A method and apparatus for multi-directional hydraulic forming of a four-way pipe fitting

Abstract

This invention provides a method and apparatus for multi-directional hydraulic forming of four-way pipe fittings, relating to the field of pipe fitting forming technology. The method includes: determining the diameter of the initial pipe blank and the size of the diameter-changing zone of the variable-diameter pipe blank based on the size of the target pipe; calculating the internal pressure p1, axial reduction Δl, and supporting internal pressure p2; determining the length of the initial pipe blank; preparing the initial pipe blank; placing the initial pipe blank into an axially hydraulic forming mold for axial pressing to obtain a variable-diameter pipe blank; placing the variable-diameter pipe blank into a circumferentially hydraulic forming mold for circumferential pressing to obtain a double-protruding pipe blank; and removing the ends of the protruding portions of the double-protruding pipe blank to obtain the target pipe. This invention significantly reduces the forming load, effectively solving the problems of high internal high-pressure forming pressure, difficulty in replenishing material in the intermediate deformation zone, and easy occurrence of cracking defects in four-way pipe fittings. It avoids the thinning and cracking of branch pipes and connection areas, and the resulting four-way pipe fittings have uniform wall thickness, complete structure, and excellent performance.

Description

Technical Field

[0001] This invention relates to the field of pipe forming technology, and more specifically, to a method and apparatus for multi-directional hydraulic forming of four-way pipe fittings. Background Technology

[0002] Lightweight, high-precision, and long-life irregularly shaped thin-walled components, such as four-way pipe fittings, are commonly used in aerospace engine piping systems. Currently, multi-way pipe fittings are often produced using welding methods, such as stamping two halves separately and then welding them together, or inserting and welding branch pipes onto the main pipe. However, welded pipe fittings suffer from technical drawbacks such as uneven weld quality and post-weld deformation. Furthermore, stress concentration at the weld joints easily leads to fatigue damage and cracking, severely affecting the reliability of the components. Internal high-pressure forming technology is an advanced lightweight forming technology for multi-way pipe fittings, using its entire... Integral four-way pipe fittings not only improve reliability but also meet the requirements for lightweight components. However, when using internal high-pressure forming for multi-way pipe fittings, it is difficult to replenish material in the branch pipe of the deformation zone in the middle of the fitting, resulting in severe wall thinning and easy cracking defects, affecting product quality. This is especially true for high-strength (high-temperature alloys, martensitic heat-resistant stainless steel, titanium alloys, etc.) and small-diameter (diameter < 20 mm, diameter-to-thickness ratio < 10) integral four-way pipe fittings, which require very high forming pressures (up to 300 MPa or more) when using internal high-pressure forming. For example, when the diameter of the pipe blank is 15 mm, the wall thickness is 1.5 mm, the yield strength is 500 MPa, and the tensile strength is 900 MPa, if a multi-way pipe fitting with a fillet radius of 3 mm needs to be formed using internal high-pressure forming, the forming pressure needs to be at least 350 MPa. Moreover, high-strength pipes generally have poor plasticity. During the forming process, the high internal pressure causes extremely high frictional resistance between the pipe blank and the mold, making it difficult for the material at both ends to flow into the middle deformation zone. Ultimately, the branch pipes in the middle deformation zone are prone to cracking defects due to severe wall thinning. Summary of the Invention

[0003] The problem to be solved by the present invention is that the existing integral four-way pipe fittings formed by internal high pressure not only have high forming pressure, but also have difficulty in feeding material into the branch pipe in the middle deformation zone, which easily leads to cracking defects. Therefore, the present invention can effectively reduce the forming pressure and realize integral forming of high-strength four-way pipe fittings with large thickness-to-diameter ratio such as high-temperature alloy stainless steel, martensitic heat-resistant stainless steel, and titanium alloy under low load.

[0004] Therefore, the present invention provides a method for multi-directional hydraulic forming of a four-way pipe fitting, comprising the following steps:

[0005] S1. Determine the diameter of the initial tube blank and the size of the diameter-changing zone of the variable-diameter tube blank based on the size of the target tube;

[0006] S2. Calculate the internal pressure p1 and axial reduction Δl required to press the initial tube blank into the variable diameter tube blank, and the supporting internal pressure p2 required to press the variable diameter tube blank into the double-protruding tube blank.

[0007] S3. Determine the initial tube blank length based on the axial reduction Δl and the target tube length;

[0008] S4. Prepare the initial tube blank;

[0009] S5. Place the initial tube blank into an axially charged hydraulic pressing mold, and perform axial pressing according to the internal pressure p1 and the axial pressing amount Δl to obtain the variable diameter tube blank;

[0010] S6. Place the variable diameter tube blank into the circumferential hydraulic pressing mold and press it circumferentially according to the internal support pressure p2 to obtain a double-protruding tube blank.

[0011] S8. Remove the end of the protruding portion of the double-protruding tube blank to obtain the target tube.

[0012] Optionally, in step S1, the diameter of the initial tube blank is equal to the diameter of the straight section of the target tube, the perimeter of the variable diameter section of the tube blank is equal to the perimeter of the axial section at the branch of the target tube, and the length of the variable diameter section is less than or equal to the diameter of the branch of the target tube.

[0013] Optionally, in step S2, p s ≤p1≤2p s p2≤p s , where p s The yield pressure of the initial tube blank;

[0014]

[0015] Where V is the volume of the variable diameter region of the variable diameter tube blank, η is the average thinning rate, 0≤η≤5%, d0 is the diameter of the initial tube blank, t is the wall thickness of the initial tube blank, and l0 is the length of the variable diameter region.

[0016] Optionally, in step S3, the initial tube blank length = the target tube length + Δl.

[0017] Optionally, the process may further include the following steps between S6 and S8:

[0018] S7. Anneal the double-protruding tube blank.

[0019] Optionally, removing the protruding portion of the double-protruding tube blank at the end includes:

[0020] Holes are cut and flanges are turned at the ends of the two protrusions of the double-protrusion tube blank.

[0021] Compared with the prior art, the beneficial effects of the multi-directional hydraulic forming method for four-way pipe fittings of the present invention are:

[0022] This invention first involves preliminary preparation. The diameter of the initial tube blank to be formed and the dimensions of the variable diameter region of the variable diameter tube blank, formed by pressing the initial tube blank into a variable diameter tube blank using an axially energized hydraulic die, are determined based on the dimensions of the variable diameter region of the variable diameter tube blank and the parameters of the initial tube blank. Then, the internal pressure p1 and axial reduction Δl required for pressing the initial tube blank into a variable diameter tube blank using an axially energized hydraulic die, as well as the supporting internal pressure p2 required for pressing the variable diameter tube blank into a double-protruding tube blank using a circumferentially energized hydraulic die, are calculated based on the axial reduction Δl and the length of the target tube. The initial tube blank is then prepared according to the obtained initial tube blank length and diameter. This completes the preparation work. The initial tube blank is placed in an axially purged hydraulic die and axially pressed according to an internal pressure p1 and an axial reduction Δl to obtain a variable diameter tube blank. The internal pressure ensures that the initial tube blank is always supported outward during the pressing and shortening process, preventing it from collapsing inward during pressing. The obtained variable diameter tube blank is then placed in a circumferentially purged hydraulic die and circumferentially pressed according to a supporting internal pressure p2 to obtain a double-protruding tube blank. The supporting internal pressure ensures that the variable diameter tube blank is always supported outward during the pressing process, preventing it from collapsing inward during pressing. The protruding part of the double-protruding tube blank is the branch pipe of the target tube. The top of the protruding part of the double-protruding tube blank is removed to obtain the target tube. The present invention relates to a four-way pipe fitting. First, an initial pipe blank is axially pressed to shorten its length. The shortened portion protrudes circumferentially from the middle of the initial pipe blank, forming a variable-diameter pipe blank. This protruding portion is the variable-diameter region, which is an annular area with straight pipe sections at both ends. Subsequently, a circumferentially pressurized die presses the variable-diameter region, pressing it towards the two branch pipe sections of the target pipe. This transforms the variable-diameter region into two protruding portions of a double-protruding pipe blank. Finally, the ends of the two protruding portions are removed, allowing them to connect with the outside environment, forming branch pipes and obtaining a four-way pipe fitting. In this process, the material used to form the branch pipes comes from the initial pipe blank during axial pressing. The circumferential protrusions formed during the pressing process ensure sufficient material for forming the branch pipes, preventing thinning and cracking of the branch pipes and connecting areas, improving the overall structural integrity of the four-way fittings, and solving the problems of difficult material replenishment and easy cracking defects in the deformation zone of the internal high-pressure formed four-way fittings. Moreover, the obtained four-way fittings have uniform wall thickness, complete structure, and excellent performance. Compared with the existing internal high-pressure forming methods, the internal pressure of this application is generally lower than the yield internal pressure of the pipe material during hydraulic forming, and only plays a supporting role. Furthermore, the forming pressure required by this application is low, and the tonnage of the mold pressing equipment is small. It is suitable for the integral forming of high-strength four-way fittings with large thickness-to-diameter ratios such as high-temperature alloys and stainless steel.

[0023] In addition, to solve the above problems, the present invention also provides a four-way pipe fitting multi-directional hydraulic forming device for realizing the above-mentioned four-way pipe fitting multi-directional hydraulic forming method. The four-way pipe fitting multi-directional hydraulic forming device includes an axial hydraulic forming mold and a circumferential hydraulic forming mold.

[0024] Optionally, the axially charged hydraulic mold includes a first upper mold, a first lower mold, a support spring, an upper sealing punch, a lower sealing punch, and a limiting bolt. The first upper mold and the first lower mold are respectively provided with cavities that penetrate the first upper mold and the first lower mold in a vertical direction. The two cavities are connected to form a first mold cavity. The first upper mold is provided with a countersunk hole, and the first lower mold is provided with a threaded hole. The limiting bolt passes through the countersunk hole and is threadedly connected to the threaded hole. The first upper mold and the limiting bolt are slidably connected. The shape of the first mold cavity matches the shape of the variable diameter tube blank. The initial tube blank is used to be placed in the first mold cavity. The upper sealing punch and the lower sealing punch are used to seal both ends of the initial tube blank and to drive the first upper mold and the first lower mold to move towards each other. The upper sealing punch or the lower sealing punch is provided with a first fluid inlet.

[0025] Optionally, the circumferential hydraulic die includes a second upper die, a second lower die, a left sealing punch, and a right sealing punch. The lower surface of the second upper die and the upper surface of the second lower die are respectively provided with groove structures that penetrate the second upper die and the second lower die in a horizontal direction. The second upper die and the second lower die are used to move towards each other. The two groove structures are used to form a second die cavity. The shape of the second die cavity matches the shape of the double-protruding tube blank. The variable diameter tube blank is used to be placed in the second die cavity. The left sealing punch and the right sealing punch are used to seal both ends of the variable diameter tube blank. A second fluid inlet is provided on the left sealing punch or the right sealing punch.

[0026] Optionally, the four-way pipe fitting multi-directional hydraulic forming device further includes a mold clamping and pressing system and a liquid filling and pressurizing system. The mold clamping and pressing system is used to press the axial hydraulic forming mold or the circumferential hydraulic forming mold, and the liquid filling and pressurizing system is used to fill the mold cavity of the axial hydraulic forming mold or the mold cavity of the circumferential hydraulic forming mold with liquid.

[0027] Compared with the prior art, the beneficial effects of the four-way pipe fitting multi-directional hydraulic forming device of the present invention are roughly the same as those of the above-mentioned four-way pipe fitting multi-directional hydraulic forming method, and will not be repeated here. Attached Figure Description

[0028] Figure 1 This is one of the flowcharts for the multi-directional hydraulic forming method of the four-way pipe fitting described in the embodiments of the present invention;

[0029] Figure 2 This is the second flowchart of the multi-directional hydraulic forming method for the four-way pipe fitting described in this embodiment of the invention;

[0030] Figure 3 This is a schematic diagram of the structure of the variable diameter tube blank according to an embodiment of the present invention;

[0031] Figure 4 for Figure 3 Side view of DD;

[0032] Figure 5 for Figure 3 Middle EE side view;

[0033] Figure 6 This is a schematic diagram of the structure of the double-protrusion tube blank according to an embodiment of the present invention;

[0034] Figure 7 for Figure 6 Middle FF side view;

[0035] Figure 8 This is a schematic diagram of the target tube structure according to an embodiment of the present invention;

[0036] Figure 9 for Figure 8 Middle CC side view;

[0037] Figure 10 This is one of the structural schematic diagrams of the axial hydraulic pressing mold described in the embodiments of the present invention;

[0038] Figure 11 This is a second schematic diagram of the axial hydraulic pressing mold described in an embodiment of the present invention;

[0039] Figure 12 This is one of the structural schematic diagrams of the circumferential hydraulically pressurized mold described in the embodiments of the present invention;

[0040] Figure 13 for Figure 12 Side view of AA;

[0041] Figure 14 This is a second schematic diagram of the structure of the circumferential hydraulic mold described in an embodiment of the present invention;

[0042] Figure 15 for Figure 14 Side view of BB (British Barbie);

[0043] Figure 16 This is a schematic diagram of the axial hydraulic forming device for the four-way pipe fitting described in an embodiment of the present invention;

[0044] Figure 17This is a schematic diagram of the circumferential hydraulic forming device for four-way pipe fittings according to an embodiment of the present invention.

[0045] Explanation of reference numerals in the attached figures:

[0046] 11-Initial tube blank; 12-Reducing diameter tube blank; 121-Reducing diameter zone; 122-Straight pipe zone; 13-Double-protrusion tube blank; 131-Protrusion portion; 14-Target pipe; 141-Branch pipe; 2-Axial hydraulic filling die; 21-First upper die; 22-First lower die; 23-Support spring; 24-Upper sealing punch; 25-Lower sealing punch; 26-Limiting bolt; 27-First sealing ring; 28-First fluid inlet; 29-Cavity; 3-Circumferential hydraulic filling die; 31- 32-Second upper die; 33-Left sealing punch; 34-Right sealing punch; 35-Second fluid inlet; 36-Second sealing ring; 37-Internal support; 38-Groove structure; 4-Mold closing and pressing system; 41-Displacement sensor; 42-Displacement drive structure; 43-Motor; 5-Liquid filling and pressurization system; 51-Solenoid directional valve; 52-Relief valve; 53-Oil tank; 54-Hydraulic pump; 55-Pressure booster; 56-Pressure sensor; 6-Control system. Detailed Implementation

[0047] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0048] It should be noted that in the description of this invention, the orientations or positional relationships indicated by terms such as "upper," "lower," "left," "right," "top," "bottom," "front," "back," "inner," and "outer" are based on the orientations or positional relationships shown in the accompanying drawings and are only for the convenience of describing this invention. They are not intended to indicate or imply that the device referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as limiting the scope of protection of this invention.

[0049] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature.

[0050] Furthermore, although specific embodiments have been described herein, it should be understood that these embodiments are merely examples of the principles and applications of the invention. Therefore, it should be understood that many modifications can be made to the exemplary embodiments, and other arrangements can be designed without departing from the spirit and scope of the invention as defined by the appended claims. It should be understood that different dependent claims and features herein can be combined in ways not used as described in the original claims. It is also understood that features described in conjunction with individual embodiments can be used in other embodiments.

[0051] To solve the above problems, such as Figure 1 and Figures 3 to 9 As shown, the present invention provides a method for multi-directional hydraulic forming of a four-way pipe fitting, comprising the following steps:

[0052] S1. Determine the diameter of the initial tube blank 11 and the size of the variable diameter region 121 of the variable diameter tube blank 12 based on the size of the target tube 14;

[0053] S2. Calculate the internal pressure p1 and axial compression Δl required to press the initial tube blank 11 into the variable diameter tube blank 12, and the supporting internal pressure p2 required to press the variable diameter tube blank 12 into the double-protruding tube blank 13.

[0054] S3. Determine the length of the initial tube blank 11 based on the axial reduction amount Δl and the length of the target tube 14;

[0055] S4. Prepare the initial tube blank 11;

[0056] S5. Place the initial tube blank 11 into the axially charged hydraulic pressing mold 2, and perform axial pressing according to the internal pressure p1 and the axial pressing amount Δl to obtain the variable diameter tube blank 12.

[0057] S6. Place the variable diameter tube blank 12 into the circumferential hydraulic pressing mold 3 and press it circumferentially according to the internal support pressure p2 to obtain the double protrusion tube blank 13.

[0058] S8. Remove the end of the protruding portion 131 of the double-protruding tube blank 13 to obtain the target tube 14.

[0059] In this embodiment, preliminary preparations are first performed. The diameter of the initial tube blank 11 used for forming is determined based on the desired size of the target tube 14, and the dimensions of the diameter-changing region 121 of the variable-diameter tube blank 12 formed by pressing the initial tube blank 11 into the variable-diameter tube blank 12 using the axially charged hydraulic die 2. Then, based on the dimensions of the diameter-changing region 121 of the variable-diameter tube blank 12 and the parameters of the initial tube blank 11, the internal pressure p1 and axial reduction Δl required for pressing the initial tube blank 11 into the variable-diameter tube blank 12 in the axially charged hydraulic die 2, as well as the supporting internal pressure p2 required for pressing the variable-diameter tube blank 12 into the double-protruding tube blank 13 using the circumferentially charged hydraulic die 3, are calculated. Finally, the length of the initial tube blank 11 is calculated using the axial reduction Δl and the length of the target tube 14. Prepare the initial tube blank 11 according to the obtained initial tube blank 11 length and diameter. After preparation, place the initial tube blank 11 into the axially charged hydraulic pressing mold 2 and perform axial pressing according to the internal pressure p1 and axial pressing amount Δl to obtain the variable diameter tube blank 12. The internal pressure ensures that the initial tube blank 11 is always supported by an outward force during the pressing and shortening process, preventing the initial tube blank 11 from collapsing inward during pressing. Then, place the obtained variable diameter tube blank 12 into the circumferentially charged hydraulic pressing mold 3 and perform circumferential pressing according to the supporting internal pressure p2 to obtain the double-protruding tube blank 13. The supporting internal pressure ensures that the variable diameter tube blank 12 is always supported by an outward force during the pressing process, preventing the variable diameter tube blank 12 from collapsing during pressing. The inwardly recessed, double-convex tube blank 13's protruding portion becomes the branch pipe 141 of the target pipe 14. Removing the top of the protruding portion 131 of the double-convex tube blank 13 yields the target pipe 14, i.e., a four-way fitting. In this invention, the initial tube blank 11 is first axially pressed to shorten its length. The shortened portion protrudes circumferentially from the middle of the initial tube blank 11, forming a variable-diameter tube blank 12. The protruding portion is the variable-diameter region 121 of the variable-diameter tube blank 12. The variable-diameter region 121 is an annular area with straight pipe regions 122 at both ends. Subsequently, the circumferentially charged hydraulic die 3 presses the variable-diameter region 121, pressing the circumferentially surrounding variable-diameter region 121 towards the positions of the two branch pipe 141 areas of the target pipe 14, thus... The reducing zone 121 is transformed into two protruding portions 131 of the double-protruding tube blank 13. Finally, the ends of the two protruding portions 131 are removed, allowing the protruding portions 131 to connect with the outside, forming a branch pipe 141, thus obtaining a four-way pipe fitting. In this process, the material used to form the branch pipe 141 comes from the circumferential protrusion formed during the axial pressing of the initial tube blank 11. This ensures that there is sufficient material for forming the branch pipe 141, avoiding thinning and cracking of the branch pipe 141 and the connecting area, improving the overall structural integrity of the four-way pipe fitting, solving the problem of difficult material replenishment and easy cracking defects in the deformation zone of the internal high-pressure formed four-way pipe fitting, and obtaining a four-way pipe fitting with uniform wall thickness, complete structure, and excellent performance.

[0060] Specifically, compared with existing internal high-pressure forming methods, the internal pressure in this application is generally lower than the yield internal pressure of the pipe during hydraulic forming, and only plays a supporting role. Moreover, the forming pressure required by this application is low and the tonnage of the mold pressing equipment is small. It is suitable for integral forming of high-strength, high-thickness-to-diameter ratio four-way pipe fittings made of high-temperature alloys, stainless steel, etc., such as high-temperature alloys, martensitic heat-resistant stainless steel, titanium alloys, etc. The diameter of the four-way pipe fitting is usually less than 20mm; the included angle between the two branch pipes 141 is 120 to 180°.

[0061] Optionally, in step S1, the diameter of the initial tube blank 11 is equal to the diameter of the straight section 122 of the target tube 14, the perimeter of the variable diameter section 121 of the variable diameter tube blank 12 is equal to the perimeter of the axial section at the branch tube 141 of the target tube 14, and the length of the variable diameter section 121 is less than or equal to the diameter of the branch tube 141 of the target tube 14.

[0062] In this embodiment, the diameter of the initial tube blank 11 is set to the diameter of the target tube 14. This setup suffices only to machine the branch tube 141, without needing to change the diameter of the initial tube blank 11. The outer perimeter of the variable diameter tube section is set to the perimeter of the axial section of the branch tube 141 of the target tube 14. Figure 9 The perimeter of the structure is determined to ensure that the cross-sectional perimeters of the variable diameter section 121 of the variable diameter billet 12 and the branch pipe 141 of the target pipe 14 at the same axial position are equal. The perimeter of the variable diameter section 121 can be calculated based on the diameter of the variable diameter section 121. The length of the variable diameter section 121 is set to be less than or equal to the length of the branch pipe 141 of the target pipe 14 to prevent the variable diameter section 121 from being too large to fit into the circumferential hydraulic mold 3.

[0063] Optionally, in step S2, p s ≤p1≤2p s p2≤p s , where p s The yield pressure of the initial tube blank 11;

[0064]

[0065] Where V is the volume of the variable diameter region 121 of the variable diameter tube blank 12, η ​​is the average thinning rate, 0≤η≤5%, d0 is the diameter of the initial tube blank 11, t is the wall thickness of the initial tube blank 11, and l0 is the length of the variable diameter region 121.

[0066] In this embodiment, the following formula is used:

[0067] p s ≤p1≤2p s p2≤p s ,and

[0068] The calculated internal pressure p1, support internal pressure p2, and axial reduction Δl are specific values, where V is the volume of the reducing region 121 of the reducing tube blank 12, which can be obtained from the length and diameter of the reducing tube blank 12; η is the average thinning rate, 0≤η≤5%; d0 is the diameter of the initial tube blank 11; t is the wall thickness of the initial tube blank 11; l0 is the length of the reducing region 121; and p... s The yield pressure of the initial tube blank 11 is given by the internal pressure p1, the support internal pressure p2, and the axial reduction Δl, which can be any value as long as they are within the range of the calculation results.

[0069] Yield pressure of initial tube blank 11 Where σ s The initial yield strength of the initial tube blank 11 is given.

[0070] Optionally, in step S3, the length of the initial tube blank 11 is equal to the length of the target tube 14 plus Δl.

[0071] In this embodiment, the length of the initial tube blank 11 is calculated to be equal to the length of the target tube 14 plus the axial reduction Δl. The axial reduction Δl is the shortened length of the target tube blank 14. This setting ensures that the length of the processed four-way fitting is the target length.

[0072] Specifically, the target pipe 14 is set to a length of 120 mm, a straight pipe section 122 diameter of 14 mm and a wall thickness of 1.2 mm, and a branch pipe 141 diameter of 10 mm. Based on the above dimensions, the diameter of the reducing section 121 of the reducing pipe blank 12 can be set to 21 mm, the length l0 to 13 mm, the initial pipe blank 11 diameter d0 to 14 mm, the wall thickness t to 1.2 mm, and the initial yield strength to σ. s =400MPa; the initial yield pressure of the initial tube blank 11 was calculated to be p. s =69MPa, axial pressure reduction Δl =5.2mm, therefore, the range of internal pressure p1 is 69-138MPa, the range of supporting internal pressure p2 is 0-69MPa, and finally the internal pressure is selected as 100MPa, the supporting internal pressure is 69MPa, and the length of the initial tube blank 11 is 125.2mm.

[0073] Optionally, such as Figure 2 As shown, the process between step S6 and step S8 also includes:

[0074] S7. Anneal the double-protruding tube blank 13.

[0075] In this embodiment, by annealing the double-protruding tube blank 13, residual stress can be eliminated, plasticity can be restored, and deformation and cracking can be avoided.

[0076] Optionally, removing the end of the protruding portion 131 of the double-protruding tube blank 13 includes:

[0077] Holes are cut and flanges are turned at the ends of the two protrusions of the double-protrusion tube blank 13.

[0078] In this embodiment, by cutting and flanging the ends of the double-protruding tube blank 13, a branch pipe 141 communicating with the outside is obtained, and the connection performance of the end of the branch pipe 141 is improved.

[0079] Specifically, laser cutting can be used to cut holes in the protruding portion 131 of the double-protruding tube blank 13, and punching or drawing methods can be used to flanging the protruding part to finally obtain a four-way pipe fitting.

[0080] Another embodiment of the present invention provides a four-way pipe fitting multi-directional hydraulic forming device for implementing the above-mentioned four-way pipe fitting multi-directional hydraulic forming method. The four-way pipe fitting multi-directional hydraulic forming device includes an axial hydraulic forming mold 2 and a circumferential hydraulic forming mold 3.

[0081] Compared with the prior art, the beneficial effects of the four-way pipe fitting multi-directional hydraulic forming device of this embodiment are roughly the same as the beneficial effects of the above-described four-way pipe fitting multi-directional hydraulic forming method, and will not be repeated here.

[0082] Specifically, the four-way pipe fitting multi-directional hydraulic forming device includes a four-way pipe fitting axial hydraulic forming device and a four-way pipe fitting circumferential hydraulic forming device. The four-way pipe fitting axial hydraulic forming device includes an axial hydraulic forming mold 2, and the four-way pipe fitting circumferential hydraulic forming device includes a circumferential hydraulic forming mold 3.

[0083] Optionally, such as Figure 10 and 11 As shown, the axially inflatable hydraulic mold 2 includes a first upper mold 21, a first lower mold 22, a support spring 23, an upper sealing punch 24, a lower sealing punch 25, and a limiting bolt 26. The first upper mold 21 and the first lower mold 22 are respectively provided with cavities 29 extending vertically through them. The two cavities 29 are connected to form a first mold cavity. The first upper mold 21 has a countersunk hole, and the first lower mold 22 has a threaded hole. The limiting bolt 26 passes through the countersunk hole. The countersunk hole is threadedly connected to the threaded hole. The first upper die 21 is slidably connected to the limiting bolt 26. The shape of the first die cavity matches the shape of the variable diameter tube blank 12. The initial tube blank 11 is used to be set in the first die cavity. The upper sealing punch 24 and the lower sealing punch 25 are used to seal both ends of the initial tube blank 11 and to drive the first upper die 21 and the first lower die 22 to move towards each other. The upper sealing punch 24 or the lower sealing punch 25 is provided with a first fluid inlet 28.

[0084] In this embodiment, a first upper die 21 and a first lower die 22 are arranged vertically along the Z-axis, and cavities 29 extending along the Z-axis are formed on the first upper die 21 and the first lower die 22. An upper sealing punch 24 is connected to the upper side of the first upper die 21, and a lower sealing punch 25 is connected to the lower side of the first lower die 22. The upper sealing punch 24 and the lower sealing punch 25 can move towards each other, pressing the first upper die 21 and the first lower die 22 together. The two cavities 29 are connected and closed to form a... The first mold cavity has a shape corresponding to the shape of the variable diameter tube blank 12. The first upper mold 21 has a countersunk hole extending along the Z-axis, and the upper surface of the first lower mold 22 has a threaded hole extending along the Z-axis. The screw end of the limiting bolt 26 passes through the countersunk hole from the upper side and is screwed into the threaded hole, fixing the limiting bolt 26 to the first lower mold 22. The first upper mold 21 can slide along the screw of the limiting bolt 26. The limiting bolt 26 is located between the first upper mold 21 and the first lower mold. A support spring 23 is fitted onto the middle part, and a limiting bolt 26 specifies the extension and retraction direction of the support spring 23 to prevent the support spring 23 from shifting during extension and retraction. The nut of the limiting bolt 26 can be completely embedded in the countersunk hole. That is, when the first upper die 21 slides along the screw of the limiting bolt 26 within a set range, the sliding distance, that is, the distance between the first upper die 21 and the first lower die 22, is equal to the axial pressing amount Δl. The limiting screw can be set to adjust the distance between the first upper die 21 and the first lower die 22 according to different axial pressing amounts Δl. The nut of the limiting bolt 26 will not protrude from the countersunk hole, so that the first upper die 21 and the first lower die 22 can always interact through elastic force within a certain distance range. When pressing is required, the initial tube blank 11 is first placed in the cavity 29 of the first upper die 21 and the first lower die 22, and the upper sealing punch 24 and the lower sealing punch 25 are connected to the upper and lower sides of the first upper die 21 and the first lower die 22 to seal the initial tube blank 11. Figure 10 As shown, at this time, fluid is introduced into the initial tube blank 11 through the first fluid inlet 28 opened on the upper sealing punch 24 or the lower sealing punch 25 until the internal pressure p1 is reached. Then, the upper sealing punch 24 and the lower sealing punch 25 are driven to move towards each other, pressing the first upper die 21 and the first lower die 22 together. The two cavities 29 are connected and closed, and the initial tube blank 11 is pressed into a variable diameter tube blank 12 according to the shape of the cavity 29. Figure 11 As shown, after the pressing is completed, the support spring 23 facilitates the reset of the first upper mold 21 and the second upper mold 31 after the pressing is completed.

[0085] Specifically, a first sealing ring 27 is provided between the upper sealing punch 24, the lower sealing punch 25 and the initial tube blank 11 to ensure sealing and facilitate the filling of liquid into the initial tube blank 11 so that the pressure inside the initial tube blank 11 reaches the internal pressure p1.

[0086] Optionally, such as Figures 12 to 15 As shown, the circumferential hydraulic mold 3 includes a second upper mold 31, a second lower mold 32, a left sealing punch 33, and a right sealing punch 34. The lower surface of the second upper mold 31 and the upper surface of the second lower mold 32 are respectively provided with groove structures 38 that penetrate the second upper mold 31 and the second lower mold 32 in the horizontal direction. The second upper mold 31 and the second lower mold 32 are used to move towards each other. The two groove structures 38 are used to form a second mold cavity. The shape of the second mold cavity matches the shape of the double-protruding tube blank 13. The variable diameter tube blank 12 is used to be placed in the second mold cavity. The left sealing punch 33 and the right sealing punch 34 are used to seal both ends of the variable diameter tube blank 12. A second fluid inlet 35 is provided on the left sealing punch 33 or the right sealing punch 34.

[0087] In this embodiment, a second upper mold 31 and a second lower mold 32 are arranged vertically along the Z-axis, and groove structures 38 extending and penetrating along the X-axis are formed on the lower surface of the second upper mold 31 and the upper surface of the second lower mold 32. When the two groove structures 38 are closed, a second mold cavity is formed. The shape of the second mold cavity corresponds to the shape of the double-protruding tube blank 13. During pressing, the variable diameter tube blank 12 is first placed between the two groove structures 38, and the left sealing punch 33 and the right sealing punch 34 are connected to both ends of the groove structure 38 to seal the variable diameter tube blank 12. Liquid is injected into the variable diameter tube blank 12 through the second fluid inlet 35 on the left sealing punch 33 or the right sealing punch 34 until the pressure reaches the supporting internal pressure p2. Figure 12 and Figure 13 As shown, the second upper die 31 and the second lower die 32 are then driven to move towards each other, pressing the second upper die 31 and the second lower die 32 together. The two groove structures 38 are connected and closed, and the variable diameter tube blank 12 is pressed into a double-protruding tube blank 13 according to the shape of the groove structure 38, as shown. Figure 14 and Figure 15 As shown.

[0088] Specifically, a second sealing ring 36 is provided between the left sealing punch 33, the right sealing punch 34 and the reducing tube blank 12 to ensure sealing and facilitate liquid filling into the reducing tube blank 12 so that the internal pressure of the reducing tube blank 12 reaches the supporting internal pressure p2. During the circumferential filling and pressing process, an internal support 37 can be provided inside the reducing area 121 of the reducing tube blank 12 to prevent inward concavity during the pressing process. The internal support 37 structure can be a support frame, which can be a rigid structure or an elastic structure.

[0089] Optionally, such as Figure 16 and Figure 17As shown, the four-way pipe fitting multi-directional hydraulic forming device also includes a mold clamping and pressing system 4 and a liquid filling and pressurizing system 5. The mold clamping and pressing system 4 is used to press the axial hydraulic forming mold 2 or the circumferential hydraulic forming mold 3. The liquid filling and pressurizing system 5 is used to fill the mold cavity of the axial hydraulic forming mold 2 or the mold cavity of the circumferential hydraulic forming mold 3 with liquid.

[0090] In this embodiment, by setting up a mold pressing system 4 to drive the upper sealing punch 24 and the lower sealing punch 25, the second upper mold 31 and the second lower mold 32 to move towards each other, it is convenient to press. A liquid filling and pressurizing system 5 is set up to fill the initial tube blank 11 located in the first mold cavity and the variable diameter tube blank 12 located in the second mold cavity with liquid, so that the pressure inside the initial tube blank 11 and the variable diameter tube blank 12 reaches the standard.

[0091] Specifically, the mold clamping and pressing system 4 includes a displacement sensor 41, a displacement drive structure 42, and a motor 43. The displacement drive structure 42 can be a ball screw or a telescopic rod. The motor 43 drives the displacement drive structure 42, which is connected to the upper sealing punch 24, driving the upper sealing punch 24 to move to the lower sealing punch 25. The lower sealing punch 25 can be fixed on the worktable. Another set of displacement drive structures 42 and motors 43 are connected to the second upper mold 31. The second lower mold 32 is fixed on the worktable, facilitating the movement of the second upper mold 31 and the lower mold 32. The second die 32 is pressed together, and the displacement drive structure 42 is also equipped with a displacement sensor 41 to facilitate the detection of the movement distance; the liquid filling and pressurization system 5 includes an electromagnetic reversing valve 51, an overflow valve 52, an oil tank 53, a hydraulic pump 54, a booster 55, and a pressure sensor 56. The hydraulic pump 54 draws hydraulic oil and fills the initial tube blank 11 or the variable diameter tube blank 12 through the electromagnetic reversing valve 51 and the booster 55. The electromagnetic reversing valve 51 reverses and releases pressure, the overflow valve 52 protects the oil circuit to prevent excessive pressure in the oil circuit, and the pressure sensor 56 detects the pressure value.

[0092] The four-way pipe fitting multi-directional hydraulic forming device also includes a control system 6. The control system 6 is electrically connected to the displacement sensor 41 and the pressure sensor 56, and can obtain data on axial compression Δl, internal pressure p1, and support internal pressure p2 in real time. It can also control the internal pressure p1, support internal pressure p2, and axial compression Δl in real time through the electromagnetic reversing valve 51 and the motor 43.

[0093] While the present invention has been disclosed above, its scope of protection is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention, and all such changes and modifications will fall within the scope of protection of the present invention.

Claims

1. A method for multi-directional hydraulic forming of a four-way pipe fitting, characterized in that, Includes the following steps: S1. Determine the diameter of the initial tube blank (11) and the size of the variable diameter zone (121) of the variable diameter tube blank (12) according to the size of the target tube (14); The diameter of the initial tube blank (11) is equal to the diameter of the straight section (122) of the target tube (14), the perimeter of the variable diameter section (121) of the variable diameter tube blank (12) is equal to the perimeter of the axial section at the branch pipe (141) of the target tube (14), and the length of the variable diameter section (121) is less than or equal to the diameter of the branch pipe (141) of the target tube (14). S2. Calculate the internal pressure required to press the initial tube blank (11) into the variable diameter tube blank (12). p 1 and axial reduction The supporting internal pressure required for pressing the variable diameter tube blank (12) into a double-convex tube blank (13). p 2; ； in V The volume of the diameter-changing region (121) of the variable-diameter tube blank (12) is given. For the average thinning rate, 0 ≤ ≤5%, d 0 is the diameter of the initial tube blank (11). t The wall thickness of the initial tube blank (11) is... The length of the variable diameter region (121); S3, based on the axial reduction amount The length of the initial tube blank (11) is determined by the length of the target tube (14); The length of the initial tube blank (11) = the length of the target tube (14) + ； S4. Prepare the initial tube blank (11); S5. Place the initial tube blank (11) into the axially accelerated hydraulic forming mold (2), and pressurize it according to the internal pressure. p 1 and the axial compression amount Axial pressing is performed to obtain the variable diameter tube blank (12); S6. Place the variable diameter tube blank (12) into the circumferentially charged hydraulic mold (3), and press it according to the internal pressure of the support. p 2. Circumferential pressing is performed to obtain a double-protruding tube blank (13); S8. Remove the end of the protruding portion (131) of the double-protruding tube blank (13) to obtain the target tube (14).

2. The method for multi-directional hydraulic forming of a four-way pipe fitting according to claim 1, characterized in that, In step S2, p s ≤p1≤2p s p2≤p s , where p s The yield pressure of the initial tube blank (11).

3. The method for multi-directional hydraulic forming of a four-way pipe fitting according to claim 1, characterized in that, Between step S6 and step S8, the following is also included: S7. Anneal the double-protruding tube blank (13).

4. The method for multi-directional hydraulic forming of a four-way pipe fitting according to claim 1, characterized in that, The removal of the protruding portion (131) of the double-protruding tube blank (13) includes: Holes are cut and flanges are turned at the ends of the two protrusions of the double-protrusion tube blank (13).

5. A multi-directional hydraulic forming device for four-way pipe fittings, characterized in that, The four-way pipe fitting multi-directional hydraulic forming method as described in any one of claims 1 to 4 is provided, wherein the four-way pipe fitting multi-directional hydraulic forming device includes an axial hydraulic forming die (2) and a circumferential hydraulic forming die (3).

6. The four-way pipe fitting multi-directional hydraulic forming device according to claim 5, characterized in that, The axially inflatable hydraulic mold (2) includes a first upper mold (21), a first lower mold (22), a support spring (23), an upper sealing punch (24), a lower sealing punch (25), and a limiting bolt (26). The first upper mold (21) and the first lower mold (22) are respectively provided with cavities (29) that penetrate vertically through the first upper mold (21) and the first lower mold (22). The two cavities (29) are connected to form a first mold cavity. The first upper mold (21) has a countersunk hole, and the first lower mold (22) has a threaded hole. The limiting bolt (26) passes through... The first upper die (21) is slidably connected to the limiting bolt (26) through the countersunk hole and threaded to the threaded hole. The shape of the first die cavity matches the shape of the variable diameter tube blank (12). The initial tube blank (11) is used to be set in the first die cavity. The upper sealing punch (24) and the lower sealing punch (25) are used to seal both ends of the initial tube blank (11) and to drive the first upper die (21) and the first lower die (22) to move towards each other. The upper sealing punch (24) or the lower sealing punch (25) is provided with a first fluid inlet (28).

7. The four-way pipe fitting multi-directional hydraulic forming device according to claim 5, characterized in that, The circumferential hydraulic die (3) includes a second upper die (31), a second lower die (32), a left sealing punch (33), and a right sealing punch (34). The lower surface of the second upper die (31) and the upper surface of the second lower die (32) are respectively provided with groove structures (38) that penetrate the second upper die (31) and the second lower die (32) in the horizontal direction. The second upper die (31) and the second lower die (32) are used to move towards each other. The two groove structures (38) are used to form a second die cavity. The shape of the second die cavity matches the shape of the double-protruding tube blank (13). The variable diameter tube blank (12) is used to be placed in the second die cavity. The left sealing punch (33) and the right sealing punch (34) are used to seal the two ends of the variable diameter tube blank (12). A second fluid inlet (35) is provided on the left sealing punch (33) or the right sealing punch (34).

8. The four-way pipe fitting multi-directional hydraulic forming device according to claim 5, characterized in that, It also includes a mold clamping and pressing system (4) and a liquid filling and pressurizing system (5). The mold clamping and pressing system (4) is used to press the axially filled hydraulic mold (2) or the circumferentially filled hydraulic mold (3). The liquid filling and pressurizing system (5) is used to fill the mold cavity of the axially filled hydraulic mold (2) or the mold cavity of the circumferentially filled hydraulic mold (3) with liquid.

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