A liquid-filled forming method for a small-radius bent pipe and a forming device thereof
By using a step-by-step controlled liquid filling molding method for bent tubes, and utilizing pre-forming and final forming molds, the problems of uneven wall thickness and thickening and wrinkling in the forming of small-radius bent tubes were solved. This method achieved a forming effect with thinner and more uniform bent tube wall thickness, meeting the application requirements of aero-engines.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- XIAN JIAYE AVIATION TECH
- Filing Date
- 2025-10-30
- Publication Date
- 2026-07-21
AI Technical Summary
Existing small-radius pipe bending forming processes suffer from problems such as excessive thinning on the outer side of the bend, excessive thickening or even wrinkling on the inner side of the bend, and excessive thinning on the inner side of the straight section at the pipe end, which affect the production stability and service life of the parts.
A step-by-step controlled liquid filling forming method for bent pipes is adopted. Through pre-forming and final forming steps, the thinning of the outer side of the bend, the thickening of the inner side of the bend, and the thinning of the inner side of the straight section of the pipe end are controlled respectively. By utilizing the design of the pre-forming mold and the final forming mold, the forming of the bent pipe with small wall thickness reduction and good wall thickness uniformity can be achieved.
Effectively control the thinning on the outer side of the bend, avoid thickening and wrinkling on the inner side of the bend, ensure good uniformity of the wall thickness of the bend, improve the overall quality of the pipe fitting, and meet the application requirements of aero-engines.
Smart Images
Figure CN121222902B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of small radius bend technology, and more specifically, it relates to a method for liquid filling and forming small radius bends. This invention also relates to a device for liquid filling and forming small radius bends. Background Technology
[0002] In the piping design of aerospace engines, to save space, reduce weight, and maintain strength, designers typically choose elbow parts with a relative bending radius r / D < 1 and a relative wall thickness t / D < 0.05, i.e., thin-walled, small-radius bends. Initially, stamping and welding were used to form these small-radius bends, but due to their numerous drawbacks, a bending-expansion composite forming process was later proposed. This process involves first using a CNC bending machine to bend a bend with an outer diameter slightly smaller than the bend's and a relative bending radius slightly larger. Then, an internal high-pressure bulging process is used to expand the pre-made bend into a small-radius bend using internal high-pressure liquid. With the continuous development of the aerospace industry, the performance requirements for aerospace engines are gradually increasing, placing new demands on the manufacturing of internal engine components. For thin-walled, small-radius bends, greater attention is paid to issues such as maximum wall thickness reduction and wall thickness uniformity, which undoubtedly places higher demands on existing forming processes. Existing bending and bulging composite forming processes offer a holistic forming approach, but the bulging stage often employs single-step forming. This results in the following problems with the formed parts: ① excessive thinning on the outer side of the bend; ② excessive thickening or even wrinkling on the inner side of the bend; ③ excessive thinning on the inner side of the straight section at the pipe end. While these problems in bent pipe parts may generally meet customer requirements, they primarily impact the stability of part manufacturing, directly increasing the scrap rate. Furthermore, the overall service life and performance of the parts will be significantly reduced.
[0003] Existing technology includes a method for forming a bent pipe, published under publication number CN111906164B. This method involves welding two semi-circular arc-shaped parts together to form a bent pipe. The welding process begins by spot welding the two semi-circular arc-shaped parts together, creating two discontinuous weld seams. These two weld seams are then continuously welded together. During continuous welding, the weld point moves along the weld seam from the outside of the bent pipe. A gas protection box is placed on the inside of the bent pipe, moving synchronously with the weld point along the weld seam, thus providing gas protection for the weld. This invention achieves continuous gas-protected welding of the weld seam during the butt welding of bent pipes, improving work efficiency and ensuring the welding quality of large-diameter bent pipes. However, this technology does not address the technical problem and solution of this application. Summary of the Invention
[0004] The technical problem to be solved by the present invention is to provide a method for liquid filling and forming small-radius bends that is simple in steps, involves a relative bending radius r / D<1 and a relative wall thickness t / D<0.05, and ensures that the wall thickness of the bend is small and the wall thickness uniformity is good after forming and processing. At the same time, it can slow down the thickening or even wrinkling on the inner side of the bend, improve the overall quality of the pipe, and meet the application requirements of aero-engines.
[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: This invention relates to a method for liquid filling and molding of small-radius bent pipes, comprising a pre-forming step and a final forming step; S1. During the preforming step, the bent intermediate tube 1 is placed into the preforming positioning cavity 3 of the preforming mold 2, positioned by the straight pipe sections 18 at both ends of the bent intermediate tube 1 and the straight pipe sections 19 at both ends of the preforming positioning cavity 3. The forming area A is the first deformation area. The distance between the first inner curved side arc-shaped constraint part 6 of the preforming positioning cavity 3 and the inner curved side 5 of the bent intermediate tube 1 is small, and the distance between the first outer curved side arc-shaped constraint part 4 and the outer curved side 7 of the bent intermediate tube 1 is large. The curved inner expansion area 15 is provided on both sides of the curved constraint part 6, and there is no expansion area outside the curved inner expansion area 15; liquid is filled into the curved intermediate tube 1 placed in the pre-forming positioning forming cavity 3. The distance between the curved inner side 5 and the first curved inner side arc-shaped constraint part 6 of the curved intermediate tube 1 is small, the amount of deformation under force is small and the thickness is small. The distance between the curved outer side 7 and the first curved outer side arc-shaped constraint part 4 is large, the amount of deformation under force is large and thinning is inevitable. The straight tube sections 18 at both ends of the curved intermediate tube are pushed into the forming area A to effectively control the thinning of the curved outer side 7.
[0006] S2. In the final forming step, the intermediate pipe 1 of the bent pipe is formed through the pre-forming step to form the intermediate bent pipe product 9 with the same shape as the pre-forming positioning cavity 3. The intermediate bent pipe product 9 is placed into the final forming positioning cavity 11 of the final forming mold 10, and positioned by the straight pipe sections 20 at both ends of the intermediate bent pipe product 9 and the straight pipe sections 21 at both ends of the final forming positioning cavity 11. The forming area B is the second deformation area. The distance between the inner side 8 of the straight section of the intermediate bent pipe product 9 and the inner side expansion area 12 of the straight section of the final forming positioning cavity 11 is large, and there is a deformation area 24 in the forming area B. The outer side 22 of the straight section of the intermediate finished product of the bent pipe 9 coincides with the outer expansion area 23 of the straight section of the final formed pipe opening of the final forming positioning cavity 11; the inner side 13 of the bent intermediate finished product 9 coincides with the second inner curved arc-shaped constraint part 16 of the final forming positioning cavity 11; the outer side 14 of the bent intermediate finished product 9 coincides with the second outer curved arc-shaped constraint part 17 of the final forming positioning cavity 11; the deformation area in the forming area B is only the deformation area 24 in the forming area B, and the straight pipe sections 20 at both ends of the intermediate finished product of the bent pipe 9 are pushed into the deformation area 24 in the forming area B to control the thinning of the inner expansion area 12 of the straight section.
[0007] S3. Liquid is filled into the interior of the intermediate finished product 9 of the bent tube in the final forming positioning cavity 11. The inner side 8 of the straight section of the intermediate finished product 9 of the bent tube is deformed by force, thereby forming the intermediate finished product of the bent tube and forming the small radius bent tube 25 of the final product.
[0008] Before the preforming step, the pipe material is first bent into a bent intermediate pipe 1; in the S1 preforming step, the straight pipe sections 18 at both ends of the bent intermediate pipe 1 are of the same diameter as the straight pipe sections 19 at both ends of the preforming positioning cavity 3; in the S2 final forming step, the straight pipe sections 20 at both ends of the bent intermediate finished product 9 are of the same diameter as the straight pipe sections 21 at both ends of the final forming positioning cavity 11.
[0009] The preforming mold 2 includes a first preforming mold assembly and a second preforming mold assembly. The first preforming mold assembly and the second preforming mold assembly are respectively provided with preforming positioning and forming cavities 3, and the two preforming mold assemblies are arranged symmetrically.
[0010] The final forming mold 10 includes a first final forming mold assembly and a second final forming mold assembly. The first final forming mold assembly and the second final forming mold assembly are respectively provided with a final forming positioning cavity 11. The two final forming mold assemblies are arranged symmetrically.
[0011] When the inner side 5 and outer side 7 of the bent intermediate pipe 1 are deformed by force, the outer side 7 is thinned by axial deformation material replenishment to avoid excessive thinning; the inner side 5 deforms and extends towards the inner side expansion zone 15; after the inner side 5 and outer side 7 of the bent intermediate pipe 1 are deformed by force, the first inner side arc-shaped constraint part 4 fits the inner side 5, and the first outer side arc-shaped constraint part 6 fits the outer side 7.
[0012] After the inner side 8 of the straight section of the intermediate finished product 9 of the bent pipe is deformed by force, the inner side 8 of the straight section of the intermediate finished product 9 of the bent pipe fits into the expansion zone 12 of the straight section of the first pipe opening, and the thinning of the inner side of the straight section of the pipe opening is controlled by the material replenishment through axial deformation.
[0013] The first curved inner arc-shaped constraint part 6 and the first curved outer arc-shaped constraint part 4 of the pre-forming positioning molding cavity 3 and the second curved inner arc-shaped constraint part 16 and the second curved outer arc-shaped constraint part 17 of the final forming positioning molding cavity 10 have the same position, size and shape. The pre-forming mold 3 and the final forming mold 10 are both made of metal.
[0014] The small radius bend product mentioned refers only to the small radius bend product area 26. The remaining small radius bend transition section 27 and small radius bend straight pipe section 28 are all supplementary parts of the process.
[0015] The present invention also relates to a small radius bend liquid filling forming device that has a simple structure, ensures small wall thickness reduction and good wall thickness uniformity of the bend, and can slow down the thickening or even wrinkling of the inner side of the bend, improve the overall quality of the pipe fitting, and meet the application requirements of aero-engines.
[0016] It includes a preforming mold 2 and a final forming mold 10. The preforming positioning cavity 3 of the preforming mold 2 includes a first inner curved arc-shaped constraint part 4 and a first outer curved arc-shaped constraint part 6. The inner curved arc-shaped constraint part 4 is provided with a recessed inner curved expansion area 15. The ends of the straight pipe sections 19 at both ends of the preforming positioning cavity 3 of the preforming mold 2 are connected to the filling pipe of the filling equipment.
[0017] The final forming mold 10 has a final forming positioning cavity 11 including a second curved inner arc-shaped constraint part 16 and a second curved outer arc-shaped constraint part 17. The final forming positioning cavity 11 has a first pipe opening straight section expansion zone 12 located on the inner side 8 of the first pipe opening straight section of the pre-forming positioning cavity 3.
[0018] The working principle and beneficial effects of the technical solution adopted in this invention are as follows: The small-radius bent pipe liquid filling forming method of the present invention requires the use of a pre-forming mold and a final forming mold during the bending forming process. Based on the plastic deformation mechanism of bent pipe bulging, the present invention adjusts the control of three aspects—thinning control on the outer side of the bend, thickening control on the inner side of the bend, and thinning control on the inner side of the straight section at the pipe opening—from the existing synchronous dynamic control of single-step forming to step-by-step control. Specifically: the first step only controls the thickening on the inner side of the bend and the thinning on the outer side of the bend; the second step only controls the thinning on the inner side of the straight section at the pipe opening and the thinning on the outer side of the bend. As mentioned above, specifically, since the first step only controls the thickening on the inner side of the bend and the thinning on the outer side of the bend, it is necessary to exclude the influence of the thinning on the inner side of the straight section at the pipe opening. Therefore, the pre-forming positioning forming cavity 3 is designed such that there is no expansion area other than the inner expansion area 15 on both sides of the arc-shaped constraint part 6 on the inner side of the first bend; only the outer and inner sides of the middle pipe of the bend deform, that is, only the bent part is formed. This profile design allows for effective control of thinning on the outer side of the bend during the pressure deformation of the intermediate tube under liquid filling. Furthermore, the inner side, due to its smaller bulging area and lower material accumulation, effectively controls thickening and prevents wrinkling. This is intermediate configuration one. After the first forming step, both the inner and outer sides of the bend are changed from being unfitted to fitting the pre-forming positioning cavity before forming to fitting the pre-forming positioning cavity of the pre-forming mold. The second step only controls the thinning of the inner side of the straight section at the tube opening and the thinning of the outer side of the bend. Therefore, it's necessary to eliminate the influence of thickening on the inner side of the bend. For this purpose, during final forming, the finished intermediate tube is placed in the final forming positioning cavity of the final forming mold. During the second forming step, since both the inner and outer sides of the bend from the first step are fitted to the mold, the bulging area is only the straight section area at the tube opening. This allows for independent control of thinning on the inner side of the straight section at the tube opening through axial material feeding, eliminating concerns about thickening or wrinkling on the inner side of the bend. This is intermediate configuration two, which then forms the finished product. The step-by-step forming method in this invention can design the most suitable intermediate configuration according to different bending parts, thereby controlling the wall thickness uniformity and wall thickness reduction rate of the bending parts and improving product quality. Attached Figure Description
[0019] The following is a brief explanation of the contents depicted in the accompanying drawings and the markings therein: Figure 1 This is a schematic diagram of the intermediate tube of the small-radius bent tube fluid filling molding according to the present invention. Figure 2 This is a schematic diagram of the structure of the preforming mold assembly of the preforming mold according to the present invention; Figure 3 This is a schematic diagram of the structure during the preforming of the intermediate tube of the bent pipe according to the present invention; Figure 4 This is a partially enlarged structural diagram of the pre-forming process of the intermediate tube of the bent pipe according to the present invention; Figure 5 This is a schematic diagram of the intermediate finished product of the bent pipe according to the present invention; Figure 6 This is a schematic diagram of the intermediate finished product and final forming mold of the bent pipe according to the present invention; Figure 7 This is a schematic diagram of the final forming process of the pipe bend described in this invention; Figure 8 This is a partially enlarged structural diagram of the final forming of the bent pipe according to the present invention; Figure 9 This is a schematic diagram of the small-radius bend described in this invention; Figure 10 This is a schematic diagram of the structure of the final product described in this invention; The labels in the attached drawings are as follows: 1. Intermediate tube of the bend; 2. Pre-forming mold; 3. Pre-forming positioning cavity; 4. First bend outer arc-shaped constraint part; 5. Inner side of the bend of the intermediate tube; 6. First bend inner arc-shaped constraint part; 7. Outer side of the bend of the intermediate tube; 8. Inner side of the straight section; 9. Finished intermediate tube; 10. Final forming mold; 11. Final forming positioning cavity; 12. Inner expansion zone of the straight section at the end of the final formed tube; 13. Inner side of the bend of the finished intermediate tube; 14. Outer side of the bend of the finished intermediate tube; 15. Inner expansion zone of the pre-forming bend. 6. Inner arc-shaped constraint part of the second bend; 17. Outer arc-shaped constraint part of the second bend; 18. Straight pipe sections at both ends of the intermediate pipe of the bend; 19. Straight pipe sections at both ends of the pre-forming positioning cavity; 20. Straight pipe sections at both ends of the finished intermediate pipe of the bend; 21. Straight pipe sections at both ends of the final forming positioning cavity; 22. Outer side of the straight section of the finished intermediate pipe of the bend; 23. Expansion zone on the outer side of the straight section of the final forming pipe opening; 24. Deformation zone in forming area B; 25. Small radius bend of the final product; 26. Small radius bend product area; 27. Transition section of the small radius bend; 28. Straight pipe section of the small radius bend. Detailed Implementation
[0020] The following description, with reference to the accompanying drawings, provides a more detailed explanation of the specific embodiments of the present invention, including the shape and structure of each component, the relative positions and connections between the parts, the functions and working principles of each part: As attached Figure 1 -Appendix Figure 10 As shown, the present invention is a method for liquid filling and forming of a small radius bent pipe, including a pre-forming step and a final forming step; S1. During the preforming step, the bent intermediate pipe 1 is placed into the preforming positioning cavity 3 of the preforming mold 2, using the straight pipe sections 18 at both ends of the bent intermediate pipe 1 and the straight pipe sections 19 at both ends of the preforming positioning cavity 3 as positioning references. The forming area A is the first deformation area, and the preforming positioning cavity is... The distance between the inner curved side arc-shaped constraint part 6 of the first bend of the cavity 3 and the inner curved side 5 of the intermediate tube 1 is small, while the distance between the outer curved side arc-shaped constraint part 4 of the first bend and the outer curved side 7 of the intermediate tube 1 is large. The inner curved side arc-shaped constraint part 6 of the pre-forming positioning cavity 3 is close to the inner curved side 5 of the intermediate tube 1, and the outer curved side arc-shaped constraint part 4 is close to the outer curved side 7 of the intermediate tube 1. Recessed inner curved expansion areas 15 are provided on both sides of the inner curved side arc-shaped constraint part 6, and the inner curved expansion area 15 is taken as... There is no expansion zone outside; liquid is filled into the interior of the bent intermediate tube 1 in the pre-forming positioning cavity 3. The distance between the inner side 5 of the bend and the arc-shaped constraint part 6 of the first bend is small, resulting in small deformation and thinning. The distance between the outer side 7 of the bend and the arc-shaped constraint part 4 of the first bend is large, resulting in large deformation and thinning. Pushing the straight tube sections 18 at both ends of the bent intermediate tube into the forming area A can effectively control the thinning of the outer side 7 of the bend. S2. In the final forming step, the bent intermediate tube 1 is formed by the pre-forming step, forming the outer... The intermediate bent tube 9, which is similar to the pre-forming positioning cavity 3, has straight pipe sections 20 at both ends of the intermediate bent tube 9 with the same diameter as the straight pipe sections 21 at both ends of the final forming positioning cavity 11. The intermediate bent tube 9 is placed in the final forming positioning cavity 11 of the final forming mold 10, and positioned by the straight pipe sections 20 at both ends of the intermediate bent tube 9 and the straight pipe sections 21 at both ends of the final forming positioning cavity 11. The forming area B is the second deformation area. The distance between the inner straight section 8 of the intermediate finished product 9 and the inner straight section expansion area 12 of the final forming positioning cavity 11 is large, resulting in a deformation area 24; the outer straight section 22 of the intermediate finished product 9 coincides with the outer expansion area 23 of the final forming pipe opening straight section of the final forming positioning cavity 11; the inner curved section 13 of the intermediate finished product 9 coincides with the second curved inner arc-shaped constraint part 16 of the final forming positioning cavity 11; the outer curved section 14 of the intermediate finished product 9 coincides with the final forming positioning cavity 11. The second curved outer arc-shaped constraint part 17 overlaps; in the forming area B, only the deformation area 24 remains in the forming area B. The straight pipe sections 20 at both ends of the intermediate finished product 9 are pushed into the deformation area 24 in the forming area B, effectively controlling the thinning of the inner expansion area 12 of the straight section; S3. Liquid is filled into the interior of the intermediate finished product 9 in the final forming positioning cavity 11, and the inner side 8 of the straight section of the intermediate finished product 9 is deformed by force, realizing the forming of the intermediate finished product and forming the small radius bent pipe 25 of the final product.The above steps address the shortcomings of existing technologies and propose improved technical solutions. When forming a bent pipe, a pre-forming mold and a final forming mold are required. The method of this invention, based on the plastic deformation mechanism of bent pipe bulging, adjusts the control of three aspects—thinning control on the outer side of the bend, thickening control on the inner side of the bend, and thinning control on the inner side of the straight section at the pipe end—from the existing synchronous dynamic control of single-step forming to step-by-step control. Specifically: the first step only controls the thickening on the inner side of the bend and the thinning on the outer side of the bend; the second step only controls the thinning on the inner side of the straight section at the pipe end and the thinning on the outer side of the bend. As mentioned above, specifically, since the first step only controls the thickening on the inner side of the bend and the thinning on the outer side of the bend, it is necessary to eliminate the influence of the thinning on the inner side of the straight section at the pipe end. Therefore, the intermediate pipe 1 of the bend, which is not connected to the first straight pipe section 8 and the second straight pipe section 9 of the bend, is placed in the pre-forming positioning cavity 3 of the pre-forming mold 2, i.e., only the bent portion is formed, as shown in the appendix. Figure 1 -Appendix Figure 3 As shown. In this profile design, when the intermediate tube 1 of the bent pipe is deformed under pressure during liquid filling, the axial deformation of the intermediate tube 1 effectively controls the thinning of the outer side of the bend, and the inner side of the bend, due to its smaller bulging area and less material accumulation, can effectively control the thickening of the inner side, avoiding wrinkling problems. This is the first intermediate configuration. After the first step of forming, both the inner and outer sides of the bent intermediate tube 1 are changed from not being attached to the pre-forming positioning cavity 3 before forming to being attached to the pre-forming positioning cavity 3 of the pre-forming mold. The second step only controls the thinning of the inner side of the straight section of the pipe opening and the thinning of the outer side of the bend, so it is necessary to eliminate the influence of the thickening of the inner side of the bend. Therefore, during the final forming, the finished intermediate tube is placed in the final forming positioning cavity 11 of the final forming mold 10. During the second step of forming, since both the inner and outer sides of the bend formed in the first step are attached to the mold, the bulging area is only the straight section area of the pipe opening. In this way, the thinning of the inner side of the straight section of the pipe opening can be controlled separately by axial material feeding, without worrying about the thickening or even wrinkling of the inner side of the bend. As shown in the attached figure. Figure 4 -Appendix Figure 6 As shown. This is intermediate configuration two, which is then formed into the finished product. The step-by-step forming method in this invention can design the most suitable intermediate configuration according to different bent pipe parts, thereby controlling the wall thickness uniformity and wall thickness reduction rate of the bent pipe parts and improving product quality. The small radius bent pipe liquid filling forming method described in this invention ensures small wall thickness reduction and good wall thickness uniformity of the bent pipe, while slowing down the thickening or even wrinkling on the inside of the bend, improving the overall quality of the pipe fitting, and meeting the requirements of small radius bent pipe liquid filling forming device for aero-engine applications.
[0021] Before the preforming step, the raw material of the pipe is first bent into a bent intermediate pipe 1. In the first step, only the bent intermediate pipe 1 is processed. This allows the axial deformation of the bent intermediate pipe 1 during the pressure deformation and forming process to effectively control the thinning of the outer side of the bend. Furthermore, the inner side of the bend has a smaller expansion area and is less prone to material accumulation, which can effectively control the thickening of the inner side and avoid wrinkling. Then, the final forming is carried out.
[0022] The preforming mold 2 includes a first preforming mold assembly and a second preforming mold assembly. Each preforming mold assembly has a preforming positioning cavity 3, and the two preforming mold assemblies are arranged symmetrically. In the first processing step, the preforming mold is required. The two preforming mold assemblies are joined together to form the preforming mold, with the preforming positioning cavity 3 in the center.
[0023] The final forming mold 10 includes a first final forming mold assembly and a second final forming mold assembly. The first and second final forming mold assemblies are each provided with a final forming positioning cavity 11, and the two final forming mold assemblies are arranged symmetrically. In the second processing step, the final forming mold is required. The two final forming mold assemblies are engaged to form the final forming mold, with the final forming positioning cavity 11 in the center.
[0024] When the inner side 5 and outer side 7 of the intermediate pipe 1 are deformed under stress, the outer side 7 is thinned by axial deformation material replenishment to avoid excessive thinning; the inner side 5 deforms and extends towards the inner expansion zone 15; after the inner side 5 and outer side 7 of the intermediate pipe 1 are deformed under stress, the first inner arc-shaped constraint part 4 fits against the inner side 5, and the first outer arc-shaped constraint part 6 fits against the outer side 7. After the inner side 8 and inner side 9 of the first straight section of the intermediate pipe end are deformed under stress, the inner side 10 of the first straight section of the intermediate pipe end fits against the first straight section expansion zone 12, and the inner side 11 of the second straight section fits against the second straight section expansion zone 13, and the thinning of the inner side of the straight section is controlled by axial deformation material replenishment. The above steps, through the first and second steps, avoid the following technical problems existing in the prior art: ① excessive thinning of the outer side; ② excessive thickening or even wrinkling of the inner side; ③ excessive thinning of the inner side of the straight section. Achieve the following: ① The outer side of the bend will not be excessively thinned; ② The inner side of the bend will not be excessively thickened or wrinkled; ③ The inner side of the straight section at the pipe opening will not be excessively thinned.
[0025] The inner curved constraint part 6 and the outer curved constraint part 4 of the pre-forming positioning cavity 3 are identical in position, size, and shape to the second inner curved constraint part 16 and the second outer curved constraint part 17 of the final forming positioning cavity 10. Both the pre-forming mold 3 and the final forming mold 10 are made of metal. In this structure, the partial structures of the forming cavities of the final forming mold and the pre-forming mold overlap. During the final forming step, the bent pipe is constrained at the portion already formed in the pre-forming step, and only the inner side of the straight section of the pipe opening is formed.
[0026] The final product of the small radius bend processing technology refers only to the small radius bend product area 26. The small radius bend transition section 27 and the small radius bend straight section 28 are supplementary parts of the process. After the small radius bend is formed, the straight section 27 and the small radius bend straight section 28 are removed to finally obtain the small radius bend product area 26.
[0027] The present invention also relates to a small radius bend liquid filling forming device that has a simple structure, ensures small wall thickness reduction and good wall thickness uniformity of the bend, and can slow down the thickening or even wrinkling of the inner side of the bend, improve the overall quality of the pipe fitting, and meet the application requirements of aero-engines.
[0028] The small-radius bend liquid-filling molding device includes a pre-forming mold 2 and a final forming mold 10. The pre-forming positioning molding cavity 3 of the pre-forming mold 2 includes a first inner curved arc-shaped constraint part 6 and a first outer curved arc-shaped constraint part 4. The inner curved arc-shaped constraint part 6 is provided with a recessed inner curved expansion zone 15. The ends of the straight pipe sections 19 at both ends of the pre-forming positioning molding cavity 3 in the pre-forming mold 2 are connected to the liquid filling pipeline of the liquid filling device. The final forming positioning molding cavity 11 of the final forming mold 10 includes a second inner curved arc-shaped constraint part 16 and a second outer curved arc-shaped constraint part 17. The final forming positioning molding cavity 11 is provided with a first pipe opening straight section expansion zone 12 at the position 8 inside the first pipe opening straight section of the pre-forming positioning molding cavity 3. The above-mentioned liquid-filling molding device can be reliably applied to the liquid-filling molding of small-radius bends. During molding, it needs to be filled with liquid in conjunction with a liquid filling device to achieve stress deformation of the pipe and solve the corresponding technical problems.
[0029] The present invention has been described above by way of example with reference to the accompanying drawings. Obviously, the specific implementation of the present invention is not limited to the above-described manner. Any improvements made by adopting the inventive concept and technical solution of the present invention, or the direct application of the inventive concept and technical solution of the present invention to other occasions without modification, are all within the protection scope of the present invention.
Claims
1. A method for filling and molding a small-radius bent pipe with liquid, characterized in that: Including preforming and final forming steps; S1. In the preforming step, the bent intermediate tube (1) is placed in the preforming positioning cavity (3) of the preforming mold (2), and positioned by the straight pipe sections (18) at both ends of the bent intermediate tube (1) and the straight pipe sections (19) at both ends of the preforming positioning cavity (3). The forming area A of the preforming positioning cavity (3) is the first deformation area. The distance between the first inner curved restraint part (6) of the preforming positioning cavity (3) and the inner curved part (5) of the bent intermediate tube (1) is small. The distance between the first outer curved restraint part (4) and the bending of the bent intermediate tube (1) is small. The outer side (7) has a large distance, and the inner side of the first bend arc-shaped constraint part (6) is provided with a concave inner side expansion area (15) on both sides, and there is no expansion area outside the inner side expansion area (15); liquid is filled into the middle tube (1) of the bend tube placed in the pre-forming positioning molding cavity (3), the inner side of the bend tube (5) of the bend tube (1) has a small distance from the inner side of the bend tube (5) to the first inner side arc-shaped constraint part (6), the amount of deformation under force is small and the thickness is small, the outer side of the bend (7) has a large distance from the outer side of the bend arc-shaped constraint part (4), the amount of deformation under force is large and there will inevitably be thinning, the straight tube sections (18) at both ends of the bend tube are pushed into the molding area A, effectively controlling the thinning of the outer side of the bend (7); S2. In the final forming step, the intermediate pipe (1) of the bent pipe is formed by the pre-forming step to form the intermediate bent pipe product (9) with the same shape as the pre-forming positioning cavity (3). The intermediate bent pipe product (9) is placed in the final forming positioning cavity (11) of the final forming mold (10). The straight pipe sections (20) at both ends of the intermediate bent pipe product (9) and the straight pipe sections (21) at both ends of the final forming positioning cavity (11) are used for positioning. The forming area B of the final forming positioning cavity (11) is the second deformation area. The inner side (8) of the straight section of the intermediate bent pipe product (9) is connected to the final forming cavity. The spacing between the inner expansion zones (12) of the straight section of the positioning molding cavity (11) is large, and there is a deformation zone (24) in the molding area B; the outer side (22) of the straight section of the intermediate finished product of the bent pipe (9) coincides with the outer expansion zone (23) of the straight section of the final molded pipe opening of the final molding positioning molding cavity (11); the inner side (13) of the bent intermediate finished product (9) coincides with the second inner curved arc-shaped constraint part (16) of the final molding positioning molding cavity (11); the outer side (14) of the bent intermediate finished product (9) coincides with the second outer curved arc-shaped constraint part (17) of the final molding positioning molding cavity (11); The second deformation zone is only the deformation zone (24) in the forming zone B. The straight pipe sections (20) at both ends of the finished product in the middle of the bend are pushed into the deformation zone (24) in the forming zone B to control the thinning of the expansion zone (12) inside the straight section. S3. Fill the interior of the intermediate finished product (9) of the bent tube into the final forming positioning cavity (11). The inner side (8) of the straight section of the intermediate finished product (9) of the bent tube is deformed by force, so as to form the intermediate finished product of the bent tube and form the small radius bent tube (25) of the final product.
2. The method for filling and forming a small-radius bent pipe with liquid according to claim 1, characterized in that: Before the preforming step, the pipe material is first bent into a bent intermediate pipe (1); during the S1 preforming step, the straight pipe sections (18) at both ends of the bent intermediate pipe (1) are equal in diameter to the straight pipe sections (19) at both ends of the preforming positioning cavity (3); during the S2 final forming step, the straight pipe sections (20) at both ends of the bent intermediate finished product (9) are equal in diameter to the straight pipe sections (21) at both ends of the final forming positioning cavity (11).
3. The method for liquid filling and forming small-radius bent pipes according to claim 1 or 2, characterized in that: The preforming mold (2) includes a first preforming mold assembly and a second preforming mold assembly. The first preforming mold assembly and the second preforming mold assembly are respectively provided with preforming positioning and forming cavities (3). The two preforming mold assemblies are arranged in a symmetrical structure.
4. The method for liquid filling and forming small-radius bent pipes according to claim 1 or 2, characterized in that: The final molding mold (10) includes a first final molding mold assembly and a second final molding mold assembly. The first final molding mold assembly and the second final molding mold assembly are respectively provided with a final molding positioning cavity (11). The two final molding mold assemblies are arranged in a symmetrical structure.
5. The method for liquid filling and forming a small-radius bent pipe according to claim 1 or 2, characterized in that: When the inner side (5) and outer side (7) of the bent pipe intermediate tube (1) are deformed by force, the outer side (7) is thinned by axial deformation material feeding to avoid excessive thinning; the inner side (5) is deformed and extended to the inner side expansion zone (15); after the inner side (5) and outer side (7) of the bent pipe intermediate tube (1) are deformed by force, the first inner side arc-shaped constraint part (6) fits the inner side (5) and the first outer side arc-shaped constraint part (4) fits the outer side (7).
6. The method for liquid filling and forming a small-radius bent pipe according to claim 1 or 2, characterized in that: After the inner side (8) of the straight section of the intermediate finished product (9) of the bent pipe is deformed by force, the inner side (8) of the straight section of the intermediate finished product (9) of the bent pipe fits the inner expansion area (12) of the straight section, and the thinning of the inner side of the straight section of the pipe is controlled by the material replenishment of axial deformation.
7. The method for liquid filling and forming a small-radius bent pipe according to claim 1 or 2, characterized in that: The first curved inner arc-shaped constraint part (6) and the first curved outer arc-shaped constraint part (4) of the pre-forming positioning molding cavity (3) and the second curved inner arc-shaped constraint part (16) and the second curved outer arc-shaped constraint part (17) of the final forming positioning molding cavity (11) have the same position, size and shape. The pre-forming mold (2) and the final forming mold (10) are both metal structures.
8. A small-radius bent pipe liquid filling forming apparatus for implementing the small-radius bent pipe liquid filling forming method according to any one of claims 1 to 7, characterized in that: The preforming mold (2) and the final forming mold (10) are included. The preforming positioning cavity (3) of the preforming mold (2) includes a first inner curved arc-shaped constraint part (6) and a first outer curved arc-shaped constraint part (4). The first inner curved arc-shaped constraint part (6) is provided with a recessed inner curved expansion area (15). The ends of the straight pipe sections (19) at both ends of the preforming positioning cavity (3) of the preforming mold (2) are connected to the filling pipeline of the filling equipment.
9. The small-radius bent pipe liquid filling and forming device according to claim 8, characterized in that: The final forming mold (10) includes a second curved inner arc-shaped constraint part (16) and a second curved outer arc-shaped constraint part (17). The final forming mold (11) has a straight section inner expansion zone (12) located inside the first pipe straight section (8) of the pre-forming positioning mold (3).