A horizontal assembly and welding method for ultra-long cylindrical sections with circumferential seams

Abstract

This application provides a horizontal assembly and welding method for ultra-long cylindrical sections with circumferential seams, comprising: hoisting the long cylindrical section into a horizontal fixture and controlling the horizontality of the long cylindrical section and the coaxiality of the cylindrical section axis with the axis of the support mechanism; adjusting the roundness of the assembled cylindrical section by controlling the support tension of the inner support fixture and using an auxiliary local external pressure method; eliminating local misalignment after cylindrical section assembly by local positioning welding and local correction; and eliminating local gaps after cylindrical section assembly by in-situ milling of the cylindrical section end face and full positioning seam sealing welding, wherein the milling includes rough milling and fine milling. This application enables the horizontal assembly and welding of ultra-long cylindrical section propellant tanks for next-generation medium-sized launch vehicles with circumferential seams, solving the problem of deformation during horizontal assembly of thin-walled ultra-long weak rigid cylindrical section products, reducing product production costs, and improving product assembly and welding efficiency, providing effective technical support for a high-efficiency, mass production model for rocket propellant tank products.

Description

Technical Field

[0001] This application belongs to the field of rocket tank welding technology, and particularly relates to a horizontal assembly welding method for ultra-long cylindrical sections with circumferential seams. Background Technology

[0002] Foreign mainstream long-section rocket propellant tanks, represented by the Vulcan and SLS rockets, all adopt a vertical assembly and welding scheme, and generally feature thickened designs in the tank structure to improve rigidity. However, the vertical assembly scheme places higher demands on the design and construction of the propellant tank plant, significantly increasing plant costs and introducing numerous engineering risks associated with high-altitude operations. Furthermore, traditional welding methods and equipment for "short-section" propellant tanks cannot meet the requirements for ensuring assembly precision and implementing welding processes for "long-section" propellant tanks, presenting significant technical bottlenecks.

[0003] The existing circumferential welding method for long cylindrical storage tank bodies has the following main disadvantages:

[0004] (1) The vertical assembly and welding method requires the construction of a new high-span factory building, which has high manufacturing costs;

[0005] (2) The vertical assembly welding method has high equipment investment costs and requires the investment of section lifting devices to meet the vertical assembly requirements.

[0006] (3) Vertical assembly welding method limits the choice of welding process. Usually, friction stir welding or plasma arc welding is required to achieve "horizontal welding" of circumferential seam. The process is complicated, the equipment upgrade cost is high, and the production efficiency is low.

[0007] In summary, the existing vertical assembly and welding method for long cylindrical sections is costly and has low production efficiency, making it unsuitable for high-efficiency, mass production of rocket propellant tanks. Summary of the Invention

[0008] In view of this, this application aims to propose a horizontal assembly welding method for ultra-long cylindrical sections with circumferential seams to solve at least one of the above-mentioned problems.

[0009] To achieve the above objectives, the technical solution of this application is implemented as follows:

[0010] This application provides a horizontal assembly welding method for ultra-long cylindrical sections with circumferential seams, including:

[0011] The long cylindrical section is hoisted into the horizontal tooling, and the horizontality of the long cylindrical section and the coaxiality of the cylindrical section axis and the axis of the support mechanism are controlled.

[0012] The roundness of the assembled cylinder section is adjusted by controlling the supporting tension of the internal support fixture and by using an auxiliary local external pressure method.

[0013] Local misalignment after cylinder section assembly is eliminated by local positioning welding and local correction. Local gaps after cylinder section assembly are eliminated by in-situ milling of cylinder section end faces and full positioning sealing welding. Among them, milling includes rough milling and fine milling.

[0014] Furthermore, before the cylindrical section is placed on the frame, the front and rear ends of the long cylindrical section are machined on a horizontal lathe, and the middle position of the long cylindrical section is fixed with the help of a flipping auxiliary tool.

[0015] After the cylinder section is mounted, the shell section support ring fixture is used to support one side of the cylinder section to the theoretical roundness. By moving the fixture bed, the other side of the cylinder section is aligned with the fixture head box bottom assembly, and the inner support expansion ring is used to tighten the welding end face so that the coaxiality of the front and rear ends of the tightened cylinder section meets the predetermined range.

[0016] Furthermore, the welding spindle installed in the horizontal tooling includes an extension frame, an intermediate connecting section, and a support shaft;

[0017] The extension frame has a cage-like structure, with one end connected to the flange of the flower plate at the foot of the bed, and the other end connected to the flange of the intermediate connecting section or to the support shaft. The intermediate connecting section has a tapered structure.

[0018] The support shaft is connected to the intermediate connecting section or directly connected to the extension frame.

[0019] Furthermore, the extension frame is composed of multiple support tubes and support rings. The multiple support tubes are arranged in a spaced-around manner to form a circular sleeve with a hollow internal structure. The multiple support rings are arranged at intervals on the multiple support tubes. One end of the support tube is connected to the flange of the flower plate at the end of the bed, and the other end is connected to the flange of the intermediate connecting section or to the support shaft.

[0020] Furthermore, the extension frame, intermediate connecting section, and support shaft are all made of aluminum alloy.

[0021] Furthermore, the supporting tension of the inner support fixture is controlled to pre-tighten the cylinder section so that the support block pad fits against the inner side of the welding area of ​​the cylinder section. The supporting tension is increased to make the diameter of the cylinder section at the butt joint equal to or slightly larger than the diameter in the natural state by 0-1mm.

[0022] The weld area is tightened by an auxiliary external pressure chain.

[0023] Furthermore, the locations of local misalignments and gaps are determined and marked. Small-current positioning welding is performed on both sides of the misalignment, and then the local misalignment is eliminated by heating correction.

[0024] The method employs a small current positioning welding technique throughout the entire circle, utilizing the shrinkage principle of positioning welding to eliminate local gaps through seam sealing.

[0025] Furthermore, a 3-5mm milling allowance is reserved on the welding edge of the long cylindrical section before it is placed on the frame. After the cylindrical section is leveled on the frame, the allowance is removed by rough milling.

[0026] By moving the bed mechanism, try to align the circumferential seam of the cylinder section and check whether the assembly clearance meets the process requirements. If not, perform precision milling on the welded end face.

[0027] Compared with existing technologies, the horizontal assembly welding method for ultra-long cylindrical sections with circumferential seams described in this application has the following advantages:

[0028] This application discloses a horizontal assembly and welding method for ultra-long cylindrical sections with circumferential seams. This method enables the horizontal assembly and welding of ultra-long cylindrical propellant tank sections for next-generation medium-lift launch vehicles. It reduces plant and equipment investment costs, solves the deformation problem during horizontal assembly of thin-walled, ultra-long, and weakly rigid cylindrical sections, and improves assembly and welding efficiency while lowering production costs. This provides effective technical support for a high-efficiency, mass-production model for rocket propellant tanks. Attached Figure Description

[0029] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0030] Figure 1 This is a flowchart illustrating a horizontal assembly and welding method for an ultra-long cylindrical section with circumferential seam, as described in an embodiment of this application.

[0031] Figure 2 This is a schematic diagram of a typical long storage tank structure as described in the embodiments of this application;

[0032] Figure 3 This is a schematic diagram of the horizontal assembly of the long cylindrical section as described in the embodiments of this application;

[0033] Figure 4 This is a schematic diagram of the positioning welding gap elimination method described in the embodiments of this application;

[0034] Figure 5 This is a simulation diagram of the deformation of the extended spindle in the conventional mode described in the embodiments of this application;

[0035] Figure 6 This is a schematic diagram of the welding spindle structure described in an embodiment of this application;

[0036] Figure 7 This is a simulation diagram of the deformation of the welding spindle described in the embodiment of this application.

[0037] Explanation of reference numerals in the attached figures:

[0038] 1-Extension frame; 2-Intermediate connecting section; 3-Support shaft. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with specific embodiments and the accompanying drawings.

[0040] It should be noted that, unless otherwise defined, the technical or scientific terms used in the embodiments of this application should have the ordinary meaning understood by one of ordinary skill in the art to which this application pertains. The terms "first," "second," and similar terms used in the embodiments of this application do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed after the word and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are only used to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0041] To meet the mass production needs of future medium-sized launch vehicles, a "long-section welding" tank manufacturing scheme is proposed. By adopting "long-section welding", the circumferential seam of the tank is reduced, which can effectively improve the production efficiency of the tank products, enhance the overall performance of the cylinder section, and save the tank processing cost.

[0042] Typical long cylindrical tank structure as follows Figure 2 As shown, however, long-section storage tanks suffer from the characteristics of excessively long sections and weak rigidity. Typical tank products have a diameter of 2.25m, and the tank body adopts a structure composed of single or few sections. The length of a single section is 6-8m, the welding thickness is 4-5mm, and the skin thickness is as low as less than 2mm. Compared with traditional storage tanks, the reduced structural rigidity increases the difficulty of tank assembly and welding.

[0043] Explanation of technical terms:

[0044] Horizontal welding: This is the welding mode used when assembling and welding the circumferential seam of a long cylindrical tank. The welding device is parallel to the horizontal line. Traditional horizontal welding uses a flat welding mode, where the welding torch is perpendicular to the horizontal line.

[0045] Cylindrical segment butt joint circumferential seam: The storage tank contains multiple cylindrical segments, and the weld structure between the cylindrical segments is butt joint, which is the cylindrical segment butt joint circumferential seam.

[0046] Misalignment: The amount of misalignment between the two butt joints of the weld after assembly.

[0047] Welding spindle: The core equipment for circumferential welding of long cylindrical sections, used to support the welding inner expansion ring.

[0048] This application employs TIG welding technology, aiming to achieve the welding production of the circumferential seam of ultra-long cylindrical tank sections in a horizontal configuration. The embodiments of this application are described in detail below with reference to the accompanying drawings.

[0049] Please see Figure 1 As shown in the figure, this embodiment provides a horizontal assembly welding method for ultra-long cylindrical sections with circumferential seams, which specifically includes the following steps:

[0050] Step S101: Hoist the long cylindrical section into the horizontal fixture and control the horizontality of the long cylindrical section and the coaxiality of the cylindrical section axis with the axis of the support mechanism.

[0051] Specifically, in this embodiment, a rapid assembly and alignment method for the long cylindrical section is defined as follows:

[0052] After the long cylindrical section is hoisted into the horizontal box-type circumferential welding equipment, it is necessary to ensure the horizontality of the section's trajectory and the coaxiality of the section's axis with the axis of the support mechanism. A quick method to ensure the horizontality of the cylindrical section is as follows:

[0053] A. As Figure 3 As shown, before mounting, the front and rear ends of the long cylindrical section are machined by a horizontal lathe to ensure that the parallelism of the front and rear ends is no more than 1.5mm and the coaxiality is no more than 0.5mm.

[0054] B. Use a special flipping auxiliary tool to fix the middle position of the long cylinder section to avoid local plastic deformation during the flipping process.

[0055] C. After the cylinder section is mounted, the tooling guarantee method is adopted. The shell section support ring tooling is used to support one side of the cylinder section to the theoretical roundness and ensure that the coaxiality with the tail plate is no more than 1mm. By moving the bed, the other side (welding end face) of the cylinder section is aligned with the head box bottom assembly, and the welding end face is tightened with the inner support expansion ring. After tightening, the coaxiality of the front and rear ends of the cylinder section is ≤2mm.

[0056] D. Place a rail trailer under the long cylindrical section. The rail trailer provides auxiliary support to the long cylindrical section and prevents the product from deforming and sagging.

[0057] Step S102: Adjust the roundness of the assembled cylinder section by controlling the supporting tension of the inner support fixture and using an auxiliary local external pressure method.

[0058] Specifically, in this embodiment, the thickness of the circumferential welded area of ​​the ultra-long cylindrical section is between 4-5mm. The cylindrical section itself has weak rigidity and the welded area has weak resistance to deformation. In order to achieve automatic TIG welding, the misalignment of the assembly must be no more than 0.5mm and the assembly gap must be no more than 0.3mm.

[0059] Adjusting the misalignment during assembly to control the roundness of the assembled cylinder section: The welding inner support tool first uses a small horizontal support force to ensure that the support block pad is in contact with the inner side of the cylinder section welding area; then the support block is forcefully supported to ensure that the cylinder section receives sufficient support tension. At this time, the diameter of the cylinder section joint circumferential seam is equal to or slightly larger than the diameter in its natural state by 0-1mm; then the weld area is tightened by an auxiliary external pressure chain.

[0060] Step S103: Eliminate local misalignment after cylinder section assembly by local positioning welding and local correction, and eliminate local gaps after cylinder section assembly by in-situ milling of cylinder section end face and full positioning sealing welding. The milling includes rough milling and fine milling.

[0061] Specifically, in this embodiment, the assembly gap is adjusted as follows: Before mounting the long cylindrical section, a 3-5mm milling allowance is reserved on the welding edge. After the cylindrical section is mounted and leveled, the allowance is removed by rough milling. By moving the bed mechanism, the circumferential seam of the cylindrical section is tried to be aligned to check whether the assembly gap meets the 0.3mm process requirement. If it does not meet the requirement, the welding end face is finely milled. After fine milling, the assembly gap can be further reduced.

[0062] Position welding plus local correction method: such as Figure 3 As shown, considering engineering conditions, this embodiment proposes a positioning welding plus local correction method to eliminate local misalignment and gaps after assembly. First, the location of the local misalignment and gap is determined and marked; small-current positioning welding is performed on both sides of the misalignment, and then a heating correction method is used to eliminate the local misalignment; for local gaps, a full-circle small-current positioning welding method is used, which utilizes the principle of positioning welding shrinkage to close the gap, and usually ends the arc at the maximum gap.

[0063] The above steps utilize a two-step milling process, both under and on the frame, to ensure the parallelism of the cylinder sections before welding. Specialized tooling is used to control the deformation during the long cylinder section's flipping process, thereby ensuring the horizontality of the long cylinder section after it is mounted on the frame, and the coaxiality of the cylinder section's axis with the support mechanism's axis. Methods for controlling misalignment and gaps have been developed. These methods involve adjusting the assembly roundness by using pre-tensioning with support force to achieve final tension, supplemented by localized external pressure, and eliminating misalignment through localized positioning welding and correction. Finally, localized gaps are eliminated through in-situ milling of the cylinder section end faces and fully positioned sealing welding.

[0064] It should be noted that the horizontal welding fixture, flipping auxiliary fixture, internal support fixture, and auxiliary external pressure chain used in this embodiment are all existing common equipment. This embodiment has not made any improvements to them, and will not be described in detail here.

[0065] In some embodiments, the welding spindle installed in the horizontal tooling includes an extension frame 1, an intermediate connecting section 2, and a support shaft 3, all of which are made of aluminum alloy.

[0066] The extension frame 1 has a cage-like structure and is composed of multiple support tubes and support rings. The multiple support tubes are arranged in a spaced-around manner to form a circular sleeve with a hollow internal structure. The multiple support rings are arranged on the multiple support tubes at intervals. One end of the support tube is connected to the flange of the flower plate at the foot of the bed, and the other end is connected to the flange of the intermediate connecting section 2 or to the support shaft 3. The intermediate connecting section 2 has a tapered structure.

[0067] Specifically, in this embodiment, the difficulty in achieving circumferential welding of the long cylindrical section lies in realizing the accessibility and lightweight design of the long spindle.

[0068] 1) Requirements Analysis:

[0069] The spindle length is modified according to the product size, increasing by 3000-4500mm from the traditional length. The tail extension length is increased accordingly, the coarse cross-section length of the spindle is lengthened, and the fine cross-section length is shortened.

[0070] 2) Stress analysis after extension of traditional spindle

[0071] like Figure 5 As shown, the stress analysis of the traditional spindle after extension shows an equivalent stress of 50.9 MPa and a flexural deformation of 8.29 mm under a 1t end load. The stress analysis of the modified spindle shows a similar equivalent stress of 47 MPa under a 1t end load, but a flexural deformation of 22.3 mm, approximately three times that of the normal spindle. Under this deformation condition, the spindle tilts severely and can no longer meet the normal function of the welded support ring.

[0072] The welding spindle in this embodiment adopts a squirrel cage structure, such as Figure 6 As shown, the design scheme divides the welding spindle into three parts, with the specific structure as follows:

[0073] The first part is the cage-type extension frame 1, which connects to the flower plate at the right side and the foot of the bed. The connecting flange diameter is 1200mm, which is smaller than the inner diameter of the Φ2250 shell section support bore of 1444mm. At the same time, according to the grooved structure of the flower plate, 8 φ80×5 support steel pipes are evenly distributed, and 8 M20 bolts are connected at the corresponding radial positions. The inner hole of the connecting flange is 600mm, which is larger than the main shaft diameter of 360mm, allowing the main shaft to move inside without interference.

[0074] The second part is the middle cone section, which is connected to the left flange of the cage-type extension frame 1 on one side and to the support shaft 3 on the other side.

[0075] Among them, there are currently two types of support shafts 3, one with a diameter of 180mm and the other with a diameter of 150mm, depending on the inner hole of the inner support, to meet the through-hole requirements of different manhole flange diameters.

[0076] The length of the cage-type extension frame 1 is designed to be less than the current maximum length of the main shaft (4500mm). The length of the tapered section and the support shaft 3 is designed to be between 1200-1500mm. The support shaft 3 can be mounted on either the tapered section or the cage-type extension frame 1, ensuring that the internal support mechanism can work within a range of 7000mm.

[0077] The overall mass of the welding spindle is controlled within 1 t, and the flexural deformation is doubled compared to the current situation. Considering the auxiliary role of the cylinder support trolley and the headstock support, as well as the improvement of overall rigidity after the inner support is rounded, and without a retraction action similar to that of the spindle, the welding spindle described in this embodiment is feasible.

[0078] Regarding material selection, the spindle adopts an aluminum alloy design with a cylindrical wall thickness of 20mm, reducing the overall weight to 850kg. Under the same boundary conditions, the equivalent stress is 39.1MPa, the maximum deformation is 6mm, and it occurs at the end of the thinner shaft. Figure 7 As shown in the analysis, this solution not only significantly reduces the weight of the tooling, but also effectively improves the overall rigidity and strength of the tooling, meeting the product process requirements.

[0079] The welding spindle equipment described in this embodiment can achieve circumferential welding of internal supports for 7000mm long cylindrical sections. It adopts a lightweight alloy structure, reducing the total weight of the equipment to 850Kg, thus achieving the goal of lightweighting. Under the condition of bearing the weight of products and tooling, the deflection is no more than 6mm, which meets the welding process requirements.

[0080] The welding method described in this embodiment enables horizontal assembly and welding of the circumferential seam of ultra-long cylindrical tanks for new-generation medium-sized launch vehicles. It has low plant and equipment investment costs, solves the problem of deformation during horizontal assembly of thin-walled, ultra-long, and weakly rigid cylindrical tank products, and improves product assembly and welding efficiency while reducing product production costs. It provides effective technical support for a high-efficiency, mass production model for rocket tank products.

[0081] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered within the scope of the claims and specification of the present invention.

[0082] The embodiments of this application are intended to cover all such substitutions, modifications, and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the embodiments of this application should be included within the protection scope of this application.

Claims

1. A horizontal assembly welding method for ultra-long cylindrical sections with circumferential seams, characterized in that, include: The long cylindrical section is hoisted into the horizontal tooling, and the horizontality of the long cylindrical section and the coaxiality of the cylindrical section axis and the axis of the support mechanism are controlled. The roundness of the assembled cylinder section is adjusted by controlling the supporting tension of the internal support fixture and by using an auxiliary local external pressure method. Local misalignment after cylinder section assembly is eliminated by local positioning welding and local correction. Local gaps after cylinder section assembly are eliminated by in-situ milling of cylinder section end faces and full positioning sealing welding. Among them, milling includes rough milling and fine milling. The welding spindle installed in the horizontal fixture includes an extension frame, an intermediate connecting section, and a support shaft. The extension frame has a cage-like structure, with one end connected to the flange of the flower plate at the foot of the bed, and the other end connected to the flange of the intermediate connecting section or to the support shaft. The intermediate connecting section has a tapered structure. The support shaft is connected to the intermediate connecting section or directly connected to the extension frame; The extension frame consists of multiple support tubes and support rings. The multiple support tubes are arranged in a spaced-around manner to form a circular sleeve with a hollow internal structure. The multiple support rings are arranged at intervals on the multiple support tubes. One end of the support tube is connected to the flange of the flower plate at the end of the bed, and the other end is connected to the flange of the intermediate connecting section or to the support shaft.

2. The method according to claim 1, characterized in that: Before the cylindrical section is placed on the frame, the front and rear ends of the long cylindrical section are machined by a horizontal lathe, and the middle position of the long cylindrical section is fixed with the help of a flipping auxiliary tool. After the cylinder section is mounted, the shell section support ring fixture is used to support one side of the cylinder section to the theoretical roundness. By moving the fixture bed, the other side of the cylinder section is aligned with the fixture head box bottom assembly, and the inner support expansion ring is used to tighten the welding end face so that the coaxiality of the front and rear ends of the tightened cylinder section meets the predetermined range.

3. The method according to claim 1, characterized in that: The extension frame, intermediate connecting section, and support shaft are all made of aluminum alloy.

4. The method according to claim 1, characterized in that: Control the supporting tension of the inner support fixture to pre-tighten the cylinder section so that the support block pad fits against the inner side of the welding area of ​​the cylinder section. Control and increase the supporting tension so that the diameter of the cylinder section at the butt joint is equal to or slightly larger than the diameter in the natural state by 0-1mm. The weld area is tightened by an auxiliary external pressure chain.

5. The method according to claim 1, characterized in that: The locations of local misalignment and gaps are determined and marked. Small current positioning welding is performed on both sides of the misalignment. Then, the local misalignment is eliminated by heating correction. The method employs a small current positioning welding technique throughout the entire circle, utilizing the shrinkage principle of positioning welding to eliminate local gaps through seam sealing.

6. The method according to claim 1, characterized in that: Before mounting, leave a 3-5mm milling allowance on the welded edge of the long cylindrical section. After mounting and leveling the cylindrical section, remove the allowance by rough milling. By moving the bed mechanism, try to align the circumferential seam of the cylinder section and check whether the assembly clearance meets the process requirements. If not, perform precision milling on the welded end face.

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