Laser welding method for ring joint of ring assembly structure

Abstract

The application provides a ring-shaped combined structure ring seam laser welding method, which comprises the following steps: sequentially connecting multiple connecting rings and a bent pipe end to end to form a semi-ring-shaped combined structure; spot welding multiple welding points on any one ring-shaped welding seam; coating the outer surface of any one ring-shaped welding seam to prevent air leakage; injecting protective gas from one end of the semi-ring-shaped combined structure to exhaust the air in the semi-ring-shaped combined structure, then sealing the end of the semi-ring-shaped combined structure; welding the upper half of multiple ring-shaped welding seams by adopting a full-position welding process; turning over the semi-ring-shaped combined structure which has completed half of the welding; sequentially welding the other half of the multiple ring-shaped welding seams by adopting the full-position welding process; repeating the above steps to complete the welding of the other semi-ring-shaped combined structure. The two semi-ring-shaped combined structures which have completed the welding are connected by bolts and nuts to form a ring-shaped combined structure, which reduces the clamping requirement, simplifies the clamping process, reduces the turning over difficulty, and realizes self-locking butt joint assembly.

Description

Technical Field

[0001] This invention relates to the field of laser welding technology, and more specifically, to a laser welding method for a ring-shaped composite structure circumferential seam. Background Technology

[0002] Laser welding, as a precision, efficiency, and speed welding method, has been increasingly widely used in various fields of manufacturing, especially in the manufacturing of large thin-walled irregular structural parts for aerospace, where it has better adaptability due to its high quality and small deformation.

[0003] The upper stage, acting as a "space tug," possesses autonomous orbital maneuverability and can be repeatedly ignited to deliver one or more payloads into designated orbits, meeting diverse launch mission requirements and significantly enhancing the flexibility of launch vehicle missions. Using a toroidal propellant tank in the upper stage allows for the complete inheritance of the original upper stage's technical specifications, greatly increasing its payload capacity. After the toroidal propellant is used up, it is jettisoned, significantly reducing the overall mass of the launch vehicle and maximizing the payload velocity increment. Currently, toroidal propellants have been successfully applied to upper stages abroad, such as the Briz-M and Fregat-SB upper stages.

[0004] A Chinese patent application with publication number CN111762343A discloses a jettisonable bicomponent common-bottom annular tank for spacecraft, comprising an annular tank body, a central cylinder, and a separation device. The annular tank body is symmetrically equipped with a first connecting ring, a second connecting ring, and ring segments, both of which have lugs. The central cylinder has an upper frame, a lower frame, and stringers. The lugs and stringers are bolted to connect the annular tank body to the central cylinder to jointly bear external loads. The upper and lower frames are separation surfaces, and the separation device is located on these surfaces, enabling the annular tank body to be jettisoned. The single-layer common-bottom assembly of the connecting rings allows the annular tank body to form a bicomponent structure, capable of simultaneously carrying fuel and oxidizer.

[0005] The annular propellant tank is an irregularly shaped structural component used in the upper stage of a launch vehicle. Its shape resembles a swimming ring. Currently, it is made of titanium alloy, with an outer diameter of φ3200mm, a cross-sectional diameter of φ500mm, and a bend wall thickness of 2mm. It belongs to a large-size thin-walled irregularly shaped structural component. It is formed by connecting the connecting ring and the bend sequentially by an annular weld. In order to control welding deformation, laser welding process is used. Due to the special structure, all-position welding process is required and it is difficult to weld in one step. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the purpose of this invention is to provide a laser welding method for circumferential seams of annular composite structures.

[0007] According to the present invention, a laser welding method for a ring-shaped combined structure is provided. The welding method includes the following steps: Step S1, connecting multiple connecting rings and multiple bent pipes end to end in sequence to form a semi-ring-shaped combined structure;

[0008] Step S2: Spot weld multiple weld points on any one circumferential weld seam;

[0009] Step S3: Cover the outer surface of any circumferential weld to prevent air leakage;

[0010] Step S4: After injecting protective gas into one port of the semi-annular combined structure to vent the air inside the semi-annular combined structure, seal the port of the semi-annular combined structure.

[0011] Step S5: Use all-position welding process to weld the upper half of multiple circumferential welds in sequence;

[0012] Step S6: Flip the semi-circular assembly structure, which has been partially welded, over.

[0013] Step S7: Use all-position welding process to weld the other half of multiple circumferential welds in sequence;

[0014] Step S8: Repeat steps S1-S7 to complete the welding of the other semi-circular composite structure.

[0015] Step S9: Connect the two welded semi-circular structures with bolts and nuts to form a circular structure.

[0016] Preferably, step S1 includes the following sub-steps:

[0017] Step S1.1: Make a bottom locking stop on the connecting ring, insert the end of the bend into the bottom locking stop and lock it to the bottom of the connecting ring, and connect multiple connecting rings and multiple bends end to end in sequence to form a semi-circular combination structure.

[0018] Step S1.2: Use a tire-mounting fixture to lay the semi-circular assembly flat and clamp it.

[0019] Preferably, for step S1.1, the depth of the bottom stop is 0.5 mm and the width is 2 mm.

[0020] Preferably, for step S1, the accuracy of sequentially connecting multiple connecting rings and multiple bends end to end is:

[0021] The gap should not exceed 0.2mm, the misalignment should not exceed 0.2mm, and the overall flatness should not exceed 0.5mm.

[0022] Preferably, for step S3, the covering material is an airtight material.

[0023] Preferably, for step S4, the protective gas includes high-purity argon, the flow rate of which does not exceed 20 L / min, and the filling volume is more than twice the volume of the semi-annular combined structure.

[0024] Preferably, for step S5, the upper part of the semi-annular combined structure includes two welding processes, one on the inner side and one on the outer side, with the all-position welding torch posture gradually transitioning from vertical welding to horizontal welding each time.

[0025] Preferably, the welding process parameters are: laser power 2500W-4500W, welding speed 2m / min, defocusing amount 0mm, and gas flow rate 20L / min.

[0026] Preferably, in step S5, the upper half of the circumferential weld bead is removed, and the upper half of the circumferential weld bead is welded.

[0027] After welding is completed, the upper half of the circumferential weld seam is removed and welded again until the upper half of all circumferential weld seams is welded.

[0028] Preferably, in step S9, the connecting ring at the connection point of the two semi-annular combined structures is provided with a through hole that allows bolts to pass through.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] 1. This invention reduces clamping requirements and simplifies the clamping process by dividing the ring-shaped assembly structure into two semi-ring-shaped assembly structures, especially reducing the difficulty of flipping and other actions during product welding. A special locking bottom joint is prepared on the connecting ring, which can achieve self-locking docking assembly without the assistance of tooling. At the same time, it eliminates the need for gas protection on the back of the weld. The locking bottom stop can also improve the reliability of welding penetration.

[0031] 2. By employing a closed-encapsulation method and injecting high-purity argon gas, this invention can create an internal inert gas atmosphere, effectively preventing oxidation of the back side of the weld during the welding process.

[0032] 3. This invention decomposes the circumferential seam into four weld seams connected end to end. The welding posture of the four weld seams is all changed from vertical welding to horizontal welding position, with a span of about 90°, which greatly reduces the process and repositioning difficulty of the all-position welding process and improves the stability of the welding process. Attached Figure Description

[0033] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0034] Figure 1 This is a schematic diagram illustrating the overall structure of the welding method of this invention.

[0035] Figure 2 This is a top view of the overall structure of the ring-shaped composite structure, which is the main feature of this invention.

[0036] Figure 3 This is a schematic diagram illustrating the main locking bottom connection structure of the present invention;

[0037] Figure 4 This is a schematic diagram illustrating the welding principle in step S5 of the present invention.

[0038] The figure shows: 1. Semi-circular combined structure; 2. Connecting ring; 3. Bend; 4. Through hole. Detailed Implementation

[0039] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several changes and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0040] Example

[0041] like Figure 1 As shown, according to the present invention, a laser welding method for a ring-shaped composite structure circumferential seam includes the following steps:

[0042] Step S1: Connect multiple connecting rings 11 and multiple bends 12 end to end in sequence to form a semi-circular combined structure 1. Step S1 includes the following sub-steps: Step S1.1: Create a locking bottom stop on the connecting ring 11. Insert the end of the bend 12 into the locking bottom stop and lock it to the connecting ring 11. Connect multiple connecting rings 11 and multiple bends 12 end to end in sequence to form a semi-circular combined structure 1. The depth of the locking bottom stop is 0.5mm and the width is 2mm. Step S1.2: Use a fitting fixture to lay the semi-circular combined structure 1 flat and clamp it. The accuracy of connecting multiple connecting rings 11 and multiple bends 12 end to end in sequence is: the gap does not exceed 0.2mm, the misalignment does not exceed 0.2mm, and the overall flatness does not exceed 0.5mm.

[0043] Step S2: Spot weld multiple weld points on any one circumferential weld seam. The number of weld points shall not be less than 6, and the length of each weld point shall not be less than 10mm. Spot welding process parameters: laser power 1500W-2500W, pulse frequency 30Hz, duty cycle 50%, welding speed 2m / min, defocusing amount 0mm, gas flow rate 20L / min.

[0044] Step S3: Cover the outer surface of any circumferential weld to prevent air leakage. The covering material should be airtight, such as plastic film or electrical tape.

[0045] Step S4: After injecting protective gas into one port of the semi-annular combined structure 1 to purge the air inside the semi-annular combined structure 1, the port of the semi-annular combined structure 1 is sealed. The protective gas includes high-purity argon, the flow rate of which does not exceed 20 L / min, and the filling volume is more than twice the volume of the semi-annular combined structure 1.

[0046] Step S5: Using all-position welding, sequentially weld the upper half of multiple circumferential welds approximately 180°. The upper half of the semi-circular composite structure 1 includes two welding operations: one on the inner side and one on the outer side. Each time, the all-position welding torch posture gradually transitions from vertical to horizontal welding. Welding process parameters: laser power 2500W-4500W, welding speed 2m / min, defocusing amount 0mm, gas flow rate 20L / min. Remove the upper half of the circumferential weld cover and weld the upper half of the circumferential weld. After welding, remove the upper half of the next circumferential weld cover and perform the welding operation until the upper half of all circumferential welds is welded.

[0047] Step S6: Flip over the semi-circular assembly structure 1, which has been partially welded.

[0048] Step S7: Use all-position welding process to weld the other half of multiple circumferential welds in sequence.

[0049] Step S8: Repeat steps S1-S7 to complete the welding of the other semi-circular combined structure 1.

[0050] Step S9: Connect the two welded semi-annular composite structures 1 with bolts and nuts to form a ring composite structure. The connecting ring 11 at the connection of the two semi-annular composite structures 1 is provided with a through hole 13 that allows the bolt to pass through.

[0051] Dividing the annular assembly structure into two semi-annular assembly structures 1 reduces clamping requirements and simplifies the clamping process, especially reducing the difficulty of flipping and other actions during product welding. A special locking bottom joint is fabricated on the connecting ring 11, enabling self-locking butt joint assembly without tooling assistance. This eliminates the need for gas protection on the back of the weld, and the locking bottom stop also improves the reliability of weld penetration. Using a closed encapsulation and injecting high-purity argon gas creates an internal inert gas atmosphere, effectively preventing oxidation on the back of the weld during welding. The circumferential seam is decomposed into four welds connected end-to-end. All four welds are shifted from a vertical to a horizontal position, spanning approximately 90°, significantly reducing the process and shifting difficulty of all-position welding and improving the stability of the welding process.

[0052] Preferred example

[0053] Based on an embodiment, according to the present invention, a method for laser welding of circumferential seams in a ring-shaped composite structure is provided. A ring-shaped storage tank has a maximum outer diameter of Ф3000mm, a minimum inner diameter of Ф2000mm, and a cross-sectional circumference of Ф500mm. For ease of manufacturing, the ring-shaped storage tank is divided into two symmetrical semi-circular composite structures, which are manufactured separately and then screwed together. Each semi-circular ring structure is composed of five connecting rings 11 and four bent pipes 12 welded together via eight circumferential weld seams. The bent pipes 12 are 2mm thick and made of TC4 titanium alloy. A schematic diagram of the sixteen weld seam positions of the entire ring-shaped storage tank is shown below. Figure 1 As shown.

[0054] The welding method for the annular storage tank is as follows: The annular assembly structure is divided into two semi-annular assembly structures 1, which are screwed together. Each semi-annular assembly structure 1 includes five connecting rings 11 and four bent pipes 12, connected end to end. There are eight annular welds at the connection point, and the connection is achieved by laser welding. The steps include:

[0055] S1. The joint design involves assembly and clamping. A locking stop is made on the connecting ring 11, locking the bottom of the bend 12. At the corner of the locking joint on the connecting ring 11, a groove 0.5mm deep and 2mm wide is machined. Using a fitting fixture, the five connecting rings 11 and four bends 12 are connected end-to-end and clamped flat. The accuracy requirements for the end-to-end connection are: gap not exceeding 0.2mm, misalignment not exceeding 0.2mm, and overall flatness not exceeding 0.5mm.

[0056] S2. Uniform spot welding: Twelve spot welds are made on eight circumferential welds, each with a length of 20mm. Spot welding process parameters: laser power 2000W, pulse frequency 30Hz, duty cycle 50%, welding speed 2m / min, defocusing amount 0mm, gas flow rate 20L / min.

[0057] S3. Sealing and covering: The outer surface of the eight circumferential welds is covered with electrical tape to prevent air leakage.

[0058] S4. Inject argon gas. Inject high-purity argon gas through the lower inlet of the semi-annular tank, keeping the upper outlet open. After purging the internal air, plug the upper outlet. The argon gas flow rate is 10 L / min, and the filling volume reaches twice the volume of the semi-annular tank. Then stop filling and plug the upper outlet.

[0059] S5. Formal welding of the upper half: Weld the upper half of the eight weld seams approximately 180° using all-position welding. Remove the upper half of the circumferential weld seam cover and weld the upper half of the circumferential weld seam; weld the upper half approximately 180° in two stages, one on the inside and one on the outside, gradually transitioning the all-position welding torch posture from vertical to horizontal welding for each stage, welding approximately 90° per stage. Welding process parameters: laser power 2500W-4500W, welding speed 2m / min, defocusing amount 0mm, gas flow rate 20L / min. After welding is completed, remove the upper half of the next weld seam cover, and so on to complete the welding of the upper half of all eight weld seams.

[0060] S6. Overall flip: The semi-circular assembly structure that has been partially welded is flipped over and placed flat and clamped using the tire-mounting fixture.

[0061] S7. Following the method in S5, complete the welding of the remaining weld seams to form a semi-circular composite structure.

[0062] S8. Weld the other semi-circular assembly structure according to S1-S7.

[0063] S9. Screw the two semi-circular combined structures together to form a circular combined structure.

[0064] In the description of this application, it should be understood that the terms "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0065] Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. Unless otherwise specified, the embodiments and features described in this application can be arbitrarily combined with each other.

Claims

1. A method for laser welding a circumferential seam of a ring-shaped composite structure, characterized in that, The welding method includes the following steps: Step S1: Connect multiple connecting rings (11) and multiple bends (12) end to end in sequence to form a semi-circular combined structure (1). Step S2: Spot weld multiple weld points on any one circumferential weld seam; Step S3: Cover the outer surface of any circumferential weld to prevent air leakage; Step S4: After injecting protective gas into one port of the semi-annular combined structure (1) to vent the air inside the semi-annular combined structure (1), the port of the semi-annular combined structure (1) is closed. Step S5: Use all-position welding process to weld the upper half of multiple circumferential welds in sequence; Step S6: Flip over the half-welded semi-circular assembly structure (1) as a whole; Step S7: Use all-position welding process to weld the other half of multiple circumferential welds in sequence; Step S8: Repeat steps S1-S7 to complete the welding of the other semi-circular combined structure (1); Step S9: Connect the two welded semi-circular combined structures (1) with bolts and nuts to form a ring combined structure; Step S1 includes the following sub-steps: Step S1.1: Make a bottom locking stop on the connecting ring (11), insert the end of the bend (12) into the bottom locking stop and lock it to the bottom of the connecting ring (11), and connect multiple connecting rings (11) and multiple bends (12) end to end in sequence to form a semi-circular combination structure (1). Step S1.2: Use a tire-mounting fixture to lay the semi-circular assembly structure (1) flat and clamp it. For step S5, the upper part of the semi-circular combined structure (1) includes two welding processes: inner and outer. The posture of the all-position welding gun gradually transitions from vertical welding to flat welding each time. For step S5, remove the upper half of the circumferential weld cover and weld the upper half of the circumferential weld. After welding is completed, the upper half of the wrapping of the next circumferential weld is removed and welded, until the upper half of all circumferential welds is welded. The semi-ring composite structure (1) is made of TC4 titanium alloy material; Welding process parameters: laser power 2500W-4500W, welding speed 2m / min, defocusing amount 0mm, gas flow rate 20L / min.

2. The laser welding method for the circumferential seam of the annular composite structure as described in claim 1, characterized in that, For step S1.1, the depth of the bottom stop is 0.5mm and the width is 2mm.

3. The laser welding method for the circumferential seam of the annular composite structure as described in claim 1, characterized in that, For step S1, the accuracy of sequentially connecting multiple connecting rings (11) and multiple bends (12) end to end is: The gap should not exceed 0.2mm, the misalignment should not exceed 0.2mm, and the overall flatness should not exceed 0.5mm.

4. The laser welding method for the circumferential seam of the annular composite structure as described in claim 1, characterized in that, For step S3, the covering material is an airtight material.

5. The laser welding method for the circumferential seam of the annular composite structure as described in claim 1, characterized in that, For step S4, the protective gas includes high-purity argon, the flow rate of which does not exceed 20 L / min, and the gas filling volume is more than twice the volume of the semi-annular combined structure (1).

6. The laser welding method for the circumferential seam of the annular composite structure as described in claim 1, characterized in that, For step S9, the connecting ring (11) at the connection of the two semi-annular combined structures (1) is provided with a through hole (13) that allows the bolt to pass through.

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