A hot air pressure forming process and mold for a flanged 3D curved tubular preform

Abstract

This invention discloses a hot pneumatic forming process and mold for a 3D bent tubular blank with a flange, comprising the following steps: Step 1, optimizing the product design to verify that it meets the flange forming conditions; Step 2, bending the tube blank; Step 3, placing the bent tube blank in a pre-forming mold for flange pre-forming; Step 4, placing the pre-formed tube blank in a hot pneumatic forming mold for flange hot pneumatic forming. This invention overcomes the technical difficulties of flange forming, poor mold adaptability, and insufficient welding strength in traditional processes through segmented control, a combined hot and cold forming process, and innovative mold design, achieving high-precision and high-efficiency forming and meeting the modern automotive industry's demand for lightweight, high-strength structural components.

Description

Technical Field

[0001] This invention relates to a pneumatic forming mold and forming process, and more particularly to a hot pneumatic forming process and mold for a flanged 3D curved tubular blank. Background Technology

[0002] Traditional hot pneumatic forming technology has many limitations in the design and manufacturing of tubular die blanks, especially in terms of welding processes and vehicle safety. Specifically, when welding tubular components to other die blanks, welding is typically only possible by filling the gap between the two blanks. This welding method not only limits the flexibility of vehicle design but also results in insufficient weld strength, leading to a decrease in the overall torsional stiffness of the welded assembly and consequently affecting vehicle safety.

[0003] To overcome the aforementioned shortcomings, developing a hot-pressurized forming die blank with weldable flanges along its axial length would effectively solve the problem. During welding, the flanged tubular component can utilize the same welding method as other die blanks in the vehicle, avoiding the limitations of gap-filling welding and significantly improving the torsional stiffness of the welded assembly and overall vehicle safety. However, in practice, the following problems have been found in the forming process of flanged tubular components:

[0004] Flange forming is difficult, and the flange area needs to be formed by double-layer superposition. The control of cross-sectional line length fluctuation is complicated and can easily lead to uneven material distribution.

[0005] Poor mold adaptability; existing molds are difficult to coordinate the control of 3D bending cross-section and flange forming, which can easily lead to insufficient flange precision or cavity deformation.

[0006] Therefore, there is an urgent need for a new flanged 3D curved tube blank forming process to meet the modern automotive industry's demand for lightweight, high-strength structural components. Summary of the Invention

[0007] To address the shortcomings of the aforementioned technologies, this invention provides a hot air pressure forming process and mold for 3D curved tubular blanks with flanges.

[0008] To solve the above technical problems, the technical solution adopted by the present invention is: a hot air pressure forming process for a flanged 3D bent tubular preform, comprising the following steps:

[0009] Step 1: Optimize product design to verify that it meets the flange forming conditions;

[0010] Step 2: Bend the straight tube blank into a tube shape;

[0011] Step 3: Place the bent pipe blank into a preforming mold for flange preforming;

[0012] Step 4: Place the pre-formed flange blank into a hot air forming mold for hot air forming of the flange.

[0013] Furthermore, the flange forming conditions in step one are determined by calculating the length of each section in the axial direction of the product and verifying whether it meets the requirement that the fluctuation rate of the section length is within 15%. If it meets the requirement, proceed to step two; if it does not, optimize the section length of the straight tube blank by adjusting the width of the formed welded flange to ensure that the fluctuation rate of the section length is controlled within 15%.

[0014] Furthermore, the straight tube blank to be formed in step one is a round tube blank or a square tube blank.

[0015] Furthermore, step two, the bending of the straight tube blank, involves bending the straight tube blank according to the axial shape of the mold blank to form a preliminary 3D bending structure.

[0016] Furthermore, in step three, flange preforming involves placing the bent pipe blank into a preforming mold. At room temperature, the double-layer welded flange area is preformed using the press force and mold constraint of the preforming mold, thus completing the initial forming of 90% of the flange's dimensions and shape.

[0017] Furthermore, in step four, the flange hot pneumatic forming involves heating the pre-formed tube blank to the target temperature to soften it and reduce its deformation resistance; the heated tube blank is then placed into the hot pneumatic forming mold, and the mold blank is deformed by the internal high-pressure gas to accurately form the cavity dimensions; the hot pneumatic forming mold is then used to finish the flange area and improve the flange accuracy.

[0018] A preforming mold in a hot air pressure forming process for a flanged 3D curved tubular preform includes an upper mold insert mounted on a top plate and a lower mold insert mounted on a bottom plate. The upper tube blank semi-groove of the upper mold insert and the lower tube blank semi-groove of the lower mold insert together form a flange preforming space.

[0019] Furthermore, the preforming mold also includes an upper pressure head and a lower pressure head. The upper pressure head is movably connected to the top plate via a nitrogen spring. The initial position of the upper pressure head is driven by the nitrogen spring, causing one side of the upper pressure head space to descend relative to the upper mold insert, and causing the upper tube blank semi-groove of the upper mold insert to be vertically misaligned with the side of the upper pressure head that forms the pressure head space. The lower pressure head is connected to the bottom plate. The side of the lower pressure head that forms the pressure head space is aligned with the lower tube blank semi-groove of the lower mold insert. The descending upper pressure head pre-presses the hot metal tube blank placed on the lower pressure head. The preformed tube blank and flange area blank are formed by the double-layer superposition of the pressure head space and the flange preforming space.

[0020] A hot pneumatic forming mold for a 3D curved tubular blank with a flange is disclosed. The hot pneumatic forming mold includes an upper mold system and a lower mold system. The upper mold system and the lower mold system are stacked in two layers to form a flange hot pneumatic forming space. The second upper pressure head of the upper mold system and the second lower pressure head of the lower mold system pre-press each other to form a second pressure head space. The formed tube blank and the flange area blank are formed by the double-layer stacking of the second pressure head space and the flange hot pneumatic forming space.

[0021] Furthermore, the ports of the second pressure head space are connected to a sealing and inflation system located on the lower mold system. The sealing and inflation system drives the sealing punch connected to the external air supply end through the cylinder pressure assembly to press and inflate the port of the flanged tube blank.

[0022] This invention discloses a hot pneumatic forming process and mold for 3D curved tubular blanks with flanges. Through innovations in segmented control, efficient forming, and quality assurance, it overcomes technical challenges in traditional processes such as difficult flange forming, poor mold adaptability, and insufficient welding strength, demonstrating significant inventiveness. By employing a combined hot and cold forming process and innovative mold design, high-precision and high-efficiency forming of 3D curved tubular parts with flanges is achieved, meeting the demands of the modern automotive industry for lightweight, high-strength structural components. Attached Figure Description

[0023] Figure 1 This is a process flow diagram of the present invention.

[0024] Figure 2 This is a schematic diagram of the overall structure of the hot air pressure forming mold of the present invention.

[0025] Figure 3 This is a schematic diagram of the structure after the No. 2 upper mold insert and the No. 2 lower mold insert are joined together.

[0026] Figure 4 This is a schematic diagram of the structure after the No. 2 upper pressure head and the No. 2 lower pressure head are closed.

[0027] Figure 5 This is a schematic diagram of the lower mold system.

[0028] Figure 6 This is a schematic diagram of a sealed inflation system.

[0029] Figure 7 This is a schematic diagram showing the state of a round tube blank after bending and forming.

[0030] Figure 8 This is a schematic diagram of the overall structure of the preforming mold of the present invention.

[0031] Figure 9This is a schematic diagram of the upper mold of the preforming mold of the present invention.

[0032] Figure 10 This is a schematic diagram showing the final state of the round tube blank after flange forming.

[0033] In the diagram: 110a, Upper die insert No. 1; 120a, Top plate No. 1; 130a, Upper pressure head No. 1; 140a, Nitrogen spring No. 3; 210a, Lower die insert No. 1; 220a, Base plate No. 1; 230a, Lower pressure head No. 1; A, Upper die system; B, Lower die system; C, Sealing and inflation system; 110, Upper die insert No. 2; 111, Upper tube blank semi-groove; 120, Top plate No. 2; 130, Upper pressure head No. 2; 140, Nitrogen spring No. 1; 150 1. Upper die guide sleeve; 210. Second lower die insert; 211. Lower tube blank semi-groove; 220. Second base plate; 230. Second lower pressure head; 240. Lower die guide post; 310. Second pressure head space; 320. Flange hot air pressure forming space; 400. Hydraulic cylinder; 410. Hydraulic cylinder mounting base; 420. Connecting disc; 430. Second nitrogen spring; 440. High-pressure air pipe; 450. Sealing docking disc; 460. Moving guide post; 470. Sealing punch. Detailed Implementation

[0034] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0035] like Figure 1 The hot air pressure forming process for a flanged 3D bent tubular preform shown includes the following four steps:

[0036] Step 1: Optimize the product design to verify that the flange forming conditions are met. This involves designing the straight tube blank to be formed to verify that it meets the flange forming conditions. The flange forming conditions are determined by calculating the diameter of the straight tube blank and verifying whether it meets the requirement that the cross-sectional length fluctuation rate is within 15%. If it meets the requirements, proceed to Step 2. If it does not meet the requirements, optimize the cross-sectional length of the straight tube blank by adjusting the width of the welded flange to ensure that the cross-sectional length fluctuation rate is controlled within 15%. The straight tube blank to be formed can be a round tube blank or a square tube blank.

[0037] Table 1 shows example data on optimizing the cross-sectional length of a straight tube blank by adjusting the width of the formed welded flange in this embodiment. The data illustrates the relationship between the flange width, the rate of change of the cross-sectional length, and the final cross-sectional length.

[0038]

[0039] Table 1

[0040] Step two involves bending the straight tube blank into a tube shape. Specifically, the straight tube blank is bent according to the axial shape of the die blank to form a preliminary 3D bent structure. This step utilizes a CNC system to precisely control the bending machine, die, and testing equipment. Combined with material pretreatment and springback compensation technology, this achieves high-precision and high-efficiency tube bending processing. Figure 7 As shown, taking a round tube blank as an example, the state after the tube is bent is displayed.

[0041] Step three involves placing the bent pipe blank into a pre-forming mold for flange pre-forming; specifically, as shown... Figure 8 and Figure 9 As shown, the pipe blank formed by bending is placed into the preforming mold. Under normal temperature conditions, the double-layer superimposed welded flange area is preformed by the press force and mold constraint of the preforming mold, completing the preliminary forming of 90% of the flange size and shape. Among them, the preforming mold used in step three includes the first upper mold insert 110a installed on the first top plate 120a and the first lower mold insert 210a installed on the first bottom plate 220a. The upper pipe blank semi-groove of the first upper mold insert and the lower pipe blank semi-groove of the first lower mold insert together form the flange preforming space. The preforming mold also includes an upper pressure head 130a and a lower pressure head 230a. The upper pressure head 130a is movably connected to the top plate 120a via a nitrogen spring 140a. The initial position of the upper pressure head is driven by the nitrogen spring, causing one side of the upper pressure head space to descend relative to the upper mold insert 110a, and causing the upper tube blank semi-groove of the upper mold insert to be vertically misaligned with the side of the upper pressure head that forms the pressure head space. The lower pressure head is connected to the bottom plate, and the side of the lower pressure head that forms the pressure head space is aligned with the lower tube blank semi-groove of the lower mold insert. The descending upper pressure head pre-presses the hot metal tube blank placed on the lower pressure head. The preformed tube blank and flange area blank are formed by the double-layer superposition of the pressure head space and the flange preforming space. This process is called preforming flange, which involves placing the bent tube blank into a preforming mold (forming at room temperature), and using the force of the press and the constraint of the mold to press out 90% of the size and shape of the welded flange formed by the double layer stacking.

[0042] Step four involves placing the pre-formed flange blank into a hot pneumatic forming mold for hot pneumatic forming of the flange. Specifically, the pre-formed blank is heated to the target temperature to soften it and reduce its deformation resistance. The heated blank is then placed into the hot pneumatic forming mold, where high-pressure gas deforms the blank to precisely form the cavity dimensions. The hot pneumatic forming mold is then used to finish the flange area, improving flange accuracy. Figure 10 As shown, taking a round tube blank as an example, the final flange shape is shown.

[0043] It should be further explained that the forming process of flanged blanks is more complex than that of blanks without flanges. Pneumatic forming of blanks without flanges only requires considering the forming of the cavity, while blanks with flanges need to consider not only the cavity but also the flange area. The flange area is formed by double-layer stacking; therefore, when calculating the blank, the cross-sectional length of the stacked area must be accurately calculated, and the overall cross-sectional length along the axial length of the entire blank must be considered to ensure it is within the allowable range of the forming process (i.e., cross-sectional length fluctuation rate ≤ 15%). There are also significant differences in the forming methods: In the cold forming stage with flanges, external force is needed to roughly form the double-layered flange area to ensure that the flange dimensions meet 90% of the initial forming requirements. In the hot pneumatic forming stage, after heating and softening, high-pressure gas is used to refine the cavity and flange area, further improving the forming accuracy. This segmented forming process (cold forming + hot pneumatic forming) not only increases the complexity of the process steps but also places higher demands on mold design, material deformation control, and forming accuracy. By adjusting the flange stacking dimensions, optimizing the cross-sectional line length fluctuation rate, and combining the cold and hot co-forming process, high-precision and high-strength manufacturing of flanged mold blanks is finally achieved.

[0044] Therefore, the hot pneumatic forming mold employs an upper mold system and a lower mold system. These two systems are stacked in a double-layered manner to form the flange hot pneumatic forming space. The second upper pressure head of the upper mold system and the second lower pressure head of the lower mold system pre-press each other to form a second pressure head space. The formed tube blank and flange area blank are jointly formed through the double-layered stacking of the second pressure head space and the flange hot pneumatic forming space. The hot pneumatic forming mold also includes a sealing inflation system. This system uses a cylinder pressure assembly to drive a sealing punch connected to an external air supply end to press and inflate the port of the flanged tube blank.

[0045] Specifically, such as Figure 2-5 The illustrated 3D curved tubular preform hot pneumatic forming mold includes an upper mold system A, a lower mold system B, and a sealing and inflation system C. The upper mold system A and lower mold system B achieve mold opening and closing operations through longitudinal displacement, forming a double-layered flange hot pneumatic forming space after mold closing. The sealing and inflation system C drives a sealing punch through a cylinder pressure assembly to punch and inflate the tube preform end. A second upper mold insert 110 is fixedly connected to a second top plate 120 of the upper mold system. Four longitudinally arranged upper mold guide sleeves 150 are also provided on the second top plate 120 of the upper mold system to achieve longitudinal displacement of the upper mold system.

[0046] The second lower mold insert 210 is fixedly connected to the second base plate 220 of the lower mold system. Four lower mold guide posts 240 are matched on the second base plate 220 of the lower mold system. Each lower mold guide post 240 is slidably set in an upper mold guide sleeve 150 to realize the longitudinal displacement of the upper mold system above the lower mold system, and finally realize the mold closing of the second upper mold insert 110 and the second lower mold insert 210.

[0047] The upper die insert 110 forms an upper tube blank semi-groove 111, and the lower die insert 210 forms a lower tube blank semi-groove 211. Therefore, the upper die insert and the lower die insert match each other to form a mold, and the upper tube blank semi-groove 111 and the lower tube blank semi-groove 211 enclose the flange hot air pressure forming space.

[0048] The second upper pressure head 130 is movably connected to the top plate 120 via the first nitrogen spring 140. The initial position of the second upper pressure head 130 is driven by the first nitrogen spring 140, causing one side of the second pressure head space 310 to descend relative to the second upper mold insert 110, and causing the upper tube blank semi-groove 111 of the second upper mold insert 110 to be vertically misaligned with the side of the second pressure head 130 forming the second pressure head space 310. The second lower pressure head 230 is connected to the bottom plate 220. The side of the second lower pressure head 230 forming the second pressure head space 310 is aligned with the lower tube blank semi-groove 211 of the second lower mold insert 210. The descending second upper pressure head 130 pre-presses the hot metal tube blank placed on the second lower pressure head 230. Before mold closing, the hot metal tube blank is first placed in the lower tube blank semi-groove 211. The two ends of the hot metal tube blank are fixed in advance by the downward-protruding second upper pressure head 130, forming the second pressure head space 310 with the second lower pressure head 230. It closes the mold before the second upper mold insert 110 and the second lower mold insert 210, thereby better controlling the shape and position of the tube blank and creating more favorable conditions for subsequent pneumatic forming, thereby improving the forming effect. After the second pressure head space 310 is formed, the first nitrogen spring 140 of the second upper pressure head 130 is compressed. The reaction force generated by the first nitrogen spring 140 drives the second upper pressure head 130 to continuously press the second lower pressure head 230, ensuring the stability of the second pressure head space 310.

[0049] The cylinder pressure assembly includes a hydraulic cylinder 400, which is mounted on a hydraulic cylinder mounting base 410 connected to the base plate 220. A connecting disc 420 is fixedly connected to the hydraulic cylinder 400. The connecting disc 420 is movably connected to a sealing docking disc 450 via a second nitrogen spring 430. The sealing docking disc 450 moves at the upper limit of the connecting disc 420 via a movable guide post 460. A sealing punch 470 is connected to the piston end of the hydraulic cylinder 400. The sealing punch 470 is also movably inserted through the center of the sealing docking disc 450. The sealing punch 470 is connected to the air supply end via a high-pressure air pipe 440. The second upper pressure head 130 and the second lower pressure head 230 together form a sealing end groove at their ends. The center of the sealing end groove is the port of the second pressure head space 310. When stamping and inflating, the sealing mating disc 450 matches and abuts against the sealing end groove. The sealing punch 470, which is movably installed in the sealing mating disc, can pass through the sealing mating disc 450 and be stamped to the port of the second pressure head space 310.

[0050] The cylinder pressure assembly utilizes the thrust generated by the hydraulic cylinder 400 to achieve the docking of the sealing docking disc 450 with the sealing end groove of the second pressure head space 310. The hydraulic cylinder 400 is mounted on the hydraulic cylinder mounting seat 410 on the base plate 220. When the piston of the hydraulic cylinder 400 is activated, it pushes the connecting disc 420, which is movably connected to the sealing docking disc 450 via the second nitrogen spring 430. Under the limiting action of the movable guide post 460, the sealing docking disc 450 can move on the connecting disc 420, thereby achieving accurate docking with the sealing end groove. It should be understood that the movable guide post 460 can move within the guide hole on the connecting disc 420, and its limited displacement is achieved through the blocking action of its own stop and the guide hole. Simultaneously, the sealing punch 470 is connected to the air supply end through the high-pressure air pipe 440. When the sealing punch 470 passes through the center of the sealing docking disc 450, it can punch to the port of the second pressure head space 310, thereby achieving stamping and pneumatic forming. The advantage of this arrangement is that the hydraulic cylinder 400 can provide stable and controllable pressure, ensuring that the pressure can be precisely applied to the required position during stamping and pneumatic forming, improving forming accuracy. At the same time, the matching docking of the sealing docking disc 450 and the sealing end groove can effectively seal the port of the second pressure head space 310, preventing gas leakage and ensuring stable forming pressure. The coordinated operation of the hydraulic cylinders 400 on both sides and the sealing punch 470 enables rapid and efficient stamping and pneumatic forming, thereby improving the efficiency of the entire production process. Note that while one sealing punch 470 is inflating, the other side should remain non-deflated. This design ensures rapid pressure application to the tube blank during forming, contributing to improved dimensional consistency and surface quality of the forming die blank and flange. The hot pneumatic forming die, through the coordinated operation of the upper die system, lower die system, and sealing inflation system, achieves high-precision and high-efficiency forming of 3D bent tubular parts with flanges.

[0051] In summary, the main features of the process of this invention are:

[0052] Segmented control: By combining cold preforming and hot finishing, high-precision control of flange and cavity dimensions is ensured. Efficient forming: The hot pneumatic forming process simultaneously completes the finishing of the cavity and flange, reducing subsequent processing steps. Quality assurance: Cross-sectional line length fluctuation ≤15%, high flange forming accuracy, and significantly improved welding strength.

[0053] This invention employs a segmented forming process combining cold preforming and hot finishing. In the cold preforming stage, external force is used to roughly form the double-layered flange area, ensuring that the flange dimensions meet 90% of the initial forming requirements. In the hot gas pressure forming stage, after softening by heating, high-pressure gas is used to finish the cavity and flange area, further improving forming accuracy. This segmented forming process not only increases the complexity of the process steps but also places higher demands on mold design, material deformation control, and forming accuracy.

[0054] The preforming mold achieves preforming of the flange area through the double-layer superposition of an upper pressure head and a lower pressure head; the hot gas pressure forming mold forms the flange hot gas pressure forming space through the double-layer superposition of an upper mold system and a lower mold system, and achieves precise high-pressure gas inflation forming through a sealed inflation system. These mold designs not only improve forming accuracy but also significantly enhance production efficiency.

[0055] Meanwhile, by precisely calculating the diameter of the straight tube blank and verifying whether it meets the requirement that the cross-sectional length fluctuation rate is within 15%, the cross-sectional length of the straight tube blank was optimized, ensuring the uniformity of material distribution. This method of controlling cross-sectional length fluctuation is innovative and effectively solves the forming defects caused by uneven material distribution in traditional processes.

[0056] In summary, a combined cold and hot forming process, integrating cold preforming and hot finishing, has enabled the manufacture of flanged die blanks with high precision and high strength. This combined cold and hot forming process not only improves forming accuracy but also significantly enhances welding strength and overall vehicle safety.

[0057] The above embodiments are not intended to limit the present invention, and the present invention is not limited to the examples given above. Any changes, modifications, additions or substitutions made by those skilled in the art within the scope of the technical solution of the present invention are also within the protection scope of the present invention.

Claims

1. A hot pneumatic forming process for a flanged 3D curved tubular preform, characterized in that, Includes the following steps: Step 1: Optimize product design to verify that it meets the flange forming conditions; Step 2: Bend the straight tube blank into a tube shape; Step 3: Place the bent pipe blank into a preforming mold for flange preforming; Step 4: Place the pre-formed flange blank into a hot air forming mold for hot air forming of the flange. The preforming mold in the hot air pressure forming process of the flanged 3D curved tube blank includes an upper mold insert installed on a top plate and a lower mold insert installed on a bottom plate. The upper tube blank semi-groove of the upper mold insert and the lower tube blank semi-groove of the lower mold insert together form a flange preforming space. The preforming mold also includes an upper pressure head and a lower pressure head. The upper pressure head is movably connected to a top plate via a nitrogen spring. The initial position of the upper pressure head is driven by the nitrogen spring, causing one side of the upper pressure head forming the pressure head space to descend relative to the upper mold insert. This causes the upper tube blank semi-groove of the upper mold insert to be vertically misaligned with the side of the upper pressure head forming the pressure head space. The lower pressure head is connected to a bottom plate. The side of the lower pressure head forming the pressure head space is aligned with the lower tube blank semi-groove of the lower mold insert. The descending upper pressure head pre-presses the hot metal tube blank placed on the lower pressure head. The preformed tube blank and flange area blank are formed by the double-layer superposition of the pressure head space and the flange preforming space.

2. The hot pneumatic forming process for a flanged 3D bent tubular preform according to claim 1, characterized in that: The flange forming conditions in step one are determined by calculating the length of each section in the axial direction of the product and verifying whether it meets the requirement that the fluctuation rate of the section length is within 15%. If it meets the requirement, proceed to step two; otherwise, adjust the width of the formed welded flange and optimize the length of the straight tube blank to ensure that the fluctuation rate of the section length is controlled within 15%.

3. The hot pneumatic forming process for a flanged 3D bent tubular preform according to claim 1 or 2, characterized in that: The straight tube blank to be formed in step one is either a round tube blank or a square tube blank.

4. The hot pneumatic forming process for a flanged 3D bent tubular preform according to claim 1, characterized in that: Step two, the bending forming of the straight tube blank, involves bending the straight tube blank according to the axial shape of the mold blank to form a preliminary 3D bending structure.

5. The hot pneumatic forming process for a flanged 3D bent tubular preform according to claim 1, characterized in that: The flange preforming in step three involves placing the bent pipe blank into a preforming mold. Under normal temperature conditions, the double-layer welded flange area is preformed using the press force and mold constraint of the preforming mold, completing the initial forming of 90% of the flange's size and shape.

6. The hot pneumatic forming process for a flanged 3D bent tubular preform according to claim 1, characterized in that: The fourth step, flange hot pneumatic forming, involves heating the pre-formed tube blank to the target temperature to soften it and reduce its deformation resistance; placing the heated tube blank into the hot pneumatic forming mold, and using the internal high-pressure gas to deform the blank to accurately form the cavity dimensions; and using the hot pneumatic forming mold to finish the flange area and improve the flange accuracy.

7. The hot pneumatic forming process for a flanged 3D bent tubular preform according to claim 6, characterized in that: The hot air pressure forming mold includes an upper mold system and a lower mold system. The upper mold system and the lower mold system are stacked in two layers to form a flange hot air pressure forming space. The second upper pressure head of the upper mold system and the second lower pressure head of the lower mold system pre-press each other to form a second pressure head space. The formed tube blank and flange area mold blank are jointly formed by the double layer superposition of the second pressure head space and the flange hot air pressure forming space.

8. The hot pneumatic forming process for a flanged 3D bent tubular preform according to claim 7, characterized in that: The ports of the second pressure head space are respectively connected to a sealing and inflation system located on the lower mold system. The sealing and inflation system drives the sealing punch connected to the external air supply end through the cylinder pressure assembly to press and inflate the port of the flanged tube blank.

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