Multi-wave narrow-wave pitch corrugated pipe forming method

Abstract

The invention relates to a multi-wave narrow-wave-pitch corrugated pipe forming method. The method comprises the following steps that S1, sealing clamps are installed at the two ends of a pipe blank; s2, the pipe blank provided with the sealing clamp is placed in a left mold and a right mold, and a bulge distance is reserved between the left mold and the right mold; s3, hydraulic oil is injected from a liquid through hole of the sealing clamp, and the pipe blank is subjected to bulging to form a bulge; s4, the left mold and the right mold are closed, and corrugation pressing is completed; s5, releasing the pressure, and opening the left mold and the right mold to a proper distance; s6, an insert is installed on the left mold or the right mold, and the formed corrugations are wrapped by the insert and the left mold or the right mold; and S7, the step S3 to the step S6 are repeated, and forming of all waveforms of the corrugated pipe is completed in sequence. According to the method, the forming process conditions of each waveform formed by the method are consistent, the waveform at the two ends of the corrugated pipe and the waveform at the middle part of the corrugated pipe are consistent in material supplementing amount and forming boundary conditions, and the consistency of the formed waveform height and the waveform thickness reduction amount is high.

Description

Technical Field

[0001] This invention relates to the field of high-pressure forming technology for pipes, and more specifically, to a method for forming multi-wave narrow-pitch corrugated pipes. Background Technology

[0002] The accumulator uses a metal bellows as the elastic element, with a very small wall thickness and corrugation pitch (e.g., a pipe thickness of 0.15 mm and a corrugation pitch of 2 mm). During the forming process, due to the small corrugation pitch, it is difficult for tools using mechanical forming methods to enter the narrow slit, making hydroforming a more suitable method.

[0003] Hydroforming of pipes utilizes high-pressure liquid applied to the inner wall of the pipe, forcing the material to yield and deform, while controlling the liquid pressure to ensure the outer wall of the pipe conforms to the mold, thus forming the shape. Traditional hydroforming of pipes primarily involves controlling the liquid pressure and the axial load of the pusher to achieve multi-wave, one-time forming.

[0004] For multi-wave, narrow-pitch parts, it is difficult for the axial load of the pusher to be transmitted into the deformation zone of the middle corrugation, making it extremely difficult to replenish the material in the middle corrugation. This results in inconsistent wave heights between the middle and end waveforms and significant variations in material thickness. Consequently, the middle corrugation often cracks due to severe material thinning. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a method for forming multi-wave narrow-pitch corrugated pipes, which can solve the problems of inconsistent wave height and serious material thickness variation in traditional multi-wave one-time forming.

[0006] The technical solution adopted by this invention to solve its technical problem is: a method for forming a multi-wave narrow-pitch bellows, comprising the following steps: S1. Install sealing clamps at both ends of the tube blank; S2. Place the tube blank with the sealing clamp installed inside the left and right molds, leaving a bulge distance between the left and right molds; S3. Inject hydraulic oil into the liquid passage of the sealing fixture to cause the tube blank to expand and form a bulge; S4. The left and right molds are closed to complete the pressing of the corrugations; S5. Release the pressure, and open the left and right molds to the appropriate distance; S6. Install the insert on the left or right mold, and the insert and the left or right mold cover the formed corrugations. S7. Repeat steps S3-S6 to complete the shaping of all waveforms of the bellows in sequence.

[0007] According to the above scheme, step S5 also includes: continuing to increase the liquid pressure to make the tube blank fit more closely to the left mold and the right mold, and shaping the corrugations.

[0008] According to the above scheme, both the left mold and the right mold include a split upper mold and a lower mold, which are connected by bolts.

[0009] According to the above scheme, the insert is fixed to the left mold or the right mold by positioning pins and bolts.

[0010] According to the above scheme, the sealing clamp includes a left end clamp and a right end clamp, and the left end clamp and the right end clamp are provided with an outer jaw and an inner jaw.

[0011] According to the above scheme, the outer jaw and the inner jaw have conical surfaces with the same slope. Before sealing, the inner jaw is inserted into the tube blank. The end of the tube blank is provided with a process reduction opening. The slope of the process reduction opening is consistent with the slope of the conical surfaces of the outer jaw and the inner jaw. The length of the process reduction opening is less than the length of the conical surface of the inner jaw.

[0012] According to the above scheme, the inner and outer jaws of the right-end clamp are provided with liquid passage holes.

[0013] According to the above scheme, the method for controlling the relative positions of the left and right end fixtures during the forming process is as follows: During the initial stage of bulging, the sealing clamp is positioned at the farthest point on the left and right sides of the tube blank, maintaining the maximum distance. During the mold closing stage, the distance gradually decreases as the mold closing action is performed. During the shaping stage, the clamping clamp is maintained at the position after mold closing. During the mold opening stage, the clamping clamp is maintained at the position after mold closing.

[0014] According to the above scheme, the method for controlling the relative positions of the left and right molds during the forming process is as follows: The distance between the left and right molds remains at S1 during the bulging stage, decreases to 0 during the mold closing stage, remains at 0 during the shaping stage, and opens to S2 during the mold opening stage, where S2 = 2S1.

[0015] According to the above scheme, a sealing ring is provided between the sealing fixture and the left mold and the right mold.

[0016] The multi-wave narrow-pitch bellows forming method of the present invention has the following beneficial effects: For multi-wave narrow-pitch corrugated pipes, the forming process conditions of each waveform formed by the method of the present invention are consistent. Whether it is the waveform at both ends of the corrugated pipe or the waveform in the middle part, the amount of material added and the boundary conditions of forming are consistent. The wave height and the amount of waveform thickness reduction after forming are highly consistent, and the forming quality is greatly improved. Attached Figure Description

[0017] The present invention will be further described below with reference to the accompanying drawings and embodiments. In the accompanying drawings: Figure 1 This is a schematic diagram of the apparatus used in the multi-wave narrow-pitch bellows forming method of the present invention; Figure 2 This is a schematic diagram of the mold opening state; Figure 3 This is a schematic diagram of the mold in the closed state; Figure 4 This is a schematic diagram of the hydraulic oil pressure control strategy of the present invention; Figure 5 This is a schematic diagram of the mold and pusher load control strategy of the present invention. Detailed Implementation

[0018] To provide a clearer understanding of the technical features, objectives, and effects of the present invention, specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0019] like Figure 1-3 As shown, the multi-wave narrow-pitch bellows forming method of the present invention includes the following steps: S1. Install sealing clamps at both ends of tube blank 4; S2. Place the tube blank 4 with the sealing clamp installed inside the left mold 1 and the right mold 2. Leave a bulge distance S1 between the left mold 1 and the right mold 2. This distance is determined according to the amount of material required for corrugation forming. S3. Inject hydraulic oil into the liquid passage of the sealing fixture and control the liquid pressure P1 to make the tube blank 4 expand and form a bulge. The height of the bulge is D1. The hydraulic oil pressure P1 determines the height of the bulge. S4. The left mold 1 and the right mold 2 are closed, and the hydraulic oil pressure is increased to P2. When the left mold 1 and the right mold 2 are fully closed, the tube blank 4 fits the mold cavity under the combined action of the mold and the hydraulic oil, and fills the crests and troughs of the bellows well, thus completing the pressing of the waveform. S5. Continue to increase the hydraulic oil pressure to P3, so that the tube blank 4 fits the mold cavity further, and the corrugations are shaped to further ensure the corrugation height and waveform of the corrugated tube. S6. After holding the pressure for a period of time, the hydraulic oil is depressurized, and the left mold 1 and the right mold 2 open to an appropriate distance S2 to prepare for the next waveform forming. S7. Install the insert 3 on the right mold 2. The insert 3 and the right mold 2 cover the formed corrugations. In subsequent operations, the formed corrugations will no longer deform. At this time, the left mold 1 and the insert 3 form the next corrugation forming working area. The distance between the two is S1. S8. Repeat steps S3-S7 to complete the shaping of all waveforms of the bellows in sequence.

[0020] Preferably, both the left mold 1 and the right mold 2 are designed as half molds, including a split upper mold and a lower mold, which are connected by bolts.

[0021] Preferably, the insert 3 adopts a semi-mold structure and is fixed to the right mold 2 by positioning pins and bolts.

[0022] Preferably, the sealing fixture includes a left-end fixture and a right-end fixture, both of which are provided with outer jaws 5 and inner jaws 6. Before sealing, the tube blank 4 needs to undergo a shrinkage process to ensure that the slope of the shrinkage is consistent with that of the fixture. After the sealing fixture is installed, the sealing fixture and the tube blank 4 form a whole, and even during the forming process, the two maintain an integral state.

[0023] Preferably, the outer jaw 5 and the inner jaw 6 have conical surfaces with the same slope. Before sealing, the inner jaw 6 is inserted into the tube blank 4. The end of the tube blank 4 is provided with a process reduction opening. The slope of the process reduction opening is consistent with the slope of the conical surfaces of the outer jaw 5 and the inner jaw 6. The length of the process reduction opening is less than the length of the conical surface of the inner jaw 6.

[0024] Preferably, the inner jaw 6 and outer jaw 5 of the right-end clamp are provided with fluid passage holes 7 for injecting hydraulic oil. The inner jaw 6 and outer jaw 5 of the left-end clamp are connected by bolts 9.

[0025] Preferably, a sealing ring 8 is provided between the sealing clamp and the left mold 1 and the right mold 2.

[0026] The process route involved in this invention consists of the following main steps: bulging, mold closing, shaping, and mold opening. These four steps form a work cycle, and one cycle completes one waveform. The above cycles are repeated sequentially to complete the forming of multiple waveforms.

[0027] The loading path involved in this invention includes hydraulic oil pressure control and motion control of the sealing fixture and mold. The hydraulic oil pressure control strategy is detailed in the appendix. Figure 4 The hydraulic oil pressure is controlled in four stages: bulging, mold closing, shaping, and mold opening. The pressure increases from 0 to P1 during bulging, continues to increase from P1 to P2 during mold closing, increases from P2 to P3 during shaping, and decreases from P3 to 0 during mold opening. Here, P1 is the bulging pressure, and P1 = 2hs. b / d (h - wall thickness of the bellows, s) b - The tensile strength of the material, d - the inner diameter of the bellows), P2 is the mold closing pressure, and its pressure value is recommended to be P2=1.1~1.5 P1, P3 is the shaping pressure, and its pressure value is recommended to be P3=1.5~2 P1.

[0028] Mold motion control strategies such as Figure 5(Diagram of mold fixture motion control) The mold adopts a displacement control strategy. The relative position of the mold (distance between the left and right molds) is controlled as follows during the four stages of mold expansion, mold closing, mold shaping and mold opening: S1 is maintained during the mold expansion stage, S1 is reduced to 0 during the mold closing stage, the mold closing state is maintained at 0 during the mold shaping stage, and the mold opens to S2 during the mold opening stage, where S2 = 2S1.

[0029] Sealing clamp control strategy such as Figure 5 The fixture control employs a displacement control strategy. In the four stages of bulging, mold closing, shaping, and mold opening, the relative position (distance) of the two sealing fixtures is controlled as follows: At the beginning of bulging, the sealing fixtures are positioned at the farthest point of the tube blank 4, maintaining the maximum distance. During the mold closing stage, the distance gradually decreases as the mold closes. During the shaping stage, the fixtures maintain their position after mold closing. Finally, during the mold opening stage, the fixtures maintain their position after mold closing. In short, to maintain the seal at both ends of the tube, after establishing a seal in the initial stage, the two sealing fixtures move together with both ends of the tube blank 4, with the distance decreasing only during the mold closing stage and remaining unchanged in the other stages.

[0030] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims. All of these forms are within the protection scope of the present invention.

Claims

1. A method for forming a multi-wave narrow-pitch bellows, characterized in that, Includes the following steps: S1. Install sealing clamps at both ends of the tube blank; S2. Place the tube blank with the sealing clamp installed inside the left and right molds, leaving a bulge distance between the left and right molds; S3. Inject hydraulic oil into the liquid passage of the sealing fixture to cause the tube blank to expand and form a bulge; S4. The left and right molds are closed to complete the pressing of the corrugations; S5. Release the pressure, and open the left and right molds to the appropriate distance; S6. Install the insert on the left or right mold, and the insert and the left or right mold cover the formed corrugations. S7. Repeat steps S3-S6 to complete the shaping of all waveforms of the bellows in sequence.

2. The method for forming a multi-wave narrow-pitch bellows according to claim 1, characterized in that, Step S5 also includes: continuing to increase the liquid pressure to make the tube blank fit more closely to the left and right molds, and shaping the corrugations.

3. The method for forming a multi-wave narrow-pitch bellows according to claim 1, characterized in that, Both the left and right molds consist of a separate upper mold and a lower mold, which are connected by bolts.

4. The method for forming a multi-wave narrow-pitch bellows according to claim 1, characterized in that, The insert is fixed to the left or right mold by locating pins and bolts.

5. The method for forming a multi-wave narrow-pitch bellows according to claim 1, characterized in that, The sealing clamp includes a left clamp and a right clamp, and the left clamp and the right clamp are provided with an outer jaw and an inner jaw.

6. The method for forming a multi-wave narrow-pitch bellows according to claim 5, characterized in that, The outer jaw and the inner jaw have conical surfaces with the same slope. Before sealing, the inner jaw is inserted into the tube blank. The end of the tube blank is provided with a process reduction opening. The slope of the process reduction opening is the same as the slope of the conical surfaces of the outer jaw and the inner jaw. The length of the process reduction opening is less than the length of the conical surface of the inner jaw.

7. The method for forming a multi-wave narrow-pitch bellows according to claim 5, characterized in that, The right-end clamp has liquid passage holes on its inner and outer jaws.

8. The method for forming a multi-wave narrow-pitch bellows according to claim 5, characterized in that, The method for controlling the relative positions of the left and right end fixtures during the forming process is as follows: During the initial stage of bulging, the sealing clamp is positioned at the farthest point on the left and right sides of the tube blank, maintaining the maximum distance. During the mold closing stage, the distance gradually decreases as the mold closing action is performed. During the shaping stage, the clamping clamp is maintained at the position after mold closing. During the mold opening stage, the clamping clamp is maintained at the position after mold closing.

9. The method for forming a multi-wave narrow-pitch bellows according to claim 1, characterized in that, The method for controlling the relative positions of the left and right molds during the forming process is as follows: The distance between the left and right molds remains at S1 during the bulging stage, decreases to 0 during the mold closing stage, remains at 0 during the shaping stage, and opens to S2 during the mold opening stage, where S2 = 2S1.

10. The method for forming a multi-wave narrow-pitch bellows according to claim 1, characterized in that, A sealing ring is provided between the sealing clamp and the left mold and the right mold.

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