After threading the positioner turntable 1 and base 2, insert the lower rod 4-1 into the base and screw it in. Adjust the position of the front bottom section 3 so that the threaded holes around the manhole flange hole are aligned with the threaded holes on the upper part of the base 2, and then screw the base 2 and the front bottom section 3 together.

[0031] S2: Connect the chassis 5-1 and the small guide rail 5-2. Adjust the position of the small guide rail 5-2 so that its threaded hole aligns with the threaded hole of the chassis 5-1, and screw it in to secure it. Repeat this process for 8 sets of connections. Connect the small guide rail 5-2 and the side top block 5-3. Adjust the position of the side top block 5-3 so that its threaded hole aligns with the threaded hole of the small guide rail 5-3, and screw it in to secure it. Repeat this process for 8 sets of connections. Alternately slide the four sets of large support block assemblies 5-4 and small support block assemblies 5-5 into the rails of the small guide rail 5-2. The locking screw 5-6 passes through the side top block 5-3 and contacts the ends of the large support block assemblies 5-4 and small support block assemblies 5-5, but without applying force. Place the transition pad 4-2, the two adjusting pads 4-3, and the inner support assembly 5 onto the lower rod 4-1 in sequence. Keep the positions of each component in the inner support assembly 5 facing downwards towards the front bottom section 3, while ensuring that the area to be welded is located at the center of the inner support circle formed by the large support block assemblies 5-4 and small support block assemblies 5-5. Connect the upper rod 4-4 and the lower rod 4-1, rotate the upper rod 4-4, and through the threaded tightening force, make the upper rod 4-4 act tightly and fix the inner support assembly 5.

[0032] S3: Adjust the position of the cylindrical section 8 so that it fits onto the inner support circle of the large support block assembly 5-4 and the small support block assembly 5-5, aligning it with the front bottom section 3. Fit the upper pressure ring 4-5 onto the upper rod 4-2. Through the screwing force of the nut 4-6, the upper pressure ring 4-5 acts on the cylindrical section 8, driving the joint position of the cylindrical section 8 and the front bottom section 3 to fit tightly. Two sets of ring-type external pressure components 6 are respectively installed at a position of about 20mm from the weld seam. Tightening the bolts realizes the clamping and fixing of the external pressure components 6 on the surface of the weldment.

[0033] S4: The welding program is programmed so that the stir welding spindle 7, carrying the retractable stirring head, applies a set rotational speed, welding pressure, and tilt angle to the area to be welded, and then remains stationary. After a brief application at the starting position, the welding positioner 1, carrying the barrel section 8, front bottom section 3, spindle assembly 4, and inner support assembly 5, rotates at a certain speed. The stir welding spindle 7, carrying the retractable stirring head, continuously applies the welding head to the joint and promotes the welding of the contact surfaces of the barrel section 8 and the front bottom section 3. After the barrel section 8 and the front bottom section 3 have rotated one revolution, the welding positioner 1 stops operating. The stir welding spindle 7 then applies the retractable stirring head to retract the stirring needle, achieving complete keyhole-free friction stir welding of the circumferential weld, and then withdraws from the weld area.

[0034] S5: Remove the ring-shaped external pressure assembly 6. Manually remove each component of the inner support assembly 5 one by one through the gap between the upper part of the base 2 and the manhole flange hole. First, remove the locking screws 5-6 and the side top block 5-3. Slightly retract the small support block assembly 5-5. Remove the screws to separate the small guide rail 5-2 and the chassis 5-1. Remove the disassembled parts through the manhole flange hole at the bottom of the front bottom section 3. Similarly, retrieve the large support block assembly 5-4 and the corresponding small guide rail 5-2. Remove the nuts 4-6 and the upper pressure ring 4-5 in sequence. Remove the pressure storage box from the direction of the upper rod 4-4 to complete the welding part retrieval.

[0035] This invention relates to the clamping of small pressure tanks of different heights. It involves assembling a matching internal support assembly, a mandrel assembly, and an external clamping fixture. The internal support assembly is axially adjustable based on the weld position via the mandrel assembly's adjusting shims, adapting to the welding of the bottom sealing circumferential seam of pressure tanks of different heights. The internal support assembly adopts a split design, consisting of a large support block assembly, a small support block assembly, a side top block, and a small guide rail connected mechanically. After the bottom sealing weld is completed, it can be manually disassembled and removed through the front bottom manhole flange, solving the problem of the internal support assembly being unable to be removed after the bottom sealing weld. The mandrel assembly also adopts a split design, consisting of an upper rod, a lower rod, a transition shim, an adjusting shim, and an upper pressure ring. This ensures the fixation and structural rigidity of the internal support assembly while facilitating disassembly after welding. The external clamping fixture uses a narrow, circumferential external pressure assembly. Its segmented structure allows the clamping force to be evenly applied to both sides of the circumferential weld, preventing warping and deformation of the weld joint during the welding process, which could lead to forming defects.

[0036] This invention is not limited to the specific embodiments described above. The invention extends to any new feature or combination disclosed in this specification, as well as any new method or process step or combination disclosed herein.

Claims

1. A device for sealing the bottom circumferential seam of small pressure tanks of different heights, characterized in that, include: The base has a hollow cylindrical structure in the middle, with a keyway structure on the inner wall for driving the spindle assembly to rotate at a constant speed. The outer wall has a pre-set threaded through hole for fixing and connecting the spindle assembly. The upper part is composed of an inner circle and an outer circle connected by strips. The outer circle matches the manhole flange hole of the small pressure tank. The space between the strips is used to reserve operating space for removing the inner support assembly. The mandrel assembly includes a lower rod, an upper rod, an adjusting pad, an upper pressure ring, and a nut. The lower rod is a stepped cylindrical structure that connects to the base and supports the inner support assembly. The upper rod is also a stepped cylindrical structure that connects to the lower rod and fixes the inner support assembly. The upper rod and the lower rod are detachably connected. The adjusting pad is fitted onto the lower rod to adjust the axial height of the inner support assembly. The upper pressure ring is fitted onto the upper rod to press the cylindrical section of the small pressure tank. The nut cooperates with the upper rod to lock the upper pressure ring, ensuring a tight fit between the weld seam of the cylindrical section and the front bottom section. The inner support assembly adopts a split design, including a chassis, a large support block assembly, a small support block assembly, a small guide rail, a side top block, and a locking screw. The chassis is fitted onto the spindle assembly. The small guide rail and the side top block are connected to the chassis. The large support block assembly and the small support block assembly can move along the small guide rail. The large support block assembly and the small support block assembly are alternately distributed, and their outer edges form a circular inner support to support the inner wall of the weld. The locking screw passes through the side top block and abuts against the end face of the large support block assembly or the small support block assembly to push or lock the large support block assembly or the small support block assembly, so that its outer edge abuts against and supports the inner wall of the weld. The chassis, the small guide rail, the side top block, the large support block assembly, the small support block assembly, and the locking screw are detachably connected, and can be removed through the manhole flange holes in the disassembled state. The narrow-shaped encircling external pressure assembly includes a segmented external pressure sleeve that surrounds both sides of the weld and applies radial clamping force to both sides of the weld to prevent warping and deformation of the joint.

2. The device for sealing the bottom circumferential seam of small pressure tanks of different heights according to claim 1, characterized in that, The adjusting pad is fitted onto the lower rod, and the axial height of the inner support assembly is adjusted by changing the number or thickness of the adjusting pad.

3. The clamping device for bottom-sealing friction stir welding of a small pressure tank according to claim 1, characterized in that, The lower rod comprises, from bottom to top, the following: a first cylindrical section with a key block that engages with the keyway structure of the base; a second cylindrical section with distributed through holes that engage with the pre-set threaded through holes on the outer wall of the base; a third cylindrical section for supporting the inner support assembly; a fourth cylindrical section with a key block for engaging and driving the inner support assembly; and a fifth cylindrical section with a threaded rod at the top for connecting to the upper rod.

4. The device for sealing the bottom circumferential seam of small pressure tanks of different heights according to claim 1, characterized in that, The upper rod comprises, from bottom to top, the following sections: a first cylindrical section with a concentric cylindrical cavity that corresponds to and engages with the lower rod; a second cylindrical section with a threaded hole that engages with and connects to the lower rod; a third cylindrical section; and a fourth cylindrical section with a lead screw at the end for connecting a nut, and a small through hole at the bottom for easy assembly and disassembly of the rod.

5. The device for sealing the bottom circumferential seam of small pressure tanks of different heights according to claim 3, characterized in that, The spindle assembly also includes a transition pad, which is fitted onto the third cylindrical section of the lower rod and located below the adjustment pad.

6. The device for sealing the bottom circumferential seam of small pressure tanks of different heights according to claim 4, characterized in that, The upper pressure ring is sleeved on the top of the fourth cylindrical section of the upper rod. The nut is locked in place with the screw at the end of the fourth cylindrical section. By tightening the nut, the upper pressure ring is axially pressed against the cylindrical section of the small pressure tank, so that the weld between the cylindrical section and the front bottom section is tightly fitted.

7. The device for sealing the bottom circumferential seam of small pressure tanks of different heights according to claim 1, characterized in that, The segmented external pressure sleeve is composed of multiple segments connected by screws to form a ring structure, so that the force on both sides of the weld is uniform.

8. A method for sealing the bottom circumferential seam of a small pressure tank using the device described in any one of claims 1-7, characterized in that, Includes the following steps: S1: Threaded connection welding positioner and base, insert the lower rod into the base and screw it in, adjust the position of the front bottom section so that the threaded holes around the manhole flange hole are aligned with the threaded holes on the upper part of the base, and then screw the base and the front bottom section together. S2: Connect the chassis and the small guide rail and screw them together. Connect the small guide rail and the side top block and screw them together. Slide the large support block assembly and the small support block assembly alternately into the small guide rail. The locking screw passes through the side top block. Place the transition pad, the adjusting pad and the inner support assembly onto the lower rod in sequence. Connect the upper rod and the lower rod. Fix the inner support assembly by tightening the thread. S3: Adjust the position of the cylinder section so that it fits onto the circular inner support formed by the large support block assembly and the small support block assembly and aligns with the front bottom section. Fit the upper pressure ring onto the upper rod. Use the screwing force of the nut to make the joint position of the cylinder section and the front bottom section fit tightly. Set narrow ring-type external pressure components on both sides of the weld and tighten them to achieve clamping and fixing. S4: The stir welding spindle, carrying the retractable stirring head, applies the set rotation speed and welding pressure to the area to be welded and then remains stationary. The welding positioner, carrying the front bottom section, mandrel assembly, inner support assembly, and cylinder section, rotates at the set speed. The stir welding spindle, carrying the retractable stirring head, continuously applies the welding joint to promote the welding of the contact surfaces of the cylinder section and the front bottom section. After one rotation, the stirring needle is retracted to achieve keyless stir friction welding and then withdrawn from the weld area. S5: Remove the narrow-shaped encircling external pressure assembly, remove the locking screws and side top blocks and retract the small support block assembly, separate the small guide rail and chassis and remove the disassembled parts through the manhole flange hole at the bottom of the front bottom section, retract the large support block assembly and the corresponding small guide rail, remove the nut and upper pressure ring, and remove the small pressure tank from the upper rod direction.

9. A method for sealing the bottom circumferential seam of a small pressure tank according to claim 8, characterized in that, In step S2, the locking screw passes through the side top block and contacts the end face of the large support block assembly or the small support block assembly but does not apply force, keeping the positions of each component in the inner support assembly facing downwards toward the front bottom section, while ensuring that the area to be welded is located at the center of the circular inner support composed of the large support block assembly and the small support block assembly.

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