An additional air pressure assisted device and method for hot forming of a profiled thin-walled tube

Abstract

The application discloses a kind of additional air pressure auxiliary special-shaped thin-walled pipe fitting hot forming device and method, belong to metal component forming manufacturing technical field, using resistance heating metal pipe material, control heating rate and temperature obtain electric plasticity and good microstructure, improve forming performance;Pipe material forming stage can control the rate of pressure loading and the size of pressure in pipe, realize the synergistic effect of strain hardening and strain rate hardening of titanium alloy hot forming, effectively improve the uniformity of pipe fitting wall thickness;Quenching stage in mould carries out zoning temperature control to mould, controls the quenching cooling rate of forming pipe fitting, obtains gradient structure according to the performance requirement of different deformation zone of component;Forming pipe fitting occurs stress relaxation under the action of temperature and pressure, wherein, additional tensile stress is generated by internal pressure, prestress is applied by horizontal cylinder axial loading, promotes stress relaxation to form under the joint action of deformation and high temperature, reduces residual stress, reduces springback, improves the strength and dimensional accuracy of forming pipe fitting.

Description

Technical Field

[0001] This invention relates to the field of metal component forming and manufacturing technology, and in particular to a thermoforming apparatus and method for irregularly shaped thin-walled tubes with additional pneumatic assistance. Background Technology

[0002] Titanium alloy and high-temperature alloy shaped thin-walled metal tubing are key components in high-end aerospace equipment, such as aero-engine air intakes and high-thrust rocket engine nozzles. For different applications, commonly used raw materials include titanium alloys, heat-resistant high-strength steel, and high-temperature alloys. These materials have high deformation resistance at room temperature and low limiting expansion rates. However, the parts have low elastic modulus, high springback, and poor dimensional accuracy after forming. Therefore, traditional cold forming methods such as internal high-pressure forming are difficult to manufacture these complex shapes, requiring higher forming temperatures to improve forming performance and accuracy. Currently, existing conventional forming methods mainly include weld forming, superplastic forming, and hot gas forming.

[0003] Welding involves stamping thin metal sheets into annular semi-shells, then welding the edges together after edge correction. Its disadvantages include significant springback in stamped parts, low dimensional accuracy, uneven deformation in the weld and heat-affected zone, high welding difficulty, and complex microstructure evolution at the weld, resulting in significantly weakened properties compared to the base material. Subsequent heat treatment is required to further stabilize the microstructure and eliminate residual welding stress. Compared to integral forming, the formed components have lower strength coefficients, and their microstructure, properties, and dimensional accuracy are difficult to control precisely, making it difficult to meet the high reliability and integrated development requirements of high-end equipment.

[0004] Superplastic forming utilizes the high elongation of metallic materials under specific temperature and strain rate conditions to achieve integral forming of tubular components with complex cross-sections. However, superplastic forming involves high forming temperatures and slow deformation rates, resulting in significant wall thickness inconsistencies and performance degradation in the formed tubular components. Furthermore, it is limited to fine-grained materials and equipment dimensions, leading to high manufacturing costs and long production cycles, making it difficult to meet the large-scale production needs of such components in the aerospace field.

[0005] Hot gas expansion forming involves injecting high-pressure gas into a high-temperature, sealed tube blank. Under this internal pressure, the tube blank rapidly expands and deforms to fit the mold, obtaining the desired irregular thin-walled tube. This technology is currently an advanced manufacturing technology for integrally formed lightweight alloy thin-walled tubes. However, the internal stress state during the tube forming process is complex, and significant springback is likely to occur after cooling. Further process improvements are needed to enhance the dimensional accuracy of the formed tubes.

[0006] In summary, existing forming methods suffer from low production efficiency, low forming accuracy, and weak component performance, all of which fail to meet the forming requirements of thin-walled complex irregular-shaped tubular components in the aerospace field. Therefore, to address the manufacturing challenge of coupling forming accuracy and component performance in such complex irregular-shaped tubular components, there is an urgent need for a new generation of integrated shape and property control forming technology that can simultaneously ensure the accuracy, strength, and production efficiency of the formed components, thus solving the bottleneck problem of precision forming of thin-walled complex irregular-shaped tubular components. Summary of the Invention

[0007] The purpose of this invention is to provide a thermoforming device and method for irregularly shaped thin-walled tubes with additional pneumatic assistance, which solves the shortcomings of the prior art. This method integrates thermoforming, heat treatment and heat straightening processes to achieve integrated forming of metal thin-walled tubes with controlled shape and properties, thereby greatly improving production efficiency while ensuring the performance and dimensional accuracy of the parts.

[0008] To achieve the above objectives, the present invention provides a thermoforming apparatus for irregularly shaped thin-walled tubes with additional pneumatic assistance, including a zoned temperature-controlled mold, a self-resistance heating system, a pneumatic control system, and an axial force and displacement control system.

[0009] The partition temperature control mold is divided into an upper mold and a lower mold. The upper mold and the movable slider are fixed to the movable slider by bolts. The lower mold, the heat insulation plate and the water cooling plate are fixedly installed on the lower platform of the mold closing press.

[0010] The partition temperature control mold also includes a forming mold and a temperature control heating element. The forming mold has a through hole, and the temperature control heating element is disposed inside the through hole and connected to an external temperature control box. The forming mold also has a thermocouple.

[0011] The self-resistance heating system includes a high-frequency switching power supply, wires, and copper electrodes. The copper electrodes are disposed at both ends of the closed tube blank and are used to clamp the part to be formed. The copper electrodes are electrically connected to the high-frequency switching power supply through the wires.

[0012] The forming pneumatic control system includes a high-pressure air source and a pneumatic control cabinet. The input end of the pneumatic control cabinet is connected to the high-pressure air source, and a gas passage is provided between the output end of the pneumatic control cabinet and the end cap of the closed tube blank.

[0013] The axial force and displacement control system includes a horizontal cylinder and a force sensor. The force sensor is located at the output end of the horizontal cylinder and is fixedly connected to the horizontal cylinder.

[0014] Preferably, it also includes a closed tube blank and a mold closing press;

[0015] One end of the closed tube blank is welded with a sealing plate, and the other end is welded with a sealing head. The axial force and displacement control system is provided on one side of the sealing plate, and the air pressure control system is provided on one side of the sealing head. The partition temperature control molds are symmetrically arranged on the upper and lower sides of the closed tube blank, and the partition temperature control molds are connected to the mold closing press.

[0016] The mold clamping press includes a servo cylinder and a moving slide block, wherein the servo cylinder is connected to the moving slide block.

[0017] Preferably, the closed tube blank is one of α-type titanium alloy, near-α-type titanium alloy, α+β-type titanium alloy, iron-based superalloy, cobalt-based superalloy, and nickel-based superalloy.

[0018] Preferably, the forming mold is made of low-carbon steel or H-type steel. 13 It is one of Ni7N, and the outside of the forming mold is wrapped with asbestos.

[0019] Preferably, the cooling channel in the water-cooled plate is a flowing ambient temperature water-cooled channel, which is arranged in a straight or conformal manner.

[0020] The present invention also provides a method for thermoforming irregularly shaped thin-walled tubular parts with additional pneumatic assistance, comprising the following steps:

[0021] Step 1: Connect the temperature control heating element to the temperature control box to control the temperature of the forming mold to T1, and keep the temperature uniform at all points inside the mold by heat preservation.

[0022] Step 2: Use a self-resistance heating system to rapidly heat the metal tube to the forming temperature T2 at a heating rate H to obtain a microstructure with good plasticity;

[0023] Step 3: After the metal pipe is heated to the target temperature, the slider at the mold closing press drives the upper mold to quickly close and maintain pressure, while adjusting the forming air pressure control system to pressurize the metal pipe at a certain rate. Inflate and pressurize to a gas pressure of p. Metal tube forming and in-mold quenching are carried out simultaneously. The horizontal cylinder moves axially synchronously to apply stress to the sealing plate and regulate the stress state inside the formed tube.

[0024] Step 4: By controlling the temperature and air pressure of the mold, the forming grout is kept at a constant mold temperature T1 and gas pressure p for 30 minutes. The formed pipe will experience stress relaxation under constant temperature and pressure, and at the same time, the sealing plate will be subjected to additional tensile stress under the high pressure inside the pipe.

[0025] Step 5: Unload the internal air pressure and axial stress of the horizontal cylinder in the closed tube blank, remove the copper electrode, open the mold and take out the part, cut the sealing plate and end cap of the closed tube blank and cut off the excess, and complete the forming and manufacturing of the metal irregular thin-walled tube.

[0026] Preferably, in step one, the forming mold adopts a zoned temperature control method, and the temperature control range T1 is 0 to 700°C.

[0027] Preferably, in step two, the metal tube is a titanium alloy or a high-temperature alloy, the forming temperature T2 range is 700-1000℃, and the heating rate H range is 1-100℃ / s.

[0028] Preferably, in step three, the pressure range of the mold-closing press is 50 to 1000 t.

[0029] Preferably, in step three, the high-pressure gas introduced into the sealed tube blank is one of air, nitrogen, or argon, wherein the pressurization rate is... The pressure ranges from 0.05 to 5 MPa / s, and the gas pressure p ranges from 0.1 to 20 MPa.

[0030] Therefore, the present invention employs the above-mentioned apparatus and method for thermoforming irregularly shaped thin-walled tubes with additional pneumatic assistance, which has the following advantages compared with the prior art:

[0031] (1) High forming accuracy: The temperature and internal pressure of the pipe forming process are controllable. By optimizing the process parameters, a pipe with uniform wall thickness can be obtained. The pipe forming and in-mold quenching are carried out simultaneously to avoid excessive thermal stress in the subsequent cooling process, which can cause shape distortion. The horizontal cylinder can apply prestress axially throughout the forming process to regulate the internal stress state of the pipe forming process. The sealing plate can generate additional tensile stress under the action of air pressure in the pipe to eliminate residual stress after quenching and improve forming accuracy.

[0032] (2) High forming efficiency: The use of current self-resistance heating avoids heat loss during the transfer of metal pipes from the heating furnace to the mold, greatly shortening the heating cycle; This method combines hot gas expansion forming of pipes, in-mold quenching and stress relaxation into one process, realizing integrated forming control of metal pipes, eliminating the need for subsequent heat treatment and shaping processes, and greatly improving production efficiency.

[0033] (3) Controllable microstructure and properties: The current output can be adjusted to control the forming temperature and heating rate of the metal tube, obtain electroplasticity and a well-matched phase distribution and grain size, and improve forming performance; the mold temperature can be adjusted to control the cooling rate of the in-mold quenching of the formed tube, obtain the phase transformation, grain size and intergranular compound precipitation trend required for the strength of the component; at the same time, the mold temperature can be controlled in zones, and a gradient microstructure can be obtained according to the performance requirements of different deformation zones of the tube.

[0034] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0035] Figure 1This is a structural diagram of a thermoforming device for irregularly shaped thin-walled tubes with additional pneumatic assistance according to the present invention;

[0036] Figure 2 This is a flowchart of a method for thermoforming irregularly shaped thin-walled tubular parts with additional pneumatic assistance according to the present invention;

[0037] Figure 3 This is a schematic diagram of the thermoforming of irregularly shaped thin-walled tubes with additional pneumatic assistance according to the present invention;

[0038] Figure 4 This is a diagram illustrating the mechanism of the high-pressure stress relaxation and shaping process in the mold of the irregular thin-walled tube of the present invention;

[0039] Figure 5 This is a window diagram of the hot forming process of titanium alloy pipe fittings according to Embodiment 1 of the present invention;

[0040] Figure 6 This is a window diagram of the hot forming process of high-temperature alloy pipe fittings according to Embodiment 2 of the present invention.

[0041] Figure Labels

[0042] 1. Sealed tube blank; 2. Sealing plate; 3. End cap; 4. Servo cylinder; 5. Moving slider; 6. Upper mold; 7. Lower mold; 8. Water-cooled plate; 9. Heat insulation plate; 10. Temperature control heating element; 11. Thermocouple; 12. Copper electrode; 13. Pneumatic control cabinet; 14. High-pressure air source; 15. Horizontal cylinder; 16. Force sensor. Detailed Implementation

[0043] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0044] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0045] Example 1

[0046] Figure 1 This is a structural diagram of a thermoforming apparatus for irregularly shaped thin-walled tubes with additional pneumatic assistance according to the present invention. Figure 1 As shown, the present invention provides a thermoforming device for irregular thin-walled tubes with additional pneumatic assistance, comprising: a zoned temperature-controlled mold, a self-resistance heating system, a pneumatic control system, and an axial force and displacement control system;

[0047] The zoned temperature control mold is divided into an upper mold 6 and a lower mold 7. The upper mold 6 and the movable slider 5 are fixed to the movable slider 5 by bolts, and the lower mold 7, the heat insulation plate 9 and the water cooling plate 8 are fixedly installed on the lower platform of the mold closing press. The mold closing pressure is controlled by the pressure control system of the mold closing press to reduce the heat exchange between the mold and the external equipment during the metal pipe forming process and prevent high temperature damage to the pressure control related sensors.

[0048] The zoned temperature control mold also includes a forming mold and a temperature control heating element 10. The forming mold has a through hole, and the temperature control heating element 10 is set inside the through hole. The temperature control heating element is set according to the deformation field of the part and is connected to an external temperature control box. The forming mold also has a thermocouple 11. The temperature information monitored by the thermocouple 11 can be fed back to the temperature control box to heat and keep the different zones of the forming mold warm.

[0049] The self-resistance heating system includes a high-frequency switching power supply, wires, and copper electrodes 12. Here, copper electrodes 12 represent the self-resistance heating system. Copper electrodes 12 are located at both ends of the closed tube blank 1 and are used to clamp the part to be formed. The copper electrodes 12 are electrically connected to the high-frequency switching power supply through the wires. In the self-resistance heating system, the high-frequency switching power supply provides the current required for the tube heating process. The rated output voltage of the power supply is 15V, and the rated output current is 10000A. The high-frequency switching power supply is connected to the copper electrodes through the wires. The copper electrodes clamp both ends of the closed tube blank. The high-voltage DC current output by the high-frequency switching power supply flows through the metal tube through the wires and is rapidly heated by its own resistance. The power supply current output can also be adjusted by the temperature data of the thermocouple on the surface of the metal tube during the heating process, thereby controlling the temperature and heating rate of the metal tube before forming, avoiding excessive oxidation of the tube surface caused by open and slow heating conditions, and controlling the microstructure evolution of the blank during the heating stage.

[0050] The forming gas pressure control system includes a high-pressure gas source 14 and a gas pressure control cabinet 13. The input end of the gas pressure control cabinet 13 is connected to the high-pressure gas source 14, and a gas passage is provided between the output end of the gas pressure control cabinet 13 and the end cap 3 of the closed tube blank 1, which is used to control the gas pressure and pressurization rate delivered to the closed tube. Depending on the material of the metal tube, the high-pressure gas can be selected from air, nitrogen, argon or helium.

[0051] The axial force and displacement control system includes a horizontal cylinder 15 and a force sensor 16. The force sensor 16 is located at the output end of the horizontal cylinder 15 and is fixedly connected to the horizontal cylinder 15. During the gas-filling forming process of the closed tube blank, the sealing plate 2 at one end undergoes outward bending deformation. The horizontal cylinder 15 can apply stress to the sealing plate 2 through axial loading to adjust the internal stress state of the metal tube forming process.

[0052] In addition, the device also includes a closed tube blank 1 and a mold closing press;

[0053] One end of the closed tube blank 1 is welded with a sealing plate 2, and the other end is welded with a head 3. An axial force and displacement control system is provided on one side of the sealing plate 2, and a pneumatic control system is provided on one side of the head 3. The partition temperature control molds are symmetrically arranged on the upper and lower sides of the closed tube blank 1, and the partition temperature control molds are connected to a mold closing press.

[0054] The mold closing press includes a servo cylinder 4 and a moving slider 5. The servo cylinder 4 is connected to the moving slider 5 and plays a role in controlling the mold closing pressure during the forming process. The upper mold 6 is fixed on the moving slider and is driven up and down by the servo cylinder 4. The mold closing pressure can be adjusted to control the mold closing pressure during the metal tube forming, in-mold quenching and stress relaxation stages.

[0055] Among them, the closed tube blank 1 is one of α-type titanium alloy, near-α-type titanium alloy, α+β-type titanium alloy, iron-based superalloy, cobalt-based superalloy, and nickel-based superalloy. The forming die is made of low-carbon steel, H... 13 It is one of Ni7N, and the outside of the forming mold is wrapped with asbestos. The cooling channel in the water-cooled plate 8 is a flowing room temperature water-cooled channel, which is arranged in a straight or conformal manner.

[0056] Example 2

[0057] Figure 2 This is a flowchart of a method for thermoforming irregularly shaped thin-walled tubular components with additional pneumatic assistance according to the present invention. Figure 3 This is a schematic diagram of the hot forming of irregularly shaped thin-walled tubular parts with added pneumatic assistance according to the present invention, as shown below. Figure 2 and Figure 3 As shown, the present invention also provides a method for thermoforming irregularly shaped thin-walled tubular components with additional pneumatic assistance, comprising the following steps:

[0058] Step 201: Connect the temperature control heating element through the temperature control box to control the temperature of the forming mold to T1, and keep the temperature uniform at all points inside the mold through heat preservation.

[0059] Step 202: Use a self-resistance heating system to rapidly heat the metal tube to the forming temperature T2 at a heating rate H to obtain a microstructure with good plasticity;

[0060] Step 203: After the metal tube is heated to the target temperature, the slider at the mold closing press drives the upper mold to close quickly and maintain pressure, while adjusting the forming air pressure control system to pressurize the metal tube at a certain rate. Inflate and pressurize to a gas pressure of p. The metal tube is rapidly formed under internal pressure. Due to the temperature difference between the forming mold and the closed tube blank, in-mold quenching will begin simultaneously after the closed tube blank is attached to the forming mold. The metal tube forming and in-mold quenching are carried out simultaneously. The sealing plate at one end of the closed tube blank expands to a hemispherical shape under internal high pressure. The horizontal cylinder moves axially synchronously to apply stress to the sealing plate and regulate the internal stress state of the formed tube.

[0061] Step 204: By controlling the temperature and air pressure of the mold, the forming grouting is kept at a constant mold temperature T1 and gas pressure p for 30 minutes. The formed pipe will experience stress relaxation under constant temperature and pressure. At the same time, the sealing plate will be subjected to additional tensile stress under the high pressure inside the pipe, which will further eliminate the residual stress generated by quenching in the grouting mold and ensure the strength and dimensional accuracy of the formed part.

[0062] Step 205: Unload the internal air pressure and axial stress of the horizontal cylinder in the closed tube blank, remove the copper electrode, open the mold and take out the part, cut the sealing plate and end cap of the closed tube blank and cut off the excess, and complete the forming and manufacturing of the metal irregular thin-walled tube.

[0063] Example 3

[0064] Figure 4 This is a diagram illustrating the mechanism of high-pressure stress relaxation and shaping process in the mold of irregularly shaped thin-walled tubular components, such as... Figure 4 As shown, components obtained after hot forming of metal tubing exhibit significant springback, often requiring further shaping. Hot shaping is based on the stress relaxation effect, which refers to the decrease in internal stress over time when the total strain of the material remains constant. During this process, the elastic strain of the material transforms into plastic strain, leading to a reduction in springback after unloading. The metal tubing retains a relatively high temperature after forming. Simultaneous in-mold quenching lowers the tubing temperature to the mold temperature T1. Under the influence of the mold temperature and the internal air pressure, the metal tubing undergoes a significant stress relaxation effect, reducing the springback of the hot-formed thin-walled tubing. The residual stress in the formed tubing approaches the stress relaxation limit with increasing relaxation time. Figure 4 In a), the mold temperature T during the stress relaxation stage. a >T b The higher the temperature, the faster the stress relaxation occurs, the lower the stress relaxation limit stress, and the smaller the springback Δε. Figure 4 In b), during the stress relaxation stage, the end cap of the formed tube is subjected to additional tensile stress under the high pressure inside the tube, which further reduces the internal stress of the formed tube and regulates the stress relaxation process of the part. Under the premise of improving the accuracy of the part, the temperature window of the forming mold is further widened. By increasing the axial stress, the mold temperature during the in-mold quenching stage can be reduced, energy consumption can be reduced, and the in-mold quenching cooling rate of the formed tube can be increased, thereby regulating the microstructure and properties.

[0065] Example 4

[0066] Figure 5 This is a process window diagram illustrating the coordinated control of strength and precision in the hot forming and in-mold quenching of titanium alloy pipe fittings, as shown below. Figure 5 As shown, taking TC4 titanium alloy as an example, it includes:

[0067] Step 401: Using a temperature control box, adjust the heating power of the heating element to heat the mold to 350℃ and keep it at that temperature for 5 minutes to ensure uniform temperature.

[0068] Step 402: The TC4 titanium alloy tube has a wall thickness of 1.5mm, a diameter of 60mm, and a length of 200mm. Adjust the power supply current output and rapidly heat the titanium alloy tube to 950℃ at a heating rate of 50℃ / s. Rapid heating can effectively reduce the grain growth tendency and obtain a microstructure with good plasticity.

[0069] Step 403: After the TC4 titanium alloy tube is heated to 900℃, the press drives the slide block to quickly close the mold, apply pressure and maintain pressure, and adjust the air pressure control system to pressurize the TC4 titanium alloy tube to 15MPa at a pressurization rate of 0.2MPa / s. Tube forming and in-mold quenching are carried out simultaneously. At the same time, the horizontal cylinder is axially loaded to control the stress state of the tube during the forming process. During this process, the tube temperature gradually drops from 900℃ to 350℃. Due to the fast cooling rate of the mold quenching, the high-temperature β phase undergoes a complete martensitic transformation to generate a high-strength α′ phase.

[0070] Step 404: After the TC4 titanium alloy tube has completely cooled to 350°C, it is held at a mold temperature of 350°C and an internal gas pressure of 15MPa for 30 minutes to induce stress relaxation. At the same time, an additional tensile stress is applied to the sealing plate at one end of the tube to eliminate the residual tensile and compressive stresses generated by the martensitic phase transformation and mold quenching stress. This controls the stress state of the formed tube during the stress relaxation stage, thereby improving the dimensional accuracy of the formed parts.

[0071] Step 405: Unload the internal air pressure and axial stress of the horizontal cylinder of the closed pipe fitting, remove the copper electrode, open the mold and take out the part, cut the sealing plate and end cap of the closed pipe fitting and cut off the excess, and complete the forming and manufacturing of the TC4 titanium alloy irregular thin-walled pipe fitting.

[0072] Example 5

[0073] Figure 6 This is a process window diagram illustrating the coordinated control of strength and precision in hot forming and in-mold quenching of high-temperature alloy pipe fittings, as shown below. Figure 6 As shown, taking GH3128 as an example, it includes:

[0074] Step 501: Using a temperature control box, adjust the heating power of the heating element to heat the mold to 1160℃ and keep it at that temperature for 5 minutes to ensure uniform temperature.

[0075] Step 502: The GH3128 has a wall thickness of 1mm, a tube diameter of 60mm, and a length of 200mm. Adjust the power supply current output and rapidly heat the tube to 1160℃ at a heating rate of 50℃ / s. Rapid heating can effectively reduce the grain growth tendency and obtain a microstructure with good plasticity.

[0076] Step 503: After the GH3128 tube is heated to 1160℃, the press drives the slide block to quickly close the mold, apply pressure and maintain pressure, and adjust the air pressure control system to pressurize the GH3128 tube to 10MPa at a pressurization rate of 0.1MPa / s. Tube forming and in-mold quenching are carried out simultaneously. At the same time, the horizontal cylinder is axially loaded to control the stress state of the tube during the forming process. During the forming process, the tube temperature gradually decreases from 1160℃ to 600℃. This process has a relatively fast cooling rate, resulting in the precipitation of high-strength γ′ phase and carbides with a size range of 100 to 200nm.

[0077] Step 504: After the GH3128 tube has completely cooled to 600℃, it is held at a mold temperature of 600℃ and an internal gas pressure of 15MPa for 30 minutes to induce stress relaxation. At the same time, an additional tensile stress is applied to one end of the tube to eliminate the residual tensile and compressive stresses generated by the mold quenching stress. This controls the stress state of the formed tube during the stress relaxation stage, thereby improving the dimensional accuracy of the formed parts.

[0078] Step 505: Unload the internal air pressure and axial stress of the horizontal cylinder of the closed pipe fitting, remove the copper electrode, open the mold and take out the part, cut the sealing plate and end cap of the closed pipe fitting and cut off the excess, and complete the forming and manufacturing of the GH3128 irregular thin-walled pipe fitting.

[0079] Therefore, the present invention employs the aforementioned thermoforming apparatus and method for irregularly shaped thin-walled tubes with additional pneumatic assistance. By using self-resistance heating to seal the tube blank, the plasticity of the metal tube is improved. The heating rate is adjustable, greatly improving heating efficiency and shortening the production cycle. Simultaneously, it can control the microstructure evolution of the metal tube before forming, improving forming performance. Tube thermal expansion, in-mold quenching, and stress relaxation combine thermoforming, heat treatment, and hot straightening of the metal tube into a single process, significantly improving formability and production efficiency. During the in-mold quenching stage, the mold can be temperature-controlled in zones to regulate the quenching cooling rate, and a gradient structure can be obtained according to the performance requirements of different deformation zones of the component. During the in-mold stress relaxation stage, the formed tube is continuously kept warm and flexibly supported by internal pressure. Simultaneously, the axial loading of the horizontal cylinder regulates the internal stress state of the formed tube, eliminating residual stress generated by in-mold quenching, reducing component springback, and improving the strength and dimensional accuracy of the formed tube.

[0080] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A thermoforming apparatus for irregularly shaped thin-walled tubular components with additional pneumatic assistance, characterized in that, This includes zoned temperature-controlled molds, self-resistance heating systems, air pressure control systems, and axial force and displacement control systems. The partition temperature control mold is divided into an upper mold and a lower mold. The upper mold and the movable slider are fixed to the movable slider by bolts. The lower mold, the heat insulation plate and the water cooling plate are fixedly installed on the lower platform of the mold closing press. The partition temperature control mold also includes a forming mold and a temperature control heating element. The forming mold has a through hole, and the temperature control heating element is disposed inside the through hole and connected to an external temperature control box. The forming mold also has a thermocouple. The self-resistance heating system includes a high-frequency switching power supply, wires, and copper electrodes. The copper electrodes are disposed at both ends of the closed tube blank and are used to clamp the part to be formed. The copper electrodes are electrically connected to the high-frequency switching power supply through the wires. The forming pneumatic control system includes a high-pressure air source and a pneumatic control cabinet. The input end of the pneumatic control cabinet is connected to the high-pressure air source, and a gas passage is provided between the output end of the pneumatic control cabinet and the end cap of the closed tube blank. The axial force and displacement control system includes a horizontal cylinder and a force sensor. The force sensor is located at the output end of the horizontal cylinder and is fixedly connected to the horizontal cylinder. It also includes closed tube blanks and mold closing presses; One end of the closed tube blank is welded with a sealing plate, and the other end is welded with a sealing head. The axial force and displacement control system is provided on one side of the sealing plate, and the air pressure control system is provided on one side of the sealing head. The partition temperature control molds are symmetrically arranged on the upper and lower sides of the closed tube blank, and the partition temperature control molds are connected to the mold closing press. The mold clamping press includes a servo cylinder and a moving slide, wherein the servo cylinder is connected to the moving slide. The molding method of the above-mentioned device includes the following steps: Step 1: Connect the temperature control heating element to the temperature control box to control the temperature of the forming mold. T 1. Furthermore, the temperature inside the mold is kept uniform through heat preservation. Step 2: Use a self-resistance heating system to heat the metal pipe at a certain rate. H Rapidly heat to forming temperature T 2. Obtain a microstructure with good plasticity; Step 3: After the metal pipe is heated to the target temperature, the slider at the mold closing press drives the upper mold to quickly close and maintain pressure, while adjusting the forming air pressure control system to pressurize the metal pipe at a certain rate. Inflate and pressurize until the gas pressure is [value missing]. p Metal tube forming and in-mold quenching are carried out simultaneously. The horizontal cylinder moves axially synchronously to apply stress to the sealing plate and regulate the stress state inside the formed tube. Step 4: By controlling the temperature and air pressure of the mold, the molding and grouting process is kept at a constant mold temperature. T 1 and gas pressure p The tube is held at a constant temperature and pressure for 30 minutes, and stress relaxation occurs under these conditions. At the same time, the sealing plate is subjected to additional tensile stress under high pressure inside the tube. Step 5: Unload the internal air pressure and axial stress of the horizontal cylinder in the closed tube blank, remove the copper electrode, open the mold and take out the part, cut the sealing plate and end cap of the closed tube blank and cut off the excess, and complete the forming and manufacturing of the metal irregular thin-walled tube.

2. The thermoforming apparatus for irregularly shaped thin-walled tubes with additional pneumatic assistance according to claim 1, characterized in that, The closed tube blank is one of the following: α-type titanium alloy, near-α-type titanium alloy, α+β-type titanium alloy, iron-based superalloy, cobalt-based superalloy, and nickel-based superalloy.

3. The thermoforming apparatus for irregularly shaped thin-walled tubes with additional pneumatic assistance according to claim 1, characterized in that, The forming mold is made of low carbon steel, H... 13 It is one of Ni7N, and the outside of the forming mold is wrapped with asbestos.

4. The thermoforming apparatus for irregularly shaped thin-walled tubes with additional pneumatic assistance according to claim 1, characterized in that, The cooling channels in the water-cooled plate are flow-through, ambient-temperature water-cooled channels, arranged in a straight or conformal manner.

5. The thermoforming apparatus for irregularly shaped thin-walled tubes with additional pneumatic assistance according to claim 1, characterized in that, In step one, the forming mold adopts a zoned temperature control method, and the temperature control range is... T 1 represents 0~700℃.

6. The thermoforming apparatus for irregularly shaped thin-walled tubular components with additional pneumatic assistance according to claim 1, wherein in step two, the metal tubing is a titanium alloy or a high-temperature alloy, and the forming temperature is... T The temperature range is 700~1000℃, and the heating rate is... H The range is 1~100℃ / s.

7. The thermoforming apparatus for irregular thin-walled tubes with additional pneumatic assistance according to claim 1, wherein in step three, the pressure range of the mold clamping press is 50~1000t.

8. The thermoforming apparatus for irregularly shaped thin-walled tubes with additional pneumatic assistance according to claim 7, wherein in step three, the high-pressure gas introduced into the sealed tube blank is one of air, nitrogen, or argon, wherein the pressurization rate is... The gas pressure is 0.05~5 MPa / s. p The pressure ranges from 0.1 to 20 MPa.

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