Cryogenic two-point incremental forming and in-die creep age forming apparatus and processing method

Abstract

The application discloses an ultra-low-temperature two-point incremental forming and in-die creep age treatment device and treatment method, and is based on the strength / plasticity dual-effect of an aluminum alloy plate formed by ultra-low-temperature forming and the acceleration effect on the aging strengthening process, a mixed process device capable of realizing the integration of ultra-low-temperature forming and creep age strengthening treatment is designed. The device is aimed at the process characteristics of two-point incremental forming, ensures that the formed surface has suitable lubricating conditions while realizing the forming in an ultra-low-temperature environment, realizes the creep age treatment of the ultra-low-temperature workpiece by using a supporting die to realize controllable loading and heating of the formed plate, significantly shortens the aging time, corrects the shape through the creep effect, and improves the forming precision. The device solves the problems of poor formability of the plate, long post-treatment time and low forming precision in the traditional forming process. The device realizes the efficient and high-precision forming of a high-strength aluminum alloy complex curved surface thin-walled structural part.

Description

Technical Field

[0001] This invention relates to an ultra-low temperature two-point progressive forming and in-mold creep aging treatment device for the efficient and high-precision manufacturing of high-strength complex curved aluminum alloy thin-walled components, belonging to the field of multi-process hybrid processing technology. Background Technology

[0002] Incremental sheet forming (ISF) is a flexible sheet metal forming process with high flexibility and formability. With the continuous development of ISF fundamental research, two-point incremental forming (TPIF) has emerged. As a variant of ISF, TPIF enhances forming stability by using an additional full or partial die on the other side of the sheet metal, further improving forming performance and accuracy. Currently, the main limitations to ISF development are twofold: Firstly, the poor plasticity of difficult-to-deform materials such as aluminum alloys at room temperature exceeds the forming limit when processing complex shapes. While traditional hot-assisted forming processes improve sheet plasticity, the strength loss due to dynamic material recovery at high temperatures remains a significant challenge. Additional post-processing techniques such as aging hardening after high-temperature forming severely reduce production efficiency. Secondly, incrementally formed parts have poor geometric accuracy; sheet springback is the cause of geometric errors in most areas of the formed parts.

[0003] In recent years, cryogenic forming technology has emerged to overcome the shortcomings of traditional hot forming processes. Aluminum alloys, as face-centered cubic materials, exhibit a double-increase effect when deformed at cryogenic temperatures, meaning both strength and plasticity increase simultaneously. This provides feasibility for producing high-strength, complex-structured aluminum alloy parts using cryogenic environments. With the continuous development of cryogenic technology, new cryogenic forming processes have been proposed, such as cryogenic stamping, cryogenic rolling, and cryogenic tubular hydraulic bulging. Currently, the proposed cryogenic incremental forming processes only target single-point incremental forming (SPIF). For complex curved thin-walled structures, the forming accuracy of cryogenic single-point incremental forming is insufficient to meet the rapid forming requirements of high-precision parts. Warping and springback of the sheet metal during forming are significant reasons for reduced forming accuracy. Two-point incremental forming (TPIF) effectively suppresses springback phenomena such as the "pillow effect" of the sheet metal by using a supporting mold, significantly improving springback accuracy. The combination of ultra-low temperature and two-point progressive forming process is currently facing challenges. Studies have shown that immersing the sheet in liquid nitrogen for cooling will lead to serious deterioration of surface quality and will not be able to further improve the forming performance of the sheet.

[0004] Cryogenic forming not only enhances the formability of sheet metal through a strength / plasticity enhancement effect but also significantly impacts the age-hardening properties of materials. Existing research indicates that cryogenic forming accelerates the aging process of materials, achieving shorter age-hardening times compared to room-temperature parts. This results in a significantly faster age-hardening rate in subsequent aging processes. For example, a research team at Shanghai Jiao Tong University has proposed a pre-hardening cryogenic forming process for aluminum alloy sheets, utilizing deep cryogenic forming to improve post-processing efficiency and achieve efficient production of complex thin-walled high-strength aluminum alloy components. Creep Aging Forming (CAF) is an advanced forming technology with advantages such as short lead times and low cost. CAF utilizes creep deformation caused by stress at high temperatures, causing the sheet metal to deform within its elastic zone, thus avoiding the introduction of excessive residual stress. This process effectively suppresses springback and improves forming accuracy. Currently, due to the limitations of forming equipment, there is a discontinuity between the cryogenic forming process and the post-aging treatment. After the sheet is formed, the part needs to be transferred to the corresponding post-processing equipment to continue the next process stage. The excessively long transfer and transportation time reduces production efficiency and affects the performance of the part. Therefore, how to continuously achieve cryogenic forming and aging strengthening treatment under the same equipment is also an important problem that urgently needs to be solved. Summary of the Invention

[0005] To achieve an integrated process for ultra-low temperature two-point progressive forming, creep aging strengthening, and straightening treatment of high-strength aluminum alloy sheets, this invention provides an ultra-low temperature two-point progressive forming and in-mold creep aging treatment device, which mainly has the following functions: 1. To achieve two-point progressive forming of sheets under ultra-low temperature conditions, utilizing the dual-effect of cryogenic strength and plasticity to improve the forming performance of the sheets; 2. To use a supporting mold to heat the ultra-low temperature formed parts, achieving rapid aging strengthening of the parts and improving the strength of the parts in a short time to meet actual production needs; 3. To achieve creep aging treatment within the mold, utilizing the high-temperature creep effect to further straighten the formed parts and improve the forming accuracy of the parts.

[0006] To achieve the above functions, the present invention adopts the following technical solution:

[0007] In a first aspect, this invention proposes a device for achieving ultra-low temperature two-point progressive forming, creep aging strengthening, and straightening treatment of high-strength aluminum alloy sheets. The device includes a two-point progressive forming module, a creep aging treatment module, a cooling medium circulation feeding module, and a control system. The two-point progressive forming module includes a forming tool, an upper clamping mold, a lower clamping mold, and a supporting mold. The creep aging treatment module includes a driving device, a heating element, a temperature measuring device, and a force sensor. The cooling medium circulation feeding module includes a liquid nitrogen storage chamber. The top of the liquid nitrogen storage chamber is open, and the target sheet is placed on top of it. The upper and lower clamping molds are used to clamp the edge of the target sheet and slide up and down along guide posts vertically arranged in the storage chamber. The supporting mold is located below the sheet and is also placed inside the liquid nitrogen storage chamber. A liquid nitrogen overflow hole is provided on the liquid nitrogen storage chamber. The liquid nitrogen storage chamber is connected to a liquid nitrogen container and a liquid nitrogen pump. The temperature measuring device monitors the temperature of the target sheet in real time. The heating element and force sensor are located on the supporting mold, which is driven by the driving device. The control system controls the creep aging treatment module and the cooling medium circulation feeding module.

[0008] As a further technical solution, a three-dimensional force sensor is also included. The three-dimensional force sensor is set below the entire liquid nitrogen storage cavity to monitor the forming force in the X, Y, and Z directions of the target sheet in real time during the forming process.

[0009] As a further technical solution, the driving device is installed at the bottom of the support mold, driving the support mold to move towards or away from the target plate.

[0010] As a further technical solution, the multiple heating elements are distributed inside the support mold to heat the target plate.

[0011] As a further technical solution, the temperature measuring device mainly consists of a multi-channel temperature measuring instrument and a thermocouple, with the thermocouple measuring end connected to the edge of the target board to monitor the temperature of the target board in real time.

[0012] As a further technical solution, the force sensor is installed inside the support mold, with the force-bearing surface in contact with the target plate, and is used to monitor the pressure of the support mold on the target plate.

[0013] As a further technical solution, the liquid nitrogen storage chamber is provided with a liquid nitrogen inlet and a liquid nitrogen outlet on both sides of the bottom. An inlet solenoid valve is installed at the liquid nitrogen inlet, and an outlet solenoid valve is installed at the liquid nitrogen outlet.

[0014] As a further technical solution, liquid nitrogen is sprayed out from the liquid nitrogen container, passes through the inlet solenoid valve, hydraulic sensor, liquid nitrogen storage chamber, outlet solenoid valve, and liquid nitrogen pump in sequence, and returns to the liquid nitrogen container to achieve circulation.

[0015] As a further technical solution, the sidewall of the liquid nitrogen storage chamber is provided with multiple liquid nitrogen overflow holes arranged vertically in sequence and connected to the liquid nitrogen transport pipeline.

[0016] Secondly, based on the aforementioned ultra-low temperature two-point progressive forming and in-mold creep aging treatment device, the present invention also proposes a method for processing target sheet metal using the aforementioned ultra-low temperature two-point progressive forming and in-mold creep aging treatment device, as follows:

[0017] Place the target plate on the support mold and fix it by clamping the mold with the upper and lower parts.

[0018] The thermocouple wires in the temperature measuring device are welded / glued to the perimeter of the target board. The temperature change of the board is monitored in real time by a multi-channel temperature measuring instrument, and the temperature signal is fed back to the control system.

[0019] Liquid nitrogen flows into the liquid nitrogen storage chamber, and the device enters the cooling stage. The control system monitors the temperature of the target plate and the pressure of the transport pipeline in real time.

[0020] When the pressure inside the liquid nitrogen storage chamber is too high, the liquid nitrogen storage chamber will leak.

[0021] Once the temperature of the target plate drops to the set temperature and remains stable, the device enters the forming stage. The forming tool begins to form the target plate according to the predetermined trajectory. The plate moves slowly downward under the clamping of the mold, and the overflowing liquid nitrogen is discharged through the liquid nitrogen overflow hole to the liquid nitrogen transport pipeline to enter the circulation.

[0022] After the first forming stage, the liquid nitrogen in the liquid nitrogen storage chamber is emptied, the heating element is activated, and the device enters the heating stage.

[0023] When the temperature measuring device detects that the temperature of the target plate has stabilized to the set temperature, the forming tool contacts the clamping mold and remains stationary. The motor drives the lead screw to make the supporting mold apply pressure to the plate upward. The force sensor provides real-time feedback on the plate pressure. The control system controls the motor to keep the pressure on the plate constant. The device enters the creep aging strengthening treatment stage and continues for a set time. At the same time, the creep effect is used to further correct the shape of the formed part.

[0024] After the creep aging treatment is completed, the heating element is turned off and the forming tool is moved to a non-working position.

[0025] The beneficial effects of this invention are as follows:

[0026] 1. This invention designs a processing device that integrates ultra-low temperature two-point progressive forming and aging heat treatment processes. The device achieves two-point progressive forming of sheet metal at ultra-low temperatures through liquid nitrogen circulation cooling. The heating function of the sheet metal is realized by modifying the support mold. This structural design allows ultra-low temperature formed parts to be directly aged and strengthened within the forming mold without the need for transfer, which greatly improves processing efficiency. At the same time, the short-term aging hardening effect produced by ultra-low temperature forming reduces the aging strengthening time required for the part to reach the strength required for production.

[0027] 2. The integrated device for ultra-low temperature two-point progressive forming and aging treatment designed in this invention can achieve in-mold creep aging forming of ultra-low temperature formed parts. The device drives the supporting mold through a designed driving device, causing the target sheet to creep. The creep effect is used to strengthen the part while simultaneously correcting its shape. The device combines ultra-low temperature forming and creep aging forming processes, thereby improving forming accuracy.

[0028] 3. This invention addresses the unique processing characteristics of the two-point incremental forming process by proposing a device capable of achieving two-point incremental forming at ultra-low temperatures. By designing a dedicated liquid nitrogen storage chamber structure, the forming plane can be raised and lowered within the chamber. This device enables continuous processing in an ultra-low temperature environment (-170℃). The overflow structure designed in this device ensures that the forming surface is dry and lubricated. Utilizing the strength and plasticity enhancement effect of aluminum alloys at ultra-low temperatures, the forming performance of the sheet metal is significantly improved. Attached Figure Description

[0029] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0030] Figure 1 This is the overall device design drawing of the present invention;

[0031] Figure 2 It is a feedback and control roadmap;

[0032] Figure 3 This is a process roadmap for 7050 ultra-low temperature two-point progressive forming and in-mold creep aging;

[0033] In the diagram: the spacing or dimensions between parts are exaggerated to show their positions; the diagram is for illustrative purposes only. 1 Electric liquid nitrogen pump, 2 Outlet solenoid valve, 3 Liquid nitrogen overflow hole, 4 Temperature measuring device, 5 Target plate, 6 Heating element, 7 Force sensor, 8 Forming tool, 9 Upper clamping mold, 10 Guide post, 11 Sliding pair, 12 Control system, 13 Lower clamping mold, 14 Support mold, 15 Hydraulic sensor, 16 Inlet solenoid valve, 17 Lead screw, 18 Motor, 19 Liquid nitrogen pipeline, 20 Self-pressurizing liquid nitrogen tank, 21 Liquid nitrogen storage chamber, 22 Three-dimensional force sensor. Detailed Implementation

[0034] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0035] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, unless otherwise expressly indicated by the invention, the singular form is also intended to include the plural form. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0036] As described in the background section, existing technologies have shortcomings. To address these technical problems, this invention proposes a cryogenic two-point progressive forming and in-mold creep aging treatment device. This device combines cryogenic two-point progressive forming with creep aging forming, utilizing the dual-effect of cryogenic strength and plasticity enhancement to improve the forming performance of aluminum alloy sheets. Simultaneously, the addition of a creep aging treatment process achieves short-term aging strengthening of the formed parts and improves forming accuracy. Through a single-sided contact cooling method, the device provides a dry lubricating environment for the cryogenic two-point progressive forming process. A motor-driven lead screw moves the support mold to obtain constant load conditions. The heating unit on the support mold maintains a constant aging heat treatment temperature for the sheet material through contact heating, ultimately achieving short-term creep aging forming of the cryogenic parts.

[0037] The following is combined Figure 1 , Figure 2 The present invention will be described in detail below. The specific structure is as follows: The present invention provides an ultra-low temperature two-point progressive forming and in-mold creep aging treatment device, which mainly includes a two-point progressive forming module, a creep aging treatment module, a cooling medium circulation feeding module and a control system.

[0038] The two-point progressive forming module includes a forming tool 8, an upper clamping mold 9, a lower clamping mold 13, guide pillars 10, a target sheet 5, a sliding pair 11, a support mold 14, and a three-dimensional force sensor 22. The upper clamping mold 9 has an L-shaped cross-section, with the protruding part acting as a protective wall to surround the forming area and prevent liquid nitrogen from overflowing into the forming area and thus deteriorating the lubrication environment. The inner wall of the liquid nitrogen storage cavity 21 is provided with a sliding guide rail to form a sliding pair 11 with the outer side of the clamping mold. The target sheet 5 can move up and down along the four guide pillars 10 under the clamping of the upper clamping mold 9 and the lower clamping mold 13. The support mold 14 is placed in the center of the device directly below the sheet. The three-dimensional force sensor 22 is located below the entire liquid nitrogen storage cavity 21 and monitors the forming force of the target sheet 5 in the X, Y, and Z directions in real time during the forming process.

[0039] The creep aging treatment module includes a motor 18, a lead screw 17, heating elements 6, a temperature measuring device 4, and a force sensor 7. The motor 18 is connected to the lead screw 17 and drives the lead screw 17 to rotate. The other end of the lead screw 17 is connected to the support mold 14. The motor 18 can control the support mold 14 to move up and down through the lead screw 17. Multiple heating elements 6 are distributed inside the support mold 14 for heating. The temperature measuring device 4 mainly consists of a multi-channel thermometer and a thermocouple. The thermocouple temperature measuring end is connected to the edge of the target plate 5 to monitor the temperature of the target plate in real time. The force sensor 7 is set inside the support mold 14, with the force-bearing surface in contact with the target plate 5, and is used to monitor the pressure of the support mold 14 on the target plate 5.

[0040] The cooling medium circulation feeding module includes a liquid nitrogen storage chamber 21, a liquid nitrogen transport pipeline 19, a self-pressurized liquid nitrogen container 20, a hydraulic sensor 15, an outlet solenoid valve 2, an inlet solenoid valve 16, and an electric liquid nitrogen pump 1. The top of the liquid nitrogen storage chamber 21 is open, and the target plate is directly placed on the top of the liquid nitrogen storage chamber 21 and in contact with the liquid nitrogen. The bottom of the liquid nitrogen storage chamber 21 has liquid nitrogen inlets and outlets on both sides, which are connected to the liquid nitrogen transport pipeline 19. The liquid nitrogen inlet is equipped with an inlet solenoid valve 16, and the liquid nitrogen outlet is equipped with an outlet solenoid valve 2. There are four guide pillars 10 inside the liquid nitrogen storage chamber 21, and a threaded hole in the center of the bottom is connected to a lead screw 17. The side wall of the liquid nitrogen storage chamber 21 has multiple liquid nitrogen overflow holes 3 arranged vertically in sequence and connected to the liquid nitrogen transport pipeline 19. Liquid nitrogen is sprayed out from the self-pressurized liquid nitrogen container 20, passes through the inlet solenoid valve 16, the hydraulic sensor 15, the liquid nitrogen storage chamber 21, the outlet solenoid valve 2, and the electric liquid nitrogen pump 1 in sequence, and returns to the container to achieve circulation.

[0041] The control system 12 is connected to the inlet solenoid valve 16, the electric liquid nitrogen pump 1, the outlet solenoid valve 2, the hydraulic sensor 15, the motor 18, the heating element 6, the temperature measuring device 4, and the force sensor 7. The temperature measuring device 4, the hydraulic sensor 15, and the force sensor 7 respectively feed back the temperature signal of the plate, the pressure signal in the cavity and pipeline, and the pressure signal of the plate supported by the mold 14 to the control system 12. The control system 12 controls the inlet solenoid valve 16, the electric liquid nitrogen pump 1, the outlet solenoid valve 2, the heating element 6, and the motor 18 to perform cooling, heating, temperature control, and creep forming operations on the target plate.

[0042] In this embodiment, the bottom of the plate and the outside of the clamping mold are surrounded by a liquid nitrogen storage chamber. The upper and lower clamping molds and the liquid nitrogen storage chamber are connected by guide rails to form a sliding pair, forming a closed space below the target plate to store liquid nitrogen and cool the target plate. The self-pressurized liquid nitrogen container can continuously supply liquid nitrogen to the device. Liquid nitrogen is transported into the liquid nitrogen chamber through a liquid nitrogen transport pipeline. Liquid nitrogen inlet and liquid nitrogen outlet are respectively set at both ends of the bottom of the liquid nitrogen storage chamber. Liquid nitrogen is sprayed out from the self-pressurized liquid nitrogen container, enters the chamber through a solenoid valve, and is discharged through the liquid nitrogen outlet after filling and flows back to the self-pressurized liquid nitrogen container, realizing liquid nitrogen circulation feeding.

[0043] Furthermore, the temperature measuring device monitors the temperature of the target sheet in real time through a low-temperature thermocouple. When the temperature drops to an ultra-low temperature (around -170℃), the forming tool runs along the shape trajectory of the bottom support mold, while the target sheet moves downward along the guide post, achieving two-point progressive forming at ultra-low temperatures.

[0044] Furthermore, the upper clamping mold is designed with a protective wall to surround the processing area, preventing overflowing liquid nitrogen from flowing into the forming area and thus affecting the surface quality of the formed part.

[0045] The side wall of the liquid nitrogen storage chamber is provided with vertically arranged liquid nitrogen overflow holes that are connected to the liquid nitrogen transport pipeline. As the forming plate moves downward, the liquid nitrogen overflow holes discharge the overflowing liquid nitrogen into the circulation pipeline.

[0046] Electromagnetic switching valves and pressure sensors are installed at the inlet and outlet pipes of liquid nitrogen. During the cooling phase of the device, the inlet solenoid valve opens and the outlet solenoid valve closes, allowing liquid nitrogen to quickly fill the device and cool it down. Hydraulic sensors detect the pressure in the circulation pipeline and the liquid nitrogen storage chamber. When the device is full of liquid nitrogen, the pressure inside the chamber increases, at which point the inlet solenoid valve closes and the device enters the forming phase.

[0047] An electric liquid nitrogen pump is installed in the pipeline at the liquid nitrogen outlet to increase the discharge flow rate and rapidly empty the liquid nitrogen from the device. During the forming process, a three-dimensional force sensor displays and records the forming process in real time.

[0048] After the first pass of cryogenic two-point progressive forming is completed, the device can directly begin in-mold creep aging treatment. The electromagnetic switch valve at the liquid nitrogen inlet is closed, and the electric liquid nitrogen pump is turned on to empty the liquid nitrogen storage chamber. Subsequently, the heating unit inside the support mold is activated, and the target sheet is heated in contact through heat conduction from the mold. The temperature of the target sheet is monitored in real time by a temperature measuring device. When the temperature reaches the target aging temperature, the control motor drives the lead screw to slowly move the support mold upward. The force sensor above the support mold monitors the force on the sheet in real time, keeping the load on the sheet constant, thus achieving in-mold creep aging treatment.

[0049] By utilizing the enhanced effect of ultra-low temperature on the aging dynamics of aluminum alloys, the device can significantly shorten the aging strengthening time. At the same time, creep aging strengthening treatment can achieve the straightening of the first-pass formed parts and improve the forming accuracy of the parts.

[0050] Based on the above-described apparatus, this embodiment also provides a specific processing method, as follows:

[0051] Place the target plate on the support mold and fix it by clamping the mold with the upper and lower parts.

[0052] The thermocouple wires in the temperature measuring device are welded / glued to the perimeter of the target board. The temperature change of the board is monitored in real time by a multi-channel temperature measuring instrument, and the temperature signal is fed back to the control system.

[0053] Liquid nitrogen flows into the liquid nitrogen storage chamber, and the device enters the cooling stage. The control system monitors the temperature of the target plate and the pressure of the transport pipeline in real time.

[0054] When the pressure inside the liquid nitrogen storage chamber is too high, the liquid nitrogen storage chamber will leak.

[0055] Once the temperature of the target plate drops to the set temperature and remains stable, the device enters the forming stage. The forming tool begins to form the target plate according to the predetermined trajectory. The plate moves slowly downward under the clamping of the mold, and the overflowing liquid nitrogen is discharged through the liquid nitrogen overflow hole to the liquid nitrogen transport pipeline to enter the circulation.

[0056] After the first forming stage, the liquid nitrogen in the liquid nitrogen storage chamber is emptied, the heating element is activated, and the device enters the heating stage.

[0057] When the temperature measuring device detects that the temperature of the target plate has stabilized to the set temperature, the forming tool contacts the clamping mold and remains stationary. The motor drives the lead screw to make the supporting mold apply pressure to the plate upward. The force sensor provides real-time feedback on the plate pressure. The control system controls the motor to keep the pressure on the plate constant. The device enters the creep aging strengthening treatment stage and continues for a set time. At the same time, the creep effect is used to further correct the shape of the formed part.

[0058] After the creep aging treatment is completed, the heating element is turned off and the forming tool is moved to a non-working position.

[0059] Implementation Case:

[0060] Taking a 1mm thick 7050-W (solution state) aluminum alloy sheet as an example, this paper details the specific process by which the device achieves ultra-low temperature two-point progressive forming and in-mold creep aging treatment. Figure 3 This is a process route diagram for the 7050 alloy unit.

[0061] 1. According to the "Heat Treatment Specification for Wrought Aluminum and Aluminum Alloys", 7050 sheet was subjected to solution heat treatment at a temperature of 475℃ and a holding time of 30min to obtain the target sheet 7050-W.

[0062] 2. Place the target sheet material on the support mold and fix it by clamping the mold with the upper and lower clamps;

[0063] 3. Weld / glu the thermocouple wires in the temperature measuring device to the perimeter of the target board, monitor the temperature change of the board in real time through a multi-channel temperature measuring instrument, and feed the temperature signal back to the control system;

[0064] 4. Open the solenoid switch valve (inlet) and the self-pressurized liquid nitrogen container, close the outlet solenoid switch valve, and liquid nitrogen flows into the liquid nitrogen storage chamber. The device enters the cooling stage, and the control system monitors the temperature of the target plate and the pressure of the transport pipeline in real time.

[0065] 5. When the pressure inside the liquid nitrogen storage chamber is too high, the control system will open the outlet solenoid valve to release the liquid.

[0066] 6. When the temperature of the target plate drops to -170℃±5℃ and remains stable, the device enters the forming stage. The forming tool begins to form the target plate according to the predetermined trajectory. The three-dimensional force sensor continues to move along with the forming process. The plate moves slowly downward under the clamping of the mold. The overflowing liquid nitrogen is discharged through the liquid nitrogen overflow hole to the liquid nitrogen transport pipeline to enter the circulation.

[0067] 7. After the first stage of forming, open the electromagnetic switch valve (inlet), close the self-pressurized liquid nitrogen container, turn on the electric liquid nitrogen pump to quickly empty the liquid nitrogen in the liquid nitrogen storage chamber, start the heating element, and the device enters the heating stage. According to the "Heat Treatment Specification for Wrought Aluminum and Aluminum Alloys", the target aging temperature is 160℃.

[0068] 8. When the temperature measuring device detects that the temperature of the target plate has stabilized at 160℃, the forming tool contacts the clamping mold and remains stationary. The motor drives the lead screw to apply pressure to the plate by supporting the mold. The force sensor provides real-time feedback on the plate pressure. The control system controls the motor to keep the pressure on the plate constant. The device enters the creep aging strengthening treatment stage, which lasts for 6 hours. At the same time, the formed part is further corrected through the creep effect.

[0069] 9. After the creep aging treatment is completed, the heating element is turned off, the motor is turned off, and the forming tool is moved to a non-working position.

[0070] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A device for ultra-low temperature two-point progressive forming and in-mold creep aging treatment, characterized in that, It includes a two-point progressive forming module, a creep aging treatment module, a cooling medium circulation feeding module, and a control system; The two-point progressive forming module includes a forming tool, an upper clamping mold, a lower clamping mold, and a supporting mold. The upper clamping mold has an L-shaped cross-section, with the protruding part serving as a protective wall surrounding the forming area. The creep aging treatment module includes a drive device, a heating element, a temperature measuring device, and a force sensor; The cooling medium circulation feeding module includes a liquid nitrogen storage chamber; the top of the liquid nitrogen storage chamber is open, the target plate is placed on top of it, and upper and lower clamping molds are used to clamp the edge of the target plate and slide up and down along the guide posts vertically set in the liquid nitrogen storage chamber. Below the target plate is a support mold, which is also set in the liquid nitrogen storage chamber; a liquid nitrogen overflow hole is provided on the liquid nitrogen storage chamber; and the liquid nitrogen storage chamber is connected to a self-pressurized liquid nitrogen container and a liquid nitrogen pump. The liquid nitrogen storage chamber has a liquid nitrogen inlet and a liquid nitrogen outlet on both sides of the bottom. An inlet solenoid valve is installed at the liquid nitrogen inlet, and an outlet solenoid valve is installed at the liquid nitrogen outlet. Liquid nitrogen is sprayed out from the self-pressurized liquid nitrogen container, passes through the inlet solenoid valve, hydraulic sensor, liquid nitrogen storage chamber, outlet solenoid valve, and liquid nitrogen pump in sequence, and returns to the self-pressurized liquid nitrogen container to achieve circulation. The temperature measuring device monitors the temperature of the target board in real time. The heating element and force sensor are set inside the support mold. The driving device drives the support mold to move towards or away from the target board. The control system controls the creep aging treatment module and the cooling medium circulation feeding module. After the two-point progressive forming is completed, the device directly begins in-mold creep aging treatment, utilizing the strengthening effect of ultra-low temperature to shorten the aging strengthening time.

2. The ultra-low temperature two-point progressive forming and in-mold creep aging treatment device as described in claim 1, characterized in that, It also includes a three-dimensional force sensor, which is located below the entire liquid nitrogen storage chamber to monitor the forming force in the X, Y, and Z directions of the target sheet in real time during the forming process.

3. The ultra-low temperature two-point progressive forming and in-mold creep aging treatment device as described in claim 1, characterized in that, The drive device is installed at the bottom of the support mold.

4. The ultra-low temperature two-point progressive forming and in-mold creep aging treatment device as described in claim 1, characterized in that, Multiple heating elements are distributed inside the support mold for heating the target plate.

5. The ultra-low temperature two-point progressive forming and in-mold creep aging treatment apparatus as described in claim 1, characterized in that, The temperature measuring device mainly consists of a multi-channel temperature measuring instrument and a thermocouple. The thermocouple measuring end is connected to the edge of the target board to monitor the temperature of the target board in real time.

6. The ultra-low temperature two-point progressive forming and in-mold creep aging treatment apparatus as described in claim 1, characterized in that, The force sensor is installed inside the support mold, with its force-bearing surface in contact with the target plate, and is used to monitor the pressure exerted by the support mold on the target plate.

7. The ultra-low temperature two-point progressive forming and in-mold creep aging treatment apparatus as described in claim 1, characterized in that, The side wall of the liquid nitrogen storage chamber is provided with multiple liquid nitrogen overflow holes arranged vertically in sequence and connected to the liquid nitrogen transport pipeline.

8. A method for processing a target sheet material using the ultra-low temperature two-point progressive forming and in-mold creep aging treatment apparatus according to any one of claims 1-7, characterized in that, as follows: Place the target plate on the support mold and fix it by clamping the mold with the upper and lower parts. The thermocouple wires in the temperature measuring device are welded or glued to the perimeter of the target board. The temperature change of the target board is monitored in real time by a multi-channel temperature measuring instrument, and the temperature signal is fed back to the control system. Liquid nitrogen flows into the liquid nitrogen storage chamber, and the device enters the cooling stage. The control system monitors the temperature of the target plate and the pressure of the liquid nitrogen transport pipeline in real time. When the pressure inside the liquid nitrogen storage chamber is too high, the liquid nitrogen storage chamber will leak. Once the target plate temperature drops to the set temperature and remains stable, the device enters the forming stage. The forming tool begins to form the target plate according to the predetermined trajectory. The three-dimensional force sensor is set below the entire liquid nitrogen storage chamber to monitor the forming force of the target plate in the X, Y, and Z directions in real time during the forming process. As the forming process continues, the target plate moves slowly downward under the mold clamping, and the overflowing liquid nitrogen is discharged through the liquid nitrogen overflow hole to the liquid nitrogen transport pipeline to enter the circulation. After the first stage of forming, the liquid nitrogen in the liquid nitrogen storage chamber is emptied, the heating element is activated, and the device enters the heating stage. When the temperature measuring device detects that the temperature of the target plate has stabilized to the set temperature, the forming tool contacts the clamping mold and remains stationary. The motor in the drive device drives the lead screw to make the supporting mold apply pressure to the target plate. The force sensor provides real-time feedback on the pressure of the target plate. The control system controls the motor to keep the pressure on the target plate constant. The device enters the creep aging strengthening treatment stage and continues for a set time. At the same time, the creep effect is used to further correct the shape of the formed part. After the creep aging treatment is completed, the heating element is turned off and the forming tool is moved to a non-working position.

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