Large expansion amount pipe forming device and forming method

Abstract

The application discloses a large-expansion-amount pipe forming device and a forming method, and relates to the technical field of metal forming manufacturing. The large-expansion-amount pipe forming device is a fluid-mold combined forming device. The sealing punch with a fluid channel is used in cooperation with a forming mold, so that the combination of the internal high-pressure bulging and medium filling and pressing of a pipe blank is realized, the large-expansion-amount pipe can be integrally formed under the premise of ensuring the uniformity of the wall thickness, the device has the advantages of high production efficiency and low cost, and is suitable for batch production. The large-expansion-amount pipe forming method realizes the integral forming of the large-expansion-amount pipe under the premise of ensuring the uniformity of the wall thickness. Through the reasonable design of the reducing process and the increasing process, the pipe expansion rate of the internal high-pressure process can be further reduced, the internal forming pressure is further reduced, energy saving and emission reduction are realized.

Description

Technical Field

[0001] This invention relates to the field of metal forming and manufacturing technology, and in particular to a forming apparatus and method for forming large expansion tubes. Background Technology

[0002] Current technology indicates that it is difficult to achieve integral forming of pipe fittings with large expansion capacity. Due to the large expansion capacity and complex structure of local surfaces of the fittings, the industry often adopts a technique of forming local surfaces separately and then welding them to the main body of the fitting to obtain large expansion capacity pipe fittings in batches. Because the fittings have weld seams, microcracks or even cracking failures can easily occur at the weld seams during service due to stress concentration. At the same time, since the local surfaces are formed separately, the thermal stress generated during welding can cause deformation in the weld area, reducing the dimensional accuracy of the fittings.

[0003] Internal high-pressure forming is an advanced technology for manufacturing integral hollow tubular structures, offering significant advantages in both structural and material lightweighting. However, internal high-pressure forming of metal tubular components has a limiting expansion rate; for metal tubular components with an expansion rate exceeding 200%, direct forming using internal high-pressure forming technology is not feasible. Furthermore, during internal high-pressure forming, the tubular blank undergoes circumferential tensile deformation, while the tube wall thins along its thickness direction. For profiles with localized characteristics, the wall thickness distribution is uneven, thus affecting the quality of the tubular component. Summary of the Invention

[0004] The purpose of this invention is to provide a forming device and method for large expansion tubes, which can achieve the overall forming of large expansion tubes while ensuring uniform wall thickness. This solves the problem that existing large expansion tubes with an expansion rate of over 200% cannot be directly formed by traditional internal high-pressure forming technology, and that traditional internal high-pressure forming technology easily leads to uneven wall thickness of the expansion surface of the tube.

[0005] To achieve the above objectives, the present invention provides the following solution: The present invention provides a large expansion tube forming device, comprising: a forming mold, the forming mold including an upper mold and a lower mold, wherein after the upper mold and the lower mold are closed, a forming cavity adapted to the outer contour of the target tube is formed between them; a sealing punch, wherein a fluid flow channel is provided in the sealing punch, the sealing punch is used to seal and connect with the end of the tube blank, and a pressure medium is introduced into the tube blank through the fluid flow channel, so that the tube blank forms the target tube under the dual action of the forming mold and the pressure medium; the sealing punch is provided on both sides of the forming mold, respectively used to seal and connect with both ends of the tube blank; and a punch adjusting mechanism, the punch adjusting mechanism being connected to the sealing punch, used to drive the sealing punch to move closer to or away from the tube blank in the forming cavity.

[0006] Optionally, the sealing punch includes an inner sealing punch and an outer sealing punch sleeved outside the inner sealing punch. The outer sealing punch is used to adapt to the outer contour of the tube blank end, and the inner sealing punch is used to seal the end inserted into the tube blank. The fluid flow channel is opened inside the inner sealing punch.

[0007] Optionally, the outer sealing punch is clearance-fitted with the outer contour of the tube blank end, and the inner sealing punch is interference-fitted with the inner contour of the tube blank end.

[0008] Optionally, the pressure medium is a liquid pressure medium or a gas pressure medium.

[0009] Optionally, the punch adjustment mechanism is a three-dimensional adjustment platform.

[0010] Optionally, the punch adjustment mechanism includes an axial adjustment unit, which includes: a first cylinder seat disposed on the side of the forming mold; an axial drive cylinder disposed on the first cylinder seat, the piston rod of the axial drive cylinder being coaxial with the circular cross-section of the tube blank, and a spring push plate disposed at the end of the piston rod of the axial drive cylinder; a spring, one end of which is connected to the spring push plate, and the other end of which is connected to the sealing punch; the axial drive cylinder is used to drive the sealing punch closer to or away from the tube blank in the forming cavity, and each sealing punch is connected to one of the axial adjustment units.

[0011] Optionally, the punch adjustment mechanism further includes a guide rail and a floating adjustment unit. The guide rail is horizontally disposed on the side of the forming mold, and a slider is slidably mounted on the guide rail. The floating adjustment unit includes: a second cylinder seat disposed on the slider; a floating drive cylinder disposed on the second cylinder seat and vertically disposed, with the first cylinder seat disposed at the top of the piston rod of the floating drive cylinder; the bottom of any of the axial adjustment units is provided with the floating adjustment unit and the guide rail.

[0012] This invention also proposes a method for forming large expansion tubes, implemented using any of the large expansion tube forming devices described above, comprising the following steps: S1, calculating the expansion rate of the target tube based on the maximum and minimum equivalent diameters of the target tube, and determining the tube blank diameter in conjunction with the mechanical properties of the tube blank material; S2, pre-treating the tube blank according to the shape profile of the target tube to obtain a pre-formed tube; S3, placing the pre-formed tube in the forming cavity of the forming mold, and sealing both ends of the pre-formed tube using the sealing punch, and introducing a pressure medium into the pre-formed tube through the fluid flow channel in the sealing punch, so that the pre-formed tube forms the target tube under the dual action of the forming mold and the pressure medium; S4, removing the formed target tube.

[0013] Optionally, in step S1, the maximum and minimum cross-sectional perimeters of the target pipe fitting are first obtained, and then the equivalent diameter of the maximum cross-section and the equivalent diameter of the minimum cross-section are calculated based on the corresponding cross-sectional perimeters.

[0014] Optionally, step S2 includes: step S1, in the tube blank, for the portion of the target tube section with an equivalent diameter smaller than the diameter of the tube blank, a diameter reduction process is performed, and for the portion of the target tube section with an equivalent diameter larger than the diameter of the tube blank, a diameter increase process is performed, to obtain a primary preformed tube; step S2, according to the shape profile of the target tube, the diameter increase portion of the primary preformed tube is preformed to obtain the preformed tube.

[0015] Optionally, the primary preformed tube and the preformed tube are subjected to heat treatment after forming.

[0016] The present invention achieves the following technical effects compared to the prior art:

[0017] The large expansion tube forming device proposed in this invention is specifically a fluid-mold composite forming device. By using a sealing punch with a fluid flow channel in conjunction with a forming mold, it achieves the combination of high-pressure expansion forming inside the tube blank and medium filling and pressing, enabling the large expansion tube to be integrally formed while ensuring uniform wall thickness. It has the advantages of high production efficiency and low cost, and is suitable for mass production.

[0018] The large expansion tube forming method proposed in this invention achieves the overall forming of large expansion tubes while ensuring uniform wall thickness. Through the rational design of the diameter reduction and diameter increase processes, the expansion rate of the tubes in the internal high pressure process can be further reduced, thereby reducing the forming internal pressure and achieving energy saving and emission reduction. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the structure of the large expansion tube forming device disclosed in the embodiment of the present invention.

[0021] Figure 2 for Figure 1 An enlarged structural schematic diagram of the sealing punch at point A in the disclosed large expansion tube forming device.

[0022] Figure 3 This is a schematic diagram of the tube blank filling medium state disclosed in the embodiments of the present invention.

[0023] Figure 4 This is a schematic diagram of the tube blank filling and pressing process disclosed in the embodiments of the present invention.

[0024] Figure 5 This is a schematic diagram of the overall internal high-pressure forming of the tube blank as disclosed in the embodiment of the present invention.

[0025] The attached figures are labeled as follows: 100, large expansion tube forming device; 1, upper mold; 2, lower mold; 3, sealing punch; 31, inner sealing punch; 32, outer sealing punch; 33, fluid flow channel; 4, punch adjustment mechanism; 41, axial drive cylinder; 42, spring push plate; 43, spring; 44, guide rail; 45, floating drive cylinder; 5, tube blank; 6, pressure medium; 7, upper mold frame; 8, lower mold frame. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] One of the objectives of this invention is to provide a large expansion tube forming device that can achieve the overall forming of large expansion tubes while ensuring uniform wall thickness. This solves the problem that existing large expansion tubes with an expansion rate exceeding 200% cannot be directly formed using traditional internal high-pressure forming technology, and that traditional internal high-pressure forming technology easily leads to uneven wall thickness of the tube expansion surface.

[0028] Another object of the present invention is to provide a method for forming large expansion tubes based on the above-mentioned large expansion tube forming apparatus.

[0029] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0030] Example 1

[0031] like Figures 1-5 As shown, this embodiment provides a large expansion tube forming device 100, which mainly includes a forming mold, a sealing punch 3, and a punch adjustment mechanism. The forming mold includes an upper mold 1 and a lower mold 2. After the upper mold 1 and the lower mold 2 are closed, a forming cavity adapted to the outer contour of the target tube is formed between them. A fluid flow channel 33 is provided in the sealing punch 3. The sealing punch 3 is used to seal the end of the tube blank 5 and to introduce a pressure medium 6 into the tube blank 5 through the fluid flow channel 33 so that the tube blank 5 forms the target tube under the dual action of the forming mold and the pressure medium 6. Sealing punches 3 are provided on both sides of the forming mold, respectively for sealing the two ends of the tube blank 5. The punch adjustment mechanism is connected to the sealing punch 3 and is used to drive the sealing punch 3 to move closer to or away from the tube blank 5 in the forming cavity.

[0032] In this embodiment, as Figure 2 As shown, the sealing punch 3 is a composite structure with internal and external components. Specifically, it includes an inner sealing punch 31 and an outer sealing punch 32 sleeved around the inner sealing punch 31. The inner sealing punch 31 is cylindrical, and the outer sealing punch 32 is sleeve-shaped. The inner sealing punch 31 is embedded inside the outer sealing punch 32, and a gap is left between the inner sealing punch 31 and the outer sealing punch 32 for the insertion of the tube blank 5 sidewall. The head of the outer sealing punch 32 is used to fit around the outer periphery of the end of the tube blank 5, and the inner contour of the head of the outer sealing punch 32 is adapted to the outer contour of the end of the tube blank 5, for example, through a clearance fit. The inner sealing punch 31 is used to seal the end inserted into the tube blank 5. A seal can be achieved between the outer wall of the inner sealing punch 31 and the inner wall of the tube blank 5 through an interference fit, or by providing a sealing ring or other sealing element on the outer wall of the inner sealing punch 31, thus achieving a seal between the inner sealing punch 31 and the tube blank 5 after insertion, preventing leakage of the pressure medium 6 filled into the tube blank 5. The fluid flow channel 33 is formed inside the inner sealing punch 31, and the first end of the fluid flow channel 33 penetrates the axial front end of the inner sealing punch 31 (the end near the tube blank 5). The second end of the fluid flow channel 33 can extend axially along the inner sealing punch 31 and penetrate the axial rear end of the inner sealing punch 31, or it can be like... Figure 2As shown, the fluid flow channel 33 is arranged sequentially through the side walls of the inner sealing punch 31 and the outer sealing punch 32. The second end of the fluid flow channel 33 is mainly used for connecting an external medium supply device, and its specific location depends on actual needs. It is particularly important to emphasize that the connection between the fluid flow channel 33 and the medium supply device will not interfere with the adjustment mechanism of the sealing punch 3.

[0033] In this embodiment, the available pressure medium 6 can be a liquid pressure medium or a gas pressure medium. Generally, a liquid pressure medium is preferred.

[0034] In this embodiment, the aforementioned punch adjustment mechanism is mainly used to adjust the orientation of the sealing punch 3 relative to the tube blank 5, so as to ensure that the inner sealing punch 31 of the sealing punch 3 is coaxial with the tube blank 5 and accurately inserted. The punch adjustment mechanism can be an existing XYZ three-dimensional electric adjustment platform, or a hydraulic cylinder group or a pneumatic cylinder group can be set as needed to meet the multi-directional position adjustment of the sealing punch 3. As a preferred solution, the punch adjustment mechanism in this embodiment adopts a hydraulic cylinder group structure, which specifically includes an axial adjustment unit, a guide rail 44 and a floating adjustment unit. The axial adjustment unit includes a first hydraulic cylinder seat and an axial drive hydraulic cylinder 41. The axial drive hydraulic cylinder 41 is set on the first hydraulic cylinder seat. A spring push plate 42 is provided at the end of the piston rod of the axial drive hydraulic cylinder 42. The spring push plate 42 is connected to the sealing punch 3 through a spring 43. The axial drive hydraulic cylinder 41 is mainly used to drive the sealing punch 3 to move closer to or away from the tube blank 5 in the forming cavity, thereby realizing the sealing insertion or mutual separation of the inner sealing punch 31 and the tube blank 5 in the sealing punch 3. The aforementioned guide rail 44 is horizontally positioned on the side of the forming mold, extending from front to back and perpendicular to the extension / retraction direction of the axial drive cylinder 41. A slider (not shown in the figure) is slidably mounted on the guide rail 44. The slider can be driven to move along the guide rail 44 by a slide cylinder, electric slide, or other structure, or it can be manually adjusted. The floating adjustment unit includes a second cylinder seat and a floating drive cylinder 45. The second cylinder seat is mounted on the aforementioned slider to achieve forward and backward adjustment of the floating adjustment unit. The floating drive cylinder 45 is mounted on the second cylinder seat and is vertically positioned. The first cylinder seat of the axial adjustment unit is mounted on the top of the piston rod of the floating drive cylinder 45 to achieve lifting and lowering adjustment of the axial drive cylinder 41. The aforementioned floating drive cylinder 45, guide rail 44, and slider cooperate with each other to precisely adjust the orientation of the axial drive cylinder 41 relative to the tube blank 5, thereby ensuring that the piston rod of the axial drive cylinder 41 is coaxial with the circular cross-section of the tube blank 5. Each sealing punch 3 is connected to a punch adjustment mechanism.

[0035] In this embodiment, to avoid interference between the use of the sealing punch 3 and the use of the forming mold, a groove for accommodating the sealing punch 3 is provided on the side walls of the upper mold 1 and the lower mold 2 of the forming mold. During the process of the axial drive cylinder 41 driving the sealing punch 3 closer to or away from the tube blank 5, the outer wall of the outer sealing punch 32 of the sealing punch 3 is in sliding engagement with the groove. The end of the tube blank 5 located in the forming cavity of the forming mold extends into the groove, ensuring that the sealing punch 3 can achieve a sealing insertion with the end of the tube blank 5 within the stroke range of the groove. Furthermore, to improve the pressing effect of the axial drive cylinder 41 on the sealing punch 3, the spring push plate 42 can be in sliding engagement with the tail of the sleeve-structured outer sealing punch 32, such as... Figure 1 , Figure 4 and Figure 5 As shown, the spring push plate 42 slides in cooperation with the inner wall of the outer sealing punch 32. Under the driving action of the axial drive cylinder 41, when the head of the outer sealing punch 32 in the sealing punch 3 is abutted against the bottom of the groove and can no longer slide, the piston rod of the axial drive cylinder 41 can continue to push the spring push plate 42 to slide in the outer sealing punch 32 to compress the spring 43. During the forming process of the tube blank 5, the sealing punch 3 maintains the sealing state of the end of the tube blank 5 under the dual action of the axial drive cylinder 41 and the spring 43, which is beneficial to maintain the pressure inside the tube blank 5 during the forming process.

[0036] In use, the tube blank 5 is first placed into the cavity of the lower mold 2 of the forming mold. Then, the positions of the corresponding sealing punches 3 are adjusted by the punch adjustment mechanisms 4 on both sides of the mold, so that both ends of the tube blank 5 are sealed and inserted with the corresponding sealing punches 3. Afterwards, a liquid pressure medium is injected through a high-flow pipeline, and the tube blank 5 completes pressurization and staged sealing under the action of the sealing punches 3. When the internal pressure of the tube blank 5 reaches the preset value, the upper and lower molds are closed. Under the combined action of the forming mold and the internal liquid pressure medium, the tube blank 5 completes the internal high-pressure expansion and hydraulic pressing processes in sequence. After shaping, the finished tube can be removed. This solution solves the technical problem of achieving mass production of large-expansion tube fittings through integral forming in industry, while ensuring the advantages of low cost, high precision, and stable quality. The following is a detailed description of the large-expansion tube fitting forming method using the above-mentioned large-expansion tube fitting forming device 100. This large-expansion tube fitting forming method includes the following steps:

[0037] Step S1: Calculate the expansion rate of the target pipe fitting based on its maximum and minimum equivalent cross-sectional diameters. Combine this with the mechanical properties of the pipe blank material to determine the diameter of the pipe blank 5. First, obtain the maximum and minimum cross-sectional perimeters of the target pipe fitting. Then, calculate the maximum and minimum equivalent cross-sectional diameters based on these perimeters. The quotient of the maximum and minimum equivalent cross-sectional diameters, expressed as a percentage, represents the expansion rate of the target pipe fitting. The maximum expansion rate and maximum shrinkage rate of the pipe blank along the circumferential direction are obtained from the mechanical properties of the pipe blank material. Combined with the expansion rate of the target pipe fitting, the diameter of the pipe blank is determined so that the sum of the expansion rates during the diameter increase, pre-forming, and internal high-pressure forming processes is less than the maximum expansion rate of the pipe blank, and the shrinkage rate during the diameter reduction process is less than the maximum shrinkage rate of the pipe blank. The diameter increase and pre-forming processes are optional.

[0038] Step S2: First, in the tube blank, for the part of the target tube section with an equivalent diameter smaller than the tube blank diameter, a diameter reduction process is performed; for the part of the target tube section with an equivalent diameter larger than the tube blank diameter, a diameter increase process is performed to obtain a primary preformed tube. Then, according to the shape profile of the target tube, the diameter increase portion of the primary preformed tube is preformed to obtain a preformed tube.

[0039] The target pipe fitting is a large-expansion metal pipe fitting with an expansion rate exceeding 200%, and its perimeters along the axial direction are unequal, i.e., the equivalent diameters of each section are unequal. For the portion of the target pipe fitting whose equivalent diameter is smaller than the diameter of the pipe blank, a diameter reduction process is formulated based on the value of the equivalent diameter. That is, if there are n equivalent diameters smaller than the diameter of the pipe blank, then the diameter reduction process consists of n passes, and n diameter reduction dies are used. After the diameter reduction process, the mechanical properties of the pipe blank change, and its ability to undergo uniform plastic deformation decreases. Based on the circumferential shrinkage rate of the pipe blank during the diameter reduction process, the degree of plastic deformation of the pipe blank in this process is evaluated, and then it is determined whether heat treatment is required. The above-mentioned diameter reduction process is an existing process, and its details will not be elaborated further. After the process, heat treatment is selectively applied to the reduced-diameter pipe fitting based on the changes in the mechanical properties of the pipe blank.

[0040] Correspondingly, for the portion of the target pipe fitting whose equivalent diameter is larger than the pipe blank diameter, a diameter-increasing process scheme is formulated based on the value of the equivalent diameter. This involves the reduced-diameter pipe fitting undergoing hydraulic bulging in the diameter-increasing mold. After the material adheres to the mold, the resulting increased-diameter pipe fitting is removed. Based on the changes in the mechanical properties of the pipe blank after the diameter-increasing process, the increased-diameter pipe fitting can be selectively heat-treated.

[0041] Considering that the specific shape of the target pipe fitting is difficult to achieve in a single high-pressure forming process, the diameter-enlarging pipe fitting can be selectively pre-formed. This involves placing the diameter-enlarging pipe fitting in a pre-forming mold and hydraulically expanding it. After the material adheres to the mold, it is removed to obtain the final pre-formed pipe fitting. Correspondingly, based on the changes in the mechanical properties of the pre-formed pipe blank, the pre-formed pipe fitting can be selectively heat-treated.

[0042] Step S3: Place the preformed tube into the cavity of the lower mold 2. Adjust the sealing punch 3 through the punch adjustment mechanism 4 so that the axial ends of the preformed tube are sealed by the corresponding sealing punch 3. Then, inject liquid of a certain pressure into the preformed tube through the fluid flow channel 33 to pressurize the inside of the preformed tube. After the upper mold 1 and the lower mold 2 are closed, continue to inject liquid into the preformed tube so that the preformed tube expands and deforms under the action of liquid pressure and sticks to the inner wall of the forming cavity, and finally obtains a large expansion integral tube.

[0043] Step S4: Remove the formed target pipe.

[0044] As mentioned above, traditional processes struggle to achieve integral forming of pipe fittings with expansion rates exceeding 200%. This technical solution combines internal high-pressure bulging with hydraulic pressing to achieve integral forming of large-expansion pipe fittings, while maintaining advantages such as low cost, high precision, and stable quality, making it suitable for mass production of large-expansion pipe fittings. In the specific forming process, the reasonable design of the diameter reduction and diameter increase processes further reduces the expansion rate of the pipe fitting during the internal high-pressure process, thereby reducing the forming internal pressure and achieving energy conservation and emission reduction. Since both the diameter reduction and diameter increase processes involve circular cross-section bulging, the resulting pipe fitting wall thickness is uniformly distributed along the circumferential direction. Due to the reasonable cross-sectional perimeter design in the preceding steps, the cross-sectional perimeter of the pipe fitting remains essentially unchanged during the internal high-pressure process. The cross-section only changes shape when it comes into contact with the mold, while the wall thickness remains essentially unchanged. Therefore, the resulting large-expansion integral pipe fitting has a uniform wall thickness distribution across all cross-sections.

[0045] It should be noted that, for those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and that the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention, and no reference numerals in the claims should be construed as limiting the scope of the claims.

[0046] Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this invention. Furthermore, those skilled in the art will recognize that, based on the ideas of this invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this invention.

Claims

1. A large expansion capacity tubular fitting forming device, characterized in that, include: A forming mold, comprising an upper mold and a lower mold, wherein after the upper mold and the lower mold are closed, a forming cavity is formed between them that is adapted to the outer contour of the target pipe; the side walls of the upper mold and the lower mold are provided with sliding grooves; A sealing punch is provided for sealing connection with the end of a tube blank. The sealing punch includes an inner sealing punch and an outer sealing punch sleeved outside the inner sealing punch. The outer sealing punch is adapted to the outer contour of the end of the tube blank. The inner sealing punch is used to seal the end inserted into the tube blank. A fluid flow channel is formed inside the inner sealing punch, and a pressure medium is introduced into the tube blank through the fluid flow channel so that the tube blank is formed into the target tube under the dual action of the forming mold and the pressure medium. The outer wall of the outer sealing punch slides with the slide groove. The end of the tube blank located in the forming cavity extends into the slide groove so that the sealing punch can be sealed and inserted into the end of the tube blank within the stroke range of the slide groove. The forming mold is provided with sealing punches on both sides for sealing connection with both ends of the tube blank, respectively. A punch adjustment mechanism is provided, connected to the sealing punch, for driving the sealing punch closer to or away from the tube blank in the forming cavity. The punch adjustment mechanism includes an axial adjustment unit, which comprises a first cylinder seat, an axial drive cylinder, and a spring. The first cylinder seat is disposed on the side of the forming mold, and the axial drive cylinder is disposed on the first cylinder seat. The piston rod of the axial drive cylinder is coaxial with the circular cross-section of the tube blank, and a spring push plate is provided at the end of the piston rod. One end of the spring is connected to the spring push plate, and the other end is connected to the sealing punch. The axial drive cylinder is used to drive the sealing punch closer to or away from the tube blank in the forming cavity. Each sealing punch is connected to one of the axial adjustment units. The spring push plate slides against the inner wall of the tail of the outer sealing punch. Under the driving action of the axial drive cylinder, when the sealing punch moves closer to or away from the tube blank in the forming cavity... When the head of the external sealing punch is abutted against the bottom of the groove and cannot continue to slide, the piston rod of the axial drive cylinder can continue to push the spring push plate to slide inside the external sealing punch to compress the spring. Under the dual action of the axial drive cylinder and the spring, the sealing punch maintains a sealing state on the end of the tube blank to maintain the pressure inside the tube blank during the forming process. The punch adjustment mechanism also includes a guide rail and a floating adjustment unit. The guide rail is horizontally arranged on the side of the forming mold, and a slider is slidably installed on the guide rail. The floating adjustment unit includes a second cylinder seat and a floating drive cylinder. The second cylinder seat is arranged on the slider, and the floating drive cylinder is arranged on the second cylinder seat, and the floating drive cylinder is arranged vertically. The first cylinder seat is arranged at the top of the piston rod of the floating drive cylinder. The bottom of any axial adjustment unit is equipped with the floating adjustment unit and the guide rail.

2. The large expansion tube forming device according to claim 1, characterized in that, The outer sealing punch is clearance-fitted with the outer contour of the tube blank end, and the inner sealing punch is interference-fitted with the inner contour of the tube blank end.

3. The large expansion tube forming device according to claim 1, characterized in that, The pressure medium is a liquid pressure medium or a gas pressure medium.

4. A method for forming large expansion tube fittings, implemented using the large expansion tube fitting forming apparatus as described in any one of claims 1 to 3, characterized in that, Including the following steps: S1. Calculate the expansion rate of the target pipe fitting based on the maximum and minimum equivalent diameters of the target pipe fitting, and determine the pipe blank diameter by combining the mechanical properties of the pipe blank material. S2. Based on the shape and contour of the target pipe fitting, pre-process the pipe blank to obtain a pre-formed pipe fitting; S3. Place the preformed tube in the forming cavity of the forming mold, and use the sealing punch to seal both ends of the preformed tube. Then, introduce a pressure medium into the preformed tube through the fluid flow channel in the sealing punch, so that the preformed tube forms the target tube under the dual action of the forming mold and the pressure medium. S4. Remove the formed target pipe fitting.

5. The method for forming large expansion tubular components according to claim 4, characterized in that, In step S1, the maximum and minimum cross-sectional perimeters of the target pipe fitting are first obtained, and then the equivalent diameter of the maximum cross-section and the equivalent diameter of the minimum cross-section are calculated based on the corresponding cross-sectional perimeters.

6. The method for forming large expansion tubular components according to claim 4 or 5, characterized in that, Step S2 includes: Step S1: In the tube blank, for the portion of the target tube section with an equivalent diameter smaller than the diameter of the tube blank, a diameter reduction process is performed; for the portion of the target tube section with an equivalent diameter larger than the diameter of the tube blank, a diameter increase process is performed to obtain a primary preformed tube. Step S2: Based on the shape and contour of the target pipe fitting, pre-form the diameter-increasing portion of the primary pre-formed pipe fitting to obtain the pre-formed pipe fitting.

7. The method for forming large expansion tubular components according to claim 6, characterized in that, After the primary preformed pipe and the preformed pipe are formed, they are subjected to heat treatment respectively.

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