A method for superplastic forming and diffusion bonding of titanium alloy heat resistant panels

Abstract

The present application belongs to the field of material processing technology, and particularly relates to a superplastic forming diffusion bonding forming method of titanium alloy heat-resistant wall plate, which comprises the following steps: S1, designing and manufacturing a mold according to the profile of a product process model, and designing a blank part; S2, processing the profile of the blank part, processing a gas passage, and marking a parting line for isolating agent coating; S3, cleaning the surface of the blank; S4, assembling and seal welding the blank part; S5, installing the blank in the mold, heating and vacuumizing the mold; S6, pressurizing the blank part, so that diffusion bonding is realized at the part not coated with the isolating agent; S7, superplastically forming the blank part, and then cooling and taking out the blank part; and S8, finely processing the blank part, so as to obtain a three-layer plate structure heat-resistant wall plate product. The technical scheme controls the shape and size of the product through a forming mold, completes the forming of a titanium alloy product with a complex structure, shortens the preparation process of the heat-resistant wall plate product, and reduces the manufacturing cost.

Description

Technical Field

[0001] This invention belongs to the field of materials processing technology, and in particular relates to a superplastic diffusion bonding forming method for titanium alloy heat-resistant wall panels. Background Technology

[0002] Superplastic forming / diffusion bonding (SPF / DB) technology has developed rapidly since the 1970s. It utilizes the excellent elongation and good diffusion properties of metallic materials with specific microstructures in the high-temperature range. During thermal cycling, appropriate pressure is applied to diffusely bond the mating parts of the material, while the separated parts undergo superplastic forming, thus creating an integral hollow structure. This technology can form complex integral structures in a single step, effectively improving material utilization, shortening processing cycles, and reducing manufacturing costs compared to traditional riveting and welding processes. Therefore, titanium alloy SPF / DB technology has become an advanced lightweight manufacturing technology. Developed countries, led by the United States, have vigorously promoted the application of this technology in the aerospace and military fields, achieving significant results. This technology started relatively late in China, but after decades of development, especially in the last 20 years, domestic titanium alloy superplastic forming / diffusion bonding technology has developed rapidly. TC4 titanium alloy two-layer structure skins, panels, and other structural components have been widely used in various new aircraft models. However, three-layer plate structures are still not mature enough due to their greater technical difficulty, and their engineering level is not high. There are few domestic manufacturers capable of producing three-layer plate structures using this technology, and most of them produce only single-grade titanium alloy plates. Reports on superplastic forming / diffusion bonding components of multi-type titanium alloy combined three-layer plate structures are even rarer.

[0003] In recent years, new aircraft have gradually developed towards higher altitudes and higher speeds, which has placed new demands on the airframe structure, such as aircraft skin and panels: integration, lightweighting, and high-temperature resistance. Therefore, high-temperature resistant titanium alloy materials such as Ti60 (600℃) and Ti65 (650℃) and their forming processes have become bottleneck issues for new models.

[0004] Meanwhile, titanium alloy superplastic forming or superplastic forming / diffusion bonding processes are often carried out at high temperatures. The mold heating and post-forming cooling are time-consuming, resulting in long production times for individual parts and extremely high machine tool occupancy. Workers often need to work in shifts to install molds, raise temperatures, and remove parts to meet production demands. Superplastic pneumatic bulging, due to its complexity, has a lower part yield rate compared to other sheet metal forming processes. However, opening the mold at high temperatures can easily cause parts to absorb hydrogen and oxygen, leading to part scrap. This makes it difficult to visually observe whether the part has been fully formed. Therefore, it is necessary to adopt relevant methods to monitor whether the part has been fully formed. If the part is not fully formed or leaks air, forming can be terminated, the furnace opened, the part removed, and the next blank molded at high temperature. This significantly reduces the cooling and reheating time, thereby improving production efficiency. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a superplastic forming diffusion bonding method for titanium alloy heat-resistant wall panels. Specifically, it is a superplastic forming-diffusion bonding method for a multi-type titanium alloy composite three-layer plate structure heat-resistant wall panel. This method uses three different grades of titanium alloy plates, such as TC4, Ti60, and Ti65, to form a three-layer plate structure heat-resistant wall panel through superplastic forming / diffusion bonding. Simultaneously, it solves the problem of monitoring the forming degree of superplastic forming parts.

[0006] The technical solution adopted to achieve the above objectives is as follows: A method for superplastic diffusion bonding of a titanium alloy heat-resistant wall panel, characterized by comprising the following steps: S1, Mold Design and Fabrication: Add process edges to the titanium alloy heat-resistant wall panel to obtain a process model of the part. Design and fabricate a mold based on the outline of the process model. The titanium alloy heat-resistant wall panel includes a model upper panel, a middle core plate, and a model lower panel. S2, Blank Design and Machining: Based on the structural design of the manufacturing process model, blank parts are designed. The blank parts include upper panel blank, core board blank and lower panel blank. After machining the outer contours of the upper panel blank, core board blank and lower panel blank, ventilation grooves are machined on the upper panel blank and the separation line of the release agent coating is engraved. S3, Blank surface treatment: Use acetone to clean the corresponding diffusion areas of the upper panel blank, core board blank and lower panel blank, and then use distilled water or pure water to clean the surfaces of the upper panel blank, core board blank and lower panel blank. S4, Blank assembly and sealing: Apply release agent to the superplastic forming area of ​​the upper and lower panel blanks, spot weld the core blank to the lower panel blank, then align the edges of the upper and lower panel blanks coated with release agent, seal the area around the upper and lower panel blanks, and seal the air inlet pipe at the location of the venting groove. S5, Mold installation: After cleaning the mold, apply a layer of release agent to the inside of the mold, then install the sealed blank into the mold, and finally connect the mold to the superplastic equipment to heat and vacuum the mold. S6, Diffusion bonding: Apply a pressure of 2.5~3MPa per unit area to the upper panel blank, lower panel blank and core board blank to achieve diffusion bonding in the uncoated parts; S7, Superplastic forming: According to the usage requirements of the superplastic equipment, adjust the valve of the superplastic equipment forming pipeline, start the air pressure control system of the forming pipeline, so that it performs superplastic air pressure expansion according to the set pressure-time curve, and enters the pressure holding state when it reaches 2.0MPa. After holding the pressure for 10 minutes, superplastic forming is achieved. After unloading the air pressure, the mold is cooled. S8, Unloading: When the mold temperature cools down to below 400℃, lift the mold and the titanium alloy heat-resistant wall panel parts inside it from the equipment platform to the fitter's platform, and remove the titanium alloy heat-resistant wall panel parts from the mold. S9, Machining: The titanium alloy heat-resistant wall panel parts are finely processed according to the external dimensions of the parts processed by the three-dimensional digital model to obtain the heat-resistant wall panel parts with a three-layer plate structure.

[0007] Preferably, in step S1, designing and manufacturing the mold based on the contour of the part's process model includes the following steps: S11, Add process edges around the titanium alloy heat-resistant wall panel part, and transition the upper panel of the model to the lower panel of the model at an angle to obtain the part process model; S12, the mold is divided into an upper mold and a lower mold. The cavities of the upper mold and the lower mold are designed according to the outline of the part process model, so that the cavity surfaces of the upper mold and the lower mold are consistent with the outline of the part process model. S13, functional structural units are machined on the upper mold and the lower mold respectively. The functional structural units include positioning holes, temperature measuring holes, lifting holes, sealing strips and venting grooves. Several venting holes are set on the cavity surface of the upper mold. The venting holes are connected to the outside through the venting pipe inside the upper mold.

[0008] Preferably, in step S11, in the structure where the upper panel of the model transitions to the lower panel of the model at an angle, the angle between the transition area and the lower panel of the model is 30°~40°.

[0009] Preferably, the upper panel blank is made of Ti65 material, the core board blank is made of Ti60 material, and the lower panel blank is made of TC4 material.

[0010] Preferably, in step S5, the heating and vacuuming treatment of the mold includes the following steps: Piping connection: Connect the forming pipes of the superplastic equipment to the mold; Heat the mold to the required molding temperature and hold it at that temperature for 1 hour. Vacuum the pipeline, evacuate the mold through the forming pipeline, and then introduce low-pressure argon gas at 0.1-0.3 bar, cycle 3 times, and keep the pressure at 0.1-0.3 bar constant.

[0011] Preferably, in step S6, the method of applying a pressure of 2.5~3MPa per unit area is as follows: argon gas is injected into the mold cavity through the ventilation pipe of the upper mold at a rate of 0.5MPa per minute, and when the pressure reaches 2.5~3MPa, the pressure is maintained for 150~180 minutes.

[0012] Preferably, in step S7, during the superplastic forming process, the pressure changes in the forming pipeline are monitored in real time.

[0013] Preferably, in step S2, the thickness of the upper panel blank, the core board blank, and the lower panel blank is 1 mm.

[0014] Preferably, in step S2, the separator coating boundary line includes the outline of the diffusion area between the core board blank and the lower panel blank, and the outline of the diffusion area between the core board blank and the upper panel blank.

[0015] Preferably, the release agent is boron nitride or yttrium oxide, and the mold release agent is boron nitride or yttrium oxide. The beneficial effects of the present invention are: This invention discloses a superplastic forming / diffusion bonding forming method for multi-type titanium alloy composite three-layer plate structure heat-resistant wall panels. By controlling the shape and size of the parts through forming molds, the method completes the forming of complex titanium alloy parts, shortens the preparation process of the heat-resistant wall panel parts, and reduces manufacturing costs. The method employs a process of diffusion bonding followed by superplastic forming, achieving diffusion bonding at the contact points between the upper panel, core panel, and lower panel, while superplastic forming is achieved at the parts coated with the release agent. This enables superplastic forming / diffusion bonding of three-layer plate structure heat-resistant wall panels composed of three different grades of titanium alloy plates (TC4, Ti60, and Ti65), forming complex hollow heat-resistant wall panels in a single step. This significantly improves the structural integrity of the parts, increases their specific strength and specific stiffness, and improves the welding rate of diffusion bonding. The parts exhibit advantages such as high dimensional accuracy, good overall performance, light weight, and high temperature resistance. Furthermore, this process shortens the processing cycle, increases material utilization, and reduces manufacturing costs. Attached Figure Description

[0016] Figure 1 This is a basic implementation flowchart of the technical solution; Figure 2 This is a schematic diagram of the monitoring system for superplastic pneumatic bulging in this technical solution; Figure 3 This is a schematic diagram of the blank parts being loaded into the mold structure for this technical solution. Figure 4 This is a schematic diagram of the lower mold structure of the mold in this technical solution; Figure 5 This is a schematic diagram of the upper mold structure of the mold in this technical solution; Figure 6 This is a schematic diagram of the lower panel blank structure of the blank part in this technical solution; Figure 7 This is a schematic diagram of the upper panel blank structure of the blank part in this technical solution; Figure 8 This is a schematic diagram of a three-layer heat-resistant wall panel component.

[0017] In the picture: 1. Gas source system; 2. First branch of pipeline; 3. Third branch of pipeline; 4. Second branch of pipeline; 5. First pressure regulating module; 6. Third shut-off valve; 7. First displacement sensor; 8. First motor; 9. First buffer gas cylinder; 10. First pressure sensor; 11. First shut-off valve; 12. Upper mold; 13. Upper panel blank; 14. Lower panel blank; 15. Lower mold; 16. Second shut-off valve; 17. Second pressure sensor; 18. Second motor; 19. Second buffer gas cylinder; 20. Trapezoidal lead screw; 21. Second displacement sensor; 22. Fourth shut-off valve; 23. Second 24. Pressure regulating module; 25. Third pressure regulating module; 26. Upper sealing space; 27. Lower sealing space; 28. Positioning hole I; 29. ​​Blank positioning hole; 30. Lifting hole I; 31. Temperature measuring hole I; 32. Ventilation groove I; 33. Positioning hole II; 34. Lifting hole II; 35. Temperature measuring hole II; 36. Ventilation groove II; 37. Clearance hole; 38. Ventilation hole; 39. Sealing stalk; 40. Lower panel superplastic forming area; 41. Lower panel venting groove; 42. Upper panel superplastic forming area; 43. Upper panel venting groove; 44. Blank part; 45. Core board blank. Detailed Implementation

[0018] To make the purpose, technical solution and advantages of the invention clearer, the technical solution of the invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of the invention, but not all embodiments.

[0019] Therefore, the following detailed description of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0020] Example 1 This embodiment discloses a superplastic diffusion bonding forming method for titanium alloy heat-resistant wall panels. As a basic implementation scheme of this technical solution, it includes the following steps: S1, Mold Design and Fabrication: Add process edges to the titanium alloy heat-resistant wall panel to obtain a process model of the part. Design and fabricate a mold based on the outline of the process model. The titanium alloy heat-resistant wall panel includes a model upper panel, a middle core plate, and a model lower panel.

[0021] S2, Blank design and processing: Based on the structural design of the manufacturing process model, blank part 44 is designed. Blank part 44 includes upper panel blank 13, core board blank 45 and lower panel blank 14. After machining the outer contour of upper panel blank 13, core board blank 45 and lower panel blank 14, ventilation grooves are machined on upper panel blank 13 and lower panel blank 14 by CNC machining and the dividing line of the release agent coating is engraved.

[0022] S3, Blank surface treatment: Clean the corresponding diffusion areas of the upper panel blank 13, core board blank 45 and lower panel blank 14 with acetone, and then clean the surfaces of the upper panel blank 13, core board blank 45 and lower panel blank 14 with distilled water or pure water.

[0023] S4, Blank assembly and sealing: Apply release agent to the superplastic forming area of ​​the upper plate blank 13 and the lower plate blank 14, spot weld the core plate blank 45 to the lower plate blank 14, then align the edges of the upper plate blank 13 and the lower plate blank 14 after applying the release agent, seal the area around the upper plate blank 13 and the lower plate blank 14, and seal the air inlet pipe at the position of the venting groove.

[0024] S5, Mold Installation: After cleaning the mold, apply a layer of release agent to the inside of the mold, then install the sealed blank into the mold, and finally connect the mold to the superplastic equipment to heat and vacuum the mold.

[0025] S6, diffusion bonding: Apply a pressure of 2.5~3MPa per unit area to the upper panel blank 13, the lower panel blank 14 and the core board blank 45 to achieve diffusion bonding in the uncoated areas.

[0026] S7, Superplastic forming: According to the usage requirements of the superplastic equipment, adjust the valve of the superplastic equipment forming pipeline, start the air pressure control system of the forming pipeline, so that it performs superplastic air pressure expansion according to the set pressure-time curve, and enters the pressure holding state when it reaches 2.0MPa. After holding the pressure for 10 minutes, superplastic forming is achieved. After unloading the air pressure, the mold is cooled.

[0027] S8, Unloading: When the mold temperature cools down to below 400℃, lift the mold and the titanium alloy heat-resistant wall panel parts inside it from the equipment platform to the fitter's platform, and remove the titanium alloy heat-resistant wall panel parts from the mold. S9, Machining: The titanium alloy heat-resistant wall panel parts are finely processed according to the external dimensions of the parts processed by the three-dimensional digital model to obtain the heat-resistant wall panel parts with a three-layer plate structure.

[0028] Example 2 This embodiment discloses a superplastic forming diffusion bonding method for titanium alloy heat-resistant wall panels. As a preferred embodiment of this technical solution, it includes the following steps: S1, Mold Design and Fabrication: A process edge is added to the titanium alloy heat-resistant wall panel to obtain a process model. The mold is designed and fabricated based on the outline of the process model. The titanium alloy heat-resistant wall panel includes a top panel, a middle core plate, and a bottom panel of the model. The mold design and fabrication based on the outline of the process model includes the following steps: S11, add process edges around the titanium alloy heat-resistant wall panel part, and transition the upper panel of the model to the lower panel of the model at an angle to obtain the part process model; further, in the structure where the upper panel of the model transitions to the lower panel of the model at an angle, the angle between the transition area and the lower panel of the model is 30°~40°.

[0029] S12, the mold is divided into upper mold 12 and lower mold 15. The cavities of upper mold 12 and lower mold 15 are designed according to the outer contour of the part process model, so that the cavity surfaces of upper mold 12 and lower mold 15 are consistent with the outer contour of the part process model. S13, functional structural units are machined on the upper mold 12 and lower mold 15 respectively. These functional structural units include positioning holes, temperature measuring holes, lifting holes, sealing strips 38, and venting grooves. Several venting holes 37 are provided on the cavity surface of the upper mold 12, and these venting holes 37 communicate with the outside through venting pipes 39 inside the upper mold 12. Specifically, as shown... Figure 3 and Figure 4 As shown, specifically, the lower mold 15 has a positioning hole I 27, a billet positioning hole 28, a lifting hole 30, a temperature measuring hole 31, and a venting groove I 31, and the upper mold 12 has a positioning hole II 32, a lifting hole II 33, a temperature measuring hole II 34, a venting groove II 35, a clearance hole 36, a venting hole 37, a sealing stalk 38, and a venting pipe 39. The venting hole 37 communicates with the outside through the venting pipe 39 inside the upper mold 12.

[0030] S2, Blank design and processing: Based on the structural design of the process model of the part, blank part 44 is designed. Blank part 44 includes upper panel blank 13, core board blank 45 and lower panel blank 14. After machining the outer contour of upper panel blank 13, core board blank 45 and lower panel blank 14, ventilation grooves are machined on upper panel blank 13 and lower panel blank 14 and the separation line of the release agent coating is engraved. S3, Blank surface treatment: Use acetone to clean the corresponding diffusion area surfaces of the upper panel blank 13, core board blank 45 and lower panel blank 14, and then use distilled water or pure water to clean the surfaces of the upper panel blank 13, core board blank 45 and lower panel blank 14. S4, Blank assembly and sealing: Apply release agent to the superplastic forming area of ​​the upper plate blank 13 and the lower plate blank 14, spot weld the core plate blank 45 to the lower plate blank 14, then align the edges of the upper plate blank 13 and the lower plate blank 14 after applying the release agent, seal the area around the upper plate blank 13 and the lower plate blank 14, and seal the air inlet pipe at the position of the venting groove. S5, Mold installation: After cleaning the mold, apply a layer of release agent to the inside of the mold, then install the sealed blank into the mold, and finally connect the mold to the superplastic equipment to heat and vacuum the mold. S6, diffusion bonding: Apply a pressure of 2.5~3MPa per unit area to the upper panel blank 13, the lower panel blank 14 and the core board blank 45 to achieve diffusion bonding in the uncoated parts; S7, Superplastic forming: According to the usage requirements of the superplastic equipment, adjust the valve of the superplastic equipment forming pipeline, start the air pressure control system of the forming pipeline, so that it performs superplastic air pressure expansion according to the set pressure-time curve, and enters the pressure holding state when it reaches 2.0MPa. After holding the pressure for 10 minutes, superplastic forming is achieved. After unloading the air pressure, the mold is cooled. S8, Unloading: When the mold temperature cools down to below 400℃, lift the mold and the titanium alloy heat-resistant wall panel parts inside it from the equipment platform to the fitter's platform, and remove the titanium alloy heat-resistant wall panel parts from the mold. S9, Machining: The titanium alloy heat-resistant wall panel parts are finely processed according to the external dimensions of the parts processed by the three-dimensional digital model to obtain the heat-resistant wall panel parts with a three-layer plate structure.

[0031] Example 3 This embodiment discloses a superplastic forming diffusion bonding method for titanium alloy heat-resistant wall panels. As a preferred embodiment of this technical solution, it includes the following steps: S1, Mold Design and Fabrication: Add process edges to the titanium alloy heat-resistant wall panel to obtain a process model of the part. Design and fabricate a mold based on the outline of the process model. The titanium alloy heat-resistant wall panel includes a model upper panel, a middle core plate, and a model lower panel.

[0032] S2, Blank Design and Machining: Based on the structural design of the manufacturing process model, blank part 44 is designed. Blank part 44 includes upper panel blank 13, core plate blank 45, and lower panel blank 14. After machining the outer contours of upper panel blank 13, core plate blank 45, and lower panel blank 14, ventilation grooves are machined on upper panel blank 13 and lower panel blank 14 using CNC machining, and the separator coating boundary line is engraved. Among them, upper panel blank 13 is machined using Ti65 material, core plate blank 45 is machined using Ti60 material, and lower panel blank 14 is machined using TC4 material.

[0033] S3, Blank surface treatment: Clean the corresponding diffusion areas of the upper panel blank 13, core board blank 45 and lower panel blank 14 with acetone, and then clean the surfaces of the upper panel blank 13, core board blank 45 and lower panel blank 14 with distilled water or pure water.

[0034] S4, Blank assembly and sealing: Apply release agent to the superplastic forming area of ​​the upper plate blank 13 and the lower plate blank 14, spot weld the core plate blank 45 to the lower plate blank 14, then align the edges of the upper plate blank 13 and the lower plate blank 14 after applying the release agent, seal the area around the upper plate blank 13 and the lower plate blank 14, and seal the air inlet pipe at the position of the venting groove.

[0035] S5, Mold Installation: After cleaning the mold, apply a layer of release agent to the inside of the mold. Then, install the sealed blank into the mold. Finally, connect the mold to the superplasticizer and perform heating and vacuuming treatment on the mold. The heating and vacuuming treatment of the mold includes the following steps: Piping connection: Connect the forming pipes of the superplastic equipment to the mold; The mold is heated to the required forming temperature and held at that temperature for 1 hour. Specifically, the thermocouple is connected to the corresponding instrument and inserted into the temperature measuring holes on the upper mold 12 and the lower mold 15 to heat the mold.

[0036] Vacuum the pipeline, evacuate the mold through the forming pipeline, and then introduce low-pressure argon gas at 0.1-0.3 bar, cycle 3 times, and keep the pressure at 0.1-0.3 bar constant.

[0037] S6, Diffusion Bonding: Apply a pressure of 2.5~3 MPa per unit area to the upper panel blank 13, lower panel blank 14, and core board blank 45 to achieve diffusion bonding in the uncoated areas. Specifically, argon gas is introduced into the mold cavity through the vent pipe 39 of the upper mold 12 at a rate of 0.5 MPa per minute. When the pressure reaches 2.5~3 MPa, it is maintained for 150~180 minutes.

[0038] S7, Superplastic Forming: According to the usage requirements of the superplastic equipment, adjust the valves in the forming pipeline, activate the air pressure control system of the forming pipeline, and allow it to perform superplastic air pressure expansion according to the set pressure-time curve. When it reaches 2.0 MPa, it enters the pressure holding state and holds the pressure for 10 minutes to achieve superplastic forming. After unloading the air pressure, the mold is cooled. Furthermore, the pressure changes in the forming pipeline are monitored in real time throughout the entire superplastic forming process.

[0039] S8, Unloading: When the mold temperature cools down to below 400℃, lift the mold and the titanium alloy heat-resistant wall panel parts inside it from the equipment platform to the fitter's platform, and remove the titanium alloy heat-resistant wall panel parts from the mold. S9, Machining: The titanium alloy heat-resistant wall panel parts are finely processed according to the external dimensions of the parts processed by the three-dimensional digital model to obtain the heat-resistant wall panel parts with a three-layer plate structure.

[0040] Example 4 This embodiment discloses a superplastic forming diffusion bonding method for titanium alloy heat-resistant wall panels. As a preferred embodiment of this technical solution, it includes the following steps: S1, Mold Design and Fabrication: A process edge is added to the titanium alloy heat-resistant wall panel to obtain a process model. The mold is designed and fabricated based on the outline of the process model. The titanium alloy heat-resistant wall panel includes a top panel, a middle core plate, and a bottom panel of the model. The mold design and fabrication based on the outline of the process model includes the following steps: S11, add process edges around the titanium alloy heat-resistant wall panel part, and transition the upper panel of the model to the lower panel of the model at an angle to obtain the part process model; further, in the structure where the upper panel of the model transitions to the lower panel of the model at an angle, the angle between the transition area and the lower panel of the model is 30°~40°. S12, the mold is divided into upper mold 12 and lower mold 15. The cavities of upper mold 12 and lower mold 15 are designed according to the outer contour of the part process model, so that the cavity surfaces of upper mold 12 and lower mold 15 are consistent with the outer contour of the part process model. S13, functional structural units are machined on the upper mold 12 and the lower mold 15 respectively. The functional structural units include positioning holes, temperature measuring holes, lifting holes, sealing strips 38 and ventilation grooves. Several ventilation holes 37 are set on the cavity surface of the upper mold 12. The ventilation holes 37 are connected to the outside through the ventilation pipes 39 inside the upper mold 12.

[0041] S2, Blank Design and Machining: Based on the structural design of the manufacturing process model, blank part 44 is designed, including upper panel blank 13, core plate blank 45, and lower panel blank 14. Further, upper panel blank 13 is machined from Ti65 material, core plate blank 45 from Ti60 material, and lower panel blank 14 from TC4 material. Even further, the thickness of upper panel blank 13, core plate blank 45, and lower panel blank 14 is all 1mm. After machining the outer contours of upper panel blank 13, core plate blank 45, and lower panel blank 14, ventilation grooves are machined on upper panel blank 13 and lower panel blank 14 using CNC machining, and the separator coating boundary line is engraved. The separator coating boundary line includes the diffusion area contour lines of core plate blank 45 and lower panel blank 14, and the diffusion area contour lines of core plate blank 45 and upper panel blank 13.

[0042] S3, Blank surface treatment: Clean the corresponding diffusion areas of the upper panel blank 13, core board blank 45 and lower panel blank 14 with acetone, and then clean the surfaces of the upper panel blank 13, core board blank 45 and lower panel blank 14 with distilled water or pure water.

[0043] S4, Blank Assembly and Sealing: Apply a release agent to the superplastic forming areas of the upper plate blank 13 and the lower plate blank 14. Spot weld the core plate blank 45 onto the lower plate blank 14. Then, align the edges of the upper plate blank 13 and the lower plate blank 14 after applying the release agent, seal the area around the upper plate blank 13 and the lower plate blank 14, and seal the air inlet pipe at the location of the vent groove. The release agent used is boron nitride or yttrium oxide.

[0044] S5, Mold Installation: After cleaning the mold, apply a layer of release agent to the inside of the mold. Then, install the sealed blank into the mold. Finally, connect the mold to the superplasticizer and perform heating and vacuuming treatment on the mold. The release agent used is boron nitride or yttrium oxide. The heating and vacuuming treatment of the mold includes the following steps: Piping connection: Connect the forming pipes of the superplastic equipment to the mold; Heat the mold to the required molding temperature and hold it at that temperature for 1 hour. Vacuum the pipeline, evacuate the mold through the forming pipeline, and then introduce low-pressure argon gas at 0.1-0.3 bar, cycle 3 times, and keep the pressure at 0.1-0.3 bar constant.

[0045] S6, Diffusion Bonding: Apply a pressure of 2.5~3 MPa per unit area to the upper panel blank 13, lower panel blank 14, and core board blank 45 to achieve diffusion bonding in the uncoated areas. Specifically, argon gas is introduced into the mold cavity through the vent pipe 39 of the upper mold 12 at a rate of 0.5 MPa per minute. When the pressure reaches 2.5~3 MPa, it is maintained for 150~180 minutes.

[0046] S7, Superplastic Forming: According to the usage requirements of the superplastic equipment, adjust the valves in the forming pipeline, activate the air pressure control system of the forming pipeline, and allow it to perform superplastic air pressure expansion according to the set pressure-time curve. When the pressure reaches 2.0 MPa, it enters the pressure holding state and holds the pressure for 10 minutes to achieve superplastic forming. After unloading the air pressure, the mold is cooled. Furthermore, during the superplastic forming process, the pressure changes in the forming pipeline are monitored in real time. Based on the monitored pressure changes, it can be determined whether the part has been fully superplastic formed and whether a malfunction has occurred.

[0047] S8, Unloading: When the mold temperature cools down to below 400℃, lift the mold and the titanium alloy heat-resistant wall panel parts inside it from the equipment platform to the fitter's platform, and remove the titanium alloy heat-resistant wall panel parts from the mold. S9, Machining: The titanium alloy heat-resistant wall panel parts are finely processed according to the external dimensions of the parts processed by the three-dimensional digital model to obtain a three-layer plate structure heat-resistant wall panel part composed of three different grades of titanium alloy plates, namely TC4, Ti60 and Ti65.

[0048] Using this technical solution, the welding rate of the diffusion connection area of ​​the obtained titanium alloy heat-resistant wall panel can reach 97.82%, and the minimum wall thickness of the superplastic forming area is 0.86 mm.

[0049] This technical solution controls the shape and size of the part through forming molds, completing the forming of complex titanium alloy parts, shortening the preparation process of heat-resistant wall panels and reducing manufacturing costs. After the blank diffusion surface is cleaned to meet the requirements, a process of diffusion bonding followed by superplastic forming is adopted. Within a specific process window, diffusion bonding is achieved at the contact parts between the upper panel, core plate, and lower panel, while the parts coated with release agent are superplastic formed, forming a complex hollow heat-resistant wall panel in one step. The diffusion bonding area is a surface connection, which greatly improves the structural integrity of the part and increases its specific strength and specific stiffness compared with traditional spot welding or riveting. In this forming method, the diffusion pressure is applied by air pressure, resulting in uniform stress on the diffusion surface, improving the welding rate of the diffusion bonding. Furthermore, the stress concentration at the transition between the superplastic and diffusion areas is small, resulting in high overall performance of the formed heat-resistant wall panel. The part has advantages such as high dimensional accuracy, good overall performance, and light weight. Moreover, this process shortens the processing cycle, has high material utilization, and low manufacturing costs. Because the heat-resistant wall panel operates at temperatures ranging from 650℃ for the top panel, 350℃ for the bottom panel, and 600-350℃ for the core panel, three different grades of titanium alloy were used to accommodate the heat load distribution. Traditional processes only allow for the selection of one material based on the maximum load. This new forming method enables the superplastic forming / diffusion bonding of three-layer heat-resistant wall panels using a combination of TC4, Ti60, and Ti65 titanium alloy sheets. This allows the use of lower-cost TC4 sheet material while maintaining consistent heat resistance, thus reducing costs. Furthermore, the good plasticity of TC4 titanium alloy improves the overall performance of the finished product.

[0050] Example 5 This embodiment discloses a superplastic diffusion bonding forming method for titanium alloy heat-resistant wall panels. As a preferred embodiment of this technical solution, to address the real-time pressure monitoring required by this technical solution, a pneumatic monitoring system is also proposed, such as... Figure 1As shown, the upper mold 12 is connected to the first pressure regulating module 5 via the first shut-off valve 11, the first pressure sensor 10, the first gas cylinder buffer mechanism, and the third shut-off valve 6 in sequence; the lower mold 15 is connected to the second pressure regulating module 23 via the second shut-off valve 16, the second pressure sensor 17, the second gas cylinder buffer mechanism, and the fourth shut-off valve 22 in sequence; the third pressure regulating module 24 is connected between the upper mold 12 and the lower mold 15; the first pressure regulating module 5, the second pressure regulating module 23, and the third pressure regulating module 24 are connected to the gas source system 1 via the first branch of the pipeline 2, the second branch of the pipeline 4, and the third branch of the pipeline 3, respectively. The first gas cylinder buffer mechanism includes a first buffer gas cylinder 9, which is connected to a first motor 8 via a trapezoidal screw 20, and a first displacement sensor 7 is connected to the trapezoidal screw 20; the second gas cylinder buffer mechanism includes a second buffer gas cylinder 19, which is connected to a second motor 18 via a trapezoidal screw 20, and a second displacement sensor 21 is connected to the trapezoidal screw 20. Based on the aforementioned structure, the motor drives the trapezoidal lead screw 20 to reciprocate, pushing the piston and thus controlling the capacity of the buffer cylinder. After the motor stops working, the trapezoidal lead screw 20 can achieve mechanical self-locking of the moving pair. The displacement sensor can measure the position of the piston and, according to the PLC's mathematical operation instructions, convert it into a digital display value of the buffer cylinder's capacity.

[0051] With the support of the above-mentioned pneumatic monitoring system structure and working principle, such as Figure 2 As shown, the upper mold 12 and the upper panel blank 13 form an upper sealed space 25 with a volume of V1 before forming, and the lower mold 15 and the lower panel blank 14 form a lower sealed space 26 with a volume of V2 before forming. To improve the detection accuracy of the system, the volume V3 of the first buffer gas cylinder 9 should be adjusted to 0.5V1~1.5V1, and the volume of the second buffer gas cylinder 19 should be adjusted to 0.5V2~1.5V2.

[0052] Taking the forming of a two-layer plate structure superplastic forming / diffusion connection part of TC4 and GJB2921 as an example, the entire forming and monitoring process is described as follows: Before installing the mold, check the opening and closing of the pipeline shut-off valves. Close the first shut-off valve 11 and the second shut-off valve 16, and open the third shut-off valve 6 and the fourth shut-off valve 22.

[0053] The parts are sealed by welding, then molded and heated. When the temperature reaches 200-250℃, a vacuum is drawn between the sheet metal parts, and low-pressure argon gas (0.2 bar) is introduced for protection. When the temperature reaches 700-720℃, the main cylinder of the machine tool applies a clamping force of 0.5 MPa to form a sealed cavity between the sheet metal and the mold. At this time, the first branch 2 and the second branch 4 of the pipeline are simultaneously evacuated, and low-pressure argon gas is introduced. This process is repeated three times, and after each cycle, a pressure of 0.3 bar is maintained. The temperature continues to rise, and when it reaches the forming temperature of 900-920℃, the pressure of the main cylinder is increased to 1.5 MPa (the tonnage of the main cylinder is set according to the projected area of ​​the part), and the pressure is maintained for 2 hours.

[0054] After the diffusion connection is completed, the third shut-off valve 6 and the fourth shut-off valve 22 are closed. At this time, the first branch 2 and the second branch 4 of the pipeline are still at a low-pressure protection pressure of 0.3 bar. After the shut-off valves are closed, they are isolated from the gas source system 1. Then, superplastic forming is performed according to the set pressure-time curve, and the feedback values ​​of the first pressure sensor 10 and the second pressure sensor 17 are monitored.

[0055] The relationship between gas volume, pressure, and temperature is: PV = nRT; where P is the pressure, V is the gas volume, n is the number of molecules (considered a constant), and T is the absolute temperature.

[0056] Once the target temperature is reached, the superplastic forming machine (superplastic equipment) maintains the temperature, and the system temperature no longer changes. The volume of the piping used in the system is much smaller than the volume of the buffer gas cylinder and can be ignored. At this point, it can be determined that if the forming is sufficient, the pressure P1 of the first pressure sensor 10 can be calculated using P1 / 0.3 = (V3 + V1) / V3. The theoretical feedback value of the first pressure sensor 10 should be P1 = 0.3 * (V3 + V1) / V3.

[0057] Similarly, the theoretical feedback value of the second pressure sensor 17 can be calculated as P2 = 0.3 * (V4 + V2) / V4.

[0058] During the superplastic forming process, if the values ​​of the first pressure sensor 10 and the second pressure sensor 17 remain basically unchanged, it indicates that the pipeline is blocked and air cannot enter. If the feedback values ​​of the first pressure sensor 10 and the second pressure sensor 17 gradually increase, and at a certain time their feedback values ​​suddenly increase to be consistent with the forming pressure of the third branch 3 of the pipeline, and no longer change, it indicates that the part has cracked and started to leak air. If the feedback values ​​of the first pressure sensor 10 and the second pressure sensor 17 gradually increase, and the pressure can eventually reach 0.95P1~P1- and 0.95P2~P2 respectively, it indicates that the part is fully formed.

[0059] It should be noted that if air blockage or part breakage is detected during the forming process through monitoring, the mold can be opened directly, the faulty part removed, and the next blank placed in. This can save a significant amount of heating and cooling time, improving machine tool utilization and production efficiency. It is suitable for superplastic forming of single-layer sheets, and for superplastic forming / diffusion bonding processes of two-layer and multi-layer sheets, providing process monitoring.

Claims

1. A method for superplastic diffusion bonding forming of a titanium alloy heat-resistant wall panel, characterized in that, Includes the following steps: S1, Mold Design and Fabrication: A mold is fabricated based on the manufacturing process model of the titanium alloy heat-resistant wall panel component. The titanium alloy heat-resistant wall panel component includes a top panel, a middle core plate, and a bottom panel. Mold fabrication includes the following steps: S11, Add process edges around the titanium alloy heat-resistant wall panel part, and transition the upper panel of the model to the lower panel of the model at an angle to obtain the part process model; S12, the mold is divided into an upper mold (12) and a lower mold (15). The cavities of the upper mold (12) and the lower mold (15) are designed according to the outline of the part process model, so that the cavity surfaces of the upper mold (12) and the lower mold (15) are consistent with the outline of the part process model. S13, functional structural units are processed on the upper mold (12) and the lower mold (15) respectively. The functional structural units include positioning holes, temperature measuring holes, lifting holes, sealing strips (38) and ventilation grooves. Several ventilation holes (37) are set on the cavity surface of the upper mold (12). The ventilation holes (37) are connected to the outside through the ventilation pipes (39) inside the upper mold (12). S2, Blank design and processing: Based on the structural design of the part process model, blank parts (44) are designed. Blank parts (44) include upper panel blank (13), core board blank (45) and lower panel blank (14). After machining the outer contours of upper panel blank (13), core board blank (45) and lower panel blank (14), ventilation grooves are machined on upper panel blank (13) and lower panel blank (14) and the separation line of the release agent coating is engraved. S3, Blank surface treatment: Use acetone to clean the corresponding diffusion area surfaces of the upper panel blank (13), core board blank (45) and lower panel blank (14), and then use distilled water or pure water to clean the surfaces of the upper panel blank (13), core board blank (45) and lower panel blank (14). S4, Blank assembly and sealing: Apply release agent to the superplastic forming area of ​​the upper plate blank (13) and the lower plate blank (14), spot weld the core plate blank (45) to the lower plate blank (14), then align the edges of the upper plate blank (13) and the lower plate blank (14) coated with release agent, seal the area around the upper plate blank (13) and the lower plate blank (14), and seal the air inlet pipe at the position of the ventilation groove; S5, Mold installation: After cleaning the mold, apply a layer of release agent to the inside of the mold, then install the sealed blank into the mold, and finally connect the mold to the superplastic equipment to heat and vacuum the mold. S6, diffusion bonding: Apply a pressure of 2.5~3 MPa per unit area to the upper panel blank (13), the lower panel blank (14) and the core board blank (45) to achieve diffusion bonding in the uncoated parts; S7, Superplastic forming: According to the usage requirements of the superplastic equipment, adjust the valve of the superplastic equipment forming pipeline, start the air pressure control system of the forming pipeline, so that it performs superplastic air pressure expansion according to the set pressure-time curve, and enters the pressure holding state when it reaches 2.0MPa. After holding the pressure for 10 minutes, superplastic forming is achieved. After unloading the air pressure, the mold is cooled. S8, Unloading: When the mold temperature cools down to below 400℃, lift the mold and the titanium alloy heat-resistant wall panel parts inside it from the equipment platform to the fitter's platform, and remove the titanium alloy heat-resistant wall panel parts from the mold. S9, Machining: The titanium alloy heat-resistant wall panel parts are finely processed according to the external dimensions of the parts processed by the three-dimensional digital model to obtain the heat-resistant wall panel parts with a three-layer plate structure.

2. The superplastic forming diffusion bonding method for titanium alloy heat-resistant wall panels as described in claim 1, characterized in that, In step S11, in the structure where the upper panel of the model transitions to the lower panel of the model at an angle of 30° to 40°, the angle between the transition area and the lower panel of the model is 30° to 40°.

3. The superplastic forming diffusion bonding method for a titanium alloy heat-resistant wall panel as described in claim 1, characterized in that, In step S2, the upper panel blank (13) is processed using Ti65 material, the core board blank (45) is processed using Ti60 material, and the lower panel blank (14) is processed using TC4 material.

4. The superplastic forming diffusion bonding method for a titanium alloy heat-resistant wall panel as described in claim 1, characterized in that, In step S5, the heating and vacuuming process of the mold includes the following steps: Piping connection: Connect the forming pipes of the superplastic equipment to the mold; Heat the mold to the required molding temperature and hold it at that temperature for 1 hour. Vacuum the pipeline, evacuate the mold through the forming pipeline, and then introduce low-pressure argon gas at 0.1-0.3 bar, cycle 3 times, and keep the pressure at 0.1-0.3 bar constant.

5. The superplastic forming diffusion bonding method for a titanium alloy heat-resistant wall panel as described in claim 1, characterized in that, In step S6, the method of applying a pressure of 2.5~3 MPa per unit area is as follows: Argon gas is injected into the mold cavity through the ventilation pipe (39) of the upper mold (12) at a rate of 0.5 MPa per minute. When the pressure reaches 2.5~3 MPa, the pressure is maintained for 150~180 minutes.

6. The superplastic forming diffusion bonding method for a titanium alloy heat-resistant wall panel as described in claim 1, characterized in that, In step S7, during the superplastic forming process, the pressure changes in the forming pipeline are monitored in real time.

7. The superplastic forming diffusion bonding method for a titanium alloy heat-resistant wall panel as described in claim 1, characterized in that, In step S2, the thickness of the upper panel blank (13), the core board blank (45) and the lower panel blank (14) is 1 mm.

8. The superplastic forming diffusion bonding method for a titanium alloy heat-resistant wall panel as described in claim 1, characterized in that, In step S2, the dividing line of the release agent coating includes the outline of the diffusion area of ​​the core board blank (45) and the lower panel blank (14), and the outline of the diffusion area of ​​the core board blank (45) and the upper panel blank (13).

9. The superplastic forming diffusion bonding method for a titanium alloy heat-resistant wall panel as described in claim 1, characterized in that, The release agent is boron nitride or yttrium oxide, and the mold release agent is boron nitride or yttrium oxide.

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