Hot-state air pressure forming process and mold for 3D bent pipe mold blank with flange

Abstract

The invention discloses a hot-state air pressure forming process and a hot-state air pressure forming die for a 3D bent pipe die blank with a flange, and the hot-state air pressure forming process comprises the following steps: step 1, optimizing product design to verify that a flange forming condition is met; secondly, the pipe blank is subjected to pipe bending forming; thirdly, a pipe blank formed by the bent pipe is placed in a pre-forming die to be subjected to flange pre-forming; and fourthly, the preformed pipe blank is placed in a hot-state air pressure forming die to be subjected to flange hot-state air pressure forming. Through segmented control, a cold and hot synergistic forming process and innovative mold design, the technical problems that in a traditional process, flanges are difficult to form, mold adaptability is poor, welding strength is insufficient and the like are solved, high-precision and high-efficiency forming is achieved, and the requirements of the modern automobile industry for light-weight and high-strength structural parts are met.

Description

Technical Field

[0001] The invention relates to a pneumatic forming die and a forming process, and in particular to a hot pneumatic forming process and a die for a 3D curved tube mold blank with a flange. Background Art

[0002] In traditional hot gas forming technology, there are many limitations in the design and manufacture of tubular molds, especially in terms of welding process and vehicle safety. When tubular parts are welded to other molds, they can usually only be welded by filling the gap between the two molds. This welding method not only limits the flexibility of vehicle design, but also reduces the overall torsional stiffness of the welded assembly due to insufficient welding strength, thus affecting the safety of the vehicle.

[0003] In order to overcome the above defects, if a hot gas pressure forming die with a welding flange on the axial length of the tubular die can be developed, the above problems can be effectively solved. When welding the tubular parts with flanges, the same welding method can be used as other die blanks of the whole vehicle, avoiding the limitations of gap filling welding, and significantly improving the torsional stiffness of the welding assembly and the safety of the whole vehicle. However, in practice, it is found that the forming process of tubular parts with flanges has the following problems:

[0004] Flange forming is difficult, the flange area needs to be formed by double-layer stacking, and the cross-section line length fluctuation control is complex, which can easily lead to uneven material distribution;

[0005] The mold adaptability is poor, and the existing mold is difficult to take into account the coordinated control of 3D bending variable cross-section and flange forming, which can easily lead to insufficient flange accuracy or cavity deformation.

[0006] Therefore, a new flanged 3D curved tube blank forming process is urgently needed to meet the modern automotive industry's demand for lightweight, high-strength structural parts. Summary of the invention

[0007] In order to solve the shortcomings of the above-mentioned technology, the present invention provides a hot gas pressure forming process and a mold for a 3D curved tube mold blank with a flange.

[0008] In order to solve the above technical problems, the technical solution adopted by the present invention is: a hot gas pressure forming process of a 3D curved tube mold blank with a flange, comprising the following steps:

[0009] Step 1: Optimize product design to verify that flange forming conditions are met;

[0010] Step 2, bending the straight tube blank into a tube;

[0011] Step 3, placing the tube blank formed by bending the tube into a preforming mold for flange preforming;

[0012] Step 4: placing the flange preformed tube blank in a hot gas pressure forming mold for hot gas pressure forming of the flange.

[0013] Furthermore, the flange forming condition in step one is to calculate the length of each cross-section line in the axial direction of the product and verify whether it meets the requirement that the fluctuation rate of the cross-section line length is within 15%. If it is satisfied, step two is executed; if not, the width of the formed welding flange is adjusted to optimize the cross-section line length of the straight tube blank to ensure that the fluctuation rate of the cross-section line length is controlled within 15%.

[0014] Furthermore, the linear tube blank to be formed in step 1 is a round tube blank or a square tube blank.

[0015] Furthermore, in step 2, the straight tube blank is bent according to the axial shape of the mold blank to form a preliminary 3D bent structure.

[0016] Furthermore, the flange preforming in step three is to place the bent tube blank into the preforming mold, and preform the double-layer superimposed welded flange area at room temperature with the help of the press force and mold constraint of the preforming mold to complete the preliminary forming of 90% of the size and shape of the flange.

[0017] Furthermore, in step four, the hot gas pressure forming of the flange is to heat the preformed tube to the target temperature to soften it and reduce its deformation resistance; the heated tube is placed in a hot gas pressure forming mold, and the mold is deformed to accurately form the cavity size by the internal high-pressure gas, and the hot gas pressure forming mold is used to perform finishing on the flange area to improve the flange accuracy.

[0018] A preforming mold in a hot gas pressure forming process for a 3D curved tube blank with a flange includes an upper mold insert No. 1 installed on a top plate No. 1 and a lower mold insert No. 1 installed on a bottom plate No. 1. The upper tube blank half groove of the No. 1 upper mold insert and the lower tube blank half groove of the No. 1 lower mold insert together form a flange preforming space.

[0019] Furthermore, the preforming mold also includes an upper ram No. 1 and a lower ram No. 1. The upper ram No. 1 is movably connected to the No. 1 top plate through a No. 3 nitrogen spring. The initial position of the upper ram No. 1 is driven by the No. 3 nitrogen spring to form one side of the No. 1 ram space and to move downward relative to the No. 1 upper mold insert, and to make the upper tube blank half groove of the No. 1 upper mold insert and the side of the No. 1 ram space formed by the No. 1 upper ram misaligned up and down; the No. 1 lower ram is connected to the No. 1 bottom plate, and one side of the No. 1 ram space formed by the No. 1 lower ram is aligned with the lower tube blank half groove of the No. 1 lower mold insert. The downward-protruding upper ram No. 1 pre-presses the hot metal tube mold blank placed on the No. 1 lower ram, and the preformed tube blank and flange area mold blank are formed by the double-layer superposition of the No. 1 ram space and the flange preforming space.

[0020] A hot pneumatic forming mold in a hot pneumatic forming process for a 3D curved tube mold with a flange, the hot pneumatic forming mold comprising an upper mold system and a lower mold system, the upper mold system and the lower mold system are opened and closed to form a double-layer superposition to form a flange hot pneumatic forming space, a No. 2 upper pressure head of the upper mold system and a No. 2 lower pressure head of the lower mold system are pre-pressed to form a No. 2 pressure head space, and the formed tube blank and flange area mold blank are formed by the double-layer superposition of the No. 2 pressure head space and the flange hot pneumatic forming space.

[0021] Furthermore, the ports of the No. 2 pressure head space are respectively connected to a sealing inflation system located on the lower die system. The sealing inflation system drives a sealing punch connected to the external air supply end through a cylinder pressure component to punch and inflate the port of the flanged tube blank.

[0022] The present invention discloses a hot gas pressure forming process and mold for a flanged 3D curved tube mold blank. Through innovations in segmented control, efficient forming, quality assurance, etc., it overcomes the technical difficulties of flange forming difficulties, poor mold adaptability, insufficient welding strength, etc. in traditional processes, and has significant creativity. Through the hot and cold collaborative forming process and innovative mold design, high-precision and high-efficiency forming of flanged 3D curved tube parts is achieved, meeting the needs of the modern automotive industry for lightweight and high-strength structural parts. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a process flow chart of the present invention.

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

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

[0026] Figure 4 It is a schematic diagram of the structure after the No. 2 upper ram and the No. 2 lower ram are molded together.

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

[0028] Figure 6 It is a structural diagram of the sealing and inflation system.

[0029] Figure 7 It is a schematic diagram of the state of the round tube billet after bending.

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

[0031] Fig. 9It is a structural schematic diagram of the upper mold of the preforming mold of the present invention.

[0032] Fig.10 This is a schematic diagram of the state of the round tube blank after the final flange is formed.

[0033] In the figure: 110a, No. 1 upper die insert; 120a, No. 1 top plate; 130a, No. 1 upper pressure head; 140a, No. 3 nitrogen spring; 210a, No. 1 lower die insert; 220a, No. 1 bottom plate; 230a, No. 1 lower pressure head; A, upper die system; B, lower die system; C, sealing and inflating system; 110, No. 2 upper die insert; 111, upper tube blank half groove; 120, No. 2 top plate; 130, No. 2 upper pressure head; 140, No. 1 nitrogen spring; 150 , upper die guide sleeve; 210, No. 2 lower die insert; 211, lower tube blank semi-groove; 220, No. 2 bottom plate; 230, No. 2 lower ram; 240, lower die guide column; 310, No. 2 ram space; 320, flange hot gas pressure forming space; 400, hydraulic cylinder; 410, hydraulic cylinder mounting seat; 420, connecting disc; 430, No. 2 nitrogen spring; 440, high-pressure air pipe; 450, sealing docking disc; 460, movable guide column; 470, sealing punch. DETAILED DESCRIPTION

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

[0035] like Figure 1 The hot gas pressure forming process of a flanged 3D curved tube blank shown in the figure includes the following four steps:

[0036] Step 1: optimize product design to verify that flange forming conditions are met, that is, the linear tube blank to be formed is designed to verify that flange forming conditions are met. The flange forming conditions are calculated by calculating the diameter of the linear tube blank and verifying whether it meets the requirement that the fluctuation rate of the cross-sectional line length is within 15%. If it is satisfied, step 2 is executed; if not, the cross-sectional line length of the linear tube blank is optimized by adjusting the width of the formed welding flange to ensure that the fluctuation rate of the cross-sectional line length is controlled within 15%; wherein, the linear tube blank to be formed adopts a round tube blank or a square tube blank;

[0037] Table 1 is an example data of optimizing the cross-sectional length of a straight tube blank by adjusting the width of a formed welding flange in this embodiment, and the data shows the relationship between the flange width, the cross-sectional length change rate, and the final cross-sectional length;

[0038]

[0039] Table 1

[0040] Step 2: bend the straight tube blank into shape; specifically, bend the straight tube blank according to the axial shape of the mold blank to form a preliminary 3D bending structure; this step can achieve high-precision and high-efficiency tube bending processing by accurately controlling the tube bending machine, mold and testing equipment through the CNC system, combined with material pretreatment and rebound compensation technology, such as Figure 7 As shown, taking the round tube blank as an example, the state of the bent tube after forming is shown.

[0041] Step 3: Place the tube blank formed by bending the tube into a preforming mold for flange preforming; specifically, Figure 8 and Fig. 9 As shown, the tube blank formed by the bent tube is placed in the preforming mold, and the double-layer superimposed welding flange area is preformed at room temperature with the help of the press force and mold constraint of the preforming mold to complete the preliminary forming of 90% of the size and shape of the flange; wherein, the preforming mold used in step three includes an upper mold insert 110a installed on a top plate 120a and a lower mold insert 210a installed on a bottom plate 220a, and the upper tube blank half groove of the No. 1 upper mold insert and the lower tube blank half groove of the No. 1 lower mold insert are enclosed to form a flange preforming space. The preforming mold also includes an upper ram 130a No. 1 and a lower ram 230a No. 1. The upper ram 130a is movably connected to the top plate 120a No. 1 through a nitrogen spring 140a. The initial position of the upper ram No. 1 is driven by the nitrogen spring No. 1 so that one side of the No. 1 ram space is downwardly moved relative to the upper die insert 110a, and the upper tube blank half groove of the No. 1 upper die insert and the side of the No. 1 ram space formed by the upper ram No. 1 are misaligned up and down; the lower ram No. 1 is connected to the bottom plate No. 1, and one side of the No. 1 ram space formed by the lower ram No. 1 is aligned with the lower tube blank half groove of the No. 1 lower die insert. The lowered upper ram No. 1 pre-presses the hot metal tube mold blank placed on the lower ram No. 1, and the preformed tube blank and the flange area mold blank are formed by the double-layer superposition of the No. 1 ram space and the flange preforming space. This process is the pre-forming of the flange, that is, putting the bent tube into the pre-forming die (forming at room temperature), and using the force of the press and the constraint of the die to press out 90% of the size and shape of the welded flange formed by the double-layer superposition;

[0042] Step 4: Place the preformed tube blank of the flange in a hot air forming mold for hot air forming of the flange. Specifically, heat the preformed tube blank to the target temperature to soften it and reduce its deformation resistance; place the heated tube blank in the hot air forming mold, use the internal high-pressure gas to deform the mold blank to accurately form the cavity size, and use the hot air forming mold to perform finishing on the flange area to improve the flange accuracy. Fig.10 As shown, taking the round tube blank as an example, the final flange is shown after forming.

[0043] It should be further explained that the forming process of the mold with flange is more complicated than that of the mold without flange. The pneumatic forming of the mold without flange only needs to consider the forming of the cavity in place, while the mold with flange needs to consider not only the forming of the cavity, but also the forming of the flange area. The flange area is formed by double-layer superposition. Therefore, when calculating the tube, the cross-sectional line length of the superposition area must be accurately calculated, and the overall cross-sectional line length in the axial length direction of the entire mold must be coordinated to ensure that it is within the range allowed by the forming process (that is, the cross-sectional line length fluctuation rate ≤15%). There are also significant differences in the forming methods of the two: cold forming stage with flange: external force is required to roughly form the double-layer superimposed flange area to ensure that the flange size reaches 90% of the initial forming requirements. Hot pneumatic forming stage: after heating and softening, the cavity and flange area are refined by high-pressure gas to further improve the forming accuracy. This segmented forming process (cold forming + hot pneumatic forming) not only increases the complexity of the process steps, but also puts higher requirements on mold design, material deformation control and forming accuracy. By adjusting the flange stacking size, optimizing the cross-sectional line length fluctuation rate, and combining the hot and cold collaborative forming process, high-precision and high-strength manufacturing of flanged mold blanks can be ultimately achieved.

[0044] Therefore, the hot gas pressure forming mold includes an upper mold system and a lower mold system, and the upper mold system and the lower mold system are opened and closed to form a flange hot gas pressure forming space. The No. 2 upper pressure head of the upper mold system and the No. 2 lower pressure head of the lower mold system are pre-pressed to form a No. 2 pressure head space. The formed tube blank and flange area mold blank are formed by the double-layer superposition of the No. 2 pressure head space and the flange hot gas pressure forming space. The hot gas pressure forming mold also includes a sealing and inflation system, which drives the sealing punch connected to the external air supply end through the cylinder pressure component to punch and inflate the port of the flanged tube blank.

[0045] Specifically, Figure 2-5 The hot pneumatic forming mold for a variable-section 3D curved tube-like mold blank shown in the figure includes an upper mold system A, a lower mold system B, and a sealing and inflating system C. The upper mold system A and the lower mold system B realize the opening and closing operation through longitudinal displacement, and a double-layered flange hot pneumatic forming space is formed after the mold is closed. The sealing and inflating system C drives the sealing punch through the cylinder pressure component to punch and inflate the tube blank port. The No. 2 upper mold insert 110 is fixedly connected to the No. 2 top plate 120 of the upper mold system. Four upper mold guide sleeves 150 arranged in the longitudinal direction are also arranged on the No. 2 top plate 120 of the upper mold system to realize the longitudinal displacement of the upper mold system.

[0046] The No. 2 lower mold insert 210 is fixedly connected to the No. 2 base plate 220 of the lower mold system. Four lower mold guide pillars 240 are matched and arranged on the No. 2 base plate 220 of the lower mold system. Each lower mold guide pillar 240 is slidably arranged 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 No. 2 upper mold insert 110 and the No. 2 lower mold insert 210.

[0047] An upper tube blank half groove 111 is formed on the No. 2 upper mold insert 110, and a lower tube blank half groove 211 is formed on the No. 2 lower mold insert 210. Therefore, the No. 2 upper mold insert and the No. 2 lower mold insert match each other to form a mold, and the upper tube blank half groove 111 and the lower tube blank half groove 211 together form a flange hot gas pressure forming space.

[0048] The No. 2 upper ram 130 is movably connected to the top plate 120 through the No. 1 nitrogen spring 140. The initial position of the No. 2 upper ram 130 is driven by the No. 1 nitrogen spring 140 to move downward relative to the No. 2 upper die insert 110 on one side of the No. 2 upper ram 130 to form the No. 2 ram space 310, and to make the upper tube blank half groove 111 of the No. 2 upper die insert 110 and the No. 2 upper ram 130 form the No. 2 ram space 310. The No. 2 lower ram 230 is connected to the bottom plate 220, and the No. 2 lower ram 230 forms the No. 2 ram space 310 on one side and is aligned with the lower tube blank half groove 211 of the No. 2 lower die insert 210. The downward-moving No. 2 upper ram 130 pre-presses the hot metal tube mold blank placed on the No. 2 lower ram 230. Before mold closing, the hot metal tube mold blank is first placed in the lower tube blank semi-groove 211, and the two ends of the hot metal tube mold blank are fixed in advance by the No. 2 upper ram 130 that is protruding downward, forming a No. 2 ram space 310 with the No. 2 lower ram 230, and the mold is closed before the No. 2 upper mold insert 110 and the No. 2 lower mold insert 210, so as to better control the shape and position of the tube blank, create more favorable conditions for subsequent gas pressure forming, and thus improve the forming effect. After the No. 2 ram space 310 is formed, the No. 1 nitrogen spring 140 of the No. 2 upper ram 130 is compressed, and the reaction generated by the No. 1 nitrogen spring 140 drives the No. 2 upper ram 130 to continuously press the No. 2 lower ram 230, thereby ensuring the stability of the No. 2 ram space 310.

[0049] The cylinder pressure assembly includes a hydraulic cylinder 400, which is mounted on a hydraulic cylinder mounting seat 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 through a No. 2 nitrogen spring 430. The sealing docking disc 450 moves to the upper limit position of the connecting disc 420 through a movable guide column 460. A sealing punch 470 is connected to the piston end of the hydraulic cylinder 400. The sealing punch 470 is also movably arranged in the center of the sealing docking disc 450. The sealing punch 470 is connected to the air supply end through a high-pressure air pipe 440. The No. 2 upper pressure head 130 and the No. 2 lower pressure head 230 jointly form a sealing end groove at the end, and the center of the sealing end groove is the port of the No. 2 pressure head space 310. During stamping and inflation, the sealing docking disc 450 matches and abuts against the sealing end groove, and the sealing punch 470 movably inserted in the sealing docking disc can pass through the sealing docking disc 450 and punch to the port of the No. 2 pressure head space 310.

[0050] The cylinder pressure assembly uses 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 bottom plate 220. When the piston of the hydraulic cylinder 400 is activated, it pushes the connecting disc 420, and the connecting disc 420 is movably connected to the sealing docking disc 450 through 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, so as to achieve accurate docking with the sealing end groove. It should be understood that the movable guide post 460 can move in the guide hole on the connecting disc 420, and realize the limited displacement of the movable guide post 460 through the blocking action of its own block and the guide hole. At the same time, 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 be punched to the port of the second pressure head space 310, so as to achieve stamping and inflation forming. The advantage of this arrangement is that the hydraulic cylinder 400 can provide stable and controllable pressure, ensuring that the pressure can be accurately applied to the required position during the stamping and inflation forming process, thereby improving the 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, prevent gas leakage, and ensure the stability of the forming pressure. Through the coordinated work of the hydraulic cylinders 400 and the sealing punches 470 on both sides, rapid and effective stamping and inflation forming can be achieved, thereby improving the efficiency of the entire production process. Note that when the sealing punch 470 on one side is inflated, the other side should remain in a non-deflated state. The above design ensures that pressure is quickly applied to the tube blank during the forming process, which helps to improve the dimensional consistency and surface quality of the forming die blank and flange. The hot gas pressure forming die achieves high-precision and high-efficiency forming of 3D curved tube parts with flanges through the coordinated work of the upper die system, the lower die system, and the sealing and inflation system.

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

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

[0053] The present invention adopts a segmented forming process that combines cold preforming with hot finishing. In the cold preforming stage, the double-layered flange area is roughly formed with the help of external force to ensure that the flange size reaches 90% of the initial forming requirements; in the hot gas pressure forming stage, after heating and softening, the cavity and flange area are finished with high-pressure gas to further improve the forming accuracy. This segmented forming process not only increases the complexity of the process steps, but also puts higher requirements on mold design, material deformation control and forming accuracy.

[0054] The preforming die realizes the preforming of the flange area through the double-layer superposition of the No. 1 upper pressure head and the No. 1 lower pressure head; the hot air pressure forming die forms the flange hot air pressure forming space through the double-layer superposition of the upper mold system and the lower mold system, and realizes the precise inflation of high-pressure gas through the sealed inflation system. These mold designs not only improve the forming accuracy, but also significantly improve the production efficiency.

[0055] At the same time, by accurately calculating the diameter of the straight tube and verifying whether it meets the requirement of section line length fluctuation rate within 15%, the section line length of the straight tube is optimized to ensure the uniformity of material distribution. This section line length fluctuation control method is creative and effectively solves the forming defects caused by uneven material distribution in traditional processes.

[0056] In summary, the hot-cold synergistic forming process combining cold preforming with hot finishing has achieved high-precision and high-strength manufacturing of flanged mold blanks. This hot-cold synergistic forming process not only improves the forming accuracy, but also significantly improves the welding strength and vehicle safety.

[0057] The above implementation modes are not limitations of the present invention, and the present invention is not limited to the above examples. Changes, modifications, additions or substitutions made by technicians in this technical field within the scope of the technical solution of the present invention also belong to the protection scope of the present invention.

Claims

1. A hot gas pressure forming process for a 3D curved tube mold with flange, characterized in that: The following steps are involved: Step 1: Optimize product design to verify that flange forming conditions are met; Step 2, bending the straight tube blank into a tube; Step 3, placing the tube blank formed by bending the tube into a preforming mold for flange preforming; Step 4: placing the flange preformed tube blank in a hot gas pressure forming mold for hot gas pressure forming of the flange.

2. The hot gas pressure forming process of the flanged 3D curved tube mold blank according to claim 1, characterized in that: The flange forming condition in the step one is to calculate the length of each cross-section line in the axial direction of the product and verify whether it meets the requirement that the fluctuation rate of the cross-section line length is within 15%. If it meets the requirement, step two is executed; if not, the cross-section line length of the straight tube blank is optimized by adjusting the width of the formed welding flange to ensure that the fluctuation rate of the cross-section line length is controlled within 15%.

3. The hot gas pressure forming process of the flanged 3D curved tube mold blank according to claim 1 or 2, characterized in that: The linear tube blank to be formed in the step 1 is a round tube blank or a square tube blank.

4. The hot gas pressure forming process of the flanged 3D curved tube mold blank according to claim 1, characterized in that: The second step of bending the straight tube blank is to bend the straight tube blank according to the axial shape of the mold blank to form a preliminary 3D bending structure.

5. The hot gas pressure forming process of the flanged 3D curved tube mold blank according to claim 1, characterized in that: The flange preforming in step three is to place the bent tube blank into a preforming mold, and preform the double-layer superimposed welding flange area at room temperature with the help of the press force and mold constraint of the preforming mold to complete the preliminary forming of 90% of the size and shape of the flange.

6. The hot gas pressure forming process of the flanged 3D curved tube mold blank according to claim 1, characterized in that: The flange hot gas forming in step 4 is to heat the preformed tube to the target temperature to soften it and reduce its deformation resistance; the heated tube is placed in a hot gas forming mold, and the mold is deformed by the internal high-pressure gas to accurately form the cavity size, and the hot gas forming mold is used to perform finishing on the flange area to improve the flange accuracy.

7. A preforming die in a hot gas pressure forming process for a flanged 3D curved tube-like mold blank as claimed in claim 1, characterized in that: The preforming mold includes an upper mold insert No. 1 installed on a top plate No. 1 and a lower mold insert No. 1 installed on a bottom plate. The upper tube blank half groove of the No. 1 upper mold insert and the lower tube blank half groove of the No. 1 lower mold insert together form a flange preforming space.

8. The hot gas pressure forming process of the flanged 3D curved tube mold blank according to claim 7, characterized in that: The preforming mold also includes an upper ram No. 1 and a lower ram No. 1, and the upper ram No. 1 is movably connected to the top plate No. 1 through a nitrogen spring No.

3. The initial position of the upper ram No. 1 is driven by the nitrogen spring No. 3 so that one side of the No. 1 ram space is formed and moved downward relative to the No. 1 upper mold insert, and the upper tube blank half groove of the No. 1 upper mold insert and the side of the No. 1 ram space formed by the upper ram No. 1 are misaligned up and down; the lower ram No. 1 is connected to the bottom plate No. 1, and one side of the No. 1 ram space formed by the lower ram No. 1 is aligned with the lower tube blank half groove of the No. 1 lower mold insert, and the lowered upper ram No. 1 pre-presses the hot metal tube mold blank placed on the No. 1 lower ram, and the preformed tube blank and the flange area mold blank are formed by the double-layer superposition of the No. 1 ram space and the flange pre-forming space.

9. A hot gas pressure forming die in a hot gas pressure forming process for a 3D curved tube-like mold blank with flange as claimed in claim 1, characterized in that: The hot pneumatic forming mold includes an upper mold system and a lower mold system, and the upper mold system and the lower mold system are opened and closed to form a double-layer superposition to form a flange hot pneumatic forming space. The No. 2 upper pressure head of the upper mold system and the No. 2 lower pressure head of the lower mold system are pre-pressed to form a No. 2 pressure head space, and the formed tube blank and flange area mold blank are formed by the double-layer superposition of the No. 2 pressure head space and the flange hot pneumatic forming space.

10. The hot gas pressure forming process of the flanged 3D curved tube mold blank according to claim 9, characterized in that: The ports of the No. 2 pressure head space are respectively connected to a sealing and inflation system located on the lower die system. The sealing and inflation system drives a sealing punch connected to the external air supply end through a cylinder pressure component to punch and inflate the port of the flanged tube blank.

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